Research On Fine Coal Separation In The Dense Medium Column

The separation of+3-13mm fine coal has become a primal problem affecting the yield and benefit of steam coal.The existing equipment is insufficient for the fine coal.Although dense-medium cyclone has good effect on separating 0.5mm particles,the higher cost and special coal quality that fine power coal is more brittle and muddy make it fail to separate in dense-medium cyclone.The dense-medium shallow slot separator mainly beneficiates the lump coal,so the machine has a bad effect on separation of fine coal particles.Forced reduction of the lower limit of separation is bound to reduce the amount of processing and increase the cost of separation.Separation upper limit of liquid solid fluidized bed and spiral separator are lower and they fail to separate the fine power coal.The effective recovery of+3-13mm steam coal is great significial to improve the comprehensive utilization rate of resources and environmental protection.In the experiment,selecting 6 sampling points in the axial direction of the separation column and the sampling points are located at 0%,20%,40%,60%,80%and 100%of the separation column.In the experiment of particle force and motion,the resultants force and motion state of the particles are studied with the aid of the dynamometer system and the high-speed dynamic particle motion recording system.In the particle separation test,the relationship between the effect of particle separation and the medium density,the flow rate of the rising medium,the height of the separation column and the feed amount are studied.The particle force and motion tests show that separation of particles are separated into two types in the medium.One is the separation of large particles and the other is the separation of small particles.The separation of large particles is according to the Archimedes principle.When the particles density are larger than the medium density,the particles sink to the bottom of the separation column.When the particles density are less than the medium density,the particles float on the top of the separation column.When the particles density are equal to the density of the medium,the part of the particles are mainly separation from the upper part of the column because of the interference of the rising medium flow.The separation of small particles is under the combined action of Archimedes’s principle and interference settlement law.When the particle density are less than the medium density,they floats on the top of the separation column.When the particle density equals the density of the suspension,most particles will float to the top of the separation column and less particles suspend in the separation column.When the particle density are larger than the density of the suspension,more particles will sink to the bottom of the separation column,and the settlement velocity of less particles,which are subjected to interference settlement,are so slow as static.The particle separation experiments show that when the medium flow increase from 1.0m³/h to 2.2m³/h,the possible deviation（E value）of the separation column decreases and then increases.When the medium flow is 1.3m³/h,E value achieves the minimum value 0.070g/m³,the recoverable rate of the combustible body achieves 72.76%and the quantity efficiency achieves 89.35%.When the density of the suspension increases from 1.4g/cm³ to 1.7g/cm³,the actual separation density increases gradually and the E value decreases and then increases.When the medium density is 1.5 g/cm³,the actual separation density is 1.54 g/cm³ E value achieves 0.086g/cm³,and the recovery rate of the combustible body is 70.40%,the quantity efficiency achieves 86.39%.When the height of the separation column increases from 1100mm to1600mm,the actual separation density and E value gradually both decrease.When the height is 1600mm,the actual separation density is higher than the medium density about0.02g/cm3,the E value is 0.162 g/cm³,the recoverable rate of the combustible body is81.55%,and the quantity efficiency is 88.98%.When the feed quantity increases,the actual separation density and the E value increase gradually.When the feed volume is0.075t/h,the actual separation density is closest to the density of the medium.At this time,the E value is 0.072 g/cm³,the combustible body recovery rate is 85.15%,and the quantity efficiency is 96.50%.Through the orthogonal experiments,the medium density,the rising velocity of the medium,the height of the separation column and the feed volume are obtained by the order which are sensitivity to the combustible body recovery rate,as follows:the flow of medium>the height of the column>the density of the suspension>the amount of feed.The linear relation of the experimental model is as follows:F₁（Q,ρ,H,Q_F）=-0.035×Q-0.26×ρ+0.35×H-1.03×Q²-0.13×ρ²-0.13×H²Through the orthogonal experiments,the medium density,the rising velocity of the medium,the height of the separation column and the feed volume are obtained by the order which are sensitivity to the quantity efficiency,as follows:the flow of medium>the density of the suspension>the amount of feed the height of the column.The linear relation of the experimental model is as follows:F₂（Q,ρ,H,Q_F）=5.16×Q+1.76×ρ-3.56×H+0.40×Q_FQ、ρ、H、Q_F represent medium flow rate,medium density,column height and feed volume.