Desalination,63(1987)1-55 Elsevier Science Publishers B.V., Amsterdam -
Printed in The Netherlands
Sea Water Desalination in Kuwait Experience
A Report on 33 Years
A.A.J. AL-ZUBAIDI Development Centre, Ministry 71651 Shamiya (Kuwait)
Water Resources 12020, Shamiya,
of Electricity
& Water,
P.O. Box
ABSTRACT Kuwait has been fully dependent for its fresh water supplies on sea water Multi-Staqe Flash Distillation Distillation Plants for the last 33 Years. Plants (#SF) have been successfully used in Kuwait for about 30 years, during commissioning, which period Kuwait has gained wide experience in the design, operation and maintenance of MSF Distillation Plants. This paper attempts to cover this long and unparalleled experience. Survey of all existing Power & Distillation Stations is presented and the reasons The behind the development of the Dual-Purpose Plants are explained. Main design historical development of MSF Distillation is also charted. features which characterize Kuwait's Plants are outlined. A summary of the experience gathered over the years concerning Plants Operation & Maintenance investigations and research into the viability of other is given. Finally, desalination methods are summarized.
I
INTRODUCTION Kuwait is located
covers
most
weather
of the
Arabian
conditions,
has very limited In the past, collection
of
in an arid area which is an extension
The collected 1925
to
Kuwait
electrical
new
era
relatively supply.
of
of
fresh
Kuwait
development,
The accelerated
demand
high
needed
of small,
OOll-9X4/87/$03.50
rates
of
for
the
medium
special
upon the types
past
on
of
during the
boats
called
small
income was established and
As
diesel
industrialization
development
needing power
was due to the big rise in
the huge increase
immigration
to start
as well as electrical
into the of
and heavy industries
power and fresh water
primitive
Later on,
by
the
in both utilities
of the
introduction
in
modernization
of living of the population,
of electrical
some
less than 1 MW.
of fresh water supplies
as a result
was
water
of oil in Kuwait, enough
huge quantities
which
water supplies
into
relied
totaling
the standard
force
water
some 100 miles away from Kuwait city.
in Iraq,
supply,
by severe
of rivers and lakes and
of fresh water.
rain
imported
sets of limited capacity
With the discovery a
is characterised
water was used in the dry season.
1950
"Dhows" from Shatt-Al-Arab its
area
relied for their fresh
quantities
period
for
resources
the Kuwaities small
This
of rain water and absence
under-ground
wells.
generating
peninsula.
scarcity
of the desert which
supplies.
0 1987 Elsevier Science Publishers B.V.
the
in the population
country country,
requiring
of
a labour and
the
large quantities
2 modernization
In order to affect this development, Kuwait
realised
electrical Ministry
of
securing
the basic
power
need for securing
and fresh
Electricity
adequate
such vital supplies
(M.E.&W.)
in order
and reliable
The state
water supplies.
& Water
and industrialization,
to
of Kuwait
assume
to meet
the
the ever
sources of
entrusted
the
responsibility
of
increasing
demands
of
these vital necessities. For steam
electrical power
power
stations
Kuwait
generation,
utilizing
the
relied
available
fuel
on conventional which
includes
crude oil, and gas oil. As for the huge fresh water supplies, the
sea
for
obtaining
production
of fresh
which
common
are
respective From
to
utilities
the
economical
savings
"Dual-Purpose
stages
of
power
raw
power
water
generation
and
Kuwait
realised
of combining Plants", in
generation
and
both and
the
early
plants
the
factors
and
their
to a great extent. the
(Power
been the
1950's
oil,
for
are many
production
appreciated
utilities
it has
needed
There
water
heavy
Kuwait turned to
supplies
processes.
are linked and inter-related
development
electrical
necessary
by distillation
both
beginning
termed
the
water
thermal
to
& Water)
practice
design
and distillation
advantages in what
since
and
production
and is
the early
construct plants
both
side by
side on the same site. This
paper
desalination
II
will
review
the
in Kuwait and accumulated
SURVEY OF POWER GENERATION At
present,
generation are fully
there
are
established
A seventh
water.
while
sea
water
STATIONS
stations
of distilled
of
over the last 33 years.
PRODUCTION
dual-purpose
and operational(l),
Power Generation
first
station(2,31.
dual-purpose
in
Kuwait
for
the
Five of these stations
the sixth
station
station is still in the planning
water production units called
& Water Production plant
built
The power generation
the non-condensing,
back-pressure
plant,
is in the
stage. These
MIGPD
(454.6 m3/dayl, plant
due to
giving
a total
its limited
Kuwait
was
in
1953
in 1953,
very low performance
consisted
type each with
output of 1.0 MIGPD
capacity,
has
been out
units are concerned, ratio
at
Shuwaikh
of three steam turbines
type each having a capacity
also installed
As far as the distillation
of relatively
in
Station.
plant consisted
'A' raft of the submerged-tube
power years.
experience
developments
are:
1) Shuwaikh The
and
& DISTILLATION six
of power and production
stage of construction. stations
emergence
(2.5 - 3.11,
of
of 0.75 MU. The
of 10 distillation a capacity
of 0.1
(4546 ml/day). of service
The
for many
these were inefficient, and had relatively
very
3 high operational and replaced flash
subsequently having
type,
performance
and maintenance
a
During
the period
still in operation. MIGPD
of
4.0
the first
plant
MIGPD
demolished
(18184
in 1967
m3/day)
having
at Shuwaikh 'A' station
of the extraction/condensing
type were
The extension units
These
type.
extension
extension
to the distillation
called
'8'
units were
1968 by two distillation
each
type,
were
called
distillation
submerged-tube in
capacity
1954/1955,
Power generation
4x7.5 MW steam turbines
later
in 1970 by unit product
units
'New A' which was of the multi-stage and
a
ratio of 8.
completed.
0.1
These
costs.
a capacity
also demolished
units
(Bl & 821
of 2.0 MIGPD
added
were
of the
of
the
and replaced
multi-stage and
of
of ten
also
in 1967
(9092 m'/day)
was
and are
plant consisted
which
raft,
station consisting
flash
a performance
ratio of 8. During
the
years
1957/1958
station was completed This
plant
was
an extension
to the
power
by adding 4x10 MW steam turbines
demolished
few
years
An extension
ago.
out during the same period.
'C & D' raft, consisted
of four units, each with a capacity
of the then new multi-stage
ratio of 3.5.
These distillation
type to be built on commercial after that date,
of much
bigger
the world's
out of service
of 6.0 MIGPD
added,
first units
new distillation
units
(2273
a performance of their
until 1976 and
and kept as emergency
(27276 m'/day)
'6'
type.
called
of 0.5 MIGPD
having
basis. These units were utilized
in 1982 with-three
capacities
The plants
(MSFl design,
units were
they were taken
by. They were replaced
flash
called
to the distillation
plants was also carried
m'/dayl,
plants
of the condensing
stand-
(Dl, D2 & D3)
and higher performance
ratio of 8.
In 1961 'C' Power units consisting were coannissioned. A year earlier capacity
of 1.0 MIGPD
multi-stage
These
(Gl & 621,
in 1965, commissioned units
five
commissioned
in 1977.
in 1968.
gas
turbines
the total present
station
(El & E2) each with a
These two units were of the units
apart from the units mentioned
each with a product capacity each with
of 1 MIGPD a capacity
so
(Fl & F2) of 2 MIGPD
All these units, as well as, all subsequent
(MSF) with a performance
Therefore,
units
steam turbines
ratio of 5.6. The distillation
and another two units
conznissioned in Kuwait
concerned,
Shuwaikh
added.
units were added,
were two units
distillation flash type
were
MW condensing
any longer.
Four more distillation
comnissioned
3x30
two distillation
(4546 m3/dayl
flash type with a performance
are not in existence
far.
of
since
then
are
of the
multi-stage
ratio of 8. As far as the power plants are
each
having
installed
a
capacity
of
power and distillation
are 324 MW and 32 MIGPD respectively.
40.5
MW
were
capacities
of
4
2) Shuaiba This
North Power Generation
station
consists
each with
type,
of five
an installed
cotmaissioned over the period capacity
another
three
in
(22730 m'/day) Therefore,
1965-1969.
units and
1968,
five
power
units were
gas turbines,
each with
a
finally
each
with
an installed
plants
MIGPD. The distillation Therefore,
installed
capacity
of,
three
during
1965-
a capacity
of
2 MIGPD
a capacity
of
5 MIGPD
(D) with
power and distillation
capacities
of
of
Station.
of the extraction/ These
134 MW.
condensing
power
units
were
a capacity
of 5
1970-1974. of six
units,
units were commissioned
the total installed
each with
over the period
power and distillation
1971-1975.
capacities
of Shuaiba
are 804 MW and 30 MIGPD respectively.
This station with a capacity
consists
& Water Production
Station.
of seven extraction/condensing
steam
of 150 MW. These power units were commissioned
Six more gas turbines,
each with a capacity
turbines,
each
over the period
of 18 MW were added and
in 1981.
The distillation MIGPD
plants which consist
(27276
m3/day), unit
were
distillation
capacity
of 1.0 MIGPD was commissioned
be used to evaluate of anti-scalent Therefore, East station
the performance
additives the
(A81,
of seven units,
commissioned
Another
which
is
installed
an
over
period
of utilizing
1978-1979.
unit
This experimental
and reliability
power
each with a capacity the
acid-treatment
in 1985.
for the prevention
total
with
a
unit is to acid instead
of scale.
and distillation
capacities
of Doha
are 1158 MW and 43 MIGPD respectively.
5) Doha West Power Generation This station
consists
1983-1984.
& Water Production
of eight steam turbines
type, each with a capacity the period
unit
with
& Water Production
consist
4) Doha East Power Generation
commissioned
each
of six steam turbines
over the period
South station
& C2) one
they consist
of lMIGP0 commissioned
are 400 MW and 14 MIGPD respectively.
consists
The distillation
6.0
Two more
are concerned,
Cl
South Power Generation
commissioned
of
The
in 1971.
the total present
This station
1977-1979.
plants
(B,
commissioned
North station
3) Shuaiba
type,
of the extraction/condensing
of 70 MW.
A2 & A3) each with a capacity
commissioned
Shuaiba
Station.
of 25 MW were added in 1969.
(Al,
1966,
steam turbines
capacity
As far as the distillation units
& Water Production
Station. of the extraction/condensing
of 300 MW. These power units were commissioned
over
5 The distillation
plants were
installed
of four units each with a capacity 1983-1984.
Stage
II consisted
7.2 MIGPD, commissioned
of twelve
over the period
the total
Therefore,
over
two stages.
of 6.0 MIGPD,
installed
units
Stage I consisted
commissioned each with
over the period
a capacity
of 6.0 -
capacities
are 2400
1984-1985.
power and distillation
MW and 96 MIGPD respectively.
6) Al-Zour This consist
four
with
a total
be constructed
each with a capacity
capacity
side', type,
it will each with
The power plants of 111 MW.
These
over two
stages.
Stage
I will
of 6.0-7.2 MIGPD. The first unit
in 1987.
the total installed
Eventually,
power
condensing
by the end of 1986.
plants will
of eight units,
should be commissioned
On the
of the extraction/
gas turbines
units should be completed The distillation
Station.
stage.
The first unit is under comnissioning.
of 300 MW.
also include
consist
& Water Production
is in the construction
of eight steam turbines
a capacity will
Power Generation
station
power and distillation
capacities
will
be
2511 MW and 96 MIGPD respectively.
7) Sabiya Power Generation
& Water Production
This new station which beyond
is designed
1990's, is still in the preliminary
stages. Work done so far consists
power
respectively.
and
distillation
the power
and preparatory
of consultative
it is estimated
In conclusion, installed
Station.
to satisfy
and water planning
By 1990, it is envisaged
and design
services.
that by the end -of 1986, capacities
demands
will
be
5372
the total actual MW
that the two capacities
and
208 MIGPD
will be 7084 MW
and 246 MIGPD respectively(l).
III
DEVELOPMENT
OF DUAL-PURPOSE
PLANTS
1) Introduction The combination
of both
production
in what
economical
solutions.
that
is termed
some of the partly
expanded
concerned,
as a completely
it is definitely
steam
generation
plants,
significant
and
distillate
offers very
feature
of this
in the steam turbines
for producing
flash distillation
not be considered
power
dual-purpose
A special
as the heat input necessary the multi-stage
electrical
plant.
distillate Although
wasted energy
water
water
attractive
and
combination
is
can be utilized
from
the extracted
sea water
in
steam should
as far as the power
plant
is
a very cheap source of energy for the distillation
6 plant compared
to the cost of energy
is not part of a dual-purpose the unused
steam actually
Dual-purpose reliability, satisfy
plants simple
the daily
required
enhances
the efficiency
should be suitably
operation
varying
plant which
the utilization
of some of
of the power cycle.
designed
to satisfy controllability,
They
and economy.
and seasonal
by a distillation
Furthermore,
system.
consumers
should
also
be designed
requirements
for
to
power
and
supply
and
continuously
and
fresh water. There
is
distillate
a
fundamental
difference
between
electrical
supply.
The electrical
power
demand varies
water
as the electrical
energy cannot be stored,
it has been generated. instant
it
is
in
demand
consumption
varies
also varies
seasonally
The distilled amounts and
Therefore,
of brackish
carried
connected
to and integrated are designed
and water
the
plants
in distilled
is that
and they
day
Different
multi-stage different
while
flash
be
distilled constant
are minimum,
Another
important
type
(MSFI.
types. These are:
on drinking
storage
many
the
system is
fluctuations reserve
water production
for
water
to
reservoirs.
days.
in
need Thus,
although
they could vary
feature
of distillation
at their full
limitations
rated capacity
in design
load in case of power generating
or/and
to
units could
on the demand.
Plants
of the dual-purpose
water production
It
suitable
distributed
and to act as strategic
could
Of Dual-Purpose
arrangements
with
The water distribution
due to possible
depending
Arrangements
the distilled
being
need to be run continuously
be varied continuously
2) Possible
and
water production
scale formation,
day to day.
is blended
and underground
the required
seasonally.
or as near to it as possible minimize
This
and from
plants
before
system.
production
not
monthly
consumption.
to take up the daily and short-term
Therefore,
variations
the day
out
with elevated
case of emergencies.
weekly,
the
once
at the
in order to satisfy WHO standards
by the water distribution
throughout
to
consumed
be generated
the year.
consumers
vary
power must
equal
from the distillation
water
in both water demand
be
throughout
throughout
treatments
These reservoirs
it should be directly
electrical
shall
continuously
water
appropriate
and
power
plants are possible.
plant is concerned, The power
plant
it is nearly
generating
units
As far as
always of the could
be of
a) Gas Turbines these
In
relatively
Power Plants the
plants,
exhaust
high temperature
heat energy
and water
reduction
in
the
with reduction operation
electrical
in distillate
and to secure
boilers
may
be
distillation more electric
of
plants
including
while
electricity
the
in relation
heating
steam steam
to
pressure turbine
in
electrical in the
suitable
and thus
do not have to use a specific to burn
kinds of steam turbines; Condensing
back-pressure
generation
is expanded
for heating
is then
as
turbines
for
generate
fuel for the
any kind of fuel
condensing,
are mainly
in the
as
providing
back-pressure,
used for electricity
and extraction/condensing well
heat
turbines
heating
steam
are used for
water
are therefore
circulating
brine.
heater Steam
These turbines
turbines
ensure
the
ratio
constant
mainly
distillation
plants.
turbines
relatively
are
with power
these
Furthermore, too
small
turbines
generation
This
it condenses
exhaust
giving
its
back
for
with no condensers
and
is pumped
the
be
be met
ratio
of
distillate
water
it suffers from the fact that this upon
the
electric
to meet
cannot
will
and temperature
plants.
condensate
highest
However,
depends
The
type.
to the power generated. and
where
are designed
production is
electricity.
low pressure
in the distillation
into the brine
of the non-condensing
Back-pressure
live steam of high pressure to generate
is at relatively
purposes
introduced
to the
steam turbines,
in the steam turbine
reuse in the boiler cycle.
electrical
coupled
gas oil, heavy oil, or crude oil.
steam from the turbine
and suitable
operation
automatically
as any
To ensure better flexibility
outputs
be possible
In the case of back-pressure
latent
be
plant
is lost
production.
and temperature
steam
will
a back-pressure
normally
and extraction/condensing.
exhaust
on the distillation
could be used. The live steam produced
It should
There are three main
distillate
at
power generation
in operation
generation
distillate
electrical
mainly
water production.
to
through
steam.
steam boilers
generation,
are
Power Plants
Steam turbines generation
which
power.
b) Steam Turbines
for
and depends
power
higher
expanded
plants
turbine
steam is then used as the heat input
that flexibility
fired waste heat boilers
power,
gas
the ratio between
is fixed, This means
ratio.
the
plant.
gas turbines,
production
performance
from
The produced
in these gases.
for the water distillation When utilizing
gases
are passed into a waste heat boiler to recover the
high
ensured with
steam
power
generated
demand. and
reduction
demand
The
any
for by
the these
flexibility
reduction
in the
in
of the
distillation
plant output. adequate
Such plants are suited for cases where
production
electrical distillate considered
of
distilled
with
design,
the
In
water
production,
whereas
requirements ratio
coupled
this
generation.
Extraction/condensing
The
water
power
as a secondary
the
Live
steam
steam
turbines
power
power
stage
from
the
permit
generation
generation
boiler
in the turbine
in the turbine,
pressure
and
pass-out.
pass-out
steam
for to
generated. heat
to
the
condensate
cooling
which
is almost
exhaust
be disposed
are important
ensure non-reliance
3) Main Advantages The advantages
Saving
in
Operational
lower than the single-purpose
plants.
expanded
in
mainly
be
relatively
brine
heater
low
extracted
as
giving
is pumped
its
back for
steam which is not
lower
stages
additional
to waste. feed
is
At a certain
is
the
thus
The
the
can
be
its latent
exhaust
steam
The energy
cheap value
for any significant
the latent heat which
of
power
giving
cycle.
is of relatively
energy
can
temperature,
plants
in the condenser
plants
production.
power.
Steam condensate
in the boiler
of low thermal
and
of the low energy
pressure,
to individual
of
as it
electrical
in any case need to
both electrical
power generation
and flexibility
in the design
water to
of one system on the other.
And Limitations
Of Dual-Purpose
of dual-purpose
the
and distillate
should be considered
Capital
Plants
plants are:
Investment
of
the
Boiler
Installation
and
Fuel
Costs.
The combined
advantage
is
of by condensation.
In this arrangement, production
generation
production
steam of
in the
is discharged
used in the distillation
and posseses
pressure
of heating
steam is condensed
the steam
a)
is
exhaust
water
steam
the
of both utilities.
distillation
brine.
is pumped back for reuse
power generation
load
is
water
water
of electric
is condensed
plants
condenser
This exhaust
for
The remainder
distillation the
at high
quantity
suitable
latent heat to the recirculating
required
power
and distillate
generation
specific
reuse in the boiler cycle.
turbines
base
product
ample adaptation
and distillate
being
for the
temperature
This
constant
main
electrical
varied within wide ranges to satisfy the requirements
expanded
a
to ensure
product.
of electrical between
it is important
boiler installation sumnation electrical
of saving This
dual-purpose
saving
of individual generation
in the boiler in
capacity
boiler
plant selected.
in case of dual-purpose
boiler
capacities
and water production installation
combined
costs
capacity
in case plants.
plants is of separate
This has the
in case of dual-purpose
depends
upon
the
type
of
9 Another boiler
advantage
as
capacity purpose
in
the
of combining
case
of
is relatively plants.
higher
This results
size which contribute
distillation
plants.
capital
cost
investment
purpose
plants.
has
electrical
cooling water
in case
the
advantage
generation
culverts
are relatively
dual-purpose
plants
intakes for single-purpose
cost.
Plants cheap
performance
Culverts as well
as compared
with
as distillation
the necessary
installations,
sea water
the
single
of
Sea water intake
therefore
building
plants
quantities
intake and discharge
to
for the
reducing
Installations
water production.
costly
value in
ratio
plants in comparison
plants
common
for single-
of considerably
near the sea for securing
saving in building
of
in low optimum
and feed water for distillate
and discharge considerable
boilers
boiler due to the increased
of the Distillation
Intake & Discharge
power
need to be constructed
boiler
combined
saving in fuel operating
for the distillation
cl Saving in the Sea Water
in one
the
wasted heat energy of relatively
results
This
installations
that
any of the individual
Cost Investment
plants
is
in higher efficiency
of partly
case of dual-purpose
Steam
than
for both
plants
to a considerable
b) Saving in the Capital The availability
steam boilers
dual-purpose
separate
there is culverts
individual
plants.
d) Waste Heat Energy The utilization production
of part of the waste
of distilled
the cost of the above unit cost. Therefore water
el Reduction
unused waste
in the Operational
overhead
which costs.
distillate
lower
& Maintenance
boiler
l.esult in
less
water unit production
maintenance
cost.
power plants unit cost
to the distillation
in dual-purpose
and Overheads
sea water and
of reducing
in the
by loading production
production
plants
in case of single-purpose
of
than the plants.
Costs.
of sharing various
installation,
This has the advantage
power
costs for the combined
productions
plants enjoy the benefits
such as administration, culverts,
heat energy
are considerably
costs for separate
Dual-purpose
heat energy from
lower the electric
the total production
and electricity
corresponding
water,
common
intake
operational
facilities
and discharge
costs
both electrical
and
less
energy and
10 f) Utilization
of Services
The installations production
on the same site
of both electrical
are inter-connected
power
and thus
generation
and
rely on each other
distilled
water
for some of their
services. Distilled steam
water
boilers
and
of high
purity
in the
power
plants,
this make-up
site.
This
eleminates
As
saving
in
for
distillation
auxiliaries power
power
brine,
on
the
same
costs and minimum
g) Improvement
sea
site
the
power
water
which
Cycle Thermal
water from the distillation
station boiler cycle at relatively improving
combined
dual-purpose plants on the
pumping
and
costs,
unit as required
in case
is needed
and
for
distillate
driving
This from
plants
is readily
available
result
in
in
saving
the
pumps.
electrical
losses.
of the Combined
Condensate
of
in the
power generation.
in the case of dual-purpose
plant
transmission
as
and
of small make-up
electrical
plants,
such
purposes
from distillation
transportation
plant of electrical
feed
In case
cycle.
available
the need for installation
electrical the
in
for make-up
generation
feed is readily
results
of single-purpose
plant
is needed
cycle
Efficiency
plants
is returned
high temperature.
thermal
back to the power
This has the advantage
efficiency
in
case
of
of
dual-purpose
plants.
dual-purpose
Although, limitations. demand ratio
The electrical
is less variable of
drop
in electrical
design aspects electrical
load,
reliability
additional Kuwait,
mostly load
between
and
and
while
allowing
capacity,
of
both
investment
Many
Such of
of the dual-purpose
and back-pressure
of electrical
power generation
any reduction
a reduction
in the
these
utilization
of waste
water
heat energy.
The
periods
Therefore,
far
special
in order to enable reducing plants
design
design
plants
steam turbines
in electrical
distillate
water
to
operate
at
at the same time the flexibility
special
to distillate
whereas
seasonally.
low demands
aspects
are
involve
is the limited flexibility
in
power and water demands.
are characterized
power generation production.
will
in
production.
Generally,
aspects
adapted
design to satisfy the proper balance between
Gas turbines
fact that
only
distillation
and ensuring
systems.
later.
limitation
the
also have some
nature,
varies
high
they
ratio of drop in water demands.
costs.
economic
is of varying
steady
and will be discussed
Another
advantages,
should be taken into consideration
their full production and
have many
load demand
and
exceeds the corresponding
the
plants
They
by low ratio
They suffer from the will be accompanied also
ensure
the electricity
the
by
best
that would
be
generated
by the steam
flow to the evaporator
normal amount of electricity generating
generated
is considerably
by the turbine.
lower than the
Therefore,
units will have to be added or extraction/condensing
other power
steam turbines
will have to be used. Extraction/condensing electric
power
the demands
before
of distillate
being
expelled
is less efficient.
the
design higher
and
in
condensing
steam turbines.
conditions
in one
must
lead
capital
The final limitation any problems
reflect
thermal
some more electric of the
the overall
in the
steam power plants.
heat
energy
utilization
of steam for the distillation use
of
specially
investment
on the
dependent
In The Operation
experience
part
in a condenser,
to overcome
that one system is not totally
Kuwait
to
cost
be considered
4) Kuwait Experience
Once
than
designed in
the
any difficulties
turbines standard
special
design
and also to ensure
on the other.
Of Dual-Purpose
operation
of
the two systems,
Therefore,
other.
plants may
steam
case
stems from the fact that by combining
might
of
to satisfy
In the case of higher capacity power generating
of big quantities
resulting
of the ratio
in order
water and the rest produces
of energy
complicate
the variation production
by condensation.
in the boiler must be wasted
extraction
water
only part of the waste heat is utilized
generated
units,
enables
to distilled
of both. In these turbines
in the production power
steam turbines
generation
of
Gas turbines
Plants
dual-purpose
plants
in Kuwait are mainly
is
limited
to
used for peaking
and system emergencies The high in Kuwait plants
and low demand
fall
more
demand
periods
for both electrical
At
high
units will be operating period,
simultaneously
such
remain reasonably
units that
of the
both
demand
water
will
available
(MIGPD)
plants
of the power units, The design
be
all
taken
capacities
and fresh
water
This makes dual-purpose electrical
power
and
high load factor while at for
annual
relative
to
overhauling the
demands
constant.
is
extraction/condensing dual-purpose
period
at a relatively
The ratio of the annual peak demands, fresh
power
at the same time of the year.
attractive.
distillation low
almost
25.
turbines utilize
and
in 1985 of electrical
This as
high
a
ratio
result
is coupled
of
power
best
Kuwait's
Depending
(MW) and
be met
with
existing
on the capacity
with one or two distillation
to the unit principle
special factors
could
most
this type of turbines.
each unit
is according
There are certain
about
units.
system.
which are taken into consideration
design to ensure
high flexibility
and reliability
power generation
and distillation
production
in the operation
systems
in the
of both the
so that no system will be
l? fully dependent
on the other in order to meet satisfactorily
under
different
fresh
water.
investment
conditions,
These
Normally
rating
units (MCR).
are
(Pressure
variable
decreases
not
dependent
with reduced
MCR full
for
of
regulating
distillation
and
capital
more
than
Load of Steam Turbine 80%
stable continuous
The condition
rating.
the
of
point
The
load.
their
maximum
load of steam turbines of the extraction
of the steam turbine
extraction
and to obtain adequate
steam
heating
the
flexibility
to give at all steam turbine steam
Pressure
output.
power
additional
pressure
load on the steam turbine.
are designed
quantity
distillate
loaded
at Partial
at the extraction
upon
To ensure the best economy steam turbines
Output
continuous
and Temperature)
and
for electrical involve
as follows:
The minimum
is about 30% of the maximum
demand
considerations
of Full Rated Distillate power
continuous
is
population
design
and they may be summarized
a) Production
steam
the
special
at all times and
steam
required
controllers pressure
for the production
are provided the
to
in operation,
loads down to 27% of
on the
suitable
of the rated
extraction
value
as
line
per
the
plants requirements.
b) Direct Steam Supply from the Boiler During
low electrical
the steam quantity distillation of
the
boiler
unit requirements.
distillation by expanding
desuperheaters are
appropriate
from
the
boiler
distillation
without
Therefore,
utilizing steam
required
through steam
is normally
sized
steam
the
obtained
necessary
conditions plant
to
power
load is low,
point will be lower than the
the design must allow the operation
live
for distillation
Operation:
Electrical
of non-availability
possible any
condensers
this
when the turbine
period,
at the extraction
ensure
directly
pressure
(Pressure
operation.
This
adequate
steam
and
from
the
reducers
and
Temperature)
stand-by supply
supply for
the
operation,
it
units.
c) Single-Purpose
shall be
plant
to the
that
In case
demand
and pressure
to
generate
extraction
steam
must be designed
Power Generation
of the distillation the for
maximum
plant
continuous
distillation
to be able to condense
for
rating
plants.
of the
turbine
Therefore,
all the steam flow.
the
13 d) Single-PurposeOperation: Distillate Production In case of non-availabilityof the steam turbines, it shall be possible to run the boiler separately for distillate water production only.
Boilers are
designed for minimum stable load of operation in order to satisfy the steam requirements for full rated capacity of the distillation plant. e) Operation of Distillate Plants from other Power Units The whole power generation and distillation production system are designed according to the unit principle operation. However, in order to provide the highest degree of flexibility and independence in operation for both systems, an inter-connecting comnon header system is provided for low pressure steam supply to the distillation plants.
With this provision any power unit can
supply any distillation plant as and when needed.
Future expected electrical power demands as well as fresh water demands are estimated based on the expected increase in population future consumption patterns, and anticipated industrial expansion in the future.
Such expected
future yearly demands are projected for a period of ten years and over. These estimates are constantly revised and updated. Based on
these estimates,
future power generation and distillation
production stations are planned and designed bearing in mind the following facts: i. Ratio of electrical power and water demands. ii.Five years period is normally allowed from the initial planning till the units are in operation. iii.The construction period of power units normally takes about 36 to 42 months, whereas in the case of distillation plants, this period is normally 24 months.
IV
HISTORICAL DEVELOPENT OF NSF IN KUWAIT Before a historical review of the developments of multi-stage flash (MSF)
distillation plants in Kuwait is given, it is useful to state the principle of MSF distillation. A simplified block diagram of a typical MSF Evaporator is attached. A liquid at a given pressure has its own saturation temperature. This temperature decreases as the pressure drops. Therefore, a liquid under such saturated condition contains maximum amount of heat energy and will boil or vaporize if either additional heat is supplied or pressure is reduced.
TO RESERVOIR
SECrlON
STEAM
HEAT INPUT
HEATING
TO EVAPORATOR
SIMPLIFIED
HEAT
BLOCK
RECOVERY
DIAGRAM
SECTION
OF A TYPICAL
M.S.F:
q-
PARTITIffl
SEA
SEA
EVAPORATOR
7
PUMP
GAS
L- ANlI-FOAM
NCN-CONMNSABLE
@I
WATER
PRODUCT VAPOUR
m
m m
STEAM CONDENSATE
m
SEA WATER BRINE
&l
OISCHARGE
a
LEGEND
FLATE
INTAKE
TUB
WATER
WATER
EXCHANGE
DISTILLATE
HEAT
15 When
a
liquid
chamber
in which
boiling
point
inmediately
at
saturation
the vapour
of the
"MSF"
distillation water
of
stages are operated driving
sea
each
section,
Recirculating
brine
is finally
is still
hot enough
added
brine
in
condenser
tubes.
so that a proper a portion
The flashed caused
the
flash
being
carried
the demister,
stage condensers distillate
tray.
where
stage flows
into
almost
constitute
recovery
section, The
steam
in
it flows into the occurs. As
lower pressure,
it
a series of inter-connected
into the heat recovery
brine to maintain
a material
is complete
and
constant
section is
balance
it goes
sea water is circulating
of heat that was
added
The cooling
is salt free,
process
by
the heat
stage condenser.
orifice,
a
all
section.
by the heating
to maintain
section,
results
Therefore, intercept
in droplets
any
such
inside the
it condenses
After
and
tube
first
stage
to
prevent
the
bundle
and drops
The distillate last
them
from
passes through
cool tube
surfaces
the
turbulence
contaminating
the vapour releases
to
heater
at the upper part of
the vapour
with relatively
in the tubes.
the
the violent
of brine
droplets
on the
of heat
in the brine
sea water apart from
is arranged
tray.
in the
on being
back to the sea.
however,
a demister
into contact
from
or
are maintained
heat
is returned
In the process of condensing,
in cascade
collected.
through
is maintained.
heat to the brine or sea water
finally
reducing
cycle
out into the distillate it comes
temperature
feed water is discharged
produced
to
of
at each
produce
sea water is used to reject or discharge
heat balance
chamber
stages
side
vapour
it
vapour.
to
is divided All
the heat recovery
as blow-down
in order
to the amount
vapour.
evaporator
fact
These pressures
last stage
recirculating
by the flashing
upward moving
this
sea water feed from the heat rejection
The cooling
vapour
that the
temperature,
and initial flash evaporation
is discharged
used as a make-up
a level
the final stage.
In the heat rejection
is equivalent
unheated
"flash evaporation",
to boil again at a slightly
quantity
The brine
an
this flashed
pressures.
tube
while passing
level. Make-up
sufficient
repeated.
the
a pressure
from the
but a portion
evaporator.
which
process
of
last three
to its terminal
until it reaches
The unflashed
concentration
into
of the evaporator
repeats the flashing
section,
the
by flashed
then through
first stage chamber
flash chambers,
flows heated
heated
the brine heater,
the brine
lower
while the rest constitute
where it is gradually brine
advantage
successively
Usually,
is called
The MSF
feed.
at such
by condensing
under vacuum condition.
the ejectors.
rejection
water
at
full
into
its incoming
This phenomenon
take
introduced
is below
is then obtained
plants
from
stages
is
is maintained
liquid
boils or vaporizes.
distilled number
pressure
resident
and high purity distillate
temperature
into the its latent
produced
stage
of the
where
in each it is
16 The following historical review covers all MSF units that have been installed in Kuwait during the last 30 years.
Some of the early plants had
already been dismantled, however, relatively more attention is given to these plants,
as *their design manifested the
real
development of
the
MSF
distillation process. Only design aspects which are unique to each plant is discussed. The review given should be coupled with the information given in Tables 1,2,3 and 4
regarding plants general characteristics and design
parameters for the heat input, each plant.
heat recovery and heat rejection sections of
Plants that appear in the tables are those that are still in
operation, and plants of identical design are grouped together. Shuwaikh 'C' & 'D' From 1953 until 1957, submerged-tube type.
all sea water desalination plants were of the
Due to the rapid development of Kuwait and the urgent
need for more potable water, distillation capacity.
it was decided to enlarge the sea water
In January 1956,
the Government of Kuwait issued
specificationsfor two distillation units to be added to the Shuwaikh plants. These two units with a production capacity of 0.5 MIGPD each, primarily of the submerged-tube type,
were to be
and optionally of the newly developed
flash-type(4). The expectation was to receive offers only for submerged-tube evaporators due to Kuwait's own previous experience in operating such a plant, as well as the limited work done on flash-type evaporators in commercial production throughout the world at that time. Westinghouse Co. offered 4-stage flash-type evaporators and,
after various considerations,it was decided to accept their
offer subject to modifications and tests on a proto-type plant at their factory before final approval of the design could be granted. After
extensive
discussions between
M.E.&W.'s Design
Engineers and
Westinghouse Chief Designer, the company was asked to introduce a number of modifications into their design.
The recommended alterations covered many
mechanical design features regarding materials, pumps,
etc.
But the most
important ones were those which affected the performance of the plant - for example,
an external loop seal for interstage flash brine control.
The
original design arrangement to prevent vapour lock was not accepted, as it would have led to an increase in brine levels in the stages, thus resulting in carry-over of dissolved solids into the distillate.
It was suggested that
Westinghouse use short inter-connecting pipes between stages with an orifice in the bottom of the pipes.
This they accepted. Dissatisfaction was also
expressed regarding the dimensions of the bottom stage,
as with the high
vacuum present, carry-over was expected. The Kuwaiti side was worried about
17
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21 scale formation temperature Hagevap
was
93.3"C
on the outside
where a maximum
brine
in order to operate maintained should
inside
be made
purity
of
baffles
area to condense
especially the
in the fourth
heat
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offered
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was
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the distillate.
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was
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must be
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to cascade the vapour before
specified
evaporators,
the tubes ppm)
was
to scale
that conditions
due
were
to
the
two vertical
it reached
the heat
the vapour velocity
was high
stage which is under a higher vacuum.
transfer
especially
The coefficient
if
scale
should
inside the tubes.
Westinghouse their
inside
in the
chamber
top brine
suggested
of submerged-type
it was requested
so as to avoid
as
treatment
of about 82-88°C
trouble.
disitllate
of the
chemical
of the tubes
temperature
the tubes
the
since the recommended
with scale until then was confined
surface
without
plates in each flash transfer
and
for acid cleaning
the
arrangement
of
(200°F)
Kuwait experience
(PD8).
formation
especially
inside the tubes,
design
agreed
and to
to introduce
build
size in cross section, a) Brine control
most
a proto-type
of the recommended for two
stages,
alterations
which
would
into
be full
and to study the following:
between
stages.
b) Purity of distillate. c) Scale formation The pilot orifices entry
tests.
plant
of
tests
11.43 cm
of the
top
for the brine
(4.5 in)
flash
orifice
operation
unsatisfactory
size to
and 175-245
ppm is obtained
respectively,
resulting
justified
concern
the
as originally
Tests were carried
showed
purity point
the baffles
velocity
stages
from the first,
over
at the of
the exact
that
the original
of view.
plates.
the
second, distillate
dimensions
design
was
This was mainly due
The dimensions purity
third
were then
of 30,
40, 60
and fourth stages
of 85 ppm. This clearly
of the
fourth
stage
flash
designed. out with reduced
equal to that for full load. The first
that
balance
However,
loads and at a top brine temperature
(nearly 3°C higher than design) with a brine velocity
100 hours.
and
keep the
load,
so that distillate
in average product shown
indicated
on site.
from the distillate
altered to reduce the vapour
96.11"C
the flash
optimum
pilot plant
to the small vapour path between
chamber
between
at full load and reduced
of the
stages
is the
size was to be determined
Initial
between
diameter
chamber
brine levels in all stages
control
was with
Two series
of tests
were carried
4 ppm and the second
with
of
inside the tubes out,
each for
2.3 ppm of Hagevap
22 The conclusion
compound. scalent
additive
was decided The
was that
internal
surfaces
paint.
of the
Inspection
light
and acid cleaning
of
all
constructed top
of
proto-type
revealed
the
final
the
very
of steel,
pumps
were
top,
were
as an anti-
This
sludge it
were
was
coats
accepted
the
and
cylindrical
the
stainless
In the
plant
was
stages heater
and distillate
of all heat exchangers
of
the plant
two-flow
baffles,
with
had blistered
Also,
of four rectangular
venting nozzles,
all made
painted
studied on the proto-type.
partitions,
and the tubes
while the brine nozzles,
recirculating
chambers
that the finishing
Each unit consisted
On
formation.
flash
design
The shell and all internal
were made Cu.Ni,
other.
suitable
coats were not affected.
procedures
accordingly.
each
placed.
above,
was
using acid.
in many parts but that the primary start-up
compound
but that it would not stop sludge
could be cleaned
epoxy-type
Hagevap
were made
on was
trays
of 70/30
and also sea water and brine steel.
All pumps
were motor
adjustments,
the plant
driven. When the first performed high
unit was commissioned
very well,
(150 ppm
and
except
occasionally
figure of 80 ppm). that
the
bottom
corrected
path
flash
the
was
small
steel
to
over
chamber
for
of the distillate
1500
its
demisters
was fixed
ppm against
and
a design
side as it suspected
duty.
However,
this
(absent from original
in the bottom stage the
condenser
was
tubes.
was
design)
in the vapour flow This
dropped
the
to less than 80 ppm.
revealed
originating
the operation
Shuwaikh
which
flash
The unit operation
installed
stage
of the distillate
with debris
increased
a stainless
thickness
between
salinity
normal salinity
This was not a shock to the Kuwaiti
by using
of adequate
after
that the average
the clogging
from the sea.
and performance
of the
of some of the brine heater tubes
To solve this problems unit,
a strainer
with
which affected fine
holes
was
on the sea water feed make-up.
El & E2
In 1958, evaporators
there was
still little
of
output.
specifications
large
for the required
the art is carried a
out.
Therefore,
invited
to
which
previous
work done by these companies
for tendering
for the required
from
were
16 firms
received
it
on multi-stage was
decided
plant before a thorough
Companies
questionnaire
data available
having covered
plant.
with full
experience all
The response details.
not
to
(MSF) issue
survey of the state of with
design
in this field,
flash
such plants, aspects,
were
including
in order to be considered was excellent
Eight
and replies
firms showed
that they
23 either their
manufactured design
submitting
on
flash a
evaporators
The specifications
in detail,
production
considered
or
proved
eligible
maintenance,
variations
physical
and allowable
The best commercial
for
MSF plant,
instrumentation,
design consisted
heat rejection
stages(5).
heating
some
temperature
to be
brine control, to
insure
easy
for steam and brine. and J.
Weir for a 1.0 MIGPD was signed. The
23 for heat gain and 3 for heat rejection.
The new feature in
equipment
by G.
of 19 stages only,
streams
specifications
precautions
were made before the contract
offer was for 26 stages,
The final
of
offer was submitted
but many alterations
The quantities
in sizes of flash stages,
position
maximum
specifications.
as were most of the material
such as pumps and their drivers,
scrubbing,
separate
were
were more or less design
taken in design regarding
original
conercial
hence
specifications(41.
of steam and sea water were given,
vapour
for
and
proto-type,
the
heat
with 16 heat gain stages and 3
in this design was the presence
gain
section;
one
for
of 2
recirculating
brine, the other for sea water feed. The sea water feed from the outlet of the heat gain
section
exit mixed
with
was
The designer
outlet.
then
feature
aggressive corrosion
was
nature
redesigned
sea
by the
little or no trouble
weirs
of tests on a proto-type (Professor
changed
of weirs
was agreed
and
on
(heater)
from the points
as
experience
with
exemplified
section
water
by
boxes.
the
the
very
severe
Since we had
brine in the water boxes, the plant was brine
brine
in the heat gain
control
were
section.
questioned
out in the presence
Also,
and a serious
of the design author
originally
suggested
the height surface
of the flash
in the heater was
due to our insistence
based
experience.
Apart from the introduction water feed make-up, brine
automatically
upon after changing
plates. The heat exchange
to double the surface
temperature, the
troubles.
of demisters
and the fine
and since flash evaporators
low
device from the brine operating
heater section
advantageous
previous
Kuwait
recirculating
and adding baffle
on previous
in top
in
were carried
input
Silver).
The type chambers
water
of
heat rejection
for interstage
deaerating
in the flash chambers.
because
with concentrated
to have only
the control
this arrangement
and corrosion
rejected
of
suffered
to a separate
brine from the heat
considered
of view of heat transfer This
admitted
the recirculating
an electronic
pressure outlet
steam
controller
feed
temperature
strainer
on the sea
are very sensitive
to the
was
main
fitted
heater
from the heater.
This
to changes to
by
control
a sensing
avoided
many
24 Shuwaikh
'F' and Shuaiba
North
These plants were supplied were installed North
during
production
in Shuwaikh 1965-1966
'A' Plants by Weir Westgarth
and three
as part
1 MIGPD
plants were
of a complete
The distillate
station.
Ltd, U.K. - two 1 MIGPD plants
new
produced
power
from
installed
at Shuaiba
generation
and water
the plant
had a guaranteed
purity of not more than 30 ppm TDS, and the performance
ratio was 8. Each unit
consisted
and
of
30 stages:
27 stages
The heat input section,
gain.
pass flow type and situated The material
made
of
first
recovery
which was cylindrical
near ground
and second stages of the heat gain section,
This
aluminum-brass.
while
was
deposition
the
first
plant
and corrosion
and the first
few
in
Kuwait
stages
damage of
gathered
heat recovery
confined
section.
heater,
section tubes had also suffered from sea water corrosion.
control heat
feature
in this
room at each site.
rejection
This suits
section
plant
is complete
Also, a constant
was
maintained
Kuwait as the peak water
i.e. there is no need to increase feed temperature tubes
ensured
of the heat rejection
passing the required
ensuring
and electricity
during
from
winter.
a central
feed to the operation.
occur
in summer,
The constant
flow
to Heat
stable
demands
in winter.
of low sea water
section
quantity
control
sea water temperature
all year,
production
avoidance
remote
aluminum
up till then
were mainly
rejection
new
and heat
where
the brine
The
heat
the rest of the tubes were
due to the fact that experience
brass tubes were used, scale
for
'E' plant, except that the tubes of
section were made of 70/30 Cu Ni,
had shown that
3 stages
in shape, was of double-
level.
was almost the same as for
the brine heater, rejection
for heat
velocity
sea water inside the
This was affected
from the outlet of the heat rejection
by by-
section to
the suction of the sea water pump. The sea water feed to the last flash chamber was controlled the chamber,
while brine blow-down
brine in the recirculation blow-down
control
pump discharge.
operated
in the last stage.
stages
of
efficiency The tests
contractor's the
of these
works
full-sized
of each stage, were very
useful
on
Later this was changed in conjunction
of the
so that the
with the
brine
section was controlled
plant
plants were
approved,
a proto-type
on which
can
distillate
be
Also,
represented
purity,
and resulted
brine mass flow per unit width, height of the stages.
by the level in
by the concentration
level by the
from it.
Before the final design in the
automatically
The steam to the heat input
outlet brine temperature
out
was controlled
in
adjustment number
in
tests
were carried
3 to
4 successive
order
and inter-stages changes
study
the
in stage widths to reduce
of the interstage
of stages
to
brine control.
was changed
orifice from
size, and
33 stages
as
25 stipulated
in the original
out to determine
flow inside the heat transfer
Shuwaikh
'G' & Shuaiba
These plants installed
in
commissioned
during
a performance three
section
arranged
(1
as
a special
by Westinghouse
one
ratio
similar
very
in
the
of
8.
Each
gearbox
similar
case
to the 19 mm
of
North.
plants 30 ppm
of 22 heat
pass cylindrical
'F' and
'A' plants.
plants. borehole
to
change
the
were
were
sea
from
design
capable
of producing
brine
plants,
necessitating
Many troubles
had been
and because
water to design
point of view.
an
instrumental
panel
in
the
central
One main difference
feed to the plant was controlled
by the
pump discharge.
by I.H.I.
Ltd.
Japan.
Two 2 MIGPD plants were
on the site of the submerged-tube
similar plants were also installed 1968,
and
25.4
'C'
These plants were supplied at Shuwaikh
water
as in previous
of drive.
of the brine in the brine recirculating
North
against
design of power transmission
although
controlled
The type
of horizontal
direction
from this
the plants,
'B' & Shuaiba
installed
recovery
heat input
The tubes in the
diameter
room which were very similar to the A & F plants.
Shuwaikh
during
The
unit consisted
previous
however was that the sea water make-up conductivity
plants were
of not more than
(0.75 in) outside
level, were suspect from the reliability
control
purity
were of the vertical
over the years
plants
Two 2.0 MIGPD
at Shuaiba
stages and a single
speed steam turbines
of these problems,
The
Ltd.
plant
had a guaranteed
had however
pumps
but the variable
experienced
uniform
in three tiers on top of each other.
section
in)
and
heat rejection
were
recirculating
were carried
'B'
1967-1968
stages,
mm
tests
tubes.
were supplied
TDS and
heat input
North
Shuwaikh
The plants
Hydraulic
design to 30 stages.
the best shape for the water boxes in order to ensure
had a performance
at Shuaiba
North.
plant raft
The plants,
ratio of 8 and a distillate
'B'.
Two
commissioned
guaranteed
purity
of not more than 30 ppm TDS. Each unit consisted stages,
and a single
of two tiers,
pass cylindrical
heat input and heat rejection and 25.4
mm
section. type. control
(1 in) outside
plants
room.
were
heat
sections were diameter
The steam turbines The
22 heat recovery
fully
stages,
3 heat rejection
input
section.
19 mm
(0.75 in) outside
The tubes
tubes
were
fitted
for the pumps
were
of the conventional
automatic
and
were
in the
controlled
heat
from
of the
diameter, recovery vertical a central
Shuwaikh
'A'
The plant was supplied guaranteed
distillate
was
of 8,
erected
submerged
tube
recovery
stages,
input section The
by I.H.I.
on the
plants
had
3 heat
site
was
stages
in
1970
plants,
as single units
although
adhering despite
the first
of
23
heat
cylindrical
heat
of
larger
to M.E.&W.
the
capacity
was
specifications.
large throughputs
and the
pumps were driven by vertical
large capacity
plant was the elimination
speed steam turbines.
isolating
and
feature
by-pass
of the
valves
at the
large
plants to date in Kuwait have had by-pass allow manual
control
plant
was
designed
room, serving
Shuaiba
North
capacity
to
'0' - Shuaiba
contract
of
remaining production
for
units
station
be
automatically
South
'Al'
valves. the control
valve
to
controlled
from
the
central
- 'A4'
by Alsthom
Ltd.,
desalination One
5.0 MIGPD.
four
control around
of
other
a total of six other plants.
These plants were supplied largest
bore
valves
All
if necessary(2).
control
the
where
consisted
and distillate
brine recirculating,
One noticeable
The
unit
and a single-pass
and
strictly
similar to the previous
variable
'A' raft,
The
and
ratio
level.
The pumps were sea water,
original
installed.
rejection
commissioned
supplied
than 30 ppm TDS and performance
of the
been
sited at ground
plant
Ltd. This plant of 4.0 MIGPD capacity
purity of no more
were
unit
was
installed
in Shuaiba
and constituted,
plants
in
installed in
South which
a
the
in
new
world,
Shuaiba
power
at that time, with
generation
lies adjacent
a
North,
unit
and the and
water
to the Shuaiba
North
Station. The performance
ratio
of the plants
ground
stages
and
level(6).
trays
distillate
stages
cylindrical
in general,
some changes
of
steel.
were all driven
were
Nos.l-14,
The pumps,
by electric
brine
blow-down
alternative
provision
discharge
pass
pipe.
taken
from
also
supplied
pump
contrary
heat
conformed
introduced.
a guaranteed
input
ducts
pump suction
two
in
3 heat
sited
at
M.E.&W.
plate
of the
all
stages,
piping were all made previously
followed,
motors. was
supplied
with
this
plant
recirculating separate
pump
units
discharge. each
with
but
there
was
via the recirculation
In the other units so far mentioned,
in
stages,
to then existing
to the practice
to allow brine to be rejected
the brine
distillate
section
The bottom
distillate
box in last stage, and distillate
of stainless
A
single
The plants, but
specifications, distillate
a
with
Each unit had 22 heat recovery
purity of not more than 30 ppm. rejectin
was 8,
the brine blow-down The
its
steam
own
ejectors
condenser
an
pump was were giving
21 complete
working
supplied
with
and stand-by
each
venting were cooled
condensers
using distilled
(1.25in) outside
diameter
to the circular and more
were
control
room.
Before
all
final
were
approval
operational
of the
sections
cascade
had 31.75mm
section
and
model
it possible
conditions(6).
The
tube plates.
designed
in the are
had 44.45
tests
representing
on
the
The
chambers. from
a central
the performance
to test
were
This is due
to provide better
flash
operated
was given,
a proto-type
made
tubes
vapour
controlled
of the design
using
which
the
by the unit.
and heat rejection
of the condenser
condensation
verified
for
The tube plates in all the heat exchangers
automatically
assembly,
steam ejector was also
ejectors
and the tubes in the heat recovery
diameter.
arrangement
efficient
plants
stages
the
while all the other plants had rectangular
circular,
units
of
water produced
The tubes in the heat input section
mm (1.75 in) outside
A quick-start
facilites. The
unit.
of these
a real
each chamber proto-type
size
under
six
actual
confirmed
the
following: -
dimensions
of the flash chambers.
-
dimensions
of the orifices
-
efficiency
of the vapour-brine
-
values of heat transfer
Shuaiba South The
two
previously
with
four
These demanded than
more
stages,
were
ejectors.
The
employed, temperature
at
of
Shuaiba
5.0
ratio
units
resistance
air
and
were
characterized
in
M.E.&W.
by cacade
of by
the
from the first gases produced
control
using
non-condensing
which
and medium
they
are
gases passed
temperature
in each
parts
were of 23
relative
smaller
The trend of
the
to use
evaporator
new practice. during
stage were orifices.
a
purity of
the
flashing
stages by means of the air
efficiently, through
the
specifications.
South.
produced
and final
extraction
which
distillate
by their
different
gases
units
to
and a brine heater.
units at Shuaiba
materials
added
of Japan and consisted
of 8 and a guaranteed
non-condensible
extracted
were
The
South.
by I.H.I. stages,
MIGPD
the by now well-established
to the other
Noncondensing
final stage discharge
(demisters).
The pumps were all motor driven as a standard
ingress
operation
plants
a performance
30 ppm.
corrosion
The
capacity
3 heat rejection
size compared
continued.
a
in 1975 were manufactured
The two units satisfied
physical
separators
coefficients.
each
mentioned
heat recovery
less
chambers.
'A5' & 'A6'
plants
commissioned
between
vent
zones and discharged
accumulated
in the
In order to perform a
by-pass
pipe outside
from
method the
is
high-
the system via
28 the final ejector
Sea
stage(7).
water
was
but instead
condenser,
not
used
distilled
as the
cooling
water produced
water
of
steam
in the evaporator
was
used. The tubes outside 44.50 mm sections
(1.75 in
diameters
were 25.41 mm (1.0 in), 31.75 ma (1.25 in), and
1 in the heat input, Proto-type
respectively.
heat
testing
rejection,
was carried
and
heat
recovery
out before final design
could be accepted.
Ooha East
'Al - A7'
The seven plants units
(Al-A31,
which
were
period
were erected
while
stage
manufactured
by
II
over two
stages.
Stage
I consisted
of four
units
(A4-A7).
consisted
I.H.I.
of
Japan
were
of three
The plants
all commissioned
over the
1978-1979.
The
capacity
of
capacity
was
capacity
operating
performance
each
installed
ratio
each consists
unit
was
6.0 MIGPO, Since then
in Kuwait.
at low temperature
first
time
the standard
distillate
stages,
purity
such
a unit
desalination
(90°C) is 6.0 MIGPD.
of 8 and guaranteed
of 23 heat recover
the
of less than
3 heat rejection
unit
The units with a
stages,
30 ppm,
and a brine
heater. The plants
design
accommodating capacity. emphasis the
satisfied
was paid
included
however
stronger
all the main
to better
demisters
instrumentation
the
condenser
venting
and
the
vented directly above system
of
last
specifications
related
features
material
frames
and
to the higher
in different
fixing
as,
product
so far mentioned.
selection better
as well
More
parts of and
arrangements,
and control.
Up till now with plants of capacity involved
M.E.&W.
all the necessary *design aspects
The design
unit,
enhanced
basically
the first stage
of
from 1 upto 5 MIGPD, the venting
and second the
upper
to the last stage. However,
was inadequate
and another
to the last stage was introduced(81.
stages deck
directly
(possibly
stage
for bigger units-of
venting
line from stage
This modification
system
to the ejector
enhanced
No.141
is
6.0 MIGPD, the No.6 directly the efficiency
of the unit.
Shuwaikh The Shuwaikh during systems.
'Ill, D2 & 03' three
plants
Power 1982. Heating
manufactured
Generation They
and Water
utilized
the
steam was supplied
by
Babcock-Hitachi
Production existing
sea
K.K.,
Station water
from the existing
and
were
added
to
were coanaissioned
intake
and
discharge
power generators.
29 Each unit was designed ratio
for a product capacity
of 8 and a guaranteed
unit consisted
distillate
of 21 heat recovery
purity
of 6.0 MIGPD,
of less than
30 ppm
3 heat rejection
stages,
a performance TDS.
The
stages and a heat
input section. The design
of the units followed
and was basically differences
did exist regarding
extent
gases,
specifically
of
is carried
of the unit.
of
filteration
is passed
venting
oxygen of
the
oxygen content achieved
deaerator
by
is vented
stage
to the
(No.241
in cascade
while
through
vent
which discharged second
start-up
and from there
input
rejection sections
and
heat
section.
of
sea water
to the last stage
water
rings
the
air
make-up
packed
Further
sodium
through
and the
after
deaerator
reduction
bisulphite.
ejector
of The
system.
The
the vent condenser.
The
1st and 2nd stages are vented
13th and 19th stages are vented to stages
The 24th stage
are vented
which
in turn
to the next
is vented
to the inter-condenser.
to the atmosphere.
tubes
outside
recovery The
are made
alloy
to the first
The inter-condenser dischargd
The starting
diameters
sections
tubes
(66% Cu,
and
material
Doha West
30% Ni,
out of aluminium
boxes were made of carbon
to
ejector
the
is
after
is used for
were 31.75
for
the
38.10 mm
(1.50 in) for the
mm
in)
(1.25
heat
input
section
for and
the heat rejection
is now an improved
2% Fe and 2% Mn), while the rest of the
brass
alloy.
The
distiller
shell
and water
steel.
"Phase I"
Doha West,
phase
which were erected Italy,
of
and stages Nos.1 & 2 of the heat recovery
copper-nickel tubes
sea
to 70 ppb.
intermediate
ejector,
selection
purposes.
The heat transfer heat
stage
deaeration
pall
by
The 7th,
some
for this unit called for the
injection
pipes.
stage ejector,
condenser
is reduced
stage ejector
the
material
attached
the
polyproplene
1st stage
vented
to the
so that chamber
is accomplished
However
tubes(9).
whereby
the
specifications,
of non-condensible
general
specifications
the
to the inter-condenser.
the last stage
through
is
designed
deaerator,
is vented to the first
brine heater directly
were
the design
an external
where the dissolved
deaerator
to the heat transfer
out in an integral
However,
utilization
dissolved
detailed
'A' plants.
and venting
and
treatment,
so far mentioned
feed
M.E.&W.
the deaeration
chemical
with respect
All units make-up
closely
similar to the design of Doha East
I involved
the
by a joint venture
were commissioned
erection
of four
plants.
between
Reggiane,
AMN,
over the period
1983 - 1984.
These
plants,
and TMT, all of
The units, each with a
30 rated capacity maximum
of 6.0 MIGPD, were designed
distillate
heat recovery The design and was
provide
units
in many
(10,111.
flexibility
30 ppm TDS.
3 heat rejection
of these
similar
improvements
purity of less than
stages,
stages,
followed
respects
with a performance
closely
the specifications
to previous
operation
ranging
Each unit consisted
of 21
and a brine heater.
unit design
To allow ease of operation of
ratio of 8 and a
with
of M.E.&W., certain
added
these units were designed
from
70
-
110%
of
rated
to
product
capacity. Before the final design was approved, design parameters
on a proto-type
these units is conceptually
the contractor
plant
a separate
(11).
as it is joined physically
achieve
general
a better
polypropylene remaining A
pall
concept,
namely
in the design
had been utilized tube cleaning
different
the
in Kuwait.
was
modes;
added to Doha
unit
while
desulphation
has
been
top
to
with
scavenge
any
System
was
Taprogge
unit
is provided
with
of a strainer
and heat recovery
brine
heater
a ball
section,
The system was designed
of
tubes
a
to have
only
and
section.
brine
stages
decarbonator, desulphation
& Water
Doha West Phase
Production
Station
unit with a rated capacity
at high temperatures
designed
to
operate
of 121,
temperature at
130
utilizing
of 1.0
acid treatment
to
here that this is the only unit
both containing which
three
different
of 121°C is achieved
and
modes;
138°C
includes
the
with
at
a
Operation
acid treatment
utilization
ratio of 10 at 121°C and guaranteed
30 ppm TDS,
and a brine
in
130 and 138°C respectively.
of
a
to the acid treatment(l2,13).
a performance
unit,
Power Generation
supplying
acid treatment.
unit in addition
The unit with
by the companies
It should be recalled
operation
purity of less than rejection
pumps.
cleaning
East
top brine temperatures
at a maximum only,
used
cleaning
principally
This experimental
to operate
scale formation.
in Kuwait which utilizes The
also
in order to
is packed
'A8'
MIGPD was designed
maximum
deaerator
part
This was the first time this system
Each distillation
and two recirculating operating
and coannissioned in 1985.
prevent
is
balls
units.
This unit which was manufactured I plants
vacuum
bisulphite
foam
of these
of both brine heater
Doha East
in the design of
it is an integral
to the main distiller
The
system. The system consists
ball collector,
cleaning
Sodium
although
all the
oxygen.
new
introduced
two
arrangement.
rings.
The deaerator
vessel,
of the Evaporator
had to verify
consists
heater.
of 25 heat recovery
The
design
includes
pall ring type packing.
consists
of four
columns
distillate
stages,
a deaerator
3 heat and a
It also incorporates containing
anionic
a
resin
31 Two of these
beds.
columns
are in operation
two are being regenerated(l4). considerably
The material
at any one time while selection
in order to combat the expected
the other
of the unit was enhanced
increase
in corrosion
attack due
to the use of the acid treatment. This
unit
treatment
is
to
be
used
to
(high temperature)
evaluate
MSF
in comparison
distillation
with
utilizing
anti-scalent
acid
additives
(low
temperature).
Doha West
"Phase II"
II
Phase
of Doha West
consists
of 12 units each with
7.2 MIGPD. The plants were designed, of three Japanese
companies.
Heavy
and Mitsui
Industries
period
units
were
polyphosphate additives,
& Co.
designed
additives with
respectively.
a
consists
Engineering
concepts
operate
Co.,
Mitsubishi over the
of Doha West
thing regarding
that
paid
to
stages,
phase
The enhanced
The
steel,
using
ratio
special
of
8.0
an
II
enhanced
material
materials ceiling
Nos.19
- 23
plants
polymer 8.65
from 6.0
Each unit basically
stages,
incorporates
over the years(l51.
and
selection of
a brine heater
all the major design But perhaps,
selection no doubt
of the Nos.1
stainless
from
emphasis
and the added
in stages
316L
are made
given
to
corrosion
add
to
the
will increase
surfaces
316L
protection
flash
could
chambers
protected
with
epoxy
orifices
plates
are
remaining
coating. all
made
- 12 & 24 are made
steel,
while
stainless
stages
The flash from
of
316L
boxes
from
steel.
brine
from carbon
The front
in addition
stainless
the
the ceiling
steel.
are made
be clearly
and
plates in and
rear
steel.
Nos.1 - 6 & 24 are made from 316L stainless
in the
units
the life-span
plates in stages Nos.1 - 6 & 24 are also clad with 316L stainless bottom plate in stages
the most
costs considerably.
construction
plates
the
material
as it will
future maintenance
but are clad with
above
using
and
of the unit to be increased
3 heat rejection
selection
it is advisable
the unit and reduces
heater.
(llO.O°Cl
(90.56"C)
the design of these units is the much more attention
material
Although, costs,
in the
temperature
performance
the production
that have been introduced
control.
low
equipments.
noticable was
at
to 7.2 MIGPD at high temperature.
of 21 heat recovery
The design
capital
to
and high temperature
This enables
and auxiliary
The
of 6.0 -
by a consortium
All the units were commissioned
corresponding
MIGPD at low temperature
stages
These were Sasakura
a capacity
and erected
1984 - 1985.
The
seen
manufactured,
carbon
The
steel also. steel
and
to the weirs
and
Tube
supports
in
32 - 6 are also made for 316L stainless
stages Nos.1
boxes are concerned,
Nos.1
- 4/5 though made
steel.
As far as the water
of carbon
steel,
are clad with
90/10 Cu-Ni. A large
number
installed chambers flash
to
of sacrificial
provide
cathodic
and water boxes,
chambers
anodes
protection
protection
and protection
made
out of iron of
coated
of stainless
of copper
and zinc metals
mild
alloy tubes
in
steel
steel against against
flash
pitting inlet
are
in the
attack
in
the heat exchangers.
V
DESIGN FEATURES OF MSF PLANTS
SPECIAL
The latest design for
plants
suitable over
with
well
the
last
thirty
worthwhile
to
have to
available
that
materials
by the
Kuwait
that
These specifications vast
MSF
must
experience.
special features,
plants
have
the
be
have evolved
accumulated
some of the design
all
21 They
are
and reliable
of fresh
design,
types of material
production
be stable
source
sound engineering
capital
enriched
years,
and
units in Kuwait calls
it is
following
main
features:
1) They only
parameters
Gulf environment.
in some details
record
of MSF distillation
established
for the Arabian
Before we discuss
general
specifications
water
ensuring
of construction part
of
a
of electrical
and operational
in Kuwait.
adequate
dual-purpose
they
are the
can be guaranteed
transfer
system;
Dual-purpose
because
This
heat
and proper corrosion
power. costs.
in operation
areas,
by
adequate
allowances.
the
plants
other lead
part
being
to saving
the
in both
The systems designs must allow for flexibility
in operation. 3) They are based on the cross-tube an
arrangement
recirculation
is
superior
to
on balance,
5) Until
recently,
temperature
of or
90°C.
similar
scale deposits. brine
additives.
arrangement.
are motor driven
It
This
is
was
plants
llO"C,
believed
designed
dictated
anti-scalent
of
They
that such
are also
of the
design.
as experience
has shown that,
drive even for big auxiliaries
pump.
all plants were
Recently,
temperature
as it is believed
to the once-through
motor drive is better than turbine
like the brine recirculation
compounds
long-tube
type which is superior
41 All the plant auxiliaries
arrangement
by that
by
additives
to operate the
are
fact
used
have been designed utilizing additive
special treatment
at a maximum that
for
the
to operate polymer is
brine
polyphosphate prevention
of
at a maximum anti-scalent
superior
to
acid
33 treatment.
However,
an experimental
the aim of evaluating overall
operational
6) The level
of
each
reliability
maintenance
and
functional
shall
for operation
latest
distillation
plant
neat
and
shall
arranged
systems
The evaporator
operation
between
provide
with
affect
on
the greatest
operation
into
provides
and
account
the
ease of access
of each unit shall be capable
of
70 to 110% of rated capacity.
specifications
and requirements
for of
taking
which
(16)
demand
that
plants must satisfy many requirements.
design parameters
recently,
and its
convenience
orderly
of the various
M.E.&W.
acid treatment
availability,
and maintenance.
stable and continuous
The
be
of
and plant life-time.
distillation
and
requirements
plant has been commissioned
aspects
reliability
design
of
different
the
design
of
the
Some of the most important
are the following:
1) Rated capacity The distillation sea water
plant shall have the capacity
in Kuwait under the highest
The design
must allow
full rated
output throughout
water temperature
in winter
is 14°C.
enable
the rated
product
increasing
anti-scalent
additives
2) Performance
entrance
is produced
conditions
while
the
steam
sea
in the design must be made, to when
depends mainly
ratio is considered
3) Brine Top Maximum
in order
to attain
however,
tendency be made,
ratio of 8,
of low
heater
after
pressure
using
special
of 110°C.
i.e.
steam
eight Kg.
having
any desuperheating water)
the capital
consumption
performance
additive
from
The minimum
at top brine temperature
desuperheating
ratios,
ratio
It is desirable
one Kg.
to the main (including
performance
to
the year.
to 7.2 MIGPD
with a performance
per
With higher performance
has
6.0 MIGPD,
of 32°C in summer.
Ratio
as total condensate
increases
Allowance capacity
to enable operation
The plant shall be designed of distillate
to produce
sea water temperature
design
and measured
into the main heater.
cost of the distillation
decreases.
Selection
on the steam energy
costs.
of
the
plant optimum
The most optimum
to be 8.
Temperature
to have the brine maximum higher
plant
efficiency
for scale formation bearing
in mind,
and the temperature
temperature
and a reduction
increases
the
as high as possible
type
too.
and
that can be attained.
Hence,
dosage
in capital
cost,
an optimization
of the anti-scalent
34 With brine
polyphosphate heater
operation which
is
as
limited
above
to
the maximum
represents
brine
temperature
represents
hydrolysis
this temperature,
are used,
This temperature
which
90.5'C,
leads to loss of effectiveness
additives
maximum
the
treatment,
the
brine
the
limit
for
of the polyphosphate
temperature
occurs
If special polymer
and sludge formation.
the design maximum
leaving
safe
could
be raised
to 110°C.
brine top temperature.
4) Brine Concentration In order
to limit
scale formation,
ratio of the recirculating With an average
1.5.
to a recirculating
brine
temperature
concentration,
which
is the
is kept at around
TDS to the sea water TDS,
sea water TDS of about 45000 ppm, this ratio corresponds
brine TDS of 67,000 ppm.
5) Brine Recirculation The
brine
the brine
Ratio
recirculation of 9O"C,
ratio
is around
for
plants
operating
In plants
12.67.
at
where
a maximum
brine
a higher temperature
could be used, this ratio will be lower.
6) Brine flow Rate per Width of the Flash Chamber The brine mass flow rate 810,000 to
Kg/hr/m
control
the
at 100% of rated brine
equilibrium
losses.
temperature
will
chamber while
per unit width of the flash
levels Operation
require
operation
This
capacity.
in
the
at
higher
at higher
flash
110%
brine
chamber
is mainly
chambers
of
rated
flow
rate
temperature
and
necessary to
capacity per
is limited to
and
unit
in order
minimize same
width
at 100% of rated
nondesign
of
flash
capacity
will
result in lower brine flow rate per unit width of flash chamber.
7) Fouling
Factors
The performance and
adequacy
recovery,
of
of the design
plant
of
depends
the
and heat rejection
heat
mainly
sections,
perform
its duty as per design requirements. as expected,
the
duty
of these
the whole
sections
the correct the
heat
performance input,
each
of the plant
other
towards
the
heat
is equipped
If any of these sections
performance
complement
for
such that each section
perform
then
upon
exchangers
to
does not
is affected overall
as
plant
performance. In the design of MSF distillation margin
of
scale
build-up
for scale prevention.
to take
Therefore,
based on this fact by providing
plants in Kuwait,
place
is made
the design
allowance
despite
for a certain
the use of chemicals
of all the heat exchangers
extra surface area to compensate
are
for the above
35 fouling
by
The
scaling.
fouling
derived
from past experience
fouling
factors
The above formation hours
and they vary from one section to another.
(average)
Section
fouling
0.004826
(average)
factors
higher
acid cleaning
are
These
m*k/W
0.005678 m'k/W
ensure
on the heat exchanger
and
in the design
0.008517 m2k/W
Section
Heat Rejection
to be considered
are:
Heat Input Section Heat Recovery
factors
adequate
extra surface
tubes and thus ensure
average
production
will arise.
Moreover,
rates
longer number of running
for the plant
it will ensure
to allow for scale
before
any need for
longer life for the plant
due to less total number of acid cleanings.
8) Number of Stages The design
must include
ample and adequate
number of stages
so that the unit will operate
its long service
life without
not be less than 24, arranged
abnormal
heat transfer
surface
in a satisfactory
stoppages.
areas and
manner
during
The number of stages shall
in two tiers.
9) Feed Water Treatment The feed make-up after
screening
additives
water to the unit is treated
with
are used,
3.20
With the use of special resulting
about llO"C, 7.2 MIGPD.
To prevent
an anti-foam
In
section
heat
intake screens.
to
polyphosphate-like not
exceed
in production,
in the stages,
90.56"C.
could be raised to i.e.
from 6 to
it is necessary
to add
Chlorine to the
deaeration
of
recirculating
sea water where
is carried
to
in
intake
sea
is injected
unit
In addition
system
the
the
brine
make-up to
reduce
feed, the
sodium level
of
zero ppm.
in the
exchangers,
supply
intervals.
When must
this temperature
20% increase
occuring
complete
injected
fouling
chlorination. water
strainers. temperature
additives,
in around foaming
ensure
to is
oxygen to practically Marine
polymer
size
brine
additive
agent.
order
bisulphite
mm holes
the maximum
with an anti-scalent
system
water
is
by continuous
addition
to
high
the chlorination, out
using
trash
and
in the
flowing, dosing rate
heat rejection controlled
by
of 2 ppm to the sea
shock
screening
racks,
is
of
dosing
for
sea water
stationary
short in the
and travelling
36 101 Heat rxcnangers
Tubes Sizes
All heat exchangers
tubes
shall
The wall
31.75 aua (1.25 in).
not
have
thickness
internal
diameters
of the tubes
shall
of
less than
not be less than
1.22 mm (18 SWG). With
smaller
clogging
tube
sizes,
of the tubes
formation,
with
there
debris
which in turn induces
11) Brine & Sea Water Velocity The brine
and sea
water
is
a
tendency
and foreign
corrosion
partial
or
complete
and accelerated
scale
damage of the tubes.
In Heat Exchangers
velocity
of
material
through
Tubes
the
heat exchangers
tubes
shall
not be less than 1.83 m/set and not more than 2.13 m/set. With
low velocity and
increased, requirements
through
on the
the tubes,
other
will increase
hand,
considerably
high
formed
on the inside
to failure
of these tubes and outages
of the plant.
is
the
most
ensuring
optimum
steam
supply
giving
heater
suitable
reducers.
internal
The design (10
prevent
the
leading
the above range of
of
safety
and
in
the
superheated
at
approximately temperature
by the necessary
even distribution
plates and baffles
by
desuperheaters
of steam over the tubes,
are used.
At The Heater Outlet
brine pressure
Psig)
of damaging
of tubes
exceed the brine outlet
is controlled
To ensure
impingement
13) Brine Pressure
barg
Thus,
margin
is slightly
not in any case
more than 14°C. This temperature and pressure
enough
surfaces
is
power
To Brine Heater
to the
and should
zero barg,
electrical
long life of the tubes and the plant.
12) Steam Inlet Temperature The
scale formation
and there is a possibility
protective
velocities
for
velocities,
the normal
meanwhile
coating
the tendency
with
at
rated
phenomenon
at the heater outlet
output
of the
local
boiling
of
plant
should not be less than 0.69
and
to take
shall place
be at
high any
enough
part
to
of the
heater or in the connecting
pipe, or in the brine entry box to the first flash
chamber.
is
operation. the
extra
discharge
The
above
limit
It can be affected head
required
and
by proper by
reliable design
suitably
and
safe
limit
of the brine
designed
orifice
for
plant
pump to provide plates
in
the
Orifices
The design of the evaporator from one stage to the next plant
ensure
pipe and brine inlet box to the first flash chamber.
14) Brine & Distillate
the
to
for
all
rates
is such that the flow
stage
is automatically
of outputs
by ensuring
of brine
and distillate
self-regulating correct
design
throughout of orifices,
37 and weirs.
nozzles,
All orifices,
20% above the flow required
nozzles
and weirs must be designed
for the full rated output,
with 15-
in order to control
the
levels in each stage. Brine
flashing
orifices losses
shall
devices
provide
through
the
difference
pressure
loss through
pressure
difference
orifices
will
first
Therefore,
stages
the
is
prime
brine
minimum stages
and
to
for the higher temperature stages
in excessive
in the higher
Brine pressure
where
provide
the
higher
stages where the
Incorrect
is high.
splashing
design
of
temperature
stages and the performance
brine stages
of the plant
considerably. difference
stage
and
is considerably the
vacuum
the above high pressure
high between the brine before entry
prevailing
in
the
reduction
exert high pressure
difference
and
at the
same
loss. The design
time
first
flash
chamber.
to the first stage is considered in order
The design of the brine entry orifice
of pressure
with
small
of the brine entry to the first stage and to control vapours.
importance.
temperature
very
special design brine entry orifice
to overcome
of
of
lower
is
of the lower temperature
The pressure the
the
the orifices between
design
flashing
for
between
result
will be affected
to
efficient
orifices
pressure
and flooding
(orifices)
to limit the velocity
brine carry-over
with the
of stage No.1 allows two stages change
of direction
of flow
shall ensure the absence of hammering
to and
local flashing. The distillate
transfer
ducts with suitable distillate
levels
from one stage to another
weirs/orifices in each
stage
and adjustable can be adjusted
must be through
mechanisms
adequate
in order that the
from the outside,
while the
unit is running.
151 Brine Level Brine correct
level
in the stages
must
design of brine orifices
per unit width
of the flash
result in an adequate lower losses
free height
specifications
This is ensured
and weirs and by limiting
chamber
to within
and consequently
from
by
the brine mass flow
acceptable
of the demisters
in the flash chambers
plant. The design
be as low as possible.
limits.
This will
the brine surface
better
performance
and
of the
call for a brine level of about 0.5 m.
16) Oemisters Demisters
of not less than
stage for efficient bottom support accessible,
scrubbing
frames
detachable,
securely
152.40 mm
thickness
of the vapours. attached
shall
The demisters
to each other.
and easy to examine
be provided
and replace.
in each
must have top and
The demisters
must be
38 17) Demister The
Height
distance
the
vapours
produced
level to the bottom
surface
of the demisters
the distillate
purity.
out with vapours design
High distance
travel
from
is important
brine maximum
to the control
allows some of the heavy droplets
to fall back to the flashing
specifications
the flashing
call for a demister
brine solution.
of
carried
Therefore,
the
height from the bottom of the stages
of not less than 2.13 m.
18) Vapour Release The
release
surfaces
shall
vapours. this
Velocity
velocity be as
The maximum
is ensured
by
of
the
produced
low as possible vapour release
providing
vapours
from
to minimize
velocity
adequate
the
brine
flashing
carry-over
brine
with
shall not exceed 4.0 m/set,
cross
sectional
area
(length
the and
& width)
for the flash chambers.
19) Vapour Velocity
Through
The vapour velocity is the
final
vapours
after the demisters
condensation
stage
of
scrubbing
velocity
the last
stage.
different
flash
Vapour paths
This
is ensured
the
vapour
ensuring
20) Distillate
by
The design of the evaporator
of the
limiting drop
better performance
and
distillate
measured
a net
transfer
maximum
purity
at distillate
and over-load brine
permissible
with the
purity after
must be restricted,
the area of vapour existing
increase the
vapour
paths
specific
velocity
through
the
in the
volumes.
as the temperature
vapour
losses
so that it is
than 9.0 m/set in
of the
through
the
demisters
are
of the plant.
shall prevent the carry-over
at all rates of output.
tray and cascaded
have
out
product
tubes surface.
through box
The distillate
from
the
last
stage
condition
of
pump
not more outlet
sea water
concentration
in the flash chambers.
30 ppm
a complete
of the product
as total
at all loads up to full
and at varying
temperature,
than
ratios
of brine droplets
shall be collected
each stage ensuring
first stage of the bottom tier. The total distillate shall
carried
as it
Purity
with the vapour distillate
to the
stage lengths
pressure
salts
stage and not higher
by varying
according
Moreover,
decreases.
demisters,
the demisters
in the first
and accordingly
the
the distillate
at the condenser
through
chambers
shall be as low as possible
and
will determine
of these vapours
The vapour
minimized
the demisters
vapour
not higher than 2.0 m/set
stage
Demisters
through
top tier
to the
in the last stage dissolved rated
temperatures, and
in a
water seal
highest
solids
production
and with the brine
levels
39 21) Deaeration The
feed
condensible minimum
of Feed Make-Up make-up
gases
make-up
to remove sea
carbon
water.
shall contain
water
A suitable
levels.
provided
sea
is deaerated
The
suitable
containing
to reduce
integral
deaerator air and
dioxide,
deaerator
packing
shall
contain
shall ensure
dioxide
(CO21 that may be present. by the injection
ensure
minimum
suitably
corrosion
the
levels
to the vent condenser
vacuum
type
system.
oxygen
The design of
in the plant.
oxygen
is important
The deaerator
and to the major ejector
shall not
(02) and any carbon
of dissolved This
and
spray nozzles
leaving the deaerator
bisulphite.
shall be from the
counter-current
steam injection
The level
of sodium
under
non-
gases to
non-condensibles
100 ppb of dissolved
reduced
of
of these
a system of feed water
that the feed water
at any time more than
quantities
working
other
be of
material,
near the top of the tower and stripping the deaerator
dissolved
the concentrations
is further in order to
shall be vented
system.
22) Venting Venting of non-condensible heat exchangers. form
an insulating
the
heat
through
the
non-condensible
gases
from
to seventh
chambers
demands
chambers
tubes
thus
affecting
venting
of each
and when present
reducing
considerably the
overall
and rapid extraction
stage
and minimizing
that, the first flash chamber,
(cascaded),
to the steam ejector flash
in the design of
of
non-
around the tubes is of prime importance.
specifications
flash
and
efficient
heat exchangers
gases movement
The design
remaining
tubes,
factor
conductivity
over the heat exchange
of the plant. Therefore,
condensible
directly
blanket
transfer
performance
gases plays an important
The gases have very low thermal
and the brine
condenser
shall
heater
shall
or by any other approved
be vented
in cascade
and/or
the second be vented
methods.
The
in groups through
the ejectors.
23) Evaporator The
shell shall 2.07
barg
internal plate
Shell
structural
design
be capable hydraulic
height
pressure,
of the
of top deck
of the
of being
evaporator completely measured
evaporator
(inside
from
to inside)
shell filled
at
the
bottom
excluding
must
be sound.
The whole
with water
and subjected
bottom
the
plate
of
of
bottom
stiffeners
shall
shell.
to The
deck
to top
not
be less
than 8.3 m. Each
stage
maintenance, replaceable
shall such
internal
shall be placed
be that
provided it
will
equipment.
at the opposite
with be
access
possible
The manhole
door to
for
remove
door for
entry
side of the distillate
duct.
inspection and into
install
and any
the stages
The distillate
40 the brine
duct in each stage,
and distillate
inter-connecting
from top
boxes
tier to bottom tier,
and the brine entry box to stage NO.l, shall be provided
with
Permanent
access
doors.
and
adequate
venting
points
also
shall
be
provided.
24) Heat Exchangers The
design
avoiding
Water Boxes
of
the
turbulence
may collect.
water
boxes
and stagnation
Even distribution
water boxes shall be easily provided
Each
distillation
duty
air
ejectors
main
heater, at
points
necessary
removable
shall
gain
the
through
areas where
from the outside, inspection,
and man-holes
cleaning,
box
sludge The
shall be
and maintenance.
and Each
heat set
from
with
rejection of
air
sections
ejectors
independent
Each
quantity
gases
be
provided
air ejector
of non-condensible
full
from the
and to maintain
must
The condensers
condensers.
the evaporator.
calculated
duplicate
of air and non-condensible
tube single-pass
product
150% of the maximum
flow
or low pressure
be provided
the removal
load.
straight
by distillate
smooth
& Condensers unit
for
heat
full
ensure
of water in all tubes must also be ensured.
for each water box to permit
25) Steam Air Ejectors
vacuum
must
design
with
the
shall be cooled is designed
gases
for
released
by
the sea water feed make-up. In addition
to the duplicate
shall be provided up purposes
main air ejectors,
for each unit,
capable
one quick start air ejector
of venting
the whole unit for start-
in not more than two hours.
26) Pumps The general be
in
such
a way
dismantling directly
heating,
at a minimum
facilitate
without
continuous,
or noise.
maintenance
All pumps
motor,
supports,
shall
of
pumps
conditions
have strength,
of
is
avoided
and metal thickness
operation
at fouled
without
speed gears. undue
the
condition.
ensure
cavitation
Pumps casings
to assure
alignment. process
that
characteristics
of loading.
sufficient
The plant design must include the following
possible
All pumps shall be designed
shall
and
stable under all conditions
weight,
accurate
loading
impellers
least
at constant
must be as high as possible,
over efficiency.
and
the
etc. shall
or multiplication
safe and reliable
Though efficiency
casings
with
piping,
be driven
reduction
110% of full rated product capacity
pumps must remain
maintain
as to
shall have priority
design all
of the pumps, motors,
breaking.
must ensure vibration
robust design
under
so
and joint
from AC electric
The design
The
arrangements
pumps:
of the shall
long life and
41 a) Sea Water Supply
Pump
At least one sea water The
unit. head
capacity
at no flow
spindle
supply pump
of each
shall
not
b) Brine Recirculation one brine
shall not be less than
exceed
4.9
The
bar.
pump
12500 m3/hr
shall
be
of
and the vertical
70% of full rated vertical
spindle
capacity
of service
for each unit.
of providing
unit.
If
not less than
The pump shall be of the
capable
of performing
its duties
having due regard to the temperature,
density
brine.
Pump
One distillate
pump for each unit shall be provided,
the full rated output
of the evaporator.
to
the
distillate
capable
The pump discharge
header and to the distillate
connected
systems.
shall be provided
of each evaporator
heat of recirculating
c) Distillate
distillate
pump
each pump must be capable
axial or mixed flow types,
under all conditions and specific
Pump
recirculation
two pumps are provided,
be
for each distillation
axial or mixed flow types.
At least
to
pump
shall be provided
make-up
main
supply
The pump shall be of the vertical
header which line
spindle
and
of delivering
is connected
to a
are respectively
the
boiler
make-up
axial or mixed flow types.
d) Heater Drain Pump The heater drain
pump shall
be capable
of the condensate
from the distillation
of the horizontal
type.
e) Brine Blow-Down
to ensure
pump shall be provided
that
the
other pump, create vortices the last flash chamber. shall be made blow-down
from
pump
the full
The heater drain
rated output pump shall be
Pump
One brine blow-down be taken
of delivering
unit.
suction
of the pump does not interfere
or prevent
Suitable
for each unit. Precautions
efficient
connections
the recirculating
is out of service.
brine
mixing
with
of the feed make-up
with necessary pump discharge
The pump shall
shall
isolating in case
any in
valves
the brine
be of the vertical
spindle
axial or mixed flow types. f) Sea Water Recirculation At least temperature velocity
Pump
one pump for each and
through
to
ensure
unit
minimum
the heat rejection
shall flow
be provided, necessary
tubes.
to
to maintain maintain
sea water
the
required
The pump may be of the horizontal
type. g) Chemical Pumps
Dosing
required
Pumps
for chemical
dosing
shall
be of
the positive
displacement
type with variable
stroke to enable varying the dosage of chemicals
ppm of the make-up
feed.
h) Other pumps such as sump pit pumps and bearing
cooling
from O-6.0
pumps, etc.
42 27) Piping & Pipe Fittings The design vapours, control
must
air,
include
valves,
safety
hangers,
supports,
all the necessary
with the necessary
etc.
valves,
etc.
piping
expansion
for steam,
by-pass
steam traps,
to ensure
for each unit,
water,
isolating
joints,
lines,
drains,
a complete
gas,
valves, pipe
and efficient
installation.
28) Materials
Selection
Materials withstand
within
service
in the operation ensure
& Protective
the
conditions.
is expected
maintenance or/and
after
This
selected selection
plants.
service.
carefully
In certain
we
have
to
be
suitable
to
is based on our long experience
The material
selection
is designed
parts of the plants,
or in case of some areas which
construction,
supplementary
The material
Systems
are
of distillation
long and reliable
corrosion
plant
opted
are not
for
high
to
where high
accessible
for
quality
materials
plant many
components
section,
and in the
protection.
selection
for some of the distillation
are as follows: a) Heat Exchange All tubes first
and
second
cupro-nickel
stages
input of
section,
the
heat
alloy with a chemical
2%, and Manganese recovery
Tubes
in the heat
2%.
heat rejection
recovery
analysis
The condenser
2%.
shall
662,
tubes in the remaining
shall be made of aluminium
section,
76X, Zinc 22%, and Aluminium
section,
of Copper
be made
Nickel
30%,
of
a
Iron
stages of the heat
brass with an analysis
All tubes are of 18 SWG thickness
of Copper equivalent
to 1.22 mm. bl Heat Exchangers Tube plates
Tube Plates & Supports
in the recovery
and rejection
Brass of not less than 38.10 mn thickness. tube plates
and both ends shall be flared.
sections Tubes
Tube
supports
of
spaced at required and to maintain
suitably painted
intervals
adequate shall
shall
be made
be expanded
of Naval into the
The tube plates of the brine heater
shall be made of Naval Brass and have a thickness
19.05 mn and suitably
shall
material
be provided.
in order to prevent
of not less than 75 mm. of
thickness
The tube
not
supports
less
than
shall
be
undue
tube sag and vibration
transfer
duct and the condenser
tubes configuration.
c) Distillate The distillate
Ducts, Trays & Condenser ducts and trays,
Shell
distillate
shell shall all be made of 316L stainless
steel of not less than 10 nmi thick.
If the shell walls are used as sides of the duct, tray or condenser
shell 316L
43 stainless When
steel
different
protected
doubling
plate
materials
are
such that no corrosion
d) Brine & Distillate The
brine
stainless be
of not less than connected
weir
stainless
steel
lined
distillate
orifices
be
suitably
adjusting
mechanisms
shall
be made
of
316L
used for the brine entry box in stage No.1 shall
with
steel. Suitable
shall be fitted.
shall
and Weirs
and
steel. The material
carbon
they
may take place.
Orifices
assembly
3 mm thick
together,
316L
stainless
cathodic
and nozzles
steel
protection
or
wholly
as needed
made
of
shall be provided.
shall be made of suitable
stainless
316L The
steel.
e) Demisters The demisters frames
shall
demisters contact
mesh with not less than 15.24 cm thickness
be manufactured
from 316L stainless
steel.
shall also be made of the same material. with
the
steel doubling
demisters
shall
be
suitably
for the
The stage partition
wall in
protected
plate of not less than 3 mm thick
and the supporting
All supports
with
316L
stainless
and of not less than
30 ems
width. f) Venting Venting stainless
& Splashing
baffles
Baffles
plates
in
steel of not less than
which are provided
when needed
Plates
all
heat
exchangers
shall
6 mm in thickness.
be
made
Splashing
shall be made from 316L stainless
of
baffle
316L
plates
steel.
g) Flash Chambers The evaporator of low carbon steel
surfaces
allowance
over
and mechanical The
and heat exchangers
having
of flash
not more than shall
be designed
nominal
walls
thickness
unit shall be made
content.
with
All internal
a minimum
required
and
last
flash
chamber
walls
shall
of 12.70 mm, and in any case, all walls shall have a thickness
the rest of the flash chambers, bottom plates
and walls
The remaining
flash chambers
a minimum
of each
carbon
chambers
and above
top and bottom plates,
wall
plates
0.15%
corrosion
for by
structural
minimum
corrosion
considerations.
first
allowance
shell
steel
corrosion
(sides,
shall
the four sides and
first tier ceiling
corrosion
including
of 6.35 mn.
bottom
a
of not less than 38.10 mm.
walls,
a minimum
walls,
allowance
top, middle,
interstage have
have
including
allowance
heat exchanger
plates)
and the
of 9.53 mn.
walls
shall have
In any case the thickness
and partition
For
of any
shall not be less than
19.05 lml. Protective
coating
The protective and
vacuum
quality
and
of flash chambers
coatings
must
conditions. painted
with
coats each with a minimum
All
internal
surfaces must be carried
be able to withstand surfaces
a minimum
must of one
dry film thickness
be
the temperature,
shot
primer
blasted coat
and
of 127 microns.
to
the
three
out.
moisture required finishing
44 h) Deaerator The
deaerator
shall
be made
stainless
steel and painted
to
against
guard
resistance stainless
316L stainless
material
lined
coating
packing
used
support
structure
The make-up
used to inject
internally
shall
be made shall
316
protected
from corrosion
be made
feed spray nozzles
the stripping
with
and cathodically
The
steel and painted.
cross pipe assembly
steel
The packing
corrosion.
material.
of
with protective
from
316L
and the perforated
steam shall
all be made from
steel.
i) Water Boxes The water approved
boxes
coating
shall
allowance
of 9.53 mm.
less than
19.05 mm.
connecting
piping
resin
coal
microns.
tar
be made
of mild
and cathodically
shall
paint,
self-valcanizing
adequately
boxes
rubber
of water
and the heat recovery
be given each
one
coat
primer
to
coat
a minimum
to
a minimum
an
boxes shall not be
and three film
section
total
with
corrosion
section water boxes and
dry
of the heat rejection
paint
protected
and shall have a minimum
In any case the thickness The heater
The water
steel
protected
dry
coats
of epoxy
thickness
of
127
shall be coated with
film
thickness
of
765
microns. An alternative
material
this case all water adequately resisting
selection
for the water boxes is also specified.
boxes and connecting
protected material
with internal
piping
In
shall be made from mild steel
lining or cladding
of an approved
corrosion
such as 70/30 Cu.Ni, and 90/10 Cu.Ni.
j) Brine Heater The
heater
thick,
shell
and suitably
stainless
condenser
titanium from
be made
protected.
from
mild
Venting
steel
baffle
of
plates
not
less
shall
than
be made
19 mm of 316L
steel.
k) Vent & Ejector The
shall
Condensers
tubes
of
the
vent
not less than 20 SWG thick.
316L
stainless
guard against
steel,
corrosion.
not
ejector
condensers
shall
The shell of the condenser
less than
The tube
plates
water boxes shall be made from carbon 90/10 Cu.Ni and cathodically
&
protected
9 mn shall
thick
suitably
be made
be
made
of
shall be made protected
of 70/30 Cu.Ni.
to The
steel clad with not less than 3 mm thick to avoid corrosion
problems.
1) Pumps All
parts
recirculating etc.
are
of
the
sea
water
and brine blow-down
supply
and
made from 316L stainless
with
suitable
casings,
pumps,
shafts,
steel. The brine recirculating
shall be made from mild steel. The pumps barrels shali be provided
recirculating
pumps including
cathodic
brine
impellers, pump barrel
, suction and discharge piping
protection
and shall
be coated
with
45 epoxy resin coal tar paint or an approved used
and
three
coats
each with
bitumen compound.
a minimum
dry film
A primer shall be
thickness
of
127 microns
shall be applied. The casing
of the distillate
from zinc free bronze, from stainless
pump and heater condensate
and the shaft, impeller
pump shall
and barrels,
be made
etc. shall be made
steel.
Any strainers
shall
be made
from
316L
pumps shall have 70/30 Cu.Ni cooling
stainless
The
steel.
bearings
in
coils and fittings.
m) Piping Sea water externally
carrying
coated
However,
pipes
with
sections
shall
be made
12 mn epoxy
near the
resin
evaporator
from
carbon
and encased
shall
steel
internally
and
in reinforced
concrete.
from carbon
steel pipe
be made
spools clad with not less than 3 nan thick 90/10 Cu.Ni.
Pipes with diameters
of
50 mm and less shall be made from 90/10 Cu.Ni. brine to or from the unit shall be made from mild steel with
Pipes carrying a minimum
corrosion
allowance
of 9.53 mn and shall be suitably
protected.
piping for distillate
service
shall be made from 316L stainless
be suitably
against
any corrosion
protected
29) Instrumentation Complete
running
plants
of
the
main
and
controlling
plant
at various
instrumentation
systems
They must be designed
must be supplied.
safety of the working The
steel and must
damage.
& Control
measuring
distillation
All
operating
conditions
and
for
to ensure must
the
smooth
ensure
the
staff and equipment.
instrumentation
and
control
systems
shall
consist
of
the
following: a1 Overall bl Backup
distributed analogue
digital
control
cl Data acquisition,
control
system.
system.
data logging
and process computer
system.
d) Power supply system. e) Complete
local instrumentation
f) Logic sequence 9) Announciation
and interlock
30) Tube Cleaning
operation
of
both
shall
or abrasive
system.
Systems
A ball tube cleaning tubes
system.
and alarm system.
hl Fire alarm and fire fighting
the
and control
system for all auxiliaries.
the
system which heat
be flexible,
balls or both.
input
shall be designed and
so that
heat
it will
recovery
to provide cleaning sections.
be possible
The
of
system
to use either plain
46 A complete,
safe,
reliable
and easy for maintenance
acid cleaning
system
shall also be provided.
31) Proto-Type
Testing
Over and above all the special distillation
plants,
commercial
plants
specifications
precautions
and if the Contractor having
normally
the
same
considered
in the design of our
has not tried his offered
capacity
ask for the building
as
the
and testing
offered
design on one,
the
of a proto-type
plant
of the main plant. The
proto-type
plant
order to simulate
shall
consist
shall be of the same dimensions configuration demisters venting
such
size
as
and
stage
viewing shall
height,
arrangements,
of the
inter-stage
the
Verification
at
distillate its flash
of
'Manufacturers to
requirements.
in
ducts,
heat
are
and
out
recirculating
equipments
plant
wall
dimensions,
orifices,
flash chambers
in the test, only four
and purity
of the
depending
or five
upon
stages will
flows
on the
hydraulic pump
performance
complying
with
of the distillate
and that the methods are
are carried
out.
flow
design
tests the
All
plant must
to build
are
be
"test water boxes"
and is
and
of control
satisfactory.
proto-type
such as pumps, motors,
where
their
from
flow, etc. The proto-type chambers
is required
the
ensure
is different
allow
to the main unit design
concerning
Works'
weirs,
to
vapour
carried
the contractor
brine
and
exchangers,
of that of the main plant.
of the different
the production
distillate which
flash chambers,
orifices
a transparent
are represented
design,
all auxiliary
equipments
shall have
are as per design guarantees, brine,
necessary,
verify
stages
of the main plant.
prove that
when alterations
Whenever
Also,
six stages
adjustments
considered,
to
plant
of varying
as representative
other parameters
necessary
and
of the plant is being simulated,
The tests shall
brine
it shall be one-tenth
brine flow,
Although
be accepted
six successive
plant concerning
height, trays
etc., as per the dimensions
which section
of
and
distillate
proto-type
the flashing,
demisters,
least
etc. Only, the width of the proto-type
have the facility
main plant.
at
as the main
length
that of the main plant, where One side
of
the whole number of stages of the main plant. The proto-type
fluid
dynamics.
sometimes
demanded.
etc, shall be assembled carried
design
and
out
on
these
specifications
VI
OPERATIONAL L MAINTENANCE EXPERIENCE
1) Operational The
Experience
extensive
Electricity evolved
& Water
from
gathered
and
detailed
(M.E.&W.)
the vast
specifications
for the design
experience
regarding
over the last thirty years.
experienced
team
continuously
of
project
in order
of the plants, thus ensuring
which
the efficient normally
more efficient
out under
and reliable
an
whereby
the question
bottom
flow,
chemicals
brine,
to
pressures
in
orifices commercial
two
major
of on
and brine
of
The taking
and prove
over of plant
is to
cooling
water feed,
stages have
the
flow
and water been
by internal
pressures
patterns,
boxes,
and the
established,
leaving
plates
removal
plates
levels,
plant
heat
flow streams
orifice
and
water
the
brine recirculation
The three main
concentration.
are controlled
and
are top brine temperature,
make-up
differential
observing
causes
of
the
brine
side
of
of the
heat
venting
of
loss
non-condensible
steam consumption
whenever
These tests
has over the years managed
The final setting of these orifices
increased
acid
tests must be
must demonstrate
engineers
operational
temperature
reduction
with
plants.
of
are carried
out
temperatures
is then
and
After
analysis.
in
non-
the
ready
for full
performance
are the
operation.
presence scales
the
settings
updated
out on the design
a problem.
levels,
and
are
up an
operators,
of
and venting
gases.
studying
has built
over by M.E.&W.
M.E.&W.
have
plant
team
dosing
establish
condensible
The
however,
of
and maintenance
and reliability
taken
conditions,
sea water temperature,
distillate
order
carried
and reliable
design of the plant.
temperature,
section,
in Kuwait,
specifications
the main items which can be controlled
brine
rejection
plants
Ministry
of taking over a new plant does not constitute
experienced
Initially
the
performance
stringent
not easy for anybody,
create
after
and
out before the plant is officially
are carried
the
operation
all the improvements
After any plant has been set up, carried
of MSF plants
by
Over this time M.E.&W.
engineers,
to cover
issued
production,
transfer
of
it proves
of
the
rise
heat
of the
can
gases,
the tubes
necessary.
distillation
on the
vapour
exchanger heating
plant side
and
tubes.
steam
the This
pressure
formation results
be
controlled
and proper heat
input
and
by
correct
scale control recovery
of
in a
in the heater, The fouling
and a drop in the last stage vacuum.
surfaces
non-condensible cleaning
of
gases
and
efficient
methods
sections
coupled
with
acid
The degree plant
of fouling
is being run.
that might
Operation
occur
depends
of the plant
on the manner
under
unsuitable
conditions
cause a plant to foul in a much shorter time than anticipated reducing
the
efficiency
plant fouling
of
The
plant.
operational
The inlet
will
by design,
factors
that
thus affect
to heat input section
steam temperature
the difference
between the
to the brine heater
steam and the outlet
14°C. This is to prevent
lead to rapid scaling,
2) Brine flow velocity
inside tubes
The normal design Reducing
brine velocity
this
velocity
must be controlled
brine temperatures
any local boiling
the heater tubes which
m/set.
the
are:
11 Inlet steam temperature
exceed
the
in which
of the brine flowing through
thus hindering
heat transfer.
inside the tubes ranges
to
below
1.52
so that
should not
m/set
from 1.83 to 2.13
will
accelerate
scale
brine pressure
outlet
concentration
ratio
formation. 31 Brine pressure To prevent
outlet from heater
any local boiling
from the heater
should be kept at 0.69 barg.
41 Brine concentration With should
the be
quality kept
in the tubes the minimum
ratio of
at
sea water
Increasing
1.5.
the
in Kuwait, this
ratio
brine will
mean
increased
scale
formation. 5) Chlorination
of sea water
Apart from screening to
prevent
any
rejection
section.
ineffective flashing
This
screening,
range.
inlet sea water,
biological
fouling and
chlorination
occuring
any
inside
debris
that
is carried the
might
be
of
the
present
will affect the bottom brine temperature
As a result the productivity
out in order
tubes
and performance
due
heat to
and hence the
of the unit will
be affected. 6) Chemical Until using
Treatment
a few
years
polyphosphate
limits
the
hydrolysis
top
condensers When
"HAGEVAP" many years
which
distillation
.
This chemical
9O"C,
leading
adheres
efficiency
first
plant
designed
the
operate
chemical,
this
temperature
formation
of calcium
heating
surfaces
of the
of the unit.
introduced
to
to
to
of this
as above
to the
manufacturers proved
were
The utilization
about
occurs
readily
was by
plants
only.
to
the thermal
recommended
starting
dosing
polyphosphate
sludge
or "PD8"
distillation
temperature
and reduces
MSF
originally
all
chemical
brine
of the
ortho-phosphate
ago
in was
Kuwait, a
be successful
1955 at a dosage rate of 4 ppm(l71.
the
proprietary and was
chemical mixture used for
49 It was
realised
formation
that
and at the
if
a
of 90°C, higher plant output investigations
along these
of chemicals purchasing
contains
which proved
recommended
essential
stay
additives additive
did
dosage
chemical(l81.
and mixing
compound.
used
of this
By
them,
the
The mixture
sulfonate
This mixture
a mixture
which
and 2% anti-foam
proved
as successful
since
then.
A
mixture
was
found
proper, to
be
scale formation.
abreast
prevention
chemicals
been
scale
It was during
developed
as the proprietary
has
inhibit
will result.
49% lignin
and
would
a top brine temperature
laboratories
than the original
and homogenous
to control
which
above
efficiency
rate of 4.5 ppm.
additive,
uniform
used
the constituent
49% sodium tri-polyphosphate,
the
To
and greater
proved to be cheaper
continuous,
scale
was
operation
to be as good
agent was used at a dosage as
allow
lines that M.E.&W.
in bulk quantities
end product
chemical
same time
of
and
developments
due to
not completely
in
chemical
the fact
that
prevent
scale,
which might give an improved
treatment
of
sea water
polyphosphate-based the
search
performance
for
scale control
was
on for
any
and is cost effective
new
at the
same time. Over scale
the
last
sixteen
formation
performance tested
were
as far as
(191 included
proved effective
years
many
scale Darex
40,
Another
Calnox
214 and
of 93"C,
polymer
scalent additive be superior further
In order
and Belgard
Belgard
EVN.
of Belgard
EVN,
performance
it was necessary
obtained
reliable
the
heater
EVN was initiated
at a dosage
fouling
with that obtained
additive(20).
'F' plants.
factor during
rate
during
Belgard
The next
of a new antiBelgard
EVN to
additives.
operation
between
the performance
low
additives
at a top brine
polyphosphate
of polyphosphate
instrumentation(22). temperature
polyphosphate
(231, using a dose rate of 2.0 ppm. EVN is quite
effective
as a scale
as low as 2.0 ppm.
It was also found
this trial
only far
the polyphosphate
The
its much higher unit price.
calibrated
long-term
their
P-35 was also tested,
comparison
to monitor
The short term trial did prove that additive
These
(21) confirmed
EVN was that it enabled
out a proper
data, a trial of Belgard
control
H.
with polyphosphate-based
was however
prevent
their unit price made
as the polyphosphate
long time using carefully
having
Vaptreat
Cyanamer
The trial
compared
to
determine
Some of the additives
out on the Shuwaikh
of 105°C. The disadvantage
for a reasonably After
called
to carry
to
out on this plant was for the evaluation
in performance
attraction
temperature
designed
order
however,
additive,
All the above trials were carried to be carried
in
is concerned.
but this did not prove to be as effective
trial
additives
tested
inhibition
upto a temperature
them uneconomical.
polymer
operationally
was not trial,
that
less compared
but its rate of increase
50 was also
smaller.
demonstrated
Another
105"C, thus enabling By
now
it
concerned,
trial
the capability
had
more distillate been
Belgard
EVN was superior
(6 MIGPD) running
EVN,
that
consumption that
the
EVN
high
was
when using
polyphosphate.
scale
prevention
The trial which
of
cost
lasted for a whole year was
of both additives
units
but
Belgard
also
to
factors. EVN,
effective
polyphosphate
over such a long
monitor
the
steam
The trial did reveal
chemical
compared
treatment
to
using
polyphosphate
the need to acid clean a unit was less frequent This
due to acid cleaning,
is
using two large
price
more
Furthermore,
as
out1251
capacity
unit
treatment.
damage
far
of both units and other operational
despite
Belgard
as
with one unit utilizing
EVN.
product
up to
a trial was carried
the performance
high
EVN which
due to the much
and the other using Belgard
using
Belgard
However,
devised time
on
scale deposition
to polyphosphate.
simultaneously,
not only to monitor
out
to prevent
output.
established
higher unit price of Belgard units
(24) was carried
of the additive
is very
important
and thus
longer
as it means
unit life.
than
less corrosion
Belgard
EVN is now
freedom
from scale
being used in many of the MSF plants in Kuwait. An important
feature
formation
on
attention
is paid
sludge
the
formation
output,
of an MSF plant
brine
side
of
to chemical does take
increase
an onload
input
and
heat
hydrochloric
exchanger
place
system
and this condition
condition,
which
recovery
tube
cleans
sections.
surfaces
Nevertheless,
very
if
slow
is evident
close
scale or
from falling
and high steam consumption.
To
the plants in Kuwait are acid washed
the
surfaces
For
this
of the
purpose
tubes
inhibited
in the heat 33
percent
acid is used.
Although treatment
heat
treatment.
in heat input shell pressure,
restore the plant to a clean using
the
is the comparative
Kuwait
chose
the
additive
as a means of controlling
damage and the high quality were carried
out
treatment
in preference
scale deposition,
of control
to the
acid
due to fear of corrosion
acid treatment
demands,
(26) in order to assess the applicability
some studies
and suitability
of
acid treatment.
This interest
in acid treatment
culminated
in the design and
erection
experimental
unit
A8),
the
of
evaluating 138°C.
an
operation
The unit which was recently
corrosion
rates and methods
2) Maintenance Proper operational
(Doha
using acid treatment
East
up to a maximum
commissioned
for
purposes
brine temperature
of of
will also be used to monitor
of its control.
Experience
maintenance
coupled
practices,
ensures
This leads to increased
with
good
plant
high reliability,
productivity
design
and
and enhanced
and reduced water costs.
satisfactory availability.
51 The
maintenance
planned
carried the
maintenance,
from operational An annual
problems
planned
out
period
first inspected report
when
is prepared
which
describes
far
as
is related
the
mechanically protective repaired
evaporator by water
coating
supervision
the of
engineers, Inspections from
the
before
Water
independent
VII
work
involved
far as Kuwait
is concerned,
well developed
systems
Many studies years. and
costs
of
specifications
solar
and
and silt.
METHODS
respective
strict
of
Close station
specifications.
out by M.E.&W. These
engineers
inspectors
in a position
out according
The
pipes are
contractors.
the
(WRDC).
are
to ensure
that
to specifications.
& RELATED
sea water
RESEARCH
desalination
is based on
out into the possibilities
other desalination
methods,
water.
provided It should
that the MSF method
and that Kuwait was actively
The most important
aspect of this development
is the reliability
of the MSF plants due to its
engineering
different
carried
desalination in
plant(281
supervision
of
as
design.
were
distillation
desalination
by
As
cleaned
could be given.
for both sea water and brackish
and evaluations
These covered
Electrodialysis
Centre
state some years back,
in this development.
are
a final inspection
by
follow
are carried
many studies were carried
a very mature
out
daily
must
OF OTHER DESALINATION
methods
debris
scale,
and are therefore
be borne in mind when studying has reached
out
Development
tubes
water boxes and connecting
if not all of Kuwait's
by other desalination
and formulates
data of the unit during the
condenser
carried
work
work has been carried
most,
the MSF method,
is
carried
maintenance
Resources
a complete
The maintenance
out.
for unit start-up
and after maintenance
INVESTIGATIONS Although
is
of the unit
work is finished,
approval work
of the stations,
the maintenance
all
any sludge,
After maintenance out, before
the
Each unit is
work.
concerned,
jet to remove
the
has out
all items of the unit and its auxiliaries.
maintenance
as
plants
is carried
is at its lowest.
condition
of the flash chambers,
adequately.
of
is
programme
During this inspection
all the operational
covers
general
as indicated
of the plant.
work to be carried
to the maintenance
work
the unit is carried Most
the
from
of all distillation
demand
after shut-down.
for the maintenance
The maintenance
apart systems
The maintenance
now.
work also takes into account, year which
includes, defective
of maintenance
the water
immediately
recommendations
plant of all
any
prior to the shut-down
programme
been in effect for many years over the winter
on
maintenance
out by M.E.&W. methods,
Kuwait(271, and more
commissioning
over the last 20
and included performance
recently of
a
the 60000
performance
of
0.2
MIGPD
preparation IGPD
of
brackish
Electrodialysis Compression alternative the
methods
years,
based
on
these
desalination
for
continuous
desalting Even
monitoring
of
processes
brackish
so
many
and
The general
of desalinations(30).
communities.
for 0.1 MIGPD Mechanical
and comparisons
of
suitable
isolated
specifications
unit(29),
and
technologies mainly
plant, proposed
distillation
or
of
TDS
were
these
of the
processes
waters not
for
reached over
developments
that
low
them
conclusion the
is
Vapour
recommendations
for
found
are
small to
and
be
cost
effective. Much more interest its recognized carried The
was paid to desalination
greater
out by Water Resources
studies
different result
carried
of these
brackish
water
certainly Kuwait
included
and
and
a promising in
Fund
As
far
as
programne
was
sea
and GKSS Research osmosis
in
research
plant
plant consists 0.66
different
osmosis the
Kuwait
(35)
membrane
proper
evaluation
existing
reverse
namely,
pre-treatment into the
data generated
kinds
techno-economic
needed, of
The
operational
depends
of
& Water lines,
Reverse
a as
and that
Osmosis Recently,
Osmosis mobile
problems
concerned,
a
Development
joint Centre
Research
(KISR),
of sea water reverse an
experimental
Production with
osmosis
osmosis
will
of most
study. The commercial
in Kuwait will mainly
is
Resources
a total
lines,
and
Station.
The
capacity
utilizes
of
three
hollow fine fibres,
and
for the last two years.
by the operation
evaluation
selection
far
conclusion
water Reverse
spiral wound,
of sea water reverse
in Kuwait.
as
RO(34).
for Scientific
plate and frame. The plant has been operational It is hoped that
water
establishment
production
two-stage
systems;
that
of
As
of desalination
on this
Pilot plant testing
the
separate
The
concluded
Kuwait
Water
East Power Generation
of three
MIGPD.
prompted
in
Institute
Centre of Germany.
at Doha
testing
performance.
method
brackish
by M.E.&W.
plants,
International
an of
(RO), due to (31-33) were
of 0.25 MIGPD.
between
M.E.&W.,
Kuwait
pilot
based
for 13 brackish
reverse
established
(WRDC) representing
about
establish
capacity
water
of
operational
It was
advancement
Osmosis studies
(R&D) established
RO is an attractive
has issued specifications
units each with a product
many
it was
evaluations,
to
the
Centre
overall
potential.
1976
for
by Reverse 1969,
operation
evaluating
studies
proposed or
Development
is concerned,
has
Committee M.E.&W.
out
membranes,
Starting
potential.
of this plant will enable
under
include suitable
membrane
that might
utilization
on this evaluation.
environmental
establishing
conditions
the
systems,
be faced,
level
and finally
of sea water reverse
of
insight a
osmosis
53 Research
5 Development
In order to initiate and to investigate
and advice
cooperation
with
Development
the
Centre
United
their suitability
technical
assessments
Kuwait
matters,
in close
did set up in 1968 the Water Resources
types of desalination
methods
and assessment
of
for Kuwait.
Extending
studies of different
advice
regarding
desalination
the
design
methods.
specifications
of
various
plants.
Specific
different
on all water-related
Nations,
of various
2) Techno-economic
4)
obtain
of WRDC include the following:
1) Investigation
3)
and development,
(WRDC).
The activities
desalination
research
studies
components
on
forms
various
in the
of
desalination
corrosion
plants
damage
and the
suffered
water
by
distribution
system. 5) Inspection
of desalination
plants
before
and
after
annual
maintenance
work. 6)
Active
involvement
in
the
operation
of
Doha
Reverse
Osmosis
Plant
(DROP). 7)
Performance
and
cost
used in the desalination 8)
Investigations
plumbing 9) whether
systems
Chemical
water
Organization 10)
into
the
and assessment and
sea water,
potable
evaluations
brackish,
different
damage
anti-scalent
out
analyses
to
of
ensure
on drinking
of
Engineers
The author wishes
to thank
suffered
by
water chemical
brine, distillate
carried
(WHO) standards
Training
corrosion
of different
bacteriological
is
of
additives
plants.
different
or potable. compliance
domestic
water
treatments. kinds
of
water,
Quality control of with
World
Health
water.
and
Operators
in
different
Dr.
Fatma Al-Awadi,
fields
of
water
treatment.
ACKNOWLEDGEMENTS
Resources thank
Development
Mr.
Sadek
Centre,
Bou-Hamad,
Power and Distillation
Plants,
wishes to thank all personnel
for her encouragement. Chief
Engineer
for reviewing of the Ministry
present who have made this work possible, by providing
technical
information
for
Deputy Director The author wishes Operation
this paper.
and especially
also to
& Maintenance
Finally,
of Electricity
of Water
of
the author
& Water,
past and
those who have helped
or helped in the preparation
of this work.
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