GB416483A - Process of treating sugar solutions - Google Patents

Abstract

416,483. Purifying sugar solutions. DEHN, F. B., 103, Kingsway, London.- (California Packing Corporation; 101, California Street, San Francisco, U.S.A.) Feb. 16, 1933, No. 4824. [Class 127.] Impure-sugar solutions of all kinds containing invert sugar and sucrose are fermented in such a manner as to convert the invert sugar into alcohol without destroying the sucrose, an alkaline earth oxide or hydroxide or aluminium oxide or aluminium cream is then added in amount sufficient to precipitate the organic impurities only, and the alcohol is distilled from the solution after the precipitated impurities have been removed, leaving a purified solution of sucrose. An additional quantity of alcohol may be added to the solution before the precipitation of the impurities, and in this case, especially when treating molasses of low glucose content, the fermentation step may be omitted. As applied to the treatment of saccharine liquids from sugar cane, the process may be carried out by sending the sugar syrup obtained by the initial evaporation of the clarified juice from a tank 10 to a crystallizing pan 11, wherein crystallization takes place, giving rise to a first massecuite. This massecuite is then sent to centrifugal separators 12 wherein a first molasses is obtained, which may be either returned to the same or to a second crystallizing pan 13. A certain amount of syrup from the tank 10 may also be sent to the pan 13 by a line 14. The second massecuite from the pan 13 is sent to the centrifugals 12<1>, and the second molasses thus obtained sent to a storage tank 14 from which it may be withdrawn as required into a dilution tank 15, the raw sugar from the centrifugals 121 being washed and bagged. In the dilution tank 15 the molasses is diluted to between 35 and 65‹ Brix and the fermentation of the invert sugar allowed to take place ; the use of special selectively fermenting yeasts being unnecessary. Fermentation proceeds in tanks 16, 17, 18, &c., and the resulting molasses, containing 2 to 10 per cent of alcohol, is sent to a tank 19 wherein a small quantity of an alkaline earth metal oxide or hydroxide, such as milk of lime, is added by a line 20. An additional quantity of alcohol equal in volume to that of the molasses is preferably added from a tank 22 by a line 21 before the addition of the alkaline earth oxide or hydroxide, to stop the fermentation and to facilitate the precipitation and separation of the impurities. The addition of the lime may take place before that of the alcohol, if desired. The solution is then filtered in the filter 23 and discharged into a tank 24, the filter press being washed with alcohol from a tank 25 and then blown with steam or with steam and air to recover the alcohol in a condenser 26, from which the condensed alcohol returns to the tank 25. The alkalinity of the solution in the tank 24 may be neutralized by carbon dioxide brought from the fermenters 16, 17, 18 by a line 27, or by means of sulphuric, phosphoric, or any other acid forming relatively insoluble calcium and potassium salts, such acid being supplied from a tank 28. The solution neutralized to a pH value between 6À6 and 7À2 is filtered at 29, and the solution sent through a line 30 to an evaporator 31 in which the alcohol is recovered, the alcohol vapours passing through condensers 32 and the alcohol being returned by a line 33 to the tanks 25 and 22. The dealcoholized solution is sent by a line 34 to an evaporator 35 and then to a crystallizing pan 36, from which the mass may be discharged into a centrifuge 37, the molasses separated at 38 being adapted for subsequent treatment by the Steffens or barium process for the extraction of the remaining sugar. The solution from line 34 may otherwise be sent by a line 39 to the initial refining operations. In a modification, the liquid from the filter 23 may be sent direct to the still 31, eliminating the neutralizing operation 24 and the filtration operation 29. The dealcoholized syrup in this case is freed from precipitated matter in the filter 40, neutralization with a suitable acid, having been effected if necessary. As a further modification, the organic impurities may be precipitated in the tank 19, filtered off at 23, and the filtrate neutralized in the tank 24 before dealcoholization in the still 31. The sugar solution coming from the still 31 then requires filtration in a filter 40. Instead of providing separate units, for example, filters 23, 29, and 40 or centrifugals 12, 12<1>, and 37, the same unit may be used at different times for the various operations.