Operation of a Mixing Seal Valve in Calcium Looping for CO2 Capture

Calcium looping has attracted a great deal of attention among researchers investigating CO2 capture systems. Energy consumption in the regeneration reactor is one of the most important issues. However, as a high-temperature process, calcium looping enables an efficient heat recovery in the capture process itself. The objective of this study is to reduce the energy consumption in the calciner by increasing the temperature of the solids entering this reactor. A calcium looping system including a mixing seal valve is modeled and analyzed to determine the potential advantages this configuration entails. The influence of different seal valve aeration gases, carbonator inventories and solid circulation between reactors is assessed. The reduction of the fuel consumption when the mixing seal valve is aerated with flue gas tends to dilute the CO2 stream. When using CO2, the achievement of substantial energy savings may imply an important increase of the solid flows in the system. Aeration of the mixing seal valve with both gases, so that each gas aerates one exit, is also proposed to address these issues. Results show a significant potential in terms of coal and oxygen savings and reduction of the CO2 generated in the capture system.