Iron-Based oxygen carrier aided oxy-fuel combustion of biomass in fluidized Beds: Effects of types of oxygen carriers and biomass ash

Oxygen carrier-aided combustion (OCAC) in biomass combustion has the potential to improve fuel conversion efficiency and reduce CO 2 emissions. However, the key mechanisms of oxygen carriers (OCs) in OCAC remain unclear, and the influence of biomass ash on combustion characteristics hinders the industrial application of this technology. In this study, a bench-scale bubbling fluidized bed experimental apparatus is employed, utilizing three types of biomass (sawdust, rice husk, and wheat straw) as fuels, and AR-Fe 2 O 3 , hematite, and steel slag as OCs. The focus is on assessing the influence of OCs on the combustion characteristics of biomass, as well as exploring the effects of ash on these characteristics, all within the atmosphere of 10% O 2 and 90% CO 2 maintained at a temperature of 850℃.The results indicate that AR-Fe 2 O 3 , with high lattice oxygen content and substantial oxygen storage capacity, does not engage in competitive gaseous oxygen (O 2 (g)) uptake with biomass char but instead facilitates efficient oxygen transfer, accelerates the carbon reaction rate, shortens the burnout times, and elevates the generation of CO. Conversely, hematite and steel slag reduce CO generation through low content lattice oxygen reactions with CO, then the oxygen vacancies compete with biomass char for O 2 (g), leading to slower combustion rates and longer burnout times. Although ash in raw biomass char maybe hinder combustion, the structural modifications induced by demineralization are dominant under short reaction times, significantly enhancing combustion performance. The findings providing a guidance for OC selection and biomass pretreatment strategies, supporting the optimization of OCAC for industrial biomass energy applications.