基于带式穿流干燥模型的热泵污泥干燥

Heat pump sludge drying based on belt through-flow drying model

利用恒温恒湿箱进行了多种温度下的污泥样品穿流干燥试验,由所获的污泥干燥特性曲线归纳出水分扩散系数。通过对多层带式穿流干燥过程中水分、热量的传递、平衡分析,构建起描述其稳定运行状态的热动力学模型。根据带式穿流干燥的特点,设计出自下而上的逆向扩散迭代算法推求泥层中的水分分布,再进入湿度场和温度场的耦合计算,模拟得到泥料平均含水率沿带长的分布,以及穿流空气的温湿度变化情况。随后在干燥除湿热泵系统理论分析中,代入带式穿流干燥的热动力学模型的解算步骤,获得不同进口温湿度条件下最佳蒸发温度和最佳除湿能效。最后,选取一种工况做有约束的干化工艺分析,所得结果显示,理论上减薄泥层、缩短干化时长在产能和能效方面都相对较好。

The through-flow drying experiments of sludge samples at various temperatures have been carried out by using a constant temperature and humidity box,and the moisture diffusion coefficient is concluded from the obtained sludge drying characteristic curve.By analyzingthe moisture and heat transfer and the balance in the multi-layer belt through-flow drying process,a thermodynamic model describing its steady operation state is constructed.According to the characteristics of belt drying,a reverse diffusion iterative algorithm from bottom to top is designed to calculate the moisture distribution in sludge layer,and then the coupling calculation of the humidity field and the temperature field is finished.The distribution of the average moisture content of the sludge along the belt length is obtained,and the temperature and humidity changes of the through flowing air are investigated.Subsequently,in the theoretical analysis of the drying and dehumidifying heat pump system,the solution steps of the thermodynamic model of multi-layer belt through-flow drying are added in,the best evaporation temperature and the best dehumidification energy efficiency under different inlet temperature and humidity conditions have been acquired.Finally,a constrained working condition is selected to do drying process analysis.The results show that thinning the sludge layer and shortening the drying time are benefit to the rise of productivity and energy efficiency.