Continuous CO2 Capture from Flue Gases Using a Dual Fluidized Bed Reactor with Calcium-Based Sorbent

CO2 capture using multiple carbonation and calcination reaction looping is an emerging postcombustion capture technology. Dual fluidized bed reactors are the key technology to fulfill the carbonation/calcination looping process. Dual bubbling fluidized bed reactors were constructed to demonstrate the process feasibility of continuous CO2 capture from flue gases. First, a cold model of the dual bubbling fluidized bed reactor was built and tested on the foundation of analyzing different types of dual fluidized bed reactors. Long-term stable operation and continuous solids circulation between the two reactors was achieved in the cold model. The solids circulation rate increased with increasing bed material height, solid injection nozzle diameter, and hole diameter on the solid injection nozzle. Second, a hot model of the dual bubbling fluidized bed reactor was constructed. The sorbent particles successfully circulated between the carbonator and the regenerator at high temperatures and the CO2 in the flue gases was continuously captured by the Ca-based sorbent, dolomite. Experimental results indicate that similar to 95.0% CO2 capture efficiency could be achieved. In the carbonator, about 70.4% CaO in the sorbent was converted to CaCO3, In the regenerator, the CaCO3 did not decompose completely with more than 13.9 wt % CaCO3 still in the sorbent leaving the regenerator. The carbonation temperature and the sorbent attrition were found to significantly influence the carbonation/calcination looping process.