| The Integrated Gasification Humid Air Turbine Cycle (IGHAT) combines the advantages of advanced coal gasification technology Integrated Coal Gasification Combined Cycle (IGCC) and high performance Humid Air Turbine (HAT) Cycle, which is a high-efficiency, low-consumption and low -specific investment coal-cleaning utilization energy-saving power generation system. Note that the system of IGHAT is complex and difficult to be controlled, therefore, the research of IGHAT is still at theoretical stage. In order to push this high-efficiency clean power generation technology into the engineering test stage, the steady-state and dynamic performance is necessary to be studied. There have been fairly perfect models for steam turbine system, compressor, gas turbine and combustion chamber etc. for IGHAT system. With this background, the purpose of this thesis is to establish theoretical models and carrying out the steady-state and dynamic simulation study on the key components of IGHAT, gasifier and saturator, design and build the saturator experimental system, discuss and analyze the heat transfer and mass transfer performance and gas-liquid flow characteristic, and validating the saturator model with experimental data.In order to achieve the research objective mentioned above, the work is expanded from three aspects:According to the processing feature of Shell gasifier, the coal gasification reactions, heat-transfer between gas side and slag side, phase change of slag and flow behavior of fluid slag layer was analyzed and discussed. A coal gasification model was built based on mass conservation, momentum conservation and energy conservation, which can describe the steady-state and dynamic behavior of the outlet variables of gasifier including the gasification temperature, coal gas component contents, thickness of solid slag layer and fluid slag layer.Based on the related parameters of the gasifier in Demkolec IGCC demonstration project, the steady-state and dynamic simulation research of El Cerrejon Coal, Drayton Coal, petroleum Coke and Datong Coal was carried out. In steady-state simulation, not only the influence of the oxygen-to-coal ratio and steam-to-coal ratio into furnace on the coal gas component contents, gasification temperature and thickness of slag layer was analyzed, but also the variation characteristics of gasification and slag layer thickness under different slag specific heat and slag deposit flux was obtained. The dynamic response rules of key outlet variables were obtained when the inlet oxygen-to-coal ratio and stem-to-coal ratio undergoes a fundamental step change. It is found that all the outlet variables have long-time inertial elements, in which, the response time of gas side variables are shorter than that of slag side variables. Otherwise the dynamic response rules of gas side variables and gasification temperature under different coals and physical properties of slag were compared, and it is found that the slag specific heat showed obvious influence on steady-state value of the outlet variables, and the slag deposit flux showed obvious influence on dynamic response time.According to packed saturator, the heat-transfer and mass-transfer characteristic of air side, water side and packing side and the gas-liquid flow characteristic in packing channels. Based on mass conservation, momentum conservation and energy conservation, the governing equations of air, water and packing are built. The saturator was subdivided into several cells in the air flow direction, and each cell was modeled individually. The model was built, connected and solved on Simulink environment by using Runge-Kutta method, which can describe the steady-state and dynamic behavior of the outlet variables of each cell of saturator including the state-variables of air and liquid fluid, packing pressure drop and packing liquid holdup.The model convergence and the rationality of cells number were analyzed, and the steady-state and dynamic simulation study was carried out based on the design condition of Swedish demonstration unit. In steady-state simulation, the distribution of the state-variables of air and liquid fluid, heat-transfer and mass-transfer flow in the axial direction was presented, the results show that the heat-transfer and mass-transfer flow in each cell increases in air flow direction. Also the influence rules on outlet variables under different inlet variables were analyzed and discussed in detail. The dynamic response rules of outlet variables of packed saturator caused by the disturbance on inlet variables were obtained in the dynamic simulation study. Under the design condition, when there is a step change on inlet variables, the outlet variables show different inertia time. Find that the outlet temperature takes 50s to stabilize at a new value, which is longer than pressure drop and liquid holdup.An experimental system of packed saturator was designed and built, which completed the online measuring and collecting of temperature, humidity, flow and pressure of air and water, and presented an indirect calculating method to get the packing liquid holdup during the condition process by using the weight and liquid level data. The related steady-state and dynamic experiment study of the saturator packed with 250Y metal mellaple packing was carried out under laboratory environment. The steady-state experimental results present the variation rules of heat-transfer, mass-transfer and air-liquid flow variables, which indicate that the water-to-air ratio couldn't be used as the only criterion on judging the performance of saturator, and the inlet flow should be considered together, viz. the air-liquid load. Based on the pressure drop data of dry packing and with different water inlet flow, a pressure drop correlating equation according to 250Y metal mellaple packing was presented. The dynamic experimental results obtain the response curves of outlet variables of saturator when there is a disturbance on inlet variables, which agree with the simulation result under the same condition well.
|
PDF Full Text Request