Pickling method and pickling equipment for steel strip

Abstract

Provided is pickling technology capable of suppressing a reduction in treatment capacity in pickling treatment while efficiently performing sludge removal treatment. A pickling method for a steel strip according to the present invention involves removing scale generated on the surface of a steel strip by immersing the steel strip in a hydrochloric acid solution stored in a pickling tank while transporting the steel strip containing silicon, the pickling method being characterized by comprising: a step for supplying the hydrochloric acid solution stored in the pickling tank to a cyclone filter to remove suspended matter caused by the scale contained in the hydrochloric acid solution; and a step for heating the hydrochloric acid solution by means of a heat exchanger.

Description

Steel strip pickling method and pickling equipment

[0001] The present invention relates to a method and equipment for pickling a steel strip.

[0002] In the production of steel sheets, a steel strip produced by a hot rolling process is subjected to continuous pickling, which involves immersing the steel strip in a pickling solution made of a strong acid such as hydrochloric acid or sulfuric acid to peel off and remove scale formed on the surface of the steel strip.

[0003] The pickling solution used in continuous pickling treatment tends to have an increased metal concentration and a decreased descaling performance as the continuous pickling treatment progresses. Therefore, as a method for suppressing the increase in the metal concentration in the pickling solution, for example, a method has been proposed in which suspended matter is removed from the sulfuric acid solution extracted from the pickling tank using a cyclone and a filter, and a part of the clean solution after passing through the filter is passed through an ion exchange resin to recover free acid and return the free acid to a circulation tank (see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2007-204821

[0005] The aforementioned Patent Document 1 further discloses the addition of a pickling accelerator when a decrease in pickling weight loss occurs. However, pickling accelerators have an immediate effect but are not long-lasting. Furthermore, because pickling accelerators cause excessive dissolution of base iron, it is necessary to remove the sludge generated in the pickling solution. Furthermore, with the use of the aforementioned ion exchange resin, the exchange groups become saturated and the adsorption effect of free acid decreases with prolonged use. Therefore, the ion exchange resin must be replaced periodically. Thus, the addition of a pickling accelerator or the use of an ion exchange resin can reduce the processing capacity of the pickling process.

[0006] Furthermore, in recent years, in addition to stainless steel sheets, electrical steel sheets, high-strength steel sheets, etc. have also been manufactured. For example, electrical steel sheets and high-strength steel sheets have a high silicon (Si) content, and silicon-derived sludge is likely to be generated during continuous pickling treatment. Therefore, there is a growing demand for pickling technology that can efficiently remove sludge while preventing a decrease in processing capacity during pickling treatment.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a pickling technique that can efficiently remove sludge while suppressing a decrease in processing capacity in the pickling treatment.

[0008] One aspect of the method for pickling a steel strip is a method for removing scale formed on the surface of a silicon-containing steel strip by immersing the steel strip in a hydrochloric acid solution contained in a pickling tank while transporting the steel strip, and is characterized by comprising the steps of: supplying the hydrochloric acid solution contained in the pickling tank to a cyclone filter to remove floating matter caused by scale contained in the hydrochloric acid solution; and heating the hydrochloric acid solution using a heat exchanger.

[0009] The step of heating the hydrochloric acid solution is preferably carried out on the hydrochloric acid solution from which suspended matter has been removed using a cyclone filter.

[0010] Furthermore, it is preferable that the critical particle size of the suspended matter separated by the cyclone filter is equal to or smaller than a predetermined value, specifically, 12 μm or smaller.

[0011] In addition, one aspect of the present invention provides a steel strip pickling equipment having a pickling tank containing hydrochloric acid in a conveying line for a silicon-containing steel strip, in which the conveyed steel strip is immersed, and characterized in that the equipment has a cyclone filter that removes floating matter resulting from scale contained in the hydrochloric acid from the hydrochloric acid contained in the pickling tank, and a heat exchanger that heats the hydrochloric acid.

[0012] The heat exchanger is preferably disposed in a passage through which the hydrochloric acid solution from which suspended matter has been removed by the cyclone filter is returned to the pickling tank.

[0013] Furthermore, it is preferable that the critical particle size of the suspended matter separated by the cyclone filter is equal to or smaller than a predetermined value, specifically, 12 μm or smaller.

[0014] According to the present disclosure, it is possible to provide a pickling technology that efficiently removes sludge while preventing a decrease in processing capacity in the pickling process.

[0015] FIG. 1 is a schematic diagram showing one embodiment of a steel strip pickling system according to the present invention. FIG. 2 is a schematic perspective view showing an example of a cyclone filter. FIG. 3 is a schematic diagram showing the relationship between the particle size and removal rate of suspended matter removed by a cyclone filter in the hydrochloric acid solution contained in the pickling tank and the water contained in the water washing tank. FIG. 4 is a schematic diagram showing an example of a removal device using a cyclone filter. FIG. 5 is a graph showing the relationship between the particle size and amount of sludge contained in the hydrochloric acid solution when the sludge removal process is performed using the removal device shown in FIG. 4. FIG. 6 is a graph showing the amount of sludge generated in a continuous pickling system and the change over time in the amount of sludge remaining in the hydrochloric acid solution after sludge removal using a cyclone filter. FIG. 7 is a comparison table showing the change over time in the particle size distribution of sludge contained in the hydrochloric acid solution contained in the pickling tank. FIG. 8 is a graph showing the change over time in the amount of sludge generated in the pickling tank of the pickling system. FIG. 9 is a schematic diagram showing a pickling system according to another embodiment.

[0016]

[0023] Hereinafter, one embodiment of a pickling plant for a steel strip according to the present embodiment will be described with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of the pickling plant for a steel strip according to the present embodiment. The pickling plant 1 has a pickling tank 2 as well as a water washing tank and a drying tank (not shown).

[0017] The pickling tank 2 is provided for immersing the steel strip S transported in the direction A in Figure 1 in the pickling solution contained in the pickling tank 2. By immersing the steel strip S in the pickling solution contained in the pickling tank 2, scale (oxide film), rust, etc. formed on the surface of the steel strip S are removed. Note that although Figure 1 illustrates a pickling equipment having one pickling tank 2, the pickling equipment may have two or more pickling tanks 2 along the transport direction of the steel strip S. Below, a case will be described in which, for example, hydrochloric acid solution is used as the pickling solution.

[0018] In this embodiment, a steel sheet having a high silicon (Si) content, such as an electrical steel sheet or a high-strength steel sheet, will be described as the steel sheet S to be pickled in the pickling equipment 1. The Si content of the steel sheet S is, for example, 1.0 to 3.5%.

[0019] A new acid tank 3 is connected to the pickling tank 2 via a pipe 4. The new acid tank 3 contains new hydrochloric acid. A pump 5 is provided on the pipe 4. The hydrochloric acid contained in the new acid tank 3 is supplied to the pickling tank 2 via the pipe 4 by driving the pump 5.

[0020] A cyclone filter 6 is connected to the pickling tank 2 via a pipe 7. A pump 8 is disposed in the pipe 7. The hydrochloric acid solution contained in the pickling tank 2 is supplied to the cyclone filter 6 via the pipe 7 by driving the pump 8. That is, by driving the pump 8, the hydrochloric acid solution contained in the pickling tank 2 is extracted and supplied to the cyclone filter 6.

[0021] As shown in Fig. 2, the cyclone filter 6 has a filter body 61, a supply pipe 62, and a discharge pipe 63. The filter body 61 is composed of an upper body portion 61a and a lower body portion 61b. The upper body portion 61a is formed in a cylindrical shape with a closed top surface. The lower body portion 61b is provided below the upper body portion 61a and is formed in a funnel shape with an open bottom surface.

[0022] The cyclone filter 6 causes the hydrochloric acid solution flowing in from the supply pipe 62 to swirl inside the filter body 61. As a result, suspended matter (hereinafter referred to as sludge) SL contained in the hydrochloric acid solution is separated into a dirty solution in which the sludge SL with a high specific gravity has been concentrated, and a clean solution (hereinafter referred to as clean solution) from which the sludge SL with a high specific gravity has been removed. The clean solution is sent to the pickling tank 2 via a pipe 9 connected to a discharge pipe 63. Meanwhile, the dirty solution is discharged from a discharge port 64 to a recovery tank 15. The sludge SL contained in the hydrochloric acid solution is metal sludge containing iron oxide (Fe, Mn, Si, Al, etc.).

[0023] Returning to FIG. 1 , the recovery tank 15 includes a first tank 15a and a second tank 15b. The first tank 15a stores the contaminated liquid discharged from the discharge port 64 of the cyclone filter 6. When the contaminated liquid is stored in the first tank 15a, the sludge SL contained in the contaminated liquid settles to the bottom of the first tank 15a. The sludge SL that settles in the first tank 15a is sent to the waste acid tank 18 via a pipe 16 by driving a pump 17 disposed in the pipe 16. Meanwhile, the supernatant liquid of the contaminated liquid stored in the first tank 15a flows to the second tank 15b. The supernatant liquid stored in the second tank 15b is sent to the pickling tank 2 via a pipe 19 as clean liquid by driving a pump 20 disposed in the pipe 19.

[0024] A heat exchanger 21 is connected to the pickling tank 2 via a pipe 22. A pump 23 is disposed in the pipe 22. The hydrochloric acid solution contained in the pickling tank 2 is sent to the heat exchanger 21 via the pipe 22 by driving the pump 23.

[0025] The heat exchanger 21 exchanges heat between the hydrochloric acid solution flowing through the pipe 22 and a heat exchange medium circulating within the heat exchanger 21, thereby heating the hydrochloric acid solution flowing through the pipe 22. The hydrochloric acid solution heated by the heat exchanger 21 is sent to the pickling tank 2 through the pipe 22.

[0026] The control device 25 controls each part of the pickling equipment 1 to perform continuous pickling treatment in the pickling equipment 1. In Fig. 1, measurement signals from the thermometer 24, control signals to each pump, and control signals to the heat exchanger 21 are indicated by dotted lines. In Fig. 1, control signals to the equipment for transporting the steel strip S are omitted.

[0027] The continuous pickling process in the pickling equipment 1 shown in Figure 1 will be described. A control device 25 starts the continuous pickling process by operating each part of the pickling equipment 1. As a result, the steel strip S is transported in the direction A in Figure 1, and the transported steel strip S is immersed in the hydrochloric acid solution contained in the pickling tank 2. When the steel strip S is immersed in the hydrochloric acid solution, scale and rust formed on the surface of the steel strip S are removed.

[0028] Furthermore, when the continuous pickling treatment in the pickling equipment 1 is started, the control device 25 outputs an operation signal to the pump 8 to operate the pump 8. When the pump 8 is operated, the hydrochloric acid solution contained in the pickling tank 2 is supplied from the pickling tank 2 to the cyclone filter 6 via the piping 7. The hydrochloric acid solution supplied to the cyclone filter 6 is separated into clean solution and dirty solution. The separated clean solution is sent to the pickling tank 2 via the discharge pipe 63 and the piping 9 connected to the discharge pipe 63, and the dirty solution is discharged from the discharge port 64 to the first tank 15a of the recovery tank 15.

[0029] The control device 25 also outputs operation signals to the pumps 17 and 20 to operate these pumps 17 and 20. For example, when the pump 17 is operated, the sludge SL that has settled to the bottom of the first tank 15a is sent to the waste acid tank 18 via the pipe 16. When the pump 20 is operated, the clean liquid stored in the second tank 15b is sent to the pickling tank 2 via the pipe 19.

[0030] During the continuous pickling process, the control device 25 receives a measurement signal from a thermometer 24 provided in the pickling tank 2. When the temperature of the hydrochloric acid obtained from the measurement signal from the thermometer 24 is equal to or lower than a predetermined first temperature, the control device 25 outputs an operation signal to the heat exchanger 21 and the pump 23 to operate the heat exchanger 21 and the pump 23. As a result, the hydrochloric acid extracted from the pickling tank 2 is heated by the heat exchanger 21 and sent to the pickling tank 2. When the temperature of the hydrochloric acid obtained from the measurement signal from the thermometer 24 exceeds a predetermined second temperature, the control device 25 outputs an operation stop signal to the pump 23 and the heat exchanger 21. That is, the control device 25 controls the operation of the pump 23 and the heat exchanger 21 so as to maintain the temperature of the hydrochloric acid contained in the pickling tank 2 at the predetermined second temperature. The above-mentioned first and second temperatures are temperatures for appropriately performing the continuous pickling treatment, and are set based on, for example, the dissolution rate of the steel strip S in the pickling solution and the transport speed of the steel strip S. The first and second temperatures are temperatures determined, for example, by experiments or simulations.

[0031] The limit particle size d of the sludge SL that can be removed by the cyclone filter 6 is ｃ can be calculated by the following formula (1).

[0032]

[0033] The removal rate Δη of the sludge SL removed by the cyclone filter 6 can be calculated by the following equation (2).

[0034]

[0035] Here, the symbols in the above formulas (1) and (2) are as follows: ｃ : Limit particle size (μm) d ｐ : Arbitrary particle size (μm) D ｃ D: diameter of the upper body 61a of the cyclone filter 6 (cm) ｉ D: diameter of supply pipe 62 of cyclone filter 6 (cm) ｏ D: diameter of the discharge pipe 63 of the cyclone filter 6 (cm) ｕ ρ: diameter of outlet 64 of cyclone filter 6 (cm) h: effective height of cyclone filter 6 (cm) Q: flow rate of pickling solution (L / min) ｓ : particle density (g / cm ３ ) ρ ｌ : density of pickling solution (g / cm ３ ) μ: Viscosity of pickling solution (cP) φ: Volume concentration (vol%)

[0036] FIG. 3 shows the critical particle size d of the sludge SL removed by the cyclone filter 6. ｃ 10 is a graph showing the relationship between the critical particle size d and the removal rate Δη. ｃ is the particle size at which the removal rate in the cyclone filter 6 is 50%. ｃ can be calculated from the above-mentioned formulas (1) and (2).

[0037] As shown in FIG. 3, for example, the limit particle size when the hydrochloric acid solution contained in the pickling tank 2 is supplied to the cyclone filter 6 is d ｃ ', the critical particle size d ｃ ' is d ｃThe limit particle size when water contained in a water washing tank (not shown) is supplied to the cyclone filter 6 is d ｃ ", then the critical particle size d ｃ " is d ｃ ″=8.7 μm.

[0038] Therefore, the limit particle size d to be removed from the hydrochloric acid solution is ｃ Using a removal device 70 using a cyclone filter 6 with a particle size of 15.9 μm, when hydrochloric acid solution stored in a storage tank 71 was supplied to the cyclone filter 6, the amount of sludge SL removed by the cyclone filter 6 was measured.

[0039] As shown in FIG. 4, the removal device 70 includes a storage tank 71, a cyclone filter 6, a pipe 72 for flowing hydrochloric acid liquid from the storage tank 71 toward the cyclone filter 6, a pipe 73 for flowing clean liquid from the cyclone filter 6 toward the storage tank 71, and a recovery pod 74 for recovering dirty liquid discharged from the cyclone filter 6.

[0040] In the above configuration, the pipe 72 is provided with a pump 75, a flow meter 76, and a pressure meter 77. The pipe 73 is provided with a flow meter 78 and a pressure meter 79.

[0041] Below, the particle size of sludge SL contained in the contaminated liquid collected in the collection pod 74 using the above-mentioned removal device 70 and the amount of sludge removed were measured. In this measurement, an example will be described in which the amount of sludge SL in the hydrochloric acid liquid stored in the storage tank 71 is 2 L, and the rate of hydrochloric acid liquid sent from the storage tank 71 to the cyclone filter 6 is 42 L / min. The particle size of the sludge SL and the amount of sludge removed were measured every 10 minutes after the pump 75 was driven.

[0042] Fig. 5 is a diagram showing the relationship between the particle size of sludge SL removed in the removal device 70 and the amount of sludge removed. Note that Fig. 5 illustrates a cumulative amount of sludge SL removed, and describes a case where the particle size distribution of the sludge SL previously stored in the storage tank 71 is approximately 100 µm or less. As shown in Fig. 5, it was found that in the cyclone filter 6, sludge SL in the hydrochloric acid solution stored in the storage tank 71 is removed in order of particle size, starting with the larger particles.

[0043] Next, in the pickling equipment 1 shown in FIG. 1, a test was conducted to remove suspended matter from a hydrochloric acid solution using a cyclone filter 6 in which the limit particle size dc of suspended matter to be removed was set to 12 μm or less.

[0044] 6 is a graph showing the distribution of sludge volume before the start of the test and 16 minutes after the start of the test. The black squares in FIG. 6 represent the distribution of sludge volume before the start of the test, and the white squares represent the distribution of sludge volume 16 minutes after the start of the test. This shows that 16 minutes after the start of sludge removal by the cyclone filter 6, sludge SL with a particle size of 15 μm or more has been removed.

[0045] Next, the removal rate of sludge SL was measured when sludge SL contained in hydrochloric acid solution was removed using cyclone filters 6 with limit particle sizes of 10.5 μm and 14.9 μm. Hereinafter, the case where a cyclone filter 6 with a limit particle size of 10.5 μm was used is referred to as Example 1, and the case where a cyclone filter 6 with a limit particle size of 14.9 μm was used is referred to as Example 2. Furthermore, the case where no cyclone filter was used is referred to as Comparative Example. The Si content of the steel plate S in Examples 1 and 2 and the Comparative Example was 2.6%.

[0046] In measuring the sludge SL removal rate, in all of Inventive Examples 1 and 2 and the Comparative Example, the initial temperature of the hydrochloric acid solution stored in the pickling tank 2 was set to 95°C, and the sludge SL removal rate was measured after 16 minutes.

[0047] 7, it was found that in Inventive Example 1, the temperature of the hydrochloric acid in the pickling tank 2 was maintained at the initial temperature of 95°C even 16 minutes after the start of measurement. In Inventive Example 1, the sludge removal rate after 16 minutes had passed from the start of measurement was 72%, and the particle size of the sludge SL contained in the hydrochloric acid was, for example, 10 μm.

[0048] In Example 2, it was found that the temperature of the hydrochloric acid solution in the pickling tank 2 dropped from the initial temperature of 95°C to 90°C after 16 minutes had passed since the start of measurement. In Example 2, the removal rate of sludge SL after 16 minutes had passed since the start of measurement was 65%, and the particle size of the sludge SL contained in the hydrochloric acid solution was, for example, 15.9 µm.

[0049] On the other hand, in the comparative example, it was found that the temperature of the hydrochloric acid solution in the pickling tank 2 dropped from the initial temperature of 95°C to 80°C after 16 minutes had passed from the start of measurement. Also, in the comparative example, the removal rate of sludge SL was 0% after 16 minutes had passed from the start of measurement, and the particle size of the sludge SL contained in the hydrochloric acid solution was, for example, 50 µm.

[0050] From these measurement results, it was found that the removal rate of sludge SL can be improved by reducing the limit particle size in the cyclone filter 6 and by increasing the temperature of the hydrochloric acid solution stored in the pickling tank 2.

[0051] FIG. 8 is a graph showing the temporal change in the amount of sludge SL generated in the pickling tank 2 of the pickling equipment 1. For example, when the pickling equipment 1 starts operating, the amount of sludge SL generated in the pickling tank 2 increases proportionally with time. Conventionally, a certain amount of sludge SL is removed from the pickling tank 2, for example, once a month. Therefore, the amount of sludge SL settling in the pickling tank 2 changes in a sawtooth pattern, as shown by the dotted line in FIG. 8 . In contrast, in this embodiment, the hydrochloric acid stored in the pickling tank 2 is supplied to a cyclone filter 6 to remove the sludge SL. As a result, the amount of sludge SL settling in the pickling tank 2 changes in a sawtooth pattern, similar to the conventional method. However, the amount of sludge contained in the hydrochloric acid is small, and it has been found that the sludge amount can be brought close to the target value for the amount of sludge SL contained in the hydrochloric acid.

[0052] In this embodiment, the case where the path for removing sludge SL contained in the hydrochloric acid by the cyclone filter 6 and the path for heating the hydrochloric acid by the heat exchanger 21 are separated is described, but as shown in Fig. 9, it is also possible to provide a heat exchanger 21 in the pipe 19 connecting the recovery tank 15 to the pickling tank 2, heat the clean liquid sent from the recovery tank 15 to the pickling tank 2 in the heat exchanger 21, and return the heated clean liquid to the pickling tank 2. This makes it possible to maintain the temperature of the hydrochloric acid stored in the pickling tank 2 at the above-mentioned second temperature.

[0053] Although not shown, it is also possible to provide a heat exchanger 21 in the pipe 9 connected to the discharge pipe 63 of the cyclone filter 6, heat the clean liquid flowing from the discharge pipe 63 of the cyclone filter 6 into the pipe 9 in the heat exchanger 21, and return the heated clean liquid to the pickling tank 2. In this case, too, it is possible to maintain the temperature of the hydrochloric acid solution contained in the pickling tank 2 at the above-mentioned second temperature.

[0054] In this embodiment, the critical particle size dc of the sludge SL to be removed by the cyclone filter 6 is calculated based on the removal performance of the cyclone filter 6. However, ｃ is also a predetermined value determined based on the efficiency of the heat exchanger 21 used. Therefore, the critical particle size d of the sludge SL removed by the cyclone filter 6 is ｃ It is also possible to determine this based on the efficiency of the heat exchanger 21 used.

[0055] <Summary of Effects> The method for pickling steel strips of this embodiment is a method for pickling steel strips S in which scale formed on the surface of the steel strips S is removed by immersing the steel strips S in hydrochloric acid solution contained in a pickling tank 2 while transporting the silicon-containing steel strips S, and includes a step of supplying the hydrochloric acid solution contained in the pickling tank 2 to a cyclone filter 6 to remove floating matter caused by scale contained in the hydrochloric acid solution, and a step of heating the hydrochloric acid solution using a heat exchanger 21.

[0056] According to this, by passing the hydrochloric acid solution contained in the pickling tank 2 through the cyclone filter 6, suspended matter having a particle size exceeding the limit particle size of the cyclone filter 6 is removed, thereby reducing the amount of sludge settling in the pickling tank 2. Furthermore, by heating the hydrochloric acid solution contained in the pickling tank 2 using the heat exchanger 21, it is possible to avoid reducing the dissolution rate of the steel strip S in the hydrochloric acid solution contained in the pickling tank 2. As a result, in the pickling treatment of the steel strip S, the pickling treatment of the steel strip S can be performed without slowing down the conveying speed of the steel strip S.

[0057] The step of heating the hydrochloric acid solution is carried out on the hydrochloric acid solution from which suspended matter has been removed by the cyclone filter 6 .

[0058] According to this, heat exchange is performed in the heat exchanger 21 using clean liquid from which at least a portion of the sludge SL has been removed, making it possible to suppress clogging caused by the adhesion of sludge SL to the heat exchanger 21.

[0059] Furthermore, it is preferable that the critical particle size of the suspended matter separated by the cyclone filter 6 is equal to or smaller than a predetermined value.

[0060] This allows sludge SL with small particle sizes to remain in the hydrochloric acid solution contained in the pickling tank 2, thereby reducing the amount of sludge SL that settles in the pickling tank 2. As a result, the cycle of the work to remove sludge SL that settles in the pickling tank 2 can be extended, and the load associated with this work can be reduced.

[0061] The same effect can be obtained even in the case of the pickling equipment of the present invention that enables the above-mentioned pickling method for steel strips.

[0062] 1 Pickling equipment 2 Pickling tank 6 Cyclone filter 21 Heat exchanger 61 Filter body 62 Supply pipe 63 Discharge pipe 64 Discharge port S Steel strip SL Floating matter (sludge)

Claims

1. A method for pickling a silicon-containing steel strip, which removes scale formed on the surface of the steel strip by immersing the steel strip in a hydrochloric acid solution contained in a pickling tank while transporting the steel strip, the method comprising the steps of: supplying the hydrochloric acid solution contained in the pickling tank to a cyclone filter to remove suspended matter caused by the scale contained in the hydrochloric acid solution; and heating the hydrochloric acid solution using a heat exchanger.

2. The method for pickling steel strips according to claim 1, characterized in that the step of heating the hydrochloric acid solution is carried out on the hydrochloric acid solution from which the suspended matter has been removed by the cyclone filter.

3. A method for pickling steel strips as set forth in claim 1 or claim 2, characterized in that the limit particle size of the suspended matter separated in the cyclone filter is equal to or less than a predetermined value.

4. A method for pickling steel strips according to claim 3, characterized in that the limit particle size of the suspended matter is 12 μm or less.

5. A pickling plant for a silicon-containing steel strip, having a pickling tank containing a hydrochloric acid solution in which the steel strip being transported is immersed, within a transport line for the steel strip, characterized by comprising: a cyclone filter that removes floating matter resulting from scale contained in the hydrochloric acid solution from the hydrochloric acid solution contained in the pickling tank; and a heat exchanger that heats the hydrochloric acid solution.

6. The steel strip pickling equipment according to claim 5, wherein the heat exchanger is disposed in a path that returns the hydrochloric acid solution from which the suspended matter has been removed by the cyclone filter to the pickling tank.

7. A steel strip pickling facility as set forth in claim 5 or 6, characterized in that the limit particle size of the suspended matter separated in the cyclone filter is equal to or less than a predetermined value.

8. The pickling equipment for steel strips according to claim 7, characterized in that the limit particle size of the floating matter is 12 μm or less.

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