METHOD OF AUTOMATIC CONTROL OF PRODUCT DRYING PROCESS IN FREEZE DRIER Russian patent published in 1998 - IPC

FIELD: automation of freeze drying of ferment preparations in microbiological, medical, pharmaceutical and food industries. SUBSTANCE: product initial and final moisture content at the drier inlet and outlet respectively, residual pressure in freeze chamber, flow rate of vapors discharged from freeze chamber, flow rate of refrigerants fed to desublimation still, refrigerant temperature at the desublimation still inlet and outlet are measured, the current value of heat flow discharged from the desublimation still cooling element is being continuously measured, and according to the product initial moisture content, the residual pressure in the freeze chamber is determined by influence on the flow rate of water vapors discharged from the freeze chamber; the residual pressure is corrected according to the final product moisture content, and the flow rate of refrigerant to the desublimation still is determined according to the flow rate of water vapors discharged from the freeze chamber; the relation between the flow rates of discharged water vapors and refrigerant are corrected according to the value of heat flow discharged from the desublimation still cooling element by influencing the refrigerant flow rate; at a deviation of the product final moisture content from the preset value towards increase the flow rate of water vapors discharged from the freeze chamber is increased by influencing the vacuum-pump capacity, and at a deviation of the product final moisture content from the preset value towards decrease the flow rate of water vapors discharged from the freeze chamber is decreased; at a deviation of the current value of heat flow discharged from the desublimation still cooling element from the preset value towards decrease the flow rate of refrigerant to the desublimation still is increased, and at a deviation of it towards increase the flow rate of refrigerant to the desublimation still is decreased; connection of the subsequent section of the desublimation still with disconnection of the previous one for recovery is accomplished when the current value of heat flow discharged from the desublimation still cooling surface attains the limiting minimum value. EFFECT: reduced power consumption, enhanced accuracy and reliability of control. 3 cl, 1 dwg, 1 tbl