Apparatus and process for producing a superheated steam

An apparatus for producing a superheated steam, the apparatus comprising:

• a primary heater comprising a radiant section and a convection section, a convective heat transfer conduit in communication with a source of water and passing through said convection section to provide a steam stream;
• a secondary heater, comprising a radiant section and a secondary heat transfer conduit in communication with the convective heat transfer conduit, said secondary heat transfer conduit passing through said radiant section of the secondary heater to provide a superheated steam stream;
• and
• a flue gas conduit configured to deliver a flue gas stream from the radiant section of the secondary heater to the convection section of the primary heater and transfer heat to said convective heat transfer conduit.

A process of producing a superheated steam, comprising:

• heating a water stream in a convection section of a primary heater to produce a steam stream;
• passing said steam stream to a secondary heater;
• heating said steam stream in the secondary heater to produce a superheated steam stream;
• and
• adding water to said steam stream downstream of said secondary heater to desuperheat said steam stream but increase the steam flow rate.