Transformation and migration mechanism of carbon and sulfur in lignite’s chemical looping gasification using carbide slag

Abstract

In the process of lignite’s chemical looping gasification using carbide slag, carbon, and sulfur are present in both the gas and solid phases. To analyze the migration and transformation of carbon and sulfur in lignite’s chemical looping gasification using carbide slag, theoretical calculations along with experiments were conducted. The results showed that the migration transformation of carbon consisted of three main parts. First part was the transformation of organic carbon to inorganic gaseous carbon, which was followed by the mutual transformation of inorganic gaseous carbon. Finally, the inorganic carbon in gas was transformed into solid phase. The transformation of gaseous inorganic carbon to solid inorganic carbon, and that of inorganic carbon to gaseous carbon occurred at the reaction temperature of more than 1073 K. During the reaction, the migration transformation of sulfur consisted of two main steps. The transformation of organic sulfur to inorganic gaseous sulfur (H2S) through lignite’s gasification, and the transformation of inorganic gaseous sulfur (H2S) to inorganic solid sulfur (CaS). In-situ solidification of sulfur could be achieved through lignite-H2S-CaS reaction. This work provides fundamental knowledge about the mechanism of the transformation of carbon and sulfur during lignite’s chemical looping gasification and provides support for controlling the in-situ solidification of sulfur and carbon-containing gases during lignite’s chemical looping gasification using carbide slag.