Apparatus for generating olefin and by-products, in particular for extracting ethylene and acetic acid, in particular by converting ethane and oxygen, in particular by thermal and/or catalytic processes; evaporators, in particular for generating water vapour; heat exchangers, other than parts of machines, in particular for heating or cooling gases or liquids, in particular with quenching tanks; thermal and/or catalytic reactors, in particular for gas-gas reactions; gas cleaners and purifiers,...