W.R. Grace & Company (Grace) has teamed with the University of South Carolina (USC), Battelle Memorial Institute, and Catacel Corporation to develop a unique rapid PSA process for cost-effective post-combustion CO2 capture from coal-fired power plants. The rapid PSA process could enable CO2 capture from a 550 megawatt (MW) power station with no more than a 35 percent increase in the cost of electricity (COE). PSA is a favorable process for CO2 capture as adsorption and desorption are achieved with electrical energy rather than with the extraction of steam from the power plant’s steam cycle, which is important for retrofitting into existing plants.
This project will build on promising results from a previously developed proprietary PSA cycle configuration for CO2 capture from a coal-fired power plant that demonstrated a total separation energy of 25 kilojoules per mole (kJ/mol) compared to 39 kJ/mol for a monoethanolamine system. The new PSA cycle is capable of achieving over 90 percent CO2 recovery and over 95 percent CO2 purity using commercial 13X zeolite pellets. Although this CO2 capture technology could be retrofitted to a coal-fired power plant, the adsorption columns would be exceedingly large and thus capital intensive. The project team will develop a rapid version of the proprietary PSA process, taking advantage of a much shorter cycle time—30 seconds compared to 300 seconds for a conventional PSA cycle. This would increase the feed throughput, a measure of the size of the adsorption columns, by a factor of 10 or more, concomitantly decreasing the column size by an order of magnitude or more. The new process could significantly reduce both the capital costs and plant footprint, while also reducing the operating costs.
The rapid PSA concept is conceptually simple but difficult to implement. The key to the success of this project is finding a suitable match between the adsorbent and the PSA cycle configuration for a full-scale rapid PSA process. A select team of experts has been assembled to demonstrate the feasibility of the rapid PSA concept for CO2 capture at the bench scale, and their research will focus on the materials, structure, and PSA cycle.
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 coalfired power plants in the event of carbon constraints.
Pulverized coal (PC) plants burn coal in air to produce 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 10–15 percent by volume. Post-combustion 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. Solid sorbent-based technologies have the potential to effectively reduce the energy penalties and costs associated with post-combustion CO2 capture for both new and existing PC-fired power plants. Pressure swing adsorption (PSA) technology is commonly used for gas separation and has the potential to remove CO2 from flue gas by adsorbing the CO2 at high pressure and then desorbing it at a low pressure.
Bench-scale development of the unique rapid PSA technology—based on a successful, previously developed PSA cycle—will confirm the capability of this technology to cost-effectively capture CO2 from coal-fired flue gas. This technology holds promise to achieve the DOE goals of capturing at least 90 percent of the CO2 with less than a 35 percent increase in the COE when scaled to a 550 MW coal-fired power plant.
Primary Project Goal
The project goal is to develop and test a bench-scale, cost-effective, rapid PSA process for post-combustion CO2 capture from coal-fired power plants such that, when scaled to a 550 MW coal-fired power plant, it could achieve the DOE goal of less than 35 percent increase in the cost of electricity.
The specific project objectives are the development of (1) an attrition resistant and low pressure drop structured adsorbent based on commercial 13X zeolite that is compatible with the high velocities associated with rapid PSA operation, and (2) a rapid PSA cycle configuration in concert with the structured adsorbent so that the resulting rapid PSA process delivers exceptional performance at reduced capital and operating costs.
Design and construct a single-column rapid PSA test bed with standard commercial zeolitic adsorbents.
Perform baseline testing and compare test results to conventional pelletized adsorbent material.
Develop and optimize a simulation model to improve the adsorbent 3-D structure based upon the baseline study results.
Explore alternative operational strategies using process modeling and data to further optimize the rapid PSA process.
Incrementally improve the zeolite adsorbent materials to mitigate any weaknesses identified in baseline testing.
Investigate possible optimizations of the adsorbent, structure materials, and manufacturing process to reduce size and cost of the optimized structure.
Based on optimized adsorbent, bed structure, and PSA process, develop and test a multi-column rapid PSA test bed on simulated coal-fired flue gas.
Validate scale-up economics for the adsorbent structure production processes and prepare a final techno-economic feasibility study for a 550 MW coal-fired power plant.
Complete an environmental, health, and safety assessment of the rapid PSA technology.
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