Study On Drying Technology Of Bleached Shellac

The drying of bleached shellac is an important part of the production. For its long hours, large covering of area, high labor intensity, influenced by the climate and the color of the product hard to controlling, it become to the strong bottleneck of production. The research of drying process of bleached shellac is not reported in China. The paper come from the thermal properties of bleached shellac and find drying ways within its softening temprature. By studying the bleached shellac drying at room temperature, vacuum freeze-drying, fixed bed drying, vacuum drying, microwave-vacuum drying methods on drying curve and drying rate curves, found that vacuum drying and microwave-vacuum drying is the better drying method, and then their conditions were optimized. On the basis of the drying, the paper improved the washing process, then found the pretreatment of bleached shellac, and the pretreatment process were studied. Thereafter, the combination of pretreatment+ drying method is studied. The results show that:1,The soften temperature of bleached shellac is 23.3～80.5℃, the average melting point of 62.5℃.2,Microwave-vacuum drying is the best drying methods of bleached shellac, the optimum conditions is:for the pressure of 3.0kPa, the microwave power 795W, drying time of 30min. In these conditions,the color index of the product is 0.90.3,The pretreatment process of bleached shellac was studied. The experimental results showed that the best conditions were:liquid ratio of 1:6, stirring speed of 300 turn/min, temperature of 33℃, washing time of 11min. After pretreatment process, the dehydration rate of bleached shellac is 69.29%. The initial water content and salt content are greatly reduced in the process. The process could be widely applied in industrial production.4,The combination of pretreatment and drying were studied. The results showed that pretreatment+microwave-vacuum drying method is the best method:the drying time, product quality and drying energy consumption are better than other drying methods. The pretreatment conditions are:liquid ratio of 1:6, stirring speed of 300 turn/min, temperature of 33℃, washing time of llmin; the microwave-vacuum drying part conditions are:pressure of 3.0kPa, microwave power 795W, drying time of 17min.