A preparation method of 6N selenium

Abstract

The present invention provides a method for preparing 6N selenium, belonging to the field of high-purity metal preparation. The present invention provides a method for preparing 6N selenium, comprising the following steps: immersing a crystallizer into a 4N selenium melt for rotational crystallization to obtain 6N selenium. The present invention utilizes the different physical and chemical properties of each element during the cooling and solidification process to exhibit different distribution behaviors, and some elements tend to remain in the liquid phase, while some elements tend to remain in the solid phase. The interfacial shear force generated by the rotation of the melt achieves the thinning of the solute boundary layer at the liquid-solid interface, prompting impurities to be forcibly removed from the boundary layer, achieving stable growth of crystals, and thus crystallizing high-purity selenium; the temperature gradient of the liquid phase region near the liquid-solid interface is increased by the rotation of the melt, and the increase in the temperature gradient makes the crystallization faster, thereby improving the preparation efficiency. The preparation process of the present invention does not generate waste gas and wastewater, and is a low-pollution, low-energy consumption preparation process.

Description

Technical Field

[0001] The invention relates to the field of high-purity metal preparation, and in particular to a method for preparing 6N selenium. Background Art

[0002] Selenium has semiconductor properties and photosensitivity, which have led to the development and preparation of advanced materials such as gallium selenide and copper indium gallium selenide, resulting in an increasing demand for selenium in the fields of electronic semiconductors and solar energy. Currently, selenium has become a key raw material to support the development of high-tech and high-end materials.

[0003] At present, the main raw material for extracting selenium is copper anode mud. About 90% of selenium is recovered and extracted from copper anode mud. Selenium is insoluble in electrolyte due to its positive charge, and finally forms anode mud and settles at the bottom of the electrolytic cell. Copper anode mud can be comprehensively recovered and treated through processes such as sulfuric acid roasting and aqueous solution chlorination to obtain crude selenium. Crude selenium cannot be directly used in industry due to its low purity. It needs to be purified through purification processes to be better used. The main purification processes include oxidative volatilization, hydrogen selenide decomposition, vacuum distillation and zone smelting.

[0004] The oxidation volatilization method uses the property of selenium dioxide being easily soluble in water to purify selenium, and can obtain 99.99% of selenium, but it has the disadvantages of a long process flow and a low recovery rate of selenium. The hydrogen selenide decomposition method uses the characteristics of the selenium reaction that the impurity metal does not react with hydrogen at a certain temperature to purify selenium, and can obtain more than 99.9999% of selenium, but it should be noted that hydrogen selenide gas is toxic and needs to be carried out in a closed environment to prevent poisoning. The regional smelting method uses the different solubility of impurities in the solid state and the molten state in selenium to separate the impurities. This process can purify selenium from 4N to 5N or 6N after repeated operations, but it has the disadvantage of low production efficiency. In the document "Purification and Preparation of High-Purity Selenium", a chemical impurity removal method is used, which mainly includes three steps: oxidation of selenium, separation and purification of oxidized selenium, and preparation of high-purity selenium. Repeated operations and vacuum distillation can obtain 6N pure selenium, but the process of this method is long and relatively complicated.

[0005] Patent CN113772634A discloses a method for preparing 5N high-purity selenium particles. The temperature of a quartz tube in a quartz distillation furnace is controlled to perform vacuum distillation. After the distillation, the molten selenium liquid is transferred to a granulation furnace for heating, stirring, slag removal, and cooling to obtain 5N selenium particles. The purification effect of this process is not ideal, and only 4N selenium can be purified to 5N, and the process production process is relatively long. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing 6N selenium. The preparation method of the present invention has high efficiency, simple process and no generation of waste gas or waste water.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing 6N selenium, comprising the following steps:

[0009] The crystallizer is immersed in a 4N selenium melt for rotational crystallization to obtain 6N selenium.

[0010] Preferably, the 4N selenium also includes tellurium <10 ppm, arsenic <5 ppm, lead <5 ppm, antimony <5 ppm, sulfur <40 ppm, and the remainder is one or more of aluminum, copper, iron, nickel and magnesium.

[0011] Preferably, the method for preparing the melt comprises the following steps:

[0012] 4N selenium is placed in a rotating crucible of a rotating crystallization furnace, the air in the rotating crystallization furnace is removed, a protective gas is filled in, and then heated to melt.

[0013] Preferably, the heating and melting temperature is 290-350°C.

[0014] Preferably, the crystallizer is made of quartz or graphite.

[0015] Preferably, the temperature of the crystallizer is 220-250°C.

[0016] Preferably, the rotational crystallization is melt rotation, and the rotation speed of the melt is 90 to 150 r / min. Preferably, the rotational crystallization time is 90 to 150 min.

[0017] The present invention provides a method for preparing 6N selenium, comprising the following steps: immersing a crystallizer into a 4N selenium melt for rotational crystallization to obtain 6N selenium. The present invention utilizes the different physical and chemical properties of each element during the cooling and solidification process to exhibit different distribution behaviors, and some elements tend to remain in the liquid phase, while some elements tend to remain in the solid phase. The interfacial shear force generated by the melt rotation achieves the thinning of the solute boundary layer at the liquid-solid interface, prompting impurities to be forcibly removed from the boundary layer, achieving stable growth of crystals, and thus crystallizing high-purity selenium; the melt rotation causes the temperature gradient of the liquid phase region near the liquid-solid interface to increase, and the increase in the temperature gradient makes the crystallization faster, thereby improving the preparation efficiency. In addition, the preparation process of the present invention does not generate waste gas and wastewater, and is a low-pollution, low-energy consumption and high-efficiency preparation process; the process flow is relatively simple and the production cost is low, with great economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing 6N selenium, comprising the following steps:

[0020] The crystallizer is immersed in a 4N selenium melt for rotational crystallization to obtain 6N selenium.

[0021] In the present invention, the 4N selenium preferably also includes tellurium <10ppm, arsenic <5ppm, lead <5ppm, antimony <5ppm, sulfur <40ppm, and the remainder is one or more of aluminum, copper, iron, nickel and magnesium.

[0022] In the present invention, the method for preparing the melt comprises the following steps:

[0023] 4N selenium is placed in a rotating crucible of a rotating crystallization furnace, the air in the rotating crystallization furnace is removed, a protective gas is filled in, and then heated to melt.

[0024] In the present invention, the method of removing air preferably includes repeated vacuuming.

[0025] In the present invention, the heating and melting temperature is preferably 290 to 350°C, more preferably 300 to 320°C.

[0026] In the present invention, the material of the crystallizer is preferably quartz or graphite.

[0027] In the present invention, the temperature of the crystallizer is preferably 220-250°C, more preferably 230-240°C.

[0028] In the present invention, the rotational crystallization is preferably melt rotation, the rotation speed of the melt is preferably 90-150 r / min, more preferably 100-120 r / min. The rotation of the melt is preferably driven by a rotating crucible, the rotation speed of the rotating crucible is the rotation speed of the melt.

[0029] In the present invention, the rotational crystallization time is preferably 90 to 150 min, more preferably 100 to 140 min, and further preferably 120 to 130 min.

[0030] The process flow chart of the method of the embodiment of the present invention is as follows Figure 1 As shown: After evacuating to a slight negative pressure, argon gas is filled in, and then 4N refined selenium is melted and rotary crystallized to obtain 6N high-purity selenium.

[0031] The preparation method of 6N selenium provided by the present invention is described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] The refined selenium raw material (Se99.991%, tellurium 10ppm, lead 4ppm, antimony 3ppm, sulfur 37ppm, aluminum 6ppm, copper 2ppm, iron 8ppm, magnesium 7ppm, arsenic 4ppm, silicon 4ppm, tin 5ppm) is placed in a rotating crucible, evacuated to remove the air in the furnace and repeated for many times, then filled with nitrogen, and then heated to 300°C to make the refined selenium solid become molten refined selenium, the crystallization temperature is controlled to 225°C, the crystallizer with a temperature of 225°C is quickly immersed in the melt, the crucible speed is controlled to 100r / min, and rotary crystallization is carried out for 90min. After the crystallization time is over, the material is taken out and tested, and the selenium purity reaches the 6N standard.

[0034] Example 2

[0035] The refined selenium raw material (Se99.995%, tellurium 5ppm, lead 3ppm, antimony 4ppm, sulfur 18ppm, aluminum 4ppm, copper 2ppm, iron 2ppm, magnesium 3ppm, arsenic 2ppm, silicon 3ppm, tin 4ppm) is placed in a rotating crucible, evacuated to remove the air in the furnace and repeated for many times, then filled with nitrogen, and then heated to 305°C to make the refined selenium solid become molten refined selenium, the crystallization temperature is controlled to 230°C, the crystallizer with a temperature of 230°C is quickly immersed in the melt, the crucible speed is controlled to 110r / min, and rotary crystallization is carried out for 100min. After the crystallization time is over, the material is taken out and tested, and the selenium purity reaches the 6N standard.

[0036] Example 3

[0037] Put refined selenium raw materials (Se99.998%, tellurium 2ppm, lead 1ppm, antimony 1ppm, sulfur 8ppm, aluminum 2ppm, copper 1ppm, iron 1ppm, magnesium 0.5ppm, arsenic 1ppm, silicon 2ppm, tin 0.5ppm) in a rotating crucible, evacuate to remove air in the furnace and repeat several times, then fill with nitrogen, and then heat to 310°C to make the refined selenium solid become molten refined selenium, control the crystallization temperature to 240°C, quickly immerse the crystallizer at a temperature of 240°C in the melt, control the crucible speed to 120r / min, and perform rotary crystallization for 120min. After the crystallization time is over, take out the material and test it. The selenium purity reaches the 6N standard.

[0038] Some process parameters and results of Examples 1 to 3 are shown in Table 1, and the impurity content after crystallization is shown in Table 2.

[0039] Table 1 Partial process parameters and results of Examples 1 to 3

[0040] Raw material ingredients Melting temperature Crystallization temperature Crystallization speed Crystallization time result Se99.99% 300℃ 225℃ 90min 90min 99.99994％ Se99.995% 305℃ 230℃ 110r / min 100min 99.99995％ Se99.998% 310℃ 240℃ 120r / min 120min 99.99995％

[0041] Table 2 Impurity content after crystallization of Examples 1 to 3 (ppm)

[0042] Te Pb Sb S Al Cu Fe Mg As Si Sn Example 1 0.08 0.05 0.03 0.05 0.05 0.05 0.1 0.1 0.02 0.02 0.05 Example 2 0.05 0.04 0.02 0.04 0.05 0.04 0.08 0.08 0.02 0.05 0.03 Example 3 0.05 0.04 0.03 0.02 0.04 0.05 0.07 0.09 0.03 0.04 0.04

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing 6N selenium, characterized in that: The following steps are involved: The crystallizer is immersed in a 4N selenium melt for rotational crystallization to obtain 6N selenium; The composition of the 4N selenium is: Se99.995%, tellurium 5ppm, lead 3ppm, antimony 4ppm, sulfur 18ppm, aluminum 4ppm, copper 2ppm, iron 2ppm, magnesium 3ppm, arsenic 2ppm, silicon 3ppm, tin 4ppm; The temperature of the crystallizer is 230°C, and the rotation speed of the melt is 110r / min; The preparation method of the melt comprises the following steps: 4N selenium is placed in a rotating crucible of a rotating crystallization furnace, the air in the rotating crystallization furnace is removed, a protective gas is filled in, and then heated to melt; The heating and melting temperature is 305°C; The time of the rotation crystallization is 100 min.

2. The preparation method according to claim 1, characterized in that: The material of the crystallizer is quartz or graphite.

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