US2366727A - Method of conditioning water - Google Patents

Description

Patented Jan. 9, 1945 METHOD or ooNnmo'NrNe WATER Lewis 0. Gunderson, Park Ridge, in, asslgnor to Dearborn Chemical Qompany, Chicago, BL, a corporation of Illinois No Drawing. Application April 18, 1M0, Serial No. 330,316

12 Claims. .(Ci. 210-23) Thi invention relates to a method of conditioning water for the preventing of foaming in steam boilers. More particularly, the invention pertains to a method of the nature indicated involving the addition of predominantly hydrophobic organic compounds whose molecules comprise one central polar radical together with a plurality of long radial hydrocarbon chains.

Foaming of boiler water is not, as commonly thought, equivalent; to an accumulation of foam on top ofthe 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 When steam is rapidly withdrawn from a boiler with resultant foaming there is no water surface within the boiler correlated with the water level indiby myriads of bubbles until the thus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 the plane of 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 1 groups, the sulfate, sulfonate, sulfone, sulfamate, amine, amide, carbonate, thiocarbo'nate, carbamate, carboxyl, hydroxyl, thiocarbamate, phosphate, mercaptan, ether and ester radicals. These polar radicals should preferably not be subject to saponiiication under boiler conditions and should further 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 thereto of predominantly hydrophobic surfaceactive organic compounds whose molecules oomprise one central polar radical of a specified nature together with a plurality of hydrocarbon chains grouped radially in reference to the polar' radical.

Another important object of this invention is to provide a method of conditioning boiler water comprising the addition of an organic compound of the type disclosed in the preceding paragraph in which the radial hydrocarbon chains may be either straight or branching and comprise at least 10 or 12 and preferably 16 carbon atoms.

A further important object of this invention is to provide a method of conditioning boiler water comprising the addition of an organic compound of the type disclosed in the next but one preceding paragraph in which the polar radical is selected from a class consisting of the quaternary .radicals, in particular, the quaternary ammonium radicals, the sulfate, sulfonate, sulfone, sulfamate, amino, amide, carbonate, thiocarbonate, phosphate, carbamate, thiocarbamate, carboxyl, hydroxyl, mercaptan, ether and ester radicals, Preferably those which are not subject to saponification under boiler conditions and which are hydrophilic enough to inhibit, largely or completely, volatilization with steam.

Other and further objects of the present invention will become apparentv 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.

Stable aqueous foams are thought to be stabilized by organic substances of a high molecular weight whose molecules include terminal polar or hydrophilic radicals. Soaps are an example. Such substance are considered to be only polarly soluble and hence preferentially adsorbed in the gas-liquid interface with a large hydrocarbon portion (hydrocarbon tail) extendin 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-activesubstances of the nature indicated effect the formation of opredominantly 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 p 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 be-- tween the oil and the metallic surface of the valves. pounds which tend to promote foaming.

Most organic matter naturally present in boiler feed water is too soluble or too slightly surfaceactive 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 sufiicient to effect boiler foaming is obtained when under certain conditions dissolved hydrophilic organic matter having terminal polar radicals 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 sufllciently 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.

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,

The latter substances are polar com-' 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 dispersed gels or sols produced by the interaction of heavy metal salts with silica or alkali silicates. Such inorganic hydrophilic colloids may be stabilized by the addition of organic protective colloids such as dextrine, gelatine, gums, tannin and the like.

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 allon 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 except at intervals when certain of the factors mentioned are causing temporary or more or less permanent adsorption of hydrophilic 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 concen-- trated 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 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 inone 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.

My co-pending application, United States Serial No. 261,683, filed March 13, 1939, entitled "Method of conditioning water, discloses methods of conditioning water for boiling comprising the addition thereto oi predominantly hydrophobic surface-active organic compounds whose molecules comprise widely spaced hydrophilic radicals which are thought to cause horizontal orientation of the molecules in the steam-water interface with formation of an expanded type of surface film, preferably, a gaseous type of film.

My co-pending application, United States Serial No. 305,959, filed November 24, 1939, entitled Method of conditioning water, deals particularly with the inhibition of foaming by the addition to the boiler water of'specified classes of predominantly hydrophobic surface-active orfilms of the gaseous type.

In distinction from the methods of my copending applications the methods according to the present invention involve the addition to.

boiler water of predominantly hydrophobic surface-active organic compounds whose molecules comprise a plurality of long hydrocarbon chains spaced by a hydrophilic radical from which the hydrocarbon chains radiate. If only two hydrocarbon chains are provided in the molecule, the same may be arranged in straight line with each other and the spacing radical, in which case the hydrocarbon chains may be described as terminal with reference to the polar radical.

The compounds of the present invention are thought to form surface films 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.

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 groups. The kinetic energy of the hydrophilic radical is thought to induce violent oscillations of the long hydrocarbon chains, with consequent lateral displacement of the surfaceactive organic molecules to produce the maximum of lateral displacement effecting the formation of a surface film of the gaseous type. The polar groups of different molecules are shielded from each other by the terminal or radial hydrocarbon chains, so that the tendency of the polar groups to efiect a lateral movement of the molecules by causing the long hydrocarbon chains to oscillate vigorously.

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 tion precludes formation of a layer of polarly,

oriented water molecules. The efficiency of.this foam inhibiting surface film is not necessarily dependent 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 iurface film are likewise reduced to a minimum, hus removing the two repelling influences preventing coalescence of steam bubbles. .pothesis 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 most efiicient of the compounds of the present invention are those thatare most highly surface-active and at the same time have sufficient hydrophilic characteristics to prevent steam volatilization. The hydrophilic and hydrophobic portions of said molecules are also 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 steam-water interface whereby maxi- I mum 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 nonsaponifiable, non-hydrolyzable type, to enhance their chemical stability under boiler conditions wherein high temperatures and high alkalinities obtain. At the same time the polar radicals are sufliciently 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 chemicall modified, adsorbed or volatilized, and, specifically, so long as the hydrophilic radical is not adsorbed on the surface of colloidal or microscopic particles suspended or dispersed in the aqueous phase, whereby the hydrophilic anchorage is destroyed.

Examples of classes of .compounds and of specific compounds according to this invention more efiective than the conventional castorpil emul- This hysion for the prevention oil foaming of boiler water are listed herelnbelow.

I. Com ounds containing quaternary groups.

(a) etra alkylated compounds having saturated alkyl chains.

Exam les:

(1 Tetra eetyl ammonium bromide (C ieHaa) NBr (2) Tetra stearyl ammonium bromide (Cit r (b) Tet i g alkylated compounds comprising unsaturated alkyl Exam les:

(1; Tetaa oleyl glmmonium bromide i Hash Br Q (2) Tetra cetylated ricinoleyl ammonium bromide (CHr(CH2)6-CH(oCUES!)-CHQ-CHICH-(CHI) )|NBI Amines.

(a) Dior tri-alkylated amines having saturated alkyl chains. Examples:

(l) Tricetyl amine C 10113:) sN (2) Distearyl amine CiH37)2NH I ((2) Dior tri-alkylated amines having unsaturated alkyl chains. Exam les:

(l Trioleyl amine CisH 3N (2) Triiicinoleyl amine (CHa--(CH2)5-0HOHF-CHrCHlCH-(CflzhhN (3) Di-(9-octadecenc-l2-cetoxy) amine (CH3"(CH2)6-OH(0C15H33)'CErCHZCH-(CHflIhNH (4) Tri-(9-octadecene-l2-cetoxy) amine (CHa-(CHflhCH(OCioHaa)-CH:-CH:CH-(CH|)I)IN III. Amides.

CH3( H2)5 ltHtD-CHPCHiCH-(flz)! (2) Dicetyl sulfate C1eHas-0S0sCisHaa V. Sulfonates. I

Examp s' le (1) Dicetifil sulfonate (cetyl ester of cetyl sulfonic acid) l0 i6 33 (2) Dicetylated ricinol sulfonate (cetylated ricinoleyl ester of cetylated ricinoleyl sulionic acid) CHr(CH2)5-CH(OCreHsa)-CH:CHZCH-(CH2)FS0:

CHr-(CHgk-CH(OCinH3a)CH:CH:CH(CH2)s- VI. Compounds containing a central ester group together with at least 2 radial hydrocarbon chains containing at least 10 carbon atoms apiece.

Examples:

(1) Dralecyl ester of laurio acid I have found that although ester groups attached to short hydrocarbon chains are readily saponifiable under boiler water conditions, ester groups attached to long hydrocarbon chains are veryresistant'to saponification, having a. serviceable life several times greater than that of conventional castor oil emulsions. The hydrocarbon chains should not be long enough to unduly overbalance the polar groups whose kinetic energy causes the lateral expansion effecting the formation of gaseous films.

Th hydrocarbon chains of the compounds of groups I to VI may be either straight or branching.

The foam inhibiting substances of this invention, of which the above disclosed compounds and types of compounds are illustrative examples,

either singly or in various combinations, may be added to boiler waters as alcoholic solutions (or dissolved in other organic solvents), or as aqueous emulsions or dispersions, in amounts from 0.2 part per million 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 i my United States Patent No. 1,911,756, dependent upon the rate of loss of foam inhibiting material I from the boiler by adsorption, agglomeration, decomposition or volatilization, on the efllcacy of the foam inhibiting substance, on the amount 01 water soluble wetting agents and/or other foam producing agents present, and like factors.

There exist considerable differences as to emcacy, stability, adsorption affinities and other characteristics as between the various types of foam inhibiting substances disclosed hereinabove andras between the individual members thereof. Those skilled in the art will at once recognize these difierences and will know how to adapt any particular foam inhibiting substances to their particular purposes. The following remarks will serve as an additional guide to those skilled in the art, to lead them, in. the light of their previous experiences, to the proper application of the principles of this invention to their particular problems.

In any case, the number, nature and arrangement of the radial hydrocarbon chains and more or less central hydrophilic radical is so balanced as to produce a predominantly hydrophobic character coupled with high surface-activity, minimum volatility with steam, and maximum of lateral displacement to produce a gaseous type of film characterized by great expansion.

The addition of foam inhibiting compounds according to the present invention may be accomplished by addition of the hereinabove mentioned depressants which are capable of inhibiting the adsorption of the foam inhibiting compounds on solid particles dispersed in the boiler water. Carboxylic acids such as citric, tartaric, succinic and like acids are effective depressants. From about 0.2 to 1 part per million or more of carboxylic acids may be added.

Soluble compounds of heavy metals, particularly manganese, thorium, tin, zirconium, molybdenum, lead, zinc, copper, iron, tungsten, cadmium, mercury, antimony, bismuth and titanium, may also be added in amounts ranging from 0.2 to 2 or more parts per million. If the boiler feed waters are deficient in soluble silica compounds, soluble silicates may be added, in amounts such as 25 parts per million, to form, with the heavy metal compounds, siliceous micelles having a. silicametal oxide or hydroxide ratio of at lease two 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 salts in presence of inorganic micelles may be described as self-conditioned? against foaming. It may be advisable, however, when adding feed water to such self-conditioning boiler water, also to add small amounts of 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, not my purpose to limit the patent ranted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. The method of conditioning water for boiling which comprises incorporating therewith a tetra alkylated quaternary organic compound each of whose alkyl chains comprises at least 12 carbon atoms.

2. The method of conditioning water for boiling which comprises incorporating therewith a tetra alkylated quaternary ammonium compound each of whose alkyl chains comprises at least 12 carbon atoms.

3. The method of conditioning water for boiling which comprises incorporating a tetra cetyl ammonium halide therewith.

4. The method of conditioning water for boiling which comprises incorporating a tetra stearyl ammonium halide therewith.-

5. The method of conditioning Water for boiling which comprises incorporating a tetra oleyl ammonium halide therewith.

6. The method of conditioning water for boiling which comprises incorporating a tetra cetylated ricinoleyl ammonium halide therewith.

7. The method of conditioning water for steam generation which comprises incorporating with said water a foam inhibiting composition including a surface-active predominantly hydrogeneration which comprises incorporating with said water a foam inhibiting composition in- I cluding a surface-active predominantly hydro rphobi-c organic substance represented by the formula in which R represents a hydrocarbon chain containing at least 12 carbon atoms, R1 represents at least one hydrocaibon chain containing at least 12 carbon atoms and X represents a radiv steam generation which comprises incorporating with said water a foam inhibiting composition including a surface-active predominantly hydrophobic organic substance represented by the formula in which R represents a hydrocarbon chain con- .hydrophobic organic substance represented by phobic organic substance represented by the formula R-X-Rr in which R represents a hydrocarbon chain containing at least 10 carbon atoms, R1 represents at least one hydrocarbon chain containing at least 10 carbon atoms and X represents a radical selected from the group consisting of the N, NH, NCO and NHCO radicals.

8. The method of conditioning water for steam generation which comprises incorporating with said water a foam inhibiting composition including a surface-active predominantly hydrophobic organic substance represented by the formula taining at least 12 carbon atoms, R1 represents at least one hydrocarbon chain containing at the formula R-X--R1 in which R represents a hydrocarbon chain containing at least 12 carbon atoms, R1 represents at least one hydrocarbon chain containing at least 12.carbon atoms and X represents a radicalselected from the group. consisting of the N, NH, NCO and NHCO radicals, said method further including incorporating a depressant with said water.

12. The method of conditioning water for steam generation which comprises incorporating with said water a form inhibiting composition including a surface-active predominantly hydrophobic organic substance represented by the formula R-X-Ri in which R. represents a hydrocarbon chain containing at least 12 carbon atoms, R1 represents at least one hydrocarbon chain containing at least 12 carbon atoms and X represents a radical selected from the group consisting of the N. NH, NCO and NHCO radicals, said method further including incorporating with said water a depressant comprising a. carboxylic acid.

LEWIS O. GUNDERSON.