GB889823A - Improvements in purification of sugar solutions - Google Patents

Abstract

889,823. Purifying sugar solutions. AMERICAN SUGAR REFINING CO. June 13, 1960 [June 22, 1959], No. 20680/60. Class 127. In a continuous purification process, hot sugar solution of constant viscosity is passed upwardly and uniformly through an elongated vertical column, e.g. 30 to 40 feet high and 12 feet in diameter, in counter-current to a downwardly flowing bed of adsorbent, e.g. bone char or activated carbon. In the arrangement shown diagrammatically, sugar solution, preferably having a pH above 7.0, e.g. between 7.2 and 7.5, is freed from dissolved gases, e.g. air, and introduced via an inlet 2 near the bottom of an insulated and heated column 1, and is distributed by pipes 3 to flow upwardly through the column to a purified solution outlet 4 via an overflow device 5 and trough 6, whilst adsorbent is fed through a series of lines 7 to pass downwardly, through soaking chambers 8 and a body of purified sugar solution, to reach the top level 32 of a bed of adsorbent, which is expanded, e.g. to 5% to 15% of its settled volume, by the upwardly flowing sugar solution. From the conically shaped bottom of the column, a slurry of spent char and sugar solution passes through lines 10 and a line 11 to a series of crossover pipes 12, having control valves and located at different levels, to regulate the slurry overflow, both to a line 13, leading to a de-liquoring device 14, and to a by-pass line 15a. Deliquored spent char and slurry combine in a line 15 for downward descent through a desweetening column 16, in counter-current to an upward flow of water fed in near the foot of the column 16 through an inlet 17 and distribution pipes 70, sweet-water e.g. around 30‹ Brix, leaving the column via a collecting trough and outlet 18. Bone char slurry leaves the column at the bottom via lines 19, 20 and cross-over pipes 21 to enter a de-ashing column 23, constructed similarly to column 16, from which waste water leaves to the sewer through an outlet 25, whilst de-ashed char passes through line 26 and cross-over pipes 27 for filtration and regeneration. More than one column 1 may be used if desired. Lines 9, 83 extend into the columns to enable samples of liquor to be drawn, and 38, 80 represent differential pressure cells to determine and regulate the level 32. The sugar solution to be purified preferably lies between 60‹ and 65‹ Brix, has a temperature of from 160‹ to 180‹ F., a viscosity of from 6.7 to 8.2 c.p.s. and is passed upwardly through the column in amount 3 to 10 times the volume of adsorbent passing down the column; it may be adjusted in pH by adding to it lime or calcium sucrate. Suitable forms of apparatus are described in detail and, in an alternative procedure, the adsorbent fed to the top of the purifying column may be formed into a slurry with purified sugar solution before admission to the column. U.S.A. Specifications 2,352,932 and 2,735,823 are referred to.