Sequential Modeling of Coal Volatile Combustion in Fluidized Bed Reactors

Abstract

A sequential model to predict the combustion behavior of a coal’s volatile matter during coal gasification, simulated by propane in a combustor is introduced and evaluated. For this, an industrial fluidized bed combustor is divided into several submultiphase reactors based on the physical behavior of interacting phases. This is achieved by considering the volatile gas as a completely mixed stream passing through the emulsion phase and as plug flow through the bubble phase. To simulate the events inside each subreactor, two models were used: a dynamic two-phase model for hydrodynamic characterization (called the hydrodynamic submodel) and a reaction kinetic submodel for obtaining the chemical evolution of subreactors. Also, an energy balance and temperature-dependent distribution of bubble sizes were embedded in the model. Considering the physical and chemical characteristics of the system, it has become possible to specify the proper number of simulation stages by introducing a new dimensionless number. The model was compared to several sets of experimental measurements in terms of the most important operating parameters derived from the literature, and an excellent consistency was achieved. The main motivation behind the current study was to provide a reliable, yet easy-to-achieve, modeling and simulation methodology by fundamental chemical engineering concepts to predict aspects of the behavior of volatile matter in processes producing energy from coal. This work opens up a new way of modeling coal’s volatile matter combustion, especially for its optimization and scale up.

One-Dimensional Modeling of an Entrained Coal Gasification Process Using Kinetic Parameters

“…Pulverized coal and hot gas stream of steam and oxygen are mixed at the reactor entrance and travel concurrently through the reactor. The dispersion of coal in gas is considered to move in plug flow axially through the reactor [16,17]. In the present model, we followed a partitioning zonal approach.…”

Global Gas-Phase Oxidation Rates of Select Products from the Fast Pyrolysis of Lignocellulose

“…To calculate the gas apportioned to each PFR and CSTR, several correlations from the literature were used to calculate the two-phase theory parameters (Table 3). 29,30 The two-phase theory correlations (Table 3) were derived from experimental studies of fluidized beds. While several of the parameters are universally accepted (e.g., minimum fluidization velocity and Archimedes number), several methods for calculating the bubble diameter have been proposed.…”

Three-dimensional full loop simulation of solids circulation in an interconnected fluidized bed

“…(31), which was widely employed to calculate the minimum fluidized velocity for Geldart type B particles [42][43][44][45]. To investigate the effect of operating gas velocity on the solids circulation rate, the minimum fluidization velocity was calculated as 0.02367 m/s according to Eq.…”