Chemical Looping Combustion of wood pellets in a 150 kWth CLC reactor

Abstract

Carbon-negative solutions have got increased attention in the recent years as being a necessary measure to mitigate climate change and limit the global temperature rise to 2°C. Bio-Energy Carbon Capture and Storage (BECCS) is at present the most mature and the only large-scale technology that can achieve CO2 negative emissions. One attractive option for realising BECCS is by using chemical looping combustion (CLC) technology in combination with sustainable biomass as fuel (bio-CLC). Bio-CLC is a very promising CO2 capture technology because of the potentially low energy penalty and low CO2 capture cost. Bio-CLC pilot scale tests in a 150 kWth CLC reactor system has been carried out using ilmenite as oxygen carrier and whole wood pellets as fuel. The work is part of the project "Negative CO2 Emissions with Chemical Looping Combustion of Biomass", one of three ongoing flagship projects funded by the Nordic Energy Research. Fuel feeding rate was kept stable at a fuel power equivalent to 140 kWth. The operation of the reactor was then nearly auto-thermal, as the only additional heating of the reactor was preheating of the primary air for the air reactor. The minimum oxygen demand was calculated to about 23% and the CO2 capture efficiency varied between 94 – 97%. The specific fuel reactor inventory during the test was 140 – 180 kg/MW. This is low compared to what is used in most other studies and is mainly a consequence of the fuel reactor being a CFB type of reactor, operating close to a fast fluidization mode. Even though significant amount of additional oxygen is needed for full fuel conversion, the results may be considered good bearing in mind the relatively small size, and thus short residence time, of the reactor compared to an industrial scale reactor, and the low-cost oxygen carrier material used