EXERGETIC COMPARISON OF TWO IGCC POWER PLANTS WITH DIFFERENT COAL FEED DESIGN
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The characteristics of Texaco gasifier and shell gasifier in IGCC gasification sub-system are introduced briefly.The influence of air separation sub-system to the IGCC Integration characteristics was discussed,The features of gas turbine which is suited to burn low heat value syngas was also described.Four ways of carbon dioxide capture are analyzed.The key restrictive factors for IGCC faster development were pointed out.It was pointed out finally that the IGCC will have stronger and stronger competitiveness through continuous researching and development.
Wood gas generator
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The selection of the gasifier in an Integrated Gasification Combined Cycle (IGCC) plant affects both downstream process configurations and net plant efficiency considerably. It is well known that a Shell gasifier using dry coal has lower operating pressure, higher carbon conversion, lower CO2 production and lower H2/CO ratio compared to a General Electric Energy (GEE) gasifier using coal slurry. These differences also affect how to configure downstream processes when an IGCC is retrofitted for carbon capture. The net plant efficiency decreases by different extents depending on the gasifier type as shown in the DOE NETL report The aim of this study is to elucidate how the differences between the two gasifiers correspond to the difference in plant performance without and with carbon capture. To achieve this, detailed process simulations of the two IGCC plants and an integrated Selexol carbon capture unit have been carried out based on literature configurations using the commercial software Honeywell UniSim Design R400®. From the analysis of the results an explanation is presented as to why the wet slurry gasifier configuration has a lower net efficiency loss when the carbon capture unit is integrated.
Wood gas generator
Coal slurry
Carbon fibers
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Using software ThermoFlex,a model of 200 MW IGCC system was established based on two-stage coal-slurry gasification technology,so as to study the effects of following factors on performance of the IGCC system,such as the gasification temperature,coal-slurry concentration,gasification pressure and purity of oxygen,etc.Results show that both the gross and net efficiency of power generation decrease with rising gasification temperature and pressure;higher net efficiency is to be obtained at a flow of higher purity oxgen;raising coal supply ratio(γsc) at the second stage may help to improve the system performance under same conditions of gasification temperature(or purity of oxygen,or gasification pressure).Whereas under the varying conditions of coal-slurry concentration,the designed value of carbon conversion can be achieved based on adjustment of oxygen-coal mass ratio along with the variation of γsc.
Wood gas generator
Coal slurry
Carbon fibers
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An integrated gasification combined cycle (IGCC) is a technology that uses a high pressure gasifier to turn coal, a carbon based fuels into pressurized gas, this is also known as synthesis gas or syngas. The IGCC system consist of 4 main structures; air compression and separation unit, gasifier, combustion and steam turbine and heat recovery generator.A meta-analysis was conducted to investigate possible relationships between the efficiency and types of gasifiers used in the integrated gasification combined cycle in terms of the key thermodynamic laws. Through this analysis correlations were established between varying coal compositions, types of gasification systems and thermal efficiency. It was found that the updraft gasifier had the highest efficiency across most reports, thus making this procedure the most efficient with today’s current knowledge in terms of the thermodynamic principles associated with coal-fired power plants. It was also established that coal with lower moisture content will generally allow a system to be more efficient.
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Thermal efficiency
Air separation
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Gasifier is one of the critical devices in an integrated gasification combined cycle(IGCC) power plant,and the selection of gasifiers has significant impact on the overall efficiency of the whole system.In this study,four different IGCC configurations,employing Shell gasifier,GE gasifier with quench,GE gasifier with heat recovering,and MHI air-blown gasifier,were designed and simulated by GT Pro software respectively.Based on the obtained performance parameters through simulation,both of the efficiency variations of IGCC system when employing various entrained-flow gasification technologies and the inherent mechanisms causing these changes were analyzed.Results show that the energy conversion and distribution of the whole system depend heavily on the feedstock characteristics,choosing of oxidants and methods of syngas sensible heat recovery.In the IGCC system employing Shell gasifier,most of the energy in coal is converted to the chemical energy of syngas,which can contribute to a high overall efficiency,whereas in the systems employing GE gasifier with heat recovery and MHI air-blown gasifier,a larger portion of energy in coal is converted to the sensible heat of syngas,which could be utilized in the following processes.
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By way of analyzing the operating characteristics of a gasifier in an integrated gasification combined cycle (IGCC) power plant the basic configuration of a control system of the gasifier has been determined. On the basis of the gasifier dynamic characteristics a control system was designed. The results of its simulation indicate that the coupling factor between the two major links of the gasifier, namely, its temperature and syngas heating value, is relatively low. By using the control system designed by the authors its is possible to fulfill the main control aim of the gasifier.
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Wood gas generator
Exergy efficiency
Air separation
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Wood gas generator
Bituminous coal
Coal slurry
Process Simulation
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Integrated gasification combined cycle (IGCC) power plants have become more attractive after the emission regulations of the thermal power plants. IGCC power plants enable to control emissions which cause global warming. Low grade lignites, biomass and wastes can be utilized by this technology. This study deals with the thermodynamic analysis of an IGCC power plant. Energy and exergy analysis are carried out for a Texaco type gasifier, one stage, oxygen blown and slurry fed. Cold gas cleaning (fuel gas treatment) system is considered for the simulations, performed in THERMOFLEX software. A parametric study is also carried out to show the effects of the O2 purity, fuel supply temperature, gasifier temperature and H2O content of the slurry to the IGCC performance. Net power and net electric efficiency are calculated to be 389.669 MW and 43.53% respectively. Exergy efficiency of the simulated IGCC is found to be 40.36% and the highest exergy destruction is observed in gasifier and the combustion chamber of the gas turbine.
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On this paper,on the basis of introducing some important requirements of technical performances for gasifiers used in IGCC power plant,analysed the differences of those technical characteristics between Shell gasifier and Texaco gasifier in detail,then the effects of those differences on net efficiency and cost of electricity of IGCC power plant were further discussed.
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