Combustion device in tube nested boiler and its method of combustion

Abstract

In a combustion device, a boiler is provided with a water tube nest in which combustion, flame holding, fuel-air mixing, and heat absorption are carried out by each water tube in a tube nest. The arrangement of this combustion device enables elimination of the conventional burner and furnace. Fuel supply devices are provided upstream of the water tube nest to supply fuel or a fuel-air mixture. One or several combustion catalysts are provided across the gas flow direction in the boiler to promote combustion. In one arrangement, the fuel supply devices are fuel supply tubes, and fuel or fuel and air are supplied to the fuel supply tubes and spouted from fuel injection nozzles thereof. The fuel supply tubes and water tubes are arranged such that the row of fuel supply tubes is spaced upstream from the first water tube row, such that L.gtoreq.3D where L is the pitch between the fuel supply tube row and the first water tube row, and D is the diameter of the water tubes. Also, P.gtoreq.2D where P is a longitudinal pitch between the water tube rows. A suitable number of fins having a suitable angle and height can be provided on the water tubes and/or the fuel supply tubes. U-shaped or other openings can be made in the fins.