Eco friendly chemical looping combustion
Combustion of fossil fuels to power human activities produces carbon dioxide — a significant contributor to global climate change. Post-combustion carbon capture technologies represent an important step in the transition to renewable energy sources. Chemical looping boilers show great promise as they have low energy requirements. With this technology, hydrocarbons are oxidised in a fluidised bed reactor system. EU-funding of the project 'Innovative oxygen carriers uplifting chemical-looping combustion' (INNOCUOUS) enabled scientists to improve on a lab-scale concept with an eye on industrial implementation. The original chemical looping combustion concept relies on expensive and hazardous nickel-based oxygen carriers. INNOCUOUS sought to achieve reasonable performance at the industrial scale with novel eco-friendly oxygen-carrier particles. Thus, work included both selection of new oxygen carriers and technical improvements in the fluidised bed reactor design. Scientists investigated both nickel-free materials and mixed oxides using a minimal amount of nickel. From 160 samples, the team narrowed the field to a few promising candidates that were inexpensive and eco-friendly. These were successfully employed in 10 kilowatt and 120 kilowatt reactors with 100% fuel conversion (as opposed to 98-99% of nickel oxide materials) and carbon dioxide separation. Scientific work has led to nine publications with several more in various stages of publication. While the cost of a chemical looping boiler is more than that of a common gas-fired boiler, it is not prohibitive. Also, there is room for optimisation to make sure that the benefits outweigh the costs. INNOCUOUS partners successfully replaced nickel-containing oxygen carriers in a chemical looping boiler with eco-friendly alternatives and simultaneously achieved complete fuel conversion, bringing the technology one step closer to implementation.
Keywords
Chemical looping combustion, carbon capture, nickel, oxygen carriers
