Quadrangular type multi-tube once-through boiler

A quadrangular type multi-tube once-through boiler unit comprising:

• a boiler casing having four side-walls including a first pair of opposing relatively wide end walls and a pair of opposing relatively narrow side walls,
• each wall having an inner side,
• a water tube assembly in which a plurality of vertical water tubes are arranged parallel each other in said boiler casing, each of said vertical water tubes including an upper end connected to an upper header and a lower end connected to a lower header,
• a burner means, having a combustion system, provided on one end of said pair of side walls in said boiler casing,
• an exhaust gas discharging means provided on an other end of said pair of side walls in said boiler casing,
• a burner duct connected to said burner means,
• a blower equipped to one end of said burner duct,
• said water tube assembly including a pair of water tube rows each arranged along the inner side of each of said side walls, each of adjacent water tubes of said pair of water tube rows being connected with partition members to form first and second water tube walls,
• said pair of water tube walls, said upper header and said lower header forming a combustion gas path for allowing substantially linear passage of the combustion gas from the side of said burner means to the side of said exhaust gas discharging means, and
• said water tube assembly further including a plurality of vertical water tubes arranged between said pair of water tube walls to constitute a plurality of water tube lines from the first line to an n-th line from said burner means side to said exhaust gas discharging means side in said combustion gas path and the first line of water tube in said water tubes being arranged adjacent to the combustion surface of said burner means.