Patent ID: 7575931

Claim:
In a multi-component gas mixture that is emitted by an emissions source and contains one or more nitrogen oxide gases, and in which one or more nitrogen oxide gases is reduced by reaction with a reducing agent that is injected into the gas mixture, a method of controlling the reaction of reduction, comprising (a) determining information related to the compositional content of the gas mixture wherein the information comprises one or more of the following (i) the individual concentration within the gas mixture of a nitrogen oxide gas, (ii) the individual concentration within the gas mixture of a reducing agent, (iii) the individual concentration within the gas mixture of oxygen, and (iv) the collective concentration within the gas mixture of a group of two or more nitrogen oxide gases; (b) determining from the information determined in step (a) a first operating characteristic of the reaction of reduction that is not in a desired relationship to a second operating characteristic thereof; and (c) providing an adjustment to the relationship between the first and second operating characteristics, wherein providing the adjustment comprises (i) adjusting the amount or frequency of injection of reducing agent, (ii) employing a plurality of injectors to inject reducing agent and adjusting the timing of injection by injectors in different locations, (iii) heating or cooling the gas mixture, and/or (iv) employing a reduction catalyst and heating or cooling a reduction catalyst; wherein the information determined in step (a) comprises an output of one or more gas analyzers that comprises an array of chemo/electro-active materials comprising Ni a Zn b O x ,Sb a Sn b O x , and Ta a Ti b O x ; wherein a, b, and c are each independently in the range of about 0.0005 to about 1; and wherein x is a number sufficient so that the oxygen present balances the charges of the other elements present in the chemo/elelctro-active material.