CFD Simulation Of Hydrodynamics In A Novel Gas-Solid Fluidized Bed Reactor For Concentrated Solar Thermal Applications

In the current study a CFD investigation of a novel directly-irradiated fluidized bed(DIFB)for solar-driven chemical processing is reported.The autothermal reactor principle is applied to multiphase flow of fluidized solids in this reactor: a gas-solid suspension is preheated in a tubular riser before to being exposed to radiative flux and further heated in a concentrated solar receiver.Solids leaving the receiver flow counter currently in an annular dipleg coaxial to the riser,causing preheating.The dipleg could be designed so as to make the solid particles circulate downflow with gravitational.Computational fluid dynamic study was conducted under non-reactive conditions and at moderate radiative flux,thus moderate temperatures,with the goal of demonstrating the feasibility and operability of the autothermal reactor.Solid’s circulation and temperatures were showed by their contours in the riser and annulus under simulated solar irradiance using P-1 and DO solar models.Euler-Euler approach has been used to model gas-solid two-phase flow.Mass,momentum and energy equations of turbulent flow have been solved using realizable k- and SST k-(?) models based on Reynolds-average Navier-stokes equations(RANS).Simulations indicate that solid particles have an excellent circulation within riser to annulus up flow and downflow.However,more particles in the bed storage with sensible heat exchange between bed solids and downflow solids enhanced preheating of inlet gas.Furthermore,solid particles have been participated along the riser and annulus making excellent flow of circulation and heat exchange between phases.Particles in the bed storage with no movement as particle within riser and annulus in a motion because of gas carrier through riser and gravitational downflow through annulus.Some improvements have been also set to the main geometry and better participation of solids within riser and annulus has been discussed also.Combing the riser(inner pipe)with the annular channel realizes external and internal circulations of particles,improves ability of fluidization of particles,and enhances heat transfer ability of fluidized bed reactors.