CN111321425B - Molten salt chlorination TiCl production4Comprehensive recycling method of discharged waste salt - Google Patents

Molten salt chlorination TiCl production4Comprehensive recycling method of discharged waste salt Download PDF

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CN111321425B
CN111321425B CN202010195415.4A CN202010195415A CN111321425B CN 111321425 B CN111321425 B CN 111321425B CN 202010195415 A CN202010195415 A CN 202010195415A CN 111321425 B CN111321425 B CN 111321425B
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molten salt
chlorination
salt
chloride
ticl
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CN111321425A (en
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王兆文
尹华意
石忠宁
高炳亮
刘风国
胡宪伟
杨酉坚
陶文举
刘爱民
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Northeastern University China
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/04—Electrolytic production, recovery or refining of metals by electrolysis of melts of magnesium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
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    • C25B1/26—Chlorine; Compounds thereof
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    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/02—Electrolytic production, recovery or refining of metals by electrolysis of melts of alkali or alkaline earth metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/36—Alloys obtained by cathodic reduction of all their ions
    • C—CHEMISTRY; METALLURGY
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    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof
    • C25C7/025—Electrodes; Connections thereof used in cells for the electrolysis of melts
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/06—Operating or servicing

Abstract

Molten salt chlorination TiCl production4The comprehensive recovery and utilization method of discharged waste salt is characterized by that said method utilizes molten salt to chlorinate to produce TiCl4Deeply chlorinating the discharged waste salt, chlorinating impurities in the waste salt into low-boiling-point chlorides, separating the low-boiling-point chlorides from the chlorinated molten salt, and performing rectification separation and purification; pre-electrolyzing a molten salt mixture containing high-boiling-point chloride to remove impurities, then performing step-by-step electrolytic separation, firstly separating Mg, then taking liquid metal Bi as a cathode, graphite as an anode, taking a cathode product as a Bi-Ca alloy, and performing vacuum distillation on the Bi-Ca alloy to obtain metal Ca and liquid metal Bi, and returning low-calcium molten salt to a molten salt chlorination method to prepare TiCl4And (5) electrolyzing the rest part. The method improves the production benefit, provides a method for recycling waste salt, greatly reduces the production cost of titanium metallurgy, is environment-friendly, and is suitable for application and popularization in industrial production.

Description

Molten salt chlorination TiCl production4Comprehensive recycling method of discharged waste salt
Technical Field
The invention relates to TiCl production through molten salt chlorination4A comprehensive recycling method of discharged waste salt, in particular to a method for preparing aluminum-silicon alloy by deep chlorination of molten salt, aluminum electrolysis of chloride, and thermal reduction of silicon aluminum chloride, and electrolytic separation of alkali metal chloride, belonging to the technical field of inorganic chemistry.
Background
In recent years, with the rapid development of the electrolytic titanium industry in China, the demand for titanium resources is rapidly increased. Therefore, a large amount of high titanium slag containing high calcium is applied to TiCl4In the production, most of the titanium resources with high calcium content adopt a molten salt chlorination process technology, so that a large amount of waste salt is generated in the production process. Most of the waste salt is treated in a landfill mode, pollutes the environment and is a problem to be solved urgently in the healthy development of the titanium industry. Therefore, valuable elements such as Al, Si, Ca, Mg, Na and K in the waste salt are extracted by adopting a proper process, and part of the treated NaCl and KCl molten salt is returned to the molten salt chlorination process, so that the waste salt can be comprehensively utilized, the pollution to the environment is avoided, and the method has important significance for the production of the titanium metallurgy industry.
At present, TiCl is produced by a molten salt chlorination method4The method for treating the discharged waste molten salt is shown in figure 4. The method utilizes the hydrometallurgy principle to separate soluble components from insoluble components in the molten salt, and uses alkali to neutralize and separate the soluble components. The method mainly comprises the steps of mixing NaCl, KCl and MgCl2、CaCl2Dissolving the components in water, adjusting the pH value to precipitate calcium and Mg, and evaporating water to obtain sodium chloride and potassium chloride crystals. The method only carries out harmless treatment on the waste salt, and does not recycle valuable elements to realize the recycling of the waste salt.
The invention 2011104200361 discloses a method for producing TiCl by treating molten salt chlorination4The method for producing the waste molten salt adopts the steps of preserving heat and standing at the temperature of 500-900 ℃, layering, namely an upper layer (a floating layer), a middle layer (a molten salt layer) and a lower layer (a precipitation layer), and then layering. The upper layer is coke mixed with a small amount of molten salt, and the coke can be returned to the molten salt chlorination furnace for repeated use after separation or waste coke is recycled; the molten salt in the middle layer is subjected to iron and manganese removal reduction treatment, cooled to room temperature and subjected to iron and manganese removal reduction treatmentWater treatment and Na2CO3After treatment, the molten salt can be completely recycled, and Mn-Fe alloy (or metal Mn) and MgCO can be produced3And CaCO3Micro powder, AlCl3、SiCl4And Cl2And using the waste heat of the waste molten salt and treating Cl-containing-The wastewater can obtain economic and social benefits. The method utilizes the first pyrogenic separation and then the wet treatment, so that the energy consumption is high in the process, the high-temperature waste heat cannot be utilized, the flow is long, and the process is relatively complex.
Disclosure of Invention
Aiming at the prior molten salt chlorination method to produce TiCl4In the process, the discharged waste molten salt pollutes the environment, and the invention provides a method for producing TiCl by molten salt chlorination4A comprehensive recycling method of discharged waste salt. The invention aims to comprehensively recycle valuable elements in waste salt and eliminate environmental pollution, designs and develops a process technology of deep chlorination-multistage electrolysis of the waste salt, can solve a series of problems of high chlorine consumption, large sodium chloride molten salt consumption, waste salt pollution and the like in the titanium metallurgy industry, can obtain products of metal Al, Al-Si alloy, Mg, Ca and the like by treating the waste salt by using the technology, and can return the chlorine product to a molten salt chlorination process for use. Not only improves the production benefit, but also provides a method for recycling the waste salt.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the invention relates to TiCl production through molten salt chlorination4The comprehensive recycling method of the discharged waste salt comprises the following steps:
step 1: deep chlorination
Production of TiCl by chlorination of molten salts4The discharged waste salt is put into a deep chlorination furnace for deep chlorination, and impurities in the waste salt are chlorinated into low-boiling-point chlorides to obtain chlorinated molten salt;
wherein, the low-boiling-point chloride escapes from the chlorinated molten salt for separation to obtain a molten salt mixture containing the high-boiling-point chloride;
step 2: rectification separation and purification
Rectifying, separating and purifying the low-boiling-point chloride;
and step 3: pre-electrolysis for removing impurities
Pre-electrolyzing the molten salt mixture containing high-boiling-point chloride to remove impurities to obtain purified chlorinated molten salt;
and 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the decomposition voltage U is controlled to be 2.4V<U is less than or equal to 3.0V to obtain metal Mg and Cl2After the electrolysis is finished, MgCl in the molten chloride salt is chloridized2The mass percentage concentration of the molten salt is less than 2 percent, and residual molten salt is obtained;
(2) continuously electrolyzing the residual molten salt, controlling the decomposition voltage U to be not less than 3.2V and not more than 3.5V, adopting liquid metal Bi as a cathode, graphite as an anode, taking a cathode product as Bi-Ca alloy, taking an anode product as chlorine, and electrolyzing to obtain low-calcium molten salt; CaCl in low-calcium molten salt2The mass percentage concentration of the active carbon is 2 to 5 percent;
(3) vacuum distilling the cathode product Bi-Ca alloy to obtain metal Ca and liquid metal Bi, and returning the liquid metal Bi to the previous step to be used as a cathode raw material;
and 5: low calcium molten salt treatment
TiCl preparation by low-calcium molten salt returning molten salt chlorination method4And (3) electrolyzing the rest part, wherein the decomposition voltage U of the electrolysis is more than or equal to 3.8V and less than or equal to 4.0V, the mixed metal of Na and K is obtained at the cathode and can be used as a metal reducing agent, and chlorine gas obtained at the anode is collected.
In the step 1, the impurity is Al2O3、SiO2、TiO2、FeCl2The corresponding low-boiling chloride is AlCl3、 SiCl4、TiCl4And FeCl3。
In the step 1, the deep chlorination is to introduce a chlorination gas into molten salt for chlorination to produce TiCl4Deep chlorination is carried out in the discharged waste salt; wherein the deep chlorination temperature is 600-900 ℃, and the volume concentration of chlorine in the chlorination gas is more than 70%.
In the step 1, the high-boiling-point chloride is chloride with a boiling point higher than the deep chlorination temperature, specifically NaCl, KCl and MnCl2、MgCl2And CaCl2And the like.
In the step 2, AlCl is adopted3Preparing liquid metal aluminum and chlorine by adopting an electrolysis method, and reducing SiCl by using the liquid metal aluminum4Preparing aluminum-silicon intermediate alloy and aluminum chloride, wherein the reaction temperature is 700-1000 ℃, and the obtained aluminum chloride is returned to a molten salt electrolytic bath for electrolysis to prepare liquid metal aluminum and chlorine; FeCl separated by rectification3Can be used as a product.
In the step 3, the impurity removal process is as follows:
firstly, controlling the decomposition voltage U to be more than or equal to 1.8V and less than or equal to 2.0V, and electrolyzing to remove residual Fe to obtain a primary sponge iron product;
and removing Mn to obtain the primary sponge manganese product when the decomposition voltage U is controlled to be not less than 2.2V and not more than 2.4V.
In the step 3, in the impurity removal process, the adopted temperature is the deep chlorination temperature, and the cathode and the anode both adopt graphite electrodes.
In the step 4(1), the graphite is used as an anode, the stainless steel is used as a cathode, the electrolysis temperature is 650-800 ℃, and the current density is 0.1-1.0A/cm2The electrolysis time is 8-16 h.
The molten salt is chloridized to produce TiCl4The comprehensive recycling method of the discharged waste salt obtains chlorine as the raw material for deep chlorination in the step 1, and the chlorine can also be returned to molten salt chlorination for producing TiCl4In the working procedure.
The invention relates to TiCl production through molten salt chlorination4The comprehensive recycling method of the discharged waste salt has the beneficial effects that:
by implementing the technical scheme of the invention, the problem of environmental pollution of the waste salt can be solved, valuable metals and chlorine elements in the waste salt can be recovered, the chlorine generated by electrolysis can reduce the chlorine supplement amount in the chlorination process of the high titanium slag molten salt, and meanwhile, outsourcing chloride molten salt is not needed to be used in the chlorination process, the chloride molten salt can be recycled, and the outsourcing chloride molten salt is not needed to be used in the chlorination process. In addition, the technology can produce metal products such as Al, Ca, Mg, Al-Si alloy and the like, greatly reduces the production cost of titanium metallurgy, is environment-friendly, and is suitable for application and popularization in industrial production.
The invention relates to TiCl production through molten salt chlorination4The comprehensive recycling method of the discharged waste salt has the following advantages: the used raw materials are all waste materials, and the raw materials do not need to be purchased, so that the cost is low; multiple metal products can be separated by multi-stage electrolysis, and the obtained product has high purity.
The invention provides a method for deep chlorination-multistage electrolysis of waste salt based on the purpose of comprehensive utilization of the waste salt, solves the problem of waste salt pollution in the titanium metallurgical industry, increases benefits and improves the comprehensive level of the aluminum-titanium metallurgical industry in China.
Drawings
FIG. 1: FIG. 1 of a pre-electrolyzer of the invention in example 1;
FIG. 2: the diagram of the magnesium electrolysis device in the embodiment 1 of the invention;
FIG. 3: the calcium electrolysis device in the embodiment 1 of the invention;
in the above figure, 1-graphite crucible, 2-graphite anode, 3-anode gas-collecting hood, 4-graphite crucible cover, 5-insulating layer, 6-electrode guide rod, 7-graphite cathode, 8-fused salt mixture containing high boiling point chloride; 9-steel plate cathode, 10-purified chlorinated molten salt; 11-boron nitride crucible cover, 12-chlorine gas collecting conduit, 13-residual molten salt, and 14-metal bismuth cathode.
FIG. 4 is a flow chart of a treatment process of waste molten salt discharged in TiCl4 production by a traditional molten salt chlorination method.
FIG. 5 shows the molten salt chlorination production TiCl of the present invention4A process flow chart of the comprehensive recycling method of the discharged waste salt.
Detailed Description
The present invention will be described in further detail with reference to examples.
The waste salt sample extracted by the invention comes from a certain titanium factory, the sample is directly crushed and ground for analysis, and the components of the waste salt are as follows: 29.4% NaCl, 8.2% KCl, 8.8% CaCl2，26.8％MgCl2，12.5％FeCl2，2.1％FeCl3，3.9％MnCl2，2％TiO2， 1.3％Al2O3，2.0％SiO2，3％C。
In the following examples, AlCl3The electrolytic method for preparing liquid metal aluminum and chlorine adopts an aluminum chloride multi-chamber electrolytic cell, which can be seen in patent 202010108035.2.
Example 1
Molten salt chlorination TiCl production4The comprehensive recycling method of the discharged waste salt has a process flow chart shown in figure 5, and comprises the following steps:
step 1: deep chlorination
Taking 200g of waste salt, putting the waste salt into a deep chlorination furnace for deep chlorination, wherein the chlorination temperature is 850 ℃, deep chlorination gas is introduced, the volume concentration of chlorine is 80%, the volume concentration of oxygen is 15%, and the balance is argon, and the chlorination time is 30min, so that chlorination furnace tail gas and a molten salt mixture containing high-boiling-point chloride are obtained;
step 2: rectification of low-boiling chlorides
Separating low-boiling-point chloride from chlorination furnace tail gas, and rectifying to obtain 4.7 g of aluminum chloride, 10.2 g of silicon chloride, 35.2 g of ferric chloride and the like; wherein the mass purity of the rectified chloride is more than 99%;
and step 3: pre-electrolysis for removing impurities
152 g of fused salt mixture containing high-boiling-point chloride remained in the chlorination furnace, and the components are NaCl, KCl and MgCl2， CaCl2，MnCl2And also a small amount of FeCl3。
Putting the fused salt mixture containing high boiling point chloride into an electrolytic tank for 30min pre-electrolysis (the structural schematic diagram of the pre-electrolysis device is shown in figure 1, wherein in the pre-electrolysis device, a graphite crucible 1 and a graphite crucible cover 4 are closed to form a closed space, a cathode and an anode are respectively a graphite cathode 7 and a graphite anode 2, the cathode and the anode are both electrified through an electrode guide rod 6, an insulating layer 5 is arranged at a through hole of the electrode guide rod penetrating through the graphite crucible cover 4, an anode gas collecting cover 3 is arranged at the graphite anode 2 and used for collecting chlorine generated by the graphite anode 2, the fused salt mixture 8 containing high boiling point chloride is placed in the graphite crucible 1 for pre-electrolysis, the pre-electrolysis temperature is 850 ℃, the decomposition voltage is controlled to be 1.8V, the cathode and the anode of the electrolytic tank are both graphite electrodes, and the fused salt mixture on the graphiteTaking out the cathode of the sponge iron, replacing the cathode with a new graphite cathode, controlling the decomposition voltage to be 2.2V, electrolyzing at 850 ℃ for 30min to obtain purified chlorinated molten salt with low sponge manganese and impurities for graded electrolysis, wherein the purified chlorinated molten salt comprises the components of 40% NaCl, 11% KCl and 13% CaCl2，36％MgCl2。
And 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the purified chlorinated molten salt is placed in a closed electrolytic cell (the structural schematic diagram of the magnesium electrolysis device is shown in figure 2), a graphite anode 2 and a steel plate cathode 9 are adopted in the magnesium electrolysis device, a graphite crucible 1 and a graphite crucible cover 4 are closed to form a closed space, the cathode and the anode are electrified through an electrode guide rod 6, an insulating layer 5 is arranged at a through hole of the electrode guide rod penetrating through the graphite crucible cover 4, an anode gas collecting cover 3 is arranged at the graphite anode 2 and used for collecting chlorine gas generated by the graphite anode 2, and the purified chlorinated molten salt 10 is placed in the graphite crucible 1 for electrolytic magnesium removal. The electrolysis temperature is 800 deg.C, the decomposition voltage is controlled at 3.0V, and the current density is 0.2-0.8A/cm2And electrolyzing for 8h, and conveying chlorine to an alkali liquor absorption tower for treatment. Obtaining 12 g of metal Mg, and the mass purity is more than 99%. The remaining molten salt was about 80 grams.
(2) Putting the rest molten salt into an electrolytic tank (the structural schematic diagram of the calcium electrolysis device is shown in figure 3:) for electrolysis, wherein in the calcium electrolysis device, a graphite crucible 1 and a graphite crucible cover 4 are closed to form a closed space, metal bismuth and the rest molten salt 13 are added into the graphite crucible 1, the metal bismuth is deposited below the graphite crucible due to high density, a boron nitride crucible sleeve 11 is arranged in the side wall of the graphite crucible, the anode is a graphite anode 2, the cathode is a metal bismuth cathode 14, the anode is electrified through an electrode guide rod 6 penetrating through the graphite crucible cover 4, an insulating layer 5 is arranged at the contact part of the electrode guide rod 6 and the graphite crucible cover 4, the cathode is electrified through the electrode guide rod 6 connected with the graphite crucible 1, a chlorine collecting conduit 12 is penetrated through the graphite crucible cover 4 and used for collecting chlorine generated by the graphite anode 2, an insulating layer 5 is arranged at the through hole of the electrode guide rod penetrating through the graphite crucible cover 4, the electrolysis temperature is 750 ℃, and the decomposition voltage is controlled to be 3.5V, electrolyzing for 10h to obtain a Bi-Ca alloy (the mass percentage concentration of Ca in the Bi-Ca alloy is 5%) on a cathode, wherein the components of the residual low-calcium molten salt are as follows: 78.2% NaCl, 21.3% KCl, 0.5% CaCl2The weight was 58 g.
(3) And (3) carrying out vacuum separation on the Bi-Ca alloy in a vacuum distillation furnace at the temperature of 700 ℃ for 30min and the vacuum degree of 10 Pa. The obtained metallic calcium is 4.5 g, the purity is more than 99.9 percent, and the metallic bismuth is returned for use.
And 5: low calcium molten salt treatment
And (3) putting the residual low-calcium molten salt into an electrolytic cell, electrolyzing for 2 hours at the electrolysis temperature of 750 ℃ under the condition that the decomposition potential is controlled to be 4.0V to obtain 8 g of a mixture of metal sodium and metal potassium (the mass percentage concentration of K is about 10%), and returning the residual molten salt to the molten salt chlorination process for use.
Wherein, the aluminum chloride after the rectification of the low boiling point chloride in the step 2 can be used for electrolysis, and the aluminum chloride electrolysis test is as follows: preparing electrolyte LiCl 51% -NaCl 44% -AlCl 35 percent (mass percentage concentration) is put into an aluminum chloride multi-chamber electrolytic bath for electrolysis, and the current density is 0.7A/cm2And (3) introducing aluminum chloride steam during electrolysis at 820 ℃, and electrolyzing for 10 hours to obtain 160 g of metal Al, wherein the mass purity is more than 99.8%.
The silicon chloride obtained can be subjected to a silicoaluminothermic reduction experiment: the silicon chloride gas was introduced into the reactor at a reduction temperature of 780 ℃. The aluminum-silicon alloy is obtained, contains 22 percent (mass percent) of silicon, contains a gas phase component which is a mixture of aluminum chloride and silicon chloride, and is sent to an aluminum chloride electrolysis process after rectification and separation of the aluminum chloride, and the silicon chloride is recycled.
Example 2
Molten salt chlorination TiCl production4The comprehensive recycling method of the discharged waste salt comprises the following steps:
step 1: deep chlorination
Taking 500g of waste salt, putting the waste salt into a deep chlorination furnace for deep chlorination at the chlorination temperature of 800 ℃, introducing deep chlorination gas, wherein the volume concentration of chlorine is 85 percent, the volume concentration of oxygen is 10 percent, and the balance is argon, and the chlorination time is 60min to obtain chlorination furnace tail gas and a molten salt mixture containing high-boiling-point chloride;
step 2: rectification of low-boiling chlorides
Separating low-boiling-point chloride from chlorination furnace tail gas, and rectifying to obtain 12.5 g of aluminum chloride, 26.2 g of silicon chloride, 88.2 g of ferric chloride and the like; wherein the mass purity of the rectified chloride is more than 99%;
and step 3: pre-electrolysis for removing impurities
380 g of fused salt mixture containing high-boiling-point chloride remained in the chlorination furnace, and the components are NaCl, KCl and MgCl2， CaCl2，MnCl2Also a small amount of FeCl3。
Putting a molten salt mixture containing high-boiling-point chloride into an electrolytic cell for 60min pre-electrolysis (the structural schematic diagram of a pre-electrolysis device is shown in figure 1), controlling the decomposition voltage to be 1.9V at 750 ℃, adopting graphite electrodes as cathodes and anodes of the electrolytic cell, obtaining sponge iron on the graphite cathode, taking out the cathode, replacing the cathode with a new graphite cathode, controlling the decomposition voltage to be 2.2V, electrolyzing for 60min at 750 ℃, obtaining purified molten chloride with lower sponge manganese and impurities for graded electrolysis, wherein the purified molten chloride comprises the following components: 40% NaCl, 11% KCl, 13% CaCl2，36％MgCl2。
And 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the purified molten chloride salt is put into a closed electrolytic cell (the structural schematic diagram of a magnesium electrolysis device is shown in figure 2), graphite is used as an anode, and a steel plate is used as a cathode. The electrolysis temperature is 680 ℃, and the current density is 0.2-0.9A/cm2Electrolyzing for 10h, and conveying chlorine to an alkali liquor absorption tower for treatment. 32 g of metal Mg is obtained, and the mass purity is more than 99 percent. The remaining molten salt was about 215 grams.
(2) Putting the residual molten salt into an electrolytic cell (the structural schematic diagram of a calcium electrolysis device is shown in figure 3:) for electrolysis, wherein the anode is graphite, the cathode is metal bismuth, the electrolysis temperature is 800 ℃, the decomposition voltage is controlled at 3.4V, the electrolysis time is 8h, a Bi-Ca alloy (the mass percentage concentration of Ca in the Bi-Ca alloy is 8%) is obtained on the cathode, and the residual molten saltThe low-calcium molten salt comprises the following components: 76.2% NaCl, 21.5% KCl, 2.3% CaCl2The weight is 150 g. The rest low-calcium fused salt is returned to the fused salt for chlorination to prepare TiCl4The process is used.
(3) And (3) carrying out vacuum separation on the Bi-Ca alloy in a vacuum distillation furnace at the temperature of 700 ℃ for 30min and the vacuum degree of 10 Pa. 11 g of calcium metal is obtained, the mass purity is more than 99.9 percent, and the bismuth metal is returned for use.
Wherein, the aluminum chloride obtained in the low boiling point chloride rectification process of the step 2 can be used for electrolysis, and the aluminum chloride electrolysis test comprises the following steps: preparing electrolyte LiCl 51-NaCl 44-AlCl 35 percent (mass percentage concentration) is put into an aluminum chloride multi-chamber electrolytic bath for electrolysis, and the current density is 0.7A/cm2And (3) introducing aluminum chloride steam during electrolysis at 820 ℃, and electrolyzing for 10 hours to obtain 160 g of metal Al, wherein the mass purity is more than 99.8%.
The silicon chloride obtained can be subjected to a silicoaluminothermic reduction experiment: the silicon chloride gas was introduced into the reactor at a reduction temperature of 780 ℃. The aluminum-silicon alloy is obtained, contains 22 percent (mass percent) of silicon, contains a gas phase component which is a mixture of aluminum chloride and silicon chloride, and is sent to an aluminum chloride electrolysis process after rectification and separation of the aluminum chloride, and the silicon chloride is recycled.
Example 3
Molten salt chlorination TiCl production4The comprehensive recycling method of the discharged waste salt comprises the following steps:
step 1: deep chlorination
Taking 1000g of waste salt, putting the waste salt into a deep chlorination furnace for deep chlorination at the chlorination temperature of 900 ℃, introducing deep chlorination gas, wherein in the deep chlorination gas, the volume concentration of chlorine is 75%, the volume concentration of oxygen is 10%, and the balance is argon, and the chlorination time is 90min to obtain chlorination furnace tail gas and a molten salt mixture containing high-boiling-point chloride;
step 2: rectification of low-boiling chlorides
Separating low boiling point chloride from chlorination furnace tail gas, rectifying to obtain 24.5 g of aluminum chloride, 51.2 g of silicon chloride, 175.4 g of ferric chloride and the like; wherein the mass purity of the rectified chloride is more than 99%;
and step 3: pre-electrolysis for removing impurities
761 g of fused salt mixture containing high boiling point chloride remained in the chlorination furnace, and the components are NaCl, KCl, MgCl2， CaCl2，MnCl2Also a small amount of FeCl3。
Putting the fused salt mixture containing high-boiling-point chloride into an electrolytic cell for 90min pre-electrolysis (the structural schematic diagram of a pre-electrolysis device is shown in figure 1), controlling the decomposition voltage to be 1.8V at 700 ℃, adopting graphite electrodes for the cathode and the anode of the electrolytic cell, obtaining sponge iron on a graphite cathode, taking out the cathode, replacing the cathode with a new graphite cathode, controlling the decomposition voltage to be 2.2V, electrolyzing for 90min at 700 ℃, obtaining purified fused chloride with lower sponge manganese and impurities for graded electrolysis, wherein the purified fused chloride comprises the following components: 40% NaCl, 11% KCl, 13% CaCl2，36％MgCl2。
And 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the purified molten salt is put into a closed electrolytic cell (the structural schematic diagram of the magnesium electrolysis device is shown in figure 2), graphite is used as an anode, and a steel plate is used as a cathode. The electrolysis temperature is 700 ℃, and the current density is 0.1-0.8A/cm2And electrolyzing for 16h, and conveying chlorine to an alkali liquor absorption tower for treatment. 62 g of metal Mg is obtained, and the mass purity is more than 99 percent. The molten salt remained about 460 grams.
(2) And (2) putting the residual molten salt into an electrolytic cell (the structural schematic diagram of a calcium electrolysis device is shown in figure 3:) for electrolysis, wherein the anode is graphite, the cathode is metal bismuth, the electrolysis temperature is 850 ℃, the decomposition voltage is controlled at 3.3V, the electrolysis time is 6h, a Bi-Ca alloy (the mass percentage concentration of Ca in the Bi-Ca alloy is 10%) is obtained on the cathode, and the components of the residual low-calcium molten salt are as follows: 75.2% NaCl, 19.8% KCl, 5% CaCl2And a weight of 312 grams.
(3) And (3) carrying out vacuum separation on the Bi-Ca alloy in a vacuum distillation furnace at the temperature of 700 ℃ for 30min and the vacuum degree of 10 Pa. 22 g of calcium metal with the mass purity of more than 99.9 percent is obtained, and the bismuth metal is returned for use.
Wherein, the low boiling point chlorine in step 2The aluminum chloride obtained in the rectification process of the compound can be used for electrolysis, and the aluminum chloride electrolysis test comprises the following steps: preparing electrolyte LiCl 51-NaCl 44-AlCl 35 percent (mass percentage concentration) is put into an aluminum chloride multi-chamber electrolytic bath for electrolysis, and the current density is 0.7A/cm2And (3) introducing aluminum chloride steam during electrolysis at 820 ℃, and electrolyzing for 10 hours to obtain 160 g of metal Al, wherein the mass purity is more than 99.8%.
The silicon chloride obtained can be subjected to a silicoaluminothermic reduction experiment: the silicon chloride gas was introduced into the reactor at a reduction temperature of 780 ℃. The aluminum-silicon alloy is obtained, contains 22 percent (mass percent) of silicon, contains a gas phase component which is a mixture of aluminum chloride and silicon chloride, and is sent to an aluminum chloride electrolysis process after rectification and separation of the aluminum chloride, and the silicon chloride is recycled.
Example 4
Molten salt chlorination TiCl production4The comprehensive recycling method of the discharged waste salt comprises the following steps:
step 1: deep chlorination
Taking 5000g of waste salt, putting the waste salt into a deep chlorination furnace for deep chlorination at the chlorination temperature of 750 ℃, introducing deep chlorination gas, wherein in the deep chlorination gas, the volume concentration of chlorine is 90%, the volume concentration of oxygen is 8%, and the balance is argon, and the chlorination time is 120 min; obtaining chlorination furnace tail gas and a molten salt mixture containing high-boiling-point chloride;
step 2: rectification of low-boiling chlorides
Separating low-boiling-point chloride from chlorination furnace tail gas, and rectifying to obtain 251 g of aluminum chloride, 254 g of silicon chloride, 880 g of ferric chloride and the like; wherein the mass purity of the rectified chloride is more than 99%;
and step 3: pre-electrolysis for removing impurities
3802 g of fused salt mixture containing high-boiling-point chloride remained in the chlorination furnace, wherein the components are NaCl, KCl and MgCl2， CaCl2，MnCl2Also a small amount of FeCl3。
Placing molten salt mixture containing high boiling point chloride into an electrolytic cell for 120min pre-electrolysis (structural schematic diagram of pre-electrolysis device is shown in figure 1), controlling decomposition voltage at 650 deg.C1.9V, graphite electrodes are adopted by the cathode and the anode of the electrolytic cell, sponge iron is obtained on the graphite cathode, the cathode is taken out, a new graphite cathode is replaced, the decomposition voltage is controlled to be 2.2V, electrolysis is carried out for 90min at 650 ℃, purified chlorinated molten salt with lower sponge manganese and impurities is obtained and is used for graded electrolysis, and the purified chlorinated molten salt comprises the following components: 40% NaCl, 11% KCl, 13% CaCl2，36％MgCl2。
And 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the purified molten chloride salt is put into a closed electrolytic cell (the structural schematic diagram of a magnesium electrolysis device is shown in figure 2), graphite is used as an anode, and a steel plate is used as a cathode. The electrolysis temperature is 750 ℃, and the current density is 0.1-1.0A/cm2Electrolyzing for 12h, and conveying chlorine to an alkali liquor absorption tower for treatment. 322 g of metal Mg is obtained, and the mass purity is more than 98 percent. The remaining molten salt was about 2188 grams.
(2) And (2) putting the residual molten salt into an electrolytic cell (the structural schematic diagram of a calcium electrolysis device is shown in figure 3:) for electrolysis, wherein the anode is graphite, the cathode is metal bismuth, the electrolysis temperature is 700 ℃, the decomposition voltage is controlled at 3.2V, the electrolysis time is 10h, a Bi-Ca alloy (the mass percentage concentration of Ca in the Bi-Ca alloy is 5%) is obtained on the cathode, and the components of the residual low-calcium molten salt are as follows: 77.2% NaCl, 21.8% KCl, 1% CaCl2And a weight of 1520 grams. And returning the residual low-calcium molten salt to the molten salt chlorination process for use.
(3) And (3) carrying out vacuum separation on the Bi-Ca alloy in a vacuum distillation furnace at the temperature of 700 ℃ for 30min and the vacuum degree of 10 Pa. 112 g of calcium metal with purity more than 99.9 percent is obtained, and the bismuth metal is returned for use.
Wherein, the aluminum chloride obtained in the low boiling point chloride rectification process of the step 2 can be used for electrolysis, and the aluminum chloride electrolysis test comprises the following steps: preparing electrolyte LiCl 51-NaCl 44-AlCl 35 percent (mass percentage) is put into an aluminum chloride multi-chamber electrolytic cell for electrolysis, and the current density is 0.7A/cm2And (3) introducing aluminum chloride steam during electrolysis at 820 ℃, and electrolyzing for 10 hours to obtain 160 g of metal Al, wherein the purity is more than 99.8%.
The silicon chloride obtained can be subjected to a silicoaluminothermic reduction experiment: the silicon chloride gas was introduced into the reactor at a reduction temperature of 780 ℃. The aluminum-silicon alloy is obtained, contains 22 percent (mass percent) of silicon, contains a gas phase component which is a mixture of aluminum chloride and silicon chloride, and is sent to an aluminum chloride electrolysis process after rectification and separation of the aluminum chloride, and the silicon chloride is recycled.

Claims (6)

1. Molten salt chlorination TiCl production4The comprehensive recycling method of the discharged waste salt is characterized by comprising the following steps:
step 1: deep chlorination
Production of TiCl by chlorination of molten salts4The discharged waste salt is put into a deep chlorination furnace for deep chlorination, and impurities in the waste salt are chlorinated into low-boiling-point chlorides to obtain chlorinated molten salt; deep chlorination is to introduce a chlorination gas into a molten salt for chlorination to produce TiCl4Deep chlorination is carried out in the discharged waste salt; wherein the deep chlorination temperature is 600-900 ℃, and the volume concentration of chlorine in the chlorination gas is more than 70%; the impurity is Al2O3、SiO2、TiO2、FeCl2The corresponding low-boiling chloride is AlCl3、SiCl4、TiCl4And FeCl3；
Wherein, the low-boiling-point chloride escapes from the chlorinated molten salt for separation to obtain a molten salt mixture containing the high-boiling-point chloride; the high-boiling-point chloride is chloride with boiling point higher than deep chlorination temperature, specifically NaCl, KCl, MnCl2、MgCl2And CaCl2；
Step 2: rectification separation and purification
Rectifying, separating and purifying the low-boiling-point chloride;
and step 3: pre-electrolysis for removing impurities
Pre-electrolyzing the molten salt mixture containing high-boiling-point chloride to remove impurities to obtain purified chlorinated molten salt;
and 4, step 4: step-by-step electrolytic separation
And (3) carrying out step-by-step electrolytic separation on the purified chlorinated molten salt:
(1) the decomposition voltage U is controlled to be 2.4V<U is less than or equal to 3.0V to obtain metal MgAnd Cl2After the electrolysis is finished, MgCl in the molten chloride salt is chloridized2The mass percentage concentration of the molten salt is less than 2 percent, and residual molten salt is obtained;
(2) continuously electrolyzing the residual molten salt, controlling the decomposition voltage U to be not less than 3.2V and not more than 3.5V, adopting liquid metal Bi as a cathode, graphite as an anode, taking a cathode product as Bi-Ca alloy, taking an anode product as chlorine, and electrolyzing to obtain low-calcium molten salt; CaCl in low-calcium molten salt2The mass percentage concentration of the compound is 2% -5%;
(3) vacuum distilling the cathode product Bi-Ca alloy to obtain metal Ca and liquid metal Bi, and returning the liquid metal Bi to the step 4(2) to be used as a cathode raw material;
and 5: low calcium molten salt treatment
TiCl preparation by low-calcium molten salt returning molten salt chlorination method4And (3) electrolyzing the rest part, wherein the decomposition voltage U of the electrolysis is more than or equal to 3.8V and less than or equal to 4.0V, the mixed metal of Na and K is obtained at the cathode and can be used as a metal reducing agent, and chlorine gas obtained at the anode is collected.
2. Molten salt chlorination to produce TiCl according to claim 14The comprehensive recycling method of the discharged waste salt is characterized in that in the step 2, AlCl is adopted3Preparing liquid metal aluminum and chlorine by adopting an electrolysis method, and reducing SiCl by using the liquid metal aluminum4Preparing aluminum-silicon intermediate alloy and aluminum chloride, wherein the reaction temperature is 700-1000 ℃, and the obtained aluminum chloride is returned to a molten salt electrolytic bath for electrolysis to prepare liquid metal aluminum and chlorine; FeCl separated by rectification3Can be used as a product.
3. Molten salt chlorination to produce TiCl according to claim 14The comprehensive recycling method of the discharged waste salt is characterized in that in the step 3, the impurity removal process is as follows:
firstly, controlling the decomposition voltage U to be more than or equal to 1.8V and less than or equal to 2.0V, and electrolyzing to remove residual Fe to obtain a primary sponge iron product;
and removing Mn to obtain the primary sponge manganese product when the decomposition voltage U is controlled to be not less than 2.2V and not more than 2.4V.
4. Molten salt chlorination to produce TiCl according to claim 14The comprehensive recycling method of the discharged waste salt is characterized in that in the step 3, the adopted temperature is the deep chlorination temperature in the impurity removal process, and the cathode and the anode both adopt graphite electrodes.
5. Molten salt chlorination to produce TiCl according to claim 14The comprehensive recycling method of the discharged waste salt is characterized in that in the step 4(1), graphite is used as an anode, stainless steel is used as a cathode, the electrolysis temperature is 650-800 ℃, and the current density is 0.1-1.0A/cm2The electrolysis time is 8-16 h.
6. Molten salt chlorination to produce TiCl according to claim 14The comprehensive recycling method of the discharged waste salt is characterized in that the TiCl is produced by the chlorination of the molten salt4The comprehensive recycling method of the discharged waste salt obtains chlorine gas as the raw material for deep chlorination in the step 1, and the chlorine gas returns to the molten salt for chlorination to produce TiCl4In the working procedure.
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