|Title||Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants|
|Contributor||Levasseur, Armand; Andrus, Herb; Kenney, James; Turek, David; and Kang, Shin|
|Spatial Coverage||Kauai, Hawaii|
|Subject||AFRC 2013 Industrial Combustion Symposium|
|Description||Paper from the AFRC 2013 conference titled Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants by Carl Edberg|
|Abstract||Alstom Power Inc. (Alstom) is a leader in the evaluation and commercialization of Oxy-Combustion with current efforts on several technology platforms [Oxy-Pulverized Coal (PC), Metal Oxide Chemical Looping Combustion (MeOx CLC) and Limestone Chemical Looping Combustion (LCL-C™)] addressing the design and operational integration of all major components. This paper provides an overview of Alstom's development and commercialization efforts for Oxy-PC Combustion and LCL-C™ technologies for CO2 capture from fossil fired power plants. Alstom has completed extensive pilot testing which has established a firm foundation for large-scale demonstration plants and subsequent commercial plants. Oxy-Combustion technology builds upon proven coal-based power generation and is complementary to conventional boiler and steam power plant technology, including its evolution towards ultra-supercritical steam conditions, increased sizes (>1000 MW) and advanced environmental controls. Alstom has amassed extensive pilot and commercial experience from facilities including: the 15 MWth PC tangentially fired oxy-pilot Boiler Simulation Facility (BSF) in CT, USA, the 3 MWth CFB pilot Multi-Use Test Facility (MTF) in CT, USA, the 100 kW flexible Chemical Looping pilot at Chalmers University in Sweden, the 1 MWth MeOx Chemical Looping facility in Darmstadt, Germany, and the 3 MWth Limestone Chemical Looping (LCL-CTM) Test Facility in CT, USA. Alstom was the supplier of the 30 MWth boiler, firing system and ESP for the integrated oxy plant at Schwarze Pumpe, Germany and was also the supplier for the boiler modifications for the 30 MW integrated oxy project in Lacq, France. Alstom has also developed and pilot tested air pollution control equipment [Electrostatic Precipitator (ESP), Fabric Filter (FF), Flue Gas Desulfurization (FGD), flue gas condenser (FGC), and gas-processing unit (GPU)] relevant to the oxy combustion process as applied to steam power. This paper provides recent pilot facility testing results for both Oxy-PC Combustion and LCL-C™ technologies. This includes an overview of the comprehensive testing performed on the 15 MWth BSF PC oxy-pilot under our joint US Department of Energy development program, as well as recent results from this facility with combined advanced oxy-boiler operation. Additionally, pilot facility results are presented from recent testing at the 3 MWth LCL-C™ Test Facility showing autothermal operation.|
|Rights||No copyright issues|
2013 AFRC Industrial Combustion Symposium Kauai, Hawaii - September 22-25, 2013 Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants Carl Edberg, Armand Levasseur, Herb Andrus, James Kenney, David Turek and Shin Kang ALSTOM Power, Inc., 200 Great Pond Drive, Windsor, CT 06095, USA Abstract Alstom Power Inc. (Alstom) is a leader in the evaluation and commercialization of Oxy-Combustion with current efforts on several technology platforms [Oxy-Pulverized Coal (PC), Metal Oxide Chemical Looping Combustion (MeOx CLC) and Limestone Chemical Looping Combustion (LCL-C™)] addressing the design and operational integration of all major components. This paper provides an overview of Alstom's development and commercialization efforts for Oxy-PC Combustion and LCL-C™ technologies for CO2 capture from fossil fired power plants. Alstom has completed extensive pilot testing which has established a firm foundation for large-scale demonstration plants and subsequent commercial plants. Oxy-Combustion technology builds upon proven coal-based power generation and is complementary to conventional boiler and steam power plant technology, including its evolution towards ultra-supercritical steam conditions, increased sizes (>1000 MW) and advanced environmental controls. Alstom has amassed extensive pilot and commercial experience from facilities including: the 15 MWth PC tangentially fired oxy-pilot Boiler Simulation Facility (BSF) in CT, USA, the 3 MWth CFB pilot Multi-Use Test Facility (MTF) in CT, USA, the 100 kW flexible Chemical Looping pilot at Chalmers University in Sweden, the 1 MWth MeOx Chemical Looping facility in Darmstadt, Germany, and the 3 MWth Limestone Chemical Looping (LCL-CTM) Test Facility in CT, USA. Alstom was the supplier of the 30 MWth boiler, firing system and ESP for the integrated oxy plant at Schwarze Pumpe, Germany and was also the supplier for the boiler modifications for the 30 MW integrated oxy project in Lacq, France. Alstom has also developed and pilot tested air pollution control equipment [Electrostatic Precipitator (ESP), Fabric Filter (FF), Flue Gas Desulfurization (FGD), flue gas condenser (FGC), and gas-processing unit (GPU)] relevant to the oxy combustion process as applied to steam power. This paper provides recent pilot facility testing results for both Oxy-PC Combustion and LCL-C™ technologies. This includes an overview of the comprehensive testing performed on the 15 MWth BSF PC oxy-pilot under our joint US Department of Energy development program, as well as recent results from this facility with combined advanced oxy-boiler operation. Additionally, pilot facility results are presented from recent testing at the 3 MWth LCL-C™ Test Facility showing autothermal operation. Introduction Activities related to global energy supply are estimated to contribute approximately 26% of the total worldwide anthropogenic greenhouse gas emissions (1). In the US, electricity production alone accounts for 33% of total anthropogenic greenhouse gas emissions and 38% of total anthropogenic CO2 emissions (2). The blend of power generation sources and fuels plays a direct role in the magnitude of overall CO2 emissions, with some fuels being more carbon intensive than others. In 2011, coal accounted for 42% of the electricity generated in the US, but contributed 80% of the CO2 emissions from the power sector (2). Although coal remains an abundant resource in the US, current and forecast legislation will dictate that new technologies be developed and commercialized to reduce CO2 emissions if it is to remain a major energy source. To facilitate meaningful reductions within an acceptable timeframe and economic limits, new technologies will be required that can be applied to greenfield projects and retrofit to the existing fleet. The development of promising CO2 capture technologies is being pursued by US and European power equipment suppliers in collaboration with utility companies, industrial gas suppliers, governmental agencies such as the US Department of Energy (DOE) and the European Union, academia and representatives from other engaged industries. Alstom is developing a portfolio of solutions to address this challenge, being active in both the oxy-combustion and post-combustion areas of study. Alstom is a leader in the evaluation and commercialization of oxy-combustion technologies. In an oxy-combustion process, the fuel is reacted with oxygen in such a manner as to produce an exhaust gas of high purity CO2 by isolating and excluding nitrogen from the combustion oxidant. This reduces the energy penalty associated with cleaning and liquefying the CO2 in the exhaust gas stream due to the higher available concentration. Another potential benefit is equipment size reductions due to the reduced total exhaust gas flow. Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 2 Oxy-combustion builds upon existing commercial technologies for coal-based power generation and is complementary to conventional boiler and steam power plant technology. Primarily relying on adaptation and integration of proven industrial equipment, the technology may be applied to both new plants and as retrofits for existing units (3). Progressive technology developments such as the evolution towards ultra-supercritical steam conditions, increased sizes (>1000 MW) and advanced environmental controls may also be synergistically applied to oxy-combustion processes. Alstom has pursued several innovative oxy-combustion technology platforms: Oxy-Pulverized Coal (PC), Metal Oxide Chemical Looping Combustion (MeOx CLC) and Limestone Chemical Looping Combustion (LCL-C™) with comprehensive efforts addressing the design and operational integration of all major components. Oxy-PC technology is a conventional oxy-combustion technology with cryogenic air separation units (ASUs) whereas MeOx CLC and LCL-C™ are advanced, "transformational" oxy-combustion technologies that do not require the use of an energy and capital-intensive ASU. This diverse suite of technologies provides a mix of near-term commercial technology and longer-term development efforts which promise higher efficiencies, lower cost of electricity and a reduced footprint. In pursuit of these technology developments, Alstom has relied upon a methodical approach involving in-house engineering tools, process modeling and screening, laboratory and bench-scale testing, computational fluid dynamics (CFD) and combustion modeling, small laboratory pilot testing, laboratory prototype testing and field demonstrations. Pilot scale tests provide invaluable insight into process performance and frequently reveal new design considerations and impacts that had not previously been predicted. Operating an appropriately sized pilot scale unit greatly reduces scale-up uncertainty and enhances the predictive capability necessary to proceed to the demonstration or commercial scale. This paper describes the basic technology and development process for two of the aforementioned oxy-combustion technologies currently being pursued by Alstom: Oxy-PC Combustion and LCL-C™. Additionally, a pilot scale facility for each of these technologies is described and a sampling of test data is discussed. OXY-PC COMBUSTION Oxy-PC Combustion Process In the oxy-PC combustion process, the pulverized coal is burned in an atmosphere consisting of recirculated flue gas which has been mixed with a high purity oxygen stream. As a result of excluding the atmospheric nitrogen which would typically accompany combustion air, the resulting flue gas consists largely of CO2 and water vapor, as well as other additional minor gas components attributable to fuel-specific constituents (Figure 1). These typically undesirable components of the flue gas can be separated by commercial state-of-the-art flue gas cleaning processes so that a high purity CO2 stream is formed, which is then liquefied for storage in saline aquifers, depleted oil and gas fields, or available for other industrial purposes such as enhanced oil recovery (EOR). Figure 1 - Typical Flue Gas Composition with Oxy-PC Combustion Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 3 There are many areas of study that must be considered when designing an oxy-PC unit. In an oxy-PC boiler, the required back-end clean-up equipment and the gas recycle take-off location are primarily influenced by the fuel quality; in particular by the coal's sulfur content, which determines acid dew point and corrosion potential. Optimized process configurations can avoid corrosion issues, keeping sulfur compound concentrations within ranges typically found in conventional boilers. The following diagram (Figure 2) shows a simplified process schematic of the Oxy-PC combustion process with several of the possible oxygen injection locations and gas recycle locations identified. In oxy-PC boilers using coals with low sulfur concentrations, flue gas recirculation directly downstream of the primary particulate removal device may be considered, while in the case of higher coal sulfur concentrations a desulfurization step is required prior to the recirculation point in order to reduce the flue gas sulfur dioxide concentration in the boiler to an acceptable level. Figure 2 - Simplified Process Schematic for Oxy-PC Combustion The combustion of fuel in a mixture of recirculated flue gas and oxygen results in changes in the combustion behavior and in the combustion products, which has an impact on the traditional design parameters of a boiler (4) (5). The change in the flue gas composition has an influence on heat transfer as well as on ash conversion and on resulting fouling or slagging of the heat transfer surfaces. In addition, higher sulfur compound concentrations in the flue gas may require adapted material selections to avoid detrimental corrosion impacts. The selected flue gas recirculation rate plays a pivotal role in controlling the combustion temperature and the heat flux profile throughout the boiler, while also impacting the relative sizing of pressure part surfacing and downstream pollution control equipment. The investigation of traditional PC burner performance in a tangential firing system with changes to primary and secondary gas compositions as well as the integration of potential supplemental oxygen injection is essential for commercialization of the oxy-PC combustion technology. Special attention must also be paid to minimizing air in-leakage into the system as much as possible in order to avoid diluting the exhaust gas and increasing the energy required for CO2 purification and compression. The addition of the ASU for oxygen supply and gas-processing unit (GPU) for CO2 cleaning and compression requires detailed analysis for successful integration and to enable safe and reliable operation of the overall plant. All of the fundamental avenues of investigation mentioned above have been the subject of completed or currently on-going Alstom investigations into oxy-combustion issues both in laboratory and pilot plants. The observations and experience amassed in these studies further strengthens previous experimental work and bolsters knowledge of the combustion and firing technology intrinsic to a boiler OEM. Oxy-PC Combustion Development For more than ten years, Alstom has been involved in numerous public and private research projects and initiatives targeting the development and commercialization of oxy-PC technology. Lab scale activities and pilot plants have provided invaluable information about underlying fundamental principles, performance of individual boiler components, and experience with the integrated oxy-PC combustion chain. Pilot plants have contributed significant operational experience with the integrated system including: safe handling and design of oxygen systems, start-up, shutdown, transitions between air-firing and oxy-air separation unit T-fired boiler pulverizer coal oxygen CO2 gas processing unit flue gas cooler sulfur control particulate control air nitrogen "air" heater Secondary gas recycle Primary gas recycle 3 2 1 5 4 C B A E D P f p Oc p ASp GCf A AC ti o Pilot Scale Fac firing as well a plants where A • Vatten Septem This p fired o precip the co • TOTA Alstom • Alstom which enviro organi Observations a combustion fun plants in demon Alstom has bee Station in Nort potential bioma Group and BO Competition. U followed by the Alstom's 15M Alstom's Boile CT location (Fi ime-temperatu of development cility Contribu as dynamic beh Alstom developm nfall - Schwar mber 2008. 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Oxy-PC Combu ombustion pe the US DOE knowledge ba n of oxy-PC c own below (Fig ct located at D or 90% CO2 ca g of Alstom Po bidders in the in 2015. This t of operation in ted at Alstom' designed to re tory of testing wer Plants list of pilot issioned in and a GPU. in full oxy-lectrostatic directly in July 2009. ustion pilot erformance, and other ase of oxy combustion gure 3). Drax Power apture with ower, Drax e UK CCS would be n 2019. s Windsor, eplicate the in support Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 5 The BSF was retrofit for oxy-PC firing capability in 2009 as part of a US DOE Cooperative project. This project included testing designed to provide detailed information on oxy-combustion behavior and the implications on boiler design and operation. Primary objectives of the project included (10) (4): • Design and develop an innovative oxy-fuel firing system for existing tangentially-fired boilers that minimizes overall capital investment and operating costs. • Evaluate the impacts of oxy-fuel process variables and firing system design options on boiler performance and design in pilot scale tests at the 15 MWth BSF. • Determine the changes in fuel related boiler impacts during oxy-combustion for a range of coal types. • Evaluate and improve engineering and CFD boiler design and predictive tools for oxy-combustion applications The furnace is a four corner unit with a tangential firing system including three elevations of coal injection and two levels of separated overfire air, similar to the tangential firing system illustrated in Figure 5. In tangential firing systems, mixing of fuel and air (or oxygen) occurs throughout the furnace, whereas in wall fired systems the mixing occurs primarily near the burner nozzle. The furnace walls and heat transfer surfaces of the 15MWth BSF are cooled by a surrounding water jacket. Steam that is generated is vented off at atmospheric pressure so that a constant sink temperature is maintained in the surfaced areas of the furnace. The lower furnace water-walls are refractory lined to raise the surface temperature and maintain an appropriate furnace gas temperature history. Under a US DOE Cooperative Agreement, Alstom has conducted a comprehensive oxy-fired boiler development program including BSF testing of a cross-section of coals. BSF modifications for oxy-PC combustion testing were completed in Front View Top View Figure 4 - Boiler Simulation Facility (BSF) Furnace Elevation View Top View of Fireball Corner Windbox Figure 5 - Tangential-firing system with Separated Overfire Air Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 6 August 2009. A detailed description of the BSF and modifications for oxy-combustion has been reported previously (10) (12). Major facility equipment additions included an oxygen supply and injection system, multiple gas recirculation systems, a fabric filter for additional particulate removal options, a NIDTM dry scrubbing system for SO2 removal options, and new instrumentation and controls. Figure 6 shows a schematic of the BSF configured for oxy firing. Figure 6 - Schematic of BSF Configured for Oxy-PC Firing These facility modifications allow the flexibility to test with a base air-fired mode as well as with three different oxy-fired process configurations: • Warm Recycle Mode: the secondary flue gas recycle is taken after the fabric filter without the NID™ in service • Sulfur Capture Mode: the secondary flue gas recycle is taken after the fabric filter with the NID™ dry scrubber in service • Hot Recycle Mode: the secondary flue gas recycle is taken before the air preheater and fabric filter In all oxy-PC combustion cases, the primary flue gas recycle is cooled and passed through the fabric filter and condenser. As of July 2013 there have been nine oxy-combustion test campaigns executed in the BSF with six different fuels: • Powder River Basin (PRB) sub-bituminous, September 2009 • Natural Gas, December 2009 • West Virginia low-sulfur bituminous, January-February 2010 • Illinois high-sulfur bituminous, April 2010 • North Dakota lignite (Falkirk), October 2010. • Lusatian dry lignite (Schwarze Pumpe dry lignite), July 2011 • West Virginia low-sulfur bituminous, December 2011 (2nd Generation Concepts Phase I) • PRB sub-bituminous, September-October 2012 (2nd Generation Concepts Phase II) • Illinois high-sulfur bituminous, October 2012 (2nd Generation Concepts Phase III) Test Results Facility operation and performance were favorable during both air and oxy-combustion testing for all fuels tested at the 15MWth BSF. Combustion and process conditions could be easily changed and controlled. The facility could operate under various oxy process scenarios and could produce flue gas containing more than 90% CO2 on a dry basis. Table 1 shows the flue gas compositions for high-sulfur bituminous coal and Lusatian lignite during air and oxy conditions with and without sulfur capture in the main gas recycle loop. Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 7 Table 1 - Typical Steady-State Gas Compositions Unburned Carbon Figure 7 shows how the unburned carbon in fly ash sampled at the BSF economizer outlet varied with oxygen levels in the flue gas for different test fuels. Unburned carbon was low during all of these tests and typically decreased with higher O2 in the flue gas. In general, unburned carbon was lower for the oxy-combustion cases than air-combustion. The low unburned carbon levels during oxy-fired tests are likely due to increased furnace residence time associated with lower volumetric gas flow rate and carbon gasification reaction rates increasing with increasing CO2 and H2O in the recycled flue gas. As expected, unburned carbon with the bituminous coal was higher than the PRB sub-bituminous and lignite fuels. The reactive PRB sub-bituminous and lignite fuels had very low unburned carbon (<1% C in ash) typical of levels observed in utility tangentially-fired boilers. PRB Sub-Bituminous Schwarze Pumpe Lignite High-Sulfur Bituminous Figure 7 - Unburned Carbon in Fly Ash Sulfur Concentrations Due to reduced nitrogen dilution with oxy-firing conditions, SO2 concentrations are increased by a factor of 4 to 5 (see Table 1). The SO2 emissions during oxy-combustion tests on a mass basis were in general about 10% lower than during air-combustion tests. Decreases in SO2 emissions are primarily due to removal of SO2 from the system in the primary gas recycle condenser and with interactions between SO2 at high concentrations and the alkali ash constituents. The SO2 concentrations during oxy-firing when the secondary gas recycle was treated by the NIDTM system (sulfur capture efficiency of > 95%) were only slightly higher than during air firing. The higher sulfur and moisture concentrations in the flue gas during oxy-firing results in higher acid dewpoint temperatures, and the potential for low temperature corrosion. SO2 and SO3 measurements in the flue gas were conducted at selected operating conditions at both oxy pilot facilities. Figure 8 shows SO2 and SO3 measurements conducted at the outlet of the 15MWth BSF economizer during the high sulfur bituminous, North Dakota and Lusatian lignite test campaigns. Measurements were conducted during air firing and during different oxy-combustion process scenarios for each of the test campaigns. Results indicate that SO3 concentrations during oxy-firing are primarily dependent on SO2 concentrations in the gas and net SO2-to-SO3 conversion rates are generally similar for air and oxy-firing. Air Oxy Oxy w/Sulfur Capture Air Oxy Oxy w/Sulfur Capture O2 (% Dry) 3.0 3.0 2.0 2.7 2.6 2.6 CO2 (% Dry) 16 93 85 17 91 89 H2O (%) 8 19 26 10 23 29 SO2 (ppm Dry) 2,350 10,150 3,150 650 1,700 800 High Sulfur Bituminous Lusatian Dried Lignite 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.0 1.0 2.0 3.0 4.0 5.0 % O2 in Flue Gas % Carbon in Ash Oxy Firing Air Firing Utility Unit A Utility Unit B Utility Unit C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.0 1.0 2.0 3.0 4.0 5.0 % O2 in Flue Gas Oxy Firing Air Firing 0.0 1.0 2.0 3.0 4.0 5.0 0.0 1.0 2.0 3.0 4.0 5.0 % O2 in Flue Gas Oxy Firing Air Firing Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 8 High-Sulfur Bituminous North Dakota Lignite Schwarze Pumpe Lignite Figure 8 - SO3 Measurements taken at the Economizer Outlet during 15 MWth BSF Testing Due to the design of the BSF heat exchangers, most of the SO3 was removed from the recycled gas, which may not be the case in commercial systems with hot recirculation. To determine the impact of recirculated SO3 in a commercial unit, the recycle gas was spiked with SO3 during some tests with North Dakota lignite. The SO3 concentration was increased from a level less than 10 ppm to as high as 160 ppm. As shown in Figure 8, the SO3 concentration leaving the furnace was unchanged at 40-50 ppm. This is most likely due to the high temperature reduction of SO3 in the furnace to SO2 and the reducing environment in the burner zone. NOx Emissions The emission of nitrogen oxides (NOx) is an environmental concern in the design and operation of conventional air-fired combustion power plants. In the oxy-combustion process, environmental emissions of NOx must still meet regulatory limits, and there is the additional consideration for the operation of the GPU and the quality of sequestered gas. The formation of NOx during the combustion process is complex process, highly dependent upon the time-temperature-stoichiometric history inside the boiler and the fuel being fired. For all BSF test campaigns, baseline air-fired testing is conducted to establish comparative performance and emissions data for the test coal. Figure 9 shows the NOx levels at the boiler outlet over a range of different windbox stoichiometries for the BSF and selected utility boilers. For a constant total oxygen input to the boiler, as more oxygen is shifted to the overfire locations, the stoichiometry in the windbox decreases. For each fuel, NOx emissions measured during baseline air firing in the BSF were consistent with utility boiler experience and generally were low. 0 25 50 75 100 125 150 175 200 225 250 0 2,500 5,000 7,500 10,000 12,500 SO2 ppmv SO3 ppmv Air Oxy w/SOx control Oxy w/fabric filter 1% conversion 2% 3% 0 10 20 30 40 50 60 70 80 0 1,000 2,000 3,000 4,000 SO2 ppmv SO3 ppmv Air Oxy w/fabric filter Oxy w/out fabric filter Oxy w/SO3 spike 1% conversion 2% 3% 0 5 10 15 20 25 30 35 40 45 50 0 500 1,000 1,500 2,000 2,500 SO2 ppmv SO3 ppmv Air Oxy w/SOx control Oxy w/fabric filter 1% conversion 2% 3% Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 9 Figure 9 - NOx emissions versus windbox stoichiometric ratio, BSF and utility boilers Figure 10 shows charts of NOx levels at the boiler outlet for air and oxy-firing over a range of different windbox stoichiometries. The chart on the left in Figure 10 shows data for air and oxy-firing at the 15 and 30 MWth pilot facilities firing the same fuel, while the chart on the right shows data for oxy-firing at the 15MWth BSF firing a variety of fuels. Test data shown in both charts in Figure 10 represents selected tests series with similar outlet oxygen concentrations. NOx emissions measured during air and oxy-firing are consistent between the two pilots. At both pilots the NOx levels decrease with decreasing windbox stoichiometry for both air and oxy-firing. The NOx emissions during oxy-firing at both pilots were typically less than approximately 50% of the NOx levels during air firing at comparable firing conditions. NOx levels as low 0.05 lb/MMBtu were measured for all coals tested in the 15MWth BSF. Figure 10 - NOx emissions versus Windbox Stoichiometric Ratio (15 and 30 MWth Tests) Reduced NOx emissions with oxy-combustion is attributable to several factors. Since most atmospheric N2 is removed, the formation of thermal NOx is reduced. The residence time in the furnace substoichiometric zone for NOx reduction is increased with oxy-combustion by the lower volumetric flow rates and by recirculating the flue gas to the combustor relative to air-combustion. A portion of the NOx returning in the recycle streams is reburned in the furnace, providing an additional net reduction leaving the system. Additionally, the elevated concentrations of CO, CO2 and H2O in the oxy-combustion environment can impact combustion and NOx formation/destruction chemistry. PRB Sub-Bit Coal 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 NOx emissions, lb/MMBTU Utility Unit A BSF Utility Unit B WV Low S. Bit Coal Windbox Stoichiometric Ratio Utility Unit C BSF IL High S. Bit Coal Utility Unit D BSF Utility Unit E Lignite Staging Tests 15 MWth BSF & 30 MWth Oxy PP 0.00 0.10 0.20 0.30 0.40 Windbox Stoichiometry NOx emissions (lb/MMBTU) 30MWth Air 30MWth Oxy 15MWth Air 15MWth Oxy Oxy Combustion Staging Tests 15 MWth BSF - All Fuels Windbox Stoichiometry SP Lignite ND Lignite High S Bit Low S Bit PRB Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 10 Thermal Performance In the oxy-combustion process flue gas is recycled to the boiler to moderate the furnace temperatures and reduce peak heat flux. The quantity and distribution of recycled flue gas and oxygen into the boiler will alter the heat release pattern and the heat absorption in the combustor. For each fuel, tests were done to vary the recycle rate, and therefore the global O2 content of the recycle. The percentage of the total heat input that is absorbed in the furnace up to the horizontal furnace outlet plane (HFOP) is shown in Figure 11 for different coals tested in the 15MWth BSF. Heat absorption is calculated from the measured gas temperature at the HFOP. For the test points shown, the total oxygen input was held constant and quantity of gas recycle was varied to change the global concentration. As expected, furnace heat absorption increased as the global oxygen concentration increased and the mass flow through the boiler decreased. Therefore, increasing the global oxygen concentration shifts more of the heat duty to the furnace from the downstream convection sections. Although the percentage of furnace heat absorption changed for the different coals, test results consistently indicated that a global O2 level in the range of 26-28% can achieve furnace heat absorption similar to air firing. Figure 11 - Heat absorption up to the Horizontal Furnace Outlet Plane (HFOP) The heat flux magnitude and distribution are important boiler design parameters that impact pressure part surface temperatures and material requirements. Furnace heat flux magnitude and distribution can be controlled by a number of factors, including the gas recirculation rate/global oxygen concentration, the distribution of recirculated gas, and the split of oxygen to the different windbox levels and to the overfire levels. A comparison of the vertical heat flux profiles as global oxygen concentration is varied is shown in Figure 12 for different test fuels. The plots represent an averaged planar value for incident heat flux to the furnace walls calculated from several heat flux probe measurements taken around the perimeter of the furnace at various elevations. Consistent with results in Figure 11, furnace heat flux increased as global oxygen concentrations increased. 0% 10% 20% 30% 40% 50% 20 25 30 35 40 Global O2 content, % Furnace Heat Absorption PRB Sub-Bit 20 25 30 35 40 Global O2 content, % High Sulfur Bit 20 25 30 35 40 Global O2 content, % ND Lignite 20 25 30 35 40 Global O2 content, % Air Oxy SP Lignite P Fca M A im a o u f s c Pilot Scale Fac Low Figure 13 com conditions. It w and oxygen inje Modeling Alstom has app mprovement o attention to sev oxidation and g user-defined su further improve sulfur bitumino color scale is id 0 5 10 15 20 25 To Furnace Height, ft High, 4 Mediu Low, 4 cility Contribu w Sulfur Bit mpares heat flu was possible to ection location plied computat of boilers sinc veral aspects; i gasification re ubroutines to re e predictive ca ous coal case in dentical for bot tal heat flux 46 m, 47 48 Furnace Height, ft utions to Alstom 2013 Hig Figure 12 ux profiles dur o match air fire ns. Alstom 15 M ND Lignite lon tional fluid dyn ce the early 1 including gas actions, as we efine and impr apabilities. Figu n Figure 12. Th th cases. The C To High Med Low, Figure 13 Air Total He m's Technology 3 AFRC Indust gh Sulfur Bit - Heat Flux P ring air and ox ed heat flux pr MWth BSF ng-Term Test namics (CFD) 990s. Applyin and particle ph ell as sulfur ch rove the outpu ure 14 shows he values show CFD results com otal heat flux , 62 ium, 63 , 61 3 - Heat Flux Oxy eat Flux y Development trial Combustio 11 Profiles versus xy-firing for s rofiles quite cl tools such as A ng these tools hase radiation hemistry. Alsto ut of these simu CFD simulatio wn are incident mpare well wit T Profiles for A t Efforts for Ox on Symposium ND Lignite Recirculation selected high s losely during o Alstom 15 MWth IL High Sulfur T ANSYS FLUE to the oxy-co properties, ga om has develop ulations and ha ons of the BSF t (not absorbed th pilot probe m Total heat flux High, 9 Medium Low, 93 Air and Oxy Fi Oxy Air Total Heat Flu xy-Combustion n Rate sulfur bitumin oxy-firing by v BSF Test ENT® software ombustion pro as phase chemi ped several pr as several on-g F during air an d) heat flux to mapping measu 1 m, 92 3 iring ux n for Steam Pow SP Lignite ous coal and varying gas re e to modeling ocess requires istry, heterogen roprietary subm going internal nd oxy-firing fo the furnace wa urements. Total heat flux High Med Low wer Plants lignite test ecycle rates and design additional neous char models and projects to for the high alls and the h, 127 dium, 117 w, 130 Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 12 The 15 MWth BSF furnace heat flux also compares well with utility boilers based on air-fired simulations calibrated with experimental data. Figure 15 shows CFD simulations for two field units burning PRB and the BSF firing PRB coal under similar air firing conditions. Similar heat flux is seen for the BSF and the utility boilers. The magnitude and heat flux profiles for the BSF fall between those for these two field unit simulations. Incident heat fluxes in the BSF were measured to confirm and validate CFD predictions. Figure 15 - Comparison of CFD Simulations of Wall Heat Flux During Air-Firing Alstom is aggressively pursuing the commercialization of oxy-PC combustion technology for power plant applications and has been executing comprehensive pilot test programs to work towards that goal. Significant knowledge has been gained from testing in these large oxy-fired pilot facilities. By testing with the same fuel in each pilot under similar operating conditions, a link was established allowing comparison of the 30 MWth pilot results to the broader range of results obtained in the BSF. The BSF results are also linked with large utility experience under air-fired operation, providing a basis for extrapolation of the pilot oxy-fired results. Results for pilot test programs and other Alstom development efforts provide a sound foundation to proceed to the next step and design large-scale (300-450 MWe) boilers for an oxy-PC combustion demonstration. Air-fired Oxy-fired Figure 14 - CFD Simulations of BSF Wall Heat Flux Profiles 850 MWe Utility Boiler 750 MWe Utility Boiler 15 MWth BSF P L L Cc‘ cr T"e th in RCo Cc mf er Wc R Ac L Ap to Spt Pilot Scale Fac LIMESTONE LCL-C™ Pro Chemical Loop combusting co chemical loop combustion to regenerated by The LCL-C™ "looped" in a r exothermic oxi he endothermi nert solids (e.g Referencing Fi CaSO4. The ho oxygen from th CaSO4 + 2C completes the " must be drained form CaSO4 re exothermic Ox recirculation of When the amou combustion sys Reducer, and s Although there configuration to LCL-C™ De Alstom has sign power generatio o the overall p Starting in 1974 product gas. A echnology was cility Contribu E CHEMICA ocess ping technolog al via a solid '. In the ‘Redu form CO2. Th being burned i concept repres regenerative ma dation reaction c reduction rea g., ash) or exce igure 16, the e ot, oxygen-con he CaSO4 to fo CaS + 2 CO2 loop". Fresh C d from the Red egenerates calc xidizer and th f solid particles unt of oxygen stem. The end steam used for e are other m o be the early c evelopment nificant experi on. A number rocess. 4 the company 120-ton per da s further refine utions to Alstom 2013 AL LOOPIN gy is an advan oxygen carrie ucer' reactor, c he depleted ox in air. sents a new hig anner to extrac ns is transferre action. The ‘th ss calcium soli Figure 16 - C exothermic Ox ntaining CaSO orm CaS (solid . The CaS is th CaCO3 is adde ducer to maint cium compoun he endothermic s between the r delivered via t d products of th generating ele modes of opera commercial ap ience in studyin of these techno y was involved ay pilot plant ( ed and used in a m's Technology 3 AFRC Indust NG COMBUS nced oxy-comb er. This proce coal is introduc xygen carrying gh temperature ct oxygen from d by the ‘therm ermal loop' is ids. Chemical Loop xidizer reactor O4 is transporte d) plus pure CO hen transported ed to the system ain the mass b nds in the loop c Reducer can reactors. This f the CaS / CaSO he process are ectric power. T ation possible plication. ng and develop ologies may be d in the develop equivalent to number of de y Development trial Combustio 13 STION (LCL bustion process ess utilizes two ced into an oxy g medium is th e process wher m air for purpo mal loop' of so distinct from t ping Combust oxidizes CaS ed to the Redu O2 (gas). The C d back to the O m to capture fu balance. The co p to keep chem n be satisfied forms the "ther O4 loop is suff e CO2 out of t The steam is g including syn ping advanced e directly adapt pment of a coa 12-15 MW) w emonstration p t Efforts for Ox on Symposium L-C™) s capable of p o reactors, a ygen carrying hen transported reby limestone ses of combus olids circulation the ‘chemical l tion with CO2 to form CaSO ucer reactor w CO2 gas produ Oxidizer to repe uel-bound sulfu ontinuous requ mical reactivit independently rmal loop". ficiently high t the Oxidizer fo generated by h ngas generatio combustion an ted for use in c al gasification p was built and op lants in the Un xy-Combustion producing a hig ‘Reducer' and medium which d to the ‘Oxid -derived calciu stion (Figure 1 n to satisfy the loop' and can e Capture O4 using pre-he where coal is i uct is available eat the process fur and form C uirement to cap ty high. The h y of the chem to burn all the or sequestratio eat from the O on, Alstom co nd gasification chemical loopi process aimed perated for 3-½ nited States and n for Steam Pow gh purity CO2 d ‘Oxidizer' to h will release dizer' reactor w um based comp 6). Surplus hea e energy requir employ either eated air: CaS introduced and for use or seq (i.e. regenerat aSO4. The exc pture fuel-boun heat balance be mically active coal, the loop on, vitiated air Oxidizer (See F onsiders the C n processes for ing or are comp at producing a years (Figur d Japan. wer Plants stream by o form the oxygen for where it is pounds are at from the rements for chemically S + 2O2 d strips the questration: e) and thus cess CaSO4 nd sulfur to etween the solids by becomes a out of the Figure 16). Combustion coal based plementary low BTU e 17). This P S( d A ATpv th o I T T tu u Pilot Scale Fac Figure 17 - W Subsequently, i (Figure 18). CF design efforts a CFB shares m A new effort in The objective w process used a version of chem his technology of the art PC-fi In the late 199 The LCL-C™ P • Bench • Design • Testin campa o o o • Study • 15 Foo • Design The results from urn were used used for testing cility Contribu Windsor, CT C in the mid-198 FB unit sizes h are currently un many of the sam n the gasificati was to develop solids recycle mical looping. y could deliver red boiler. 0's Alstom ini Process has be h scale testing ( n and construc ng of chemical aigns, which in Solid oxide Studies of g Control Sys of advanced ch ot and 40 Foot n, construction m the prelimin as the design g (Figure 19). utions to Alstom 2013 Coal Gasificat 80's, Alstom p have increased nderway to dev me solids hand ion field was i p a process tha loop to transfe This design stu a coal-based p itiated a subse en developed a TGA, Drop Tu tion of a 65 kW l looping chem ncluded (CaS, and CaS gasification, wa stem Developm hemical loopin Cold Flow Mo n, operation and ary bench scal basis for the sm m's Technology 3 AFRC Indust tion Pilot Plan pioneered the i d from demonst velop a large s dling, circulatio initiated by Al at could produ fer the necessar udy demonstra power plant in quent effort to at Alstom throu ube Test Furna Wth Limestone mistry in the P SO4) reactions ater-gas shift, h ment. ng control meth odel (CFM) Te d testing of a 3 e tests were us mall-scale 65 k y Development trial Combustio 14 nt introduction of tration scale (1 cale 600 MWe on and control stom in 1997 w uce syngas for ry oxygen to th ated the feasibi a footprint and o investigate an ugh a systemat ace, 4" Bubblin Chemical Loo PDU through c hydrogen and C hods and senso esting MWth LCL-C sed to determin kWth Limeston t Efforts for Ox on Symposium Figu f Circulating F 15 MW) in the e+ CFB unit w challenges fou with the aim o gas turbines w he system, as w ility of the chem d envelope sig nd potentially tic developmen ng Fluidized B oping Process D collaboration w CaCO3 reaction ors with the DO ™ Prototype t ne the reaction ne Chemical L xy-Combustion ure 18 - Typic Fluid Bed (CFB e 1980's to ne with ultra-super und within che of leveraging e without an oxy well as an Oxi mical looping gnificantly sma develop the ch nt approach tha ed) Development U with the US D ns. OE test facility. rates of the pri Looping pilot th n for Steam Pow al CFB B) technology arly 400 MW rcritical steam c emical looping. existing CFB t ygen plant. The idizer and fuel process, and sh aller than the cu hemical loopin at has included Unit (PDU) in 2 DOE through s imary reaction hat was built in wer Plants y in the US today, and conditions. . echnology. e proposed reactor - a howed that urrent state ng process. d: 2003. several test ns, which in n 2003 and Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 15 Figure 19 - Alstom's 65 kWth LCL-C™ Process Development Unit (PDU) Beginning in 2003, Alstom began executing a series of development programs on the 65 kWth PDU facility under a US DOE, National Energy Technology Laboratory (NETL) Cooperative Agreement. Phase I, II & III programs have been completed. Testing in the 65MWth PDU verified much of the important chemistry and solids transport (using cold flow model testing in parallel) required for the LCL™ process. The PDU represented a successful scale-up in capacity of over a factor of 100 from the previous bench scale work. Additionally, the use of transport reactors operating at high solids loadings for high volumetric efficiencies was verified and the ability to recycle solids between the various reactors was verified. Alstom has also completed Phase IVA on the 3 MWth prototype under another US DOE/NETL Cooperative Agreement, which was completed in September, 2013. Alstom's 3 MWth LCL-C™ Prototype presented the first opportunity to develop the entire integrated process at a size which eliminated the requirement for external heating (as required for the PDU), i.e., able to operate under auto-thermal conditions. The Prototype is a scale-up in capacity of a factor of approximately 50 over the PDU and once optimized will provide a sufficient basis for successful scale-up to a commercial-sized demonstration plant (25 to 100 MWe). The prototype has recently completed the goal of operating a 40-hour extended auto-thermal test. Alstom is currently proposing additional optimization testing on the 3 MWth Prototype and is working with a host-site to begin Pre-FEED and FEED studies aimed at beginning construction on a demonstration plant by 2018. The current Alstom roadmap for LCL-C™ development is shown below (Figure 20). Figure 20 - Alstom's LCL-C™ Development Roadmap P 3 T ws as e Pilot Scale Fac MWth LCL The 3 MWth LC was originally serve as the Ch added to consti shows the orig equipment was cility Contribu L-C™ Prototy CL-C™ Protot configured as hemical Loopi itute the remain ginal MTF faci incorporated i Fi utions to Alstom 2013 ype Test Fac type was const a circulating ing Prototype' nder of the Ch ility in the righ in the left hand Figure 21 - igure 22 - Sch m's Technology 3 AFRC Indust cility tructed by mak fluidized bed s Oxidizer rea hemical Loopin ht hand view, d view. Incorporation ematic Diagra y Development trial Combustio 16 king use of Al (CFB) boiler actor. A Reduc ng Prototype w as well as the n of MTF into am of the 3 M t Efforts for Ox on Symposium stom's existing pilot plant. Th cer system an which was com e modified fac o LCL-C™ Pr MWth LCL-C™ xy-Combustion g Multi-use Te he existing CF nd additional a mpleted in Dece cility configura rototype Prototype n for Steam Pow est Facility (M FB pilot was m auxiliary equip ember of 2010 ation once all o wer Plants MTF) which modified to pment were . Figure 21 of the new Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 17 Figure 22 depicts a simplified process schematic of the LCL-C™ Prototype facility. The Oxidizer receives solids containing CaS from the Reducer via a bottom outlet seal pot connection (RBO). The Oxidizer is designed to capture oxygen from air utilizing a stream of recirculated oxygen carrier solids. The Oxidizer operates at about 1,900 oF and 1.0 ata. The basic chemistry in the Oxidizer is shown in the following reaction. CaS + 2O2 CaSO4 + Heat The intent is to form hot CaSO4 in the Oxidizer with a minimal amount of excess air utilized. The hot CaSO4 represents a very effective oxygen carrier due to its high oxygen loading in addition to carrying heat to the appropriate locations. Leaving the Oxidizer there is a gas stream consisting of mostly nitrogen with a small amount of excess oxygen, which is separated from the solids in a cyclone and then cooled and finally exhausted to the atmosphere through the stack. The solids, which are now enriched with fresh CaSO4, are metered into the Reducer reactor through a seal pot control valve (LSPCV) into the "Cactus" (named for its resemblance to the saguaro cactus) where they mix with solids recirculating around the Reducer loop. The fuel is also metered into the Reducer reactor directly above the ‘Cactus". Gas which enters the Reducer in the "Octopus" (named for its 8 ports spaced around the riser) transports the solids up the Reducer. Here the coal reacts with the available oxygen from the CaSO4. When the Reducer is operated with an excess of available reactive oxygen, the gas leaving the Reducer is mainly CO2 and H2O. This gas flows through a series of cyclones, where hot solids are removed and recirculated. The Reducer operates at a temperature range of 1600 to 1800 oF and at a pressure between 1.0 - 2.5 ata. The principal reactions, which are overall endothermic, are shown below: CO2 + C + Heat 2CO Gasification of Carbon CaSO4 + 4CO CaS + 4CO2 Oxidation of CO CaSO4 + 4H2 (in Coal) CaS + 4H2O Oxidation of H2 Similarly, the hydrogen and sulfur in the fuel is combusted in a multi-step process: forming reduced species (e. g., H2, CH4, H2S) which may be further oxidized. Sulfur in the coal can be captured by lime from the added ash or limestone, for example, by: CaO+ H2S CaS + H2O Process steam may also be introduced into the Reducer reactor and the Sorbent Activation Heat Exchanger (SAHE) for the purpose of solids activation. Some of the recirculating solids which return through the Main Seal Pot Control Valve (MSPCV) through the cactus are not re-entrained, but rather fall downward into the RBO. This rate is controlled by the seal pot control valve at the bottom of the RBO. This constitutes the path for the reduced CaS from the Reducer to return to the Oxidizer. Solids entering the Oxidizer through the RBO are entrained upward through the Oxidizer reactor by air fed to the bottom of the Oxidizer riser. Solids may be drained from the bottom of the Oxidizer through a water-cooled ash screw to avoid a buildup of material and to remove the excess sulfur. Once above auto-thermal conditions, temperature in the Reducer is controlled to the required level by splitting the flow of hot re-circulated solids leaving the cyclone between an un-cooled stream and one that flows through the SAHE. Both streams are then metered back to the Reducer reactor through the MSPCV. Installation of the Prototype was completed in late 2010 followed by the shake-down and commissioning of the facility. Shakedown and subsequent air testing revealed the necessity for some minor equipment, controls and electrical modifications, which were completed in early 2011. As testing proceeded, several additional modifications were made to the prototype based on operating results to improve stability and performance. The major equipment changes made were: • The fuel feed system was changed due to intermittent feeding issues. Changes included: o Raising the height of the coal conveyor discharge o Increasing the size of the two rotary valves (4" up to 8") o Increasing the distance between the two rotary valves o Incorporating a radiation break and water-cooled coal feed chute into the reactor with a silicon carbide liner Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 18 • The Oxidizer Cyclone was moved to be directly over the Lower SPCV. This reconfigured the Reducer Pressurizing Column (RPC) into a straight vertical column. As shown in Figure 21 the original RPC had a short 60 degree slanted section from where the Oxidizer cyclone was located. The bend in the RPC seemed to cause solids to hang up and stop flowing so it was replaced by a straight section. The current arrangement of the Prototype is shown in Figure 23. Figure 23 - Current Arrangement of the Prototype Test Results 2011 Test Campaigns Test plans for 2011 involved commissioning of all systems to enable coal firing, initial coal firing tests aimed at gaining operating experience and determining chemical looping performance. These objectives were successfully completed. Plans for 2011 also called for operating the Prototype auto-thermally, however due to equipment limitations auto-thermal operation was not achieved until 2012. Three coal tests campaigns were executed during 2011. The first coal test (May 2011), determined that the firing rate of the warm-up burners was not high enough to raise the unit to the temperature required for injecting natural gas directly into the reactors. (in a reasonable amount of time). The warm-up burners were upgraded and during the second coal test (June 2011) the unit was brought high enough in temperature to achieve light-off of gas injection directly into the reactors. More importantly, this test also showed conclusive evidence that the chemical looping reactions were taking place. Based on CO2 concentrations in the Reducer and coal feed rates, it was determined from this test that reaction rate performance was similar to that observed during testing of the 65 kWth PDU. As described earlier, the third coal test (September-October 2011) revealed deficiencies in the coal feed system (which caused coal feed interruptions) and the Reducer pressurizing column (which caused solids re-circulation interruptions). Although troublesome, this test series provided valuable operator training, improved data acquisition and analysis capabilities and provided data important to future test design. 2012 Test Campaigns After making the required modifications identified during 2011, testing resumed in May 2012. Plans called for a series of three systematic tests, each one building on the previous results to achieve auto-thermal operation. The first was planned to ~65 Feet Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 19 concentrate on Reducer performance, the second on Oxidizer performance and the last on auto-thermal operation. However, during the Oxidizer test, performance was improved sufficiently to transition directly to auto-thermal operation. Therefore, the third test was redirected to study sulfur capture and retention, which is critical to the success of the process. Figure 24 reflects a sampling of data taken during the July 2012 testing. In these figures, the shaded regions indicate periods of coal (or charcoal) firing. • the top plot shows the feed rate of coal to the Reducer and natural gas to the Oxidizer • the second plot shows the temperatures at the top of the two risers • the third plot shows the % CO2 and CO in the dry Reducer outlet gas Figure 24 - Coal Firing Periods during the July 2012 Prototype Testing On the afternoon of July 25, coal feed rate was ramped up and natural gas injection to the Oxidizer was reduced, until approximately 18:00 hours the natural gas was turned off completely. As seen in Figure 25, the temperatures started to drop - there was insufficient CaS being oxidized to maintain the temperature in the Oxidizer (and therefore the Reducer as well). The natural gas was turned on again to maintain the temperatures as the coal was further increased. Finally at about 01:30 on Ad.pc Ad.cr P8.cr Ad.pc 0 200 400 600 800 fuel feed rate, lb/hr Tue 07/24 Wed 07/25 Thu 07/26 Fri 07/27 coal gas Ad.pc Ad.cr P8.cr Ad.pc 1400 1600 1800 2000 riser outlet temperature, °F Tue 07/24 Wed 07/25 Thu 07/26 Fri 07/27 oxidizer reducer Ad.pc Ad.cr P8.cr Ad.pc 0 20 40 60 80 reducer gas, % dry Tue 07/24 Wed 07/25 Thu 07/26 Fri 07/27 CO2 CO Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 20 the 26th, the gas was shut off and the temperatures were maintained - i. e., self-sustained auto-thermal operation. This was followed by auto-thermal operation with crushed Pittsburgh #8 coal. Figure 25 - First Auto-Thermal Operation Alstom achieved stable, auto-thermal, coal-only operation with the 3 MWth Prototype in July 2012 for 12 hours on two different coals (Pittsburgh and Adaro) as shown in Figure 25. Auto-thermal operation is a critical step in the development of LCL-C™ technology to demonstrate its technical viability. Prior to this successful operation, all previous chemical looping tests had required the use of supplemental energy to drive the chemical looping reactions. Previous non-auto-thermal bench and 65 kWth PDU tests were electrically heated. All of the non-auto-thermal 3 MWth Prototype tests were heated with supplemental natural gas which was fired in the Oxidizer to help drive the chemical looping reactions. By contrast, during the successful auto-thermal tests, the 3 MWth Prototype was operated exclusively on coal which was fed to the Reducer with air fed only to the oxidizer. No supplemental fuel of any kind was required. Nearly full design coal flow was attained. Attaining auto-thermal performance necessarily required that all of the following factors were occurring: • Coal is combusted in the Reducer to CO2 via hot CaSO4, forming CaS • CaS is burned in the Oxidizer forming hot CaSO4 for the Reducer • LCL-C™ chemical looping reactions are self-sustaining • Solids circulation and exchange may be maintained • The sizing factors used for the Reducer and Oxidizer systems are proven within expected targets • These results justify further testing which can be reasonably expected to provide a firm basis for a successful LCL-C ™ demonstration on a large-scale field validation facility. 2013 Test Campaign The main objective of the May 2013 prototype testing was to demonstrate that auto-thermal operation could be sustained for an extended period - 40 hours was the target. One of the modifications to the prototype before the May test was the addition of a solids ‘Gate' in the RBO, which was expected to result in steadier flow through the RBO and reduce the tendency for the reducer dip-leg to flush. 0 200 400 600 800 1000 1200 lb/hr 07/25 12:00 07/26 00:00 07/26 12:00 1000 1200 1400 1600 1800 2000 °F Oxidizer T Reducer T Pitt 8 flow Adaro flow Gas Flow Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 21 The Prototype unit achieved the objective of extended auto-thermal operation during a test run from May 9 - 11, 2013 (See Figure 26). Figure 26 - Overview of May 2013 Auto-thermal operation Throughout the test campaign, operators were able to maintain steady Reducer solids circulation with only occasional loss of dip leg solids inventory. Solids inventory was maintained by adding ash from a commercial circulating fluidized bed unit during the test. The significance of the achievements during the recent prototype test campaigns is that most of the critical technical assumptions and potential technical issues for the LCL-C™ process have been confirmed, and potential solutions to these issues demonstrated at a pilot scale. It clearly suggests that further testing and process optimization will lead to successful demonstration at a full scale. CONCLUSIONS Testing at the 15 MWth BSF and other oxy-PC combustion pilot facilities has enabled Alstom to progress towards the point of a commercial offering, with a demonstration scale project the next step along the development path. As mentioned previously, Alstom has been selected for award of the FEED contract for the White Rose demonstration project located at Drax Power Station in North Yorkshire, UK. This will be the next step in the evolution of oxy-PC combustion technology. Similarly, testing at the 3 MWth LCL-C™ prototype and other Alstom chemical looping pilot facilities has developed this transformative technology from initial paper studies up to a scale where commercial design predictions are now verifiable. Additional planned prototype testing will continue to refine and improve process performance with the goal of achieving an optimized design suitable for a demonstration plant. Alstom bench and pilot scale testing has proven to be an invaluable tool in the development and commercialization of each of these promising technologies for CO2 capture. These facilities allow a methodical and progressive approach to developing and commercializing new technology. Testing of promising and ambitious process and equipment variations may be executed economically at this scale, while still providing meaningful cross-correlations to performance in larger units. These pilot efforts and supporting bench scale tests serve to minimize risk and ensure Alstom is able to confidently proceed to the next steps of development. 0 200 400 600 800 1000 1200 lb/hr Thu 05/09 Fri 05/10 Sat 05/11 Sun 05/12 1000 1200 1400 1600 1800 2000 °F coal flow gas flow red temp ox temp Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 22 DISCLAIMER Information disclosed herein is furnished to the recipient solely for the use thereof as has been agreed upon with ALSTOM and all rights to such information are reserved by ALSTOM. The recipient of the information disclosed herein agrees, as a condition of its receipt of such information, that ALSTOM shall have no liability for any direct or indirect damages including special, punitive, incidental, or consequential damages caused by, or arising from, the recipient's use or non-use of the information. Portions of this paper were prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ACKNOWLDGEMENTS The authors acknowledge the contribution of US and European agencies which have provided instrumental leadership and funding to bring these technologies to their current state of development. A special mention is given for the outstanding support offered by the US DOE and the guidance and direction of the NETL Project Managers, Tim Fout, Steven Mascaro and Bruce Lani. Pilot Scale Facility Contributions to Alstom's Technology Development Efforts for Oxy-Combustion for Steam Power Plants 2013 AFRC Industrial Combustion Symposium 23 REFERENCES 1. Climate Change 2007: Syntheis Report. s.l. : IPCC Integovernmental Panel on Climate Change, 2007. 2. Inventory of U.S. Greehouse Gas Emissions and Sinks: 1990-2011. s.l. : United States Environmental Protection Agency, 2013, April. 3. Nsakala, N., et al., et al. Engineering Feasibility of CO2 Capture on an Existing US Coal Fired Plant. Washington D.C. : First National Conference on Carbon Sequestration, 2001, May. 4. 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