Sequential modeling of coal volatile combustion in fluidized bed reactors

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.