A demister sounds like a good idea. You could experience some liquid carryover during foaming or other upsets, and amine in your gas stream to the incinerator can plug the burner tips with amine salts.
Is this acid gas to go to a Claus plant or just an incinerator?
we have almost the same incinerator D/S amine unit i think you dont need that demister. to prevent liquid carry over you can put HHL trip to trip incinerator