Pickling method for cold-rolled strip steel, acid recycling method, device and system

Abstract

The present invention provides a pickling method, an acid recycling method, a device and a system for cold-rolled strip steel. The pickling method comprises the following steps: performing push-pull pickling on difficult-to-pickle strip steel with a first pickling solution, and performing pre-desilication during and / or after the push-pull pickling to obtain a first post-pickling solution. An acid solution is added to the first post-pickling solution to obtain a second pickling solution. The second pickling solution is used to perform acid rolling and tandem pickling on easy-to-pickle strip steel to obtain a second post-pickling solution. In the above pickling method for cold-rolled strip steel, the utilization rate of free acid is high, which is beneficial to the stable, smooth and safe operation of the subsequent acid regeneration system in the external environment. It can avoid the waste of free acid caused by directly performing acid regeneration on high-concentration free acid subsequently, and the potential safety hazard to the acid regeneration system.

Description

Technical Field

[0001] The present invention relates to the field of pickling, and in particular to a pickling method for cold-rolled strip steel, an acid recycling method, a device and a system. Background Art

[0002] Pickling is an important process in the production process of cold-rolled strip steel. The purpose is to remove iron oxide on the surface of the strip steel, adjust the coil weight, cut off the cracked edges, and provide qualified billets for the rolling mill, so that the cold rolling mill can smoothly produce qualified strip steel products. As one of the pickling methods, push-pull pickling has the advantages of simple unit equipment and strong adaptability to changes in strip steel varieties.

[0003] When push-pull pickling is used to clean difficult-to-clean steel grades such as silicon steel, it is necessary to increase the concentration of the pickling solution. However, in this case, the subsequent acid regeneration system has high energy consumption and is prone to safety problems. Summary of the Invention

[0004] The main object of the present invention is to provide a pickling method for cold-rolled strip steel, an acid recycling method, a device and a system, so as to solve the technical problems that the acid regeneration system has high energy consumption and is prone to safety problems when push-pull pickling is used for difficult-to-clean steel grades.

[0005] To achieve the above object, the present invention provides a pickling method for cold-rolled strip steel, including the following steps:

[0006] Perform push-pull pickling on difficult-to-clean strip steel with a first pickling solution, and perform pre-desilication during and / or after the push-pull pickling to obtain a first pickled solution. Among them, the concentration of free acid in the first pickling solution is 230-250 g / l. The concentration of free acid in the first pickled solution is 125-135 g / l.

[0007] Supplement an acid solution to the first pickled solution to obtain a second pickling solution. Among them, the concentration of free acid in the second pickling solution and the dosage of the second pickling solution meet the pickling requirements of the tandem cold rolling and pickling line.

[0008] Perform tandem cold rolling and pickling on easy-to-clean strip steel with the second pickling solution to obtain a second pickled solution.

[0009] According to an embodiment of the present application, the step of performing pre-desilication during the push-pull pickling includes:

[0010] Perform pre-desilication on the pickling intermediate solution between the third-stage pickling and the fourth-stage pickling of the push-pull pickling. The push-pull pickling includes multiple stages of pickling performed in sequence. The pickling intermediate solution is the pickling solution obtained from the previous stage of pickling.

[0011] According to an embodiment of the present application, the step of performing push-pull pickling on difficult-to-clean strip steel with a first pickling solution further includes:

[0012] Scrub the silica gel substance formed on the surface of the difficult-to-wash strip intermediate during the pickling process. The difficult-to-wash strip intermediate is the strip in any stage of the pickling process.

[0013] According to an embodiment of the present application, the concentration of free acid in the second pickling solution is 170 - 190 g / l. The dosage of the first pickling solution is 4 - 5 m 3 / h; the dosage of the second pickling solution is 10 m 3 / h.

[0014] The present invention also provides an acid recycling method for cold-rolled strip, comprising the following steps:

[0015] The above pickling method.

[0016] Perform an acid regeneration step on the second pickling solution to obtain regenerated acid, and adjust the concentration of free acid in the regenerated acid to form the first pickling solution.

[0017] According to an embodiment of the present application, performing the acid regeneration step on the second pickling solution includes:

[0018] Heat the second pickling solution, dissolve scrap steel, adjust the pH of the solution after dissolution to 3.5 - 4.4, and then perform precipitation separation to obtain the treated acid, which is a ferrous chloride solution.

[0019] Roast the treated acid to obtain furnace gas. After cooling the furnace gas, absorb the cooled furnace gas with rinsing water to obtain regenerated acid. The furnace gas includes HCl gas.

[0020] According to an embodiment of the present application, the steps of roasting the treated acid to obtain furnace gas and cooling the furnace gas include:

[0021] Roast the treated acid under the condition of introducing air to obtain iron oxide powder and furnace gas. Cool the furnace gas through heat exchange with a coolant to obtain the cooled furnace gas. The coolant is the treated acid or rinsing water.

[0022] According to an embodiment of the present application, the coolant is rinsing water, and the rinsing water after heat exchange absorbs the furnace gas to obtain regenerated acid.

[0023] According to an embodiment of the present application, the temperature of the furnace gas is 420 - 450 °C, and the temperature of the cooled furnace gas is 90 - 95 °C.

[0024] The present application also provides a cold-rolled pickling device, comprising:

[0025] A push-pull pickling device, comprising a plurality of pickling components arranged in sequence, respectively used for pickling the difficult-to-wash strip.

[0026] A pre-desilication device is arranged between pickling tanks, inside pickling tanks or after a push-pull pickling device to cooperate with the push-pull pickling device to form a first pickling post-liquid.

[0027] An acid solution replenishing device is connected to the push-pull pickling device and is used to replenish acid solution after receiving the first pickling post-liquid to obtain a second pickling solution.

[0028] An acid rolling tandem pickling device is connected to the acid solution replenishing device to receive the second pickling solution. The acid rolling tandem pickling is used for pickling easy-to-pickle strip steel.

[0029] An acid regeneration device is connected to the acid rolling tandem pickling device and is used to regenerate acid from the second pickling post-liquid to obtain regenerated acid and adjust the concentration of the regenerated acid to form a first pickling solution.

[0030] The present application also provides a cold rolling pickling system, including:

[0031] A push-pull pickling device includes a plurality of pickling components arranged in sequence and is respectively used for pickling difficult-to-pickle strip steel.

[0032] A pre-desilication device is arranged between pickling tanks, inside pickling tanks or after a push-pull pickling device to cooperate with the push-pull pickling device to form a first pickling post-liquid.

[0033] An acid solution replenishing device is connected to the push-pull pickling device and is used to replenish acid solution after receiving the first pickling post-liquid to obtain a second pickling solution.

[0034] An acid rolling tandem pickling device is connected to the acid solution replenishing device to receive the second pickling solution. The acid rolling tandem pickling is used for pickling easy-to-pickle strip steel.

[0035] An acid regeneration device is connected to the acid rolling tandem pickling device and is used to regenerate acid from the second pickling post-liquid to obtain regenerated acid and adjust the concentration of the regenerated acid to form a first pickling solution.

[0036] According to an embodiment of the present application, the acid regeneration device includes a leaching tower, a reaction tank, a sedimentation tank, a heat exchanger, a roasting furnace, an absorption tower, a rinsing water container and a regenerated acid tank.

[0037] The leaching tower is connected to the acid rolling tandem pickling device, and the leaching tower, the reaction tank and the sedimentation tank are connected in sequence and are respectively used for successively leaching scrap steel with the second pickling post-liquid, adjusting the pH of the leached solution to 3.5 - 4.4, and separating by sedimentation to obtain treated acid.

[0038] The roasting furnace is connected to the sedimentation tank and is used to roast the treated acid to obtain furnace gas.

[0039] The heat exchanger includes a heat medium part and a refrigerant part. The heat medium part is connected to the roasting furnace, and the refrigerant part is connected to the sedimentation tank to receive the treated acid or connected to the rinsing water container to receive rinsing water.

[0040] The absorption tower is respectively connected to the heat exchanger and the rinsing water container.

[0041] One end of the regenerated acid tank is connected to the absorption tower, and the other end is connected to at least one of the push-pull pickling device and the tandem cold mill pickling device.

[0042] According to an embodiment of the present application, the sedimentation tank, the roasting furnace and the heat exchanger are arranged in sequence, and the refrigerant is partially connected to the rinsing water container.

[0043] According to an embodiment of the present application, a return pipe is further included between the rinsing water container and the heat exchanger for returning the rinsing water used as the refrigerant in the heat exchanger to the rinsing water container.

[0044] According to an embodiment of the present application, the inlet end of the rinsing water container is connected to at least one of the push-pull pickling device and the tandem cold mill pickling device to receive and store the rinsing water in the pickling step.

[0045] In the above pickling method of cold-rolled strip steel, since the free acid concentration of the first pickling solution is relatively high, the free acid concentration of the first post-pickling solution is also relatively high. After the free acid is supplemented in the first post-pickling solution, the easy-to-wash strip steel is continuously pickled in the tandem cold mill, making full use of the property of the high free acid concentration in the first post-pickling solution. After pickling in the tandem cold mill, the free acid in the second post-pickling solution is greatly reduced, reaching the safety standard for acid regeneration. In the above pickling method of cold-rolled strip steel, the utilization rate of free acid is high, which is beneficial to the stable and safe operation of the subsequent acid regeneration system outside, and can avoid the waste of free acid caused by directly performing acid regeneration on the high-concentration free acid subsequently, as well as the potential safety hazards to the acid regeneration system. Description of the Drawings

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0047] Figure 1 is a flowchart of push-pull pickling in the related art;

[0048] Figure 2 is a flowchart of tandem cold mill pickling in the related art;

[0049] Figure 3 is a flowchart of the acid recycling method for cold-rolled strip steel according to an embodiment of the present application;

[0050] Figure 4It is a flow chart of the acid recycling method for cold-rolled strip steel in an embodiment of the present application.

[0051] The realization of the object of the present invention, its functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings.

[0052] 100. Push-pull pickling device; 200. Pre-desilication device; 300. Acid replenishment device; 400. Acid rolling and pickling integrated device; 500. Acid regeneration device; 510. Leaching tower; 520. Reaction tank; 530. Sedimentation tank; 540. Heat exchanger; 550. Roaster; 560. Absorption tower; 570. Rinsing water container; 580. Regenerated acid tank; 511. Spent acid tank; 512. Treated acid tank; 571. Rinsing water tank; 572. Rinsing water tank Specific embodiments

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] It should be noted that all directional indications (such as up, down,...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0055] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0056] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0057] The present application provides a pickling method for cold-rolled strip steel, including the following steps:

[0058] S100: The difficult-to-clean strip steel is pickled in a push-pull manner using a first pickling solution, and pre-desiliconization is carried out during and / or after the push-pull pickling to obtain a first post-pickling solution. Among them, the concentration of free acid in the first pickling solution is 230-250 g / l (that is, the concentration of free acid in the first pickling solution when it is ready for push-pull pickling is 230-250 g / l). The concentration of free acid in the first post-pickling solution is 125-135 g / l.

[0059] The difficult-to-clean strip steel includes, for example, grain-oriented silicon steel, high-grade non-oriented silicon steel, and high-grade medium-high carbon steel. For the convenience of explaining the following embodiments, the difficult-to-clean strip steel is taken as an example of grain-oriented silicon steel for explanation. Other steel grades are relatively easy to clean and can be called easy-to-clean strip steel. Generally speaking, the production volume of the difficult-to-clean strip steel is relatively small. The production volume of the easy-to-clean strip steel is relatively large. The pickling speed of the push-pull pickling process is relatively small, while the pickling speed of the tandem cold rolling and pickling process is relatively large. Therefore, the push-pull pickling equipment is used to pickle the difficult-to-clean strip steel, and the tandem cold rolling and pickling equipment is used to pickle the easy-to-clean strip steel, so that the processing capacity of each pickling equipment can be reasonably utilized, the resources can be reasonably allocated, and the idle of the equipment processing capacity is not caused.

[0060] Since, in the related art, see Figure 1 , the push-pull pickling equipment generally does not have a tension leveling and descaling machine, shot peening facilities, etc., and actually does not have the production capacity for pickling silicon steel. In order to improve the pickling efficiency, it has to increase the concentration of free acid in the pickling solution.

[0061] The tandem cold rolling and pickling rarely produces difficult-to-pickle varieties, so the concentration of free acid in its pickling solution is relatively low. Therefore, there is a large difference in the concentration of the pickling solution between the push-pull pickling tandem cold rolling and pickling and the tandem cold rolling and pickling. Moreover, the difference in the processing speed between the tandem cold rolling and pickling and the push-pull pickling also leads to a difference in the flow rate of the pickling solution between the push-pull pickling tandem cold rolling and pickling and the tandem cold rolling and pickling.

[0062] Therefore, see Figure 1 and Figure 2 , in the related art, the tandem cold rolling and pickling and the push-pull pickling are independent of each other, using independent pickling solutions, and using their respective corresponding acid regeneration systems to regenerate the pickled liquid (called the post-pickling solution) after pickling, so that the acid can be recycled. That is to say, a set of acid regeneration system serving the tandem cold rolling and pickling and a set of acid regeneration system serving the push-pull pickling need to exist at the same time, resulting in a relatively high equipment cost and operation cost of the acid regeneration system.

[0063] Moreover, there is also a problem with this method. A large amount of free acid remains in the post-pickling solution of the push-pull pickling. Directly carrying out acid regeneration of a large amount of free acid will not only cause the waste of free acid, but also pose a safety hazard to the acid regeneration system.

[0064] Specifically, the pickling solution after pickling enters the leaching tower for acid regeneration. The free acid dissolves scrap steel (such as strip side filaments) to generate hydrogen, and this reaction is an exothermic reaction. Therefore, only the concentration of free acid in the waste acid can be controlled not to exceed 60 g / l. If the pickling solution after pickling is much greater than 60 g / l, there will be a risk of explosion.

[0065] When the concentration of free acid in the pickling solution after pickling is too high, the time for dissolving side filaments in the leaching tower is longer than that of the waste acid with a free acid concentration not exceeding 60 g / l, thus affecting the hourly capacity of regenerating acid in acid regeneration. As a result, the energy consumption of acid regeneration is high and the acid production efficiency is low.

[0066] On this basis, the applicant has conducted a large number of studies and provided a pickling method for cold-rolled strip steel. In step S100, the first pickling solution performs push-pull pickling on the difficult-to-pickle strip steel.

[0067] The push-pull pickling includes multi-stage pickling. Exemplarily, it includes five stages of pickling, specifically including first-stage pickling, second-stage pickling, third-stage pickling, fourth-stage pickling, and fifth-stage pickling arranged in sequence, and their arrangement order is opposite to the running order of the strip steel.

[0068] Silicon in the strip steel exists in the form of silicon mud. The viscous silicon mud remains on the surface of the strip steel, preventing the improvement of pickling speed and efficiency. On the other hand, the silicon mud in the pickling solution is very likely to remain in the pickling pipeline, causing the diameter of the pickling pipeline to become smaller or even causing the pickling solution pipeline to be blocked, thus affecting the pickling speed and efficiency.

[0069] Therefore, pre-desilication treatment is carried out during and / or after the push-pull pickling process to reduce the silicon content in the first pickling solution after pickling, and further reduce the silicon content in the subsequent second pickling solution, reducing the influence of silicon.

[0070] In some embodiments, pre-desilication treatment is carried out during the push-pull pickling process. After several stages of pickling (such as the third pickling), a large amount of silicon exists in the pickling intermediate solution. The pickling intermediate solution refers to the solution obtained from the previous stage of pickling.

[0071] In this case, pre-desilication can be carried out on the pickling intermediate solution. The method of pre-desilication can be to directly add a flocculant to precipitate in the corresponding solution (such as the pickling intermediate solution) to precipitate the silicon in it. In some embodiments, pre-desilication is carried out on the pickling intermediate solution between the third-stage pickling and the fourth-stage pickling of the push-pull pickling. That is, a pre-desilication step is set between the third-stage pickling and the fourth-stage pickling to carry out pre-desilication on the pickling intermediate solution.

[0072] Of course, pre-desilication treatment can also be carried out after the push-pull pickling, that is, pre-desilication is carried out on the pickling intermediate solution obtained from the last stage of pickling.

[0073] During the pickling process, silicon in the intermediate pickling solution will adhere to the strip steel during pickling (which can be called the strip steel intermediate), and this part of silicon can be called silicon mud or silica gel substance. In some embodiments, the step of push-pull pickling of the difficult-to-pickle strip steel with the first pickling solution further includes using a brush roll to brush off the silica gel substance formed on the surface of the difficult-to-pickle strip steel intermediate during the pickling process. The difficult-to-pickle strip steel intermediate can be the strip steel in any stage of pickling. The brushing method can be carried out in pickling components corresponding to the third-stage pickling, fourth-stage pickling, and fifth-stage pickling, such as pickling tanks, using a brush roll for brushing.

[0074] The first pickling post-liquid is the pickling solution after pre-desilication. It can be understood that one or several of the above pre-desilication methods can be used for pre-desilication. The concentration of free acid in the first pickling post-liquid is 125 - 135 g / l.

[0075] S200: Add an acid solution to the first pickling post-liquid to obtain the second pickling solution. Among them, the concentration of free acid, the silicon content, and the dosage of the second pickling solution in the second pickling solution meet the pickling requirements of the tandem cold rolling mill.

[0076] The acid solution can be a single-component acidic solution or can include multiple acidic solutions. For example, after the first pickling post-liquid is pre-desilicated again, a new acid solution (such as fresh hydrochloric acid with a concentration of 30 - 31%) and a regenerated acid solution are added.

[0077] Adding the acid solution simultaneously increases the concentration of free acid and the dosage of the second pickling solution in the second pickling solution, thereby meeting the pickling requirements of the tandem cold rolling mill.

[0078] In some embodiments, the concentration of free acid in the second pickling solution is 170 - 190 g / l, which is slightly higher than the concentration of the pickling solution of a single tandem cold rolling mill to overcome the influence of residual silicon in the second pickling solution.

[0079] In some embodiments, the dosage of the first pickling solution is 4 - 5 m 3 / h; the dosage of the second pickling solution is 10 m 3 / h.

[0080] S300: Use the second pickling solution to perform tandem cold rolling mill pickling on the easy-to-pickle strip steel to obtain the second pickling post-liquid.

[0081] In this step, the second pickling solution performs tandem cold rolling mill pickling on the easy-to-pickle strip steel. The tandem cold rolling mill pickling also includes multi-stage pickling. Exemplarily, it includes three stages of pickling, specifically including primary pickling, secondary pickling, and tertiary pickling arranged in sequence, and their arrangement order is opposite to the running order of the strip steel.

[0082] During the process of pickling the easy-to-pickle strip steel with the second pickling solution, a large amount of free acid is consumed. Therefore, the free acid in the first pickling post-liquid is fully utilized, reducing the waste of acid solution. Moreover, the free acid in the second pickling post-liquid is greatly reduced, meeting the safety standards for acid regeneration, which can avoid the waste of free acid caused by directly performing acid regeneration on high-concentration free acid subsequently and the potential safety hazards to the acid regeneration system.

[0083] In the above pickling method for cold-rolled strip steel, due to the relatively high concentration of free acid in the first pickling solution, the concentration of free acid in the first pickling post-liquid is also relatively high. After replenishing free acid to the first pickling post-liquid, pickling of the easy-to-pickle strip steel is continued on the tandem cold rolling and pickling line, making full use of the property of the high concentration of free acid in the first pickling post-liquid. After pickling on the tandem cold rolling and pickling line, the free acid in the second pickling post-liquid is greatly reduced, meeting the safety standards for acid regeneration. In the above pickling method for cold-rolled strip steel, the utilization rate of free acid is high, which is beneficial to the stable and safe operation of the subsequent acid regeneration system outside, and can avoid the waste of free acid caused by directly performing acid regeneration on high-concentration free acid subsequently and the potential safety hazards to the acid regeneration system.

[0084] This application also provides an acid recycling method for cold-rolled strip steel. Referring to Figure 3 and Figure 4 , it includes the following steps:

[0085] S100 - S300: The steps S100 - S300 can be referred to the foregoing content and will not be elaborated here.

[0086] S400: Perform an acid regeneration step on the second pickling post-liquid to obtain regenerated acid, and adjust the concentration of free acid in the regenerated acid to form the first pickling solution.

[0087] Since in the above pickling method for cold-rolled strip steel, push-pull pickling and tandem cold rolling and pickling are used in combination, during the subsequent acid regeneration process, only one set of acid regeneration equipment is required to meet the acid regeneration requirements, saving equipment and operation costs.

[0088] In some embodiments, performing the acid regeneration step on the second pickling post-liquid includes:

[0089] S410: Heat the second pickling post-liquid successively, dissolve scrap steel, adjust the pH of the solution after dissolution to 3.5 - 4.4, and then perform precipitation and separation to obtain the treated acid, and the treated acid is ferrous chloride solution.

[0090] In this step, the second pickling post-liquid can be heated with steam, which can accelerate the reaction rate of dissolving scrap steel in the second pickling post-liquid.

[0091] When dissolving scrap steel, hydrogen and the solution after dissolution are generated by the reaction of the second pickling post-liquid with side wire. The solution after dissolution includes the ferrous chloride solution generated by the reaction of the second pickling post-liquid with side wire.

[0092] During the push-pull pickling and tandem cold rolling pickling process, the corresponding pickling solutions all react with the strip steel. Therefore, the second post-pickling solution also contains a large amount of ferrous chloride. Additionally, the ferrous chloride solution formed by the reaction of the second post-pickling solution with the edge wire. After leaching, the concentration of ferrous chloride in the solution is as high as 360 - 440 g / l.

[0093] After the solution after leaching is added with ammonia water to adjust the pH value to 3.5 - 4.4 and aerated, it is separated by the sedimentation tank 530. The supernatant is the treated acid. During this process, flocculent iron hydroxide precipitate is formed. The iron hydroxide precipitate has an adsorption effect and can adsorb other impurities such as silicon in the solution after leaching. Therefore, the supernatant, i.e., the treated acid, has fewer impurities and is basically a ferrous chloride solution. The treated acid can be stored in the treated acid tank 512.

[0094] S420: Roast the treated acid to obtain furnace gas. After cooling the furnace gas, use rinsing water to absorb the furnace gas to obtain regenerated acid. The furnace gas includes HCl gas.

[0095] When roasting the treated acid, roast the treated acid under the condition of introducing air to obtain iron oxide powder and HCl gas. The HCl gas is the main component of the furnace gas. After cooling the furnace gas, use rinsing water to absorb the furnace gas to obtain regenerated acid.

[0096] In some embodiments, referring to Figure 3 and Figure 4 , the steps of roasting the treated acid to obtain furnace gas and cooling the furnace gas include:

[0097] Roast the treated acid under the condition of introducing air to obtain iron oxide powder and furnace gas.

[0098] The reaction formula for this step is: The reaction formula for this step is:

[0099]

[0100] The specific roasting temperature can be 580 - 650 °C.

[0101] Cool the furnace gas by heat exchange with a coolant. The coolant is the treated acid or rinsing water.

[0102] In this step, the furnace gas is cooled by heat exchange with the coolant, such as in a heat exchanger 540 (specifically, it can be a Venturi device). The following takes the heat exchange in the Venturi device as an example for illustration.

[0103] In some embodiments, referring to Figure 3 , the coolant is the treated acid.

[0104] In this embodiment, the processing acid first undergoes heat exchange through a Venturi device and then is calcined in a roasting furnace 550. The furnace gas generated by the roasting furnace 550 is transported to the Venturi device. In the Venturi device, the coolant temperature rises and the furnace gas temperature drops. The rinsing water is the rinsing water used in the push-pull pickling and / or the tandem pickling process of pickling and cold rolling, and can be stored in a rinsing water container 570. The rinsing water container 570 may include a rinsing water tank 571 and a rinsing water tank 572, which are communicated with each other. The rinsing water tank 571 directly collects the rinsing water. The rinsing water tank 572 is communicated with the Venturi device and an absorption tower 560 to provide the rinsing water.

[0105] Specifically, the rinsing water is used to wash the residual acid solution on the strip surface with hot demineralized water and steam condensate after pickling. Therefore, the rinsing water includes free acid (about 5-10 g / l) and a small amount of iron ions. The cooled furnace gas can be absorbed by the rinsing water in the absorption tower 560 to obtain regenerated acid.

[0106] In other embodiments, referring to Figure 4 , the coolant is the rinsing water.

[0107] In this embodiment, the processing acid first undergoes calcination in the roasting furnace 550. The furnace gas generated by the roasting furnace 550 is transported to the Venturi device. The rinsing water is transported to the Venturi device. In the Venturi device, the rinsing water temperature rises and the furnace gas temperature drops to obtain cooled furnace gas. The rinsing water after heat exchange absorbs the furnace gas to obtain regenerated acid.

[0108] Since the second pickling post-liquid actually undergoes push-pull pickling and tandem pickling of pickling and cold rolling, and then dissolves the edge wire in the leaching tower 510, the concentration of ferrous chloride in the processing acid is high. Therefore, the processing acid first undergoes calcination and then exchanges heat in the Venturi device with the rinsing water as the refrigerant.

[0109] Specifically, the concentration of the processing acid is high and it is directly sprayed into the roasting furnace 550 instead of entering the Venturi device for heat exchange. Therefore, there is no crystallization causing blockage of the Venturi device and no blockage of the acid liquid pipeline supplying the roasting furnace 550, resulting in production downtime, and the production of acid regeneration is more stable and smooth. The concentration of metal ions in the rinsing water is low and it is not easy to crystallize in this case, thus avoiding blockage of the Venturi device itself or the pipeline connected to the Venturi device due to crystallization.

[0110] In addition, the rinsing water is heated by the furnace gas and a part of the water is volatilized. The rinsing water not only realizes concentration by heat exchange in the Venturi device but also absorbs hydrogen chloride mist, and also absorbs hydrogen chloride mist in the absorption tower 560.

[0111] Due to the relatively high temperature of the furnace gas, such as 450 °C, to a certain extent, it restricts the absorption of hydrogen chloride aerosol by the rinsing water. Moreover, the structural design of the Venturi device is mainly based on the consideration of heat exchange, rather than for the absorption of hydrogen chloride aerosol by the rinsing water. Therefore, the rinsing water in the Venturi device can only absorb a part of the hydrogen chloride aerosol. In the Venturi device, due to heat exchange, the temperature of the furnace gas drops significantly, forming cooled furnace gas with a temperature of about 90 - 95 °C.

[0112] After the cooled furnace gas enters the absorption tower 560, due to its relatively low temperature and the structural design of the absorption tower 560 mainly for promoting absorption, the cooled furnace gas comes into full contact with the rinsing water after heat exchange. Therefore, it can absorb the hydrogen chloride aerosol in the cooled furnace gas more fully, thereby obtaining a regenerated acid with a relatively high concentration of free acid (170 - 190 g / l). In this way, two-stage absorption is achieved, the absorption of hydrogen chloride aerosol is more thorough, and the environmental protection pressure is reduced.

[0113] In this embodiment, more rinsing water is utilized. On the one hand, it reduces the occurrence of crystallization accidents in the Venturi device. On the second hand, it reduces the amount of unutilized rinsing water discharged into the wastewater treatment station, reduces the discharge of acidic wastewater, and reduces the cost of the wastewater treatment station for treating wastewater, achieving system emission reduction.

[0114] The temperature of the furnace gas is 420 - 450 °C, and the temperature of the cooled furnace gas is 90 - 95 °C.

[0115] In some embodiments, with reference to Figure 3 and Figure 4 , the present application further provides a cold rolling pickling device, including:

[0116] A push-pull pickling device 100, including a plurality of pickling components arranged in sequence, respectively used for pickling difficult-to-pickle strip steel.

[0117] A pre-desiliconization device 200, arranged between pickling tanks, inside pickling tanks or after the push-pull pickling device 100, to cooperate with the push-pull pickling device 100 to form a first pickling post-liquid, and then perform pre-desiliconization.

[0118] An acid liquid replenishment device 300, communicated with the push-pull pickling device 100, used to receive the first pickling post-liquid after re-pre-desiliconization and replenish free acid to obtain a second pickling liquid.

[0119] An acid rolling tandem pickling device 400, communicated with the acid liquid replenishment device 300 to receive the second pickling liquid. The acid rolling tandem pickling is used to pickle easy-to-pickle strip steel.

[0120] After the free acid is supplemented to the first pickling post-liquid in the above cold rolling pickling device, the easy-to-pickle strip steel is continuously pickled in the tandem cold rolling mill. The property that the concentration of the free acid in the first pickling post-liquid is high is fully utilized. After pickling in the tandem cold rolling mill, the free acid in the second pickling post-liquid is greatly reduced, reaching the safety standard for acid regeneration. The above cold rolling pickling device has a high utilization rate of free acid, which is beneficial to the stable and safe operation of the subsequent acid regeneration system outside. It can avoid the waste of free acid caused by directly performing acid regeneration on high-concentration free acid subsequently, and the potential safety hazards to the acid regeneration system.

[0121] This application also provides a cold rolling pickling system, referring to Figure 3 and Figure 4 , which can be used to implement the pickling method of cold rolled strip steel. The cold rolling pickling system includes:

[0122] The push-pull pickling device 100 includes a plurality of pickling components arranged in sequence, which are respectively used to pickle the difficult-to-pickle strip steel. Among them, the difficult-to-pickle strip steel can use the first pickling solution. Exemplarily, the concentration of the free acid in the first pickling solution is 230-250 g / l.

[0123] The pre-desiliconization device 200 is arranged between pickling tanks, inside pickling tanks or after the push-pull pickling device 100 to cooperate with the push-pull pickling device 100 to form the first pickling post-liquid, and then pre-desiliconization is carried out. Exemplarily, the concentration of the free acid in the first pickling post-liquid is 125-135 g / l.

[0124] The acid solution supplement device 300 is connected to the push-pull pickling device 100, and is used to receive the first pickling post-liquid after re-pre-desiliconization and supplement free acid to obtain the second pickling solution.

[0125] The tandem cold rolling mill pickling device 400 is connected to the acid solution supplement device 300 to receive the second pickling solution. The tandem cold rolling mill pickling is used to pickle the easy-to-pickle strip steel.

[0126] The acid regeneration system is connected to the tandem cold rolling mill pickling device 400 and is used to regenerate the second pickling post-liquid to obtain regenerated acid, and adjust the concentration of the free acid in the regenerated acid to form the first pickling solution.

[0127] In the above cold rolling pickling system, after the free acid is supplemented to the first pickling post-liquid, the easy-to-pickle strip steel is continuously pickled in the tandem cold rolling mill. The property that the concentration of the free acid in the first pickling post-liquid is high is fully utilized. After pickling in the tandem cold rolling mill, the free acid in the second pickling post-liquid is greatly reduced, reaching the safety standard for acid regeneration. The above cold rolling pickling system has a high utilization rate of free acid, and the subsequent acid regeneration system operates stably and safely. It can avoid the waste of free acid caused by directly performing acid regeneration on high-concentration free acid subsequently, and the potential safety hazards to the acid regeneration system.

[0128] In some embodiments, referring toFigure 3 and Figure 4 The acid regeneration device 500 includes a leaching tower 510, a reaction tank 520, a sedimentation tank 530, a heat exchanger 540, a roasting furnace 550, an absorption tower 560, a rinsing water tank 571, and a regenerated acid tank 580.

[0129] The leaching tower 510 is connected to the acid pickling line pickling device 400. The leaching tower 510, the reaction tank 520, and the sedimentation tank 530 are connected in sequence, and are respectively used for leaching scrap steel with the second pickling solution, adjusting the pH of the leaching solution to 3.5 - 4.4, and separating to obtain treated acid. In some other embodiments, the acid regeneration device 500 further includes a waste acid tank 511. The leaching tower 510 is connected to the acid pickling line pickling device 400 through the waste acid tank 511.

[0130] The roasting furnace 550 is connected to the sedimentation tank 530 and is used for roasting the treated acid to obtain furnace gas. In some other embodiments, the acid regeneration device 500 further includes a treated acid tank 512. The roasting furnace 550 is connected to the sedimentation tank 530 through the treated acid tank 512.

[0131] The heat exchanger 540 includes a heat medium part and a refrigerant part. The heat medium part is connected to the roasting furnace 550, and the refrigerant part is connected to the sedimentation tank 530 to receive the treated acid, or is connected to the rinsing water tank 571 to receive the rinsing water.

[0132] The absorption tower 560 is respectively connected to the heat exchanger 540 and the rinsing water tank 571.

[0133] One end of the regenerated acid tank 580 is connected to the absorption tower 560, and the other end is connected to at least one of the push - pull type pickling device 100 and the acid pickling line pickling device 400.

[0134] The acid regeneration effect of this kind of acid regeneration device 500 is relatively good.

[0135] In some embodiments, referring to Figure 4 , the sedimentation tank 530, the roasting furnace 550, and the heat exchanger 540 are arranged in sequence, and the refrigerant part is connected to the rinsing water container 570.

[0136] In this embodiment, the coolant is rinsing water. Specifically, the treated acid in the sedimentation tank 530 is first roasted in the roasting furnace 550. The furnace gas generated by the roasting furnace 550 is transported to the Venturi device. The rinsing water is transported to the Venturi device. In the Venturi device, the rinsing water is heated, and the furnace gas is cooled to obtain cooled furnace gas. The rinsing water after heat exchange absorbs the furnace gas to obtain regenerated acid.

[0137] Since the second pickling solution has actually undergone push - pull type pickling and acid pickling line pickling, and then the edge wires are dissolved in the leaching tower 510, the concentration of ferrous chloride in the treated acid is high. Therefore, the treated acid is first roasted, and then heat - exchanged in the Venturi device with the rinsing water as the refrigerant.

[0138] Specifically, the acid concentration for treatment is high, and it is directly sprayed into the roasting furnace 550 instead of entering the Venturi device for heat exchange. Therefore, there is no crystallization causing blockage in the Venturi device, nor is there blockage in the acid liquid pipeline supplying the roasting furnace 550, resulting in production interruption. The production of acid regeneration is more stable and smooth. The metal ion concentration in the rinsing water is low, and it is not easy to crystallize in this case, thus avoiding blockage of the Venturi device itself or the pipelines connected to the Venturi device due to crystallization.

[0139] In addition, the rinsing water is heated by the furnace gas and a part of the water is volatilized. The rinsing water not only realizes concentration through heat exchange in the Venturi device but also absorbs hydrogen chloride aerosol. Additionally, it absorbs the hydrogen chloride aerosol in the absorption tower 560.

[0140] Moreover, the concentration of ferrous chloride in the rinsing water is low, so the water content is high and the cooling effect is better. This is more conducive to reducing the temperature of the furnace gas to reach a lower temperature of the cooled furnace gas. The temperature of the cooled furnace gas is lower. On the one hand, it is conducive to the absorption of hydrogen chloride gas in it, reducing the loss caused by unabsorbed hydrogen chloride. On the other hand, it can reduce the impact of the cooled furnace gas on the absorption tower and the packing in the absorption tower. The materials of the absorption tower and the packing in the absorption tower are high molecular polymers, which are prone to heat deformation at high temperatures, affecting their service life. And the deformation of the packing will also affect the absorption of the cooled furnace gas. Therefore, in the case of a lower temperature of the cooled furnace gas, it is conducive to extending the service life of the absorption tower and increasing the absorption efficiency of the absorption tower for the cooled furnace gas.

[0141] In some embodiments, a return pipe is further included between the rinsing water container 570 and the heat exchanger 540 for returning the rinsing water used as a refrigerant in the heat exchanger 540 to the rinsing water container 570. That is, the rinsing water after heat exchange returns to the rinsing water container 570.

[0142] Due to the relatively high temperature of the furnace gas, such as 450 °C, to a certain extent, it limits the absorption of hydrogen chloride aerosol by the rinsing water. Moreover, the structural design of the Venturi device is mainly based on the consideration of heat exchange, not for the absorption of hydrogen chloride aerosol by the rinsing water. Therefore, the rinsing water in the Venturi device can only absorb a part of the hydrogen chloride aerosol. In the Venturi device, due to heat exchange, the temperature of the furnace gas drops significantly, forming cooled furnace gas with a temperature of about 90 - 95 °C.

[0143] After the cooled furnace gas enters the absorption tower 560, due to its lower temperature and the structural design of the absorption tower 560 mainly for promoting absorption, the cooled furnace gas is in full contact with the rinsing water after heat exchange. Therefore, the hydrogen chloride aerosol in the cooled furnace gas can be more fully absorbed, and thus a regenerated acid with a relatively high concentration of free acid (170 - 190 g / l) can be obtained. In this way, two - stage absorption is achieved, the absorption of hydrogen chloride aerosol is more thorough, and the environmental protection pressure is reduced.

[0144] In this embodiment, a larger amount of rinsing water is utilized. On the one hand, the crystallization accident of the Venturi device is reduced. On the other hand, the amount of rinsing water that cannot be utilized discharged into the wastewater treatment station is reduced, the discharge amount of acidic wastewater is reduced, the cost of the wastewater treatment station for treating wastewater is reduced, and system emission reduction is achieved. Moreover, the loss of the acid retained in the pickling and acid regeneration systems is reduced, and acid loss is decreased.

[0145] In some embodiments, a return pipe is further included between the rinsing water container 570 and the heat exchanger 540 for returning the rinsing water as a refrigerant in the heat exchanger 540 to the rinsing water container 570. That is, the rinsing water after heat exchange returns to the rinsing water container 570 again.

[0146] In some embodiments, the inlet end of the rinsing water container 570 is communicated with at least one of the push-pull pickling device 100 and the tandem cold rolling pickling device 400 to receive and store the rinsing water in the pickling step.

[0147] In the above technical solution of the present invention, the above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A pickling method for cold-rolled strip steel, characterized in that, It includes the following steps: Use a first pickling solution to perform push-pull pickling on difficult-to-pickle strip steel, and perform pre-desilication during and / or after the push-pull pickling to obtain a first pickled solution; wherein, the concentration of free acid in the first pickling solution is 230-250 g / l; the concentration of free acid in the first pickled solution is 125-135 g / l; the difficult-to-pickle strip steel includes grain-oriented silicon steel, high-grade non-oriented silicon steel, and high-grade medium-high carbon steel; Supplement acid solution to the first pickled solution to obtain a second pickling solution; wherein, the concentration of free acid in the second pickling solution and the dosage of the second pickling solution meet the pickling requirements of the tandem cold rolling and pickling line; Use the second pickling solution to perform tandem cold rolling and pickling on easy-to-pickle strip steel to obtain a second pickled solution; the easy-to-pickle strip steel is strip steel that is easier to clean than the difficult-to-pickle strip steel; The concentration of free acid in the second pickling solution is 170 - 190 g / l; the dosage of the first pickling solution is 4 - 5 m 3 / h; the dosage of the second pickling solution is 10 m 3 / h.

2. The pickling method according to claim 1, characterized in that, The step of performing pre-desilication during the push-pull pickling process includes: Perform pre-desilication on the pickling intermediate solution between the third-stage pickling and the fourth-stage pickling of the push-pull pickling. The push-pull pickling includes multiple stages of pickling performed in sequence; the pickling intermediate solution is the pickled solution obtained from the previous stage of pickling.

3. The pickling method according to claim 1, characterized in that The step of using the first pickling solution to perform push-pull pickling on the difficult-to-pickle strip steel further includes: Brush off the silica gel substance formed on the surface of the intermediate of the difficult-to-pickle strip steel during pickling; the intermediate of the difficult-to-pickle strip steel is the strip steel during any stage of pickling.

4. A method for acid recycling of cold-rolled strip steel, characterized in that, It includes the following steps: The pickling method according to any one of claims 1 to 3; Perform an acid regeneration step on the second pickled solution to obtain regenerated acid, and adjust the concentration of free acid in the regenerated acid to form the first pickling solution.

5. The acid recycling method according to claim 4, characterized in that, The step of performing an acid regeneration step on the second pickled solution includes: Heat the second pickled solution, soak scrap steel, adjust the pH of the solution after soaking to 3.5-4.4, and then perform precipitation separation to obtain a treated acid, and the treated acid is a ferrous chloride solution; Roast the treated acid to obtain furnace gas, cool the furnace gas, and use rinsing water to absorb the cooled furnace gas to obtain regenerated acid. The furnace gas includes HCl gas.

6. The acid recycling method according to claim 5, characterized in that, The step of roasting the treated acid to obtain furnace gas and cooling the furnace gas includes: Roast the treated acid under the condition of introducing air to obtain iron oxide powder and furnace gas; cool the furnace gas through heat exchange with a coolant to obtain the cooled furnace gas, and the coolant is the treated acid or the rinsing water.

7. The acid recycling method according to claim 6, wherein The coolant is the rinsing water, and the rinsing water after heat exchange absorbs the furnace gas to obtain the regenerated acid.

8. The acid recycling method according to claim 6, characterized in that The temperature of the furnace gas is 420-450 °C, and the temperature of the cooled furnace gas is 90-95 °C.

9. A cold rolling and pickling equipment, characterized in that, It includes: Push-pull pickling device, including a plurality of pickling components arranged in sequence, respectively used for pickling difficult-to-pickle strip steel; the push-pull pickling device uses a first pickling solution to perform push-pull pickling on the difficult-to-pickle strip steel, and the concentration of free acid in the first pickling solution is 230-250 g / l; the dosage of the first pickling solution is 4-5 m 3 / hour, and the difficult-to-pickle strip steel includes grain-oriented silicon steel, high-grade non-oriented silicon steel and high-grade medium-high carbon steel; A pre-desilication device, which is arranged between the pickling components, inside the pickling components, or after the push-pull pickling device to cooperate with the push-pull pickling device to form a first pickled solution; the concentration of free acid in the first pickled solution is 125-135 g / l; An acid solution supplement device, which is connected to the push-pull pickling device and is used to receive the first pickled solution and then supplement acid solution to obtain a second pickling solution; The pickling device of the tandem cold rolling mill is connected to the acid solution replenishing device to receive the second pickling solution; the pickling of the tandem cold rolling mill is used for pickling the easily pickled strip steel; the concentration of free acid in the second pickling solution is 170-190 g / l; the dosage of the second pickling solution is 10 m 3 / hour; the easily pickled strip steel is the strip steel that is easier to clean than the difficult-to-pickle strip steel; The acid regeneration device is connected to the pickling device of the acid rolling tandem mill, and is used for acid regenerating the second pickling solution to obtain regenerated acid, and adjusting the concentration of the regenerated acid to form the first pickling solution.

10. The cold rolling pickling equipment according to claim 9, characterized in that, The acid regeneration device includes a leaching tower, a reaction tank, a sedimentation tank, a heat exchanger, a roasting furnace, an absorption tower, a rinsing water container and a regenerated acid tank; The leaching tower is connected to the pickling device of the acid rolling tandem mill, and the leaching tower, the reaction tank and the sedimentation tank are connected in sequence, and are respectively used for leaching scrap steel with the second pickling solution in sequence, adjusting the pH of the solution after leaching to 3.5-4.4, and separating by precipitation to obtain treated acid; The roasting furnace is connected to the sedimentation tank and is used for roasting the treated acid to obtain furnace gas; The heat exchanger includes a heat medium part and a refrigerant part; the heat medium part is connected to the roasting furnace, and the refrigerant part is connected to the sedimentation tank to receive the treated acid, or is connected to the rinsing water container to receive rinsing water; The absorption tower is respectively connected to the heat exchanger and the rinsing water container; One end of the regenerated acid tank is connected to the absorption tower, and the other end is connected to at least one of the push-pull pickling device and the pickling device of the acid rolling tandem mill.

11. The cold rolling and pickling equipment according to claim 10, characterized in that, The sedimentation tank, the roasting furnace and the heat exchanger are arranged in sequence, and the refrigerant part is connected to the rinsing water container.

12. The cold rolling and pickling equipment according to claim 11, characterized in that, A return pipe is further included between the rinsing water container and the heat exchanger, and is used for returning the rinsing water as a refrigerant in the heat exchanger to the rinsing water container.

13. The cold rolling and pickling equipment according to any one of claims 10 to 12, characterized in that, The inlet end of the rinsing water container is connected to at least one of the push-pull pickling device and the pickling device of the acid rolling tandem mill to receive and store the rinsing water in the pickling step.

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