A two-fluid model simulation of an industrial moving grate waste incinerator

Abstract

CFD modelling and simulation is an effective means of optimizing the design and operation of moving grate waste incinerators. Conventional approach models the grate combustion and the furnace combustion separately by using an in-bed/over-bed coupling procedure. In this paper, a comprehensive two-fluid reacting model that integrates the gas-solid grate incineration and the gas turbulent combustion in one scheme is developed for industrial incinerators. Realistic grate geometry and direct simultaneous coupling of the fuel bed and the freeboard gas phase are realized. According to different treatments of the solid phase, the whole incinerator is divided into three regions, namely the packed bed region, the fall region and the furnace region. The kinetic theory of granular flow (KTGF) is introduced to describe the rheological properties of waste particles, and the Ergun model is used for the gas-solid drag. Thermal conversion of wastes is characterized by the heterogeneous reactions of moisture evaporation, devolatilization, char-O2 combustion and the homogeneous reactions of hydrocarbons combustion. Distributions of temperatures and gas species are predicted and validated by measurements. Particle properties are calculated to reveal the grate incineration characteristics. Effects of waste throughput on the incineration are also investigated. Overall, the present model provides a new methodology of in-bed and over-bed integration for the moving grate incinerator simulation.