JP2021014601A - Shallow bath type pickling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shallow bath type pickling apparatus capable of suppressing the accumulation of sludge at the bottom of a pickling tank. SOLUTION: A plurality of pickling tanks containing a pickling liquid are arranged in a steel strip in a plate-passing direction, and are adjacent to each other from a pickling tank in the latter stage in the plate-passing direction to a pickling tank in the front stage in the plate-passing direction. In a shallow bath type pickling device in which the pickling liquid overflows over the dam plates provided between the pickling tanks and a steel strip is passed through the pickling liquid contained in the pickling tank. At the bottom of any one of the pickling tanks, an injection nozzle that ejects the pickling liquid upward in the direction opposite to the plate passing direction of the steel strip is provided, and the number of injection nozzles on the inlet side is the number of injection nozzles on the outlet side. A shallow bath type pickling device characterized by being larger than the number of. [Selection diagram] Fig. 2

Description

The present invention relates to a shallow bath type pickling apparatus capable of suppressing sludge accumulation at the bottom of a pickling tank.

The steel strip after hot rolling is pickled to remove scale and the like adhering to the surface of the steel strip before cold rolling. Specifically, a plurality of pickling tanks containing the pickling liquid are arranged in the plate direction, and the steel strip is immersed in the pickling liquid while continuously passing through the plurality of pickling tanks for pickling. May be done.

Examples of the pickling method include a jet pickling method (also referred to as a Box jet method), a Deep tank method, and a Short tank method. The jet pickling method is a method of directly spraying the pickling liquid onto the steel strip using a jet nozzle. In the jet pickling method, in order to make it easier for the jet of the pickling liquid to hit the steel strip, a water tank with a very shallow bottom is used as the pickling tank, or a separate box is provided in the pickling tank and inside the box. Is used to generate a jet. The jet pickling method can improve the cleaning efficiency of steel strips, but has a problem that the introduction cost of equipment is high.

Further, the Deep tank method is a method in which a steel strip is drooped (with a large catenary) in a deep-bottomed pickling tank. In the Deep tank method, it is necessary to hold a large amount of acid liquid, and there is a problem that the liquid level cannot be controlled and the plate passing speed cannot be increased.

On the other hand, the shallow bath type pickling device that adopts the shallow tank method is a device that passes a plate while reducing the catenary by applying tension to the steel strip in a medium-shallow bottom pickling tank. .. In the shallow bath type pickling apparatus, a weir plate is provided between the pickling tank in the front stage and the pickling tank in the rear stage. Stirring of the pickling liquid in the shallow bath type pickling device includes the overflow of the pickling liquid from the subsequent pickling tank to the previous pickling tank via the dam plate and the accompanying flow accompanying the passing of the steel strip. It is supposed to be done by. Shallow bath type pickling equipment is already widely used because of its simple structure and low cost construction.

However, in the shallow bath type pickling device, the steel strip is passed through near the liquid level in the pickling tank with tension applied, so the distance between the steel strip and the bottom surface of the pickling tank is large. There is a problem that it is relatively large and it is difficult for liquid to flow at the bottom of the pickling tank. As a result, the pickling liquid stays at the bottom of the pickling tank, and sludge generated by washing the steel strip is likely to be deposited on the bottom of the pickling tank. Due to the tendency of sludge to accumulate, it is necessary to frequently stop the plate passing and then clean the pickling tank, which reduces productivity.

For example, when the scale generated on the surface of a steel strip such as ordinary steel or silicon steel after hot rolling is continuously removed, when the steel strip is pickled, the surface scale or metal and the pickling liquid are formed. The compound becomes sludge and accumulates and aggregates at the bottom of the pickling tank. As sludge builds up and aggregates on the bottom of the pickling tank, part of the heat exchanger that is placed in the pickling tank and heats the pickling liquid is buried in the sludge, or aggregates and coarsens sludge. Due to the accompanying flow of the steel strip, a large amount of it soars into the pickling liquid and adheres to the steel strip, causing abnormal quality of the steel strip. Therefore, sludge removal work in the pickling tank before the accumulated amount reaches the limit value. Need to be done.

The sludge removal work is performed by removing the pickling liquid from the pickling tank and then sucking the sludge from the outside to remove it, or manually removing the sludge by scooping it. Then, it is necessary to stop the operation regularly, which reduces the productivity.

On the other hand, as a method of removing sludge during operation, a method of introducing sludge accumulated on the bottom surface of the pickling tank into a suction or discharge port (see Patent Documents 1 and 2) and installation in the pickling tank. A method is known in which a pickling solution is blown from an ejector or a nozzle to discharge sludge in a suspended state out of the pickling tank (see Patent Documents 3, 4, 5 and 6).

Further, Patent Document 7 discloses a method in which an injection nozzle is installed on the bottom surface of a pickling tank to suppress sludge accumulation by a jet flow.

Japanese Unexamined Patent Publication No. 06-128773 Japanese Unexamined Patent Publication No. 2000-334218 Japanese Unexamined Patent Publication No. 10-324987 Japanese Unexamined Patent Publication No. 10-018068 Japanese Unexamined Patent Publication No. 2004-355301 Japanese Unexamined Patent Publication No. 2016-176132 JP-A-2018-090891

In the shallow bath type pickling tank, a predetermined amount of acid liquid is stored in each of the pickling tanks in the later stage so that the liquid level of the acid liquid gradually increases with the weir between the pickling tanks as a boundary. There is. The liquid level is adjusted by a liquid filling operation prior to the start of the plate passing operation of the steel strip so as to be higher than the steel strip pass line in the tank by a predetermined amount (about 100 mm). The acid solution to the pickling tank is replenished in a timely manner (continuously or intermittently) in the last pickling tank by the acid solution supply pipe, but as described above, the acid from the bottom to the top of the pickling tank The flow of the liquid is very slow, and sludge (sludge particles with a particle size of φ300 μm or less) produced by the reaction between the steel strip (particularly the steel strip containing a high silicon component) and the pickling liquid is in the pickling tank. There was a problem that a considerable amount (for example, height 300 mm / 3 months) was deposited on the bottom.

On the other hand, the method of sucking the sludge accumulated on the bottom surface of the pickling tank as in Patent Documents 1 and 2 requires the installation of the pipe in the tank and the driving device of the pipe in the tank, which is costly. There's a problem.

Further, as in Patent Documents 3 to 6, in the method of blowing the pickling solution and discharging the sludge in a suspended state to the outside of the pickling tank, the amount of the pickling solution required to remove the accumulated sludge is large. There is a problem of increasing.

Further, as in Patent Document 7, if the injection nozzle is simply provided at the bottom of the pickling tank, sludge is temporarily wound up by the jet flow, but in the end, sludge accumulates at a place where the flow in the tank stays. Problems can arise. According to the study by the present inventors, it was found that sludge is more likely to accumulate on the inlet side than on the outlet side in the tank because the sludge collides with the weir plate provided on the inlet side of the tank. It was. Therefore, it is difficult to solve the problem that sludge stays on the entry side in the tank by simply installing the injection nozzle without considering the arrangement of the injection nozzle according to the position in the tank.

The present invention has been made in view of the above circumstances, and a plurality of pickling tanks containing the pickling liquid are arranged in the steel strip in the plate-passing direction, and the pickling tank is passed from the subsequent pickling tank in the plate-passing direction. The pickling liquid overflows over the dam plate provided between the adjacent pickling tanks toward the front pickling tank in the plate direction, and the pickling liquid contained in the pickling tank is filled with a steel strip. Regarding the shallow bath type pickling device through which the steel is passed, a shallow bath type pickling device capable of suppressing the accumulation of sludge at the bottom of the pickling tank, particularly the accumulation of sludge on the entrance side of the pickling tank is provided. The purpose is to do that.

In order to solve the above problems, the present invention has the following features.

[1] A plurality of pickling tanks containing the pickling liquid are arranged in the steel strip in the plate-passing direction, and adjacent acids are arranged from the pickling tank in the latter stage in the plate-passing direction to the pickling tank in the front stage in the plate-passing direction. In a shallow bath type pickling device in which the pickling liquid overflows over the dam plates provided between the washing tanks and a steel strip is passed through the pickling liquid contained in the pickling tank, at least eventually. At the bottom of one of the pickling tanks, a group of injection nozzles for ejecting the pickling liquid upward in the direction opposite to the plate passing direction of the steel strip is provided, and the injection nozzle groups are arranged in a plurality of rows in the plate passing direction. A shallow bath type pickling apparatus provided, wherein the number of injection nozzles constituting the injection nozzle group on the inlet side is larger than the number of injection nozzles constituting the injection nozzle group on the outlet side.

[2] The shallow bath type pickling apparatus according to the above [1], wherein the height position of the injection port of the injection nozzle is within 80 mm from the bottom surface of the pickling tank.

[3] The shallow bath type pickling device according to the above [1] or [2], wherein the elevation angle of the injection nozzle is 10 ° to 15 °.

[4] The shallow bath type pickling apparatus according to any one of [1] to [3], wherein the injection nozzle group is provided in the frontmost pickling tank in the plate-passing direction.

According to the present invention, by adjusting the number and arrangement of nozzles in the pickling tub, the liquid flow in the tub is controlled, whereby sludge accumulation at the bottom of the pickling tub, especially the entry side of the pickling tub. It is possible to obtain a shallow bath type pickling device capable of suppressing the accumulation of sludge in the water.

FIG. 1 is a diagram showing a basic configuration of a shallow bath type pickling apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of arrangement of injection nozzles at the bottom of the pickling tank. 3 is an enlarged view of the injection nozzle group of FIG. 2, FIG. 3A is an enlarged view of the nozzle pipe 12, and FIG. 3B is an enlarged view of the injection nozzle 11.

An embodiment of the present invention will be described with reference to the drawings.

First, FIG. 1 is a diagram showing a basic configuration of a shallow bath type pickling apparatus according to an embodiment of the present invention. FIG. 1 (a) is a side view, and FIG. 1 (b) is a plan view.

In the shallow bath type pickling apparatus 1, a plurality of pickling tanks are arranged along the plate passing direction of the steel strip 5, and here, three pickling tanks 2a to 2c (collectively, "pickling tanks"). 2 ”is sometimes referred to.) Is provided. The pickling liquid 4 is housed in the pickling tank 2. Weir plates 3a and 3b are provided between the adjacent pickling tanks. Although not shown in detail, the final pickling tank 2c is continuously or intermittently replenished with new pickling liquid 4. When the pickling liquid becomes excessive in each pickling tank 2, the pickling liquid 4 overflows over the dam plates 3b and 3a in order, and moves from the last pickling tank 2c side to the frontmost pickling tank 2a side. The pickling solution flows. Although not shown, the excess pickling liquid 4 in the pickling tank 2a at the front stage is discharged to the outside of the tank by an overflow pipe or the like. In the example of FIG. 1, the weir plate 3a on the front stage side is lower than the weir plate 3b on the rear stage side, and the pickling liquid on the front stage side is higher than the pickling tank on the rear stage side. The surface is gradually lowered. The number of pickling tanks is not limited to the example shown in FIG. Further, in the shallow bath type pickling device 1, unlike a jet pickling type device that is generally used, it is not necessary to provide a separate box in the pickling tank.

By continuously immersing the steel strip 5 in the pickling liquid 4 of the pickling tank 2, the scale and the like adhering to the front and back surfaces of the steel strip 5 are washed. The through plate of the steel strip 5 is in a state of being tensioned by a pinch roll 6 provided in the front stage of the pickling tank 2a in the front stage and a ringer roll 7 provided in the rear stage of the pickling tank 2c in the last stage. It is passed through. As a result, the steel strip 5 is passed through in a substantially horizontal state with almost no hanging downward. By passing the steel strip 5 under tension, it is not necessary to make the pickling tank a deep bottom, the volume of the pickling liquid required for pickling can be reduced, and the liquid level can be controlled. It will be easy. In this way, the steel strip 5 is passed from the pickling tank 2a in the front stage to the pickling tank 2c in the rear stage in the direction opposite to the flow of the pickling liquid 4 due to the overflow at the dam plate.

Further, in each pickling tank 2, a skid 8 protruding upward from the bottom surface of the tank and a seal roll 9 in contact with the skid 8 are provided. The steel strip 5 is passed through while being sandwiched between the skid 8 and the seal roll 9. The lower surface of the seal roll 9 is located below the liquid levels 4a to 4c.

In the shallow bath type pickling apparatus 1, the steel strip 5 is passed through the vicinity of the liquid level of the pickling liquid 4. The distance between the upper surface of the steel strip 5 and the liquid levels 4a to 4c is relatively small, and the distance between the lower surface of the steel strip 5 and the bottom of the pickling tanks 2a to 2c is relatively large. As an example, the ratio of the distance (distance A) from the bottom surface of the pickling tank to the pass line of the steel strip (the height of the bottom surface of the steel strip) with respect to the height from the bottom surface of the pickling tank to the liquid level is It may be about 80% to 90%. Further, as an example of the above-mentioned distance A, about 80 mm to 120 mm can be mentioned.

Further, in the shallow bath type pickling device, the pickling liquid overflows from the pickling tank on the exit side to the pickling tank on the entrance side through the dam plate described above, and when the steel strip is passed through, the vicinity of the steel strip. The pickling solution is agitated by the accompanying flow of the pickling solution generated in.

According to the overflow of the pickling liquid, the pickling liquid above the steel strip, that is, the pickling liquid in the vicinity of the liquid surface is agitated. On the other hand, the pickling liquid located below the steel strip is difficult to be agitated because the overflow is hindered by the steel strip itself.

According to the accompanying flow of the pickling liquid, the pickling liquid is agitated in the vicinity of the upper and lower surfaces of the steel strip. However, under conditions such as a shallow bath type pickling apparatus where the distance between the steel strip and the bottom of the pickling tank is relatively large, stirring of the pickling liquid at the bottom of the pickling tank is unlikely to occur.

Next, FIG. 2 is a diagram showing a main part of a shallow bath type pickling apparatus according to an embodiment of the present invention. FIG. 2A is a side view, and FIG. 2B is a plan view.

As described above, in the shallow bath type pickling device, the pickling liquid tends to stay at the bottom of the pickling tank, and sludge produced by the reaction between the steel strip and the pickling liquid accumulates at the bottom of the pickling tank. There is a problem. Therefore, in the present embodiment, as shown in FIG. 2, an injection nozzle 11 for ejecting the pickling liquid upward in the direction opposite to the plate passing direction of the steel strip 5 is installed at the bottom of the pickling tank 2. Promotes the stirring of the pickling solution at the bottom of the pickling tank 2 and suppresses the accumulation of sludge on the bottom of the pickling tank.

Specifically, a nozzle pipe 12 is installed at the bottom of the pickling tank 2 so as to extend in a direction orthogonal to the plate-passing direction of the steel strip 5, and the nozzle pipe 12 is opposite to the plate-passing direction of the steel strip 5. The injection nozzle 11 is installed so as to eject the pickling solution upward in the direction. The nozzle pipe 12 is connected to a pump (not shown) arranged outside the pickling tank 2. In addition, the flow velocity required for the sludge to float is calculated from the gravity and buoyancy obtained from the particle size of the sludge and the resistance generated when moving in the pickling solution. Then, using a pump arranged outside the pickling tank 2, a part of the pickling liquid is once passed through the liquid drain pipe (not shown) installed in the pickling tank 2 once. The pickling liquid is again ejected from the injection nozzle 11 into the pickling tank 2 so that a flow velocity equal to or higher than the flow velocity required for the sludge to float can be obtained at a place where the sludge is easily deposited by pulling it out. As a result, sludge that has settled toward the bottom of the pickling tank 2 (including sludge that has already accumulated on the bottom of the pickling tank 2 in some cases) is suspended and overflows from the pickling tank 2. It is discharged to the outside of the pickling tank 2 together with the pickling solution.

A series of injection nozzles 11 provided in one nozzle pipe 12 is referred to as an injection nozzle group. In addition, although only one injection nozzle 11 may be provided in one nozzle pipe 12, the example is also referred to as an injection nozzle group. By arranging a plurality of nozzle pipes 12 in the plate-passing direction, a plurality of injection nozzle groups are provided in a row in the plate-passing direction. It is preferable that each injection nozzle group is provided along the width direction of the steel strip. In this case, it is preferable that each injection nozzle group (more specifically, each nozzle pipe 12) is completely parallel to the width direction of the steel strip, but as shown in FIG. 3A, in the plan view. An error within about ± 30 ° with respect to the width direction of the steel strip can be tolerated.

The nozzle pipe 12 may be provided so as to be inclined by changing the height according to the position in the width direction.

In particular, by directing the injection nozzles in each injection nozzle group in the tank in the direction opposite to the plate passing direction, the flow of the accompanying flow generated from the entry side to the exit side in the vicinity of the steel strip is reversed. A liquid flow from the outlet side to the inlet side can be generated near the bottom of the tank. As a result, the liquid flow is prevented from being formed in only one direction in the tank, and the stirring ability of the liquid is improved. When the injection nozzle faces in the direction opposite to the plate passing direction, the axial direction of the injection nozzle and the plate passing direction are substantially parallel in the plan view. The axial direction of the injection nozzle in the plan view is preferably completely parallel to the plate-passing direction, but as shown in FIG. 3 (b), an error within about ± 30 ° with respect to the plate-passing direction is acceptable. can do.

On the other hand, according to the study by the present inventors, it has been found that sludge tends to accumulate especially on the entry side of the pickling tank when the injection nozzle is directed in the direction opposite to the plate direction. It was also found that as a cause of the accumulation of the sludge, the liquid flow from the injection nozzle collides with the accompanying flow, the weir plates 3a, 3b, etc. on the entry side of the tank, so that the liquid tends to stagnate. Therefore, in the present invention, the number of injection nozzles 11 constituting the inlet nozzle group is made larger than the number of injection nozzles 11 constituting the outlet nozzle group in one pickling tank. In FIG. 2B, the number of injection nozzles of the nozzle group located on the most inlet side (left side of the figure) is 5, and the number of injection nozzles of the nozzle group located on the outermost side is 1, which is located in the middle. The number of injection nozzles in the nozzle group is 3. By increasing the number of injection nozzles provided in a row, not only the injection force is simply increased by the number of injection nozzles, but also the injection flows of adjacent injection nozzles interfere with each other, and the injection flow becomes a steel strip. The effect of warping in the width direction can be suppressed to a small extent, and the injection force of the injection nozzle group increases.

As described above, by making the number of nozzles on the inlet side larger than the number of nozzles on the exit side, a higher injection force is realized on the inlet side than on the outlet side. As a result, the retention of sludge on the side entering the pickling tank can be suppressed. As described above, in the present invention, by adjusting the direction and the number of the injection nozzles, it is possible to improve the stirring ability of the liquid and prevent sludge from staying on the entry side of the pickling tank.

As an example, in order to prevent sludge particles having a diameter of 15 μm to 35 μm, which are by-produced by the reaction between the steel strip 5 and the pickling liquid, from accumulating on the bottom of the pickling tank 2, the injection amount by the injection nozzle 11 Is preferably 9.8 L / min. The flow velocity of the jet is preferably 3.0 mm / s or more. At this flow velocity, sedimentation of sludge particles having a diameter within the above range can be reliably prevented.

The height position where the injection nozzle 11 is installed is preferably located near the bottom surface of the pickling tank 2 because the pickling liquid is ejected upward. For example, the height position of the injection port of the injection nozzle 11 may be set to be within 80 mm from the bottom surface of the pickling tank 2. By setting the height position of the injection port within the above range, sludge particles accumulated on the bottom of the pickling tank 2 can be reliably agitated. The height position of the injection port may be determined based on the lowest position of the opening of the injection nozzle 11.

However, it is preferable that the nozzle pipe 12 is installed away from the bottom surface of the pickling tank 2. As a result, a flow path for the pickling liquid can be formed between the nozzle pipe 12 and the bottom surface of the pickling tank 2, and the pickling liquid can be prevented from staying around the nozzle pipe 12.

The elevation angle θ (angle formed between the central axis and the horizon of the injection nozzle 11) of the injection nozzle 11 can generate a liquid flow sufficient to sufficiently stir the pickling liquid at the bottom of the pickling tank 2. Moreover, it is preferable to adjust the angle so that the back surface of the steel strip 5 is not scratched by the ejected liquid flow. For example, θ = 10 ° to 15 °.

The installation pitch of the injection nozzle 11 in the steel strip width direction may be determined in consideration of the relationship with the nozzle diameter (injection port diameter) of the injection nozzle 11.

By using the same material (preferably polypropylene) as the pickling tank 2 for the injection nozzle 11, it is possible to eject a required flow rate while withstanding the environment of the pickling liquid for a long period of time.

Further, the nozzle pipe 12 is made of a material having acid resistance to the pickling liquid and heat resistance at the operating temperature, and is made of a material of the pickling tank 2 so as to allow deformation due to a temperature rise of the pickling liquid. It is desirable to use materials with the same coefficient of thermal expansion.

If the nozzle pipe 12 is provided with supports made of the same material (preferably polypropylene) as the pickling tank 2 so as to withstand the liquid resistance (reaction) when the pickling liquid is ejected from the injection nozzle 11. Good. The support has a structure in which the nozzle pipe 12 can be expanded and contracted on the support so that the nozzle pipe 12 can be deformed due to the temperature rise of the pickling liquid.

Further, when the inner diameter of the nozzle pipe 12 is set to an appropriate size (for example, inner diameter 80A), the flow velocity in the nozzle pipe 12 is limited, and the pickling liquid is ejected from the injection nozzle 11 into the pickling tank 2. It is desirable to reduce the required capacity of the pump used. The pump may have a pumping capacity of a pressure lower than the withstand voltage of the nozzle pipe 12, and may have acid resistance and can be continuously operated for a long time.

The plurality of injection nozzle rows in which the number of injection nozzles is adjusted as described above may be provided in any of the pickling tanks 2a to 2c, but it is particularly preferable to provide them in the frontmost pickling tank 2a. In the pickling tank 2a at the front stage, since the pickling liquid that has already been used for pickling flows from the pickling tank at the rear stage, sludge tends to accumulate, and the effect of providing the above-mentioned injection nozzle row is effective. Is particularly large.

In this way, in the present embodiment, the accumulation of sludge at the bottom of the pickling tank 2 can be accurately suppressed. Further, as an incidental effect, the unreacted pickling liquid at the bottom of the pickling tank 2 is promoted to be replaced with the pickling liquid that has reacted with the steel strip 5 in the vicinity of the steel strip 5, and the steel strip 5 is descaled. Can also be promoted.

1 Shallow bath type pickling device 2, 2a, 2b, 2c Pickling tank 3a, 3b Weir plate 4 Pickling liquid 4a, 4b, 4c Liquid level 5 Steel strip 6 Pinch roll 7 Ringer roll 8 Skid 9 Seal roll 11 Injection nozzle 12 Nozzle piping

Claims (4)

A plurality of pickling tanks containing the pickling liquid are arranged in the steel strip in the plate-passing direction, and the pickling tanks adjacent to each other are arranged from the latter pickling tank in the plate-passing direction to the front-stage pickling tank in the plate-passing direction. In a shallow bath type pickling device in which a pickling liquid overflows over a dam plate provided between them and a steel strip is passed through the pickling liquid contained in the pickling tank.
At the bottom of at least one of the pickling tanks, a group of injection nozzles for ejecting the pickling liquid upward in the direction opposite to the plate passing direction of the steel strip is provided.
A plurality of rows of the injection nozzle groups are provided in the plate passing direction.
A shallow bath type pickling apparatus characterized in that the number of injection nozzles constituting the injection nozzle group on the inlet side is larger than the number of injection nozzles constituting the injection nozzle group on the outlet side. The shallow bath type pickling apparatus according to claim 1, wherein the height position of the injection port of the injection nozzle is within 80 mm from the bottom surface of the pickling tank. The shallow bath type pickling device according to claim 1 or 2, wherein the elevation angle of the injection nozzle is 10 ° to 15 °. The shallow bath type pickling apparatus according to any one of claims 1 to 3, wherein the injection nozzle group is provided in the frontmost pickling tank in the plate-passing direction.

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