Acid regeneration method, acid recycling method, device and system for pickling recovery liquid

Abstract

The present invention provides an acid regeneration method, an acid recycling method, a device and a system for pickling recovery liquid. The acid regeneration method includes the following steps: immersing pickling recovery liquid in scrap steel, adjusting the pH of the solution after immersion to 3.5 - 4.4, and then separating by precipitation to obtain treated acid, where the treated acid is a ferrous chloride solution. The pickling recovery liquid is the pickling solution after pickling cold-rolled strip steel. Roasting the treated acid under the condition of introducing air to obtain furnace gas, and the furnace gas includes HCl gas. Cooling the furnace gas by heat exchange with rinsing water to obtain cooled furnace gas. Absorbing the cooled furnace gas with an absorption liquid to obtain regenerated acid. The absorption liquid is rinsing water or rinsing water after heat exchange. The treated acid is directly sprayed into the roasting furnace instead of entering the Venturi device for heat exchange, so there is no crystallization causing blockage of the Venturi device and no blockage of the acid liquid pipeline for the roasting furnace, resulting in production stoppage, and the acid regeneration production is more stable and smooth.

Description

Technical Field

[0001] The present invention relates to the field of pickling, and in particular to an acid regeneration method, an acid recycling method, a device and a system for pickling recovery liquid. Background Art

[0002] Pickling is an important process in the production process of cold-rolled strip steel. Its purpose is to remove iron oxide on the surface of the strip, adjust the coil weight, cut off the cracked edge, and provide qualified billets for the rolling mill, so that the cold rolling mill can smoothly produce qualified strip steel products.

[0003] However, problems such as blockage of Venturi equipment and pipelines are likely to occur during the subsequent acid regeneration of the pickling solution after pickling cold-rolled strip steel. Summary of the Invention

[0004] The main object of the present invention is to provide an acid regeneration method, an acid recycling method, a device and a system to solve the technical problem that blockage of Venturi equipment and pipelines is likely to occur during the subsequent acid regeneration of the pickling solution after pickling cold-rolled strip steel.

[0005] To achieve the above object, the present invention provides an acid regeneration method for pickling recovery liquid, including the following steps:

[0006] Immerse the pickling recovery liquid in scrap steel, adjust the pH of the solution after immersion to 3.5 - 4.4, and then precipitate and separate to obtain treated acid, where the treated acid is a ferrous chloride solution. The pickling recovery liquid is the pickling solution after pickling cold-rolled strip steel.

[0007] Roast the treated acid under the condition of introducing air to obtain furnace gas, and the furnace gas includes HCl gas.

[0008] Cool the furnace gas and rinsing water through heat exchange to obtain cooled furnace gas.

[0009] Absorb the cooled furnace gas with an absorbent to obtain regenerated acid. The absorbent is rinsing water or rinsing water after heat exchange.

[0010] According to an embodiment of the present application, it includes the following steps:

[0011] The temperature of the furnace gas is 420 - 450 °C, and the temperature of the cooled furnace gas is 90 - 95 °C.

[0012] According to an embodiment of the present application, the absorbent is rinsing water after heat exchange.

[0013] According to an embodiment of the present application, the concentration of the ferrous chloride solution is 360 - 440 g / l.

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

[0015] The difficult-to-wash strip steel is pickled in a push-pull manner using a first pickling solution to obtain a first post-pickling solution.

[0016] An acid solution is added to the first post-pickling 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 mill.

[0017] The easy-to-wash strip steel is pickled by the tandem cold rolling mill using the second pickling solution to obtain a second post-pickling solution.

[0018] The second pickling solution is used as the pickling recovery solution, and acid regeneration is carried out using the above-mentioned acid regeneration method for the pickling recovery solution to obtain regenerated acid.

[0019] The concentration of free acid in the regenerated acid is adjusted to form a first pickling solution.

[0020] According to an embodiment of the present application, the concentration of free acid in the first pickling solution is 230 - 250 g / l. The concentration of free acid in the first post-pickling solution is 125 - 135 g / l.

[0021] 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.

[0022] According to an embodiment of the present application, the step of pickling the difficult-to-wash strip steel using the first pickling solution further includes:

[0023] Brushing the silica gel substance formed on the surface of the intermediate of the difficult-to-wash strip steel during pickling. The intermediate of the difficult-to-wash strip steel is the strip steel in any stage of pickling.

[0024] The present application also provides an acid regeneration system for pickling recovery solution. The acid regeneration system 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.

[0025] The leaching tower, the reaction tank, and the sedimentation tank are connected in sequence, and are respectively used for leaching scrap steel with the pickling recovery solution, adjusting the pH of the leached solution to 3.5 - 4.4, and separating by precipitation to obtain a treated acid.

[0026] The roasting furnace is connected to the sedimentation tank and is used for roasting the treated acid to obtain furnace gas.

[0027] The heat exchanger includes a hot medium part and a cold medium part. The hot medium part is connected to the roasting furnace, and the cold medium part is connected to the rinsing water container to receive rinsing water. The sedimentation tank, the roasting furnace, and the heat exchanger are arranged in sequence.

[0028] The absorption tower is connected to the heat exchanger and the rinsing water container respectively.

[0029] The regenerated acid tank is connected to the absorption tower.

[0030] According to an embodiment of the present application, a reflux pipe is further included between the rinsing water container and the heat exchanger, for returning the rinsing water as a refrigerant in the heat exchanger to the rinsing water container.

[0031] The present application also provides a cold rolling pickling system, including:

[0032] A push-pull pickling device, including a plurality of pickling components arranged in sequence, respectively used for pickling difficult-to-pickle strip steel.

[0033] A pre-desilication device, arranged between pickling tanks, inside pickling tanks or after the push-pull pickling device, to cooperate with the push-pull pickling device to form a first pickling recovery liquid.

[0034] An acid solution replenishing device, connected to the push-pull pickling device, for receiving the first pickling recovery liquid and then replenishing the acid solution to obtain a second pickling solution.

[0035] An acid rolling tandem pickling device, 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.

[0036] In the above acid regeneration system, the leaching tower is connected to the acid rolling tandem pickling device, and the regenerated acid tank is connected to the push-pull pickling device, providing regenerated acid as part of the raw materials for the first pickling solution.

[0037] 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 acid rolling tandem pickling device, to receive and store the rinsing water in the pickling step.

[0038] In the above pickling method of cold-rolled strip steel, the treatment acid is directly sprayed into the roasting furnace instead of entering the Venturi device for heat exchange. Therefore, there is no crystallization causing blockage of the Venturi device, nor is there blockage of the acid solution pipeline for the roasting furnace resulting in production stoppage, and the production of acid regeneration is more stable and smooth. The metal ion concentration in the rinsing water is relatively low and is not easily crystallized in this case, thus avoiding blockage of the Venturi device itself or the pipeline connected to the Venturi device due to crystallization. Brief Description of the Drawings

[0039] 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 also be obtained based on the structures shown in these drawings.

[0040] Figure 1 It is a flowchart of push-pull pickling in the related art;

[0041] Figure 2 is a flow chart of pickling in a tandem cold rolling and pickling line of related technologies;

[0042] Figure 3 is a flow chart of the acid recycling method for cold-rolled strip steel according to an embodiment of the present application.

[0043] The realization of the object of the present invention, functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings.

[0044] 100. Push-pull pickling device; 200. Pre-desilication device; 300. Acid replenishment device; 400. Tandem cold rolling and pickling device; 500. Acid regeneration system; 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; 570. Rinsing water container; 572. Rinsing water tank; Detailed Embodiments

[0045] 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 of 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 fall within the protection scope of the present invention.

[0046] 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.

[0047] 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.

[0048] 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 them. 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.

[0049] After extensive research, the applicant found that the concentration of ferrous chloride in the treated acid obtained from the pickling solution after cold rolling strip steel in the related art is too high. The pickling recovery solution first passes through a heat exchange device such as a Venturi device to cool down, and then enters a roasting furnace. The furnace gas generated by the roasting furnace then enters the Venturi device.

[0050] In the Venturi device, the treated acid is used as a refrigerant to cool the furnace gas. Correspondingly, the furnace gas heats the treated acid. Since the concentration of ferrous chloride in the treated acid is too high, and after heating, the ferrous chloride in it is prone to crystallization and block the Venturi device or the pipeline connected to the Venturi device.

[0051] Based on this, the present application provides an acid regeneration method for pickling recovery solution, which includes:

[0052] S410: Immerse the pickling recovery solution in scrap steel, adjust the pH of the solution after immersion to 3.5 - 4.4, and then precipitate and separate to obtain the treated acid, where the treated acid is a ferrous chloride solution; the pickling recovery solution is the pickling solution after cold rolling strip steel.

[0053] In this step, for example, the second pickling solution is heated and immersed in scrap steel in sequence. In this step, the second pickling solution can be heated by steam, which can accelerate the reaction rate of the second pickling solution to immerse scrap steel.

[0054] Immerse scrap steel, and the second pickling solution reacts with the edge wire to generate hydrogen and the solution after immersion. The solution after immersion includes the ferrous chloride solution generated by the reaction of the second pickling solution and the edge wire.

[0055] Add ammonia water to the solution after immersion to adjust the pH value to 3.5 - 4.4, aerate, and then separate through a sedimentation tank 530. The supernatant is the treated acid. In this process, flocculent iron hydroxide precipitate is generated. The iron hydroxide precipitate has an adsorption effect and can adsorb other impurities such as silicon in the solution after immersion. Therefore, the supernatant, that is, 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.

[0056] S420: Roast the treated acid under the condition of introducing air to obtain furnace gas, where the furnace gas includes HCl gas.

[0057] 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.

[0058] The reaction formula for this step is: The reaction formula for this step is:

[0059]

[0060] The specific roasting temperature can be 580 - 650 °C.

[0061] S430: Cool the furnace gas and the rinsing water through heat exchange to obtain the cooled furnace gas.

[0062] In this step, the furnace gas and the coolant are cooled through heat exchange, for example, in a heat exchanger 540 (specifically, a Venturi device). The following takes the heat exchange in the Venturi device as an example for illustration.

[0063] Refer to Figure 3 , and the coolant is rinsing water.

[0064] The rinsing water is the rinsing water for the push-pull pickling and / or the tandem pickling and rolling pickling process, 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 the absorption tower 560 to provide the rinsing water.

[0065] 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 contains 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 the regenerated acid.

[0066] In this embodiment, the treatment acid is first roasted in a roasting furnace 550, and 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 the cooled furnace gas. The rinsing water after heat exchange absorbs the furnace gas to obtain the regenerated acid.

[0067] Since the second pickling solution actually undergoes push-pull pickling and tandem pickling and rolling pickling, and then dissolves the edge wire in the leaching tower 510, the concentration of ferrous chloride in the treatment acid is high. Therefore, the treatment acid is first roasted and then exchanges heat in the Venturi device with the rinsing water as the refrigerant.

[0068] Specifically, the concentration of the treatment 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, nor is there blockage of the acid liquid pipeline supplying the roasting furnace 550, resulting in production stoppage. The production of acid regeneration is more stable. The concentration of metal ions in the rinsing water is relatively 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.

[0069] In addition, the rinsing water is heated by the furnace gas and a part of the water is volatilized. The rinsing water is concentrated not only by heat exchange in the Venturi device but also absorbs the hydrogen chloride mist, and also absorbs the hydrogen chloride mist in the absorption tower 560.

[0070] 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 °C.

[0071] S440: Absorb the cooled furnace gas with an absorption liquid to obtain regenerated acid; the absorption liquid is rinsing water or the rinsing water after the heat exchange.

[0072] After the cooled furnace gas enters the absorption tower 560, due to the relatively low temperature and the structural design of the absorption tower 560 mainly considering 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 absorbed more fully, and thus 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.

[0073] In this embodiment, more rinsing water is utilized. On the one hand, the occurrence of crystallization accidents in the Venturi device is reduced. On the second hand, the amount of rinsing water that cannot be utilized discharged into the wastewater station is reduced, the discharge amount of acidic wastewater is reduced, the cost of the wastewater station for treating wastewater is reduced, and system emission reduction is achieved.

[0074] In some embodiments, the temperature of the furnace gas is 420 - 450 °C, and the temperature of the cooled furnace gas is 90 - 95 °C.

[0075] In some embodiments, the absorption liquid is the rinsing water after the heat exchange.

[0076] In some embodiments, the concentration of the ferrous chloride solution is 360 - 440 g / l.

[0077] The concentration of the ferrous chloride solution under this condition is relatively high, which is more suitable for the acid regeneration method of the above pickling recovery liquid.

[0078] This application provides a pickling method for cold-rolled strip steel, including the following steps:

[0079] S100: Push-pull pickle the difficult-to-pickle strip steel with a first pickling solution to obtain a first pickled solution. Exemplarily, 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 preparing for push-pull pickling is 230 - 250 g / l). The concentration of free acid in the first pickled solution is 1 + 25 - 135 g / l.

[0080] The difficult-to-clean strip steel includes oriented electrical steel, high-grade non-oriented electrical steel, and high-grade medium-high carbon steel. For the convenience of explaining the following embodiments, the oriented electrical steel is taken as an example to illustrate the difficult-to-clean strip steel. 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.

[0081] Since, in the related art, refer to Figure 1 , generally, the push-pull pickling equipment is not equipped with a tension leveling and descaling machine, shot blasting facilities, etc., and actually does not have the production capacity for pickling silicon steel. In order to improve its pickling efficiency, it has to increase the free acid concentration of the pickling solution.

[0082] For the tandem cold rolling and pickling, it rarely produces difficult-to-pickle varieties, so the free acid concentration of 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 the pickling solution of 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 the pickling solution of the tandem cold rolling and pickling.

[0083] Therefore, refer to 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 (referred to as the pickled 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 simultaneously, resulting in a relatively high equipment cost and operating cost of the acid regeneration system.

[0084] Moreover, there is also a problem with this method. A large amount of free acid remains in the pickled solution after push-pull pickling. Directly regenerating 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.

[0085] Specifically, the pickled solution after pickling enters the leaching tower of the acid regeneration system. The free acid dissolves scrap steel (such as strip steel side filaments) to generate hydrogen, and this reaction is an exothermic reaction. Therefore, it is only possible to control the free acid concentration in the waste acid not to exceed 60 g / l. If the pickled solution after pickling is much greater than 60 g / l, there will be a risk of explosion.

[0086] When the free acid concentration in the pickling post-liquid is too high, the time for dissolving edge wires in the leaching tower is longer than that in spent acid with a free acid concentration not exceeding 60 g / l, thus affecting the hourly capacity of acid reproduction to produce regenerated acid. As a result, the energy consumption of acid regeneration is high and the acid production efficiency is low.

[0087] On this basis, after a large amount of research, the applicant provides 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.

[0088] 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.

[0089] 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 extremely easy to remain in the pickling pipeline, resulting in a smaller diameter of the pickling pipeline or even blocking the pickling solution pipeline, thus affecting the pickling speed and efficiency.

[0090] 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 post-liquid, and further reduce the silicon content in the subsequent second pickling solution, reducing the influence of silicon.

[0091] In some embodiments, pre-desilication treatment is carried out during the push-pull pickling process. After pickling through the first few stages (such as the third pickling), a large amount of silicon exists in the pickling intermediate liquid. The pickling intermediate liquid refers to the washing liquid obtained from the previous stage of pickling.

[0092] In this case, pre-desilication can be carried out on the pickling intermediate liquid. The method of pre-desilication can be to directly add a flocculant to precipitate in the corresponding solution (such as the pickling intermediate liquid), so that the silicon therein precipitates. In some embodiments, pre-desilication is carried out on the pickling intermediate liquid 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 liquid.

[0093] 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 liquid obtained from the last stage of pickling.

[0094] During the pickling process, silicon in the intermediate pickling solution adheres to the strip steel during pickling (which can be referred to as 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 to use a brush roll to brush off in the pickling components corresponding to the third-stage pickling, fourth-stage pickling, and fifth-stage pickling, such as pickling tanks.

[0095] The first post-pickling solution 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 post-pickling solution is 125 - 135 g / l.

[0096] S200: Add an acid solution to the first post-pickling solution to obtain the second pickling solution. Among them, the concentration of free acid, 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.

[0097] The acid solution can be a single-component acidic solution or can include multiple acidic solutions. For example, after the first post-pickling solution 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.

[0098] Adding the acid solution simultaneously increases the concentration of free acid in the second pickling solution and the dosage of the second pickling solution, thereby meeting the pickling requirements of the tandem cold rolling mill.

[0099] 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.

[0100] 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.

[0101] S300: Use the second pickling solution to perform tandem cold rolling mill pickling on the easy-to-pickle strip steel to obtain the second post-pickling solution.

[0102] 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.

[0103] 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 post-pickling solution is fully utilized, reducing the waste of acid solution. Moreover, the free acid in the second post-pickling solution is greatly reduced, meeting the safety standard 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.

[0104] In the above pickling method for cold-rolled strip steel, since the concentration of free acid in the first pickling solution is relatively high, the concentration of free acid in the first post-pickling solution is also relatively high. After replenishing free acid to the first post-pickling solution, the easy-to-pickle strip steel is continuously pickled in the tandem cold rolling mill, making full use of the property of high concentration of free acid in the first post-pickling solution. After pickling in the tandem cold rolling mill, the free acid in the second post-pickling solution is greatly reduced, meeting the safety standard 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.

[0105] S400: Use the second pickling solution as the pickling recovery solution and perform acid regeneration by the above acid regeneration method for the pickling recovery solution to obtain regenerated acid.

[0106] During the push-pull pickling and the pickling process in the tandem cold rolling mill, the corresponding pickling solutions react with the strip steel. Therefore, the second post-pickling solution also contains a large amount of ferrous chloride. In addition, the ferrous chloride solution formed by the reaction of the second post-pickling solution with the side wire. After leaching, the concentration of ferrous chloride in the solution is as high as 360 - 440 g / l. Therefore, it is more suitable for the above acid regeneration method for the pickling recovery solution.

[0107] S500: Adjust the concentration of free acid in the regenerated acid to form the first pickling solution.

[0108] In this step, adjusting the concentration of free acid in the regenerated acid to form the first pickling solution enables the acid to be recycled.

[0109] Since in the above pickling method for cold-rolled strip steel, the push-pull pickling and the pickling in the tandem cold rolling mill are used in combination, in the subsequent acid regeneration process, only one set of acid regeneration equipment is required to meet the acid regeneration requirements, saving equipment and operating costs.

[0110] This application also provides an acid regeneration system. Refer to Figure 3 , the acid regeneration system 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 container 570, and a regenerated acid tank 580.

[0111] The leaching tower 510 is connected to the pickling unit 400 of the tandem cold rolling mill. 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 system 500 further includes a waste acid tank 511. The leaching tower 510 is connected to the pickling unit 400 of the tandem cold rolling mill through the waste acid tank 511.

[0112] 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 system 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.

[0113] 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 rinsing water container 570 to receive rinsing water.

[0114] The absorption tower 560 is respectively connected to the heat exchanger 540 and the rinsing water container 570.

[0115] The regenerated acid tank 580 is connected to the absorption tower 560.

[0116] In some embodiments, referring to Figure 3 , 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.

[0117] 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.

[0118] Since the second pickling solution has actually undergone push-pull pickling and pickling in the tandem cold rolling mill, and then the side 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 rinsing water as the refrigerant.

[0119] Specifically, the concentration of the treated 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, nor is there blockage of the acid liquid pipeline for the roasting furnace 550 resulting in production stoppage, and the production of acid regeneration is more stable. 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 pipelines connected to the Venturi device due to crystallization.

[0120] In addition, the rinsing water is heated by the furnace gas, and a part of the water is volatilized. The rinsing water is concentrated by heat exchange in the Venturi device and also absorbs the hydrogen chloride aerosol. In addition, the hydrogen chloride aerosol is absorbed in the absorption tower 560.

[0121] 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.

[0122] Since the temperature of the furnace gas is relatively high, such as 450 °C, to a certain extent, it limits the absorption of the 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 the 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 a cooled furnace gas, and its temperature is about 90-95 °C.

[0123] 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 considering 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 (from 170 to 190 g / l) can be obtained. In this way, two-stage absorption is achieved, the absorption of the hydrogen chloride aerosol is more thorough, and the environmental protection pressure is reduced.

[0124] Moreover, the concentration of ferrous chloride in the rinsing water is low. Therefore, compared with the treated acid, it has a higher water content and better cooling effect, which is more conducive to the furnace gas cooling to reach a cooled furnace gas with a relatively low temperature. The relatively low temperature of the cooled furnace gas is beneficial to the absorption of the hydrogen chloride gas therein, reducing the loss of unabsorbed hydrogen chloride, and 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 relatively low temperature of the cooled furnace gas, it is beneficial to extend the service life of the absorption tower and increase the absorption efficiency of the absorption tower for the cooled furnace gas.

[0125] In this embodiment, more rinsing water is utilized. On the one hand, the occurrence of crystallization accidents in the Venturi device is reduced. On the second hand, the amount of unutilizable rinsing water 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. And the loss of the acid retained in the pickling and acid regeneration system is reduced, and acid loss is reduced.

[0126] In some embodiments, a reflux pipe is further included between the rinsing water container 570 and the heat exchanger 540, which is used to return 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.

[0127] Referring to Figure 3 , the present application also provides a cold rolling pickling device, including:

[0128] A push-pull pickling device 100, including a plurality of pickling components arranged in sequence, which are respectively used for pickling difficult-to-pickle strip steel.

[0129] A pre-desiliconization device 200, which 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 a first pickling post-liquid, and then perform pre-desiliconization.

[0130] An acid solution replenishing device 300, which is communicated with the push-pull pickling device 100, is used to replenish free acid after receiving the first pickling post-liquid after pre-desiliconization again to obtain a second pickling solution.

[0131] An acid rolling tandem pickling device 400, which is communicated with the acid solution replenishing device 300 to receive the second pickling solution. The acid rolling tandem pickling is used for pickling easy-to-pickle strip steel.

[0132] The present application also provides a cold rolling pickling system. Referring to Figure 3 , it can be used to implement the pickling method of cold rolled strip steel. The cold rolling pickling system includes:

[0133] A push-pull pickling device 100, including a plurality of pickling components arranged in sequence, which are respectively used for pickling difficult-to-pickle strip steel. Among them, the difficult-to-pickle strip steel can use the first pickling solution. Exemplarily, the concentration of free acid in the first pickling solution is 230-250 g / l.

[0134] A pre-desiliconization device 200, which 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 a first pickling post-liquid, and then perform pre-desiliconization. Exemplarily, the concentration of free acid in the first pickling post-liquid is 125-135 g / l.

[0135] An acid solution replenishing device 300, which is communicated with the push-pull pickling device 100, is used to replenish free acid after receiving the first pickling post-liquid after pre-desiliconization again to obtain a second pickling solution.

[0136] An acid rolling tandem pickling device 400, which is communicated with the acid solution replenishing device 300 to receive the second pickling solution. The acid rolling tandem pickling is used for pickling easy-to-pickle strip steel.

[0137] The acid regeneration system, the leaching tower 510 is connected to the pickling line pickling device 400, and the regenerated acid tank 580 is connected to the push-pull pickling device 100 to provide regenerated acid as part of the raw material for the first pickling solution.

[0138] In the above cold rolling pickling system, after the free acid is supplemented in the first pickling post-liquid, the easy-to-pickle strip steel is continuously pickled in the pickling line. The property of the high concentration of free acid in the first pickling post-liquid is fully utilized. After pickling in the pickling line, 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 smoothly 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.

[0139] In some embodiments, the inlet end of the rinsing water container 570 is connected to at least one of the push-pull pickling device 100 and the pickling line pickling device 400 to receive and store the rinsing water in the pickling step.

[0140] 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 directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. An acid regeneration method for pickling recovery liquid, characterized in that, It includes the following steps: After immersing scrap steel in the pickling recovery liquid and adjusting the pH of the solution after immersion to 3.5 - 4.4, precipitate and separate to obtain the treated acid, and the treated acid is ferrous chloride solution; the concentration of the ferrous chloride solution is 360 - 440 g / l; the pickling recovery liquid is the pickling solution after pickling cold-rolled strip steel; Roast the treated acid under the condition of introducing air to obtain furnace gas, and the furnace gas includes HCl gas; Cool the furnace gas and the rinsing water through heat exchange to obtain cooled furnace gas; Absorb the cooled furnace gas with an absorbent to obtain regenerated acid; the absorbent is rinsing water or the rinsing water after the heat exchange; Among them, the steps for generating the pickling recovery liquid include: Push-pull pickle the difficult-to-pickle strip steel with the first pickling solution to obtain the first pickled solution; 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 the 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; The easy-to-wash strip steel is pickled by the second pickling solution in a pickling and rolling online process to obtain the second pickled solution after pickling; the easy-to-wash strip steel is a strip steel that is easier to clean than the difficult-to-wash 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; Use the second pickled solution as the pickling recovery liquid.

2. The acid regeneration method of the pickling recovery liquid according to claim 1, characterized in that It includes the following steps: The temperature of the furnace gas is 420 - 450 °C, and the temperature of the cooled furnace gas is 90 - 95 °C.

3. The acid regeneration method of the pickling recovery liquid according to claim 1, wherein The absorbent is the rinsing water after the heat exchange.

4. The acid regeneration method according to any one of claims 1 to 3, characterized in that, The step of push-pull pickling the difficult-to-pickle strip steel with the first pickling solution 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 in any stage of pickling.

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