CO2 capture for gas turbines: an integrated energy-efficient process combining combustion in oxygen-enriched air, flue gas recirculation, and membrane separation

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.

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Co2 Capture for the Silicon Process-Effects of Flue Gas Recirculation

SSRN Electronic Journal ◽

10.2139/ssrn.3926089 ◽

2021 ◽

Author(s):

Vegar Andersen ◽

Hanna Katariina Knuutila ◽

Lucas Braakhuis ◽

Edin Myrhaug ◽

Kristian Etienne Einarsrud ◽

...

Keyword(s):

Co2 Capture ◽

Flue Gas ◽

Flue Gas Recirculation ◽

Process Effects ◽

Gas Recirculation

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Improvement of Gas Turbine Combustion Reactivity Under Flue Gas Recirculation Condition With In-Situ Hydrogen Addition

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-59182 ◽

2009 ◽

Cited By ~ 6

Author(s):

Dieter Winkler ◽

Pascal Mu¨ller ◽

Simon Reimer ◽

Timothy Griffin ◽

Andre´ Burdet ◽

...

Keyword(s):

Gas Turbine ◽

Co2 Capture ◽

Flue Gas ◽

Co2 Concentration ◽

Oxygen Depletion ◽

Hydrogen Addition ◽

Flue Gas Recirculation ◽

Combustion Reactivity ◽

Gas Recirculation

Carbon Capture and Storage (CCS) solutions are currently being assessed in order to address appropriately the climate change challenge. Post-combustion CO2 capture is one of the technologies proposed for both coal-fired and gas-fired power plants. In Natural Gas Combined Cycle (NGCC), the flue gas is treated after the Heat Recovery Steam Generator (HRSG) in a so-called post-combustion CO2 capture module through use of solvents. The size of systems envisaged for the capture of CO2 scales with volumetric flow to be treated together with the CO2 concentration contained in the flue gas. Flue Gas Recirculation (FGR) is proposed as a means to increase CO2 concentration in the flue gas together with a net reduction of volumetric flow to be treated by the CO2 capture module. One of the limiting factors of this technology is the vitiation of air within gas turbine combustor and the associated reduction in oxygen concentration. This paper analyses the influence of air vitiation upon combustion in a generic premix lean industrial burner. Tests are carried out under representative inlet pressure and temperature levels. Variation of inlet oxidizer composition is simulated with the addition of nitrogen and carbon dioxide to the inlet air. It is observed that CO emission increases with oxygen depletion at a fixed residence time, signaling a reduction of combustion reactivity. In addition, NOx emission is shown to be sensitive to oxygen depletion. In order to mitigate reduction of combustion reactivity, hydrogen is added to the fuel, up to 20% in volume. As another alternative, a Catalytic Partial Oxidation (CPO) reactor is used in-situ in order to reform the fuel to different syngas blends. These syngas is then used as fuel, which enables the enhancement of the combustion reactivity counter-acting the impact of FGR conditions. The hydrogen addition appears to help improving the reactivity of the flame, making this concept relevant for operation under vitiated air condition.

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Flue Gas Recirculation in Gas Turbine: Investigation of Combustion Reactivity and NOX Emission

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-59221 ◽

2009 ◽

Cited By ~ 8

Author(s):

Felix Guethe ◽

Marta de la Cruz Garci´a ◽

Andre´ Burdet

Keyword(s):

Gas Turbine ◽

Flue Gas ◽

Gas Turbines ◽

Nox Emission ◽

Moderate Increase ◽

Fuel Injector ◽

Flue Gas Recirculation ◽

Combustion Reactivity ◽

Gas Recirculation ◽

The Impact

Flue gas recirculation (FGR) is a promising technology for the optimization of post-combustion CO2 capture in natural gas combined cycle (NGCC) plants. In this work, the impact of FGR on lean gas turbine premix combustion is predicted by analytical and numerical investigations as well as comparison to experiments. In particular the impact of vitiated air condition and moderate increase of CO2 concentration into combustion reactivity and NOx emission is studied. The influence of inlet pressure, temperature and recirculated NOx are taken as parameters of this study. Two different kinetic schemes are used to predict the impact that FGR has on the combustion process: the GRI3.0 and the RDO6_NO, which is a newly compiled mechanism from the DLR Stuttgart. The effects of the FGR on the NOx emissions are predicted using a chemical reactor network including unmixedness as presumed probability density function (PDF) to account for real effects. The magnitude and ratio of prompt to post-flame thermal NOx changes with the FGR-ratio producing less post flame NOx at reduced O2 content. For technical mixtures (i. e. an industrial fuel injector), NOx emission can be expected to be lower with the vitiation of the oxidizer. This is due to several effects: at low O2 concentration, the highest possible adiabatic flame temperatures for stoichiometric conditions decreases resulting in lower NOx when averaged over all mixing fractions. Further effects result from lower post flame NOx production and the role of “reburn” chemistry, actually reducing NOx (recirculated from the exhaust), which might become relevant for the high recirculation ratios, where parts of the flame would operate at rich stoichiometry at given unmixedness. Therefore in general for each combustor technical mixing could decrease NOx with respect to perfect mixing at high FGR-ratio assuming the engine can still be operated. Although the findings are quite general for gas turbines the advantage that reheat engines have in terms of operation are highlighted. For reheat engines this can be understood as an extension of the “reheat concept” and used as the next step in the goal to achieve minimal emissions at increasing power. In addition, NOx emission obtained in FGR combustion reduces even further when the engine pressure ratio increases, making the concept particularly well suited for reheat engines.

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Combustion Under Flue Gas Recirculation Conditions in a Gas Turbine Lean Premix Burner

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-23396 ◽

2010 ◽

Cited By ~ 2

Author(s):

Andre´ Burdet ◽

Thierry Lachaux ◽

Marta de la Cruz Garci´a ◽

Dieter Winkler

Keyword(s):

Gas Turbine ◽

Flue Gas ◽

Gas Turbines ◽

Nox Reduction ◽

Nox Emission ◽

Stable Operation ◽

Engine Operation ◽

Flue Gas Recirculation ◽

Gas Recirculation ◽

Co Emission

An EV burner as installed in Alstom’s dry low NOx gas turbines was experimentally investigated under different Flue Gas Recirculation (FGR) and engine conditions. FGR enables the reduction of the high exhaust volume flow while significantly increasing the exhaust CO2 concentration. This may substantially improve the post-combustion capture of CO2. However, FGR introduces consequent changes in the gas turbine combustion process mainly because of the oxygen depletion and CO2 increase within the oxidizer. N2 and CO2 were mixed with air in order to obtain at the burner inlet a synthetic oxidizer mixture reproducing O2 and CO2 levels spanning different FGR levels of interest for engine operation. In addition, various degrees of unmixedness of the reactive mixture were investigated by varying the ratio of fuel injected at different port locations in the investigated burner set. Stable operation was achieved in all tested conditions. The lean premix flame shifts downstream when O2 is depleted due to the decrease of the reactivity, although it always stays well within the combustion chamber. The potential for NOx reduction when using FGR is demonstrated. Changes of the NOx formation mechanism are described and compared to the experimental data for validation. Unmixedness appears to be less detrimental to NOx emission when under high FGR ratio. However, CO emission is shown to increase when FGR ratio is increased. Meanwhile, with the present gas turbine combustor, the CO emission follows the equilibrium limit even at high FGR ratio. Interestingly, it is observed that when the burner inlet pressure is increased (and consequently the inlet burner temperature), the increase of CO emission due to FGR is lowered while the NOx emission stays at a very low level. This present an argument for using a higher cycle pressure in gas turbines optimized for FGR operation.

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Characteristics and flame appearance of oxy-fuel combustion using flue gas recirculation

Fuel ◽

10.1016/j.fuel.2021.120775 ◽

2021 ◽

Vol 297 ◽

pp. 120775

Author(s):

Mohsen Abdelaal ◽

Medhat El-Riedy ◽

Ahmed M. El-Nahas ◽

Fathy R. El-Wahsh

Keyword(s):

Flue Gas ◽

Fuel Combustion ◽

Flue Gas Recirculation ◽

Gas Recirculation

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Experiment investigation of coal MILD-Oxy combustion integrated with flue gas recirculation at a 0.3 MW th furnace

Fuel Processing Technology ◽

10.1016/j.fuproc.2017.04.002 ◽

2017 ◽

Vol 162 ◽

pp. 126-134 ◽

Cited By ~ 13

Author(s):

Zhihui Mao ◽

Liqi Zhang ◽

Xinyang Zhu ◽

Chuguang Zheng

Keyword(s):

Flue Gas ◽

Flue Gas Recirculation ◽

Gas Recirculation

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Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm NOx Burner With Periodic Flue Gas Recirculation

Volume 1: Turbo Expo 2004 ◽

10.1115/gt2004-53410 ◽

2004 ◽

Cited By ~ 4

Author(s):

Jochen R. Kalb ◽

Thomas Sattelmayer

Keyword(s):

Natural Gas ◽

Flue Gas ◽

Gas Content ◽

Stable Operation ◽

Reacting Flow ◽

Nox Emissions ◽

Lean Blowout ◽

Fresh Mixture ◽

Flue Gas Recirculation ◽

Gas Recirculation

The technological objective of this work is the development of a lean-premixed burner for natural gas. Sub-ppm NOx emissions can be accomplished by shifting the lean blowout limit (LBO) to slightly lower adiabatic flame temperatures than the LBO of current standard burners. This can be achieved with a novel burner concept utilizing periodic flue gas recirculation: Hot flue gas is admixed to the injected premixed fresh mixture with a mass flow rate of comparable magnitude, in order to achieve self-ignition. The subsequent combustion of the diluted mixture again delivers flue gas. A fraction of the combustion products is then admixed to the next stream of fresh mixture. This process pattern is to be continued in a cyclically closed topology, in order to achieve stable combustion of e.g. natural gas in a temperature regime of very low NOx production. The principal ignition behavior and NOx production characteristics of one sequence of the periodic process was modeled by an idealized adiabatic system with instantaneous admixture of partially or completely burnt flue gas to one stream of fresh reactants. With the CHEMKIN-II package a reactor network consisting of one perfectly stirred reactor (PSR, providing ignition in the first place) and two plug flow reactors (PFR) has been used. The effect of varying burnout and the influence of the fraction of admixed flue gas have been evaluated. The simulations have been conducted with the reaction mechanism of Miller and Bowman and the GRI-Mech 3.0 mechanism. The results show that the high radical content of partially combusted products leads to a massive decrease of the time required for the formation of the radical pool. As a consequence, self-ignition times of 1 ms are achieved even at adiabatic flame temperatures of 1600 K and less, if the flue gas content is about 50%–60% of the reacting flow after mixing is complete. Interestingly, the effect of radicals on ignition is strong, outweighs the temperature deficiency and thus allows stable operation at very low NOx emissions.

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