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Production of Low Oxygen Content Gas Turbine Combustion Diluent Streams

IP.com Disclosure Number: IPCOM000019410D
Publication Date: 2003-Sep-12
Document File: 7 page(s) / 252K

Publishing Venue

The IP.com Prior Art Database

Abstract

This report describes a method to reduce the oxygen content of a nitrogen feed stream to a gas turbine. The oxygen contained in the nitrogen stream is reacted with a fuel to produce a low residual oxygen content. The treated stream is used in a gas turbine to improve operation. The operation of a gas turbine can be improved through the addition of a low oxidant bearing stream. One area in which it is used is to reduce oxides of nitrogen, a major source of pollution. Introduction of an inert stream into the fuel or into the combustor area will lead to a lower adiabatic flame temperature. A lower flame temperature results in reduced formation of oxides of nitrogen or NOx. If the oxidant concentration in this inert gas stream is too high, then its ability to reduce the formation of NOx is reduced. Of equal importance are the safety implications of mixing an oxidizing stream with a hot fuel stream.

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Production of Low Oxygen Content Gas Turbine Combustion Diluent Streams

This report describes a method to reduce the oxygen content of a nitrogen feed stream to a gas turbine. The oxygen contained in the nitrogen stream is reacted with a fuel to produce a low residual oxygen content. The treated stream is used in a gas turbine to improve operation.

The operation of a gas turbine can be improved through the addition of a low oxidant bearing stream. One area in which it is used is to reduce oxides of nitrogen, a major source of pollution. Introduction of an inert stream into the fuel or into the combustor area will lead to a lower adiabatic flame temperature. A lower flame temperature results in reduced formation of oxides of nitrogen or NOx. If the oxidant concentration in this inert gas stream is too high, then its ability to reduce the formation of NOx is reduced. Of equal importance are the safety implications of mixing an oxidizing stream with a hot fuel stream.

The industry will typically use either water, steam or nitrogen as the inerting stream. Water or steam injection requires a source of demineralized water, and a boiler in the case of steam injection. The nitrogen usually originates from an air separation device. The air separation device must be designed so that the correct purity can be achieved. Reducing the oxygen content in large nitrogen byproduct streams adds cost and increases the power requirement.

It is possible for a cryogenic air distillation unit to provide the necessary purity to meet the objective of NOx suppression. A stream of air may be removed from a gas turbine and used within the cryogenic air distillation unit, as shown in Figure 4. However, for high combustor pressures in the gas turbine, it becomes increasing difficult to perform the required separation of the air feed. Priority is usually given to the oxygen enriched product stream 305, as this is typically supplied to the customer at medium to high purity. In order to meet the purity of the oxygen enriched product stream 305 the oxygen content of the low oxidant gas stream 107 must increase. At air feed pressures, about 250 psia, this level of oxidant is still low enough for it to be used in the suppression of NOx. However, above 250 psia a simple double column cryogenic air separation must be modified in order to meet the required purity. Solutions described in the prior art include the purging of gas from the low pressure column, and increasing the number of stages of separation. Both of these lead to a reduction in column economics through either increase in capital cost, or a reduction in the flow of gas returned to the turbine. Cryogenic air distillation units which draw a portion of their air from a gas turbine and returned the waste gas are unable to do so because the pressure of the gas turbine is too high to both achieve the oxygen enriched product stream 305 and the inert concentration of the low oxidant gas stream 107. Other processes such as ads...