A reverse catenary muffle, and method of forming same, includes a planar lower surface, and first and second sidewalls extending upwardly in parallel relation from opposite, first and second edges, respectively, of the lower surface. A concave arch-shaped upper surface extending from upper ends of the first and second sidewalls wherein upper portions of the arch-shaped upper surface are defined at an interconnection of the upper surface with the sidewalls, and a central portion of the upper surface spaced from the lower surface.

A heat-recovering oven system based on temperature gradient comprises: multiple chambers arranged in a sequence, the chambers configured for operating at various temperatures according to a temperature gradient arrangement that spans the sequence; a conveyor configured for transporting product through the multiple chambers in the sequence for heat treatment according to the temperature gradient arrangement; and multiple temperature-segregated heat exchanger systems, each heat exchanger system including a heat exchanger, a conduit to at least one of the chambers based on its temperature in the temperature gradient arrangement, and a return conduit from the at least one chamber to the heat exchanger.

A heat treatment furnace may include: a furnace body including an entrance and an exit; a lower plate member disposed in the furnace body; an upper plate member disposed above the lower plate member, wherein the upper plate member is configured to allow the plurality of objects stacked in an up-down direction to be placed thereon; an intermediate member interposed between the lower plate member and the upper plate member in the up-down direction and attached to the lower plate member; and a pusher configured to push the upper plate member forward from the entrance toward the exit. The upper plate member may move forward above the lower plate member. A sliding resistance between the upper plate member and the intermediate member may be smaller than a sliding resistance between the upper plate member and the lower plate member.

A reverse catenary muffle, and method of forming same, includes a planar lower surface, and first and second sidewalls extending upwardly in parallel relation from opposite, first and second edges, respectively, of the lower surface. A concave arch-shaped upper surface extending from upper ends of the first and second sidewalls wherein upper portions of the arch-shaped upper surface are defined at an interconnection of the upper surface with the sidewalls, and a central portion of the upper surface spaced from the lower surface.

A heat-recovering oven system based on temperature gradient comprises: multiple chambers arranged in a sequence, the chambers configured for operating at various temperatures according to a temperature gradient arrangement that spans the sequence; a conveyor configured for transporting product through the multiple chambers in the sequence for heat treatment according to the temperature gradient arrangement; and multiple temperature-segregated heat exchanger systems, each heat exchanger system including a heat exchanger, a conduit to at least one of the chambers based on its temperature in the temperature gradient arrangement, and a return conduit from the at least one chamber to the heat exchanger.