Researches On Principle And Industrial Application Of Biomass Gasification In Fluidized Bed

As one kind of biomass thermal chemistry conversion technology, biomass gasification has attracted more and more attentions in recent years. Its aim is attaining more possible combustible gases (such as H₂, CO, CH₄ et al.). Due to advantages of excellent gas-solid mixing, uniform bed temperature, intensive mass and heat transfer and easy scale-up, fluidized bed gasifier is thought as the most promising reactor among all kinds of biomass gasifier. At present, the main problems of biomass gasification in fluidized bed are the followings: the tar content in the product gas is rather high and tar conversion or removal is rather difficult; the product gas heating value is low when air was used as gasification agency; the scale-up rule of fluidized bed gasifier hasn't be built up until now; the simulation results of modeling of biomass gasification in fluidized bed is very poor, these problems directly and significantly hinder the application of biomass gasification technology.To solve these problems, Funded by the National High Technology Research and Development Program of China (the '863' Program), the hydrodynamic characteristics of biomass particles in a cold fluidized bed and a cold circulating fluidized bed, the characteristics of biomass gasification in a lab-scale fluidized bed gasifier, the characteristics of high temperature tar cracking in a carbon furnace and the operation performances of industrial biomass gasification and power generation systems were studied in the present paper.The fluidization hydrodynamics of different biomass particles were firstly investigated at room temperature in different diameter fluidized beds in the thesis. The experimental results have shown: 1) The pure biomass particles (such as sawdust /rice husk et al.) also could be fluidized. 2) The different biomass particles showed different characteristics of fluidization. Sawdust particles more easily achieved good fluidization than rice husk particles. When the gas velocity exceeded the complete fluidization velocity U_cf, bubbling fluidization was observed when sawdust was used as bed material, however channeling was often observed when rice husk was fluidized.3) the diameter of bed and the height of bed material also had significant effects on fluidization quality. The 'wall effect' couldn't be ignored when the diameter of bed was less than 0.1 m, the bigger diameter facilitated to improve fluidization...