Flue gas

[3] At power plants, flue gas is often treated with a series of chemical processes and scrubbers, which remove pollutants.

Electrostatic precipitators or fabric filters remove particulate matter and flue-gas desulfurization captures the sulfur dioxide produced by burning fossil fuels, particularly coal.

[4] Nitrogen oxides are treated either by modifications to the combustion process to prevent their formation, or by high temperature or catalytic reaction with ammonia or urea.

In the United States, there is a rapid deployment of technologies to remove mercury from flue gas—typically by absorption on sorbents or by capture in inert solids as part of the flue-gas desulfurization product.

They are now under active research as a method for CO2 capture for long-term storage as a means of greenhouse gas remediation, and have begun to be implemented in a limited way commercially (e.g. the Sleipner West field in the North Sea, operating since 1996).

A typical flue gas from the combustion of fossil fuels contains very small amounts of nitrogen oxides (NOx), sulfur dioxide (SO2) and particulate matter.