Gas flow furnace

A gas recirculating furnace for leading a recirculating gas current heated by an out-of-furnace heat source into the furnace to heat a heating target, comprising:

• heating chambers which are provided on both side walls of the furnace and have heat sources to heat the recirculating gas current that is yet to be injected into the furnace;
• and an out-of-furnace circulating path for connecting the heating chambers to take out the recirculating gas current in the furnace to the outside of the furnace and flow it back into the furnace, the out-of-furnace circulating path including:
• regenerative beds provided in the vicinity of recirculating gas current inlet and outlet openings of the heating chambers, respectively;
• a circulating fan;
• a passage switching device for selectively and alternately connecting an intake side and a discharge side of the circulating fan to one of the regenerative beds to change a flow direction of the gas current to the regenerative beds;
• and a heat removing means for performing heat removal or dilution in order to change the gaseity of the recirculating gas current in a section between the both regenerative beds, thereby forming in the furnace a high-temperature strong recirculating current which inverts the flow direction of the gas current by periodical changeover of the passage switching apparatus.