(22f) Capture of CO2 from Combustion Flue Gas Using the Carbozyme Liquid Membrane Permeator – Results of Pilot-Scale Testing

Carbozyme, Inc. has developed a biomimetic technology that appears to offer significant cost and performance advantages over monoethanolamine (MEA) scrubbing systems for capture of CO2 from combustion flue gases. The Carbozyme technology is based on separation of CO2 from a mixed gas stream as a bicarbonate, whose reaction is catalyzed by carbonic anhydrase (CA), an enzyme found in plants and animals. The process uses a microfluidic design that features a layer of CA in a thin liquid film, called a contained liquid membrane (CLM), contained between two polymer membranes.

A $4.8-million cooperative agreement with the U.S. Department of Energy has been secured to further develop and scale up the Carbozyme process for the capture of CO2 from power plant flue gas. A multistep approach has been adopted to further develop the Carbozyme process, including the following activities:

? The composition of the flue gases most likely to be encountered at coal-fired facilities in the nation's power-generation fleet are being estimated based on coal type, burner configuration, and downstream pollution control devices.

? A prototype CLM module is being fabricated and installed downstream of the pollution control equipment on a 42.2-MJ/h (40,000-Btu/h) combustion and environmental process simulator (CEPS) system at the Energy & Environmental Research Center (EERC).

? Four, 250-h tests on the CEPS will evaluate the ability of the Carbozyme CLM to capture CO2 from flue gases generated during the combustion of natural gas, lignite, subbituminous coal, and bituminous coal at both steady-state and upset conditions. Longer-term (~2000-h) testing is planned. The resulting data will be used to validate and further scale up the technology 10-fold.

? The scaled-up Carbozyme CLM system will be installed as a multimodule, skid-mounted system on a 527.5?MJ/h (500,000-Btu/h) combustion system at the EERC where it will be evaluated during a 1-wk test. Data collected will be used to determine CO2 capture efficiency and to estimate capture costs using this technique.

To date, activities have focused on estimating the composition of the flue gases that the Carbozyme CLM system will encounter. Direct measurements of flue gas composition were not feasible because very few power plants provide detailed compositional data for their flue gases. Instead, it was determined that flue gas compositions would have to be estimated for as broad a range of coals and pollution control devices as possible. The coals that are most commonly used for electricity generation in the U.S. were identified and their proximate and ultimate analyses obtained. The most common plant configurations (i.e., boiler type and attendant pollution-control devices) were determined for the entire U.S. power production fleet. The coal analyses and plant configurations were input into the Carnegie Mellon Integrated Environmental Control Model (IECM) to generate nearly 100 flue gas composition estimations. Comparison of the various flue gases identified a range for each flue gas component that could be expected. The results indicate that SOx and NOx concentrations may be high enough to affect the pH of the CLM. Therefore, a secondary acid-gas scrubber has been designed, fabricated, and installed on the combustion test system. The next steps include fabrication and installation of the CLM on the EERC's 42.2-MJ/h (40,000-Btu/h) combustion system and initial testing.