Fluidynamics Modelling for a Fixed Bed Gasifier Using Laplace Transform Finite Difference Method

Abstract

The fluidynamics presented in this paper for a fixed bed gasifier consists of estimating the volume fraction fields of gas and solid phases, as well as the velocity fields of gas and solid phases and the pressure inside the fixed bed. However, understanding of the flow characteristics has an important role in understanding of the operation of the gasifier. The analyzed system consists of the fundamental equations of mass balance for the gas and solid phases, as well as the equations of momentum balance for gas and solid phases and an equation for the pressure given by the sum of the momentum balance equations of the gas and solid phases. The sets of equations developed form a system of one-dimensional partial differential equations (PDEs). The PDEs system has been transformed in a coupled ordinary differential equation (ODEs) system using Laplace Transform. The ODEs system has been solved using an implementation of the finite difference method (FDM). The objective of this work is to obtain the profiles of state variables such as volume fraction of gas (ɛg) and solid phases (ɛs), the velocity profiles of gas (vg) and solid phase (vs) and pressure field (pf).