INDUSTRIAL AND ENGINEERING CHEMISTRY
654
volume in pores larger than 70 A. radius. As the radii of the larger pores are decreased in service, the smaller pores produced from them add t o the total area a t a rate which first increases it and then, for many cycles, keeps it substantially constant. Bone char possesses the valuable property of generating large pores ( + l o 0 A. radius) very rapidly during the early cycles of its “life.” By this mechanism it compensates, in part, for its principal natural deiect, which is the concentration of a large fraction of its volume in pores smaller than 70 A. radius. Primarily because of a more rapid increase in true specific gravity, the bulk density of bone char increases more rapidly than that of Synthad (3-38 This appears t o correlate with a more rapid deterioration in color- and ash-removal power on the part of the bone char. The porosity and the p H properties of Synthad C-38 appear t o be less sensitive t o ewessive reburning temperatures than those of bone char. In a gcneral way, the large differences in area between new bone char, A service char, and B service char correlate with their differences in color- and ash-removal power, and, as a consequence, it is obvious that granular adsorbents for sugar refinery use should be so handled as to maintain the maximum possible area. However, the gradual deterioration in activity which occurs with repeated use and reactivation cannot be explained in detail on the basis of either total area or available area, unless the extremely small area in pores larger than 300 A. radius is of primary importance in the functioning of the char. This possibility seems scarely credible, but it is being investigated.
ACKNOW LEDGRIENT The authors are grateful to Baugh and Sons Co., Atellon Infititute, and the Revere Sugar Refinery for permission to publish this material. S. 31. Wilson (deceaied) of Baugh and Sons Co iecognized
Vol. 43, No. 3
the importance of developing a bone char replacement, and the investigation was initiated as a result of his efforts. Georgc 1.1. Beal of Mellon Institute, by sustaining the donor’s confidenw i i i the practicality of the project, ensured its requisite support. J. R. West assisted in the exploratory period of the investigation. R. A. Finkel did much of the work on the production of synthetic hydroxyapatit,e and on the compositing and granulating of the product. Violct Rivlin carried out the labolatory reactivation experiments. She and P. P. Halenda made inost of the nitrogen adsorpt’ionmeasurements. R . G. Capell improved the hardness of the product, contributed to the study of porosit,y, and assisted in carbonizing t’he commercial sample of Synthad C-38. G. A. Leitch (deceased) was in charge of the pilot, plant, for making Synthad intermediate. H. F. Mcllurdie of the Satiorial Bureau of Standards proviticti the photomicrographs of Synt,had and bone char. H. P. Klug and Leroy Alexander of hlellon Institute provided the x-ray diffraction patterns and the estimates of hydroxyapxtito size. The aut,hors are deeply grattiful to John W,L o w , vice prcsident of the Revere Sugar Refinery, whose cooperation made possible the full scale comparison of Synt,had (3-38 and bone char. The collaboration of the entire operating staff of thc refinery i p responsible for the successful conduction of t,his experirnciit.
LITERATU13E CITED ( I ) Barrett, E. P., and Joyner, L. G . , J . Am. Ch,em,. h c . , 7 3 , 978 (1951). (2) Brunauer, S.,Eiiiniett, 1’. H., and Teller, E., Ibid., 60, :309 (1938). RECEIVED Rlarch 1, 10.50. Preseiited i n part a t t h e Technical Sessioii Bone C h a r Research, Nxtioiial Bureau of Standards, Washington, I). C . , January 27 a n d 28, 1949, mid i n part a t the S i n t h Annual hieetiiig of Sugar Industry technician^, Inc., New T o r k , N a y 18 a.nd IO, 1‘34Y.
efecation with Soybean Flours d
LIE TIEN CHANGl iVutiona1 Bureau of Industrial Research, Nunking, Chinu
Soybean flour has heen found to be ail excellent raw sugar liquor defecant. When full fat soy flour or defatted soy flour is mixed with w-ashed raw sugar liquor and the mixture is heated, a heavy flocculent precipitate is formed. This is believed to he the coagulation of soybean protein. This precipitate enmeshes suspended matter and adsorbs some colloids, iucluding an appreciable amount of coloring matter. By controlling the heat, the precipitate is floated to the top of the sugar liquor, leaving the liquor clear and much lighter in color. The results obtained i n experiments indicate that this new defecating process is not only practical but also economical; the used soy flour, high in protein and ash, can be recovered and used as cattle feed or fertilizer.
A
N E W process utilizing soybean materials in defecating raw sugar liquor is described. When soybean flour or soybean meal flour in water dispersion is mixed with washed raw sugar liquor and the mixture is heated, a flocculent precipitate is formed which enmeshes the suspended matter and adsorbs some colloids. 1
Present address, c/o Savannah Sugar Refining Corp., Savannah, Ga.
By controlling the heat, the floc or flocculent prrcipitaic I & floated t o the top of the sugar liquor, leaving the liquor clrizr and much lighter in color. The resulting clear liquor, dran n out from the bottom of the treating tank, is ready for decolorization. Experiments have shown that this new process is practical and economical; the used soybean or soybean meal cake can bc used for cattle feed or fertilizer. SOYBEAW MATERIALS
Both soybeans and soybean ineal were effective for the dehcation of raw sugar liquor; soybeans worked bettcr than the mral, Tyhich is the resulting portion of soybean after most of it. oil has been removed. With soybeans the coagulated floc Ras a little larger, and separation was easier This map be due t o the f,ict, that the protein in soybean meal has been denatured t o wnic extent by heat and moisture during processing ( 1 ) . I n both the pressing and extraction processes, denaturation probably occurs a t several places: I n the prcssing process the soybean is fiist heated in a dryer t o remove excess moisture, and a great amouat of heat is produced during the prcssing. In the solvent cxtrwtion process the soybean is often heated t o increase eaw of flahing
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1951
and t o adjust the moisture content, and the residual solvent is frequently removed by the use of steam dryers. One major effect of denaturation is the reduction of water solubility of protein. The protein in the soybean meal, therefore, is less watersoluble than that in the original soybean. I t is believed that the soluble part of soybean protein is responsible for the defecation function.
655
( 3 ) OF SOYBEAN AND DEFATTED SOYFLOUR TABLE I. ANALYSIS Analysis, % ’ Moisture Protein (N X 6.25) Oil
Soybean 8.05 39.46 18.32 4.13 30.04
Ash
Carbohydrate
Defatted Soy Flour 7.04 51.79 0.58 6.54 34.05
duplicate to obtain an average value. The solubility of protein was calculated as follows: Total soluble nitrogen in water extract Solubility = x 100 Total nitrogen in original sample COAGULATION OF SOYBEAN MATERIALS
Results of a number of coagulation tests (Table 11, A) indicated that the coagulation of soybean protein was probably due t o a reaction between the protein and the ash in the sugar liquor, whereas the sugars and coloring matter had no effect. Ion exchangers removed only the ionized mineral matter, but the bone char removed both. Thus the ionized ash content in the ion exchange-treated liquor should be much lower than that in the bone char decolorized liquor, although the total ash content of the former was higher. This seemed t o indicate that only the ionizable part of the ash was responsible for the coagulation.
6
7
8
9
IO
II
PH Figure 1.
OF SOYBEAN MATERIALS TABLX 11. COAGULATION
I
Solubility of Defatted Soy Flour Protein at Different pH
The soybean and soybean meal are best employed for defecation in the form of finely ground flour, called “full fat soy flour” and ‘(defatted soy flour,” respectively, in the soybean industry. On the market, there are two kinds of defatted soy flour: one, which has been processed a t a comparatively lower temperature, is for industrial use with a higher water-soluble protein content, and the other, which has been toasted t o enhance the nutritive value, is destined for use in cattle feeds. The latter was not effective for defecation because solubility of the protein is greatly reduced by toasting. Oil content of the soy flour had no effect on defecation. Therefore, the less expensive defatted soy flour of lower oil content is satisfactory. The defatted soy flour resulting from the solvent extraction process is preferable t o that from the pressing process because of its lower oil content, higher water-soluble protein content, and lower price. Although the coagulated floc of full fat soy flour wa8 a little larger and its separation from the sugar liquor somewhat easier than that of the defatted soy flour, no appreciable difference in defecation result was noticed. The defatted soy flour used in this work was a by-product of the solvent extraction process passing a 200-mesh screen. Its analysis by established methods ( 3 ) is shown in Table I. The soybeans, bought on the local market, were yellow and small grained (Table I). The origin and history of this soybean are not known. It was ground into flour, and the portion passing through a 60-mesh screen was used. The solubility of the defatted soy flour protein varied with p H ; the highest value was p H 10.0 as shown in Figure 1. The solubility was determined by the single extraction method ( 4 ) : Soy flour (2.5 grams) was mixed with 100 ml. of distilled water which had been limed to a definite p H (determined with a Macbeth glass electrode p H meter). The mixture was shaken mechanically for 30 minutes, and the p H was again determined. ThesecondreadingwastakenasthepHof thedispersion;pHusually showed a drop of 0.1 or 0.2. The dispersion was filtered through a KO.4 Whatman paper. Ten ml. of the filtrate were analyzed for nitrogen by the Kjeldahl method. Analyses were run in
Run 1 2 3
4
Run
No.
A. WITHOUT METALLICCHLORIDE Treatment Change Observed Soybean Material Full fat or defatted flour Heated to 80’ C. Heavy precipitates plus raw sugar liquor Full fat or defatted flour Heated to boiling No coagulationb plus water or white sugar liquor Full fat or defatted flour Heated to boiling No coagulation (0.5% .of total solids) plus ion exchangetreated raw sugar liquor ash reduced to 0.085%) Fu\l f a t or defatted. flour Heated to boiling Coagulated (0.5% of total solids) plus bone char-decolorized raw sugar liquor (ash, 0.029%)
5Flour2
Amount Added, Grams B.
1 2 3 4 5 6
7 8 Blank
1.80 1.20 0.60 0.36 0.12
30’
...
NO
“O 6.1
Turned milky.
20
6.3
Coagulated: floc floated to top of sugar liquor
2
6.4 6.5
No coagulation
...
c.
coagulation
5, 5.91
200 loo 60
0.06 0.024 0.012
Change Observed
pH
CALCIUM CHLORIDE
MAQNEsIUhi
CHLORIDE
a Precipitate believed due to coagulation of soybean protein; sorbed some oolloids and enmeshed suspended matter in liquor. b Coagulation ocaurred on additions of few drops of molasses. c Coloring matter almost entirely removed.
floc ad-
The metallic constituents of raw sugar ash are calcium, magnesium, iron, aluminum, potassium, and sodium. Relative amounts a8 well as total amounts vary widely among different samples. The acidic constituents of the ash are phosphate, sulfate, chloride, and carbonate. I n a n attempt t o find out which constituents are responsible for the coagulation, the following experiments were made.
Lots of 200 rams of 60.0’ Brix white sugar li uor were prepared by dissofving regular granulated sugar in %istilled water to which different amounts of metallic chlorides had been added.
INDUSTRIAL AND ENGINEERING CHEMISTRY
656
Then 0.6 gram of full fat EO^ flour (0.5% on the total solids) was mixed into each lot. The mixtures were heated t o 100" C., and changes observed. The p H of the sugar liquor was determined after the so flour was mixed. A blank was run under similar conditions 1 t h no salt added. The results obtained with calcium and magnesium chlorides are shown in Table 11, B and C. Similar experiments with potassiuni and sodium chlorides showed no coagulation Experiments Tvere also made with aluminum and ferric chlorides, but due t o the ease of hydrolysis of these salts when heated, it was impossible t o determine whether the flocculent precipitate formed v a s due t o hydrolysis of salt or coagulation of protein. However, in experiments under different conditions ( 2 ) aluminum and ferric chlorides coagulated dilute water extracts of defatted soy flour without heating. These results agree with the agc old method of making "tofu" (coagulated soybean curd) in China. Since ancient times, the Chinese have used calcium sulfate and magnesium sulfate a s coagulating agents for soybean proteins to separate them from aqueous extracts. Smith, Circle, and Brother (5)also found that the soluble calcium and magnesium salts had an adverse effect on the dispersibility of soybean protein. Table TI shows that the soybean flour coagulated only in the mixtures in which calcium chloride of 4 t o 20y0 of its lveight had been added. This indicated coagulation required the presence of a drfinite amount o f calcium chloride; the soybean protein did not coagulate when too much or too little calcium salt was present, Work is being carried out by the author in an attempt t o establish the quantitative relationship. Similar experiments, made with insoluble calcium carbonate and oxalate, showed that neither caused coagulation. These results indicated that only the calcium ion was responsible for the coagulation and corroborated the results obtained with sugar liquors treated by ion exchangers and with bone char. Tests with sodium sulfate, phosphate, and carbonate indicated that the acidic constituents of ash had no effect. The effect of heat on coagulation was studied in the experiments reported in Table 111.
TABLE
111. EFFECTO F T E M P E R l T U R E
Mixture Full fat soy flour (0.5% total solids) Calcium chloride (10% of flour) JThite sugar liquor (60° Brix) Run S o .
Heated to,
5
80
6
85
7
8
9
10
90
C.
95 100 102 (boiling)
\ J
ON
COAGULATION Grams 0.06 0.06 200.0
Change Observed
Coagulated; part of medium floc floated t o top of liquor Coagulated; most of large floc floated t o tow - of liauor Coagulated; nearly all of large floc floated t o t o p of liquor
~~
Experiments with magnesium chloride gave the same results as with the calcium chloride. Heating helped the progress of reaction, and the coagulation started a t 75' C. Heating t o a higher temperature resulted in larger floc and caused the floc to float to the top of the sugar liquor. These results corroborated those obtained with the raw sugar liquor a t about 80" C., but because of the dark appearance of raw sugar liquor, it was not possible to observe a t exactly what temperature the coagulation started. The effect of p H o n coagulation was studied by adjusting the p H of dilute soybean milk t o different values. The soybean milk was prepared by grinding water-softened soybeans with a hand mill and filtering through a cloth. The resulting milk was 3.7" Brix. Ten ml. of the milk TTere further diluted with 150
Vol. 43, No. 3:
ml of distilled water. The p H of the dilute milk was 6.9. Different amounts of dilute hydrochloric acid or sodium hydroxide solution were added to lots of the dilute milk to adjust to different p H values, and then the changes were observed. The results are shown in Table IV.
TABLE IV. EFFECT OF pH R u n No. 1 t o 12
PH 9 . 5 to 6 . 1
13
5.7
14
5.4) 5.0
15 16 17 18 19 20
44:4.3:
1
21
4.1 1 3 9 , 3.7 3.5J 3.4
24 25 26
3.3 3.2 3.1 3.0
22 23
27 28
O N CO-4GCLATIOX
Change observed No coagulations Partly coagulated
Coagulated: floc settled t o bottom of solutionb
Mostly coagulated; upper part of solution appeared slightly cloudy Partly coagulated; upper part of solution appeared cloudy Sinal1 part coagulated N o coagulationC
2.9 Samples of runs 1 t o 10 yellowed a little on addition of sodium hydroxide solution. b This ooagulated milk was again mixed a n d adjusted t o p H 2.9 with HC1 solution; the floc disappeared, and milk appeared the same as before ooagulation. C Milk appeared a little whiter.
As indicated in Table IV, the soybean milk coagulated within the p H range 3.5 to 5.4. These results agreed generally with those obtained by Smith and Circle ( 4 ) ,who found that the protein in soybean had a minimum solubility a t p H 4.2. The p H of regular washed raw sugar liquor is usually within 6.0 t o 6.5. Therefore, the coagulation of soy flour in the ran' sugar liquor is not due to the effect of pH. DEFECATlON
Many experiment,s were made to find the optimum conditions for defecation. The procedure which follows gave t,he best result both in laboratory and plant scale experiments: The sugar liquor used in the experiments was taken from the melter in the refinery. This liquor, generally called "melt liquor" in the sugar industry, was the washed raw sugar dissolved in high purity sweet water. Defatted soy flour was mixed wit,h water t o about ten times its weight, with a mechanical stirrer. (Compressed air was unsuitable for mixing because it produced foam.) The rat,io of flour and water has litt'le effect on the dispersion of the protein, and the ratio used gave a light dispersion which was easy t o handle. To aid the extraction of protein, it is advisable t o lime the dispersion t o a pH around 10.0 with milk of lime. For a good defecat,ion of the regular washed raw sugar liquor, t'he minimum amount of defatted soy flour required was 0.2 t o 0.3% on the total solids in the sugar liquor. The quantity varied with the quality of the sugar liquor. Since the soybean protein started t o coagulat,e at, 75" C., the temperature of the sugar liquor m-as kept at, about 70" C. when the soy flour dispersion was added. This was to prevent coagulation before it was well mixed. The addition of soy flour cawed some drop in pH of the sugar liquor, and the drop increased with the amount of soy flour used, as shown by Table V. As it is the pract'ice in the sugar industry t o keep the p H of defecated liquor around 7.0, t'he washed sugar liquor should be limed to p H 7.5 to 8.0. I n addition t o the adjustment of pH, liming may also supply some calcium ion which is required for the coagulation of soybean protein. After the defatted soy flour dispersion \vas well mixed into the sugar liquor, the mixtcre vias heated to 100" C. in two stages-to 90" C. with consta.nt mechanical stirring and from 90" to 100" C. TTithout stirring. The first stage of heating
March 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE V. DROPIN p H
Washed Sugar Liquor,a p H After Liming
Run No.
A.
p H After Addition of Soy Flour
p H Drop Due t o
p H After
t,"le$%.
% ?3!
p H Drop Due,to Heating
Total pH Drop
Defatted soy flour (0.3 g., 0.25y0 on total solids) 0.1 6.1 0.1 6.0 6.2 0.4 6.5 0.1 6.9 7.0 0.6 7.3 6.7 0.2 7.5 0.6 0.2 7.8 7.2 8.0 0.6 7.6 0.3 8.2 8.5 0.6 0.1 8.3 8.9 9.0 0.6 ... 8.9 9.5 9.5 10.0 ... 0.5 9.5 10.0 0.4 10.3 ... 9.9 10.3
0.2 0.5 0.8 0.8 0.9 0.7 0.6 0.5 0.4
Defatted soy flour (0.6 g., 0.5% on total solids) 6.1 0.1 5.9 0.2 6.2 6.7 0.3 6.3 0.4 11 7.0 0.5 7.1 0.4 6.6 7.5 12 0.6 7.5 0.5 6.9 8.0 13 0.6 8.2 0.3 7.6 14 8.5 0.6 8.8 0.2 8.2 15 9.0 8.7 0.6 9.3 0.2 16 9.5 0.1 9.9 9.8 0.5 17 10.0 10.3 9.8 0.5 10.3 18 a Lots of 200 grams of washed sugar liquor, 60' Brix, p H 6.1 liming. B.
10
...
0.3 0.7 0.9 1.1 0.9 0.8 0.8 0.5 0.5 before
to effect the coagulation, could be carried out as fast as possible, but the second stage of heating, t o effect the separation of the coagulated floc from the sugar liquor, had t o be controlled t o obtain good separation. Experience showed t h a t 30 minutes was good practice. Heat was applied from the bottom of the treating tank by the use of a steam coil or steam-jacketed bottom. The regular "blowup" tank, fitted with steam coils and mechanical stirrer, served the purpose very well. When the soybean protein was coagulated the floc remained in suspension in the sugar liquor, and stirring was stopped a t 90' C. Because the heat was applied from the bottom only, an upward and downward current was maintained in the liquor. The hotter liquor a t the bottom rose, while the colder liquor a t the top descended. The floc with the suspended matter enmeshed was carried upward by the upward current. When it reached the top of the liquor, the floc did not move with the downward current. Finally a heavy blanket of scum was formed on the top of the sugar liquor, leaving the lower part clear. The scum was so concentrated that it was very easy t o separate or skim off. The clear liquor was drawn from the bottom of the tank. The scum left in the tank was then washed t o the mud tank for later treatment.
TABLE VI.
Soy Flour, Grams
R u n No. A.
n
1 2 3 4 5 6 7 8 9 10 Kieselguhr treated liquor
B. 11 12 13 14 15 16 Kieselguhr treated liquor
COLORREMOVAL BY DEFATTED SOYFLOUR % SOY
Flour on Total Solids
Washed r a w sugar 0.1 0.24 0.2 0.48 0.3 0.72 0.4 0.96 0.5 1.20 0.6 1.44 0.7 1.68 1.92 0.8 0.9 2.16 1.0 2.40
., .
...
Color Readin@ (at pH 6.1) Red Green Blue liquor, 50.0 58.5 67.5 68.5 71.0 71.5 73.0 75.5 77.0 78.0 47.0
p H 6.4, color 30.0 12.0 3 3 . 0 14.0 4 3 . 0 18.4 4 5 . 5 20.0 5 0 . 0 23.0 5 0 . 5 23.0 52.5 23.0 55.0 26.0 56.0 27.0 5 6 . 5 27.5 25.5 9.6
Total Color Units
Color Removal,
units 148.1 133.2 119.0 96.9 91.8 83.0 82.5 77.7 74.2 70.4 69.9 148.1
Washed raw sugar liquor, p H 6.3, color units 170.90 1.2 0.5 6 3 . 0 4 2 . 0 16.0 104.73 2.4 1.0 75.0 51.0 23.0 80.37 1.5 78.0 5 1 . 0 24.0 3.6 77.87 4.8 2.0 79.0 54.0 26.0 72.90 6.0 2.5 8 0 . 0 65.0 2 7 . 0 70.60 7.2 3.0 82.2 57.0 2 8 . 0 67.43 41.0 20.0 7 . 0 170.90
...
.. .
%
10.06 19.04 34.57 38.01 43.94 44.29 47.54 49.90 52.46 52.80
...
38.73 52.97 54 44 57 34 58.69 60.54
...
657
During the second stage of heating, the progress of the separation of floc was followed by taking samples at definite time intervals from a sampling line connected to the side of the tank a t a point about 1 foot below the surface of the sugar liquor. When the sample appeared clear, the defecation was completed. The speed of heating was controlled by adjusting the pressure of the steam. If the separation was slow, the steam pressure was cut down. The liquor drawn from the bottom of the tank was clear, except that sometimes a trace of fine floc was present. However, the floc was of such a size that it was easily caught by the bone char and removed from the char with the backwashing water. Filtration was not necessary. Experiments showed that this trace of fine floc was also easily removed by filtering through sand or cloth filter. Both gave brilliantly clear liquor with a very high rate of flow and long cycle. The openings of common filter cloth were too large for the fine floc, and it was advisable to precoat the cloth with high flow kieselguhr at the beginning of each cycle. Experiments were made with washed raw sugar liquor between 60" hqd 70" Brix. No differences in results were noticed. However, at 65 O t o 70' Brix, the second stage of heating should a little slower.
50 55
-I
4
5
4540-
a 35K
3
30-
* 2520 I5t
I
I
d
0.1
' I I I I I I 0.2 0.3 0.4 0.5 0.6 0.7 0.8 09
I
% OF DEFATTED SOY FLOUR ON TOTAL SOLIDS Figure 2. Color Removal of Defatted Soy Flour This procedure worked equally well with both high and low purity raw sugar liquors. I n other words, the purity of the raw sugar liquor had little effect on the defecation result. COLOR REMOVAL
The coagulated soy floc adsorbed an appreciable amount of the coloring matter from the sugar liquor. The amount of color removed increased with the amount of soy flour used, as is shown by the results of the experiments reported in Tables VI. Defatted soy flour was mixed into lots of 400 grams of washed raw sugar liquor of 60.0" Brix. The mixtures were heated to 100" C. and filtered through a filter paper. The color of the filtrates was determined with a Hess-Ives tint-photometer ( 6 ) , after they were adjusted to 80.0" Brix and the same pH. T h e color readings were translated into the Meade-Harris units of color. Another 400 grams of the same washed raw sugar li uor was mixed with 1.2 grams of standard grade kieselguhr. %he mixture was heated and filtered under the same conditions. T h e color readings of the kieselguhr treated liquor were taken as the original color of the sugar liquor. From the difference in color
.
658
INDUSTRIAL AND ENGINEERING CHEMISTRY hrII.
TABLE
COLOR
Color Readings --__(at p H 6 0 ) Red Gseen Bliie 60.0 30.0 10.0 37.0 5.0 17.0 70.0 18.0 42.0 47.0 9.0 24.0 65.0 15.0 38 0 20.0 42.0 7.0 60.0 32.0 13.0 15.0 4.0 37.0 00.0 8.0 25.0 30.0 4.0 11.0 ~
~ n n S o .
Treatment Soy flour Kieselguhr S o y flour Kieselguhr soy flour Kieselguhr Soy flour Kieselguhr Soy flour Kieselguhr
TABLE T'III.
C O h I P l R I S O S OB' C O L O R
AKD
Run Yo.
I 2
a
HCieselguhr
PHOSPHORIC Am--T,rm
...
Total Color Units 133.2 190.9 97.4 151,s 109.3 170.1 122.4 195.3 152.6 219.2
Color Removal,
%
30.20 35:7l 35:74
Run S o . 1 2 3 Kieselguhr treated liquorb a
b
SOY
Flour on Total Solids" 0.3 0,O
1.0
l.l
Color Readings ( P H 6.7) Red Green Blue 42.0 15.0 4.0 48.0 17.0 5.0 53.0 21.0 6.0 30.0 8.0 LOG
Total Color Units 19.84 182.3
Color Removal,
166.0
65.03
% 46.25 50.61
...
369.1
hIixttires heated t o 100' C. and filierrd. Kieselguhr (0.5yoof total solids). Reading estimated a3 liquor was too dark to rend exactly.
3i:i3 30:i8
...
B Y SOY TRI:LTIIENTS
Total Color Units
%
C
ILE\IOvAL
A m o u n t of S o y Flour or PzOs % on Color Readings total . ( a t 1111 6.2) Gsains solids Red Green Blue
0.72 1.20 2.50
TABLE x. DECOLORIZATION B Y S O Y FLOUR
REXOVAL W I T H DIFFEREI~T RAW S U G A R LIQUORS
Washed raw sugar liquor, 60.0" Brix, p H 6.2 Defatted soy flour, 0.3y0 on total solids Kieselguhr, 0.5% on the total solids
Vol. 43, No. 3
Washed raw iugat liquor 60.0' Brix, pH 6.5 Defatted soy Hour, 0.3%'on total solids Activated carbon, 0.5% on total solids
FLOUR
color Removal,
7%
A . S o y flour tseatnirnl 13.0 121.93 59.0 33.0 0.3 17.0 99.23 iO.0 42.0 0.5 7 3 0 69.17 87 0 57 0 1.0 . . . 41 0 20.0 7 . 0 170.9
TABLEXI. COLORREMOI-AL B Y SOY FLOUR AND CARBON
Tieatrnentn S o y Hoiir Carbon
Soy flour and carbon
Kieselgrihr a
28.67 41.98 59.56
Color Readings (at pH 6.4) Gieen Blue 43.0 19.0 50.0 31.0 65.0 41.0 29.0 12.0
Red 63.0 61.0 79.0 50.0
-
Total Color Units 98.3 78.2 51.6 134.3
Color Removal,
% 26.81 41.77 62.58
...
1Iixturrs heated t o 100' C. in 10 niisiutei and filtered.
...
t.reI1 .. -..tPd -
liquor B. Phosphoric acid-lime treatment 20.0 78.53 85.0 55.0 0.172 O.O! 25.0 66.93 61.0 0.120 0 . 0 ~ 87.0
4 5
TABLE Ix.
54.08 60.84
FLCUR DEFECATED SUGAR LIIQ~OR
DECOLORIZ.4TION O F S O Y
R'ashed raw sugar liquos, 60.0° Brix, pH 5.9. A. DEI-FCATIOX Kieselguhr Defatted Sor Floiir ( 0 . 3 R on Total Solids) (0.3% on total solid>) Color readings ( a t p1-I 5 . 8 ) 37.0 Red 57 0 16.0 Green 31 0 5.0 Bine 11 0 192.9 Total color units 130 6 ... Color r e m o l d , 32 35
B.
Aniount of carbon on total solids) Color readings (at pH 5.8) Red Green Blue Total color units Colorremoval, %
~ECOLORIX.4TIOS
Soy Flour Defecated Liquor 0.1 0.2 0.3 0.4 0.5
82.0 60.0 32.0 61,30 54.41
88.0 67.0 35.0 52.33 61.08
44.0 74.0 46.0 4 4 , 0 3 37.73 67.26 71.94 91.0
71.0 41.0
97.0 80.0 52.0 30.03 77.64
Kieselguhr Defecated Liquor 0.5
79.0 68.0 42.0 49.33 63.32
between the soy flour and kiesrlguhr treated liquors, the percentage of color removal was calculated. A part of the results given in Table VI are plotted in Figure 2. Results of experiments with different samples of washed raw sugar liquor taken from the refinery on five consecutive mornings indicated (Table VII) that the color removed by the same amount of soy flour varied with the samples, but no definite relationship could be established. The removal of color by the soy flour treatment and the phosphoric acid-lime treatment were compared in the following experiments. Lots of the same washed raw sugar liquor (400 grams, 60.0' Brix, p H 6.5) were treated separately with defatted soy flour and phosphoric acid and lime; color removals are shown in Table VIII. I n the phosphoric acid-lime treatment, the
desired amount of orthophosphoric arid was mixed into the washed raw sugar liquor, then the mixture was limed t o pR 7.0, heated t o 100" C., and filtered through a filter paper. Experiments on decolorizing soy flour and kieselguhr defecated liquors with activated carbon (Table I X ) indicated that about 40% less of activated carbon \?-as required for the sugar liquor defecated with defatted soy flour. Soy flour vias a good decolorizing material foi the kieselguhr defecated sugar liquor, as shown in Table X. U S E OF SOY FLOUR WITH CARBON
Soy flour could be used advantageously with activated carbon in treating washed raiy sugar liquor as the soy flour served as defecating agent and the carbon served as decolorizing agent. The defecation and decolorization were thus carried out in one operation. Experiments (Table X I ) showed that the combined decolorizing power of soy flour and carbon was only a little lower than the sum of their respective decolorizing powers when they were used separately. The activated carbon RaE satisfactorily removed with the BOY flour scum by heat control as shown in the followiiig experiment: Defatted soy flour (33 pounds) and activated carbon (55 pounds) were mixed with 1638 gallons of washed raw sugar liquor (60.0' Brix, adjusted to pH 8.4 with milk of lime). The mixture was heated to 90 O C. with slow mechanical stirring, from 90" to 100" C. without stirring.
Temp. of 4i uor,
e.
Time, Minutes
65
70 80 90 95 100
Appearance of Liquor S o coagulation Coagulated; floc in suspension
50 65
Some floc in suspension Clear with trace of fine floc in suspemion
Results of similar experiments indicated that the soy flour used with the carbon should be a t least 40% of the weight of carbon used. Amounts lower than this did not give satisfactory
March 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY WASHED RAW ,SUGAR LIQUOR
DEFATTED SOY FLOUR
USED SOY FLOUR
AND FIRST
Ir--l PEI
‘
USED’CAREON
FILTRATION
I 4
TO VACUUM PAN Figure 3.
Procedure of Treating Sugar Liquor with Soy Flour and Carbon
separation. The operation of treating sugar liquor with .soy flour and carbon is best accomplished according to the procedure shown in Figure 3. -4s compared with the prevailing process, the defecation step and the filtrations which usually follow the defecation and the first decolorization are eliminated. The cost of operation would thereby be reduced. USED SOY FLOUR CAKE
The soy flour scum left in the treating tank was treated in much the same way as the kieselguhr mud. No difficulty has been experienced. The soy flour scum was washed t o a mud tank with hot water, then filtered through cloth, and sweetened off. Both filtration under pressure and filtration under vacuum gave satisfactory results. The resulting cake, after washing, was compact and easy t o scrape off. One air-dried sample of the used defatted soy flour cake was ground into pow7der and analyzed as follows:
Moisture Protein (N X 6.25)
Oil Ash
Per Cent 9.70 49.13 2.77 7.29
The calculated analysis (dry basis) of this sample differed from that of the original soy flour used: Oil,
Protein,
%
Defatted soy flour Used soy flour cake Difference ) I
*
55.72 54.41 -1.31
%
0.62 3.07 +2.45
Ash,
%
7.03 8.07 +1.04
The great increase of oil contrnt in the used soy flour cake ma8 probably due t o the fatty and waxy matter in the sugar liquor that was caught by the floc, as in the kieselguhr mud. The oil and waxy content of the kieselguhr mud was 1.14 to 1.84% ( 2 ) . Because of its high protein content, soy flour cake can be used for cattle feed. I t s gray appearance might be objectionable, but it can be mixed with regular soy flour or other colored feed t o some extent without impairing the appearance, the palatability, and the feed value of the latter. The fact t h a t the used soy flour cake is high both in ash and protein indicates it would be of value as a fertilizer. The major part of the ash is potassium. CONCLUSIONS
1. At a price of about $130 per ton for defatted soy flour, this new process would be relatively expensive, if the used soy flour cake were not sold as cattle feed or fertilizer (the press cakes from other processes is generally waste).
659
2. The price of feed and fertilizer is dependent on the analysis. All the soy flour used in the process is recovered as cake with practically no loss, and its protein content is about the same as that of the original soy flour. Therefore, it might be poesible to sell the recovered cake a t a price approximating t h e cost of the soy flour. 3. High color removal and simpler operation would also help reduce the cost of operation. 4. This process requires heating to 100” C. However, a8 compared with the Williamson process using phosphoric acid and lime, any loss because of inversion could be kept a t a very low rate by careful control of p H and temperature. 5. The differences noted in processing time and size of floc may be due to variation in the amount of ionized mineral matter in the sugar liquor, as it was found that a definite amount of calcium ion is required for the coagulation of soybean protein. When the exact relationship between coagulation and t h e amount of mineral matter is established, it might be advisable to adjust the mineral content t o improve the coagulation. 6. This process was satisfactory with both high and low purity raw sugar liquore and other refinery liquors such as remelt liquors and soft sugar liquors. It did not work well with aEnation sirup, probably because of the presence of too much ionized mineral matter for coagulation of the soybean protein. The process has also been used successfully to defecate sugar cane juice. 7 . For regular raw sugar liquor, the least amount of defatted soy flour required for a good defecation was 0.2% on the total solids. However, in a few instances, 0.1% was found t o be sufficient. Amounts lower than 0.1% did not give satisfactory results. 8. It was hoped that the use of sodium carbonate solution t o adjust p H instead of milk of lime would convert some of the calcium and magnesium ions into insoluble carbonate and reduce their effect on coagulation. Results showed that defatted soy flour as low as 0.05y0on the total solids gave satisfactory defecation, and if large scale experiments give the same results, the amount of soy flour could be reduced further; t h e process would then be economical even if the used soy flour cake were not recovered. 9. Although this new process was discovered in work with sugar liquor, it seems possible that it might be used for other liquors which contain the required mineral matter for coagulation. If the liquor does not contain the required mineral matter, the coagulation could be achieved by the addition of soluble calcium or magnesium salts. ACKNOWLEDGMENT
These experiments were conducted a t the Savannah Sugar Refinery, which supplied all the materials and equipment. The author wishes t o express his sincere appreciation t o W. W. Sprague and F. M. Exley for their interest and t o T. A. Stokes for his valuable suggestions. Gratitude is also due to E. G. Clarke, G. Fawcett, R. J. Herring, and R. J. Stokes for their help in the experimental work. LITERATURE CITED
(1)Beckel, A. C.,Bull, W. C., and Hopper, T. H., IND. ENG.CHEM., 34,973(1942). (2)Chang, L. T.,unpublished papers. (3) National Soybean Process Association, Chicago, Ill., “Handbook of Analytical Methods for Soybeans and Soybean Products,” 1946. (4)Smith, A. K., and Circle, S. J., IND.ENG.CHEM.,30, 1414 (1938). (5) Smith, A. K., Circle, S. J., and Brother, G . H., J . Am. Chem. Soc., 60,1316(1938). (6) Spencer, G. L., and Meade, G. P., “Cane Sugar Handbook,” 8th ed., New York, John Wiley & Sons, Inc., 1945. RECEIVED October 18, 1950.
