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INDUSTRIAL A N D ENGINEERING CHEMISTRY
It is advisable to make the pump and valve and operate these manually for a time in order to determine where the contacts should be sealed in. The resistances should be wound a t first so that they may be adjusted to the operation of the pump before being made permanent. In general,
Vol. 16, No. 7
where a relay does not throw a t the time it should, the trouble can be remedied by increasing the voltage to that relay. If a relay tends to operate a t the wrong time, increasing the resistance in the lines which connect it to the other circuits will remedy this trouble.
Super-Defecation of Cane Juice' By W. D. Home 176 PARKAvE., YONKERS, N. Y
I
N THE long struggle to The process here described has been devised to secure the advantages venting the disadvantages develop the raw sugar of complete precipitation of all the impurities that lime will throw of excessive alkalinity and industry1 defecationhas lime salts in the defecated down, without incurring the disadvantages of working u p highly ever Played an important alkalincjuice. This is accomplished, through a patented process, by juice. This combination r o l e . I n s o l u b l e matter, liming to a certain point between al?plinity to litmus and allplinity was finally accomplished earth, and trash, as well as through the expediency of to phenolphthalein, heating, settling, and decanting. The decanted juice is then treated with a specially prepared phosphatic reagent, t w o P r e c i p i t a t i o n s and P r e c i p i t a b l e substances, have had to be eliminated, Separations, as in double which precipitates the lime and other bases; the solution is slightly reheated and settled. The juice, thus raised considerably more than carbonation, but without while Preserving the Sucrose and invert sugar from deusual in purity, and lighter colored and cleaner, yields more abunthe need of such elaborate s t r u c t i v e a g e n c i e s and and expensive plant, or the dant and more readily worked sugars. The phosphafic precipitate use of so much lime-itself is used as cane fertilizer, thus conserving its cost. avoiding increase of color. Causticlime has proved to an expensive item. Treatbe the most suitable reagent ment with sulfurous oxide t o cause precipitation of phosphatic and certain organic con- had also to be avoided on account of dangers of inversion, stituents and to neutralize the acidity natural to all cane nonpermanence of the bleaching effected, and the fatal injuices. The most advisable amount of lime to use is often completeness of the precipitation of lime by this process, difficult to determine, for if too little is used the precipitation with the consequent troubles of cloudy sirup, scaling on heatof impurities is not so complete as might be, and if too much ing coils and tubes, dull looking sugars, and a frequent tendis added there follows a destruction of invert sugar, darkening ency to invert and deteriorate in the finished products. of the color of the solution, and increase of ash. I n this case, Of all the methods of precipitating the very small amount of unfortunately, there is no "happy medium," for the two op- residual lime from the defecated juice that depending upon the posing requirements overlap each other. use of phosphoric oxide proved the best, and in practice it Efforts were made years ago to harmonize these opposite has been found so easy and inexpensive of operation as to tendencies by adding a suitable amount of lime to produce eliminate any serious objections on this which so often proves complete precipitation and, after heating, adding sufficient to be the crucial point in newly proposed methods of operation. other reagents to neutralize the excessive alkalinity. This' PROCEDURE apparently rational procedure, however, has never become The cold, strained juice from the mill is limed to a point established, because it does not yield satisfactory results inasmuch as lime exercises a specifically selective activity about one-third to two-thirds of the way between alkalinity when applied to the juice of the sugar cane-first neutralizing to litmus and alkalinity to phenolphthalein, according to the more highly ionized acid bodies, then those of weaker determination through prior tests of the point of complete ionization, and finally forming insoluble precipitates with a Precipitation. This can be conveniently accomplished by series of mineral and organic substances, producing new treating 100 cc. of juice with successive portions of dilute bodies, some of them highly colored, which are only insoluble milk of lime (made by grinding 1 gram of the lime to be used i n an alkaline menstruum. This is the reason why the in 100 CC. of water), heating to about 90" C., filtering, and testprecipitate partly redissolves on the neutralization of the ing the filtrate with more limewater. In house operation the excess of lime, and for dragging all these impurities through degree of alkalinity can be determined by titrating with the factories in the production of millions of tons of raw sugar 0.1 N hydrochloric acid back to neutrality to litmus or by annually, with all the attendant disadvantages, not only to titrating with 0.1 AT sodium hydroxide to neutrality to phethe raw sugar maker, but to the refiner, who also bears all the nolphthalein and thus checking in a few s ~ o n d sagainst burden of excessive insoluble matter, color, and ash through- the desired alkalinity. The sufficiently limed juice, which now contains 0.01 to out the operations in the refinery. To meet the various exactions of this particular situation 0.02 per cent of lime beyond alkalinity to the most delicate the writer, after considerable work, succeeded a few years litmus Paperl is now heated to Cause Precipitation of the ago in developing a process, now protected by United States various Precipitable matters. and foreign patents, which meets the requirements of the case The temperature required for this step varies in different and should prove of benefit, not only in the fabrication of the juices, LQUisiana juice often giving apparently Complete precipitation a t 40.6" C. (105" I?.), while juice in Cuba raw sugar, but in refining it as well. A comprehensive review of the field indicated the need of needs a higher temperature; but in all cases, with the proper securing the benefits of the full amount of lime and of circum- addition of lime, complete Precipitation may be had a t temperatures far the point* 1 Presented before the Division of Sugar Chemistry at the 67th Meeting After proper liming the juice is heated and settled, the ofthe American Chemical Society, Washington, D C., April 21 to 26, 1924.
July, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
volume of the precipitate being 10 to 20 per cent larger than usual, owing to the increased amount of impurities thrown down. The time of subsidence of this precipitate is, if anything, only a trifle longer than usual, because of the greater alkalinity rather than the increased volume of precipitate. The clear juice is then decanted, using either intermittent blowups or continuous settlers, of which there are several well-known types, and the precipitate is disposed of in any of the usual methods. Having thus eliminated all the impurities that lime is capable of precipitating, but having produced an alkalinity in the juice which would be too strong for the prolonged periods of heating in the multiple effects and in the pans, the next step is to eliminate the lime and the alkalinity from the clarified juice. This is accomplished by means of about 0.15 pound of phosphoric oxide per ton of juice, applied as phosphoric acid or some soluble phosphate or, best, as a suitable combination of them. The composition of this reagent varies considerably with the nature of the juice. I n fact, the range of variation in treatment a t this point has proved so large as to have called for an amount of research which is too extended to detail in this brief communication. The properly neutralized juice is reheated slightly to facilitate the formation and subsidence of the second precipitate, which consists principally of dicalcic phosphate, together with phosphate of iron, derived from the polyphenols of iron, in the juice, and some other basic phosphates. This precipitate is very flocculent and, while rather small in volume, is sufficient to carry down with it the bagacillo and other matters left in suspension after the lime defecation. It settles very quickly, giving extraordinarily clear juice, which can be decanted in 20 minutes or even sooner, when using intermittent blowups, and requiring about 60 per cent as much settling capacity as the first defecation. The second precipitate may be very advantageously separated in a continuous separator, where such is available. Ordinarily, the second precipitate may be combined with the first in the mud tanks, to be diluted, reheated, settled, and decanted, for there is no reaction between these two precipitates or their accompanying solutions when mixed together, and they form a mixture that filter-presses freely and quickly, yielding dry, hard cakes. All the phosphoric oxide of the reagents used passes into this second precipitate in a form almost entirely of immediate availability as plant food, and should therefore be returned to the soil. This conserves nearly the entire money value of the phosphatic materials, which may thus be quite properly looked upon as a very small amount of fertilizer for the growing cane, which can be used in the factory, without materially impairing its manurial value, before applying it to the crops in the field. Ordinarily, from 300 to 400 pounds of phosphatic fertilizer material are recommended to the acre growing an average of 20 to 30 tons of cane. I n this method of defecation the amount of phosphatic material, costing scarcely more than fertilizer, will come at most to only one-tenth to one-thirtieth of this proportion. In cases where the defecation mud is returned to the mills, it is advisable to keep the phosphatic precipitate separate and return it l,o the fields, where each dollar’s worth of phosphate will produce, according to competent authorities, a large return above the investment.
DIscussIoN OF RESULTS This process was operated with complete technical success upon the entire juice of a large Cuban factory during the last week of the run in 1921 and again a t another Cuban factory on the entire output during the last month of the run last year, very satisfactory results with in all determinable respects.
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The purity of the juice was raised a degree more than by the ordinary defecation, the juice and meladura were much cleaner and considerably lighter colored than before, the ash in the juice was reduced by about 40 per cent, and the keeping period of the juice considerably increased during shutdowns. That the rise in purity was a true rise and not due to the destruction of levorotatory bodies was evinced by the fact that the difference between the direct polarization and the Clerget polarization in the resulting final molasses was as great as usual. The mud produced and filter-pressed was about 13 per cent more in volume than in previous processes, only a small part of which is to be attributed to the phosphate and the extra lime added. The sugars produced were of two grades-a first sugar, very brilliant, slightly washed, and polarizing about 99; and a second sugar, also unusually clean, carrying all the molasses from the first, and polarizing a little over 96.0. Part of the first sugar was easily washed up to a purity of 99.86 by using 3 gallons of water to a full charge in a 40-inch centrifugal. The first sugar was disposed of very advantageously for direct consumption. The second sugar contained an average of only about 0.3 per cent of ash, just about half as much as Cuban centrifugals have averaged for the past twenty-one years. This low ash content in juice makes for better yields and was reflected remarkably in the steadily lowering ash in final molasses during the month’s run. This ash fell steadily from 11.53 per cent at the beginning to 6.26 per cent a t the end of the run. The considerable diminution of impurities in the juice by this process of treatment was shown by the fact that the amount of final molasses produced per bag of sugar fell steadily from 7.76 gallons a t the beginning to 6.55 gallons a t the end of the month. The effort of every manufacturer is to get the maximum amount of sugar out of the juice and into the bag of raw sugar and to lose as little as possible in molasses and other wastes. This is all helped by the earliest possible elimination of melassigenic substances and the freer passage of cleaner juice throughout the steps of manufacture. Through the early removal of a greater part of the mineral and organic impurities from the juice, that part of the sucrose which these substances habitually carry into the final molasses will be liberated for crystallization and will thus substantially increase the yield of merchantable raw sugar. The process outlined above can be very readily installed in any raw cane sugar factory by the addition of about 60 or 70 per cent of the present juice-settling capacity, together with simple provision for adding the reagents and means for moving the juice through the additional settlers. Houses installing new modern settlers can, by keeping the old ones, inaugurate the operation of this process with but trifling expense. An additional point of interest in this method of defecating cane juice lies in the improved character that sugars so made possess for refining. Their smaller amount of insoluble matter insures greater ease in affination, with the production of a washed sugar of 99.5 purity as against the usual 99.0 purity. Their defecation is easier and their smaller amount of color renders their decolorization by bone black or by decolorizing carbon much more effective. Perhaps their most important feature to the refiner is their extraordinarily low ash, which insures a better bone black or carbon purification and a larger yield of refined sugar. The Treasury Department has adopted a supplemental list OF standards of strengths of dyes and coal-tar colors for the purpose of assessing duty on these products under Paragraph 28 of the Tariff Act. The new list is supplemental t o Treasury Decision 40,192 of May 17, 1924, and adds about seventy-five more colors to the list of standard strengths.
