Apparatus and process for the production of olefins

The present invention relates to an apparatus for reacting a first gaseous reactant stream with a second gaseous reactant stream to form a gaseous product stream, wherein the apparatus comprises at least one first supply means for the first gaseous reactant stream, at least one second supply means for the second gaseous reactant stream, a catalyst zone, a product quench zone and a waste heat boiler, wherein the product quench zone is positioned downstream of the catalyst zone and comprises a plurality of quench tubes, and wherein the waste heat boiler is positioned downstream of the exits of the quench tubes and comprises a plurality of boiler tubes, the waste heat boiler having a surface on which gas exiting the exits of the quench tubes impinges.