Method for low NOx combustion of syngas/high hydrogen fuels

Abstract

The present invention provides a method for low NOx combustion of high hydrogen content fuels in gas turbines. In the method of the present invention, at least a portion of the fuel is combusted under fuel rich conditions and a portion of resulting reaction heat is transferred to combustion air prior to non-premixed combustion of the fuel.

Description

CROSS-REFERENCE [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 683,719 filed May 23, 2005.FIELD OF THE INVENTION [0002] The present invention relates to a method for ultra-low NOx combustion of high hydrogen content fuels. In one embodiment, the present invention provides a method for lowering the adiabatic flame temperature of a fuel prior to non-premixed combustion. BACKGROUND OF THE INVENTION [0003] With energy usage directly related to economic growth, there has been a steady increase in the need for increased energy supplies. In the U.S., coal is abundant and comparatively low in cost. Unfortunately, conventional coal-fired steam plants, which are a major source of electrical power, are inefficient and pollute the air. Thus, there is a pressing need for cleaner, more efficient coal-fired power plants. Accordingly, Integrated Gasification Combined Cycle (“IGCC”) coal technology systems have been developed which can achieve significantly improve...

AI Technical Summary

Benefits of technology

[0009] It has now been found that using a reactor such as that described in U.S. Pat. No. 6,394,791, the stoichiometric flame front temperature (“SFFT”) of high hydrogen content fuels can be reduced sufficiently to provide ultra-low NOx non-premixed combustion. By reacting a sufficient amount of a fuel under fuel rich conditions and transferring at least a portion of the heat of reaction to combustion air, the SFFT is reduced.

Problems solved by technology

Unfortunately, conventional coal-fired steam plants, which are a major source of electrical power, are inefficient and pollute the air.

As a result of the high flame speed of hydrogen, flashback is an issue with premixed dry low NOx combustion systems.

Flashback remains an issue with the use of syngas as well.

Regardless of whether carbon dioxide is recovered or whether air or oxygen are used for syngas production, hydrogen content of the gas typically is too high to allow use of conventional dry low NOx premixed combustion for NOx control.

Even so, exhaust gas cleanup still may be required.

Thus, such systems, though cleaner and more efficient, typically cannot achieve present standards for NOx emissions without removal of NOx.

A further problem is that the presence of diluent in the fuel increases mass flow through the turbine often requiring the bleeding off of compressor discharge air.

Since bleed off of compressor air must be limited to allow sufficient air for combustion and turbine cooling, the amount of diluent which can be added to the fuel is limited.

Typically, NOx cannot be reduced below about ten parts per million (“ppm”) without operational problems, including limited flame stability.

There are further efficiency loss issues.

If nitrogen is added to dilute the fuel gas, there is an energy penalty related to the need to compress the nitrogen to the pressure required for mixing with the fuel gas.

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