Performance simulation and analysis of peanut drying in box-shaped reversing ventilation dryer

In order to understand the operating characteristics of fixed bed reversing ventilation drying of peanut and provide suitable parameters for the box type reversing ventilation drying equipment, a series of partial differential equations was established based on the heat and mass transfer between peanut and air. On this basis, the finite difference method was used to simulate the drying process. The effects of the length of ventilation drying time from bottom to top in the left and right drying chambers, the reversing time in the reversing drying stage, and the ventilation volume per unit volume on the drying behavior were analyzed. The optimal ventilation and drying parameters were determined by uniform design and comprehensive weighted scoring method. The results showed that in the bottom-up ventilation stage, the heat was mainly used to heat peanut materials and rapidly evaporate the water in peanut pod surfaces. The drying and heating rate of the lower, middle, and upper materials was different, and it was easy to form a large moisture gradient. In the reversing ventilation drying stage, the material temperature fluctuated like a wave, which could effectively control the drying uniformity of the whole bed. Shortening the ventilation time from bottom to top was helpful to reduce energy consumption and moisture difference, but it had little impact on drying time and productivity. In addition, the change of reversing time had little influence on time consumption, productivity, energy consumption, and moisture content difference. The increase of ventilation volume would help to reduce drying time, water difference, and productivity, but energy consumption would also increase rapidly. Uniform design and synthetical weighted marks were used for solving optimal ventilation parameters. The results showed that the comprehensive effect of batch drying was the best when the ventilation volume was 1 394 m~3/（m~3h） with moisture content greater than 25%, 838 m~3/（m~3h） with moisture content between 15%-25%, and 1 760 m~3/（m~3h） with water content less than 15%. Finally, the accuracy of the model simulation was verified by the verification experiment. The results showed that the correlation coefficient between the simulation results and the experimental results was more than 0.98, which reflected that the simulation could accurately describe the changes in material temperature and moisture content in the drying process. This study provided a reference for the improvement of peanut reversing ventilation drying equipment and process optimization.