Study On Drying Process Of Closed Circulating Heat Pump Fluidized Bed

Closed-loop drying is a drying operation in which the drying medium is recycled in the closed system.It has remarkable characteristics such as solvent recovery,safety,environmental protection,good product quality and so on.A heat pump is a device that absorbs heat from a low temperature heat source and discharges a large amount of heat which can be used at a higher temperature.The organic combination of the heat pump and the closed circulation drying can not only recover the amount of heat in the exhaust gas but also save a great deal of cooling capacity for cooling t he exhaust gas.It has significant energy saving effect and broad application prospects.This paper presented a closed-loop heat pump drying process using partial exhaust gas recirculation in a fluidized bed.The diameter of the distribution plate is 188 mm.The PVC was used as the drying material,and the air was used as the fluidizing and drying medium.The influence of inlet temperature and humidity on the fluidization and drying characteristics of PVC was studied.The constant rate period and falling rate period of drying kinetics models respectively were MR(28)a(10)bt and exp()nMR(28)-kt.The models were used to calculate the PVC fluidization drying process.The simulation analysis of the closed cycle heat pump fluidized bed drying process of partial exhaust gas recirculation was carried out.The effects of cycle ratio,evaporative temperature,condensing temperature on the drying system of C OP and SMER were obtained.The experimental results were: the evaporation temperature was 20 ?,the higher the condensation temperature,the smaller the COP and SMER of the drying system;when the condensation temperature is 105 ?,the higher the evaporation temperature,the higher the C OP and SMER of the drying system.When the evaporation temperature is 20 ? and the condensation temperature is 75 ?,the greater the exhaust gas cycle ratio,the COP and SMER of the drying system are larger.Under the same conditions,the results of the simulation show that the SMER of part of the exhaust cycle of the closed-loop heat pump fluidized bed drying system were higher than that of the conventional closed-loop heat pump fluidized bed drying system.The energy saving effect is remarkable.The research results have certain theoretical and practical significance to promote the industrial application of closed loop heat pump drying process.