Enhanced Sewage Sludge Gasification by Bauxite‐Modified Carbide Slag for Hydrogen‐Rich Syngas Production with In Situ CO2 Capture

Abstract

Calcium‐looping gasification is attractive to dispose massive sewage sludge for hydrogen‐rich syngas with in situ CO2 capture but still challenged by apparent drop of CO2 sorbent reactivity, sorbent attrition, and uncertainty of sorbent performance during multi‐cycle gasification. Herein, bauxite‐modified carbide slag is prepared as a cheap CaO‐based CO2 sorbent by a simple mechanical mixing method. Based on physical and chemical characterization as well as thermogravimetric analyses, it is found that the bauxite‐modified carbide slag (CS) contained the inert component of mayenite, which is beneficial to improve pore characteristic and promote stability and mechanical strength of sorbent during multi‐cycle CO2 capture. Fluidized bed gasification tests verify that adding carbide slag increases H2 yield and efficiency of sewage sludge gasification. Moreover, appropriate increase in reaction temperature and steam flow rate enhances sewage sludge gasification with bauxite‐modified carbide slag. During multi‐cycle fluidized bed gasification, modified carbide slag CS‐5 (with 5 wt% bauxite) presents more stable performance and better anti‐attrition characteristic in comparison to carbide slag without modification. After five cycles of fluidized bed gasification, the yield and concentration of H2 are increased while the fraction of fine particles produced by attrition is largely decreased for CS‐5 in comparison to ordinary carbide slag.