| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 94 === ABSTRACT
In this study, all the experiments were carried out in a pilot scale vortexing fluidized bed combustor of 0.75 m I.D. and 4.6 m in height. Sawdust was used as the fuel, and silica sand was employed as the bed material.
The effects of various operating conditions on NOx and N2O emissions were investigated, and the main operating parameters studied were bed temperature, excess air, and the method of bed temperature control.
The experiment results show that most formation of NOx and N2O take place in splashing zone, and then reduce in secondary air injection zone and freeboard. This is due to high volatile matter content of sawdust. Under each different operating condition, the N2O emissions are very small, and it can consider to be ignored. The NOx emission increases with the bed temperature. The NOx emission increases with excess air ratio from 10% to 40%, but the contrary result was found at a higher excess air ratio. At the static bed height of 20 cm, there is a lowest NOx emission. In addition, the amount of NOx is more with the method of water injection than heat transfer tube in bed temperature control.
Sawdust burns easily, and its heating value achieves above 3000 kcal/kg. Furthermore, the nitrogen oxides emissions from sawdust combustion conform to the environmental protection regulations. Thus sawdust could be a good choice for biofuel.
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