Abstract: An apparatus such as a crucible furnace for heating a vessel such as a crucible comprises an enclosure surrounding the vessel so that a flow path exists between the enclosure and the vessel which has an outer surface forming the inner boundary of the flow path. The flow path extends all around the vessel. First and second gas fired burners open into the flow path to discharge their hot combustion product gases into the path. Associated with each burner is a respective heat regenerator. When the first burner is in firing mode its emitted hot combustion product gases circulate around the flow path and leave through the second burner, which is in flueing mode, and heat the associated regenerator. Then when the second burner is in firing mode that heated regenerator heats the combustion air used by the second burner.

Abstract: A fuel fired burner assembly comprises a fuel supply conduit (2) terminating in a nozzle (1) which extends with annular clearance (8a) into a combustion chamber (7) located within a tunnel (3). The nozzle (1) is provided with radially directed outlet passages (18) which convey the fuel from the conduit (2) to the clearance (8a) where the fuel mixes with air entering the clearance (8a) from passages (15), (16) and (8b). These passages formed between the tunnel body (3), an outer tunnel sleeve (11) and an intermediate sleeve (14) between the body (3) and the sleeve (11). The nozzle (1) is also provided with a through-going aperture (19) which is located between two adjacent fuel ports (18) and which is axially offset from the nozzle axis. Extending through the aperture (19) with annular clearance (20) is an electrically operated flame detection probe (21) whose electrode tip (22) is disposed within the central section (6) of the tunnel (3).

Abstract: The present invention relates to a fuel-fired heating element of the tubular kind particularly though not exclusively for use as an immersed heating tube in molten metals, salts or fluidized beds of solid particles for conductive heating or for use in an enclosed or partially enclosed chamber to provide radiant and convective heating.The element includes a tubular housing 1 having one end 2 closed and an opening to provide an outlet 4 for combustion products. A burner assembly 6 is received with an annular clearance 51 within the housing between the outlet 4 and the closed end 2 and is arranged to direct its combustion products as a stream towards the closed end 2.The tube 7 encloses with clearance three axially aligned tubes 60, 61 and 62 whose external and internal diameters decrease sequentially from the burner 6 to the end 2.