The tower with constant burning flame is called Flare Stack alternatively known as Gas Flare.
Flare Stack, is a gas combustion device used in industrial plants such as petroleum refineries, chemical plants, natural gas processing plants as well as at oil or gas production sites having oil wells, gas wells, offshore oil and gas rigs and landfills.
So, what purpose have a flare stack holds?
It is used as a last line of defense/safety for refineries, petrochemical and gas processing plants.
The flare system consists of the Flare Stack and a flare header. A very large network of pipes coming from the different processes feed into the header. Whenever there is an upset or an emergency situation, all the extremely flammable hydrocarbons need to be vented out. But these cannot be just put in the atmosphere like the steam from our food pressure cookers. A vapor cloud would be extremely hazardous and catastrophic. To ensure that these escaping gases get burned to Carbon dioxide and water vapor, a flame is always kept burning on the top. It is a necessary evil (waste of gas).
The location of a fire stack is also very important. It is located far away from the main processing complex in the downwind direction. It is very tall so that radiation heat may not affect people and equipments.
Now you know!!
Source:: , LH