To improve thermal efficiency and maintainability by restraining stock from being burnt and stuck to a grate or a top plate, and restraining plugging of a flame hole part.
An annular burner 1 provided with the inward flame hole part 8 is provided in an opening 15 of the top plate 14, and a first flow straightening body 20 is provided thereon through a first clearance 19. A second flow straightening body 22 is further provided thereon through a second clearance 21, and an inner peripheral end part 23 of the second flow straightening body 22 is shielded with a frame body 16 of the grate 18. A first air flow 35 is allowed to flow into the first clearance 19 to converge flames 34 to the center, and a second air flow 37 is allowed to flow into the second clearance 21 to cool the frame body 16 and the top plate 14, thus restraining stock from being burnt and stuck thereto. Consequently, when the stock spreads to the second flow straightening body 22, it flows down on the first flow straightening body to restrain plugging of the flame hole part 8. High thermal efficiency and excellent maintainability can thereby be simultaneously secured.
Tomoyasu Sakaguchi
Hiroki Naito
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