Once Through Steam Generator with 100% Quality Steam Output

A system for deriving superheated steam for steam assisted gravity drainage (SAGD) injection or other application, said system comprising:

• an once through steam generator (OTSG) comprising:
• a burner operable to generate a flue gas;
• a radiant section containing furnace tubes that are exposed to radiant flame heat of the burner;
• a convection section having a flue gas inlet for admission of said flue gas from said radiant section into said convection section for travel therethrough in a flue gas pathway to an opposing flue gas outlet, and convection tubes situated between said flue gas inlet and said flue gas outlet in fluid communication with the flue gas pathway for exposure of said convection tubes to said flue gas travelling therethrough, an upstream end of said convection tubes being connected to a feed water inlet and a downsteam end of said convection tubes being connected to the furnace tubes, whereby a feed water stream flowing through said convection and furnace tubes undergoes partial conversion to steam;
• a steam-water separator connected to said furnace tubes in downstream relation thereto to receive a two-phase steam-water flow resulting from said partial conversion of the feed water stream, and perform separation of said two-phase steam-water flow into blowdown water and dried steam;
• superheater tubes installed in said convection section in fluid communication with the flue gas pathway for exposure to said flue gas travelling therethrough, said superheater tubes being connected to a steam outlet of said steam-water separator in downstream relation thereto to receive the dried steam and convert the dried steam to superheated steam using the heat of the flue gas;
• and
• a desuperheater connected to the superheater tubes in downstream relation thereto to receive the superheated steam therefrom at a steam inlet of said desuperheater, and also connected to a blowdown outlet of the steam-water separator to receive the blowdown water therefrom, the desuperheater being configured to vaporize said blowdown water using the superheated steam from the superheater tubes to generate a superheated steam output from said desuperheater for use by the SAGD injection or other application.