JUNE, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
bonds. Unequal tension on the double-face liner and on the single-faced board to which it is being applied may cause slippage of the paper after the first contact to give unsymmetrical bonds. Board and box strengths are related to bond structure. Bonds reinforced by adequate shoulders give boards of good strength. Reinforcement of liner and corrugating medium by a thin layer of adhesive extending beyond the shoulders may appreciably increase compression strength of boxes. In tests of shearing strength, nonsymmetry of the single-face bonds is reflected in strengths greaterwhentestsaremadeinone direction than in the Other’ bonds similarly affect board strength.
611
With the background on favorable joint structure provided by studies of the above type, adhesive regulation and machine operation can be guided to advantage by a critical visual examination of board slit to reveal the shoulders of the adhesive joint. Additional applications of this information in the direction of modification of machine operation and of silicate are self-evident. The studies described are being continued to gather further information of value in ensuring most efficient use of silicate as a fiberboard adhesive. 3, 1938. Contribution 177 from the Experim en&.l Station, and from the Experimontal Laboratory, Crasselli Chemioala De partment, E. I. du Pont de Nemours & Company, Inc.
INDIUM OCCURRENCE, RECOVERY, AND USES R. E. LAWRENCE AND L. R. WESTBROOK Grasselli Chemicals Department, E. I. du Pont de Nemours & Company, Inc., Cleveland, Ohio
This paper is essentially a review of the available literature on the subject, summarized on the basis of the authors’ work on analysis and separation of the element from process residues. The history and occurrence of the element are dealt with briefly. The physical and chemical properties are compiled from a survey of the literature with careful selection of the most accurate values based on the latest information available.
I
NDIUM was discovered in the summer of 1863 by Reich and Richter (36) during a spectrographic examination of
crude zinc chloride liquors from a black zinc blend from the Himmelfahrt mine of Freiberg. It was named “indium” from the prominent indigo blue lines characteristic of its spectrum. It has been found in a variety of ores, chiefly in zinc blends (16),in amounts up to 0.2 per cent and in smaller quantities in residues from the distillation of spelter. Romeyn (38)reported that some random samples from the pegmatite dyke in western Utah analyzed 1to 2.8 per cent indium and 0.5 to 1.2 per cent scandium. It is also found associated with cadmium, thallium, and gallium in by-products of the lithopone industry. Other ores in which it is reported to have been found are wolframite, iron carbonate, cassiterite, sphalerite, iron sulfide, pyrrhotite, franklinite, rhodonite, phlogopite, manganotantalite, samarskite, hubnerite, alunite, smithsonite, calamine from Oriela, Italy, and copper from Oker, Germany. It is also present in the solar spectrum. Kulberg (19) stated that indium has been found in a large vein in the western part of the United States to the extent of
The various quantitative and qualitative schemes mentioned in the literature are reviewed briefly, and the procedures used by the authors are outlined. The process developed by the au.thors for the recovery of indium in the form of pure metal from process residues from .zinc operations is described, and references to processes used by others are given. Proposed uses for indium are reviewed, including a number of recently patented applications. 2 ounces per ton in a complex ore containing sulfides of lead, zinc, iron, copper, silver, and gold, which is believed to be one of the largest indium-bearing ore deposits in the world; this may refer t o the pegmatite dyke in western Utah.
Physical Properties The physical properties of indium are as follows:
155’ C . Thermal expayion. (17)I/L d l / d t at 20° C. Hardness (9) Brinell Tensile strenith. 99.71% pure (57), lb./sq. in.
9 x 10-6 29 x 10-4
33 x 1 0 - 6 1 15,980
According to Wyckoff (49, the crystalline structure of indium is given as unit cell, face-centered tetragonal: a, = 4.583 A., Q = 4.936 A., four atoms per unit cell with positions 000,o ‘ / z
1/2, ‘/2
0 l/2,
‘/2
‘12
0.
612
INDUSTRIAL AND ENGINEERING CHEMISTRY
Goldschmidt (12) reports the atomic radius of indium as being 1.569 A. According to Reich and Richter (S6),the Bunsen flame is colored bluish red by indium salts, and the flame spectrum gives two principal lines, 4511.55and 4101.95, which lie close to the violet potassium line. The 4101.95 line, however, is observed only when a large amount of indium is present. The spark spectrum furnishes these two lines, and in addition a number of other lines; the more important are 3256.22, 3039~46,2941~39,2890~35,2710~39, and 2306.20.
Chemical Properties Indium is silvery white, softer than lead, malleable, ductile, and crystalline. When a bar of the pure metal is bent, i t has a characteristic high-pitched “cry” similar to tin. At room temperature indium is stable in dry air; on heating, it burns with a blue flame to indium trioxide (InzOs). It is less volatile than zinc or cadmium but will sublime when heated in hydrogen or in a vacuum. The surface of indium is stable up to a point a little beyond its melting point; above this point a film of indium trioxide is formed. Indium unites directly with the halogens when warm; when heated with sulfur, the two elements unite with incandescence. Indium dissolves slowly in cold dilute mineral acids but more rapidly when heated. Hydrogen is evolved, and a salt of the metal is formed. Cold concentrated sulfuric acid dissolves indium with evolution of hydrogen and separation of anhydrous indium sulfate; with hot concentrated sulfuric acid, sulfur dioxide is evolved; with concentrated hydrochloric acid, the metal rapidly dissolves with the evolution of hydrogen. With nitric acid, nitric oxide is evolved, and ammonia is formed from the reduction of nitric acid. Indium is not attacked by a solution of potassium hydroxide. Acetic acid does not dissolve it, but a solution of oxalic acid does. Chemically, indium resembles zinc in some respects and aluminum and iron in others; it is classified with the latter elements in the usual systems of qualitative separations. It is trivalent in its stable compounds, and its sulfate forms alums with monovalent metal sulfates. Indium also acts as a bivalent element, and some monovalent compounds have been reported. Indium forms amalgams with mercury and alloys with silver, gold, platinum, palladium, lead, copper, and certain other metals. I n the periodic table it is found in Group I11 with boron, aluminum, scandium, and gallium, yttrium preceding it. The fifteen rare earths, thallium, and actinium follow it in atomic weight and number. It has next to the lowest melting point in its periodic group. An important compound of indium as a source for other compounds is the trioxide, prepared by calcining the hydroxide, carbonate, nitrate, or sulfite. The pure trioxide is yellow in color and occurs in two forms: ( a ) yellow, noncrystalline, and compact or powdered mass, soluble in acids; ( b ) yellow trigonal crystals very resistant to acids. The lather form is produced a t high temperatures. Boiling with dilute :sulfuric acid is a good means of separating the two forms.
Methods of Extraction Methods of extracting indium from ores and indium-bearing residues vary in detail, depending on the nature of the ore ,or residue. I n practically all cases final purification and recovery as metal are accomplished by electrolytic methods. Metallic indium can also be obtained by heating the oxide with carbon or in an atmosphere of hydrogen, by heating the oxide with metallic sodium under a layer of dry sodium chloride, and by electrochemical displacement from aqueous solu-
VOL. 30, NO. 6
tions of its salts by metallic zinc. In the authors’ experience (43) the most persistent impurity and most difficult to separate by precipitation is iron, which accounts for the use of electrolytic methods in the final state of purification. Reich and Richter (36) extracted indium from black blend from the Himmelfahrt mine of Freiberg by dissolving the blend in nitric acid and separating the Group I1 metals by hydrogen sulfide and filtration. I n the filtrate the indium was separated from zinc and manganese by repeated precipitation of the indium with an excess of ammonia. The indium hydroxide was then dissolved in acetic acid and precipitated as the sulfide with hydrogen sulfide. Separation from the balance of the iron was effected by dissolving the sulfide in hydrochloric acid, oxidizing the solution with nitric acid, and then adding ammonia or sodium carbonate in small amounts to precipitate a small quantity of indium oxide with the iron. On further addition of ammonia, the filtrate from this precipitate yielded pure indium hydroxide. Winkler (4) treated indium-bearing zinc with a quantity of dilute sulfuric acid insufficient t o dissolve all the metal, and obtained a spongy mass of lead, copper, arsenic, iron, indium, cadmium, and zinc, which was removed by filtration and treated for the recovery of indium. Separation from iron was effected by precipitation of the indium as hydroxide by means of barium carbonate. Winkler also separated indium from iron by treating the solution with an equal amount of sodium chloride and evaporating it to dryness. The product was extracted with cold water and treated with hydrogen sulfide. This process was repeated a number of times to remove all the iron. Bayer (2) separated indium from iron by precipitation of indium as the basic sulfite. Mathers (24) dissolved indium-iron hydroxides free of zinc in hydrochloric acid, added an excess of potassium thiocyanate, and extracted the mixture with ether. I n this extraction ferric thiocyanate was removed. Dennis and Geer (7) separated indium from iron and aluminum chlorides by treating an alcoholic solution of the anhydrous chlorides with pyridine; a colorless precipitate of indium pyridine chloride, InCls.3CsHsN, was obtained, and the iron and aluminum chlorides remained in solution. Thiel (40) purified the oxide by transforming it into the bromide, InBra, and subliming the product in a stream of carbon dioxide; the ferrous bromide remained. The wet-press mud process residue, containing iron, cadmium, lead, copper, nickel, zinc, tin, indium, and other materials, is treated with dilute sulfuric acid a t approximately 200’ C. with constant stirring until all the metallic constituents are dissolved. I n this treatment an appreciable amount of acid-insoluble material accumulates, consisting chiefly of lead sulfate and siliceous matter. After settling, the insoluble portion is separated by filtration and washing. The filtrate containing the indium and other metals is treated with zinc slabs a t an elevated temperature to precipitate the indium and other metals replaceable by zinc. The precipitated metal sponge is removed from the solution and the zinc slabs by filtration and washing. This operation separates the indium from the greater part of the iron present in the mud, particularly if the solution is kept slightly acid a t all times. The crude sponge consists of cadmium and indium, together with some lead, nickel, tin, and copper. It is also contaminated with basic compounds of iron, zinc, and aluminum, together with some silica. About 10 per cent of the washed sponge is reserved; the balance is slurried with hot water, and enough hot dilute sulfuric acid is added to dissolve preferentially most of the cadmium present. This can be accomplished without loss of indium if care is used as to the amount of acid added. After the last portion of acid is added, the 10 per cent reserve sponge is introduced and the whole is slurried. Any indium going into solution in this process will be reprecipitated as metallic
JUNE, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
indium by the reserve sponge added a t the end of the procedure. The sponge from the operation is filtered, washed, dissolved in an excess of hot diIute sulfuric acid, and then filtered to remove lead as the sulfate or metal and other insoluble matter. The filtrate contains principally indium, copper, and cadmium, together with small amounts of nickel, iron, tin, and aluminum. The filtrate from this step is treated with a large excess of ammonium hydroxide to precipitate the indium and to redissolve zinc, cadmium, nickel, and copper hydroxides formed during the neutralization. The mixture is then digested for one-half to one hour to ensure complete precipitation of the indium and its conversion to a dense form which makes filtration and washing easier. After settling, the indium hydroxide, together with any iron hydroxide present, is washed by decantation with hot dilute ammonium hydroxide until free from cadmium and copper, as indicated by chemical tests on the wash solution. ' The indium hydroxide is filtered and washed further, and the filter cake is dried and ignited to the trioxide. This indium trioxide may still contain as impurities iron, lead, cadmium, copper, tin, zinc, calcium, and magnesium from the water used. This impure indium oxide may be used directly for the production of 97 to 98.5 per cent metallic indium by electrodeposition. When high-purity metallic indium is desired, the impure oxide is further treated with c. P. chemicals and distilled water. The process consists essentially in dissolving the oxide in dilute sulfuric acid and filtering off the insoluble portion. T h e filtrate is then treated with Horse-Head zinc shavings to precipitate the indium and other metals replaceable by zinc; the solution is kept slightly acid during this step. The metallic sponge is removed by filtration and washed with very dilute sulfuric acid and finally with water. At this stage the indium sponge should be practically free of iron. The last traces of indium are removed from the filtrate by means of ammonium hydroxide for inclusion with the next batch of impure indium hydroxide to be purified. After being washed, the indium sponge is dissolved in a small excess of sulfuric acid and gassed with hydrogen sulfide to remove the Group I1 metals. After removal of the sulfide precipitate by filtration and excess hydrogen sulfide by boiling, the indium in the -filtrate is precipitated with an excess of ammonia, heated to boiling, washed by decantation with hot dilute ammonia, and filtered. A spectrographic examination of the hydroxide is then made to determine whether further purification is required. The iron in the indium hydroxide a t this stage is usually low enough so that the indium can be completely separated from it by electrodeposition (43). This is carried out in a bath made by dissolving 200 grams of indium trioxide in 600 ml. of water containing 120 ml. of 96 per cent sulfuric acid, .adding 250 grams of sodium citrate crystals, and diluting to 1liter.
-
Analyses of Indium Bearing Residues The qualitative detection of indium is best accomplished b y means of the spectrograph. According to Dennis and Bridgernan (6) as little as 0.0013 mg. of indium can be detected by examination of the spark spectrum of hydrochloric acid solutions. Microchemically (6) it may be detected in the precipitated hydroxides of indium, gallium, and aluminum by reaction with cesium chloride, cesium sulfate, or hexamethylene tetramine. Quantitatively, indium may be determined by several methods of procedure; the one used by the authors on impure metallic indium, indium salts, and process residues from zinc .operations will be discussed.
613
The process residue, containing approximately one per cent indium on the dry basis is digested with dilute sulfuric acid until solution is effected, with the exception of some lead sulfate and insoluble silica and gangue. After filtration of the insoluble precipitate, the filtrate is treated with zinc shavings until all the iron has been reduced and practically all the free acid consumed. While still slightly acid and with an excess of zinc shavings present, the precipitated metals and excess zinc shavings are filtered off and washed with hot water. The precipitated metals and excess zinc shavings are then dissolved in dilute nitric acid, and the solution is treated with an excess of ammonia and ammonium chloride and boiled until only a faint odor of ammonia is noticeable. The precipitated hydroxides of indium, aluminum, iron, gallium, germanium, etc., are filtered, washed with hot 2 to 3 per cent ammonium chloride solution, and then dissolved in dilute hydrochloric acid. The recipitation with ammonia, filtration, and washing are re eateaa second time to remove most of the zinc, cadmium, an3 copper. Further purification from heavy metals is effected by dissolving the hydroxides in dilute hydrochloric acid, adjusting the acidity to 2 normal and saturating the solution with hydrogen sulfide. After the mixture is warmed to coagulate the recipitated sulfides of the Group I1 metals, they are removed {y atration and washed with hydrogen sulfide water. The filtrate is then boiled to remove the excess hydrogen sulfide, treated with an excess of potassium hydroxide, and boiled. The resulting precipitate of indium hydroxide containing some iron hydroxide is filtered, washed, and dissolved in acetic acid; after dilution with water and addition of ammonium acetate, the indium is precipitated as the sulfide by means of hydrogen sulfide. The indium sulfide is filtered, washed, dissolved in hydrochloric acid, and reprecipitated as the hydroxide as before. The h a 1 precipitate of indium hydroxide is then ignited to indium trioxide in a tared porcelain crucible at a proximately 700" C . The purity of the oxide is then determine$ by means of the spectrograph, and any further treatment is based on the impurities shown by the spectrographic examination. The following table (16)shows the reaction of a number of common reagents on solutions of indium salts, which are of analytical interest : Reagent Ammonium hydroxide Potassium hydroxide, sodium hydroxide Organic bases, such as dimethylamine, guanidine, and piperidine Hydroxylamine Ammonium carbonate Sodium carbonate Barium carbonate Potassium ferrocyanide Potassium ferricyanide Potassium chromate Potassium dichromate
Potassium thiocyanate Hydrogen sulfide
Ammonium sulfide Sodium sulfide Metallic zinc and cadmium
Compound and Remarks
White gelatinous indium hydroxide, insol. in excess of reagent White gelatinous indium hydroxide, sol. in excess of reagent, repptd. on boiling or addition of ammonium chloride Quantitativeprecipitation Indium hydroxide Indium carbonate, sol. in excess, repptd. on boiling Indium carbonate, insol. in excess Basic carbonate of indium White ppt. No ppt. Yellow ppt. No ppt. No ppt. Yellow indium sulfide from neutral or slightly acid solns. White indium hydrosulfide or indium-ammonium sulfide Yellow ppt. sol. in excess to colorless soln., repptd. by addition of hydrochloric acid Metallic indium sponge
Tartaric and citric acids prevent complete precipitation of indium hydroxide by the alkalies.
New and Proposed Uses Various uses for indium have been proposed from time to time, and in some instances the practical aspects of the proposed applications have been worked out experimentally. The most practical use for indium a t present appears to be as a constituent of precious metal alloys for jewelry and cast
,
614
*
INDUSTRIAL AND EN(3INEERING CHEMISTRY
dental work, of dental amalgams, and of silver and other alloys to which it is said to impart tarnish resistance. When used a t the rate of 0.5 to 5 per cent in a precious metal alloy (39)containing gold, palladium, silver, and copper, it is said to be of particular importance in controlling or improving color, tarnish resistance, melting range, hardness, and strength. Silver-indium alloys ( I S ) , containing 1 to 25 per cent indium, have been developed for plating silverware to prevent tarnishing. The tarnish resistance increases with indium content. However, it has been stated (10) that 42 per cent of indium is required in silver to inhibit tarnish by alkali sulfides entirely. Moreover, silver alloys containing over 40 per cent of indium are hard and brittle and therefore impractical. The most practical procedure for producing tarnish-proof plated ware is first to plate the base metal with silver and then cover the silver plate with a predetermined amount of indium followed by a heat treatment which cause8 the indium layer to diffuse into the surface of the silver plate and thus form a surface layer of high-indium silver. Indium will amalgamate with mercury, and this property has been utilized in a patent (IS) for a dental amalgam base consisting of 95 per cent mercury and 5 per cent indium. It is claimed that when this base is combined with an amalgamating alloy for dental fillings, indium imparts to the finished filling superior compressive strength, freedom from objectionable setting changes, freedom from objectionable flow under pressure, and exceptional resistance to tarnish. The presence of indium does not interfere with other dental requirements, such as susceptibility to carving for a limited time, absence of granular sandy consistency, and susceptibility to receiving and retaining a polish. When added to glass mixtures (28) containing sulfur compounds, indium oxide imparts a light yellow to dark yellowamber color, depending on the amount of oxide used. One part oxide in two thousand parts is said to give a beautiful yellow color to the glass. Polished indium plate (SO) provides a brilliant reflecting surface. When Wood’s metal is alloyed with about 18 per cent indium @ I ) , the resulting alloy has a melting point of 46.5” C. and has been proposed for use as a molding material. The low melting point, high boiling boint, and high coefficient of expansion of indium indicate that it might find use in high-temperature quartz thermometers or temperature-control equipment. . A British patent (SI) is said to cover the use of indium as a constituent of bearing metal, and it is believed that some of the more important manufacturers of bearing metals are now studying the use of indium in various compositions. The therapeutic action of indium has been studied briefly by Levadite, Bardet, and others (do). .Yon Oettingen (3%) investigated the toxicity and pharmacology of indium compounds, and discovered a peculiar and markedly delayed toxic effect following injections of soluble indium compounds into mice.
Bibliography Auger, Lafontain, and Casper, Compt. rend., 180,376-8 (1925). (2) Bayer, C. J., Ann., 158,372 (1871). (3) Boisbaudran, Ber., 10,92(1877);Compt. rend., 83,636 (1876). (4) Carey and Rogers, J . Am. Chem. SOC.,49,216-17 (1927). (5) Chamot, E. M., and Mason, C. W., Handbook of Chemical MicroscoDy, Vol. PI,New York, John Wiley & Sons, 1931. (6) Dennis and Bridgeman, J. Am. Chem. Soc., 40, 1534. 1549-57 (1918). (7) Dennis and Geer, Zbid., 26,437(1904);Ber., 37,961 (1904). (8) Doran (to Anaconda Copper Mining Co.), U. 8. Patent 2,052,387 (Aug. 25, 1936). (9) Edwards, J . Inst. Metals, 20, 61 (1918). (10) Engineer. Met. Supplement. Feb. 26, 1937. (1)
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(11) Geilmann and Wrigge, 2. anoro. allgem. Chem., 209, 129-38 (1932). (12) Goldschmidt, 2.physik. Chem., 133,397-419 (1928). (13) Gray (to Oneida Community, Ltd.), U. S. Patents 1,847,941 (March 1, 1932); 1,849,293 (March 15, 1932); 1,935,630 (Nov. 21, 1933); 1,959,668(May 22, 1934). (14) Guertler, W., and Pirani, M., 2. Metallkunde, 11, 1-7 (1919). (15) Hartley and Ramage, J. Chem. Soc., 71,533 (1897). (16) Hope, Ross, and Skelly, IND.ENQ.CHEM.,Anal. Ed., 8, 51-2 (1936). (17) International Critical Tables, New York, McGraw-Hill Book CO., 1927-29. (18) JungAeisch, Bull. SOC. chim., [2]31,50 (1879). (19) Kulbarg, H.O.,radio talk on “Indium,” Station WAAB, Dec. 20, 1935. (20) Levadite et al., Compt. rend., 193, 404-6 (1931); 194, 325-7 (1932);Chem. Zentr., 11, 2632 (1932). (21) Little, A. D.Inc., Indus. Bull. 107 (Dec.. 1935). (22) McCutcheon (to Oneida Community, Ltd.), U. S. Patents 1,855,455(April 26,1932); 1,886,825(Nov. 8, 1932) (23) Martini, Mikrochemie, 6,28-33 (1928). (24) Mathers, 2. anorg. Chem.. 40, 1220 (1907);J. Am. Chem. SOC., 29, 485 (1907). (25) Mellor, “Comprehensive Treatise on’ Inorganic and Theoretical Chemistry,” Vol. V, London and New York, Longmans, Green and Co., 1924. (26) Moser and Siegmann, Monatsh., 55, 14-24 (1930). (27) Mott, Trans. Am. Electrochem. SOC.,34, 255 (1918). (28) Murray, IND. ENQ.CHEM.,26, 903-4 (1934). (29) Murray (to Oneida Community, Ltd.), U. S. Patents 1,839,800 (Jan. 5, 1932); 1,847,622(March 1. 1932); 1,965,251 (July 3, 1934). (30) Natl. Glass Budpet, Sept. 22, 1934. (31) Neurath, J., Firm of, British Patent 283,862(Jan. 17,1927). (32) Oettingen, W. F.von, Proc. SOC.Exptl. Biol. Med., 29, 1185-93 (1932). (33) Papish and Holt, 2.anorg. allgem. Chem.. 192,90-6 (1930). (34) Pietsch and Roman, Ibid., 220,219-24 (1934). (35) Putnam, Roberts. and Selchow, Am. J. Sci., 15,423-30 (1928). (36) Reich and Richter, J . pralct. Chem., 89,441; 90, 179; 92, 480 (1863). (37) Roberts-Austen, Proc. Rom. SOC.,43,425 (1888). (38) Romeyn, J. Am. Chem. SOC.,55,3899-3900 (1933). (39) Taylor (to Spyco Smelting & Refining Co.), U. S. Patents 1,965,012 (July 3. 1934): 1.987.451 (Jan. 8. 1935). (40) Thiel, Z . an&. Chem.,’ 39, 119 (1904);40,286 (1905);Ber., 37, 176 (1904). (41) Warin& EnQ. Mining J . , 129,64 (1930). (42) Warren, E.B., private communication, 1937, (43) Westbrook, Trans. Am. Electrochem. Soc., 57, 289-96 (1930). (44) Winkler, J . prakt. Chem., 94, 1, 95, 414 (1865);98, 344 (1866); 102,273 (1867). (45) Wyckoff, R. W. G., “Structure of Crystals,” A. C. S. Monograph 19A,2nd ed., supplement for 1930-34,New York, Reinhold Pub. Corp., 1935. RECEIVED January 19, 1938 Presented as part of the Symposium on the Lass Familiar Elements, the Second Annual Symposium of the Division of Physical and Inorganic Chemistry, American Chemical Society, held in Cleveland, Ohio, December 27 to 29,1937.
FIGURE
1.
DISTILLERY OB' IilRAM WALKER
M. E.
Mili Fermenters s. Stills A . Adrniaitratioa B . R"tt1i"K
DI.
& SONS, he., PEORIA, ILL
Solid csibon dioxide
CP. Cereal by-products
If. n i g h wines W . Weiehouues, eight in t w o
TOW
C. Cistern and shipping BL. Bsiie!ing M S . Mechine shop C. Garage
DISTILLERY BY-PRODUCTS L. c. COOLEY 1438 Kingston Avenue, Chicago. 111.
ISTII,I,ERY by-products from a grain distillery are cnrhun dioxide, which will be reserved for separate
treatment, and stock food or distillers' dried grains. The importance of the latter can be judged by the output and value. The output of the plant to be described here is approximntely 150 tons daily. To produce such a quantity calls for an investment in buildings and machinery of almost 82%000,000, a steam consumption of nearly 4,500,000 pound? daily, and a water consumption of around 5,500,000 gallons. The amount of raw material (corn, rye, and malt) required in n distillery producing 150 tons of feed daily is 20,000 bushels o r 560 tons, and the alcohol yield is from 100,OOO to 104,000 gallons of 100-proof alcohol ( I , 2 ) . The value of distillers' dried grains yarizx from $17.00 to $30.00 per ton.
Historical Review Prior t o prohibition the methods of reeovering values from grain distillery wastes were, in principle, much like the rncthods used today except that the machinery now has n greater capacity per unit, takes a little less steam and water, and requires less labor. In order to removc ialoohol from the fermented grain mash, dealcoholizing eolurnns or beer stills were and are now used, with open steam jets in the bottoms and condensers at the tops for alcohol and water vapors. The condensed steam, spent grain, and most of the mashing water Came out of the bottom of each beer still at a concentration of 615
about 4.8 to 6.0 per cent total solids (suspended and dissolved) and ran to the sewer or WBS treated in one of three ways. The waste, called "distillery slop" or "spent mash," was often screencd, and the screenings were sold wet or dry for stock feed,or the liquid from the screenings was evaporated to a sirup and added to the partially dried grains for further drying. Thirdly, and as practiced in many distilleries, the water and spent grains were run down through troughs to which were chained thousands of head of cattle being fattened on the trip from the western ranges to the market. The objection to dumping spent mash in a stream is that it seriously depletes the oxygen there and thus destroys fish. Where the waste material becomes deposited on the banks or on a sand bar, decay sets in and the odor is objectionable. In cases where it was permissible to dump the liquid from the screenings into the sewer or where the sanitary authorities attempted to stop all dumping, the arguments which followed involved the question of what it cost to evaporate and dry the residue in the liquid. If the liquid could be dumped into the sewer, leaving the screenings to be dried, nearly 85 per cent of the steam cost could be saved and practically all of the wat,er cost. The investment for building and equipment would be cut in half, the labor saving would be about 70 per cent, and the amount of feed produced would be approximately half. Since repeal local boards of health ofteu prohibit the f e d ing of dairy cattle with spent. mash hy the old methoils so
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VOL. 30, NO. 6
that distillers are forced to assume the expense of recovering all the solids. Except in very small distilleries or where the laws do permit dumping into streams or large bodies of water, it is necessary to screen, evaporate, and dry the solids in the spent mash.
der of the screen length the baffles scrape the partially drained grain over the screen so that it finishes draining as much as possible before it falls off the end of the screen into a deep copper hopper. Each screen is nearly 8 feet wide and 25 or 30 feet long, and is made of stainless-steel plate with 1-mm. holes
Modern Practice
throughout its length. The liquid which passes through the screens runs down the bottom of the sloping box on which each screen is supported and passes out at the end through a copper drain to a storage tank on the second floor. The feed to the screens may be a maximum of 43,000 gallons per hour, equivalent to 1070 bushels of grain. The normal load is about 30,000 gallons hourly. The total solids in the spent mash vary in amount with the method of preparing the mash. Ground grain is mashed with warm water after cooking and cooling @),or a portion of the warm water may be replaced with cooled screen effluent from the screen effluent storage tank up to 30 per cent of the volume of a fermenter. Using screen effluent increases the proportion of solids in spent mash up to possibly 6 per cent. Effluent from water mash may have as little as 4.5 per cent. The solids retained on the screen are grain hulls, proteins, unfermentable substances, and some dead yeast cells. The temperature of the spent mash leaving the stills is approximately 220" F. so that it flashes as it is discharged from the feed pipe into the screen weir box and gives off a large amount of vapor during its passage down the screen. For this reason, above each screen is a, transite hood connected to a fan-exhausted ventilator. The liquid leaving the screens cools to 196" or 190" F. and contains about 3.6 per cent total solids. The original screens were made of thin Muntz metal plate but were replaced by stainless steel.
Dne of the most modern and best equipped plants for the recovery of by-products from grain distillery waste is the Cereal Products Division of Hiram Walker & Sons, Inc., a t Peoria, Ill. (Figure 1). The building is three stories high, built of steel, concrete, and brick and consistent in architecture with the design of the whole distillery. The equipment is arranged at elevations and in the sequence indicated by the flow sheet (Figure 2). The spent mash enters the system by a pipe shown in the upper left-hand corner of Figure 1. The stillhouse where the spent mash originates has four beer stills and a three-chamber periodic still. Each still is equipped with a walking-beam pump with variable stroke. The cylinders are arranged in pairs, each pair having a motor and speed reducer. One cylinder of a pair is used to pump beer feed to the top of the column; the other, possibly with a slightly different length of stroke, removes the spent mash from the bottom section of the still and forces it through two copper pipe lines approximately 400 feet long to the top floor of the cereal products building.
Screens On the top floor of the cereal products building are five sloping screens set in boxes which are provided with a distributing weir a t the top or head end into which the mixed liquid and solid spent mash is fed by a pipe from a three-way bronze cock; there is one of these cocks in each of the two mains. I n this way feed can be taken from either main to one screen. The spent mash overflows the weir and passes down the screen; it is restrained from rushing down too fast by moving baffles which impede the flow during the first 5 or 6 feet of its passage and form small pools back of each moving baffle so that the liquid has time to drain through. Over the remain-
Presses After the drained grain, with about 80 per cent water, has fallen into one of five copper hoppers, it feeds directly into one of five rotary presses erected on a balcony just under the second floor. The presses are built of a special alloy with stainless-steel perforated plates and rotate a t about 5 r. p. m. although the speed range is from 1 t o 7 r. p. m. A 10-horse-
JUNE, 1938
INDUSTKIAI, AND ENGINEEIUNG CHEMISTRY
power motor is used. The capacity varies with the dryness of the output. A t 80 per cent water these presses take 9000 pounds each per hour and put out 6300 pounds containing 65 per cent water. Capacity is controlled by the dryer operator who changes the speed reducer to as many points as are required to keep the hoppers nearly full without flowing over on the floor. The feed to the screens and hence the amount of solids to the presses is not necessarily uniform in solid content because of shutting down or starting some of the stills during the operation of the others. Each point on the press speed reducer is equivalent to an output of nearly 900 pounds of wet grain. The liquid effluent contains about 2.8 to 3.1 per cent solids a t 180" F. and is run into a tank and mixed with recovered grain from the dryer dust collectors into a slurry and pumped over the sereens again.
Centrifugals If the process were conducted without evaporators but merely with screens and dryers, the next step would be for the pressed feed to fall through a chute into a dryer. However, the need for complete recovery of all the solids in the spent mash calls for evaporation of the efauent from the screens. During the building of the new distillery, development work on waste recovery was carried on a t a temporary distillery in Peoria where methods of waste disposal were studied by the research department. It was finally discovered that by passing the screen effluent through centrifugals,a small percentage of material could he removed which wonld Ieavc a clarified
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effluent in such condition that its viscosity when evaporated to ahout 50 per cent solids was not greatly different from that of screen effluent evaporated to 25 per cent solids but without centrifuging. The use of centrifugals is one of the most progressive steps which has been taken in the recovery of distillery wastes. Instead of sending sirup to the dryers with 25 to 27 per cent solids and the balance water, sirup is mined with wet grain starting with 42 and as high as 60 per cent solids. The steam required to evaporate a pound of water in the dryers is ahout 1.3 pounds. In the evaporators ahout 0.26 pound of steam is required to remove a pound of water under the most favorable conditions, and 0.4 pound a t other times; therefore it pays to concentrate the sirup as highly ss possible in the evaporators and leave less work to be done in the dryers. This ideal is accomplished by centrifuging the screen effluent before evaporating it. There are twelve centrifugals. Eight of them operate a t 800 r. p. m. with ?&horsepower motors, and four operate a t 900 r. p. m. with 25-horsepower motors. The centrifugals are constructed with 40-inehdiameter bronze baskets without perforations and with stainless-steel shells (Figure 3). The bulged head of the overhead eonstant-level feed tank can he seen near the top center. In Figure 4, on top of the centrifugal a horizontal shaft is shown a t the right with two pairs of lock nuts and a handwheel. This is the skimmer which removes the t.hin layer of fluid from the sludge cake after a hatch is spun. The large handwheel at the left raises or lowers the discharging plow which is swung into or ont of the cake by the short lever. Feed to the centrifugal is controlled hy the valve and long handle shown near the center
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VOL. 30. NO. 6
lengthened slightly. Normally a centrifuge is run ahout 60
pan condenser; the amount of water is controlled by a 1%
minutes, including time for bringing it up to running speed,
inch gate valve and is varied only enough to maintain as high or low a vacuum and consequently as high or low a temperature in the finishing pan as is required to keep the viscosity of the sirup from increasing too much for the evaporative capacity of the pan. One of the water rate charts has B pressure-recording pen. The two outside charts are threepen charts. One pen shows the steam temperature in each fist-effect steam chest, one pen shows the rate of flow of steam, and the third pen shows the rate of flow of liquid to each f i s t effect. In the name plate above each outside chart is a small dial showing the reading of the integrator of the feed meter. Eearly on a level with the clock are two charts with two pens each. One pen gives the temperature of the vapor to the third-effect condenser and the other the temperatiire of the condenser leg pipe. Figure 6 shows the finishing pan, condenser, and panel board. On the vertical center line and near the hottom of the panel is a recording ammeter by which the operators accurately judge the condition of the sirup. The six switch panels and lights above the ammeter control the operation of t r o cleaning-fluid pumps, the main agitator motor for the finishing pan, the water supply to the finishing-pan condenser, and two pumps for transferring 25 to 30 per cent sirup from either third effectto the finishing pan. Mounted on the finishing pan is a large Bourdon gage indicating vapor pressure in the finishing-pan steam chest, and near the ladder is a mercury U-tube for indicating vacuum or pressure. This gage is piped to several parts of the finishing pan, catchall, condenser, and third effects in order to study pressure conditions when l e a b or other troubles are suspected. The feed entering the triple effects has about 3 or 3.2 per cent solids, and the concentration in each body is about 4.5, 8.0, and 25 per cent, respectively. The operating teinperatures are first-effect steam 250" F., vapor 225', secondeffect vapor 195', third-effect vapor 125'. The maximum steam consumption when running both triple effects and
braking down after !illing, and then dumping. The cake of sludge accumulates on the horizontal ring baffles and against the wall of the basket. After the feed is shut off a few minutes, running brings a layer of thin slop to the surface which is siphoned off by a pipe. Then the speed is reduced by push-hntton control to about 50 r. p. m. for unloading. In fact, the momentum of the load is used to keep the basket revolving during the unloading period so that the operator merely jogs the switch occasionally to keep the basket turning a t the right speed while he manipdates the unloading plow which reaches into the cake and removesthe sludge to the open center of the basket. The sludge, which contains about 80 per cent water, falls to a brass conveyor and is later mixed with dry feed and sirup. The effluent from the centrifugals, having changed in solid content from 3.7per cent (screen effluent) down to about 3.2 per cent, has also cooled to about 150' or 160' F. and is stored in a copper tank on the second floor, which is provided with a remote level-reading gage.
Evaporators The evaporator plant consists of six cast-iron bodies with copper tubes, tube sheets, and central downtakes, and is erected on the third floor. Final concentration is accomplished in a cast-iron 6nishing pan equipped with a mechanical circulator in the central downtake, and with copper tubes and tube sheets. The vapor piping is so arranged that the six bodies can he operated as two triple effects, the finishing pan being heated by direct low-pressure steam or by vapor from either first effect or by both. When the load from the stills is light enough, the bodies can be operated as a quintuple effect, usin. one or both first effectsto heat the second effect. The finishing pan is heated in the same manner as when operating with two triple effects. Another advantage of the quintuple effect is that it saves water as well as steam, since only one condenser needs to be operated. Condenser water from the two third effects at about 90' F. is pumped to the finishing-pan condenser, the great quantity (about 3000 gallons per minute) overcoming the disadvantage of the high injection temperature. The temperature rise is ahout 20" to 25" F. The two condensers on the triple effects have steam-jet air ejectors which use about 400 pounds per hour of 250.pound pressure steam in two stages. KO jets are used on the finishing-pan condenser. The use of air ejectors saves a total of about 1 5 N gallons of water per minute. Four technically trained operators work in three shifts, so arranged that one man works 6 days and is off 56 hours. I n this manner the evaporators are always being operated or cleaned throughout a 7 d a y week. Operating control is made positive and simple by indicating and recording thermometers, and by effluent and steam flowmeters arranged on a panel hoard standing near the first effects (Figure 5). On the vertical center line below the clock is a two-Den chart which records the temperature of the water into ind out of the condenser on the finishing pan. At each side are liquid-level gages showing the level of screen effluent and of clarified screen effluent. On each side of and between the liquid level gages are ten small panels with starting and stopping buttons and indicator lights for the feed, condensate, and transfer pumps. In the two outside glass-covered circles are the integrators showing total pounds of condenser water to each tripleeffect evaporator, known as the north side and south side. Above in the next horizontal row are four charts. The two nearer the center show the rate of flow of water to each condenser. No rate isshown to the finishing-
FIGURE 5. EVAPORATOR GAQEBOARD
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INDUSTRIAL AND ENGINEERING CHEMISTRY
finishing pan is 132,000 pounds of steam per hour, and the evaporation per pound of steam is about 2.3 pounds, feeding clarified screen efluent a t 140" F. When running quintuple effect, the evaporation per pound of steam is about 3.5 pounds, and the amount of steam used is 60,000 pounds per hour. These figures apply when evaporating clarified screen effluent from bourbon mashes which are mostly of corn with but little rye. On all-rye mash, which is seldom run, the operation is much more difficult; the screens have less capacity and the viscosity rises in the evaporators with small increases in concentration. Occasionally mixtures of corn and rye are used with rye slightly in excess, and then the operation of the equipment is not badly upset, although reduced in capacity. The operating conditions when running as a quintuple effect are steam 244" F., first-effect vapor 226", second-effect 216 ", third-eff ect 194", f ourth-effect 176 ", fifth-effect 128". Vapor is being taken from the first effect to the finishing pan a t this time, and the temperature of the steam side of the finishing pan is 222" F., vapor side, 132". The injection water to the quintuple-effect condenser has a temperature of about 55", and the down-leg temperature is 90" to 95" F. The finishing-pan condenser has a water inlet temperature of 90" and a leg temperature of 110" F. Low-pressure steam (20 pounds per square inch pressure) is provided either by reducing valves from the boiler main or by the exhaust from the turbines, and is carried through a 20-inch main to the evaporators. The condensed steam from each first effect is pumped back to the powerhouse from a condensate receiver, 4 feet in diameter and 6 feet long, with a steel diaphragm in the middle vertically so that each first effect is served by its individual receiver, one in each end of the tank. Each end is provided with two floats actuating electric switches which stop or start the pump motors as required for maintaining a minimum volume of condensate in the receiver and consequently a nearly constant head on each pump. The pumps are located on the first floor, 20 feet below the receiver. The condensate in each second effect passes through a float-controlled valve to a flash pot which admits the mixture of vapor and hot condensate to the steam chest of the third effect from which a barometric leg removes the condensate to a hot well below the first floor. A float chamber connected to the second-effect steam chest controls the valve which admits condensate to the flash pot. As the flow of condensate from the second effect increases, the level in the float chamber rises and opens the valve enough to take care of the increased flow, or vice versa. Feed to either first effect is controlled by a float chamber which operates according to the change in level of the liquid in the first effect. A rod from the float chamber operates a &nch globe-type valve in the feed line. Feed from body to body is regulated by float-controlled valves, but, instead of relying on the difference in pressure which exists between each body and the next one, a pump is used to transfer the feed. If a larger pipe were installed, it might be possible to transfer the feed without pumps, but then fluctuations in body pressure would be added to other variables and would oppose smooth regulation. The feed flows parallel with the heat from the first effect to the last on account of the character of the material being handled. The flow of steam is controlled to each first effect by a 12-inch globe valve, around which is piped a smaller globe valve used to control the pressure closely and which is also used during cleaning periods when only a small amount of steam is required and damage to the 12-inch valve from wire drawing can be avoided. The original installation using an 18-inch gate valve with chain wheel and chains was too laborious to handle and not adaptable to throttling conditions.
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The finishing pan has to be operated in batches because the coefficient of heat transfer a t 42 to 60 per cent solids is so low that the pan cannot carry the required load when operated continuously at such a high density. Feed is pumped into the finishing pan from either of the last effects as nearly as possible in a steady stream, keeping a constant level. At a certain ammeter reading indicated by practice, the feed is reduced or shut off completely, and the pan .is boiled down, the vacuum is broken, and the sirup is sampled and dumped quickly through a large gate valve out of the cone bottom into one of two heavy sirup tanks on the first floor. The heavy sirup tanks are of steel, provided with coils which are supplied with low-pressure steam (3-10 inch vacuum) in order to keep the sirup at a fluid temperature. As another precaution, the sirup is circulated constantly by pumping with a heavy bronze steam magma pump from the bottom of a tank back into the top of it. In order to keep track of the amount of sirup made and used, one tank is used for receiving sirup from the finishing pan and the other to supply the mixing system with sirup. When one tank is filled, the other is empty; then the valves are switched and the roles reversed. It takes about 5 minutes to empty the finishing pan. Then the bottom valve is closed, the water pump to the condenser is started which exhausts the air from the pan, and the pan is filled from the third effects. Every week end all the evaporator bodies are cleaned in order to remove from the heating surfaces the small amount of scale and organic matter which accumulates during the week and which seriously reduces the capacity during the following 4 days if not completely removed. A regular cleaning schedule has been developed which calls for a hot water rinse and short boiling period, then a boiling period of 3 hours with a chemical solution, followed by a water rinse. The amount of alkali is surprising which can remain on the heating surface and neutralize some of the descaling acid bath which follows. The acid solution is about 0.5 per cent hydrochloric. I n order to avoid handling too great a volume of chemical solution, the bodies are washed consecutively, the two f i s t effects being pumped out into the two second effects, etc., and finally the solutions are pumped into the finishing pan. The concentration of the cleaning solutions is mairitained by adding more chemical when need is shown by titrating a sample with a pH indicator. In order to remove the scale completely, it is essential to keep up the chemical concentrations.
Conveyors Involved in complete recovery of solids is the need for drying the sirup, which is difficult to accomplish; the sirup should be spread out thin on dry feed while being carried through the dryers. This process requires a long and expensive conveying and mixing system. I n all, there are 500 feet of Muntz metal conveyors. The conveyors vary in diameter from 9 to 24 inches, have Munt.z metal flights, and are driven by a total connected load of 300 horsepower, using gear-head motors. Muntz metal is used to withstand the corrosion of the moist feed. I n order to preserve good sanitary conditions, the entire recovery system from screens to dryers is carefully cleaned every week end. The cleaning job takes about 12 or 14 hours, and eight men are required t o scrape the conveyors and flights, sweep and hose the floors, and wash the centrifuges and screens. Two men have a regular Sunday job of cleaning and inspecting the dryers. The conveyors are used to carry wet feed from the rotary presses up a sloping conveyor into which sirup is pumped, and then the mixture is dropped into another conveyor a t the second floor which receives dried feed from the hot side of
(Reading from top to ham)
FIGURE 6. FINISHING PAN,GAGEBOARD, THIRD EFFECT
FIGURE7. FEEDOUTGETSTEAM INLET ENDSOF DRYERS FIGURE 8. FEEDINLET END OF DRYER Frorm~9. BULKFESDIAMDIXO FAN
the surge bin (Figure 2), and also sludge from the centrifugals. The combined load is then carried to B stationary stainlesssteel mixer just above the first floor which is provided with paddles and cut flights mounted on two shafts. From the mixers the load of wet and dry feed, sludge, and sirup is carried back to the second floor to another conveyor vhich distributes a portion for each dryer through bronze vane feeders operated by variable-speed drives to Muntz metal chutes down to the dryers on the Grst fioor. If at some time the vane feeders do not take from the distributing conveyor all of the mixture, then the excess is carried back to the head end by additional conveying equipment until the operator in his regular rounds discovers the condition and alters the drives on enough vane feeders to redistribute the excess. All the conveyor motors are wired to operate in sequence with one another and with the presses and Eeeders, so that if any one unit is obstructed with foreign material, the conveyors leading up t.o it. "kick out" and a Klaxon soiiiids an alarm.
Dryers Steam for the dryers is taken directly from the 250pound main a t 100" F. superheat through a reducing valve a t 125 pounds per square inch to a header in the dryer house for distribution to each dryer after desuprrbeating. There are five steam-tube rotary dryers (Figures 7 and 8). Each dryer has a steel shell which is 8 feet 6 inches in diameter and 26 feet 8 inches long, and is lined with large boiler tubes. Through the center of each dryer is built a steel mandrel which is steam-jacketed and which heats the grain falling on it and also the air blown through it. The dryers rotate a t about 6 r. p. m. and itre driven by 20-horsepower motors through back gears. Heat is supplied by 125-pound steam through rotary joints (Figure 7), and the condensate passing through traps, flashes to the 80-pound steam supply. At maximum load one dryer can r e move 6000 pounds of moisture per hour. Air is blown through the dryers by forced and induced draft fans, the former blowing through steam-heated coils and the latter taking the moisture-laden air through a large transite duct near the roof. There are two induceddraft fans, one a t each end of the duct, and each has a capacity of 80,000 cubic feet per minute. To withstand the corrosive vapors, they are built of special materials. Vapors reach the duct from the dryers through five rectaugdar stacks which carry air and dust to large dust-catching chambers, each of which is connected to the duct. The air to the dryers a t about 294" F. passes through the mandrel to the end of the dryer and then back over the grain and tubes to the stack, issuing at a h u t 160' F. and saturated. Feed falls out of the dryer a t about 180" F. to a Redlcr conveyor which runs a t about 94 feet per
INDUSTRIAL AND ENGINEERING CHEMISTRY
JUNE, 1938
minute in a pit under the first floor and which carries the feed u p above the third floor over the feed storage bins. Before the Redler conveyor was installed, the feed from each dryer was blown by a fan up to a storage bin. This system required 110 horsepower more than the Redler conveyor and was subject to rapid deterioration in fans and piping, due to the sandblasting effect of the feed. The dust collectors are chambers about 15 feet long, 8 feet wide, and 8 feet high, built with transite walls sheathed with copper and with copper floors. Water-flooded copper eliminator plates are built opposite the vapor and dust inlet; in the rest of the space the reduction in velocity allows practically all the dust to settle. A constant stream of water is sprayed on the floor of each dust collector to wash out the dust. The washings are run over a vibrating screen which drops the feed into the slurry tank previously mentioned. The continuous washing system is estimated to save 15 dryer hours daily in addition to reducing an appreciable amount of water which went to the evaporators with the former system of washing out the dust collectors several times daily with a hose. Under the latter system the opening of a dust collector for cleaning cut down the draft through the dryer and thus reduced its capacity. The five storage bins are built of sheet steel with sloping bottoms to permit the feed to slide out to vane feeders for passage to the conveyor just under the third floor, which carries the feed to the shipping system. In order to reach the shipping system, the feed is carried to a high-speed bucket elevator which raises it to a surge bin on the third floor. The surge bin is divided into a hot and a cool compartment. The hot compartment supplies part of the feed which is needed as a “carrier” for the sludge and sirup through the dryers. Some carrier feed is also taken directly from the Redler conveyor before it goes to the storage bins. Feed which is to be shipped passes out of the hot compartment over a shaking screen to separate flaky feed from balls which are damp and dry out to hard pills. The balls are crushed or rolled flat so that they will dry easily and are sent on with the carrier feed; the flakes are dropped into a cooled air stream which is drawn up into two deep cyclone separators, the feed being cooled during this passage until it is suitable for sacking without danger of spontaneous combustion. The air from the cyclone separators goes to a fan and then out through a water-spray dust scrubber. From the bottom of the deep cyclones the cooled feed is conveyed to the cool compartment which supplies two weighing and sacking stations.
Sacking The dried feed (distillers’ dried grains) can be shipped in bulk in boxcars or can be sacked and shipped in cars or trucks from either one of the two weighing and sacking stations through automatic scales. Each scale has a capacity of 240 sacks per hour of 100 pounds each. The sacks are hung on the scale hopper by one man, filled when the automatic scale dumps, guided through the sewing machine by the second man, dropped through the square hole in the floor to a chute, and conveyed to a boxcar where a man stows them according to the requirements of the American Railway Association in order to prevent shifting. Figure 9 shows the sack chute in the rear (the third). Shipments in bulk are loaded as shown in Figure 9 by the use of a blower. From the scale the feed falls through the pipe into a rectangular duct which connects the blower discharge to the metal box set in the wall. The feed and air pass through the box and are spouted into the car. Just inside the car door the spout has a head on it with two 90” elbows so that the feed is blown to each end of the car. The air would escape through cracks in the car and through the
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doorway, carrying much dust, except for a canvas hood over the door and except for a duct which connects the car to the suction side of the blower. The percentage analysis of the feed from bourbon mashes is : Crude rotein (minimum) Crude fat (minimum) Carbohydrates, N-free extract (minimum) Fiber (maximum) Moisture
28 6 35 13 6-9
Ventilation Usually a ventilation system is installed in a plant to benefit the health or comfort of the workers, to remove fumes, etc. I n this plant a ventilation system is needed not only to remove heat and humidity for the comfort of the employees but because in winter the entrance of cold air into the building through doors or windows causes enough fog to interfere with operations. Part of the ventilation is accomplished on the first floor by the forced-draft fans in removing 30,000 cubic feet of air per minute from near the ceiling over the dryers. On the second floor a sheet copper duct extends along the powerhouse wall over the mixed-feed conveyor where vapor accumulates. Hot air and vapor come up from the press balcony through openings around the copper hoppers ‘spaced a t intervals in the floor along this wall. From this long duct a connection is made to a fan on the third floor which discharges through the wall near by. I n winter when heating is required, this same fan with a capacity of 50,000 cubic feet per minute (20 horsepower) takes dry cold air from out of doors over heating coils, and blows it into the second-floor duct to displace the warm moist air near the powerhouse wall on the second floor. Heated air is also blown to two places above the third floor to displace moist air which passes out of the hoods over the screens in part but mostly out of three roof ventilators which handle 3000 cubic feet per minute each with 3-horsepower motors. The hoods over the screens are provided with Bifurcators a t about 2000 cubic feet per minute each. If needed, warm air can be blown down to the first floor.
Acknowledgment Grateful acknowledgment is made to the staff of Hiram Walker & Sons, Inc., for assistance in preparing this articlenamely, to E. R. Luney, L. P. Weiner, C . s. Boruff, W. F. Biggs, B. L. Bailie, C. H. Rogers, and S. D. Bullock.
Literature Cited (1) Boruff, C. S., IND.ENG.CHEM., News Ed.,15, 307-9 (1937). (2) Cooley, L. C., Chem. & Met. Eng., 41,183-6 (1934). RECEIVED January 25, 1938.
