Process for reducing content of hydrogen and oxygen elements in electrolytic pure iron by using reduction furnace

Abstract

The invention provides a process for reducing the content of hydrogen and oxygen elements in electrolytic pure iron by using a reduction furnace. The electrolytic method for preparing the pure iron is one in the field of hydrometallurgy, and the content of hydrogen and oxygen elements in the product can reach thousands of ppm. In order to reduce the content of hydrogen and oxygen elements in the electrolytic pure iron, the pure iron prepared through electrolysis is cut into small rectangular pieces with the width being 10-20 mm and the length being about 20-40 mm, and then the surface layers of the iron pieces are removed through grinding; carrying out high-temperature vacuum drying on the iron sheet of which the surface layer is removed, and removing water vapor and gas in the iron sheet; and the dried iron sheet is subjected to high-temperature reduction through a rotary atmosphere reduction furnace, so that the content of hydrogen and oxygen elements in the electrolytic pure iron is further reduced. Through matching of the three steps and the corresponding process, the content of hydrogen and oxygen in the electrolytic pure iron can be reduced by 90% or above. According to the method, hydrogen and oxygen elements in the electrolytic pure iron can be effectively removed, and the quality of the electrolytic pure iron is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-purity iron production, in particular to a process for reducing the content of hydrogen and oxygen elements in electrolytic pure iron by using a reduction furnace. Background Art

[0002] With the continuous development of science and technology, cutting-edge technologies such as the electronics industry and the semiconductor industry have increasingly higher requirements for materials, especially for the purity of the basic materials used. As far as the material itself is concerned, it has always been believed that a certain unique property of the material depends on the content of impurities, and the higher the purity of the metal, the more likely it is to change the properties of the material. Among them, pure iron, as a new type of iron-based material supported by the state, is a key basic raw material for the preparation of advanced steel materials and has very important application value. Its various performances are affected by purity. Internationally, N (the first letter of nine in English) and numbers are generally used to represent the purity of iron. For example, the purity of industrial pure iron is 2N~3N, 4N is high-purity iron, and 5N~6N is ultra-pure iron; ultra-high purity iron has good ductility, corrosion resistance, soft magnetic properties and electrical conductivity, etc., which can significantly improve the performance of materials such as steel, semiconductors, and amorphous materials, and greatly improve the performance of materials in terms of heat resistance and corrosion resistance, which is conducive to promoting the development of aerospace, energy and new semiconductor industries.

[0003] The preparation methods of pure iron generally include pyrometallurgy, hydrometallurgy and combined preparation. Among them, electrolysis, as one of the hydrometallurgy methods, has attracted widespread attention due to its advantages such as simple process, low cost, less pollution and low energy consumption. However, the content of gas elements in the electrolytic pure iron prepared by electrolysis has always been at a high level, with an oxygen content of up to thousands of ppm, which not only reduces the purity of the electrolytic iron, but also harms its performance. Therefore, it is urgent to explore how to remove or reduce the content of gas elements in electrolytic pure iron. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the content of hydrogen and oxygen elements in electrolytic pure iron has not been effectively removed, which not only reduces the purity level of pure iron, but also has an adverse effect on the performance and quality of pure iron. Among them, the content of hydrogen and oxygen elements in the pure iron prepared by electrolysis accounts for the largest proportion of the total impurity element content, and a subsequent process is required to treat the electrolytic iron sheet to reduce the content of gaseous elements hydrogen and oxygen. In view of the technical problem that the content of gaseous elements (mainly hydrogen and oxygen) in the electrolytic pure iron produced by the prior art has been high and difficult to reduce, resulting in the electrolytic iron purity not meeting the standard, and it is easy to oxidize and difficult to maintain the silvery white luster for a long time, the present invention provides a process for reducing the content of hydrogen and oxygen elements in electrolytic pure iron using a reduction furnace, by adopting the method of grinding, vacuum drying and reducing atmosphere reduction and matching suitable equipment and reasonable reduction parameters, the content of hydrogen and oxygen elements in the electrolytic iron is greatly reduced, and the purity and quality of the electrolytic iron are further improved.

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

[0006] A process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace, characterized in that it comprises the following steps:

[0007] Step 1, shearing the pure iron prepared by electrolysis into electrolytic pure iron sheets of a certain size;

[0008] Step 2, grinding the electrolytic pure iron sheet to obtain a clean electrolytic pure iron sheet with the surface oxide layer and hydrolysis products removed;

[0009] Step 3, drying the clean electrolytic pure iron sheet to obtain a dry electrolytic pure iron sheet with residual moisture and gas removed from the surface;

[0010] Step 4, placing the dried electrolytic pure iron sheet into a reduction furnace for reduction treatment to obtain a reduced electrolytic pure iron sheet with low hydrogen and oxygen content, in which the weight content of oxygen and hydrogen in the electrolytic pure iron sheet is reduced to at least the next order of magnitude;

[0011] Step 5, vacuum-packing the reduced electrolytic pure iron sheets with low hydrogen and oxygen content.

[0012] The electrolytic pure iron sheet in step 1 has a width of 1 to 20 mm and a length of 1 to 40 mm.

[0013] Step 2 involves using a grinder.

[0014] Step 3 includes using a rotary high temperature vacuum drying oven, the drying temperature is 100 to 300°C, the drying time is 1 to 24 hours, and the vacuum pressure value is ≤1.0*10 -2 Pa.

[0015] Step 4 includes using a rotary atmosphere reduction furnace, the reducing medium is a reducing atmosphere CH4 or H2, the reduction temperature is 600-1000°C, the reduction time is not less than 12h, and the reducing gas medium flow rate is not less than 0.1L / min.

[0016] Step 4 includes placing the dried electrolytic pure iron sheet into the reduction furnace, sealing the feed port, starting the furnace tube rotation button, opening the nitrogen valve to introduce nitrogen to fully exhaust the air in the furnace tube, then slowly introducing a reducing atmosphere and setting the reduction temperature and reduction time after the flow rate stabilizes, heating to a certain temperature and then cooling down to take out the electrolytic pure iron sheet, and continuously introducing a reducing medium during the cooling process to prevent the electrolytic pure iron sheet from absorbing oxygen during the cooling process.

[0017] Step 4 includes: reduction treatment so that the weight content of hydrogen and oxygen in the electrolytic pure iron sheet is reduced by more than 90%. When the weight content of oxygen in the electrolytic pure iron sheet is 2000ppm, the oxygen content is reduced to below 200ppm after reduction treatment. When the weight content of hydrogen in the electrolytic pure iron sheet is more than 20ppm, the hydrogen weight content is reduced to below 1ppm after reduction treatment.

[0018] The technical effects of the present invention are as follows: the present invention is a process for reducing the hydrogen and oxygen content in electrolytic pure iron by using a reduction furnace, which can effectively remove the hydrogen and oxygen content in the electrolytic pure iron and further improve the quality of the electrolytic pure iron.

[0019] The present invention firstly shears the pure iron plate prepared by electrolysis, reduces the size of the iron sheet, and is conducive to the implementation of subsequent grinding, drying and reduction processes. The grinding and removal of the surface layer involved in the present invention reduces the content of hydrogen and oxygen elements in the first step; the high-temperature vacuum drying treatment involved in the present invention directly removes the water vapor and gas content in the electrolytic pure iron, and reduces the content of hydrogen and oxygen elements in the pure iron in the second step; the third step of the present invention selects a rotary furnace for reduction treatment, so that the electrolytic pure iron raw material is fully in contact with the reducing medium in the furnace to achieve complete reduction; using a reducing atmosphere as a reducing agent, the reducing atmosphere is easy to combine with oxygen, and the oxygen content in the electrolytic pure iron can be reduced; the reduction temperature is set to 600-1000°C, and the reduction time is not less than 12h; the reduced electrolytic pure iron is taken out of the furnace and vacuum packaged; through the above process, the gas content in the electrolytic pure iron is greatly reduced, when the oxygen content is 2000ppm, it can be reduced to less than 200ppm, and when the hydrogen content is above 20ppm, it can be reduced to less than 1ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a macroscopic morphology diagram of the electrolytic iron before treatment in Example 1 of the present invention.

[0021] Figure 2 This is a macroscopic morphology of the electrolytic iron after being reduced for 72 hours in Example 1 of the present invention.

[0022] Figure 3 This is a diagram showing changes in the content of hydrogen and oxygen elements in electrolytic iron in Example 1 of the present invention. Figure 3 The weight content of oxygen in the electrolytic pure iron before treatment in the medium reduction furnace is 2200ppm. The weight content of oxygen in the electrolytic pure iron after treatment in the reduction furnace is as follows: 630ppm after 24h (h is the time unit hour) of medium reduction, 290ppm after 72h of medium reduction, and 68ppm after 144h of medium reduction. Figure 3 The weight content of hydrogen in the electrolytic pure iron before treatment in the medium reduction furnace is 20ppm. The weight content of hydrogen in the electrolytic pure iron after treatment in the reduction furnace is as follows: 1ppm after 24h of medium reduction, <1ppm after 72h of medium reduction, and <1ppm after 144h of medium reduction.

[0023] Figure 4 This is a diagram showing changes in the content of hydrogen and oxygen elements in electrolytic iron in Example 2 of the present invention. Figure 4 The weight content of oxygen in the electrolytic pure iron before treatment in the medium reduction furnace is 1800ppm. The weight content of oxygen in the electrolytic pure iron after treatment in the reduction furnace is as follows: 320ppm after 24h of medium reduction, 65ppm after 72h of medium reduction, and 24ppm after 144h of medium reduction. Figure 4 The weight content of hydrogen in the electrolytic pure iron before treatment in the medium reduction furnace is 60ppm. The weight content of hydrogen in the electrolytic pure iron after treatment in the reduction furnace is as follows: <1ppm after 24h of medium reduction, <1ppm after 72h of medium reduction, and <1ppm after 144h of medium reduction.

[0024] Figure 5 This is a microstructure diagram of electrolytic iron after treatment according to Example 1 of the present invention.

[0025] Figure 6 This is a microstructure diagram of electrolytic iron after treatment according to Example 2 of the present invention. DETAILED DESCRIPTION

[0026] Below is the attached figure ( Figure 1-Figure 6 ) and Examples illustrate the present invention.

[0027] Figure 1 This is a macroscopic morphology diagram of the electrolytic iron before treatment in Example 1 of the present invention. Figure 2 This is a macroscopic morphology of the electrolytic iron after being reduced for 72 hours in Example 1 of the present invention. Figure 3 This is a diagram showing changes in the content of hydrogen and oxygen elements in electrolytic iron in Example 1 of the present invention. Figure 4 This is a diagram showing changes in the content of hydrogen and oxygen elements in electrolytic iron in Example 2 of the present invention. Figure 5 This is a microstructure diagram of electrolytic iron after treatment according to Example 1 of the present invention. Figure 6This is a microstructure diagram of electrolytic iron after treatment in Example 2 of the present invention. Figures 1 to 5 The present invention provides a process and method for reducing the content of hydrogen and oxygen in electrolytic pure iron, which belongs to the technical field of high-purity metal production. The preparation of pure iron by electrolysis is a method in the field of hydrometallurgy, and the content of hydrogen and oxygen in its product can reach thousands of ppm. In order to reduce the content of hydrogen and oxygen in electrolytic pure iron, the pure iron prepared by electrolysis is sheared into rectangular small pieces with a width of about 10 to 20 mm and a length of about 20 to 40 mm, and then ground to remove the surface layer of the iron sheet; the iron sheet with the surface removed is subjected to high-temperature vacuum drying to remove water vapor and gas in the iron sheet; the dried iron sheet is subjected to high-temperature reduction in a rotary atmosphere reduction furnace to further reduce the content of hydrogen and oxygen in the electrolytic pure iron. Through the above three steps and corresponding process matching, the content of hydrogen and oxygen in the electrolytic pure iron can be reduced by more than 90%. The present invention can effectively remove the content of hydrogen and oxygen in the electrolytic pure iron, and further improve the quality of the electrolytic pure iron.

[0028] A process and method for reducing the content of hydrogen and oxygen in electrolytic pure iron, firstly cutting the prepared electrolytic pure iron plate to obtain small pieces with a width of 1 to 20 mm and a length of 1 to 40 mm, then grinding to remove the surface layer of the iron sheet; subjecting the iron sheet with the surface layer removed to high-temperature vacuum drying to remove water vapor and gas in the iron sheet; and subjecting the dried iron sheet to high-temperature reduction in a rotary atmosphere reduction furnace to further reduce the content of hydrogen and oxygen in the electrolytic pure iron. After the above steps, the content of hydrogen and oxygen in the electrolytic pure iron can be reduced by more than 90%.

[0029] Pure iron prepared by electrolysis is selected as raw material, and the hydrogen content in the raw material is higher than 10ppm and the oxygen content is higher than 100ppm.

[0030] The pure iron prepared by electrolysis is cut into small iron sheets with a width of 1 to 20 mm and a length of 1 to 40 mm.

[0031] The iron flakes obtained are ground to remove surface oxides and hydrolysis products, and the first step is to reduce the gas element content in pure iron.

[0032] The iron sheets that have been cut and ground to remove the surface layer are subjected to high-temperature vacuum drying to reduce the gas and water vapor content in the pure iron. The second step is to reduce the gas element content in the pure iron.

[0033] Drying temperature 100 ~ 300 ℃, vacuum degree not less than 1.0 * 10 -2 Pa, drying time is not less than 2h.

[0034] The electrolytic iron flakes after high-temperature vacuum drying are subjected to high-temperature reduction to further reduce the hydrogen and oxygen content in the pure iron.

[0035] The reducing medium may be CH4, H2 or other reducing gases or solids.

[0036] The rotary atmosphere reduction furnace has a rotation frequency of 1 to 8 revolutions per minute during use. The rotary atmosphere reduction furnace can increase the contact area and time between the iron sheet and the reducing medium.

[0037] The reduction temperature of the electrolytic iron sheet is 600-1000°C, the reduction time is not less than 12 hours, and the flow rate of the reducing gas medium is not less than 0.1L / min.

[0038] Regarding reduction temperature and time, high temperature is conducive to reducing the content of hydrogen and oxygen elements in the iron sheet.

[0039] After shearing, grinding, high-temperature vacuum drying and reduction treatment, the hydrogen and oxygen contents in the electrolytic iron sheet are greatly reduced, with the reduction degree exceeding 90%.

[0040] The process and method for reducing the content of hydrogen and oxygen elements in electrolytic pure iron of the present invention has a complete set of technologies and solutions.

[0041] The invention discloses a process and method for reducing the content of hydrogen and oxygen elements in electrolytic iron. The process comprises the following steps: selecting pure iron prepared by electrolysis as raw material, firstly cutting the large-size electrolytic iron plate prepared by electrolysis into iron sheets with a width of 1 to 20 mm and a length of 2 to 40 mm; putting the cut iron sheets into a grinder for grinding to remove the surface layer, thereby reducing the gas element content of the surface layer; putting the ground electrolytic iron sheets into a rotary high-temperature vacuum drying oven for drying, thereby removing the water vapor and gas content in the electrolytic iron sheets, and further reducing the gas element content in the electrolytic iron sheet matrix; the drying oven temperature is set at 100 to 300° C., and the drying time is 1 to 24 hours; The dried iron flakes are subjected to reduction treatment. The reduction equipment and process mainly select a rotary atmosphere furnace as the reduction equipment. The dried electrolytic iron flakes are placed in the furnace, the feed port is sealed, the furnace tube rotation button is started, the nitrogen valve is opened, and nitrogen is introduced for 30 minutes to fully exhaust the air in the furnace tube. Then, the reducing atmosphere is slowly introduced, and the gas flow rate is controlled at more than 0.5L / min. After the flow rate is stable, the reduction temperature and reduction time are set, and the temperature is started to rise. During the reduction process, the reducing atmosphere is continuously introduced as a reducing agent. The reduction temperature is set to 600-1000°C, and the reduction time is not less than 24h. The reduced electrolytic pure iron is stored in vacuum packaging.

[0042] Preferably, the specific steps include:

[0043] Step 1: Shearing of electrolytic iron plate

[0044] The pure iron prepared by electrolysis is sheared into small electrolytic iron sheets with a width of 1 to 20 mm and a length of 2 to 40 mm;

[0045] Step 2: Grinding of electrolytic iron sheets

[0046] The sheared electrolytic iron sheets are ground to remove the surface oxide layer and hydrolysis products, and the grinding time is not less than 1 hour.

[0047] Step 3: Drying

[0048] The sheared electrolytic iron sheets are placed in a rotary high-temperature vacuum drying oven for drying to remove the residual moisture and gas in the electrolytic iron;

[0049] Step 4: Restore

[0050] The electrolytic pure iron sheet is subjected to reduction treatment, the reduction temperature is 600-1000°C, the reduction time is not less than 12 hours, and a reducing medium is selected as a reducing agent;

[0051] Step 5: Vacuum storage

[0052] The electrolytic pure iron after reduction treatment is vacuum packed to isolate oxygen for subsequent long-term storage.

[0053] Preferably, the vacuum drying temperature is set at 100-300°C, and the vacuum degree is not less than 1*10 -2 Pa.

[0054] Preferably, the reduction temperature is 600-1000° C., the reducing medium is H2, and the reduction time is not less than 24 hours.

[0055] Preferably, after the above treatment, the hydrogen and oxygen contents are reduced by more than 90%. For example, when the oxygen content is 2000 ppm, it can be reduced to less than 200 ppm after reduction, and when the hydrogen content is more than 20 ppm, it can be reduced to less than 1 ppm after the above treatment.

[0056] Example 1

[0057] In this embodiment, a process for reducing the content of hydrogen and oxygen in electrolytic pure iron is mainly introduced, and the specific process parameters are set as follows:

[0058] (1) The pure iron prepared by electrolysis is cut into small iron sheets and ground for 2 hours to remove the surface layer. Then, the small iron sheets are placed in a high-temperature vacuum drying oven with a vacuum degree of 10-2Pa and dried for 2 hours. After drying, the small iron sheets are placed in a rotary atmosphere reduction furnace for reduction. The reducing medium is NH3, the reduction temperature is 600°C, and the reduction time is set to 24h, 72h and 144h respectively. The specific operation flow of the reduction process is to seal the feed port, start the furnace tube rotation button, open the nitrogen valve to pass nitrogen for 30 minutes, fully exhaust the air in the furnace tube, and then slowly pass in a reducing atmosphere. The gas flow rate is controlled at 0.5L / min. After the flow rate is stable, set the reduction temperature and reduction time, start heating, and cool down and take out after the temperature reaches the temperature and keeping it warm for a corresponding time. During the cooling process, the reducing medium is continuously passed in to prevent the electrolytic iron sheet from absorbing oxygen during the cooling process; after the reduction is completed, the electrolytic iron sheet is vacuumed and stored. The macroscopic morphology of the electrolytic iron sheet before and after the above process is as follows Figure 2 As shown by Figure 2 It can be seen that after the above treatment, the rust on the surface of the electrolytic iron disappeared, and the surface showed a silvery white metallic luster; the changes in the hydrogen and oxygen content of the electrolytic iron sheet after the above treatment are as follows: Figure 3 Its microstructure is shown in Figure 5 shown.

[0059] Example 2

[0060] This embodiment is basically the same as embodiment 1, except that the reduction temperature is set to 1000°C; the macroscopic morphology of the electrolytic iron before reduction is as follows: Figure 1 and Figure 2 As shown in the figure, the surface of a large amount of electrolytic iron after reduction is all silvery white. The change of oxygen content before and after reduction is shown in the figure. Figure 4 As shown in Figure 2, after reduction treatment, the oxygen content dropped by more than 90%; its microstructure is shown in Figure 2. Figure 6 shown.

[0061] Example 3

[0062] This embodiment is basically the same as embodiment 1, except that the reduction temperature is set to 800° C. and the reduction time is changed to 72 h.

[0063] Example 4

[0064] This embodiment is basically the same as embodiment 1, except that the reduction time is changed to 120 hours.

[0065] Example 5

[0066] This embodiment is basically the same as embodiment 1, except that the reduction temperature is set to 900° C. and the reduction time is changed to 120 h.

[0067] 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 reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace, characterized in that: The following steps are involved: Step 1, cutting the electrolytic pure iron plate into electrolytic pure iron sheets; Step 2, grinding the electrolytic pure iron sheet to obtain a clean electrolytic pure iron sheet with the surface oxide layer and hydrolysis products removed; Step 3, drying the clean electrolytic pure iron sheet to obtain a dry electrolytic pure iron sheet with residual moisture and gas removed from the surface; Step 4, placing the dried electrolytic pure iron sheet into a reduction furnace for reduction treatment to obtain a reduced electrolytic pure iron sheet with low hydrogen and oxygen content, in which the weight content of oxygen and hydrogen in the electrolytic pure iron sheet is reduced to at least the next order of magnitude; Step 5, vacuum-packing the reduced electrolytic pure iron sheets with low hydrogen and oxygen content.

2. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: The electrolytic pure iron sheet in step 1 has a width of 1 to 20 mm and a length of 2 to 40 mm.

3. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: Step 2 involves using a grinder.

4. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: Step 3 includes using a rotary high temperature vacuum drying oven, the drying temperature is 100 to 300°C, the drying time is 1 to 24 hours, and the vacuum pressure value is ≤1.0*10 -2 Pa.

5. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: Step 4 includes using a rotary atmosphere reduction furnace, the reducing medium is CO or ultrapure carbon powder or CH4 or H2, the reduction temperature is 600-1000°C, the reduction time is not less than 12 hours, and the reducing gas medium flow rate is not less than 0.1L / min.

6. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: Step 4 includes placing the dried electrolytic pure iron sheet into the reduction furnace, sealing the feed port, starting the furnace tube rotation button, opening the nitrogen valve to introduce nitrogen to fully exhaust the air in the furnace tube, then slowly introducing a reducing atmosphere and setting the reduction temperature and reduction time after the flow rate stabilizes, heating to a certain temperature and then cooling down to take out the electrolytic pure iron sheet, and continuously introducing a reducing medium during the cooling process to prevent the electrolytic pure iron sheet from absorbing oxygen during the cooling process.

7. The process for reducing the content of hydrogen and oxygen in electrolytic pure iron by using a reduction furnace according to claim 1, characterized in that: Step 4 includes: reduction treatment so that the weight content of hydrogen and oxygen in the electrolytic pure iron sheet is reduced by more than 90%. When the weight content of oxygen in the electrolytic pure iron sheet is 2000ppm, the oxygen content is reduced to below 200ppm after reduction treatment. When the weight content of hydrogen in the electrolytic pure iron sheet is more than 20ppm, the hydrogen weight content is reduced to below 1ppm after reduction treatment.

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