Study On Oil Agglomeration Of Hard-to-float Ultra-fine Coal Using Waste Vegetable Oil

With the existing flotation equipment,contamination of the concentrate by gangue minerals occurs by slime coating,entrapment,as well as entrainment of micro-and nano-sized particles,which leads to the excessive ash content of flotation concentrate.Oil agglomeration is a suitable alternative to flotation because it is more selective for ultra-fine particles,however,with higher cost.In this thesis,ultra-fine coal was taken as the research project,oil agglomeration by waste vegetable oil was used,effect of different operating parameters on oil agglomeration performance and their significance was investigated,optimum oil agglomeration test conditions were obtained,selectivity of oil agglomeration for ultra-fine coal was proved while the whole oil agglomeration process was studied.The main conclusions are as follows:The particle size distribution,density distribution,mineral composition and floatability of ultra-fine coal sample were investigated.The ash content of ultra-fine coal sample is 33.49%,the yield of-0.045 mm is 74.82% and the main gangue minerals are quartz and kaolinite.The floatability grade is difficult to float when the required ash content is 10.00%The effect of different operating parameters on oil agglomeration performance and their significance was investigated and optimum oil agglomeration test conditions were obtained.The concentrate ash content decreased with the increase of stirring speed and stirring time,however,the oil agglomeration performance deteriorated when the stirring time was too long(35 min).Oil dosage has significant effect on oil agglomeration performance while solid content has little effect on oil agglomeration performance.According to the Box-behnken design,stirring time has significant effect on combustible recovery and oil dosage has significant effect on concentrate ash content.The selectivity of oil agglomeration for ultra-fine coal was proved.The oil agglomeration experiments were undertaken by artificial mixture of low-ash coal particles and gangue particles in different proportions.The test results and SEM spectrum analysis verified that the selectivity of oil agglomeration process to ultra-fine particles.The oil agglomeration process of ultra-fine coal was studied.The whole oil agglomeration process can be divided into three stages: floc formation,agglomerate growth and balance.During the whole process,-0.045 mm low-ash particles gradually transfer from small agglomerates to larger agglomerates,eventually forming clean coal products with low ash content.Besides,in the oil agglomeration process,larger particles are mainly distributed near the liquid level and close to the wall of the beaker.The kinetics of whole oil agglomeration process can be defined by second-order rate expression.