formed and carried in or wherein the floor unit 45 and the fuel block 48 are integrally formed and carried in would have greater work efficiency forming blocks such as the duct block 47 or the fuel block 48 and integration thereof with the floor unit 45 are performed nearby the installation site or in a plant rectangular ducts are formed of casing in a box shape with supports provided inside the ducts and thermal insulation and cladding sheets on the outside and dampers and expansion joints provided along the way round ducts are formed of casing in a cylindrical shape with thermal insulation and cladding sheets on the outside and expansion joints provided along the way the duct block 47 has at least duct casing panels internal supports and dampers and is configured beforehand in a block form so as to be within the hoisting limit load of the crane fuel pipes are configured of straight piping bent piping joints for connection thereof and supports for supporting these with the steel structure the fuel block 48 has at least fuel pipes and supporting devices supporting members thereof and is configured beforehand in a block form so as to be within the hoisting limit load of the crane a second floor unit 50 is assembled above the first floor unit 45 with a duct block 47 and stoker 51 being carried in an attached fig1 illustrates the duct block 47 and stoker 51 being installed using multiple cranes 46 next as shown in fig3 and 4 second level steel.