Dual Alkali Approaches for the Capture and Separation of CO2

Abstract

The Solvay process utilizes two alkalis in sequential order to convert CO2 to sodium carbonate for commercial use. The ability to transform CO2 into sodium carbonate cost-effectively would be a breakthrough in CO2 sequestration by providing benign long-term storage of CO2. However, the Solvay process was not designed for CO2 sequestration and is not practical for use in the sequestration of CO2 from fossil fuel power plants. This paper investigates methods to modify the process in order to make it effective for the control of power plant CO2 emissions. The new modified process, called the Dual Alkali Approach, attempts to replace either or both bases, ammonia and lime, in the Solvay process with other compounds to make CO2 capture and separation efficient. Ammonia was replaced with different amines in aqueous solutions of salts and it was found that bicarbonate precipitation did occur. A method to regenerate the amine in the second step has not been implemented. However, the second step in the Solvay Process has been implemented without using lime, namely, ammonia has been regenerated from an ammonium chloride solution using activated carbon. The HCl adsorbed in the activated carbon was removed by water to regenerate the activated carbon.