Basic Separation Theory Of Fine Oxidized Coal In The Rotational-gradient Composite Force Field

The energy structure based on coal determines the basic energy position of coal will be long-term and stable.Reduce energy consumption and pollutant emissions in washing process,vigorously develop the precision processing of coal washing,coal depth upgrading and quality classification are the important measure to promote the structural reform of supply-side field of coal industry during the period of 13 th Five-Year Plan.The high efficiency separation technology of fine difficult-to-float coal based on the severe surface hydrophilicity desires the significant breakthroughs.In this paper,the response rules of the separation properties of particles to the the separation environment in the composite force field were analyzed.The difference of particle separation characteristics were discussed.The complex phenomena such as delamination and migration of the particles in the separation process were revealed,and the mechanism was analyzed.The numerical simulation method was used to study the complex flow characteristics.The influence mechanism of the key operating parameters on the separation process were analyzed from the micro level,flow gradient separation theory of compound stress field was perfected,and the gradient separation process was revealed.The high efficiency separation of fine coal was realized,and the application field was extended to clean process of low rank coal.The characteristics of coal were studied.The separation properties of density and size composition were obtained,mineral occurrence characteristics in the particles with different grades were revealed,and the occurrence regularity model of mineral was established.In this part,the feasibility and necessity of the enhanced gravity separation of fine oxidized coal with the characteristics of serious hydrophilicity were described.The influence rule and mechanism of the single centrifugal force field on the particle group stratification were analyzed.Single centrifuge test was designed to analyze the sedimentation and stratification of fine particles in a single centrifugal force field.With the help of image reconstruction,the temporal and spatial distribution of particle distribution in the single centrifugal field was analyzed.The low difference of ash content between layers shows the low efficiency of single centrifugal force field for accurate stratification.The single direction force cannot improve the stratified environment of the particles dominated by the density difference.Simple centrifugal gravity separation process cannot improve the efficiency of separation.The shear delamination characteristics of particles in composite force field were studied.Based on the diversity of the separation environment,shear layer test in composite force field was performed to determine the influence of the separation parameters on the ash content difference of the layered structure.Based on the dynamic characteristics of the particles,the mechanism of loose stratification in the composite force field was analyzed.The results show that the particle can achieve high efficiency in the composite force field.Fluidization water pressure and centrifugal force need to be fit to optimize the separation efficiency.The effect of particle size on particle settling was weakened in the stratification environment.The response rules of the particle separation properties to the key separation parameters were studied.The gradient feature of particle migration direction was analyzed.High distribution rate of ultrafine particles in the overflow with high ash content caused the pollution of clean coal.The balance model of yield and ash of clean coal were proposed.The multivariate linear regression model that the response law of the clean coal yield(ash)to the centrifugal force and fluidization pressure of narrow particle size was established.The minimum separation size in the composite force field was studied,and the response rule of minimum separation size to the key parameters was analyzed.The pre-desliming process of untrafine particles through cyclone was put forward.The minimum separation size was calculated based on surface wave theory and the short distance settlement theory.The D20 BKrebs was used to pre-desliming,and the ultrafine particle content(-0.045mm)was reduced from 17% to 4% under the optimum conditions.The effect of enhanced gravity separation of desliming product was significant,and the ash content can be reduced to 4%.The self-generated medium theory based on all grain size separation was proposed.The calculation model of the density of autogenous medium was put forward.The effect of compound force field on the removal rate of minerals was studied.The fractional release experiment was carried out in the composite force field,and the gradient distribution of the ash content of the product was analyzed.The removal rate of mineral matter accords with the first-order kinetic theory.The migration process of particle in the composite force field was analyzed by the stochastic process theory.The response rules of the mismatch particles to the key parameters were studied.The results show that the separation parameters have a significant effect on the content of the mismatch,and the irregularity of the particle shape significantly improves the mismatch content.The removal efficiency of impurity elements by complex force field was studied.The results showed that the removal of the Al,Si element that rich in clay minerals was significant,and the removal rate was above 80%.The flow field in the composite force field was studied from the macroscopic and microscopic aspects by means of high speed dynamic test and multiphase flow numerical calculation.The radial gradient separation characteristics in the separation region were analyzed.The influence of centrifugal force and fluidization water pressure on fluid velocity were analyzed.The increasing centrifugal force can significantly improve the tangential velocity,axial velocity and radial velocity.The fluidization water pressure has little influence on the tangential velocity and axial velocity of the fluid,but it can effectively improve the radial velocity of the fluid.The characteristics of turbulence gradient along the radial direction were studied.The turbulent kinetic energy and turbulent dissipation rate were used to analyze the turbulent flow characteristics.In the near wall region,the characteristics of high turbulent flow energy and high turbulence dissipation rate were obtained,which made the settling particles disperse sufficiently and made the mismatch particles return to the separation region.In the far wall region,the quasi laminar flow pattern was found,and the stable separation environment was helpful for the fine particle stratification.The innovative sorting machine with continuous and precise separation based on compound force field separation mechanism was proposed,which can effectively avoid the technical defects of non-continuous separation of traditional centrifuge separator.The key structure design was finished,and the entity manufacture of the separator was completed.