Study On Parameter Optimization And Automatic Process Control Of Double Layer Sunflower Seed Dryer

Sunflower seeds,as an important cash crop in Inner Mongolia,can effectively improve regional economy and build excellent local brands by deep processing and production of high-quality sunflower seeds.Sunflower seed drying is one of the deep processing methods.The production of high-quality boiled sunflower seeds benefits from good baking equipment and technology,including the exploration of sunflower seed baking and drying characteristics,sunflower seed dryer structure design and baking heat flow field optimization,automatic control system design,quality evaluation standards,etc.The main contents of the paper are as follows:(1)Through literature research,the PAGE model in the thin layer drying model was used to represent the drying characteristics of sunflower seeds,and the curve of moisture content changing with time under fixed working conditions was fitted.According to the drying characteristic curve,sunflower seed drying can be divided into three stages:preheating,constant speed and decreasing speed.The efficient drying process of sunflower seeds was explored,including medium fire in preheating stage,high fire in constant speed stage,low fire in decreasing speed stage,and corresponding time range.(2)The double-layer full-layer-type sunflower seed dryer is taken as the research object.The uniformity of drying process is the main factor affecting the drying quality of sunflower seeds.The traditional uniformity evaluation method is only applicable to the dryer whose drying medium is not fully covered.The dryer was optimized based on FLUENT module and response surface optimization module in ANSYS software.The cross section size of hot air inlet,flow rate and thickness of baking medium were taken as design variables,and the temperature standard deviation of a cross section of drying layer was taken as the optimization objective.The response surface model based on genetic clustering was established and the interaction of factors was analyzed.The optimal solution was selected by screening method and verified by finite element method.Simulation results show that heat flow after the first drying layer,the flow rate tends to be stable,so the first layer can be optimized.This method is suitable for flow field optimization of full-layer dryer.Based on the optimized heat flow field of the dryer combined with the boundary conditions determined by the above drying characteristics,the simulation of single-layer baking time was carried out.The uniformity of the upper surface of the lower baking layer is taken as the evaluation standard of whether the baking is complete,and the complete baking time in the constant speed stage of the baking layer is simulated,so as to develop a more accurate process.(3)Based on PLC and touch screen integrated machine,the double-layer automatic baking control system for deep processing of sunflower seeds was built,including the control system of the double-layer automatic baking linkage mechanism for deep processing of sunflower seeds and the feedback control system of the temperature of sunflower seeds baking thermal conductivity field.The former is mainly responsible for controlling the movement state of the double-layer dryer,including turning,unloading,conveyor belt opening and closing.The latter is mainly responsible for the control of sunflower seed heating state,including the adjustment of hot oil valve,hot air temperature feedback,air door size adjustment,the opening and closing of the air motor.Design corresponding primary and secondary power supply,control circuit as the basis of the control system,write based on Mitsubishi PLC trapezoidal diagram program with coolmayHMI software to write man-machine interface to achieve the above control.(4)on the basis of sunflower seeds for moisture content,rate of exploding shells,such as quantitative indicators,and loose brittleness,color,aroma and other qualitative evaluation indicators,construction of sunflower seeds processing quality grade evaluation grade standard,to sunflower seeds processing baking process parameters of total score for the final comprehensive evaluation index,in order to obtain extreme baking temperature and duration of temperature rise rate and its optimal baking process.Finally,after the physical prototype field test,the equipment is simple to operate and stable,and is suitable for the control of sunflower seed double-layer grain dryer.