Combustion-based emission reduction method and system

Abstract

In a combustion apparatus having multiple primary fuel inputs and a flue gas exhaust, a method for controlling combustion of a fuel in the combustion chamber in which a concentration of at least one flue gas component indicative of fuel / oxidant ratio in flue gases is measured at a plurality of locations proximate the flue gas exhaust, each location corresponding to one of the primary fuel inputs. An overall average concentration of the at least one flue gas component is then determined, based upon which a delta value, the difference between the overall average and the flue gas component concentration at each location, for the at least one flue gas component at each of the locations is determined. Based upon the delta values obtained, the fuel input rate is adjusted as necessary for each of the primary fuel inputs, such that the delta value is either reduced or increased to zero.

Description

[0001] 1. Field of the Invention[0002] This invention relates to a method and system for controlling combustion-based emissions from solid-, liquid- or gaseous-fuel fired combustors. More particularly, this invention relates to combustors having multiple fuel inputs such as grate-fired spreader-stokers, which typically employ multiple solid fuel feeders, and furnaces having multiple liquid- and / or gaseous-fuel fired burners.[0003] 2. Description of Related Art[0004] Furnaces having multiple primary fuel inputs invariably suffer from unbalanced primary fuel distribution. This can lead to non-uniform stoichiometry in the primary combustion regions or zones, which, in turn, results in increases in the formation of NO.sub.x, CO and, in the case of solid fuel combustors, particulates. In addition, uneven primary fuel distribution in stoker systems leads to grate problems including piling and rat-holing.[0005] There are a substantial number of control schemes for controlling and optimizin...

AI Technical Summary

Benefits of technology

[0009] It is one object of this invention to provide a method and apparatus for controlling pollutant emissions from solid-, liquid-, or gaseous-fuel fired combustors having multiple primary fuel inputs, such as multi-feeder stokers.

[0011] It is still a further object of this invention to provide a method and apparatus for controlling pollutant emissions from solid-, liquid-, or gaseous-fuel fired combustors having multiple primary fuel inputs by controlling individually the amount of primary fuel introduced into the combustors through each of the primary fuel inputs so as to regulate primary fuel distribution within the combustor.

[0014] In accordance with the method of this invention for controlling combustion of a primary fuel in a combustion chamber having a plurality of primary combustion regions corresponding to multiple primary fuel inputs and a flue gas exhaust, a concentration of at least one flue gas component that is indicative of fuel / oxidant ratio in the flue gases generated by the combustion is measured at a plurality of locations proximate the flue gas exhaust, resulting in a plurality of measured concentrations. Each of the locations at which the measurements are made corresponds to one of the primary combustion regions. To dampen measurement noise and reduce unnecessary control fluctuations, the real-time measurements of the at least one flue gas component are processed into a localized rolling average signal. An overall average concentration of the at least one flue gas component is determined from the plurality of real-time measured concentrations. Thereafter, a delta value for the at least one flue gas component at each of the locations is determined. Delta values are the result of the difference between the at least one flue gas component concentration at each location and the overall average concentration of the at least one flue gas component. Positive delta values indicate excess fuel while negative delta values indicate a shortage of fuel. Based upon the determination of delta values, the fuel input rate for each of the primary combustion regions is adjusted, as necessary, either by increasing or decreasing the fuel input rate, until the delta value is reduced or increased to zero.

Problems solved by technology

Furnaces having multiple primary fuel inputs invariably suffer from unbalanced primary fuel distribution.

This can lead to non-uniform stoichiometry in the primary combustion regions or zones, which, in turn, results in increases in the formation of NO.sub.x, CO and, in the case of solid fuel combustors, particulates.

In addition, uneven primary fuel distribution in stoker systems leads to grate problems including piling and rat-holing.

Notwithstanding the substantial strides that have been made toward reducing flue gas emissions from stokers and other fossil fuel fired furnaces, non-uniformity of the combustion, particularly in stokers and furnaces employing multiple primary fuel inputs, which non-uniformity can result in increased emissions, remains a concern.

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