GB884089A - Improvements in and relating to drying materials in crumb form - Google Patents

Abstract

884,089. Drying materials in crumb form. BLAW-KNOX CO. June 8, 1960 [June 10, 1959], No. 20110/60. Class 34(2) In a process for drying materials in crumb form, e.g. emulsion polymer crumbs, liquid is expressed from the crumbs in a compression zone under conditions producing a substantial increase in the temperature of the crumbs, drawing off the expressed liquid, extruding the heated crumbs into a decompression zone, comminuting the material as it passes into the decompression zone and maintaining both a temperature and a vacuum in the decompression zone sufficiently high to cause retained liquid to vaporize. Apparatus for carrying out the process comprises expressing liquid from the crumbs by an extruder 2, the screw 3 of which performs mechanical work on the crumbs to substantially increase their temperature, removing the expressed liquid through a drain 11c, extruding the heated crumbs into a decompression zone 5 wherein a vacuum is maintained to vaporize the remaining liquid in the crumb and wherein the crumb is comminuted, and the dried crumb proceeds to a second extruder 6 for extruding the consolidated product through an extrusion head 10. The extruder 2 has sections 11, 12, the former comprising cylindrical and tapered chambers 11a, 11b respectively to compress the crumb and to enable the screw 3 to raise the crumb temperature. The section 12 has a heating jacket 13 to heat the crumb prior to passing to a rotary disc valve 16 operated by a handle 17 and having apertures 16a which register with apertures 18a in a parallel stationary plate 18 to control the back pressure within the extruder 2. The crumb passes through a passageway 19 in the main wall 21 of the decompression zone 5 where it is severed and comminuted by a helical knife 33 formed as flights on a shaft 28 driven by a motor 30. The zone 5 has means 24 communicating with a vacuum pump (not shown) by which air and vaporized moisture is withdrawn from the zone and the zone also has a heating jacket 22 to maintain the temperature of the crumb. The comminuted product is downwardly urged by gravity and the helical knife past a combined observation glass and dwell stage 36 into the extruder 6.