JPS60190587A - Lithium continuous manufacture and installation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention involves electrolyzing lithium chloride in a molten salt mixture and then separating the lithium! The present invention relates to a method for continuously producing lithium, which comprises the steps of: and an apparatus used for the production.

[Prior art]

For example, US Pat.
No. 3590 discloses that in the production of silane, lithium is produced by electrolysis from lithium chloride contained in a molten salt mixture containing lithium chloride and at least some alkali chloride and/or super-alkali chloride. has been proposed. The method has at least one of the following features.

(1) Semi-continuous method - an electrolytic cell is charged with an electrolytic mixture, the mixture is electrolyzed with the desired amount of lithium chloride, and the remaining mixture is then replenished with fresh lithium chloride.

(2) Use complex and cumbersome equipment to separate the produced lithium from the molten salt mixture within the electrolyzer itself, while preventing recombination of the lithium and the generated gaseous t= . This is done, for example, by carefully controlling the bath atmosphere above the lithium layer, or by using a diaphragm in the bath between the anode and cathode.

OBJECTIVE OF THE INVENTION 1 It is an object of the present invention to provide a simplified continuous process for producing lithium by electrolyzing lithium chloride in a molten salt mixture and then separating the lithium product.

SUMMARY OF THE INVENTION In the method of the present invention, lithium chloride is continuously electrolyzed in a molten salt mixture in a first step.

In this case, the produced lithium is not separated from the molten salt mixture in the electrolytic cell, but the mixture of metallic lithium and molten salt mixture is drawn out of the electrolytic cell. This greatly simplifies electrolysis operations. In the second step, the metallic lithium and molten salt mixture drawn out from the electrolytic cell are fed to a decanter, where the lithium is separated from the molten salt. The molten salt can preferably be recycled into the feed to the electrolyzer after filtration (if necessary).

[Preferred features and effects] The present invention has the following preferred features.

(1) Electrolysis is performed without using a diaphragm between the anode and cathode, and a natural rapid circulation of electrolyte occurs in the space between the anode and cathode.

(2) By coating the anode with an insulating refractory material down to the surface of the electrolyte, it is possible to prevent the anode from being attacked by lithium floating on the surface of the electrolyte, and to prevent direct reoxidation of lithium on the anode surface. Prevention.

(3) On the other hand, chlorine generated by electrolysis can be drawn out continuously without being diluted with an inert gas, which enables its direct industrial use.

(4) Finally, the decanter to which lithium and molten salt are supplied from the electrolytic cell consists of a supernatant separation section (decant section) and a withdrawal valve section, and the lithium is separated and drawn out in the supernatant separation section. The molten salt is separated in the valve section, drawn off and, after filtration, preferably recycled to the electrolyzer.

[Detailed Description of the Invention] The electrolyte consists of a molten salt mixture consisting mainly of lithium chloride and chlorides of at least other alkali and/or alkali-earth elements. 61, which melts together with lithium nitride at a temperature of about 320-360°C:
Form a mixture. Examples of binary compounds that can be used include lithium chloride and potassium chloride.1. In addition to lithium chloride and potassium chloride, sodium chloride, rubidium chloride, strontium chloride,
Mention may be made of chlorides selected from magnesium chloride, calcium chloride and barium chloride.

In both cases, electrolysis takes place in a liquid medium. Electrolysis is about 4
The mixture of molten salts fed to the electrolyzer should be sufficiently close to the eutectic composition of the mixture used with the excess lithium chloride subjected to electrolysis, since it must be carried out at temperatures between 00 and 500 °C, preferably around 500 °C. It is advantageous to have the composition.

Thus, when using a mixture of lithium chloride and potassium chloride as the electrolyte, at about 450° C. the lithium chloride in this mixture is replaced by Li Cl in the molten salt mixture.
Approximately 56 to 69 mol% at the inlet and outlet, expressed in moles of
It can vary between.

In this case the population concentration is greater than the outlet concentration. Lithium chloride can be used in an excess of up to 10 mol % relative to the eutectic composition of the lithium chloride-potassium chloride molten salt mixture.

The first feature of the method of the invention is its continuity. In other words,
The electrolytic cell is continuously supplied with a liquid consisting of a molten salt mixture containing lithium chloride as an electrolyzable substance, and the electrolysis products chlorine, metallic lithium and dissolved salt are continuously withdrawn from the electrolytic cell.

Another feature of the process of the invention is that lithium is not separated from the molten mixture in an electrolytic cell.

This feature, combined with the natural circulation described in more detail below, results in the molten salt preventing the recombination of the lithium that lies on its surface with the chlorine that forms the atmosphere above the electrolyte surface. . Therefore, there is no need to be particularly careful in separating the electrolyte from the chlorine atmosphere. Furthermore, electrolysis can be carried out without using a diaphragm in the rapid natural circulation of the electrolyte.Natural circulation is achieved simply by the entrainment action of Ju elementary bubbles generated at the anode to the electrolyte surface. Although it is possible to use a circulation method other than this natural circulation, it is not necessary because the electrolyte is vertically entrained by the upward movement of the chlorine bubbles in the space between the anode and the cathode. , the electrolyte descends through the space behind the cathode and enters the space between the anode and cathode through suitably arranged openings. It is advantageous to provide means for recycling the electrolyte in the electrolytic cell. Yes, the circulation speed of the electrolyte is large.If the speed of the electrolyte flowing through the anode and cathode utl in the absence of natural circulation is expressed as VO, the speed V actually obtained by natural circulation is about 100 times Va. (The average of the experiments conducted is 0.5-5 cm
/second = 1).

To allow for natural circulation of the electrolyte, the top of the tube is immersed, preferably wide-mouthed.

The back motion of the electrolyte, combined with this preferred wide-mouthed geometry of the cathode, drives lithium to the walls of the electrolyzer, where overflow naturally removes it and minimizes recombination with chlorine.

On the other hand, the anode is well protected against attack from lithium floating on the surface by a jacket of insulating refractory material extending into the electrolytic bath. As the refractory material, use a substance that is inert to the products with which it comes into contact at the electrolysis temperature, that is, mainly molten salt, chlorine and lithium.
This material must be electrically insulating. Such anode-coated shrines include aluminum, quartz, silica,
oxide, zirconia, berylum oxide, etc. can be used.

Another feature of the present invention is that it includes a step in which the lithium product and molten salt exiting the electrolytic cell are separated in a decanter. The decanter consists of a supernatant separation section (decant section) and an exhaust valve, and the supernatant separation section is preferably 0.1
It has an area S expressed by <S/Q<0.3. Here, Q is the feed flow to the decanter at 1 m 3 /h, and S is the area 112 of the supernatant separation section. The light surface phase is the lithium which is separated off in a decanter, and the remaining heavy phase constituted by the molten salt is preferably recycled to the electrolyser feed stream after filtration if necessary. In performing this recirculation, lithium chloride is added to the feed stream to the electrolyzer to
Although the temperature is maintained within the above range, it is preferable that the amount of lithium chloride added corresponds to the amount consumed in electrolysis.

The molten salt mixture is preferably filtered through a porous metal material such as fritted stainless steel.

The temperature of the decanter is preferably the same as or close to the temperature of the electrolytic cell.

The method of the present invention uses a combination of an electrolytic cell and a decanter,
It may have the following preferred characteristics.

(1) The electrolytic cell has a coated anode and a surrounding cathode. The upper part of the cathode is immersed in the bath and is preferably wide-mouthed, with an opening formed in the lower part of the cathode.

(2) Feeding the electrolytic cell is preferably carried out by introducing the molten salt mixture into the bottom of the electrolytic cell.

(3) The electrolytic cell is equipped with outlet means for drawing off the molten salt mixture and metallic lithium on the one hand into the decanter and on the other hand for drawing off the chlorine gas. This outlet means consists of an overflow 1" which flows into the decanter and an outlet for the gas phase above the electrolyte.

(4) The decanter to which the mixture is supplied from the electrolyzer 4fff at a flow rate IQ includes (a) a supernatant separation region with a surface area S, (b) a means for extracting the light phase (lithium) by overflow, and (C) a valve part. and the heavy phase (molten salt mixture) consisting of the weir.
and a withdrawal means.

[Description of Embodiments] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

The electrolytic cell 1 is constructed from stainless steel, and the cathode 2 is likewise formed from stainless steel in a cylindrical shape. The cathode 2 is welded to the bottom of the electrolytic cell 1, and an opening 3 is provided at the bottom to allow circulation of the electrolyte in the electrolytic cell. The upper part 4 of the cathode 2 is positioned so as to be kept below the surface of the electrolyte (the surface formed when the cell is in operation) and has a wide mouth.

Yangti [! 6 consists of a cylindrical graph eye 1- placed inside the cathode 2, covered with alumina from the part above the electrolyte to the part below the surface of the electrolyte (also the surface during operation). Covered by 10.

The supply of the molten salt mixture takes place by a conduit 5 opening into the bottom of the electrolytic cell 1 directly below the location located between the anode 6 and the cathode 1.

Gas (chlorine) is drawn out through a conduit 9 installed at the top of the electrolytic cell 1.
This is done by The withdrawal of the mixture obtained from the electrolysis takes place by means of a conduit 7, the height of which is determined by the level of electrolyte in the electrolytic cell 1.

It can be seen that the chlorine gas generated during electrolysis is extracted from the AfV14U1 without being diluted with, for example, an inert gas.

This feature becomes important when chlorine gas is used industrially as it is.

Decanter 8 receives a mixture of stream 1Q from electrolysis 4Pi through conduit 7. The decanter 8 has a supernatant separation section 11 with a surface area S and a light phase (metallic lithium) formed by an overflow port 12.
heavy phase withdrawal means consisting of a section 13, a weir outlet 14 and advantageously also a buffer sump 16. The heavy phase is mainly a molten salt mixture and is filtered through filtration device 1.
5 and electrolytic g! via conduit 5! Recirculated to l1.

The lithium chloride content in the electrolyte is adjusted by preferably replenishing the buffer reservoir 16 with the amount of lithium chloride consumed in the electrolysis. On the other hand, the circulation of molten j'g is carried out in reservoir 16.
This can be done by a pump 17 that can be installed at the outlet of the pump.

Next, a detailed description of the invention will be presented.

The electrolytic cell 1 used in the example has a diameter of 0.7 m and a height of 1 m, the cathode 2 has an inner diameter of 0.34 m, and the anode 6 has a diameter of 0.3 m and its top portion is covered with an aluminum pipe. It was.

The decanter 8 has a cylindrical shape with a diameter of 0.5 m and a height of 0.5111 mm, and the surface area of the supernatant separation section is 0.2 m2.
A feed flow Φ of 113/h was used.

A pump 17 was disposed next to the buffer reservoir 16, and molten salt was applied and filtered under pressure through a fritted stainless steel filter 15.

The experimental flow rate (pipe 5) was 1 m3. /h, and the electrolytic current (
It was 5000Δ. The following results were obtained.

Electrolyte population (pipe 5) KCI flow Hi = 11111 mini 11111 mole CI flow ff! = 18518 mol/h (62.5 mol/molten salt 100) Electrolytic cell outlet (pipe 7) KCI flow rate = 11111 mol/h 1-iCI flow rate - 18351 mol/h (62.3 mol/molten salt 100 ) 1-i flow rate - 167 mol/h Electrolytic cell gas outlet (pipe 9) C'l 2 flow ftt = 83.5 mol/h Stream 7 is divided into two by decanter 8, the first flow 14 is molten L
It consists of a homogeneous heavy phase of i Cl and KCI, and the second stream 12 consists of a light phase of li corresponding to the electrolysis products.

The salt recovered in the reservoir 16 is continuously filtered through porous metal in the filter 15 and then recycled to the electrolyte.

In the above experiment (13), a LiCl deficit of 167 mol/h was made up in buffer reservoir 16.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an apparatus used in the present invention. The upper part of the figure is as follows. 1: Electrolytic cell 2: Cathode 3: Frontage 4: Upper part of cathode 6: Anode 7: Conduit 8: Decanter 9: Conduit 10: Alumina coating 11: Supernatant separation section (decant section) 12: Overflow port 13: Valve part 14: Exhibition ['' 15: Filtration device 16: Buffer reservoir 17: Bomb

Claims (1)

[Scope of Claims] 1) Lithium chloride in a molten salt mixture is continuously electrolyzed between the cathode and anode of an electrolytic cell, and the lithium produced and the lithium produced are not separated from the molten salt mixture in the electrolytic cell. A first step of drawing out a mixture consisting of a molten salt mixture from the electrolytic layer, feeding the drawn out mixture to a decanter to separate lithium from the molten salt, and preferably returning the lithium-separated molten salt to the electrolytic cell. A continuous production method for circulating lithium. 2) The manufacturing method according to item 1 above, wherein rapid natural circulation of the mixture is caused without using a corneal membrane between the anode and the cathode. 3) The anode is coated with an insulating material up to the surface of the electrolytic chamber to protect it from attack by lithium floating on the surface of the electrolyte and to prevent re-oxidation of lithium on the anode surface. The IN method payment described in paragraph 1 above. 4) The manufacturing method according to item 1 or 2, wherein the chlorine generated by electrolysis is extracted as is without being diluted with an inert gas. 5) The decanter consists of a supernatant separation section (decant section) and a draw-out valve section, from which the separated lithium in the supernatant separation section is drawn out, while the molten salt separated in the well is filtered and then transferred to an electrolytic tank. The manufacturing method according to item 1 above, wherein the manufacturing method is recycled. 6) The electrolyte consists of lithium chloride and potassium chloride, ffl of lithium chloride 1. 2. The method according to item 1, wherein the concentration is in the range of 56 to 69% Li Cl based on the outlet, expressed in moles in the molten salt mixture, and the concentration is greater on the inlet side than on the outlet side. 7) The manufacturing method according to item 1 above, wherein the supernatant separation section has a surface area S expressed by 0.1<S/Q<0.3 (where Q is the flow rate). 8) It consists of an electrolytic cell and a decanter, said cell having an anode and a cathode surrounding it, the upper part of said cathode having a wide-mouthed shape immersed in the electrolyte, and the lower part having a wide-mouthed shape immersed in the electrolyte. The tank further has an inlet for the molten salt mixture at the bottom, an overflow outlet for drawing out the molten salt and metallic lithium, and an outlet for the chlorine gas. - is a lithium production device connected to the overflow outlet and comprising an overflow supernatant separation section with an area S for drawing out the light phase (lithium) and a barb for drawing out the heavy phase (molten salt mixture); . 9) The tank is made of stainless steel, the cathode is made of stainless steel, has a cylindrical shape, and the bottom part is fixed to the bottom of the tank, and the anode is made of graphite, has a cylindrical shape, and the top part is made from above the electrolyte surface. The inlet for the molten salt mixture opens directly below the space between the anode and cathode, and the outlet for the chlorine gas is located at the top of the tank. 9. The manufacturing apparatus according to item 8, wherein the overflow outlet is at a level determined by the height of the electrolyte in the tank, and the valve portion of the deno-jitter has a weir-like outlet and a buffer reservoir connected thereto.