(494c) Absorption of CO2 Into Aqueous Potassium Carbonate Solution Promoted by Carbonic Anhydrase Enzyme for Post-Combustion CO2 Capture

Authors: 
Lu, Y. - Presenter, University of Illinois at Urbana-Champaign
Ye, X. - Presenter, University of Illinois at Urbana-Champaign
Rostam-Abadi, M. - Presenter, University of Illinois at Urbana-Champaign
Patton, R. - Presenter, US DOE/ National Energy Technology Laboratory


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.