Study On Mcrowave Drying Technology Of Rice And Optimization Of Drying Device

China is a traditional agricultural country,which has a long history of rice planting,rich types of planting,wide planting area,and harvest a large number of fresh rice every year.However,the newly harvested rice is still undergoing vigorous biochemical reactions because of its high water content and high activity.The respiration will make rice produce a large amount of carbon dioxide,and continuously release heat,which promotes the sharp rise of internal temperature of rice and also consumes a large amount of nutrients.When the internal temperature reaches a critical value and is in a suitable temperature range,harmful bacteria in rice will multiply in large quantities,resulting in a short period of quality deterioration and decay of rice.At present,the drying methods of rice in most parts of China are mainly traditional drying methods,such as hot air,steam and electric heating.They are all drying methods from outside to inside by heating the surface of rice first,then absorbing heat from the surface,and gradually penetrating into the interior of rice.Microwave drying is different from them,it is a method of heating the internal medium of rice,and then gradually diffusion drying the whole.Compared with the traditional drying method,microwave drying has the advantages of fast drying rate,energy saving,uniform drying,clean and non-polluting,and automatic control.Therefore,it has been paid more and more attention in the drying field of various industries in China.In this paper,the drying process and temperature-humidity characteristics of rice were further studied by comparing the effects of hot air drying with traditional drying methods and microwave drying with new drying methods,and the existing drying devices were optimized.The specific methods are as follows :(1)According to the two experimental methods of microwave drying and hot air drying of rice,the experimental data of moisture content,water activity and temperature change of rice in the same time were measured.The fitting and comparative analysis were carried out by using the method of control experiment.The influence of different drying methods on the water activity of rice was further studied,which has guiding significance for reducing the reproduction of bacteria in rice and improving the quality of rice.(2)Microwave power,vacuum degree and paving thickness were selected as experimental influence factors to conduct single factor experiment on dry rice and judge its influence degree.According to the principle of orthogonal experiment,the single factor experiment was optimized by orthogonal experiment,and the optimal conditions of microwave drying rice were obtained.Then the grey system theory is used to analyze the technological conditions of microwave drying rice,calculate the grey correlation index,and discuss the effect of the main factors.(3)In order to reveal the electric field distribution law of the microwave cavity and the change law of the heat-wet stress of rice in the process of microwave drying rice,a three-dimensional geometric model of rice grains was constructed by image method,and the electric field,temperature and humidity and stress changes of rice during microwave drying were calculated by COMSOL Multiphysis software,and the temperature and humidity characteristics of rice drying were analyzed,and the research results provided a research basis for improving the uniformity of microwave drying and enhancing the drying effect.(4)Based on the microwave hot-air drying rice process experiment and rice drying simulation analysis,the structural design of the drying chamber was mainly carried out,and the structure of the existing drying rice experimental device was optimized.The main contents of the study include the structural design of the drying chamber,the overall structural design,the design of the main components and the working mechanism of the drying equipment.