| With the development of China's coal industry and the continuous improvement of the degree of mechanization of coal mining,the coal powder content in raw coal increases gradually.According to statistics,the coarse slime accounted for approximately 20% of raw coal,this part contains clean coal(ash 10%)about 60%,if not properly handled coarse slime,itcaused the waste of resources.Because of the simple structure and process,water only cyclone has been received much attention in the separation of coarse slime,through structural optimization and improvement,the separation result is better than the traditional water onlycyclone.By referencing the basic structure of DWP cyclone and Vorsyl cyclone,aiming to the disadvantages of clean coal loss present in the water only cyclone underflow,a novel multi-product cyclone with underflow scavenger was proposed.The overflow of the first-stage separation cyclone is directly connected to a hydrocyclone,the underflow of which discharges clean coal,while part of the overflow is introduced as a scavenger wash.The underflow of the first-stage separation cyclone is connected to a scavenger cyclone,producing two products including the middlings and the rejects.The novel separation device can thus realize the simultaneous discharge of four products including the clean coal,the middlings,the rejects and the fine overflow for a single feed.Taking the coal slime of-2mm from Tunlan Coal Preparation Plant as a sample,firstly probed into the structure of the scavenger through experimental study,main separation cyclone and scavenger of the structure parameters are determined,it is concluded that the central tube structure is the best.Next aftermain separation cyclone directly connect to the hydrocyclone,investigate thedepth of overflow pipe of main separation and the flushing flow of scavenger.The results show that with the increase of the depth of overflow pipe,clean coal distribution rate and ash content increased,middling and gangue distribution rate,ash content all increased;To ensure a qualified clean coal,the depth of the vortex finder in the first-stage cyclone should be in the range of 190 mm to 200mm;increase the flushing flow,the scavenger concentration and separation force increase,sorting more completely,the distribution rate and ash content of middlingdecrease,gangue distribution rate and ash content increase,ash content of clean coal slightly increase;with the two stage scavenger,can get two qualified middling products and higher ashcontent of gangue.In order to further shorten the sorting process and improve the utilization rate of space,design a new type of coaxial to take cyclone discharge,transform the scavenger and research central overflow pipe relative insertion depth and flush flow effect on separation results.The results show that,with the increase of central overflow pipe relative insertion depth,distribution rate and ash of clean coal and middling were decreased,the distribution rate and ash of gangue were increased;when the relative insertion depth maintain 10 mm,clean coal ash content is 10.12%,middling ash content is 47.23%,gangue ash content is 66.56%,and it can achieve good separation effect;adjusting the flush flowcan adjust the concentration and separation force size of scavenger.At last,the experiment of flotation tailings is carried out,and the results show that the equipment has a certain effect on different coal types.Through CFD numerical simulation,indicating that the increase of scavenger had little influence on the main separation,only caused resistance to underflow discharge;the scavenger has sorting function,and to a certain extent the lower cone can enhance the separation force;the axial velocity of the central region is upward and the order of magnitude is large,and has basically no water;when the water flow increases,the axial velocity of the main selection is increased,and the resistance of the main discharge is increased,which can be verified by the test results of slightly increased clean coal ash. |
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