Rice University will develop a novel gas absorption process for CO2 capture that is projected to have considerably lower capital and operating costs than the conventional monoethanolamine process. The unique process combines the absorber and desorber columns, separated by a microporous ceramic membrane, into a single integrated unit. Conventional CO2 capture processes consist of a column that absorbs CO2 with a liquid solvent, and a separate column that desorbs CO2 from the solvent. Researchers at Rice University have determined that it is possible to integrate the absorber and desorber sections into a single unit. The integrated absorber/desorber arrangement will reduce space requirements, an important factor for retrofitting existing coal-fired power plants with CO2 capture technology.
This novel capture process uses ceramic foam contactors with complex, highly-interconnected structures for the absorption and desorption of CO2. The ceramic gas-liquid contactors have favorable characteristics for mass transfer with large geometric surface areas, up to ten times that of conventional packing. Additionally, the contactors will be chemically functionalized to enhance the absorption and desorption processes. The resulting functionalized packing is anticipated to increase the rate of CO2 absorption into the solvent, making it feasible to use slow-reacting amines with low heats of regeneration. Commercially available solvents with well-documented performance will be examined. In the integrated unit, a microporous ceramic membrane allows for selective permeation of the CO2-rich liquid from the absorber section through the membrane and into the CO2 desorbing side. The desorber section is operated under a moderate vacuum to separate the CO2 from the solvent at reduced temperatures, which provides the cost-saving advantage of using low-grade heat from the plant.
Rice University will perform an initial analysis to estimate the technical and economic feasibility of the process. A bench- scale prototype will then be developed to implement the complete CO2 separation process and tests will be conducted to study various aspects of fluid flow in the process. A model will be developed to simulate the two-dimensional (2-D) fluid flow and optimize the CO2 capture process. Test results will be used to develop a final techno-economic analysis and identify the most appropriate absorbent as well as optimum operating conditions to minimize capital and operating costs. This analysis will indicate the feasibility of integrating the process into a 550 megawatt electric (MWe) coal-fired power plant. An environmental, health, and safety (EH&S) assessment of the capture process will also be completed.
The mission of the U.S. Department of Energy/National Energy Technology Laboratory (DOE/NETL) Carbon Capture Research & Development (R&D) Program is to develop innovative environmental control technologies to enable full use of the nation’s vast coal reserves, while at the same time allowing the current fleet of coal-fired power plants to comply with existing and emerging environmental regulations. The Carbon Capture R&D Program portfolio of carbon dioxide (CO2) emissions control technologies and CO2 compression is focused on advancing technological options for new and existing coal-fired power plants in the event of carbon constraints.
Pulverized coal plants burn coal in air to generate steam and comprise 99 percent of all coal-fired power plants in the United States. Carbon dioxide is exhausted in the flue gas at atmospheric pressure and a concentration of 10 to 15 percent by volume. Postcombustion separation and capture of CO2 is a challenging application due to the low pressure and dilute concentration of CO2 in the waste stream, trace impurities in the flue gas that affect removal processes, and the parasitic energy cost associated with the capture and compression of CO2. Post-combustion CO2 control technologies include the use of solvents, solid sorbents, and membranes, alone or in beneficial combinations. Improvement in the performance of these technologies as well as the development of novel cost-effective processes using these technologies are key to affordable carbon capture for coal-fired power plants.
Primary Project Goal
The primary project goal is to develop, test, and optimize (at bench scale) a novel gas separation process with the potential to reduce the cost of CO2 capture from coal-fired power plants and meet the DOE goals of capturing 90 percent of the CO2 with less than a 35 percent increase in the cost of electricity.
Project objectives are to (1) develop a CO2 capture process that uses a single integrated unit that combines both the absorber and desorber columns, (2) use waste heat for absorbent regeneration instead of low-pressure steam by operating the desorber section of the integrated unit under vacuum, (3) functionalize the ceramic gas-liquid contactors for enhanced gas absorption and desorption, and (4) develop a 2-D model to simulate the CO2 absorption process and optimize the material properties (i.e., pore-size distribution, aspect ratio, etc.) to attain the best process performance.
Perform an initial techno-economic analysis.
Design and fabricate a bench-scale stainless steel prototype for the combined absorber/desorber CO2 separation process.
Implement and demonstrate the bench-scale CO2 capture process using simulated flue gas.
Conduct studies to measure the heat and mass transfer characteristics of the ceramic foam.
Conduct experiments to functionalize the absorption and desorption substrates.
Evaluate the impact of functionalization on the mass transfer behavior of the ceramic foam.
Complete development of a 2-D model to simulate gas and liquid flow in the capture process and compare simulation results with experimental measurements.
Perform a sensitivity analysis and process optimization.
Complete an exergy (available energy) and techno-economic analysis.
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