Abstract: A bendable hard type water tube includes a first tube with one end installed with a first seat, a second tube having one end installed with a second seat, a first buckle, a second buckle, a rotary shaft installed between the second buckle and the first buckle, a third buckle, an elastic body. The outer sides of the first buckle, second buckle, and third buckle are formed with a plurality of teeth. A resisting portion is installed on the press and resists against the third buckle. When a force is applied to the press, the angle between the first tube and second tube can be changed. When the press is released, the first tube is buckled with the second tube so as to change the direction of water flow to match the requirement of spraying water.

Abstract: The invention provides a water-tube boiler which allows further NOx reduction and CO reduction with a simple construction of the boiler body and the burner itself. The water-tube boiler includes a first water tube array made up of a plurality of first water tubes arranged into an annular shape, a combustion chamber defined inside the first water tube array, a first opening defined at part of the first water tube array, a cooling water tube array made up of a plurality of cooling water tubes arranged into an annular shape in a zone within the combustion chamber where burning-reaction ongoing gas is present, gaps provided between adjacent cooling water tubes so as to permit the burning-reaction ongoing gas to flow through, and a burning-reaction continuing zone, where burning reaction is continuously effected, provided between the cooling water tube array and the first water tube array, whereby the burning-reaction ongoing gas generally uniformly contacts the individual cooling water tubes.

Abstract: Boiler efficiency is further improved and the whole boiler body is slimmed down by totally improving heat transfer surfaces confronting gas flow passages, i.e., by forming the heat transfer surface structure into three stages, and moreover by making effective use of the whole heat transfer surfaces of water tubes equipped with fully circumferentially finned water tubes.

Abstract: A water-tube boiler which allows further NOx reduction and CO reduction to be implemented with an uncomplicated construction of the boiler body itself, and which is improved in boiler efficiency. The water-tube boiler includes a first water tube array made up of a plurality of first water tubes arranged into an annular shape and a combustion chamber inside the first water tube array.