GB621797A - Improved method and apparatus for the continuous crystallization in vacuo of sugar solutions and the like - Google Patents

Abstract

<PICT:0621797/III/1> <PICT:0621797/III/2> Sugar and like solutions are continuously crystallized in vacuo by feeding the solution to the first of a series of heated and interconnecting compartments to commence the evaporation and crystallization, and causing the resulting mass to flow continuously through the succeeding compartments in each of which the mass receives a continuous controlled additional supply of the solution, the displacement of the mass being effected by a difference in the level of the mass in successive compartments or by a difference of pressure between successive compartments. The solution fed to the first compartment may be nearly saturated, and may be seeded before or after it enters the compartment. In the vertical apparatus shown, the annular chamber constituted by axial tube 1 and casing 2 is divided into five compartments 31-35 of increasing volume by means of radial partitions 3 extending from the bottom of the casing up to cap-member 4. The tubular heater 6 may be common to all the compartments or may be itself divided into compartments. The crystallizing mass in compartment 31 circulates through the heating tubes and annular chamber 8, and part of it passes through opening 9 into compartment 32; the transfer being guided by deflector 10 and partition 11. After flowing through the compartments, in each of which it receives a continuous flow of saturated solution through an adjustable cock, the mass is removed from compartment 35 through opening 12 in axial tube 1. The steam pressure inside heater 6 is adjusted so as to properly associate the simultaneous evaporation and crystallization. In exceptional cases, it is possible to adjust the heating by acting on the proportion of incondensable gases in the upper portion of the heater. The speed of evaporation as a whole is adjusted by providing the pipe connecting dome 5 to the condenser with an automatic vacuum regulator. If the displacement of the mass is effected by pressure differences, these are controlled by adjusting the cross-sections of steam-outlets 13, 131 and 132. In a modification, the heater 6 is secured directly to axial tube 1. A horizontal apparatus is also described.