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.
This paper presents the results of an evaluation of advanced combined cycle gas turbine plants with precombustion capture of CO2 from natural gas. In particular, the designs are carried out with the objectives of high efficiency, low capital cost, and low emissions of carbon dioxide to the atmosphere. The novel cycles introduced in this paper are comprised of a high-pressure syngas generation island, in which an air-blown partial oxidation reformer is used to generate syngas from natural gas, and a power island, in which a CO2-lean syngas is burnt in a large frame machine. In order to reduce the efficiency penalty of natural gas reforming, a significant effort is spent evaluating and optimizing alternatives to recover the heat released during the process. CO2 is removed from the shifted syngas using either CO2 absorbing solvents or a CO2 membrane. CO2 separation membranes, in particular, have the potential for considerable cost or energy savings compared with conventional solvent-based separation and benefit from the high-pressure level of the syngas generation island. A feasibility analysis and a cycle performance evaluation are carried out for large frame gas turbines such as the 9FB. Both short-term and long-term solutions have been investigated. An analysis of the cost of CO2 avoided is presented, including an evaluation of the cost of modifying the combined cycle due to CO2 separation. The paper describes a power plant reaching the performance targets of 50% net cycle efficiency and 80% CO2 capture, as well as the cost target of 30$ per ton of CO2 avoided (2006 Q1 basis). This paper indicates a development path to this power plant that minimizes technical risks by incremental implementation of new technology.
This paper presents the results of an evaluation of advanced combined cycle gas turbine plants with pre-combustion capture of CO2 from natural gas. In particular, the designs are carried out with the objectives of high efficiency, low capital cost and low emissions of carbon dioxide to the atmosphere. The novel cycles introduced in this paper are comprised of a high-pressure syngas generation island, in which an air-blown POX reformer is used to generate syngas from natural gas, and a power island, in which a CO2-lean syngas is burnt in a large frame machine. In order to reduce the efficiency penalty of natural gas reforming, a significant effort is spent evaluating and optimizing alternatives to recover the heat released during the process. CO2 is removed from the shifted syngas using either CO2 absorbing solvents or a CO2 membrane. CO2 separation membranes, in particular, have the potential for considerable cost or energy savings compared to conventional solvent-based separation and benefit from the high pressure level of the syngas generation island. A feasibility analysis and a cycle performance evaluation are carried out for large frame gas turbines such as the 9FB. Both short term and long term solutions have been investigated. An analysis of the cost of CO2 avoided is presented, including an evaluation of the cost of modifying the combined cycle due to CO2 separation. The paper describes a power plant reaching the performance targets of 50% net cycle efficiency and 80% CO2 capture, as well as the cost target of 30$ per ton of CO2 avoided. This paper indicates a development path to this power plant that minimizes technical risks by incremental implementation of new technology.
In this paper, a new gas turbine cycle with integrated post-combustion CO2 capture is presented. The concept advantageously uses an intercooled gas turbine in combination with exhaust gas recirculation to enable CO2 separation at elevated concentration and pressure. Therefore, less energy is required for the CO2 separation process. In addition, due to the reduced volume flow entering the CO2 separation unit, the costs of the CO2 separation equipment are significantly reduced. The performance and cost of CO2 avoided of the power cycle have been analyzed. The results show that the concept is able to reach high CO2 capture rates of 80% and above. When accounting for CO2 capture and compression, nearly 50% (LHV) combined cycle net efficiency is obtained based on an existing medium scale intercooled gas turbine. Furthermore, the cycle has an even higher efficiency potential if applied to larger intercooled gas turbine combined cycles in the future. Using CO2 separation membrane technology which is currently under development, the cost of CO2 avoided is estimated at 31 $/tCO2 based on a medium scale intercooled gas turbine. A future scaled-up configuration based on a large-frame intercooled gas turbine has the potential to meet 30 $/tCO2 cost of CO2 avoided.
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