JPH0226939Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a low-pass or semi-low-pass type steel strip pickling apparatus.

[Prior art]

There are various types of pickling equipment that removes surface oxides (scale) by passing steel strips through pickling (hydrochloric acid solution, sulfuric acid solution, etc.). Therefore, low-bath type or semi-low-bath type pickling equipment with a shallow pickling tank depth is becoming widely used.

To explain a low-bath type hydrochloric acid pickling apparatus as an example, in FIG. 3, 2 is a pickling tank, 3 is a waste acid receiving tank, and W is a material to be pickled (steel strip).

The pickling tanks 2 are usually 3 to 5 tanks (3 tanks in the figure) arranged in series, each containing an acid solution (liquid temperature: about 75 to 85°C). Each of the pickling tanks 21 to 23 is partitioned by a capped tile weir 18, and each tank is provided with a plurality of intermediate weirs 19 (two in the figure). The intermediate weir 19 is slightly lower than the capped tile weir 18 so as not to obstruct the flow of the acid solution in the tank, and has spaces on both sides with the tank walls.

A pickling material presser roll 7 is disposed above each capped tile weir 18. Although not shown, presser rolls 7 are also disposed above the intermediate weir 19, and the material to be pickled W is held between the top surface of these weirs and the presser rolls.

The material W to be pickled is introduced from the left side in the figure, and surface oxides are removed while passing through the acid solution in each pickling tank 21, 22, 23 along the entry side ringer roll 6 and presser roll 7. , and is sent to the next process via the double ringer roll 8 on the output side.

Each of the pickling tanks 21 to 23 has a sub tank 9.
1 to 93 are attached, and as needed (for example, when the line operation is stopped), the acid solution in each pickling tank is pumped through the conduit 10 by the pump 11, or by opening and closing valves (not shown) to the sub tanks 91 to 93. When the operation is restarted, the pump 13 is connected via the conduit 12.
The pickling tanks 21 to 23 are returned to the pickling tanks 21 to 23.

The acid solution has a predetermined composition (HCl: about 90 to 140 g/l,
iron content: 70 to 110 g/l), and the final pickling tank (in the example shown in the figure, the third pickling tank 2) is
3, and then overflowing the top of the capped tile weir 18 that partitions each pickling tank,
It flows from the third pickling tank 23, through the second pickling tank 22, to the first pickling tank 21, which is the most downstream tank, and during this time, it reacts with the surface oxides of the material to be pickled W, and the waste acid ( HCl:
about 10 to 70 g/l, iron content: about 110 to 165 g/l) and flows into the waste acid receiving tank 3. The waste liquid that has flowed into the waste acid receiving tank 3 is sent from the drain port at the bottom of the tank through a conduit 4 to an acid recovery device (not shown), and after being regenerated, it is sent to the most upstream tank via a supply conduit 5. It is returned to the third pickling tank 23. For example, the amount is 2
~ several m ² /Hr.

The capped tile weir 18 and intermediate weir 19 of each pickling tank 21 to 23 are such that the acid solution in each pickling tank is stopped by the capped tile weir 18, and unless the liquid level exceeds a certain height, The acid solution level in each pickling tank does not flow into the next pickling tank, so the level of the acid solution in each pickling tank is
The height of the liquid level in each pickling tank increases sequentially from the pickling tank 21 to the third pickling tank 23, and the height of the liquid level in each pickling tank is the level of the material to be pickled, that is, the pass line when the material to be pickled W is being passed. It is designed to be located approximately 100mm higher than the

When the line starts operating, the speed at which the material to be pickled W is passed varies depending on the material and size of the material to be pickled, but it is generally as high as 150 to 300 m/min.
The acid solution on the upper surface of the material to be pickled W is drawn toward the exit side as the material to be pickled is fed. Therefore, the acid liquid level L in each of the pickling tanks 21 to 23 rises toward the outlet side as shown in the figure, and becomes stable in a certain equilibrium state during sheet threading.

Therefore, each pickling tank 21 to
An excess amount of acid solution remains in the tank 23, exceeding the amount stored when the line is stopped. The amount of excess acid solution remaining depends on the scale of the device, the speed of passing the material to be pickled, the width of the plate, the number of decelerations, etc., but usually reaches about 2 to several cm ³ . For example, when replenishing the third pickling tank 23 with acid solution from the conduit 5 at a flow rate of 5 cm ³ /Hr, it takes more than 1 hour after the replenishment starts until the acid solution starts flowing into the waste acid receiving tank 3. In this case, it can be estimated that approximately 5 cm ³ of surplus acid solution remains in the pickling tank.

[Problem to be solved]

However, if for some reason the line operation is suddenly stopped or the speed of passing the material to be pickled, which is moving at high speed, is slowed down, the bulge in each of the pickling tanks 21 to 23 will be reduced. Surplus acid solution held in the state (as mentioned above, the surplus amount is
(usually 2 to several cm ³ or more) loses its previous holding power, and the excess amount flows back toward the waste acid receiving tank 3 all at once. Its force is so rapid that it overflows from the waste acid receiving tank 3.

In addition, while the line operation is stopped, each pickling tank 21 to 2
The acid solution in each sub-tank 91 to 93, which had been transferred from No. 3, was transferred to each pickling tank 21 to 23 before restarting operation.
When the waste acid is returned to the waste acid tank 3, if a surplus acid solution exceeding the capacity of each pickling tank is sent in, the surplus rapidly flows into the waste acid receiving tank 3 in exactly the same manner as described above.

The acid liquid flowing into the waste acid receiving tank 3 in this way is
The third pickling tank 23 and the second pickling tank 22 contain a large amount of relatively fresh acid solution with a high HCl concentration, and are still in a usable state.
Therefore, if this is sent to the recovery process as waste acid, there will be a loss in terms of the acid solution consumption rate and the load on the acid recovery device. Especially as pickling lines become more complex and faster due to automation etc.
As the frequency of line outage increases, the above losses become significant.

In the above explanation, a low-bath type pickling apparatus was taken as an example, but the situation is the same for a semi-low-bath type pickling apparatus, although there are differences in degree.

The present invention has been made to solve these problems.

[Technical means and effects]

The low-bus type or semi-low-bus type pickling equipment of the present invention has a weir installed at the bottom of the waste acid receiving tank connected to the most downstream pickling tank, and the inside of the tank is used as the front chamber on the pickling tank side. The front chamber is divided into two chambers, a rear chamber on the opposite side, and a drain port is provided at the bottom of each chamber, and the front chamber is used as a waste acid receiving part to receive waste acid flowing in during steady operation. It is characterized in that, while being connected to the acid recovery device, the rear chamber is used as an excess acid liquid receiving section for receiving excess acid liquid that flows in when the operation is stopped, and its drain port is connected to an acid liquid storage tank.

According to the present invention, when a large amount of acid solution flows back into the waste acid receiving tank when line operation is stopped in an emergency, some of it flows into the waste acid receiving part (front chamber), but a large amount of the acid solution flows back into the waste acid receiving tank. The part flows into the surplus acid liquid receiving part (rear chamber) and is led to a system path different from the waste acid treatment system path,
Collected in storage tank. The recovered acid solution is directly returned to the pickling tank and reused.

〔Example〕

FIG. 1 is a longitudinal section showing the tank structure of the waste acid receiving tank 3 in the device of the present invention, and FIG. 2 is a plan view showing the entire device.

In Fig. 1, 31 is a weir provided at the bottom of the waste acid receiving tank 3, and the tank 3 is divided into a front chamber 3a on the pickling tank 2 side and a rear chamber 3b on the opposite side by the weir 31. The chambers 3a and 3b are divided into sections, and drain ports 32 and 33 are provided at the bottom of each chamber, and the drain port 32 of the front chamber 3a is connected to an acid recovery device (not shown) through a conduit 4. The drain port 33 of the rear chamber 3b is connected to the conduit 14
As shown in FIG. 2, it is connected to the newly installed acid solution storage tank 15. The device of this invention is
Other than these points, the configuration of other parts does not need to be particularly different from that of FIG. 3.

The front chamber 3a is a part that receives waste acid flowing at a constant flow rate from the most downstream tank (first pickling tank 21) during steady operation of the line. is equal to the replenishment flow rate of acid solution to the most upstream tank (third pickling tank 23 in the figure), which is usually a small amount of about 2 to several cm ³ /Hr. The drain port 32 and conduit 4 at the bottom have a water flow rate of about 2 to several cm ³ /Hr.
The weir 31 is designed to have critical dimensions that do not impede the reception and flow of waste acid, and the height of the weir 31 is also extremely low.

The rear chamber 3b is a part that receives a large amount of acid liquid that flows in at once during an emergency stop of the line or when the sheet passing speed ^is reduced. so that it can be accommodated at once,
In addition, the drain port 33 and the conduit 14 are designed to have a relatively large capacity and size so that the stored acid solution can pass through them smoothly.

In the above equipment, if line operation is stopped from a steady state or the threading speed is reduced,
Due to the structure of the waste acid receiving tank 3, a portion of the large amount of acid solution flowing into the waste acid receiving tank 3 from the pickling tank 2 flows into the front chamber 3a, but most of it is received in the rear chamber 3b. . The acid solution received in the rear chamber 3b is separated from the waste acid recovery system and is passed from the drain port 33 to the conduit 14.
The acid liquid is collected in the acid liquid storage tank 15 through the process.

The acid solution recovered in the acid solution storage tank 15 is a mixed solution of the acid solutions retained in each of the pickling tanks 21 to 23, and its composition is usually around 65 to 105 g/l of HCl. This composition is based on the intermediate pickling tank (in the example shown)
This approximately corresponds to the acid solution composition of the second pickling tank 22). Therefore, the acid solution storage tank 15 is connected to the pickling tank 22 through the conduit 17.
The acid solution in the acid solution storage tank 15 is transferred to the pickling tank 22 by the pump 16 at the same time as the restart of the line operation.
It can be reused by feeding it into the tank at a constant flow rate.

The acid solution replenished from the acid solution storage tank 15 to the second pickling tank 22 reacts with the surface oxide of the material W to be pickled W together with the acid solution replenished to the third pickling tank 23, and
Flows from the pickling tank 22 to the first pickling tank 21, and HCl10
The waste acid flows into the waste acid receiving tank 3 in a degraded state with an iron content of about 70 g/l and an iron content of 110 to 165 g/l. Waste acid receiving tank 3
As mentioned above, the waste acid collected in the tank is sent through the conduit 4 to an acid recovery device (not shown), where it is regenerated, and then returned to the third pickling tank 23 through the conduit 5. It is.

In the above explanation, the case where the number of pickling tanks is three was taken as an example, but even in the case of other number of tanks, the surplus acid solution can be recovered and reused in exactly the same way as above, and Needless to say, it does not matter whether it is a low-bus type or a semi-low-bus type.

[Effect of idea]

According to the present invention, acid liquid suddenly flows from the pickling tank in the event of an emergency stop of pickling line operation, deceleration of strip threading speed, or return of acid liquid from the subtank to the pickling tank when restarting operation. Most of the waste acid can be recovered and reused as a pickling solution without overflowing from the waste acid receiving tank.

Therefore, the acid solution supplied to the pickling tank is effectively used for pickling treatment without waste, which greatly contributes to reducing the basic unit of acid solution and pickling cost and reducing the load on the acid recovery device.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical sectional view of the tank structure of the waste acid receiving tank in the device of the present invention, Fig. 2 is a plan view of an embodiment of the device of the present invention, and Fig. 3 is a longitudinal sectional view of the conventional example. A sectional view is a plan view. 2, 21, 22, 23: pickling tank, 3: waste acid receiving tank, 31: weir, 3a: front chamber, 3b: rear chamber, 15:
Acid solution storage tank, W: material to be pickled.

Claims (1)

[Scope of claim for utility model registration] In a low-bus type or semi-low-bus type steel strip pickling equipment in which a waste acid receiving tank is installed in the lowest downstream tank of multiple pickling tanks, a weir is provided at the bottom of the waste acid receiving tank. The inside of the tank is divided into two chambers: a front chamber on the side of the pickling tank and a rear chamber on the opposite side, and a drainage port is provided at the bottom of each chamber, so that liquid flows into the front chamber from the pickling tank during steady operation. As a waste acid receiving part that receives waste acid, its drainage port is connected to the acid recovery equipment through a conduit, while the rear chamber serves as an acid liquid receiving part that receives excess acid liquid that flows from the pickling tank when the operation is stopped, and its drainage port is connected to the acid recovery equipment through a conduit. Steel strip pickling equipment in which the liquid inlet is connected to the acid liquid storage tank through a conduit.