Patent ID: 9134021
Filing Date: 2015-09-15
Classification: F22B

Abstract:
1. A boiler structure comprising: a number of boiler evaporation tubes that are arranged vertically on a wall surface that form a furnace wall of a furnace, the boiler evaporation tubes being heated in the furnace to produce steam from water flowing inside the tubes; wherein the vertically arranged boiler evaporation tubes are formed by connecting a plurality of straight tubes each having same outer diameter, inner diameters of the straight tubes in a burner part of the furnace are set at varying wall thickness of the straight tubes such that the inner diameters are set according to the furnace heat flux experienced by the straight tubes in the burner part in such a way that in a region where the furnace heat flux is highest, the inner diameter is set to be the smallest, and the inner diameters in the burner part are set in a stepwise manner according to the furnace heat flux that varies in accordance with a distance in a boiler height direction of the burner part, wherein at least three different inner diameters of the boiler evaporation tubes are set to correspond to at least three steps from the bottom part of the furnace to the burner part of the furnace and at least three different inner diameters of the boiler evaporation tubes are set to correspond to at least three steps above the burner part of the furnace, the three different inner diameters of the boiler evaporation tubes corresponding to said at least three steps from the bottom part to the burner part are same as the respective three inner diameters of the boiler evaporation tubes corresponding to said at least three steps above the burner part.