A novel Integrated Vacuum Carbonate Absorption Process (IVCAP) for post-combustion CO2 capture is being developed by the Advanced Energy Technology Initiative of the Institute of Natural Resource Sustainability at the University of Illinois at Urbana-Champaign. The solvent used in the process is potassium carbonate (PC). A unique feature of this process is its ability to use either waste or low quality steam from a power plant's low pressure turbine for CO2 desorption. As a result, electricity loss due to steam extraction is significantly lower than that of mono-ethanol-amine (MEA) processes. However, a key technical issue for the IVCAP is the slow absorption rate of CO2 into the PC solution. In this study, the carbonic anhydrase (CA) enzyme was experimentally evaluated as a biocatalyst to promote the rate of CO2 absorption into PC solutions.
The activity of the CA enzyme and its long-term chemical and thermal stability were evaluated using a stirred cell reactor under various conditions of temperature, enzyme dosage level, concentration of PC solution, initial CO2 loading in the solution, CO2 partial pressure, and concentrations of various contaminants. It was found that the rate of CO2 absorption was promoted by 3-15 times at a dosage level of 300 mg/L CA between 25°C and 50°C. The CA enzyme exhibited a stable activity over a two-month period. Activity tests over a longer time are in progress. The effect of typical impurities in a flue gas on the enzyme activity was simulated by exposing the CA enzyme to a solution containing SO42- (0.1-0.9M), NO32- (0.05-0.2M) and Cl- (0.3-0.7M), either individually or in a mixture. It was revealed that the enzyme lost only less than 11% of its initially activity.
Process engineering data collected to date indicate that the CA enzyme is a promising catalyst for promoting the rate of CO2 absorption into the PC solution. Ongoing research is focusing on testing several CA enzymes obtained from different sources, developing a CA immobilization method, and evaluating the potential application of the IVCAP for simultaneous removal of SO2 and capture of CO2 from coal combustion flue gases.
See more of this Group/Topical: Topical 1: Separation Needs for Energy Independence and Environmental Sustainability