A water-
fire tube boiler of a low discharging high-performance vertically-arranged boiler casing type relates to eight boiler series, namely a large or middle water-fire tube
grate firing, a chamber
combustion, hot-water, steam, and phase-change and distributed type
cogeneration boiler. The invention comprises a longitudinal
barrel, a crossbar collecting box, a wall-cooling tube, a vertically-arranged boiler casing, a screw-thread fire tube and the like. The invention changes
flue direction of current water-fire tube boilers from a longitudinal
flue which is horizontally returned in front and back direction to a transversal
flue which is vertically returned in up and down direction. Twice large dilatancies are naturally realized before
smoke enters into the flue, and the vertically-arranged boiler casing is entirely barely heated in the rear portion of the flue of the boiler. The volume of a furnace and the flue and a radiative-
convective heating surface are significantly enlarged with same size and same quantity of steel consumption, a five return journey of a whole forced-circulating waterway for
coal and hot water is only provided with a baffle board, and a three journey of a whole forced-circulating waterway for gas (oil) is not provided with any baffle boards. Inlet water roses slowly after entering into the boiler casing, and firstly washes an upper tube sheet, and then enters into a rising tube. The invention eliminates tube explosion, tube-
plate fracture and flue abrasion, the initial discharging concentration of
smoke is greatly reduced, and consumption of steel and
electricity is decreased.