Method for deep removal and recovery of impurities from electrolytic nickel in sections

Abstract

The application discloses a method for segmentally deeply removing and recovering impurities in electrolytic nickel, and the electrolytic nickel is first placed in an induction smelting furnace, is heated to be melted to obtain a melt, and is sequentially subjected to smelting, refining and pouring to obtain high-purity nickel; during smelting, the vacuum degree is controlled to be 100-200 Pa, the smelting temperature is 1500-1520 DEG C, and the smelting time is 20-30 min; during the smelting process, impurity metal A is recovered in a No. 1 condensation and collection device; during refining, the vacuum degree is controlled to be 0.1-2 Pa, the refining temperature is 1540-1560 DEG C, and the refining time is 20-40 min; during the refining process, impurity metal B is recovered in a No. 2 condensation and collection device. The method can effectively reduce the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn and Se elements in the electrolytic nickel, meets the demand of high-temperature alloys on high-quality nickel raw materials, and simultaneously realizes preliminary separation of Cu, Zn, Pb, Bi, Se and other volatile impurity elements.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and metal materials, and particularly 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.

[0003] The influence of the nickel matrix raw material on the composition of nickel-based superalloys is primarily its purity, specifically the content of impurity elements in the matrix nickel. Impurity elements introduced from the raw materials (typically non-metallic impurities such as P, S, and Si, as well as metallic and metalloid impurities such as Pb, Sn, As, Te, and Bi) have very low solubility in the alloy and tend to concentrate significantly at key locations such as grain boundaries, forming low-melting-point compounds or reducing interfacial bonding strength. Furthermore, these impurities can significantly reduce the alloy's mechanical properties (such as creep resistance and fatigue resistance) and processing properties (such as hot working or weldability). Some impurity elements can significantly affect the alloy's overall performance even at the ppm level.

[0004] A domestic military enterprise has established internal control standards for nickel metal used in high-temperature alloys in high-end fields. Its Class A 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 Class B requirements, and Pb only meets the Class C requirements. In addition, the Sb content has exceeded the standard in recent years.

[0005] According to the above requirements, electrolytic nickel must be deeply removed 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 the 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 solutions:

[0008] The present invention provides a method for stepwise deep removal and recovery of impurities in electrolytic nickel. The electrolytic nickel is first placed in an induction melting furnace, heated to melt to obtain a melt, and the melt is sequentially smelted, refined, and poured to obtain high-purity nickel.

[0009] 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;

[0010] During the refining, the vacuum degree is controlled to be 0.1-2 Pa, the refining temperature is 1540-1560 DEG C, and the refining time is 20-40 min; during the refining, the impurity metal B is recovered in the No. 2 condensation collection device.

[0011] The method in the application is aimed at nickel metal with relatively high content of copper, lead, zinc, bismuth and other impurities. For such metal, the impurities are directly removed by using the vacuum distillation method, which is subject to the kinetic process, has long smelting time, low separation depth, and high evaporation rate, and long-term production by using this process will cause certain economic loss. The application adopts the vacuum smelting method, and through accurate control of the vacuum degree and the smelting temperature, Cu, Zn, Sb with large separation coefficient from Ni, and Pb and Bi with large proportion in the electrolytic nickel are preferentially volatilized in low vacuum and enriched in the No. 1 condensation collection device, while other impurity metals are volatilized at higher vacuum degree and higher temperature during the refining and finally enriched in the No. 2 condensation collection device. By the method of the application, the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn and Se elements in the electrolytic nickel can be effectively reduced, the demand of high-temperature alloy for high-quality nickel raw material can be met, and the preliminary separation of Cu, Zn, Pb, Bi, Se and other impurity elements can be achieved.

[0012] In the preferred scheme, the purity of the electrolytic nickel is greater than or equal to 99.92%, and preferably 99.92-99.95%.

[0013] In the preferred scheme, in the electrolytic nickel, the content of Cu is greater than or equal to 20 ppm, the content of Zn is greater than or equal to 10 ppm, the content of Pb is greater than or equal to 15 ppm, the content of Bi is greater than or equal to 10 ppm, and the content of Sb is greater than or equal to 10 ppm.

[0014] In the actual operation process, the electrolytic nickel raw material is first cut into small pieces, such as 40 mm*40 mm small pieces.

[0015] In the preferred scheme, the electrolytic nickel is placed in front of the induction smelting furnace, the outlet of the induction smelting furnace cavity is connected with three-stage pumps, which are rotary vane pumps, Roots pumps and oil diffusion pumps, heating devices are arranged between the pipelines of each pump for pipeline heat preservation, a three-way valve is arranged at the outlet of the rotary vane pump, and the three-way valve is connected with the No. 1 condensation collection device and the No. 2 condensation collection device.

[0016] In the actual operation process, new electrolytic nickel is used for furnace washing, and smelting is performed after the furnace washing.

[0017] In a preferred embodiment, the electrolytic nickel is first placed in an induction melting furnace, the lid is closed, the cooling circulating water system is started, and vacuum is applied. When the pressure in the furnace reaches <1000 Pa, preferably 500-800 Pa, power is supplied for melting. The melting time is 70-90 min, preferably 80 min.

[0018] In actual operation, a staged temperature increase method is adopted. When the furnace temperature is 1000℃, it is kept warm for 15 minutes and then the temperature is continued to be increased to ensure gas discharge, and then the temperature is continued to be increased to melt the electrolytic nickel.

[0019] In a preferred embodiment, the pouring temperature is 1560°C to 1570°C, preferably 1565°C.

[0020] 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 minutes.

[0021] 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.

[0022] In a preferred embodiment, the impurity metal A includes Cu, Zn, Pb, Bi, and Se.

[0023] The solution of the present invention has the advantage of achieving segmented recovery of different impurity elements while removing low-boiling-point impurity elements from electrolytic nickel in a single step. The basic principle is that in a nickel metal melt, the evaporation rate of each impurity element increases with increasing vacuum. Therefore, by setting different vacuum evaporation conditions, different impurity elements can be separated and recovered to a certain extent.

[0024] Principles and advantages

[0025] The solution of the present invention utilizes the difference in evaporation rates of various impurity elements in the nickel metal melt. By precisely controlling the vacuum degree and melting temperature, Cu, Zn, and Sb, which have a large separation coefficient from Ni, and Pb and Bi, which account for a large proportion in electrolytic nickel, are preferentially volatilized in a low vacuum and enriched in the No. 1 condensation collection device. Other impurity metals are volatilized at a higher vacuum degree and higher temperature during refining and ultimately enriched in the No. 2 condensation collection device. The method of the present invention can not only effectively reduce the content of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn, and Se elements in electrolytic nickel, meeting the demand for high-quality nickel raw materials for high-temperature alloys, but also achieve preliminary separation of Cu, Zn, Pb, Bi, Se and other impurity elements.

[0026] The vacuum distillation method used in the present invention is an experimental method based on physical principles. Its main process is to carry out a closed reaction in a vacuum furnace. It is simple to operate, has no gas or dust emissions, and is pollution-free to the environment. It is a green metallurgical method.

[0027] 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.

[0028] The electrolytic nickel raw material and vacuum nickel mother ingot in the solution 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

[0029] Figure 1 Device connection diagram of the present invention. DETAILED DESCRIPTION

[0030] To facilitate 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 scope of protection of the present invention is not limited to the following specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical 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.

[0032] 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.

[0033] 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.

[0034] Example 1

[0035] The steps include:

[0036] Step 1: Preparation of raw materials and equipment

[0037] (1) Using Ni9992 electrolytic nickel as raw material, cut into 50mm×50mm small pieces;

[0038] (2) The outlet of the induction melting furnace 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 pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect the No. 1 condensate collection device and the No. 2 condensate collection device respectively.

[0039] (3) Use new electrolytic nickel material to wash the furnace, and then smelt it after washing the furnace.

[0040] Step 2: Vacuum Induction Melting

[0041] (1) Start the vacuum negative pressure system: After loading, close the cover, start the cooling circulating water system, turn on the Roots pump to vacuum for 20 minutes, and when the pressure in the furnace reaches <1000Pa, power is supplied for melting. Melting is carried out in a staged temperature raising manner. When the furnace temperature is 1000℃, keep it warm for 15 minutes and then continue to raise the temperature to ensure gas discharge. The melting time is 70~90 minutes;

[0042] (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.

[0043] Step 3: Vacuum Induction Refining

[0044] (1) After the smelting is completed, 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.

[0045] (2) After refining, pouring is carried out and the pouring temperature is controlled at 1560℃~1570℃.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Comparative Example 1

[0051] The steps include:

[0052] Step 1: Preparation of raw materials and equipment

[0053] (1) Using Ni9992 electrolytic nickel as raw material, cut into 50mm×50mm small pieces;

[0054] (2) The outlet of the induction melting furnace 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 pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect the No. 1 condensate collection device and the No. 2 condensate collection device respectively.

[0055] (3) Use new electrolytic nickel material to wash the furnace, and then smelt it after washing the furnace.

[0056] Step 2: Vacuum Induction Melting

[0057] (1) Start the vacuum negative pressure system: After loading, close the cover, start the cooling circulating water system, turn on the Roots pump to vacuum for 20 minutes, and when the pressure in the furnace reaches <1000Pa, power is supplied for melting. Melting is carried out in a staged temperature raising manner. When the furnace temperature is 1000℃, keep it warm for 15 minutes and then continue to raise the temperature to ensure gas discharge. The melting time is 70~90 minutes;

[0058] (2) After the charge is completely melted, the Roots pump and the oil diffusion pump are turned on in sequence to enter the melting period. The outlet of the pipeline is connected to the No. 1 collection condensation device. The vacuum degree during the melting period is 0.1~2Pa, the melting temperature is 1540℃, and the melting time is 20min.

[0059] (3) After smelting, pouring is carried out and the pouring temperature is controlled at 1560℃~1570℃.

[0060] Comparative Example 2

[0061] According to the method and equipment for segmented deep removal and recovery of impurities in electrolytic nickel described in Example 1, the smelting vacuum in step 2 is controlled at 20-30 Pa.

[0062] Comparative Example 3

[0063] According to the method and equipment for staged deep removal and recovery of impurities in electrolytic nickel described in Example 1, the smelting temperature in step 2 is controlled at 1540°C.

[0064] 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. The results were then compared with the composition of the electrolytic nickel raw materials, as shown in Table 1:

[0065]

[0066] As can be seen from Table 1, the content of elements S, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Mg, Al, Mn, and Se in Ni was significantly reduced by vacuum distillation in a vacuum induction melting furnace. The S content was reduced from 5 to 0.42~0.58, a decrease of 94%; the As content was reduced from 5 to 1.5~2.1, a decrease of 60%; the Mn content was reduced from 1 to 0.03~0.048, a decrease of 99.5%; the Sn content was reduced from 1 to 0.028~0.118, a decrease of 88%; the Cu content was reduced from 25 to 0.0019~0.025, a decrease of 99.5%; and the Zn content was 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%; and the Se content decreased from 5 to 0.001, a decrease of 99.9%. After vacuum induction melting, the contents of the metal elements Zn, Cd, Pb, Bi, Mg, and Se were below 0.005ppm, the contents of Cu, Mn, and Sb were reduced to below 0.05ppm, and the content of Sn was reduced to below 0.1ppm. The removal effect of Co was not significant, and the contents of Si, Fe, and Al increased slightly. Through vacuum induction melting, deep separation of Cu, Zn, Cd, Sn, Sb, Pb, Bi, Mg, Mn, Se elements and Ni is achieved.

[0067] 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 detected. The composition was compared with that of the electrolytic nickel raw materials, as shown in Tables 2 and 3:

[0068]

[0069]

[0070] As can be seen from the content of each element in Table 2 and Table 3, the impurity metals in different smelting stages can be recovered by regulating the vacuum degree and smelting temperature, so as to preliminarily separate the impurity metals. In the No. 1 recovery device, the Cu, Zn, Pb, Bi and Se elements are effectively enriched, and the content of the Cu element is increased from 25 ppm to 0.23-0.24%; the content of the Zn element is increased from 16 ppm to 0.14-0.15%; the content of the Pb element is increased from 18 ppm to 0.16-0.17%; the content of the Bi element is increased from 10 ppm to 0.09%; and the content of the Se element is increased from 5 ppm to 0.05%, all of which are enriched by about 100 times. Meanwhile, the content of the remaining easily separable metal elements is less than 50 ppm. In the No. 2 recovery device, the content of each impurity element is close, and the content of the remaining easily volatile impurity elements is higher than that in the No. 1 recovery device, and is less than 100 ppm, except for the Cu, Zn, Pb, Bi and Se elements.

[0071] In the above table, 1#, 2#, 3#, 4#, 5#, 6#, 7# and 8# respectively correspond to Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3.

[0072] The above is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacement or change according to the technical scheme and concept of the present application within the disclosed scope, which is also within the protection scope of the present application.

Claims

1. A method for the stepwise deep removal and recovery of impurities from electrolytic nickel, characterized by: The electrolytic nickel is first placed in an induction melting furnace, heated to melt to obtain a melt, and the melt is sequentially smelted, 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., and the refining time is 20-40 min. During the refining process, the impurity metal B is recovered in the No. 2 condensation collection device.

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%.

3. The method for stepwise deep removal and recovery of impurities in electrolytic nickel according to claim 1, wherein: 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, wherein: Before placing the electrolytic nickel in the induction melting furnace, the outlet of the induction melting furnace is first 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 pump to insulate the pipeline. A three-way valve is installed at the outlet of the rotary vane pump to connect to the No. 1 condensation collection device and the 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: Place the electrolytic nickel in the induction melting furnace first, close the lid, start the cooling circulating water system, and evacuate. When the pressure in the furnace reaches <1000Pa, power is supplied for melting. The melting time is 70~90min.

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.

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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