Dynamic Simulation Of Opposed Multi-Burner Coal-Water Slurry Gasification System

Dynamic simulation of the gasifier, which is essential for gaining its dynamic characteristics, can help to develop a control system and optimize operational strategies. This work presents a steady-state model of a commercial-scale opposed multi-burner(OMB) gasifier and a dynamic model of the gasification system with the UniSim.In this study, a reactor network model (RNM) was established based on the simplified flow field of the gasifier and the reaction kinetic models. The particle and gas RTD of RNM are obtained by the Markov chain stochastic model. The gas and particle RTD for RNM are in accord with the results of computational fluid dynamics (CFD). In the steady-state simulation, the simulation results show good agreement with the industrial data. To ensure discharging slags in liquid, the optimal oxygen-coal ratio in operation should be controlled in a value of 476Nm3(O2)/m3 (CWS) or so with 60.5 percent of the CWS for the Shenfu coal. The impact of the coal-water slurry (CWS) concentration, oxygen concentration, heat loss, CWS flow and oxygen flow to the gasification results are quantitative analysed.The steady-state model can be transformed into the dynamic model through defining the equipments sizes, adding the valves and the control system. The pressure driven solution is adopted by the dynamic model. With the dynamic model, the specific online reset process (ORP) of the OMB CWS gasifier is studied firstly. For ORP, the peak deviation of the temperature is about 33℃, and that of the pressure is 106 kPa. The simulation results indicate that the fluctuation ranges of the operation temperature and pressure of the gasifier are controllable, and the OMB CWS gasifier can be operated in security with liquid slagging. In addition, a temperature control strategy, which is cascade controlled by "temperature control-oxygen/coal ratio control-oxygen flow control", is established. The dynamic responses of gasification system to the ±1.5 percentage point disturbances for the CWS concentration are investigated. The peak deviation of the temperature is about 24-26℃ under the tardiness temperature control. Four different temperature control strategies are investigated to control the CWS concentration drop. An appropriate temperature control strategy is adopted to investigate the four disturbances for the same temperature change. This parameter of temperature controller works well. A new temperature control loop is established to deal with the heat value of coal variation ±5%.