PURPOSE: To provide a water tube boiler capable of unifying the temperature distribution of respective water tubes, increasing heat transfer efficiency and reducing the generation of NOx and CO while having an annular boiler body structure, easy to manufacture and same as a conventional structure.
CONSTITUTION: A burner 3 is arranged so as to inject fuel gas horizontally against a multitude of water tubes 5 arrayed in up-and-down direction. A fore water tube group 6, in which a plurality of water tubes 5 are arranged immediately before the downstream side of the burner 3 in two rows with a predetermined distance, is formed by a part of the water tubes 5. First row side water tube walls 7-1, 7-1, consisting of a plurality of water tubes 5 connected in parallel, and a rear water tube wall 9-1 are provided at both sides and the rear surface of the fore water tube group 6 so as to form a rectangular combustion chamber by the other water tubes 5. Second row side water tube walls 7-2, 7-2 are provided at the outer side of the first row side water tube walls 7-1, 7-1. Combustion gas, burnt in the combustion chamber 8, is passed through gas passages 15, 16 from gaps 10, 10 provided between the first row side water tube walls 7-1, 7-1 and the rear water tube wall 9-1, then, is discharged out of a flue 13.
OBARA OKITSUGU
ABE TADAAKI
Next Patent: ONCE-THROUGH TYPE WASTE HEAT BOILER