Experimental study on ash reduction by classification flotation

Abstract

ABSTRACT Poor endowment conditions, with abundant reserves of high-impurity and low- quality coal resources, characterize the coal resources in our country. As the primary source of carbon emissions, the coal industry faces a critical challenge in actively contributing to environmental protection and carbon reduction within the context of striving for carbon peak and carbon neutrality. With the widespread application of mechanized coal mining and the deteriorating geological conditions of coal resources, coal slurry particles have become increasingly fine. Additionally, a large amount of gangue minerals mixes with the coal slurry, resulting in an increase in ash content and a decrease in floatability. This places higher demands on the separation of high-ash, difficult-to-float coal slurry. This issue has become a core concern that needs to be addressed within the coal industry. This study employs a classification flotation technology to reduce ash content and improve the quality of low-quality coal slurry. The research primarily focuses on the flotation ash reduction effects of the grain size of −0.5 mm and classified grain-size coal slurry under various pulp concentrations, collector concentrations, and frother concentrations. It also analyzes the impact of a rougher and two cleaner flotation processes on the flotation efficiency. Experimental results indicate that the optimal reagent concentrations and process parameters differ for each particle size of the coal slurry. Under the best flotation conditions, the experimental results for the rougher and two cleaner flotation processes are as follows: For the grain size of −0.5 mm coal slurry, the clean coal yield is 48.40%, with an ash content of 11.02%. For the grain size of − 0.5 + 0.125 mm coal slurry, the clean coal yield is 50.53%, with an ash content of 10.72%. For the grain size of − 0.125 + 0.045 mm coal slurry, the clean coal yield is 49.56%, with an ash content of 9.24%. For the grain size of −0.045 mm coal slurry, the clean coal yield is 48.73%, with an ash content of 10.97%. Notably, the classified grain-size coal slurry exhibits higher clean coal yields and lower ash content than the grain size of −0.5 mm coal slurry, highlighting the significant importance of classification flotation for coal slurry.