Membrane-Sorbent Hybrid System for Post-combustion Carbon Capture
The electricity produced from fossil fuels is essential to the world’s prosperity and security. On the other hand, increasing atmospheric CO2 concentration caused by the fossil fuel combustion are causing concerns regarding global warming. Although there are several methods for separating CO2 from the flue gases at existing coal-fired power plants, all of them have significant drawbacks, including loss of efficiency and increased capital and operating costs that dramatically increase the cost of electricity. TDA Research, Inc. (TDA), in collaboration with Membrane Technology Research Corporation (MTR) and the University of California, Irvine, has developed a low-cost, high-capacity sorbent that will integrate into a membrane-sorbent hybrid, post-combustion carbon capture system to remove CO2 from coal-fired power plant effluents. Previously in Phase I, we optimized the sorbent to meet the needs of the application. Our preliminary analysis results indicates that the sorbent system is operated in a concentration swing mode it will have a significantly lower cost than an equivalent membrane system, increasing the economic viability of the carbon capture process. Sorbent improvements also enabled lower oxygen transfer rates from the boiler air intake side to the flue gas side. In our Phase II work, we designed, tested, and optimized a lab-scale (approximately 7-liter) radial sorbent contactor that demonstrated excellent CO2 scrubbing capability while significantly decreasing the permanent pressure drop (unrecoverable pressure loss was reduced by more than a factor of 2 while maintaining the same sorbent volume and flue gas flow rate). Using the new radial bed concept, TDA retrofitted an existing 4-bed test system (previously used in DE- SC0006239 and DE-FE0007580 to demonstrate sorbent only vacuum swing adsorption (VSA) based cycles demonstrating 90% carbon capture and 95% CO2 purity in a single stage) to utilize the optimized radial sorbent beds while also holding a small single-element CO2 transport membrane made by our partners MTR. With the membrane installed, additional modifications were made to accommodate the new flow pathway and to provide vacuum (on the membrane instead of the sorbent beds) to assist the membrane flux. Initial testing at TDA’s Golden, CO labs demonstrated good CO2 removal and stability (lab-testing used a high-fidelity flue gas simulant generated from the industrial-grade bulk gases: CO2, N2, O2, and H2O). Following this test, TDA conducted a 3-week field trial at Thermosolv (formerly the Western Research institute in Laramie, WY) where 1 to 4 SCFM coal-derived flue gas from a lab-scale coal-fired boiler was used to demonstrate long-term stability with the membrane-sorbent hybrid CO2 capture system under coal-derived flue gas. During this test, supplemental CO2 was injected at the membrane inlet in order to simulate the effects of CO2 recycle through the coal boiler. The demonstration achieved the DOE target of ≥ 90% CO2 capture with a CO2 product purity in the 60-70% range (on a dry basis, which is equivalent to about 55-65% on wet basis) which matches with MTRs large-sale, single-stage membrane demonstrations. In our Phase IIB work, TDA designed and created a new test system for the hybrid membrane-sorbent system that was capable of processing coal-derived flue gas at 42 kWe (approximately 100 SCFM of flue gas). This represented a roughly 25X increase in scale from the Phase II test. In order to achieve this level of performance, TDA significantly increased the sorbent bed size, piping size, and membrane size. For this test MTR provided a larger membrane housing that incorporated a pair of 8” spiral-wound membranes in parallel. The housing was mounted on a free-standing skid that TDA designed to stack vertically atop the sorbent system in order to maintain a compact footprint. The membrane skid included the membrane housing and feed, permeate, and retentate isolation valves along with a membrane bypass valve used for isolating the membrane and sorbent sub-systems during startup/shutdown. TDA completed the balance of plant design and incorporated a liquid ring compressor for the flue gas admission and a liquid ring vacuum pump to boost the driving force (CO2 partial pressure) across the membrane. For this scale of testing, supplemental CO2 would have been excessively expensive, so TDA developed a CO2 recycle system that fed back the product CO2 (membrane permeate into the unit’s feed). System fabrication was completed in the fall of 2019 and the system was shipped to the Wyoming integrated test Center at the Dry Fork Station power plant and initial setup and commissioning was completed in Q4 of 2019. Testing was started in January of 2020 and continued through July 2020, with testing spread out over 3 distinct campaigns (a total of about 870 hours). While running at roughly 1 tonne/day of CO2 processed, the system demonstrated ≥ 90% CO2 capture in several modes of operation while obtaining a CO2 purity (membrane permeate/product stream) ranging from about 55–65% (wet basis). The process simulation study carried out by UCI suggested a plant efficiency of 31.48% for a super-critical coal fired power plant equipped with the membrane-sorbent hybrid system for carbon capture, which is well above what can be achieved by the state-of-the-art amine scrubbing technology (28.40%). The cost of CO2 captured for MTR-TDA hybrid system is $40.0 per tonne compared to $56.5 per tonne for amine-based system on 2011 $ basis.
- Research Organization:
- TDA Research, Inc.
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0011885
- OSTI ID:
- 1708836
- Type / Phase:
- SBIR (Phase IIB)
- Report Number(s):
- TDA-2050-PIIB-FR
- Country of Publication:
- United States
- Language:
- English
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