(Invited) Electrochemical Membrane Technology for Carbon Dioxide Capture from Flue Gas
Authors: Ghezel-Ayagh Hossein , Jolly Stephen , Dobek Frank , Chimbole Frank , Willman Carl 
Published: February 2020

To address the concerns about climate change resulting from emission of CO2 by power plants and industrial facilities, FuelCell Energy, Inc. (FCE) has developedthe Combined Electric Power and Carbon-dioxide Separation (CEPACS) system. The CEPACS system utilizes Electrochemical Membrane (ECM) technology derived from the Company’s molten carbonate fuel cell-based Direct FuelCell® products. The system separates CO2 from the flue gas of other plants and produces electric power using a supplementary fuel. FCE is currently evaluating the use of ECM to cost effectively separate CO2 from the flue gas of Pulverized Coal (PC) power plants under cooperative agreements with the U.S. Department of Energy (DOE). The overarching objective of the current project is to verify that the ECM can achieve at least 90% CO2 capture from the flue gas with a cost of electricity (COE) 30% lower than baseline approaches. The objectives will be achieved through pilot-scale testing of a MW-class CEPACS system using a slipstream of flue gas from a PC plant.

The potential of ECM for separating more than 90% of CO2 from the flue gas of a PC plant has been experimentally verified. ECM materials tolerance levels to various contaminants in the flue gas including SO2, HCl, Hg, and SeO2 have been identified. The contaminant levels expected from the flue gas clean-up subsystem were also estimated and compared with the ECM tolerance levels. The analysis showed that the ECM tolerance levels are well above the contaminant levels expected in the ECM cathode feed gas. Ability of ECM to destroy NOx components in the flue gas was confirmed in the laboratory tests. Testing showed that 70-80% of all NOx was destroyed at high inlet NOx concentrations of over 200 ppm. This significant finding may result in further reduction of the incremental COE associated with the CEPACS system, if credits are given to elimination of the selective catalytic reduction process step for NOx control in the PC plant.

The Technical and Economic Feasibility studies were conducted, including assessments of performance and cost of an ECM-based CO2 capture system for retrofitting a 550 MW PC plant with 90% capture. The CEPACS system generates 421 MW of additional power after compensating for the auxiliary power requirements of CO2 capture and compression. The economic analysis included estimation of the CEPACS plant cost and the incremental COE for ECM-based CO2 capture. The CEPACS technology has the potential to meet DOE’s goal of ≤35% increase in COE for post-combustion CO2 capture. The CEPACS system can also meet the DOE’s target cost of <$40/tonne CO2 captured.

A bench-scale ECM-based CO2 capture system was designed and fabricated. The objective of the demonstration is to show the capability of full-size ECM cells to separate >90% of CO2 from a simulated PC plant flue gas stream during extended operation. The system utilizes an ECM stack containing 14 full-area cells with a total electrochemical membrane area of 11.7 m2. Peak gross DC output is ~10 kW, with capability for high-purity liquid CO2 production of ~100 tons/year. The stack has operated for more than 10,000 hours and has demonstrated very stable electric power generation while separating 93% of carbon from flue gas at a constant CO2 flux of 116 cc/s/m2.

In this presentation, the status of the ECM technology and its application for carbon capture will be reviewed. The results of trace contaminants experiments, characterization of ECM tolerance to key flue gas contaminants, ECM technology NOx removal capabilities, bench scale full-area ECM stack testing, and the techno-economic studies of CEPACS systems will be discussed. Plans for pilot-scale testing of the technology will as part of a recently-awarded DOE cooperative agreement will also be reviewed. Finally, the benefits and commercialization activities related to the ECM technology will be presented.