JP2009162408A - Exhaust gas treatment method and exhaust gas treatment equipment for electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method and exhaust gas treatment equipment for an electric furnace, which cools an exhaust gas of high temperature generated from the electric furnace with high accuracy with a simple constitution. <P>SOLUTION: This exhaust gas treatment equipment of the electric furnace comprises: a combustion chamber for burning the exhaust gas of high temperature generated from the electric furnace 1; a direct duct directly linked to an exhaust side of the combustion chamber at its one end; and a dust collecting machine 7 connected with the other end side of the direct duct. A spray cooling mechanism 11 for spraying the evaporable spray water of particle size of 120 μm or less to the exhaust gas for cooling the same, is disposed in the direct duct. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the operation of an electric furnace facility for steel making for producing steel by melting and refining scrap or scrap and hot metal together, this invention cools and cleans high-temperature exhaust gas generated from the electric furnace. The present invention relates to a furnace exhaust gas treatment method and an exhaust gas treatment apparatus.

Conventionally, high-temperature exhaust gas generated in the process of heating and melting iron scrap or iron scrap and hot metal in a steelmaking electric furnace and refining the resulting molten metal is sucked and discharged from the electric furnace, and is water-cooled attached to the electric furnace. After being guided to a combustion tower and burned, the exhaust gas is cooled via a direct duct including a water-cooled duct, guided to a dust collector, collected, and then discharged into the atmosphere.
The exhaust gas temperature generated in the electric furnace reaches 1500 ° C., and CO in the exhaust gas is burned and removed by the combustion tower, so that the combustion tower is water-cooled, and the direct drawing that leads the exhaust gas after the combustion tower The duct employs a water-cooled duct to pass the high-temperature exhaust gas and cool the high-temperature exhaust gas. Indirect cooling is provided by a duct. The dust collector is generally a dry dust collector composed of a bag filter, and the water cooling duct length is determined and designed so that the appropriate dust collection temperature is 250 ° C. or less which is the heat resistance temperature of the filter cloth ( Patent Document 1).

Conventionally, an exhaust gas cooling duct extending from an exhaust gas combustion tower to a dust collector requires a long extension distance for exhaust gas cooling, and various proposals have been made regarding exhaust gas cooling in order to reduce maintenance and equipment costs.
For example, in Patent Document 2, high-temperature exhaust gas generated from the electric furnace during the operation process of the steel furnace is indirectly cooled by a water cooling duct, led to a water spray spray cooling tower, and directly cooled by spray water, and thus cooled. In addition, an exhaust gas treatment method has been proposed in which building dust collection gas is combined with the exhaust gas, cooled, guided to a dust collector, and exhausted after the exhaust gas is cleaned by the dust collector. Further, in Patent Document 3, after exhaust gas is supplied to an electric furnace exhaust gas combustion tower and burned, combustion waste gas is supplied to a scrap preheating line, and then the exhaust gas is cooled by a gas cooler. Separately from the direct line to the line, a water cooling bypass (water cooling duct) is provided from the combustion tower, and the water cooling bypass and the hood line extending from the building dust collection hood are merged. An exhaust gas treatment method for an electric furnace has been proposed as a dust collection system in which a branch line is branched in the middle and one of the branches branches into a line from the gas cooler.

Further, Patent Document 4 proposes an exhaust gas treatment method for an electric furnace in which exhaust gas cooled by a water cooling duct is guided to a water spray cooling tower and further cooled.
Furthermore, as a proposal for newly providing a cooling device for cooling the exhaust gas exiting the combustion tower, Patent Documents 5, 6 and 7 describe an electric furnace in which an exhaust gas cooling tower is disposed downstream of the combustion tower and the exhaust gas is sprinkled and cooled. An exhaust gas treatment method has been proposed.
Japanese Patent No. 3867304 Japanese Patent Laid-Open No. 11-114361 Japanese Patent Laid-Open No. 08-210786 JP-A-11-179130 JP 2003-260335 A JP 2002-5580 A Japanese Patent Laid-Open No. 11-140550

  However, in the conventional exhaust gas treatment method for an electric furnace described in Patent Document 2, the exhaust gas is led to a water spray spray cooling tower and directly cooled with spray water. The water spray spray cooling tower becomes a large-scale facility for removing moisture, and the exhaust gas treatment itself becomes difficult due to a significant increase in the amount of dust collected by the building dust collection gas that is joined to adjust the temperature. There is a problem and nothing has been realized.

The conventional exhaust gas treatment method for an electric furnace described in Patent Document 3 is the same, and the gas cooler itself becomes a large-scale facility, and the conventional method described in Patent Document 2 is used to join the building dust collection gas. As in the example, the amount of dust collecting air is greatly increased and the exhaust gas treatment itself becomes difficult.
Further, Patent Document 4 proposes an exhaust gas treatment method for an electric furnace in which exhaust gas cooled by a water cooling duct is guided to a water spray cooling tower and further cooled, but as described in Patent Documents 2 and 3, The spray cooling tower itself becomes a large-scale facility that is large-scale for cooling by the water-cooled duct, and there are few advantages.

Furthermore, in the example proposed in Patent Documents 5 to 7 in which the exhaust gas cooling tower is arranged downstream of the combustion tower, that is, in the proposal for newly providing a cooling device for cooling the exhaust gas that has exited the combustion tower, This is exhaust gas cooling applied after burning high-temperature exhaust gas to be sucked and exhausted, and there is a problem that the cooling tower capacity is required to be very high and it must be a large-scale apparatus.
Accordingly, the present invention has been made paying attention to the problems of the above-described conventional example, and an exhaust gas treatment method for an electric furnace and an exhaust gas capable of cooling high-temperature exhaust gas generated from the electric furnace with high accuracy with a simple configuration. The object is to provide a processing apparatus.

  In order to achieve the above object, an exhaust gas treatment method for an electric furnace according to claim 1 is directed to a combustion chamber provided with a high-temperature exhaust gas generated from the electric furnace and burned, and then the exhaust gas is directly drawn into a duct. In an exhaust gas treatment method for an electric furnace, which is supplied to a dust collector via a dust collector and discharged after dust collection, sprayable water having a particle size of 120 μm or less that can be evaporated is cooled on the exhaust gas in the direct duct. It is characterized by doing so.

Moreover, the exhaust gas treatment method for an electric furnace according to claim 2 is the invention according to claim 1, wherein the spray water is applied in a region where the temperature of the exhaust gas in the direct duct is in a range of 800 ° C to 300 ° C. It is characterized by spraying.
Furthermore, the exhaust gas treatment method for an electric furnace according to claim 3 is the invention according to claim 1, wherein the spray water is used in a region where the temperature of the exhaust gas in the direct duct is in the range of 500C to 400C. It is characterized by spraying.

Furthermore, the exhaust gas treatment method according to claim 4 is the invention according to any one of claims 1 to 3, wherein the spray water is injected into the exhaust gas from a plurality of injection nozzles in a plurality of regions of the direct duct. It is characterized by.
Still further, an exhaust gas treatment method for an electric furnace according to a fifth aspect is the invention according to any one of the first to fourth aspects, wherein at least one of a particle size and a flow rate of the spray water is determined as an inlet side exhaust gas temperature of the dust collector. Is controlled to be within the allowable temperature range of the dust collector.

  An exhaust gas treatment apparatus for an electric furnace according to claim 6 includes a combustion chamber for burning high-temperature exhaust gas generated from the electric furnace, a direct pulling duct having one end directly connected to the exhaust side of the combustion chamber, and the direct pulling In an exhaust gas treatment apparatus for an electric furnace provided with a dust collector connected to the other end of the duct, spray cooling is performed by spraying vaporized spray water having a particle size of 120 μm or less onto the exhaust gas into the direct duct and cooling the exhaust gas. A mechanism is provided.

  Furthermore, an exhaust gas treatment apparatus for an electric furnace according to a seventh aspect includes a combustion chamber for burning high-temperature exhaust gas generated from the electric furnace, a direct pulling duct having one end directly connected to the exhaust side of the combustion chamber, and the direct pulling In an exhaust gas treatment apparatus for an electric furnace equipped with a dust collector connected to the other end of the duct, the sprayable water having a particle size of 120 μm or less disposed in the direct duct is sprayed on the exhaust gas and cooled. Control of at least one of spray flow rate and particle size sprayed by the spray cooling mechanism according to the exhaust gas temperature detecting means disposed on the inlet side of the dust collector, and the exhaust gas temperature detected by the exhaust gas temperature detecting means And spray water control means.

Furthermore, the exhaust gas treatment apparatus for an electric furnace according to claim 8 is the invention according to claim 6 or 7, wherein the spray spray mechanism is configured such that the temperature of the exhaust gas in the direct duct is in a range of 800 ° C to 300 ° C. It is characterized by being arranged in a region to be.
Still further, the exhaust gas treatment apparatus for an electric furnace according to claim 9 is the invention according to claim 6 or 7, wherein the spray spray mechanism is configured such that the temperature of the exhaust gas in the direct duct is in a range of 500C to 400C. It is characterized by being arranged in a region to be.

An exhaust gas treatment apparatus for an electric furnace according to a tenth aspect is the invention according to any one of the sixth to ninth aspects, wherein the spray cooling mechanism includes a plurality of injection nozzles in a plurality of regions of the direct duct. It is characterized by being configured to inject spray water into exhaust gas.
Furthermore, the exhaust gas treatment apparatus for an electric furnace according to claim 11 is the invention according to any one of claims 6 to 10, wherein the direct duct is a water-cooled duct portion on the combustion chamber side and an air-cooling on the dust collector side. It is characterized by comprising a duct part.

  According to the present invention, the exhaust gas discharged from the electric furnace is burned in the combustion chamber and supplied to the dust collector through the direct pulling duct in a state where CO is removed. By spraying and cooling spray water of 120 μm or less, it is possible to effectively cool the exhaust gas below the allowable temperature of the dust collector without providing a large cooling facility such as a spray cooling tower. For this reason, it becomes possible to reduce the air volume of the cold air for temperature control supplied to the entrance side of a dust collector, and can improve the exhaust gas processing amount discharged | emitted from an electric furnace.

Here, the exhaust gas temperature supplied to the dust collector is arranged in the dust collector by controlling at least one of the flow rate and particle size of the spray water sprayed on the exhaust gas in the direct duct based on the exhaust gas temperature on the dust collector inlet side. It can be accurately controlled below the heat resistance temperature of the filter cloth.
Furthermore, since spray water with a particle size of 120 μm or less is used, the spray water will completely evaporate in the exhaust gas, so that the water in the duct and the filter cloth of the dust collector do not get wet or get wet. There is no problem of dust adhesion due to the use of water or a decrease in dust collection effect.

  Moreover, the spray water sprayed on the exhaust gas in the direct drawing duct efficiently cools the exhaust gas by spraying in the region where the exhaust gas temperature is in the range of 800 ° C to 300 ° C, preferably in the range of 500 ° C to 400 ° C. be able to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an exhaust gas treatment apparatus for an electric furnace according to the present invention. In the figure, reference numeral 1 denotes an electric furnace for steel making, in which iron scrap or iron scrap and molten iron are heated and melted and refined, and at this time, high-temperature exhaust gas is generated.
High-temperature exhaust gas generated in the steelmaking electric furnace 1 is sucked into the combustion chamber of the combustion tower 4 from the furnace lid elbow 2 through the sliding tube 3. At this time, outside air is sucked into the exhaust gas discharged from the furnace lid elbow 2 through the slide tube 3 and mixed so that the mixing ratio with the exhaust gas becomes, for example, 70% exhaust gas and 30% outside air, and both are mixed to about 1500 ° C. Is sucked into the combustion tower 4 at a high temperature.

In the combustion tower 4, the sucked exhaust gas is burned to burn unburned gas components such as CO and H ₂ in the exhaust gas. A direct drawing fan 6 is connected to the exhaust gas outlet of the combustion tower 4 via a direct drawing duct 5 of a relatively long distance (90 m or more), and a dry dust collector 7 in which the outlet side of the direct drawing fan 6 is constituted by a bag filter. It is connected to the.
Here, the direct drawing duct 5 has a water cooling duct 5w on the combustion tower 4 side, an air cooling duct 5a on the direct drawing fan 6 side, and a building dust collection gas of 60 ° C., for example, on the inlet side of the direct drawing fan 6 of the air cooling duct 5a. A dilution cold air duct 8 for supplying the air is connected. An electric damper 9 is disposed at a connection portion between the diluted cold air duct 8 and the air cooling duct 5a. In this direct duct 5, it is necessary to reduce, for example, 800 ° C. exhaust gas exhausted from the combustion tower 4 to 250 ° C. or less, which is the heat resistance temperature of the filter cloth of the dry dust collector 7. For this purpose, the exhaust gas temperature in the direct duct 5 is in the range of 800 ° C. to 300 ° C., preferably in the range of 500 ° C. to 400 ° C. There is provided a spray cooling mechanism 11 for supplying spray water which evaporates by contact with the.

As shown in FIG. 2, the spray cooling mechanism 11 divides, for example, the water cooling duct 5w into, for example, four cooling zones C1 to C4 along the flow path of the exhaust gas, and each cooling zone C1 to C4 includes a water cooling duct 5w. Spray water sprayed by a plurality of N sprays SP1 to SPn is disposed so as to be sprayed only on exhaust gas without reaching the inner wall of the water-cooled duct 5w.
The sprays SP1 to SPn in the cooling zones C1 to C4 store the compressed air supplied from the compressor 12 in the receiver tank 13, and the compressed air stored in the receiver tank 13 is provided for each cooling zone C1 to C4. In addition, the cooling water is supplied from the direction orthogonal to the air flow path through the flow meters FA21 to FA24 provided for the respective cooling zones C1 to C4. The By adjusting the flow meters FA11 to FA14 and FA21 to FA24, spray water which is evaporated when it comes into contact with the exhaust gas with a particle size of 120 μm or less is sprayed from the sprays SP1 to SPn in the cooling zones C1 to C4.

  Here, between the receiver tank 13 and the flow meters FA11 to FA14, the main flow paths LM1 to LM4 in which the control valves V11 to V14 are inserted, and the control valves V1 to V4 are bypassed and a relatively small flow rate is obtained. Bypass channels LB1 to LB4 for supplying compressed air are provided. Control valves V21 to V24 are interposed between the cooling water supply port and the flow meters FA21 to FA24.

  Here, the reason why the particle size of the spray water sprayed from the sprays SP1 to SPn is set to 120 μm or less is that when the particle size of the spray water exceeds 120 μm, the spray water does not completely evaporate when it comes into contact with the exhaust gas. In a state where moisture is contained, it will be supplied to the dry dust collector 7, which will wet the filter cloth and reduce the dust collection efficiency, and by setting the particle size of the spray water to 120 μm or less, The spray water is completely evaporated when it comes into contact with the exhaust gas, so that the exhaust gas does not contain moisture.

Further, the exhaust gas temperature T1 on the inlet side of the cooling zone C1 is detected by the thermometer 21, the exhaust gas temperature T2 on the front side of the dilution air duct 8 is detected by the thermometer 22, and the exhaust gas temperature on the outlet side of the direct fan 6 is further detected. T3 is detected by the thermometer 23.
The exhaust gas temperatures T1 to T3 detected by the thermometers 21 to 23 are input to the exhaust gas cooling control device 30 as spray water control means, and the exhaust gas cooling control device 30 performs spraying based on the exhaust gas temperatures T1 to T3 of each part. The electric damper 9 controls the number of sprays sprayed with the spray water of the sprays SP1 to SPn in the cooling zones C1 to C4 of the cooling mechanism 11 and controls the flow rate of the diluted cold air supplied from the diluted cold air duct 8 to the air cooling duct 5a. Control the opening.

  That is, the exhaust gas cooling control device 30 executes the cooling control process shown in FIG. In this cooling control process, first, the exhaust gas temperatures T1 to T3 detected by the thermometers 21 to 23 are read in step S1, and then the process proceeds to step S2 to determine whether or not the exhaust gas temperature T1 is less than 250 ° C. When T1 <250 ° C., the process proceeds to step S3 to control the control valves V11 to V14 and V21 to V21 to V24 to be closed, and then the process proceeds to step S4 to control the electric damper 9 to be closed. Then, the process returns to step S1. Note that the criterion of 250 ° C. is that the heat resistance temperature of the filter cloth of the dust collector 7 is 250 ° C. in this example, and it may be set to a temperature that does not exceed the heat resistance temperature of the filter cloth.

On the other hand, when the determination result of step S2 is T1 ≧ 250 ° C., the process proceeds to step S5, and after calculating the spray water spray flow rate for the exhaust gas based on the inlet side temperature T1 of the cooling zone C1, the process proceeds to step S6.
In this step S6, the number of cooling zones C1 to C4 for spraying spray water from the sprays SP1 to SPn is calculated based on the calculated spray water spray flow rate, and then the process proceeds to step S7 to spray the calculated spray water. Depending on the number of cooling zones C1 to C4, the control valves V11 to V14 and V21 to V24 for supplying spray water to the cooling zones C1 to C4 are controlled to open and close, and then the process proceeds to step S8.

  In this step S8, the exhaust gas temperature on the outlet side of the direct drawing fan 6 is based on the exhaust gas temperature T2 on the front side of the diluted cold air duct 8 and the exhaust gas temperature T3 on the outlet side of the direct drawing fan 6, and the heat resistance temperature of the filter cloth of the dry dust collector 7 The diluted cold air flow rate is calculated so as to be within a temperature range of 250 ° C. or lower and higher than the dew point temperature, for example, 150 ° C. Then, the process proceeds to step S9, and the electric damper 9 is opened based on the calculated diluted cold air flow rate. The degree θ is calculated, and then the process proceeds to step S10, the calculated opening degree θ of the electric damper is output to the electric damper 9, and the process returns to step S1.

Next, the operation of the above embodiment will be described.
Now, in the electric furnace 1 for steel making, assuming that the refining for heating and melting iron scrap or iron scrap and hot metal is finished and immediately before starting the next refining, in this state, as shown in FIG. The exhaust gas temperature T0 of the water-cooled duct 5w directly connected to the combustion tower 4 of the direct pulling duct 5 is reduced to about 150 ° C. as shown by a thick solid line in FIG. 4, and the exhaust gas temperature T on the inlet side of the cooling zone C1 is also shown in FIG. 4, the exhaust gas temperature T2 before the connection of the diluted cold air duct 8 decreases to about 150 ° C. as shown by a thin solid line in FIG. As shown by a thin broken line in FIG. 4, the exhaust gas temperature T3 also decreases to about 150 ° C., and the diluted cold air temperature T4 maintains approximately 60 ° C. as shown by a thin broken line in FIG.

In this state, since the exhaust gas temperature T2 on the inlet side of the cooling zone C1 is about 150 ° C., the exhaust gas cooling control device 30 determines that spraying of spray water is not necessary, and proceeds from step S2 to step S3. Then, the control valves V11 to V14 and V21 to V24 are controlled to be closed, and then the process proceeds to step S4 and the electric damper 9 is controlled to be closed.
At this time, a small amount of compressed air from the receiver tank 13 is supplied to the sprays SP1 to SPn in the cooling zones C1 to C4 via the bypass channels LB1 to LB4 and the flow meters FA11 to FA14, respectively. SP1 to SPn are prevented from being clogged.

  In this state, when steel scrap or iron scrap and hot metal is introduced into the steelmaking electric furnace 1 and refining is started, the exhaust gas temperature T0 on the outlet side of the water-cooled duct 5w directly connected to the combustion tower 4 is increased accordingly. At the same time, the exhaust gas temperature T1 on the inlet side of the cooling zone C1 also rises. When the exhaust gas temperature T1 becomes 250 ° C. or higher, the exhaust gas cooling process shown in FIG. Then, the spray water amount Lw is calculated based on the exhaust gas temperature T1.

At this time, when the exhaust gas temperature T1 has just exceeded 250 ° C., the calculated spray water flow rate Lw is also a small value. Therefore, when the number of cooling zones for spraying spray water is calculated in step S6, the number of cooling zones Becomes “0”, and the control valves V11 to V14 and V21 to V24 are kept closed.
However, when the exhaust gas temperature T1 in the cooling zone C1 further rises and the spray water spray flow rate Lw calculated in step S5 reaches the flow rate at which the cooling water is sprayed from one cooling zone, first, the leading cooling zone C1 When selected, the control valves V11 and V21 corresponding thereto are controlled to open.

  Therefore, a predetermined flow rate of air is supplied to the sprays SP1 to SPn in the cooling zone C1, and a predetermined flow rate, for example, 70 to 200 times (weight ratio) of cooling air is supplied to the sprays SP1 to SPn in the cooling zone C1. Then, spray water having a particle size of 120 μm or less, sprayed from the sprays SP1 to SPn and having a particle size of 120 μm or less that contacts the exhaust gas and evaporates in a short time is sprayed toward the exhaust gas. As a result, the exhaust gas temperature is lowered by the heat of vaporization when the spray water evaporates with the exhaust gas, and the exhaust gas temperature T2 on the front side of the diluted cold air duct 8 is controlled to, for example, 250 ° C. or lower.

  In this state, since the exhaust gas temperature T2 on the front side of the diluted cold air duct 8 rises to around 250 ° C., the diluted cold air volume Lc is calculated in step S8 in the process of FIG. 3 based on the exhaust gas temperature T2, and the calculated diluted cold air is calculated. The opening degree θ of the electric damper 9 is calculated based on the amount Lc (step S9), and the opening degree θ is output to the electric damper 9 (step S10). For this reason, the dilution cold wind is supplied from the dilution cold wind duct 8 to the air cooling duct 5a on the front side of the direct drawing fan 6, so that the exhaust gas temperature on the outlet side of the direct drawing fan 6 is, for example, about 150 ° C. sufficiently higher than the dew point. Be controlled.

The exhaust gas cooling control process is not limited to the process of FIG. 3, the spray water spray flow rate Lw and the diluted cold air flow Lc are calculated in step S5 in FIG. 3, and the processes of steps S6 and S7 and the processes of steps S9 and S10 are performed. May be performed in parallel.
Further, in the process of FIG. 3, the exhaust gas temperature T2 is controlled based on 250 ° C., but when the heat resistance temperature of the filter cloth is 250 ° C., the control is desirably performed at a low temperature side of 220 ° C. It is desirable to avoid a temperature rise due to control unevenness.

The cooled exhaust gas is supplied to the dry dust collector 7 so that the dry dust collector 7 collects dust. At this time, the exhaust gas temperature is controlled to be higher than the dew point and lower than the heat resistance temperature of the filter cloth, so that it is possible to reliably prevent the filter cloth from getting wet and causing thermal loss and thus ignition.
Thereafter, when the refining in the electric furnace 1 for steel making is finished, the exhaust gas temperature in the direct duct 5 again decreases to around 150 ° C., the exhaust gas temperature T1 on the inlet side of the cooling zone C1 decreases, and is calculated in step S5. When the spray water flow rate Lw is less than the spray water flow rate sprayed in one cooling zone C1, the control valves V11 and V24 are controlled to be closed, and the exhaust gas temperature T1 on the inlet side of the cooling zone C1 is less than 250 ° C. From step S2 to step S3, the closed state of the control valves V11 and V21 is maintained, and only a small amount of air for preventing clogging is supplied to the sprays SP1 to SPn of the cooling zones C1 to C4. At the same time, the electric damper 9 of the diluted cold air duct 8 is controlled to be closed.

  After that, when a new refining is started in the steelmaking electric furnace 1, if the exhaust gas temperature flowing into the direct drawing duct 5 becomes higher than the previous time, in the process of FIG. Since the calculated spray water spray flow rate Lw is increased and the number of cooling zones calculated in step S6 is increased accordingly, the process proceeds to step S7, and the number of control according to the calculated number of cooling zones is controlled. Sprays with a particle size of 120 μm or less that can be evaporated at a predetermined flow rate from the sprays SP1 to SPn in the cooling zones C1 to Ci by controlling the valves V11 to V1i (i is 2, 3, 4) and V21 to V2i to be opened. Water is sprayed on the exhaust gas. For this reason, the exhaust gas temperature is lowered by the cooling drop temperature corresponding to the number of cooling zones, and the dilution cold air having the air volume based on the exhaust gas temperature T2 upstream of the predetermined amount of the dilution cold air duct is supplied from the dilution cold air duct 8. The exhaust gas temperature T3 on the outlet side of the direct drawing fan 6 is controlled to around 200 ° C., for example.

  In this way, according to the above embodiment, the exhaust gas is cooled by spraying the spray water on the exhaust gas in the direct pulling duct 5 disposed between the combustion tower 4 and the direct pulling fan 6. Exhaust gas cooling control can be performed accurately. That is, when spray water that completely evaporates with respect to the exhaust gas in the combustion tower 4 is sprayed, the exhaust gas temperature can be cooled from 1500 ° C. to about 1300 ° C. to about 200 ° C., but this combustion tower 4 Even if the exhaust gas temperature is lowered by about 200 ° C., the exhaust gas temperature in the direct duct 5 is only slightly lowered and the cooling efficiency is low.

  On the other hand, when spray water having a particle size of 120 μm or less that completely evaporates with respect to the exhaust gas is sprayed in the direct duct 5 as in this embodiment, the cooling temperature is lower than the cooling drop temperature in the combustion tower 4. Although the exhaust gas temperature can be reliably lowered although the temperature drop is low, the exhaust gas cooling efficiency can be increased and the exhaust gas temperature supplied to the dry dust collector 7 can be accurately controlled within the allowable temperature range.

  Moreover, by providing the spray cooling mechanism 11 in the region where the exhaust gas temperature of the direct duct 5 is 500 ° C. to 400 ° C., the spray water sprayed from the sprays SP1 to SPn has a relatively large particle size of about 120 μm to 60 μm. The amount of air supplied to the sprays SP1 to SPn and the amount of cooling water are relatively easy to control, the cooling efficiency is the best, and the exhaust gas temperature can be accurately controlled.

Further, a spray cooling system 11, it is possible to lower precisely an exhaust gas temperature, reduced to 300 to 400 nm ³ / min about the air volume of the diluted cool air supplied from a conventional example 1300 Nm ³ / min from the diluted cold air duct 8 For this reason, the ratio of the suction amount of the exhaust gas from the steelmaking electric furnace 1 to the suction force of the direct pulling fan 6 can be increased, and the flow rate of the direct pulling duct 5 is increased and the pressure loss increases. However, the suction amount of the exhaust gas from the steelmaking electric furnace 1 can be significantly increased from, for example, 1000 Nm ³ / min to 1500 Nm ³ / min, and the exhaust gas suction efficiency from the steelmaking electric furnace 1 can be significantly increased. it can.

Further, since it is only necessary to install the spray cooling mechanism 11 in the direct duct 5, it is possible to cool the exhaust gas with high accuracy with a simple and small configuration without requiring a large facility such as a cooling tower.
In the above embodiment, the spray cooling mechanism 11 is described in the case where the spray cooling mechanism 11 is provided in the region where the exhaust gas temperature of the direct duct 5 is 400 ° C. to 500 ° C. However, the present invention is not limited to this. Even if the spray cooling mechanism 11 is arranged in the region where the exhaust gas temperature of the direct drawing duct 5 is 800 ° C. to 300 ° C., the cooling effect is somewhat reduced, but the same effect as the above embodiment can be obtained. Here, when the spray cooling mechanism 11 is provided in a region where the exhaust gas temperature of the direct drawing duct 5 exceeds 800 ° C., the cooling drop temperature of the exhaust gas temperature can be increased, but on the outlet side of the direct drawing fan 6. When the control accuracy of the exhaust gas temperature is deteriorated and the spray cooling mechanism 11 is provided in the region where the exhaust gas temperature of the direct drawing duct 5 is less than 300 ° C., the width of the cooling drop temperature becomes narrow, and the direct drawing fan 6 As the exhaust gas temperature control accuracy on the outlet side deteriorates, it is necessary to control the particle size of spray water sprayed from the sprays SP1 to SPn to 20 μm or less, for example. In addition, it is necessary to increase the control accuracy of the cooling water amount, and it becomes difficult to put it to practical use.

Moreover, although the said embodiment demonstrated the case where the number of cooling zones was determined based on the exhaust gas temperature T1 of the entrance side of the cooling zone C1, it is not limited to this, Cooling zone C1-C4 The number of sprays to be sprayed may be determined from the spray water spray flow rate Lw from the total number of sprays arranged in the above.
Further, in the above embodiment, the exhaust gas cooling control process executed by the exhaust gas cooling control device 30 is the control of the diluted air amount next to the control of the control valves V11 to V14 for the cooling zones C1 to C4 as shown in FIG. However, the present invention is not limited to this. As shown in FIG. 5, the supply control of the spray water to the cooling zones C1 to C4 is performed by omitting steps S4, S9 and S10 in FIG. The spray water supply control process that performs only the process and the diluted cold air control process that omits steps S3 and S5 to S7 in FIG. 3 described above may be executed separately as shown in FIG.

Furthermore, in the said embodiment, although the case where the flow rate of the spray water sprayed with respect to exhaust gas was controlled based on exhaust gas temperature T1 was demonstrated, it is not limited to this, Spray SP1-based on exhaust gas temperature T1 The amount of spray water sprayed from SPn and the spray water particle size may be controlled.
Furthermore, in the above-described embodiment, the case where the spray cooling mechanism 11 is feedforward controlled based on the exhaust gas temperature on the inlet side of the cooling zone C1 has been described. However, the present invention is not limited to this. Feedback control may be performed based on the exhaust gas temperature T2 on the upstream side or the exhaust gas temperature T3 on the outlet side of the direct drawing fan 6, or both feedforward control and feedback control may be performed.

  Furthermore, in the above-described embodiment, the case of controlling the amount of diluted cold air supplied from the diluted cold air duct 8 has been described. However, the amount of diluted cold air is set from the cooling state in the spray cooling mechanism 11 with respect to the exhaust gas temperature T1, or diluted. The amount of cold air may be controlled to a constant amount.

It is a schematic block diagram which shows the electric furnace exhaust gas processing apparatus which concerns on this invention. It is a block diagram which shows a spray cooling mechanism. 3 is a flowchart showing an example of an exhaust gas cooling processing procedure executed by the exhaust gas cooling control device 30. It is a time chart which shows the relationship between the exhaust gas temperature change and spray water quantity with which it uses for description of operation | movement of this invention. It is a flowchart which shows an example of the spray water supply control processing procedure performed with an exhaust gas cooling control apparatus. It is a flowchart which shows an example of the dilution cold wind control processing procedure performed with an exhaust gas cooling control apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric furnace for steelmaking, 4 ... Combustion tower, 5 ... Direct duct, 5w ... Water cooling duct, 5a ... Air cooling duct, 6 ... Direct suction fan, 7 ... Dry dust collector, 11 ... Spray cooling mechanism, 12 ... Compressor, 13 ... Receiver tank, 21-23 ... Thermometer, 30 ... Exhaust gas cooling control device, V11-V14, V21-V24 ... Control valve

Claims (11)

Exhaust gas treatment for an electric furnace in which high-temperature exhaust gas generated from an electric furnace is guided to a combustion chamber installed and burned, and then the exhaust gas is supplied to a dust collector via a direct duct and discharged after dust collection. In the method
An exhaust gas treatment method for an electric furnace, characterized in that spray gas having a particle size of 120 μm or less that can be evaporated is sprayed on the exhaust gas in the direct duct and cooled.   The exhaust gas treatment method for an electric furnace according to claim 1, wherein the spray water is sprayed in a region where the temperature of the exhaust gas in the direct duct is in a range of 800C to 300C.   2. The exhaust gas treatment method for an electric furnace according to claim 1, wherein the spray water is sprayed in a region where the temperature of the exhaust gas in the direct duct is in a range of 500 ° C. to 400 ° C. 3.   The exhaust gas treatment method for an electric furnace according to any one of claims 1 to 3, wherein the spray water is injected into the exhaust gas from a plurality of injection nozzles in a plurality of regions of the direct duct.   The at least one of the particle size and flow rate of the spray water is controlled so that the exhaust gas temperature on the inlet side of the dust collector is within the allowable temperature range of the dust collector. An exhaust gas treatment method for an electric furnace according to Item. Electricity comprising a combustion chamber for burning high-temperature exhaust gas generated from an electric furnace, a direct pulling duct having one end directly connected to the exhaust side of the combustion chamber, and a dust collector connected to the other end of the direct pulling duct In furnace exhaust gas treatment equipment,
An exhaust gas treatment apparatus for an electric furnace, characterized in that a spray cooling mechanism for spraying and cooling the spray gas having a particle size of 120 μm or less that can be evaporated on the direct duct is provided. Electricity comprising a combustion chamber for burning high-temperature exhaust gas generated from an electric furnace, a direct pulling duct having one end directly connected to the exhaust side of the combustion chamber, and a dust collector connected to the other end of the direct pulling duct In furnace exhaust gas treatment equipment,
A spray cooling mechanism for spraying and cooling the exhaust gas with an evaporable spray water having a particle size of 120 μm or less disposed in the direct duct, an exhaust gas temperature detecting means disposed on the inlet side of the dust collector, and the exhaust gas An exhaust gas treatment apparatus for an electric furnace, comprising spray water control means for controlling at least one of a spray flow rate and a particle size sprayed by the spray cooling mechanism according to an exhaust gas temperature detected by a temperature detection means.   The exhaust gas of an electric furnace according to claim 6 or 7, wherein the spraying mechanism is disposed in a region where the temperature of the exhaust gas in the direct duct is in a range of 800 ° C to 300 ° C. Processing equipment.   8. The exhaust gas of an electric furnace according to claim 6, wherein the spraying mechanism is disposed in a region where the temperature of the exhaust gas in the direct duct is in a range of 500 ° C. to 400 ° C. 9. Processing equipment.   10. The spray cooling mechanism according to claim 6, wherein the spray cooling mechanism is configured to inject spray water into exhaust gas from a plurality of injection nozzles in a plurality of regions of the direct drawing duct. 10. Exhaust gas treatment equipment for electric furnaces.   The exhaust gas of an electric furnace according to any one of claims 6 to 10, wherein the direct duct is composed of a water cooling duct portion on the combustion chamber side and an air cooling duct portion on the dust collector side. Processing equipment.

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