A novel desulphurization process of coal water slurry via sodium metaborate electroreduction in the alkaline system

摘要

The present work investigated an alternative desulfurization process for coal water slurry (CWS) using sodium metaborate (NaBO_2) electroreduction under the ambient conditions. Desulfurization efficiency improved with the increases of NaBO_2 concentration, electrolytic time, and electrolytic voltage, while with the decreases of coal particle size and CWS concentration. Up to 50% desulfurization efficiency was obtained in the <109urn (140 mesh) coal under the optimized conditions of CWS (50g/L), NaBO_2 (13.2 g/L), NaOH (1 g/L), electrolytic voltage (3.5 V), and electrolytic time (4 h). Furthermore, the possible reaction mechanism of electrochemical desulfurization (ED) was that NaBO_2 was converted into NaBH_4 by means of the electrochemical reduction (ER) on the cathode, which induced transformation of pyritic sulfur (PS) and organic sulfur (OS) in the coal into H_2S and S~(2-), and S~(2-) in the solution was further oxidated into SO~(2-)_4(SS) on the anode.