Experimental Research On Biomass Gasification In A Double Fluidized Bed

With the decreasing of fossil fuel resources and the emission limitation of greenhouse gases, biomass energy becomes one of the most important renewable energy. As a clean, pollution-free and renewable energy, the development and utilization of biomass energy has attracted the world attention. Double circulating fluidized bed technology is an emerging technology arose in recent years. In biomass fluidized decoupled gasification craft, decoupling reaction of the high-activity volatiles and the low-activity semi-coke is achieved through the fluidized way based on the reactivity of different composition of biomass by low activity of semi-coke combustion powering for highly active volatile pyrolysis. In this technology process, the fuel gas is not diluted by the semi-coke combustion gas and the quality of bio-gas is improved. At atmospheric pressure, it can produce medium caloric value gas without pure oxygen conditions. It is very promising technology for biomass gasification.In this thesis, physico-chemical properties of biomass raw materials and its ash composition XRF spectrum were analyzed. Based on the concept of the double fluidized bed, a cold test system with a combustor of100mm in diameter and3000mm in height and a gasifier of200mm in diameter and1700mm in height was built. The test results showed that the test system has a good performance and it can meet the requirements needed by experiments. The system circulation volume would be impacted by combustion furnace fluidizing air flow, recycle device fluidizing air flow, biomass stack height and the height diameter ratio. As the result of the experiment, system circulation volume can be reached0.24kg/s. Design temperature difference of combustor and gasifier is100℃under the conditions, gained through theoretical calculations of the heat by circulating ash is79.49MJ/h, it can ensure better gasification reactions.Based on the cold test, a hot state system, which has the same size as the cold model, was built. The test system includes:dual circulating fluidized bed gasifier, the ignition system, feeding system, air supply system and data acquisition system. The sand with a diameter of0-0.6mm as inertia particales and wood pellets as gasification feed, the gascification experiments were conducted in the dual circulating fluidized bed gasifier. A medium calorific value of gas which was9.19MJ/m3...