| 摘要 |
Nitrogen oxides, NOx, resulting from the excess air combustion of solid fuels in a combustor or burner in a furnace are reduced. By introducing sufficient additional fuel to the combustion gases in the furnace downstream of the primary combustion zone, a fuel rich gas zone is created in a temperature range that favors the conversion of NOx to nitrogen, N2. Further downstream sufficient additional air is added to complete the combustion of any unburned fuel. Alternatively, the fuel rich gas zone can be confined to a central region of the furnace. In that case, final combustion takes place when the fuel rich gas mixes with the untreated gas further downstream in the furnace. The preferred embodiment of this invention is to introduce the additional fuel in said downstream combustion zone as solid particles dispersed in aqueous droplets of varying size that vaporize throughout the furnace gas zone being treated. The dispersed solid fuel particles burn as they evolve from the droplets. Special injectors atomize the aqueous droplets into the combustion gas and disperse them throughout the optimum NOx reduction temperature zone. Alternatively, the fuel rich combustion zone can be produced with injection of liquid fuel droplets. A third alternative is to use pyrolysis gas emitted from the partial gasification of a solid fuel. A fourth alternative is to inject pulverized coal particles or shredded biomass particles into the optimum NOx reduction zone. The present staged combustion method using these fuels and fuel injection methods can be combined with other NOx reduction processes to yield large overall NOx emission reductions.
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