Behavior of Selenium during Chemical-Looping Gasification of Coal Using Copper-Based Oxygen Carrier

Abstract

The migration and transformation behavior of selenium during coal chemical looping gasification (CLG) under the impact of a CuO/Bentonite (Ben) oxygen carrier (OC) were studied in a batch fluidized bed reactor. In the CLG process, the total percentage of selenium released in gaseous phase was 73.06%. In the conventional gasification process, 91.71% of the total selenium was released in a gaseous state. The addition of CuO/Ben OC apparently promoted the transformation from gaseous selenium to particulate selenium. The oxygen–carbon ratio (O/C) played an important role in affecting the fraction of gaseous selenium released in the gasification process, with results showing that the amount of selenium adsorbed by CuO/Ben OC was added along with the increase in OC. By means of X-ray photoelectron spectroscopy (XPS) characterization, we found that the reduced CuO/Ben OC contained a small amount of Cu2Se due to the oxidation and adsorption of selenium onto their porous surface. The regeneration performance of the CuO/Ben OC was favorable after 10 regeneration cycles of the CLG process. The increase in the pore volumes and specific surface areas contributed to the enhanced capacity of retaining selenium for CuO/Ben OC.

Keywords

• selenium
• chemical-looping gasification
• CuO/bentonite oxygen carrier
• transformation mechanism
• migration