Thesis Outlines

There are eight chapters in this thesis. Chapter 1 introduces the background of project and outlines the study aims and methodology. Meanwhile, the publications during the period of the Ph.D. study are listed in the next section.

Chapter 2 provides a detailed description of an IGCC power plant. The history of gasification technologies and the widely used commercial gasification technologies are outlined and compared. The working principles of shift reactor, sulphur removal unit and combined cycle power plant are depicted in this chapter as well. This chapter is aiming to reveal the whole picture of the IGCC power plant and the blueprint of the IGCC model developed in this work.

Chapter 3 presents the development of a zero-dimension Texaco gasifier model. This model is capable of predicting the syngas composition with the given feed stock and oxidant parameters. The detailed derivation of mass balance and energy balance equations are outlined. The model is then validated by comparing the simulation results of different types of coal under pre-defined working conditions. The comparison of simulation results with data from published references and industry data provided by THU reveals that this model can

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give accurate prediction of syngas stream. Meanwhile, the impact of the key parameter changes such as coal slurry concentration, oxygen/coal ratio and working pressure are studied. To show the model flexibility, it is also used for the steady state simulation of Shell gasifier in the end of this chapter.

Chapter 4 focuses on the development of a dynamic model of Shell-slagging gasifier. Shell gasifier is selected because its unique slagging characteristic offers conservation of energy and mass. The detailed derivation of mass balance and energy balance equations are mainly presented in this chapter, the dynamic performance of Shell gasifier (slag layers thickness, syngas output contents concentrations, temperature files of syngas, slag layers and refractory wall and cold gas efficiency) with step changes of oxygen and steam inputs are studied as well.

Chapter 5 presents the background knowledge of Thermolib toolbox first; the gas phase and liquid phase calculation equations are detailed. The theories used in Thermolib for stream state calculation are the main focus in this part. Since the auxiliary modules of the gasification enabled module plant (GEM) are developed based on Thermolib, it is necessary to introduce the theory to explain the basic working principles of Thermolib blocks. The second part of the chapter introduces the modules of water quench for Texaco gasifier, gas quench and heat recovery for Shell gasifier, shift reactor with heat recovery for both Texaco and Shell gasifiers. The heat exchanger which utilises heat released by the endothermic water gas shift reaction is modelled to study the process of generating low pressure (LP) and high pressure (HP) steam for the HRSG module in power generation section. The shifted syngas is then treated by COS hydrolysis reactor and a simplified H2S removal unit, the sulphur removal model is built to represent the process of removing the sulphides.

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Chapter 6 starts from outline of the development of power generation plant, which is formed by gas turbine, HRSG and electricity generator. The gas turbine module is developed based on Brayton cycle while the single stage HRSG is developed based on Rankine cycle. In order to study the integration of shift reactor with power generation plant, a two stage HRSG is developed and validated based on an internal research report (M.Karmarkar, 2005). The dynamic performance of the combined cycle based on Texaco gasifier is studied.

In order to study the impact of ACs-based PSA unit to the IGCC power plant, the experiment and simulation work conducted by the University of Birmingham is introduced in Chapter 7. The work starts from the pure isotherm tests for two ACs samples (unmodified AC and modified AC). N2 is used to represent H2 in this part. Several isotherm models are built and compared for the adsorption capacity prediction, which aims to provide a viable model to predict the cyclic outputs of the PSA process. The multicomponent DSL model is found to give the best prediction results for CO2/N2 mixture adsorption; it is then used as the basic unit for PSA cyclic model. Finally the 9 steps 8 beds PSA model simulation results provide relative high purity and capture rate for both of CO2 and N2. The results are used to build a model which is then connected with the IGCC power plant model; the efficiency losses on different CO2 capture rate are then simulated. At the end of Chapter 7, the potential of using CO2/H2 for the PSA process is discussed based on the experiment data provided by the University of Nottingham; it is concluded that the CO2/N2 predicts a worse separation than CO2/H2 separation, which indicates that the actual efficiency losses for CO2/H2 separation should be lower.

Chapter 8 provides the main conclusions and limitations of the project work. The potential future work is discussed and suggested in the chapter.

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Appendix A detailed a research project based on the combined cycle power (CHP) plant elaborated on the campus of the University of Warwick. The model is developed with Thermolib and Simulink and simplified controllers are applied. The CHP model simulation results for different seasons are compared with the operation data collected from the University of Warwick and the dynamic performance of the CHP power plant is analysed.