Flue Gas Recirculation in a Gas Turbine: Impact on Performance and Operational Behavior

2011 ◽  
Author(s):  
Frank Sander ◽  
Richard Carroni ◽  
Stefan Rofka ◽  
Eribert Benz
Keyword(s):  
Power Plant ◽  
Co2 Capture ◽  
Flue Gas ◽  
Power Plants ◽  
Combustion Process ◽  
Combined Cycle ◽  
Flue Gas Recirculation ◽  
Overall Performance ◽  
Gas Recirculation ◽  
The Impact

The rigorous reduction of greenhouse gas emissions in the upcoming decades is only achievable with contribution from the following strategies: production efficiency, demand reduction of energy and carbon dioxide (CO2) capture from fossil fueled power plants. Since fossil fueled power plants contribute largely to the overall global greenhouse gas emissions (> 25% [1]), it is worthwhile to capture and store the produced CO2 from those power generation processes. For natural-gas-fired power plants, post-combustion CO2 capture is the most mature technology for low emissions power plants. The capture of CO2 is achieved by chemical absorption of CO2 from the exhaust gas of the power plant. Compared to coal fired power plants, an advantage of applying CO2 capture to a natural-gas-fired combined cycle power plant (CCPP) is that the reference cycle (without CO2 capture) achieves a high net efficiency. This far outweighs the drawback of the lower CO2 concentration in the exhaust. Flue Gas Recirculation (FGR) means that flue gas after the HRSG is partially cooled down and then fed back to the GT intake. In this context FGR is beneficial because the concentration of CO2 can be significantly increased, the volumetric flow to the CO2 capture unit will be reduced, and the overall performance of the CCPP with CO2 capture is increased. In this work the impact of FGR on both the Gas Turbine (GT) and the Combined Cycle Power Plant (CCPP) is investigated and analyzed. In addition, the impact of FGR for a CCPP with and without CO2 capture is investigated. The fraction of flue gas that is recirculated back to the GT, need further to be cooled, before it is mixed with ambient air. Sensitivity studies on flue gas recirculation ratio and temperature are conducted. Both parameters affect the GT with respect to change in composition of working fluid, the relative humidity at the compressor inlet, and the impact on overall performance on both GT and CCPP. The conditions at the inlet of the compressor also determine how the GT and water/steam cycle are impacted separately due to FGR. For the combustion system the air/fuel-ratio (AFR) is an important parameter to show the impact of FGR on the combustion process. The AFR indicates how close the combustion process operates to stoichiometric (or technical) limit for complete combustion. The lower the AFR, the closer operates the combustion process to the stoichiometric limit. Furthermore, the impact on existing operational limitations and the operational behavior in general are investigated and discussed in context of an operation concept for a GT with FGR.

Process Analysis of Selective Exhaust Gas Recirculation for CO2 Capture in Natural Gas Combined Cycle Power Plants Using Amines

2017 ◽  
Author(s):  
Maria Elena Diego ◽  
Jean-Michel Bellas ◽  
Mohamed Pourkashanian
Keyword(s):  
Natural Gas ◽  
Co2 Capture ◽  
Flue Gas ◽  
Power Plants ◽  
Exhaust Gas Recirculation ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Natural Gas Combined Cycle ◽  
The Cost ◽  
Gas Recirculation

Post-combustion CO2 capture from natural gas combined cycle (NGCC) power plants is challenging due to the large flow of flue gas with low CO2 content (∼3–4%vol.) that needs to be processed in the capture stage. A number of alternatives have been proposed to solve this issue and reduce the costs of the associated CO2 capture plant. This work focuses on the selective exhaust gas recirculation (S-EGR) configuration, which uses a membrane to selectively recirculate CO2 back to the inlet of the compressor of the turbine, thereby greatly increasing the CO2 content of the flue gas sent to the capture system. For this purpose, a parallel S-EGR NGCC system (53% S-EGR ratio) coupled to an amine capture plant using MEA 30%wt. was simulated using gCCS (gPROMS). It was benchmarked against an unabated NGCC system, a conventional NGCC coupled with an amine capture plant (NGCC+CCS), and an EGR NGCC power plant (39% EGR ratio) using amine scrubbing as the downstream capture technology. The results obtained indicate that the net power efficiency of the parallel S-EGR system can be up to 49.3% depending on the specific consumption of the auxiliary S-EGR systems, compared to the 49.0% and 49.8% values obtained for the NGCC+CCS and EGR systems, respectively. A preliminary economic study was also carried out to quantify the potential of the parallel S-EGR configuration. This high-level analysis shows that the cost of electricity for the parallel S-EGR system varies from 82.1–90.0 $/MWhe for the scenarios considered, with the cost of CO2 avoided being in the range of 79.7–105.1 $/tonne CO2. The results obtained indicate that there are potential advantages of the parallel S-EGR system in comparison to the NGCC+CCS configuration in some scenarios. However, further benefits with respect to the EGR configuration will depend on future advancements and cost reductions achieved on membrane-based systems.

Experimental Investigation of a Fuel Flexible Generic Gas Turbine Combustor With External Flue Gas Recirculation

2014 ◽  
Author(s):  
Stefan Fischer ◽  
David Kluß ◽  
Franz Joos
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flue Gas ◽  
Power Plants ◽  
Numerical Study ◽  
Combined Cycle ◽  
Gas Turbine Combustor ◽  
Combustion Behavior ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

Flue gas recirculation in combined cycle power plants using hydrocarbon fuels is a promising technology for increasing the efficiency of the post combustion carbon capture and storage process. However, the operation with flue gas recirculation significantly changes the combustion behavior within the gas turbine. In this paper the effects of external flue gas recirculation on the combustion behavior of a generic gas turbine combustor was experimentally investigated. While prior studies have been performed with natural gas, the focus of this paper lies on the investigation of the combustion behavior of alternative fuel gases at atmospheric conditions, namely typical biogas mixtures and syngas. The flue gas recirculation ratio and the fuel mass flow were varied to establish the operating region of stable flammability. In addition to the experimental investigations, a numerical study of the combustive reactivity under flue gas recirculation conditions was performed. Finally, a prediction of blowout limits was performed using a perfectly stirred reactor approach and the experimental natural gas lean extinction data as a reference. The extinction limits under normal (non-vitiated) and flue gas recirculation conditions can be predicted well for all the fuels investigated.

Comparison of Methane and Natural Gas Combustion Behavior at Gas Turbine Conditions With Flue Gas Recirculation

2010 ◽  
Author(s):  
Dieter Winkler ◽  
Simon Reimer ◽  
Pascal Mu¨ller ◽  
Timothy Griffin
Keyword(s):  
Natural Gas ◽  
Flame Front ◽  
Gas Turbine ◽  
Flue Gas ◽  
Power Plants ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Synthetic Natural Gas ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

The efficiency and economics of carbon dioxide capture in gas turbine combined cycle power plants can be significantly improved by introducing Flue Gas Recirculation (FGR) to increase the CO2 concentration in the flue gas and reduce the volume of the flue gas treated in the CO2 capture plant [1], [2]. The maximum possible level of FGR is limited to that corresponding to stoichiometric conditions in the combustor. Reduced excess oxygen, however, leads to negative effects on overall fuel reactivity and thus increased CO emissions. Combustion tests have been carried out in a generic burner under typical gas turbine conditions with methane, synthetic natural gas (mixtures of methane and ethane) and natural gas from the Swiss net to investigate the effect of different C2+ contents in the fuel on CO burnout. To locate the flame front and to measure emissions for different residence times a traversable gas probe was designed and employed. Increasing the FGR ratio led to lower reactivity indicated by a movement of the flame front downstream. Thus, sufficient flame burnout—indicated by low emissions of unburned components (CO, UHC)—required a longer residence time in the combustion chamber. Adding C2+ or H2 to the fuel moved the flame zone back upstream and reduced the burnout time. Tests were performed for the various fuel compositions at different FGR ratios and oxidant preheat temperatures. For all conditions the addition of ethane (6 and 16% vol.) or hydrogen (20% vol.) to methane shows comparable trends. Addition of hydrogen to (synthetic) natural gas which already contains C2+ has less of a beneficial effect on reactivity and CO burnout than the addition of hydrogen to pure methane. A simple ideal reactor network based on plug flow reactors with internal hot gas recirculation was used to model combustion in the generic combustor. The purpose of such a simple model is to generate a design basis for future tests with varying operating conditions. The model was able to reproduce the trends found in the experimental investigation, for example the level of H2 required to offset the effect of oxygen depletion due to simulated FGR.

scholarly journals Process Analysis of Selective Exhaust Gas Recirculation for CO2 Capture in Natural Gas Combined Cycle Power Plants Using Amines

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Maria Elena Diego ◽  
Jean-Michel Bellas ◽  
Mohamed Pourkashanian
Keyword(s):  
Natural Gas ◽  
Co2 Capture ◽  
Flue Gas ◽  
Power Plants ◽  
Exhaust Gas Recirculation ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Natural Gas Combined Cycle ◽  
The Cost ◽  
Gas Recirculation

Postcombustion CO2 capture from natural gas combined cycle (NGCC) power plants is challenging due to the large flow of flue gas with low CO2 content (∼3–4 vol %) that needs to be processed in the capture stage. A number of alternatives have been proposed to solve this issue and reduce the costs of the associated CO2 capture plant. This work focuses on the selective exhaust gas recirculation (S-EGR) configuration, which uses a membrane to selectively recirculate CO2 back to the inlet of the compressor of the turbine, thereby greatly increasing the CO2 content of the flue gas sent to the capture system. For this purpose, a parallel S-EGR NGCC system (53% S-EGR ratio) coupled to an amine capture plant (ACP) using monoethanolamine (MEA) 30 wt % was simulated using gCCS (gPROMS). It was benchmarked against an unabated NGCC system, a conventional NGCC coupled with an ACP (NGCC + carbon capture and storage (CCS)), and an EGR NGCC power plant (39% EGR ratio) using amine scrubbing as the downstream capture technology. The results obtained indicate that the net power efficiency of the parallel S-EGR system can be up to 49.3% depending on the specific consumption of the auxiliary S-EGR systems, compared to the 49.0% and 49.8% values obtained for the NGCC + CCS and EGR systems, respectively. A preliminary economic study was also carried out to quantify the potential of the parallel S-EGR configuration. This high-level analysis shows that the cost of electricity (COE) for the parallel S-EGR system varies from 82.1 to 90.0 $/MWhe for the scenarios considered, with the cost of CO2 avoided (COA) being in the range of 79.7–105.1 $/ton CO2. The results obtained indicate that there are potential advantages of the parallel S-EGR system in comparison to the NGCC + CCS configuration in some scenarios. However, further benefits with respect to the EGR configuration will depend on future advancements and cost reductions achieved on membrane-based systems.

Modelling the Effect of External Flue Gas Recirculation on NOx and CO Emissions in a Premixed Gas Turbine Combustor With Chemical Reactor Networks

2018 ◽  
Author(s):  
V. Prakash ◽  
J. Steimes ◽  
D. J. E. M. Roekaerts ◽  
S. A. Klein
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Recirculation Zone ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Part Load ◽  
Flue Gas Recirculation ◽  
Reactor Networks ◽  
Gas Recirculation ◽  
The Impact

The increasing amount of renewable energy and emission norms challenge gas turbine power plants to operate at part-load with high efficiency, while reducing NOx and CO emissions. A novel solution to this dilemma is external Flue Gas Recirculation (FGR), in which flue gases are recirculated to the gas turbine inlet, increasing compressor inlet temperature and enabling higher part load efficiencies. FGR also alters the oxidizer composition, potentially leading to reduced NOx levels. This paper presents a kinetic model using chemical reactor networks in a lean premixed combustor to study the impact of FGR on emissions. The flame zone is split in two perfectly stirred reactors modelling the flame front and the recirculation zone. The flame reactor is determined based on a chemical time scale approach, accounting for different reaction kinetics due to FGR oxidizers. The recirculation zone is determined through empirical correlations. It is followed by a plug flow reactor. This method requires less details of the flow field, has been validated with literature data and is generally applicable for modelling premixed flames. Results show that due to less O2 concentration, NOx formation is inhibited down to 10–40% and CO levels are escalated up to 50%, for identical flame temperatures. Increasing combustor pressure leads to a rise in NOx due to thermal effects beyond 1800 K, and a drop in CO levels, due to the reduced chemical dissociation of CO2. Wet FGR reduces NOx by 5–10% and increases CO by 10–20%.

Thermo-Economic Assessment Under Electrical Market Uncertainties of a Combined Cycle Gas Turbine Integrated With a Flue Gas-Condensing Heat Pump

2020 ◽  
Author(s):  
Alberto Vannoni ◽  
Andrea Giugno ◽  
Alessandro Sorce
Keyword(s):  
Power Plant ◽  
Power Systems ◽  
Gas Turbine ◽  
Heat Pump ◽  
Flue Gas ◽  
Power Plants ◽  
Greenhouse Gas Emission ◽  
Capital Expenditure ◽  
Combined Cycle ◽  
Gas Turbine Power Plant

Abstract Renewable energy penetration is growing, due to the target of greenhouse-gas-emission reduction, even though fossil fuel-based technologies are still necessary in the current energy market scenario to provide reliable back-up power to stabilize the grid. Nevertheless, currently, an investment in such a kind of power plant might not be profitable enough, since some energy policies have led to a general decrease of both the average price of electricity and its variability; moreover, in several countries negative prices are reached on some sunny or windy days. Within this context, Combined Heat and Power systems appear not just as a fuel-efficient way to fulfill local thermal demand, but also as a sustainable way to maintain installed capacity able to support electricity grid reliability. Innovative solutions to increase both the efficiency and flexibility of those power plants, as well as careful evaluations of the economic context, are essential to ensure the sustainability of the economic investment in a fast-paced changing energy field. This study aims to evaluate the economic viability and environmental impact of an integrated solution of a cogenerative combined cycle gas turbine power plant with a flue gas condensing heat pump. Considering capital expenditure, heat demand, electricity price and its fluctuations during the whole system life, the sustainability of the investment is evaluated taking into account the uncertainties of economic scenarios and benchmarked against the integration of a cogenerative combined cycle gas turbine power plant with a Heat-Only Boiler.

Overall Performance of Advanced H2/Air Cycle Power Plants Based on Coal Decarbonisation

2005 ◽  
Author(s):  
M. Gambini ◽  
M. Vellini
Keyword(s):  
Power Plant ◽  
Hydrogen Production ◽  
Power Plants ◽  
Coal Gasification ◽  
Combined Cycle ◽  
Fuel Gas ◽  
Production Section ◽  
Pinch Technology ◽  
Energy Economy ◽  
Overall Performance

In this paper the overall performance of a new advanced mixed cycle (AMC), fed by hydrogen-rich fuel gas, has been evaluated. Obviously, hydrogen must be produced and here we have chosen the coal gasification for its production, quantifying all the thermal and electric requirements. At first, a simple combination between hydrogen production section and power section is performed. In fact, the heat loads of the first section can be satisfied by using the various raw syngas cooling, without using some material streams taken from the power section, but also without using part of heat, available in the production section and rejected into the environment, in the power section. The final result is very poor: over 34%. Then, by using the Pinch Technology, a more efficient, even if more complex, solution can be conceived: in this case the overall efficiency is very interesting: 39%. These results are very similar to those of a combined cycle power plant, equipped with the same systems and analyzed under the same hypotheses. The final result is very important because the “clean” use of coal in new power plant types must be properly investigated: in fact coal is the most abundant and the cheapest fossil fuel available on earth; moreover, hydrogen production, by using coal, is an interesting outlook because hydrogen has the potential to become the main energy carrier in a future sustainable energy economy.

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