Research into ways to mitigate greenhouse gas emissions in coal-fired power plants got another boost recently from the U.S. Department of Energy (DOE). Nearly $24 million was dispersed to projects that study the capturing of carbon dioxide (CO2) for sequestration. The DOE's Carbon Sequestration Program is managed by the National Energy Technology Laboratory. Grant recipients will contribute nearly $8 million in cost-sharing for the program.
"Carbon sequestration promises to significantly reduce America's greenhouse gas emissions even as our economy grows. This combination helps protect the global climate, while promoting job creation and a high standard of living," DOE Secretary Bodman said. "The key to successful carbon sequestration is technology development, including technologies to capture greenhouse gases such as CO2 before they are released to the atmosphere."
The DOE is putting more emphasis on clean coal programs aimed at using the nation's abundant source of coal in a more environmentally sensitive way. In addition, President Bush's Global Climate Change Initiative calls for an 18 percent reduction in U.S. greenhouse gas intensity by 2012. Balancing the growing demand for energy with increasing support for more environmental controls has the government searching for new technology solutions.
Sequestration uses a variety of methods to remove greenhouse gases from power plant emissions or the air itself, and securely store those gases in geologic formations, soils and vegetation, or in other environmentally safe forms. The newly selected projects will focus on three pathways to CO2 capture:
- Pre-combustion, in which fuel is gasified to form a mixture of hydrogen and CO2, called synthesis gas or syngas, and CO2 is captured from the syngas before it is combusted.
- Post-combustion, which involves capturing CO2 from flue gas after fuel has been combusted in air.
- Oxycombustion, in which fuel is combusted in pure or nearly pure oxygen rather than air, producing an exhaust mixture of CO2 and water that can easily be processed to produce pure CO2.
The projects total more than $31 million in investment, including nearly $8 million in cost-sharing from the recipients.
UOP LLC, (Des Plaines, Ill.), a Honeywell Company, in collaboration with several universities, will work together on a three-year project to develop novel microporous metal organic frameworks (MOFs) and an associated process for the removal of CO2 from coal-fired power plant flue gas. The technical approach covers all aspects of product development, from narrowing down a broad list of MOFs as potential CO2 sorbent candidates to evaluation of commercial viability. Success will be defined by a selective CO2 adsorbent with good thermal stability and contaminant tolerance and a low-cost process for flue gas CO2 capture ready to be demonstrated at the pilot plant scale. (DOE share: $2,238,171; recipient share: $559,543; duration: 36 months)
The University of Akron, (Akron, Ohio), is developing an efficient, low-cost CO2 capture system consisting of metal monoliths with parallel square channels whose surfaces are coated with a nanostructured/hydrophobic zeolite-grafted amine. The metal monoliths provide low pressure drop and efficient heat transfer; the zeolites offer ultra-high CO2 capture and low energy regeneration at 100-120 C. The research will integrate the metal monolith with established chemistry, material synthesis and low-cost fabrication techniques. Low raw material costs and the application of metal monoliths will lead to breakthrough technology for significantly effective capture of CO2 from the flue gas of coal-fired power plants. (DOE share: $764,995; recipient share: $156,702; duration: 48 months)
University of Notre Dame, (Notre Dame, Ind.) will focus on the development of a new liquid absorbent for efficient post-combustion capture of CO2 from coal-fired power plants. Ionic liquids are salts that are liquid in their pure state near ambient conditions. Because they are salts, they possess essentially no vapor pressure. They also have high thermal stability and their properties can be tuned by judicious choice of the cation, anion and constituent groups. The goal of this project is to exploit these unique properties to develop ionic liquid solvents for the economic post-combustion capture of carbon dioxide. The technology has the potential of being used in existing absorption processes as well as with membrane processes. To do this, researchers are using a combination of atomistic simulations and targeted experimentation. Along with its partners, the Department of Chemical and Biomolecular Engineering at the university will also carry out design and economic studies of a process using ionic liquids as well as build a working prototype absorption unit. (DOE share: $2,214,590; recipient share: $793,861; duration: 36 months)
Carbozyme, Inc., (Monmouth Junction, N.J.), will be conducting two projects. The first will develop a pre-pilot, scaled-up, design to extract CO2 from flue gas derived from many different ranks of coal. Carbozyme is developing a contained liquid membrane permeator for the selective capture of CO2 from flue gas. The core technology utilizes the ability of the enzyme catalyst carbonic anhydrase to rapidly and selectively convert CO2 to bicarbonate and then to reverse this reaction. The chemical facilitation results in a significant enrichment of CO2 as compared to the other gases in the feed stream that must rely on physical absorption to cross the liquid membrane. The technology has been demonstrated using artificial gas mixtures as well as combustion product from methane and propane. Dry CO2 concentrations up to 95 percent have been demonstrated. (DOE share: $4,799,175; recipient share: $1,370,430; duration: 36 months)
The second Carbozyme project will continue work on a novel CO2 capture process. The focus of this next generation work is to improve the permeance of the Carbozyme enzyme catalyzed selective CO2 capture technology beyond anything achieved heretofore. The approach uses careful regulation of pH to drive this acid-base chemistry beyond that achieved in the current generation technology. The approach relies on patented technology for both the baseline process and the next generation improvements. Additional patent applications are in process. If successful, this next generation technology will be incorporated in the "Near-Zero Emission PC Power Plant" project to allow the permeators to decrease in size and cost. (DOE share: $944,807; recipient share: $229,863; duration: 36 months)
RTI International -- trade name of Research Triangle Institute (Research Triangle Park, N.C.) -- will expand on the process they have developed to capture CO2 from power plant flue gas. RTI is developing a novel technology to capture CO2 from power plant flue gas using a dry, inexpensive, and regenerable carbonate-based sorbent. Sodium carbonate captures CO2 in the presence of water to form sodium bicarbonate. Upon heating, the bicarbonate decomposes into a CO2/steam mixture that can be converted into a pure CO2 gas stream. This process is suited for retrofit in existing coal-fired plants incorporating "wet" flue gas desulphurization. The new process promises significantly lower cost and capital requirements compared to conventional monoethanolamine (MEA) technology. Under a new DOE-funded project, RTI's bench-scale process will be scaled-up and demonstrated at an actual coal-fired combustion facility. (DOE share: $3,211,997; recipient share: $803,175; duration: 36 months)
Membrane Technology and Research, Inc. (Menlo Park, Calif.) will develop a cost-effective membrane-based process to separate carbon dioxide from coal-powered electric power plant flue gas, and to deliver supercritical CO2 to a pipeline for sequestration. The technical challenge of this program is to develop composite membranes that are highly permeable to CO2 combined with a high CO2/N2 selectivity. The Achilles' heel of previously proposed membrane-based processes for this application was large membrane area. Membrane area scales inversely with gas permeance; assuming other operating parameters are unchanged, doubling the permeance halves the membrane area needed to perform the same separation. Using new high-performance MTR membranes to be refined in this program, simulation calculations suggest that the total energy of separation and liquefaction of CO2 will consume about 16 percent of the power generated by the plant. (DOE share: $788,266; recipient share: $197,067; duration: 24 months)
Praxair plans to develop a combustion process based on oxygen transport membrane (OTM) that can capture carbon dioxide (CO2) from coal power plants. The economics of oxygen combustion processes are currently limited by the parasitic power that is required for cryogenic oxygen production in conventional air separation units. When thermally integrated in a coal power plant, Praxair's OTM technology has the potential to reduce the parasitic power consumption required for oxygen production by 70-80 percent as compared to cryogenic oxygen production. A successful outcome of the project would be an OTM-based oxygen combustion process that meets Department of Energy goals for CO2 capture and OTM manufacturing technology ready for pilot-testing. (DOE share: $4,742,780; recipient share: $2,553,806; duration: 36 months)
SRI International (Menlo Park, Calif.) will fabricate a technically and economically viable CO2-capture system based on a promising membrane material for pre-combustion-based capture of CO2. (DOE share: $4,047,695; recipient share: $1,036,159; duration: 36 months)