CO₂ Capture Membrane Process for Power Plant Flue Gas

Abstract

Because the fleet of coal-fired power plants is of such importance to the nation's energy production while also being the single largest emitter of CO₂, the development of retrofit, post-combustion CO₂ capture technologies for existing and new, upcoming coal power plants will allow coal to remain a major component of the U.S. energy mix while mitigating global warming. Post-combustion carbon capture technologies are an attractive option for coal-fired power plants as they do not require modification of major power-plant infrastructures, such as fuel processing, boiler, and steam-turbine subsystems. In this project, the overall objective was to develop an advanced, hollow-fiber, polymeric membrane process that could be cost-effectively retrofitted into current pulverized coal-fired power plants to capture at least 90% of the CO₂ from plant flue gas with 95% captured CO₂ purity. The approach for this project tackled the technology development on three different fronts in parallel: membrane materials R&D, hollow-fiber membrane module development, and process development and engineering. The project team consisted of RTI (prime) and two industrial partners, Arkema, Inc. and Generon IGS, Inc. Two CO₂-selective membrane polymer platforms were targeted for development in this project. For the near term, a next-generation, high-flux polycarbonate membrane platform was spun into hollow-fiber membranes that were fabricated into both lab-scale and larger prototype (~2,200 ft²) membrane modules. For the long term, a new fluoropolymer membrane platform based on poly(vinylidene fluoride) [PVDF] chemistry was developed using a copolymer approach as improved capture membrane materials with superior chemical resistance to flue-gas contaminants (moisture, SO₂, NOx, etc.). Specific objectives were: - Development of new, highly chemically resistant, fluorinated polymers as membrane materials with minimum selectivity of 30 for CO₂ over N₂ and CO₂ permeance greater than 300 gas permeation units (GPU) targeted; - Development of next-generation polycarbonate hollow-fiber membranes and membrane modules with higher CO₂ permeance than current commercial polycarbonate membranes; - Development and fabrication of membrane hollow fibers and modules from candidate polymers; - Development of a CO₂ capture membrane process design and integration strategy suitable for end-of-pipe, retrofit installation; and - Techno-economic evaluation of the "best" integrated CO₂ capture membrane process design package In this report, the results of the project research and development efforts are discussed and include the post-combustion capture properties of the two membrane material platforms and the hollow-fiber membrane modules developed from them and the multi-stage process design and analysis developed for 90% CO₂ capture with 95% captured CO₂ purity.