Why are some industrial chimneys so high, like what’s the difference if it’s 150 or 300 meters?
In: Engineering
Industrial chimneys allow the reclamation of gasses that will seperate and condense based on altitude and cooling as the exhaust rises. Some of these smokestacks are built to channel those chemicals back for reuse. Happens a lot on Petro chemical factories.
Something I’ve not seen mentioned in other replies: It can depend a lot on local landscape and microclimate/airflow
e.g. a factory in a valley might need a taller stack to avoid issues with local smog.
The solution to pollution is dilution – The mantra that was hammered into everyone in my Chem eng degree.
Pollution is seemingly not a thing if you dilute it enough, and the higher the chimney the wider the dispersion amongst the local area. The chimney will be calculated from a factor of the offgas (waste gasses) and local regs around the release of these gasses.
Hopefully this is no longer a phrase that people in the industry still use today, but it was about 7/8 years ago 🙁
One, A chimney is a “zero-energy” vaccum cleaner.
Two, The more smoke you create, the higher suction you need. The sides are keeping it in and the height provides a pressure differential. The higher you go, lesser is the air pressure around compared to ground.
Three, Some pollutants require to be let off higher up. It gives more time for sulphur and nitrogen compounds to burn up.
It’s the same reason big trucks have exhaust pipes elevated above the truck cab. The marginal benefit of exhausting pollutants at a higher elevation. It’s easier for manufactures to do so than to actually have to develop clean engine tech. (IMO EV when the whole life cycle is considered may not be any better than today’s gas feed engines)
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