Experiment Study On Rice Husk Gasification In Circulating Fluidized Bed

Circulating Fluidized Bed (CFB) is most suitable for large-scale utilization with huge potential application prospect compared with other conversion routes. In this thesis, the structural characters and running principles of CFB were probed and discussed in details. The gasification test was performed in circulating fludized bed gasifier, with rice husk as feedstock and silicon sand as bed material. the gasification process should be transferred from steady combustion of rice husk, with the furnace temperature raised to above 800 centigrade by adjusting the ratio of air to feedstock.The cold-state experiments were found: The resistance of CFB distributor grows along with the increase of air input. This must cause higher electricity consumption by air blower. The phenomenon of bridging caused by agglomeration easily occurred due to poor fluidity of rice husk. The fluidity of quartz sand was much better than it. The pressure curve was stable and consistent with the theoretical curve in the tests of critical fluidized rate. Experiments on feed back equipment found that normal feed back could be increased with wind rate.When the returned stock was circulated normally, the temperature of the hearth is distributed uniformly with small fluctuation in a narrow range. Otherwise, the temperature would show high fluctuating action. Gasification temperature in hearth increased with the growing of air equivalence ratio (ER) which had a great influence on the hot gas components and calorific value. It is favorable to gasification reaction when ER is around 0.28. The increase of temperature contributes to push reduction reaction forward in gasification process, and enhance the yield of flammable gas component. Meanwhile, the higher temperature was obtained by burning the flammable gas. Experiments revealed that the most reasonable gasification reaction happened at 750℃or so. The inertia bed material, quartz sand who acted as thermal carrier and circulating assistant, had played an important role in keeping the stable running of CFB. The thermal storage of sands could heat the rice husk. And the good fluidity of sands could enhance the circulating of coke and rice husk. The mixture of sand and rice husk could be circulated well when the particle size was controlled in the range of 0.4~0.6mm. The CFB can not run well using other mixed feedstock with different sizes, which is partly decided by the fluidity of mixed feedstock.