Countercurrent pickling regeneration oxidation recycling device and method

Abstract

The invention relates to a countercurrent pickling regeneration oxidation recycling device and method, and belongs to the technical field of stainless steel production. In the countercurrent pickling regeneration oxidation cyclic utilization device, an outlet of a first pickling tank is connected with an inlet of a regeneration kettle through a fluid delivery pump; an outlet of the regeneration kettle is connected with an inlet of the oxidation kettle through a fluid delivery pump; an outlet of the oxidation kettle is connected with an inlet of the (n + 1) th pickling tank through a fluid conveying pump; and the pickling tanks are reversely communicated through pipelines: the outlet of the (n + 1) th pickling tank, the inlet of the nth pickling tank,..., the outlet of the second pickling tank and the inlet of the first pickling tank. Pickling fluid in the first pickling tank firstly passes through the regeneration kettle, then passes through the oxidation kettle, then enters the (n + 1) th pickling tank, then sequentially flows through the nth pickling tank and the (n-1) th pickling tank until the pickling fluid flows back to the first pickling tank and finally flows back to the regeneration kettle, so that a countercurrent pickling regeneration oxidation recycling system is formed, the acid mud amount and the pickling cost can be comprehensively reduced, and the pickling surface quality is improved; and harmful gas is avoided.

Description

[0001] This application is a divisional application of a patent application entitled "A Countercurrent Pickling Regeneration and Recycling System and Process", the original application was filed on March 23, 2023, application number 202310288106.5. Technical Field

[0002] This application relates to the field of stainless steel production technology, specifically to a countercurrent pickling, regeneration, oxidation, and recycling device and method. Background Technology

[0003] Stainless steel possesses numerous excellent properties, including high corrosion resistance, and has been widely used in various industrial sectors and daily life. Currently, the stainless steel production industry mostly employs a mixed acid pickling process using HNO3 and HF. However, this pickling process still has some problems. On the one hand, the pickling process for stainless steel generates environmental pollution, such as NO produced by the reaction of HNO3 with low-valent oxides on the stainless steel surface. X Issues include the formation of SiF4 gas from SiO2 and HF in stainless steel oxides, and the treatment of nitrite wastewater. On the other hand, stainless steel pickling with mixed acids results in surface mottling and localized corrosion. Furthermore, current stainless steel pickling processes generate large amounts of pickling sludge, leading to excessively high costs. While using a nitric acid system with lime only produces heavy metal hydroxide precipitates with minimal sludge, the pickling environment is harsh, costs are high, and it generates large amounts of high-concentration calcium nitrate solution, causing environmental problems. Using a roasting method to treat pickling wastewater incurs high investment (approximately 50 million RMB) and operating costs. Reducing pickling sludge and treating pickling wastewater are challenging and critical issues in this industry. Therefore, the development of new stainless steel pickling processes is urgently needed. Summary of the Invention

[0004] This application proposes a countercurrent pickling regeneration oxidation recycling device and method to comprehensively reduce the amount of acid sludge and pickling costs, improve the surface quality of pickled surfaces, and avoid the generation of harmful gases.

[0005] On the one hand, this application provides a countercurrent pickling regeneration oxidation recycling device, comprising: There are n+1 sulfuric acid pickling tanks, fluid transfer pumps, regeneration kettles, and oxidation kettles; where n is a positive integer; The outlet of the first pickling tank is connected to the inlet of the regeneration tank via the fluid transfer pump; The outlet of the regeneration reactor is connected to the inlet of the oxidation reactor via the fluid transfer pump; The outlet of the oxidation reactor is connected to the inlet of the (n+1)th pickling tank via the fluid transfer pump; The pickling tanks are connected in reverse order through pipelines: the outlet of the (n+1)th pickling tank → the inlet of the nth pickling tank → … → the outlet of the 2nd pickling tank → the inlet of the 1st pickling tank. The first pickling tank is provided with an acid inlet for supplementing sulfuric acid; the sulfuric acid concentration of the pickling liquid in the first pickling tank is N1 < 200 g / L, the total metal ion concentration is Me1 < 160 g / L, and the Fe 3+ concentration C 1-Fe3+ < 5 g / L. The regeneration kettle is provided with an oxalic acid dosing port; the pickling fluid B flowing out of the regeneration kettle satisfies: the sulfuric acid concentration N B > 120 g / L, the total metal ion concentration Me B < 50 g / L. The oxidation kettle is provided with an oxidizing agent injection port and a Fe 3+ ion supplementing device; the pickling fluid C flowing out of the oxidation kettle satisfies: the Fe 3+ concentration C C-Fe3+ > 5 g / L. The sulfuric acid concentration N n+1 of the pickling liquid in the n+1 pickling tank is 200-420 g / L, the total metal ion concentration Me n+1 < 50 g / L, and the Fe 3+ concentration C n+1-Fe3+ ≥ 5 g / L.

[0006] Optionally, the oxidizing agent is selected from one of hydrogen peroxide, oxygen or ozone.

[0007] Optionally, the Fe 3+ ion supplementing device contains ferric sulfate or ferric nitrate.

[0008] Optionally, the C 1-Fe3+ is 0.1-1 g / L.

[0009] Optionally, the C n+1-Fe3+ is 25-30 g / L.

[0010] Optionally, the reverse flow pickling regeneration oxidation circulation utilization device further comprises a passivation tank; The passivation tank is arranged between the outlet of the oxidation kettle and the inlet of the n+1 pickling tank; The Fe 3+ concentration C D-Fe3+ of the pickling fluid in the passivation tank is greater than 10 g / L and greater than C n+1-Fe3+ , and the total metal ion concentration is lower than that of the n+1 pickling tank.

[0011] Optionally, the sulfuric acid pickling time of the first to n+1 pickling tanks is arranged in a decreasing manner.

[0012] In another aspect, the application also provides a reverse flow pickling regeneration oxidation circulation utilization method, which uses the reverse flow pickling regeneration oxidation circulation utilization device and comprises the following steps: When the sulfuric acid concentration of the pickling solution in the first pickling tank is ≤200 g / L or the total metal ion concentration is ≥160 g / L, the pickling solution is pumped into the regeneration kettle as pickling fluid A; Oxalic acid H2C2O4 is added in the regeneration kettle to precipitate Fe 2+ , Ni 2+ and Cu 2+ as oxalate, and after solid-liquid separation, pickling fluid B is obtained, which has a sulfuric acid concentration >120 g / L and a total metal ion concentration <50 g / L; The pickling fluid B is pumped into the oxidation kettle to oxidize Fe 2+ to Fe 3+ ; or Fe 3+ ion supplements are added into the oxidation kettle at the same time, so that the Fe 3+ concentration in the pickling fluid C flowing out is >5 g / L; The pickling fluid C is pumped into the (n+1)th pickling tank, and then sequentially flows countercurrently through the nth, …, first pickling tanks; Sulfuric acid is supplemented to the inlet of the first pickling tank to maintain the sulfuric acid concentration in the tank at <200 g / L; When the pickling fluid discharged from the first pickling tank again meets the condition of sulfuric acid concentration ≤200 g / L or total metal ion concentration ≥160 g / L, it is returned to the regeneration kettle as a new round of pickling fluid A to realize closed circulation.

[0013] Optionally, before the pickling fluid C is pumped into the (n+1)th pickling tank, the method further comprises: The pickling fluid C flowing out of the oxidation kettle is first pumped into a passivation tank, and is kept at 30-70°C for 130-400 s to increase the Fe 3+ concentration to be greater than 10 g / L and greater than C n+1-Fe3+ , to obtain pickling fluid C'; and then the pickling fluid C' is pumped into the (n+1)th pickling tank.

[0014] Optionally, the countercurrent pickling regeneration and oxidation circulation utilization method further comprises: The stainless steel workpiece sequentially undergoes pickling in the first pickling tank to the (n+1)th pickling tank, and the pickling time of each tank is set in a decreasing manner.

[0015] Compared with the prior art, the application has the following beneficial technical effects: The application adopts a countercurrent sulfuric acid pickling and oxidation process, the pickling solution is regenerated and utilized in a circulating manner, the amount of acid sludge and the pickling cost can be comprehensively reduced, and harmful gases such as NO X gas and SiF4 gas are not generated, and the environmental pollution problem caused by harmful gases in the mixed acid pickling process is completely solved. At the same time, the entire process greatly reduces the plate surface roughness and effectively improves the pickling surface quality. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Schematic diagram of the reverse-flow pickling regeneration oxidation recycling device used for Example 1 of the present application; Figure 2 Schematic diagram of the reverse-flow pickling regeneration oxidation recycling device used for Example 3 of the present application. DETAILED DESCRIPTION

[0017] The present application will be further described in detail below in conjunction with specific examples.

[0018] In one aspect, the present application provides a reverse-flow pickling regeneration oxidation recycling device, which comprises a pickling tank and a fluid delivery pump, and is an external oxidation system for the pickling tank, further comprising a regeneration kettle and an oxidation kettle. The pickling tank, the regeneration kettle and the oxidation kettle are each provided with a fluid delivery pump. The pickling tank is a sulfuric acid pickling tank, and n+1 pickling tanks are provided, where n is a positive integer greater than or equal to 1. Further, n in the present application can be preferably 1, 2, 3, 4, 5, 6, 7, 8 or 9, and further n is preferably 2.

[0019] Referring to Figure 1 , the pickling fluid in the first pickling tank first passes through the regeneration kettle, then passes through the oxidation kettle, and then enters the n+1 pickling tank, and then sequentially flows through the n pickling tank, the n-1 pickling tank, and then flows back to the first pickling tank, and finally flows back to the regeneration kettle, forming a reverse-flow pickling regeneration oxidation recycling system.

[0020] wherein the sulfuric acid acidity in the first pickling tank is N1, the sulfuric acid acidity in the n+1 pickling tank is Nn+1, and the values of N1 to Nn+1 decrease in turn. The total metal ion concentration in the first pickling tank is Me1, the total metal ion concentration in the n+1 pickling tank is Me n+1 , and the value of Me1 is the largest, and the values of Me1 to Me n+1 increase in turn. The Fe n+1 concentration in the first pickling tank is C1, the Fe n+1 concentration in the n+1 pickling tank is Cn+1, and the value of C1 is the largest, and the values of C1 to Cn+1 decrease in turn. 3+ 1-Fe3+ 3+ n+1-Fe3+ n+1-Fe3+ n+1-Fe3+ 1-Fe3+

[0021] Further, in the first pickling tank, the sulfuric acid acidity N1 is less than 200 g / L, the total metal ion concentration Me1 is less than 160 g / L, the Fe 3+ concentration C1 is less than 5 g / L, and preferably C1 is 0.1-1 g / L. 1-Fe3 1-Fe3+

[0022] ​​​​​​​​​Furthermore, in the pickling solution of the (n+1)th pickling tank, the sulfuric acid concentration is 200 < N. n+1 <420g / L, total metal ion concentration Me n+1 <50g / L, Fe 3+ Concentration C n+1-Fe3+ ≥5g / L, C is preferred n+1-Fe3+ It is 25~30g / L.

[0023] Furthermore, the regeneration reactor of this application contains a regenerating agent, which is H2C2O4. Alternatively, the regeneration reactor is a freeze crystallization device, which removes metal sulfate salts through freeze crystallization to achieve regeneration.

[0024] In this application, the pickling fluid flowing out of the regeneration reactor is pickling fluid B, wherein the sulfuric acid concentration in pickling fluid B is >120 g / L, and the total metal ion concentration in pickling fluid B is Me. B , and Me B <50g / L.

[0025] This application employs countercurrent pickling, which makes the oxidized Fe-containing... 3+ The pickling solution flows in reverse, which helps to improve the passivation effect. Simultaneously, after the pickling solution flows out of the first pickling tank, a large amount of Fe... 3+ Consumption converted into Fe 2+ This method can improve the efficiency of acid regenerator use. This application regenerates the waste acid in the first pickling tank by adding oxalic acid to the waste acid solution to precipitate ferrous, nickel, and copper ions into oxalate, thereby reducing the concentration of metal ions in the waste acid and increasing the concentration of sulfuric acid in the pickling solution. In the above regeneration process of this application, sulfuric acid is appropriately added to the first pickling tank to ensure the acidity requirements of the regenerated pickling solution.

[0026] Furthermore, the oxidation reactor described in this application is equipped with an oxidant, which includes one or a combination of two or more of air, oxygen, ozone, hydrogen peroxide or concentrated sulfuric acid, preferably hydrogen peroxide, oxygen or ozone.

[0027] Furthermore, Fe can also be simultaneously provided on the oxidation reactor. 3+ Ion replenishment device, the Fe 3+ The ion replenishment device is equipped with Fe for replenishing the acid washing fluid C. 3+ Fe ions 3+ Ion supplement, the Fe 3+ Ion supplements containing Fe 3+ Salts of ions, such as ferric nitrate and ferric sulfate.

[0028] The pickling fluid flowing out of the oxidation reactor is pickling fluid C, and the pickling fluid C contains Fe. 3+ The concentration is C C-Fe3+ And CC-Fe3+ >5g / L.

[0029] This application involves oxidizing the regenerated pickling solution: by adding oxidizing agents such as hydrogen peroxide or nitric acid, the ferrous ions in the regenerated solution are oxidized to ferric ions, or ferric salts are added to obtain a pickling solution containing high levels of ferric ions, which is then returned to the pickling tank for reuse. The oxidation process described in this application cannot remove all ferrous ions, therefore an oxidation and appropriate supplementation of ferric ions is necessary to ensure sufficient ferric ion concentration to meet the pickling requirements.

[0030] Further, see Figure 2 The countercurrent pickling regeneration oxidation recycling device described in this application also includes a passivation tank, which is located between the n+1th pickling tank and the oxidation vessel. The pickling fluid passes through the oxidation vessel and then through the passivation tank into the n+1th pickling tank.

[0031] In the passivation tank described in this application, the total metal ion concentration is Me. D Me D <Me n+1 Fe 3+ Concentration of C D-Fe3+ And C D-Fe3+ >C n+1-Fe3+ And C D-Fe3+ >10g / L, C is preferred D-Fe3+ >22g / L.

[0032] On the other hand, this application also provides a countercurrent pickling regeneration oxidation recycling method, the process including a stainless steel pickling process and a pickling solution regeneration oxidation countercurrent process, using the aforementioned countercurrent pickling regeneration oxidation recycling device.

[0033] The stainless steel pickling process includes n+1 pickling cycles: the stainless steel to be pickled is sequentially placed into pickling tanks 1 through n+1 for n+1 sulfuric acid pickling cycles, with a pickling temperature of 50~95℃; n is a positive integer greater than or equal to 1. In the pickling solution of the 1st pickling tank, the sulfuric acid concentration N1 < 200 g / L, the total metal ion concentration Me1 < 160 g / L, and the Fe... 3+ Concentration C 1-Fe3 <5g / L, C is preferred. 1-Fe3+ The concentration is 0.1~1 g / L. In the pickling solution of the (n+1)th pickling tank, the sulfuric acid concentration is 200 < N. n+1 <420g / L, total metal ion concentration Me n+1 <50g / L, Fe 3+ Concentration C n+1-Fe3+ ≥5g / L, C is preferred n+1-Fe3+ It is 25~30g / L.

[0034] Furthermore, the sulfuric acid pickling time in the first to the (n+1)th pickling tanks is generally set to decrease progressively. The preferred sulfuric acid pickling time in the first pickling tank is 60-180 seconds. The preferred sulfuric acid pickling time in the (n+1)th pickling tank is 30-90 seconds.

[0035] The specific steps of the pickling solution regeneration oxidation countercurrent process are as follows: (1) The first sulfuric acid pickling tank discharges pickling fluid A, which includes divalent iron ions, divalent nickel ions or divalent copper ions; the sulfuric acid concentration of pickling fluid A is ≤200g / L, or the total metal ion concentration of pickling fluid A is ≥160g / L. (2) Pickling fluid A enters the regeneration kettle and undergoes a regeneration reaction with the regenerating agent H2C2O4 or undergoes freeze crystallization to achieve regeneration, obtaining regenerated pickling fluid B; the sulfuric acid concentration in pickling fluid B is >120 g / L, and the total metal ion concentration Me B <50g / L; (3) The regenerated pickling fluid B enters the oxidation reactor to increase Fe. 3+ The concentration of Fe in the pickling fluid C was determined to obtain the pickling fluid C; 3+ Concentration C C-Fe3+ >5g / L; (4) Pickling fluid C enters the n+1 to 1st pickling tanks to participate in the n+1st sulfuric acid pickling steps, and sulfuric acid is added to the 1st pickling tank; (5) The pickling fluid A that has completed the pickling step re-enters the regeneration tank to complete the process of countercurrent, regeneration and recycling of the pickling solution.

[0036] In this application, the appropriate metal ion concentration is controlled during the oxidation process. As pickling proceeds, the metal ion concentration increases. After regeneration from the first pickling tank, the concentration is kept as close as possible to that of the previous batch of metal ions entering the tank, which helps to ensure stable pickling.

[0037] The process of this application only produces metal oxalate precipitate or metal salt after freeze crystallization, and no longer produces neutralization mud, which greatly reduces the amount of mud. The precipitate or metal salt obtained can be used directly as a valuable product.

[0038] Further, in step (3), the pickling fluid B undergoes an oxidation reaction through the oxidant in the oxidation reactor, causing Fe... 2+ Transformed into Fe 3+ Increase Fe 3+ The concentration. Or, simultaneously through the Fe 3+ Fe in the ion replenishment device 3+ Ion supplements increase Fe 3+ The concentration of Fe. 3+ The ion replenishment device is equipped with Fe for replenishing the acid washing fluid C. 3+ Fe ions3+ Ion supplement, the Fe 3+ Ion supplements containing Fe 3+ Salts of ions, such as ferric nitrate and ferric sulfate.

[0039] Furthermore, the countercurrent pickling regeneration oxidation recycling method further includes the following steps in its stainless steel pickling process: after pickling, the stainless steel enters a passivation tank for passivation reaction, with a passivation temperature T of 30~70℃ and a passivation time of 130~400s, ultimately obtaining bright white stainless steel with a passivation layer. The pickling solution regeneration oxidation countercurrent process also includes the following steps: the pickling fluid C passes through the passivation tank to obtain pickling fluid C', which then enters the (n+1)th pickling tank.

[0040] Example 1 like Figure 1 As shown, a countercurrent pickling, regeneration, oxidation, and recycling device includes a pickling tank and a fluid transfer pump. The device is an external oxidation system for the pickling tank and also includes a regeneration kettle and an oxidation kettle. Fluid transfer pumps are installed between the pickling tank, the regeneration kettle, and the oxidation kettle. The pickling tank is a sulfuric acid pickling tank, and there are n+1 pickling tanks, where n is a positive integer greater than or equal to 1.

[0041] The pickling fluid in the first pickling tank first passes through the regeneration kettle, then through the oxidation kettle, and then enters the (n+1)th pickling tank. It then flows through the nth pickling tank and the (n-1)th pickling tank in sequence until it flows back to the first pickling tank in countercurrent flow, and finally flows back to the regeneration kettle, forming a countercurrent pickling, regeneration, oxidation and recycling system.

[0042] The sulfuric acid concentration in the first pickling tank is N1, and the sulfuric acid concentration in the (n+1)th pickling tank is N. n+1 And N n+1 The values ​​decrease sequentially up to N1. The total metal ion concentration in the first pickling tank is Me1, and the total metal ion concentration in the (n+1)th pickling tank is Me. n+1 And Me1 has the largest value, and Me n+1 The values ​​of Me1 increase sequentially. Fe in the first pickling tank... 3+ Concentration of C 1-Fe3+ Fe in the (n+1)th pickling tank 3+ Concentration of C n+1-Fe3+ And C n+1-Fe3+ The value of C is the largest, and C n+1-Fe3+ To C 1-Fe3+ The values ​​decrease sequentially.

[0043] In the pickling solution of the first pickling tank, the sulfuric acid acidity N1 < 200 g / L, the total metal ion concentration Me1 < 160 g / L, and the Fe... 3+ Concentration C 1-Fe3+ <5g / L. In the pickling solution of the (n+1)th pickling tank, the sulfuric acid acidity is 200 < N. n+1<420g / L, total metal ion concentration Me n+1 <50g / L, Fe 3+ Concentration C n+1-Fe3+ ≥5g / L.

[0044] The regeneration reactor contains a regenerating agent, H₂C₂O₄. The pickling fluid flowing out of the regeneration reactor is pickling fluid B. The sulfuric acid concentration in pickling fluid B is >120 g / L, and the total metal ion concentration in pickling fluid B is Me. B , and Me B <50g / L.

[0045] The oxidation reactor contains an oxidant, which includes one or more of air, oxygen, ozone, hydrogen peroxide, or concentrated sulfuric acid, preferably hydrogen peroxide, oxygen, or ozone. Alternatively, Fe is also provided on the oxidation reactor. 3+ Ion replenishment device, Fe 3+ The ion replenishment device is equipped with Fe for replenishing the acid washing fluid C. 3+ Fe ions 3+ Ion supplements, Fe 3+ Ion supplements containing Fe 3+ Salts of ions. The pickling fluid flowing out of the oxidation reactor is pickling fluid C, and pickling fluid C contains Fe. 3+ The concentration is C C-Fe3+ And C C-Fe3+ >5g / L.

[0046] The stainless steel oxide scale was completely removed after pickling using the countercurrent pickling, regeneration, oxidation, and recycling device described in Example 1, with no residue remaining.

[0047] Example 2 This application discloses a countercurrent pickling, regeneration, oxidation, and recycling device, comprising a pickling tank and a fluid transfer pump. This device is an external oxidation system for the pickling tank, and also includes a regeneration vessel and an oxidation vessel. Fluid transfer pumps are installed between the pickling tank, the regeneration vessel, and the oxidation vessel. The pickling tank is a sulfuric acid pickling tank, n=1, and two pickling tanks are provided.

[0048] The pickling fluid in the first pickling tank first passes through the regeneration kettle, then through the oxidation kettle, and then enters the second pickling tank. It then flows through the second pickling tank in sequence until it flows back to the first pickling tank in the countercurrent flow, and finally flows back to the regeneration kettle, forming a countercurrent pickling, regeneration, oxidation and recycling system.

[0049] The sulfuric acid concentration in the first pickling tank is N1, and the sulfuric acid concentration in the second pickling tank is N2. The total metal ion concentration in the first pickling tank is Me1, and the total metal ion concentration in the (n+1)th pickling tank is Me2. Fe in the first pickling tank... 3+ Concentration of C 1-Fe3+ Fe in the second pickling tank3+ Concentration of C 2-Fe3+ .

[0050] In the pickling solution of the first pickling tank, the sulfuric acid acidity N1 < 200 g / L, the total metal ion concentration Me1 < 160 g / L, and the Fe... 3+ Concentration C 1-Fe3+ <5g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity is 200 < N2 < 420g / L, the total metal ion concentration is Me2 < 50g / L, and Fe... 3+ Concentration C 2-Fe3+ ≥5g / L.

[0051] The regeneration reactor contains a regenerating agent, H₂C₂O₄. The pickling fluid flowing out of the regeneration reactor is pickling fluid B. The sulfuric acid concentration in pickling fluid B is >120 g / L, and the total metal ion concentration in pickling fluid B is Me. B , and Me B <50g / L; The oxidation reactor contains an oxidizing agent, specifically hydrogen peroxide. Fe is also present on the oxidation reactor. 3+ Ion replenishment device, Fe 3+ The ion replenishment device is equipped with Fe for replenishing the acid washing fluid C. 3+ Fe ions 3+ Ion supplements, Fe 3+ Ion supplements containing Fe 3+ Salts of ions. The pickling fluid flowing out of the oxidation reactor is pickling fluid C, and pickling fluid C contains Fe. 3+ The concentration is C C-Fe3+ And C C-Fe3+ >5g / L.

[0052] The countercurrent pickling, regeneration, oxidation, and recycling device of Example 1 was used for pickling. The stainless steel oxide scale was completely removed after pickling, leaving no residue.

[0053] Example 3 like Figure 2 As shown, this embodiment, based on Embodiment 1, further includes a passivation tank. The passivation tank is located between the (n+1)th pickling tank and the oxidation reactor. The pickling fluid passes through the oxidation reactor and then through the passivation tank into the (n+1)th pickling tank. The total metal ion concentration in the passivation tank is Me. D Me D <Me n+1 Fe 3+ Concentration of C D-Fe3+ C D-Fe3+ >C n+1-Fe3+ And C D-Fe3+ >10g / L, C is preferred D-Fe3+ >22g / L.

[0054] The stainless steel surface after pickling and passivation is free of oxide scale residue and has a bright white passivation layer, resulting in excellent surface quality.

[0055] Example 4 The difference between this embodiment and Embodiment 1 is that n=3. The countercurrent pickling, regeneration, oxidation, and recycling device described in Embodiment 4 is used for pickling, resulting in complete removal of the stainless steel oxide scale after pickling, with no residue remaining.

[0056] Example 5 The difference between this embodiment and Embodiment 1 is that n=4. The countercurrent pickling, regeneration, oxidation, and recycling device described in Embodiment 5 is used for pickling, resulting in complete removal of the stainless steel oxide scale after pickling, with no residue remaining.

[0057] Example 6 The difference between this embodiment and Embodiment 1 is that n=5. The countercurrent pickling, regeneration, oxidation, and recycling device described in Embodiment 6 is used for pickling, resulting in complete removal of the stainless steel oxide scale after pickling, with no residue remaining.

[0058] Example 7 Stainless steel sample preparation: Prepare samples with dimensions of... Annealed black stainless steel sheets are processed into sizes using a saw. Small pieces.

[0059] The prepared stainless steel sample was pickled, including a first sulfuric acid pickling and a second sulfuric acid pickling.

[0060] The first sulfuric acid pickling involves immersing the stainless steel to be treated in a first pickling tank, submerging it in the sulfuric acid pickling solution for pickling at a temperature of 50-95°C for 60-180 seconds. The pickling solution in the first pickling tank has a sulfuric acid concentration of N1 = 110 g / L, a total metal ion concentration of Me1 = 100 g / L, and Fe... 3+ Concentration C 1-Fe3+ =0.5g / L.

[0061] The second sulfuric acid pickling involves immersing the stainless steel, which has undergone the first pickling, in a second pickling tank, submerging it in the sulfuric acid pickling solution. The second pickling tank is used for sulfuric acid pickling for 30-90 seconds at a temperature of 50-85°C, until the black oxide scale on the stainless steel surface is completely removed, yielding the pickled stainless steel. The pickling solution in the second pickling tank has a sulfuric acid concentration of N2 = 400 g / L, a total metal ion concentration of Me2 = 30 g / L, and a Fe content of [missing information]. 3+ Concentration C 2-Fe3+ =20g / L.

[0062] After pickling, rinse the stainless steel with plenty of water, then rinse repeatedly with plenty of deionized water, then rinse with alcohol, and finally dry it with a hair dryer. Pack it into a resealable bag for later use.

[0063] The pickling solution regeneration oxidation countercurrent process specifically includes the following steps: (1) Pickling fluid A is discharged from the first pickling tank. Pickling fluid A includes ferrous ions, nickel ions, or copper ions. The sulfuric acid concentration of pickling fluid A is ≤50g / L, or the total metal ion concentration is ≥160g / L; (2) Pickling fluid A enters the regeneration kettle and reacts with regenerating agent H2C2O4 to obtain regenerated pickling fluid B and metal sludge; (3) The regenerated pickling fluid B enters the oxidation reactor to increase Fe. 3+ The concentration of the pickling fluid C was determined to obtain the pickling fluid C. (4) The pickling fluid C eventually enters the second pickling tank to participate in the second sulfuric acid pickling step. After the second sulfuric acid pickling, the pickling fluid D is obtained. (5) Pickling fluid D flows back into the first pickling tank to participate in the first sulfuric acid pickling step. Pickling fluid A, which has completed the pickling step, enters the regeneration tank again to complete the process of backflow, regeneration and recycling of pickling solution.

[0064] After pickling, the oxide scale on the stainless steel completely falls off, leaving no residue.

[0065] Example 8 Based on Example 7, in step (3) of the pickling solution regeneration oxidation countercurrent process, the oxidation vessel is equipped with a hydrogen peroxide oxidant, and Fe is simultaneously placed on the oxidation vessel. 3+ Ion replenishment device, Fe 3+ The ion replenishment device is equipped with Fe for replenishing the acid washing fluid C. 3+ Ferric sulfate supplements for ions, supplementing Fe 3+ After ionization, it enters the second pickling tank.

[0066] After pickling, the oxide scale on the stainless steel completely falls off, leaving no residue.

[0067] Example 9 Based on Example 8, this embodiment further includes the following steps in the stainless steel pickling process: after pickling, the stainless steel enters a passivation tank for passivation reaction. The passivation temperature T is 62℃, and the passivation time is 180s, ultimately yielding bright white stainless steel with a passivation layer and no oxide scale residue, resulting in good stainless steel plate surface quality. The pickling solution regeneration oxidation countercurrent process further includes the following steps: the pickling fluid C passes through the passivation tank, and C in the passivation tank... 3-Fe3+ =15g / L, to obtain pickling fluid C', which then enters the second pickling tank.

[0068] Example 10 The difference between this embodiment and Embodiment 9 is that in the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 80 g / L, the total metal ion concentration Me1 = 120 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =3g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 410g / L, the total metal ion concentration Me2 = 25g / L, and Fe... 3+ Concentration C 2-Fe3+ =20g / L. C in the passivation tank 3-Fe3+ =22g / L.

[0069] After pickling and passivation, the stainless steel surface has no oxide scale residue, and the passivation layer is bright white, resulting in excellent surface quality.

[0070] Example 11 Based on Example 9, this embodiment further includes the following steps in the pickling solution regeneration oxidation countercurrent process: the pickling fluid C passes through Fe... 3+ The ion replenishment device supplements Fe by adding ferric nitrate. 3+ After ionization, it enters the passivation tank.

[0071] In the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 100 g / L, the total metal ion concentration Me1 = 80 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =0.8g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 350g / L, the total metal ion concentration Me2 = 15g / L, and Fe... 3+ Concentration C 2-Fe3+ =25g / L. The passivation reaction was carried out in a passivation tank at a passivation temperature of 65℃ and a passivation time of 150s.

[0072] After pickling and passivation, the stainless steel surface has no oxide scale residue, and the passivation layer is bright white, resulting in excellent surface quality.

[0073] Example 12 The difference between this embodiment and embodiment 11 is that the passivation reaction is carried out in the passivation tank, the passivation temperature T is 55°C, and the passivation time is 300s.

[0074] After pickling and passivation, the stainless steel surface has no oxide scale residue, and the passivation layer is bright white, resulting in excellent surface quality.

[0075] Example 13 The only difference between Example 13 and Example 1 is that the regeneration vessel is a cryogenic crystallization device. The regeneration vessel, acting as a crystallization vessel, has chilled water circulating through its jacket for cooling and solid-phase crystallization. Filtration separates the solid and liquid phases, yielding ferrous sulfate heptahydrate as granular crystals, a valuable product; while the outflowing pickling fluid is pickling fluid B.

[0076] Comparative Example 1 The difference between this comparative example and Example 8 is that in the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 350 g / L, the total metal ion concentration Me1 = 180 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =12g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 280g / L, the total metal ion concentration Me2 = 200g / L, and Fe... 3+ Concentration C 2-Fe3+ =3g / L.

[0077] Even with a 5-minute extension of the pickling time, the oxide scale on the stainless steel after pickling cannot be completely removed, leaving a significant amount of residue and affecting the regeneration and recycling process of the pickling solution.

[0078] Comparative Example 2 The difference between this comparative example and Example 10 is that in the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 400 g / L, the total metal ion concentration Me1 = 180 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =7g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 280g / L, the total metal ion concentration Me2 = 200g / L, and Fe... 3+ Concentration C 2-Fe3+ =2g / L.

[0079] Even with a 5-minute extension of the pickling time, the oxide scale on the stainless steel after pickling cannot be completely removed, leaving a significant amount of residue and affecting the regeneration and recycling process of the pickling solution.

[0080] Comparative Example 3 The difference between this comparative example and Example 11 is that in the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 350 g / L, the total metal ion concentration Me1 = 200 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =15g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 300g / L, the total metal ion concentration Me2 = 230g / L, and Fe... 3+ Concentration C 2-Fe3+ =1g / L. C in the passivation tank 3-Fe3+ =0.3g / L.

[0081] The oxide scale on stainless steel after pickling and passivation cannot be completely removed, and a bright white and dense passivation film cannot be formed, which also affects the regeneration and recycling process of the pickling solution.

[0082] Comparative Example 4 The difference between this comparative example and Example 12 is that in the pickling solution of the first pickling tank, the sulfuric acid acidity N1 = 360 g / L, the total metal ion concentration Me1 = 200 g / L, and the Fe... 3+ Concentration C 1-Fe3+ =6g / L. In the pickling solution of the second pickling tank, the sulfuric acid acidity N2 = 310g / L, the total metal ion concentration Me2 = 300g / L, and Fe... 3+ Concentration C 2-Fe3+ =0.5g / L. The passivation reaction was carried out in a passivation tank at a passivation temperature T of 90℃ for 90s.

[0083] The oxide scale on stainless steel after pickling and passivation cannot be completely removed, and a bright white and dense passivation film cannot be formed, which also affects the regeneration and recycling process of the pickling solution.

[0084] The countercurrent pickling, regeneration, oxidation, and recycling apparatus and method described in this application include n+1 sulfuric acid pickling tanks and a fluid transfer pump, as well as a regeneration kettle and an oxidation kettle. The pickling fluid in the first pickling tank first passes through the regeneration kettle, then the oxidation kettle, and then enters the (n+1)th pickling tank. It then flows sequentially through the nth pickling tank and the (n-1)th pickling tank until it flows back countercurrently to the first pickling tank, and finally returns to the regeneration kettle. Regeneration is achieved through reagent regeneration or low-temperature crystallization, forming a countercurrent pickling, regeneration, oxidation, and recycling system. Using this application for stainless steel countercurrent pickling and passivation allows for complete recycling of the pickling solution, significantly reducing acid sludge and pickling costs, and producing no NO. X Harmful gases such as SiF4 gas are generated.

[0085] The countercurrent pickling regeneration oxidation recycling device and method described in this application can not only completely solve the NO problem in the mixed acid pickling process. X This invention addresses environmental pollution issues and can also improve the surface quality of pickled surfaces. The regenerated pickling solution is oxidized in a separate oxidation reactor, converting low-valence ions into high-valence ions, while simultaneously improving the Fe content of the oxidized solution. 3+ The pickling solution flows in the opposite direction, which not only accelerates the pickling process but also provides a passivation effect. On the other hand, after the pickling solution flows out of the first pickling tank, a large amount of Fe... 3+ Consume and transform into Fe 2+This process improves the efficiency of acid regenerator utilization. The entire process significantly reduces surface roughness and iron loss. Furthermore, since the volatile oxidant is not carried into the pickling tank, the problem of oxidant volatilization at high pickling temperatures is avoided. In addition, the method and process used in this application no longer generate neutralization sludge, greatly reducing the amount of sludge. Moreover, it allows for overall recycling and reuse, comprehensively reducing pickling costs.

Claims

1. A reverse flow pickling regeneration oxidation recycling device, comprising: n+1 pickling tanks of sulfuric acid, fluid delivery pumps, a regeneration kettle and an oxidation kettle; wherein n is a positive integer; wherein the outlet of the first pickling tank is connected to the inlet of the regeneration kettle through the fluid delivery pump; the outlet of the regeneration kettle is connected to the inlet of the oxidation kettle through the fluid delivery pump; the outlet of the oxidation kettle is connected to the inlet of the n+1 pickling tank through the fluid delivery pump; each pickling tank is reversely connected through a pipeline: the outlet of the n+1 pickling tank→the inlet of the n pickling tank→…→the outlet of the 2 pickling tank→the inlet of the 1 pickling tank; The first pickling tank is provided with an acid feeding port for supplementing sulfuric acid at the inlet; the sulfuric acid concentration of the pickling solution in the first pickling tank is N1 < 200 g / L, the total metal ion concentration Me1 < 160 g / L, and the Fe 3+ concentration C 1-Fe3+ < 5 g / L; The regeneration kettle is provided with an oxalic acid charging port; the pickling fluid B flowing out of the regeneration kettle satisfies: sulfuric acid acidity N B >120g / L, total metal ion concentration Me B <50g / L; The oxidation kettle is provided with an oxidant injection port and Fe 3+ The ion supplementing device; the pickling fluid C flowing out of the oxidation kettle satisfies: Fe 3+ Concentration C C-Fe3+ >5g / L; the sulphuric acid acidity N of the pickling liquor in the (n+1)th pickling tank n+1 is 200-420 g / L, the total metal ion concentration Me n+1 <50 g / L, Fe 3+ concentration C n+1-Fe3+ ≥ 5 g / L.

2. The reverse flow pickling regeneration oxidation recycling apparatus according to claim 1, characterized by, the oxidizing agent is selected from one of hydrogen peroxide, oxygen or ozone.

3. The reverse flow pickling regenerative oxidation recycling device according to claim 1, characterized by, The Fe 3+ The ion supplementing device contains ferric sulfate or ferric nitrate.

4. The reverse flow pickling regenerative oxidation recycling device according to claim 1, characterized by, The C 1-Fe3+ is 0.1-1 g / L.

5. The reverse flow pickling regenerative oxidation recycling device according to claim 1, characterized by, The C n+1-Fe3+ is 25-30 g / L.

6. The reverse flow pickling regenerative oxidation recycling device according to claim 1, characterized by, a passivation tank is further included; the passivation tank is arranged between the outlet of the oxidation kettle and the inlet of the n+1 pickling tank; Fe concentration of the pickling fluid in the passivation tank 3+ C D-Fe3+ greater than 10 g / L and greater than C n+1-Fe3+ total metal ion concentration is lower than the (n+1)th pickling tank.

7. The reverse flow pickling regenerative oxidation recycling device according to claim 1, characterized by, the pickling time of the 1st to n+1st pickling tanks of sulfuric acid is arranged in a decreasing manner.

8. A reverse flow pickling regeneration oxidation recycling method characterized by, The reverse flow pickling regeneration oxidation recycling device according to any one of claims 1 to 7 is used, comprising the following steps: when the sulfuric acid concentration of the pickling liquid in the 1st pickling tank is ≤200 g / L or the total metal ion concentration is ≥160 g / L, it is pumped into the regeneration kettle as pickling fluid A; In the regeneration kettle, oxalic acid H2C2O4 is added to precipitate Fe 2+ , Ni 2+ and Cu 2+ as oxalate, and after solid-liquid separation, an acid pickling fluid B is obtained, with sulfuric acid acidity > 120 g / L and total metal ion concentration < 50 g / L; Pump acid wash fluid B into the oxidation kettle, add Fe 2+ to the oxidation kettle 3+ ; or simultaneously add Fe 3+ ion supplements to the oxidation kettle, so that the Fe 3+ concentration in the effluent acid wash fluid C is > 5 g / L pickling fluid C is pumped into the n+1st pickling tank, and then sequentially flows reversely through the nth, …, 1st pickling tanks; sulfuric acid is supplemented to the inlet of the 1st pickling tank to maintain the sulfuric acid concentration in the tank at <200 g / L; when the pickling fluid discharged from the 1st pickling tank again satisfies the condition of sulfuric acid concentration ≤200 g / L or total metal ion concentration ≥160 g / L, it is returned to the regeneration kettle as the pickling fluid A of a new round to realize closed circulation.

9. The reverse flow pickling regenerative oxidation cycle utilization method as claimed in claim 8, characterized by, Before pumping pickling fluid C into the n+1st pickling tank, further comprising: The pickling fluid C from the oxidation kettle is first pumped into the passivation tank, and is allowed to stay at 30-70°C for 130-400 s, so that Fe 3+ The concentration is increased to more than 10 g / L and more than C n+1-Fe3+ , to obtain pickling fluid C'; then the pickling fluid C' is pumped into the nth+1 pickling tank.

10. The reverse flow pickling regenerative oxidation cycle utilization method according to claim 8, characterized by, further comprising: stainless steel workpieces are sequentially pickled in the 1st to n+1st pickling tanks, and the pickling time of each tank is arranged in a decreasing manner.

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