Biomass combustion with in situ CO sub(2) capture by CaO in a 300 kW sub(th) circulating fluidized bed facility

• Published in: International journal of greenhouse gas control Vol. 29; pp. 142 - 152
• Main Authors: Alonso, M, Diego, ME, Perez, C, Chamberlain, J R, Abanades, J C
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• ISSN: 1750-5836
• DOI: 10.1016/j.ijggc.2014.08.002

This paper reports experimental results from a new 300 kW sub(th) calcium looping pilot plant designed to capture CO sub(2) "in situ" during the combustion of biomass in a fluidized bed. This novel concept relies on the high reactivity of biomass as a fuel, which allows for effective combustion around 700 degree C in air at atmospheric pressure. In these conditions, CaO particles fed into the fluidized bed combustor react with the CO sub(2) generated during biomass combustion, allowing for an effective CO sub(2) capture. A subsequent step of regeneration of CaCO sub(3) in an oxy-fired calciner is also needed to release a concentrated stream of CO sub(2). This regeneration step is assumed to be integrated in a large scale oxyfired power plant and/or a larger scale post-combustion calcium looping system. The combustor-carbonator is the key reactor in this novel concept, and this work presents experimental results from a 300 kW sub(th) pilot to test such a reactor. The pilot involves two 12 m height interconnected circulating fluidized bed reactors. Several series of experiments to investigate the combustor-carbonator reactor have been carried out achieving combustion efficiencies close to 100% and CO sub(2) capture efficiencies between 70 and 95% in dynamic and stationary state conditions, using wood pellets as a fuel. Different superficial gas velocities, excess air ratios above stoichiometric requirements, and solid circulating rates between combustor-carbonator and combustor-calciner have been tested during the experiments. Closure of the carbon and oxygen balances during the combustion and carbonation trials has been successful. A simple reactor model for combustion and CO sub(2) capture in the combustor-carbonator has been applied to aid in the interpretation of results, which should facilitate the future scaling up of this process concept.