The effect of a magnetic field on steam purity

Desolinarion - Elsevicr

THE EFFECT

Publishing

Company,

OF A MAGNETIC

Amsterdam

FIELD

- Printed

in The

ON STEAM

Netherlands

PURITY

M. YOVCHEY 7 Thor

Petrovsstrect. Sofia / Bttlgaria)

(Rcccived

June

The

different

18. 1971; in rtviscd form March IO, 1972)

effect

of a magnetic

field

on

steam

purity

was

studied

salts and sea water after they had been passed through

by

examining

a magnetic

field

Results showed this effect to be negligible which means that magnetic treatment of the feed water of steam boilers or of evaporators to prevent scale formation does not decrease the purity of the steam.

in a steam

Km SO -

generator.

S, S,

-

transfer factor of the steam. SJS, initial liquid salinity before boiling. mg/kg. boiling liquid salinity at the moment of measuring, boiling liquid salinity. mg,/kg

S, 3’

-

saturated steam salinity. mg/kg concentration factor of the boiling

7,

-

condensate specific electric conductivity. S/m boiling liquid specific electric conductivity, S/m

;‘I -

mgjkg

solution

Reduction of the scale-forming properties of some diamagnetic liquids after passage through a magnetic field has been used (I; to prevent scale formation on the heat exchange surfaces of some boilers and evaporators. This method. known as magnetic water treatment. has not been properly explained. although there is some basis for relating the antiscale effect to changes in the hydratation characteristic of the ions participating

in the scale formation ($4). The apparatus used consists of one or several magnetic fields which are intersected by treated water. Usually they are installed in the feed water line of the steam boilers or the evaporators. As the magnitude of the relaxation time of the effect is not known so far. it is necessary that the distance between the apparatus and the steam boiler should be as short as possible. Use of magnetic treated water for scale prevention may cause further

difiwlties.

It is not known.

for instance

whether

it increases

or decreases

steam

Desalination, I 1 (1972) 379-384

30

Xl. YOVC11Ev

Therefore \ve decided to study pretreated by a magnetic field. As is known. saturated steam is phase system of a dry saturated steam whose content is identical to the liquid In the most general case. steam

purity.

the purity

of the steam of boiling

water

not a homogeneous system. but is a twoand a dispersed liquid phase (carry over) in the boiler or evaporator. purity can be expressed by the transfer

factor Km. the ratio between the saturated steam salinity salinity S,. The transfer factor A;, is determined by

S, and the boiling

liquid

At pressures as low as S MN/m * the saturated steam salinity S, can be expressed by the amount of salts dissolved in the steam transferred liquid phase. Rearing in mind that the salinity can be determined by mea wing the conductivity. we can study E;,

=

the magnetic

field cn‘ect on steam

purity

by

_?c_

(2)

;‘f

The type of equipment (5) used for this purpose (Fig. ) consists of a magnetic apparatus (A) and a laboratory steam generator (B). A more detailed description

of the construction

of (A) is given in (2).

5

A Fig. 1. Set-up of the laboratory installation A - bicontour magnetic apparatus. B - labonrory

swam

generator.

The magnetic apparatus used in these investigations is of the “bicontour” type and has a 0.2T induction force. The time between magnetic treatment and evaporation is from 30 to 60 min approximately. The rate of flow is 0.2 mjs. It is known that under thkse conditions the antiscale effect of the field is better. The laboratory steam generator consists of an electricaliy heated flask (I). a measuring device (2), pia!inum electrodes (3). a cooler (4). and a condensate

measuring The measuring The heat

device sample device flux is

(5). first passes through the magnetic apparatus (A) and enters the (2). Then it enters the flask (I) which is not in the magnetic field. about 16 kW/m2, its constant steady value is controlled by a Desolinorion. 11 (1972)

379-381

EFFECT

OF A MAGXETIC

special

FIELD

thcrmoregulator.

quantity

is measured

OS

The

STEAM

kssk

by (2). The

381

PURITY

(1)

sample

is appropriately

resistance

insulated.

is measured

The sample by electrodes (3)

submerged in the liquid. The steam obtained in the flask (1) then passes through the cooler (3). and the condensate is collected and measured by measuring device (5). The sample resistance enables us to determine the specific electric conductivity 7, of the boiling liquid. The conductivity of the condensate y’, obtained through boiling the sample is dcfincd by dividing it into fractions depending on the concentration factor N. X is the ratio between the boiling solution concentration at the moment of measuring and the initial concentration of the same solution: S K = ..’

St,

The experiments

were carried

out as follows:

The liquid was treated by the magnetic field and then heated to its boiling point. the rate of heating being constant. As soon as the liquid starts boI!ing. Y! and ;‘, wcrc measured. The control sample vsas magnetic apparatus. Our investigations as some typical mixtures

Ei;, ws

treated

estitnated

in the

and A:, vs N dependence constructed.

same

way

but

not

passed

include almost all salts pclluting natural and natural waters including sea water.

through waters

the

as well

x1o-4

2 Concentration --O--O--

4

3 factor

Fig. 2’. &/A’ for CaSOA solution rrcated by magnetic field. --8--O--

N control Desolinarion, 11 (1972) 379-384

382

M. YOVCHEV

L

4

.D

Concentration Fig. 3. --O--O--

tread

&/A’

by

factor h’

for CM32 solution magnetic

field.

-+-a-

cent roi

These salts (4) fall into three groups according to their bchaviour in the steam-generating processes: A. Unstable salts with temperature incrcasc of the solution up to the boiling point (Ca(HCO,),. Mg(HCO,),). B. Salts stable to their boiling points but with a limited solubility at this temperature (CaSO,). C. Salts stable to the boiling temperature with a solubility practically unlimited at this temperature (MgC12. MgSOJ. NaHCO,. NaCI and Na,SOJ. The 7-8 me:;1 concentration solution is made \\ith every salt from group A. B and C. Our main results are shown in Figs. 2. 3 and 3. Fig. Z shows the A;,‘N dependence for the CaSO, solution (group B). It can be seen that: 1) A’” is approximately constant after the initial fraction has evaporated in both samples no matter whether treated by a magnetic field or not. The large increase in A;, for the initial fractions could be explained by the high superheating necessary to initint, n boiling. The dissolved CO, might have some influence. 2) Kmhas different values in the magnetically treated samples and in the control when N = constant. This difference is due to the effect of the magnetic field. It shows that the steam purity is higher when a magnetically treated liquid is Dcsolinotion. 1 I (1972) 379-384

383

x10-4

_+-_____._i-__ -i

-

_.. ..-..

,7-l .,--_ i__--+-i.__ -t__ .

-,.

t i

I

____

i

t

.-I-

7-r !

j

-1-i

I

t

I 1.. -. -+_-_--_--t-_--_ i

L-ri -.

!

’

-.--

-7

::

_!._!!! -j__ ._i .i_..‘Ti

-.+._i__, 1

2

Fig. J.

and

SO;

factor

Ei,,,‘.V for wa water

treated

cvaporatai.

4 K

3

Concentration --O--O--

j

bp magnetic

This could - ions

field, --O--O--

be esplained

control

with the changes

of the hydratation

of CaC +

(4).

Fig. 3 shows the E;J.V dependence for a solution of CaCI, (Group C). Here too the transfer factors change in accordance with the above consideration. the difference being due to the magnetic field effect. From the above, it follo\vs that Group B and C salts have a definite magnetic field effect on steam purity. This is expressed in the difference between the values

of the corresponding

transfer

factor K,,.

The case for Group A salts is difkrent. accurate measurements \\ere not obtained KJN the transfer

dependence factors

Because of the CO, in the condensate, and no conclusion could be drawn.

for sea water is shown in Fig. 4. The absolute

are considerably

(4 to 5 times)

and C salts and were essentially independent This is possibly due to the higher specific probably changes the quantity of the liquid

lo\\er

than

those

values of

of Group

B

of the treatment by the magnetic field. weight of the samples studied transported by the steam. Desaharion,

which

11 (197.2) 379-384

M. YOVCHEV

384

The effect of the magnetic is negligible, although the purity

field on steam purity evaporated is increased slightly for solutions

from sea water of stable calcium

salt. Hence the magnetic treatment of feed Hater in steam boilers or sea water in evaporators to prevent sc& formation does not decrease the purity of the steam. Thud this method can bc used in sea water evaporators without any complications conccming steam purity. HEFERESCES 1. THE0 \‘t RHAIRES, Lc lmilCnKln1 mi8pXiqUc 2. 3. 4.

5.

tks hqllidCS CCnIre Ia corrosion

13 Irr incruslalion,

Rev. Sot-. ny. ful~e iqtyrs. et inrfmtriclr. I1 (1957) 464177. G. GESIY, Chofcrtr cr inrftmrie. IV61. p. 136. \‘. 1. b~lSEWi0 Tepioener~ctirn. M. YWCHEV, Thcsi.s. Higher

AYD S. M. PETROV. On the physico-chenlical hasi\ of niltgnctic uacr trcatmtxt. 9 ( 1962). On the magneric field usage for water trc;ltmcnr in thcrmocncrgctic units. lnsri!rtfe of .4Jt~rhonirai am/ FJerlrical Enginerrinp, .S+a. 1967.

M. Yovctiw. A method for a comparative imcstigation of water solution passed through a magnetic field. Electrical

Engineering,

Ann&.

of the c~btallization Higher lnstitutc of

in conccntntion Mcchamwi and

&~fiu, 20( 1) ( 1966).

Drsdinarion.

11 (1972)

379-384