Why are some industrial chimneys so high, like what’s the difference if it’s 150 or 300 meters?
In: Engineering
Industrial processes produce exhaust gases, which contain pollutants (toxic substances).
Having too large concentration of a pollutant in the near-ground air is bad, because people will get poisoned. So concentrations are limited by laws and other documents (depending on country), and factories need to comply.
Fortunately, when there is a flow of air and a pollutant is placed into it, it gets dispersed (actually, true for any gas or liquid).
If we imagine a “chimney” exhausting gases, and if we move in the direction of the wind at level of the chimney – pollutant concentration will diminish.
At the ground level, however, pollutant concentration will go up to some maximum concentrations, then go down.
And the higher the chimney is, the further away from it the max. ground-level concentration will be achieved, and the smaller that concentration will be.
So, to NOT exceed the limit of the concentration, a factory needs to either purify the exhaust, or to build a tall chimney. Or both. And the state may require factories to always have at least certain level of purification system.
(Also some answers here state tall chimneys are to generate draft – well… In a lot of processes exhaust is pumped by blowers, so draft may be used, but main reason is to disperse the pollutants.)
Latest Answers