| Integrated Gasification Humid Air Turbine(IGHAT)cycle is a new power generation system which combines gasification technology together with humid air turbine(HAT)cycle.The gasification technology and HAT cycle are the represents of the clean coal technology and advanced gas turbine power generation system,respectively.The new power system draws great attention to the energy field because of its high specific power,high efficiency and low emission,and also because that it can utilize the coal as the fuel directly,which meets the Chinese special energy structure.However,IGHAT cycle is still on the theory research stage and there are only limited numbers of HAT cycle plants.Therefore,with the development of modeling and simulation technology,building simulation platform and designing control system of IGHAT cycle have a great significance for its development.The main works of this paper contains:Based on Shell entrained-flow gasifier,the relationship between pressure and flow is analyzed.Then the model based on volume-resistance characteristics method is built,utilizing state equations to calculate pressure and flow rate.The new model can well predict the volume inertia of the system and its influence on the pressure,temperature as well as gasification reaction speed and can show the transportation delay of gasifier.Furthermore,the control strategy based on this model is discussed and the temperature and heating value control is designed to analyze the coupling of the multiple-input multiple-output(MIMO)system and its influence on control effect.The decentralized PID control method and fuzzy control method are utilized to design control strategy.The results show that fuzzy control can consider the temperature and heating value control together,resulting in faster speed and lower deviation.Humidification experiments are done through a packing saturator test rig to analyze the heat and mass transfer properties.A novel saturator model is built based on operating line and saturation curve.The enthalpy difference between them is treated as the potential force for both heat and mass transfer,and the global transfer coefficient is utilized to describe these two processes.The new modeling method simplifies the calculation process and avoid the simulation error due to the fact that the two coefficients of conventional method are difficult to be obtained.The global transfer coefficient is analyzed by the experimental data of the saturator test rig.The results show that the water temperature is the max potential of heat and mass transfer while the air parameters and air-to-water flow ratio influence the global transfer coefficient more.The accuracy of the model is also proven through the experimental data.The gas turbine,heat exchanger component models and IGHAT cycle system model based on modular modeling method are built.The system is a non-iterative dynamic model with fast calculation speed,which can meet the requirement of realtime simulation.Then the HAT cycle test rig taken as the simulation object.The humidification and heating-up process of constant fuel rate experiment is simulated.The results show that the leakage loss,heat loss and power loss is the main reason that the system cannot achieve the design parameters.Then the dynamic responses of pressure and temperature of combustor,high-pressure turbine and power turbine are calculated.During the humidification process,the pressure of combustor increases 3715 Pa while the temperature decreases 63.2K,which is consistent with the experimental data and shows the accuracy of the system model.Based on the existing HAT cycle test rig,the IGHAT cycle system model is built with the combination of heat exchangers such as recuperator and economizer,as well as gasifier system.The fuel switch simulation is done first.Considering the operation experience of Integrated Gasification Combined Cycle(IGCC)and the simulation results,the lowest output limit for fuel switch is set as 60 kW.Then the saturator startup simulation is done.A feedforward is designed to avoid the oscillation caused by the power control.The surge margin of compressor is analyzed.The results show that the IGHAT cycle system decreases the surge margin to 13.7%.Although the margin is still higher than the alert limit 10%,it is much lower than the margin of simple cycle at 21.19%.An air bleed system should be considered due to this result.Based on the above analysis,considering the control experience of mature gas turbine power station,IGHAT control logic and strategy is designed preliminarily,containing startup control,power control,fuel switch control,saturator control and pressure ratio control.Based on the simulation results of IGHAT cycle system,the control logic is configured on Ovation distribution control system and an IGHAT cycle virtual control system platform is built.Taking the IGHAT cycle model as the control object,building the connection between model and control system,the model-in-the-loop control platform is eventually set up.The new platform built by Visual Studio,calls Ovation API and Windows API by MFC to build a shared memory zone to link model and control system.Finally,the simulation from full speed no load condition to full power condition is done by the model-in-loop platform,confirming the feasibility of the control logic on the real industry control system.Finally,a novel IGHAT cycle system based on Siemens V94.3A gas turbine is designed.A simulator based on this power plant is built through Ovation DCS.Then operation on this simulator is done.The output power of the IGHAT cycle reaches 403.255 MW with efficiency 42.71%.Low component efficiency caused by off-design performance and low humidity caused by high pressure is the main reasons that limits the system performance. |
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