CFD modelling of the co-gasification of biomass and coal particles in fluidised beds

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Description/Abstract

The rapid depletion of oil and the environmental impact of combustion has motivated the search for clean combustion technologies. Fluidised bed technology (FBT) works by suspending a fuel over a fast air inlet whilst sustaining the required temperatures. Using biomass or a mixture of coal/biomass as the fuel, FBC provides a low-carbon combustion technology whilst operating at low temperatures. Computational modelling has shown great advancement in its predictive capability and reliability over recent years. Two-fluid modelling (TFM) has become a viable tool for the modelling of the hydrodynamic and heat transfer processes in fluidised beds yet the inclusion of reaction kinetics is still in the early stages due to their complexity. Such reaction kinetics need to be implemented by means of a user defined function (UDF) into the commercial software ANSYS 12.0 as current built in models are not available. In this paper, two-fluid modelling is used to model a bubbling fluidised bed gasifier (BFBG) using four solid phases namely, biomass, coal and two types of char. The devolatilisation model and heterogeneous reactions are implemented and the simulated gases produced are compared to experimental results from the literature