The Semiclosed Recuperated Cycle With Intercooled Compressors

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Hans E. Wettstein
Keyword(s):  
Gas Turbine ◽  
Fossil Fuels ◽  
Combined Cycle ◽  
Component Technology ◽  
Exhaust Gas ◽  
Combustion Gas ◽  
Electric Power Supply ◽  
Low Load ◽  
Fierce Competition ◽  
Gas Recirculation

The gas turbine combined cycle (GTCC) is the best currently available choice, if gaps in the renewable electric power supply need being filled with power from fossil fuels. The GTCC manufacturers are in a fierce competition responding to these needs, especially for the best part load efficiency, the fastest load ramp capability and for the lowest low load power parking at an acceptable NOx and CO emission level. But there is an option outperforming the GTCC technology for the above mentioned requirements, which is theoretically known since years but it has not yet been practically developed. It is the semiclosed recuperated cycle (SCRC). Wettstein (2013) has described this recently in “The Air Breathing Semiclosed Recuperated Cycle and Its Super Chargeable Predecessors,” Gas Turbine World 2013, March/April Issue, Vol. 42, No. 2). The SCRC does not require any component technology, which is not yet proven in operating large commercial GTCC or GT plants. But of course the cycle integration is a different one, requiring a specific design of the components. An inherent side feature of the SCRC is the exhaust gas composition, which corresponds to a near-stoichiometric combustion gas. This allows comparing the SCRC with a (CO2−) capture ready GTCC having exhaust gas recirculation. The above mentioned article, the thermodynamic performance analysis of a SCRC with an adiabatic compressor is described. But the cycle becomes even more attractive with an intercooling stage in each of the two compressors. Here, this is quantified with another detailed thermodynamic analysis. Additionally, also an ideal case with isothermal compression is analyzed. The latter is of course unrealistic for a practical realization. But it indicates the potential of using more than one intercooling stage per compressor. The aim of this paper is to quantitatively compare the three variants with adiabatic, intercooled and isothermal compressors. In all three cases the same turbine and recuperator temperature limitations are used while some other cycle data assumptions are adapted to the compressor technology in order to achieve an optimal performance level for each variant. The thermodynamic results have been cross-checked with a breakdown of the exergy losses in the three variants. The final results for base load operation indicate that the intercooled variant could become the best choice.

The Semi-Closed Recuperated Cycle With Intercooled Compressors

2014 ◽  
Author(s):  
Hans E. Wettstein
Keyword(s):  
Fossil Fuels ◽  
Combined Cycle ◽  
Component Technology ◽  
Exhaust Gas ◽  
Combustion Gas ◽  
Electric Power Supply ◽  
Thermodynamic Performance ◽  
Low Load ◽  
Fierce Competition ◽  
Gas Recirculation

The Gas Turbine Combined Cycle (GTCC) is the best currently available choice, if gaps in the renewable electric power supply need being filled at short notice with power from fossil fuels. The GTCC manufacturers are in a fierce competition responding to these needs, especially for the best part load efficiency, the fastest load ramp capability and for the lowest low load power parking at an acceptable NOx and CO emission level. But there is an option outperforming the GTCC technology for the above mentioned requirements, which is theoretically known since years but it has not yet been practically developed. It is the Semi-Closed Recuperated Cycle (SCRC). The author has described this recently in an article [1] with the title “The air breathing semi-closed recuperated cycle and its super chargeable predecessors”. The SCRC does not require any component technology, which is not yet proven in operating commercial GTCC or GT plants. But of course the cycle integration is a different one, requiring a specific design of the components. An inherent side feature of the SCRC is the exhaust gas composition, which corresponds to a near-stoichiometric combustion gas. This allows comparing the SCRC with a (CO2-) capture ready GTCC having exhaust gas recirculation. The above mentioned article [1] describes the thermodynamic performance analysis of a SCRC with an adiabatic compressor. But the cycle becomes even more attractive with an intercooling stage in each of the two compressors. Here this is quantified with another detailed thermodynamic analysis. Additionally also an ideal case with isothermal compression is analyzed. The latter is of course unrealistic for a practical realization. But it indicates the potential of using more than one intercooling stage per compressor. The aim of this paper is to quantitatively compare the three variants with adiabatic, intercooled and isothermal compressors. In all three cases the same turbine and recuperator temperature limitations are used while some other cycle data assumptions are adapted to the compressor technology in order to achieve an optimal performance level for each variant. The thermodynamic results have been cross-checked with a breakdown of the exergy losses in the three variants. The final results for base load operation indicate that the intercooled variant could become the best choice.

Improving Combined Cycle Part Load Performance by Using Exhaust Gas Recirculation Through an Ejector

2021 ◽  
Author(s):  
Majed Sammak ◽  
Chi Ho ◽  
Alaaeldin Dawood ◽  
Abdurrahman Khalidi
Keyword(s):  
Gas Turbine ◽  
Heat Rate ◽  
Heating System ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Entrainment Ratio ◽  
Ambient Temperatures ◽  
Air Heating ◽  
Rate Improvement ◽  
Gas Recirculation

Abstract The gas turbine inlet air heating system has been used for improving the combined cycle heat rate at part load operation, which has a positive impact on the combined cycle profitability and fuel consumption. The paper objective was to introduce a new gas turbine inlet air heating system. The inlet air heating system studied in this paper was exhaust gas recirculation into inlet air compressor through an ejector. The ejector motive flow was defined as the compressor bleed air from the compressor discharge section while the ejector entrainment flow was defined as the recirculated exhaust gases from the gas turbine exhaust duct. This study was performed on generic gas turbine and combined cycle model. The selected combined cycle model was 1-on-1 (one gas turbine, one heat recovery steam generator and one steam turbine train). The heat recovery steam generator was a 3-pressure level with reheat. The combined cycle heat rate improvement at different ejector entrainment ratio varying from 0.5 to 5 with 0.5 intervals was studied. The selected ejector area ratio was set to 25 which together with the motive to suction pressure ratio gave an entrainment ratio of 2.5. The selected ejector entrainment ratio of 2.5 was aligned with the common practice design of the ejectors. The ejector motive flow was limited to 1% of compressor inlet air flow. Furthermore, the combined cycle heat rate improvement at different combined cycle loads were analysed. The analysis was performed on combined cycle loads from 90% to 40% load with a 10% interval and at the ambient temperatures 7°C, 15°C and 35°C. At the ambient temperatures 7°C, 15°C and 35°C, the combined cycle heat rate improvement was measured at loads below 80%. The combined cycle heat rate improvements proved greater at lower combined cycle loads and lower ambient temperatures. The combined cycle heat rate improvement was 0.67% at the ambient temperature 15°C and 60% combined cycle load. On the other hand, the combined cycle heat rate improvement was 1.4% at 40% combined cycle load and ambient temperature 7°C.

Investigation of a Gas Turbine Process With Reheat Combustion at Flue Gas Recirculation and Oxyfuel-Conditions

2017 ◽  
Author(s):  
Florian Beenken ◽  
Franz Joos
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Co2 Sequestration ◽  
Fossil Fuels ◽  
Pressure Ratio ◽  
Electrical Power ◽  
Exhaust Gas ◽  
Power Station ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

In near future electrical power generation will still be supplied by fossil fuels. To reach the targets of the conference on climate change in Paris 2015 one method proposed is the CO2 sequestration and usage or alternatively storage. Compared to coal-fired power station the amount of CO2 in the exhaust gas of gas turbine power station is much less and therefore more difficult to remove. To enhance the efficiency of the CO2-sequestration process enrichment of the CO2 in the exhaust gas could be a solution. This can be achieved by exhaust gas recirculation or by burning with pure O2 instead of air avoiding a lot of N2 in the exhaust gas, called Oxyfuel process. The work concerns to investigations of a reheat gas turbine operating with flue gas recirculation as well as with Oxyfuel operation. The thermodynamic process has been modeled in detail considering the additional demand of cooling of the combustors and the turbines at Oxyfuel process. Additional combustion experiments have been carried out with flue gas recirculation as well as with Oxyfuel conditions burning Natural Gas with O2 in a CO2 environment to investigate the flame stability and extinction limit. The thermophysical properties, like specific heat capacity and sound velocity, are strongly altered by the high content of CO2 and H2O in the fluid of the turbine as well as of the compressor. For example during Oxyfuel conditions the pressure ratio is expected to decrease to about 78% of air operation. The influence of flue gas recirculation and Oxyfuel process to the gas composition as well as to the heat transfer and exit conditions are discussed.

Semi-Closed Gas Turbine/Combined Cycle With Water Recovery and Extensive Exhaust Gas Recirculation

1996 ◽  
Author(s):  
Bruno Facchini ◽  
Daniele Fiaschi ◽  
Giampaolo Manfrida
Keyword(s):  
Gas Turbine ◽  
Water Injection ◽  
Combined Cycle ◽  
Point Of View ◽  
Exhaust Gas ◽  
Water Recovery ◽  
Gas Treatment ◽  
High Level ◽  
Gas Recirculation ◽  
Gas Turbine Cycle

This innovative gas turbine cycle can offer several advantages over conventional cycles from the point of view of environmental friendship. The basic idea of SCGT/CC (Semi-Closed Gas Turbine/Combined Cycle with water recovery) is to cool down the exhaust temperatures to allow full condensation of the water vapor, and recirculate a large part of the exhaust gases to the compressor. The condensed water can then be reinjected by means of a pump at compressor delivery. The working gas composition is thus close to that corresponding to stoichiometric combustion, which opens the possibility of applying techniques for CO2 recycling and general exhaust gas treatment. An increase in work output is connected to water injection, while a high level of efficiency is maintained as the compressor work is reduced and the cycle parameters are tuned for the exhaust of this turbine.

Modified Rankine HRSG Beats Triple-Pressure System

1996 ◽  
Author(s):  
Peter Eisenkolb ◽  
Martin Pogoreutz ◽  
Hermann Halozan
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Fossil Fuels ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Pressure System ◽  
Exergy Losses

Gas-fired combined cycle power plants (CCP) are presently the most efficient systems for producing electricity with fossil fuels. Gas turbines have been and are being improved remarkably during the last years; presently they achieve efficiencies of more than 38% and gas turbine outlet temperatures of up to 610°C. These high outlet temperatures require modifications and improvements of heat recovery steam generators (HRSG). Presently dual pressure HRSGs are most commonly used in combined cycle power stations. The next step seems to be the triple-pressure HRSG to be able to utilise the high gas turbine outlet temperatures efficiently and to reduce exergy losses caused by the heat transfer between exhaust gas and the steam cycle. However, such triple-pressure systems are complicated considering parallel tube bundles as well as start up operation and load changes. For that reason an attempt has been made to replace such multiple pressure systems by a modified Rankine cycle with only a single-pressure level. In the case of the same total heat transfer surfaces this innovative single-pressure system achieves approximately the same efficiency as the triple-pressure system. By optimising the heat recovery from the exhaust gas to the steam/water cycle, i.e. minimising exergy losses, the stack temperature is much higher. Increasing the heat transfer surfaces means a decrease of the stack temperature and a further improvement of the overall CCP-efficiency. Therefore one has to be aware that the proposed system offers advantages not only in the case of a foreseeable increase of gas turbine outlet temperatures but also for presently available gas turbines. Using existing highly efficient gas turbines and subcritical steam conditions, power plants with this proposed Eisenkolb Single Pressure (ESP_CCP) heat recovery steam generator achieve thermal efficiencies of about 58.7% (LHV).

Evaluation of a Micro Gas Turbine With Post-Combustion CO2 Capture for Exhaust Gas Recirculation Potential With Two Experimentally Validated Models

2017 ◽  
Author(s):  
Homam Nikpey Somehsaraei ◽  
Usman Ali ◽  
Carolina Font-Palma ◽  
Mohammad Mansouri Majoumerd ◽  
Muhammad Akram ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Gas Turbine ◽  
Co2 Capture ◽  
Exhaust Gas Recirculation ◽  
Software Tools ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Capture Process ◽  
Micro Gas Turbine ◽  
Gas Recirculation

The growing global energy demand is facing concerns raised by increasing greenhouse gas emissions, predominantly CO2. Despite substantial progress in the field of renewable energy in recent years, quick balancing responses and back-up services are still necessary to maintain the grid load and stability, due to increased penetration of intermittent renewable energy sources, such as solar and wind. In a scenario of natural gas availability, gas turbine power may be a substitute for back-up/balancing load. Rapid start-up and shut down, high ramp rate, and low emissions and maintenance have been achieved in commercial gas turbine cycles. This industry still needs innovative cycle configurations, e.g. exhaust gas recirculation (EGR), to achieve higher system performance and lower emissions in the current competitive power generation market. Together with reduced NOx emissions, EGR cycle provides an exhaust gas with higher CO2 concentration compared to the simple gas turbine/combined cycle, favorable for post-combustion carbon capture. This paper presents an evaluation of EGR potential for improved gas turbine cycle performance and integration with a post-combustion CO2 capture process. It also highlights features of two software tools with different capabilities for performance analysis of gas turbine cycles, integrated with post-combustion capture. The study is based on a combined heat and power micro gas turbine (MGT), Turbec T100, of 100kWe output. Detailed models for the baseline MGT and amine capture plant were developed in two software tools, IPSEpro and Aspen Hysys. These models were validated against experimental work conducted at the UK PACT National Core Facilities. Characteristics maps for the compressor and the turbine were used for the MGT modeling. The performance indicators of systems with and without EGR, and when varying the EGR ratio and ambient temperature, were calculated and are presented in this paper.

scholarly journals Thermo-economic comparative analysis of gas turbine GT10 integrated with air and steam bottoming cycle

2014 ◽  
Vol 35 (4) ◽  
pp. 83-95 ◽  
Author(s):  
Daniel Czaja ◽  
Tadeusz Chmielnak ◽  
Sebastian Lepszy
Keyword(s):  
Economic Analysis ◽  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Small Range ◽  
Exhaust Gas ◽  
Thermodynamic Optimization ◽  
Technological Structure ◽  
The Cost ◽  
Selection Of

Abstract A thermodynamic and economic analysis of a GT10 gas turbine integrated with the air bottoming cycle is presented. The results are compared to commercially available combined cycle power plants based on the same gas turbine. The systems under analysis have a better chance of competing with steam bottoming cycle configurations in a small range of the power output capacity. The aim of the calculations is to determine the final cost of electricity generated by the gas turbine air bottoming cycle based on a 25 MW GT10 gas turbine with the exhaust gas mass flow rate of about 80 kg/s. The article shows the results of thermodynamic optimization of the selection of the technological structure of gas turbine air bottoming cycle and of a comparative economic analysis. Quantities are determined that have a decisive impact on the considered units profitability and competitiveness compared to the popular technology based on the steam bottoming cycle. The ultimate quantity that can be compared in the calculations is the cost of 1 MWh of electricity. It should be noted that the systems analyzed herein are power plants where electricity is the only generated product. The performed calculations do not take account of any other (potential) revenues from the sale of energy origin certificates. Keywords: Gas turbine air bottoming cycle, Air bottoming cycle, Gas turbine, GT10

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