Flue-gas stack

When the flue gases are exhausted from stoves, ovens, fireplaces, heating furnaces and boilers, or other small sources within residential abodes, restaurants, hotels, or other public buildings and small commercial enterprises, their flue gas stacks are referred to as chimneys.

The first freestanding industrial chimneys were probably those erected at the end of the long condensing flues associated with smelting lead.

The chimney is part of a steam-generating boiler, and its evolution is closely linked to increases in the power of the steam engine.

The taller, freestanding industrial chimneys that appeared in the early 19th century were related to the changes in boiler design associated with James Watt’s "double-powered" engines, and they continued to grow in stature throughout the Victorian period.

The invention of fan-assisted forced draft in the early 20th century removed the industrial chimney's original function, that of drawing air into the steam-generating boilers or other furnaces.

Building materials changed from stone and brick to steel and later reinforced concrete, and the height of the industrial chimney was determined by the need to disperse combustion flue gases to comply with governmental air pollution control regulations.

The equation assumes that the molar mass of the flue gas and the outside air are equal and that the frictional resistance and heat losses are negligible:.

A great many power plants are equipped with facilities for the removal of sulfur dioxide (i.e., flue-gas desulfurization), nitrogen oxides (i.e., selective catalytic reduction, exhaust gas recirculation, thermal deNOx, or low NOx burners) and particulate matter (i.e., electrostatic precipitators).

In the United States and a number of other countries, atmospheric dispersion modeling[7] studies are required to determine the flue gas stack height needed to comply with the local air pollution regulations.