US2469450A - Process for inhibiting foaming in steam boilers - Google Patents

Description

Patented May 10, 1949 PROCESS FOR INHIBITING FOAMING IN STEAM BOILERS Paul G. Bird and Arthur L. Jacoby, Western Springs, 111., assignors to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application September 19, 1942, Serial No. 459,012

4 Claims.

The present invention relates to antif-oaming 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.

One of the objects of the present invention relates to a liquid suitable for the generation of steam in steam generators and comprising Water containing therein a very small quantity of an N,N'-disubstituted diamide of an organic dibasic acid, 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, these compounds being substantially nonvolatile with the steam and stable, so that they will be retained by the water and neither they nor their decomposition products will appear in the steam and the resulting condensation thereof.

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 evaporat-ors with the steam, thus appearing in the steam lines and in the eventual condensate. Such priming has ma di d tages 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, either by excessive blowdown of the boilers or by the injection thereinto of such materials as castor oil, tallow, and the like. While these fatty materials have some small degree of efficiency, they are, on the other hand, quite deficient in that they introduce new dilficulties 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 diificulties. 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 efiectiveness 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 diflicult to use because the amounts in which they are efiicacious are very critical, and any overdosage usually aggravates the difiiculty instead of curing it.

Applicants have now discovered, however, that there is a series of compounds which may be broadly designated as N,N'- disubstituted diamides of organic dibasic acids, wherein the substituent groups may be derived from aliphatic primary or secondary amines, or amine-containing bodies; in which the dibasie acids may be either aliphatic, aromatic, or aryl-aliphatic, and may contain hetero atoms between the carboxyl groups; and the molecular weight and configuration conform to certain general specifications; all as more fully described hereinafter, which are highly eflicacious to suppress foaming.

The materials employed in the practice of the present invention may be represented by the general formula:

H H R-b'I-O c-X-c od s wherein R and R are aliphatic radicals derived from aliphatic primary or secondary amines or from more complex aliphatic and arylaliphatic amine-containing bodies as, for example, alpha alkylbenzylamines, C-alkylanilines, m-onoacylalkylenediamines, alkylalkylenediamines, partially acylated polyalkylenepolyamines, monoacylpiperazines, monoacylhydrazines, and the like; and X is an alkylene or arylene radical which may contain hetero atoms, so that the group --OCXCO represents the diacyl radical of a dibasic carboxylic acid. The radical -OCXCO- may thus be the residue of a dibasic acid such as adipic, pimelic, suberic, sebacic, azelaic, lora-ssilic, japanic, phthalic, terephtha-lic, and naphthalic. It will be obvious that when the amide linkages are formed product of about 2 mols of hexadecylamine and REFERENCES CITED about 1 mol of azaleic acid, said quantity being T suificient to substantially inhibit foaming and z fig gg i fg are of record m the priming.

4. The method of generating steam which com- 5 UNITED STATES PATENTS prises boiling, under superatmospheric pressure Number Name Date conditions, water containing an amount of total 1 892 857 speumeyer Jan 3 1933 dissolved solids tending to produce foaming and 2304475 P001 1942 priming, and a quantity of the condensation 2:328:551 g ggfi1:1;111'; sepil 1943 product of about 2 mols of hexadecylamine and 10 about 1 mol of suberic acid, said quantity being sutficient to substantially inhibit foaming and priming.

PAUL G. BIRD.

ARTHUR L. JACOBY. 15