Numerical simulation of entrained flow gasification based on properties and kinetic characteristics of pulverized coal particles

Abstract

Gasification kinetic parameters of coal char based on the random pore (RPM) model are obtained with CO2 and H2O using a high-pressure thermogravimetry analysis (TGA) under atmospheric pressure and 4.0 MPa pressure, considering the influence of internal diffusion and particle structure varying with carbon conversion. The Chemical Percolation Devolatilization (CPD) model is used to modify the actual volatile content. Through the coupling of the gasification kinetic reaction model, a comprehensive numerical simulation method of the entrained flow gasification process is established. This method is used to simulate the typical gasifier of HTL (a gasification technology of Changzheng Engineering Co.) in an industrial plant. The research shows that the intrinsic reaction parameters obtained by TGA under high pressure can give a more reasonable reaction state of coal char particles in the gasifier than that measured under atmospheric pressure, and the simulation results are in good agreement with the industrial data. In addition, HTL adopts a single top-fired burner and multi-channel swirling feed type. The particles are entrained and mixed with swirling oxygen, and the combustion reaction is completed quickly in the upper part of the gasifier. In contrast, the gasification reactions are relatively slow and mostly dominate in the recirculation zone and pipe flow zone, leading to high carbon conversion.

Three-dimensional Numerical Simulation of Entrained-Flow Gasifier and Influence of Coal Distribution at the Inlet

“…With the consideration of the reactants diffusion to the inner pore surface of particles, the reaction rate R for an nth-order reaction is expressed in Equation (2) [12] .…”

“…The particle structure is changed with the conversion of char, s in was the mass specific surface area, it is determined by the particle structure parameter Ψ 0 which according to the RPM (random pore model) [12] . Ψ 0 is dimensionless and it is calculated from TGA experimental [12] . The above char conversion model is programmed and applied in ANSYS Fluent software in the form of the UDF (user-defined function).…”