The Fundamental Research On Temperature Rising Characteristics And Deep Dehydration Of Phosphating Residue In Microwave Field

In recent years,a lot of phosphating residue has been generated inevitably in the phosphating process with the rapid development of phosphating industry in China.Phosphating residue contains a variety of heavy metals and other toxic substances.It has been become more and more important for phosphating residue to reduce the pollution to the environment,improve the resource reutilization,and recycle the valuable metals,which makes it particularly crucial to study economical and effective dehydration of phosphating residue.Microwave heating technology has been the focus in the drying field for its many unparalleled advantages compared with other heating methods.Therefore,the development of novel method of phosphating residue dehydration with microwave heating technology is extremely important for studying the deep dehydration mechanism and reducing the drying cost of materials.The preliminary investigation of deep dehydration mechanism and kinetics were taken in this work with the factors of microwave power,loading capacity,moisture content,ratio of height to diameter and particle size.The results are as follows:(1)In the study on the temperature rising characteristics of phosphating residue in microwave field,the microwave power and the ratio of height to diameter of materials have positive correlation with the temperature,and the loading capacity is on the contrary.(2)In the study on the dehydration characteristics of phosphating residue in microwave field,the influences of factors on the dehydration rate are in the order of microwave power,loading capacity,ratio of height to diameter and moisture content from high to low;microwave power is a highly significant factor and the loading capacity is a significant factor;the influences of factors on the energy utilization rate are in the order of microwave power,moisture content,loading capacity and ratio of height to diameter from high to low;the microwave power,moisture content and the ratio of height to diameter of materials have positive correlation with the dehydration rate,and the loading capacity is on the contrary;with the increase of temperature,the influences of loading capacity,ratio of height to diameter and moisture content on the energy utilization rate increase at first and then decrease;in laboratory condition,the optimal energy utilization rate is 44.6%at the microwave power of 616W,the loading capacity of 100g,the moisture content of 55.88%,the ratio of height to diameter of 1.0 and the time of 200s.(3)On the basis of study on microscopic mechanism of phosphating residue dehydration,the influences of single factors on the diffusion coefficient of water are researched.The Page's model is suitable to describe the drying process of phosphating residue,and the activation energy of the phosphating residue dehydration is 22.26W/g by fitting with the Arrhenius equation.