| In recent years,due to the climate drought,rainfall decreased,and the intensity of grassland utilization is increasing.The continuous degradation of natural grasslands has resulted in a sharp decline in productivity.Aircraft broadcasting and spraying are effective methods to recover grassland vegetation quickly,but the seeds need to be pelleted to ensure the germination rate and survival rate of seeds after sowing.Therefore,new pelleting equipment,formulation and technology of Agropyron seed were developed.For the restoration and reconstruction of degraded grassland vegetation,engineering measures shall be taken.It is of great significance to further improve the grassland ecological environment and realize the sustainable development of animal husbandry.The existing pelleting machine of Agropyron seed has many problems such as uneven powder supply,uneven spray,insufficient mechanism,unscientific formulation and poor vigor of pellets.The vibration force field is introduced into the pelleting machine of Agropyron seeds by the method of theoretical analysis,numerical simulation and experimental verification.The compound movement of vibration and rotation is used to promote the uniform mixing of the seed and pelleted powder,reduce the multi-seed rate and no seed rate,improve the single seed rate and the pelleting qualified rate,and improve the pelleted quality.In addition,the surface mechanical properties and the vigor of pelleted seeds under the vibration force field were studied.The new formulation and technology of pelletization of Agropyron seeds were determined.The main conclusions are as follows:1.The contact,adhesion,vibration mechanics and kinematics models which are consistent with the actual conditions of pelletization of Agropyron seeds are established to reveal the pelletization mechanism.The theoretical analysis and simulation results show that the vibration force field can change the impact force of materials,and increase the speed difference and dispersion between the seed and the pelleted powder.Besides,the Agropyron seeds and pelleting powder should be fully contacted and quickly mixed at different time points and in the same space to improve the quality of pelleting.2.The mathematical model between the working parameters of vibration pelleting machine and pelleting quality(single seed rate,qualified rate of pelleting)is established.It is confirmed that the introduction of vibration force field can obviously improve the qualified rate of pelleting and the rate of single seed.Besides,response surface analysis method was used to analyze the results of quadratic regression orthogonal test.The main and secondary factors that affect the qualified rate and single seed rate of Agropyron seed pelleting are as follows:the rotating speed of coater>vibration frequency of coater>tilt angle of coater.When the rotating speed of the coater is 42r/min,the vibration frequency of the coater is 20Hz,and the tilt angle of the coater is 35°,the qualified rate and single seed rate of pelleting is 83.1%and 94.9%,respectively,Furthermore,the new pelleting technology was determined.3.The surface properties of pelleted Agropyron seeds were conducted.When the pelleting formula is SF:DE(30:70),the weight loss rate of pelleted seeds with vibration is 3.3%lower than that without vibration,the disintegration time in water is 2 minutes longer than that without vibration,and the compressive strength of single seed is 4.4 N higher than that without vibration.There were significant differences between the results of variance analysis of integrity and single seed compressive strength.The results show that the introduction of vibration force field can improve the surface mechanical properties of pelleted Agropyron seeds.4.Experimental study on germination and growth of pelleted seeds with or without vibration and different material ratio was conducted.With the increase of SF content,the vigor of pelleted seeds decreased.When the formulation of pelleting material is SF:DE(30:70),the seed vigor index of pelleting seeds with and without vibration are 15.4 and 14.7,respectively.There is significant difference in variance analysis results.This formula is the best one for pelleting of Agropyron seeds.In addition,the vigor of pelleted seeds in 6 treatments were obvious better than control.Therefore,the introduction of vibration force field can not only improve the surface mechanical properties of pelleted seeds,but also improve the vigor of pelleted seeds. |
