US2485378A - Method of inhibiting foaming in steam boilers - Google Patents

Description

METHOD OF INHIBITING FOAMING IN STEAM BOILERS Lewis 0. Gunderson, Park Ridge, 111., assignor to Dearborn Chemical Company, Chicago, 111., a corporation of Illinois No Drawing. Application December 8, 1943, Serial No. 513,478

6 Claims.

This invention relates to a method of conditioning water for the prevention of foaming in waters having a tendency to foam. More particularly, the invention pertains to a method of the nature indicated involving the addition of predominantly hydrophobic surface-active organic compounds comprising either one or more basic nitrogen containing hydrophilic radicals or an oxygen and/or sulfur containing hydrophilic radical or radicals selected from a group of radicals specified hereinbelow. The addition of these compounds is combined with an addition of other surface-active compounds whose molecules comprise either basic nitrogen containing or oxygen and/or sulfur containing hydrophilic radicals. The latter surface-active compounds are selected from the group of compounds having basic nitrogen containing radicals when the hydrophobic surface-active compound comprises oxygen and/or sulfur containing radicals, and from the group of compounds having oxygen and/or sulfur containing radicals when the hydrophobic surface-active compound comprises basic nitrogen containing radicals.

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 When steam is rapidly withdrawn from a boiler with resultant foaming there is no water surface within the boiler correlated with the water level indicated in the conventional water glass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 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. 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 be only such that the bubbles last but a very few seconds after passing 2. tllie plane of the water lever indicated in the water g ass.

I have found that even the slight degree of stabilization of bubbles which suflices to cause foaming can be largely or completely inhibited by the addition to the boiler water of relatively stable, non-volatile, surface-active, predominantly hydrophobic organic substances whose molecules contain hydrophilic radicals which may be either basic or acidic in nature. More particularly, the molecules contain either a plurality of po lar radicals spaced by relatively long hydrocarbon chains or else either a single polar radical or gfoup of closely spaced polar radicals together wth a plurality of long hydrocarbon chains disposed radially in reference to the polar radical or radicals. Although the foam inhibiting effect of organic substances of the type indicated endures for a much longer time than the foam inhibiting effect .of the castor oil emulsions conventionally used for the inhibition of foaming, the effect does not last as long as could reasonably be expected from the relatively stable, non-volatile nature of the substances added.

I have further found that a surprisingly great and prolonged foam inhibiting effect can be obtained by the simultaneous or alternating addition both of foam inhibiting predominantly hydrophobic organic compounds comprising fatty acid ester-amides of hydroxy alkyl amines and surface-active compounds comprising fatty acid esters of polyhydric alcohols such as glyce'rine.

It is therefore an important object of the present invention to provide a method of conditioning water for boiling by infrequent additions of conditioning compounds.

A more specific object of this invention is to provide a method for conditioning water for boiling by the addition of compounds of two different types, one being a fatty acid ester-amide of hydroxy alkyl amine, and the other being a fatty acid ester of a polyhydric alcohol such as glycerine.

Other and further important objects of the present invention will become apparent from the following description and 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.

Stable aqueous foams are thought to be stabilized by organic substances of a high molecular weight and having terminal polar or hydrophilic groups. Soaps are an example. Such substances are considered to be only polarly soluble and hence preferentially adsorbed in the gasliquid 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-liquid interface 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.

Most organic matter 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, particularly colloidally dispersed matter, is completely wetted by the water and therefore displays practically 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 colloidally suspended matter, for instance, colloidal siliceous matter, is not only completely wetted but also enveloped by films of strongly adsorbed water.

It is believed that a bubble stabilizing effect sufficient to effect boiler foaming is obtained when under certain conditions dissolved hydrophilic organic matter having terminal polar groups such as OH, NHz, COONa, and the like, is selectively 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 groups being more or less shielded from the water. The adsorbing wetted particle and the adsorbed hydrophilic organic matter are thereby rendered sumciently hydrophobic to be surface-active while still remaining sufilciently hydrophilic to be able to set up, in steam-water interfaces, films of oriented water molecules.

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.

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.

The amount of adsorption taking place also depends on the pH value and electrolyte concentration in the boiler water as well as on the presence or absence of certain substances hereinafter designated as depressants which are capable of inhibiting adsorption. Such depressants include soluble compounds of the heavy metals, carboxylic acids such as citric acid, and others.

Conditions favoring adsorption do not usually obtain in fresh boiler feed water. Operation prolonged for a shorter or longer time 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 on 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 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 solid particles in the steam-water interface.

I have visually observed such intermittent expansion of boiler water at 250 pounds boiler pressure inside the boiler of a large modern locomotive having several high pressure sight glasses located in the steam dome of the locomotive with two 1000 watt lamps located inside the boiler to provide ample illumination. By these means I have observed how suspended matter, including calcium and magnesium carbonates and hydroxides 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, indicatin 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 effect thought to induce foaming.

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.

The most efficient of the compounds of the present invention are those that are most highly surface-active and at the same time have sufficient hydrophilic characteristics to prevent steam volatilization.

The polar radicals are therefore of the substantially non-saponifiable, non-hydrolyzable 3 type, to enhance their chemical stability under boiler conditions wherein high temperature and high alkalinities obtain.

The loss of foam inhibiting eificiency of the organic substances of this invention within certain periods of time after addition to the boiler water is thought to be due to phenomena occurring within the boiler in which phenomena the compounds are chemically modified, adsorbed or volatilized, and, specifically, the hydrophilic radical or radicals are adsorbed on the surface of the colloidal or microscopic particles suspended or dispersed in the aqueous phase, whereby the hydrophilic anchorage is destroyed.

The term colloidal used in this specification refers to the state of matter dispersed in water as particles having sizes ranging between microscopic and poly molecular. Most of these particles are visible in the ultra-microscope, but when particles approach the polymolecular size represented by primary crystal formation they are actually not visible in the ultra-microscope, although 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 affinity between certain particles and certain polar organic molecules may be highly specific.

It is believed that the surprisingly prolonged foam inhibiting effects obtained by adding to boiler water organic compounds of both of the two types disclosed hereinbelow may be due to a lessened adsorption of the foam inhibiting compounds by colloidal or microscopic particles suspended or dispersed in the boiler water. Possibly the unlike hydrophilic radicals in the two types of compounds have a mutual affinity greater than the adsorptive attraction of the colloidal or microscopic particles.

The probability that the prolongation of foam inhibiting effected by the methods of this invention is indeed due to a lessened adsorption by dispersed particles of the foam inhibiting compounds is enhanced by the fact that still greater prolongation is obtained by a simultaneous addition of depressants. The complex foam inhibiting compounds disclosed hereinabove comprising reactive polar groups often tend to be so avidly adsorbed by dispersed particles that the addition of depressants is ineffective. Apparently the addition of two types of surface-active compounds lessens the adsorptive tendency to such an extent that it can be effectively counteracted by the addition of depressants. Hydrated heavy metal oxide or hydroxide-silica micelles are particularly effective as depressants. They may be created in situ by the addition of soluble heavy metal salts as disclosed in my copending application, Serial No. 261,683, now abandoned, entitled Method of conditioning boiler water.

. Classes of compounds comprising basic nitrogen containing hydrophilic radicals include quaternary ammonium compounds, amines, carbamates and amides. In the amides the influence of the nitrogen apparently predominates over that of the oxygen also present within the same radical.

For-insuring good dispersion of the polyalkylene polyamines (including ethylene diamine) acylated with higher fatty acids, I have found it advantageous to incorporate with these acylated compounds, or with the boiler water to which these compounds are added, wetting agents such as Maprofix (sodium dodecyl alcohol sulfonate, C12H25SO4Na), Oleo Glyceryl Sulfate D (the monooleate ester of glycerine sulfate), Diglycol Stearate S (the monostearate ester of di (ethylene glycol) ether), Flotite (an extract of licorice root), Daxad 21 (a calcium salt of a lignin sulfonic acid) and the like.

A type of compound according to the present invention, which is efficient for the preventing of foaming in boiler water, includes the condensation products of a higher aliphatic acylating compound with the hydroxy alkyl amines containing hydrogen directly attached to nitrogen and a primary hydroxy group disclosed in the Reissue Patent No. 21,530 to Kritchevsky. These condensation products are obtained by the reaction with hydroxy alkyl amines or alkanol amines of higher molecular weight organic acid substances or acid-- ating compounds such as the free acids, esters of such acids such as the monoglycerides, or halides of such acids, or any other derivative thereof which will condense with the hydroxy alkyl amine or alkanol amine to split out water or acids so as to bring about a union of the two molecules. In the case of tertiary hydroxy alkyl amines such as triethanol amine, for example, only esters are formed. In those cases where a non-tertiary alkanol amine, for instance, a mono-hydroxy alkanol amine such as mono-ethanol amine, is condensed with a higher fatty acid (see Examples 1, 2 and 9 in the above mentioned reissue patent), amides and ester amides may and easily do form in predominating amounts.

In the production of these condensation products a reaction temperature must be employed which is sufficiently high to split out water or an acid as a result of the union of the molecules of hydroxy alkyl amine and higher molecular weight organic acid substance or acylating compound. For appreciable speed of reaction it is advisable to employ a temperature range of to C. Within this temperature range, a few hours will usually suffice to carry out the reaction.

The hydroxy alkyl amines or alkanol amines which may be employed in the condensation reaction include mono-ethanol amine, diethanol amine, triethanol amine, methyl diethanol amine, and, in general, primary, secondary and tertiary hydroxy alkyl amines or alkanol amines such as the propanol amines, butanol, amines, ethanol butanol amines, diethanol butanol amines, alkyl derivatives of hydroxy alkyl amines or alkanol amines, ether derivatives of hydroxy amines such as the monoethyl ether of diethanol amine, amino derivatives of polyhydroxy compounds such as 1-amino-propane-diol-2,3, and glycerol mono-amine and the like.

The higher molecular weight organic acid substances or acylating compounds which are condensed with the hydroxy alkyl amines may be selected from a large group including, for example, saturated and unsaturated carboxylic aliphatic, cycle-aliphatic, fatty and hydro-aliphatic acids, including for example, fatty acids containing at least 12 or preferably at least 16 carbon atoms, such as lauric acid, palmitic acid, myristic acid, linoleic acid, oleic acid, stearic acid, ricinolei acid, abietic acid, mixtures Of various acids such as tall oil, mono-glycerides and other esters of said acids with polyhydroxy alcohols, other derivatives of such acids, as for example, the halides such as stearic acid chloride and the like.

Of particular usefulness are the higher molecular weight fatty acids which are derived from oils and fats of animals and vegetable origin and which may be denoted as vegetal fatty acids. It will be understood, of course, that mixtures of these as well as other higher organic acids or higher organic acid substances or acylating compounds may be employed and as such may be condensed with either substantially pure hydroxy alkyl amines or mixtures thereof such as may be found, for example, in commercial products.

It is clear that the hydroxy alkyl amines and the higher fatty acids or the like may be condensed in Varying molar proportions. However, the proportions employed should be such in each instance as to yield a predominantly hydrophobic compound.

2. Q-octadecene-12-palmitate-l-ester of mono- N-cetylated hydroxy ethyl ethylene diamine:

3. 9-octadecene-12-palmitate-l-amido hydroxy ethyl ethylene diamine cetyl ether:

4. 9-octadecene-12-palmitate-l-amido hydroxy ethyl ethylene diamine palmitate:

Thus foam inhibiting compounds according to this invention may be prepared by introducing acyl and/or alkyl radicals into amines such as diethanol amine, triethanol amine, ethanol ethylene diamine and ethanol polyalkylene polyamines. Such alkyl or acyl radicals should contain at least 12 carbon atoms, preferably at least 16 carbon atoms. The compounds thus prepared have the following structures:

In which R represents a hydrocarbon chain preferably containing at least 16 carbon atoms; :1: stands for 0 or a whole number less than 1 stands for H or the COR group.

Formulae Nos. 1, 3 and 5 represent compounds characterized by the inclusion of alkyl groups while formulae Nos. 2, 4, 6, 7 and 8 show compounds comprising acyl groups, and formula No. 9 contains both alkyl and acyl groups. Formulae Nos. 1 and 2 show derivatives of diethanol amine. Formulae Nos. 3 and 4 show derivatives of triethanol amine, and formulae Nos. 5 and 6 show derivatives of ethanol ethylene diamine. Formula No. 7 shows derivatives of ethanol polyethylene polyamines, and formulae Nos. 8 and 9 show derivatives of diethanol polyethylene polyamines.'

A preferred compound within the present invention is the 9-octadecene-12-palmitic ester, l-substituted ethanol ethylene diamine cetyl ester.

Examples of specific foam inhibiting com- Examples of fatty acid ester compounds derived from glycerine include the following:

1. Castor oil.

2. Tri-12-cetyl ether of ricinoleic acid:

CHa-(CHgh-CFHOCmHarD-CHz-CHtCH-(CH2)1-C 0 0 CH2 cmcmn-cmo CmHsa)-CHg-CH:CH(CH2)1-0 o 0 CH omomn-cmo C15Hia)CHzCH:CH(CHz)7-0 o 0 CH2 3. Tri-12-palmitic ester of ricinoleic acid:

OH3(CH2)5CHO OCwH31CHZCH-(CH2)1 C 0 OCH2 CH3(CH2)5CHO o CwH;1CH:CH-(CHz)-:C o o-on CHa(CHz)s-CHO ool6H31-oH=cH oH, 1-c 00-011,

4. Di-stearin (glycerol-1-3-di-stearate):

CHgO C 0 017 35 HOH The foam inhibiting combinations of substances according to this invention may be added to boiler waters as alcoholic solution (or as solutions in other organic solvents), or, preferably, as aqueous emulsions or dispersions containing either one or both of the compounds to be combined in amounts varying from 0.2 part per million of boiler water to as much as 25 parts per million. The addition of greater amounts is possible but not economical. These additions may be made both to the feed water and by injection into the boiler, the latter at intervals, as described in my United States Letters Patent No. 1,911,765, depending on the particular boiler water being treated and the pressure, temperature and rate of steam withdrawal prevailing. It is recognized that various boiler feed waters contain ingredients of quite varying foam forming and adsorbing characteristics which further vary with seasons and with periodic contamination of water by industries and other sources of waste products.

There exists considerable differences as to efficiency, stability, permanence and other characteristics as between the various foam inhibiting combinations disclosed hereinabove. The various combinations may further vary as to efficiency, stability and the like when used with different waters. Those skilled in the art will at once recognize these differences and will know how to adapt any particular foam inhibiting combination to their particular purpose. The

preceding and following remarks will serve as an additional guide to those skilled in the art, to lead them, in the light of the general principles disclosed hereinabove together with their previous experience, to the proper application of this invention to their particular problems.

The foam inhibiting compounds to be added are preferably dispersed in an aqueous emulsion comprising dextrine, gum arabic, tannin, or like dispersing agents prepared either by thorough agitation or by means of a colloid mill. The emulsions may contain 10 per cent foam inhibitors and 20 per cent dispersing agent. These proportions may be varied within wide limits according to whether a pasty or liquid product is desired. If the two compounds of different types to be combined are both foam inhibitors, the two compounds may be mixed prior to the preparation of an emulsion, or separate emulsions of 7 the two compounds may be made which are subsequently mixed in the desired ratio.

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

I In this experiment tender tank water containing approximately 4.6 parts per million of castor oil emulsified with tannin was heated in an experimental boiler having a one-half inch steam valve. The test boiler used for experimental purposes was of a vertical type, 7% inches internal diameter by 30 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 of water 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 drawoff 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 drawoff 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 probably nearer 40 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 drawoff 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 expansion of the water by spontaneous steam bubble formation throughout the mass of the water contained in the boiler.

The feed water was concentrated by boiling until a concentration of solids in the boiler water of 180 grains per gallon was obtained. A total of 31 gallons of this feed water was required. The foaming tendency of the thus concentrated boiler water is indicated by the fact that opening the steam valve by 54 turn raised the level of the boiler water to the top of the boiler glass. ,4; turn raised the level rapidly to the top with consequent carryover.

The tests for foaming referred to hereinbelow were carried out by opening the steam valve wide.

1.50 grams of 10 per cent dispersion in distilled water with 20 per cent dextrine of Q-octadecene- 12-palmitic ester l-substituted ethanol ethylene diamine cetyl ester was injected into the boiler. Foaming was effectively inhibited, although the Water expanded appreciably upon maximum drawofi of steam, as is usual with any foam inhibitor.

After 2420 seconds more tender water was added to restore volume. The pressure dropped to pounds but there was no foaming at this pressure. The pressure was restored to 200 pounds with improved foam inhibition.

After 4870 seconds more tender tank water was added. The pressure dropped again to 100 pounds but there was no foaming. A restoration of the pressure to 200 pounds improved foam inhibition.

After 8350 seconds foam inhibition was still effective. Neither the addition of more feed water nor the drop of pressure caused foaming.

After the boiler pressure had been maintained for 9700 seconds with periodic interruptions when testing, foam inhibition was still effective. More feed water was added, the pressure falling to 100 pounds. A slight increase in expansion but no foaming was noted on testing immediately after the addition of feed water.

After 10,000 seconds foam inhibition was still effective but more expansion of the water was noted upon testing.

After 11,100 seconds foam inhibition was still satisfactory. More feed water was added. The pressure fell to 100 pounds and the water expanded to about of the height of the boiler glass on testing. The pressure was allowed to build up to 200 pounds. At 11,500 seconds foaming was still inhibited but more expansion of the water occurred.

Tests after 11,700, 11,900 and 12,100 seconds, respectively, showed no foaming.

More feed water was added after which a greater tendency of the water to expand at low pressure was noted. The pressure was restored to 200 pounds after 12,550 seconds. Foaming was still inhibited, although the foaming tendency was greater.

Tests after, respectively, 12,800, 12,950 and 13,200 seconds showed no foaming.

More feed water was added. More expansion of the water at low pressure was noted. The pressure was restored to 200 pounds after 13,400 seconds. Foaming was still inhibited although greater expansion was noted.

The test was then interrupted for two days, the water being left in the boiler.

When heat was again applied, the water was very foamy at the initiation of boiling. With all valves closed the level rose to the top of the boiler glass until about 30 pounds pressure developed when the water settled back. However, a slight opening of the valve at this pressure would carry water out of the boiler. At 200 pounds pressure considerable expansion of the water was noted, but no foaming. In other words, foam inhibition was still effective at this time, 2200 seconds after the beginning of the second part of the test.

More feed water was added to restore the volume. The pressure was reduced to 100 pounds and the water became very foamy on testing. After 2600 seconds, when the pressure had again built up to 200 pounds, the water was also quite foamy, expanding to the top of the boiler glass but falling back from this level. Foam inhibition was still effective to prevent carryover.

When after 2850 seconds the pressure fell to 120 pounds, carryover occurred. At 200 pounds boiler pressure the added compounds were also not effective. The total period of effective foam inhibition thus was 16,250 seconds.

That the above recited long period of effective foam inhibition is indeed unobvious is evident from the fact that the inhibiting effect of the conventional castor oil emulsion lasted only about 1 minute in this boiler water. That the effective life of 9-octadecene-12-palmitic ester l-substituted ethanol ethylene diamine cetyl ester, while longer than that of castor oil, still is relatively short under some conditions using certain types of feed water, is shown by the following test.

In a service test on an operative railroad locomotive 9-octadecene-12-palmitic ester l-substituted ethanol ethylene diamine cetyl ester was added repeatedly to the boiler water, in amounts approximating 3 parts per million for a period of about 2 hours, in spite of which foam inhibition continuously became more and more ineffective. A castor oil emulsion was then added in about 18 parts per million. The boiler water settled very rapidly and expansion of water in boiler was much less than when castor oil emulsion alone was used undersimilar conditions.

9-octadecene-l2-palmitic ester l-substituted ethanol ethylene diamine cetyl ester may be prepared by condensing castor oil with palmitic acid. The product is reacted with ethanol ethylene diamine. Condensation may take place involving either the hydroxyl radical or one of the amino radicals of the ethanol ethylene diamine, to yield either an ester or an amide. It is believed that both products are formed. The resulting'mixture is a fairly effective foam inhibitor. To improve its effectiveness the reaction product is cetylated, to form the following two compounds:

12 acid containing at least twelve carbon atoms, and boiling the resulting dispersion, said dispersed substances each being present in an amount of at least 0.2 part per million of boiler water.

2. The method of generating steam from a boiler Water having a tendency to foam 0n boiling which comprises dispersing into said water castor oil together with a fatty acid ester-amide of a hydroxy alkyl amine, said fatty acid containing at least twelve carbon atoms, and boiling the resulting dispersion, said dispersed substances each being present in an amount of at least 0.2 part per million of boiler water.

3. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said water castor oil and a fatty acid ester-amide of a hydroxy alkyl diamine, said fatty acid containing at least twelve carbon atoms, and boiling the resulting dispersion, said dispersed substances each being present in an amount of at least 0.2 part per million of boiler water.

4. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said water castor oil together with a fatty acid ester-amide of ethanol ethylene diamine, said fatty acid containing at least sixteen carbon atoms, and boiling the resulting dispersion, said dispersed substances each being present in an amount of at least 0.2 part per million of boiler water.

5. The method of generating steam from a boiler'water having a tendency to foam on boiling which comprises dispersing into said water castor oil and a fatty acid ester-amide of ethanol ethylene diamine, said fatty acid containing at least sixteen carbon atoms, and boiling the resulting dispersion, said dispersed substances each being presentin an amount of at least 0.2 part per million of boiler water.

6. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said water castor oil and 9-octadecene-12-palmitic ester 1-substituted ethanol ethylene diamine cetyl ester and boiling the resulting aqueous dispersion, said dis- CH3(CHZ)5CH(O O 016E141) CHz-CHI CH(CH2) 7C O O'-OH2CH2NH-CH2CHzNHCmH33 CH3(CH2)5CH(O O C1tHa1) H2CH:CH(C 2)1C ONHCH2OH2NHCHzCHg-O CmHas One Of the compounds has a terminal secondary persed ubstances each being present in an amino radical while the other compound has a terminal ether radical. At the points of condensation the first compound has an ester group and the second compound an amide group. I believe that the superior foam inhibiting properties of the mixture are due to this double balancing effect between the two compounds.

This application is a continuation-in-part of my application Serial No. 330,699, filed April 20, 1940, now abandoned.

As pointed out hereinabove, many details of this invention may be varied within a wide range without departing from the principles of this invention and it is, therefore, not the 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 boiler water having a tendency to foam on boiling which comprises dispersing into said water a substance selected from the group consisting of castor oil and castor oil esterified at its hydroxyl groups with a fatty acid containing at least sixteen carbon atoms, together with a fatty acid ester-amide of a hydroxyl alkyl amine, said fatty 75 amount of at least 0.2 part per million of boiler water.

LEWIS O. GUNDERSON.

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