US2012809A - Utilizing galvanizer's waste - Google Patents

Description

Patented Aug. 27, 1935 mimems z,012,si

altar. UTILIZING GALVANIZERS WASTE Clarence GpDeiickQSWariI, J., assignor to Westvaeo Chlorine Products, Inc., New

'No Drawing.

N, Y., a corporation of AppIication February-ZG, 1932, Serial No. 595,433

15 clai (mica-97) f lhis invention relatesto utilizing galvanizers" waste; and it comprises a methodwhereingal vanizers skimmings in coarsely broken form are leached to obtain a strong liquor and a residuenearly free of ammoniaand suitable for making zinc chlo-rld, the liquor containing ZnClz and- NI-IiCl in approximately 1:1 ratio being then treated to obtain a crystalline, fusible double salt, either with a 1:2 or a 1:3 ratio, as the case may be, suitable for return to the galvanizers, the additional NHiCl usually'necessary being obtained by an addition of that salt why a subtraction of ZnClz; in the latter event, with the production of an ammoniated zinc chlori'd, ZnC1z.2NI-Is, also usefulas a flux; and itfurther comprises certain I newand useful -flux mixtures, one being a physi cal mixture of said. ammoniated zinc chlorid with the'l:2 or-'l:3 double salt; all as more fully hereinafter set forth and as claimed;

.lngalvanizing, clean pickled iron or steel is dipped into or passed through a body of molten zinc and withdrawn; carrying a film coating of In this operation it is necessary that the zinc. two metals come into contact with clean, truly metallic surfaces and the zinc is kept coveredwith a molten floating cover, to prevent access of air and maintain a bright surface, free of oxide.'

Often the pickled iron is passed through or dipped in a solution offluxing salts prior to contact. The

floating cover or flux layer sometimes contains organic matter, such as glycerin, .to give viscosity and a frothy character; this being'mos't desirable at the point where'the iron enters the bath as it serves to remove moisture without per-- the flux is a molten saline composition and should be thin and free flowing. It is usually prepared from sal-ammoniac; ammonium chlorid. The composition of this salt layer is constantly changing and its fusibility lessening; and when it becomes comparatively infusible, some of it is skimmed oh and discarded and the layer replenished; ordinarily by addition of sal-ammoniac in some way. These skimmings are a galzanizers waste. 7

position but since they contain-ammonia in some They are of complex'and varying 'comform of combination and also chlorids, they may be regarded as containing sal-amrnoniac. These skimmings will be hereinafter called 581 34111- times called sal skimmings.

j mitting spattering of molten zinc. The body of moniac skimmings. In the art they are some-v In the present inventi0n,"the waste is treated.

in certain methodical ways to recover fusible saline materials which can goback foriuse on the "galvanizer's bath or can be used for other purposes.' l

a As statedfthe composition of the floating saline layer or. flux-- is constantly changing, but it always contains zinc chlorid, ammonium chlorid' 5 and-ammonia. Many complex combinations of zinc chlorid with ammonium chlorid and with ammonia are known; and some,for all, of them occurin .thefioating saline layer at. one time or another; 1 I

Several functions are required of the flux .layen, One :is that oil-excluding air, thereby preventing or diminishing'formation' of. zinc oxid.. For thisv purposeiitshould' be freearlowing andof low vis-v cosity. Another is that of dissolving.zinckoxid, if it isformed; it-shouldbera free solvent of zinc oxid but, should attack zinc as little as maybel The various-flux compositions mentioned. vary among each other,v in these respects. And there are really two questionsinvolved: one being maintenance of the floating glayerof the best composi tionas, a compromise o-fthese requirements and, the other isthatof'a composition}for replenish takingup zinc oxid and losing volatiles,- 1 v v As stated; replenishmentin practice isnear- 1y alwaysby sal ammoniacgthis beingsometimes y d ct. a i o of th s i comm c a s t ,v

ment of the floating layer as;it losesfusibility by,

themolten bath, Ammonium chlorid alone, that is notoccurring as such a double salt asfit forms;

with zinc; chlorid, vaporizes without -melting at t smpe irre;p -melten,z n sli and h practice ltherefore wasteful, losses by volatilization being large; Sometimes a physical mixture of powdered skimmings and sal ammoniac" is 3 proach to' maintenance of ideal conditions therein. p I Galvanizers waste; is usually, in the form of hard crusts orflchunkso 'Ifhave .found that by" coarse. grinding, .this nater'ialban 'fb'Q efficiently I I were; rith yiiet-ie ir aie'i se ri d n 5 I chlorid, thereby reducing the amount of HCl" necessary. The leached material is a better and more economical source of zinc chlorid'than the.

original skimmings. 7 I

The leach liquors contain zinc chlorid and ammonium chlorid. These occur in varying pro-' portions, often in about equimolecular-propor: I

tions; in a 1:1 ratio. The liquid is somewhat basic, which may be attributed to the presence of zinc oxid in excess or of ammonia in'excess.

The leach liquors can .begdirectly. evaporated to dryness and fusion, producing a 'fused mixture of zinc chlorid and ammoniumchlorid. Thiscan be run into water-tight cans and allowed to-solidify, directly producing afiuxwhichban. be re-:

turned to the galvanizen. Becauseof the hygroscopic qualities of the material thus'm'ade, how

ever, andforother reasons, it. is not. as satisfactory as various: preparations made as hereinafter specified. It carries not more than one: NH4C1 for each ZnClz; and this is too little-for satisfactory results. In using. it, the galvanizer must ordinarily add sal-ammoniac also. as a physical admixture; and this is unsatisfactory for the reasons stated.'.

In the present invention the leachings are treated in various ways to obtain crystalline compounds better adapted for the galvanizers use than either the concentrated and solidified liquor just described or sal-ammonia'c itself.

Zinc chlorid combines with various proportions of NH3 to formlwhat may be called ammoniated chlorids. A crystallirie'eomposition readily pro duced from the leachin'gsis the di-ammoniated chlorid, ZnCIaZNI-B. This is fusible, freely mo-" bileand forms an excellent cover. It'ha's', however, but little solvent power 'for zinc "oxid. At the temperature. of the molten zinc bath it loses NHs' and'becomes the 'mono ammo- Iniated compound, zi'iClzllflilx. This latter, inso-.

far as covering is concerned, ideal because ofits highmobility. Itis more stable toward decomposition by heat than any of the other com-' positions hereinaftei described; Because of its mobility and low viscosity, at the point where the entering metal passes through-the flux there is not even momentary exposure of molten zinc to the. atmosphere, In respect to covering power,

it is decidedly better than any of" the other fluxes. The mono-ammoniated zinc chlorid. is

however not of a physical character permitting convenient storage, shipment and use. ".But, as stated, the di-ammoniate is'converted into the mono-ammoniate in use.

There are 'severaldouble, compounds of zinc chlorid and. ammonium chlorid. Two that canbe-v conveniently prepared from the leach liquors are ZiiClaZNHtCl and ZnCI23NI-I4C1 which may be. conveniently referred to as: the 1:2. and the 1:3;

double salts.

Both. of these. doublesalts. on, the galvanizers bath are fusible'and form faifcov'erings and both.

have a solvent power for zinc oxid. Both are good'agents for replenishing an existing cover and,

both may be regarded as convenient meansfor correspondingly introducing sal-ammoniae. Naturally the 1:3 salt is better for this purpose than the 1:2.

As stated, I have found that the galvanizers waste can be leached with water to produce a solution containing zinc chlorid and ammonium chlorid in a molecular ratio approximating 1:1. I have found that by evaporating the leachings by heat and continuing the heating and concentration untilthe liquid is at a temperature of about 130 C., on cooling there is a copious deposition of crystals of the 1:2 compound. About 50 percent of the ammonium chlorid present comes out asthis salt, leaving a mother liquor impoverished in ammonium chlorid and relatively richer in zinc chlorid. By taking another portion of leachings and adding ammonium chlorid to obtain a 1:2 ratio and I heatingand concentrating to a final temperature of about 119 C., on cooling a crop of crystals is obtained of another and different composition, the product now being a double salt with a 1:3 ratio. As before, a mother liquid is left poor in ammonium chlorid. Both these salts, the 1:2 and the 1:3, are desirable fluxes for the galvanizersuse; both serve well for replenishment; both are recovered in a physical form which enables easy separation; and both are convenient for packaging and storing, because of theirnonhygroscopic and permanent properties. The 1:2 salt however is not quite as non-hygroscopic as the 1:3. I regard the 1:3 salt as the most convenient and economicalform in which the galvanizer can add replenishing sal-ammoniac.

In making the 1:2 salt without addition of ammonium chlorid to the leachings, the residual liquor'is, as stated, rich in zinc chlorid and it may.

be marketed in concentrated form as a tinning or soldering flux. The same'is true where the liquor has been enriched with ammonium chlorid, either by more salt .added as such or by additions of ammonia and HCl and then the double salt formed and removed. Sometimes, after the separation of the crop of crystals in the way vdescribed, it is economically worthwhile to add ammonium chlorid to the mother liquor rich in zinc chlorid and repeat the operation, obtaining the 1:2 or the 1:3 salt, as the case may be.

It is possible, and often economically worth while, tounite the processes previously described, first adding ammonia to leaching liquors to produce ammoniated zinc chlorid and a mother liq uor relatively rich in ammonium chlorid; and then treating this mother liquor to produce the 1:2 or the 1:3 double salt. Or, the mother liquor from a production of ammoniated zinc chlorid may be used as a source of ammonium chlorid for' production of double chlorids from another portion of lea'chings; either in the 112' or the 1:3 ratio. As will appear'hereinafter, there is commercial utility in certain physical mixtures of an armnoniated.zinc chlorid and a double chlorid,

zinc oxid is the 1:3 doublesalt but it is relatively viscous in molten form. The 1:2 double salt in its physical properties is about the same but it has less reactive power with, zincoxid; sit imports less sal-ammoniac into the bath.

In use. the covering layer loses ammonium chloridand ammonia as vapor anditxsteadily tends toward a compositionrepresenting. zinc. chlorid'with a little ammonia. It is usually dis carded before all the ammoniumchlorid disappears.

I regard di-ammoniated zinc. chlorid-Jasbeing. the best covering addition, all thingsaconsideredfi but Iv regard the 1:3 double salt. as the'best' medium forreplenishment of ammonium chlorid; With di-ammoniatedzinc chlorid and .the 1:2: and the 1:3 salts at 'handthe galvanizer isi'ri a position to control, quite accurately, theficome:

position of his working flux; using each of these individually as the circumstances may. warrant.

But 'forgeneral purposes it is better to supplyhim regulated physical mixtures of. ammoniatedzinc Physical mixtures of: this kind are easy to make, package. and use;-

chlorid and of double salts.

They are permanent in air. The particular: mixture depends somewhat on the galvanizers needs;

When working. at temperatures above i430? C. a mixture of di-ammoniate. and the 1:2 ,saltsin aboutequimolecular proportionsiis good. As za matter of theory, a mixturelof mono-ammoniated zinc chlorid with a composition containingnone molecule ofzinc chlorid and one of ammonium able article. Provision of such an articlealso gives the maximum utilization of the zinc chlorid and ammonium chlorid in the leachings. l Addi tion to the galvanizing bathzof a mixture :of the ter has been evaporated and 22 pounds of the-1:3 1 15 double salt in equimolecular proportion'with respect to zinc chlorid is equivalent in effect'to replenishment'in the fiuxing bathof mono-ammoniated zinc chlorid and ammonium chlorid.

In a specific embodiment of the present invention making the di-ammoniated zinc chlorid,

certain leachings carrying 37 per cent zinc chlorid and 12 per cent ammonium chlorid were alkalizedwith ammonia. ,The amount of ammonia required as gaseous NH3 was 6.25 per cent by 1 weight of the leachings. In using gaseous NH3 it was necessary to add water; theamount being 1.5 timesithe Weight of gas. Instead of using ammonia in gaseous-form, the commercial 25 per cent solution can be added. The alkalizedlliquid was heated to C. The liquid was cooled .to room temperature (about 20' C.) and deposited a crop of crystals of di-ammoniated zinc chlorid, the amount being 31 pounds per pounds' of the original leachings. The mother liquor was drained off and concentrated, finishing atabout' 119 C, On cooling, a crop of crystals of 1:3 double salt was deposited, the amount being approximately 7 pounds per 100 pounds of the original leach liquor. The mother. liquor was reconcentrated to. 119;? and a second crop of crystals of 1:3 double salt was deposited. This procedure could be repeated untilall of the water has been evaporated and 22 pounds of the 1:3 salt obtained, but in practice the volume of the mother liquorswas maintained at-the desired id s'al-ammoniac on the bath.

point by combining the mother liquors of several crystallizations.

In the preceding example the products were diammoniated zinc chlorid and 1:73 double salt In another embodiment 4.5 pounds of NH: were addedto 100'pounds of leachings and'26 pounds.

of ZnCl2.2NH3 obtained, then about 7 pounds of the 1:3 double salt as before. Then by concen-' trating the mother liquor to 1309 C. and cooling,

a crop of crystals of the 1:2 :salt was deposited, the amount being 10. pounds per 100 pounds'of leachings. The mother liquor was concentrated to and'more crystals of the'lz2-salt'recovered as above. This procedure was repeated until about 20 pounds of the 1:2 crystals had been ob-l tained. The'final motherliquor was'returned -to another .portion of leachings., It was possible to.

send'the mother liquor to market. after .the'ordi-- nary purification and concentration as a .tinning' and soldering flux; but this was. not. done in;thisinstance. i 1 a 7 Where it is desired to makeonlyitheulzzsalt; the leachings' may be concentrated directly to a finishingptemperature of.130 C1- Upon cooling, crystals of the 1:2 salt, are obtained, but.no 1':3 salt, l

. Aparticularly desirable and marketable com-- ;position is a physical mixture of one part by weight orthe diammoniated lzinc.v chlorid and four parts by weight of the 1:3 double salt, both.

in dry, coarse, crystalline condition. Thermix' ture can be fused into a cake :butit ismore convenient to-use it in powderedform'fl H It, is possible toremove zincchlorid in the ammoniated form from the leachingsby alkali- .zation withammoniaand concentrate the mother liquor torecover ammonium chlorid. Whereit is;

desirable to obtain a particularly pure zinc chloridwithout too much evaporation of water, itis a de-g sirable expedient to make di-ammoniated zinc chlorid and then fuse this to obtain zinc chlorid;

and NH: which is recycled; being senttback to fresh leachings. Similarl mono ammoniated zinc chlorid can be madefrom thediammoniatedzinc chlorid produced as described by distilling off one-half theammonia; the'expelled ammonia being led,

back to a portion of leach liquor. lilxpulsio riof ammonia is at about 400? C.

In one way of looking at the present invention ac in a form in which it can be more economically employed; and in another, it is returningtothe galvanizer discarded ammoniumv chlorid.

monium chloridwhich may be added in the manufacture of 'fluxes in .the' way described'is more economically utilized than where a fiux is, so to speak, extemporized by a galvanizer in castingsol' 'In the present 'inventionjdiscarded skimmings from the galvanizers are treated to subtract zinc oxid and, returned. The leaching process Iex tracts salines from a residue consisting mainly V of zincoxid; and thesesalines are returned to the galvanizer.

, What'Iclaim is:"f v p 1. In the utilization of galvanizerssal-am l' moniac skimmings byimproved processes where-i1" in "the inert components oi said skimmingsgare separated and removed fromth'e active and de'-" sirable fluxing materials, the stepsv which comprise, leaching said skimmings with water to make a strong leach liquor, adding ammonia to the liquor,,heating somewhat,and cooling to produce a crop of diammoniated zinc chlorid.

, 50L itis furnishing the galvanizers with Sal-ammonia 2. .In the-utilization of fg'alvanizers sa'l-aine moniac skimmings by improved processes wherein the inert components. of said skimmings are separated and removed fromthe activeand desirable fiuxingmaterials, the steps which c'ompriseleach ing said skimmings with v water to make a strong leach liquor, adding ammonia to the liquor; he'at-:

ing somewhat, .cooling to-produce acro-p of diammoniated zinc ."chlorid "with: separation of a mother liquor, concentrating; the m-other liquor and finishingat-aflhigh temperature, and cooling to produce a crystallization ofa zdouble saltof zinc. chlorid andammo'nium'v chloridrv "1 3. .The process of claim-:Zwhereiri the finishing V is at a temperatureof about-119 C. 4: .The process .of claim 2 whereinv the finishingis at a temperatures-of about:1'30 1C. i

'5. I'nv jthe utilization: of sal -ammoniac. skimmings troma galvanizingbath :by improved proc- '5 esses wherein the-inert components of said skimmings are separated and removed from the active. and desirable @fluxing materials, :the steps which compriseleac'hing the. .skimmings .awith water,

. 8. In the process of claim adding ammonia to the leach liquor and separatelyz'crystallizingtherefrom first diammoniated zinc chlorid and then a double chlorid of zinc and ammonium-and returning. said compounds tothe.galvanizingbatha-r I I 6. In the utilizationoff. sal'ammoniac skimi mings from galvanizing'bath's, thexprocess which able 'fiuxing materials, the steps which comprise leachingthe skimmings with waterto obtain a liquid containing Zinc chlorid and ammonium chlorid, increasing the ratio of ammonium chlorid to zinc 5 chlorid in "the liquid "and thereafter crystallizing out a double salt of z i'n'cchlorid and ammonium chlorid.

increasing the 'ratio of ammoniu chlorid to zinc chlorid which comprises subtracting zinc'chlo'rid I by addingammonia and rem as the di-ammoniate salt.

ing zinc chlorid 9. In the rocess; or 7 claim i, ,the themed or increasing "the ratio of -ammo:iiu'm chlorid to zinc chlorid which comprises adding ammonium chlorid to said liquid.

10. In the utilization vor galvanize-s Sa -mi e niac' skimmings, ."the. process which" comprises leaching said skimmings with waterto separate the inert (compon nts from the-active fluXing.

materials and crystallizing said active flinging materials from the leachin gs in .a form suitable for returntothe galvanizingbath 11. In the utilization oi-galvanizersf s'alammoniac skimmings, the process whichcomprises leaching saidskimmings with water to separate the inert components from the active-, fluxing 'materials, separately recovering. diammoniated zinc chlorid and adouble salt o fl zinc chlorid and ammonium chlorid from theleachings in the form of-fgranular crystalsand then mixing ,2 said diammoniated'zinc chlorid and-said double salt, :the mirttm'eibeing suitablev as a galvani'zers flux.

12.In.the ..utilization' of sal-ammoniac skimmings from galvanizersrluxa process of making from such skimmings a material useful in replenishing .theaflux. whichcomprises leaching the skimmings. withwater so as to make a strong solution of zinc chlorid and ammonium chlorid, treating said solution with ammonia, crystallizing'diammoniated zincchlorid from the treated solution with separationlof a mother liquor, crys-' tallizing from the mother liquor a double salt ofzinc and ammonium chlorid-in a molecular ratio of 1:3 and :mixing.:. said..double salt and said diammoniated zinc'chlorid.

i 13. In the. utilizationlof, sal-ammoniac skimmings from galvanizers fiuxa process of making from such skimmingsza material useful in replen ishing the flux. which comprises leaching the skimmings with watertso as to make a strong solutionof zinc-chlorid and ammonium chlorid, treating said solution with: ammonia, crystallizing diammoniatedzinc chlorid from the treated solutionwithseparation of a mother liquor, crystallizing from th emother, liquor a doublesalt of zinc andlammonium chlorid in a molecular ratio of 1:2 and .mixing'said double salt and said diammom'ated zinc chlorid V 14. In theutilization ofsal-ammoniac skimmings from galvanizers flux to.v produce materials useful inzreplenishing the flux, aprocess which cQmpriSesle'aching the .skimmings with water so as'to make" a strong solution of zinc and ammoniumchlorids, treating said solution with ammonia, crystallizing diammoniated 'zinc chlorid from the treated solution. withseparationof a mother liquor, concentrating the mother liquorxbyfheating it until the temperature of the liquor isabout.l19f..C., cooling the concentrated liquor and depositing crystals of a double salt of zinc and ammonium chlorid'in a molecular ratio oil :3 with separation of a second mother liquor, thenconcentrating said second mother liquor at a temperature. about;1'30 "C.:and-: cooling to deposit crystals of a double saltv of .zinc and ammonium chlorid in a molecular ratio'of 1:2.

:15. In the utilization of galvanizers Sal-ammoniac wasteto recover therefrom material useful" asja galvanizers flux, a process which comprises leaching the :galvanizers waste with water to obtaina solutioncontaining zinc chlorid and ammonium chlorid in a molecular ratio approximating .1: 1, concentrating vsaid solution byheating it until the solution is at a temperature of about 130 C.,.cooling the concentrated solution and depositing crystals of a'double salt of zinc andammonium chlorids in a molecular ratio of CERTXFICATE 0F CGRREGTION.

Patent No. 2,012,809. August 27, 1935.

CLARENCE G. DEREK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, first column, line 36, for "powder" read power; and same page and column, line 44, strike out the syllable and words "ter has been evaporated and 22 pounds of" and insert instead diammoniated salt and either the l: 2 or; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the ease in the latent Office.

Signed and sealed this 24th day of September, A. D. 1935.

Leslie Frazer (Seal) Acting Commission of Patents.