| Pu ’er is an important economic crop in Yunnan Province.In 2021,the area of Pu’er in the province will be about 220,000 hectares,the annual output of finished products will be more than 150,000 tons,and sales will reach 7.352 billion yuan.It has become an important pillar industry in Yunnan Province.Pu ’er tea is often mixed with impurities such as hair and woven bag silk during picking and processing.The traditional manual impurity removal has high cost and low efficiency,which seriously restricts the development of Pu ’er tea industry.Therefore,it is an inevitable trend to realize the mechanized impurity removal of Pu ’er tea.Aiming at this problem,a highvoltage electrostatic impurity removal machine for Pu ’er tea was developed according to the principle of electrostatic adsorption.The simulation analysis and experimental research are carried out.The results showed that the high voltage electrostatic impurity removal machine could meet the technical requirements of Pu ’er tea.The details of the study are as follows.(1)The types of impurities contained in pu-erh tea were investigated,and the main types of impurities contained in pu-erh tea were obtained as hair and woven bag silk.By analyzing the principle of high-pressure electrostatic adsorption and the force in the adsorption state of impurities,the mechanism of high-pressure electrostatic adsorption for impurity removal was elucidated,and the equation of adsorption force required for adsorption and impurity removal was deduced.(2)Using Solidworks software to design the whole structure of high pressure electrostatic debris removal machine for Pu’er tea,which mainly consists of electrostatic roller adsorption device,vibrating screen and feeding device.The optimal structural parameters of the electrostatic roller adsorption device were determined with the help of the equations for the critical value of the electric field strength required for adsorption of impurities and the magnitude of the forces on the impurities when they are adsorbed.(3)The electrostatic adsorption model was established by Somsol software to simulate the high voltage electrostatic field.The electric field distribution and vector direction of the electrostatic roller were determined by the electric field cloud map,and the feasibility of the electrostatic roller adsorption device to adsorb impurities was analyzed.Through the simulation cloud diagram and particle trajectory analysis,the output voltage range is determined to be 15 k V～35 k V,and the distance between the roller bottom and the sieve plate is 30～90 mm for adsorption impurity removal performance test.(4)A single-factor test was conducted on a test bench to analyze the effects of output voltage,distance between the bottom of the roller and the screen plate,and vibrating frequency of the vibrating screen on the removal rate and false removal rate of the high-pressure electrostatic debris removal machine.The output voltage level range is 21～29 k V,the distance between the bottom of the roller and the screen plate is 40～80 mm,and the vibration frequency of the vibrating screen is 36～44 Hz.(5)The output voltage,the distance between the bottom of the roller and the screen plate,and the vibration frequency of the vibrating screen are used as the test factors to carry out the quadratic regression orthogonal rotation combination test.Design-expert12 was used to analyze the test results,and the main order of influencing the removal rate and false removal rate were output voltage,distance between the bottom of the roller and the screen plate,and vibration frequency of the vibrating screen.After parameter optimization,the average value of high pressure electrostatic debris removal rate was 94.24% and the false removal rate was 1.36% when the output voltage was27.5 k V,the distance between the bottom of the roller and the screen plate was 41.8mm,and the vibration frequency of the vibrating screen was 40.6 Hz.The optimization results are verified by the whole machine test and meet the technical requirements of Pu-erh tea de-hybridization. |
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