Air impact pulverization–precise classification process to support ultraclean coal production

Abstract

This research demonstrates a novel technique for achieving ultraclean coal production through the coupling of pulverization, classification, and separation of Taixi anthracite. Specifically, ultrafine pulverization techniques used in noncoal fields were newly applied to coal in this study. Taixi anthracite served as the subject material, and an air impact pulverization–precise classification process was designed and demonstrated. The effects of primary variables on process outcomes were investigated, and then, the process was optimized. In order of effect, the primary variables included pulverizing pressure, secondary wind pressure, classifier II rotational speed, and classifier I rotational speed. The classified products with ash content, particle size and classification precision cascade change can be obtained, ultimately, realizing the results of quality-upgrading of coal products. Under optimal process conditions of a 0.5-MPa pulverizing pressure, 0.10-MPa secondary wind pressure, 210-Hz classifier II rotational speed, and 230-Hz classifier I rotational speed, ultraclean coal with an ash content of 1.40% was produced. Ash content gradients for different product classifications were apparent, suggesting that the separation effect can be determined through precise classification. Numerical simulation results indicated that airflow kinetic energy transformation was the primary energy source facilitating pulverization. During impact pulverization, Taixi anthracite experienced selective, differentiated, and surface pulverization effects.