scholarly journals A Thermodynamic Analysis of Two Competing Mid-Sized Oxyfuel Combustion Combined Cycles

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Egill Thorbergsson ◽  
Tomas Grönstedt
Keyword(s):  
Comparative Analysis ◽  
Gas Turbine ◽  
Power Density ◽  
Thermodynamic Analysis ◽  
Parametric Study ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Oxyfuel Combustion ◽  
Higher Power ◽  
Combined Cycles

A comparative analysis of two mid-sized oxyfuel combustion combined cycles is performed. The two cycles are the semiclosed oxyfuel combustion combined cycle (SCOC-CC) and the Graz cycle. In addition, a reference cycle was established as the basis for the analysis of the oxyfuel combustion cycles. A parametric study was conducted where the pressure ratio and the turbine entry temperature were varied. The layout and the design of the SCOC-CC are considerably simpler than the Graz cycle while it achieves the same net efficiency as the Graz cycle. The fact that the efficiencies for the two cycles are close to identical differs from previously reported work. Earlier studies have reported around a 3% points advantage in efficiency for the Graz cycle, which is attributed to the use of a second bottoming cycle. This additional feature is omitted to make the two cycles more comparable in terms of complexity. The Graz cycle has substantially lower pressure ratio at the optimum efficiency and has much higher power density for the gas turbine than both the reference cycle and the SCOC-CC.

Comparative Analysis of Different Inlet Air Cooling Technologies Including Solar Energy to Boost Gas Turbine Combined Cycles in Hot Regions

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Ahmed Abdel Rahman ◽  
Esmail M. A. Mokheimer
Keyword(s):  
Comparative Analysis ◽  
Gas Turbine ◽  
Output Power ◽  
Power Output ◽  
Combined Cycle ◽  
Air Cooling ◽  
Absorption Chiller ◽  
Absorption Chillers ◽  
Combined Cycles ◽  
Net Power Output

Cooling the air before entering the compressor of a gas turbine of combined cycle power plants is an effective method to boost the output power of the combined cycles in hot regions. This paper presents a comparative analysis for the effect of different air cooling technologies on increasing the output power of a combined cycle. It also presents a novel system of cooling the gas turbine inlet air using a solar-assisted absorption chiller. The effect of ambient air temperature and relative humidity on the output power is investigated and reported. The study revealed that at the design hour under the hot weather conditions, the total net power output of the plant drops from 268 MW to 226 MW at 48 °C (15.5% drop). The increase in the power output using fogging and evaporative cooling is less than that obtained with chillers since their ability to cool down the air is limited by the wet-bulb temperature. Integrating conventional and solar-assisted absorption chillers increased the net power output of the combined cycle by about 35 MW and 38 MW, respectively. Average and hourly performance during typical days have been conducted and presented. The plants without air inlet cooling system show higher carbon emissions (0.73 kg CO2/kWh) compared to the plant integrated with conventional and solar-assisted absorption chillers (0.509 kg CO2/kWh) and (0.508 kg CO2/kWh), respectively. Also, integrating a conventional absorption chiller shows the lowest capital cost and levelized electricity cost (LEC).

Evaluation of the Compression-Intercooled Reheat-Gas-Turbine-Combined Cycle

1984 ◽  
Author(s):  
Ivan G. Rice
Keyword(s):  
Gas Turbine ◽  
Thermodynamic Analysis ◽  
Pressure Range ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Time Increase ◽  
Efficiency Loss ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Turbine Output

Interest in the reheat-gas turbine (RHGT) as a way to improve combined-cycle efficiency is gaining momentum. Compression intercooling makes it possible to readily increase the reheat-gas-turbine cycle-pressure ratio and at the same time increase gas-turbine output; but at the expense of some combined-cycle efficiency and mechanical complexity. This paper presents a thermodynamic analysis of the intercooled cycle and pinpoints the proper intercooling pressure range for minimum combined-cycle-efficiency loss. At the end of the paper two-intercooled reheat-gas-turbine configurations are presented.

Comparative Thermodynamic Analysis of Combined and Steam Injected Gas Turbine Cycles

2003 ◽  
Author(s):  
R. Yadav ◽  
Pradeep Kumar ◽  
Samir Saraswati
Keyword(s):  
Gas Turbine ◽  
Thermodynamic Analysis ◽  
Heat Recovery ◽  
Pressure Ratio ◽  
Computer Code ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Compressor Pressure Ratio ◽  
Exergy Losses

This paper presents a comparative study of first and second law thermodynamic analysis of combined and recuperated and non-recuperated steam injected gas turbine cycles. The analysis has been carried out by developing a computer code, which is based on the modeling of various elements of these cycles. The gas turbine chosen for the analysis is MS9001H developed recently by GE and the steam cycle is having a triple-pressure heat recovery steam generator with reheat. It has been observed that the combined cycle is superior to the steam injected cycle, however, the gap narrows down with increasing compressor pressure ratio and high value of turbine inlet temperature. The detailed exergy losses have been presented in various elements of combined and steam injected cycles.

scholarly journals Optimizing a Pressurized Fluidized Bed Combustion Combined Cycle With Gas Turbine Topping Cycle

1993 ◽  
Author(s):  
D. Bohn ◽  
G. H. Dibelius ◽  
R. U. Pitt ◽  
R. Faatz ◽  
G. Cerri ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Coal Gasification ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Fluidized Bed Combustion ◽  
Steam Generation ◽  
Combined Cycles ◽  
Set Up ◽  
Topping Cycle ◽  
Pressurized Fluidized Bed Combustion

Combined Cycles for the generation of electricity or co-generation of heat and power with Pressurized Fluidized Bed Combustion (PFBC) of coal and a gas turbine topping cycle fired with a fuel suitable for gas turbines have been studied to set up optimum process parameters with respect to net efficiency, emissions including CO2, and keeping in mind the feasibility of the plant components. As a basic approach, natural gas has been considered as a fuel for the topping gas turbine. Net efficiencies up to 50% (LHV) are acheived. For the calculations, a Recursive Equality Constraint Quadratic Programming Method (RECQPM) is applied. The method is semi-implicit, i. e. the equations describing the process are solved using a non-linear equations system solver; the modular structure of the cycle is, however, made up for by programme modules set up for the relevant components/units. With the process layouts studied, the PFBC should be operated at a pressure level to allow for a compact design of the PFBC steam generator and the Hot Gas Clean-Up Unit (HGCU), and to take advantage of the pressure with respect to combustion efficiency, in-bed sulfur retention and NOx-reduction. The overall pressure ratio of the topping gas turbine, e. g. consisting of an LP-compressor plus a free running HP spool, and exhausting to the PFB combustor, should be in the range of 30. Further developments of gas turbine technology with respect to pressure ratio and turbine inlet temperature can be incorporated into the process and will be associated with an increase of overall efficiency. The heat to be extracted from the coal fired PFBC at the typical combustion temperature of 850°C allows for steam generation at conventional live steam and reheat temperatures (and pressures). The incorporation of advanced steam cycle parameters, as actually considered for pulverized coal fired boilers, would again increase the overall net efficiency of the cycle by some 5% with an increase of both the live steam and the reheat temperature from 540°C to 600°C. In contrast to conventional combined cycles with an unfired waste heat boiler for steam generation, the overall efficiency of the PFBC combined cycle with gas turbine topping cycle is only marginally affected by dual pressure steam cycle arrangements, except for very sophisticated and costly designs. To use gas from an integrated coal gasification unit rather than natural gas as a fuel for the topping gas turbine would result in an entirely coal based process. Due to the capability of the PFBC to burn residues of coal gasification and gas purification, this process, compared to pure Integrated Gasification Combined Cycles (IGCC), is less sensitive to the carbon conversion acheived. Even more, the raw gas purification might be simplified, and the process efficiency might be increased as a result of the sulphur removal to be acheived in the PFBC rather than in a raw gas sweetening process. Some preliminary findings for a process with an integrated partial gasification unit are discussed.

Thermodynamics of an Isothermal Gas Turbine Combined Cycle

1984 ◽  
Vol 106 (4) ◽  
pp. 743-749 ◽  
Author(s):  
M. A. El-Masri ◽  
J. H. Magnusson
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Extraction Process ◽  
Combined Cycle ◽  
Peak Temperature ◽  
Combined Cycles ◽  
Isothermal Gas ◽  
Technological Constraints ◽  
Cycle Efficiency ◽  
Steam Cycle

The isothermal (or multiple-reheat) gas turbine performs the combustion/work extraction process at a sustained, elevated temperature. This has distinct thermodynamic advantages in combined cycles for given peak temperature constraints. A thermodynamic model for this cycle is developed. Although based on a simple CO/CO2/O2 chemcial system the results are applicable to other reactants and dilutants. Combined cycle efficiency is reported for different gas turbine pressure ratios, peak temperatures, reactant dilution and steam cycle conditions. The range of parameters investigated starts from present-day advanced technologies and examines the potential of higher pressures and temperatures. Balances of thermodynamic availability are used to interpret the results. They show that for a given steam cycle and gas turbine pressure ratio, increasing peak temperature beyond a certain value provides sharply diminishing return. This is because the reduction in combustion irreversibility is offset by increased heat transfer irreversibility. Higher pressure ratios or steam cycle temperatures can raise this optimum peak temperature. In view of the various technological constraints, the authors’ conclusion is that an isothermal gas turbine with a peak temperature and pressure-ratio of about 1600K and 100:1, respectively, represents the most promising next step in technology. Coupled with existing advanced steam cycles this should provide efficiencies in the 60 percent range.

scholarly journals The Basic Performance of Combined Cycles and Their Optimum Gas Turbine Pressure Ratios

1995 ◽  
Author(s):  
Ruixian Cai
Keyword(s):  
Gas Turbine ◽  
Fluidized Bed ◽  
Pressure Ratio ◽  
Comparison Method ◽  
Combined Cycle ◽  
Simple Cycle ◽  
Optimum Pressure ◽  
Specific Output ◽  
Basic Performance ◽  
Combined Cycles

Based on the idea of the Comparison Method proposed by the author in 80’s, the expressions for efficiencies and power ratios between gas turbine and steam turbine of various typical combined cycles such as pressurized fluidized bed type, fully fired type and pure heat recovery types are derived. These expressions are very simple, physically clear and accurate enough. In addition, the values of optimum gas turbine pressure ratios for efficiency of these combined cycles are derived or discussed also. It is found that the optimum gas turbine pressure ratio for efficiency of pressurized fluidized bed type combined cycle can be expressed as the same as the optimum pressure ratio for specific output of the simple cycle gas turbine, and the optimum pressure ratios for efficiency of other combined cycles are only a little bit higher than the optimum pressure ratio for specific output of the simple cycle gas turbine.

A Study of Cycle Performance of Ceramic Gas Turbines

1997 ◽  
Author(s):  
H. Sugishita ◽  
H. Mori ◽  
R. Chikami ◽  
Y. Tsukuda ◽  
S. Yoshino ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Performance Improvement ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Gas Temperature ◽  
Blade Cooling ◽  
Combined Cycles ◽  
Cooling Air

A study has been carried out to assess the performance improvement of a combined cycle used for an industrial power plant when ceramic turbine components are employed. This paper presents the details of this study. Performance improvement is obtained as a result of reduced blade cooling air. In this study four different kinds of combined cycles were investigated and these are listed below: A. Combined cycle with a simple gas turbine. B. Combined cycle with an inter-cooled gas turbine. C. Combined cycle with a reheat gas turbine. D. Combined cycle with an inter-cooled reheat gas turbine. Results of this study indicate that the combined cycle with a simple gas turbine is the most practical of the four cycles studied with an efficiency of higher than 60%. The combined cycle with reheat gas turbine has the highest efficiency if a higher compressor exit air temperature and a high gas temperature (over 1000°C) to reheat the combustion system are used. A higher pressure ratio is required to optimize the cycle performance of the combined cycle with the ceramic turbine components than that with the metal turbine components because of reduced blade cooling air. To minimize leakage air for these higher pressure ratios, advanced seal technology should be applied to the gas turbines.

Thermodynamic analysis of hydraulic air compressor-gas turbine power plants

1997 ◽  
Vol 211 (5) ◽  
pp. 429-437 ◽  
Author(s):  
G Bidini ◽  
C N Grimaldi ◽  
L Postrioti
Keyword(s):  
Energy Conversion ◽  
Gas Turbine ◽  
Thermodynamic Analysis ◽  
Power Plants ◽  
Energy Conversion Efficiency ◽  
Combined Cycle ◽  
Air Compressor ◽  
Energy Conversion Systems ◽  
Combined Cycles ◽  
Air Compression

Nowadays, the most common way to improve energy conversion efficiency is the integration of different systems, thus achieving a better exploitation of the available exergy potential (e.g. combined cycles, cogeneration, etc.). As a means of producing power in hydroelectric plants hydraulic energy is commonly considered to be almost completely exploited. The aim of this paper is to analyse the possible integration of hydraulic energy sources with conventional, fossil fuel based systems; in particular, power plants based on the combination of an hydraulic air compressor (HAC) and a gas turbine are considered. In an HAC, air is entrained in the water flow in a downcomer pipe and compressed. Once separated from the water in a ‘stilling chamber’ at the bottom of the downpipe, the compressed air is supplied to a combustion chamber and then to a conventional gas turbine expander. An attractive characteristic of HACs is the capability, in principle, to perform an isothermal air compression instead of an adiabatic one, as in conventional compressors. In the present work, a thermodynamic analysis is presented of HAC-gas turbine energy conversion systems, which are compared with conventional hydroelectric and gas turbine power plants. The calculated performance levels of such systems are comparable to those of combined cycle plants, making further technical and economical investigations quite interesting.

Optimization of Advanced Liquid Natural Gas-Fuelled Combined Cycle Machinery Systems for a High-Speed Ferry

2012 ◽  
Author(s):  
Kari Anne Tveitaskog ◽  
Fredrik Haglind
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Dynamic Network ◽  
Combined Cycle ◽  
Working Fluid ◽  
Power Requirement ◽  
Pressure Steam ◽  
Combined Cycles ◽  
Liquid Natural Gas ◽  
Steam Cycle

This paper is aimed at designing and optimizing combined cycles for marine applications. For this purpose, an in-house numerical simulation tool called DNA (Dynamic Network Analysis) and a genetic algorithm-based optimization routine are used. The top cycle is modeled as the aero-derivative gas turbine LM2500, while four options for bottoming cycles are modeled. Firstly, a single pressure steam cycle, secondly a dual-pressure steam cycle, thirdly an ORC using toluene as the working fluid and an intermediate oil loop as the heat carrier, and lastly an ABC with inter-cooling are modeled. Furthermore, practical and operational aspects of using these three machinery systems for a high-speed ferry are discussed. Two scenarios are evaluated. The first scenario evaluates the combined cycles with a given power requirement, optimizing the combined cycle while operating the gas turbine at part load. The second scenario evaluates the combined cycle with the gas turbine operated at full load. For the first scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 46.3% and 48.2% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 45.6% and 41.9%, respectively. For the second scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 53.5% and 55.3% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 51.0% and 47.8%, respectively.

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