Beet Juice Evaporation Effect of Sodium Aluminate W. LAWRENCE FAITH AND CARL H.SARTORIUS' KaIanaae State College, Manhattan,Kans.
tor scale. However, only two published articles have presented quantitative data pertinent to this subject; one deals with cane juice and the other with corn sirup. Wayne (8) reports that the addition of small amounts of dry sodium aluminah with lime in cane juice defecation increases the purity of the juice and eliminates phosphates, magnesia, and silicates without resorting to overliming. Badollet and Paine (1) report that sodium aluminate removes from 3 to 20 per cent more colloids from converter liquor for corn sugar manufacture than other materials tried. The purpose of the present study was to determine the effect of the addition of small amounts of sodium aluminate to thin beet juice, particularly in regard to purity rise, colloid elimination, and scale formation in the evaporators. Obviously, determination of such effects in a commercial mill would be both slow and expensive. Therefore it was thought that a preliminary study might well be limited to a comparatively small apparatus, duplicating plant conditions as nearly as possible. To avoid further complwationr, a single point in the process-i. e., the evaporation o,f the thin juicewas chosen for this study. Although sodmn aluminate is not ordinarily added just before evaporation, it is believed that results obtained by such addition would at least indicate those which might be expected if the aluminate were added a t other stations.
NE of the most recent developments in the beet sugar industry has been the increasing use of sodium aluminate in the prooessing of the thin beet juice. This use has been the logical consequence of sodium aluminate utilization in the lie-soda water-softening process and in the prevention of silica scale in steam boilers. It has been reported (S, 6, 7) that the value of sodium aluminate in water softening is due to the formation of a flocculent precipitate with relatively high adsorptive power for both organic and inorganic colloids. The prevention of silica scale in boilers has been laid to the formation of insoluble alumino-silicates which do not adhere to the heating surfaces (4). Since colloidal material and silicates are also detrimental constituents of beet juice, sodium aluminate may he expected to aid both in juice clarification and in prevention of evaporaI
Present oddiess. Nntionnl Aluminate Corporation. Chloago, Ill
An experimental vacuum evaporator has been designed in which scale formation can be easily determined under conditions approaching those of commercial evaporation. Data obtained indicate that the addition of small amounts of sodium aluminate t o thin beet juice just before evaporation results in an increase in purity rise during evaporation of the juice. In the case of addition of sodium aluminate to juice from the Steffen's house run only (where hard water was used), the results
indicate a decrease in scale formation and a decrease in colloid content of the juice during evaporation. Based upon the reactions of sodium aluminate in water softeners and steam boilers, these results may be accounted for by (a) adsorption and neutralization of colloids by the aluminate floc and (b) reaction of sodium aluminate with silicates and other inorganic constituents of the juice t o form a precipitate which does not adhere to the evaporator heating surfaces. 872
JULY, 1936
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Experimental Method The Brix, purity, and p H of each drum of thin juice were determined just prior to evaporation. I n the runs in which (Thin juice: specific gravity, 13.8' Brix: purity, 87.7 per cent; pH. 8.16) Thick Jujcecolloid elimination was of interest, the dye value of the thin Purity sugar juice was determined by the method of Badollet and Paine (2) in total NazAlzOd Added Sp. gr. solids Purity Rise as modified by Dawson, Keane, and Paine (6). Similar deLb./iOOO Mg'' Briz terminations were made on the thick juice removed from the pal. liter % 58.2 0.0 0.0 0.0 87.7 evaporator. 87.8 00.0 0.1 0.3 35.9 Both the treated and untreated juice were evaporated 88.0 0.3 60.0 47.9 0.4 87.9 02.0 0.2 59.9 0.5 under approximately the same conditions. Between 15 and 00.0 0.2 87.9 0.0 71.9 16 gallons (57 and 61 liters) of thin juice were evaporated 88.0 0.3 62.0 83.9 0.7 00.0 95.8 88.0 0.3 0.8 in each test. The volume of thin juice remaining in the evapo88.1 63.0 0.4 107.8 0.9 rator a t the end of each run was about 2.5 gallons (9.5 liters). A sample of thick juice was then withdrawn for testing; the TABLE11. INFLUENCE OF SODIUM ALUMINATEON PURITY RISE remainder was discarded. The density of this juice varied AND COLLOID ELIMINATION OF BEETJUICE DURING EVAPORATION from about 55" to 6 4 O Brix, as shown in the tables. From (Thin juice: specific gravity. 12.3" Brix: purity, 87.6 per cent; pH, time to time the tubes were removed from the evaporator, 8.38; dye value,&045) -Thick JuiceDecrease dried, and weighed to determine the amount of scale formed, Dye Pufity in Dye if any. N a ~ A l ~Added O~ Su. Puritv value' Rise Value _ zr. -
TABLE I. INFLUENCE OF SODIUM ALUMINATEON PURITY RISE OF BEETJUICE DURINQ EVAPORATION
0
Lb./1000 gal. 0.0 0.0 0.2 24.0 47.9 0.4 71.9 0.6 0.8 95.8 1.0 119.8 a Grams night blue dye solids in solution.
Brix % Grams 88.0 62.0 025 64.0 88.4 675 88.0 64.0 585 04.0 88.6 673 64.0 89.0 577 55.0 88.7 585 required to neutralize colloids
Results 0.4 20 0.8 1.0 1.0 +28 1.4 08 1.1 00 per 100,000 grams
+E
Tables I and I1 show results using thin juice obtained when both the diffusion battery and Steffen's house were in operation. Table 111shows results using thin juice obtained during the Steffen's house run a t the end of the campaign.
Source of Beet Juice The thin juice was obtained from the plant of the Garden City Company where it was taken from the Danek filters just before it reached the evaporators. The juice was run into clean 50-gallon (190-liter) drums to which 50 grams of toluene were added to prevent fermentation during shipment. Prior to the Danek filtration, the juice from the diffusion battery was measured, heated by passing through the raw juice heaters, and pumped to the first carbonation tanks for defecation. The resulting carbonated juice was then twice filtered in hot presses and pumped into the second carbonation tanks. After this carbonation, the juice was again filtered in hot presses and sulfited a t the thin juice sulfur station. After heating, a small amount of activated charcoal was added and the juice was pumped to the Danek filters.
Experimental Evaporator The evaporator used in this work (Figure 1) was designed particularly to determine the amount of scale resulting from the evaporation of comparatively small volumes of juice under conditions approaching those used in the plant: The evaporator body is of welded steel construction and holds twenty-four 0.75-inch (19.3-mm ) horizontal brass tubes. The tubes are held in the tube sheet by rubber gaskets and conventional six-tube packing plates. Steam condensate is removed by means of a steam trap; a vent at the rear of the steam chest allows noncondensed gases to escape. Thin liquor is fed into the evaporator through a connection in the side of the body, and thick liquor is removed through an outlet in the center of the evaporator bottom. A sampling tube on the side of the body allows the operator to determine the gravity of the juice from time to time. Vacuum is maintained by a dry vacuum pump. Cooling water and condensate are removed from the jet condenser by means of a centrifugal pump. The condenser shown in Figure 1 was constructed from a discarded fire extinguisher and hence is larger than necessary. Although multiple-effect evaporation is universal practice in sugar mills, the use of more than one effect in experimental work would add little t o the value of results obtained, By using a single-eff ect experimental evaporator, all scale is deposited on a comparatively small surface, thus facilitating the determination of the amount of scale formed. The maintenance of steam pressure above atmospheric and a vacuum of about 26 inches (660 mm.) over the boiling juice approximates the over-all conditions attained in the multiple-effect evaporators in commercial mills.
0.2 PO
0.4
0.6
0.8
NceA/poQ Added 60 eo (00 Mgms. per bfer 40
1.0
/20 I
FIGURE2. EFFECTOF SODIUMALUMINATE ON PURITY RISE OF BEETJUICE DURING EVAPORATION
SCALE FORMATION. The tables do not show any data on scale formed by evaporation of the juice obtained during the normal operation of the mill. I n fact, the evaporator tubes actually lost weight during these runs, probably because of corrosion by the ammonia liberated from the boiling juice. However, during the evaporation of 75.6 gallons (286 liters) of juice from the Steffen's house run, 2.1 grams of scale were deposited. These data correspond very well with observations made in the plant, where very little scale was noticed until the last week of the campaign when the slicers were shut down and Steffen's house juice only was run through the evaporators. During this latter period a heavy incrustation was deposited on the heating surfaces. A large percentage of this heavy scale formation during Steffen's house run was undoubtedly due to the use of hard water (hardness, 348 p. p. m. calcium carbonate) in the Steffen's house as compared to the use of treated water (hardness, 3 p. p. m. calcium carbonate) in the diffusion battery.
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VOL. 28, NO. 7 ~~~
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TABLE111. EFFECTOF SODIUM ALUMINATEON BEETJUICE FROM STEFFEN’S HOUSEONLY Thin Juice---------. Purity Dye valuen Na~AlzOaAdded Vol. Evapd. ’ % Grams Lb./1000ual. MB./Ziter Gal. Liters 1-4b 11.5 90.7 780 0.0 0.0 75.6 286.0 5-6C 11.5 91.5 669 0.4 47.9 26.8 101.5 7 11.5 89.9 605 0.6 71.9 16.4 62.0 8 11.5 89.9 605 0.8 95.8 17.3 65.5 9d 11.5 89.9 605 1.0 119.8 15.6 59.0 Grams-of night blue dye required to neutralize colloids per 100,000grams solids in solution. Average of four runs; scale formed, 2.1 grams. Average of two runs to which 0.4 lb./1000 gal. NazAlzO4 (47.9mg. per liter) was added. Total evaporation in runs 5 to 9,76.1 gal. (288liters); scale formed, 0.2 gram.
Run No.
a b G
d
Sp. gr. Brix
Even so, when the Steffen’s house juice was treated with an average of 0.6 pound sodium aluminate per 1000 gallons (71.9 mg. per liter) of thin juice, scale formation from the concentration of 76.1 gallons (288 liters) of thin juice was reduced 90 per cent to 0.2 gram of scale (Table 111). The scale deposited in either case in the experimental evaporator was insufficient for analysis. However, an analysis was made of the scale obtained from the several bodies of the evaporator station in the mill (Table IV). TABLEIV. INCOMPLETE ANALYSISOF EVAPORATOR SCALE FROM PLANT OF GARDEN CITYCOMPANY Eva orator
Per Cent by Weight
sios
~ o t y ~ o .
1
4.92 8.56
4 6
5.82
2and3
0
5.04 Oxides of Fe, Al.
R~OP 1.92 4.07 21.01 21.06 Mn, Ti.
C ~ OP Z O ~ 31.5 28.7 13.0 11.4
0.87 1.27 1.54 1.38
C O 6.6 9.7 3.7 2.0
~ 808 4.09 3.22 1.84 2.11
Total Oxalate organic ( ~ 2 0 4 ) 14.17 1.29 13.43 6.52 48.13 22.80 41.53 30.58
Since silica, a constituent of this scale, is known to produce a hard dense scale, it is possible that the tendency of sodium aluminate to react with silicates may be one of the factors favoring scale reduction. Precipitation of colloids may also be an important factor since the percentage of organic material in the scale, other than combined oxalic acid, is quite high. A considerable portion of this organic material is probably elemental carbon which has passed through the Danek filters. The deep black color of the scale from the fourth and fifth bodies bears out this contention. PURITY RISE.The three curves presented in Figure 2 show the effect of various amounts of sodium aluminate on purity rise during evaporation. An approximate linear relationship is indicated. Variations in purity rise between different samples to which the same amount of sodium aluminate was added may be traced to variations in the juice itself. It is possible that variatioes in gravity, pH, and the type and quantity of colloids, lime salts, and other nonsugars present are important factors governing the increase in purity due to sodium aluminate addition. The exact relationship between these several factors offersan interesting field for further research. COLLOIDELIMINATION. Tables I1 and I11 show data relative t o the effect of sodium aluminate on colloid elimination. A definite relationship is not shown, although the data do indicate that sodium aluminate aids in precipitating some of the colloidal material present, particularly in the Steffen’s house run. Here again, the type of colloids present may be an important factor. Some variation might also be accounted for by slight differences in the time of contact between the juice and sodium aluminate before evaporation, and the temperature at which the aluminate was added. Two runs are shown in Table I1 in which the colloidal content apparently increased during evaporation. This apparent
-Thick Sp. gr. Brix 56.2 59.5 54.3 58.2 56.2
-
Juice Purity Dye value“ % Grams 91.1 705 92.7 528 90.0 90.3 577 480 90.5 480
Purity Rise
Decrease in Dye Value
0.4 1.2 0.1 0.4 0.6
75 141 28 125 125
increase could result from the precipitation of noncolloidal solids. The evaporation of the juice to a higher gravity than usual may have been the cause of such results. Lack of sufficient thin juice prevented the duplication of these particular runs. It should be mentioned, however, that in those cases where duplicate runs were made, results checked closely.
Acknowledgment The authors are deeply indebted to the Garden City Company, Garden City, Kans., for furnishing the thin juice used in this work, and to the Xational Aluminate Corporation, Chicago, Ill., for supplying a generous quantity of sodium aluminate.
Literature Cited (1) Badollet, M. S., and Paine, H. S., IND. ENG.CHEW,19,1245-6 (1927). (2) Badollet, M. S., and Paine, H. S.,Intern Sugar J., 28, 23-8, 97-103,137-40 (1926). (3) Bed, R. B., and Stevens, S., J. Soc. Chem. Ind., 50, 307-13T (1931). (4) Christman, C. H., Holmes, J. A., and Thompson, H., IND. ENQ. CHEM.,23,637-46 (1931). (5) Dawson, L. E., Keane, J. C., and Pain,, H. S., U. S. Dept. Agr., Chem. Investigations Beet Sugar Manufacture, Rept. V I ; Intern. Sugar J.,35,236-7 (1933). (6) Fink,G. J., Chem. & Met. Eng., 38,535-6 (1931). (7) Ripple, 0. J., Turre, G. J., and Christman, C. H., IND. ENG. CHEM.,20,748-52 (1928). ( 8 ) Wayne, T. S., Facts About Sugar,28, 168-72 (1931). RECEIVED May 1, 1936. Presented before the Division of Sugar Chemistry a t the 91st Meeting of the American Chemical Society, Kansas City, Mo., April 13 to 17, 1936. Part of these data was taken from a thesis submitted by C. H. Sartorius in partial fulfillment of the requirements for the degree of master of science a t Kansas State College. Contribution No. 210, Department of Chemistry.
