Attrition analysis of oxygen carriers in combustion appliances

Abstract

Carbon capture and storage (CCS) is a technology which can help reduce emissions of CO2 into the atmosphere and thereby reduce environmental impacts. Ideally, this is implemented by storing pure CO2 gas in stable geological structures. However, this can be challenging to achieve due to emissions often being a mixture of CO2, nitrogen and other byproducts. Chemical looping technology (CLT) can simplify this process by implementing an oxygen-carrying material instead of air to supply oxygen for the reaction. This removes nitrogen from the combustion process and resulting exhausts which consists of CO2 and water. The oxygen-carrying material used in CLT is often metal oxide particles circulated between two fluidized bed reactors. The harsh conditions in the systems lead to attrition of the particles and future implementation of this technology requires a material that is inexpensive, well suited for the reactions, and with a long lifespan in the process. Therefore, this study aims to analyze the attrition rate of different oxygen carrier materials, namely, ilmenite, iron sand, mill scale, LD slag, and synthetic ilmenite. Each material was also examined at different reduction degrees. The most attrition-resistant materials were ilmenite and iron sand and the least resistant were LD-slag and synthetic ilmenite. Most materials were not considerably affected by reduction. Mill scale showed increased attrition in partially oxidised and highly reduced states with cracks forming in the particles visible in SEM imagery.