What IS that…
It is a flare stack and is a safety device in our plant.
Every home has a water heater and every water heater has a pressure relief valve (PRV). If the PRV opens on your water heater it results in a little mop up.
Every tower and vessel in the refinery also has a PRV. If a PRV opens, it releases flammable hydrocarbon. All of these are therefore piped to the flare so they are safely burned rather than released to the atmosphere.
We do not always have hydrocarbon going to the flare, so it is kept lit using gas we buy from CLF&P, that way it is always ready to ignite relieved gases whenever needed.