This invention relates generally to combustion devices and, more particularly, to a multi-function burner for use with combustion devices.
During a typical combustion process within a furnace or boiler, for example, a flow of combustion gas, or flue gas, is produced. Known combustion gases contain combustion products including, but not limited to, carbon, fly ash, carbon dioxide, carbon monoxide, water, hydrogen, nitrogen, sulfur, chlorine, and/or mercury generated as a result of combusting solid and/or liquid fuels.
At least some known furnaces use air/fuel staged combustion, such as a three-stage combustion, to facilitate reducing the production of at least some of the combustion products, such as nitrogen oxide (NOx). A three-stage combustion process includes combusting fuel and air in a first stage, introducing fuel into the combustion gases in a second stage, and then introducing air into the combustion gases in a third stage. In the second stage, fuel is injected, without combustion air, to form a sub-stoichiometric, or fuel-rich, zone. During the second stage, at least some of the fuels combust to produce hydrocarbon fragments that react with NOx that may have been produced in the first stage. As such, the NOx may be reduced to atmospheric nitrogen in the second stage. In the third stage, air is injected to consume the carbon monoxide and unburnt hydrocarbons exiting the second stage. Although such air/fuel staging may achieve relatively high NOx reduction, the use of injectors that are dedicated to either air injection or fuel/air combustion may limit the operation of the furnace and may limit the flexibility in staging air and/or fuel.