Process for preparing 4N-grade pure iron through electrolysis by taking pig iron as anode

Abstract

The invention relates to a process for preparing 4N-grade pure iron by electrolysis by taking pig iron as an anode. The 4N-grade pure iron is prepared by adopting soluble pig iron as the anode, an inert titanium plate as a cathode, a mixed solution of ferrous chloride and hydrochloric acid and addition of a reagent for ensuring the stability of an electrolyte. The pH value of the electrolyte is 2-5, the temperature of the electrolyte is 60-95 DEG C, the cathode current density is 50-300 A / m < 2 >, the purity of the prepared pure iron is 99.95-99.995 wt%, and the thickness is 2-4 mm. The method has the advantages that pig iron serves as the anode material, the cost of the soluble anode material is reduced, and industrial production of 4N-grade high-purity iron is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical refining in hydrometallurgy, in particular to a process for preparing 4N grade pure iron by electrolysis using pig iron as anode. Background Art

[0002] Industry is the main body of the real economy, and the materials industry is the basic industry of the national economy. Among them, high-purity iron, as an important basic material, involves a wide range of fields such as aerospace, electronic information and military industry, and has become an important development direction in the field of new materials. There are three main routes for pure iron production: pyrometallurgy, hydrometallurgy and combined preparation. Among them, the electrolytic method for preparing pure iron is the method with the lowest cost, shortest process and strongest operability to achieve high purification or even ultra-purification of pure iron. At present, electrolytic iron has been widely used in the fields of generator gas turbine components, special alloys, sputtering targets and battery collectors. European and American countries have successively included ultra-pure electrolytic iron above grade 4N in food nutritional fortification additives, pharmaceutical additives, etc. in the national pharmacopoeia. The famous German tableware brand Zwilling has also begun to use high-purity electrolytic iron as raw material to produce green, non-coated non-stick pans. Obviously, the demand for high-purity iron and ultra-pure iron is increasing day by day, and its production and research and development have attracted much attention internationally. From the perspective of cost and mass production, the electrolytic method for preparing high-purity iron has irreplaceable advantages. The electrolytic method for preparing pure iron usually uses industrial pure iron as raw material for electrolytic production, which is relatively expensive. It has become a trend to use low-cost anode materials for electrolytic production of pure iron.

[0003] In order to maintain the stability of the electrolyte and ensure that the concentration of ferrous ions in the electrolyte does not decrease as the electrolysis continues, affecting the electrodeposition efficiency, soluble anode materials are generally used for electrolysis, because the ferrous ions required for the preparation of electrolytic iron at this time mainly come from the anode material itself. If you want to prepare electrolytic iron in batches, the demand for anode materials is also huge. In order to achieve low-cost industrial production of pure iron and achieve the goal of reducing costs and improving efficiency, low-cost anode materials should be selected. Summary of the invention

[0004] The technical problem to be solved by the present invention is as follows: In view of the technical problem that currently industrial pure iron is commonly used as an anode material for electrolytic preparation of high-purity iron, the anode material consumption is huge, the cost is too high, and it causes huge economic pressure on enterprises to achieve large-scale production. The present invention provides a process for preparing 4N grade pure iron by electrolysis using pig iron as an anode, which can directly purify pig iron into 4N grade pure iron with a purity of 99.95-99.995wt%.

[0005] The technical solution of the present invention is as follows:

[0006] A process for preparing 4N grade pure iron by electrolysis using pig iron as an anode, characterized in that it includes an anode formed by using pig iron as an anode material, and a cathode formed by using a titanium plate as a cathode material, a first anode isolation film is arranged around the anode, and a second cathode isolation film is arranged around the cathode, and the iron element dissolved from the anode pig iron into the electrolyte is deposited on the surface of the cathode titanium plate as 4N grade pure iron with a purity of 99.95 to 99.995 wt% of the iron element.

[0007] The electrolyte is controlled to have a pH of 2 to 5 with hydrochloric acid, the electrolyte temperature is 60 to 95° C., and the Fe 2+ 50~300g / L, cathode current density 50~300A / m 2 .

[0008] During electrolysis, the electrolyte flows out from the bottom of the electrolytic cell for filtration and flows into the top for circulation. The electrolyte flowing out of the cell is filtered by sedimentation and the pH is adjusted by adding acid, and finally re-enters the electrolytic cell from the top, thus forming a circulation flow of electrolyte flowing in from top to bottom.

[0009] The cathode current density adopts the method of crystallization at a low current density and growth and thickening at a high current density. The increase mode is as follows: first use 50A / m 2 Electrolysis for 1 to 24 hours, then 100A / m 2 Electrolysis for 1 to 24 hours, then 150A / m 2 Electrolyze for 1 to 24 hours, and gradually increase the current density to achieve stable electrolysis.

[0010] Before electrolysis, add 0.01-1 g / L of reducing stabilizer to ensure the stability of the electrolyte to prevent Fe 2+ To Fe 3+ To ensure the stability of the electrolyte, the electrolysis process is observed once every 24 hours and the electrolyte is maintained according to its state.

[0011] Before electrolysis, a certain amount of high-purity iron powder of grade 3N or above is added to the electrolyte and circulated and stirred for a certain period of time, and the iron powder is used to reduce and settle some metal ions in the electrolyte.

[0012] During the electrolysis process, a certain amount of 3N grade high-purity iron powder is added every 24 hours to reduce the non-ferrous metal ions in the sedimentation electrolyte.

[0013] The anode and the cathode are both plates, the first isolation film is a 600-mesh anode diaphragm that does not contact the anode, and the second isolation film is a 600-mesh cathode isolation film that does not contact the cathode plate. The anode plate has a length and width of 0.5 to 1 m and a thickness of 15 to 25 mm; the cathode plate has a length and width of 0.5 to 1 m and a thickness of 15 to 25 mm. 2, thickness 1~2mm, the plane size of the prepared 4N grade pure iron is not less than 0.25~1m 2 And the thickness is 2 to 4 mm.

[0014] The chemical composition and wt% of the pig iron are as follows: the sum of the contents of Cr and Mn elements is not higher than 0.2, the sum of the contents of Co, Ni, Cu and Zn is not higher than 0.1, C=2.5-5.5, and the remainder is Fe and other unavoidable non-ferrous elements.

[0015] The technical effects of the present invention are as follows: The present invention provides a process for preparing 4N grade pure iron by electrolysis using pig iron as an anode, which can obtain 4N grade high-purity iron and realize mass production of 4N grade electrolytic iron. The method of the present invention has a simple process, a short preparation cycle, a high yield, and a high product purity, and further reduces the cost of soluble anode materials on the basis of the electrochemical refining method. The 4N grade pure iron prepared by electrolysis of the present invention has a thickness of 2 to 4 mm and a weight of 20 to 60 kg / plate, which can be industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a scene state diagram of a process for preparing 4N grade pure iron by electrolysis using pig iron as anode for implementing the present invention.

[0017] Figure 2 This is a physical picture of the 4N grade pure iron product obtained by the first embodiment of the present invention.

[0018] Figure 3 This is a physical picture of the 4N grade pure iron product obtained by the second embodiment of the present invention.

[0019] Figure 4 This is another physical picture of a 4N grade pure iron product obtained by the second embodiment of the present invention.

[0020] Figure 5 yes Figure 2 Chemical composition weight content ppm result chart of 4N grade pure iron products.

[0021] Figure 6 yes Figure 3 Chemical composition weight content ppm result chart of 4N grade pure iron products. DETAILED DESCRIPTION

[0022] Below is the attached figure ( Figure 1-Figure 6 ) and Examples illustrate the present invention.

[0023] Figure 1 The present invention is a scene state diagram of a process for preparing 4N grade pure iron by electrolysis using pig iron as anode for implementing the present invention. Figure 1 It is the on-site condition of the implementation of the present invention. Figure 2 This is a physical picture of the 4N grade pure iron product obtained by the first embodiment of the present invention. Figure 3 This is a physical picture of the 4N grade pure iron product obtained by the second embodiment of the present invention. Figure 4 This is another physical picture of a 4N grade pure iron product obtained by the second embodiment of the present invention. Figure 5 yes Figure 2 Chemical composition weight content ppm result chart of 4N grade pure iron products. Figure 5 The weight content of iron element in 4N grade pure iron products is 99.994%, that is, the purity is 4N4 level, and the weight content of non-iron elements in ppm is as follows: P=0.73, S=0.83, B<0.01, Na=0.17, Mg<0.01, Al=0.03, Pb=0.02, Bi<0.005, Co=9.9, Si=0.02, Cl=1.7, K<0.05, Ca<0.05, Sc<0.05, Ti<0.01, V<0.01, Cr=0.05, Mn<0.05, Ni=36, Cu=2.8, Zn=3.4, Ga<0.05, Ge=0.28, As=0.39, Nb<0.05, Mo=0.12, Sn<0.05. Figure 6 yes Figure 3 Chemical composition weight content ppm result chart of 4N grade pure iron products. Figure 6 The weight content of iron in 4N grade pure iron products is 99.994%, that is, the purity is 4N4 level, and the weight content of non-iron elements in ppm is as follows: P = 0.85, S = 0.6, B < 0.01, Na = 0.04, Mg < 0.01, Al = 0.06, Pb = 0.02, Bi < 0.005, Co = 13, Si = 0.04, Cl = 0.09, K < 0.05, Ca < 0.05, Sc < 0.05, Ti < 0.01, V < 0.01, Cr = 0.09, Mn < 0.05, Ni = 36, Cu = 2.9, Zn = 2.1, Ga = 0.08, Ge = 0.42, As = 0.61, Nb < 0.05, Mo = 0.08, Sn < 0.05. Reference Figures 1 to 6 A process for preparing 4N grade pure iron by electrolysis using pig iron as an anode, comprising an anode formed by pig iron as an anode material, and a cathode formed by titanium as a cathode material, a first anode isolation film is arranged around the anode, and a second cathode isolation film is arranged around the cathode, and the iron element dissolved from the anode pig iron into the electrolyte is deposited on the cathode titanium surface as 4N grade pure iron with a purity of 99.95 to 99.995 wt% of the iron element.

[0024] The present invention discloses a process and method for preparing 4N grade high purity iron by electrolysis using pig iron as anode material and applying pulse current, wherein soluble pig iron is used as anode, inert titanium plate is used as cathode, a mixed solution of ferrous chloride and hydrochloric acid and reagents added to ensure the stability of the electrolyte are used for electrolysis to prepare 4N grade pure iron. The pH of the electrolyte is 2-5, the electrolyte temperature is 60-95°C, the Fe2+ solubility is 50-300g / L, and the cathode current density is 50-300A / m 2 The purity of the prepared pure iron is 99.95-99.995wt% and the thickness is 2-4mm. The method of the present invention has the advantages of using pig iron as the anode material, reducing the cost of soluble anode materials and realizing the industrial production of 4N grade high-purity iron.

[0025] A process for preparing high-purity iron by electrolysis using pig iron as anode, belonging to the field of electrochemical refining in hydrometallurgy, using low-cost pig iron as anode, titanium plate as cathode, a mixed solution of ferrous chloride and hydrochloric acid and a certain amount of solution stabilizer as electrolyte to prepare 4N grade pure iron, wherein the pH of the electrolyte is 2-5; the electrolyte temperature is 60-95°C; the cathode current density is 50-300A / m 2 .

[0026] Pig iron is used as the anode. The anode plate has a length and width of 0.5 to 1m and a thickness of 15 to 25mm. The cathode plate has a length and width of 0.5 to 1m. 2 , thickness 1~2mm.

[0027] The sum of the Cr and Mn content in the chemical composition of the pig iron anode plate is not higher than 0.2%, the sum of the Co, Ni, Cu and Zn content is not higher than 0.1%, and the remaining non-ferrous elements are within the scope of pig iron.

[0028] The electrolyte is mainly 50-300 g / L Fe 2+ solution, and use hydrochloric acid to control the pH value of the solution within the required range.

[0029] Electrolyte stabilizer is used to prevent Fe 2+ Reducing additives for solution oxidation and chloride salts that increase solution conductivity without affecting solution properties.

[0030] During the electrolysis process, the changes in the electrolyte were observed every 24 hours, and stabilizers were added to ensure the stability of the electrolyte.

[0031] The electrolyte is prepared by first adjusting the pH value of the pure water solution to between 4 and 5, then adding a reducing additive and then adding a sufficient amount of FeCl2 solute, stirring and dissolving evenly, and then adjusting the pH of the electrolyte to the required range.

[0032] Before electrolysis, a certain amount of high-purity iron powder of grade 3N or above is added to the electrolyte and circulated and stirred for a certain period of time, and the iron powder is used to reduce and settle some metal ions in the electrolyte.

[0033] During the electrolysis process, a certain amount of 3N grade high-purity iron powder is added every 24 hours to reduce the non-ferrous metal ions in the sedimentation electrolyte.

[0034] During the electrolysis process, pulsed direct current is used, and the current is applied in a step-by-step and gradually increasing manner, so that pure iron is more likely to adhere to the cathode plate.

[0035] The electrolysis process is characterized in that hydrochloric acid is added to adjust the pH value of the electrolyte through an automatic acid monitoring system and an automatic acid addition system.

[0036] During the electrolysis process, the electrolyte temperature range is controlled by an automatic temperature control system to reduce the storage of gas elements in the solution and reduce the gas content in pure iron.

[0037] During the electrolysis process, the electrolyte circulation adopts the "up-in and down-out" liquid circulation flow mode.

[0038] The cathode plate is provided with a 600 mesh cathode isolation film which does not contact the cathode plate, so as to prevent the hydrolysis products and insoluble products falling off the anode plate from adhering to the cathode surface during the electrolysis process and hindering the deposition of electrolytic iron.

[0039] The anode material is equipped with a 600-mesh anode diaphragm that does not contact the anode to prevent insoluble impurities and oxygen generated on the anode surface during electrolysis from flowing with the electrolyte to the vicinity of the cathode plate, which is not conducive to the deposition of electrolytic iron.

[0040] The isolation film should be made of acid-resistant material to avoid mixing new impurities during the electrolysis process and reducing the purity of the electrolytic iron.

[0041] The prepared high-purity iron has a smooth morphology and a plane size of less than 0.25 to 1 m. 2 And 4N grade pure iron with a thickness of up to 2 to 4 mm.

[0042] The total content of main metal (Cr, Mn, Co, Ni, Cu, Zn) impurities in 4N grade pure iron prepared by electrolysis does not exceed 80ppm, and the total content of gas (C, S, O, N, H) elements does not exceed 70ppm, and the purity reaches 4N (99.95-99.995%) level.

[0043] The cathode plate and the anode plate are relatively large in size, and the weight of 4N grade pure iron prepared by electrolysis reaches 20 to 40 kg per plate, which can be industrialized.

[0044] In a method for electrolyzing 4N grade pure iron using pig iron as raw material, the anode plate material is pig iron, the anode plate size is 0.5 to 1m in length and width, and the thickness is 15 to 25mm; the cathode plate material is titanium plate, the cathode plate size is 0.5 to 1m in length and width 2 , thickness 1~2mm, electrolyte Fe 2+ The concentration is 100~300g / L.

[0045] The pH of the electrolyte solution is 2 to 5, preferably 2.2 to 3.4 as the initial pH value. The electrolyte temperature is 60 to 95°C, preferably 60 to 80°C. The cathode current density is 50 to 300 A / m 2 , preferably 100 to 200 A / m 2 .

[0046] The pure iron prepared by electrolysis is mainly in plate form with a thickness of 2 to 4 mm. Subsequent processing can produce pure iron in the form of flakes with regular shape and silvery white surface.

[0047] Because soluble anode plates are used, during the electrolysis process, it is necessary to constantly observe the dissolution of the anode plates. When the dissolution is completed, they need to be replaced in time to ensure that the electrolysis process is not interrupted. When the electrolytic iron on the surface of the cathode plate collapses during the electrolysis process, it needs to be removed in time to avoid short circuits that cause the surface of the electrolytic iron to turn black.

[0048] The method of the present invention has the advantages of electrolyzing pig iron as the anode material, obtaining 4N grade high-purity iron, and realizing mass production of 4N grade electrolytic iron. The method of the present invention has simple process, short preparation cycle, high output, high product purity, and further reduces the cost of soluble anode materials on the basis of electrochemical refining method.

[0049] The first embodiment of the present invention is as follows:

[0050] In this embodiment, a process for preparing high-purity iron by electrolysis using pig iron as anode material is mainly introduced, and the specific process parameters are set as follows:

[0051] (1) The anode plate is made of cast iron with a size of 700*800*15mm 3 The cathode plate is made of polished titanium plate with a size of 700*800*2mm. 3 . Before electrolysis, the surface of the anode plate is soaked in dilute hydrochloric acid and then rinsed with pure water. The surface of the cathode plate is sanded, degreased, and cleaned with pure water. Then, an isolation film bag is put on both the anode and cathode plates. During electrolysis, the electrolyte flows out from the bottom of the electrolytic cell and is added from the top. The electrolyte flowing out of the cell is filtered by sedimentation, and acid is added to adjust the pH before it finally re-enters the electrolytic cell from the top. Figure 1 (2) Select Fe 2+The initial pH value of electrolysis is 2.2-2.4, the electrolyte temperature is 60°C, and the cathode current density is gradually increased to 50-100-150-200A / m 2 After 7 days of electrolysis, the product obtained is as follows Figure 2 Its chemical components are as follows Figure 5 shown.

[0052] The second embodiment of the present invention is as follows:

[0053] In this embodiment, a process for preparing high-purity iron by electrolysis using pig iron as anode material is mainly introduced, and the specific process parameters are set as follows:

[0054] (1) This step is the same as in Example 1. (2) Select Fe 2+ The initial pH value of electrolysis is 2.4-2.8, the electrolyte temperature is 70°C, and the cathode current density is gradually increased to 50-100-150-200A / m 2 After 7 days of electrolysis, a 2-4 mm thick electrolytic iron plate is obtained. The actual picture of high-purity iron is as follows Figure 3 , Figure 4 Its chemical composition analysis is shown in Figure 6 As shown. Figure 3 , Figure 4 It can be seen that the electrolytic iron has good stripping integrity, the surface has a silvery white metallic luster, and the substrate side is grayish white. According to the chemical composition analysis, the purity of the electrolytic iron prepared by pig iron has reached 4N4 level.

[0055] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A process for preparing 4N grade pure iron by electrolysis using pig iron as anode, characterized in that: The invention comprises an anode formed by using pig iron as the anode material, and a cathode formed by using a titanium plate as the cathode material. A first anode isolation film is arranged around the anode, and a second cathode isolation film is arranged around the cathode. The iron element dissolved from the anode pig iron into the electrolyte is deposited on the surface of the cathode titanium plate as 4N grade pure iron with a purity of 99.95 to 99.995 wt % of the iron element.

2. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: The electrolyte is controlled to have a pH of 2 to 5 with hydrochloric acid, the electrolyte temperature is 60 to 95° C., and the Fe 2+ 50~300g / L, cathode current density 50~300A / m 2 .

3. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: During the electrolyte preparation process, 0.01 to 1 g / L of solution stabilizer is added, and the stabilizer needs to be a chloride salt with reducing properties.

4. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: During the electrolysis process, the properties and state of the electrolyte were observed every 24 hours, and the electrolyte was maintained by adding solution stabilizers.

5. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: During electrolysis, the electrolyte flows out from the bottom of the electrolytic cell and is added to the top. The electrolyte flowing out of the cell is filtered by sedimentation and acid is added to adjust the pH, and finally re-enters the electrolytic cell from the top, thus forming a circulation flow of electrolyte flowing in and out from the top.

6. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: The cathode current density adopts the process of "small current film formation, large current thickening", and the current increase mode is as follows: 50~100~150~200A / m 2 Increase the amount gradually until stable electrolysis occurs, and each time the current is adjusted, there should be an interval of 1 to 24 hours depending on the cathode state.

7. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: Before electrolysis, a certain amount of high-purity iron powder of grade 3N or above is added to the electrolyte and circulated and stirred for a certain period of time, and the iron powder is used to reduce and settle some metal ions in the electrolyte.

8. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: During the electrolysis process, a certain amount of 3N grade high purity iron powder is added every 24 hours to reduce the non-ferrous metals and oxidized Fe in the sedimentation electrolyte. 2+ ion.

9. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: The anode and the cathode are both plates, the first isolation film is a 600-mesh anode diaphragm that does not contact the anode, the second isolation film is a 600-mesh cathode isolation film that does not contact the cathode plate, and the cathode plate has a length and width of 0.5 to 1 m. 2 , thickness 15 ~ 25mm; cathode plate size is 0.5 ~ 1m in length and width 2 , thickness 1~2mm, the plane size of the prepared 4N grade pure iron is not less than 0.25~1m 2 And the thickness is 2 to 4 mm.

10. The process for preparing 4N grade pure iron by electrolysis using pig iron as anode according to claim 1, characterized in that: The chemical composition and wt% of the pig iron are as follows: the sum of the contents of Cr and Mn elements is not higher than 0.2, the sum of the contents of Co, Ni, Cu and Zn is not higher than 0.1, C=2.5-5.5, and the remainder is Fe and other unavoidable non-ferrous elements.

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