热泵驱动的溶液除湿在谷物就仓干燥中的应用

Application of Grain In-bin Drying Based on Liquid Desiccant Dehumidification Driven by Heat Pump

为安全且高效地实现粮食干燥储存,设计了一套基于热泵驱动的溶液除湿谷物就仓干燥系统,并建立了系统中各部件及谷物就仓干燥数学模型。模拟了南昌地区秋季初始含水率为22%、初始温度为20℃的200 t谷物就仓干燥至安全水分的过程。分析了溶液除湿系统干燥中风量对系统干燥时间及耗能的影响,得出耗能最低的最佳通风量;提出自然通风与溶液除湿系统结合的混合干燥方式,采用最佳通风量进行干燥,分析了自然通风时长对系统干燥时间和耗能的影响;且研究了以全自然通风、溶液除湿系统及混合干燥三种方式下干燥过程中谷物含水率和COP(coefficient of performance)的变化情况。结果表明:当风量为200 m ^(3)·h^(-)1·t^(-1)时,溶液除湿系统耗能最低,干燥时间为200 h,远低于安全干燥期,干燥过程平均COP可达4.3;采用全自然通风干燥时,在安全干燥期内谷物水分无法降至安全储存要求,且干燥过程整体COP较低。采用混合干燥方式时,合理的自然通风时间有利于降低系统耗能;混合干燥方式在干燥前期采用自然通风,可充分利用其干燥能力,后期采用溶液除湿系统将谷物降至安全水分,可为实现安全、高效、节能的谷物就仓干燥过程提供一种选择。

Based on liquid desiccant dehumidification driven by heat pump,a system of grain in-bin drying was designed to achieve grain drying and storage process safely and efficiently,and the models of grain in-bin drying and each component in this system were established in this paper.This paper simulated the process of drying 200 t grain with initial moisture content of 22%and temperature of 20℃to safe moisture content in Nanchang area in autumn.The influence of air flow rate on drying time and energy consumption were analyzed when the liquid desiccant dehumidification system was adopted for drying,and the optimal air flow rate with the lowest energy consumption was obtained.A hybrid drying system combining natural ventilation and liquid desiccant dehumidification was proposed,under adopting the optimal air flow rate to dry grains,and the influences of natural ventilation drying time on drying time and energy consumption of the system were analyzed.The changes of grain moisture content and COP(coefficient of performance)during drying process under only natural ventilation,liquid desiccant dehumidification and hybrid drying were studied.Simulation results show the liquid desiccant dehumidification system has the lowest energy consumption when the air flow rate is 200 m^(3)·h^(-1)·t^(-1),and the drying time far lower than the safe drying period is 200 h.The average COP range during drying is 4.3.The moisture of grains couldn t reduce to the requirements of storage in safe drying period when only natural ventilation drying is adopted,and the COP during the drying process was relatively low.The limitation of safe drying period on natural ventilation time should be considered and selecting reasonable natural ventilation time is beneficial to save energy under hybrid drying system.Hybrid drying system could make full use of natural ventilation drying ability in the early stage of drying,and adopt the liquid desiccant dehumidification in the later drying stage to reduce grains to safe moisture content.Above results provided an alternative system for realizing a safe,efficient and energy-saving grain in-bin drying process.