Device and method for smelting magnesium and co-producing carbon nanotubes through carbon thermal reduction in vacuum arc furnace

Abstract

The invention provides a device and method for smelting magnesium and co-producing carbon nanotubes through carbon thermal reduction in a vacuum electric arc furnace, the device comprises a magnesium smelting electric arc furnace, MgO, coke, biological pyrolytic carbon and methane gas are used as raw materials to be added into molten iron in the magnesium smelting electric arc furnace for carbon thermal reduction, and mixed furnace gas containing metal magnesium steam, iron steam and CO is obtained; the mixed furnace gas is introduced into a heat compensation chamber, iron-containing chloride is introduced into a quenching condenser to be mixed with the mixed furnace gas flowing out of the heat compensation chamber so as to conduct isentropic expansion and cooling treatment on the mixed furnace gas, and then ternary mixed powder is obtained after the mixed furnace gas is cooled through a first cooling chamber; performing metal magnesium vacuum distillation and carbon annealing operation on the ternary mixed powder offline; residual gas in the first cooling chamber is subjected to secondary cooling through the second cooling chamber; and further, carbon thermal reduction magnesium smelting and carbon nanotube co-production are realized.

Description

Technical Field

[0001] This application relates to the field of magnesium smelting, and in particular to an apparatus and method for co-producing carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace. Background Technology

[0002] Carbon nanotubes, as high-performance modern carbon materials, have broad application prospects in electronics, aerospace, new energy and other fields. However, their current mainstream production method relies on CVD (chemical vapor deposition) process, which has significant technical bottlenecks and application limitations. This process requires the construction of dedicated high-precision reaction equipment, which not only involves a large initial investment in equipment, but also requires strict control of multiple parameters such as temperature, atmosphere and catalyst during the reaction process, resulting in high process complexity and high operational difficulty. At the same time, the CVD process is essentially an intermittent production mode, with low capacity of a single set of equipment and discontinuous production process, which cannot achieve large-scale continuous output. Ultimately, this results in high unit production costs and expensive market prices for carbon nanotubes. These defects directly restrict the large-scale popularization and application of carbon nanotubes.

[0003] Furthermore, in existing technologies, carbon nanotube production operates independently of other industrial processes, failing to achieve process coupling and synergistic resource utilization. This further exacerbates the problems of low production efficiency and high costs. Particularly in the magnesium smelting industry, the process generates underutilized resources such as carbon-containing gases and high-temperature reaction environments, which are not effectively linked to carbon nanotube production. This results in resource waste during magnesium smelting and fails to provide new technological pathways for low-cost, large-scale carbon nanotube production, thus limiting both the application and promotion of carbon nanotubes and the efficient utilization of resources in the magnesium smelting industry. Summary of the Invention

[0004] This application provides an apparatus and method for co-producing magnesium and carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace, thereby achieving the co-production of magnesium and carbon nanotubes.

[0005] To achieve the above objectives, this technical solution provides a device for the co-production of carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace, comprising: a magnesium smelting electric arc furnace containing molten iron, used for high-temperature electric arc heating of materials MgO and carbon in the molten iron to obtain a mixed furnace gas containing metallic magnesium vapor, iron vapor, and CO; a reheating chamber connected to the furnace gas outlet of the magnesium smelting electric arc furnace to maintain or increase the temperature of the mixed furnace gas; and a quenching condenser connected to the high-temperature furnace gas channel of the reheating chamber for introducing iron-containing chlorides to perform isentropic expansion and cooling treatment on the mixed furnace gas to obtain iron powder, solid particles, and... The furnace gas is cooled; a first cooling chamber connected to the quenching condenser is used to continuously cool the iron powder, solid particles and furnace gas to obtain a ternary mixed powder, wherein the ternary mixed powder includes magnesium, carbon and iron and their oxides; a second cooling chamber connected to the gas channel of the first cooling chamber is used to perform secondary cooling on the condensed magnesium vapor in the first cooling chamber so that the residual metallic magnesium vapor is condensed and the non-condensable gases such as CO and hydrogen are further cooled; a vacuum pump connected to the second cooling chamber is used to create a vacuum negative pressure in the magnesium smelting electric arc furnace, the reheating chamber, the first cooling chamber and the second cooling chamber.

[0006] Secondly, this solution provides a method for the co-production of carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace, comprising: adding MgO, coke, bio-pyrolysis carbon and methane gas as raw materials to molten iron in a magnesium smelting electric arc furnace for carbothermic reduction to obtain a mixed furnace gas containing metallic magnesium vapor, iron vapor and CO; passing the mixed furnace gas into a reheating chamber, and passing iron-containing chloride into a quenching condenser to mix with the mixed furnace gas flowing out from the reheating chamber to perform isentropic expansion and cooling treatment on the mixed furnace gas to obtain iron powder, solid particles and cooling furnace gas; after cooling in a first cooling chamber, the iron powder, solid particles and cooling furnace gas obtain ternary mixed powder, and the ternary mixed powder is subjected to vacuum distillation of metallic magnesium and carbon annealing offline; the gas remaining in the first cooling chamber is cooled again in a second cooling chamber; wherein the magnesium smelting electric arc furnace, the reheating chamber, the first cooling chamber and the second cooling chamber form a vacuum negative pressure.

[0007] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects: (1) This scheme uses common carbonaceous materials (such as coke, bio-pyrolysis carbon, methane pyrolysis carbon black, etc.) as carbon sources. These raw materials are inexpensive, readily available, and widely sourced, without relying on high-purity special carbon raw materials. In the magnesium smelting process, the carbon source not only participates in the carbothermic reduction reaction of magnesium oxide to generate metallic magnesium, but can also be converted into primary carbon materials (such as elemental carbon, porous carbon, etc.) required for carbon nanotubes through high-temperature pyrolysis, gas-phase reverse reaction, etc., to achieve dual use of carbon, greatly reduce the raw material cost of carbon nanotubes, and improve the overall utilization rate of carbon raw materials.

[0008] (2) This solution uses a large-scale magnesium smelting electric arc furnace as the core equipment and adopts the mature "continuous, large-furnace" production mode in the non-ferrous metal smelting field, thus breaking away from the limitations of traditional carbon nanotubes that rely on small-scale CVD equipment. The hourly production capacity of a single magnesium smelting electric arc furnace can reach more than ton-level, and the annual production capacity can easily exceed 10,000 tons-level. This not only significantly improves the production scale of metallic magnesium, but also simultaneously realizes the large-scale co-production of carbon nanotubes. The large-furnace production mode can also reduce equipment investment costs and lower the fixed cost per unit product, thus solving the pain point of "small production capacity and high investment" in traditional carbon nanotube production.

[0009] (3) The magnesium distillation furnace of this scheme can separate metallic magnesium from the ternary mixed powder through vacuum distillation to obtain pure crystalline magnesium. During the distillation heating process, the carbon material can be annealed simultaneously to improve the crystal structure and properties of carbon nanotubes. Moreover, the carbon mixture (containing carbon nanotubes, porous carbon, etc.) remaining after distillation is easy to purify by subsequent acid washing. Compared with the traditional step-by-step process of first extracting magnesium and then processing carbon, this integrated design shortens the production cycle, reduces equipment investment, and improves overall production efficiency.

[0010] (4) This scheme adopts a co-production and coupling production model, in which metallic magnesium and carbon nanotubes share core equipment such as the magnesium smelting electric arc furnace, reheating chamber, cooling chamber, and vacuum pump, as well as auxiliary facilities such as the vacuum system and heat source system, eliminating the need to build a separate production line for carbon nanotubes. During the production process, the high-temperature environment of magnesium smelting provides the necessary heat for carbon nanotube generation, and the carbon source participates in the magnesium smelting reaction while being converted into carbon nanotube raw materials, realizing the cascade utilization of energy and materials. This sharing model significantly reduces equipment investment, energy consumption, and operating costs, allowing the production cost of carbon nanotubes to be further diluted as the production scale of metallic magnesium expands, significantly enhancing the product's market competitiveness.

[0011] (5) From raw material addition and mixed furnace gas treatment to ternary mixed powder collection, this scheme achieves near-continuous production of the main process, avoiding the efficiency loss of traditional intermittent production and increasing the output per unit time. At the same time, no waste residue is generated during the production process: MgO and carbon source in the raw materials are almost completely converted into metallic magnesium, carbon nanotubes and by-product CO. A small amount of impurities can be recovered by acid washing or treated harmlessly, which meets environmental protection requirements, reduces solid waste treatment costs, and achieves clean production. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the device for co-producing carbon nanotubes by carbothermic reduction of magnesium using a vacuum electric arc furnace, as provided in this solution.

[0013] Figure 2 This is a schematic diagram of the structure of an electric arc furnace for magnesium smelting.

[0014] Figure 3 This is another structural schematic diagram of a magnesium smelting electric arc furnace.

[0015] Figure 4 This is a structural diagram of the heat exchange chamber, quenching condenser, and first cooling chamber.

[0016] Figure 5 This is a partial structural diagram of a quenching condenser.

[0017] Figure 6 This is a top view of the connection point between the first cooling chamber and the quenching condenser.

[0018] Figure 7 This is a schematic diagram of the structure of the first and second cooling chambers.

[0019] Figure 8 This is a schematic diagram of a magnesium distillation furnace system.

[0020] In the diagram: 101 Magnesium smelting electric arc furnace, 102 Electric furnace steel shell, 103 Insulation layer, 104 Graphite furnace lining, 105 Hollow top electrode, 106 Bottom electrode, 107 Furnace gas passage, 108 Slag cleaning tank, 109 Raw material tank, 110 Gas hydrocarbon storage tank, 115 Magnesium oxide iron bath immersion lance, 116 Carbon powder iron bath immersion lance, 120 Reheating chamber, 121 Reheating electrode anode, 122 Reheating electrode cathode, 123 High-temperature furnace gas passage, 201 Quenching condenser, 202 Catalyst injection pipe, 204 Catalyst storage tank, 205 Lobe-shaped nozzle, 206 Mixing channel, 207 Turbulence cone, 208 Converging tube, 209 Throat, 210 Expansion tube, 211 Parallel tube, 301 First cooling chamber, 302 303 Primary Cooling Shell Evaporator, 304 Upper Evaporator Heat Exchanger of Primary Cooling, 305 Upper Water Cooling Pipe of Secondary Cooling, 306 Constant Temperature Water Bath of Secondary Cooling, 307 Cooling Water Inlet of Secondary Cooling, 308 Cooling Water Outlet of Secondary Cooling, 309 Magnesium-Silicon-Carbon Ternary Mixed Powder, 310 Secondary Cooling Chamber, 311 Secondary Cooling Shell Evaporator, 320 Dust Collector, 321 Vacuum Pump, 322 By-product Gas Storage Tank, 501 Argon-Protected Solid Powder Briquetting Machine, 507 Carbon-Magnesium-Iron Mixed Material, 510 Metallic Magnesium Remelting Ingot Casting Machine, 601 Magnesium Distillation Furnace, 602 Heating Chamber, 603 Primary Cooling Chamber of Distillation, 604 Secondary Cooling Chamber of Distillation, 605 Vacuum Pump, 606 Constant Temperature Cooling Bath of Primary Cooling, 607 Constant Temperature Liquid Bath of Secondary Cooling, 608 Primary Crystallizing Magnesium, 609 Secondary Crystallizing Magnesium, 620 Heat Source Inlet, 621 Waste heat source outlet, 622 crystalline magnesium primary cooling coolant inlet, 623 crystalline magnesium primary cooling coolant outlet, 624 crystalline magnesium secondary cooling water inlet, 625 crystalline magnesium secondary cooling water outlet. Detailed Implementation

[0021] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with one or more embodiments of this specification. Rather, they are merely examples of apparatuses and methods consistent with some aspects of one or more embodiments of this specification as detailed in the appended claims.

[0022] It should be noted that the steps of the corresponding methods are not necessarily performed in the order shown and described in this specification in other embodiments. In some other embodiments, the methods may include more or fewer steps than described in this specification. Furthermore, a single step described in this specification may be broken down into multiple steps in other embodiments; and multiple steps described in this specification may be combined into a single step in other embodiments.

[0023] Example 1 like Figure 1 As shown, this solution provides an apparatus for the co-production of carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace, comprising: Magnesium smelting electric arc furnace 101 contains molten iron and is used to heat materials MgO and carbon in the molten iron by high-temperature electric arc to obtain a mixed furnace gas containing metallic magnesium vapor, iron vapor and CO. The supplementary heating chamber 120, which is connected to the furnace gas outlet 107 of the magnesia electric arc furnace 101, is used to maintain or increase the temperature of the mixed furnace gas. The quenching condenser 201, which is connected to the high-temperature furnace gas channel 123 of the same heat-replenishing chamber 120, is used to introduce iron-containing chloride to perform isentropic expansion and cooling treatment on the mixed furnace gas to obtain iron powder, solid particles and cooling furnace gas. The first cooling chamber 301, connected to the quenching condenser 201, is used to continuously cool the iron powder, solid particles and cooling furnace gas to obtain ternary mixed powder, wherein the ternary mixed powder includes magnesium, carbon and iron and their oxides. And a second cooling chamber 310 connected to the gas passage of the first cooling chamber 301, used to perform secondary cooling on the condensed magnesium vapor in the first cooling chamber 301 so that the crystallized residual metallic magnesium vapor is in a condensed state and further cools non-condensable gases such as CO gas and hydrogen. The vacuum pump 321 connected to the second cooling chamber 310 is used to create a vacuum negative pressure in the magnesium smelting electric arc furnace 101, the reheating chamber 120, the first cooling chamber 301 and the second cooling chamber 310.

[0024] Regarding the magnesia smelting electric arc furnace 101 in this plan: The magnesium smelting electric arc furnace 101 in this solution is a heating furnace that uses electric arc heating to isolate air and can create a vacuum. In some embodiments, the arc temperature of the magnesium smelting electric arc furnace 101 is greater than 1800°C, preferably greater than 3000°C. Furthermore, since the magnesium smelting electric arc furnace 101 is under vacuum, the carbothermic reduction reaction of magnesium oxide only needs to be controlled at a temperature above 1800°C.

[0025] The magnesium smelting electric arc furnace 101 contains molten iron. Carbon introduced into the magnesium smelting electric arc furnace 101 dissolves in the molten iron to form an iron-carbon alloy liquid with a carbon content as high as 4.3~6.9wt%. Magnesium oxide is then introduced into the molten iron to undergo a carbothermic reduction reaction with the carbon dissolved in the molten iron. Since this carbothermic reduction reaction takes place in the molten iron, the overall reaction is a liquid-solid reaction state, which is superior to the solid-solid reaction type of traditional carbon reduction magnesium smelting in terms of kinetics, mass transfer, and heat transfer.

[0026] Specifically, the carbothermic reduction reaction that occurs in molten iron is as follows: .

[0027] like Figure 2 As shown, the magnesia smelting electric arc furnace 101 includes an electric furnace steel shell 102. One side of the electric furnace steel shell 102 is provided with a slag cleaning trough 108 that is inclined downwards, and the other side is provided with a gas channel 107 that is inclined upwards. Electrodes are provided inside.

[0028] It should be noted that the magnesium smelting electric arc furnace 101 can adopt AC three electrodes, DC top and bottom dual electrodes, or an even number of DC top electrodes. In the embodiment of this scheme, the magnesium smelting electric arc furnace 101 adopts top and bottom dual electrodes. The top of the magnesium smelting electric arc furnace 101 is provided with a top electrode 105 and the bottom is provided with a bottom electrode 106. The top electrode is the cathode and the bottom electrode is the anode.

[0029] In some embodiments, both the top electrode 105 and the bottom electrode 106 are ultra-high power graphite electrodes, and the top electrode is a hollow electrode.

[0030] It should be noted that since the top electrode 105 of the magnesium smelting electric arc furnace 101 is made of graphite, under the high temperature of the electric arc, the graphite carbon is converted into carbon nanotubes (CNTs), serving as one of the sources of carbon nanotubes. The specific reaction is as follows: .

[0031] In some embodiments, the inner wall of the electric furnace steel shell 102 is provided with a graphite furnace lining 104 and a heat insulation layer 103, wherein the heat insulation layer 103 is disposed along the inner wall of the inner wall of the electric furnace steel shell 102, and the graphite furnace lining 104 is disposed on the surface of the heat insulation layer 103 and wraps the top electrode 105 and the bottom electrode 106.

[0032] like Figure 2 As shown, in some embodiments, the apparatus for the co-production of carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace further includes: Raw material tank 109 is used to contain solid materials, which include MgO, coke and bio-pyrolysis carbon; Hydrocarbon storage tank 110 is used to contain hydrocarbon gases. In some embodiments, carbon and MgO are added to the molten iron through the gaseous hydrocarbon storage tank 110 and the raw material tank 109, respectively, via hollow electrodes.

[0033] It should be noted that the solid material enters the hollow electrode under the transport of low-pressure methane gas.

[0034] In some embodiments, the solid material contains MgO particles or powder, as well as coke particles or powder and bio-pyrolytic carbon particles or powder.

[0035] like Figure 3 As shown, in some other embodiments, the apparatus for the co-production of carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace further includes: The carbon powder iron bath immersion spray gun 116 and the magnesium oxide iron bath immersion spray gun 115 are connected to the magnesium smelting electric arc furnace 101. One end of the carbon powder iron bath immersion spray gun 116 and the magnesium oxide iron bath immersion spray gun 115 is immersed in the molten iron. The magnesium oxide iron bath immersion spray gun 115 is used to spray magnesium oxide, and the carbon powder iron bath immersion spray gun 116 is used to spray carbon-containing materials.

[0036] In some embodiments, carbon-containing materials include coke particles or powder, bio-pyrolyzed carbon particles or powder.

[0037] It should be noted that the carbon injected at high speed into the hollow electrode or the immersion spray gun 116 will enter the molten iron and undergo high-temperature thermal decomposition. At this time, the organic matter will be completely thermally decomposed. In addition to releasing hydrogen and CO gas, the remaining fixed carbon will undergo reconstruction, which will most likely generate carbon nanotubes, possibly single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs), thus becoming one of the sources of carbon nanotubes. The reaction is as follows: .

[0038] In addition, the carbon composition of the magnesium smelting electric arc furnace 101 includes coke, bio-pyrolysis carbon, and carbon black particles from CH4 pyrolysis:

[0039] .

[0040] It should be noted that, as mentioned earlier, carbon and magnesium oxide undergo a carbothermic reduction reaction in molten iron to generate CO and magnesium vapor. In addition, due to the high arc temperature of the magnesium smelting electric arc furnace 101, some of the molten iron will also vaporize to form iron vapor. At this time, iron vapor, magnesium vapor, and CO furnace gas are discharged from the magnesium smelting electric arc furnace 101 as a mixed furnace gas.

[0041] In some embodiments, the temperature of the mixed furnace gas can reach 1700~2000°C.

[0042] In addition, since the entire reaction system is in an inert gas environment, the mixed furnace gas also contains argon. If methane is used to transport the gas, the mixed furnace gas will also contain a certain proportion of H2 produced by the thermal cracking of methane gas.

[0043] Regarding the supplementary heating chamber 120 in this plan: In some embodiments, the heating chamber 120 contains low-power electrodes for arc heating to raise the temperature of the mixed furnace gas. For example... Figure 3 As shown, the heating chamber 120 is equipped with a heating electrode anode 121 and a heating electrode cathode 122 for electric arc heating to raise or maintain the high temperature of the mixed furnace gas.

[0044] Furthermore, the heating chamber 120 is connected to the quenching condenser 201 through a high-temperature furnace gas channel 123 perpendicular to the heating chamber 120.

[0045] Regarding the quenching condenser 201 in this solution: It should be noted that the mixed furnace gas flowing out of the self-heating chamber 120 contains high-temperature magnesium vapor, CO gas and iron vapor, and may also carry a small amount of solid powder particles. Under the strong suction of the terminal vacuum pump 321, and based on the significant reduction in the mass flow rate of non-condensable gas caused by the final condensation of metallic magnesium vapor and the reverse reaction of CO gas, there is a large pressure difference in the quenching condenser 201 between the high-temperature furnace gas and the first cooling chamber 301, forming a pressure ratio that meets the requirements for achieving supersonic expansion.

[0046] In some embodiments, the quenching condenser 201 of this solution is connected to the catalyst storage tank 204 through the catalyst injection pipe 202. The ferric chloride in the catalyst storage tank 204 is injected into the quenching condenser 201, and the mixed furnace gas is condensed in the quenching condenser 201.

[0047] Specifically, such as Figure 4 As shown, Figure 4As shown, the quenching condenser 201 includes a mixing pipe 206, a tapering pipe 208, a throat 209, an expansion pipe 210, and a parallel pipe 211 connected in sequence. The opening diameter of the tapering pipe 208 decreases sequentially towards the throat 209, and the opening diameter of the expansion pipe 201 increases sequentially towards the parallel pipe 211.

[0048] In some embodiments, the iron-containing chloride includes partially vaporized ferric chloride (FeCl3) vapor injected at high speed from the catalyst storage tank 204, or anhydrous ferric chloride or ferric chloride powder particles sprayed with argon as the carrier gas. The iron-containing chloride enters the mixing pipe 206 in the quenching condenser 201 and mixes with the mixed furnace gas flowing out from the heat replenishment chamber 120.

[0049] like Figure 6 As shown, the injection outlet of the catalyst injection pipe 202 is designed as a wave-shaped nozzle 205, wherein the wave-shaped nozzle 205 has a wave or petal shape. The iron chloride enters the quenching condenser 201 from the catalyst storage tank 204 through the catalyst injection pipe 202 and is ejected at high speed from the wave-shaped nozzle 205, and enters the mixing channel 206 to mix with the high-temperature furnace gas.

[0050] Furthermore, a turbulence cone 207 is provided in the mixing pipeline 206, positioned relative to the injection outlet of the catalyst injection pipe 202. The turbulence cone 207 is positioned directly opposite the injection outlet of the catalyst injection pipe 202, so that the mixing effect of iron-containing chloride and mixed furnace gas is further enhanced with the assistance of the turbulence cone 207, and efficient momentum transfer mixing is achieved.

[0051] In some embodiments, the content of iron chloride is 1 to 5% of the magnesium vapor flow rate.

[0052] In some embodiments, the throat 209 and the parallel tube 211 are pipes with uniform opening diameters, and the tapering tube 208 and the expanding tube 201 are trumpet-shaped pipes.

[0053] In some embodiments, the maximum opening diameter of the expansion tube 201 is smaller than the maximum opening diameter of the contraction tube 208.

[0054] Correspondingly, the mixed high-temperature furnace gas undergoes isentropic expansion after passing through the converging tube 208, throat 209, expansion tube 210, and parallel tube 211, realizing the conversion of internal energy into kinetic energy and reaching several times the speed of sound, i.e., Ma between 1.3 and 2.6. Simultaneously, the overall temperature of the mixed furnace gas decreases at a rate of 10^6 K / s, meaning that passing through a quencher several meters long typically takes milliseconds, with an overall temperature reduction of 500-900℃. Iron vapor and ferrous chloride are reduced by magnesium vapor to obtain nano-sized metallic iron powder, which serves as the catalyst substrate for the subsequent formation of carbon nanotubes. Furthermore, if ferric chloride adsorbs a small amount of moisture, the moisture will also dissociate into hydrogen under the action of magnesium vapor and combine with magnesium to form magnesium oxide ultrafine powder, which travels along with the high-temperature furnace gas. MgO, as a support, can promote the formation of porous carbon materials, which can be used as the matrix for silicon-carbon anode materials. The reaction is shown below: .

[0055] In other words, at this time, the gas containing iron chloride or the carrier gas is injected into the high-temperature furnace gas and heated by the high-temperature furnace gas. At the same time, the magnesian reduction produces metallic iron particles, which are nano-iron powders, which act as a catalyst substrate.

[0056] It should be noted that hydrogen / argon has an activating effect on the formation of carbon nanotubes and also inhibits crystal growth. This is because the introduction of inert gases such as hydrogen and argon, as well as the vacuum negative pressure, increases the path of gas molecules and delays their collision behavior.

[0057] Furthermore, to enhance the condensation effect of the quenching condenser 201, the parallel tube 211 employs indirect cooling methods such as water cooling, air cooling, and oil cooling to cool the furnace gas using external media, thereby consolidating the rapid cooling effect of the quenching condenser 201.

[0058] Regarding the first cooling chamber 301 in this design: The first cooling chamber 301 of this scheme can continuously cool the iron powder, solid particles and cooling furnace gas. During this continuous cooling stage, the following reaction process will occur: (1) Condensation of magnesium vapor: ; (2) The reverse reaction of the carbothermic reduction of metallic magnesium: ; (3) Formation of carbon nanotubes: ; That is, under the catalysis of iron-based materials, CO and magnesium vapor react to generate high-end carbon materials such as carbon nanotubes.

[0059] In some embodiments, such as Figure 6As shown, the parallel pipe 211 enters from one side of the first cooling chamber 301 along the tangent of the inner wall of the first cooling chamber 301, so that the solid particles and the cooling furnace gas form a rotating gas in the first cooling chamber 301. Under the action of centrifugal force, the rotating gas adheres tightly to the inner wall of the first cooling chamber 301 and rotates downward, thereby achieving better cooling.

[0060] like Figure 7 As shown, the top of the first cooling chamber 301 is provided with a plurality of cold upper evaporation heat exchangers 304, the outer wall of the first cooling chamber 301 is fitted with a cold outer shell evaporation tube 303, and the bottom is provided with a cold on / off valve 302. Furthermore, the cold upper evaporation heat exchangers 304 are located above the connection point between the parallel tube 211 and the first cooling chamber 301, and the cold outer shell evaporation tube 303 covers the area below the connection point between the parallel tube 211 and the first cooling chamber 301.

[0061] Specifically, most of the swirling gas flows downward along the inner wall of the first cooling chamber 301 and is directly cooled by the outer shell evaporator 303. A small portion of the swirling gas rises and is cooled by the upper evaporator heat exchanger 304, then re-condenses and drips down or falls as powder and accumulates at the bottom of the first cooling chamber 301.

[0062] In some embodiments, the bottom of the first cooling chamber 301 contains a ternary mixed powder, which is a mixture of magnesium, carbon, and iron elements and their oxides, chlorides, and elemental forms. Specifically, the ternary mixed powder contains three products of magnesium: metallic magnesium powder as magnesium oxide and magnesium chloride; a single product of iron: nano-metallic iron powder; and carbon in various forms, including elemental carbon (including porous carbon, nano-carbon, and amorphous carbon). Figure 7 As shown, the apparatus for co-producing carbon nanotubes by carbothermic reduction of magnesium in a vacuum electric arc furnace includes an argon-protected solid powder briquetting machine 501 connected to a first cooling chamber 301. A cold-on-off valve 302 is provided at the bottom of the first cooling chamber 301. The cold-on-off valve 302 of the first cooling chamber 301 is opened periodically to collect ternary mixed powder. The ternary mixed powder is fed into the argon-protected solid powder briquetting machine 501 by means of a spiral or other means and is compacted into blocks. Then it is sent to a magnesium distillation furnace 601 for vacuum distillation to distill metallic magnesium and simultaneously achieve the purpose of annealing carbon materials.

[0063] like Figure 8As shown, an argon-protected solid powder briquetting machine 501 is connected to a magnesium distillation furnace 601. The magnesium distillation furnace 601 is used to distill the solid blocks pressed by the argon-protected solid powder briquetting machine 501 and to anneal carbon materials. In this scheme, the magnesium distillation furnace 601 is sequentially connected to a primary cooling chamber 603 and a secondary cooling chamber 604, which are used to cool the furnace gas generated during distillation. The furnace gas generated during distillation is condensed in the primary cooling chamber 603 to obtain pure crystalline magnesium 608. The furnace gas generated during distillation continues to be cooled in the secondary cooling chamber 604 to obtain a small amount of residual crystalline magnesium, and the magnesium distillation furnace 601 contains residual material 507.

[0064] In some embodiments, the temperature of the primary cooling chamber 603 is maintained at 500~1000°C. After magnesium volatilizes, it is condensed to obtain pure crystalline magnesium. The furnace gas continues to enter the secondary cooling chamber 604 for further thorough condensation.

[0065] In some embodiments, a heating chamber 602 is provided outside the magnesium distillation furnace 601. The heating chamber 602 is provided with a heat source inlet 620 and a waste heat source outlet 621 for heating the magnesium distillation furnace 601.

[0066] In some embodiments, a primary cooling chamber 603 is provided outside the primary cooling chamber 603, and a primary cooling constant temperature cooling tank 606 is provided with a crystalline magnesium primary cooling coolant inlet 622 and a crystalline magnesium primary cooling coolant outlet 623.

[0067] In some embodiments, a secondary cooling constant temperature liquid tank 607 is provided outside the distillation second cooling chamber 604. The secondary cooling constant temperature liquid tank 607 is provided with a crystalline magnesium secondary cooling water inlet 624 and a crystalline magnesium secondary cooling water outlet 625, and the distillation second cooling chamber 604 is evacuated by a vacuum pump 605.

[0068] In some embodiments, the residue 507 is a carbonaceous material such as carbon nanotubes or porous carbon, mixed with iron powder, magnesium oxide, and a small amount of magnesium chloride.

[0069] Regarding the further processing of residues: The residue 507 is post-treated to obtain carbon nanotubes. Specifically, the residue 507 is acid-washed to remove metallic iron, magnesium oxide, and a small amount of residual metallic magnesium. In some embodiments, hydrochloric acid, nitric acid, or hydrofluoric acid can be used as the acid washing medium.

[0070] In some embodiments, the residue after pickling is washed multiple times with deionized water and dried under inert gas protection in a vacuum system.

[0071] Furthermore, the dried carbon material can be finely ground and sieved to obtain carbon powder of the desired particle size. The final carbon nanotube materials and porous carbon materials are then supplied for use as conductive materials in power batteries and for the preparation of silicon-carbon anodes.

[0072] Regarding the second cooling chamber 310 in this design: Some of the magnesium vapor that evaporates from the first cooling chamber 301 continues to enter the second cooling chamber 310 to be cooled, so that metallic magnesium is collected at the bottom of the second cooling chamber 310.

[0073] The second cooling chamber 310 includes an upper water-cooling pipe 305 for the secondary cooling system. The second cooling chamber 310 is placed in a constant temperature water bath 306 for the secondary cooling system. The constant temperature water bath 306 for the secondary cooling system is provided with a cooling water inlet 307 and a cooling water outlet 308 for the secondary cooling system. A cooling on / off valve for the secondary cooling system is provided at the bottom of the second cooling chamber 310.

[0074] like Figure 1 As shown, the second cooling chamber 310 is also connected in sequence to a dust collector 320, a vacuum pump 321, and a by-product gas storage tank 322. The dust collector 320 is used to remove dust from the CO gas and pressurize it through the vacuum pump 321 before storing it in the by-product gas storage tank 322. The remaining condensed magnesium vapor, CO gas, hydrogen, etc. continue to enter the second cooling chamber 310 and are cooled by the upper water cooling pipe 305 of the second cooling chamber. Magnesium particles gather on the side wall and bottom. The remaining CO and some H2 gas enter the by-product gas storage tank 322 after passing through the dust collector and exhaust fan. It can be used to prepare other products using existing technology.

[0075] Regarding the remelting and casting of magnesium ingots: The pure crystalline magnesium produced in the distillation primary cooling chamber 603, the distillation secondary cooling chamber 604, and the secondary cooling chamber 310 is fed into the magnesium remelting ingot casting machine 510 for remelting and casting. The magnesium obtained from the remelting and casting is sold as commercial magnesium or further alloyed and processed.

[0076] Secondly, this solution provides a method for the co-production of carbon nanotubes from magnesium using an electric furnace thermal reduction apparatus, comprising the following steps: MgO, coke, bio-pyrolysis carbon and methane gas are added as raw materials to the molten iron in the magnesia electric arc furnace 101 for carbothermic reduction to obtain a mixed furnace gas containing metallic magnesium vapor, iron vapor and CO. The mixed furnace gas is introduced into the heat exchange chamber 120, and iron-containing chloride is introduced into the quenching condenser 201 to mix with the mixed furnace gas flowing out from the heat exchange chamber 120, so as to perform isentropic expansion and cooling treatment on the mixed furnace gas to obtain iron powder, solid particles and cooling furnace gas. Iron powder, solid particles and cooling furnace gas are cooled in the first cooling chamber 301 to obtain ternary mixed powder. The ternary mixed powder is then subjected to vacuum distillation of metallic magnesium and carbon annealing offline. The gas remaining in the first cooling chamber 301 is cooled again in the second cooling chamber 310; The magnesium smelting electric arc furnace 101, the reheating chamber 120, the first cooling chamber 301, and the second cooling chamber 310 form a vacuum negative pressure.

[0077] The content of the method for co-producing carbon nanotubes by electric furnace thermal reduction of magnesium will not be repeated in Example 1. Only some features involved in the method for co-producing carbon nanotubes by electric furnace thermal reduction of magnesium will be emphasized.

[0078] In some embodiments, the ternary mixed powder includes magnesium, carbon, iron, and their oxides.

[0079] In some embodiments, the ternary mixed powder is collected and fed into a magnesium distillation furnace 601, a primary cooling chamber 603, and a second cooling chamber 604 for vacuum distillation to obtain raw materials for silicon-carbon anode materials in the magnesium distillation furnace 601, condense in the primary cooling chamber 603 to obtain pure crystalline magnesium 608, and cool in the second cooling chamber 604 to obtain a small amount of residual crystalline magnesium.

[0080] In some embodiments, pure crystalline magnesium is collected from the second cooling chamber 310, the distillation primary cooling chamber 603, and the distillation second cooling chamber 604.

[0081] In some embodiments, the residue from the magnesium distillation furnace 601 is collected and post-processed to obtain carbon nanotubes.

[0082] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An apparatus for the co-production of carbon nanotubes and magnesium by the carbothermic reduction of magnesium oxide in a vacuum arc furnace, characterised in that, The device comprises: a magnesium smelting arc furnace (101), wherein the magnesium smelting arc furnace (101) contains molten iron liquid, and the magnesium smelting arc furnace (101) is used for high-temperature arc heating of materials MgO and carbon in the molten iron liquid to obtain mixed furnace gas containing metal magnesium vapor, iron vapor and CO; a heat supplement chamber (120) connected to the furnace gas outlet (107) of the magnesium smelting arc furnace (101), which is used for maintaining or increasing the temperature of the mixed furnace gas; a quenching condenser (201) connected to the high-temperature furnace gas channel (123) of the heat supplement chamber (120), which is used for introducing iron chloride to cause isentropic expansion and cooling of the mixed furnace gas to obtain iron powder, solid particles and cooled furnace gas; a first cooling chamber (301) connected to the quenching condenser (201), which is used for continuously cooling the iron powder, solid particles and cooled furnace gas to obtain ternary mixed powder, wherein the ternary mixed powder comprises magnesium, carbon and iron and oxides thereof; a second cooling chamber (310) connected to the gas channel of the first cooling chamber (301), which is used for secondary cooling of the condensed magnesium vapor in the first cooling chamber (301) to crystallize residual metal magnesium vapor into condensed state and further cool CO gas, hydrogen and other non-condensable gases; a vacuum pump (321) connected to the second cooling chamber (310), which is used for forming vacuum negative pressure in the magnesium smelting arc furnace (101), the heat supplement chamber (120), the first cooling chamber (301) and the second cooling chamber (310).

2. The apparatus for carbon nanotube co-production by the vacuum arc furnace carbothermic reduction of magnesite according to claim 1, characterized in that, The device additionally comprises a raw material tank (109) for containing solid materials, wherein the solid materials contain MgO, coke and bio-pyrolysis carbon; and a gas hydrocarbon storage tank (110) for containing gas hydrocarbon gas, wherein the carbon and MgO are added into the molten iron liquid through the hollow electrode of the magnesium smelting arc furnace (101) via the gas hydrocarbon storage tank (110) and the raw material tank (109) respectively.

3. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 1, characterized in that, The device additionally comprises a carbon powder iron bath immersion lance (116) and a magnesium oxide iron bath immersion lance (115) connected to the magnesium smelting arc furnace (101), wherein one end of the carbon powder iron bath immersion lance (116) and the magnesium oxide iron bath immersion lance (115) is immersed in the molten iron liquid, the magnesium oxide iron bath immersion lance (115) is used for spraying magnesium oxide, and the carbon powder iron bath immersion lance (116) is used for spraying carbon-containing materials.

4. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 1, characterized in that, The iron chloride includes partially gasified iron chloride FeCl3 vapor injected at high speed from a catalyst storage tank (204), or anhydrous iron trichloride and dichloride powder particles sprayed with argon as carrier gas, and the iron chloride enters a mixing pipeline (206) in the quenching condenser (201) to mix with the mixed furnace gas flowing out of the heat supplement chamber (120).

5. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 1, characterized in that, The quenching condenser (201) is connected to the catalyst storage tank (204) through a catalyst injection pipeline (202), the iron chloride in the catalyst storage tank (204) is sprayed into the quenching condenser (201), the mixed furnace gas is condensed in the quenching condenser (201), and the spray outlet of the catalyst injection pipeline (202) is designed as a lobe-shaped nozzle (205).

6. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 1, characterized in that, The ternary mixed powder contains magnesium metal powder, magnesium oxide, magnesium chloride, nano metal iron powder and elemental carbon.

7. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 1, characterized in that, The method comprises the following steps: connecting an argon-protected solid powder briquetting machine (501) to a first cooling chamber (301), and periodically opening a cold opening and closing valve (302) at the bottom of the first cooling chamber (301) to collect ternary mixed powder (309); and sending the ternary mixed powder (309) into the argon-protected solid powder briquetting machine (501) to be compacted into a block.

8. The device for carbon nanotube co-production by vacuum arc furnace carbothermic magnesium production according to claim 7, characterized in that, The argon-protected solid powder briquetting machine (501) is connected to a magnesium distillation furnace (601) for distillation of the solid block formed by the argon-protected solid powder briquetting machine (501) and annealing of carbon material, and the magnesium distillation furnace (601) is sequentially connected with a distillation primary cooling chamber (603) and a distillation secondary cooling chamber (604) for cooling of furnace gas generated in the distillation, and the furnace gas generated in the distillation is condensed in the distillation primary cooling chamber (603) to obtain pure crystalline magnesium (608), and the furnace gas generated in the distillation is further cooled in the distillation secondary cooling chamber (604) to obtain a small amount of residual crystalline magnesium (609), and the remaining residue (507) in the magnesium distillation furnace (601).

9. The device for carbon nanotube co-production by the vacuum arc furnace carbothermic reduction of magnesite according to claim 8, characterized in that, The residue (507) is post-processed to obtain carbon nanotubes, and pure crystalline magnesium is collected from the second cooling chamber (310), the distillation primary cooling chamber (603) and the distillation secondary cooling chamber (604).

10. A method of producing carbon nanotubes as a co-product of the production of magnesium by the carbothermic reduction of magnesium ores in an electric furnace, characterised in that, The method comprises the following steps: MgO, coke, bio-pyrolysis carbon and methane gas are added as raw materials into molten iron liquid in a magnesium smelting arc furnace (101) to obtain mixed furnace gas containing magnesium metal vapor, iron vapor and CO through carbothermic reduction; The mixed furnace gas is introduced into a heat supplementing chamber (120), and iron chloride containing gas is introduced into a quenching condenser (201) and mixed with the mixed furnace gas flowing out of the heat supplementing chamber (120) to perform isentropic expansion and cooling treatment on the mixed furnace gas to obtain iron powder, solid phase particles and cooled furnace gas; The iron powder, solid phase particles and cooled furnace gas are cooled through a first cooling chamber (301) to obtain ternary mixed powder (309), and the ternary mixed powder (309) is offline vacuum distilled to obtain metal magnesium and carbon annealing operation; The gas remaining in the first cooling chamber (301) is again cooled through a second cooling chamber (310) for secondary cooling; The magnesium smelting arc furnace (101), the heat supplementing chamber (120), the first cooling chamber (301) and the second cooling chamber (310) form a vacuum negative pressure.

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