Two-stage Separation And Process Intensification Of Fine Coal

With the improvement in the proportion of mechanical coal mining and rapiddevelopment of heavy-medium coal preparation, China's fine coal is gradually characterizedby size reduction, ash increase and intergrowth content raise. Fine coal separation problembecomes prominent. Perfect degree of fine coal separation process directly affects the qualityand quantity of clean coal products, dewatering operation of clean coal and tailings, andwashing water balance of the whole coal preparation plant. However, there are still manydefects as weak recovery, weak flexibility, and contradiction between recovery andproductivity in the existing fine coal separation process in our country. Inhomogeneouschanges of fine coal flotability put forward higher requirement on fine coal separationprocess design. Actual production raised higher demands for large-scale, fining andadaptability of separation devices. In view of the above difficult problems, taking processmechanism analysis, process characteristics test, process intensification test and industrialpractice as the main line, the hard-to-float bituminous coal of Tangshan Kailuan mine andanthracite coal of Henan Shenhuo mine these two kinds of representative slime were taken asresearch samples, and fine coal separation process intensification and two-stage separationmechanism were systematically studied. The following findings are obtained:Flotability process features of fine coal separation were studied. Flotation processcharacteristics of Tangshan bituminous coal and Yongcheng anthracite coal were analyzed.Changes in characteristics of the flotation rate constant of different size fine coal wereresearched. Effects of parameters as the amount of flotation reagents, flotation machinerotation rate, superficial gas velocity, and feeding concentration on flotation rate constantwere explored. By analyzing the size distribution, density and SEM of the products from thetests of flotation dynamics, flotation process behavior of fine mud was provened. Theoreticalderivation and experiment verify the common law that the floatability of floating materialbecame poor with the flotation process.Change rule of energy consumption of fine coal flotation was studied. Fine coalseparation energy consumption testing system was established, flotation productscharacteristics under different energy consumption conditions were analyzed, and therelationship between energy input and flotation rate constant was also studied. The resultsshow that the energy consumption for floating unit mass of clean coal gradually increased with the flotation process. Coarse intergrowth and micro-fine hard-to-float coal particlescould only be recycled under high energy condition.Two stages separation process of fine coal was put forward. Fine coal separationprocess was divided into fast float section and recycling section. Easy floating materialswere recycled with low energy in fast float section, and hard-to-float materials werecompulsorily recycled with higher energy in recycling section. Two stages separationmechanism was studied. The superiority of two stages separation process compared withsingle stage separation process was proved theoretically, that was to say, the more thefloatability changes in flotation, the bigger the energy distribution difference between onestage and two stage separation process. Flotation process design concept based on energytransmission and distribution was put forward. To construct more and more strong energyconditions to adapt the physical property changes of the minerals in flotation, so as to realizethe best interconnection of process design and physical property characteristics and achievethe best mineralization reaction condition.Two stages fine coal separation process based on column flotation was studied.Combining two stages separation methods, a two-stage column separation test device(FCSMC1000×2000) based on Cyclonic-Static Micro-bubble Flotation Column wasdesigned, and tests were conducted in Qianjiaying Coal Preparation Plant, Kailuan Group.From flotation fluid dynamics perspective, recovery model of two stages column separationprocess was studied, and the reliability of models was tested and verified.The results showthat, two stages column separation process was both superior to single stage flotation columnin processing power and coarse particle recovery capability.According to separation principle and process characteristics of fine coal flotation,magnifying standard and structure prototype of two stages column separation device weredetermined. Large-scale two stages column separation equipment (FCSMC3000×6000) wasdesigned and applied in Qianjiaying Coal Preparation Plant, Kailuan Group and Xuehu CoalPreparation Plant, Shenhuo Group. The results show that, both the processing capability andadaptability of two-stage column separation equipment were improved averagely comparingwith that of single stage.Process Intensification of hard-to-float fine coal flotation was studied. The results ofcoal rock dissociation and re-separation tests in the laboratory show that, when clean coalash content equals, recovery of clean coal combustible in re-separation process based on coalrock dissociation were increased by8.12percentage points compared with raw coal directflotation. The results of technological intensified separation tests on hard-to-float fine coal show that, the first stage of the two-stage column flotation process recycled easy floatingmaterials under the condition of low pressure and small circulation, the second stagerecycled difficult floating minerals under high pressure and big circulation, and theintergrowth particles were recycled by re-separation process based on coal rock dissociation.In the condition of similar clean coal ash content, the recovery of combustible was higherthan conventional separation process by10percentage points.High efficient separation technology of hard-to-float high ash fine coal based on secondresource recovery was put forward. In terms of improving concentrate's quality, there-separation process of filtrate from screen bowl centrifuge treating after the dehydrationprocess of rougher clean coal were designed in this paper, and this process reduced thecleaning pressure and system circulation. In terms of improving concentrate recovery ofcombustible, the technological process describing as classification of rougher tailings usingcyclone+dewatering of underflow from cyclone using high frequency screen+grindingdissociation and re-separation of oversize products from high frequency screen was putforward. The system with a handling capacity about400m3/h was set up in Qianjiaying coalpreparation plant in Kailuan Group. Industrial application results show that, under thecondition of similar clean coal ash content, combustion recovery of clean coal from thestudied process indicated an increase about5-10percentage points comparing with that ofonce rougher and once cleaner based on conventional flotation cell.This paper contains131pictures,58forms and156pieces of references.