Cold-state Experimental Research About Ash-returned Reactor Of CFB Gasfier

Aiming at the problem of domestic atmospheric CFB air/steam gasifier that the carbon content of flying ash is high, a measure that designing a ash-returned reactor is put forward to solve the problem in this paper. Compared to the conventional ash-returned feeder, it is able to make fly ash participate in the carbon combustion reaction which basicly not participate in the gasification reaction, therefore, guarantees the temperature of the materials sent back to the furnace be at about 1000℃, raises the gasifier temperature there by, and as a result of these, it improves the conversion percent of the carbon in coal. In addition, the tube arranged in ash-returned reactor could effectively control the temperature of the materials in the ash-returned feeder, to prevent the materials from slagging, and ensure a smooth transportation of the materials. Under the guidance of tutor, the author designed the ash-returned reactor, and researched the flows characteristics and heat transfer characteristics of the ash-returned reactor, and provided reference dates of design and operation for the after design and application of ash-returned reactor.First, in this thesis analyze the state of affairs of domestic and international energy distribution and use, summarize actuality of gasification technology, introduce the development of domestic and international atmospheric CFB air gasifier technology, and point out the widespread problem of CFB Gasifier. On the basis of referring predecessors'research and analysis of responsivity of fly ash and fly ash gasification reaction kinetics, in this paper put forward the purpose and content of the research. Secondly, on the basis of reference and combining with the actual needs of reactor, the author researched and designed the atmospheric CFB air gasifier ash-returned reactor, and constructed a cold experimental reactor bench of the ash-returned reactor. The design idea of atmospheric air CFB gasifier ash-returned reactor is to transform the ash-returned feeder to a ash-returned reactor, it could be regarded as a U-valve with its recycle room transformed to a external CFB. Ash-returned reactor not only plays the role of ash-returned feeder, but also be a burning reactor.And then we had a cold experimental research about flows characteristics of the ash-returned reactor on the ash-returned reactor experimental bench . We measured the resistance characteristic of air distributor and the material's resistance characteristic, and calculated the critical fluidizing wind speed which is 0.275 m/s in this ash-returned reactor by analyzing the curve of the material's resistance characteristic. Besides these, we focused on the impacts of fluidization wind volume speed, loose wind volume speed, height of horizontal orifice and deposit height of material and other factors on the amount of recirculating of fly ash.On the basis of the flow characteristics experiments, we continued to research the heat transfer characteristics of the ash-returned reactor. During the experiment, we found that material bed height and fluidization wind volume are the prominent factors which influence the magnitude and distribution of heat transfer coefficient in ash-returned reactor the most by orthogonal experiments. we researched the impacts of height of horizontal opening and material bed height on heat transfer characteristics of the ash-returned reactor, at the same time we focused on the impacts of fluidization wind volume, loose wind volume on heat transfer characteristics of the ash-returned reactor. The results matched with the theory of fluidized bed particle concentration distribution very well.Finally, making a comprehensive view of this paper, we got conclusions about flow and heat exchange character of the ash-returned.