Method for deeply removing and recycling impurities in electrolytic nickel in stages

Abstract

The invention discloses a method for deeply removing and recovering impurities in electrolytic nickel in a segmented manner, which comprises the following steps: placing the electrolytic nickel in an induction melting furnace, heating and melting to obtain a melt, and sequentially smelting, refining and pouring the melt to obtain high-purity nickel; during smelting, the vacuum degree is controlled to range from 100 Pa to 200 Pa, the smelting temperature ranges from 1500 DEG C to 1520 DEG C, and the smelting time ranges from 20 min to 30 min; in the smelting process, impurity metal A is recycled in a first condensation collecting device; in the refining process, the vacuum degree is controlled to be 0.1-2 Pa, the refining temperature is 1540-1560 DEG C, the refining time is 20-40 min, and in the refining process, impurity metal B is recycled through a second condensation collecting device. By the adoption of the method, the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn and Se elements in the electric nickel can be effectively reduced, the requirement of a high-temperature alloy for a high-quality nickel raw material is met, and meanwhile primary separation of Cu, Zn, Pb, Bi and Se from other volatile impurity elements is achieved.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and metal materials, and in particular relates to a method for segmented deep removal and recovery of impurities in electrolytic nickel. Background Art

[0002] In recent years, my country's aerospace industry has developed rapidly, and the performance requirements for high-temperature alloys will become increasingly stringent. In fact, in terms of the impurity control level of nickel used in high-temperature alloys, there is still a certain gap between my country and the international level.

[0003] The influence of the metal nickel matrix raw materials on the composition of nickel-based high-temperature alloys is mainly its purity, that is, the influence of the content of impurity elements in the matrix nickel. The impurity elements introduced from the raw materials (typically non-metallic impurity elements such as P, S, Si, and metal and metalloid impurity elements such as Pb, Sn, As, Te, Bi) have very low solubility in the alloy and tend to significantly concentrate at key positions such as grain boundaries to form low-melting point compounds or reduce interfacial bonding. At the same time, these impurity elements can significantly reduce the mechanical properties (such as long-lasting creep properties, special fatigue properties, etc.) and processing properties (such as hot processing or weldability) of the alloy. Some impurity elements can have a significant impact on the comprehensive properties of the alloy at the ppm level.

[0004] A domestic military enterprise has formulated internal control standards for nickel metal used in high-temperature alloys in high-end fields. Its A-level standards for Zn, Bi and Pb are 5 ppm, 0.2 ppm and 1 ppm, respectively. However, the impurity elements Zn and Bi in the electrolytic nickel of a domestic smelter only meet the B-level requirements, and Pb only meets the C-level requirements. In addition, the Sb content has exceeded the standard in recent years.

[0005] According to the above requirements, the electrolytic nickel must be deeply decontaminated to meet the raw material requirements for high-temperature alloy production, while recovering other impurity elements in the electrolytic nickel. Summary of the invention

[0006] In view of the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a method for segmented deep removal and recovery of impurities in electrolytic nickel. The method provided by the present invention can not only deeply remove impurities in electrolytic nickel, but also recover impurities in electrolytic nickel in steps.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: The present invention discloses a method for removing and recovering impurities in electrolytic nickel in stages, wherein the electrolytic nickel is first placed in an induction melting furnace, heated to melt to obtain a melt, and the melt is sequentially melted, refined, and poured to obtain high-purity nickel; During the smelting, the vacuum degree is controlled to be 100-200 Pa, the smelting temperature is 1500-1520° C., and the smelting time is 20-30 min. During the smelting process, the impurity metal A is recovered in the No. 1 condensation collection device; During the refining, the vacuum degree is controlled to be 0.1-2 Pa, the refining temperature is 1540-1560° C., the refining time is 20-40 min, and the impurity metal B is recovered in the No. 2 condensation collection device during the refining process.

[0008] The method of the present invention is aimed at nickel metal containing relatively high impurity content such as copper, lead, zinc, and bismuth. Usually, for such metals, the impurity removal is directly carried out by vacuum distillation. Due to the kinetic process, the smelting time is long, the separation depth is low, and the evaporation rate is high. The long-term production of this process will cause certain economic losses. The present invention adopts a vacuum smelting method, and by accurately controlling the vacuum degree and the smelting temperature, Cu, Zn, and Sb with a large separation coefficient from Ni, and Pb and Bi, which account for a large proportion in the electrolytic nickel, are preferentially volatilized in a low vacuum and enriched in a No. 1 condensation collection device, while other impurity metals are volatilized at a higher vacuum and a higher temperature during refining, and are finally enriched in a No. 2 condensation collection device. Through the method of the present invention, not only can the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn, and Se elements in electrolytic nickel be effectively reduced, the demand for high-quality nickel raw materials for high-temperature alloys can be met, and at the same time, Cu, Zn, Pb, Bi, Se and other impurity elements can be initially separated.

[0009] In a preferred embodiment, the purity of the electrolytic nickel is ≥99.92%, preferably 99.92-99.95%.

[0010] According to a preferred embodiment, in the electrolytic nickel, the Cu content is ≥20ppm, the Zn content is ≥10ppm, the Pb content is ≥15ppm, the Bi content is ≥10ppm, and the Sb content is ≥10ppm.

[0011] In the actual operation process, the electrolytic nickel raw material is first cut into small pieces, such as 40mm×40mm small pieces.

[0012] The preferred solution is to place the electrolytic nickel before the induction melting furnace, first connect the outlet of the induction melting furnace chamber to a three-stage pump, namely a rotary vane pump, a Roots pump and an oil diffusion pump, a heating device is set between the pipelines of each stage of the pump to insulate the pipeline, and a three-way valve is set at the outlet of the rotary vane pump to connect No. 1 condensation collection device and No. 2 condensation collection device respectively.

[0013] In the actual operation process, new electrolytic nickel material is used to wash the furnace, and then smelting is carried out.

[0014] According to a preferred solution, the electrolytic nickel is first placed in an induction melting furnace, the lid is closed, the cooling circulating water system is started, and a vacuum is drawn. When the pressure in the furnace reaches <1000Pa, preferably 500-800Pa, power is supplied for melting, and the melting time is 70-90min, preferably 80min.

[0015] In the actual operation process, the temperature is raised in stages. When the furnace temperature is 1000°C, it is kept at this temperature for 15 minutes and then the temperature is raised again to ensure that the gas is discharged. The temperature is then raised again to melt the electrolytic nickel.

[0016] In a preferred embodiment, the pouring temperature is 1560°C to 1570°C, preferably 1565°C.

[0017] In a preferred embodiment, during the smelting, the vacuum degree is controlled to be 100 Pa, the smelting temperature is 1510° C., and the smelting time is 25 min.

[0018] In a preferred embodiment, during the refining, the vacuum degree is controlled to be 0.15 Pa, the refining temperature is 1560° C., and the refining time is 30 min.

[0019] In a preferred embodiment, the impurity metal A includes Cu, Zn, Pb, Bi, and Se.

[0020] The scheme of the present invention has the advantage of achieving segmented recovery of different impurity elements on the basis of removing low-boiling-point impurity elements in electro-nickel in one step. The basic principle is that in nickel metal melt, the evaporation rate of each impurity element increases with the increase of vacuum degree, so by setting different vacuum degree evaporation conditions, different impurity elements can be separated and recovered to a certain extent.

[0021] Principles and advantages The scheme of the present invention utilizes the difference in evaporation rate of each impurity element in the nickel metal melt, and through precise control of the vacuum degree and the melting temperature, Cu, Zn, Sb with a large separation coefficient from Ni, and Pb and Bi, which account for a large proportion in the electrolytic nickel, are preferentially volatilized in a low vacuum and enriched in the No. 1 condensation collection device, while other impurity metals are volatilized at a higher vacuum degree and a higher temperature during refining, and finally enriched in the No. 2 condensation collection device. Through the method of the present invention, not only can the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn, and Se elements in electrolytic nickel be effectively reduced, the demand for high-quality nickel raw materials for high-temperature alloys can be met, and at the same time, Cu, Zn, Pb, Bi, Se and other impurity elements can be initially separated.

[0022] The vacuum distillation method used in the present invention is a test method based on physical principles. Its main process is to carry out a closed reaction in a vacuum furnace. The operation is simple, there is no gas or dust emission, and there is no pollution to the environment. It is a green metallurgical method.

[0023] The present invention uses a segmented impurity removal and recovery process to perform preliminary separation of metals on the basis of recovering metal impurities, shortening the subsequent metallurgical process and having high industrial promotion significance.

[0024] The electrolytic nickel raw material and vacuum nickel mother ingot in the scheme of the present invention are both tested for their multi-element chemical composition using a glow discharge mass spectrometer (GD-MS). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Device connection diagram of the present invention. DETAILED DESCRIPTION

[0026] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in combination with the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0027] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] The main element compositions of the nickel metal raw materials in the embodiments of the present invention and the comparative examples are shown in Table 1.

[0030] Example 1 The steps include: Step 1: Preparation of raw materials and equipment (1) Take Ni9992 electrolytic nickel as raw material and cut it into small pieces of 50 mm × 50 mm; (2) The outlet of the induction melting furnace chamber is connected to three-stage pumps, namely a rotary vane pump, a Roots pump and an oil diffusion pump. A heating device is installed between the pipelines of each stage of the pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect No. 1 condensate collection device and No. 2 condensate collection device respectively.

[0031] (3) Use new electrolytic nickel material to wash the furnace, and then smelt it after washing the furnace.

[0032] Step 2: Vacuum Induction Melting (1) Start the vacuum negative pressure system: after loading, close the cover, start the cooling circulating water system, turn on the Roots pump to evacuate for 20 minutes, and when the pressure in the furnace reaches <1000Pa, power is supplied for melting. The melting is carried out in a staged temperature raising manner. When the furnace temperature is 1000°C, keep the temperature for 15 minutes and then continue to raise the temperature to ensure gas discharge. The melting time is 70-90 minutes; (2) After the charge is completely melted, it enters the smelting phase. The outlet of the pipeline is connected to the No. 1 collection condensation device. The vacuum degree during the smelting phase is 100-200 Pa, the smelting temperature is 1500°C, and the smelting time is 25 min. Step 3: Vacuum Induction Refining (1) After smelting, the refining phase begins. The Roots pump and the oil diffusion pump are turned on in sequence. The outlet of the pipeline is connected to the No. 2 collection condensation device. The vacuum degree during the refining phase is 0.1~2Pa, the refining temperature is 1540℃, and the refining time is 20min. (2) After refining, pouring is carried out and the pouring temperature is controlled at 1560℃~1570℃.

[0033] Example 2: In the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel according to Example 1, the smelting temperature in step 2 is controlled at 1520°C.

[0034] Example 3, in the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel according to Example 2, the smelting time in step 2 is controlled at 20 minutes.

[0035] Example 4, in the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel according to Example 1, the refining temperature in step 3 is controlled at 1560°C.

[0036] Example 5, in the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel described in Example 4, the refining time in step 3 is controlled at 40 minutes.

[0037] Comparative Example 1 The steps include: Step 1: Preparation of raw materials and equipment (1) Take Ni9992 electrolytic nickel as raw material and cut it into small pieces of 50 mm × 50 mm; (2) The outlet of the induction melting furnace chamber is connected to three-stage pumps, namely a rotary vane pump, a Roots pump and an oil diffusion pump. A heating device is installed between the pipelines of each stage of the pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect No. 1 condensate collection device and No. 2 condensate collection device respectively.

[0038] (3) Use new electrolytic nickel material to wash the furnace, and then smelt it after washing the furnace.

[0039] Step 2: Vacuum Induction Melting (1) Start the vacuum negative pressure system: after loading, close the cover, start the cooling circulating water system, turn on the Roots pump to evacuate for 20 minutes, and when the pressure in the furnace reaches <1000Pa, power is supplied for melting. The melting is carried out in a staged temperature raising manner. When the furnace temperature is 1000°C, keep the temperature for 15 minutes and then continue to raise the temperature to ensure gas discharge. The melting time is 70-90 minutes; (2) After the charge is completely melted, the Roots pump and the oil diffusion pump are turned on in sequence to enter the smelting period. The outlet of the pipeline is connected to the No. 1 collection condensation device. The vacuum degree during the smelting period is 0.1~2Pa, the smelting temperature is 1540℃, and the smelting time is 20min. (3) After smelting, pouring is carried out and the pouring temperature is controlled at 1560℃~1570℃.

[0040] Comparative Example 2 According to the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel described in Example 1, the smelting vacuum degree in step 2 is controlled at 20~30Pa.

[0041] Comparative Example 3 According to the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel described in Example 1, the smelting temperature in step 2 is controlled at 1540°C.

[0042] After sampling the refined nickel, GD-MS was performed to detect 16 elements including Co, Si, S, Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Mg, Al, Mn and Se, and the composition was compared and analyzed with the electrolytic nickel raw material, as shown in Table 1:

[0043] As can be seen from Table 1, the vacuum distillation of Ni in a vacuum induction melting furnace significantly reduces the contents of elements S, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Mg, Al, Mn, and Se. The S content is reduced from 5 to 0.42~0.58, a decrease of 94%; the As content is reduced from 5 to 1.5~2.1, a decrease of 60%; the Mn content is reduced from 1 to 0.03~0.048, a decrease of 99.5%; the Sn content is reduced from 1 to 0.028~0.118, a decrease of 88%; the Cu content is reduced from 25 to 0.0019~0.025, a decrease of 99.5%; the Zn content is reduced from 6 to 0.001, a decrease of 99.9% ; The Cd content decreased from 1 to 0.004~0.007, a decrease of 99.3%; the Sb content decreased from 1 to 0.005~0.018, a decrease of 98.2%; the Pb content decreased from 8 to 0.001, a decrease of 99.9%; the Bi content decreased from 1 to 0.001, a decrease of 99.9%; the Mg content decreased from 1 to 0.001~0.007, a decrease of 99.3%; the Se content decreased from 5 to 0.001, a decrease of 99.9%. After vacuum induction melting, the contents of metal elements Zn, Cd, Pb, Bi, Mg, and Se are below 0.005ppm, the contents of Cu, Mn, and Sb are reduced to below 0.05ppm, and the content of Sn is reduced to below 0.1ppm. The removal effect of Co element is not obvious, and the contents of Si, Fe, and Al elements are slightly increased. Through vacuum induction melting, deep separation of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn, Se elements and Ni is achieved.

[0044] The metals recovered from the No. 1 and No. 2 collection and condensation devices were tested by ICP-MS, and the results of 16 elements including Co, Si, S, Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Mg, Al, Mn, and Se were tested, and the composition was compared and analyzed with the electrolytic nickel raw materials, as shown in Tables 2 and 3:

[0045]

[0046] By comparing the contents of each element in Table 2 and Table 3, it can be seen that by adjusting the vacuum degree and smelting temperature to recover the impurity metals at different smelting stages, the impurity metals can be initially separated. Among them, the Cu, Zn, Pb, Bi, and Se elements in the No. 1 recovery device were effectively enriched, among which the Cu element content increased from 25ppm to 0.23~0.24%; the Zn element content increased from 16ppm to 0.14~0.15%; the Pb element content increased from 18ppm to 0.16~0.17%; the Bi element content increased from 10ppm to 0.09%; the Se element content increased from 5ppm to 0.05%, all of which were enriched by about 100 times. At the same time, the remaining easily separable metal elements were all below 50ppm. The contents of each impurity element in the No. 2 recovery device are similar. Except for Cu, Zn, Pb, Bi, and Se elements, the contents of other volatile impurity elements are higher than those in the No. 1 recovery device, and are less than 100ppm.

[0047] In the above table, 1#, 2#, 3#, 4#, 5#, 6#, 7#, and 8# correspond to Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0048] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and invention concept of the present invention within the scope disclosed by the present invention, which shall fall within the protection scope of the present invention.

Claims

1. A method for removing and recovering impurities from electrolytic nickel in a stepwise manner, characterized in that: The electrolytic nickel is first placed in an induction melting furnace, heated to melt to obtain a melt, and the melt is sequentially melted, refined, and poured to obtain high-purity nickel; During the smelting, the vacuum degree is controlled to be 100-200 Pa, the smelting temperature is 1500-1520° C., and the smelting time is 20-30 min. During the smelting process, the impurity metal A is recovered in the No. 1 condensation collection device; During the refining, the vacuum degree is controlled to be 0.1-2 Pa, the refining temperature is 1540-1560° C., the refining time is 20-40 min, and the impurity metal B is recovered in the No. 2 condensation collection device during the refining process.

2. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: The purity of the electrolytic nickel is ≥99.9%, preferably 99.9-99.95%.

3. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: In the electrolytic nickel, the Cu content is ≥20ppm, the Zn content is ≥10ppm, the Pb content is ≥15ppm, the Bi content is ≥10ppm, and the Sb content is ≥10ppm.

4. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: Before placing the electrolytic nickel in the induction melting furnace, the outlet of the induction melting furnace chamber is first connected to a three-stage pump, namely a rotary vane pump, a Roots pump and an oil diffusion pump. A heating device is installed between the pipelines of each stage of the pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect No. 1 condensation collection device and No. 2 condensation collection device respectively.

5. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: The electrolytic nickel is first placed in an induction melting furnace, and after the cover is closed, the cooling circulating water system is started, and a vacuum is drawn. When the pressure in the furnace reaches <1000Pa, power is supplied for melting. The melting time is 70-90 minutes, preferably 80 minutes.

6. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: The pouring temperature is 1560°C to 1570°C, preferably 1565°C.

7. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: During the smelting, the vacuum degree is controlled to be 100 Pa, the smelting temperature is 1510° C., and the smelting time is 25 min.

8. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, characterized in that: During the refining, the vacuum degree was controlled to be 0.15 Pa, the refining temperature was 1560° C., and the refining time was 30 min.

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