US2461730A - Method of inhibiting foam formation in an aqueous gas-liquid system - Google Patents

Description

larly Fatented Feb. 15, 19 9 METHOD OF INHIBITIN G FOAM FORMATION IN AN AQUEOUS GAS-LIQUID SYSTEM Lewis 0. Gunderson, .Park Ridge, 111., assignor to Deal-born Chemical Co corporation of Illinois mpany, Chicago, 111., a

No Drawing. Application September 12, 1942, Serial No..458,142

4 Claims. (Cl. 252-321) steam is rapidly withdrawn from a boiler with resultant foaming there is no water surface within the boiler correlated with the water level indicated in the conventional water glass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 the boiler during rapid steam withdrawal,

The foaming of boiler water is actually a rapid expansion of the water in the 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. Small hydrophobic particles dispersed throughout the body of boiler water may act as nuclei promoting the formation of bubbles, particularly when the pressure is suddenly lowered as large amounts of steam are withdrawn from the boiler. As a consequence,- the entire volume of water in the generating area is expanded by myriads of bubbles until the thus formed so-called light water may fill the steam space and become entrained with the steam leaving the boiler.

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

I have found that even the slight degree of stabilization of bubbles which suffices to cause foaming of boiler water may be largely or completely inhibited by the addition thereto of relatively stable, predominantly hydrophobic surface-active organic compounds whose molecules comprise one or more long hydrocarbon chains, polar groups attached thereto and hydrocarbon chains attached to a majority of the polar groups. The long hydrocarbon chain or chains as well as the hydrocarbon chainsattached to the'polar groups may be straight or branching, saturated or unsaturated. substituted or unsubstituted. In any case, the long hydrocarbon chain or chains should each provide at least twelve and preferably sixteen carbon atoms. Among the polar cals.

organic compounds whose radicals contemplated may be mentioned the amine and amide groups. The hydrocarbon chains attached to the polar radicals may include long and short chains, and more than one hydrocarbon chain may be attached to one and the same polar radical. The compounds employed should preferably not be subjected to saponification or other decomposition under boiler conditions and, while predominantly hydrophobic, should still be hydrophilic enough to inhibit volatilization with steam.

It is therefore an important object of the present invention to provide a method of conditioning water for boiling comprising the addition theretocf predominantly hydrophobic surface active molecules comprise one or more long hydrocarbon chains having polar groups attached thereto together with hydrocarbon chains attached to the polar groups.

Another important object of the invention is to provide a method of conditioning boiler water comprisingthe addition of organic compounds of the type disclosed in the preceding paragraph in which the polar radicals are amine or amide groups, which compounds are not subject to sapcniflcation of decomposition under boiler co ditions and which are hydrophilic enough to inhibr't, largely or completely, volatilization with steam.

A further object of this invention is to provide compositions for conditioning water including the compounds disclosed hereinabove.

Other and further objects of the present invention will become apparent to those skilled in the art from the following description and thereto appended claims.

The methods according to the present invention will be more clearly understood in the light of the following hypotheses. However, the merits of this invention do not hinge on the correctness of these hypotheses.

Many stable aqueous foams are thought to owe their stability to the presence of organic substances of a high molecular weight whose molecules include terminal polar or hydrophilic radi- Soaps are an example. Such substances are considered to be onlypolarly soluble and hence preferentially adsorbed in the gas-liquid interface with a large hydrocarbon portion (hydrocarbon tail) extending into the gaseous phase. The dipole effects of such polar substances preferentially adsorbed in the gas-liquidlnterface around individual bubbles conceivably bring about orientation of adjacent polar water molecules forming enveloping films. Such films not only mechanically prevent close approach and coalescence of adjacent bubbles but also set up electrostatic forces mutually repelling such bubbles, for the charges on the outside of these films are of the same sign, being constituted by the similar poles of the oriented water molecules.

In other words, polar and hence surface-active substances of the nature indicated effect the formation of predominantly hydrophilic films around the bubbles which set up repulsive forces acting between individual bubbles to prevent their coalescence.

Modern locomotive boilers provided with feed water heaters, exhaust steam injectors and other auxiliary devices have provisions for returning the steam condensate from these devices to the boiler feed water which is injected into the boiler. By these means oil colloidally dispersed in the condensate enters the boiler. Much of this colloidal oil is valve oil which conventionally comprises a mineral oil compounded with some vegetable oil or. saponifiable organic substance designed to decrease the interfacial tension between the oil and the metallic surface of the valves. The latter substances are polar compounds which tend to promote foaming of the type encountered in soap solutions. The foaming of boiler waters may, therefore, in some instances be analo ous to the foaming of soap solutions and the like.

However, most organic matter naturally present in boiler feed water is too soluble or too slightly surface-active to form a surface film capable of stabilizing foam. Most of the finely divided inorganic solid matter dispersed in boiler water. articularly colloidally dispersed matter. is substantially wetted by the water and therefore displays pract cally no surface-active properties. Alkaline earth carbonates and hydroxides are examples of such solids encountered in boiler feed water or boiler water. The most strongly hydrophilic colloidallv sus ended matter. for instance. colloidal siliceous matter, is not only completely wetted but also envelope by films of strongly adsorbed water.

It is believed that a bubble stabilizing effect suilicient to effect boiler foaming is obtained when under certain conditions dissolved hydrophilic organic matter having terminal polar radicals such as H, NH2, COONa, and the like, is adsorbed on colloidal or microscopic particles dispersed in the feed water or boiler water, such as suspended soil particles, precipitated alkaline earth carbonates or hydroxides, and other dispersed particles. In such adsorption the terminal polar portions of the molecules are thought to be attached to the solid particle. which is thereby rendered less hydrophilic by the outwardly projecting hydrocarbon tails of the adsorbed. organic molecules, the polar radicals being more or less shielded from the water.

The adsorbing wetted particle and the absorbed hydrophilic organic matter are thereby rendered sufliciently hydrophobic to be surface-active while still remaining sufficiently hydrophilic to be able to set up, in steam-water interfaces, films of oriented water molecules.

The term colloida used in this specification refers to the state of matter dispersed in water as particles havine sizes ranging between microscopic and poly molecular. Most of these particles are visible in the ultra-microsco e, but when part cles approach thepoly molecular size represented by primary crystal format onthey are actually not visible in the ultra-microscope, al-

though intense illumination may make a slight Tyndall cone discernible. It is thought that these almost primary crystal particles in the outer fringe of the conventional range of colloidal particles are of considerable importance by adsorbing certain organic polar molecules under specific conditions of pH value, electrolyte concentration, temperature and other factors. Such adsorptive aflinity between certain particles and certain polar organic molecules may be highly specific.

Some particles may adsorb a sufficient amount of organic matter to be made completely hydrophobic. They are also preferentially adsorbed in the steam-water interfaces where the particles act to stabilize foam mechanically. Adsorption produced hydrophobic particles in the boiler water also act as nuclei promoting steam generation and effecting formation of a great number of small bubbles during super-heating of the boiler water due to fluctuating steam demand.

Whether any adsorption at all will take place, and, if so, to what extent, depends on the nature of the organic matter present as well as on the nature of the dispersed particles. some organic substances are adsorbed highly selectively by specific particles; others are readily adsorbed by most particles. Examples of readily adsorbed substances are arginine, histidine, lycine, other rotein degradation products belonging to the class of amino acids, and the like.

The amount of adsorption taking place also depends on the pH value and electrolyte concentration in the boiler water as well as on the longed ior a shorter or longer t me as a rule modifies pH value, electrolyte concentration, and like conditions until after a time depending upon the composition of the feed water involved. rapid withdrawal of steam begins to cause foaming and entrainment of water with steam.

For instance. in some localities the available feed water supplies are of such nature that when a concentration of grains to 200 grains per gallon of total dissolved solids is attained in the boiler water foaming occurs at a definite rate of steam takeoff. The initial concentration effective to produce foaming depends in part on the pH of the boiler water, in part on the nature and amount of the suspended particles, in part n the nature and amount of organic matter in the water, and a great deal upon the nature and amount of the inorganic substances dissolved in the water.

In other localities, concentrations of dissolved solids in boiler water many times the above disclosed figures are attainable before foaming occurs. Or, no foaming whatever may occur excent at intervals when certain of the factors mentioned are causing temporary or more or less permanent adsorption of hydrophilic organic substances and concentration of adsorbing disacomao droxides and other particles, is concentrated in the surface of the bubbles during periods of operation of the boiler when foaming occurs, corresponding with fairly definite concentrations of. alkali salts in the boiler water. At intermittent periods when foaming does not occur the positive adsorption of this suspended matter in the steam bubble surfaces appears to cease, indicating the absence of certain optimum conditions of electrolyte concentration, pH value and concentration of suspended matter which appear to be necessary to produce the "flotation efiect thought to accentuate foaming. However, the presence of suspended solid particles is not a necessary condition for the formation of foam. I have observed intermittent foaming of the type indicated wherein the bubbles formed were completely clear and no suspended solid particles were visible in the steam-water interface,

Foaming is particularly apt to occur when certain feed waters enter the boiler and are mixed with the boiler water. The organic matter in one water is then adsorbed by the suspended particles and colloidal matter in the other Water, or vice versa. In either case, surface-activity of both substances is increased bringing about conditions favorable for foam formation.

Two or more types of organic matter of different characteristics may conceivably interact to mutually reduce their solubilities, thus increasing adsorption in the steam-water interface and favoring foam formation.

Another possible explanation for the phenomena involved in foam formation in steam boilers can also be presented. Boiler water ordinarily has soil colloids dispersed therein. In boiler waters that do not contain a heavy concentration of such colloids, especially before softening by addition of alkali, these colloidal particles may be of submicronic size, in which state they would not be apt to be involved in any surface activity at the steam-water interface. However, as electrolyte concentration in the boiler water is increased, the particle size may be increased. Under these conditions the colloids may interact or become partially dehydrated so as to increase their surface activity sufiiciently to enterinto the steam-water interface. It is also possible that more concentration of the colloidal micelles referred to will result in a sufiicient number of them entering the steam-Water interface, whereby the fllms enclosing the steam bubbles would be stabilized to an extent such as to bring about boiler foaming.

The organic foam inhibitors of thi invention may be conceived as forming a colloidal dispersion which enters the steam-water interface to form the characteristic gaseous type of film re-' ferred to hereinbelcw. It is possible that the colloioally dispersed foam inhibitors bring about foam inhibition by simply coalescing the foam stabilizing colloids in the steam-water interface.

The method according to-the present invention involves the addition to boiler water of predominantly hydrophobic surface-active organic compounds whose molecules comprise at least one hydrocarbon chain including at leasttwelve carbon atoms and at least two polar groups each having at least One hydrocarbon chain attached thereto.

The compounds of the present invention are thought to form surface films of the expanded type and, more particularly, of the gaseous type. The reasons for this belief and the manner in which such films of the gaseous type are thought to inhibit foam formation are explained hereinbelow. v

The compounds of the present invention are surface-active, for'while they are predominantly hydrophobic, comprising long hydrocarbon chains, the compounds also include strongly hydrophilic group The kinetic energy of the hydrophilic radicals is thought to induce violent oscillations of the hydrocarbon chains attached thereto, with consequent lateral displacement of the surface-active organic molecules to produce the maximum of lateral displacement effecting the formation of. a surface film of the-gaseous ype.

The pronounced surface-activity of the compounds of the present invention assures that the molecules thereof will penetrate into the steamwater interface. The tendency of the molecules to expand, to be displaced laterally, rather than to associate disperses the molecules throughout the steam-water interfaces of steam bubbles formed in the boiler water. These compounds are dispersed as colloidal solutions from prepared emulsions added to the boiler feed water and/or boiler water so that some foam inhibitor will be present in the interface of each incipient steam bubble. The hydrophobic nature of the thin 'gase eous films formed in such interfaces by the moleculesof the compounds of this invention procludes formation of a layer of polarly oriented water molecules. The emciency of this foam inhibiting surface film is not necessarily depend ent upon exclusive occupation of the steam-water interface by the foam inhibiting compound. The interface may conceivably be shared with strongly surface-active terminally polar substances that may be more or less vertically oriented in this interface. But the net result is the formation of at least patches of a predominantly hydrophobic type of interfacial film wherein the hydration effect is reduced to a. minimum and the electrical charges of the surface film are likewise reduced to a, minimum, thus removing the two repelling influences preventing coalescence of steam bubbles. This hypothesis also explains why even extremely minute quantities of foam inhibiting substances are effective to inhibit foam formation. This effect is surprisingly great, being sufficient to overcome even the strong. foaming tendency induced by water soluble wetting agents.

The foam inhibiting compounds of this invention may also form micelles carrying a charge present invention are those that are most highly surface-active and at the same time have sumcient hydrophilic characteristics to prevent steam volatilization. The hydrophilic and hydrophobic portions of said molecules are else? so proportioned as to not only provide these two important characteristics but also to permit the maximum freedom of movement of the hydrocarbon chains. These molecules are thus permitted to exert to the greatest possible extent their kinetic energy derived from the polar radicals in the steamwater interface whereby maximum lateral displacement and expansion of these and other surface-active molecules in the interface is accomplished. In other words, the most efficient foam inhibiting compound is one that produces a gaseous film of greatest expansion consistent with firm anchorage to the aqueous phase to prevent steam volatilization.

The polar radicals are therefore of the relatively non-saponifiable, non-hydrolyzable type, to enhance their chemical stability under boiler conditions wherein high temperatures and h gh alkalinities obtain. At the same time the polar radicals are sumciently active so that their kinetic energy may produce the desired oscillations of the hydrocarbon chains in the steam-Water interface.

The organic substances according to this invention will continue to inhibit foam formation only as long as they are not chemically modified, adsorbed or volatilized, and, specifically, so long as the hydrophilic radical or radicals are not adsorbed on the surface of colloidal or microscopic particles suspended or dispersed in the aqueous phase, whereby the hydrophilic anchorage is destroyed. Compounds having molecules including relatively strongly hydrophilic polar radicals associated in groups are preferred in the conditioning of boiler waters and boiler feed Waters containing calcium and magnesium salts that are precipitated in the boiler water at some time or other. The reason for this preference is that any adsorption by such precipitated salts of foam inhibiting compounds of the type indicated will not interfere with foam inhibition.

Examples of classes of compounds and of specific compounds according to this invention more effective than the conventional castor oil .emulsion for the prevention of foaming of boiler water are described hereinbelow.

The foam inhibiting compounds of this invention are characterized by the presence of one or more long hydrocarbon chains and of spaced single polar groups or associated or closely associated polar groups the majority of such groups having at least one hydrocarbon chain attached thereto, and the number and length of the carbon chains provided being balanced with respect to the polar groups so that each compound as a whole is predominantly hydrophobic yet contains a sufficient number of polar groups to make the compounds distinctly surface-active.

Compounds on this order may be synthesized from hydrocarbons having a number of carbon atoms equal to that desired in the main hydrocarbon chain of the compound being synthesized. A number of conventional methods on synthesis are available for introducing the desired polar groups and hydrocarbon chains into the hydrocarbon being used as starting material. The most convenient starting material, however, is an organic acid or an ester thereof. In particular, naturally occurring fats, which are glycerides of the fatty acids, may be subjected to suitable reactions to prepare the compounds of this invention. As an example, the preparation tion into the boiler.

of foam inhibiting compounds from castor 0'. or ricinoleic acid will be described in detail hereinbelow. I

Castor oil is the glyceride. of ricinoleic acid and has the following formula: on.- oH,)|-oHoH-om-crr=cncm)r-ooo-om Castor oil is commercially used as a foam inhibiting agent, but its effective life in a boiler is quite short, its efficiency usually being destroyed within five minutes after its introduc- A more efficient foam inhibiting agent having a longer effective life may It will be noted that this compound contains three long hydrocarbon chains each having two spaced ester groups attached thereto, One ester group has attached thereto a hydrocarbon chain containing four carbon atoms while the other ester group has attached thereto a hydrocarbon chain containing three carbon atoms. In other words, the main hydrocarbon chain contains-at least twelve carbon atoms and has attached thereto spaced polar groups each having other hydrocarbon chains attached thereto, the potency of the hydrophobic hydrocarbon chains and the hydrophilic radicals being so balanced that the compound as a whole, While predominantly hydrophobic, still is strongly surface-active. Another foam inhibitor can be made by reacting one molecule of castor oil with three molecules of palmitic acid to form tripalmitated castor oil having the following formula:

A still more eiiicient foam inhibitor may be prepared by reacting two molecules of tripalmitated castor oil with three molecules of ethanol ethylene diamine to form the di (palmitated ricinoleic) ester amide of ethanol ethylenediamine having the following formula:

This compound may also be prepared by condensing two molecules of monopalmitated ricinoleic acid with one molecule of ethanol ethylene diamine, or by first forming the diricinolcic acid amide of ethanol ethylene diamine and subsequently esterifying the latter compound with palmitic acid. In place of palmitic acid any other fatty acids containingat least eight carbon atoms may be used, for instance, lauric acid.

The di palmitated ricinoleic) ester amide of ethanol ethylene diamine may be further reacted with one molecule of cetyl bromide to form a compound having the following formula:

This compound is extremely effective as a foam inhibitor and has almost indefinite eficient life in certain boiler waters. If palmitoyl bromide is used in place of cetyl bromide, there is formed a compound having the following formula: omoHorcH(oocmml)cm-cn=on cm)1-c0o H: I-COCMHM H2 cIra- 0H,)5-0H 0o018E)-cH2-cH=cH- cH,)1-oom1 This compound is also extremely effective in inhibiting foam formation.

Two molecules tripalmitated castor oil may also be reacted with three molecules ethylene diamine to form the di (palmitated ricinoleic) diamide of ethylene diamine having the following formula:

If diethylene triamine is used in place of ethylene diamine, a compound of the following formula is obtained:

The reaction product of tripalmitated castor oil or monopalmitated ricinoleic acid with diethylene triamine may be reacted with cetyl bro- -mide to form a. compound having the following The condensation product of tripalmitated castor oil or monopalmitated ricinolelc acid with di-ethylene triamine may also be reacted with palmitoyl iodide to form a compound having the following formula: CHr-(CHah-CIUOOCuHn)CHz-CH=CH-(CH2)7-CONH All of the above disclosed compounds are eflective foam inhibitors having longefiective lives under-boiler conditions. I:

More than one hydrocarbon chalnmay be attached to each of the polar groups of the foam inhibiting compounds of this invention. Thus the condensation product of tripalmitated castor oil or monopalmitated ricinoleic acid with diethylene triamine may be reacted with heptyl bromide to form a compound having the follow ing formula: CHa-(CHz)a-CH(O0CMHaQ-CHrCl'kUB-(Gfialv-C0NC1H1: v I H:

NCvHm 1: omcmn-cmooommo-cHl-omon-(cHm-o0Nc1m5 If heptoyi bromide is used in place of heptyl bromide, the corresponding 'heptoyl amide is formed.

The reaction product of di (palmitated ricinoleic) ester amide of ethanol ethylene diamine may also be reacted with heptoyl bromide to form di (palmitated ricinoleic) ester amide heptoylamide of ethanol ethylene diamine having the following formula:

NCOOQHU H, omcmlron(oocmmo cm-cmoncmn-o0o A compound'on this order may be prepared from the condensation product of tripalmitated castor oil and triethylene tion with isooctoyl bromide. The resulting compound may be designated as di (palmitated ricinoleic) tetra isooctoyl amide vof triethylene tetra-amine and has the following formula:

ens-(enliven ooouum-om-cu=on-(cum-cone0071115 tetra amine by reac- 'Amides are particularly eflective foam inhibitors. An amide including a great number of amide groups may be prepared by condensing two molecules of palmitated ricinoleic acid with one mole of hexa ethylene heptamine, then reacting the resulting product with two molecules of palmitoyl bromide to render the product suffi- -ciently hydrophobic and finally reacting the product with five molecules of acetyl bromide to completely amidize the product. The final product will have the following formula:

CHr- (CH1);-CH(OOOuHn)CH1-CH=CH-(CH1)rC ONC on,

Hz 1170 0 lS ll H: rlrcocm H: 111C 0 on. 17H:

B: 1 10.0 OH:

H: JJH: IL'C O C H H, CHg-(CHah-CHI(OOCu u)CH:CH=CH-(CH:)1-C ONC 0 on:

If desired, the compounds may be prepared or isolated, by appropriate methods, in more or less pure form. However, the compounds need not be used in pure form. In many instances, substances formed as by-products aid in inhibiting foam formation. This applies to the glycerides of ricinoleic acid formed, for instance, when two molecules of monopahnitated castor oil are condensed with one molecule of ethylene diamine. The resulting mixture of one molecule of di (monopalmityl ricinoleic) ethylene diamide and two molecules of glyceryl di-ricinoleate is a better foam inhibitor than pure di (monopalmityl) ethylene diamide.

The reaction described in the preceding paragraph also illustrates the fact that in the preparation of the fatty acid amides of the type disclosed hereinabove as eflicient foam inhibitors, it is not necessary to react the fatty acids and the amides in stoichiometrical proportions. Various molar ratios may be used.

All the above disclosed compounds are deriv-atives of ricinoleic acid characterized by the fact that the hydroxyl groups of ricinoleic acid have been esterifled and that the carboxyl group has either been esterifled or else subjected to amide formation to attach a hydrocarbon chain thereto. Any fatty acids containing at least eight carbon atoms may be used to esterify the hydroxyl group, while the ester formation or amide formation involving the carboxyl group may be carried with polyhydric alcohols, (erythritol, mannitol) sorbitol, polysaccharides and the like), monohydric alcohols, monoamines, or polyamines, sub-. stituted amines, such as ethylene diamine, ethanol ethylene diamine, diethylene triamine, triethylene tetra-amine, tetra-ethylene pentamine, ethanol amine, diethanol amine, tri-ethanol amine, and

the like. Into the ester, amine and amino-amide groups thus formed additional hydrocarbon chains, long or short, may be introduced, for instance by reaction with alkyl halides such as methyl iodide, ethyl iodide, heptyl bromide or corresponding acyl halides and the like. Instead of esterifying the hydroxyl group, this group may also be etherified by suitable reactions. For instance, one molecule castor oil may be reacted with three molecules cetyl bromide. In any case. the hydrocarbon chains introduced into the hydroxyl groups should contain at. least eight carbon atoms. These hydrocarbon chains may be branched or straight, saturated or unsaturated, and may contain one or more polar groups.

Castor oil or ricinoleic acid may also be reacted with a polycarboxylic acid or an anhydride thereof which will form an acid ester with the hydroxyl groupof the castor oil or ricinoleic acid. The ester thus obtained may then be condensed with a polyamine or an hydroxyl amine to form complex amides or ester amides wherein both the free carboxyl group from the polycarboxylic acid and the carboxyl groups from the castor oil or ricinoleic acid are amidized and esterified. The product need not be isolated, but is an effective foam inhibitor as prepared. Still better foam inhibitors may be prepared by further reacting the products with fatty acids or with alkyl or acyl halides to convert to secondary amines, amides or diamides any amino groups present in the products of the condensation. Such further reactions can also serve to introduce into the molecules one or more long hydrocarbon chains, whereby the molecules are rendered more hydrophobic.

Amides may also be prepared by reacting carboxyl group of castor oil with a polyamine or a poly hydroxyl amine or other substituted amines, such as glucosyl amine, diglyceryl ether amine, triethylene tetra-ethanol tetra-amine, and the like.

Similar compounds may also be prepared from other unsaturated fatty oils, acids or esters, polymers or oxidation product thereof, for instance oleic acid and its esters, hexadecenoic acid and its esters, erucic acid and its esters, linoleic acid and its esters, linolenic acid and its esters, elaeomargaric acid and its esters. Suitable raw materials are, for instance, polymerized castor oil, oxidized castor oil, linseed oil, corn oil, tung oil, soya bean oil, sesame oil, tall oil, fish oil, cottonseed oil, oxidation and polymerization products of such oils, and the like. In the case of unsaturated fatty acids hydroxyl groups may be introduced adjacently the position of the double, bond by oxidation, and the hydroxyl groups may then be esteriiled or etherified or amidized as done in the case of castor oil or ricinoleic acid. The resulting hydroxy acidmay then be subjected to a condensation with polyhydric alcohols or monoor polyamines or polycorboxy acids or-their anhydrides. All these reactions may be carried out in any desired sequence, to form compounds having structures generally similar to those of the above disclosed castor oil derivatives.

The following is an example of the preparation of an efiective foam inhibiting agent from an ordinary fatty oil containing a triglyceride of an unsubstituted fatty oil. One molecule triethylene tetra-amine is condensed with twothirds of a mole of, for instance, olive oil, and the reaction product is condensed, mole for mole, with a fatty acid such as oleic acid. The

i3 resulting condensation product will have the following general formula:

H B. R10 Ola-C :Ha-NH-C :He-N-CrHa-IQO Gill wherein R1 represents the alkyl residue from a fatty acid and R2 represents the alkyl residue from a fatty acid which may or may not be the fatty acid whose alkyl residue is designated by R1. v

This compound may be further reacted with an acyl halide, such as acetyl bromide, to prepare a compound having the following formula:

B ON-CgHe-N-CzHe-N-C :HA-NO CR1 0 O O O R: R: R: R:

where R: is amethyl group.

. water" The foam inhibiting compounds of this application are generally waxy solids. They are introduced in. the boiler water in the form of colloidal dispersions that may be stabilized with tannin, gum arabic, or dextrin. The dosages required are generally quite small, on the order of some few parts per million of boiler water.

The following experiment will serve as an example illustrating the application of the -principles of the present invention to a specific problem.

In this experiment, boiler water with a pronounced foaming tendency, obtained from a district traversed by the Northern Pacific Railroad, was treated in an experimental laboratory boiler having a inch steam valve. The test boiler used for experimental purposes-was of a vertical type, 7 /8 inches internal diameter by inches high, with a 10,000 watt electrical heating unit located at the bottom of the boiler. The total capacity was approximately 20 liters. For test purposes the boiler was operated with the static water level approximately half the capacity of the boiler, or 10 liters. During tests, the rate of steam withdrawal from the boiler was varied between approximately 50. and 350 gallons per hour per square foot of water surface through which the steam bubbles emerge, which is greatly in excess of the rate encountered during maximum steam drawoif in modern locomotive boiler operation, and undoubtedly exceeds the rate encountered in any modern stationary boiler operation. In a modern locomotive the rate of steam drawofi will probably never exceed 60 gallons of water per hour per square foot of water surface through which steam bubbles emerge and the average operation of such locomotives is probablynearer 20 gallons per hour per square foot of such water surface. Therefore, it will be seen that this test procedure, wherein my chemicals completely inhibited foam formation, represented abnormal conditions of steam drawoil which probably will never be attained in practice. Therefore, these tests should indicate the very great effectiveness of my chemicals in inhibiting foam formation.

These tests were normally conducted at 200 pounds boiler pressure. The wide opening of the steam valve, of course, resulted in very rapid reduction of boiler pressure. The boiler water was consequently superheated with respect to the pressure, which tended to induce ex ansion of the water by spontaneous steam bubble fortained in the boiler.

The foaming tendency of this boiler water is indicated by the fact that approximately oneeighth turn of the steam valve caused the expension of the water by formation and retention of steam bubbles therein, until the light or foam filled the boiler. The steam withdrawal was less than ten gallons per hour per square foot of water surface.

Into such water, boiling under 200 pounds per square inch steam pressure in the laboratory boiler, was injected 0.05 gram of the condensation product of cetyl bromide with the condensation product of monopalmitated castor oil and ethanol ethylene-diamine described hereinabove in the form of a colloidal suspension stabilized with dextrin. Foaming was instantly inhibited, even when the steam valve was open wide, representing a rate of steam withdrawal of 350 gallons per hour per square foot of water surface, such that the pressure suddenly dropped to 30 pounds per square inch. Foaming was emciently prevented for over sixteen thousand seconds. The effectiveness of foam prevention was tested periodically by wide opening of the steam valve, to approximate the steam withdrawal of around 350 gallons per square foot per hour of steam emitting'surface.

In general, from a trace to about fifty parts per million of foam inhibiting compounds may be added to boiler water.

The addition of foam inhibiting compounds according to the present invention may be accompanied by addition of the hereinabove men.- tioned depressants which are capable of inhibiting the adsorption of the foam inhibiting compounds on solid particles dispersed in the boiler water. Polycarboxylic acids or their salts such as citric, tartaric, succinic, and like acids are partitularly effective depressantsw From about 0.2 to 10 parts per million or more of carboxylic acids may he addcz.

Soluble compounds of heavy metals, particu larly manganese, thorium, tin, zirconium, moiybdenum, lead, zinc, copper, iron, tungsten, cad mium, mercury, antimony, bismuth, and titanium, may also be added in amounts ranging from 0.02 to 2 or more parts per million. If the boiler feed waters are deficient in soluble silica compounds, solublesilicates may be added, in amounts such as 25 parts per million, to form, with the heavy metal compounds, siliceous micelles having a silica-sesquioxide ratio of at least four to one.

Water soluble wetting agents may also be added to improve the heat transfer and boiling characteristics of the boiler water. The foam inhibiting compounds according to the present invention are potent enough to overcome the strong foaming tendency induced by these wetting agents.

When the saline concentration of boiler water has been built up to a certain degree, continued addition of foam inhibiting compounds may become unnecessary providing sufiicient inorganic micelles are present, 'as the inorganic anions in .conjunction with said inorganic micelles have a 15 boiler water, also to add small amounts of organic foam inhibiting compounds, to prevent sudden foaming due to mutual adsorption of added organic matter and solid particles already present when the boiler water is diluted suddenly.

To boiler waters tending to foam periodically as the concentration of solids therein increases, foam inhibiting compounds may be added periodically, as needed.

As pointed out hereinabove, various details may be varied through a wide range without departing from the principles of this invention and it is, therefore, notmy purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

This application is a continuation-in-part of my application Serial No. 305,959 filed November 24, 1939 (now Patent No. 2,442,768, issued June 8, 1948).

I claim as my invention:

1. The method of inhibiting foam formation in an aqueous gas-liquid system which comprises incorporating therewith a predominantly hydrophobic surface-active organic substance comprising the condensation product of a higher fatty acid and an aliphatic polyamine, said condensation product being further condensed with a higher fatty acid.

2. The method of inhibiting foam formation in an aqueous gas-liquid system which comprises incorporating therewith a predominantly hydrophobic surface-active organic substance having the formula wherein R1 and R2 represent the alkyl groups of higher fatty acids.

3. The method of inhibiting foam formation in an aqueous gas-liquid system which comprises f incorporating therewith a predominantly hydrophobic surface-active organic substance comprising the condensation product of two-thirds of a mole of triglyceride fat with one mole of triethylene tetra-mine, said product being further condensed mole for mole with a higher fatty acid.

4. The method of inhibiting foam formation in an aqueous gas-liquid system which comprises incorporating therewith a predominantly hydrophobic surface-active organic substance having the formula:

R40 0N-C1H NC,H.N-G,H4N0 C RI 0 c c R, R: R4 R4 wherein R1, Ra. Ra, R4, R5, and Re represent the alkyl groups of higher fatty acids.

LEWIS O. GUNDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

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