CO2 Capture with a Highly Flexible Calcium Looping System Using a BFB/TFB Carbonator
11 Pages Posted: 12 Feb 2019 Last revised: 20 Apr 2019
Decarbonisation of the current energy system is being globally regarded as the main approach for reducing anthropogenic CO2 emission levels and to ensure a carbon-free energy future. Yet, even though the deployment of renewable energy sources, such as solar and wind, has grown considerably in the last decades, its behavior is still intermittent and requires of additional energy backup solutions to meet the power requirements of the consumers. Conventional coal-fired power plants need therefore to operate more frequently in part load than in the past, providing larger amounts of balancing power. Carbon Capture and Storage (CCS) units installed to such power stations need to be able to respond fast and dynamically to the required power plant load fluctuations, which is regarded nowadays as a major obstacle limiting their deployment. At the Institute of Combustion and Power Plant Technology (IFK) of the University of Stuttgart, the 230 kWth Calcium Looping test facility has been modified in order to operate with a bubbling to turbulent fluidized bed (BFB/TFB) carbonator and a circulating fluidized bed (CFB) regenerator. This configuration allows to decouple flue gas and solid circulation between reactors, enabling operation of the system in full load and in different part load scenarios, down to very low flue gas loads. Experiments investigating the load flexible behavior of this novel Calcium Looping reactor configuration have been conducted in the context of the European RFCS research project FlexiCaL (Grant No. 709629). This paper introduces the main results obtained during the investigation of different load case scenarios (i.e. 100 %, 60 % and 40 %) at the BFB/TFB-CFB Calcium Looping 230 kWth pilot facility, in which carbonator CO2 capture efficiencies over 92 % were achieved during stable operation for at least 5 hours in all investigated load cases. In the regenerator, typical oxy-fuel combustion conditions with outlet CO2 volume fractions over 90 vol%dry could also be demonstrated. Additionally, this publication presents an estimation of the required carbonator area specific electric output (Acarb/Pel) for BFB systems in current power plant parks.
Keywords: Capture, Flexible, Calcium, BFB/TFB, GHGT-14
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