Heating – Work chamber having heating means – Combustion products heat work by contact
Patent
1983-09-21
1985-09-17
Camby, John J.
Heating
Work chamber having heating means
Combustion products heat work by contact
432178, 432247, F27D 1700, F27D 100
Patent
active
045417997
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a preheating furnace for elongated material, like bars, ingots, billets, and the like of metal, particularly aluminum or aluminum alloys, comprising a furnace tunnel made of continuous or segmentally joined refractory furnace shells, particularly thin-walled furnace shells, and adapted to be heated by heater elements, like burners, hot gas nozzles, and the like which extend through the shell walls and are directed toward the material introduced in longitudinal orientation in the furnace tunnel for direct heating of the same, and further comprising an exhaust gas duct disposed in the upper furnace range.
In a known furnace of this kind (DE-PS No. 1807504 which corresponds to U.S. Pat. No. 3,632,093) the thin-walled furnace shells are inserted in the furnace structure without heat insulation. This causes heat losses especially by radiation from the outside walls of the furnace shells. The exhaust gas is sucked off into the exhaust gas duct through a slot in the top of the furnace tunnel. In the path of the gas between the furnace tunnel and the exhaust gas duct heat gets lost. For this reason the efficiency of the known furnace is low. Besides, the known structure is complicated and high because the exhaust gas duct is arranged separately above the furnace tunnel.
It is the object of the invention to design a preheating furnace of the kind specified initially such that the energy supplied for heating is utilized more effectively with a simple and compact structure.
To meet this object it is provided, in accordance with the invention, in a preheating furnace of the kind specified initially that the furnace tunnel is integrated in the exhaust duct which comprises a heat insulation. Preferably the heat insulation of the exhaust gas duct covers the furnace shells of the furnace tunnel from outside at least in their central range so that the lower areas of the furnace shells remain free for purposes of assembly and maintenance.
The fact that the invention provides for much better utilization of the energy is due to the circumstance that the exhaust gas is transferred from the furnace tunnel into the exhaust gas duct without any heat losses, for instance through the upper gap between the vertically disposed furnace shell halves. By virtue of the design in accordance with the invention the central and upper portions of the furnace tunnel are sufficiently well thermally insulated by the exhaust gas duct itself, i.e. without any additional measures. Heat insulation of the lower areas of the furnace tunnel has been dispensed with on purpose to provide better accessibility for assembly work and maintenance. The inventor found out that the losses by heat radiation in the lower areas of the furnace shells are relatively small. Leaving out a heat insulation in these lower areas is highly advantageous because there remains space for the reception and accessibility of aggregates, like burners, supporting frame for the furnace shells, and the conveyor means for the material to be preheated.
The insulation members may extend vertically upwardly from the support members or they may adapt to the upper areas of the furnace shells.
A further development of the invention which is particularly advantageous as regards simple assembly and disassembly, is characterized in that heat insulation is supported by support members mounted stationarily on a support frame of the furnace and comprises removable insulation members disposed above the same, the lower members thereof affording lateral support and insulation of the furnace shells. According to a preferred embodiment of the invention with which lower and upper burner rows are provided, distributed around the circumference of the furnace tunnel, it is provided that the burners of the upper burner rows extend through removable insulation members, while the burners of the lower burner rows are located in the lower range of the furnace shells which is not heat insulated, and that each insulation member through which burners pass has the same length as correspondi
REFERENCES:
patent: 1378710 (1921-05-01), Meyerhofer
patent: 2603470 (1952-07-01), Hess
patent: 3273218 (1966-09-01), Byington
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