Abstract: Included is a method of starting up a direct heating device having a fuel introduction zone, a combustion zone and a process zone that is in heat exchange relationship with said combustion zone. Prior to the introduction of a fuel fluid into said combustion zone, an oxidant fluid, having a high temperature, is passed through the combustion zone for a warm-up time period sufficient to raise the temperature of the direct heating device to a desired temperature. Steam or a process fluid is passed through the process zone followed by the introduction of a fuel fluid into the fuel introduction zone. After the device has been heated up a process fluid is introduced through the process zone. Thereafter, the introduction of steam through the process zone may be stopped.

Abstract: A gas burner assembly for heating a subsurface formation includes an oxidant conduit, a fuel conduit, and a plurality of oxidizers coupled to the oxidant conduit. At least one of the oxidizers includes a mix chamber for mixing fuel from the fuel conduit with oxidant from the oxidant conduit, an igniter, and a shield. The shield includes a plurality of openings in communication with the oxidant conduit. At least one flame stabilizer is coupled to the shield.

Abstract: A flameless combustion heater is described, that comprises an oxidation conduit and a fuel conduit positioned within the oxidation conduit to form an oxidation zone having an inlet and an outlet, said fuel conduit having a plurality of openings that provide fluid communication from within the fuel conduit to the oxidation conduit wherein the longitudinal axis of at least one opening forms an oblique angle with the inner surface of the oxidation conduit.

Abstract: A gas burner assembly for heating a subsurface formation includes an oxidant conduit, a fuel conduit, and a plurality of oxidizers coupled to the oxidant conduit. At least one of the oxidizers includes a mix chamber for mixing fuel from the fuel conduit with oxidant from the oxidant conduit, an igniter, and a shield. The shield includes a plurality of openings in communication with the oxidant conduit. At least one flame stabilizer is coupled to the shield.

Abstract: A flameless combustion heater is described that comprises an oxidation conduit and a fuel conduit having a plurality of centralizers attached to the external wall of the fuel conduit wherein at least one centralizer or portion of a centralizer is angled with respect to the longitudinal axis of the fuel conduit.

Abstract: A flameless combustion heater system is described that comprises a flameless combustion heater; an oxidant inlet pipe; a fuel inlet pipe; and a preheater for preheating the oxidant or the fuel, said preheater comprising an oxidation catalyst. A method for starting up a flameless combustion heater is described comprising passing a fuel-oxidant mixture to a preheater comprising an oxidation catalyst to preheat the fuel or oxidant stream being fed to the heater. A method for controlling the temperature of the flameless combustion heater system is also described that comprises controlling the amount of fuel and/or oxidant that passes through the preheater.