Experimental And Numerically Simulative Study Of Biomass Clrculating Fluidized Bed Gasifier

Biomass circulating fluidized bed (CFB) gasification technology is an advanced form ofbiomass energy utilization, which is of wide-range adaptability, great capacity and continuousproductivity. The study and application of this technology are of significant importance to solvethe problem of energy and environment.In this paper, the experiments and numerical simulations are taken on the biomasscirculating fluidized bed with 100mm inner-diameter and 5m height. Through the study of thecold model experiments, the factors causing the increasing of pressure gradient of the riser are:increasing of primary air volume; decreasing of particles'diameters; increasing of solidinventories. The factors causing the increasing of system circulating mass volume are:decreasing of primary air volume; increasing of particles'diameters; increasing of solidinventories. It also takes experiments of fluidized performances of different biomass materialssuch as rice husk, saw dust, cotton stalk, and improves the fluidized performances of them bymixing river sand as bed material in.It uses method of integrally 3D numerical simulation and takes mutual influence of eachunit in consideration in simulation. It uses Euler-Euler dual fluid granular model and Gidaspowmomentum exchange model to simulate the gas-solid flow under different operating conditionsin the biomass circulating fluidized bed gasifier. The profiles of velocity vector of particlescertify that there are large-scale internal circulations of solid phase in the riser. It provides theradial and axial profiles of particles volume fraction, and radial profiles'average pressure curvesof each part of gasifier. At the bottom of the riser, the particles volume fraction and pressuregradient is high in the dense area. In the middle-part transition area and the top-part dilute area of the riser, the particle fraction volume is low, of which changing under different conditions issmall; the pressure gradient is also small in these areas. It forms pressure loop in the entirecirculating fluidized bed forcing the particles'stable circulation in the bed. It forms various sizeparticles cluster in the riser, of which the formation and dissipation are in a short time.In the thermal gasification experiments, it uses cotton stalk granular stock as biomassmaterial and river sand as bed material. The temperature of riser is uniform and stable; theproduction gas could stably combust in the air; calorific value of production gas is low; the heatloss is high due to the small-scale of the gasifier; other gasification performance showed bygasification index is medium.