US 4,309,171 AGranted

Billet heating furnace with pressurized entrance seal

AssigneeGranco Equipment, Inc.

InventorCharles B. Gentry

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Abstract

A furnace (10) has a preheater zone (12) into which exhaust gases of a combustion chamber (14) are recycled for preheating of articles passing through the furnace. The exhaust gases are supplied to the preheater zone (12) through jet pipes (18) which create a turbulent flow about the articles in the furnace (10). The exhaust gases are withdrawn by a fan (30) which is disposed in a duct (34) adjacent to the furnace entrance (13). To prevent the introduction of ambient air into the furnace (10), a pressure chamber (56), which is maintained at an elevated pressure relative to the ambient air, is provided within the preheater zone (12), with the chamber (56) pressurized by gases supplied by the jet pipes (18). A sealing arrangement defined by the pressure chamber (56) and the articles passing through the furnace prevents the introduction of cool air through the preheater zone (12). In this way, the thermal efficiency of the fuel burned within the combustion chamber (14) is maximized while a pressure balance is maintained in the furnace.

Claims18

Dependent claims

In a furnace for heating articles to an elevated temperature wherein the articles are moved serially from an entrance end of the furnace to an exit end thereof comprising:

a preheater section at an entrance end of the furnace and a heating chamber at an exit end thereof;
means in said heating chamber for directing combustible gases against the articles therein;
means for providing turbulent gas flow along the length of said preheater section;
exhaust means for drawing the exhaust gases of said combustible gases from the furnace;
said exhaust means drawing said exhaust gases from said heating chamber to said preheater section;
means for pressurizing said exhaust gases;
means for communicating said pressurized exhaust gases with said means providing turbulent gas flow;
the improvement which comprises:
means in said preheater section defining first and second chambers therein, said first chamber extending from the entrance end of the furnace along a portion of the length of said preheater section and said second chamber extending from said first chamber to said heating chamber;
and
means for maintaining said first chamber at a first pressure greater than atmospheric pressure with pressurized exhaust gases provided within said preheater section and said second chamber at a lower pressure relative to said first pressure.

8 more elements

In a method for heating articles to an elevated temperature wherein:

the articles are passed serially through preheater and heater zones in a furnace for heating;
combustible gases are supplied to said heater zone and burned therein to heat the articles;
the hot exhaust gas products of the combustible gases are removed from the preheater zone through a fan to create a negative pressure gradient extending along the furnace from the heater zone to the preheater zone;
the hot exhaust gases are pressurized and returned to said preheater zone in a turbulent flow around the articles passing through the preheater zone for preheating of the articles;
the improvement which comprises:
providing a substantially closed chamber at an entrance end of the preheater zone to define a pressure zone within said preheater zone, said closed chamber enveloping the articles passing into the preheater zone in a closely conforming relationship to define a gap seal between said closed chamber and said articles;
and
maintaining said substantially closed chamber at greater than atmospheric pressure by supplying the pressurized exhaust gases thereto while maintaining the negative pressure gradient between the heater zone and the remaining portion of the preheater zone;
wherein said pressurized chamber minimizes the induction of ambient air into the furnace without affecting the negative pressure gradient between the heater zone and the remaining portion of the preheater zone.

6 more elements

Dependencies are inferred from the claim text.