CA1274085A - Method and device for pre-heating waste metal for furnaces - Google Patents
Method and device for pre-heating waste metal for furnacesInfo
- Publication number
- CA1274085A CA1274085A CA000552950A CA552950A CA1274085A CA 1274085 A CA1274085 A CA 1274085A CA 000552950 A CA000552950 A CA 000552950A CA 552950 A CA552950 A CA 552950A CA 1274085 A CA1274085 A CA 1274085A
- Authority
- CA
- Canada
- Prior art keywords
- flue gases
- furnace
- waste metal
- heating
- gases
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
Abstract
ABSTRACT
This invention relates to a method and a device for pre-heating waste metal for furnaces, flue gases generated in a furnace (1) being supplied simultaneously or sequentially to two pre-heating places (3, 4) with waste metal containers (14), said flue gases being made to flow through a combustion chamber (19) provided with a burner (20) before being supplied to the pre-heating places (3, 4), said burner (20) producing a variable amount of hot gases for admixture with the flue gases from the furnace (1) and superheating thereof. After flowing through the waste metal containers (14) burnt flue gases are supplied to a gas cleaning plant (5) for flue gases and unburnt flue gases to the combustion chamber (19) for further combustion, after which the flue gases now burnt are supplied to said gas cleaning plant (5).
This invention relates to a method and a device for pre-heating waste metal for furnaces, flue gases generated in a furnace (1) being supplied simultaneously or sequentially to two pre-heating places (3, 4) with waste metal containers (14), said flue gases being made to flow through a combustion chamber (19) provided with a burner (20) before being supplied to the pre-heating places (3, 4), said burner (20) producing a variable amount of hot gases for admixture with the flue gases from the furnace (1) and superheating thereof. After flowing through the waste metal containers (14) burnt flue gases are supplied to a gas cleaning plant (5) for flue gases and unburnt flue gases to the combustion chamber (19) for further combustion, after which the flue gases now burnt are supplied to said gas cleaning plant (5).
Description
20368-'~23 This invention relates to a method and a devic0 ~or pre--heatiny waste metal for furnaces, ~lue gases generated in a furnace being suppliecl simultaneously or se~uentially to two pre-heating chambers with waste metal containers.
In the electric steel indusery waste metal can be utilized as main raw material in electric arc furnaces. Moreover, waste metal can be used as cooling agents in basic oxygen 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 eonnected to the furnace for post-combustion oE 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 ~rom the furnace varying in time. Moreover, the waste metal cannot be heated as cold flue gases are generated in the
In the electric steel indusery waste metal can be utilized as main raw material in electric arc furnaces. Moreover, waste metal can be used as cooling agents in basic oxygen 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 eonnected to the furnace for post-combustion oE 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 ~rom the furnace varying in time. Moreover, the waste metal cannot be heated as cold flue gases are generated in the
2~ furnace e.g. at times with no connected power.
It is the objec~ of this invention to provide an improved method and an improved device of the kind indicated above.
Accordingly, the present invention provides a method for pre-heating waste metal for furnaces, flue gases generated in a furnace being suppliecl simultaneously or sequentially to two pre-heating places with waste metal containers, characterized in that ~'! iJ~, C~
L~
2036~--523 the ~lue gases are made ~o flow through a combustion chamber provicled with a burner before being supplled -to the pre-hecltin-J
places, that the burner procluces hot gases for adml~ture with the flue gases from the furnace and superheating thereof and that burnt flue gases from the pre-heating places are supplied to a gas cleaning plant for flue gases and unburnt flue gases are supplied to the combustion chamber for post-combustion of the flue gases, after which the flue yases thus burnt are supplied to said yas cleaning plant.
In another aspect the invention provides a device for pre-heating waste metal for furnaces, flue gases yenerated in a furnace being supplied simultaneously or sequentially to two pre-heating places with waste metal containers, characterized by a eombustion chamber provided with a burner for production of a variable amount of hot gases for admi~ture with the flue gases from the furnace and superheating thereof, said combustion chamber being provided with an inlet for flue gases generated in the furnace, outlet for superheated flue gases to the pre-heating places, an inlet for unburnt flue gases from the pre-heating places, an outlet for burnk flue gases to a gas cleaning plant ~or burnt flue gases and a by-pass duct between the inlet and the outlet for supply of burnt flue gases from the pre-heating places direct to said gas cleaning plant.
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 elec-la ~ $
- 2 - 2036~-5~3 tric arc Eurnace, on one hand, and, on the other hand, ~rom the pre-heating chambers are post-combusted and destructed at a tem-perature 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 loca-tion of -the combustion chàmber is independent of the position of the electric arc fur-nace. In other words, it can thus be placed in a direct connec-tion with the pre-heating chambers. Moreover, the waste metal can also be heated at times wi-th cold flue gases from the furnace by means of the burner.
An illustra-tive example of the invention will be des-cribed 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 oxygen Eurnace are evacuated via a dust col-lector 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 Eor admixture with Elue gases from the furnace 1 and for post-com-bustion of unburnt gases from the furnace 1 and from the pre-heat-ing 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 i-ts 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 `,(~
~237~
It is the objec~ of this invention to provide an improved method and an improved device of the kind indicated above.
Accordingly, the present invention provides a method for pre-heating waste metal for furnaces, flue gases generated in a furnace being suppliecl simultaneously or sequentially to two pre-heating places with waste metal containers, characterized in that ~'! iJ~, C~
L~
2036~--523 the ~lue gases are made ~o flow through a combustion chamber provicled with a burner before being supplled -to the pre-hecltin-J
places, that the burner procluces hot gases for adml~ture with the flue gases from the furnace and superheating thereof and that burnt flue gases from the pre-heating places are supplied to a gas cleaning plant for flue gases and unburnt flue gases are supplied to the combustion chamber for post-combustion of the flue gases, after which the flue yases thus burnt are supplied to said yas cleaning plant.
In another aspect the invention provides a device for pre-heating waste metal for furnaces, flue gases yenerated in a furnace being supplied simultaneously or sequentially to two pre-heating places with waste metal containers, characterized by a eombustion chamber provided with a burner for production of a variable amount of hot gases for admi~ture with the flue gases from the furnace and superheating thereof, said combustion chamber being provided with an inlet for flue gases generated in the furnace, outlet for superheated flue gases to the pre-heating places, an inlet for unburnt flue gases from the pre-heating places, an outlet for burnk flue gases to a gas cleaning plant ~or burnt flue gases and a by-pass duct between the inlet and the outlet for supply of burnt flue gases from the pre-heating places direct to said gas cleaning plant.
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 elec-la ~ $
- 2 - 2036~-5~3 tric arc Eurnace, on one hand, and, on the other hand, ~rom the pre-heating chambers are post-combusted and destructed at a tem-perature 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 loca-tion of -the combustion chàmber is independent of the position of the electric arc fur-nace. In other words, it can thus be placed in a direct connec-tion with the pre-heating chambers. Moreover, the waste metal can also be heated at times wi-th cold flue gases from the furnace by means of the burner.
An illustra-tive example of the invention will be des-cribed 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 oxygen Eurnace are evacuated via a dust col-lector 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 Eor admixture with Elue gases from the furnace 1 and for post-com-bustion of unburnt gases from the furnace 1 and from the pre-heat-ing 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 i-ts 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 `,(~
~237~
- 3 - 2036~-523 mixed with the flue gases ~rom the furnace 1 and/or the c'hambers 3 and 4.
The combustion chamber ]9 i5 provided wit'h connecting ducts for flue gases; an inlet duct 23 for flue gases from t'he furnace 1, an outlet duct 24 for super-heated flue gases to the prè-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, respectively.
The pre-heating chambers 3 and 4 comprise each a lift-able roof 13 whic'h is intended to be sealingly adapted on top of awaste metal container 14 in the respective chamber 3 and 4. Said containers 14 which can consti-tute for example a basket or a chute placed on a carriage are preferably provided with a water-cooled jacket and a water-cooled bottom with automatic connection of cooling water and emptying of the water circuits upon charging of the was-te metal in the furnace in order to be able to withstand the high gas temperatures (500-1000C). The sealing between the covers 13 and the chambers 3 and 4, respectively, can be achieved
The combustion chamber ]9 i5 provided wit'h connecting ducts for flue gases; an inlet duct 23 for flue gases from t'he furnace 1, an outlet duct 24 for super-heated flue gases to the prè-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, respectively.
The pre-heating chambers 3 and 4 comprise each a lift-able roof 13 whic'h is intended to be sealingly adapted on top of awaste metal container 14 in the respective chamber 3 and 4. Said containers 14 which can consti-tute for example a basket or a chute placed on a carriage are preferably provided with a water-cooled jacket and a water-cooled bottom with automatic connection of cooling water and emptying of the water circuits upon charging of the was-te metal in the furnace in order to be able to withstand the high gas temperatures (500-1000C). The sealing between the covers 13 and the chambers 3 and 4, respectively, can be achieved
4~
- ~ - 2036~--523 for instance by means oE an annulclr waterseal 15.
~ he pre-heating chambers 3 and ~ are mutually connected by means oE a crosswise connection system, i.e. the chamber 3 is connected to the inlet duct 7 by means of a passage 16 while the chamber 4 is connected -to the inlet duct 6 by means of a passage 17.
In order to enable control of the flue gas Elow the ducts included in the device are provided with adjustable and controllable flue gas dampers 18.
The flow of the flue gases through the chambers 3 and 4 will be described in the following. The flue gases are led via the inlet duct 6 to -the chamber 3 containing a waste metal basket 14 next in turn to be charged. The flue gases flow through the waste metal container 14 and further through holes in the bot-tom of the con-tainer l4 into the chamber 3. The crosswise connection system makes it possible to lead the flue gases via the ducts 16 and 7 to the pre-heating chamber 4 in which the flow is in the same way as in the chamber 3. The flue gases are thereafter eva-cuated through the outlet duct 9 and the outlet 10 either to the flue gas cleaning plant 5 or to the combustion chamber 19.
The flue gases can also be led directly from the chamber 3 to the outlet 10 without passing the chamber 4.
Of course the flue gases can first be made to pass the chamber 4 if it is found that the waste metal container 14 therein is next in turn for charging. The crosswise connection system is ; - then utilized in the same way as described above.
Normally the flue gases are first supplied -to the .,~
` ~.2~
- ~ - 2036~--523 for instance by means oE an annulclr waterseal 15.
~ he pre-heating chambers 3 and ~ are mutually connected by means oE a crosswise connection system, i.e. the chamber 3 is connected to the inlet duct 7 by means of a passage 16 while the chamber 4 is connected -to the inlet duct 6 by means of a passage 17.
In order to enable control of the flue gas Elow the ducts included in the device are provided with adjustable and controllable flue gas dampers 18.
The flow of the flue gases through the chambers 3 and 4 will be described in the following. The flue gases are led via the inlet duct 6 to -the chamber 3 containing a waste metal basket 14 next in turn to be charged. The flue gases flow through the waste metal container 14 and further through holes in the bot-tom of the con-tainer l4 into the chamber 3. The crosswise connection system makes it possible to lead the flue gases via the ducts 16 and 7 to the pre-heating chamber 4 in which the flow is in the same way as in the chamber 3. The flue gases are thereafter eva-cuated through the outlet duct 9 and the outlet 10 either to the flue gas cleaning plant 5 or to the combustion chamber 19.
The flue gases can also be led directly from the chamber 3 to the outlet 10 without passing the chamber 4.
Of course the flue gases can first be made to pass the chamber 4 if it is found that the waste metal container 14 therein is next in turn for charging. The crosswise connection system is ; - then utilized in the same way as described above.
Normally the flue gases are first supplied -to the .,~
` ~.2~
- 5 - 20368-523 chamber containing the hot waste metal basket, so-called cascade heating. However, it is also possible first to supply the ~lue gases to the chamber containing the cold waste metal basket, for instance a new inserted basket. In this latter heating cycle, so-called reversible heating, a high temperature (800-lOOO~C) is obtained by means of the hot flue gases in the upper part of the cold waste metal basket. The flue gases are thereafter made to flow via the crosswise connec-tion system through the nex-t chamber with a waste metal basket previously heated in the same way. The possible unburnt flue gases after heating -the waste metal in the waste metal basket colder from the beginning will then be ignited, post-combusted and destructed to some extent in the waste metal in the waste metal baske-t hot from the beginning. Thus, in this way a started post-combustion of the flue gases already in the waste metal basket with a following post-combustion in the combustion chamber 19 provided with the burner 20 is achieved.
In case pre-heating is not concerned the gases can be evacuated from the furnace 1 directly via the by-pass duct 27 to the gas cleaning plant S.
When the device is in operation the -flue gases generated in the furnace 1 stream into the combus-tion chamber 19 via -the duc-t 23. The superheated flue qases leave the chamber 19 via the duct 24 and flow thereafter through the pre-heating chambers 3 and 4 in the way previously described. After flowing through the chambers 3 and 4 the flue gases can be led directly to the plant 5 via the ducts 10 and 30 or be recyled through the combustion cham-ber 19 via the ducts 25 and 26.
~7 ,~
~L~3~0~
In case pre-heating is not concerned the gases can be evacuated from the furnace 1 directly via the by-pass duct 27 to the gas cleaning plant S.
When the device is in operation the -flue gases generated in the furnace 1 stream into the combus-tion chamber 19 via -the duc-t 23. The superheated flue qases leave the chamber 19 via the duct 24 and flow thereafter through the pre-heating chambers 3 and 4 in the way previously described. After flowing through the chambers 3 and 4 the flue gases can be led directly to the plant 5 via the ducts 10 and 30 or be recyled through the combustion cham-ber 19 via the ducts 25 and 26.
~7 ,~
~L~3~0~
- 6 - 20368-~23 In order to increase the te~perature in the combust;on chamber l9 and to improve the power efEiciency a heat exchanger 3l is arranged between the ducts 25 and 26.
The ratio of gases generated by the burner 20 to flue gases generated in the furnace 1 can be varied thanks to the fact that the capacity of the burner 20 is adjustable steplessly. If the furnace 1 does not generate any flue gases at all the burner 20 can generate alone a sufficient amount of flue gases for pre-heating the waste metal.
When the furnace 1 is a basic oxygen -furnace there will be difficulties in leading the hot unburnt gases to the chambers 3 and 4 and the combustion chamber 19, respectively, and therefore the burner 20 in this case accounts alone for the pre-heating of the waste metal. On the other hand, the hot flue gases are more suitable for use as fuel. For example, the gases can be supplied to the fuel supply system 21 via the duct 29 after treatment.
Process control of the pre-heating device can be carried out by means of a microprocessor 28 which also controls the part systems included in -the device in addition to the control of dam-pers 18, roof lifting device (not shown) and ans 12.
The invention is not restricted to what has been shownand described, but amendments and modifications thereof are pos-sible within the scope of the inventive idea defined in the claims.
,~ ~
The ratio of gases generated by the burner 20 to flue gases generated in the furnace 1 can be varied thanks to the fact that the capacity of the burner 20 is adjustable steplessly. If the furnace 1 does not generate any flue gases at all the burner 20 can generate alone a sufficient amount of flue gases for pre-heating the waste metal.
When the furnace 1 is a basic oxygen -furnace there will be difficulties in leading the hot unburnt gases to the chambers 3 and 4 and the combustion chamber 19, respectively, and therefore the burner 20 in this case accounts alone for the pre-heating of the waste metal. On the other hand, the hot flue gases are more suitable for use as fuel. For example, the gases can be supplied to the fuel supply system 21 via the duct 29 after treatment.
Process control of the pre-heating device can be carried out by means of a microprocessor 28 which also controls the part systems included in -the device in addition to the control of dam-pers 18, roof lifting device (not shown) and ans 12.
The invention is not restricted to what has been shownand described, but amendments and modifications thereof are pos-sible within the scope of the inventive idea defined in the claims.
,~ ~
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for pre-heating waste metal for furnaces, flue gases generated in a furnace being supplied simultaneously or sequentially to two pre-heating places with waste metal containers, characterized in that the flue gases are made to flow through a combustion chamber provided with a burner before being supplied to the pre-heating places, that the burner produces hot gases for admixture with the flue gases from the furnace and superheating thereof and that burnt flue gases from the pre-heating places are supplied to a gas cleaning plant for flue gases and unburnt flue gases are supplied to the combustion chamber for post-combustion of the flue gases, after which the flue gases thus burnt are supplied to said gas cleaning plant.
2. The method of claim 1, characterized in that the amount of flue gases produced by the burner is adjusted steplessly, said burner producing a sufficient amount of hot gases alone for supply to the pre-heating places in the case when hot flue gases are not generated in the furnace.
3. The method of claim 1, characterized in that the flue gases from the furnace are supplied to the fuel supply system of the burner completely or partly.
4. The method of any one of claims 1. to 3, characterized in that the flue gases are first made to flow through the colder waste metal container, after which the flue gases are made to flow through the waste metal container, which is hotter from the beginning, in order to bring about the started post-combustion of flue gases in the latter waste metal container.
5. A device for pre-heating waste metal for furnaces, flue gases generated in a furnace being supplied simultaneously or sequentially to two pre-heating places with waste metal containers, characterized by a combustion chamber provided with a burner for production of a variable amount of hot gases for admixture with the flue gases from the furnace and superheating thereof, said combustion chamber being provided with an inlet for flue gases generated in the furnace, outlet for superheated flue gases to the pre-heating places, an inlet for unburnt flue gases from the pre-heating places, an outlet for burnt flue gases to a gas cleaning plant for burnt flue gases and a by-pass duct between the inlet and the outlet for supply of burnt flue gases from the pre-heating places direct to said gas cleaning plant.
6. The device of claim 5, characterized in that a fuel supply system of the burner is provided with an inlet for flue gases generated in the furnace.
7. The device of claim 5, characterized in that the inlet for unburnt flue gases and the outlet for burnt flue gases are connected to a heat exchanger arranged between the inlet and the outlet.
8. The device of any one of claims 5 to 7, characterized in that the device is provided with a flue gas damper for control of the flue gas flow and flue gas fans for evacuating said flue gases.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000552950A CA1274085A (en) | 1987-11-27 | 1987-11-27 | Method and device for pre-heating waste metal for furnaces |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000552950A CA1274085A (en) | 1987-11-27 | 1987-11-27 | Method and device for pre-heating waste metal for furnaces |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1274085A true CA1274085A (en) | 1990-09-18 |
Family
ID=4136956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000552950A Expired CA1274085A (en) | 1987-11-27 | 1987-11-27 | Method and device for pre-heating waste metal for furnaces |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1274085A (en) |
-
1987
- 1987-11-27 CA CA000552950A patent/CA1274085A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |