Dear members,
I am currently involved in the engineering of an ethylene cracker. In the entire petrochemical complex, there are three different types of flares:
(i) Process Flare (For combusting hot and cold flare hydrocarbon gases released during an event such as flare control valves opening, relief valves popping, etc.)
(ii) Sour Gas Flare (For H2S and oxygen containing gases released from various sections of the plant like caustic wash towers, spent caustic treatment unit)
(iii) Acetylene Flare (For flaring acetylene containing gases from butadiene extraction and MTBE units)
My questions are as follows:
(i) What is/are the reasons for having a different flare stack for acid gas and acetylene containing gases, why can't we put them directly in the common flare header going to the process flare?
(ii) For the process flare system, we have a cold blowdown drum, which receives cold flare liquids and gases (less than 0 deg C). This drum has a vaporizer in which the cold liquid is vaporized by heating with condensing methanol. The condensed methanol is then revaporized by heating with low pressure steam in another exchanger. My question is that, why can't we directly use condensing LP steam to heat the cold flare liquid instead of having two exchangers with a separate methanol cycle?
Thanks.