Eulerian-eulerian modeling of the desulphurisation process in a coal bubbling fluidised bed

Abstract

Computational fluid dynamics has proven to be a viable tool for simulating the processes that take place in fluidised beds. Increased computational power allows for non-invasive simulations for complex geometries and wide parameter ranges to be carried out which would be difficult and expensive to perform experimentally. Whilst Eulerian-Lagrangian modelling of the gaseous and particulate phases provides detailed information of the particle dynamics on a micro-scale its application to fluidised bed technologies is computationally exhaustive due to the large number of particles present within the bed. Eulerian-Eulerian modelling reduces the computational time and expense significantly and the inclusion of the kinetic theory of granular flow provides information on the particle collisions thus proving to be a viable tool for the modelling of fluidised bed technologies. Its utilisation in the studies of hydrodynamic and heat transfer processes in fluidised beds has been widely researched, however, the inclusion of reaction kinetics is still in the early stages due to its complexity.

The present work expands on our previous study of an Eulerian-Eulerian model of the gasification processes in a coal bubbling fluidised bed, which included limestone calcination, to include additional gaseous species that subsequently promote additional reactions. The inclusion of SO2 as a species activates the desulphurisation process which follows limestone calcination and is important in the reduction of SOx emissions. The present results highlight the effects of additional species on the local reactions and overall compositions of exiting emissions. Furthermore, an investigation is carried out to determine how the inclusion of additional species and reactions affect the computational performance of the simulations, which leads to discussions on whether the improvements in the results of more detailed models warrant the increase in computational time and cost.

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