Study On Characteristics Of Fine Coal Slime Classification Based On Horizontal Flow

Particle classification plays an important role in coal preparation.Through classification,part of high ash slime can be removed and flotation effect can be improved.However,the traditional classification method is inefficient and covers a large area.For example,bucket bailing pit and corner cone sedimentation tank,the hydrocyclone classification effect is good,but its feeding pressure is large,and extra fine particles will be produced in the classification process.In order to improve the above situation,this paper studies the particle classification in the gravity field and turbulent environment with the help of a self-designed horizontal flow classification device.Through the numerical simulation method,the movement rule of particles in the horizontal flow is clarified,and the two parameters of pulp concentration and feeding speed are tested and studied,and the better classification effect is obtained,which shows that the horizontal flow of particles can be used as an effective method of slime classification.The main conclusions are as follows:(1)The final settling velocity of particles is related to the shape,size and density of particles.Most theoretical formulas are derived based on regular spherical particles.For the calculation of irregular particles,the size and shape of particles need to be modified.(2)The results show that the theoretical value is slightly lower than the actual measured value,and the error of method B is smaller.Using semi empirical formula to calculate the final velocity of interference settlement of different particle size slime particles,compared with the test value,the calculation result is lower.At the same time,for particles with similar density,the calculation error increases with the increase of particle size.(3)Fluent software is used to analyze the liquid and solid-liquid two-phase flow of particles in horizontal flow,and the distribution rule of velocity field,particle trajectory and desliming rate under theoretical conditions are obtained.The simulation results show that after the fluid enters the classification device,the water speed slightly loses,and then it is far away from the feed end near the feed height,and the speed decreases significantly when it is far away from the feed end,and there is vertical diffusion;vortex appears near the wall and the center area;the water speed is large near the nozzle height,the water speed in the vortex area is second,and the water speed in the other places is low;with the increase of water speed,vortex appears The number of flows increases and the flow becomes more complex.According to DPM model,the theoretical removal rate of fine particles is obtained.The results show that the removal rate increases with the increase of feed rate,but the increase rate slows down gradually.(4)The classification experiment of slime with high fine slime content shows that the classification efficiency and desliming rate change with the feeding speed and pulp concentration.With the increase of feed rate,the classification efficiency first decreases and then increases,with a minimum value at 36.42 cm / s and 42.26 cm / s,and when the pulp concentration increases,the minimum value is on the right;with the increase of feed rate,the desliming rate fluctuates obviously at the lower feed concentration,and continues to increase at the higher concentration;with the increase of pulp concentration,the classification efficiency and desliming rate decrease.Considering the desliming rate and classification efficiency,the best classification conditions are obtained when the pulp concentration is 60 g / L and the feeding speed is 48.05 cm / s.(5)Compared with the simulation value and the test value of the removal rate of fine particles,it is found that the trend of the two changes with the speed is more consistent,and increases with the increase of the feeding speed;the simulation value of the removal rate is slightly lower than the desliming rate,and the gap becomes smaller with the increase of the feeding speed.(6)The ash content of clean coal is reduced by 1.30% and the yield of clean coal is increased by 0.94%.There are 23 figures,24 tables and 86 references in the thesis.