This paper describes experimental work performed at General Electric, Global Research Center to evaluate the performance and understand the risks of using dry low NOx (DLN) technologies in exhaust gas recirculation (EGR) conditions. Exhaust gas recirculation is viewed as an enabling technology for increasing the CO2 concentration of the flue gas while decreasing the volume of the postcombustion separation plant and therefore allowing a significant reduction in CO2 capture cost. A research combustor was developed for exploring the performance of nozzles operating in low O2 environment at representative pressures and temperatures. A series of experiments in a visually accessible test rig have been performed at gas turbine pressures and temperatures, in which inert gases such as N2/CO2 were used to vitiate the fresh air to the levels determined by cycle models. Moreover, the paper discusses experimental work performed using a DLN nozzle used in GE’s F-class heavy-duty gas turbines. Experimental results using a research combustor operating in a partially premixed mode include the effect of EGR on operability, efficiency, and emission performance under conditions of up to 40% EGR. Experiments performed in a fully premixed mode using a DLN single nozzle combustor revealed that further reductions in NOx could be achieved while at the same time still complying with CO emissions. While most existing studies concentrate on limitations related to the minimum oxygen concentration (MOC) at the combustor exit, we report the importance of CO2 levels in the oxidizer. This limitation is as important as the MOC, and it varies with the pressure and firing temperatures.
This paper describes experimental work performed at General Electric, Global Research Center to evaluate the performance and understand the risks of using Dry Low NOx (DLN) technologies in Exhaust Gas Recirculation (EGR) conditions. Exhaust Gas Recirculation is viewed as an enabling technology for increasing the CO2 concentration of the flue gas while decreasing the volume of the post-combustion separation plant and therefore allowing a significant reduction in CO2 capture cost. A research combustor was developed for exploring the performance of nozzles operating in low O2 environment at representative pressures and temperatures. A series of experiments in a visually accessible test rig have been performed at gas turbine pressures and temperatures, in which inert gases such as N2/CO2 were used to vitiate the fresh air to the levels determined by cycle models. Moreover, the paper will discuss experimental work performed using a DLN nozzle used in GE’s F-class heavy-duty gas turbines. Experimental results using a research combustor operating in partially premixed mode, incorporate the effect of applying EGR on operability, efficiency and emissions performance under conditions of up to 40% EGR. Experiments performed in fully premixed mode using DLN single nozzle combustor revealed that further reductions in NOx could be achieved and at the same time still complying with CO emissions. While most existing studies concentrate on limitations related to the Minimum Oxygen Concentration (MOC) at the combustor exit, we report the importance of CO2 levels in the oxidizer. This limitation is as important as the MOC and it varies with the pressure and firing temperatures.
In a carbon constrained world there is a need for capturing and sequestering CO2. Post-combustion carbon capture via Exhaust Gas Recirculation (EGR) is considered a feasible means of reducing emission of CO2 from power plants. Exhaust Gas Recirculation is an enabling technology for increasing the CO2 concentration within the gas turbine cycle and allow the decrease of the size of the separation plant, which in turn will enable a significant reduction in CO2 capture cost. This paper describes the experimental work performed to better understand the risks of utilizing EGR in combustors employing dry low emissions (DLE) technologies. A rig was built for exploring the capability of premixers to operate in low O2 environment, and a series of experiments in a visually accessible test rig was performed at representative aeroderivative gas turbine pressures and temperatures. Experimental results include the effect of applying EGR on operability, efficiency and emissions performance under conditions of up to 40% EGR. Findings confirm the viability of EGR for enhanced CO2 capture; In addition, we confirm benefits of NOx reduction while complying with CO emissions in DLE combustors under low oxygen content oxidizer.
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The current research provides the impact of hydrogen enrichment on gas turbine combustion characteristics. The uniqueness of this study is it isolates the hydrogen effects while minimizing the impact of other parameters that are known to influence combustion characteristics. Experiments are carried out under high operating pressure and a wide range of firing temperatures that extend from the Lean Blow Out (LBO) limit to beyond J class firing temperature. Aerodynamic effects are isolated by using a perforated plate burner to provide a simple flame structure. The study is conducted under perfectly premixed conditions to exclude the mixing effects from the problem under investigation. Air flow, residence time, pressure and temperature are all held constant to enable back to back comparison. Hydrogen enrichment is varied from 0 to 25 percent by volume while holding the combustor exit temperature constant. No cooling air or effusion air is used in the combustion zone to ensure that there is no impact on the problem under investigation and to focus the study on kinetics effects and flame shape variation. NOx, CO emissions, LBO limits as well as flame luminosity are reported. Oxygen and carbon dioxide are measured at the combustor exit and used to ensure test integrity and for confirmation of the exit temperature. A reactor network model is used to mimic the experimental work and study sensitivity. The effective residence time in the model is varied slightly to mimic the slight change observed in flame length with hydrogen addition. This basic research provides a key resolution to the contradictory results that are typically reported in the literature for the impact of hydrogen on NOx emissions.
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