Innovative Desulfurization Process of Coal Water Slurry under Atmospheric Condition via Sodium Metaborate Electroreduction in the Isolated Slot

This electrochemical reductive desulfurization (ERD) method for coal water slurry (CWS), which was an offshoot of the research Novel Desulfurization Method of Sodium Borohydride Reduction for Coal Water Slurry (Shen, Y. F.; Sun, T. H.; Jia, J. P. Energy Fuels 2011, 25, 2963–2967.), utilized cathodic reduction to change some chemical compounds into strong reducing substances that convert various forms of sulfur (S) in coal into H 2 S and S 2–, thus releasing S from coals. It was an effective way to enhance S removal from coal by adding divalent metal catalysts (Ni 2+, Mn 2+, etc.). Using the atmospheric conditions of 12 g/L of NaBO 2, 3.0 V of electrolytic voltage, 4 h of electrolytic time, 50 g/L of CWS, ≤140 mesh of coal particle size, 1.0 g/L of NaOH, and 1 mM (about 0.13 g/L) of NiCl 2 catalyst, the total sulfur (TS) of CWS can be dramatically reduced by 58.5%. The ERD described here was a predominant desulfurization process, such as mild (slight improvement of the combustion characteristics), high desulfurization efficiency, convenient operation conditions, and low expense (reuse of the filtrate and by-production of hydrogen). Moreover, the realization of the filtrate recycling and the evaluation of the hydrogen releasing rates of NaBH 4 were further helpful in cost reduction.