Effect of acidic conditions on electrochemical desulfurization of clean coal

Abstract

ABSTRACT In this study, the electrochemical indirect oxidation desulfurization of organic sulfur in coal was carried out using a diaphragmless electrolytic cell. The desulfurization effect of NaBr, HCl, HNO3, and H2SO4 in the electrolysis system with different acid concentrations of pH = 1–6 was investigated, and the reaction mechanism and desulfurization were analyzed. After the impact on coal quality. In the experiment, the clean coal with high organic sulfur content after washing from Shanxi’an Yi Coal in China was used as the raw material. After grinding, it was suspended in three different electrolyte systems of NaBr-HCl, NaBr-HNO3, and NaBr-H2SO4 to control different pH values. Desulfurization of coal particles suspended in the electrolyte is carried out by generating active oxides through electrode reaction, and the influence of desulfurization conditions on coal quality is analyzed using the whole industry analysis index and the test results of TGA, FTIR and EDS. The results show that a certain amount of NaBr and acid have different electrochemical desulfurization effects in different environments with pH = 1–6. The same acid has different desulfurization effects at different pH and different acids at the same pH, which has different effects on coal quality. There are also significant differences. The relative content of oxygen in coal samples increased after desulfurization, resulting in a decrease in the relative content of carbon, lowering the calorific value of the coal and improving the combustion performance; in the environment of HCl pH = 6, the electrolytic desulfurization reaction will cause Cl substitution reaction, H2SO4 under pH = 6 environment, the oxygen content increases significantly, causing serious deterioration of coal quality. Compared with HCl and H2SO4, HNO3 pH = 6 environment is better. It can effectively remove organic sulfur from clean coal and maintain the basic structure of coal without change, as ash content is reduced.