Determining kinetic constants for reactions of zinc oxide sorbents with syngas components

Abstract

Hot gas clean-up (HGC) technology uses special zinc oxide based sorbents. Sorbent attrition is one of the negative factors that should be improved. The current study has determined that one of the main reasons of sorbent reduction is interaction with syngas components, namely, carbon monoxide, hydrogen, methane and carbon (side reactions). In this study, kinetics of main reaction (h2s adsorption by zinc oxide) and side reactions were considered and compared. Models of chemical processes and mechanisms were considered as well. Complicated nature of HGC process was researched. It is stated that the process can run in three different phases (gas, solid, dust). Methods of TGA data calculation are presented and compared with literature. In syngas where hydrogen sulphide concentration is much lower than concentration of hydrogen and carbon monoxide, main reaction is dominant at temperatures near 300–500 °C. At 650 °C main reaction takes the second place after H2 reduction, and at 850°C it is the third after CO reduction (with diffusion resistance of product shell). Hydrogen reduction is more active than carbon monoxide reduction, that is why CO/H2 ratio in syngas should be increased for rising the HGC operation temperature. A wide range of processes (main and side reactions) was considered with the use of the same materials, equipment and methods.