Numerical simulation on the deposition characteristics of MSWI fly ash particles in a cyclone furnace

Abstract

In melting municipal solid waste incineration (MSWI) fly ash by cyclone furnace, the deposition characteristics of particles affect the slag flow and the secondary MSWI fly ash formation. In this study, the composition mechanism based on critical viscosity is selected as the particle deposition model to predict the deposition and rebound of particles on the furnace wall. The Riboud model with an accurate viscosity prediction performance is selected, then the particle deposition model is integrated into a commercial computational fluid dynamics (CFD) solver through the user-defined function (UDF) to realize the coupling of particle motion and deposition process. The results show that under the same case, the deposition rate decreases obviously with the increase of MSWI fly ash particle size. And the escape rate reaches a maximum at particle size 120 μm. Controlling the particle size of fly ash particles within 60 μm can effectively reduce the generation of secondary MSWI fly ash. During the forward movement of the fly ash inlet position, the escape of MSWI fly ash particles with large particle sizes has been significantly weakened. This measure not only lowers the post-treatment cost but also dramatically reduces the pretreatment step of MSWI fly ash before the melting and solidification process. In addition, the deposition rate and quality will reach the maximum values, respectively, along with gradually increasing MSWI fly ash input flow. Overall, this study has the guiding significance for reducing the pretreatment steps and post-treatment costs of MSWI fly ash by melting in the cyclone furnace.

Keywords: Cyclone furnace; MSWI fly ash; Particle deposition model; Particle deposition rate; Particle escape rate.