Gas Technology Institute (GTI) is developing a pressurized, oxy-coal combustor. CO2 capture is simplified when firing with oxygen instead of air. Traditional combustors cannot operate with the high oxy-coal adiabatic flame temperatures and are modified with high flue gas recirculation (FGR) or water injection that significantly reduces plant efficiency. The proposed molten bed oxy-coal combustor is a disruptive technology that offers higher efficiency than existing oxy-coal combustors by greatly reducing FGR and by operating at elevated pressure. The unique combustion and heat transfer design employs a smaller less expensive combustor and reduced gas phase heat exchanger surface area. Decreased FGR results in reduced capital and maintenance costs. Anticipated benefits include a calculated plant efficiency increase of 4%, large reduction in FGR duct and equipment sizes, lower exhaust gas volume and gas handling and cleaning equipment, reduction of boiler sizes by more than 50%, decreased convective path heat exchanger surface area and maintenance, near elimination of fine ash carryover into the exhaust gas, and recovery of ash/slag as aggregate instead of as micron sized particles.
GTI will be conducting engineering design and economic analysis based on the pressurized, oxy-coal molten bed combustor following the NETL protocol with comparisons to the specified baseline supercritical steam power plant burning Illinois #6 bituminous coal. Goals for this project include coal injector testing, engineering designs, mass and energy balance calculations around this advanced combustor, energy and exergy analysis, and corrosion assessment.
The Advanced Combustion Systems (ACS) Program of the U.S. Department of Energy/ National Energy Technology Laboratory (DOE/NETL) is aiming to develop advanced oxycombustion systems that have the potential to improve the efficiency and environmental impact of coal-based power generation systems. Currently available carbon dioxide (CO2) capture and storage technologies significantly reduce the efficiency of the power cycle. The ACS Program is focused on developing advanced oxy-combustion systems capable
of achieving power plant efficiencies approaching those of air-fired systems without CO2 capture. Additionally, the program looks to accomplish this while maintaining near zero emissions of other flue gas pollutants.
Oxy-combustion systems use high purity oxygen to combust coal and produce a highly concentrated CO2 stream that can be more easily separated out of the flue gas. First generation oxy-combustion systems utilize oxygen from a cryogenic air separation unit integrated with a boiler system that represents current state-of-the-art air-fired boiler designs. These first generation oxy-combustion systems have demonstrated technology viability; however, further research is needed to develop advanced oxy-combustion systems to progress toward meeting the DOE carbon capture goals.
Oxy-combustion system performance can be improved either by lowering the cost of oxygen supplied to the system or by increasing the overall system efficiency. NETL targets both of these possible improvements through sponsored cost-shared research into pressurized oxy-combustion and chemical looping combustion (CLC). Through the two-phase Advanced Oxy-combustion Technology Development and Scale-up
for New and Existing Coal-fired Power Plants Funding Opportunity Announcement, eight projects were recently chosen to begin Phase I. Under the 12 month Phase I effort, validation of the proposed pressurized oxy-combustion or CLC process will be accomplished through engineering system and economic analyses. Phase I projects will be eligible to apply for Phase II awards to develop and test the novel process components at the laboratory or bench scale.
The unique approach of this molten bed oxy-combustion process offers potential benefits that may not be possible through modification of existing pulverized coal boilers. The design and development work accomplished for this new type of boiler will yield relevant technical and economic information of its advantages, including a plant efficiency increase of 4 percent, large reduction in FGR duct and equipment sizes, lower exhaust gas volume and less gas handling and cleaning equipment, reduction of boiler size by more than 50 percent, decreased convective path heat exchanger surface area and maintenance, near elimination of fine ash carryover into the exhaust gas, and recovery of ash/slag as aggregate instead of as micron-sized particulates.
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