Experiment and Modeling of CO2 Capture from Flue Gases at High Temperature in a Fluidized Bed Reactor with Ca-Based Sorbents

The Cyclic CO2 capture and CaCO3 regeneration characteristics in a small fluidized bed reactor were experimentally investigated with limestone and dolomite sorbents. Kinetic rate constants for carbonation and calcination were determined using thermogravimetric analysis (TGA) data. Mathematical models developed to model the Ca-based sorbent multiple cycles of CO2 capture and calcination in the bubbling fluidized bed reactor agreed with the experimental data. The experimental and simulated results showed that file CO2 in flue gases could be absorbed efficiently by limestone and dolomite. The time for high-efficiency CO2 capture decreased with an increasing number of cycles because of the loss of sorbent activity, and the final CO2 capture efficiency remained nearly constant as the sorbent reached its final residual capture capacity. In a continuous carbonation and calcination system, corresponding to the sorbent activity loss, the carbonation kinetic rates of sorbent undergoing various cycles are different, and the carbonation kinetic rates of sorbent circulating N times in the carbonation/calcination cycles are also different because of the different residence time of sorbent in the carbonator. Therefore, the average carbonation rate was given based on the mass balance and exit age distribution for sorbent in the carbonator. The CO2 capture characteristics in a continuous carbonation/calcination system were predicted, taking into consideration the mass balance, sorbent circulation rate, sorbent activity loss, and average carbonation kinetic rate, to give useful information for the reactor design and operation of multiple carbonation/calcination reaction cycles.