Fragmentation and attrition of lignite char particles during fluidized bed gasification by CO2 were studied in a lab-scale apparatus. The influence of bed temperature 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 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 when the bed temperature and the CO2 concentration decreased. The effect of these two variables was connected to their influence on the char gasification rate. A predictive kinetic model for CO2 gasification of the lignite char was developed from the experimental results, that was able to correctly predict the evolution of carbon conversion versus time. On this basis a semi-empirical model was developed in order to simulate the evolution of carbon elutriation rate with carbon conversion degree, i.e. the gasification-assisted attrition enhancement effect. To this end, the mechanical resistance of the char particles was also characterized at different stages of char conversion by specific attrition experiments.
Attrition of lignite char during fluidized bed gasification: experimental and modeling studies.
P Ammendola;F Scala
2012
Abstract
Fragmentation and attrition of lignite char particles during fluidized bed gasification by CO2 were studied in a lab-scale apparatus. The influence of bed temperature 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 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 when the bed temperature and the CO2 concentration decreased. The effect of these two variables was connected to their influence on the char gasification rate. A predictive kinetic model for CO2 gasification of the lignite char was developed from the experimental results, that was able to correctly predict the evolution of carbon conversion versus time. On this basis a semi-empirical model was developed in order to simulate the evolution of carbon elutriation rate with carbon conversion degree, i.e. the gasification-assisted attrition enhancement effect. To this end, the mechanical resistance of the char particles was also characterized at different stages of char conversion by specific attrition experiments.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.