US2717881A - Inhibition of foaming in steam generators - Google Patents

Description

nited ITION F FOAMING IN STEAM GENERATORS No Drawing. Application December 21, 1946, Serial No. 717,822

7 Claims. (Cl. 252321) The present invention relates to antifoaming compositions which are used in steam boilers and similar steam generators, evaporators, etc., to overcome the tendency of the water therein to foam and hence to bring about the priming of the steam generator or the like.

This application is a continuation-in-part of our copending application Serial No. 436,489, filed March 27, 1942, now abandoned.

it is well known in the operation of steam boilers, such as in electric power plants, railroad locomotives and the like, or in evaporators, that the Water therein, even though initially it shows very little tendency to foam, will, when the amount of total solids therein approaches a relatively high concentration, develop a very decided tendency to foam. When this occurs, considerable quantities of water are physically carried out of the boilers or evaporators with the steam, thus appearing in the steam lines and in the eventual condensate. Such priming has many disadvantages because it tends to contaminate the steam lines, to plug or corrode the valves, and under serious conditions may even impair the cylinders and piston rods of the steam engines, or the impeller blades of turbines in which the steam is used for the generation of power.

Attempts have been made in the past to control this foaming, by excessive blowdown of the boilers or by the injection thereinto of such materials as castor oil, tallow, and the like. While these fatty materiols have some small degree of efiiciency, they are, on the other hand, quite deficient in that they introduce new difficulties which, in some instances, are worse than the conditions they are intended to cure. In the first place, these fatty acids or glycerides are unstable under the conditions existing in the boilers, particularly as the pressure and temperature increase, the high temperatures leading to rapid decomposition of the glycerides, which, if anything, will tend to increase the foaming and priming difiiculties. Furthermore, in many instances certain of the decomposition products thus produced, or sometimes even the materials themselves, have a definite volatility with steam and will, therefore, steam-distil out of the boilers, thus appearing in the steam and in the condensate. This, of course, is also very undesirable. Furthermore, such types of antifoaming agents usually have to be employed in relatively large quantities, adding not only to the expense but also to the inconvenience of operating the steam generators; and those which have a tendency to decompose do so quite rapidly, and hence their effectiveness is of short duration, which therefore necessitates the continual charging into the boilers or other steam generators of relatively large amounts of these older antifoaming agents. Moreover, such antifoaming agents are difiicult to use because the amounts in which they are efficacious are very critical, and any overdosage usually aggravates the difficulty instead of curing it.

One of the objects of the present invention is the preparation of a liquid suitable for the generation. of steam in steam generators and comprising water contates atent however, be of high molecular taining dispersed therein a very small amount of a specific type of compound whereby, when such water is heated to ;the boiling point in a steam boiler or other generator, being thereby evaporated, the concentration of solids therein will not bring about excessive foaming and the resulting priming, the added compound being substantially non-volatile with the steam and stable, so that it will be retained by the Water and neither it nor its decomposition products will appear in the steam and the resulting condensation thereof.

Another object of the invention is to provide antifoaming compositions for employment in steam generation which are readily dispersed in the water from which the steam is formed. Other objects will appear hereinafter.

In accordance with the invention it has been discovered that there is a series of compounds which may be broadly designated as symmetrical unsaturated diacylated polyamines where at least one of the acyl groups contains at least one carbon to carbon double bond and which are of a high order of efliciency when used as antifoaming and antipriming agents in steam generators operating under superatmospheric pressure conditions! These symmetrical unsaturated diacyl derivatives must, weight and should possess certain limiting characteristics as regards molecular size, as hereinafter more fully described.

Fundamentally speaking, the compounds involved in the practice of the present invention can be illustrated by the structural formula:

XC-NY-N-OZ ll I I i (l in which X and Z each represents a group selected from the class consisting of aliphatic hydrocarbon and hydroxy aliphatic hydrocarbon groups each containing at least 10 carbon atoms and at least one of the radicals X and Z containing at least one carbon to carbon double bond, and Y is the residue from a polyamine selected from the group consisting of the monoalkylene diamines and the polyalkylene polyamines. Typical acids from which the acyl groups may be derived are undecylenic (X and/or Z=l0 carbon atoms), oleic, ricinoleic (X and/or Z=l7 carbon atoms), and erucic (X and/or Z=21 carbon atoms).

The total molecular weight of the condensation prod ucts as well as the spatial configuration and the unsaturation of the radicals X and/or Z in the above identified formula apparently has a marked effect on their eflicacy as antifoaming and antipriming agents.

The compounds employed for the purpose of the invention have two terminal acyl groups which are substantially equal as regards the number of carbon atoms in each. These derivatives are, therefore, referred to as symmetrical. In the practice of the invention the total number of carbon atoms in the derivative must be at least 26 carbon atoms.

The preferred compounds for the purpose of the invention are the diacyl polyalkylene polyamines in which the acyl radicals are either oleyl groups or ricinoleyl. These compounds are prepared preferably by reacting oleic acid or ricinoleic acid or their glyceryl esters with a polyalkylene polyamine such as, for example, diethylenetriamine, triethylenetetramine, tetraethylenepentamine,

- or the corresponding polypropylene polyamines, in proportions of about 2 mols of the fatty acid for each mol of the polyalkylene polyamine. The preferred compounds contain from 38 to 50 carbon atoms.

It will be recognized that the polyalkylene polyamines contain both primary and secondary amino groups and that there is a possibility of some acylation of the secondary amino groups. The principal products obtained,

Patented Sept. 13, 1955.

however, are those in which both of the terminal primary amino groups are acylated with very little, if any, acylation of the secondary amino groups.

We shall describe hereinbelow the preparation of several'of the materials, and'while the examples disclose a few of many satisfactory preparative procedures, in most cases the same product may be obtained by more than one route.

The most used method of preparation involved the use of the acid and the amine, in nearly theoretical amounts for the product'desired, and'consisted essentially in the initial formation of the amine salt of the acid, followed by dehydration to theamide by heating. In certain cases, the use of the acid. halide was resorted to in order to introduce an acyl group. In still another very useful procedure, the fatty acid ester was used instead of the acid itself. Thus, while any usual ester can be used, such as methyl, ethyl, glycol, etc., the glycerides of the high molecular weight acids are often very readily obtainable and were the subject of much of'the preparative work.

By' heating the glyceride andth'e polyamine together in the proper proportions, the alkyline amine causes the ester to be split, liberating the fatty acid, which then reacts with theamine to give the amide. Usually, when using the triglycerides, such proportions were used that two of the three acid chains would be split off from the ester and used, and the remaining fatty acid rnono glyceride remained in the product as a harmless byproduct. However, excellent materials have also been formed where the proportion of triglyceride or other ester used was such that all the available acyl chains were used in forming the amide. Indeed, the reaction of theoretical amounts of a polyethylene polyamine and a glycerol monoester has yielded useful products.

The number of different compounds which can be prepared is quite numerous, and while we are giving a large number of examples, we do not wish to be limited to those specifically described nor to the species claimed. These examples are as follows:

Example I A mixture of 19.8 grams of oleic acid and 3 grams of a 60% aqueous solution ofethylenediamine was heated with stirring at 150 degrees C. to 160 degrees C. for 3 hours, after more cautious initial heating for the removal of the bulk of the water. The product, when cool, was a brown wax.

Example 11 A mixture of 141 grams of oleic acid and 36.5 grams of triethylenetetramine was stirred and heated at 150 degrees C. .to 160 degrees C. for 3 hours. When cool, the product was a yellow-brown wax.

Example III A mixture of 20.9 grams of ricinoleic acid and 4.4 grams of triethylenetetramine was heated with stirring at 150 degrees C. to 160 degrees C. for 3 hours. When cool, the resulting product was a dark brown, viscous oil.

Example IV A mixture of 22.6 grams of oleic acid and 4.1 grams of diethylenetriarnine was heated with stirring for 3 hours at 150 degrees C. to 160 degrees C.. When cool, the product was a low-melting brown wax.

Example V A mixture of 28 grams of castor oil and 4.4 grams of triethylenetetramine was heated with stirring at 150 degrees C. to 160 degrees C. for 4 hours. When cool, the product was a very viscous brown oil.

Example VI A mixture of 31 grams of commercial olein (oleo oil) and 5.1 grams of triethylenetetramine was stirred and heated at 150 degrees C. to 160 degrees C. for 4 hours. When cool, the product was a brown wax.

4 Example VII A mixture of 30 grams of olive oil and grams of triethylenetetramine was heated with stirring at 150 degrees C. to 160 degrees C. for 4 hours. When cool, the product was a light brown, soft wax.

Example VIII A mixture of grams of neats-foot oil and 5 grams of triethylenetetramine was heated with stirring at degrees C. to degrees C. for 4 hours. When cool, the product was a brown wax.

Example IX Example X A mixture of 11.3 grams of oleic acid and 4.1 grams of diethylenetriamine was heated with stirring at 150 degrees C. to 160 degrees C. for 2 hours. Then 10.7 grams of commercial stearic acid was added and the process continued another 2 hours. When cool, the product was a brown wax.

Example XI A mixture of 280 grams of No. 3 grade commercial castor oil and 66 grams of triethylenetetramine was heated with stirring at 150 degrees C. to 160 degrees C. for 3 hours. When cool, the product slowly solidified to a light yellow wax.

Example XII A mixture of 23.8 grams of butyl acetylricinoleate and 4.4 grams of triethylenetetramine was treated like the mixture of Example XI. The cooled product was a clear, brown, viscous oil.

Example XIII A mixture of 17.7 grams of glycol oleate and 4.4 grams of triethylenetetramine was treated like the mixture of Example XI. The cooled product was a brown wax.

Example XIV A mixture of 18.1 grams of propylene glycol oleate and 4.4 grams of triethylenetetramine was treated like the mixture of Example XI. When cool, the product was a brown grease.

Example XV A mixture of 6 parts of soybean oil and 1 part of triethylenetetramine was processed by heating with stirring at 150 degres C. to 160 degrees C. for 3 hours.

Example XVI A mixture of 6 parts of raw linseed oil and 1 part of trlethylenetetramine was processed as in Example XV.

Example XVII A mixture of 6 parts of hempseed oil and 1 part of tr1ethylenetetramine was processed as in Example XV.

Example XVIII A mixture of 6 parts of sunflower oil and 1 part of triethylenetetramine was processed as in Example XV.

Example XIX A mixture of 6 parts of sesame oil and 1 part of triethylenetetramine was processed as in Example XV.

Example XX A mixture of 6 parts of perilla oil and 1 part of triethylenetetramine was processed as in Example XV.

Example XXI A mixture of 6 parts of palm oil and 1 part of triethylenetetramine was processed as in Example XV.

Example XXII A mixture of 20.3 grams of erucic acid and 3 grams of a 60% aqueous solution of ethylenediamine was stirred and heated at 150 degrees C. to 160 degrees C. for 3 hours, after more cautious initial heating to remove the bulk of the water. When the product was cool, it was a brown Wax.

It will be recognized that various types of unsaturated fatty acids are present in the various oils described in the examples. Some of these fatty acids contain a single carbon to carbon double bond and others contain two or more carbon to carbon double bonds. In general, those fatty acids containing a single carbon to carbon double bond have given very good results in the preparation of compounds for the practice of this invention.

The number of carbon atoms in the polyamine is subject to variation but is preferably within the range of 2 (e. g., ethylenediamine) to (e. g., decamethylenediamine) for the monoalkylene polyamines and within the range from 4 (e. g., diethylenetriamine) to 8 (e. g., tetraethylenepentamine) for the polyalkylene polyamines.

The unsaturated diacyl compounds of the present invention are much easier to disperse and to handle than the corresponding saturated diacyl derivatives. These compounds, being substantially insoluble in water, ordinarily must be mixed with various other materials to render them readily dispersible, and they preferably should be handled in the liquid state to facilitate such mixing. The higher the temperature. required to maintain the compounds in a fluid form the greater is the hazard to personnel in handling them, and the greater are the chances for thermal decomposition or oxidation of the antifoam compounds and the chances for freezing of lines, pumps, and the like. Furthermore, it has been repeatedly observed that the dispersibility of the antifoam compound is better when its melting point is low. Ease of initial dispersion of the antifoam mixture and stability of the resultant dispersion so that separation of active ingredients does not occur are very important in the use of antifoams. The following data on melting points of the unsaturated diacyl derivatives herein described as compared with saturated diacyl derivatives having the same number of carbon atoms shows that the introduction of a single carbon to carbon double bond reduces the melting point by more than one-half:

RING-BALL SOFTENING POINTS OF DIACYLATED POLYETHYLENEPOLYAMINES Fatty Acid from Which Acyl Degrees Groups are Derived Amine C.

Diethylenetriamine.

IZ-Hydroxystearim- Ricinoleic This data was obtained by the A. S. T. M. method. 13-28-391.

The products hereinabove described, while not ordinarily considered as soluble in water to any great extent, may be suitably dispersed in water or emulsified therewith, so that effective amounts thereof may be introduced and be present in the water Within the steam generator under operating conditions. The emulsifying or dispersing agent used must, however, be of a kind that does not cause foaming, either by itself or by its decomposition products. The compounds may be used conjointly with each other as well as with other known antifoaming agents, such as, for example, castor oil.

The amounts of these high-molecular-weight diacyl derivatives of polyamines which are required are extremely small, and in general one grain per gallon is 6 ample. For many purposes, however, amounts of aslittle as g grain per gallon in the feed water will still give valuable results, and the amounts may be even further reduced. For example, grain per gallon of this type of condensation product will suppress foam in a boiler for from 15 to 20 minutes. Comparing this with the efficacy of castor oil used on the order of grain per gallon, which will suppress the foam for only about 30 seconds to one minute, it is obvious that if one were to use castor oil it would have to be continuously fed into the boiler, with the unavoidable accumulation in the boiler of a lot of soap produced by the reaction of the liberated fatty acids with the alkali present in the water, which would only aggravate the problem. The diacyl derivatives under discussion, however, are quite stable and do not yield undesirable by-products.

A comparison of castor oil with the material described above in Example IV showed that, while 380 parts per billion of castor oil in the feed water permitted maximum increase of dissolved solids in the boiler water from 154 to 237 grains per gallon, the same amount of the material of Example IV permitted the dissolved solids in the boiler water to increase to 2000 grains per gallon without priming or carry-over.

Depending, of course, upon the degree of concentration of solids, the dosage may be varied, but one grain per gallon is about as much as would ever have to be used even under serious conditions, and for many purposes 35 grain per gallon and even less can be used. The process is particularly effective at pressures of about 250 pounds per square inch.

The introduction of the antifoaming compounds of the present invention into the boiler may be accomplished in a number of ways. Thus, the antifoaming compositions may be dispersed or physically mixed with, say, sodium carbonate or some other material used for treating the boiler water and pumped with the feed water into the boiler by means of either an injector or a feed water pump. The compounds may also be dissolved in suitable organic Water-miscible solvents such as alcohols, ethers, ketones, etc., and introduced in small measured amounts into the feed Water entering the boiler. Suitable mechanical measuring devices which will periodically or continuously inject the required dosage of the antifoaming compounds into the feed water may be used, so that the introduction will be more or less in proportion to the steam consumption to which the steam generator is subjected. Another manner of introducing the antifoaming compounds is to form an emulsion thereof in water and then feed said emulsion either directly into the boiler or the feed water lines leading to it. The invention, therefore, is not to be limited by the manner of introduction of the antifoaming composition but rather is to be construed in the terms of the hereunto appended claims.

The preferred active antifoam ingredients are oily to waxy substantially water insoluble substances char acterized by stability in hot aqueous alkaline liquids such are used in locomotive boilers and under the conditions which are present in locomotive boilers. Compositions prepared in accordance with the invention have been demonstrated to be particularly eifective in locomotive boilers under superatmospheric pressure conditions within the range of to 300 pounds per square inch and the corresponding temperature conditions. Tests have demonstrated that these compositions are effective even at the much higher pressure and temperature conditions in stationary boilers for power plant operations, as, for example, superatmospheric pressures up to 1000l500 pounds per square inch.

Apart from the fact that the preferred active antifoam ingredients function under severe conditions where other so-called antifoam materials are ineffective, the reason for the functioning of these materials is not known. It has been proven in tests connected with the practice of this invention that these materials are.very stable to hydrolysis as compared with many other different types of compounds.

The amounts of an antifoam agent employed in inhibiting foam will depend upon several factors, among them the conditions under which the foam occurs, the amount of foam suppression desired, the percent of solids in the foaming liquid, the alkalinity, temperature, and pressure of the foaming liquid, the type and degree of agitation, and the kind of gas present in the gas phase of the foam. It is, therefore, impossible to state any rigid rules for estimating the amount of an antifoam which needs to be used. In general, the anti foam will be added in relatively small amounts, gradually increasing in size, until the foam is controlled to the extent desired.

In the prevention of priming in a power plantor locomotive boiler operating at ordinary pressures, e. g., 250 pounds, it has been found that the effective antifoam compositions of this invention, i. e., those possessing the requisite molecular size for this use, as explained above, are efficient when they are introduced into the feed. water at a concentration of the order of magnitude of 0.01 grain per gallon, based on the weight of active antifoam ingredient. Thus, a boiler operating at concentrations, which is not unusual, would'have- 0.1 grain of active antifoam per gallon of boiler water. Some foam suppression has been obtained with only 6 parts by weight of the active ingredient per billion of water in the feed water going to a boiler. Quantities of from 125 to 500 parts by weight of the active ingredient per billion of water are frequently sufficient merely to improve steam quality. Such proportions have allowed some users to operate with increaseddissolved solids of as much as over the amount permissible without the steam conditioner.

Having thus described the invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A method of generating steam which comprises boiling, under superatmospheric pressure conditions,

Water containing an amount of total dissolved solids tending tov produce foaming and priming and a quantity of diricinoleyl triethylene tetramine, said quantity being sufiicient to substantially inhibit said foaming, and priming,

2. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of dioleyl diethylene triamine, said quantity being sufiicient to substantially inhibit said foaming and priming.

3. A method of generating-'- steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming, and a foam inhibiting quantity of asymmetrical unsaturated diacylated polyamine in which each acyl group is derived from a fatty acid and contains atleast 11 carbon atoms and one carbon to carbon double bond and the polyamine is a polyethylene polyamine containing at least 3 nitrogen atoms andatleast 4 carbon atoms, the total number of carbon atoms in said unsaturated diacylated polyamine being-within the rangefrom 38 to 50.

4. A method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said Water a symmetrical unsaturated diacyl polyalkylene polyamine in which the acyl radicals are from the group consisting of oleyl and ricinoleyl and the polyamine radical is from the group consisting of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, said diacyl polyalkylene polyamine being dispersed into saidwater in an amount sufficient substantially to inhibit the tendency of said water to foam on boilingand boiling said water.

5. A method of. generatingsteamfrom a boiler water having a tendency to foam on boiling which comprises dispersing into said water dioleyltriethylenetetramine in an amount sufficient substantially to inhibit the tendency of said water to foam on boiling, and boiling said Water.

6. A method of generating steam'from a boiler water having a tendency-to foam on boiling which comprisesv dispersinginto said water oleyl stearyl diethylcnetriamine, and boiling said. water.

7. 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 to substantially inhibit foaming on boiling, a symmetrical unsaturated diacyl polyethylene polyamine in which each primary amino group. is acylated with an unsaturated-fatty acidcontaining at least eighteen carbon atoms, and heating the resulting aqueous dispersion to the boiling point, said acylated polyethylene polyamine functioning to inhibit the tendency of said water to foam on boiling.

References Cited' in the file'of this patent UNITED STATES PATENTS 2,328,551 Gun'derson Sept. 17, 1943 2,345,632 Robinson et al. Apr. 4, 1944 2,425,392 Robinson et al. Aug. 12, 1947 2,442,768 Gunderson June 8, 1948

Claims (1)

1. 7. THE METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCY TO FORM ON BOILING WHICH COMPRISES DISPERSING INTO SAID WATER, IN AN AMOUNT SUFFICIENT TO SUBSTANTIALLY INHIBIT FOAMING ON BOILING, A SYMMETRICAL UNSATURATED DIACYL POLYETHYLENE POLYAMINE IN WHICH EACH PRIMARY AMINO GROUP IS ACYLATED WITH AN UNSATURATED FATTY ACID CONTAINING AT LEAST EIGHTEEN CARBON ATOMS, AND HEATING THE RESULTING AQUEOUS DISPERSION TO THE BOILING POINT, SAID ACYLATED POLYETHYLENE POLYAMINE FUNCTIONING TO INHIBIT THE TENDENCY OF SAID WATER TO FOAM ON BOILING.