INDUSTRIAL AND ENGINEERING CHEMISTRY
1238
part of the campaign the overflow line (to the beet sheds) on the seal tank was backing up so that a considerable part of the contamination may have come from that source. This backing up of water into the seal tank makes evaluation of the other results difficult. Table E, however, shows definitely that all the vacuum lines, except that on the white pan, are contaminated. The results take on added significance when it is considered t h a t sufficient numbers of anaerobes are developing so that the relatively enormous quantities of water passing down the tail pipes are contaminated to the extent of one to three spores in 20 cc. Following the water through the seal tank and into the battery, no significant change is noted except a t the battery inlet (again neglecting some which may have entered by way of the seal-tank overflow as evidenced by the increase in flat sours). -4t the battery inlet a definite increase seems apparent. TABLE IX. BATTERY SUPPLY WATER Sample Main water tank Tail-pipe waters: 5th-body evaporator White pan Intermediate pan Raw pan Seal-tank overflow Battery supply water’ Drain Line
Flat Sours
Loop
Inlet
hniterohes
3
0
6
10 0 42 11 17
4 6
7 27
161 8 75 4s
21 15 10 42
From the foregoing it is believed that the tail-pipe vacuum lines constitute a primary source of contamination which is constantly entering the sirups through the battery.
Miscellaneous Contamination While discussion of the many increases in contamination which take place previous to standard sirup filtration is not contemplated because they have only an indirect bearing on that in the finished sugar, it is necessary to be constantly on guard against trade practices which can cause large contamination changes. Probably the most important of these is the common practice of using thin juice as a solvent or flotation agent in all parts of the factory without consideration of temperature. I n some instances sufficient cooling takes place to allow prolific thermophilic growth; also, this contaminated liquid is actually carried around one or more filtration operations. Another possibility which should be investigated is the importance of spoilage within auxiliary lines and receivers. In many instances i t is difficult to keep valves which shut off such lines tightly closed, so that the slow passage of sirup through them is more than a mere possibility; besides, it is common knowledge that such lines contain badly spoiled liquid when opened a t the end of a campaign. Hence, whenever these lines are put into service, a slug of highly contaminated liquid is started on its way through the factory.
Conclusion An attempt has been made to illustrate and account for the changes in thermophilic contamination which have a direct bearing on the finished sugar. Thermophile removal by standard sirup filtration is better than 95 per cent efficient over the greater portion of press operation. Anaerobes increase immediately following filtration, yet attempts t o demonstrate accumulation in the receiver are not conclusive. Data are given to indicate flat sour growth within the pan storage tanks on the liquor or wall surfaces. Of the succeeding operations, changes during boiling were not investigated. Further data, however, show one instance of wash water contaminated by anaerobes which were subsequently traced to
VOL,. 28, NO. 10
growth within the flfth-body evaporator steam chest. Tests of the effect of different quantities of centrifugal wash water showed no change up to 18 quarts. -4t 21 quarts, however, the contamination was definitely reduced. For what is believed to be the &st time, a primary source of anaerobe contamination within a sugar factory has been located. In addition to those in the ath-body water, large numbere of anaerobes are shown to be developing in the tailpipe vacuum system and constantly entering with the battery supply water. The data given in this report represent conditions found a t only one factory and consequently may not be representative of the industry. Yet it is hoped that this will aid other investigators in the solution of similar problems.
Acknowledgment Thanks are due the Chaska organization for their cooperation and helpful suggestions during all phases of this work, as well as the management of the American Crystal Sugar Company for permission to publish this information. Thanks are also due G . A. Vacha and the Minnesota State Canner’s Laboratory for the help and facilities which they made available.
Literature Cited (1) Bigelow, W.D.,et al., Cunner, 72, No. 16,19-20 (1931). (2) Cameron, E.J., and Bigelow, W. D., IND. ENG.CHEM.,23, 1330 (1931). 13) Owen, W.L.,and Mobley, R. L.,Facts About Sugar. 28,No. 10, 382 (1933). (4) Owen, W. L., and Mobley, R. L., IND. ENG.C H E M .24, 1043 (1932).
RECEIVED August
2, 1935.
Utilization of Alunite through Alkali Fusion J. A. TAYLOR AND F. K. CAMERON University of North Carolina, Chapel Hill,N. C.
H
UFFMAN and Cameron (3) have shown
that the mineral alunite. K2S04.A12(SO& 2&036H20, can be decomposed by fusion with alkali suliides such as those of potassium or sodium. The fusion may be effected in one step, starting with a mixture of potassium or sodium sulfate, alunite, and coal. The potassium salt is preferable to the sodium salt, since it is more easily reduced and the recovery of pure salts from the sinter is easily accomplished. Huffman’s experiments, made in small samples in crucibles, apparently required for complete disintegration of the alunite that the mix be fused to a melt. To avoid contaminations, alundum seemed the best material for the crucibles, but left a doubt as to the action of the fused melt on it. I n this paper are presented the results of (a) roasting with a rotating kiln lined with alundum and (b) the separation of the potassium salts.
Furnace Experimental runs were made on mixtures of alunite, potassium sulfate and coal, and on mixtures with part and all of the potassium sulfate replaced by otassium carbonate. The alunite was the same as that usezby Huffman and waa furnished by the Florence Mining and Milling Company of Utah.
OCTOBER. 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
These runs were carried out iii a rotary kiln, 32 inches long and 8 inches in diameter, lined with alundum. The furnace was heated to 775-800" C. by a gas burner whose flame entered the kiln from its lower or discharge end. The upper end of the furnace was enclosed by a metal box, through which the charges were fed into the kiln by means of a screw conveyor. The gases evolved during the process of the runs were discharged through a stovepipe inserted in the upper lid of this box.
Experimental Procedure In all experimental runs, the alunite, potassium carbonate, and potassium sulfate were ground to pass a 40-mesh sieve and the coal to pass 100-mesh. The coal had the following analysis: volatile matter, 17.89 per cent; carbon, 76.39; ash, 5.72; sulfur, 0.51. The calorific value was 14,897 3.t. u. per pound. With each charge approximately 3 pounds of alunite passed through the furnace. Two experimental difficulties developed. Owing to unevenness of pressure on the flame, occasional blowing back of the charge to the stack could not be avoided with a dry charge. This difficulty was surmounted by wetting the feed. It was not possible to adjust this particular equipment to maintain the charge in the furnace a sufficient length of time. The charge would pass in about 5 minutes. This difficulty could be met by returning the discharge to the feed, because the discharge was in all cases a sinter and never a melt. Occasionally the rotation of the furnace w w stopped, with the purpose of delaying the charge to the prolonged attack of the flame. Mixtures of potassium sulfate and carbonate gave a more easily attained decomposition than the potassium carbonate alone. In the latter, in order to attain a good fusion, the charge was passed through the kiln a number of times. There was no apparent tendency for any of the material passing through the kiln to adhere to the alundum liner, and a t the end of the experiments no appreciable deterioration of the liner could be detected. Some samples of the sinter had a high ash content. In leaching the sinter, especially with hot water, there was more or l a hydrolysis of the potassium aluminate. Hence some alumina as such was included in the ash along with some silica, ferric oxide, and undecornposed alunite. In four typical cases the sinter was treated with a dilute solution of hydrochloric acid. The percentage ash on the basis of original sinter used \vas reduced from 5.8, 8.9, 5.2, and 8.4, to 1.4, 1.2, 0.81, and 0.13, respectively. The resulting solution, upon the addition of ammonium hydroxide, gave a precipitate of aluniinum and ferric hydroxides. Thus, this treatment of the ash from the sinter after first leaching with water alone would not be advisable because of the solution of any iron oxide which might be present. Table I gives the experimental results obtained with different proportions of carbonate wlfate, and coal t o one part of alunite.
I.
TABLE RECOVERY O F -kLUMINA BY WITH POTASPIFM SALTS h S D C O A L IN
I'TRSICE Time: through Furnace
KnCOa I'wb
..
2 3
,
u.7
7
0.85
5 3 3 3 3
1
1
2 5
Accua1.y alunite.
h
Coal
0.8.i 1.7 2.4
0.4 0.4
... .
.
(
...
1.0 1.0 1. 3 I.& 2,0 1.4
1'4
-.
1 2 0.
:,:
1
I < d l 1, Part>
... , . . , . .
I
Part 1.0 0.4 0.6 0.4 0.5 0.6 0.6 0.6 0.5 1.0 0.6 0.4
1239
Alunite can be sintered with potassium sulfate, potassium carbonate, and coal satisfactorily in alundum-lined furnaces. The sinter can be leached, and from the leachings, alumina can be precipitated in satisfactory purity. The mother liquor contains potassium sulfate and potassium carbonate. By evaporation the sulfate can be obtained practically quantitatively and in high purity. The residue of carbonate with water and a small proportion of sulfate can be satisfactorily used for decomposing the alunite.
From these results, it appears that a generous proportion of potassium carbonate effects decomposition of the alunite about as well as mixtures of the carbonate and sulfate, provided the mix is subjected to longer heating. From an operating viewpoint, the use of the "mother liquor" is promising.
Recovery of Alumina After the sinters were leached with water, they gave a solution containing principally potassium aluminate, potassium sulfate, and potassium carbonate. Leaching with water a t 40" to 50" C. separated less alumina along with the insoluble coal ash than did leaching a t a higher temperature. Carbon dioxide was passed t'hrough the resulting mother liquor combined with the washings until complet'e precipitation of the alumina resulted. After this precipitation the liquor contained chiefly potassium carbonate and sulfates. The alumina, shown by Huffman, was satisfactorily free from contaminat ion.
Recovery and Utilization of Potassium Salts Hill and Moskowitz (2) showed that at 25" C. the solubility
of potassium sulfate is rapidly and greatly diminished by addition of potassium carbonate. The composition of the constant solution when the co-existing solid phases are KzC031.5H20 and K2S04is 52.8 per cent K2C03and 0.03 per cent K2SOc,and the solution has a density of 1.567. According to Hill and Miller ( I ) K2C03.1.5H;0is a stable hydrate in contact with solution from room temperature to above 100" C. At 50" C. the solubility of potassium sulfate is greater than a t 25" C., but the solubility curve closely follows that for 25" C. At 100" C. the solubility of potassium sulfate is still further increased. The composition of the "constant solution" in contact with the same stable solids as a t 25" C. is 61.0 per FUSIOX OF ALCZ~ITE cent K2C03and 0.11 per cent &SO4. The solution has a denAN ALUXDUM-LIKED sity of 1.633 and a boiling point of 136.5' C. Consequently, by evaporating a solution of the two salts, the sulfate alone ~ 1 ~ 0 ~ would be precipitated until the constant solution is obtained; Recovered Ash then upon cooling, the carbonate mixed with a little sulfate % % precipitates. Quite clear separations are attainable. The 48.2 14.7 93.6 8.0 use of the carbonate for effecting decomposit'ion of the alunit,e 88.9 11.2 is clearly indicated. 69.0 9.5 94.3 73.4
76.0
90.4 93.5 85.4 95.1 79.b 90.3 91.1
4.0 15.8 13.5 8.4 5.2 10.6 5,s 19.9 8.9 8.6
.\lorher liquor" wet mush of I\CCk. equivalent to 2.5 part= &COS to 1 part
Literature Cited (1) Hill, A. E., and Miller, F. W., Jr., J. Am. C'hem SOC.,49, 673 (1927). (2) Hill, A. E., and Moskowitz, Sam, Ibid., 51, 2396 (1929). (3) Huffman, E. O., and Cameron, F. K., IND. EXQ.CHEM.,28, 420 (1936). RECEIVED August 5, 1936. Presented before the Division of Industrial and Engineering Chemistry a t the 92nd hleeting of the American Chemical Society, Pittsburgh, Pa., September 7 t o 11, 1936.
