Study On Selective Grinding And Separation Of Ultra-low Ash Taixi Anthracite

In this paper, the selective crushing and separation characteristics of the ultra-low ashTaixi anthracite have been studied. The influences of two crushing forces on the selectivecrushing characteristics have been investigated, and the effect of modification agent on thegrinding efficiency of the stirred mill in the crushing process has also been studied.Qualitative analysis on the mineral disintegrate degree of the ultra-low ash Taixi anthracite arecarried out by the acid leaching method, and the influences of different crushing forces on themineral disintegrate degree are also discussed. Then the feasibility of the separating andde-ashing process by dry classification is finally analyzed.Taking ultra-low ash Taixi anthracite as the research object, a planetary ball mill and astirred mill with different acting forces are used to study the selective crushing characteristics.Single factor tests are designed to investigate the influence factors. The effects of mass ratioof the grinding ball to coal, ball gradation, rotary speed and duration time on the crushingefficiency are investigated for the planetary ball mill, and the optimum condition is15:1,1:20,275r/min and120min, respectively. The influence of the duration time of the stirred mill isalso studied, and the optimum duration time is70min. A superfine powder with particle size10μm (D97) can be obtained by both planetary ball and stirred mill through acrushing-agglomeration-scatter process, and the grinding process fits the first-ordergrinding kinetics before particle aggregation. A "first bulk then surface crushing model" and aselective-surface crushing model of ultra-low ash Taixi anthracite are proposed for theplanetary ball mill and stirred mill, respectively.Maleic anhydride (MAH), ethylenediaminetetraacetic acid (EDTA) and dodecylbenzenesulfonic acid (DBSA) have been chosen as modifiers to study the effect of modification ongrinding process by stirred mill. Three kinds of modifiers are physically coated onto the coal particles, which increase the comminuting efficiency by the grinding aid and dispersion effect.The best modifier is MAH. With the addition amount of1%, the particle size can be reducedfrom14.45μm to7.17μm.The qualitative analysis of the mineral disintegrate degree for the ultra-low ash Taixianthracite is achieved by both the coal petrographic analysis and the acid leaching method.And the effect of crushing forces on the mineral disintegrate degree has been discussed. Thesample TX6can be effectively liberated between the particle size15μm and42μm, and theuniformity of impact and milling forces is superior to the milling force alone to the mineralliberation.A separation crushing cavity has been designed to study the feasibility of the separatingand de-ashing process by dry classification. The separation test is conducted in a jetmill-classification-separation with a self-made separation crushing cavity, and the ash contentfor the product of TX6is1.44%, indicating that the separating and de-ashing process can beachieved by dry classification.