Study On The Hydrodynamics Dynamic Characteristics And Numerical Simulation Of Biomass Particle In Annular Vortex Fluidized Bed

As a clean and renewable energy,biomass energy does no harm to the environme nt.With so many characteristics,it's rich in resources,diverse in forms,it has low sulfur,low nitrogen,high volatile,high ash focal activity,zero net emissions of CO 2 and so on.The unique advantages make biomass as a research hotspot.And the annular vortexing fluidized bed combustion technology is a new type of high efficient and clean combustion technology developed in recent years.The lower is fluidized bed,the upper is annular vortexing combustor,their structure is circular.They have the characterist ics of high combustion efficiency,high desulfurization efficiency and high volumetric heat capacity,fuel wide adaptability,etc.In this paper,the annular vortexing fluidized bed cold test bench were designed and set up.Different grain of the sawdust is selected as the research object in this study.The effect of flow rates of primary air,secondary air and secondary air distribution on the vortex in a fluid-bed are investigated.In this study,the gas velocity,void fraction,particle-phase density,mass flow,and the effects of operation parameters were also discussed.And the annular vortexing fluidized bed three-dimensional model was established and was based on the particle kinetic theory.Using the FLUENT software and the Euler-Euler two fluid model to toroidal vortex fluidized bed gas-solid two phase flow are simulated.The experiment result shows that the gas tangential velocity in the outer cylinder reaches the peak in the single-phase gas flow fields of annular vortexing fluidized bed,while the axial velocity reaches the peak in the wall of the central cylinder.There is recirculation region in the wall of the outer cylinder and the backflow intens it y increases with the increase of the swirling number S.It is beneficial to strengthen the rotational flow in fluidized bed by the unequal distribution of the secondary air.The particle density appears peak in the neighborhood of the wall surfaces and the suspension layer of the higher particle density is formed in each nozzle between the secondary airs.The void fraction,?,is distributed by the inverted “C” in the dilute phase zone.The void fraction is increased with the increase of the h/R and the growth rate becomes bigger and bigger.The mass flow rate of particles increases first and then decreases with increasing the r/R and it decreases gradually with the increase of the h/R.The simulation result shows that the distribution of air flow velocity presents “wave type” in the annular space of the fluidized bed.The existence of the central cylinder enhances the vortex intensity and the mass transfer of the particles in bed,which is beneficial to the complete combustion of the fuel particles and prolong the dwell time of particles in bed.These results of simulation are expected to offer help and rationale for optimization and betterment of experimental facilities.