Attrition of lignite char during fluidized bed gasification.

Fragmentation and attrition phenomena occurring to lignite char particles during fluidized bed gasification by CO2 have been studied in a lab-scale apparatus. The influence of bed temperature, fluidizing velocity and inlet CO2 concentration on attrition and carbon conversion was investigated. Secondary fragmentation and attrition by abrasion of char particles during gasification were significant, suggesting a gasification-assisted attrition enhancement effect. This mechanism, associated to the low reactivity of the generated fines, made the loss of carbon by fines elutriation during char gasification more significant than that typically found under combustion conditions. Up to 10% of the carbon initially fed was lost in the elutriated fines. The carbon loss by elutriation increased with the fluidization velocity, and when the bed temperature and CO2 concentration decreased. The effect of these last two variables was connected to their influence on the char gasification rate.