Research On Virtual Impact Separation Technology And Separator Of Respirable Dust

Respirable dust is defined as particles with aerodynamic diameter smaller than7.07μm that can enter the human alveoli,whose sampling efficiency is 50% when aerodynamic diameter is 5μm.The main cause of pneumoconiosis is inhaling excessive respiratory dust.Therefore,strengthening online monitoring of respiratory dust concentration in coal mine workplaces is one of the effective means to reduce occupational hazards of dust.The common dust concentration measurement methods include laser scattering method,-ray method,micro-mass shock balance method,etc.To achieve accurate measurement of respirable dust concentration,it requires firstly separating the respirable dust from the total dust by using the separator.However,the existing separator cannot achieve the continuous separation.In order to realize the continuous online monitoring of respirable dust concentration,it is necessary to solve the technical problem of continuous separation,and according to the standard of Respirable Dust Measurement Instrument Sampling efficiency Measurement(MT394-1995),the separation efficiency curve of the separator should meet the standard of BMRC(British Medical Research Council)curve.This article is based on the "13th Five-Year plan" national key research and development program "Research on key Technology and Equipment of Mine Occupational Hazard Prevention"(2017YFC0805200).On the base of analysis the principles of ceramic separation technology,inertial impact separation technology and cyclone separation technology,and in view of the problem of traditional methods under continuous separation conditions,it takes virtual impact separation technology and the corresponding separator as the research object based on the theory of traditional inertial impact separation technology,while the inner flow channel layout design,flow field characteristic analysis and performance optimization research will be carried out.The main research works of this article are as follows:(1)Comparison of separation techniques satisfying BMRC curve.By comparing and analyzing the defects of the existing separation technology principle and their corresponding separator under continuous separation condition,the feasibility and importance of virtual impactor in realizing continuous and accurate on-line monitoring of respirable dust concentration were determined.(2)Separator Simulation and numerical simulation based on BMRC curve.According to the characteristics of virtual impact structure,the three dimensional simulation models were established by solidworks,and the mesh was created.The flow field was simulated by Fluent.The RNG k-model was used to solve the continuous phase through comparative analysis,and the differential equation of particle phase motion under virtual impact state was established through particle force analysis.The distribution of radial pressure,velocity,turbulent kinetic energy and dissipation rate at different sections were obtained by analyzing the distribution of diverging flow field and pressure field.The particle separation efficiency under different aerodynamic particle sizes in mine environment was calculated.(3)Development and test verification of separator.A sample respirable dust continuous separator was designed and developed based on the principle of virtual impact.According to the analysis of aerosol experiment,the separation efficiency and standard deviation of BMRC curve of the sample were both less than 5%,which meets the requirements of industry standard.(4)Analysis of effects of aerosol experiment.The influence of temperature and humidity,sampling flow and other factors on the separation efficiency was analyzed,the weight of each factor on the separation efficiency was clarified,and the feasible method to control the error was studied.