Energy and Exergy Analyses of a Natural Gas Fired Combined Cycle Cogeneration System

2007 ◽  
Author(s):  
B. Law ◽  
B. V. Reddy
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Operating Variables ◽  
Energy And Exergy ◽  
Cogeneration System ◽  
Multiple Process ◽  
Process Heat

Combined cycle cogeneration systems have the ability to produce power and process heat more efficiently, leading to higher performance and reduced green house gas emissions. In the present work the performance of a natural gas fired combined cycle cogeneration unit with multiple process heaters is investigated to study the effect of operating variables on the performance. The operating conditions investigated include, gas turbine pressure ratio, process heat loads and process steam extraction pressure. The gas turbine pressure ratio significantly influences the performance of the combined cycle cogeneration system. The process heat load influences combined cycle efficiency and combined cycle cogeneration efficiency in opposite ways. The exergy analysis is conducted to identify the exergy destruction and losses in different components of the combined cycle cogeneration unit.

EFFECT OF OPERATING VARIABLES ON THE PERFORMANCE OF A COMBINED CYCLE COGENERATION SYSTEM WITH MULTIPLE PROCESS HEATERS

2009 ◽  
Vol 33 (1) ◽  
pp. 65-74
Author(s):  
B Law ◽  
B. V. Reddy
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Operating Variables ◽  
Cogeneration System ◽  
Multiple Process ◽  
Process Heat ◽  
Topping Cycle

Combined cycle power plants with a gas turbine topping cycle and a steam turbine bottoming cycle are widely used due to their high efficiencies. Combined cycle cogeneration has the possibility to produce power and process heat more efficiently, leading to higher performance and reduced green house gas emissions. The objective of the present work is to analyze and simulate a natural gas fired combined cycle cogeneration unit with multiple process heaters and to investigate the effect of operating variables on the performance. The operating conditions investigated include, gas turbine pressure ratio, process heat loads and process steam extraction pressure. The gas turbine pressure ratio significantly influences the performance of the combined cycle cogeneration system. It is also identified that extracting process steam at lower pressures improves the power generation and cogeneration efficiencies. The process heat load influences combined cycle efficiency and combined cycle cogeneration efficiency in opposite ways. It is also observed that using multiple process heaters with different process steam pressures, rather than a single process heater, improves the combined cycle cogeneration plant efficiency.

On-Design and Off-Design Performance Analysis of a Gas Turbine Combined Cycle Using the Exergy Method

2000 ◽  
Author(s):  
Alcides Codeceira Neto ◽  
Pericles Pilidis
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Calorific Value ◽  
Combined Cycle ◽  
Exergy Destruction ◽  
Turbine Engine ◽  
Design Point

The present paper describes an on-design and an off-design performance study of gas turbine combined cycle based power plants. The exergy analysis has been carried out along with the performance assessment, considering the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within the plant components, and it is of particular interest in this investigation. A computational analysis has been carried out to investigate the effects of compressor pressure ratio and gas turbine entry temperature on the thermodynamic performance of combined gas / steam power cycles. The exergy analysis has been performed for on-design point calculations, considering single shaft gas turbines with different compressor pressure ratios and turbine entry temperatures. Nearly 100 MW shaft power gas turbine engines burning natural gas fuel have been selected in this study. The off-design calculations have been performed for one of the gas turbines selected from the on-design point studies. For this particular gas turbine engine, fuel has been changed from natural gas to a low calorific value fuel gas originated from the gasification of wood. The exergy analysis indicates that maximum exergy is destroyed in the combustor, in the case of combined gas / steam cycles burning natural gas. For these studies on-design point, the exergy destruction in the combustor is found to decrease with increasing compressor pressure ratio to an optimum value and with increasing turbine entry temperature. In the off-design case the gas turbine engine is burning low calorific value fuel originated from the gasification of wood. The maximum exergy destruction occurs in the gasification process, followed by the combustion process in the gas turbine.

H Gas Turbine Combined Cycle Technology and Development Status

1996 ◽  
Author(s):  
James C. Corman
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Environmental Control ◽  
Cooling System ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Significant Advance ◽  
Single Digit ◽  
Cycle System

A revolutionary step has been taken in the development of the Next Advance in Power Generation Systems — “H” Technology Combined Cycle. This new gas turbine combined cycle system increases thermal performance to the 60% level by increasing gas turbine operating conditions to 2600°F (1430°C) at a pressure ratio of 23 to 1. This represents a significant increase in operating temperature for the gas turbine. However, the potential for single digit NOx levels (based upon 15% O2 in the exhaust) has been retained. The combined effect of performance increase and environmental control is achieved by an innovative closed loop steam cooling system which tightly integrated the gas turbine and steam turbine cycles. Although a significant advance has been taken in performance, the new power generation system has been configured with a substantial number of proven concepts and technology programs are ongoing to validate the new features. The technical activities which support the introduction of the new turbine system have reached a point in the development cycle where the results are integrated into the design methods. This has permitted the “H” Technology to achieve a design readiness status and the first unit will be under test in late 1997.

Enhancing Energy and Economic Performances of Combined Cycle Power Plants by Means of Gas-Cycle Regeneration

2014 ◽  
Author(s):  
Roberto Carapellucci ◽  
Lorena Giordano
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Waste Heat ◽  
Pressure Ratio ◽  
Unit Cost ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Efficiency Gain ◽  
Gas Power Plant

Efficiency improvement in the gas turbine sector has been mainly driven by increasing the turbine inlet temperature and compressor pressure ratio. For a fixed technology level, a further efficiency gain can be achieved through the utilization of waste thermal energy. Regeneration is an internal recovery technique that allows the reduction of heat input required at combustor, by preheating the air at compressor outlet. Under certain operating conditions, the temperature of exhaust gas leaving the regenerator is still enough high to allow the steam production via an heat recovery steam generator (HRSG). Regeneration in steam-gas power plants (CCGT) has the potential to enhance thermal efficiency, but reduces the margins for external recovery and then the bottoming steam cycle capacity. Moreover, the reduction of exhausts temperature at gas turbine outlet requires the reconsideration of HRSG operating parameters, in order to limit the increase of waste heat at the stack. The aim of this study is to explore the potential benefits that regeneration in the gas cycle gives on the whole steam-gas power plant. The extent of energy and economic performances improvement is evaluated, varying the gas turbine specifications and the layout and operating conditions of HRSG. Hence simple and regenerative configurations based on single and multi-pressure HRSG are compared, focusing on efficiency, specific CO2 emissions and unit cost of electricity (COE).

Low-Calorific Fuel Mix in a Large Size Combined Cycle Plant

2009 ◽  
Author(s):  
Klas Jonshagen ◽  
Magnus Genrup ◽  
Pontus Eriksson
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Expansion Ratio ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Exhaust Temperature ◽  
Large Size ◽  
Combined Cycle Plant ◽  
Reheat Steam

This paper will address the effects of mixing low-calorific fuel in to a natural gas fuelled large size combined cycle plant. Three different biofuels are tested namely; air blown gasification gas, indirect gasification gas and digestion gas. Simulations have been performed from 0–100% biofuel–natural gas mixtures. The biofuel impacts on the full cycle performance are discussed. Some more in-depth discussion about turbo-machinery components will be introduced when needed for the discussion. The compressors pressure ratio will increase in order to push the inert ballast of the low calorific fuels trough the turbine. Despite the increased expansion ratio in the gas turbine, the exhaust temperature raises slightly which derives from changed gas properties. The work is based on an in-house advanced off-design model within the software package IPSEPro. Sweden’s newest plant “O¨resundsverket”, which is a combined heat and power (CHP) plant, is used as a basis for the investigation. The plant is based on a GE Frame-9 gas turbine and has a triple-pressure reheat steam cycle.

Using Hydrogen as Gas Turbine Fuel

2005 ◽  
Vol 127 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Paolo Chiesa ◽  
Giovanni Lozza ◽  
Luigi Mazzocchi
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Guide Vane ◽  
Volume Flow Rate ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Point Of View ◽  
Inert Gases ◽  
Detailed Model ◽  
Heavy Duty Gas Turbine

This paper addresses the possibility to burn hydrogen in a large size, heavy-duty gas turbine designed to run on natural gas as a possible short-term measure to reduce greenhouse emissions of the power industry. The process used to produce hydrogen is not discussed here: we mainly focus on the behavior of the gas turbine by analyzing the main operational aspects related to switching from natural gas to hydrogen. We will consider the effects of variations of volume flow rate and of thermophysical properties on the matching between turbine and compressor and on the blade cooling of the hot rows of the gas turbine. In the analysis we will take into account that those effects are largely emphasized by the abundant dilution of the fuel by inert gases (steam or nitrogen), necessary to control the NOx emissions. Three strategies will be considered to adapt the original machine, designed to run on natural gas, to operate properly with diluted hydrogen: variable guide vane (VGV) operations, increased pressure ratio, re-engineered machine. The performance analysis, carried out by a calculation method including a detailed model of the cooled gas turbine expansion, shows that moderate efficiency decays can be predicted with elevated dilution rates (nitrogen is preferable to steam under this point of view). The combined cycle power output substantially increases if not controlled by VGV operations. It represents an opportunity if some moderate re-design is accepted (turbine blade height modifications or high-pressure compressor stages addition).

Exergy Analysis of Gas-Turbine Combined Cycle With CO2 Capture Using Pre-Combustion Decarbonization of Natural Gas

2002 ◽  
Author(s):  
Hanne M. Kvamsdal ◽  
Ivar S. Ertesva˚g ◽  
Olav Bolland ◽  
Tor Tolstad
Keyword(s):  
Natural Gas ◽  
Electric Power ◽  
Gas Turbine ◽  
Co2 Capture ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Power Production ◽  
Combined Cycle ◽  
Electric Power Production ◽  
Chemical Exergy

A concept for natural-gas fired power plants with CO2 capture has been investigated using exergy analysis. The present approach involves decarbonization of the natural gas by authothermal reforming prior to combustion, producing a hydrogen-rich fuel. An important aspect of this type of process is the integration between the combined cycle and the reforming process. The net electric power production was 47.7% of the Lower Heating Value (LHV) or 45.8% of the chemical exergy of the supplied natural-gas. In addition, the chemical exergy of the captured CO2 and the compression of this CO2 to 80 bar represented 2.1% and 2.7%, respectively, of the natural-gas chemical exergy. For a corresponding conventional combined cycle without CO2 capture, the net electric power production was 58.4% of the LHV or 56.1% of the fuel chemical exergy. A detailed breakdown of irreversibility is presented. In the decarbonized natural-gas power plant, the effect of varying supplementary firing (SF) for reformer-feed preheating was investigated. This showed that SF increased the total irreversibility and decreased the net output of the plant. Next, the effects of increased gas-turbine inlet temperature and of gas-turbine pressure ratio were studied. For the conventional plant, higher pressure led to increased efficiency for some cases. In the decarbonized natural-gas process, however, higher pressure ratio led to higher irreversibility and reduced thermal-plant efficiency.

Performance Simulation of a Combined Cycle Power Generation System With Steam Injection in the Gas Turbine Combustion Chamber

2007 ◽  
Author(s):  
B. Law ◽  
B. V. Reddy
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Pressure Ratio ◽  
Steam Injection ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Work Output ◽  
Gas Turbine Combustion

In the present work the effect of steam injection in the gas turbine combustion chamber is investigated on gas turbine and steam turbine work output and on thermal efficiency of the combined cycle power plant. The operating conditions investigated include gas turbine pressure ratio and gas turbine inlet temperature. The steam injection decreases the steam cycle output and boosts the gas cycle output and the net combined cycle work output and thermal efficiency significantly.

Integration of a Pressurized-Air Solar Receiver Array to a Gas Turbine Power Cycle for Solar Tower Applications

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Peter Poživil ◽  
Aldo Steinfeld
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Rankine Cycle ◽  
Power Input ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Receiver Array ◽  
Solar Receiver

The thermal performance of an array of pressurized-air solar receiver modules integrated to a gas turbine power cycle is analyzed for a simple Brayton cycle (BC), recuperated Brayton cycle (RC), and combined Brayton–Rankine cycle (CC). While the solar receiver's solar-to-heat efficiency decreases at higher operating temperatures and pressures, the opposite is true for the power cycle's heat-to-work efficiency. The optimal operating conditions are achieved with a preheat stage for a solar receiver outlet air temperature of 1300 °C and an air cycle pressure ratio of 9, yielding a peak solar-to-electricity efficiency—defined as the ratio of the net cycle work output divided by the solar radiative power input through the receiver's aperture—of 39.3% for the combined cycle configuration.

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.

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