In-Furnace Reduction Of Nitrogen Oxide By Mixed Fuels Involving A Biomass Derivative

Abstract

A method of reducing nitrogen oxide emissions formed during fuel combustion by introducing biomass ash into a combustion chamber.

Description

PRIORITY INFORMATION [0001] This application claims priority to U.S. Patent Application No. 60 / 694,181, filed Jun. 27, 2005, the contents of which are incorporated herein by reference in their entirety.GOVERNMENT SUPPORT [0002] This invention was made with support from United States Department of Energy Grant Nos. DE-FG26-02NT41552 and DE-FG-04-NT42183. The United States government has certain rights to this inventionFIELD OF THE INVENTION [0003] The present invention relates generally to the field of reduction of nitrogen oxide emissions. More specifically one embodiment of the present invention relates to the reduction of nitrogen oxide emissions by introducing a reburn fuel with biomass-derived products, such as biomass char and biomass ashes. SUMMARY AND BACKGROUND OF THE INVENTION [0004] Reburning is a three-stage, in-furnace combustion technology designed for the reduction of nitrogen oxide (NO) by introducing a supplemental fuel above the primary combustion zone, where the ma...

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Benefits of technology

[0012] Introduction of ignite ash or biomass derivatives into the fuel-rich zones can catalyze the reduction of NO and decomposition of HCN (a NO formation precursor). This can be accomplished with at least two embodiments of the present invention. In staged operations, where part of the combustion air is supplied through the overfire air (OFA) ports above the substoichiometric (fuel-rich) combustion zone for NO reduction, the lignite ash or biomass derivatives can be injected anywhere between the burner level and OFA ports. To maximize the NO removal efficiency, it's preferable to introduce the compounds closer to the burner level. In the absence of OFA ports (unstaged combustion), the lignite ash or biomass derivatives can be strategically introduced into locally fuel-rich zones of the low-NOx burner flame via especially, designed nozzles for effective NO reduction.

[0013] Without being bound by theory or mechanism, it is believed that about 90% of NO can be effectively reduced in the reburning zone by natural gas, but the resulting nitrogen-containing intermediates (eg., HCN, NH3, and char-nitrogen) oxidize farther downstream in the burnout zone, which ultimately attribute to the observed 60% net NO reduction floor. During natural gas reburning, hydrocarbon free radicals including C, CH— and CH2, chemically reduce NO to HCN, a major reaction product in the reburning zone, A significant portion of HCN oxidizes to NO in the burnout zone that limits the overall NO reduction efficiency. During coal reburning, a significant portion of the char nitrogen oxidizes to form NO in the burnout zone. To break these reduction barriers, advanced reburning must involve means for simultaneously minimizing NO, and it

Problems solved by technology

Thus, reburning technology on its own, has not been sufficient to meet the stringent regulations established by laws.

Ashes from lignite-fired power plants are geographically limited to the Northern Great Plains (North and South Dakota and Montana), and Southern United States (Texas, Louisiana, and Mississippi).

Transportation of lignite ashes to boilers in other parts of the United States poses a cost constraint.

During natural gas reburning, hydrocarbon free radicals including C, CH— and CH2, chemically redu

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