Electric heating – Heating devices – Resistive element: igniter type
Patent
1987-01-08
1989-04-04
Paschall, M. H.
Electric heating
Heating devices
Resistive element: igniter type
219369, 219374, 219365, 432 94, 266139, F27D 1100
Patent
active
048188441
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to a furnace heating arrangement which incorporates a regenerative arrangement.
Regenerative arrangements are known for preheating combustion air for a burner, in which exhaust (or flue gases) and air are passed alternately through a heat rententive matrix. The conventional regenerative arrangement is for the flue gases to be exhausted from the interior of the furnace and for the preheated combustion air to be fed into the interior of the furnace separately from the fuel or combustible air/fuel mixture so that the flame is formed within the furnace interior. DE-PS-298292; GB-A-2056040 and EP-A-0019007 disclose such an arrangement and the latter reference also discloses the use of electrical heating in a melting furnace as a supplement to the heating due to combustion of fuel in the furnace interior, the electrodes being immersed in the melt.
U.S. Pat. No.-A-3345054 and DE-A-1758790 disclose basically similar arrangements for heating an open hearth furnace in which a separate flue path is provided for exhausting hot gases from the furnace interior through a regenerative matrix but the reverse flow of fresh combustion air is diverted, after passage through the matrix, and is fed to a burner to support the formation of a high and luminous flame which is directed into the open hearth furnace by the burner.
DE-A-2944818 discloses a self-recuperation system which differs from a regenerative arrangement in that the fresh combustion air is supplied continuously and is continuously preheated by heat exchange with a stream of hot gases within a matrix incorporated in the burner, the stream of hot gases being exhausted from the furnace continuously through the burner. The heat exchanger of the burner disclosed by this reference is formed of a ceramic material.
Another form of regenerative arrangement which is known for heating a furnace comprises two burners, each with its own regenerative arrangement, and a common changeover valve operable to connect each burner, through its own regenerative arrangement to a respective one of a forced supply of fresh air, and means for drawing exhaust gases from the interior of the furnace, through the respective burner and regenerative arrangement. Hence one of the burners is fired using air fed to it via its regenerative arrangement so that it is heated, that burner directing a stream of products of combustion into the furnace interior, while the other burner serves as an waste flue for the furnace products of combusion within the interior of the furnace being drawn through the other burner and the respective regenerative arrangement so that the latter is heated. The burners and the regenerative arrangements are formed so that all their working surfaces are ceramic. EP-A-0119786 discloses a burner for use in such a regenerative arrangement.
According to this invention there is provided a furnace heating arrangement comprising a heat retentive matrix and means operable alternately to cause a hot exhaust stream from the furnace to be passed through the matrix whereby the matrix is heated, and to cause an induction stream to be passed through the matrix to the furnace such that it is heated by heat retained in the matrix, wherein the matrix is associated with an electrical heating element which is operable to heat a stream which is passed through the matrix. The induction stream may be fresh air or recirculated furnace atmosphere.
The furnace heating arrangement operates so that heat output from the electrical heating element is distributed to and within the matrix, is collected within the matrix on exhaustion from the furnace and is transferred to the furnace subsequently. The complex heating element structures normally used to distribute heat within electric furnaces need not be used in a furnace heating arrangement in which this invention is embodied.
The matrix and the interior of the furnace may communicate with each other through a tunnel formed within a respective burner. Operation of the burner and the electrical heating element may be cont
REFERENCES:
patent: 2172105 (1939-09-01), Parker
patent: 3345054 (1967-10-01), Andonjev et al.
patent: 4141408 (1979-02-01), Garnett
patent: 4401101 (1983-08-01), Lunde
patent: 4434004 (1984-02-01), Ratschat
patent: 4532413 (1985-07-01), Ahonen
Hotwork Development Limited
Paschall M. H.
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