Simulation Analysis And Experimental Research Of Needle Roller Electrostatic Separator For Remnant Mulch Film In Machine-harvested Seed Cotton

Cotton is mainly planted with mulch film in Xinjiang,which causes remnant mulch film in cotton during machine harvesting.The exceeding of the foreign fibers in the cotton has a severe impact on the economy benefits of the cotton textile industry.The removal of the remnant mulch film in the machine-harvested cotton plays the critical role in the removal of the foreign fibers.Currently,the mechanical equipment is mainly used to free the binding between the impurities and the cotton,so that to separate the various impurities mixed in the cotton and to facilitate further impurities removal;however,its removing efficiency of removing remnant mulch film is limited.In order to improve the removal efficiency of remnant mulch film in cotton,the mechanically harvested seed cotton and the remnant mulch film were used in this study as the research objects.Based on the electrostatic separation theory,the charge properties of the seed cotton and the remnant mulch were measured,and a self-made needle roller type device was designed under laboratory conditions.The optimal parameters of device were obtained in the further.The main contributions of this study are shown as follows:(1)The charging characteristics of the seed cotton and the remnant mulch film were studied.The results showed that in the negative corona discharge,both the seed cotton and the remnant mulch film were negatively charged.When a single seed cotton was equivalent to a spherical particle,its saturated charge is about-8 n C.When the seed cotton freely fell through the area of high-voltage electrostatic field,its charging properties did not change;however,its charge was reduced.The saturation and charge of the remnant mulch film were about-35 n C.When the remnant mulch film freely fell through the high-voltage electrostatic field,its electrical properties remained unchanged,but its charge were the same as the saturated charge,indicating that the remnant mulch film could quickly reach the saturated charge once entered the electric field.Both the seed cotton and remnant mulch film could be influenced by the electric field force in the electric field.(2)The negative corona discharge in air was studied.It could be seen that the discharges were divided into two regions:(a)the region corresponding to within 1 mm of the corona pole where most ionization occurred;(b)The remainder of the ground reaching electrode,referred to as the transmission region.These two regions were distinctly different.In the negative corona,positive ions were dominant in the descending region of the corona pole(cathode),while the negative ions were dominant in the transport region.(3)The electric field distribution was simulated using COMSOL Multiphysics software.As the results showed,the electrode configuration,the electrode position,the electrode curvature,and the voltage intensity had a significant influence on the surface of the ground electrode and the distribution of the spatial electric field.The force condition of the seed cotton and the remnant mulch film in the electric field were studied.The force balance equation of the seed cotton and the remnant mulch film were established in each respective region.The electric field of the seed cotton and the remnant mulch film were obtained.The expression of the motion trajectory was obtained.The specific calculations for the force condition was carried out.The possibility of the remnant mulch film separating from the seed cotton was verified.(4)With the separation rate of remnant mulch film from seed cotton taken as the performance index,and the electrode position and voltage considered as the influencing factors,the orthogonal experiment was carried out via a self-made electrostatic separation device.The Minitab software was used to process and analyze the experimental data,and the best factors influencing the separation rate were obtained.The best coordinating parameters of each influencing factor were:voltage-40 k V,corona pole I position(30°,140~160 mm),corona pole II position(20°,140~160mm),and static electrode position(-10°,180 mm).Based on the test conducted on a self-built electrostatic separation device,the separation efficiency was 85%.The electrostatic separation prototype of remnant mulch film in the multi-channel machine-collecting seed cotton was trialproduced,and the batch tests were carried out using the optimal coordinating parameters.The results showed that the separation rate of the remnant mulch film from seed cotton could reach more than 75%.