CN104388688A - Device and method for smelting lithium through vacuum thermal reduction of metal - Google Patents

Abstract

A device and method for smelting lithium by vacuum metalothermic reduction, the device includes a heating resistance furnace and a reaction tank; a material barrel, a movable support and a support cylinder are placed in the reaction vessel; the movable support is placed on the top of the material barrel, and the support cylinder is placed on the movable support ; The collector is placed on the fixed support, and the condenser is placed on the collector; the method is carried out as follows: (1) placing the reaction material for lithium refining in the barrel; (2) closing the reaction tank, vacuuming, and feeding Cooling water, heat the material in the barrel, and carry out vacuum thermal reduction reaction; metal lithium vapor enters the collector after condensing on the condenser; (3) stop heating, pass inert gas to normal pressure, and lower the reaction tank to normal temperature , to obtain lithium metal in the collector. The device of the present invention has simple structure and convenient operation, and is suitable for large-scale production. The combination of material barrel, movable bracket and support cylinder makes it more convenient to place and take out materials.

Description

A device and method for vacuum metallothermic reduction lithium smelting

technical field

The invention belongs to the technical field of metallurgy, and in particular relates to a device and method for vacuum metallothermal reduction smelting lithium.

Background technique

Lithium metal has unique physical and chemical properties and is widely used in emerging fields such as aerospace, nuclear power generation, and energy batteries. The demand has increased dramatically in recent years. The production methods of metal lithium mainly include molten salt electrolysis and vacuum thermal reduction. Molten salt electrolysis is the main method of industrial production of lithium metal at present, and the process is mature, but the production raw material of this process is high-purity lithium chloride, and the cost is high; the harmful impurities such as sodium and potassium in the primary product are high; the anode gas is Chlorine gas pollutes the environment and corrodes equipment; the process is long. The vacuum thermal reduction method can directly use industrial-grade lithium carbonate or lithium hydroxide as a raw material with low cost; and because the vapor pressure of metal lithium and sodium and potassium is different, the crystallization position is different, so the content of harmful impurities is extremely low; in the production process No harmful gas is generated; therefore, the vacuum thermal reduction method is a lithium refining method with industrial application prospects.

The vacuum thermal reduction method can be divided into carbothermal reduction method, hydrothermal reduction method and metal thermal reduction method according to the different reducing agents. The carbothermal reduction method and hydrothermal reduction method are not easy to carry out industrial promotion due to reasons such as high reduction temperature, difficult operation, and low grade of metal lithium; and the metallothermal reduction method of silicon, aluminum and their alloys has the most industrial application value. At present, semi-industrial tests of metallothermal reduction smelting lithium have been reported in the literature. However, the main reason for limiting the promotion of this method is that the collection technology of metallic lithium is immature, which affects production efficiency, resulting in high energy consumption and high production cost per unit mass of metallic lithium.

Contents of the invention

Aiming at the above-mentioned deficiencies in the existing methods for preparing lithium metal, the present invention provides a device and method for smelting lithium by vacuum metalothermic reduction. The steam is collected directly in the reaction tank, which greatly increases the yield of lithium metal while improving production efficiency.

The vacuum metalthermal reduction lithium smelting device of the present invention comprises a heating resistance furnace and a reaction tank; the lower part of the reaction tank is located in the heating resistance furnace, and the upper part of the reaction tank is provided with a cooling water jacket; the top of the reaction tank is sealed and connected with a flange cover, The flange cover is provided with a vacuum port and an air filling hole; the reaction tank is placed with a material barrel, a movable bracket and a support cylinder; the material barrel is located at the bottom of the reaction tank and inside the heating resistance furnace, the movable support is placed on the top of the material barrel, and the support cylinder placed on a movable support; a fixed support is provided on the inner wall of the support cylinder, the collector is placed on the fixed support, the condenser is placed on the collector, and the collector and the condenser are located above the heating resistance furnace; the first thermocouple and the second Two thermocouples are inserted into the reaction tank, the bottom end of the first thermocouple is located between the collector and the condenser, and the bottom end of the second thermocouple is located in the barrel.

The above-mentioned collector consists of an annular bottom plate and inner and outer cylinders to form an integral structure, the bottom of the inner cylinder is connected with the inner edge of the annular bottom plate, and the bottom edge of the outer cylinder is connected with the outer edge of the annular bottom plate.

The above-mentioned condenser is composed of at least one condensing sheet, the condensing sheet has a ring structure, the upper and lower surfaces of the condensing sheet have the same structure as the side wall of the circular platform, and the vertical projection structure of the condensing sheet is the same as that of the collector; when the condenser When it is composed of multiple condensation sheets, each condensation sheet is arranged from top to bottom and fixed together by condensation brackets, except for the topmost condensation sheet, all other condensation sheets are provided with through holes.

In the above device, a heat preservation resistance furnace is arranged outside the reaction tank, which is located between the heating resistance furnace and the cooling water jacket.

The method for refining lithium by vacuum metalothermic reduction of the present invention is to adopt the above-mentioned device, and carry out according to the following steps:

1. Put the reaction material for lithium smelting in the material barrel; the preparation method of the reaction material for lithium smelting is: mix the lithium-containing raw material and additives uniformly, press them into spherical agglomerates, and heat them at 700-1000 ° C and vacuum Lithium-containing clinker was obtained by calcining for 1~2 hours under the condition of pressure ≤100Pa; the lithium-containing clinker and reducing agent were crushed and ground to a particle size of ≤80μm, and then mixed evenly to obtain a mixed powder, and the mixed powder was pressed into a spherical shape The agglomerate is used as a reaction material for lithium smelting;

2. Close the reaction tank with the material barrel, evacuate the reaction tank to a pressure of ≤10Pa through the vacuum port, feed cooling water into the cooling water jacket, heat the material in the material barrel through a heating resistance furnace, and act as the second thermocouple The measured temperature is 1000~1250℃, and the temperature measured by the first thermocouple is controlled to be 200~600℃, and the vacuum thermal reduction reaction is carried out. The reaction time is 1.5~6h; the metal lithium vapor generated during the reaction is in the condenser Enter the collector after condensing;

3. Stop heating after the reaction is completed. When the temperature in the reaction tank drops to the temperature measured by the first thermocouple and is lower than the melting point of metal lithium, feed inert gas into the reaction tank through the gas filling hole to normal pressure, and lower the reaction tank. To normal temperature, metal lithium is obtained in the collector.

In the above method, when preparing the reaction material for lithium refining, the lithium-containing raw material selected is lithium carbonate; the additive selected is calcium oxide, and the reducing agent selected is ferrosilicon alloy; the mixing ratio of the lithium-containing raw material and the additive is in molar ratio containing Lithium raw material : additive = 1: (2~3), the mixing ratio of lithium-containing clinker and reducing agent is (3.3-4):1 according to the molar ratio of lithium in lithium-containing clinker and silicon in reducing agent.

In the above method, after the inert gas is incorporated into the reaction tank to normal pressure, in order to ensure that the metal lithium on the condenser is fully collected, the reaction tank is heated by a thermal insulation furnace outside the reaction tank, and the temperature measured by the first thermocouple is controlled. At 200~300°C, keep warm for 0.5~2h, then turn off the heat preservation resistance furnace and lower the reaction tank to normal temperature.

In the above method, the yield of metal lithium is more than or equal to 95%.

The weight content of silicon in the above ferrosilicon alloy is between 70% and 100%.

The above-mentioned inert gas is argon.

The device of the present invention is simple in structure, easy to operate, and is suitable for large-scale production. Through the combination of material barrels, movable supports and support cylinders, it is more convenient to place and take out materials. The method of the present invention can produce less energy consumption and low cost. The yield and purity of the product are high, and it has a good application prospect.

Description of drawings

Fig. 1 is the device structure schematic diagram of vacuum metal thermal reduction smelting lithium of the present invention; Among the figure, 1, heating resistance furnace, 2, reaction material for smelting lithium, 3, bucket, 4, movable support, 5, heat preservation resistance furnace, 6. Reaction tank, 7. Cooling water jacket, 8. Fastening bolts, 9. Inflatable hole, 10. First thermocouple, 11. Vacuum port, 12. Gasket, 13. Condenser, 14. Lithium metal, 15 , collector, 16, fixed bracket, 17, support tube, 18, second thermocouple, 19, condenser bracket, 20, flange cover;

Fig. 2 is the schematic diagram of the sectional structure of the collector in the embodiment of the present invention;

Fig. 3 is the top view of Fig. 2;

Fig. 4 is the structural schematic diagram of the top layer condensation sheet in the embodiment of the present invention;

Figure 5 is a top view of Figure 4;

Step 6 is a structural schematic diagram of a condensation sheet with a through hole in Embodiment 1 of the present invention;

FIG. 7 is a schematic structural diagram of a cooling sheet with through holes in Embodiment 2 of the present invention.

Detailed ways

The materials used in the embodiment of the present invention are the material barrel, movable support, support cylinder, collector and condenser made of high temperature resistant stainless steel.

Lithium carbonate, calcium oxide and ferrosilicon alloy used in the embodiment of the present invention are commercially available industrial grade products.

Argon is selected as the inert gas in the embodiment of the present invention.

The movable support adopted in the embodiment of the present invention is ring-shaped.

In the embodiment of the present invention, when the condenser is composed of multiple condensation sheets, the through holes on the condensation sheet provided with through holes are evenly distributed on the condensation sheet, and the total area of each through hole is 15-70% of the total surface area of the condensation sheet.

In the embodiment of the present invention, the diameter of the inner circle of the condensation sheet satisfies the requirement that the first thermocouple and the second thermocouple pass through at the same time, and the height of the condensation sheet is 1/4~3/2 of the diameter of the outer circle.

Example 1

The device structure of the vacuum metalothermic reduction smelting lithium is shown in Figure 1, including a heating resistance furnace 1 and a reaction tank 6; the bottom of the reaction tank 6 is located in the heating resistance furnace 1, and the top of the reaction tank 6 is provided with a cooling water jacket 7; The top of the tank 6 is sealed with the flange cover 20, and the flange cover 20 is provided with a vacuum port 11 and an air filling hole 9;

The flange cover 20 is fixed together with the reaction tank 6 by fastening bolts 8, and a gasket 12 is arranged between the flange cover 20 and the reaction tank 6;

Wherein reaction tank 6 is placed with bucket 3, movable support 4 and support cylinder 17; Material bucket 3 is positioned at the bottom of reaction tank 6 and is positioned at the inside of heating resistance furnace 1, movable support 4 is placed on the top of bucket 3, and support cylinder 17 is placed on On the movable support 4;

A fixed support 16 is provided on the inner wall of the support tube 17, the collector 15 is placed on the fixed support 16, the condenser 13 is placed on the collector 15, and the collector 15 and the condenser 13 are located above the heating resistance furnace 1;

The first thermocouple 10 and the second thermocouple 18 are inserted in the reaction tank 6, the bottom of the first thermocouple 10 is positioned between the collector 15 and the condenser 13, and the bottom of the second thermocouple 18 is positioned in the barrel 3;

The structure of the collector is shown in Figures 2 and 3. It consists of an annular bottom plate and inner and outer cylinders. The bottom edge of the inner cylinder is connected to the inner edge of the annular bottom plate, and the bottom edge of the outer cylinder is connected to the outer edge of the annular bottom plate. connect;

Condenser 13 is made up of 3 condensing sheets, and the condensing sheet is an annular structure, and the upper and lower surfaces of the condensing sheet have the same structure as the side wall of the round platform, and the vertical projection structure of the condensing sheet is the same as that of the collector; each condensing sheet Arranged from top to bottom and fixed together by the condensation bracket 19, except for the top condensation sheet, all other condensation sheets are provided with through holes; wherein the structure of the top condensation sheet is shown in Figures 4 and 5, and the structure of the remaining condensation sheets As shown in Figure 6;

The outside of the reaction tank 6 is also provided with a heat preservation resistance furnace 5, which is located between the heating resistance furnace 1 and the cooling water jacket 7;

The method for smelting lithium by vacuum metallothermic reduction adopts the above-mentioned device, and proceeds in the following steps:

1. Lithium smelting reaction materials are placed in the feed barrel; the preparation method of the lithium smelting reaction materials is: lithium carbonate and calcium oxide are mixed uniformly at a molar ratio of 1:2 and then pressed into spherical agglomerates. Calcined at 700°C and vacuum degree ≤100Pa for 2 hours to obtain lithium-containing clinker; crush lithium-containing clinker and ferrosilicon alloy separately and grind them to a particle size of ≤80 μm, and then mix them evenly to obtain mixed powder. The mixing ratio is according to the lithium-containing clinker The molar ratio of the lithium in the material to the silicon in the ferrosilicon alloy is 3.3:1; the mixed powder is pressed into a spherical agglomerate as a reaction material for smelting lithium; wherein the weight content of silicon in the ferrosilicon alloy is 70%;

2. Close the reaction tank with the material barrel, evacuate the reaction tank to a pressure of ≤10Pa through the vacuum port, feed cooling water into the cooling water jacket, heat the material in the material barrel through a heating resistance furnace, and act as the second thermocouple The measured temperature is 1000~1250℃, and the temperature measured by the first thermocouple is controlled to be 200~600℃, and the vacuum thermal reduction reaction is carried out, and the reaction time is 6h; the metal lithium vapor generated during the reaction is condensed on the condenser After entering the collector;

3. Stop heating after the reaction is completed. When the temperature in the reaction tank drops to the temperature measured by the first thermocouple and is lower than the melting point of metal lithium, feed inert gas into the reaction tank through the gas filling hole to normal pressure, and lower the reaction tank. To normal temperature, metal lithium is obtained in the collector;

After adding inert gas into the reaction tank to normal pressure, in order to ensure that the metal lithium on the condenser is fully collected, the reaction tank is heated through the heat preservation resistance furnace outside the reaction tank, and the temperature measured by the first thermocouple is controlled at 200~300 ℃, keep warm for 0.5h, then turn off the heat preservation resistance furnace and lower the reaction tank to normal temperature;

The yield of metallic lithium was 97%.

Example 2

The device structure of the vacuum metallothermic reduction smelting lithium is the same as that of Example 1, the difference is that:

The condenser is composed of two condensing sheets, and the structure of the condensing sheet with through holes is shown in Figure 7;

The method of vacuum metallothermic reduction refining lithium is the same as embodiment 1, the difference is:

Lithium carbonate and calcium oxide are mixed at a molar ratio of 1:2.5, and calcined for 1.5 hours at 850°C and a vacuum degree of ≤100Pa to obtain lithium-containing clinker;

The mixing ratio of lithium-containing clinker and ferrosilicon alloy is 3.6:1 according to the molar ratio of lithium in lithium-containing clinker and silicon in ferrosilicon alloy; the weight content of silicon in ferrosilicon alloy is 85%;

Vacuum thermal reduction reaction, the reaction time is 4h;

Heat the reaction tank through the insulation resistance furnace outside the reaction tank, control the temperature measured by the first thermocouple at 200~300°C, and keep it warm for 1h;

The yield of metallic lithium was 96%.

Example 3

The device structure of the vacuum metallothermic reduction smelting lithium is the same as that of Example 1, the difference is that:

Condenser consists of 1 condensing sheet, no condensing sheet with through holes;

The method of vacuum metallothermic reduction refining lithium is the same as embodiment 1, the difference is:

Lithium carbonate and calcium oxide are mixed at a molar ratio of 1:3, and calcined for 1 hour at 1000°C and vacuum degree ≤100Pa to obtain lithium-containing clinker;

The mixing ratio of lithium-containing clinker and ferrosilicon alloy is 4:1 according to the molar ratio of lithium in lithium-containing clinker and silicon in ferrosilicon alloy; the weight content of silicon in ferrosilicon alloy is 98%;

Vacuum thermal reduction reaction, the reaction time is 1.5h;

Heat the reaction tank through the insulation resistance furnace outside the reaction tank, control the temperature measured by the first thermocouple at 200~300°C, and keep it warm for 2 hours;

The yield of metal lithium is 95%.

Claims (8)

1. A device for smelting lithium in vacuum metallothermic reduction, comprising a heating resistance furnace and a reaction tank; the bottom of the reaction tank is located in the heating resistance furnace, and the top of the reaction tank is provided with a cooling water jacket; the top of the reaction tank is sealed with a flange cover connection, the flange cover is provided with a vacuum port and an air hole; it is characterized in that: a material barrel, a movable bracket and a support cylinder are placed in the reaction tank; the material barrel is located at the bottom of the reaction tank and inside the heating resistance furnace, and the movable bracket is placed in the material On the top of the barrel, the support cylinder is placed on the movable support; the inner wall of the support cylinder is provided with a fixed support, the collector is placed on the fixed support, the condenser is placed on the collector, and the collector and the condenser are located above the heating resistance furnace; A thermocouple and a second thermocouple are inserted into the reaction tank, the bottom end of the first thermocouple is located between the collector and the condenser, and the bottom end of the second thermocouple is located in the barrel. 2. a kind of vacuum metal thermal reduction lithium smelting device according to claim 1, is characterized in that described collector is formed an integral structure by an annular bottom plate and inner and outer cylinder, and the bottom edge of inner cylinder and annular The inner edge of the bottom plate is connected, and the bottom edge of the outer cylinder is connected with the outer edge of the annular bottom plate. 3. The device for smelting lithium by vacuum metalothermic reduction according to claim 1, characterized in that the condenser is composed of at least one condensation sheet, the condensation sheet is in an annular structure, and the upper and lower surfaces of the condensation sheet are in contact with the circular platform. The side wall structure of the condenser is the same, and the vertical projection structure of the condensing fins is the same as that of the collector; when the condenser is composed of multiple condensing fins, the condensing fins are arranged from top to bottom and fixed together by condensation brackets, except for the most Except for the condensation sheet on the upper layer, through holes are arranged on the other condensation sheets. 4. A vacuum metalthermal reduction lithium smelting device according to claim 1, characterized in that said reaction tank is also equipped with a heat preservation resistance furnace, which is located between the heating resistance furnace and the cooling water jacket. 5. A method for vacuum metallothermic reduction of lithium smelting, characterized in that the device according to claim 1 is used, and carried out in the following steps: (1) Put the reaction material for lithium smelting in a material barrel; the preparation method of the reaction material for lithium smelting is: mix the lithium-containing raw material and additives uniformly, press them into spherical agglomerates, and heat them at 700-1000 °C and Calcining for 1~2 hours under the condition of vacuum degree ≤100Pa to obtain lithium-containing clinker; crush the lithium-containing clinker and reducing agent separately and grind them until the particle size is ≤80μm, and then mix them evenly to obtain mixed powder, and press the mixed powder into balls Type agglomerates are used as reaction materials for lithium smelting; (2) Close the reaction tank with the material barrel, evacuate the reaction tank to a pressure of ≤10Pa through the vacuum port, pass cooling water into the cooling water jacket, and heat the material in the material barrel through a heating resistance furnace. When the second thermoelectric The temperature measured by the couple is 1000~1250℃, and the temperature measured by the first thermocouple is controlled to be 200~600℃, and the vacuum thermal reduction reaction is carried out. The reaction time is 1.5~6h; the metal lithium vapor generated during the reaction is condensed After condensing on the collector, it enters the collector; (3) After the reaction is completed, stop heating. When the temperature in the reaction tank drops to the temperature measured by the first thermocouple and is lower than the melting point of metal lithium, an inert gas is introduced into the reaction tank through the gas filling hole to normal pressure, and the reaction tank Down to normal temperature, metal lithium is obtained in the collector. 6. the method for a kind of vacuum metallothermic reduction smelting lithium according to claim 5 is characterized in that when preparing the reaction material for smelting lithium, the lithium-containing raw material selected is lithium carbonate; the additive selected is calcium oxide, and the reduced The agent is ferrosilicon alloy; the mixing ratio of lithium-containing raw materials and additives is lithium-containing raw materials in molar ratio: additive = 1: (2~3), the mixing ratio of lithium-containing clinker and reducing agent is based on the lithium-containing clinker The molar ratio to silicon in the reducing agent is (3.3~4):1. 7. A method for vacuum metallothermic reduction of lithium smelting according to claim 5, characterized in that after the inert gas is incorporated into the reaction tank to normal pressure, in order to ensure that the metal lithium on the condenser is fully collected, the reaction tank is passed through the reaction tank. The external heat preservation resistance furnace heats the reaction tank, controls the temperature measured by the first thermocouple at 200~300°C, keeps the temperature for 0.5~2h, and then closes the heat preservation resistance furnace to lower the reaction tank to normal temperature. 8. A method for smelting lithium by vacuum metalothermic reduction according to claim 5, characterized in that the yield of metallic lithium is more than or equal to 95%.