METHOD FOR AUTOMATIC CONTROL OF DRYING PROCESS Russian patent published in 2003 - IPC

FIELD: process automation for drying thermolabile products such as grains and macaroni. SUBSTANCE: method involves preheating of wet product by means of waste drying agent flow followed by its drying and cooling down in evaporator, heating in heat-pump plant condenser, and feeding to drier thereby organizing closed cycle including dump of excess portion of waste drying agent or its makeup with fresh agent by controlling steam flow to heater and fan drive power , stabilizing moister content of end product, and measuring temperature of drying agent downstream of evaporator and upstream of condenser, measurement results being used to set desired refrigerating capacity of heat-pump plant by controlling compressor drive power. Product is dried out in two drying zones with intermediate cooling down in heat-transfer apparatus; one part of dried and cooled drying agent contained in heat-pump plant evaporator is supplied to heat-transfer apparatus for intermediate cooling of product and then conveyed to closed cycle upon preheating of wet product; other part is passed to heat-pump plant condenser and further to inlet of first and second drying zones in desired proportion; product temperature is additionally measured upon intermediate cooling in heat-transfer apparatus, and flowrates of dried and cooled drying agent supplied to heat-transfer apparatus for intermediate cooling and conveyed to heat- pump plant condenser is varied depending on this temperature; proportion of flowrates of drying agent supplied to these zones after heat-pump plant condenser is varied depending on measurement results of moisture content of product at outlet of drying zones; excess portion is used for regenerating evaporator section. EFFECT: reduced specific power requirement, enhanced quality of dried product. 1 cl, 1 dwg