Recovery treatment process of hot-dip galvanized steel

Abstract

The invention discloses a recovery treatment process for hot-dip galvanized steel. The recovery treatment process comprises the steps of pretreatment, dezincification treatment, rinsing treatment, continuous impurity removal treatment and evaporation treatment. The recovery treatment process for the hot-dip galvanized steel provided by the invention belongs to a short-process special process for inhibiting iron, dissolving zinc and not introducing non-zinc ions; the complete separation of a zinc coating on the surface of the hot-dip galvanized steel and the preparation of zinc chloride crystals with the zinc chloride content of not less than 95% and the iron content of 0.05-0.2% are realized through the synergistic effect of all treatment steps and parameter control; and no zinc residue is left on the surface of the hot-dip galvanized steel after dezincification, the quality reliability and stability of a steel matrix as foundry returns are guaranteed, and various defects and problems caused by the fact that traditional hot-dip galvanized steel enters furnace charges at present are solved.

Description

Technical Field

[0001] The present application relates to the field of recycling and utilization of hot-dip galvanized steel materials, and in particular to a recycling process of hot-dip galvanized steel. Background Art

[0002] For steel materials, hot-dip galvanizing is still a relatively effective and economical protective measure. Although the steel industry continues to innovate and develop, the service life of early-service steel is coming to an end. Currently, hundreds of millions of tons of scrap steel are generated each year, of which hot-dip galvanized scrap steel accounts for an increasing proportion year by year and shows a clear trend of increasing. Hot-dip galvanized steel contains iron and zinc, and its recycling has significant economic and environmental benefits. At present, the recycling process of hot-dip galvanized steel is treated the same as scrap steel. After being packaged and pressed into blocks, it is handed over to steel companies as a furnace charge to enter the steel smelting process. Production practice has proved that the zinc brought in by hot-dip galvanized steel is easily enriched in the blast furnace, causing nodules, which has a certain impact on production. Part of the zinc eventually becomes smoke dust - zinc-containing smoke dust.

[0003] In order to effectively recycle and utilize zinc resources, people have conducted extensive research on galvanized steel and zinc-containing dust over the years, and proposed pyrolysis dezincification, distillation under air or vacuum, inert gas, reducing atmosphere, alkali leaching-electrolysis recovery, etc. These methods are mainly based on pyrolysis distillation or alkali leaching-electrolysis, and have problems such as long processing flow, high cost, and complex process. Some are passive terminal treatment methods for zinc-containing dust.

[0004] The patent application with publication number CN111733333A discloses a method for dezincifying galvanized scrap steel, which involves introducing inert gas into a rotary kiln and heating to 900-1050°C for pyro-dezincification. This technical solution can achieve zinc separation to a certain extent, but has the defects of high energy consumption and low efficiency, making it difficult to meet the requirements of large-scale processing. At the same time, the separated zinc still contains other metal impurities that need to be further separated.

[0005] The patent application with publication number CN218507876U discloses a device for recycling zinc from galvanized scrap steel and zinc-containing materials. In essence, it discloses a device for crushing galvanized scrap steel, which can crush large-sized galvanized steel and improve the efficiency of pyro-desizining. In essence, it still belongs to traditional pyro-desizining.

[0006] The patent application with publication number CN113909255A discloses a galvanized scrap steel dezincification device, the core technology of which is to further crush the crushed galvanized scrap steel by stirring; its essence is to improve the crushing device of galvanized scrap steel before pyrometallurgical dezincification.

[0007] The patent application with publication number CN107500340A discloses a method for recycling zinc in galvanized scrap steel and zinc-containing materials. Its technical solution is to first pickle the galvanized scrap steel and zinc-containing materials, add hydrogen peroxide for oxidation, and add strong alkali to remove impurities; add sodium carbonate solution to precipitate zinc carbonate; then add sodium hydroxide solution to precipitate zinc hydroxide; and roast the precipitated zinc carbonate or zinc hydroxide to obtain high-purity active zinc oxide. Its core technology belongs to the acid-washing and alkali-leaching method in principle. The consumption of strong acid and strong alkali in the treatment process is large, and the process flow is long, which poses great difficulties in terms of treatment cost and quality control. Summary of the invention

[0008] The purpose of the invention is to provide a hot-dip galvanized steel recycling process, which can realize the wet short-process recycling of hot-dip galvanized steel and realize the complete recycling of zinc in the hot-dip galvanized steel.

[0009] Technical solution: The hot-dip galvanized steel recycling process of the present invention comprises the following steps:

[0010] Step 1, pre-treatment to remove dust and dirt from the surface of hot-dip galvanized steel in a cleaning tank;

[0011] Step 2, performing a dezincification treatment, using a dezincification liquid in a dezincification tank to dissolve the zinc layer on the surface of the pre-treated hot-dip galvanized steel and separate it from the steel matrix;

[0012] Step 3, performing a rinsing treatment to remove residual zinc ions and iron ions on the surface of the steel substrate after the dezincification treatment in a rinsing tank to obtain a recovered steel substrate;

[0013] Step 4, performing continuous impurity removal treatment, when the zinc ion content of the dezincifying liquid in the dezincifying tank is greater than the set zinc content threshold, performing continuous oxidation precipitation, first filtration, zinc powder reduction and second filtration treatment on the dezincifying liquid;

[0014] Step 5, performing evaporation treatment, performing evaporation treatment on the dezincification liquid after continuous impurity removal treatment, and obtaining zinc chloride crystals with a zinc chloride mass content greater than or equal to 95% and an iron mass content of 0.05% to 0.2%.

[0015] Furthermore, in step 1, during pretreatment, the cleaning liquid in the cleaning tank uses an alkaline cleaning liquid with a pH value of 9 to 10, and ultrasonic cleaning is used to assist in surface cleaning of the hot-dip galvanized steel. After the surface cleaning, the hot-dip galvanized steel is rinsed with clean water in the first rinsing tank.

[0016] Furthermore, the alkaline cleaning solution in the cleaning tank is prepared by industrial caustic soda flakes, and the cleaning time of the hot-dip galvanized steel in the cleaning tank is 3 to 8 minutes.

[0017] Furthermore, in step 2, when the dezincification treatment is performed, the dezincification liquid in the dezincification tank is a hydrochloric acid pickling liquid to which hexamethylenetetramine is added, the mass percentage of hexamethylenetetramine in the hydrochloric acid pickling liquid is 0.8-2%, and the initial pH value of the dezincification liquid is ≤5.

[0018] Furthermore, two dezincification tanks are provided and used alternately; when the pH value of the dezincification liquid in the dezincification tank is greater than 5, industrial hydrochloric acid is added to adjust the pH value of the dezincification liquid so that the pH value is maintained at a pH value ≤ 5.

[0019] Furthermore, in step 3, during the rinsing treatment, the steel substrate is rinsed for the first time in the second rinsing tank using flowing rinsing water, and then enters the third rinsing tank for the second rinse using rinsing water.

[0020] Furthermore, in step 4, when performing continuous impurity removal treatment, the zinc content threshold is set to 185 g / L, that is, when the zinc ion content of the dezincifying liquid in the dezincifying tank is 185 g / L-195 g / g / L, the dezincifying liquid is subjected to continuous oxidation precipitation, first filtration, zinc powder reduction and second filtration treatment.

[0021] Furthermore, in step 4, the oxidation precipitation treatment is to pump the dezincification liquid into the oxidation tank, add hydrogen peroxide for oxidation and assist in stirring, and then let it stand for precipitation; the first filtration treatment is to filter the dezincification liquid for the first time after standing for precipitation and pour it into the zinc powder reduction tank; the zinc powder reduction treatment is based on the volume of the dezincification liquid in the reduction tank according to 30g~80g / m 3 The zinc powder addition amount is to add zinc powder and assist in stirring, and then let it stand and settle; the second filtration treatment is to filter the dezincification liquid for the second time after standing and settling and pour it into the tank.

[0022] Furthermore, the pH value of the dezincification liquid in the oxidation tank is 3.5-4, and the pH value is adjusted by using hydrogen peroxide or hydrochloric acid so that the pH value of the dezincification liquid is maintained within the range of 3.5-4.

[0023] Furthermore, in step 5, during the evaporation treatment, the dezincification liquid is kept at 260° C. to 300° C. in an evaporator for 4 to 6 hours for evaporation treatment.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the hot-dip galvanized steel recovery and treatment process proposed in the present invention adopts a wet dezincification and continuous impurity removal process, has a short process of obvious iron suppression, zinc dissolution and no non-zinc ion introduction, and the synergistic effect of each step and parameter control realizes the complete separation of the zinc coating on the surface of the hot-dip galvanized steel and the acquisition of high-content zinc chloride crystals; while realizing the short-process separation of zinc and iron, it realizes the direct recycling of zinc resources, and achieves no zinc residue on the surface of the hot-dip galvanized steel after dezincification, ensuring the quality reliability and stability of the steel matrix as a return material. However, the traditional hot-dip galvanized steel is usually used as a furnace charge to enter the steel smelting process after being discarded, and the zinc evaporation and nodulation therein not only affect the safety of the blast furnace, but also cause a waste of zinc resources; for the collected zinc-containing smoke, the traditional pyrochlorination and electrolysis methods not only have a long process, but also a low effective recovery rate of zinc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0026] The embodiments of the present application will be described in more detail below with reference to examples. Although the embodiments of the present application are shown in the examples, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and the scope of the present application can be fully communicated to those skilled in the art.

[0027] It should be noted that the relevant detection equipment and methods involved in this application are specifically as follows, which can be fully understood by those skilled in the art:

[0028] The content of zinc chloride in the dezincification solution was determined by EDTA titration. The measurement method was carried out according to the method of "Determination of zinc chloride in a mixed solution of zinc chloride and ammonium chloride in a plating aid" on pages 387-388 of the document "Steel Pipe Hot-Dip Galvanizing Technology" (edited by Miao Lixian and Wang Lihong, Steel Pipe Hot-Dip Galvanizing Technology, Chemical Industry Press, October 2015).

[0029] The content of zinc chloride and iron in zinc chloride crystals was analyzed using ICPS-1000Ⅱ inductively coupled plasma emission spectrometer (ICP-AES) from Shimadzu, Japan. During the test, a certain amount of zinc chloride crystals were completely dissolved in analytical pure dilute hydrochloric acid solution, and the concentration of zinc ions and iron ions in the test solution was detected by ICP-AES. The content of zinc chloride and iron in zinc chloride crystals was calculated.

[0030] The galvanizing thickness of hot-dip galvanized steel is tested using a magnetic thickness gauge. Randomly select test samples from the same batch of hot-dip galvanized steel, measure 5 different points on the surface of the sample coating, and calculate the average value. Refer to GB / T4956-2003 "Magnetic method for measuring the thickness of non-magnetic coatings on magnetic metal substrates".

[0031] Use a commercially available pH test pen to test the pH value of the solution.

[0032] like Figure 1 As shown, the recycling process of hot-dip galvanized steel disclosed in the present invention comprises the following steps:

[0033] Step 1, pretreatment, removing dust and dirt on the surface of the hot-dip galvanized steel in a cleaning tank, the cleaning liquid in the cleaning tank adopts an alkaline cleaning liquid with a pH value of 9 to 10, and ultrasonic cleaning is used to clean the surface of the hot-dip galvanized steel, and after the surface cleaning, the hot-dip galvanized steel is rinsed with clean water in a first rinsing tank, the alkaline cleaning liquid in the cleaning tank is prepared by industrial caustic soda, and the cleaning time of the hot-dip galvanized steel in the cleaning tank is 3 to 8 minutes;

[0034] Step 2, performing a dezincification treatment, using a dezincification liquid in a dezincification tank to dissolve the zinc layer on the surface of the pretreated hot-dip galvanized steel from the steel matrix, the dezincification liquid is a hydrochloric acid pickling solution to which hexamethylenetetramine is added, the mass percentage of hexamethylenetetramine in the hydrochloric acid pickling solution is 0.8-2%, the initial pH value of the dezincification liquid is ≤5, two dezincification tanks are provided, and the two dezincification tanks are used alternately, and when the pH value of the dezincification liquid in the dezincification tank is greater than 5, industrial hydrochloric acid is added for adjustment, so that the pH value of the dezincification liquid is maintained at a pH value of ≤5;

[0035] Step 3, performing a rinsing treatment, removing the zinc ions and iron ions remaining on the surface of the steel substrate after the dezincification treatment in a rinsing tank to obtain a recovered steel substrate, two rinsing tanks are provided, the steel substrate is rinsed for the first time in the second rinsing tank using flowing rinsing water, and then enters the third rinsing tank for a second rinse using rinsing water;

[0036] Step 4, performing continuous impurity removal treatment, when the zinc ion content of the dezincifying liquid in the dezincifying tank is greater than the set zinc content threshold, the dezincifying liquid is subjected to continuous oxidation precipitation, first filtration, zinc powder reduction and second filtration treatment, the zinc content threshold is 185g / L, the oxidation precipitation treatment is to pump the dezincifying liquid into the oxidation tank, add hydrogen peroxide for oxidation and assist in stirring, and then let it stand for precipitation; the first filtration treatment is to filter the dezincifying liquid for the first time after standing for precipitation and pour the trough into the zinc powder reduction tank; the zinc powder reduction treatment is to filter the dezincifying liquid according to the volume of the dezincifying liquid in the reduction tank according to 30g~80g / m 3The amount of zinc powder added is to add zinc powder and assist in stirring, and then let it stand for precipitation; the second filtration treatment is to filter the dezincification liquid for the second time after standing for precipitation and pour it into the trough, the pH value of the dezincification liquid in the oxidation tank is 3.5-4, and the pH value is adjusted by hydrogen peroxide or hydrochloric acid to maintain the pH value of the dezincification liquid within 3.5-4;

[0037] Step 5, performing evaporation treatment, performing evaporation treatment on the dezincification liquid after the continuous impurity removal treatment, specifically, keeping the dezincification liquid in an evaporator at a temperature of 260° C. to 300° C. for 4 to 6 hours for evaporation treatment, and obtaining zinc chloride crystals with a zinc chloride mass content greater than or equal to 95% and an iron mass content of 0.05% to 0.2%.

[0038] Embodiment 1:

[0039] The categories of hot-dip galvanized steel to be recycled are: hot-dip galvanized steel guardrail plates, material Q235B, and the average thickness of the galvanized layer is 109μm.

[0040] Step 1: pre-treat, immerse 3 tons of guardrail panels in a batch in a cleaning tank at room temperature, the pre-treatment solution in the cleaning tank is an alkaline solution with a pH value of 9, and after ultrasonic-assisted cleaning for 3 minutes, immerse the guardrail panels in the first rinsing tank for rinsing;

[0041] Step 2, performing dezincification treatment, immersing the guardrail board treated in step 1 into a dezincification solution prepared by hydrochloric acid, wherein the initial pH value of the dezincification solution is not greater than 1, and a hexamethylenetetramine corrosion inhibitor with a mass fraction of 0.8% is added to the dezincification solution, and the dezincification time is extended by 3 minutes when bubbles visible to naked eyes just disappear on the surface of the guardrail board;

[0042] The guardrail boards are made into batches of 3 tons. After 16 batches, the pH value of the dezincification liquid is 5.1. Industrial hydrochloric acid is added to the dezincification liquid to adjust the pH value of the dezincification liquid to 1.0.

[0043] After 39 batches, the dezincification solution was tested and the zinc ion content in the dezincification solution was 190 g / L;

[0044] Step 3, performing a rinsing treatment, immersing the guardrail board after the dezincification in step 2 into a second rinsing tank at room temperature for a first rinse with flowing rinsing water, and then immersing it into a third rinsing tank for a second rinse with rinsing water, and the rinsed guardrail board is packaged and briquetted, and stored for sale;

[0045] Step 4: Continuous impurity removal treatment is performed. The dezincification liquid in the dezincification tank after the 39th batch in step 2 is pumped into the oxidation tank. The pH of the dezincification liquid is adjusted to 3.5 with industrial hydrochloric acid. Hydrogen peroxide is added to the oxidation tank and stirred. Then, the solution is allowed to settle. The solution is filtered and poured into the reduction tank at a rate of 30 g / m 3 Add zinc powder and stir it, then let it settle, filter the dezincification solution and pour it into a storage tank for later use;

[0046] Step 5, performing evaporation treatment, pumping the dezincification liquid in the storage tank treated in step 4 into an evaporator, keeping the temperature at 260° C. for 6 hours, and obtaining zinc chloride crystals after cooling; taking a certain amount of zinc chloride crystals, dissolving them in analytical grade dilute hydrochloric acid, and performing ICP-AES detection and calculation. The zinc chloride content in the zinc chloride crystals is 96.01%, and the iron content in the zinc chloride crystals is 0.05%.

[0047] 1 kg of the guardrail board after rinsing in step 3 was cut and completely dissolved with analytical pure hydrochloric acid. The zinc content in the guardrail board was detected and calculated by ICP-AES. The content was 1.1×10 -7 g.

[0048] Embodiment 2:

[0049] Types of hot-dip galvanized steel to be recycled: hot-dip galvanized steel guardrail posts, material Q235B, average thickness of the galvanized layer 97.5μm.

[0050] Step 1, pre-treatment, immerse 2 tons of columns in a batch in a cleaning tank at room temperature, the pre-treatment liquid in the cleaning tank is an alkaline solution with a pH value of 10, and after ultrasonic-assisted cleaning for 8 minutes, immerse the columns in the first rinsing tank for rinsing;

[0051] Step 2, performing dezincification treatment, immersing the column treated in step 1 in a dezincification solution prepared by hydrochloric acid, the initial pH value of the dezincification solution is ≤1, and a hexamethylenetetramine corrosion inhibitor with a mass fraction of 2% is added to the dezincification solution, and the dezincification time is extended by 6 minutes when bubbles visible to naked eyes just disappear on the surface of the column;

[0052] The columns are set up in batches of 2 tons. After 30 batches, the pH value of the dezincification liquid is tested to be 5.7. Industrial hydrochloric acid is added to the dezincification liquid to adjust the pH value of the dezincification liquid to 1.0.

[0053] After 47 batches, the dezincification solution was tested and the zinc ion content in the dezincification solution was 187 g / L;

[0054] Step 3, performing a rinsing treatment, immersing the column after dezincification in step 2 into a second rinsing tank at room temperature for a first rinse with flowing rinsing water, and then immersing it into a third rinsing tank for a second rinse with rinsing water, and the rinsed columns are packaged and briquetted, and stored for sale;

[0055] Step 4: Continuous impurity removal treatment is performed. The dezincification liquid in the dezincification tank after the 47th batch in step 2 is pumped into the oxidation tank. The pH of the dezincification liquid is adjusted to 4.5 with industrial hydrochloric acid. Hydrogen peroxide is added to the oxidation tank and stirred. Then, the solution is allowed to settle. The solution is filtered and poured into the reduction tank at a rate of 50 g / m 3 Add zinc powder and stir it, then let it settle, filter the dezincification solution and pour it into a storage tank for later use;

[0056] Step 5, performing evaporation treatment, pumping the dezincification liquid treated in step 4 into an evaporator, keeping the temperature at 280° C. for 7 hours, and obtaining zinc chloride crystals after cooling; taking a certain amount of zinc chloride crystals, dissolving them in analytical pure dilute hydrochloric acid, and performing ICP-AES detection and calculation. The content of zinc chloride in the zinc chloride crystals is 95.37%, and the content of iron in the zinc chloride crystals is 0.13%.

[0057] Step 3: After rinsing, 1 kg of the column was cut and dissolved with analytically pure hydrochloric acid. The zinc content in the column was detected and calculated by ICP-AES. The content was 1.9×10 -6 g.

[0058] Embodiment 3:

[0059] Types of hot-dip galvanized steel to be recycled: hot-dip galvanized disc-type scaffolding uprights, material Q355, average thickness of the galvanized layer 78μm.

[0060] Step 1, pre-treatment, immersing 3 tons of scaffolding poles in a batch into a cleaning tank at room temperature, the pre-treatment liquid in the cleaning tank is an alkaline solution with a pH value of 9.5, and after ultrasonic-assisted cleaning for 7 minutes, the scaffolding poles are immersed in the first rinsing tank for rinsing;

[0061] Step 2, performing dezincification treatment, immersing the scaffolding pole treated in step 1 into a dezincification solution prepared by hydrochloric acid, wherein the initial pH of the dezincification solution is ≤1, and a hexamethylenetetramine corrosion inhibitor with a mass fraction of 1.5% is added to the dezincification solution, and the dezincification time is extended by 8 minutes until the bubbles visible to naked eyes just disappear on the surface of the scaffolding pole;

[0062] The scaffolding poles are made into a batch of 3 tons. After 20 batches, the pH value of the dezincification liquid is 5.3. Industrial hydrochloric acid is added to the dezincification liquid to adjust the pH value of the dezincification liquid to 1.0.

[0063] After 32 batches, the dezincification solution was tested and the zinc ion content in the dezincification solution was 191 g / L;

[0064] Step 3, performing a rinsing treatment, immersing the scaffolding poles after dezincification in step 2 into a second rinsing tank at room temperature for a first rinse with flowing rinsing water, and then immersing them into a third rinsing tank for a second rinse with rinsing water, and the rinsed scaffolding poles are packaged and briquetted, and stored for sale;

[0065] Step 4: Continuous impurity removal treatment is performed. The dezincification liquid in the dezincification tank after the 32nd batch in step 2 is pumped into the oxidation tank. The pH of the dezincification liquid is adjusted to 4 with industrial hydrochloric acid. Hydrogen peroxide is added to the oxidation tank and stirred. Then, the solution is allowed to settle. The solution is filtered and poured into the reduction tank at a rate of 60 g / m 3 Add zinc powder and stir it, then let it settle, filter the dezincification solution and pour it into a storage tank for later use;

[0066] Step 5, performing evaporation treatment, pumping the dezincification liquid treated in step 4 into an evaporator, keeping the temperature at 290° C. for 5.5 hours, and obtaining zinc chloride crystals after cooling; taking a certain amount of zinc chloride crystals, dissolving them in analytical grade dilute hydrochloric acid, and performing ICP-AES detection and calculation. The content of zinc chloride in the zinc chloride crystals is 95.91%, and the content of iron in the zinc chloride crystals is 0.085%.

[0067] Step 3: Cut and take 1 kg of the rinsed scaffolding poles, dissolve them in analytical pure hydrochloric acid, and detect and calculate them by ICP-AES. The zinc content in the scaffolding poles is 3.4×10 -7 g.

[0068] Embodiment 4:

[0069] Types of hot-dip galvanized steel to be recycled: hot-dip galvanized angle steel for power towers, material Q235, average thickness of galvanized layer 116μm. Step 1: pre-treat, immerse 4 tons of angle steel in a cleaning tank at room temperature, the pre-treatment liquid in the cleaning tank is an alkaline solution with a pH value of 9.0, and after ultrasonic-assisted cleaning for 4 minutes, immerse the angle steel in the first rinsing tank for rinsing;

[0070] Step 2, performing dezincification treatment, immersing the angle steel treated in step 1 in a dezincification solution prepared by hydrochloric acid, wherein the initial pH of the dezincification solution is ≤1, and a hexamethylenetetramine corrosion inhibitor with a mass fraction of 1.0% is added to the dezincification solution, and the dezincification time is extended by 5 minutes when bubbles visible to naked eyes just disappear on the surface of the angle steel;

[0071] The angle steel is made into a batch of 4 tons. After 20 batches, the pH value of the dezincification liquid is 6.1. Industrial hydrochloric acid is added to the dezincification liquid to adjust the pH value of the dezincification liquid to 1.0.

[0072] After 25 batches, the dezincification solution was tested and the zinc ion content in the dezincification solution was 205 g / L;

[0073] Step 3, performing a rinsing treatment, immersing the angle steel after dezincification in step 2 into a second rinsing tank at room temperature for a first rinse with flowing rinsing water, and then immersing the angle steel into a third rinsing tank for a second rinse with rinsing water, and the rinsed angle steel is packaged and briquetted, and stored for sale;

[0074] Step 4: Continuous impurity removal treatment is performed. The dezincification liquid in the dezincification tank after the 25th batch in step 2 is pumped into the oxidation tank. The pH of the dezincification liquid is adjusted to 3.6 with industrial hydrochloric acid. Hydrogen peroxide is added to the oxidation tank and stirred. Then, the solution is allowed to settle. The solution is filtered and poured into the reduction tank at a rate of 75 g / m 3 Add zinc powder and stir it, then let it settle, filter the dezincification solution and pour it into a storage tank for later use;

[0075] Step 5, performing evaporation treatment, pumping the dezincification liquid treated in step 4 into an evaporator, keeping the temperature at 300° C. for 4.5 hours, and obtaining zinc chloride crystals after cooling; taking a certain amount of zinc chloride crystals, dissolving them in analytical pure dilute hydrochloric acid, and performing ICP-AES detection and calculation. The content of zinc chloride in the zinc chloride crystals is 96.79%, and the content of iron in the zinc chloride crystals is 0.02%.

[0076] Step 3: 1 kg of angle steel was cut and dissolved with analytical pure hydrochloric acid. The zinc content in the angle steel was detected and calculated by ICP-AES. The content was 9.8×10 -7 g.

[0077] It was found in the 23rd batch and subsequent batches of the present embodiment that the dezincification treatment speed of step 2 was significantly reduced, and the number and speed of bubbles appearing above the dezincification tank were also significantly slowed down, which also explained the priority and rationality of the zinc content threshold of 185g / L in the dezincification tank and the zinc ion content of 185g / L-195g / L in the dezincification solution being suitable for subsequent treatment.

[0078] The above describes the various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and spirit of the various embodiments described, many modifications and changes are obvious to those of ordinary skill in the art. The selection of terms used herein is intended to best explain the principles, process flows, practical applications, or improvements to the technology in the market of the various embodiments, or to enable other ordinary technicians in the art to understand the various embodiments disclosed herein.

Claims

1. A recycling process for hot-dip galvanized steel, characterized in that: The following steps are involved: Step 1, pre-treatment to remove dust and dirt from the surface of hot-dip galvanized steel in a cleaning tank; Step 2, performing a dezincification treatment, using a dezincification liquid in a dezincification tank to dissolve the zinc layer on the surface of the pre-treated hot-dip galvanized steel and separate it from the steel matrix; Step 3, performing a rinsing treatment to remove residual zinc ions and iron ions on the surface of the steel substrate after the dezincification treatment in a rinsing tank to obtain a recovered steel substrate; Step 4, performing continuous impurity removal treatment, when the zinc ion content of the dezincifying liquid in the dezincifying tank is greater than the set zinc content threshold, performing continuous oxidation precipitation, first filtration, zinc powder reduction and second filtration treatment on the dezincifying liquid; Step 5, performing evaporation treatment, performing evaporation treatment on the dezincification liquid after continuous impurity removal treatment, and obtaining zinc chloride crystals with a zinc chloride mass content greater than or equal to 95% and an iron mass content of 0.05% to 0.2%.

2. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 1, during pretreatment, the cleaning liquid in the cleaning tank uses an alkaline cleaning liquid with a pH value of 9 to 10, and ultrasonic cleaning is used to assist in surface cleaning of the hot-dip galvanized steel. After the surface cleaning, the hot-dip galvanized steel is rinsed with clean water in the first rinsing tank.

3. The hot-dip galvanized steel recycling process according to claim 2, characterized in that: The alkaline cleaning solution in the cleaning tank is prepared with industrial caustic soda flakes, and the cleaning time of hot-dip galvanized steel in the cleaning tank is 3 to 8 minutes.

4. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 2, during the dezincification treatment, the dezincification liquid in the dezincification tank is a hydrochloric acid pickling liquid to which hexamethylenetetramine is added, the mass percentage of hexamethylenetetramine in the hydrochloric acid pickling liquid is 0.8-2%, and the initial pH value of the dezincification liquid is ≤5.

5. The hot-dip galvanized steel recycling process according to claim 4, characterized in that: Two dezincification tanks are provided and used alternately; when the pH value of the dezincification liquid in the dezincification tank is greater than 5, industrial hydrochloric acid is added to adjust the pH value of the dezincification liquid so that the pH value is maintained at a pH value ≤ 5.

6. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 3, during the rinsing treatment, the steel substrate is rinsed for the first time in the second rinsing tank using flowing rinsing water, and then enters the third rinsing tank for the second rinse using rinsing water.

7. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 4, when performing continuous impurity removal treatment, the zinc content threshold is set to 185g / L, that is, when the zinc ion content of the dezincifying liquid in the dezincifying tank is 185g / L-195g / L, the dezincifying liquid is subjected to continuous oxidation precipitation, first filtration, zinc powder reduction and second filtration treatment.

8. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 4, the oxidation precipitation treatment is to pump the dezincification liquid into the oxidation tank, add hydrogen peroxide for oxidation and auxiliary stirring, and then let it stand for precipitation; the first filtration treatment is to filter the dezincification liquid for the first time after standing for precipitation and pour it into the zinc powder reduction tank; Zinc powder reduction treatment is based on the volume of the dezincification solution in the reduction tank according to 30g ~ 80g / m 3 The zinc powder addition amount is to add zinc powder and assist in stirring, and then let it stand and settle; the second filtration treatment is to filter the dezincification liquid for the second time after standing and settling and pour it into the tank.

9. The hot-dip galvanized steel recycling process according to claim 8, characterized in that: The pH value of the dezincification liquid in the oxidation tank is 3.5-4, and the pH value is adjusted by using hydrogen peroxide or hydrochloric acid so that the pH value of the dezincification liquid is maintained within the range of 3.5-4.

10. The hot-dip galvanized steel recycling process according to claim 1, characterized in that: In step 5, during the evaporation treatment, the dezincification liquid is kept at a temperature of 260° C. to 300° C. in an evaporator for 4 to 6 hours for evaporation treatment.

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