Modelling and Simulation of Transient Performance of the Semi-Closed O2/CO2 Gas Turbine Cycle for CO2-Capture

2003 ◽  
Author(s):  
Ragnhild E. Ulfsnes ◽  
Olav Bolland ◽  
Kristin Jordal
Keyword(s):  
Water Vapor ◽  
Specific Heat ◽  
Gas Turbine ◽  
Transient Behavior ◽  
Cycle Performance ◽  
Working Fluid ◽  
Transient Event ◽  
Co2 Gas ◽  
Specific Heat Ratio ◽  
Gas Turbine Cycle

One of the concepts proposed for capture of CO2 in power production from gaseous fossil fuels is the semi-closed O2/CO2 gas turbine cycle. The semi-closed O2/CO2 gas turbine cycle has a near to stoichiometric combustion with oxygen, producing CO2 and water vapor as the combustion products. The water vapor is condensed and removed from the process, the remaining gas, primarily CO2, is mainly recycled to keep turbine inlet temperature at a permissible level. A model for predicting transient behavior of the semi-closed O2/CO2 gas turbine cycle is presented. The model is implemented in the simulation tool gPROMS (Process System Enterprise Ltd.), and simulations are performed to investigate two different issues. The first issue is to see how different cycle performance variables interact during transient behavior; the second is to investigate how cycle calculations are affected when including the gas constant and the specific heat ratio in compressor characteristics. The simulations show that the near to stoichiometric combustion and the working fluid recycle introduce a high interaction between the different cycle components and variables. This makes it very difficult to analytically predict the cycle performance during a transient event, i.e. simulations are necessary. It is also found that, except for the shaft speed calculation, the introduction of gas constant and specific heat ratio dependence on the compressor performance map will have only a minor influence on the process performance.

scholarly journals Thermodynamic Analysis of Different Configurations of Combined Cycle Power Plants

2015 ◽  
Vol 5 (2) ◽  
pp. 89
Author(s):  
Munzer S. Y. Ebaid ◽  
Qusai Z. Al-hamdan
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Maximum Efficiency ◽  
Specific Work ◽  
Slight Effect ◽  
Turbine Engine ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

<p class="1Body">Several modifications have been made to the simple gas turbine cycle in order to increase its thermal efficiency but within the thermal and mechanical stress constrain, the efficiency still ranges between 38 and 42%. The concept of using combined cycle power or CPP plant would be more attractive in hot countries than the combined heat and power or CHP plant. The current work deals with the performance of different configurations of the gas turbine engine operating as a part of the combined cycle power plant. The results showed that the maximum CPP cycle efficiency would be at a point for which the gas turbine cycle would have neither its maximum efficiency nor its maximum specific work output. It has been shown that supplementary heating or gas turbine reheating would decrease the CPP cycle efficiency; hence, it could only be justified at low gas turbine inlet temperatures. Also it has been shown that although gas turbine intercooling would enhance the performance of the gas turbine cycle, it would have only a slight effect on the CPP cycle performance.</p>

Advanced High Temperature Gas-Cooled Reactor Systems

2008 ◽  
Author(s):  
Yasuyoshi Kato
Keyword(s):  
Gas Turbine ◽  
Power Conversion ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Co2 Gas ◽  
Flow Channels ◽  
Turbine Inlet ◽  
Conversion System ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Three systems have been proposed for advanced high temperature gas-cooled reactors (HTGRs): a supercritical carbon dioxide (S-CO2) gas turbine power conversion system; a new MicroChannel Heat Exchanger (MCHE); and a once-through-then-out (OTTO) refueling scheme with burnable poison (BP) loading. An S-CO2 gas turbine cycle attains higher cycle efficiency than a He gas turbine cycle due to reduced compression work around the critical point of CO2. Considering temperature lowering at the turbine inlet by 30°C through the intermediate heat exchange, the S-CO2 indirect cycle achieves efficiency of 53.8% at turbine inlet temperature of 820°C and turbine inlet pressure of 20 MPa. This cycle efficiency value is higher by 4.5% than that (49.3%) of a He direct cycle at turbine inlet temperature of 850°C and 7 MPa. A new MCHE has been proposed as intermediate heat exchangers between the primary cooling He loop and the secondary S-CO2 gas turbine power conversion system; and recuperators of the S-CO2 gas turbine power conversion system. This MCHE has discontinuous “S”-shape fins providing flow channels with near sine curves. Its pressure drop is one-sixth reference to the conventional MCHE with zigzag flow channel configuration while the same high heat transfer performance inherits. The pressure drop reduction is ascribed to suppression of recirculation flows and eddies that appears around bend corners of zigzag flow channels in the conventional MCHE. An optimal BP loading in an OTTO refueling scheme eliminates the drawback of its excessively high axial power peaking factor, reducing the power peaking factor from 4.44 to about 1.7; and inheriting advantages over the multi-pass scheme because of the lack of fuel handling and integrity checking systems; and reloading. Because of the power peaking factor reduction, the maximum fuel temperatures are lower than the maximum permissible values of 1250°C for normal operation and 1600°C during a depressurization accident.

A Novel Brayton Cycle With the Integration of Liquid Hydrogen Cryogenic Exergy Utilization

2005 ◽  
Author(s):  
Na Zhang ◽  
Noam Lior
Keyword(s):  
Energy Efficiency ◽  
Gas Turbine ◽  
Liquid Hydrogen ◽  
Utilization Efficiency ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Evaporation Process ◽  
Impact Reduction ◽  
Gas Turbine Cycle

Stored or transported liquid hydrogen for use in power generation needs to be vaporized before combustion. Much energy was invested in the H2 liquefaction process, and recovery of as much of this energy as possible in the re-evaporation process will contribute to both the overall energy budget of the hydrogen use process, and to environmental impact reduction. A new gas turbine cycle is proposed with liquefied hydrogen (LH2) cryogenic exergy utilization. It is a semi-closed recuperative gas turbine cycle with nitrogen as the working fluid. By integration with the liquid H2 evaporation process, the inlet temperature of the compressor is kept very low, and thus the required compression work could be reduced significantly. Internal-fired combustion is adopted which allows a very high turbine inlet temperature, and a higher average heat input temperature is achieved also by internal heat recuperation. As a result, the cycle ha ry attractive thermal performance with the predicted energy efficiency over 79%. The choice of N2 as the working fluid is to allow the use of air as the oxidant in the combustor. The oxygen in the air combines with the fuel H2 to form water, which is easily separated from the N2 by condensation, leaving the N2 as the working fluid. The quantity of this working fluid in the system is maintained constant by continuously evacuating from the system the same amount that is introduced with the air. The cycle is environmentally friendly because no CO2 and other pollutant are emitted. An exergy analysis is conducted to identify the exergy losses in the components and the potential for further system improvement. The biggest exergy destruction is found occurring in the LH2 evaporator due to the relatively higher heat transfer temperature difference. The energy efficiency and exergy efficiency are 79% and 52%, respectively. The system has a back-work ratio only 1/4 of that in a Brayton cycle with ambient as the heat sink, and thus can produce 30.14 MW (53.9%) more work, with the LH2 cryogenic exergy utilization efficiency of 54%.

A Solar Gas Turbine Cycle With Super-Critical Carbon Dioxide as a Working Fluid

2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Molten Salt ◽  
Gas Turbine ◽  
Thermal Power ◽  
Working Fluid ◽  
Regenerative Heat ◽  
Operation Conditions ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Solar thermal power generation system equipped with molten salt thermal storage offers continuous operation at a rated power independent of the variation of insolation. A gas turbine cycle for solar applications is studied which works in a moderate temperature range (600–850K) where molten salt stays as liquid stably. It is found that a closed cycle with super-critical state of carbon dioxide as a working fluid is a promising candidate for solar application. The cycle featured in smaller compressor work would achieve high cycle efficiency if cycle configuration and operation conditions are chosen properly. The temperature effectiveness of a regenerative heat exchanger is shown to govern the efficiency. Under the condition of 98% temperature effectiveness, the regenerative cycle with pre- and inter-cooling provides cycle efficiency of as much as 47%. A novel heat exchanger design to realize such a high temperature effectiveness is also presented.

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