Ahmed Mostafa Elkady

Application of Exhaust Gas Recirculation in a DLN F-Class Combustion System for Postcombustion Carbon Capture

This paper describes experimental work performed at General Electric, Global Research Center to evaluate the performance and understand the risks of using dry low NO x (DLN) technologies in exhaust gas recirculation (EGR) conditions. Exhaust gas recirculation is viewed as an enabling technology for increasing the CO 2 concentration of the flue gas while decreasing the volume of the postcombustion separation plant and therefore allowing a significant reduction in CO 2 capture cost. A research combustor was developed for exploring the performance of nozzles operating in low O 2 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 N 2 /CO 2 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 GEs 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 NO x 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 CO 2 levels in the oxidizer. This limitation is as important as the MOC, and it varies with the pressure and firing temperatures.

Effect of Exhaust Gas Recirculation on NOx Formation in Premixed Combustion System

*† ‡ Exhaust gas recirculation (EGR) is an enabling technology to reduce CO2 capture cost for gas-turbine-based power plants. Experiments performed in fully premixed mode using Dry Low NOx single nozzle combustor at General Electric Global Research Center also revealed NOx reduction at same flame temperature by EGR. This paper presents systematic chemical kinetics analysis to study the effect of EGR on NOx formation in lean premixed combustion system under gas turbine representative temperatures and pressures. Simulation results are first presented for perfectly premixed combustion system to study the effect of EGR at different pressures (1-30 atm), oxidizer compositions, and EGR ratios. Based on detailed analysis, dominant mechanisms responsible for NOx formation are identified for different pressures. The effect of fuel-air unmixedness is then introduced to model the industrial gas turbine combustors. It is found that NOx formation is much less sensitive to the unmixedness with EGR than the baseline case. For typical gas turbine combustors, EGR introduces large benefits (up to 50%) for raw NOx reduction at same flame temperature, and even larger reduction if NOx concentration is corrected to 15% O2.

Gas Turbine Emission Characteristics in Perfectly Premixed Combustion

In the present study, a simple perfectly premixed research burner was utilized at temperatures, pressures and residence times representative of an industrial gas turbine cycle to identify the lower limit of NOx and CO emissions, and to establish an emissions benchmark for practical gas turbine combustors. In addition to experimental data, a chemical reactor model has been utilized for the prediction of the NOx and CO, based on detailed chemical reaction mechanisms. Several current kinetics mechanisms were evaluated and subsequently compared to the experimental data. In addition, sensitivity analysis was performed to identify important reactions at the conditions tested, and will be discussed.

Exhaust Gas Recirculation Performance in Dry Low Emissions Combustors

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.Copyright

Exhaust Gas Recirculation in DLN F-Class Gas Turbines for Post-Combustion CO

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.© 2008 ASME