Integrated gasification combined cycle (IGCC) power plant design and technology
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Integrated Gasification Combined Cycle (IGCC) is rapidly emerging as one of the most promising technologies in power generation and is able to meet the most stringent emissions requirements. The IGCC systems are extremely clean and much more efficient than traditional coal fired power systems. The gasifier is the heart and most complicated unit operation with high temperatures and pressure variations in the Integrated Gasification Combined Cycle (IGCC). The dynamics inside a gasifier is very rapid and it is extremely complicated to control the high temperatures inside the gasifier and the synthesis gas (H2 + CO) composition coming out of the gasifier. This paper describes a novel technique that has been developed for varying and controlling the synthesis gas compositions coming out of the gasifier and temperature inside the gasifier by carbon dioxide gas recycle to the gasifier. In order to vary the synthesis gas composition, the gasifier temperature and other key parameters, the carbon dioxide recycle gas to the gasifier is manipulated instead of varying the coal, water and oxygen mass flow rates. A sensitivity analysis on the gasifier has been completed by varying the mass flow rate of carbon dioxide recycle gas and the oxygen gas without varying the coal slurry (coal +water) mass flow rate to analyze the synthesis gas composition, temperature, char conversion and other important parameters. Using the sensitivity analysis it has been showing that enhanced controllability of the gasifier in the IGCC is possible to meet the varying demands by recycling CO2 without the need of varying the coal, water and oxygen flow rates. The method is based on the idea that different output compositions can be achieved by making the carbon in coal slurry react with as an oxidizer instead of O2 with the help of Boudouard reaction (CO2 + C → 2CO). The two-stage oxygen blown entrained flow gasifier has been modeled using Computational Fluid Dynamics (CFD) and the coal gasification process was modeled using the Discrete Phase Method implemented in the Finite Volume FLUENT® CFD software. The physical and chemical processing of the coal slurry gasification is implemented by using FLUENT® User Defined Function’s (UDF’S). These UDF’s define the mechanism through which thecoal partiticles undergo moisture release, vaporization devolatilization, char oxidation and gasification processes. One important property of the gasifier in the Integrated Gasification Combined Cycle (IGCC) is that it can simultaneously produce synthesis gas for chemical processes as well as electricity, how much is generated of each can be balanced according to market demand.
Wood gas generator
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Integrated Gasification Combined Cycle (IGCC) is considered as a viable option for low emission power generation and carbon-dioxide sequestration. Modelling development and simulation study is essential part for the process of IGCC design and development. This PhD project is aiming to conduct the modelling and simulation study of IGCC power plant by building sub-modules such as gasifier, water gas shift reactor, acid gas removal unit, gas turbine and HRSG, etc. and connecting these modules together for the whole process study. In addition, the impact for the integration of IGCC with activated carbons-based pressure swing adsorption carbon capture process is investigated by using a PSA model developed and validated by University of Birmingham.
A simplified zero dimension gasification model is developed based on Texaco gasifier and validated by reference and industry data. The model development is based on mass balance, chemical equilibrium and energy balance. The prediction results for syngas contents concentrations are proved to be reasonably acceptable and the syngas contents changes with key input parameters changes are studied. The model is then used to generate a variable syngas stream to study the dynamic performance of the other sub-modules.
A one dimension dynamic model based on Shell slagging gasifier is developed. The model can successfully show the characteristics of slag layers formation and the syngas stream change with response to input parameters change. By using step rise of oxygen input and steam blast input, the dynamic performance of syngas temperature, syngas contents, slag mass flow rate and slag layers thickness is analysed and compared. It is found that oxygen input show relative larger impact on gasifier operation than steam blast for the studied working conditions.
Auxiliary modules in a gasification enabled plant and combined cycle power plant are modelled with Thermolib Software. Basic principles of this software are introduced. Simplified quench process, WGS with heat recovery, acid gas removal unit, gas turbine, HRSG and electrical generator are modelled by using the blocks from Thermolib. The simulation results show the dynamic changes of key output variables such as power output, syngas temperature and contents concentrations.
PSA model developed by UoB based on ACs is introduced and a 9 step 8 beds cycle model is used for the integration with IGCC model. This PSA model can achieve 80.89% CO2 capture rate with 87.33% of N2 recovery rate without any additional equipment. N2 is used to represent H2 for the simulation. Four cases for IGCC integrated with carbon capture are studied for the energy penalty analysis. It is predicted that the efficiency loss for IGCC power plant with 80.89% carbon capture will be 10.96%. The limitations of using N2 to represent H2 for the PSA model are discussed and it is predicted the real efficiency loss will be lower than the simulation results.
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Water-gas shift reaction
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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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To introduce the integrated coal gasification combined cycle ( IGCC) system in terms of its formation, gasification, purification, and the matching of gas turbine and steam turbine etc. To discuss the key techniques and give the development trend.
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Dynamic simulation
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This paper has calculated the related gasification indicators of the jet of the gasifier by using actual data.At the same time,analyzed performance of the two gasifier which is send coal by the dry and wet coal send.Focus on the analysis of the content of fly ash and gas composition on the performance of gasifier.And put forward measures to improve the efficiency of IGCC power supply-related.As an important reference provided for the selection and adjustment,fully integrated performance evaluation in the IGCC gasifier system.
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The integrated gasification combined cycle (IGCC) is a power generation technology which combines clean coal technology with a combined cycle. The system modeling is significant for design, operation and maintenance of the IGCC power plant. However, the previous IGCC modeling methods only contained a simplified compartment gasifier model, which is useful to consider the heat transfer and chemical reaction inside the gasifier, but cannot analyze the pressure and flow distribution. In order to obtain a more accurate model of IGCC system, the volume-resistance technique and modular modeling method are utilized in this paper. The new model can depict the dynamic response and distribution characteristics of the gasifier, as well as their influence on the IGCC system. The simulation result of the gasifier and IGCC system shows an obvious delay after considering pressure and flow distribution. Therefore, the proposed IGCC system model can obtain a more reliable result when considering the distribution characteristics of the gasifier.
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