In-situ removal of sulfur from high sulfur solid waste during molten salt pyrolysis

In order to address the adverse effects of high sulfur content on the subsequent use of pyrolysis char, the removal of sulfur from high sulfur solid waste during molten salts pyrolysis was studied in this work. The results show that sulfur content of molten salts pyrolysis char was significantly lower than that of general pyrolysis char because molten salts catalyzed the decomposition of organic sulfur. Moreover, the removal efficiency of sulfur in molten salts pyrolysis char was obviously enhanced with the increase of temperature and time. Especially under the condition of 850 °C and 2 h, more than 33 wt% of the sulfur in molten salts pyrolysis char was successfully removed compared with ordinary pyrolysis char. Molten salts, which provided a larger contact area between char and volatiles, promoted a large amount of easily decomposed organic sulfur-containing compounds production by the cyclization reactions between char and hydrogen sulfide at higher temperatures. Due to the adsorption of H2S by molten salt, the SH radical was released more into the molten salt in the form of H2S rather than reacting with zinc oxide to form thermal stable zinc sulfide. Both of these reasons contributed to the removal of sulfur in the molten salt pyrolysis char.