Magnesium preparation system and magnesium preparation method for preparing magnesium by using salt lake low-hydrated magnesium chloride

Abstract

The invention provides a magnesium preparation system and a magnesium preparation method for preparing magnesium by using salt lake low-hydrated magnesium chloride. The magnesium production system comprises a gas mixing part, wherein air and chlorine respectively enter a mixing cavity through an air inlet and a chlorine inlet to be mixed to form mixed gas; the mixed gas inlet is communicated with the mixed gas outlet, low-hydrated magnesium chloride containing impurities and carbon powder enter the reaction chamber through the raw material inlet, mixed gas enters the reaction chamber through the mixed gas outlet and the mixed gas inlet in sequence and reacts to generate fused magnesium chloride, and the fused magnesium chloride flows out through the material outlet; the multi-pole electrolytic bath is provided with an electrolytic chamber, a magnesium collecting chamber communicated with the electrolytic chamber, a material inlet, a gas outlet and a liquid outlet, molten magnesium chloride discharged from the material outlet enters the electrolytic chamber through the material inlet, the magnesium collecting chamber is used for receiving crude magnesium liquid generated by electrolysis of the electrolytic chamber, and chlorine generated by electrolysis of the electrolytic chamber is discharged from the gas outlet. According to the technical scheme, the problem that in the prior art, electrolysis energy consumption of a magnesium preparation system is high is solved.

Description

Technical Field

[0001] The invention relates to the technical field of low-hydrated magnesium chloride production, and in particular to a magnesium production system and a magnesium production method utilizing low-hydrated magnesium chloride in a salt lake. Background Art

[0002] The Chaerhan Salt Lake in Qinghai is the largest potash fertilizer production base in China. The production of potassium chloride is accompanied by the discharge of bischofite, and a large amount of bischofite has accumulated over the years. Bischofite is used to produce magnesium metal, high-purity magnesia, magnesium hydroxide, light magnesium carbonate, magnesium cement, etc. Among them, magnesium metal has more and more uses, and the demand is increasing year by year. The magnesium metal industry has shown strong development potential.

[0003] The electrolysis method is one of the mainstream production methods in the magnesium metal industry. Its principle is to electrolyze molten anhydrous magnesium chloride at high temperature to decompose it into magnesium metal and chlorine. The electrolysis method is an environmentally friendly magnesium metal preparation technology with the advantages of low energy consumption, continuous production, high degree of mechanization and automation, and high production indicators. At present, the global magnesium metal production capacity is nearly 1 million tons, and China's production capacity is nearly 800,000 tons. In addition, my country mainly uses the Pijiang method to refine magnesium, which has problems such as high energy consumption, high emission of carbon dioxide, and solid waste from blasting. Therefore, choosing cheap bischofite or carnallite in salt lake brine as raw materials, preparing magnesium chloride by dehydration, and then using electrolysis to produce magnesium metal is of great significance to the development of magnesium smelting in my country.

[0004] In the prior art, salt lake bischofite is generally dehydrated in a hydrogen chloride protective atmosphere to obtain low-hydrated magnesium chloride for electrolysis. However, in the above dehydration process, a side reaction will occur to produce basic magnesium chloride, and the basic magnesium chloride will be converted into magnesium oxide when entering the electrolytic cell. Impurities such as magnesium oxide and incompletely removed crystal water in the bischofite will have an adverse effect on the electrolysis process, resulting in high electrolysis energy consumption. Summary of the invention

[0005] The main purpose of the present invention is to provide a magnesium production system and a magnesium production method using low-hydrated magnesium chloride in salt lakes, so as to solve the problem of high electrolysis energy consumption of magnesium production systems in the prior art.

[0006] In order to achieve the above-mentioned object, according to one aspect of the present invention, a magnesium production system using salt lake low-hydrated magnesium chloride is provided, comprising: a gas mixing portion, defining a mixing chamber and an air inlet, a chlorine inlet and a mixed gas outlet connected to the mixing chamber, air and chlorine enter the mixing chamber through the air inlet and the chlorine inlet respectively to mix and form a mixed gas; a molten chlorination furnace, defining a reaction chamber and a raw material inlet, a mixed gas inlet and a material outlet connected to the reaction chamber, the mixed gas inlet is connected to the mixed gas outlet, low-hydrated magnesium chloride and carbon powder containing impurities enter the reaction chamber through the raw material inlet, The mixed gas enters the reaction chamber through the mixed gas outlet and the mixed gas inlet in sequence, reacts to generate molten magnesium chloride, and the molten magnesium chloride flows out through the material outlet; the multipolar electrolytic cell comprises an electrolysis chamber for electrolyzing molten magnesium chloride, a magnesium collecting chamber located at one side of the electrolysis chamber and connected with the electrolysis chamber, a material inlet connected with the electrolysis chamber, a gas outlet connected with the electrolysis chamber, and a liquid outlet connected with the magnesium collecting chamber, the molten magnesium chloride discharged from the material outlet enters the electrolysis chamber through the material inlet, the magnesium collecting chamber is used to receive the crude magnesium liquid generated by electrolysis in the electrolysis chamber, and the chlorine generated by electrolysis in the electrolysis chamber is discharged from the gas outlet.

[0007] Furthermore, the mixed gas inlet is located at the bottom of the molten chlorination furnace, and the mixed gas entering through the mixed gas inlet flows from bottom to top in the reaction chamber.

[0008] Furthermore, the multipolar electrolytic cell also has a first channel and a second channel, both for connecting the electrolytic chamber and the magnesium collecting chamber. The first channel is located above the second channel. The first channel is used to allow the crude magnesium liquid mixed with electrolyte in the electrolytic chamber to enter the magnesium collecting chamber, and the second channel is used to supply the electrolyte in the magnesium collecting chamber back to the electrolytic chamber.

[0009] Furthermore, the magnesium production system also includes a bag dust collector for removing dust brought out of the electrolytic cell by chlorine and a fan for providing fluid driving force. The bag dust collector is provided with a first inlet and a first outlet. The first inlet of the bag dust collector is connected to the air outlet, the first outlet of the bag dust collector is connected to the inlet of the fan, and the outlet of the fan is connected to the chlorine inlet.

[0010] Furthermore, the bag filter is provided with a second outlet, and the magnesium production system also includes a cooler connected to the second outlet and a drying tower connected to the cooler, the cooler is used to cool the chlorine, and the drying tower is provided with concentrated sulfuric acid to dry the chlorine.

[0011] Furthermore, the magnesium production system also includes a chlorine compressor, a chlorine liquefaction device and a liquid chlorine vaporization device which are connected in sequence. The chlorine compressor is connected to the drying tower. The chlorine liquefaction device has a second inlet, a liquid outlet and a gas outlet. The second inlet is connected to the chlorine compressor. The liquid outlet of the chlorine liquefaction device is connected to the liquid chlorine vaporization device. The gas outlet of the chlorine liquefaction device is used to discharge unliquefied chlorine and non-condensable gas.

[0012] Furthermore, the molten chlorination furnace is provided with a tail gas outlet connected to the reaction chamber. The magnesium production system also includes a tail gas treatment part, which has a accommodating chamber for accommodating alkali solution. The tail gas outlet is connected to the accommodating chamber, and the gas outlet end of the chlorine liquefaction device is connected to the accommodating chamber.

[0013] Furthermore, the magnesium production system also includes a protective gas source for providing inert protective gas, and the magnesium collecting chamber is connected to the protective gas source.

[0014] According to another aspect of the present invention, the present invention provides a magnesium production method using salt lake subhydrated magnesium chloride. The magnesium production method adopts the above-mentioned magnesium production system to produce magnesium, and the magnesium production method includes: a step of preparing subhydrated magnesium chloride using salt lake bischofite; a step of mixing air and chlorine using a gas mixing section to form a mixed gas; a step of conveying subhydrated magnesium chloride, carbon powder and the mixed gas to a molten chlorination furnace, and molten chlorinating the subhydrated magnesium chloride to generate molten magnesium chloride; and an electrolysis step of electrolyzing the molten magnesium chloride using a multipolar electrolytic cell to generate a crude magnesium solution and chlorine.

[0015] Furthermore, after the melt chlorination step and before the electrolysis step, the magnesium preparation method further includes: a detection step of detecting the moisture content and the magnesium oxide content in the molten magnesium chloride discharged from the melt chlorination furnace; a judgment step of whether the magnesium oxide content is less than 0.1%, if yes, performing the electrolysis step, if not, performing the melt chlorination step; or, after the chlorine gas and the air are mixed, the ratio of the volume of the chlorine gas to the total volume of the chlorine gas and the air is greater than or equal to 70% and less than or equal to 90%; when melt chlorinating low hydrated magnesium chloride, the heating temperature of the melt chlorination furnace is greater than or equal to 700°C and less than or equal to 800°C.

[0016] Furthermore, the molten chlorination step includes: heating subhydrated magnesium chloride to remove residual crystal water of the subhydrated magnesium chloride to form molten magnesium chloride containing magnesium oxide; and converting magnesium oxide into magnesium chloride using carbon powder, chlorine gas and air.

[0017] Furthermore, after the molten chlorination step and before the electrolysis step, the magnesium production method further comprises the step of introducing an inert protective gas into the magnesium collecting chamber.

[0018] Furthermore, after the electrolysis step, the magnesium production method further includes: a step of removing dust brought out of the electrolytic cell by the chlorine gas using a bag filter; and a step of passing a portion of the chlorine gas after dust removal into a gas mixing part using a fan.

[0019] Furthermore, the magnesium production method also includes: a step of cooling another part of the chlorine gas after dust removal by using a cooler; a step of drying the cooled chlorine gas by using a drying tower; a step of liquefying the dried chlorine gas by using a chlorine liquefaction device; and a step of passing the chlorine gas containing non-condensable gas and not liquefied into the exhaust gas treatment part.

[0020] Furthermore, the magnesium production method also includes the step of vaporizing the liquefied chlorine gas using a liquid chlorine vaporization device; or, adjusting the ratio of the dust-removed chlorine gas and air introduced into the mixing part.

[0021] By applying the technical solution of the present invention, compared with the prior art in which low-hydrated magnesium chloride containing impurities such as water and magnesium oxide is directly used for electrolysis, resulting in high electrolysis energy consumption, in this embodiment, by providing a gas mixing section and a molten chlorination furnace, on the one hand, low-hydrated magnesium chloride containing impurities such as water and magnesium oxide can be melted in the molten chlorination furnace to remove residual crystal water, thereby reducing the water content in the low-hydrated magnesium chloride; on the other hand, the mixed gas in the gas mixing section enters the molten and dehydrated melt (magnesium chloride melt and magnesium oxide melt) in the molten chlorination furnace, and with the participation of carbon powder, the harmful impurity magnesium oxide is chlorinated to convert magnesium oxide into magnesium chloride, thereby reducing the content of impurity magnesium oxide, and further preparing a magnesium chloride melt with lower magnesium oxide content and lower water content, thereby reducing the adverse effect on electrolysis, reducing the energy consumption of the multipolar electrolytic cell, and thus reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 A schematic structural diagram of an embodiment of a magnesium production system using low-hydrated magnesium chloride from a salt lake according to the present invention is shown; and

[0024] Figure 2 The schematic flow chart of an embodiment of the method for producing magnesium using low-hydrated magnesium chloride in salt lakes according to the present invention is shown.

[0025] The above drawings include the following reference numerals:

[0026] 1. Gas mixing section; 2. Molten chlorination furnace; 3. Multi-electrode electrolytic cell; 5. Bag filter; 6. Fan; 7. Cooler; 8. Drying tower; 9. Chlorine compressor; 10. Chlorine liquefaction device; 11. Liquid chlorine vaporization device; 12. Tail gas treatment section. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] It should be noted that the subhydrated magnesium chloride in the embodiment of the present invention is prepared by dehydrating salt lake bischofite under a catalytic protective atmosphere of hydrogen chloride, and contains impurities such as basic magnesium oxide and water. The impurity basic magnesium chloride in the subhydrated magnesium chloride will be converted into magnesium oxide after entering the electrolytic cell or the molten chlorination furnace. Therefore, both the subhydrated magnesium chloride raw material located in the electrolytic cell in the prior art and the subhydrated magnesium chloride raw material located in the molten chlorination furnace in this embodiment contain impurities such as magnesium oxide and water.

[0029] It should be noted that the magnesium oxide content of the subhydrated magnesium chloride in the embodiment of the present invention is less than 2%, the water content is less than 11.6%, and other impurities such as sulfate, boron, and heavy metals meet the general requirements for electrolytic magnesium.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a magnesium production system using low-hydrated magnesium chloride from salt lakes. The magnesium production system includes a gas mixing unit 1, a molten chlorination furnace 2 and a multi-electrode electrolytic cell 3. The gas mixing part 1 defines a mixing chamber and an air inlet, a chlorine inlet and a mixed gas outlet connected to the mixing chamber, and air and chlorine enter the mixing chamber through the air inlet and the chlorine inlet to mix and form a mixed gas; the molten chlorination furnace 2 defines a reaction chamber and a raw material inlet, a mixed gas inlet and a material outlet connected to the reaction chamber, the mixed gas inlet is connected to the mixed gas outlet, low-hydrated magnesium chloride and carbon powder containing impurities enter the reaction chamber through the raw material inlet, and the mixed gas enters the reaction chamber through the mixed gas outlet and the mixed gas inlet in sequence, reacts to generate molten magnesium chloride, and the molten magnesium chloride flows out through the material outlet; the multipolar electrolytic cell 3 has an electrolysis chamber for electrolyzing molten magnesium chloride, a magnesium collecting chamber located on one side of the electrolysis chamber and connected to the electrolysis chamber, a material inlet connected to the electrolysis chamber, a gas outlet connected to the electrolysis chamber, and a liquid outlet connected to the magnesium collecting chamber, the molten magnesium chloride discharged from the material outlet enters the electrolysis chamber through the material inlet, the magnesium collecting chamber is used to receive the crude magnesium liquid generated by electrolysis in the electrolysis chamber, and the chlorine generated by electrolysis in the electrolysis chamber is discharged from the gas outlet.

[0031] In the above technical scheme, compared with the prior art in which low-hydrated magnesium chloride containing impurities such as water and magnesium oxide is directly used for electrolysis, resulting in high electrolysis energy consumption, in this embodiment, by providing a gas mixing section 1 and a molten chlorination furnace 2, on the one hand, low-hydrated magnesium chloride containing impurities such as water and magnesium oxide can be melted in the molten chlorination furnace 2 to remove residual crystal water, thereby reducing the water content in the low-hydrated magnesium chloride; on the other hand, the mixed gas in the gas mixing section 1 enters the molten and dehydrated melt (magnesium chloride melt and magnesium oxide melt) in the molten chlorination furnace 2, and with the participation of carbon powder, the harmful impurity magnesium oxide is chlorinated to convert magnesium oxide into magnesium chloride, thereby reducing the content of magnesium oxide impurities, and then preparing a magnesium chloride melt with lower magnesium oxide content and lower water content, thereby reducing the adverse effects on electrolysis in subsequent processes, so as to reduce the energy consumption of the multipolar electrolytic cell, thereby reducing production costs.

[0032] Furthermore, the air entering the molten chlorination furnace 2 can, on the one hand, play a role in stirring and mixing, so that the chlorine can be evenly dispersed in the melt in the molten chlorination furnace 2, thereby improving the utilization rate of the chlorine; on the other hand, the oxygen in the air can react with part of the carbon powder to generate reducing gas CO. Compared with directly using carbon powder to react with the melt, CO is more easily evenly dispersed in the melt, thereby improving the chlorination efficiency and effect.

[0033] Preferably, in the embodiment of the present invention, the gas mixing part 1 is a buffer tank, which can evenly mix the air and chlorine and maintain the flow stability of the mixed gas introduced into the molten chlorination furnace 2, so as to make the chlorination reaction more complete.

[0034] Specifically, in the embodiment of the present invention, the main reaction of chlorinating magnesium oxide is:

[0035] 2C+O2=2CO↑

[0036] MgO+CO+Cl2=MgCl2+CO2↑

[0037] MgO+C+Cl2=MgCl2+CO↑

[0038] It should be noted that, in the embodiment of the present invention, the advantages of producing magnesium metal in the multi-electrode electrolytic cell are low power consumption, low consumption of graphite anode, generally no need to replace, small slag production, high purity of chlorine, generally greater than 95%. However, the multi-electrode electrolytic cell has very high requirements for the quality of anhydrous magnesium chloride raw materials. The magnesium oxide content in anhydrous magnesium chloride does not exceed 0.1%, and the moisture content generally does not exceed 0.08%. The moisture is the conversion value of the hydroxide element, and the molten chlorination furnace 2 can provide high-quality, low-cost anhydrous magnesium chloride raw materials for the multi-electrode electrolytic cell, that is, it can prepare anhydrous magnesium chloride raw materials that meet the requirements of the multi-electrode electrolytic cell. In this way, the effect of energy saving can be further achieved.

[0039] Preferably, in the embodiment of the present invention, the molten chlorination furnace 2 is heated to 700° C.-800° C. to perform molten chlorination on the impure low-hydrate magnesium chloride.

[0040] Preferably, in an embodiment of the present invention, dry air (dew point temperature is less than -40°C) provided by an air compression station enters the gas mixing part 1 through an air inlet.

[0041] Specifically, in the embodiment of the present invention, the mixed gas inlet is located at the bottom of the molten chlorination furnace 2, and the mixed gas entering through the mixed gas inlet flows from bottom to top in the reaction chamber.

[0042] Through the above arrangement, the mixed gas can be in contact with the melt in the reaction chamber more fully, so that it can react with the magnesium oxide more fully to improve the conversion rate of the magnesium oxide.

[0043] It should be noted that, in the embodiment of the present invention, the reaction chamber of the molten chlorination furnace mainly includes a melting chamber and a chlorination chamber connected to the melting chamber, and a material inlet is provided on the melting chamber, which mainly heats and melts the subhydrated magnesium chloride and carbon powder in the melting chamber by electrode heating. Electrodes are provided in the chlorination chamber, and a mixed gas inlet and a material outlet are provided on the chlorination chamber. The specific structure of the molten chlorination furnace is prior art and will not be repeated here.

[0044] Specifically, in an embodiment of the present invention, the multipolar electrolytic cell 3 also has a first channel and a second channel, both for connecting the electrolytic chamber and the magnesium collecting chamber. The first channel is located above the second channel. The first channel is used to allow the crude magnesium liquid mixed with the electrolyte in the electrolytic chamber to enter the magnesium collecting chamber, and the second channel is used to supply the electrolyte in the magnesium collecting chamber back to the electrolytic chamber.

[0045] In the above technical scheme, the magnesium chloride melt entering from the material inlet is electrolyzed in the electrolysis chamber to generate chlorine and crude magnesium liquid, the chlorine generated by the anode gathers above the electrolysis chamber, and the crude magnesium liquid flows to the magnesium collecting chamber through the first channel with the electrolyte. Since the density of the crude magnesium liquid is less than the density of the electrolyte, the crude magnesium liquid floats above the magnesium collecting chamber and is extracted by a ladle truck and transported to the refining and casting workshop for casting of magnesium ingots or magnesium alloys, while the electrolyte sinks below the crude magnesium liquid and circulates through the second channel to the electrolysis chamber to continue to participate in subsequent electrolysis, thereby realizing the collection of the crude magnesium liquid and the recycling of the electrolyte.

[0046] It should be noted that, in the embodiments of the present invention, the electrolytic cell slag generated in the electrolytic chamber settles to the bottom of the electrolytic cell by gravity and accumulates until it is removed after the cell is stopped.

[0047] like Figure 1As shown, in an embodiment of the present invention, the magnesium production system also includes a bag dust collector 5 for removing dust brought out of the chlorine from the electrolytic cell and a fan 6 for providing a fluid driving force. The bag dust collector 5 is provided with a first inlet and a first outlet. The first inlet of the bag dust collector 5 is connected to the air outlet, the first outlet of the bag dust collector 5 is connected to the inlet of the fan 6, and the outlet of the fan 6 is connected to the chlorine inlet.

[0048] Through the above arrangement, on the one hand, the dust brought out by chlorine from the electrolytic cell can be absorbed, thereby improving the quality of the chlorine; on the other hand, part of the chlorine generated by electrolysis can be circulated to the molten chlorination furnace 2 to chlorinate the magnesium oxide, thereby realizing recycling and reducing production costs.

[0049] It should be noted that, in the embodiment of the present invention, during the initial production process, that is, when the electrolytic cell does not generate chlorine by electrolysis, chlorine can be additionally introduced into the gas mixing part 1 to achieve a chlorination reaction.

[0050] like Figure 1 As shown, in the embodiment of the present invention, the bag filter 5 is further provided with a second outlet, and the magnesium production system further comprises a cooler 7 connected to the second outlet and a drying tower 8 connected to the cooler 7, the cooler 7 is used to cool the chlorine gas, and the drying tower 8 is provided with concentrated sulfuric acid to dry the chlorine gas. In this way, the chlorine gas can be cooled and dried in sequence, thereby improving the quality of the chlorine gas.

[0051] like Figure 1 As shown, in the embodiment of the present invention, the magnesium production system also includes a chlorine compressor 9, a chlorine liquefaction device 10 and a liquid chlorine vaporization device 11 which are connected in sequence, the chlorine compressor 9 is connected to the drying tower 8, the chlorine liquefaction device 10 has a second inlet, a liquid outlet and a gas outlet, the second inlet is connected to the chlorine compressor 9, the liquid outlet of the chlorine liquefaction device 10 is connected to the liquid chlorine vaporization device 11, and the gas outlet of the chlorine liquefaction device 10 is used to discharge unliquefied chlorine and non-condensable gas.

[0052] Through the above arrangement, the chlorine compressor can compress the chlorine to facilitate the subsequent liquefaction treatment, and then the chlorine liquefaction device 10 can liquefy the chlorine to separate the chlorine from the non-condensable gas mixed in the chlorine, and then use the liquid chlorine vaporization device 11 to vaporize the chlorine, thereby improving the purity of the chlorine to improve the quality of the chlorine.

[0053] It should be noted that in the embodiments of the present invention, the non-condensable gas includes the air entering the multi-electrode electrolytic cell and gases such as carbon monoxide and carbon dioxide generated after the molten chlorination reaction.

[0054] Specifically, in an embodiment of the present invention, the magnesium production system further includes a ratio control system, and the ratio control system is used to control the ratio of the air entering the molten chlorination furnace 2 and the chlorine gas after dust removal.

[0055] Specifically, in the embodiment of the present invention, after the chlorine gas is dedusted by the bag filter 5 (the chlorine concentration is greater than 93% Vol), a small portion of it is sent to the molten chlorination furnace 2, and most of it is liquefied and vaporized by the chlorine compressor 9, the chlorine liquefaction device 10 and the liquid chlorine vaporization device 11 and then sent to the device for producing PVC materials.

[0056] like Figure 1 As shown, in an embodiment of the present invention, the magnesium production system further includes a protective gas source for providing an inert protective gas, and the magnesium collection chamber is connected to the protective gas source.

[0057] Through the above arrangement, the space above the crude magnesium liquid in the magnesium collecting chamber can be filled with inert protective gas to provide real-time protection for the crude magnesium liquid, thereby preventing the crude magnesium liquid from being violently oxidized at a high temperature or even burning to produce a large amount of magnesium oxide, thereby avoiding the produced magnesium oxide from contaminating the crude magnesium liquid and affecting the purity of the crude magnesium liquid, and also avoiding the production of a large amount of tank slag, thereby avoiding affecting the life of the multi-electrode electrolytic cell.

[0058] Preferably, in an embodiment of the present invention, the shielding gas source is an argon gas source, which is generally produced by an air separation device.

[0059] like Figure 1 As shown, in an embodiment of the present invention, a tail gas outlet connected to the reaction chamber is provided on the molten chlorination furnace 2, and the magnesium production system also includes a tail gas treatment part 12, the tail gas treatment part 12 has a receiving chamber for receiving alkali solution, the tail gas outlet is connected to the receiving chamber, and the gas outlet end of the chlorine liquefaction device 10 is connected to the receiving chamber.

[0060] Through the above arrangement, the tail gas treatment unit 12 can absorb the tail gas discharged from the molten chlorination furnace 2 to prevent the tail gas from polluting the air.

[0061] Specifically, in the embodiment of the present invention, under the action of the chlorine liquefaction device 10, most of the chlorine will be liquefied, and the non-condensable gas and a small amount of chlorine will enter the tail gas treatment part 12 through the gas outlet and the chlorine inlet, so that the tail gas treatment can be achieved.

[0062] like Figure 2 As shown, an embodiment of the present invention provides a magnesium production method using salt lake subhydrated magnesium chloride. The magnesium production method adopts the above-mentioned magnesium production system to produce magnesium, and the magnesium production method includes: a step of preparing subhydrated magnesium chloride using salt lake bischofite; a step of mixing air and chlorine using a gas mixing unit 1 to form a mixed gas; a step of conveying subhydrated magnesium chloride, carbon powder and the mixed gas to a molten chlorination furnace 2, and molten chlorinating the subhydrated magnesium chloride to generate molten magnesium chloride; and a step of electrolyzing the molten magnesium chloride using a multipolar electrolytic cell 3 to generate an electrolysis step of crude magnesium liquid and chlorine.

[0063] In the above technical scheme, compared with the prior art that directly uses subhydrated magnesium chloride containing impurities such as water and magnesium oxide for electrolysis, resulting in high electrolysis energy consumption, in this embodiment, by conveying subhydrated magnesium chloride, carbon powder and mixed gas to the molten chlorination furnace 2, and molten chlorinating the subhydrated magnesium chloride, on the one hand, the subhydrated magnesium chloride containing impurities such as water and magnesium oxide can be melted in the molten chlorination furnace 2 to remove residual crystal water, thereby reducing the water content in the subhydrated magnesium chloride; on the other hand, the mixed gas enters the molten and dehydrated melt (magnesium chloride melt and magnesium oxide melt) in the molten chlorination furnace 2, and with the participation of carbon powder, the harmful impurity magnesium oxide is chlorinated to convert magnesium oxide into magnesium chloride, thereby reducing the content of impurity magnesium oxide, and then preparing a magnesium chloride melt with lower magnesium oxide content and lower water content, thereby reducing the adverse effect on electrolysis, reducing the energy consumption of the multipolar electrolytic cell, and thus reducing production costs.

[0064] like Figure 2 As shown, in an embodiment of the present invention, after the molten chlorination step and before the electrolysis step, the magnesium production method further includes: a detection step of detecting the moisture content and the magnesium oxide content in the molten magnesium chloride discharged from the molten chlorination furnace; a judgment step of judging whether the magnesium oxide content is less than 0.1%, if yes, performing the electrolysis step, if not, performing the molten chlorination step.

[0065] Through the above arrangement, the magnesium oxide content and water content in the magnesium chloride melt entering the multipolar electrolytic cell 3 can be controlled. On the one hand, the consumption of the graphite anode can be reduced. On the other hand, the slag can be reduced to avoid the accumulation of slag at the bottom of the electrolysis chamber affecting the normal circulation of the crude magnesium solution and the electrolyte, thereby avoiding shortening the service life of the multipolar electrolytic cell.

[0066] Preferably, in the embodiments of the present invention, the MgOHCl (basic magnesium chloride) titration method is generally used to detect the magnesium oxide content, and the Karl Fischer method is used to detect the water content.

[0067] It should be noted that, in the embodiment of the present invention, after the melt chlorination in the melt chlorination furnace 2, the measured moisture content is the converted value of the hydroxide elements. Generally, the moisture content is lower than 0.08%, and the magnesium oxide is reduced to below 0.1% to be a qualified anhydrous magnesium chloride melt.

[0068] Specifically, in the embodiment of the present invention, after the chlorine gas and the air are mixed, the ratio of the volume of the chlorine gas to the total volume of the chlorine gas and the air is greater than or equal to 70% and less than or equal to 90%; when the subhydrated magnesium chloride is melt-chlorinated, the heating temperature of the melt-chlorination furnace is greater than or equal to 700° C. and less than or equal to 800° C. In this way, not only the content of magnesium oxide can be effectively reduced, but also the subhydrated magnesium chloride can be effectively dehydrated to reduce impurities in the magnesium chloride melt.

[0069] Specifically, in an embodiment of the present invention, the molten chlorination step includes: heating subhydrated magnesium chloride to remove residual crystal water of the subhydrated magnesium chloride to form molten magnesium chloride containing magnesium oxide; and converting magnesium oxide into magnesium chloride using carbon powder, chlorine gas and air.

[0070] Through the above arrangement, the water content of low-hydrated magnesium chloride can be reduced first, the impure basic magnesium chloride can be converted into magnesium oxide, and then the generated magnesium oxide is chlorinated, so that the content of magnesium oxide can be effectively reduced.

[0071] Specifically, in an embodiment of the present invention, after the melt chlorination step and before the electrolysis step, the magnesium production method further includes a step of introducing an inert protective gas into the magnesium collecting chamber.

[0072] Through the above-mentioned arrangement, the magnesium collecting chamber can be filled with inert protective gas to provide real-time protection for the crude magnesium liquid entering the magnesium collecting chamber, preventing the crude magnesium liquid from being violently oxidized at a high temperature or even burning to produce a large amount of magnesium oxide, thereby avoiding the produced magnesium oxide from contaminating the crude magnesium liquid and affecting the purity of the crude magnesium liquid. It can also avoid generating a large amount of tank slag, thereby avoiding affecting the life of the multi-electrode electrolytic cell.

[0073] like Figure 2 As shown, in the embodiment of the present invention, after the electrolysis step, the magnesium production method further includes: a step of removing dust brought out of the electrolytic cell by chlorine gas using a bag filter 5; and a step of passing a portion of the chlorine gas after dust removal into the gas mixing part 1 using a fan 6.

[0074] Through the above arrangement, on the one hand, the dust brought out by chlorine from the electrolytic cell can be absorbed, thereby improving the quality of the chlorine; on the other hand, part of the chlorine generated by electrolysis can be circulated to the molten chlorination furnace 2 to chlorinate the magnesium oxide, thereby realizing recycling and reducing production costs.

[0075] like Figure 2 As shown, in an embodiment of the present invention, the magnesium production method also includes: a step of cooling another part of the chlorine gas after dust removal by using a cooler 7; a step of drying the cooled chlorine gas by using a drying tower 8; a step of liquefying the dried chlorine gas by using a chlorine liquefaction device 10; and a step of passing the chlorine gas containing non-condensable gas and not liquefied into the tail gas treatment part 12.

[0076] Through the above-mentioned arrangement, the chlorine can be cooled and dried in sequence, thereby improving the quality of the chlorine; then the chlorine liquefaction device 10 can liquefy the chlorine to separate the chlorine from the non-condensable gas mixed in the chlorine, and then the chlorine can be vaporized by the liquid chlorine vaporization device 11, thereby improving the purity of the chlorine and improving the quality of the chlorine.

[0077] Furthermore, the non-condensable gas and a small amount of chlorine gas will enter the tail gas treatment part 12 through the gas outlet and the chlorine gas inlet, so that the tail gas treatment can be achieved.

[0078] like Figure 2 As shown, in the embodiment of the present invention, the magnesium production method further includes the step of vaporizing the liquefied chlorine gas using the liquid chlorine vaporization device 11. In this way, the liquid chlorine can be converted into chlorine gas, so that the chlorine gas can be transported to the device for producing PVC materials to produce PVC materials.

[0079] Specifically, in an embodiment of the present invention, the magnesium production method further includes adjusting the ratio of the dust-removed chlorine gas and air introduced into the mixing part.

[0080] During the electrolysis process in the multipolar electrolytic cell 3, due to the high content of MgO, on the one hand, the consumption of the graphite anode will be accelerated, and on the other hand, the slag will increase, so that the slag will accumulate at the bottom of the electrolytic cell, thereby affecting the normal circulation of the magnesium liquid and the electrolyte and shortening the life of the electrolytic cell. Therefore, the MgO impurity content in the anhydrous magnesium chloride melt must be strictly controlled. In this embodiment, by adjusting the ratio of the dust-removed chlorine gas and air introduced into the mixing part, the conversion rate of magnesium oxide into magnesium chloride can be controlled, thereby minimizing the content of magnesium oxide.

[0081] In summary, the present invention uses magnesium chloride, which is abundant in Chaerhan, as a raw material, and utilizes a molten chlorination process to achieve economical and efficient preparation of anhydrous magnesium chloride melt with a low MgO content, and then uses a multi-electrode tank electrolysis to produce metallic magnesium, which can reduce the cost and energy consumption of producing metallic magnesium by electrolysis. At the same time, abundant renewable energy sources such as photovoltaic, solar thermal and wind energy in the western region can also be used to provide a large amount of electricity for the electrolytic magnesium industry, which is conducive to the development of a low-cost system and method for producing magnesium by electrolysis.

[0082] Embodiment 1

[0083] The preliminarily dried low hydrated magnesium chloride (MgCl2 average water content of 11%-1%, magnesium oxide content of 2%-0.5%) is transported to a molten chlorination furnace 2, heated to 700°C-800°C, then carbon powder is added, and the amount of carbon powder added is 1-5 times the theoretical amount for each ton of magnesium chloride melt obtained, and a mixed gas of chlorine and air is introduced, chlorine accounts for 70%-90%, and the amount of chlorine introduced is controlled to be 1-5 times the theoretical amount, and chlorine reacts with MgO impurities formed by hydrolysis during the dehydration process to generate magnesium chloride, thereby obtaining a magnesium chloride melt with a magnesium oxide content of less than 0.25%. The obtained anhydrous magnesium chloride melt is then transported to a multipolar electrolytic cell with a ladle car, and electrolysis is carried out at a temperature of 660°C and a current intensity of 100-165kA, and the power consumption reaches 13500kWh / ton of magnesium.

[0084] Embodiment 2

[0085] The preliminarily dried low-hydrated magnesium chloride (MgCl2 average water content of 1%-0.7%, magnesium oxide content of less than 0.5%) is transported to a molten chlorination furnace, heated to 700°C-800°C, and then carbon powder is added, and the amount of carbon powder added is 1-5 times the theoretical amount for each ton of magnesium chloride melt obtained, and a mixed gas of chlorine and air is introduced, and the chlorine accounts for 70%-90%, and the amount of chlorine introduced is controlled to be 1-5 times the theoretical amount, and the chlorine reacts with the MgO impurities formed by hydrolysis during the dehydration process to generate magnesium chloride, thereby obtaining a magnesium chloride melt with a magnesium oxide content of less than 0.12%. The obtained anhydrous magnesium chloride melt is transported to a multipolar electrolytic cell with a ladle car, and electrolysis is carried out at a temperature of 660°C and a current intensity of 100-165kA, and the power consumption reaches 11500kWh / ton of magnesium.

[0086] Embodiment 3

[0087] The preliminarily dried low-hydrated magnesium chloride (MgCl2 average water content is ≤0.5%, magnesium oxide content is ≤0.4%) is transported to a molten chlorination furnace, heated to 700°C-800°C, and then carbon powder is added. For each ton of magnesium chloride melt obtained, the amount of carbon powder added is 1-5 times the theoretical amount. A mixed gas of chlorine and air is introduced, and the chlorine accounts for 70%-90%. The amount of chlorine introduced is controlled to be 1-5 times the theoretical amount. The chlorine reacts with the MgO impurities formed by hydrolysis during the dehydration process to generate magnesium chloride, thereby obtaining a magnesium chloride melt with a magnesium oxide content of less than 0.1%. The obtained anhydrous magnesium chloride melt is then transported to a multipolar electrolytic cell with a ladle car, and electrolysis is carried out at a temperature of 660°C and a current intensity of 100-165kA. The power consumption reaches 11000kWh / ton of magnesium.

[0088] Embodiment 4

[0089] The preliminarily dried low-hydrated magnesium chloride (MgCl2 average water content ≤ 0.25%, magnesium oxide content ≤ 0.24%) is transported to a molten chlorination furnace, heated to 700°C-800°C, and then carbon powder is added, and the amount of carbon powder added is 1-5 times the theoretical amount for each ton of magnesium chloride melt obtained, and a mixed gas of chlorine and air is introduced, and the chlorine accounts for 70%-90%, and the amount of chlorine introduced is controlled to be 1-5 times the theoretical amount, and the amount of chlorine introduced is controlled to be 1-5 times the theoretical amount, and the chlorine reacts with the MgO impurities formed by hydrolysis during the dehydration process to generate magnesium chloride, thereby obtaining a magnesium chloride melt with a magnesium oxide content of less than 0.1%. The obtained anhydrous magnesium chloride melt is transported to a multipolar electrolytic cell with a ladle car for electrolysis, and electrolysis is carried out at a temperature of 660°C and a current intensity of 100-165kA, and the power consumption reaches 10000kWh / ton of magnesium.

[0090] Embodiment 5

[0091] The low-hydrated magnesium chloride (MgCl2 average water content is ≤0.05%, magnesium oxide content is ≤0.24%) after preliminary drying is transported to a molten chlorination furnace, heated to 700°C-800°C, then carbon powder is added, and the addition amount of carbon powder is 1-5 times of the theoretical addition amount for each ton of magnesium chloride melt obtained, and a mixed gas of chlorine and air is introduced, and chlorine accounts for 70%-90%, and the introduction amount of chlorine is controlled at 1-5 times of the theoretical amount, and chlorine reacts with MgO impurities formed by hydrolysis during the dehydration process to generate magnesium chloride, thereby obtaining a magnesium chloride melt with a magnesium oxide content of less than 0.1%. The obtained anhydrous magnesium chloride melt is delivered to a multipolar electrolytic cell with a ladle car, and electrolysis is carried out at a temperature of 660°C and an electric current intensity of 100-165kA, and the current efficiency decreases, and the power consumption reaches 10000kWh / ton of magnesium.

[0092] In summary, it can be seen from Examples 1 to 5 that, under the same electrolysis parameters, the lower the content of magnesium oxide impurities in the magnesium chloride melt, the lower the energy consumption of the multi-electrode electrolytic cell. Therefore, the magnesium production system of the embodiment of the present invention can reduce energy consumption, thereby reducing production costs.

[0093] From the above description, it can be seen that the above-mentioned embodiment of the present invention achieves the following technical effects: compared with the prior art that directly uses low-hydrated magnesium chloride containing impurities such as water and magnesium oxide for electrolysis, resulting in high electrolysis energy consumption, in this embodiment, by providing a gas mixing section and a molten chlorination furnace, on the one hand, low-hydrated magnesium chloride containing impurities such as water and magnesium oxide can be melted in the molten chlorination furnace to remove residual crystal water, thereby reducing the water content in the low-hydrated magnesium chloride; on the other hand, the mixed gas in the gas mixing section enters the molten and dehydrated melt (magnesium chloride melt and magnesium oxide melt) in the molten chlorination furnace, and with the participation of carbon powder, the harmful impurity magnesium oxide is chlorinated to convert magnesium oxide into magnesium chloride, thereby reducing the content of impurity magnesium oxide, and then preparing a magnesium chloride melt with lower magnesium oxide content and lower water content, thereby reducing the adverse effect on electrolysis, reducing the energy consumption of the multipolar electrolytic cell, and thus reducing the production cost.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnesium production system using low-hydrated magnesium chloride from salt lakes, characterized in that: include: A gas mixing portion (1) defines a mixing chamber and an air inlet, a chlorine inlet and a mixed gas outlet connected to the mixing chamber, and air and chlorine enter the mixing chamber through the air inlet and the chlorine inlet respectively to mix and form a mixed gas; The molten chlorination furnace (2) defines a reaction chamber and a raw material inlet, a mixed gas inlet and a material outlet all connected to the reaction chamber, the mixed gas inlet is connected to the mixed gas outlet, low-hydrated magnesium chloride and carbon powder containing impurities enter the reaction chamber through the raw material inlet, the mixed gas enters the reaction chamber through the mixed gas outlet and the mixed gas inlet in sequence, reacts to generate molten magnesium chloride, and the molten magnesium chloride flows out through the material outlet; A multipolar electrolytic cell (3), the multipolar electrolytic cell (3) comprising an electrolysis chamber for electrolyzing the molten magnesium chloride, a magnesium collecting chamber located on one side of the electrolysis chamber and connected to the electrolysis chamber, a material inlet connected to the electrolysis chamber, a gas outlet connected to the electrolysis chamber, and a liquid outlet connected to the magnesium collecting chamber, wherein the molten magnesium chloride discharged from the material outlet enters the electrolysis chamber through the material inlet, the magnesium collecting chamber is used to receive the crude magnesium liquid generated by electrolysis in the electrolysis chamber, and the chlorine gas generated by electrolysis in the electrolysis chamber is discharged from the gas outlet.

2. The magnesium production system using low-hydrated magnesium chloride from salt lake according to claim 1, characterized in that: The mixed gas inlet is located at the bottom of the molten chlorination furnace (2), and the mixed gas entering through the mixed gas inlet flows from bottom to top in the reaction chamber.

3. The magnesium production system using low-hydrated magnesium chloride from salt lake according to claim 1, characterized in that: The multipolar electrolytic cell (3) further comprises a first channel and a second channel, both for connecting the electrolytic chamber and the magnesium collecting chamber, wherein the first channel is located above the second channel, the first channel is used for allowing the crude magnesium liquid mixed with electrolyte in the electrolytic chamber to enter the magnesium collecting chamber, and the second channel is used for allowing the electrolyte in the magnesium collecting chamber to flow back into the electrolytic chamber.

4. The magnesium production system using low-hydrated magnesium chloride from salt lake according to any one of claims 1 to 3, characterized in that: The magnesium production system further comprises a bag filter (5) for removing dust brought out of the electrolytic cell by the chlorine gas, and a fan (6) for providing fluid driving force. The bag filter (5) is provided with a first inlet and a first outlet. The first inlet of the bag filter (5) is connected to the gas outlet, the first outlet of the bag filter (5) is connected to the inlet of the fan (6), and the outlet of the fan (6) is connected to the chlorine gas inlet.

5. The magnesium production system using low-hydrated magnesium chloride from salt lake according to claim 4, characterized in that: The bag filter (5) is also provided with a second outlet, and the magnesium production system further comprises a cooler (7) connected to the second outlet and a drying tower (8) connected to the cooler (7), wherein the cooler (7) is used to cool the chlorine gas, and the drying tower (8) is provided with concentrated sulfuric acid to dry the chlorine gas.

6. The magnesium production system using low-hydrated magnesium chloride from salt lake according to claim 5, characterized in that: The magnesium production system further comprises a chlorine compressor (9), a chlorine liquefaction device (10) and a liquid chlorine vaporization device (11) which are connected in sequence, the chlorine compressor (9) being connected to the drying tower (8), the chlorine liquefaction device (10) having a second inlet, a liquid outlet and a gas outlet, the second inlet being connected to the chlorine compressor (9), the liquid outlet of the chlorine liquefaction device (10) being connected to the liquid chlorine vaporization device (11), and the gas outlet of the chlorine liquefaction device (10) being used to discharge unliquefied chlorine and non-condensable gas.

7. The magnesium production system using low-hydrated magnesium chloride from salt lake according to claim 6, characterized in that: The molten chlorination furnace (2) is provided with an exhaust gas outlet connected to the reaction chamber. The magnesium production system further comprises an exhaust gas treatment unit (12). The exhaust gas treatment unit (12) has a receiving chamber for receiving alkali solution. The exhaust gas outlet is connected to the receiving chamber. The gas outlet of the chlorine liquefaction device (10) is connected to the receiving chamber.

8. The magnesium production system using low-hydrated magnesium chloride from salt lake according to any one of claims 1 to 3, characterized in that: The magnesium production system further comprises a protective gas source for providing an inert protective gas, and the magnesium collecting chamber is communicated with the protective gas source.

9. A method for producing magnesium using low-hydrated magnesium chloride from salt lakes, characterized in that: The magnesium production method adopts the magnesium production system according to any one of claims 1 to 8 to produce magnesium, and the magnesium production method comprises: The step of preparing low hydrated magnesium chloride by using salt lake bischofite; The step of mixing the air and the chlorine gas by using the gas mixing unit (1) to form a mixed gas; The subhydrated magnesium chloride, carbon powder and mixed gas are transported to the molten chlorination furnace (2), and the subhydrated magnesium chloride is melt-chlorinated to generate molten magnesium chloride; The multipolar electrolytic cell (3) is used to electrolyze the molten magnesium chloride to generate a crude magnesium solution and chlorine gas.

10. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 9, characterized in that: After the melt chlorination step and before the electrolysis step, the magnesium production method further comprises: A step of detecting the moisture content and the magnesium oxide content in the molten magnesium chloride discharged from the molten chlorination furnace; a step of judging whether the magnesium oxide content is less than 0.1%, if yes, performing the electrolysis step, if no, performing the molten chlorination step; or, After the chlorine gas and the air are mixed, the ratio of the volume of the chlorine gas to the total volume of the chlorine gas and the air is greater than or equal to 70% and less than or equal to 90%; when the subhydrated magnesium chloride is melt-chlorinated, the heating temperature of the melt-chlorination furnace is greater than or equal to 700° C. and less than or equal to 800° C.

11. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 9, characterized in that: The melt chlorination step comprises: The step of heating the subhydrated magnesium chloride to remove residual crystal water of the subhydrated magnesium chloride to form molten magnesium chloride containing magnesium oxide; The step of converting the magnesium oxide into magnesium chloride using the carbon powder, the chlorine gas and the air.

12. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 9, characterized in that: After the molten chlorination step and before the electrolysis step, the magnesium production method further includes a step of introducing an inert protective gas into the magnesium collecting chamber.

13. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 9, characterized in that: After the electrolysis step, the magnesium production method further comprises: The step of removing dust brought out of the electrolytic cell by the chlorine gas by using a bag filter (5); The step of using a fan (6) to pass a portion of the chlorine gas after dust removal into the gas mixing part (1).

14. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 13, characterized in that: The magnesium production method further comprises: A step of cooling another portion of the chlorine gas after dust removal by using a cooler (7); A step of drying the cooled chlorine gas using a drying tower (8); A step of liquefying the dried chlorine using a chlorine liquefaction device (10); The step of passing the chlorine gas containing non-condensable gas and not liquefied into the tail gas treatment part (12).

15. The method for producing magnesium using low-hydrated magnesium chloride from salt lake according to claim 14, characterized in that: The magnesium production method further comprises the step of vaporizing the liquefied chlorine gas using a liquid chlorine vaporization device (11); or, adjusting the ratio of the chlorine gas and the air introduced into the mixing part after dust removal.

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