Microwave Drying Of Minerals

The metallurgy is one of the basal industries in our national economy. As an important process in producing ores, drying determines the quality and quantity of the products. It is important to find a new drying method to instead of the conventional ones, because the later are of the low using efficiency of energy, the long drying period, the serious pollution to the environment and so on.Microwave drying occurs in the whole body of the material, which differs from the conduction heat transfer in traditional heating system. For special heating characteristics, it makes microwave drying have the quick drying speed, the product of high quantity, easiness to control produces, the high utilization of thermal energy etc. advantages, thus will make it be able to adapt the demands of the modern metallurgy produce, hope to solve the problems existed in the conventional drying methods, and have vast of development foreground.At present, the application study on microwave drying in metallurgy production is to be placed in the initial stage, and the research on the dry theories is to be started too. In addition, lagging of dry theories research will also obstruct the applied development of microwave drying. Therefore it is necessary to carry on the study to the theories of microwave drying deeply, in order to make the microwave obtain the largest economic and social performance in the metallurgy.Based on the lookup and summary of the related information, the new-type experimental equipment of microwave drying has been researched in this paper. In virtue of the equipment, the experiments of microwave drying on sphalerite, pellet and bentonite has been done. The relations between material weight, microwave power, dry time and the sphalerite dehydration rate during the process of microwave drying has been established, and then the optimized conditions of microwave drying sphalerite were obtained. At the same time, the influences of mineral weight, microwave power, diameter of drying container and drying time on the dehydration rate of the pellet and bentonite have been studied too, and the optimized conditions of microwave drying them were gotten respectively.Under the three optimized conditions above-mentioned, the results of regressionindicated that microwave drying of sphalerite, pellet and bentonite were in accord with the equation: (A-a2) ■ The process of drying can be divided three phases:l + exp(~% dtaccelerated, constant and fallen rate drying phase.It is difficult to use the classic microwave drying models to describe the drying process of the ores, because mensurating many academic parameters of material in the microwave field exists big difficulty. Currently, the approximate methods were adopted to solve the models, which make the research development of microwave drying be placed between theories estimate and experiment. In order to solve this problem, in this paper, the mathematics models of microwave drying have been set recurring to the Lumped Moisture Capacity Method and Lumped Heat Capacity Method. The models can calculate the temperature and the wet content of the ores in different time, which found a kind of more practical processing method to description the rule of the microwave drying(1) Through the theory derivation, drying pressure gradient is main impetus during drying, it was found that "Lumped Moisture Capacity Method" agrees with microwave drying law. The drying process models established were as follows:Accelerated and constant drying phase:_*jj4 e qFallen rate drying phase: M = M ' ^0 exp(( +) HMApfMe%l Jf ,J ? (t - Q) -evQvV AhvpQV(M0-M'Q)(2) Put forward "Lumped Heat Capacity Method" to found model of microwave drying law. The drying process models established were as follows: Accelerated and fallen drying phase:AhTT=C -c^ ^ap°Vt i ^aCrPSV | h %2O2V2 yQv +AhTTf -Mivbp0Vi AhT a%2 AhTConstant drying phase:AhjOn the basis of the above-mentioned microwave drying models, the wet content and temperature of the pellet in the dissimilarity time have been gotten, which are in accordance with the experiment data. In a word, the microwave drying models deduced in this paper can fit well with the drying regulation of the metallurgy material.