US2493453A - Prevention of foaming in steam generation - Google Patents

Description

Patented Jan. 3, 195% UNITED STATES PREVENTION OF FOAMING IN STEAM GENERATION No Drawing. Application October 28, 1944,

Serial No. 560,899

2 Claims.

This invention relates to a method for conditioning water and, more particularly, for eliminating foaming conditions in steam boilers.

Foaming of boiler water is not, as commonly thought, equivalent to an accumulation of foam on top of the surface of the boiler water. When steam is rapidly withdrawn from a boiler with resultant foaming, there is no Water surface within the boiler correlated with the water level indicated in the conventional water glass attached to the boiler. In other words, there is no sharp line of demarcation between solid water and foam in a boiler during rapid steam withdrawal.

The foaming of boiler water is actually a rapid expansion of the water in a steam generating area of the boiler brought about by the fact that rapidly forming small steam bubbles do not coalesce until a definite short time after their formation. As a consequence, the entire volume of water in the generating area is expanded by myriads of bubbles until the thus formed socalled light water may fill the steam space and become entrained with the steam leaving the boiler.

In other words, bubbles need not" be particularly stable to cause boiler foaming. The stability of the bubbles need only be such that the bubbles last but a very few seconds after passing the plane of the water level indicated in the Water glass.

I have now found that the slight degree of stabilization of bubbles which suffices to cause foaming of boiler water may be largely or completely inhibited by the addition to the water of a high molecular weight composition formed by a reaction of polymerized fatty acids derived from drying or semi-drying oils with a nitrogen containing substances selected from the group comprising alkylene diamines, polyalkylene polyamine, hydroxy alkyl amines containing hydrogen directly attached to nitrogen and a primary hydroxy group, and like compounds.

It is therefore an important object of the present invention to provide methods and compositions for preventing foaming in steam boilers, particularly by incorporation with said Water of the above disclosed condensation products of polymerized higher fatty acids with aliphatic nitrogen containing compositions.

Other and further features and objects of the 2 present invention will become apparent from the following detailed disclosure and appended claims.

The polymerized higher fatty acids used as such or in the form of their esters in the preparation of the foam inhibiting compounds of the present invention are derived by methods known in the art from drying or semi-drying oils, fatty acids liberated by saponification of such oils, or esters of such fatty acids.

The relationship, for instance, of linoleic acid to its polymerization products may be roughly indicated by the following formulae:

R-G-OH I 1 EO-O-R-R-C-OH II I I i no-o-a-a-o-on m A COH wherein R represents an unsaturated hydrocarbon chain.

It will be seen that the dimeric acid (Formula 11) is dibasic, and that the trimeric acid (Formula III) is tribasic. It is not believed that polymers higher than the trimer are formed.

In general, a polymerized higher fatty acid may be reacted with the above mentioned basic nitrogen containing compositions either in the form of the free acid or in the form of esters thereof. It is most convenient to use directly the acid or the ester obtained as a product of any one of the several available polymerization processes.

If desired, the free fatty acids derived by saponification from a drying or semi-drying oil such as soy bean oil, corn oil, linseed oil or the like may be polymerized by a simple heat treatment, for instance, at 265 to 275 C. for from 17 to 18 hours. The product is then subjected to distillation at from two or three millimeters of mercury for removal of the unpolymerized fraction. Such a process is disclosed in British Patent No. 428,864 issued to Imperial Chemical Industries, Ltd.

It is also possible to subject the original drying or semi-drying oils to a heat treatment at, say,

285 to 295 C. for twenty hours followed by saponification and fractional distillation under vacuum of the liberated fatty acids to remove therefrom the glycerine and the unpolymerized fatty acids. This method of preparation is also disclosed in the above identified British Patent No. 428,864.

Still another method of preparing polymerized higher fatty acid material involves the methanolysis of soy bean oil or other vegetable oils, removal of liberated 1 glycerine, polymerization of the separated methyl esters by heat treatment or, optionally, by catalytic means, and final separation of the polymerized methyl esters from the unpolymerized methyl esters by distilling oil the latter.

The extent of polymerization effected in any one of the above outlined (procedures :depends, inter alia, on the length of time :during which polymerization is carried out. For the purposes of the present invention, the dimeric acids and their esters are preferred, and the po1ymeriza-- tion is regulated accordingly. 7

It is apparent that if a dimeric acid (Formula II) is reacted, for instance, with ethylene di- This "diacylated product should have a :molecuilar 'weight "of approximately 5.84, being a'formed :from two -m'olecules :of :linoleic acid (molecular 'weight 280) and cone .molecule ethylene ,diamine (molecular weight 60), two molecules of water '(molecular'weight 18) being split off. Neverthe- -:less, the :reaction :product of the :di-meric acid derived from linoleic gacidrwith methylene zdiamine may have an actual .average molecular weight varying from 750 up to 2,800 or higher. This is believed due to the formation of linear condensation products, for instance, "two or more of the molecules designated by Formula IV being joined together by reaction of the free carboxyl groups at the ends of Formula. IV withethylene diamine. If

I have found that for the purposes of inhibiting foam formationfin -boiler water, condensation products of the above indicated nature must have a molecular :weight of .least 1,000, .and that, .-in general, the efficiency of such compounds in- .creases with .molecular weight.

.To illustrate .morefullythe preparation of the foam inhibiting compounds of :thepresentinvention, I will describe .hereinbelow in some detail sthe preparation of a polymerized soy bean fatty (acids v"amide bya process including,-as.aninter- ,mediate step, .the preparation .of a .methyl ester of ithesoybeanfatty acids. Such methanolysis can 'be effected-by the .use -of 0.25 partsodium .hydroxicle, sodium vmethoxide or potassium .hy- .droxide. The reaction .iseffected by using 2.5'0r more moles of methanol in excess of that re- 'quired, and heating at -'7.0 C.w.for two .hours. [Alkali -.-as sodium hydroxide must be=maintained in the :reaction mixture .in order to obtain as 'to settle for two hours.

.cooled and one kilogram 10f iwater added to the mixture. When the mixture hasxcooledto 40 C.,

the agitator is shut off and the mixture allowed After settling, crude glycerine (4.5 kilograms plus 1.0 kilogram water) is withdrawn from the bottom of the kettle until methyl esters (lighter color) appear in the drainage. The methyl esters removed from the kettle are covered .in a separatory funnel and returned to the kettle. Five gallons of water are added .to the kettle, the mixture is heated to C. with agitation, and allowed to settle for thirty min utes. The water is withdrawn from the bottom of the kettle, and the washing operation repeated twice. The kettle is plosed and the contents heated to 110 C. under a ;pressure of :fifteen millimeters to remove final traces -of water. :A yield of 29'kilograms of methyl-esters is-obtained.

Numerous catalysts, including sulfur dioxide and anthraquinone, may be employed :for :the

ffected by distilling ;-at pot temperatures up to :2? 0 -C. and by the :uSe of super-heatedsteam yin itheyfinal stagesnf thedistillation. :Reduced pressures of 5 to :10 millimeters ;,ar e zneeessa-ry formemOVaIrOf :alhbut :tracesof :monomeric esters. 'I-,he polymerization .and distillation ,steps, as men.- formed in 1a fifteen-gallon uarnish z-kettle, :are describediin .:detail as follows:

- :tube for introducing ;ga-s t-into :the ,kettle to -,a

gas :from the top.

.for eight hours.

point near the bottom, and a tube for removing In the kettle --,are placed 34 kilograms of methyl esters, sand. heat and t :-tion are applied. The esters ,are :warmed to 100 20., the kettle is evacuated-slowly :to ififte'en millie meters pressure :after having been :closed, and

sulfur dioxide run in through the stainless steel The gas .outlet at the top :of th kettle ,kettle; and-withdrawn continuously during therm- .mainder of the reacticn'period. The sulfur idioxide is absorbed by bubbling through water. The mixture inthe kettle is :heated-to 30 0 .zanjd maintained 'at'a temperature or .295" ;to 300 ThemiX-ture is :then :allowed-zto cool to .200" .C., and vacuum ;is slowly applied :to distill unbodied methyl -=est,ers (monomer);

The monomer is distilled under ireduced pressure .until a temperature :Land:pressureror-z'lfl" C.=.and .five to ten millimetersareobtained. Anyn'remaining monomeric -fat esters arezremoved by superheated; steam. Theresiduall dimeric esters inathze "kettle are then :cooled :to room wtemperature :in

vacuo.

The distillation yields :1937 kilograms .of monomer and 1,319 kilograms of rresidual-dimertc ses'ters. 1

Polymerization .can also be carried out by simple heating at about SOO C. The effects on soy bean methyl esters of such a bodying treatment carried out for from 2 to hours is tabulated as follows:

tylene diamine; dibutylene triamine and the like. Instead of the polyalkylene polyamines, I may use the hydroxy alkyl amines containing hydrogen directly attached to nitrogen and a primary hydroxy group, such as monoethanolamine, di-

. Residual Refractive Viscosity in Specific Trimer Dimer/Trimer Bodied E t Index at Centipoises Gravity at Monomer Dimerand .Bati

' S 8 C. at 30 C. 30/15.6 Residue (molar) Hours Per Cent j Per Cent Per Cent Per Cent The polyamide can be prepared from residual dimeric fat acids or esters thereof. The preparation runs smoothly both with esters and acids, but the reaction is somewhat faster with the acids. The preparation of polyamide from the free dimeric acid is described as follows:

In a fifteen-gallon experimental varnish kettle, 15.82 kilograms of residual dimeric fat acids are heated to 150 C. in an atmosphere of carbon dioxide and 2.30 kilograms of aqueous ethylene diamine is added slowly with vigorous stirring. The reaction proceeds with the loss of water from the kettle due to evaporation of water added in the diamine solution and the dehydration of diamine salts to give amide linkages. After all of the diamine is added (approximately two hours), the temperature is raised to 150 G. Then over a period of ninety minutes, the pressure on the reaction mixture is reduced slowly to thirteen millimeters and the temperature is raised to 200 C. If too rapid a rise of temperature or lowering of pressure is permitted, excessive foaming may result. The reaction mixture is held at 200 C. at thirteen millimeters pressure for ten minutes, and then run into a vat under an atmosphere of carbon dioxide. The charge is allowed to cool until hardened. Then it is removed by inverting and tapping the sides of the vat.

Residual dimeric fat esters may be used instead of acids. With esters, the diamine can be added directly to the esters and the mixture heated to 110 C. Water begins to distill and the reaction temperature needs to be maintained so that the temperature of the distilling vapors does not exceed to C. A short fractionating column which permits some separation of ethylene diamine from water and alcohol is helpful. When 55% of the calculated amount of distillate has been collected, the temperature is raised to C. and then the pressure reduced slowly to fifteen millimeters, and at the same time the temperature is raised to 200 C.

The preparation of a polyamide from linseed oil is carried out similarly to the preparation described hereinabove using soy bean oil as the original starting material. In all such preparations of polyamides, the time and reaction conditions are regulated so as to effect the formation of products having molecular weights of at least 1,000.

Similar foam inhibiting compounds having molecular weights of at least 1,000 may be prepared by reacting polymerized higher fatty acids or esters thereof with polyalkylene polyamines such as diethylene triamine, triethylene tetramine. tetraethylene pentamine, with propylene diamine, dipropylene triamine, tripropylene tetramine, bu-

ethanolamine, triethanolamine, methyl diethanolamine, and, in general, primary, secondary and tertiary hydroxy alkyl amines or. alkanol amines, such as propanol amines, butanol amines, ethanol butanol amines, diethanol butanol amines, alkyl derivatives of hydroxyl alkyl amines or alkanol amines, alkanol alkylene diamines, alkanol polyalkylene polyamines, ether derivatives of hydroxy amines such as a monoethyl ether of diethanol amine, amino derivatives of polyhydroxy compounds such as l-amino propane diol-2,3, and glycerol monoamine and the like.

Melamine may also be used instead of the polyalkylene polyamines for condensation with polymerized higher fatty acid compounds, as well as the condensation products of two moles of an alkylene diamine or polyalkylene polyamine with one mole of a dibasic acid such as tartaric acid, oxalic acid, sucoinic acid, citric acid, maleic acid and malic acid. These condensation products have terminal primary amino groups.

The foam preventing compounds of the present invention were prepared by condensing under suitable conditions two moles of a polymeric fatty acid compound with one mole of any one of several of the above disclosed dibasic or polybasic amines or hydroxy amines to form a product in which the primary amino groups or hydroxy groups are acylated. Good results are also obtained by additionally acylating one or more secondary amino groups when secondary amino groups are present in the acylated amine.

The foam inhibiting compositions of the present invention may be introduced into steam boiler water in the form of colloidal dispersions that may be stabilized with tannin, gum arabic or pectin. If desired, the foam inhibiting compositions may be introduced into the boiler in the form of a solution in an appropriate solvent, such as iso propyl alcohol. The dosages required are generally quite small, on the order of some few parts per million of boiler water. In general, from a trace to about fifty parts per million of foam inhibiting compounds may be added to boiler water, preferably in combination with tannin. Addition of foam inhibiting compounds may be repeated as required to prevent foaming.

Various details may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not my purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. The method of generating steam from a ammraa 2. The method of generating steam :from a boiler water having a tendency tot-foam on boiling,

which comprises dispersing into'said Water in an amount sufiicient substantially to inhibit the tendency of said wa'terto foam onjboiling a compound having a molecular weight of "at 'least 'one thousand and comprising the linear condensation product of 'one molecular proportion of ethylene 8 diamine aniitwo molecular r mportionszofmisdimer of an-unsaturated'higherifattysacidzderivedhum soy -bean ;oi1 xf-attyracids, and :boilingi-the mesultirm dispersion Ito generatersteamatherefrom.

LEWIS 0.; .GUNDERSQN.

REFERENCES .CITED The following 'aneferences are of erecord in the =fi1e .of this patent:

UNITED STATES PATENTS Number Name Date 1,892,857 Spellmeyer "Jan. 3, 21933 2,341,632 Robinson e'txal. :Apr. 4,31%4 2,347,178 Fritz et a1.. .2\pr."25,;19%4 2,379,413 Bradley wJuly 3,?1945 FOREIGN N umber -Country .Da'te 547,189 iGreattBritain Aug. 18,

Claims (1)

1. THE METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCY TO FOAM ON BOILING, WHICH COMPRISES DISPERSING INTO SAID WATER IN AN AMOUNT SUFFICIENT SUBSTANTIALLY TO INHIBIT THE TENDENCY OF SAID WATER TO FOAM ON BOILING A COMPOUND HAVING A MOLECULAR WEIGHT OF AT LEAST ONE THOUSAND AND COMPRISING A LINEAR CONDENSATION PRODUCT OF ONE MOLECULAR PROPORTION OF ETHYLENE DIAMINE AND TWO MOLECULAR PROPORATIONS OF A DIMER OF AN UNSATURATED HIGHER FATTY ACID DERIVED FROM A MEMBER OF THE GROUP CONSISTING OF LINSEED OIL FATTY ACID AND SOY BEAN OIL FATTY ACIDS, AND BOILING THE RESULTING DISPERSION TO GENERATE STREAM THEREFROM.