A two-terminal crystallization magnesium reduction reaction apparatus and method

Abstract

This invention belongs to the field of magnesium smelting technology and discloses a two-end crystallization magnesium reduction reaction device and method, including a vertical tank, an annular support base at the bottom of the vertical tank, a central cylinder sitting on the annular support base, an upper crystallization cylinder installed at the top of the vertical tank, and a lower crystallization cylinder installed at the bottom of the vertical tank; an upper cooling water jacket is provided outside the upper crystallization cylinder, and a lower cooling water jacket is provided outside the lower crystallization cylinder; a vacuum pipe is provided on the upper cooling water jacket and / or the lower cooling water jacket; a vacuum-breaking air inlet pipe is provided at the upper end of the vertical tank; by setting the upper and lower crystallization cylinders at the upper and lower ends of the vertical tank, firstly, when the vertical tank is evacuated, the airflow only passes through the upper crystallization cylinder, avoiding contamination of the lower crystallization cylinder, laying the foundation for the crystallization of high-purity magnesium crystals in the lower crystallization cylinder; secondly, it realizes the separation and control of the initial stage and the middle and later stages of magnesium reduction, so that the crude magnesium crystals and high-purity magnesium crystals in the early stage can be separated in the reduction stage in the vertical tank, the high-purity magnesium crystals are exempted from refining, shortening the process and reducing the number of steps.

Description

Technical Field

[0001] This invention belongs to the field of magnesium smelting technology, and in particular relates to a two-end crystallization magnesium reduction reaction device and method. Background Technology

[0002] The silicothermic process for magnesium smelting is a major magnesium smelting technology both domestically and internationally. Raw materials undergo three main processes: calcination, reduction, and refining, to produce primary magnesium (crude magnesium). Compared to horizontal tank smelting, the vertical silicothermic process offers advantages such as gravity-driven automatic slag removal, large charging capacity, and high production efficiency, making it an increasingly popular trend in recent years. The main equipment in vertical magnesium smelting is the vertical tank, typically a long cylindrical structure composed of upper, middle, and lower sections. The upper section is the condensation and crystallization section, the middle section is the main body, i.e., the reduction section, and the lower section is the slag removal section. These three sections are connected by flanges or (and) welding to form a sealed cavity. The condensation and crystallization section, i.e., the magnesium crystallizer, is generally installed inside the tank. The external part of the vertical tank is heated by a reduction furnace mounted on top of the reduction furnace, while a vacuum pump evacuates the interior of the tank. When the temperature inside the vertical tank is about 1200℃ and the pressure is usually around 10Pa, a reduction reaction occurs to produce magnesium vapor. The magnesium vapor crystallizes after being cooled in the magnesium crystallizer to obtain solid primary magnesium (crude magnesium). The crude magnesium is then melted, refined, and cast into ingots to obtain commercial magnesium.

[0003] In magnesium smelting, the feed pellets are first loaded into a vertical tank, then into upper and lower crystallizing cylinders. The tank is then sealed at both ends, and a vacuum is evacuated. During vacuuming, the airflow inside the tank carries powder (fine particles) adhering to the surface of the feed pellets, as well as metallic impurities from the initial reduction reaction, which contaminate the magnesium crystallizer as it passes through. This process presents two problems: first, some powder adheres to the inner wall of the magnesium crystallizer, forming a powder layer between the crystalline magnesium and the crystallizer, contaminating the initial crystallization surface and affecting the magnesium's morphology; second, during the initial magnesium production phase of the reduction reaction, the continuous contamination of the crystalline magnesium by powder and reaction impurities increases the impurity content of the metallic magnesium, significantly affecting the purity of the magnesium crystals. Summary of the Invention

[0004] The purpose of this method is to propose a two-end crystallization magnesium reduction reactor and its method, which solves the problem of contamination of the magnesium crystallizer by powder (fine material) and some broken material adhering to the surface of the feed pellets during the vacuuming process, thereby reducing the purity and efficiency of magnesium smelting; the technical solution adopted to achieve the above objective is:

[0005] A magnesium reduction reactor with two-end crystallization includes a vertical tank, an annular support base at the bottom of the vertical tank, a central cylinder sitting on the annular support base, multiple steam passages evenly distributed on the wall and bottom of the central cylinder, an upper crystallizing cylinder installed at the top of the vertical tank, a lower crystallizing cylinder installed at the bottom of the vertical tank, an upper end cover at the top of the upper crystallizing cylinder, and a lower end cover at the bottom of the lower crystallizing cylinder. The interior of the upper crystallizing cylinder is connected to the interior of the vertical tank, and the interior of the lower crystallizing cylinder is connected to the interior of the central cylinder.

[0006] An upper cooling water jacket is provided outside the upper crystallizing cylinder, and an upper water outlet pipe and an upper water inlet pipe are provided on the upper cooling water jacket. A lower cooling water jacket is provided outside the lower crystallizing cylinder, and a lower water outlet pipe and a lower water inlet pipe are provided on the lower cooling water jacket.

[0007] A vacuum pipe connected to the inside of the vertical tank is provided on the upper and / or lower cooling water jackets.

[0008] Preferably, a rigid, hollow cylinder is provided at the bottom of the lower crystallizer to support it.

[0009] Preferably, an upper control valve is installed on both the upper water outlet pipe and the upper water inlet pipe, and a lower control valve is installed on both the lower water outlet pipe and the lower water inlet pipe. A vacuum pump is connected to the vacuum pumping pipe.

[0010] Preferably, the height of the upper crystallizing cylinder is less than the height of the lower crystallizing cylinder, and the thermal radiation area between the upper crystallizing cylinder and the upper cooling water jacket is less than the thermal radiation area between the lower crystallizing cylinder and the lower cooling water jacket.

[0011] Preferably, the size of the steam vents in the central cylinder wall and bottom is smaller than the size of the magnesium raw material balls.

[0012] Preferably, a vacuum-breaking air intake pipe is provided at the upper end of the vertical tank, a control valve is installed on the vacuum-breaking air intake pipe, and the vacuum-breaking air intake pipe is connected to an inert gas source.

[0013] Preferably, a reduction furnace for heating the vertical tank is arranged outside the vertical tank.

[0014] A method for magnesium reduction reaction using a two-terminal crystallizing magnesium reduction reactor as described above includes the following steps:

[0015] Step A: While the reduction furnace continues to heat the vertical tank, a certain amount of magnesium raw material balls are loaded into the vertical tank according to production needs. The upper crystallization cylinder, upper end cover, lower crystallization cylinder and lower end cover are installed, and the upper and lower ends of the vertical tank are sealed.

[0016] Step B: Turn off the circulation water flow of the lower cooling water jacket and close the corresponding vacuum pipe of the lower cooling water jacket; increase and control the circulation water flow of the upper cooling water jacket, open the corresponding vacuum pipe of the upper cooling water jacket, and use a vacuum pump to evacuate the vertical tank. At this time, the powder and trace amounts of magnesium / metal vapor in the tank enter the upper crystallization cylinder to begin crystallization.

[0017] Step C: When the absolute pressure inside the vertical tank reaches approximately 1000-5000 Pa and the temperature of the magnesium raw material balls inside the vertical tank rises to approximately 1080-1190℃, a large amount of magnesium vapor is reduced from the magnesium raw material balls. At this time, reduce and control the circulation water flow of the upper cooling water jacket, and close the corresponding vacuum pipe of the upper cooling water jacket; increase and control the circulation water flow of the lower cooling water jacket, and open the corresponding vacuum pipe of the lower cooling water jacket. A large amount of magnesium vapor enters the lower crystallization cylinder to begin crystallization.

[0018] Step D: After magnesium reduction has been completed for 5-7 hours, close the corresponding vacuum pipe of the lower cooling water jacket, open the control valve of the vacuum breaking inlet pipe at the upper end of the vertical tank to break the vacuum until atmospheric pressure is reached, and finally discharge magnesium and slag.

[0019] Preferably, in step D, the magnesium removal step includes:

[0020] Step D1: Open the top cover of the vertical tank, remove the upper crystallizing cylinder to discharge magnesium, and at the same time reset the top cover;

[0021] Step D2: Open the lower end cover of the vertical tank and remove the lower crystallizing cylinder to extract magnesium;

[0022] Step D3: With the top cover of the vertical tank reset, lift the central cylinder from the bottom to discharge slag;

[0023] Step D4: After the slag is discharged, the central cylinder falls back to its original position by its own weight.

[0024] The beneficial effects of this invention are as follows: (1) By setting an upper crystallizing cylinder and a lower crystallizing cylinder at the upper and lower ends of the vertical tank, as well as the corresponding upper vacuum pipe and lower vacuum pipe, firstly, during the vacuuming of the vertical tank and the initial stage of the reduction reaction, the airflow only passes through the upper crystallizing cylinder, avoiding contamination of the lower crystallizing cylinder, and laying the foundation for the crystallization of high-purity magnesium crystals in the lower crystallizing cylinder; secondly, the separation and control of the initial stage and the middle and later stages of magnesium reduction are realized, so that the crude magnesium crystals with impurities in the early stage and the high-purity magnesium crystals can be separated in the reduction stage in the vertical tank, and the high-purity magnesium crystals are exempt from refining, shortening the process and reducing the number of steps.

[0025] (2) With the top cover of the vertical tank reset, the central cylinder is lifted from the bottom to discharge slag, which can effectively avoid the "chimney effect" and improve the production environment.

[0026] (3) Analysis of the magnesium crystal composition in the upper and lower crystallizing cylinders showed that the magnesium purity in the upper crystallizing cylinder was 95.72% and the magnesium purity in the lower crystallizing cylinder was as high as 99.82%, indicating a good grading effect.

[0027] (4) The present invention realizes a crystallization reaction device and a magnesium reduction reaction method that directly separates crude magnesium ingots and refined magnesium ingots at both ends during the magnesium reduction stage. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the initial stage of magnesium raw material ball reduction, one of the structural schematic diagrams of the present invention;

[0029] Figure 2 This is a schematic diagram of the initial stage of magnesium raw material ball reduction, which is the second structural schematic diagram of the present invention.

[0030] Figure 3 This is a schematic diagram of the middle and later stages of magnesium feedstock ball reduction;

[0031] Figure 4 A schematic diagram of the structure for loading magnesium raw material balls;

[0032] Figure 5 A schematic diagram of the structure for reducing slag discharge. Detailed Implementation

[0033] The invention will now be further described with reference to the accompanying drawings. Specific Implementation Example 1:

[0035] like Figure 1 As shown, a two-end crystallization magnesium reduction reaction device includes a vertical tank B1. An annular support B5 is provided at the bottom of the vertical tank B1. A central cylinder B4 is seated on the annular support B5. Multiple steam passages are evenly distributed on the wall and bottom of the central cylinder B4. The size of the steam passages is smaller than the size of the magnesium raw material balls B3, so as to ensure that magnesium vapor enters the central cylinder B4 while preventing the magnesium raw material balls B3 from entering. An upper crystallization cylinder A6 is installed at the top of the vertical tank B1, and a lower crystallization cylinder C6 is installed at the bottom of the vertical tank B1. The upper crystallization cylinder A6 is connected to the inside of the vertical tank B1, and the lower crystallization cylinder C6 is connected to the inside of the central cylinder B4, that is, it is also connected to the inside of the vertical tank B1.

[0036] An upper cooling water jacket A5 is installed outside the upper crystallizing cylinder A6. An upper water outlet pipe A3 and an upper water inlet pipe A2 are installed on the upper cooling water jacket A5. A lower cooling water jacket C5 is installed outside the lower crystallizing cylinder C6. A lower water outlet pipe C4 and a lower water inlet pipe C1 are installed on the lower cooling water jacket C5. Normally, the upper cooling water jacket A5 and the lower cooling water jacket C5 are detachably fixed to the top and bottom of the vertical tank B1, respectively. They are only removed when maintenance or replacement is required.

[0037] An upper vacuum pipe A8 is connected to the upper cooling water jacket A5 and the vertical tank B1. A lower vacuum pipe C7 is provided on the lower cooling water jacket C5 and connected to the vertical tank B1. Upper control valves A4, A9, and A1 are installed on the upper water outlet pipe A3, the upper vacuum pipe A8, and the upper water inlet pipe A2, respectively. Lower control valves C3, C8, and C2 are installed on the lower water outlet pipe C4, the lower vacuum pipe C7, and the lower water inlet pipe C1, respectively. Vacuum pumps A10 and C9 are installed on the upper vacuum pipe A8 and the lower vacuum pipe C7, respectively.

[0038] An upper end cap A11 is provided at the top of the upper crystallizing cylinder A6, a lower end cap C11 is provided at the bottom of the lower crystallizing cylinder C6, and a rigid hollow cylinder C12 is provided at the bottom of the lower crystallizing cylinder C5 to support the lower crystallizing cylinder C5.

[0039] Specific Implementation 2:

[0040] like Figures 2 to 3 As shown in Specific Embodiment 1, in order to minimize the influence of the upper crystallizing cylinder A6 on the crystallization of a small amount of magnesium vapor during the middle and later stages of magnesium reduction, the height of the upper crystallizing cylinder A6 is less than the height of the lower crystallizing cylinder C6, and the thermal radiation area between the upper crystallizing cylinder A6 and the upper cooling water jacket A5 is less than the thermal radiation area between the lower crystallizing cylinder C6 and the lower cooling water jacket C5.

[0041] Meanwhile, a vacuum-breaking air intake pipe (not shown in the figure) is provided at the upper end of the vertical tank B1. A control valve is installed on the vacuum-breaking air intake pipe, and the vacuum-breaking air intake pipe is connected to an inert gas source such as nitrogen.

[0042] Furthermore, in this embodiment, the vertical tank B1 is heated by arranging a reduction furnace B2 outside the vertical tank B1. Specific Implementation Example 3:

[0044] like Figures 2 to 5 As shown, a method for magnesium reduction reaction using the two-end crystallization magnesium reduction reaction apparatus described above includes the following steps:

[0045] Step A: While the reduction furnace B2 continues to heat the vertical tank B1, a certain amount of magnesium raw material balls B3 are loaded into the vertical tank B1 according to production needs. The upper crystallization cylinder A6 and the lower crystallization cylinder C6 are installed. The upper end cover A11 and the lower end cover C12 are connected to the vertical tank B1 and sealed by connecting bolts.

[0046] Step B: Close the circulating water flow of the lower cooling water jacket C5 and close the control valve C8 of the vacuum pipe C7 corresponding to the lower cooling water jacket C5; increase and control the circulating water flow of the upper cooling water jacket A5, open the control valve A9 of the vacuum pipe A8 corresponding to the upper cooling water jacket A5, and use the vacuum pump A10 to evacuate the vertical tank B1. At this time, the powder and trace amounts of magnesium / metal vapor in the tank enter the upper crystallizing cylinder A6 to begin crystallization.

[0047] During this stage, due to the low temperature (room temperature) of the magnesium raw material ball B3 that was just added to the vertical tank B1, local temperature fluctuations occurred, and the pressure was unstable due to vacuuming. The crude magnesium crystals A7 will bring in metal impurities such as K, Na, and Mn, as well as AL2O3 and Fe2O3 oxide impurities, which will crystallize together, resulting in a significant decrease in the purity of the crystallized magnesium. This part of the crude magnesium crystallizes in the upper crystallization cylinder A6.

[0048] Step C: When the absolute pressure inside the vertical tank B1 reaches 1000-5000Pa and the temperature of the magnesium raw material ball B3 inside the vertical tank B1 rises to 1080-1190℃, a large amount of magnesium vapor is reduced from the magnesium raw material ball B3. At this time, reduce and control the circulation water volume of the upper cooling water jacket A5, and close the control valve A9 of the vacuum pipe A8 corresponding to the upper cooling water jacket A5; increase and control the circulation water volume of the lower cooling water jacket C5, and open the control valve C8 of the vacuum pipe C7 corresponding to the lower cooling water jacket C5. A large amount of magnesium vapor enters the lower crystallizing cylinder C6 to begin crystallization.

[0049] Furthermore, by changing the heat radiation area between the lower crystallizing cylinder C6 and the lower cooling water jacket C5, as well as the temperature and flow rate of the cooling water, the temperature inside the lower cooling water jacket C5 is controlled to achieve the crystallization of high-purity magnesium crystals C10 on the inner wall of the lower crystallizing cylinder C6.

[0050] Step D: After magnesium reduction for 5-7 hours, close the control valve C8 of the vacuum pipe C7 corresponding to the lower cooling water jacket C5, open the control valve of the vacuum breaking inlet pipe at the upper end of the vertical tank B1 to break the vacuum until atmospheric pressure is reached, and finally discharge magnesium and slag.

[0051] In step D, the magnesium removal step includes:

[0052] Step D1: Open the upper cover A11 of the vertical tank B1, take out the upper crystallization cylinder A6 to discharge magnesium. This is crude magnesium crystal with impurities. Then, put the upper cover A11 back in place.

[0053] Step D2: Open the lower end cover C12 of the vertical tank B1, take out the lower crystallization cylinder C6 to extract magnesium, which is high-purity magnesium crystallization;

[0054] Step D3: With the top cover A11 of the vertical tank B1 reset, lift the central cylinder B4 from the bottom to discharge slag. After the slag is discharged, the central cylinder B4 falls back to its original position by its own weight. Specific Implementation Example 4:

[0056] Based on the above methods, specific tests were conducted. Analysis of the magnesium crystal composition in the upper crystallizer A6 and lower crystallizer C6 in this embodiment showed that the magnesium purity in the upper crystallizer was 95.72%, and the magnesium purity in the lower crystallizer was as high as 99.82%, indicating a good grading effect. The specific composition is as follows:

[0057] Analysis table of magnesium composition in C6 lower crystallizer

[0058] Laboratory items Mg Fe Si Al Cu Mn Ni Other impurities total Laboratory results (unit: %) 99.820 0.035 0.039 0.045 0.011 0.005 0.002 0.043

[0059] Analysis table of magnesium composition in upper crystallizer A6

[0060] Laboratory items Mg Fe Si Al Cu Mn Ni Other impurities total Laboratory results (unit: %) 95.720 0.125 0.113 0.098 0.055 0.009 0.007 3.873

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A two-end crystallization type magnesium reduction reaction apparatus comprising a vertical tank, characterized by, An annular support seat is arranged at the bottom of the vertical tank, and a central cylinder is arranged on the annular support seat, a plurality of steam through holes are arranged on the wall and the bottom of the central cylinder, an upper crystallization cylinder is arranged at the top of the vertical tank, and a lower crystallization cylinder is arranged at the bottom of the vertical tank; an upper end cover is arranged at the top of the upper crystallization cylinder, and a lower end cover is arranged at the bottom of the lower crystallization cylinder; the inside of the upper crystallization cylinder is connected with the inside of the vertical tank, and the inside of the lower crystallization cylinder is connected with the inside of the central cylinder; An upper cooling water jacket is arranged outside the upper crystallization cylinder, and an upper water outlet pipeline and an upper water inlet pipeline are arranged on the upper cooling water jacket; a lower cooling water jacket is arranged outside the lower crystallization cylinder, and a lower water outlet pipeline and a lower water inlet pipeline are arranged on the lower cooling water jacket; A vacuum extraction pipeline connected with the inside of the vertical tank is arranged on the upper cooling water jacket and the lower cooling water jacket; A rigid hollow cylinder for supporting the lower crystallization cylinder is arranged at the bottom of the lower crystallization cylinder.

2. The two-end crystalline magnesium reduction reaction apparatus according to claim 1, characterized by, Upper control valves are arranged on the upper water outlet pipeline and the upper water inlet pipeline, lower control valves are arranged on the lower water outlet pipeline and the lower water inlet pipeline, and a vacuum pump is connected with the vacuum extraction pipeline.

3. The two-end crystalline magnesium reduction reaction apparatus according to claim 1 or 2, characterized by, The height of the upper crystallization cylinder is smaller than the height of the lower crystallization cylinder, and the heat radiation area between the upper crystallization cylinder and the upper cooling water jacket is smaller than the heat radiation area between the lower crystallization cylinder and the lower cooling water jacket.

4. The two-end crystalline magnesium reduction reaction apparatus according to any one of claims 1 to 3, characterized by The size of the steam through holes on the wall and the bottom of the central cylinder is smaller than the size of the magnesium raw material balls.

5. The two-end crystalline magnesium reduction reaction apparatus according to any one of claims 1 to 3, characterized by A vacuum breaking air inlet pipeline is arranged at the upper end of the vertical tank, a control valve is arranged on the vacuum breaking air inlet pipeline, and the vacuum breaking air inlet pipeline is connected with an inert gas source.

6. The two-end crystalline magnesium reduction reaction apparatus according to any one of claims 1 to 3, characterized by A reduction furnace is arranged outside the vertical tank for heating the vertical tank.

7. A magnesium reduction reaction method using the two-end crystalline magnesium reduction reaction apparatus according to any one of claims 1 to 6, characterized by, The method comprises the following steps: Step A: while the reduction furnace continuously heats the vertical tank, a certain amount of magnesium raw material balls is loaded into the vertical tank according to production needs, the upper crystallization cylinder, the upper end cover, the lower crystallization cylinder and the lower end cover are installed, and the upper and lower ends of the vertical tank are sealed; Step B: the circulating water amount of the lower cooling water jacket is closed, the corresponding vacuum extraction pipeline of the lower cooling water jacket is closed, the circulating water amount of the upper cooling water jacket is controlled to be large, the corresponding vacuum extraction pipeline of the upper cooling water jacket is opened, the vacuum pump is used to extract the inside of the vertical tank, at this time, the powder and a small amount of magnesium metal vapor in the previous stage in the tank enter the upper crystallization cylinder to start crystallization; Step C: when the absolute pressure in the vertical tank reaches 1000-5000 Pa and the temperature of the magnesium raw material balls in the vertical tank rises to 1080-1190 ℃, a large amount of magnesium vapor is reduced from the magnesium raw material balls, at this time, the circulating water amount of the upper cooling water jacket is controlled to be small, the corresponding vacuum extraction pipeline of the upper cooling water jacket is closed, the circulating water amount of the lower cooling water jacket is controlled to be large, the corresponding vacuum extraction pipeline of the lower cooling water jacket is opened, and a large amount of magnesium vapor enters the lower crystallization cylinder to start crystallization; Step D: after the magnesium reduction is completed, the corresponding vacuum extraction pipeline of the lower cooling water jacket is closed, the control valve of the vacuum breaking air inlet pipeline at the upper end of the vertical tank is opened to break the vacuum until the normal pressure, and finally the magnesium is taken out and the slag is discharged.

8. The magnesium reduction reaction method according to claim 7, characterized by, In step D, the magnesium taking-out step comprises: Step D1: the upper end cover of the vertical tank is opened, the upper crystallization cylinder is taken out for magnesium taking-out, and the upper end cover is reset; Step D2: the lower end cover of the vertical tank is opened, the lower crystallization cylinder is taken out for magnesium taking-out; Step D3: in the case that the upper end cover at the top of the vertical tank is reset, the central cylinder is lifted from the bottom for slag discharging. Step D4: After the slag is discharged, the center cylinder is reset by gravity.

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