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A three-dimensional model of particulate flows using the Reynolds Averaged NavierStokes method is presented. The governing equations of the gas-solids flow are supplemented with appropriate closure equations to take into account all the relevant forces exerted on the solid particles, such as particle-turbulence interactions, turbulence modulation, particle-particle interactions, particle-wall interactions, as well as gravitational, viscous drag, and lift forces. A finite volume numerical technique was implemented for the numerical solution of the problem. The method has been validated by comparing its results with the limited number of available experimental data for the velocity and turbulence intensity of the gas-particle flow. The results show that the presence of particles in the flow has a significant effect on all the flow variables. Most notably, the distribution of all the parameters becomes asymmetric, because of the gravitational effect on the particles and particle sedimentation.

Concentration of solid particles of ash and inert material present in the combustion chamber of a circulating fluidised-bed boiler is very high, giving rise to some disadvantages. At the same time, the required temperature level in the combustion chamber is guaranteed by circulation of solid particles. In this work numerical simulation of gas-solid particle flow has been performed in the frame of a two-fluid model, namely the Eulerian approach for the dispersed phase, for conditions of the circulating fluidised bed, ranging from moderate to high mass ratios of the flow. An incorporated original model of closure of transport equations of the dispersed phase permitted to account the interparticle collisions which might be indispensable to proper numerical simulation of the process in the circulating fluidised bed under discussion. The results of this work would help to improve the processes occurring in the combustion chamber of the circulating fluidised-bed boiler.

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