JP4912111B2 - Apparatus and method for cooling exhaust gas for electric furnace - Google Patents

Description

  The present invention relates to a cooling device and a cooling method for exhaust gas generated from an electric furnace used for melting, refining, etc. of metals, and in particular, a cooling pipe connected to a rear stage of a combustion tower for burning the exhaust gas generated from the electric furnace. The present invention relates to a cooling apparatus and a cooling method for an exhaust gas for an electric furnace that is water-cooled from the outside.

  Conventionally, as a technique for cooling exhaust gas discharged from an electric furnace or the like, (1) an indirect water cooling method such as a water cooling jacket method or an indirect water cooling method in which heat is removed by contact with a pipe type duct or a water cooling pipe connected in parallel with a cooling pipe. Water-cooled type, (2) Direct water-spray cooling type that blows direct spray water into exhaust gas and removes heat, and (3) Air-cooled type that cools by external air by connecting multiple cooling pipes in parallel It is used (for example, refer to Patent Document 1).

However, the indirect water cooling type (1) requires the use of a large amount of cooling water. In general, a water cooling jacket or the like having a welded structure leaks water from the welded part, and is used for repair and maintenance. A great deal of effort is spent.
In addition, in the direct water spray spray type of (2), since spray water is blown directly into the exhaust gas by the water spray, the evaporative heat of water directly contributes to the cooling of the exhaust gas, so that the cooling efficiency is high. (1) The amount of cooling water used is less than the indirect water cooling type. However, dust adheres to the cooling tower and exhaust gas duct, drainage due to spray water that cannot evaporate, etc., or in bag filters generally placed in the cooling device, dust adheres to the filter cloth due to moisture condensation. And a great deal of labor is spent on maintenance, such as prevention of filter cloth clogging.

  On the other hand, as a typical technique of the air cooling type (3), it is disclosed in Patent Document 1, but this means that a plurality of cooling pipes are connected in parallel, and the contact area with the outside air, that is, the cooling area, is reduced. In this method, the air is cooled by outside air. Therefore, unlike the indirect water cooling type of (1) and the direct water spray spray cooling type of (2), no cooling water is used, so troubles such as water leakage and dust adhesion do not occur. Furthermore, when a vertical pipe is used as the cooling pipe, there is little adhesion of dust that can be a catalyst for the recombination of dioxin (DXN) to the cooling pipe, so there is little resynthesis of dioxin (DXN). There is an advantage.

  However, the air cooling type represented by Patent Document 1 has a cooling performance lower than that of the water cooling method, and thus a large amount of heat transfer area is inevitably required. Therefore, it is necessary to set the height of the cooling equipment, for example, the required height of the cooling pipe formed by connecting the plurality of cooling pipes in parallel, and there is a problem that the equipment cost of the cooling equipment increases.

  In the air-cooled type, since the exhaust gas temperature entering the cooling pipe is generally reduced to about 400 ° C. from the limit of use of the material constituting the cooling pipe, the combustion is specifically performed. In order to lower the exhaust gas temperature from the tower to the cooling pipe to about 400 ° C, it is necessary to provide a long exhaust pipe between the combustion tower and the cooling pipe. Is required, and there is a drawback that the installation location is limited.

Furthermore, since the exhaust gas temperature of the combustion tower, in other words, the exhaust gas temperature on the inlet side of the exhaust pipe varies greatly depending on the combustion state of the combustion tower, there is room for the exhaust gas temperature discharged from the combustion tower for both the exhaust pipe and the cooling pipe. A thermal design to hold it was necessary. This has been an obstructive factor in solving the problem that the equipment cost of the cooling equipment increases and the problem that the installation place is limited.
JP 10-89665 A

  The problem to be solved by the present invention is to provide an exhaust gas cooling apparatus and a cooling method for an electric furnace that can realize high cooling performance, space saving, and cost reduction.

The present inventor has obtained the following technical findings as a result of various experimental studies and theoretical studies to solve the above problems.
(A) As described above, an air-cooling type in which a plurality of cooling pipes are simply connected in parallel and air-cooled by outside air has low cooling performance and a large installation space for the apparatus, while a water-cooling type that uses cooling water Although the cooling performance is high, there is a negative effect due to the use of cooling water. However, when the air-cooled type and the water-cooled type are combined under predetermined conditions, high cooling performance, space saving, and cost reduction can be realized.

(B) Specifically, it is not difficult to imagine that cooling performance is improved by spraying cooling water from the spray nozzle onto the outer surface of the cooling pipe, but the amount of cooling water is increased to increase cooling performance. If the air temperature is too high, the cooling efficiency will be reduced, or the sprayed cooling water will flow down from the outer surface of the cooling pipe and the cooling pipe will be immersed in it. There is no merit of combining the two. However, if the amount of cooling water in the spray cooling means is controlled so that the outer surface temperature of the cooling pipe is maintained at 150 ° C. or higher during cooling by the spray cooling means, the cooling water adhering to the outer surface of the cooling pipe is reduced. The sprayed cooling water should not evaporate instantaneously and flow down from the outer surface of the cooling pipe. In other words, both the cooling performance that was a problem of the air cooling type and the maintainability that was a problem of the water cooling type are improved.

(C) Also, since the cooling water adhering to the outer surface of the cooling pipe evaporates instantaneously, the cooling pipe is cooled by cooling by boiling heat transfer, and the conventional cooling pipe for air cooling that is convective heat transfer Compared with, the heat transfer coefficient is several times higher, and the exhaust gas passing through the cooled pipe is cooled efficiently. That is, the cooling efficiency, which was a problem of the air cooling type, is improved.

(D) By controlling the amount of cooling water in the spray-type cooling means so that the outer surface temperature of the cooling pipe is maintained at 150 ° C. or higher when cooled by the spray-type cooling means, and eventually adheres to the outer surface of the cooling pipe. By controlling the amount of cooling water so that the generated cooling water evaporates instantaneously, the cooling performance, which was an issue of the air cooling type, is improved, so the number of necessary stages such as cooling pipes can be reduced and space saving To be able to achieve both cost and cost reduction.

(E) Furthermore, since the exhaust gas temperature discharged from the combustion tower varies greatly depending on the combustion state of the combustion tower, allowance for the exhaust gas temperature discharged from the combustion tower for both the exhaust pipe and the cooling pipe. As a result, the problem that the cooling device becomes larger as a result of this need to be solved by setting a plurality of cooling zones in the flow direction of the exhaust gas flowing through the cooling pipe.

  For example, when a cooling zone consisting of three stages, the first stage, the middle stage, and the latter stage is set in the flow direction of the exhaust gas, when the exhaust gas temperature on the inlet side to the cooling pipe is 400 ° C., the temperature is changed from 400 ° C. to 300 ° C. in the first stage. If the temperature is lowered, the temperature is lowered from 300 ° C. to 250 ° C. in the middle stage, the temperature is lowered from 250 ° C. to 200 ° C. in the latter stage, or the exhaust gas temperature on the cooling pipe is 600 ° C., the first stage The temperature of the exhaust gas that passes through each cooling zone can be arbitrarily set, for example, the temperature can be reduced from 600 ° C to 400 ° C, the temperature can be reduced from 400 ° C to 300 ° C in the middle stage, and the temperature can be reduced from 300 ° C to 200 ° C in the latter stage. Since it can be controlled, there is no need for a thermal design that provides a margin for the exhaust gas temperature discharged from the combustion tower.

  Specifically, the exhaust gas cooling efficiency is higher than in the past, and the temperature of the exhaust gas passing through each cooling zone can be arbitrarily controlled, so the inlet side temperature (cooling start temperature) of the cooling device is set to the high temperature side. This makes it possible to shorten the exhaust pipe that is installed between the combustion tower and the cooling pipe to lower the exhaust gas temperature to about 400 ° C., thereby relaxing the restrictions on the installation location And achieve cost savings.

  Based on the above findings, the present inventor has conceived an exhaust gas cooling device and a cooling method for an electric furnace that can solve the above-mentioned problems. The gist is as follows.

(1) An exhaust gas cooling apparatus for an electric furnace composed of a plurality of cooling zones connected to a subsequent stage of a combustion tower for burning exhaust gas generated from an electric furnace, which is connected in multiple stages in the flow direction of the exhaust gas Each of the cooling zones includes a cooling pipe connected in parallel in the exhaust gas flow direction, a temperature measuring means installed outside the cooling pipe, and a spray-type cooling means for cooling the outer surface of the cooling pipe with water. As a common means, the outer surface temperature of the cooling pipe is maintained at 150 ° C. or higher during cooling by the spray-type cooling means, and the cooling water attached to the outer surface of the cooling pipe evaporates instantaneously. As described above, an exhaust gas cooling apparatus for an electric furnace comprising cooling water amount control means for controlling the cooling water amount of the spray-type cooling means provided in each cooling zone.

(2) A method for cooling an exhaust gas for an electric furnace that cools the exhaust gas flowing in a cooling pipe connected in parallel to the rear stage of a combustion tower that burns the exhaust gas generated from the electric furnace, and distributes in the cooling pipe Set multiple cooling zones in the flow direction of the exhaust gas, and maintain the amount of cooling water of the spray-type cooling means that cools the outer surface of the cooling pipe in each cooling zone at 150 ° C or more. And controlling the temperature of the exhaust gas passing through each cooling zone by controlling the cooling water attached to the outer surface of the cooling pipe to evaporate instantaneously.

(A) According to the present invention, since the cooling water adhering to the outer surface of the cooling pipe evaporates instantaneously, the cooling pipe is cooled by cooling by boiling heat transfer, and the conventional air cooling that is convection heat transfer is performed. Compared to the cooling pipe, the heat transfer coefficient is several times greater, and the exhaust gas flowing through the cooling pipe can be efficiently cooled.

(B) Also, the cooling water adhering to the outer surface of the cooling pipe is heated by the high-temperature exhaust gas flowing through the cooling pipe, and instantly evaporates on the surface of the cooling pipe in a high temperature state. The sprayed cooling water does not flow down from the outer surface of the cooling pipe, and the maintenance of the entire apparatus, which has been a problem with the water cooling method, becomes easy.

(C) That is, according to the present invention, both the cooling performance that was a problem of the air cooling type and the maintainability that was a problem of the water cooling type are improved. It is possible to reduce the number of necessary cooling pipes formed by connecting the cooling pipes in parallel. This not only contributes to the cost reduction of the cooling facility, but also fundamentally solves the problem that the installation location is limited, and at the same time achieves space saving.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
FIG. 1 is a schematic front view of an electric furnace facility provided with an exhaust gas cooling apparatus 3 for an electric furnace according to the present invention, and FIG. 2 shows an electric furnace facility provided with an exhaust gas cooling apparatus 3 for an electric furnace according to the present invention. It is a schematic plan view. 3 is a schematic front view showing an embodiment of the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention, and FIG. 4 is a schematic sectional view showing an embodiment of the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention. is there.

  As shown in FIGS. 1 to 4, an exhaust gas cooling apparatus 3 for an electric furnace according to the present invention includes a plurality of cooling zones 14 </ b> A to 14 </ b> C connected to a rear stage of a combustion tower 2 that combusts exhaust gas generated from the electric furnace 1. It is the cooling device of the exhaust gas for electric furnaces comprised. That is, in the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention, a plurality of cooling zones are set in the flow direction of the exhaust gas flowing through the cooling pipe. This is the exhaust gas cooling apparatus for an electric furnace according to the present invention. One of the three features.

  The cooling zones 14A to 14C connected in a plurality of stages in the exhaust gas flow direction are respectively connected to the cooling pipes 3-i to 3-ha connected in parallel in the exhaust gas flow direction and the outside of the cooling pipe. And a spray-type cooling means 8 for cooling the outer surface of the cooling pipe with water.

  The cooling zone is not limited to the three-stage configuration including the first stage, the middle stage, and the latter stage as shown in FIGS. 3 to 4, but the temperature of the exhaust gas generated from the electric furnace 1, the cooling performance of the cooling means to be set, Or it can set freely suitably according to the conditions of the electric furnace equipment etc. which arrange | position the exhaust gas cooling device 3 for electric furnaces. Hereinafter, a case where three cooling zones are configured will be described. 2 and 4, the cooling pipe is branched into three strips from the exhaust gas pipe 11, but the number of branches is not limited to this for the same reason.

The material of the cooling pipe is not particularly limited, and a steel pipe, a copper pipe with a high cooling rate, or other pipe materials can be used.
Further, as the shape of the cooling pipe, it is desirable that the side surface shape as shown in FIG. Further, the internal shape of the cooling pipe is not particularly limited, and a pipe whose inner wall surface is not processed at all can be used. It is preferable to use one that has been processed so that the exhaust gas can move spirally when passing through the cooling pipe. In this case, since the exhaust gas that passes through the cooling pipe moves in a turbulent state in the cooling pipe, the heat can be transferred while uniformly contacting the inner wall surface of the cooling pipe.

  The electric furnace exhaust gas cooling device 3 according to the present invention includes spray-type cooling means 8 for cooling the outer surface of the cooling pipe with water, and the electric furnace exhaust gas cooling device 3 according to the present invention shown in FIGS. The schematic diagram shows an example in the case of adopting ring-shaped water supply header pipes 8a to 8f as cooling means 8 and a plurality of spray nozzles 12 installed on the inner peripheral surface of the water supply header pipes 8a to 8f. It is.

  As shown in FIG. 5, it is desirable to install the spray nozzle 12 at a position that covers the outer peripheral surface portion of the cooling pipe without gaps by water pickling sprayed and sprinkled from the plurality of spray nozzles 12. In other words, it is desirable to install a number of spray nozzles 12 that can cool the outer peripheral surface portion of the cooling pipe without a gap when the cooling water is sprayed from the plurality of spray nozzles 12.

  Similarly, the mounting positions of the ring-shaped water supply header pipes 8a to 8f are such that the outer peripheral surface of the cooling pipe is vertically moved by water pickling sprayed and sprinkled from a plurality of spray nozzles 12 provided on the upper and lower water supply header pipes. It is desirable to install in a position that covers without gaps. In other words, when the cooling water is sprayed from the plurality of spray nozzles 12 installed on the inner peripheral surfaces of the water supply header pipes 8a to 8f, the number of water supplies that can cool the outer peripheral surface portion of the cooling pipe in the vertical direction without gaps. It is desirable to install a header pipe.

  The proper injection pressure of the cooling water from the spray nozzle 12 is preferably in the range of 0.098 to 0.98 MPa. If it exceeds 0.98 MPa, the impact when the sprayed water droplet collides with the outer surface of the cooling pipe is greatly scattered, resulting in a decrease in cooling efficiency and the location where the cooling pipe is installed is immersed in water. Worsen. In addition, maintainability is reduced. Therefore, the upper limit of the injection pressure is 0.98 MPa or less. On the other hand, if the injection pressure is too low, uniform water droplet spraying is not generated, and cooling efficiency is reduced. Therefore, the lower limit of the injection pressure needs to be 0.098 or more. Therefore, as the spray nozzle 12 installed on the inner peripheral surface of the water supply header pipes 8a to 8f, it is possible to use a general-purpose spray nozzle used for various industries that can realize an injection pressure of 0.098 to 0.98 MPa. desirable.

  The amount of cooling water of the spray type cooling means 8 provided in each cooling zone described above, that is, the spray nozzle 12 installed on the inner peripheral surface of the feed water header pipes 8a to 8f is the exhaust gas cooling device 3 for an electric furnace according to the present invention. It is controlled by the cooling water amount control means 9 included in.

The amount of cooling water for the spray nozzle 12 is such that the cooling pipe attached to the outer surface of the cooling pipe instantly evaporates while maintaining the outer surface temperature of the cooling pipe at 150 ° C. or higher during cooling by the spray cooling means. It is important to set the amount of water that can be performed, which is one of the characteristics of the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention.
With such an amount of cooling water, the cooling water adhering to the outer surface of the cooling pipe is heated by the high-temperature exhaust gas flowing through the cooling pipe and instantly reaches the surface of the cooling pipe that is in a high temperature state. Evaporates. Therefore, the sprayed cooling water does not flow down from the outer surface of the cooling pipe, and the maintenance of the entire apparatus is facilitated.
Further, with such a cooling water amount, the cooling water adhering to the outer surface of the cooling pipe evaporates instantaneously, so that the cooling pipe is cooled by cooling by boiling heat transfer, which is a conventional convection heat transfer. Compared with the air-cooled cooling pipe, the heat transfer coefficient is several times greater, and the exhaust gas flowing through the cooling pipe can be efficiently cooled.
Furthermore, as described above, both the cooling performance, which was an issue of the air cooling type, and the maintainability, which was an issue of the water cooling type, are improved. The number of stages of cooling pipes connected in parallel is reduced, which not only contributes to the cost reduction of the cooling equipment, but can also realize space saving.

  FIG. 6 is an example of a graph showing the exhaust gas temperature in the cooling pipe in each cooling zone. The solid line indicates the case where the cooling water amount of the spray nozzle 12 provided in each cooling zone is controlled by the cooling water amount control means 9. The exhaust gas temperatures when cooling water is not injected from the spray nozzle 12 (corresponding to conventional air cooling) are shown. As apparent from FIG. 6, the cooling performance of the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention is high. For example, when the inlet side exhaust gas temperature is 400 ° C., the temperature is reduced to 200 ° C. Thus, the required number of cooling pipes can be reduced from the conventional three to about two.

  FIG. 7 is another example of a graph showing the exhaust gas temperature in the cooling pipe in each cooling zone. The exhaust gas temperature in the combustion tower varies greatly depending on the combustion state of the combustion tower, and the exhaust gas temperature on the inlet side of the cooling device. Shows a case where the temperature becomes as high as about 600 ° C. The solid line indicates the exhaust gas when the cooling water amount control means 9 controls the cooling water amount of the spray nozzle 12 provided in each cooling zone, and the thin line indicates the exhaust gas when the spray nozzle 12 does not inject (equivalent to conventional air cooling). Each temperature is indicated. As is apparent from FIG. 7, the cooling performance of the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention is high. For example, this is the case where the inlet side exhaust gas temperature greatly exceeds the normal 400 ° C. and reaches about 600 ° C. However, it can be seen that the temperature can be reduced to 200 ° C. This means that the temperature on the inlet side of the cooling device (cooling start temperature) can be shifted to the high temperature side.

Therefore, there is no need for a thermal design that provides a margin for the exhaust gas temperature discharged from the combustion tower as in the conventional air cooling system. For example, the exhaust gas temperature is set to 400 ° C. between the combustion tower and the cooling pipe. The exhaust gas pipe 11 for lowering to the extent can be shortened, and thereby the restriction of the installation location of the entire cooling device including the exhaust gas pipe 11 can be relaxed.
Furthermore, by cooling in the above high temperature side temperature range, it is possible to cool the temperature range that is easy to re-synthesize in a place where there is little dust that can be a catalyst, so that DXN re-synthesis can be further reduced, and the amount of DXN discharged Can be reduced.

  As shown in FIG. 7, the exhaust gas temperature of the combustion tower varies greatly depending on the combustion state of the combustion tower, and the inlet exhaust gas temperature of the cooling device may be as high as about 600 ° C., or FIG. In order to optimize the exhaust gas cooling efficiency in each cooling zone, the amount of cooling water in the spray cooling means provided in each cooling zone is based on the exhaust gas temperature even at the normal inlet exhaust gas temperature as shown in It is desirable to control. Therefore, it is desirable that the cooling zones connected in a plurality of stages in the flow direction of the exhaust gas each include the temperature measuring means 7.

  In addition, as described above, the exhaust gas cooling apparatus 3 for an electric furnace according to the present invention maintains the outer surface temperature of the cooling pipe at 150 ° C. or higher during cooling by the spray-type cooling means, and the outer surface of the cooling pipe. Since the cooling water amount that can be evaporated instantly is set to the amount of cooling water, each cooling zone is provided with the temperature measuring means 7 so that feedback control using the measured exhaust gas temperature as input is possible. Control to maintain the outer surface temperature of the pipe at 150 ° C. or higher is also facilitated.

  FIG. 8 is an explanatory diagram schematically showing the contents of control by the cooling water amount control means 9. Based on the exhaust gas temperature measured by the temperature measuring means 7 provided in each of the cooling zones 14A, 14B, 14C, the cooling water amount control means 9 passes through a water supply source pipe (not shown) to each of the elongated water supply header pipes 8A. The amount of cooling water supplied to ˜8C is set, and the opening degree of each cooling water flow rate adjustment valve 15 shown in FIG. 8 is set according to the set value. The cooling water supplied to each of the elongated water supply header pipes 8A to 8C is supplied to the plurality of ring-shaped water supply header pipes 8a to 8f via the water supply branch pipe 13, and then the plurality of spray nozzles 12 are supplied. Water is sprayed and sprayed on the outer surface of the cooling pipe.

  The cooling water amount control means 9 has various parameter values such as the exhaust gas flow rate in the cooling pipe, the specific heat of the exhaust gas, the heat transfer area in the cooling pipe in each cooling zone, the material of the cooling pipe, the feed water temperature, and the specific heat of the cooling water. The amount of cooling water is calculated using a more general heat transfer calculation, but the above calculation formula, calculation results, and judgment items are incorporated in the cooling water amount control means 9 in advance. Since feedback control using the exhaust gas temperature measured by the temperature measuring means 7 as input is possible, in this case, the calculation error of the calculation result can be corrected, and the outer surface temperature of the cooling pipe is set to 150. Control to maintain at or above ° C becomes easy.

The cooling water amount control means 9 is not particularly limited because it calculates the amount of cooling water using the general heat transfer calculation using the specific heat of the exhaust gas and the specific heat of the cooling water as parameters as described above. For example, a personal computer can be used.
Further, the temperature measuring means 7 is not particularly limited, and a thermometer or a temperature sensor that can withstand 600 ° C. can be used. The temperature measuring means 7 is preferably installed outside the cooling pipe for ease of maintenance.

  The above is a case where the ring-shaped water supply header pipes 8a to 8f and the plurality of spray nozzles 12 installed on the inner peripheral surface of the water supply header pipe are employed as the spray-type cooling means 8 for cooling the outer surface of the cooling pipe with water. However, the method of water-cooling the outer surface of the cooling pipe is not limited to this. For example, it can cool in the aspect shown in FIGS. FIG. 9 is a schematic front view showing another embodiment of the exhaust gas cooling apparatus for an electric furnace according to the present invention, and FIG. 10 is a schematic sectional view showing another embodiment of the exhaust gas cooling apparatus for an electric furnace according to the present invention. is there. FIG. 11 is a diagram schematically showing a cooling method of the cooling pipe, more specifically, a state of injection of cooling water from the spray nozzle 12.

  That is, as shown in FIG. 9, a water supply header pipe was erected so as to be parallel to the cooling pipe in the concave portion of the inverted U-shaped cooling pipe constituting each cooling zone, and installed in the water supply header pipe. The cooling water may be jetted from the spray nozzle 12 toward a predetermined range on the outer surface of the cooling pipe closest in the horizontal direction. For example, the cooling pipes shown in FIG. 9 to FIG. 11 are erected at equal intervals in the vertical and horizontal directions. In this case, cooling water is supplied from one spray nozzle 12 in four directions in the horizontal direction. By spraying, the outer periphery of one cooling pipe can be covered with four sets of spray nozzles 12. That is, the outer peripheral surface portion of one cooling pipe can be covered without a gap by water pickling sprayed and sprinkled from the four sets of spray nozzles 12. Moreover, when spraying cooling water from the spray nozzle 12, it is desirable that a number of spray nozzles 12 that can cool the outer peripheral surface portion of the cooling pipe in the vertical direction without any gaps are installed in the vertical direction.

Next, an embodiment of the present invention will be described. The conditions of the present embodiment are one condition adopted for demonstrating the feasibility and remarkable effects of the present invention, and the present invention satisfies this one condition. It is not limited.
First, regarding the conditions of the cooling pipes 3-i, 3-b, and 3-c, the shape is an inverted U-shaped steel plate, the plate thickness is 12 mm, the inner diameter is 0.5 m, the height is 30 m, and the number of steps of the inverted U-shape is Three stages with 3 branches (parallel) were prepared.
Regarding the conditions of the ring-shaped water supply header pipes 8a to 8f, those having an inner diameter of 0.8 m are prepared, and 10 spray nozzles 12 are uniformly arranged in the water supply header pipes 8a to 8f, and the vertical pipe of the cooling pipe is arranged. 84 water supply header pipes 8a to 8f provided with the spray nozzle 12 were arranged in the range of the body portion 25m per cooling pipe at intervals of 0.3 m in the vertical direction.

  Then, the amount of cooling water in each of the water cooling means for directly water cooling the outer surface of the cooling pipe is controlled to increase or decrease in each cooling zone so that the outer surface temperature of the cooling pipe during cooling does not always become 150 ° C. or lower. Specifically, the water supply amount of the cooling water from the spray nozzle 12 is maximized in the cooling zone 14A where the exhaust gas temperature is high, and the water supply amount in the cooling zone 14C where the temperature is low is minimized. Control in each zone.

  In each comparative example, the same equipment as the present invention was used, but the above water cooling was not performed and only the conventional air cooling was used.

  As is apparent from Table 1, it can be confirmed that Examples 1 to 4 of the present invention have the effects specific to the present invention. That is, the spray water continuously sprayed from the spray nozzle 12 evaporates instantaneously, and the spray water does not re-scatter and drop at the surface of each cooling pipe. Further, as shown in Invention Examples 1 to 4, the cooling efficiency at that time is such that, even if the inlet exhaust gas temperature T1 is higher than that of the conventional case of about 600 ° C., the outlet temperature T3 is the same as in Comparative Examples 1 to 2. The magnitude of the effect of the present invention appears.

1 is a schematic front view of an electric furnace facility provided with an exhaust gas cooling apparatus for an electric furnace according to the present invention. 1 is a schematic plan view of an electric furnace facility provided with an exhaust gas cooling apparatus for an electric furnace according to the present invention. It is a schematic front view which shows one form of the exhaust gas cooling device for electric furnaces which concerns on this invention. It is a schematic sectional drawing which shows one form of the exhaust gas cooling device for electric furnaces which concerns on this invention. It is a schematic diagram which shows the example of installation of the spray nozzle which is a cooling means. It is an example of the graph which shows the exhaust gas temperature in the cooling pipe in each cooling zone. It is another example of the graph which shows the exhaust gas temperature in the cooling pipe in each cooling zone. It is explanatory drawing which shows typically the control content by a cooling water amount control means. It is a schematic front view which shows another one form of the exhaust gas cooling device for electric furnaces which concerns on this invention. It is a schematic sectional drawing which shows another one form of the exhaust gas cooling device for electric furnaces which concerns on this invention. It is a schematic diagram which shows the cooling method of the cooling pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Combustion tower 3 Exhaust gas cooling device 3-I, 3-B, 3-C Cooling pipe 4 Blower 5 Dust collector 6 Building dust collector 7 Temperature measuring means 8 Cooling means 8A, 8B, 8C Long-form water supply Header pipe 8a, 8b, 8c, 8d, 8e, 8f Ring-shaped water supply header pipe 9 Cooling water amount control means 10 Dust discharge device 11 Exhaust gas pipe 12 Spray nozzle 13 Water supply branch pipes 14A, 14B, 14C Cooling zone 15 tuning valve

Claims (2)

An exhaust gas cooling apparatus for an electric furnace comprising a plurality of cooling zones connected to a subsequent stage of a combustion tower for burning exhaust gas generated from an electric furnace,
Each of the cooling zones connected in multiple stages in the exhaust gas flow direction,
A cooling pipe connected in parallel in the flow direction of the exhaust gas;
Temperature measuring means installed outside the cooling pipe;
A spray-type cooling means for water-cooling the outer surface of the cooling pipe;
As a common means, maintaining the outer surface temperature of the cooling pipe at 150 ° C. or higher during cooling by the spray-type cooling means, so that the cooling water adhering to the outer surface of the cooling pipe evaporates instantaneously, An exhaust gas cooling apparatus for an electric furnace, comprising: a cooling water amount control unit that controls a cooling water amount of a spray type cooling unit provided in each cooling zone.
A method for cooling an exhaust gas for an electric furnace for cooling an exhaust gas flowing in a cooling pipe connected in parallel to a subsequent stage of a combustion tower for burning exhaust gas generated from an electric furnace,
Set multiple cooling zones in the flow direction of the exhaust gas flowing through the cooling pipe,
The amount of cooling water of the spray type cooling means for cooling the outer surface of the cooling pipe in each cooling zone is maintained at 150 ° C. or higher so that the cooling water adhering to the outer surface of the cooling pipe is reduced. Control it to evaporate instantly,
A method for cooling an exhaust gas for an electric furnace, characterized in that the temperature of the exhaust gas passing through each cooling zone is controlled.