Study On Crushing And Refining Of Coal Middlings For Malan Coal Preparation Plant

Take the washed middlings of Malan coal preparation plant as the research object,this paper dedicates on the feeding scheme,crushing scheme,preparation scheme and product solutions,as the result,the optimized process is obtained.Firstly this paper explores the relationship between the crushing size limit of heavy medium coal middlings and the concentrate yield.It collects three samples to make sieve and float-sink tests,and studies on the crushing dissociation of the third sample in 13 mm,6mm,3mm and 1mm.The results show:(1)The quality of heavy medium coal middlings is volatile,and the ash content of three samples are 29.69%,34.67% and 43.80%;(2)The low ash component in coal middlings unbroken is few,indicating high separation efficiency of initial separation and little significance of direct refining;(3)when the crushing size limit reaches 3mm,the concentrate yield of whole grade reaches a high level;(4)After crushing dissociation,massive low ash component enters into 0.5 ~ 0.25 mm,if the lower size limit of gravity separation reduces to 0.25 mm,the concentrate yield can be significantly improved,which can take advantage of high precision,low cost,large capacity of gravity separation;(5)The fitting equation between crushing size limit and the concentrate yield of gravity product prediction of whole grade:y=e0.0015x2-0.0518x+3.0445,（R2=0.9987)At the same time,this paper explores the relationship between the ash of final coal middlings and concentrate yield.It collects four samples to make 3mm and 1mm crushing dissociation analysis.The results show:(1)The quality of final coal middlings is volatile,and the ash content of four samples are 29.82%,38.37%,44.54% and 55.16%;(2)when the crushing size limit is 3mm,the concentrate yield of +0.25 mm has reached a high level and can not obviously improve with lower crushing limit;(3)The fitting equation between the ash of final coal middlings of 3mm crushing size limit and the concentrate yield(total sample)of +0.25mm:y=72.5417-1.2177x,(R2=0.9939)On this basis,this paper designs the best process of Malan coal preparation plant: 3mm efficient crushing-0.25 mm fine grading-+0.25 mm high precision heavy medium cyclone--0.25 mm flotation.The SMJ grinder is chosen as efficient crushing equipment,with the CLS300 hydro-cyclone as fine classification equipment and the two-stagy same-density heavy medium cyclone HMCC as high precision separation equipment.According to the forecast results,the total concentrate yield can exceed 30%.Finally it studies the products,after the crushing and refining,concentrate can be directly saled as commercial coal but mixed coal middlings can not duing to high ash content and low heat which can not meet the demand of power plant.It also shows fine coal from dissociation is difficult to reduce ash through a simple(low cost)gravity method,however power coal blending can improve the calorific value of mixed coal middlings to solve this problem.