High-pressure entrained flow coal gasification is becoming increasingly important particularly in the development of Integrated Coal Gasification Combined Cycle (IGCC) technology for the production of fuels, chemicals and electricity. Coal gasification is a complex thermochemical process that can be divided in three different phases: pyrolysis, char gasification and gas phase reactions. Pyrolysis is the initial stage in any gasification process and it is modeled by applying a single rate approach. Heterogeneous reaction modeling includes the diffusion mechanism of the released gas that occurs on particles? surface. Species diffusion models are implemented via specific User Defined Functions (UDFs) developed for each gas separately. Ash deposition and slag dynamics are investigated using a specifically developed Lagrangian Particle and Slag Tracking code that elaborates particle trajectories, particle deposition (visco-elastic sticky propensity) and slag dynamics post-processing CFD flow field data. Mesh nodes are displaced according to the predicted local deposit thickness. Visco-elastic models are used to evaluated ash mechanical properties and particle adhesion behavior.Local node deposit properties, such as node temperature and heat transfer, are updated at the specific nodes using a unique grid reconstruction, where deposition has occurred (local deposit thickness greater than zero). Therefore, CFD computation takes the updated deposit boundary conditions into account. Due to the local deposit growth, heat exchange through the gasifier walls is reduced and the inner gas temperature therefore increases. If the inner temperature reaches the deposit melting temperature (which depends on the specific deposit composition) the deposit may melt and the slag begins to flow down. The proposed computational strategy aims to investigate progressive deposition and slag dynamics by means of a detailed gasification kinetic mechanism and a specifically developed numerical post-processing tool to predict ash deposition, deposit built-up and growth. The final goal is to numerically describe and predict the loss of performance of slag gasifiers via sequential steady-state simulations. The numerical strategy has been tested on an idealized entrained flow slag gasifier. The thermodynamics of pyrolysis, homogeneous and heterogeneous reactions of coal gasification process is studied and developed in an ongoing project named HotVeGas (1-50 bar, 1200-1800 oC) at the Institute for Energy Systems (Lehrstuhl für Energiesysteme) at the Technische Universität München.
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High-pressure entrained flow coal gasification is becoming increasingly important particularly in the development of Integrated Coal Gasification Combined Cycle (IGCC) technology for the production of fuels, chemicals and electricity. Coal gasification is a complex thermochemical process that can be divided in three different phases: pyrolysis, char gasification and gas phase reactions. Pyrolysis is the initial stage in any gasification process and it is modeled by applying a single rate approac...
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