Vapor compression distillation with maximum use of waste heat

3

38 (1981) Z-12 Ekevier Scientific Publishing Company.

Desulination.

Amste&am-PrintedinTheNetberbinds

VAPOR CO?,ll'RESSION DISTILLATION WITH MAXIMUM S.J.

USE

OF

WASTE

HEAT

SENATORE

Ebasco

Services

Incorporated,

New

York

ABSTRACT

vapor

The

cost

and

compression

corresponding

as a higher designed

capital

with

electrolyte that

has

subject higher

this

the

fuel

to the

The This

design

plant

The

design updated

plant.

The

more

of waste

of water

For

plant. 130°F

PR

heat

will

purpose

PR

that

example,

is $5.20/Kgal

per

The

PR plant

KBtu)

only

a centrifugal design,

be

of

is

a poly-

compressor which

250@F

is

and

(pouzrand

the

uses

a

in application,

water)

or a single

attainable

in

view,

as

this

the

design

price

$5.O/PlEXLI the fuel contribution

PR of 8 and is reduced

at a

or

stressed.

versatile

an economic

at

low

requiring

plant

is easily

from

as a low capital

product

temperature

is extremely

a dual

high

7 lbs

employ

high

brine

attractive,

to escalate.

cost

The

at maximum

to either

31)

vould

1.2.

PR VC process

be designed

of about

design

use

can

(about

to about

at a PR of 31. and

process

employes

by a diesel

An

adapted

only)

This

1.58

low

increasingly

total

temperature

of about

of

or

ratio

PR (about

higher

operates

ratio

continues

S1.34/Rgal

ratio

high

(water

becoming

is

and brine

paper,

process

performance

inhibitor.

it is well

purpose

of

scale

pressure

Either since

cost

a maximum

a pressure of

distillation low

engine

and

employs plant

descriptions

a 65,000

CFM

operates

an exhaust cost

for

across gas

estimate

a 2.35

centrifugal

and

vi11

mgd

plant

compressor.

a 4 effect water

vertical

jacket

be presented

waste and

will

The

tube heat

cost

be

presented.

compressor

foam

recovery

of product

is

driven

evaporator. scheme. water.

INTRODUCTION The

design

criteria, energy level

being

in Btu's and

if a given plant,

the

per

quantity

utilization

power

of a desalting

one

hour. of heat

of these heat one

facility

desired A key

would

of

steam

LO2 million

operate

utilizing

waste

rate

the

parameter

(enthalpy,

available

source

product

with

and

that

temperature) sources Btu/hr

must

heat other

be taken

that

is depicted

ratio

two major

the

into

in Figure as exhaust of

slightly

input

available

account

is available.

is available

a performance

requires being

1.

input

is the

The

optimum

For

example,

steam less

from

than

1

a

4

SENATORE

with

a singie

vertical

tube

effect

and

produce

300.000

gallons

per

day

of product

one

would

-42ter.

If a lower require of water

per

resulting

cycle

The

vapor

and

From

of

such

31

parameters

the process

as 5 million

in order and

Btu/hr,

to generate

performance

options

would

the

ratio

dictate

300,000

gallons

options,

the

the most

economic

to be utilized. compression

capital

distillation low

cost

ratio

This

temperat*lre

of

250°F

recomended

at

the

higher

PR

temperature design

of about

The

uses

can

ratio (about

of about

would

1.2.

and

process

performance

and

brine

inhibitor.

pressure

of about

these

analysis

a maximum

scale

is available

ratio

corresponding

a higher with

day.

cost

process

cost

ene-rgy source

a performance

a higher

higher

temperatures.

or

PR VC process

31)

7 lbs

requiring

acentrifugal

PR plant

design

pressure

ratio

The

as a low

product

The low

plant.

130°F

employ

high

be designed

(about

process

or as

is designed

a polyelectrolyte

compressor operates

that

has

a

at maximum

1.58.

design

KBtu)

PR plant

only

of

capital

per

brine

Acid

treatment

is

2.35

mgd

is

for

plant

presented. Either since

of

(water

$1.3&/Kgal The

(Btu/hr)

and

the

ratios

for

required

plant across exhaust brine

using

gas heater

ground The

water

rules current

are

that

of

or a single in this

view, fuel

as

design

the

price

contribution

is reduced

to about

scheme

additional ground must

the

the

i.e.

be extremely of

pressure vapor

the

rate,

energy

input

can

process.

simply

If performtopping

level

can

steam

cycle

be generate

compressor.

(VTFE).

The

VTFE

capital

plant

life,

cautious

the plant

or

of vapor

one

for a 2.35

dr.'.ven by a diesel

The

turbine,

compression

is presented

a 17 effect

water.

rules,

life

vapor

evaporator and

given

production

description

a gas

combination

the distillation

compressor foam

engine,

example,

a hybrid

for

process

tube

one

over

For

intermediate

turbine

recovery

cost

day

an economic

interesting

a desired

ratio

centrifugal

economic

well

water)

$5.O/?C3'TU the

a diesel

an

required,

and

producing

to the

it Is obvious

for minimum

drive

vertical

heat

while

and

a suitable

cfm

either

evaporation.

15 are

the

effect

waste

from

performance

design

a 65,700

is -i:isitive Hence,

of

at

and

in application,

attainable

at a PR of 8 and

presents

process

than

process

a four

heat

tube

when

the operation .I typical

(power

is easily from

example,

versatile

31.

vertical

implemented

purpose

PR that

attractive,

For

a porter plant

greater

a dual high

more

of waste

from

is extremely

is SS.?O/Kgal

to a distillation

calculate

be

of water

at a PR of

compression

ance

cost

steam

The

to escalate.

utilization

exhaust

to either

plant.

increasingly

continues total

low

adapted

only)

is becoming fuel

to the

can

high

it is well

purpose and

the

and

as a low component interest

employes

certain

an

temperature of water rate,

in optimizing

make

operating

engine

design

mgd

that

cost

etc.

plant

design

the

economic

known.

fuel

economics

dictated

that

serious

consideration

be given

to

SENATORE this

5

high

performance

ratio

plant

economically

competitive

with

inherent

performance

ratio

cost

low

of

the

VC-VTFE

about

$5.00

PLANT

DESIGN

The

per

process

compressor

that boiler

Steam

two

the

levels

to power

steam

at

to the first

effect

the

low-pressure

heat

increases

desuperhcated The

S J Senatore with

the

which

with

compressor water

a lover

operates

with

point results

The

and

tube

of additional downflow

effects

PIANT

for

of about

of the

result tube All

product. but

the

S°F

can

four

effects

per

with

which

are

Data

as

flow tube

production evaporator

effects

in the

upflow

of

1.95

will

are

tube

vapor sca-

the

The

system

the

boiling

Uhen

obtained

by a

This at

effects.

25OF.

concept

vertical the

with

action

tubes

the

deducted,

a Delta-T

steam.

This flow

consumption

of only

super-

collaborated

of effects.

compressor is only 3.360 water

process

As a result,

in these

8OF

is then

the

vertical of

steam

input

compressor with

foaming

the

the

heat

energy

losses

effect.

power.

with

number

area

drop

auxiliary

evaporator.

the operation

surface

foaming

vertical

of

a given

in a net

be designed

flow

permits

(Delta-T)_

operated vapor

foaming

steam turbine

vapor

from

the

process

by Gr

Sephton

low

on

as 4.S°F.

HP and these 4 mgd.

produce

conservatively

The

17 effect 0.4

mgd

operated

in

about

mode.

DESCRIPTION

Figure

2 is the

basic

flow

process

sheet

of

the

2.35

mgd

is

steam

233OF

steam.

level

superheated

of Dr H Sephton

the minimum

pressure

rhe at

exhaust.

one

supplemental

effect

coefficient

across for

successfully

vertical

mode

power

the

seawater

permits

of condenser

consumption

temperature

fact

designed

Delta-T

the

boiler;

a vapor A heat

turbine

required

separate

direction

gas

is combined

superheated

tube

into

VTE

is held

differenca

intereffect

have

the

the

as

powering

psig,

evaporator.

fourth

transfer

This

less

was

Delta-T

bundles

energy

vertical

with

addition

in a net

test

2.

d gross

elevation

heat

temperature

plant

the

under

the vertical

overall

operates

of

the

the

desalting

sacrifice

low

of

of approximately

effects

VTFE

use

foam

the

steam

of a surfactant

all

is

Btu.

backpressure

turbine

is used

to 33S°F

boiler

Corporation

in the

tube

from

temperature The

produces

steam

400

its

capital

cost

evaporator.

recovery

The

with

budgetary

engine

the

is 650°F,

it is

the water

S5/106

from

turbine.

backpressure

This

steam

other

that

the

the vertical

its

injection

enhances

factor

of

to 250°F.

Envirotech

from

The

and

of

that

evaporators

vertical-tube

heat

and

costs.

of a diesel

the heat

steam

flash

heat

costs

in the

the

generator

boiler.

fuel

four-effect

and

utilization

$12 million

consists

is generated

257'F

receives

on

recovers

a backpressure

low-pressure

and

a

that

higher

is about

plant

across

heat

multistage

hence

based

mgd

is employed

to an electric

exhaust

from

2.35

':60°F saturated,

is used

is coupled The

and

gallons

operates

energy

approximately that

the

waste

conventional

presented

thousand

for

recovery at

plant

with

diesel

driven

vapor

6

SENATORE

compression effect

desalting

No.

17 and

plant.

heats

back

to the

sea

after

feed

of 4.0

mgd

enters

is treated

with

is removed

through

the multistage

vertical

tube

is added

prior

the

first

its heat from

effect

steam

in effect down

heat

1.

This

So.

through

tubes

effect

which

is

scheme

is car-icd the

upgraded effect po%nt

NO.

likewise

flashed

down

1.

The

supplemental

at about

which

is injected

:he

compressor

the

entering

is 18.9

psia

discharge

and

source

is 29.8

is recycled

to the

1

flash

transfers heat

flashed

seawater in the

of

second This

4 is reached

as

the

heat

is

removed

and

source at

for

this

The discharge

h'o. 5. 90°

water

and

is recycled

superheat suction

into

pre:

psia.

Eight

the

compressor

of

product

train.

effect

The

250°F.

suction

superheated

acts

is about

at

vertical

tank

tubes

brine

effect

to saturation

as

flashing

the

until

effect

This

335OF.

makeup

enters

compressor

to a flash from

then

for

the

withdrawn

flashing

the discharge

is in a slightly

steam

that

heat

first

Supplemental

heating

effect

the

enters

occurs

water

each

4 from

the

then

entering

the multistage

steam

from the compressor product

through

for

carbon

proceeds

1.

and

generated

which

is the

compressor

steam

feedwater

A surfactant

the vapor

No.

on

seawater

effect.

1 is fed

compressor

:Jo. 4 and

the

No.

through

upon

of

effect

is used

in effect

plant.

process

resulting

then

exits

The

tube

is condensed

The

effect

the

and

discharge

effect

train.

the vapor

state

to the

first

of

and

The The

the

feedwater

effect.

vertical

compressor from

end

and

for

is rejected

function. process.

alkalinity The

condenser

feed

condensing

evaporator

first

The

on successively

through

effect

the

final

treatment

all

superheated

product

in the

of the

temperature

is added

vapor

Host

final

flash

t-a the first

'>team generated

back

from

high

the multistage

the vertical

whereby

only)

entering

boiler

the

5OF.

deaerator.

immediately.

from

the

to neutralize

in a slightly

of vaporization

enters

seawater

atmospheric

the

feed

this

conventional

feed

occurs

about

performed

acid

at

seawater

seawater

(product

to the

the waste

The

the

in the

effect

flashing

tubes,

the is has

sulfuric

dioxide

The

-xre to

percent

of

so

that

in order to protect the

state

centrifugal compressor from erosion effect of moisture. The

Allis

conditions years

Chalmers for

of operating

availability up

this

of centrifugal

Government

range

over

larger

multiple There

compressors. capacity

For

compressor

experience

of well

to 5 mgd.

vapor desalting

that

facilities

in the

stage

are

several

were

built over

This

field

sizes units

the or

the

been

selected

centrifugal

can

larger

are

be made

and

more

of centrifugal Chalmers

35 years.

Tte

that

author

and

built as

have has

operated

over

design

many

has

a proven

that

efficient

the

has

can

to the

compressors

and design experience with these compressor: in the Government The raw feed water would be chlorinated

to meet

compressor

compressor

machines

choice

thousands by Allis

has

as a steam

Single

90 percent. plant

for

D-30JR

facility.

produce

selection axial

flow

in this in the

30 years

US

of operating

facilities.

in the intake and sulfuric acid would

be injected into the feed treatment at a concentration sufficient to neutralize

SERATORE all

7 The

alkalinity.

be

removed

be removed with

in a vacuum

sodium

to effect

sulfite the

tube the

test

flow

of

tubes

that

are

tion

ratios

recycling

are

The

shaft

all

the

power

required

auxiliary

and

compresses

the

first

to the

and

pressure

the

be

added

reenters

for

that

contain

The

rate

of

higher

the

4 vertical

developed

sizes

each

vapor

will 450

concentra-

of

the

tubes

3.0

gpm

will

than

controls,

in

about

brine

formation

flow

BRP

the

some

by be

tests.

compressor lighting,

by

rise

the

vapor

minus

vapor

the

the

and

produced

required

by

and

air

thermodynamic

pressure flov

drop

of

requirement

temperature

of

equal

The

Delta-T

divided

by

losses,

such

the vapor

the

of

the vapor

for

to the per

effect

number

as

through

is

effect

steam

steam

es a function

increase

last

heating

of effects.

compressor

evaporator

in the

the

an amount

number

across

(BPE)

saturation

fn the vertical-tube

the

recirculates

divided

compressor

VTE

ratio for

of VTE

the

vaporization

and

reasons

potential for

required

ratio operation

for

effects

compressor

the

the

for

of

losses

due

the

circuit.

of pressure as a function

of

effect

two

in each

the

evaporator

ratio,

then

VTFE

becomes

the

the

is inversely

potential the

for

selection

an economic

capital

costs

heat

transfer

of optimum balance

of

for evaporator

compressor.

reduced

per

of

temperature

against

is increased,

is

using

ratio

Since

to pressure

or pressure compressor

surface

temperature

Important

performance

ratio.

is proportional

a number by

the

system,

tc pressure

transfer

handled the

transfer

takes

pressure

compressor

elevation

total

costs

As

that

saturation

the VTE

the

the

performance

heat

scale

pmps.

of

bundle

15 percent

is 4320

includes

for heat

desuperheating)

In a VC-VTFE

energy

plant

feed

been

15 feet.

brine

is about

etch has

will

of

then

the

ratio.

proportional across

this

temperature

point

3 shows

ratio

The

of

(after

Figure

for

compressor

effect.

to boiling

rate

which

tube

to prevent

A minimum

flow

systems

on

would

treated

be available. for that

bundles

a length

designed

This

it to the

output

effects

tube

with

effect.

potential

by a vapor

is equal

tubes

The

would

be

OPTIMIZATION

temperature

product

of Envirotech

plant.

data

would

gases

would

before

rates

the

water

etc.

VAPOR-COXPRFSSION

supplied

with

feed

Caustic 7.7

would

release

the

dissolved

deaerator

oxygen.

treatment

vapor

Sephton

each

tube.

conditioning,

and

conservatively

the

from

remaining

in

remaining

to approximately

is consistent

fluted

within

dissolved The

effluent

any

rates

by Dr

to each

plant

and

water

production

double

dioxide

An alternative

effects

the

brine

supplied

feed

flow

facilities

be modules

The

the

brine

foaming

deaerator

plant.

design

carbon

decarbonator.

to scavange

pEi of

the distillation The

resulting

in an atmospheric

for

or more

effect

the

inversely

and

amount with

the heat effects

of vapor number

transfer

are

to reduce

the

that of

must

is similarly

to decrease the volume

be

effects;

the

but

reduced.

fraction

of vapor.

For

of a

8

SENATOaE

given

performance

is less the

for

pressure

is halved. as

the number

becomes

more

ratio

a two-effect ratio

and

evaporator

system

is greater;

Thermodynamic of effects critical

than the

losses

reason

due

number

for

the

and

hence

of effects

capital

cost

a single-effect

is that

to BPE

is increased,

as the

capacity, that

the

volume

pressure

the

design

increases.

the

of vapor

drop, heat

of

system,

however,

transfer

compressor

even

though

to be pumped do

increase

surface

9

SEZATORE

FICIJRE

f

PRODUCT(GPD)VSENERGY1NPUT

II

sot W ENERGYINPUT- MtLLfONBN/HR

t

III

IIll!J

_.,_)

llI*Pb

fnlbutl

2.35 MGD DfESEL DRIVEN VAPOli COMPRESSION DESALTING FlOWSHEET

&

I-*-.-

I

* ‘1

i

1 i i If

w

SENATORE

11

FIGVRE

3

VAPCR CIRCULATION

I 1.6

1 1.6

I 1.7

1 1.8

1.9

20

30

PRESSURE RATIO

VC-WE PERFORMANCE AS A FUNCTION OF PRESSURE RATIO

SENATORR

12 REFERENCES

"Design and Economic Study of a Gas Turbine Powered Vapor Compression Plant for Evaporation of Seawater," Struthers Energy Systems, Inc.. and Pratt 6 Whitney Aircraft, Division of the United States Aircraft "PreLiminary Design of a Diesel-Towered Vapor-Compression Plant for Evaporation of Seawater," Office of Saline Water Research and Development Progress, Report X0. 276, United States Department of Interior, August 1967. S-J. Senatore and E.N. Sieder, "Conceptual Design Studies of a Dual Purpose and a Vapor-Compression Kater-Only 750 MGD Plant," Paper No. SM-113/33. International Atonic Energy Agency, Vienna, Austria 1969. S.J. Senntore, "Vapor Compression Distillation," International Congress on Desalination and Water Reuse," Nice, France. October 1979. S.J. Senator-e, "Vapor Compression" presented at the Seventh International Symposium on Fresh Water From The Sea, Amsterdam, The Netherlands, September 1980 S.J. Senatore, "Vapor Compression Distillation Combined With Waste Heat Utilization," XJSIA Sinth Annual Conference, llashington, D-C., May 31 - June 4, I'