Heating – Processes of heating or heater operation – Treating an article – container – batch or body as a unit
Patent
1987-12-14
1989-03-14
Yuen, Henry C.
Heating
Processes of heating or heater operation
Treating an article, container, batch or body as a unit
432 28, 432 72, 432180, F27D 300
Patent
active
048121177
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and a device for pre-heating waste metal for furnaces, flue gases generated in a furnace being supplied simultaneously or sequentially to two pre-heating chambers with waste metal containers.
In the electric steel industry waste metal can be utilized as main raw material in electric arc furnaces. Moreover, waste metal can be used as cooling agents in basic oxygene furnaces.
In both cases a controlled pre-heating of the waste metal will bring an improved operation economy.
Methods and devices of the kind mentioned by way of introduction are previously known where the flue gases after flowing through the pre-heating chambers are recycled to a combustion chamber or dust collector directly connected to the furnace for post-combustion of unburnt flue gases. However, it has been found that the combustion of flue gases in such a combustion chamber will be incomplete and uncontrollable due to a temperature from the furnace varying in time. Moreover, the waste metal cannot be heated as cold flue gases are generated in the furnace e.g. at times with no connected power.
It is the object of this invention to provide an improved method and an improved device of the kind indicated above, and this object has been achieved by means of the characteristic features of the method and the device defined in the claims.
One advantage of the invention in comparison with previous solutions is that the invention suggests a combustion chamber provided with a controlled burner of its own, by means of which unburnt gases from the electric arc furnace, on one hand, and, on the other hand, from the pre-heating chambers are post-combusted and destructed at a temperature controllable in time. Moreover, a larger amount of energy is added to the flue gases which is then recycled to the process via a hotter waste metal. The location of the combustion chamber is independent of the position of the electric arc furnace. In other words, it can thus be placed in a direct connection with the pre-heating chambers. Moreover, the waste metal can also be heated at times with cold flue gases from the furnace by means of the burner.
An illustrative example of the invention will be described below with reference to the enclosed drawing which shows schematically a device according to the invention.
A pre-heating device according to the invention is shown with reference to the figure. Flue gases generated in an electric arc furnace/basic oxygene furnace are evacuated via a dust collector 2 to a combustion chamber 19 provided with a burner 20 and thereafter further to two pre-heating chambers 3 and 4.
The burner 20 is intended to produce hot flue gases for admixture with flue gases from the furnace 1 and for post-combustion of unburnt gases from the furnace 1 and from the pre-heating chambers 3 and 4.
The burner 20 can be fired e.g. by means of oil, carbon powder, gas or biofuel (powder). In the figure 21 designates the fuel supply system of the burner and 22 its air supply system.
It is also possible to have the burner 20 consist of an electric plasma burner for production of hot air which can be mixed with the flue gases from the furnace 1 and/or the chambers 3 and 4.
The combustion chamber 19 is provided with connecting ducts for flue gases; an inlet duct 23 for flue gases from the furnace 1, an outlet duct 24 for superheated flue gases to the pre-heating chambers 3 and 4, an inlet duct 25 for unburnt flue gases from the chambers 3 and 4 and an outlet duct 26 for burnt flue gases to the gas cleaning plant 5 for flue gases. A by-pass duct 27 for flue gases is arranged between the inlet duct 23 and the outlet 10 and a by-pass duct 30 is arranged between the ducts 25 and 26.
The pre-heating chambers 3 and 4 are each provided with an inlet duct 6 and 7, respectively, and an outlet duct 8 and 9, respectively. The outlet ducts 8 and 9 are connected to a common outlet 10.
In order to achieve evacuation of the flue gases flue gas fans 12 with a variable speed are arranged in the outlet 10 and immediately upstream the plant 5, r
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patent: 4242084 (1980-12-01), Jamaluddin
patent: 4375958 (1983-03-01), Date et al.
patent: 4437186 (1984-03-01), Inai
patent: 4478574 (1984-10-01), Okuno et al.
NAB-Konsult
Yuen Henry C.
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