JP3103263B2 - Liquid quality control method in circulation tank of jet pickling equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jet pickling apparatus for continuously pickling steel strips, wherein each of the circulation tanks (acid solution jetted onto the steel strip surface in each pickling tank is stored). (Tank).

[0002]

2. Description of the Related Art Among methods for continuously pickling steel strips, a method in which an acid solution is jetted from a nozzle onto a steel strip in a pickling tank by a jet pickling equipment in a jet flow state is to scale a steel strip surface. It has been widely used in recent years because it can be efficiently removed. Such a jet pickling equipment includes a plurality of pickling tanks 1 to 4, as shown in FIG.
3 and a plurality of circulation tanks 11 to 13 for supplying acid solutions 8 to 10 to the pickling tanks 1 to 3, respectively.
At 3, the circulation tanks 11 to 13 are applied to the surface of the running steel strip S.
Is pickled from the pickling tank, and the acid solution projected onto the steel strip S and subjected to the descaling reaction is again discharged from the pickling tank to the corresponding circulation tank. It circulates back inside.

The circulation tanks 11 to 13 are connected to each other so that an acid solution can be sequentially flowed to an adjacent circulation tank if necessary. To the circulation tanks 12 and 11 on the inlet side in order, the pumps 2
6, 28 are provided. Furthermore, a new acid is supplied from the outlet side of the steel strip S, spent acid are discharged from the circulation tank 11 the inlet side to the spent acid tank T _H.

[0004] In such a jet pickling facility, when the steel strips having different descaling properties are continuously pickled or when the running speed of the steel strips changes, the descaling reaction ratio in the pickling tank is reduced. Since the acid concentration of the acid solution that changes and returns to the circulation tank changes, the acid concentration in the circulation tank deviates from an appropriate range, and there is a problem that an appropriate pickling process is not performed.

On the other hand, in order to carry out an appropriate pickling treatment while maintaining the acid concentration in each circulation tank within an appropriate range, Japanese Patent Application Laid-Open No. 4-318184 discloses an acid concentration and an acid concentration in each circulation tank. Depending on the liquid level, waste acid from the circulation tank and / or
Alternatively, by introducing new acid into two or more circulation tanks on the upstream side (inlet side of the steel strip), the acid concentration in each circulation tank is maintained from the upstream side to the downstream while maintaining the acid solution level in the circulation tanks. A method of controlling such that it increases linearly toward the side is disclosed.

[0006]

However, in the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-318184, the steel strips having different descaling properties as described above are continuously pickled, There is room for improvement regarding the responsiveness of adjusting the acid concentration in the circulation tank when the traveling speed of the vehicle changes.

The present invention has been made in view of such a point, and in a method of controlling liquid quality in a circulation tank of a jet pickling facility, pickling steel strips having different descaling properties continuously. It is an object of the present invention to provide a method having a high responsiveness for adjusting the acid concentration in the circulation tank when the running speed of the steel strip changes.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, obtained the following knowledge and completed the invention. That is, Japanese Patent Application Laid-Open No.
In the acid concentration control method in the circulation tank of the jet pickling equipment disclosed in Japanese Patent No. 18184, while maintaining the acid solution level in a certain range, the acid concentration in the circulation tank is maintained in a certain range. A so-called feedback control is performed in which the amount of waste acid and / or new acid from the circulation tank to two or more upstream (inlet of steel strip) circulation tanks is calculated or controlled as a control amount. It's just

However, since the liquid level of the acid solution in the circulation tank is very large, that is, the capacity is large, the acid solution in the circulation tank is substantially changed even if the above control amounts are changed and controlled by feedback. Inferior in acid concentration response. Therefore, as described above, when steel strips with different descaling properties are fed, or when the feeding speed changes,
Since the descaling reaction ratio changes, the acid concentration of the acid solution in the circulation tank also changes, but even if the feedback control is performed to follow this, the acid concentration of the acid solution in the circulation tank remains It may not be possible to sufficiently follow the feeding of the steel strip.

Therefore, in the actual continuous pickling operation, for example, it is necessary to change and control the feed speed of the steel strip having the highest responsiveness. As a result, the feed speed of the steel strip is changed and controlled in a decreasing direction. In this case, the operating rate of the continuous pickling process for the steel strip is reduced. However, in the continuous pickling operation in recent years, since the type of steel strip actually continuously fed and the feeding speed required for the pickling can be recognized in advance,
Conversely, these parameters are used as the objective function of optimization control in so-called control engineering, and the input amount (waste from the circulation tank) that can achieve the optimization control under these parameters by, for example, a so-called process computer. What is necessary is just to calculate or control the amount of the acid and / or the new acid into the two or more upstream circulation tanks) as the control amount. At this time, the acid concentration of the acid solution in the circulation tank after a predetermined time from the current time is arranged in chronological order, and the acid concentration at each time is achieved from a matrix in which each control amount for this acid concentration is changed. It is only necessary to obtain the optimum value of each control amount to be performed.

Therefore, the invention of claim 1 comprises a plurality of pickling tanks, and a plurality of circulation tanks for supplying an acid solution to each of the pickling tanks, and the steel strip running in each of the pickling tanks. The steel strip is pickled by projecting the acid solution from each of the circulation tanks in a jet state onto the surface, and the acid solution used for pickling returns from the respective pickling tanks to the corresponding circulation tanks again. While circulating, the plurality of circulating tanks control the liquid quality in each of the circulating tanks of the jet pickling equipment interconnected so that the acid solution can be sequentially flowed to an adjacent circulating tank as needed. In the method, the current hydrogen ion concentration and the liquid level in each of the circulation tanks are detected, and these detected values, the target value of the hydrogen ion concentration in each of the circulation tanks required at the present time, and the required Target value of hydrogen ion concentration in each circulation tank Based on the waste acid from the circulation tank, the new acid, and at least one of pure water,
A method for controlling the liquid quality in the circulation tank of the jet pickling equipment, wherein the method is supplied to each circulation tank as needed.

Further, the invention according to claim 2 comprises a plurality of pickling tanks, and a plurality of circulation tanks for supplying an acid solution to each of the pickling tanks, and a steel strip running in each of the pickling tanks. The steel strip is pickled by projecting the acid solution from each of the circulation tanks in a jet state onto the surface, and the acid solution used for pickling returns from the respective pickling tanks to the corresponding circulation tanks again. While circulating, the plurality of circulating tanks control the liquid quality in each of the circulating tanks of the jet pickling equipment interconnected so that the acid solution can be sequentially flowed to an adjacent circulating tank as needed. In the method, the current hydrogen ion concentration, iron ion concentration, and liquid level in each of the circulation tanks are detected,
Based on these detected values, target values of hydrogen ion concentration and iron ion concentration in each circulation tank required at the present time, and target values of hydrogen ion concentration and iron ion concentration in each circulation tank required after a predetermined time. The waste acid from the circulation tank, new acid, and at least one of pure water,
A method for controlling the liquid quality in the circulation tank of the jet pickling equipment, wherein the method is supplied to each circulation tank as needed.

The pure water means water that hardly changes the hydrogen ion concentration and the iron ion concentration in the circulation tank and does not contain ions or the like that adversely affect the descaling reaction.

[0014]

According to the first aspect of the present invention, the detected value of the hydrogen ion concentration and the liquid level in each of the circulation tanks, the target value of the hydrogen ion concentration in each of the circulation tanks required at present, and the required value after a predetermined time have elapsed. Based on the target value of the hydrogen ion concentration in each of the circulation tanks, for example, the current acid concentration adjustment amount according to the deviation of the hydrogen ion concentration detection value from the current target value, and the hydrogen ion concentration detection value From the sum of the acid concentration adjustment amount after the predetermined time according to the deviation from the target value after the predetermined time, the new acid supply amount and the waste acid supply amount to each circulation tank are calculated, and the liquid in each circulation tank is calculated. The required amount for holding the position and / or the required amount for adjusting the hydrogen ion concentration is defined as the amount of pure water supplied to each circulation tank, and depending on the supply amount, waste acid, new acid,
And pure water into each of the circulation tanks,
While ensuring that the acid concentration in each circulation tank is within the required range at the present time, when continuously pickling steel strips with different descaling properties or when the running speed of the steel strip changes, the circulation tank Since the acid concentration in each of the circulation tanks can be adjusted quickly, it is possible to perform an appropriate pickling treatment while maintaining the acid concentration in each circulation tank within an appropriate range.

According to the second aspect of the present invention, the detected values of the hydrogen ion concentration, the iron ion concentration, and the liquid level in each of the circulation tanks and the hydrogen ion concentration and the iron concentration in each of the circulation tanks which are required at present. Based on the target value of the ion concentration and the target values of the hydrogen ion concentration and the iron ion concentration in each circulation tank required after a predetermined time, for example, according to the deviation of the hydrogen ion concentration detection value from the current target value. The addition and subtraction amount of the new acid and the sum of the addition and subtraction amount of the new acid according to the deviation from the target value of the hydrogen ion concentration detection value after a predetermined time are calculated as the supply amount of the new acid to each circulation tank, Sum of the adjustment of waste acid according to the deviation of the iron ion concentration detection value from the current target value and the adjustment of the waste acid according to the deviation of the iron ion concentration detection value from the target value after a predetermined time. And calculate the waste acid supply to each circulation tank. The amount required for maintaining the liquid level of each circulation tank and / or the amount necessary for adjusting the hydrogen ion concentration and the iron ion concentration is defined as the amount of pure water supplied to each circulation tank. Thus, by feeding waste acid, new acid, and pure water into each of the circulation tanks, the steel strips having different descaling properties can be continuously formed while securing the acid concentration in each of the circulation tanks within a necessary range at the present time. The acid concentration in the circulating tank can be adjusted quickly even when pickling is carried out or the running speed of the steel strip changes. Can be performed, and the iron ion concentration in each of the circulation tanks is adjusted to a predetermined range in which the pickling time is minimized at the present time and after a predetermined time (for example, 1% in terms of FeCl ₂ concentration).
(0 to 30% by weight), it is possible to perform highly efficient pickling.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus to which the method of the present invention can be applied. In this jet pickling equipment, three pickling tanks 1 to 3 of No. 1 to No. 3 are arranged from the entrance side to the exit side along the running direction of the steel strip S, and each of the pickling tanks 1 to 3 is arranged. Reference numeral 3 is provided with a nozzle (not shown) for projecting the acid solution in a jet state on the surface of the steel strip S. Ringer rolls 4 to 7 also serving as liquid seals are provided at the entrances and exits of each of the pickling tanks 1 to 3. Also,
No. 8 to supply acid solutions 8 to 10 to the respective pickling tanks 1 to 3
No. 1 to No. 3 circulation tanks 11 to 13 are provided, and between the circulation tanks 11 to 13 and the corresponding pickling tanks 1 to 3, supply pipes 14 from the circulation tank to the pickling tank, 17,2
0, supply pumps 16, 19, 22 and return pipes 15, 18, 21 from the pickling tank to the circulation tank are provided.

Thus, in each of the pickling tanks 1 to 3, the acid solution 8 to 8 from each of the circulation tanks 11 to 13 is applied to the surface of the traveling steel strip S.
The steel strip S is pickled by projecting the nozzles 10 through the nozzles 4 to 7 in a jet state, and the acid solution projected to the steel strip S and subjected to the descaling reaction is again transferred from the pickling tank to the corresponding circulation tank. It comes back and circulates. The pump 24 is placed in the circulation tank 13 of No. 3 arranged on the exit side of the steel strip S.
The new acid tank _TN is connected to the circulating tank 11 through the pipe 23 and the flow control valve 33, and the pump 2
6, 28 and connected by a pipe 25, 27, are connected to spent acid tank T _H by the pump 30 to the entrance side of the steel strip S and the pipe 29. No.1 circulation tank 1 from new acid tank _TN
The pipe 32 heading to No. 1 is branched from the pipe 23 and
A flow control valve 37 was provided between the first circulation tank 11 and the first circulation tank 11.
A pipe 34 was branched from the pipe 32 and connected to the circulation tank 12 of No. 2, and a flow control valve 35 was connected to the pipe 34.

Thus, the new acid is supplied to each of the circulation tanks 11 to 1
3, an acid solution is supplied by the pump 24 via the flow control valves 37, 35, and 33, respectively, in predetermined amounts, and the acid solution can be sequentially flowed to an adjacent upstream (inlet side of the steel strip) circulation tank as necessary. Waste acid is discharged from the circulation tank 11 on the inlet side to the waste acid tank T.
_H is to be discharged. Further, the pipe 38 for supplying spent acid is disposed toward the circulation tank 12, 13 of the No.2 and No.3 from spent acid tank T _H, the flow control valve between the circulation tank 12 No.2 39 However, a flow control valve 40 is provided between the circulation tank 13 and No. 3.

Thus, a predetermined amount of waste acid is supplied to the circulation tanks 12 and 13 of No. 2 and No. 3 by the pump 30 via the flow control valves 39 and 40, respectively. Further, a pipe 42 for supplying pure water is arranged from the pure water tank _Tj to each of the circulation tanks 11 to 13, and a flow control valve 45 is provided between the pipe 42 and the No. 1 circulation tank 11.
Is the flow control valve 44 between the circulation tank 12 of No. 2
However, a flow control valve 43 is provided between the circulation tank 13 of No. 3 and a pump 41 is connected to the pipe 42 near the outlet of the pure water tank _Tj .

Thus, pure water is supplied to the circulation tanks 11 to 13 of No. 1 to No. 3 by the pump 41 and the flow control valve 4.
5, 44 and 43, respectively, to supply a predetermined amount. On the other hand, although not shown in FIG.
Within each circulation tank 11 to 13, the hydrogen ion concentration sensor, the iron ion concentration sensor, and level sensors, in the spent acid tank T _H, the hydrogen ion concentration sensor and iron ion concentration sensor Yes installed, FIG. In 1 jet pickling equipment, the detection values from these sensors and the target values of the hydrogen ion concentration and the iron ion concentration in each of the circulation tanks at the present time and after a predetermined time sent from the host computer are input, Based on these data, the supply amount of waste acid, new acid, and pure water to each circulation tank is calculated, and a drive signal corresponding to the calculated supply amount is output to each of the flow rate control valves. , A controller not shown in FIG.

This controller is composed of a process computer. As shown in FIG. 2, the detected values of the hydrogen ion concentration H ₁ -H ₁ in each circulating tank inputted from the respective sensors are as follows.
H ₃ , the hydrogen ion concentration detection value H _H in the waste acid tank, the iron ion concentration detection values F _{1 to} F ₃ in each circulation tank, the iron ion concentration detection value F _H in the waste acid tank, and each of the circulation tanks the liquid level detection value L ₁ ~L _3, the set minimum required liquid level is L ₀ (the circulation tank common), input from the host computer, the hydrogen ion concentration at the present time of each circulation tank 11 to 13 target value ^{_{H * 1 1 ~H * 1 3}} , a target value H ^{* 2} ₁ hydrogen ion concentration after a predetermined time to H * ² _3, the target value of iron ion concentrations in the moment ^{_{F * 1 1 ~F * 1 3}} , and the target value of the iron ion concentration after a predetermined time F ^{* 2} ₁ ~F ^{* 2}
₃ and supply amounts K _{N1 to} K _N3 to the respective circulation tanks of waste acid, new acid, and pure water, for example, as described below.
K _{H1 to} K _H3 , K _{j1 to} K _j3 are calculated, and the flow control valves 37, 35, 32 for new acid supply, the flow control valves 39, 40 for waste acid supply, pure water according to the calculated supply amounts. Supply flow control valve 4
Each drive signal N ₁ to N to vary the degree of opening of 5,44,43
_{3, H 1 ~H 3, J} 1 ~J 3 a towards the respective flow control valve and outputs. <Amount of New Acid Supply> Since the concentration of the acid solution (hydrogen ion concentration) in the pickling treatment needs to be increased as the traveling speed of the steel strip increases, the supply amount of the new acid is represented by a solid line A in the graph of FIG. As shown, it is set to a value proportional to the running speed of the steel strip. The graph in FIG. 3 shows an example in the case of hydrochloric acid having an HCl concentration of 18%. When the type of steel strip to be treated changes and the descaling reaction rate changes, it is necessary to change the concentration of the acid solution accordingly.

In this embodiment, an acid solution concentration (hydrogen ion concentration) required at the present time and an acid solution concentration (hydrogen ion concentration) required after a predetermined time are determined by a target value H at the present time and after a predetermined time of the hydrogen ion concentration. ^{_{* 1 1 ~H * 1 3,}} H * 2 1 ~H * 2 3 host computer is calculated as the hydrogen ion concentration detection value H ₁ at each actual circulation tank and the target value of the circulation tank
By an amount to compensate for deviations of the ~H ₃ to supply the new acid.

That is, the supply amount (K _N1 ) of the new acid to the No. 1 circulation tank 11 is calculated by, for example, the following equation (1). ^{_{K N1 = a 1 (H *}} 1 1 -H 1) + b 1 (H * 2 1 -H 1) ...... (1) ( where, a _1, b _{1 is, a 1 ≦ 1.0, b 1} ≦ 1.0,
A proportional constant that simultaneously satisfies a ₁ + b ₁ ≦ 1.0. Similarly, the supply amount of new acid to the No. 2 circulation tank 12 (K
_N2 ) is calculated, for example, by the following equation (2).

[0024] ^{_{K N2 = a 2 (H *}} 1 2 -H 2) + b 2 (H * 2 2 -H 2) ...... (2) ( however, a _2, b ₂ is, a ₂ ≦ 1.0, b ₂ ≦ 1.0,
Proportional constant that simultaneously satisfies a ₂ + b ₂ ≦ 1.0. Similarly, the supply amount (K) of the new acid to the circulation tank 13 of No. 3
_N3 ) is calculated, for example, by the following equation (3).

[0025] ^{_{K N3 = a 3 (H *}} 1 3 -H 3) + b 3 (H * 2 3 -H 3) ...... (3) ( However, a _3, b ₃ is, a ₃ ≦ 1.0, b ₃ ≦ 1.0,
Proportional constant that simultaneously satisfies a ₃ + b ₃ ≦ 1.0. <Waste acid supply amount> The waste acid contains ferrous chloride (FeCl ₂ ) generated by the descaling reaction of the steel strip, and the hydrogen ion concentration is lower than that of the new acid. To increase the iron ion concentration in the circulation tank,
The hydrogen ion concentration can be reduced.

As shown in FIG. 4, it is known that the descaling time (the time required for pickling) varies depending on the iron ion concentration (FeCl ₂ concentration) even when the hydrogen ion concentration (HCl concentration) is the same. That is, as can be seen from FIG. 4, the iron ion concentration in the acid solution is 10% in terms of FeCl ₂ concentration.
In the range of に な る 30% by weight, there is a peak point at which the descaling time is minimized. Therefore, when the FeCl ₂ concentration is 10 to 3
If the iron ion concentration that becomes 0% by weight is set as the target value in each circulation tank, descaling can be performed in a short time.

The iron ion concentration set in this way is
Supply of waste acid to No. 2 circulation tank 12 as target value
Quantity (K_H2) Indicates the current hydrogen ion concentration in the waste acid tank.
Degree H _HAnd iron ion concentration F_HDepending on, for example,
It is calculated by equation (4). K_H2= C_Two(H^{* 2} _Two-H_Two) / H_H+ D_Two(F^{* 2} _Two-F_Two) / F_H …… (4) (However, c_Two, D_TwoIs c_Two≦ 1.0, d_Two≦ 1.0,
c_Two+ D_TwoA coefficient that simultaneously satisfies ≦ 1.0. Similarly, the supply amount of waste acid to the circulation tank 13 of No. 3 (K
_H3) Is calculated by, for example, the following equation (5).

[0028] ^{_{K H3 = c 3 (H *}} 2 3 -H 3) / H H + d 3 (F * 2 3 -F 3) / F H ...... (5) ( However, c _3, d ₃ is, c ₃ ≦ 1.0, d ₃ ≦ 1.0,
A coefficient that simultaneously satisfies c ₃ + d ₃ ≦ 1.0. <Pure water supply amount> Since the acid level in the circulation tank is reduced by the acid solution attached to the steel strip and carried away or evaporated, as shown by the broken line B in the graph of FIG. It is necessary to make the sum of the supply amounts of new acid, waste acid, and pure water necessary for maintaining the liquid level according to the traveling speed of the liquid. Therefore, the supply amounts K _{j1 to} K _j3 of the pure water to the respective circulation tanks 11 to 13 are as _follows :
When the liquid level of each circulation tank does not reach the predetermined liquid level L ₀ due to the new acid supply amount and / or the waste acid supply amount,
BR> It is calculated as a necessary amount for maintaining a predetermined liquid level.

That is, the supply amount K _j1 of pure water to the No. 1 circulation tank 11 is calculated by the following formula (6) when L ₀ −L ₁ ≧ 0. L ₀ −L ₁ = K _N1 + K _j1 K _j1 = L ₀ −L ₁ −K _N1 (6) Also, the supply amount K of pure water to the No. 2 circulation tank 12
_j2 in the case of L ₀ -L ₂ ≧ _0, for example, is calculated by equation (7) below.

L₀-L_Two= K_N2+ K_H2+ K_j2 K_j2= L₀-L_Two-K_N2-K_H2 (7) Similarly, the supply amount K of pure water to the circulation tank 13 of No. 3_j3
Is L₀-L_ThreeIf ≧ 0, for example,
calculate. L₀-L_Three= K_N3+ K_H3+ K_j3 K_j3= L₀-L_Three-K_N3-K_H3 (8) Each supply amount K calculated in this manner._N1~ K_N3,
K_H1~ K_H3, K_j1~ K _j3As shown, each circulation tank 11-1
New acid, waste acid, and / or pure water are supplied into 3
And the hydrogen ion concentration in each of the circulation tanks 11 to 13 and
The iron ion concentration is calculated by_N1~ K_N3, K_H1~ K_H3By
Will deviate from the set value.
Is composed of a process computer.
The priority of the parameter is changed as appropriate.
From a large matrix of changes, optimization control
The optimum value of each parameter is set.

FIGS. 5 and 6 show an example of the result of controlling the liquid quality of each circulating tank based on the method of this embodiment by this apparatus in comparison with the conventional example. FIG. 5 (a),
(B) Each of Nos. 1 to 3 when pickling high-speed pickling material (A), special steel and low pickling material (B) using hydrochloric acid as the acid solution. It is a graph which shows the result of having investigated the HCl concentration in a circulation tank, (a) is a result when control of this example is not performed, and (b) is a result when control of this example is performed. It is.

When the control of the present embodiment is not performed, FIG.
As shown in (a), especially during the processing of the high-speed pickling material (A), the pickling process is almost completed in the No. 1 and No. 2 circulation tanks, so the No. 3 Although the HCl concentration becomes high, the waste acid is supplied into the No. 3 circulation tank under the control of the present embodiment, so that the HCl concentration in the No. 3 circulation tank is increased as shown in FIG. Is suppressed to an appropriate range.

FIGS. 6 (a) and 6 (b) show the results when pickling high-speed pickling material (A), special steel and low pickling material (B) using hydrochloric acid as an acid solution. is a graph showing the results of examining the FeCl ₂ concentration in each circulation tank No.1~ No.3, (a) is the result of the case without the control of this embodiment, (b) the present This is a result when the control of the example is performed.

When the control of the present embodiment is not performed, FIG.
As shown in (a), particularly during the processing of the high-speed pickling material (A), the supply of the waste acid described above causes the F
Although the eCl ₂ concentration increases, according to the control of this embodiment,
As shown in FIG. 6B, Fe in the No. 3 circulation tank
Cl ₂ concentration can be suppressed to an appropriate range. As described above, in the control of the present embodiment, parameters such as the type of the steel strip which is actually continuously fed and which can be recognized in advance and the feed speed required for pickling the steel strip are used as the objective functions of the optimization control. The acid concentration of the acid solution in the circulation tank obtained from the objective function is arranged in chronological order, and the waste acid and / or new acid from each circulation tank that can achieve this acid concentration is transferred to the upstream side (the inlet side of the steel strip). ) Can be calculated or controlled as the control amount of the two or more circulating tanks, so that the acid concentration of the acid solution in the circulating tank that changes in time series is supplied at that time. Control can be performed in advance in accordance with the type of the steel strip or its feeding speed, and as a result, control responsiveness is improved.

[0035] That is, as shown in FIG. 7, the type of the steel strip after a predetermined time has changed from A to B, and with this, the proper range of acid concentration has a portion overlapping is lower than this of the predetermined range D _A If the change to the range D _B, in the control of this embodiment, as shown in FIG. 7 (a), the target value of the acid concentration in the a steel processing, proper B steel proper range D _a of the a steel by setting the range D _B and the overlapped part (low concentration range) D a _', it is possible to shorten the response time of the control.

On the other hand, Japanese Unexamined Patent Publication No.
According to the so-called feedback control disclosed in Japanese Patent Application Publication No. 4 (1993) -1994, as shown in FIG. 7B, the target value of the acid concentration during the treatment of the steel A is the optimum value D _A0 of the acid concentration of the steel A (that is, is set in a range intermediate values of D _a), when the strip to be processed is changed to B steel, the optimum value D _B0 acid concentration of steel target value of the acid concentration B (i.e., the proper range D _B intermediate ), The response time of the control becomes longer.

Further, as shown in FIG.
The type of the band changes from A to B, and the acid concentration
The appropriate range is the predetermined range D_ALower than this and overlap
Range D without part_BIn this case, the
In the control, as shown in FIG.
The target value of the acid concentration in the tank is adjusted to the appropriate range D of the steel A. _A
Lowest value D of_ALWhen the control response
The time can be shortened. That is, the steel strip to be processed
Is changed to steel B, the acid concentration in the circulation tank
Predicate value D_ALFrom the appropriate range D of the B steel in a short time_BMost of
High value D_BHCan be changed to

On the other hand, Japanese Unexamined Patent Publication No.
According to the so-called feedback control disclosed in Japanese Patent Application Publication No. 4 (1993) -1995, similarly to the above, as shown in FIG. 8 (b), the target value of the acid concentration during the treatment of the steel A is the optimum acid concentration D of the steel A. _A0 (i.e., the intermediate value of the proper range D _a) is set to, when the strip to be processed is changed to B steel, the optimum value D _B0 acid concentration of steel target value of the acid concentration B (i.e., the proper to be set to an intermediate value) in the range D _B, the response time of the control becomes large.

Further, by improving the responsiveness of the overall control, extra control such as changing the feed speed of the steel strip in the decreasing direction as in the conventional case is reduced, and at the same time, the continuous pickling operation is performed. The operation rate will be improved. In addition, in this embodiment, the iron ion concentration in each circulation tank is detected, and the supply amount of waste acid is calculated based on the detected value.
Since the iron ion concentration in each circulation tank is maintained at a current time and after a predetermined time, in a predetermined range in which the pickling time is minimized (for example, 10 to 30% by weight in terms of FeCl ₂ concentration). Highly efficient pickling can be performed.

[0040]

As described above, according to the liquid quality control method in the circulation tank of the jet pickling equipment according to the first aspect, the current hydrogen ion concentration and the liquid level in each circulation tank are detected. Then, based on these detected values, the target value of the hydrogen ion concentration in each circulation tank required at the present time, and the target value of the hydrogen ion concentration in each circulation tank required after a predetermined time, By setting the amount of waste acid, new acid, and pure water to be supplied to each circulation tank, the steel concentration in each circulation tank can be maintained within the necessary range at the moment, and steel strips with different descaling properties can be obtained. The acid concentration in the circulation tank can be quickly adjusted even when pickling continuously or when the running speed of the steel strip changes. A washing process can be performed.

According to the liquid quality control method in the circulation tank of the jet pickling equipment according to the second aspect, the current hydrogen ion concentration, iron ion concentration, and liquid level in each circulation tank are detected. Based on these detected values, target values of hydrogen ion concentration and iron ion concentration in each circulation tank required at the present time, and target values of hydrogen ion concentration and iron ion concentration in each circulation tank required after a predetermined time. By setting the supply amount of waste acid, new acid, and pure water from the circulation tank to each circulation tank, in addition to the effect of claim 1, the iron ion concentration in each circulation tank is At this time and after a predetermined time, highly efficient pickling can be performed while maintaining the pickling time in a predetermined range that minimizes the pickling time (for example, 10 to 30% by weight in terms of FeCl ₂ concentration).

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of an apparatus configuration to which the method of the present invention can be applied.

FIG. 2 is a block diagram of a controller in the apparatus of FIG.

FIG. 3 is a graph showing a relationship between a running speed of a steel strip and a supply amount of a new acid.

FIG. 4 is a graph showing the relationship between descaling time and FeCl ₂ concentration using HCl concentration as a parameter.

FIG. 5 HC in each circulation tank of No. 1 to No. 3
5A and 5B are graphs showing the results of examining the l concentration, wherein FIG. 5A shows the results when the control of the present embodiment is not performed, and FIG. 5B shows the results when the control of the present embodiment is performed.

FIG. 6: Fe in each circulation tank of No. 1 to No. 3
It is a graph showing the results of examining the Cl ₂ concentration, indicating (a) shows the case without control of this embodiment, (b) the result when having a control of this embodiment.

7A and 7B are conceptual diagrams showing an example of a method of setting a target value of an acid concentration in the control method of this embodiment and the control method of a conventional example, and FIG. 7A shows a control method of this embodiment; b)
Indicates a conventional control method.

FIG. 8 is a conceptual diagram showing another example of a method of setting a target value of an acid concentration in the control method of this embodiment and the control method of a conventional example, and (a) shows the control method of this embodiment. ,
(B) shows a conventional control method.

FIG. 9 is a schematic configuration diagram showing a conventional jet pickling facility.

[Explanation of symbols]

1-3 San'araiso 8-10 acid solution 11-13 circulation tank S steel strip T _N new acid tank T _H spent acid tank T _j pure water tank S steel strip 23,32,34 new acid supply pipe 24 new acid Supply pump 30 Waste acid supply pump 38 Waste acid supply pipe 37,35,32 New acid supply flow control valve 39,40 Waste acid supply flow control valve 41 Pure water supply pump 42 Pure water supply pipe 45 , 44,43 Flow control valve for pure water supply

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-208100 (JP, A) JP-A-6-248479 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23G 3/02

Claims (2)

(57) [Claims] 1. A pickling tank comprising: a plurality of pickling tanks; and a plurality of circulating tanks for supplying an acid solution to each of the pickling tanks. The steel strip is pickled by projecting the acid solution in a jet state, and the acid solution used for pickling is returned from each pickling tank to the corresponding circulation tank again and circulated, and the plurality of A method for controlling the liquid quality in each of the circulation tanks of a jet pickling facility in which a circulation tank is interconnected so that an acid solution can be sequentially flowed to an adjacent circulation tank as needed. The current hydrogen ion concentration and liquid level in the tank are detected, and these detected values, the target value of the hydrogen ion concentration in each circulation tank required at the present time, and the hydrogen The circulation tank based on the target value of the ion concentration. Waste acid from, the new acid and liquid property control method of the circulation tank of the jet pickling equipment, characterized in that at least one, it is put into the respective circulation tanks as needed of pure water. 2. A pickling tank and a plurality of circulating tanks for supplying an acid solution to each of the pickling tanks, wherein each of the pickling tanks transfers a surface of a running steel strip from each of the circulating tanks. The steel strip is pickled by projecting the acid solution in a jet state, and the acid solution used for pickling is returned from each pickling tank to the corresponding circulation tank again and circulated, and the plurality of A method for controlling the liquid quality in each of the circulation tanks of a jet pickling facility in which a circulation tank is interconnected so that an acid solution can be sequentially flowed to an adjacent circulation tank as needed. The current hydrogen ion concentration, iron ion concentration, and liquid level in the tank are detected, and the detected values, target values of hydrogen ion concentration and iron ion concentration in each circulation tank required at the present time, and a predetermined time Hydrogen ion concentration in each circulation tank required later And jetting at least one of waste acid, new acid, and pure water from the circulation tank into each of the circulation tanks as necessary based on the target value of the iron ion concentration. Liquid quality control method in circulation tank of pickling equipment.