The Effect of Preparation Conditions on Microbubble Flotation Process of Ultra Clean Coal Using Box Behnken Design Model

Abstract

AbstractWhen coal is widely used as fuel, it also produces lower combustion efficiency and environmental pollution due to direct utilization of coal. The demineralization of coal to prepare ultra clean coal can improve utilization value and reduce pollutant emissions. Thus, Taixi anthracite is chosen to prepare ultra clean coal by microbubble flotation method. Box Behnken design (BBD), a response surface model is introduced as a factorial design of experiments setup and used to find those parameters, which affect the ash content and yield of ultra clean coal and to adjust these parameters in order to achieve the optimized effect. Especially, their interaction effect of different factors in flotation process could be explored by the mathematical model. To explore the mechanism of preparing ultra clean coal, X‐ray fluorescence (XRF), X‐ray diffraction (XRD) and scanning electron microscopy energy dispersive spectroscopy (SEM‐EDS) results are analysed. Combining XRF with SEM‐EDS analysis, the concentrate is polluted by composite particles with particle size of less than 2 μm and organic matter accounting for more than 95 %. Through XRD and SEM‐EDS analysis, it can be shown that a small amount of fine clay minerals including kaolinite and illite agglomerate heterogeneously with coal particles during flotation and pollute concentrate. Further, the existence of composite particles and slime coatings were the main reason of limiting deep demineralization in microbubble flotation process.