Discrete Element Simulation And Experimental Study On Pelletized Coating Of Alfalfa Seeds

Seed pelletizing technology is a seed-based processing technology that wraps seed coating chemicals,powders,and other additives evenly and effectively on the seed surface,based on the pelletizing coating equipment.Seed pelletizing not only improves seed germination and protects the seed from external biotic or abiotic stresses but is also suitable for precision sowing and ensures the integrity of the seed during mechanical transport.In this thesis,calibrate the discrete element simulation parameters of alfalfa seeds,and coating powder,the mixing mechanism and evaluation index between seeds and powder are studied,and the work of related equipment and process parameters are optimized to improve the qualification rate of alfalfa seed single-seed pelletization and the pelletization coating effect,the main work accomplished is as follows.1.The physical parameters of alfalfa seeds are measured by physical tests,and the EDEM software is used to establish the alfalfa seed model and rest angle simulation model,and the Hertz-Mindlin no-slip contact model is used to conduct the Plackett-Burman test,the steepest climb test and the Box-Behnken test to obtain the best combination of contact parameters for alfalfa seeds in turn.2.The physical parameters of the coating powder are measured by physical tests,and the best combination of contact parameters for the coating powder is obtained by using the Hertz-Mindlin with JKR contact model and conducting the Plackett-Burman test,the steepest climb test and the Box-Behnken test in turn.The contact parameters between alfalfa seeds and coating powder are calibrated by combining physical and simulation tests,and the contact parameters are obtained by fitting the equations through quadratic regression.3.Theoretically,the mixing mechanism between seeds and powders is analyzed,and the coefficient of variation is used as the evaluation index to conduct a single-factor test to determine the range of working parameters for seed pellet coating;the Plackett-Burman test is conducted,and the working parameters that had significant effects on the response values are selected from the coating pot vibration frequency,coating pot vibration amplitude,coating pot vibration direction,coating pot rotation speed and coating pot tilt angle: coating pot tilt angle,coating pot rotation speed and coating pot vibration frequency.4.Based on the results of single-factor test and Plackett-Burman test,quadratic regression orthogonal tests are conducted with different coating parameters,and the best combination of coating parameters for alfalfa seeds is obtained as follows: coating pot speed of 58r/min,coating pot tilt angle of 34°,and coating pot vibration frequency of15Hz;single powder supply quantity,single liquid supply quantity and coating time as the test parameters,and the best combination of coating parameters for alfalfa seeds is obtained as follows The optimal parameters of alfalfa seed pellet coating were obtained as follows: the optimal value of single powder supply is 10 g,the optimal value of single liquid supply is 10 ml,and the optimal value of coating time is 5min.