Effect of CO2 on high temperature chlorination behavior of calcined limestone in an innovated fixed-bed reactor

• An innovated fixed-bed reactor was designed to study the gas–solid reaction especially for high temperatures.
• The experimental results performed in this system shows good repeatability.
• The presence of CO2 enhances the apparent reaction rates of the CaO chlorination at 650 ˚C and 700 °C while accompanying a slight reduction of HCl capture capacity.
• The enhancement of reaction rate and reduction of removal efficiency were proved to be related to the carbonation behavior.

This work aimed to elaborate on the influence of CO2 on the reactivity of CaO with HCl under conditions similar to combustion environment. This study was conducted in an innovated fixed-bed reactor to investigate the influences of simulated CO2 concentrations on the chemistry of CaO with HCl at varied temperatures. Tests of sole CaO carbonation and chlorination were performed in a thermogravimetric analyzer and fixed-bed reactor, respectively, to provide fundamental information for the CaO chlorination experiments in the presence of CO2. The HCl concentrations were continuously monitored in a Fourier Transform Infrared (FTIR) cell and the repeatability tests yielded good results. These results indicated that the presence of CO2 was beneficial for the apparent reaction rates of CaO chlorination performed at 650 °C and 700 °C, compared with the case of only chlorination; nevertheless, this benefit accompanied a slight reduction of HCl capture capacity. The results were related to the CaO carbonation behavior. On the other hand, further increased CO2 concentrations had no effect on the extent of the chlorination reaction.

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