Study on Preparation of Ultra-Clean Coal Based on Ionic Liquid

Abstract

Abstract:Preparing ultra-clean coal is an important way to realize clean and efficient utilization of low rank coal. A clean and efficient method of producing ultra-clean coal is urgently needed, given the high environmental impact and corrosiveness of the chemicals used in the traditional chemical preparation of ultra-clean coal. In this paper, acidic imidazole ionic liquid was used as a leaching agent to prepare ultra-clean coal, and the effects of temperature, time and concentration on the reaction process were investigated. The ash composition of the sample and the ash removal mechanism under the ionic liquid were revealed, and the evolution law of the microstructure and functional group characteristics was clarified. The research showed that the concentration and temperature had a large influence on the ash content of the product during the leaching process, and the reaction time had a small influence. The minimum ash content of the ultra-clean coal could reach 0.89%. In the ionic liquid system, iron, calcium and magnesium in the coal were effectively removed, the iron oxide content was significantly reduced and calcium salts except calcium sulphate were effectively removed, while periclase was almost completely removed. However, the removal of silicon and aluminum was poor. Most of the alumina and silica remained in the ultra-clean coal. Extracted coal had more cracks and rougher surface than raw coal, the BET surface area decreased from 2.8579 to 2.4032. The aromaticity of coal was significantly improved and the pyrolysis curve of coal was shifted to the high temperature region after treatment, which fully proved that acidic ionic liquid improved the chemical stability and reduced the oxidation activity of coal.

Keywords: Ultra-clean coal, Clean utilization, leaching, Deashing, Ionic liquids.