Research On Concentration Of Steam Coal Using Coarse Particle Flotation

With the over-exploitation of coal resources,the quality of coal resources has been declining,and the content of coal slime in raw coal has gradually increased,so the sorting of coal slime is particularly important in the process steps of coal preparation plants.However,the size of coal slime has a great influence on the sorting effect.The particle size separation of heavy medium cyclones is generally 50mm-1mm,and the upper limit of particle size for flotation is generally 0.5mm.In this way,there is a gap in grain size between re-election and flotation.Whether or not it can effectively classify coarse slime above 0.5 mm is the key to reducing the loss of clean coal and improving the efficiency of coal preparation plants.The research group designed a wide-grained coal slurry flotation machine that has good separation effect on fine and coarse-grained coal slime,which can provide turbulent environments for coarse and fine-grained slime to be suitable for separation.And experiments confirmed that it can increase the upper limit of flotation size to 1mm.In this paper,we have carried out a structural transformation of this flotation machine:the bottom structure of the cylinder was changed to an inverted cone.This action solved the problem of difficult discharge of tailings deposits and increased tailings discharge.Then we physically modeled the actual structure and size of the flotation cell and used Fluent to simulate the gas-liquid two-phase flow in the internal flow field.It was proved that it could form different hydrodynamic environments by analyzing the pressure,velocity and turbulence intensity in the flow field,and it can effectively separate coarse and fine coal slime.We used the gradient enrichment cyclone underflow product of Tai'an Coal Yangluhe Coal Preparation Plant as a test coal sample,and conducted sorting in the laboratory test system to obtain the best parameters for better sorting effect.The results show that when the impeller speed is 1200rpm,the aeration rate is 0.5m~3/h,the pulp concentration is60g/L,and the foaming agent(secondary octanol)is 100g/t,the best sorting effect is achieved.At this time,the coal yield was 62.54%,the clean coal ash was 11.11%,the tail coal ash was 60.95%,the flotation clean coal quantity efficiency was 93.18%,and the combustible recovery rate was 84.63%.It is proved that the flotation machine after transformation can effectively sort coal samples below 1.5 mm.Subsequently,the bubble size suitable for sorting was explored by changing the size of the inlet tube aperture.The results show that the best clean coal yield,ash content,and ash content were 64.06%and 12.81%,respectively,and the tail gas ash content was 58.42%.The flotation clean coal quantity efficiency and combustible recovery rate were 89.58%and 88.44%respectively.The best clean coal yield,ash content obtained by increasing the intake pipe size were 63.47%and 11.92%respectively,and the tail coal ash content was 59.23%.The flotation clean coal quantity efficiency and combustible recovery rate were 91.55%and 86.62%,respectively,and there was no significant difference in the separation effect.Therefore,reducing the size of the intake pipe can increase the yield of the clean coal,and increasing the intake pipe size can reduce the ash content of the clean coal.