Design Of Selective Crushing Equipment For Middlings And Study On Crushing Mechanism

This thesis is supported by “12th Five-year” National Science and Technology Support Project,entitled by “Research and demonstration of key technology for high-efficient coal separation and secondary resource development”(project number: 2014BAB01B00).A selective crushing equipment for middlings has been designed.The equipment is helpful to the high efficient dissociation of coal gangue intergrowth in middlings and to prevent the products from over-crushing.The experimental study on properties of middlings,equipment structure design analysis,the discrete element analysis and the finite element analysis of the crushing equipment,the manufacture of the equipment prototype are studied.The main research works and achievements are as follows:(1)The properties of middlings are discussed through the related experimental research on the coal maceral components of middlings,including the particle size composition analysis,the density composition analysis and the re-election feasibility analysis,the coal industry analysis and the mineral composition analysis.According to the broken products obtained under different crushing methods,the dissociation characteristics are studied,and the results are compared.Meanwhile,the function expression of particle size distribution of crushed products is given.The economic benefits of recovery and utilization of middlings are analyzed,and the process flow of crushing and re-election coal of middlings is determined.(2)Aiming at the difference of mechanical strength between coal and gangue,a two-stage selective crushing equipment for middlings is designed based on the concept of selective crushing.The equipment can meet the requirements of high efficiency dissociation,low over-crushing rate and adjustable output granularity and other characteristics.The working principle of the equipment is described and the overall parameters of the equipment are determined.The whole structure of the crushing equipment is designed based on the 3D software Pro/E,and the three-dimensional model of each component and the whole machine is established.(3)The discrete element model of the selective crushing equipment for middlings is established by using EDEM software,to achieve the dynamic simulation of the whole process of the material particles from entering the crushing chamber to discharging finished product,and the process of material crushing is analyzed.The breaking effect of material is analyzed by the change of the number of broken bonds with time,the productivity of the equipment is calculated based on theoretical formula calculation and simulation calculation,and the force and wear of the crushing system are analyzed.(4)The stress and strain distribution of the key components of the crushing equipment under the condition of middlings crushing are obtained based on EDEM-FEM coupling.Then the structural defects are found,and the suggestions for improvement are put forward.The modal analysis and thermal conductivity analysis of the spindle are carried out to determine the natural vibration characteristics,the temperature distribution and the thermal deformation of the structure.The results provide the basis for the structural design and optimization of the selective crushing equipment for middlings.(5)The prototype of the selective crushing equipment for middlings is manufactured and its fragmentation and dissociation properties are studied.The analysis data of the particle size composition and density composition are obtained and compared with the dissociation test results of the jaw crusher and the hammer crusher.The conclusion shows that the selective crushing equipment for middlings.can be achieved high efficient dissociation of coal gangue intergrowth and prevent the products from over-crushing.