JPS61232205A - Production of lithium carbonate powder - Google Patents

Abstract

PURPOSE:To obtain simply and economically the titled high-purity powder with small loss in weight on heating, by adding previously LI2CO3 powder an aqueous solution of a Li compound and crystallyzing lithium carbonate powder under heating. CONSTITUTION:5-100pts.wt. Li2O3 powder having <=80mu average particle diameter based on 100pts.wt. Li2O3 to be formed by crystallization under heating is previously added to an aqueous solution containing 5-10wt% Li compound such as LiOH, etc., stirred and dispersed in the solution. The aqueous solution is heated to >=70 deg.C and >=1/2 equivalent based on LiOH in the aqueous solution of CO2 is introduced to it to give the titled powder having <=0.1wt% loss in weight on heating.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Field The present invention relates to a method for producing high purity lithium carbonate powder.

More specifically, the present invention relates to a method for producing high-purity lithium carbonate powder with a small amount of components that lose weight on heating.

The recent development of the electronics industry is remarkable, and functional elements and new ceramics based on new principles are being developed one after another. Along with this, the raw materials used are required to be of even higher purity and quality.

Lithium carbonate has recently attracted attention as a raw material for single crystals or thin films such as lithium tantalate and lithium niobate, which are components of surface acoustic wave filters, temperature and humidity sensors, and optoelectronic devices. High purity and high quality are desired.

It is important that the lithium carbonate used for this purpose has a low content of metal impurities such as alkali metals, alkaline earth metals, and transition metals, anionic impurities such as chlorine and sulfuric acid radicals, and has a low content of components lost on heating. . In other words, when producing a single crystal of lithium tantalate, lithium niobate, etc. using lithium carbonate and tantalum pentoxide or niobium pentoxide as raw materials using a platinum crucible using the Chickralski method, the weight of lithium carbonate and other components is The ratio needs to be strictly controlled to a specific ratio known as congruent mel) & Il composition, as deviations from this ratio will result in variations in the properties of the resulting product and a decrease in yield due to the occurrence of crystal cranks. Lithium carbonate with less components that lose weight on heating is desired.

However, conventional lithium carbonate contains 0.5% to several% of components other than lithium carbonate, which disappear and lose weight at temperatures above the melting point of lithium carbonate, for example, in the temperature range of 300 to 550°C, and the amount of these components varies between raw material lofts. , which varies depending on the part of the raw material used, causing errors in the amount of lithium carbonate charged, making it difficult to control the aforementioned composition ratio, and causing a decrease in performance yield.

<Prior art and problems to be solved by the invention> Crude lithium compounds, specifically recrystallization, reprecipitation,
Diaphragm electrolysis methods and the like are known.

As an example of the recrystallization method, a method is known in which an aqueous lithium carbonate solution is evaporated to precipitate lithium carbonate and impurities are removed. An example of the reprecipitation method is a method in which an aqueous lithium carbonate solution and milk of lime are reacted to form lithium hydroxide, impurities are removed as carbonate, and then reacted with carbon dioxide to precipitate lithium carbonate (US Pat. No. 4,207,297).
It has been known. Further, as an example of the diaphragm electrolysis method, a method is known in which a lithium sulfate aqueous solution is electrolyzed through a diaphragm to obtain high purity lithium hydroxide, which is then reacted with carbon dioxide to precipitate lithium carbonate (Japanese Patent Laid-Open No. 43174/1983).

However, all of these methods are related to methods for removing metal impurities and anion impurities in lithium carbonate, and up to now, single crystals of lithium niobate, lithium tantalate, etc. have been produced using the Chisri Ralski method described above. However, considering the composition of the reaction product, no effective proposals have been made regarding a method for producing high-purity lithium carbonate that has few components that lose heat and have a negative effect on performance and yield. The reality is that lithium carbonate, which has been refined using expensive equipment and costs, is unavoidably burned at a temperature of 500 to 600° C. while recontaminating the purified lithium carbonate to remove components lost by heating.

For this reason, it is desired to provide high-purity lithium carbonate with a low content of components that lose weight on heating, at least 0.1% by weight or less.

Means and operation for solving the above-mentioned problems> As a result of intensive studies by the present inventors in order to solve the above-mentioned problems and develop an economical method for producing high-purity lithium carbonate with a small amount of heat loss components, It was found that the heating loss component is generated during the crystallization operation of precipitating lithium carbonate crystals from an aqueous lithium compound solution, and its main component is water. Furthermore, the components lost on heating cannot be reduced by prolonging the crystallization time, strengthening stirring in the crystallization tank, heating or reducing pressure during crystallization, etc., but lithium carbonate can be reduced by recrystallization and reprecipitation of the lithium compound aqueous solution. When precipitating the crystals, (1) it was found that by heating the aqueous solution to a temperature of 90° C. or higher and performing crystallization, it was possible to reduce the component lost on heating in lithium carbonate to 0.1% by weight or less. (Hereinafter referred to as the first method) (1) Furthermore, before crystallization, 5 to 100 parts by weight of lithium carbonate powder is added to the lithium compound aqueous solution per 10011 parts of lithium carbonate newly produced by crystallization, and the aqueous solution The heating loss component in lithium carbonate is reduced to 0.1ftlt% by heating the liquid temperature to 70°C or higher and crystallizing it.
In particular, we have found that the weight can be reduced to 0.02% by weight or less. (Hereinafter referred to as the second method) It is conventionally known that by this method, high purity lithium carbonate with a small amount of components lost on heating can be obtained by simple means such as crystallization at a high liquid temperature and addition of lithium carbonate. This was not the case. The lithium carbonate powder obtained by crystallization does not require any treatment such as calcination, and only simple drying is required, and the yield of lithium carbonate during crystallization is significantly improved.

The configurations of these methods will be explained below.

Examples of aqueous solutions containing lithium compounds include crude lithium compounds, generally aqueous lithium carbonate solutions made from crude lithium carbonate, or aqueous solutions containing lithium compounds solubilized with well-known inorganic acids, milk of lime, etc. A purified lithium compound aqueous solution treated by a well-known recrystallization method, reprecipitation method, ion exchange method, etc. is used.

The type of lithium compound in the aqueous solution containing the lithium compound is not limited to any type as long as it changes to lithium carbonate and precipitates crystals through the reaction during crystallization, but lithium hydroxide, lithium carbonate below the saturated concentration, Lithium hydrogen carbonate and the like are preferred.

In the case of lithium hydroxide, in the first method, 5 to 1011% by weight is placed in a pressure-resistant crystallization tank equipped with a stirrer, a heating jacket, a carbon dioxide inlet, and a lithium carbonate slurry outlet.
Add a concentrated aqueous solution of lithium hydroxide, heat the aqueous solution until its temperature reaches 90°C or higher, and then crystallize carbon dioxide equivalent to more than half of the lithium hydroxide while maintaining the liquid temperature at 90°C or higher. Continuously blow into the tank to convert lithium hydroxide into lithium carbonate and precipitate it as crystals. Lithium carbonate was separated and recovered from the obtained lithium carbonate slurry by a known separation means, and after washing, it was dried by a well-known drying method.
Dry at 120°C. The components lost on heating in the resulting lithium carbonate vary depending on the temperature of the lithium hydroxide aqueous solution at the time of crystallization, and the higher the liquid temperature, the smaller the amount, i.e., the liquid temperature is 90°C.
In the above, the liquid temperature is 120% with a heating loss component of 0.1% by weight or less.
℃ or higher, high purity lithium carbonate with a heating loss component of 0.05% by weight or less can be obtained.

In addition, in the crystallization tank, the lithium carbonate powder that has precipitated as crystals is dispersed by means such as stirring so that it is sufficiently suspended and dispersed without being deposited at the bottom of the tank.If the dispersion is insufficient and the lithium carbonate powder is deposited, The amount of heat loss components in the obtained lithium carbonate increases.

Carbon dioxide is supplied continuously so that the crystallization time is at least 1 hour, preferably 3 hours or more. When carbon dioxide is rapidly supplied to precipitate lithium carbonate crystals so that the crystallization is completed within one hour, the amount of loss on heating of the resulting lithium carbonate powder increases.

In the case of lithium hydroxide, in the second method, when crystals of lithium carbonate are precipitated from a 5 to 10% by weight lithium hydroxide aqueous solution and carbon dioxide using the same crystallization tank, the crystals are precipitated in the aqueous solution prior to the start of crystallization. Lithium carbonate powder is added to the solution, stirred and dispersed, and the temperature of the aqueous solution is heated to 70°C or higher, and carbon dioxide equivalent to one-half or more of the lithium hydroxide in the aqueous solution is blown into the solution to form crystals of lithium carbonate. Let it precipitate.

In this method, compared to the first method, it is possible to obtain lithium carbonate powder with a heating loss component of 0.1% or less at a lower liquid temperature, and at a liquid temperature of 100° C. or higher, a heating loss component of 0.0%.
It is possible to obtain a lithium carbonate powder having extremely low components that lose weight on heating, such as 2IIt amount or less.

In this method as well, stirring and dispersion of the lithium carbonate powder in the crystallization tank and crystallization time are carried out in the same manner as in the first method. ``The lithium carbonate added prior to crystallization may be in the form of powder, but the average particle size is preferably 80 μm or less, more preferably 5011 μm or less. The amount added is 1 liter of lithium carbonate, which is newly precipitated as crystals by crystallization.
0 (5 to 100 parts by weight per 1 part placed, preferably 10 to 100 parts by weight)
50! This is the Ifit section. If it is less than 5 parts by weight, the effect of adding lithium carbonate powder prior to crystallization will be small;
The lithium carbonate powder to be added is lithium carbonate powder crystallized by the first method or commercially available high-purity lithium carbonate at a temperature of 550°C. A lithium carbonate powder calcined for one hour or a lithium carbonate powder separately crystallized by a second method, which has a small amount of heat loss components, is used.

In these two methods, even if the lithium compound in the aqueous solution used for crystallization is lithium carbonate or lithium hydrogen carbonate, the component lost on heating depends on the precipitation behavior of lithium carbonate, so the same effect as in the case of lithium hydroxide can be obtained. .

For example, in the case of a lithium carbonate aqueous solution having a saturated concentration or less, the aqueous solution is placed in a crystallization tank and the water is removed under reduced pressure to bring the lithium carbonate concentration to the saturated concentration or higher. In the first method, the temperature of the aqueous solution is heated to 90° C. or higher in advance to crystallize it. In the second method, prior to crystallization, lithium carbonate powder is added to the aqueous solution and the temperature of the aqueous solution is heated to 70° C. or higher to perform crystallization.

By either method, lithium carbonate powder having a heating loss component of 0.1% by weight or less can be obtained.

In the case of lithium hydrogen carbonate, a lithium hydrogen carbonate aqueous solution with a concentration of 5 to 8% by weight is placed in a crystallization tank and carbon dioxide is desorbed by reducing pressure or nitrogen gas feed to convert it into lithium carbonate and precipitate lithium carbonate crystals. In method 1, the aqueous solution is decomposed under reduced pressure and crystallized while maintaining the temperature of the aqueous solution at 90° C. or higher. In the second method, prior to crystallization, lithium carbonate powder is added to the aqueous solution in the same manner as in the case of lithium hydroxide, and the temperature of the aqueous solution is heated to 70°C or higher to decompose lithium hydrogen carbonate and crystallize lithium carbonate. is precipitated.

By either method, lithium carbonate powder having a heating loss component of 0.1% by weight or less can be obtained.

Effects of the Present Invention> In the present invention, lithium oxide can be obtained by the second method of the above two methods.

■Since the solubility of lithium carbonate in water decreases at high temperatures, the yield of lithium carbonate in the crystal carp operation is greatly improved.

■No special firing equipment is required, there is no lithium carbonate contamination associated with the firing operation, and high-purity lithium carbonate with high product value can be obtained.

Reference Example 1 A pressure-resistant crystallization tank with an internal volume of 301 equipped with a stirrer, a heating steam jacket, a lithium compound aqueous solution feeder, a lithium carbonate powder addition port, a gas injection port, an exhaust port, a lithium carbonate slurry outlet, a pressure gauge, etc. An autoclave was used.

A purified lithium hydroxide aqueous solution with a concentration of 5.2ii mass % was put into a crystallization tank from a 201 aqueous solution feeder and the rotation speed was 60O.
Bring the liquid temperature to 90℃ for about 30 minutes while stirring thoroughly at rpm.
The temperature rose to . While stirring thoroughly and keeping the liquid temperature at 90°C, carbon dioxide gas was continuously supplied into the tank from the gas inlet at a flow rate of 2.21 per minute for 4 hours, causing it to react with lithium hydroxide and crystallizing lithium carbonate. analyzed.

The change in mfft on heating of dry lithium carbonate was measured using a thermobalance, and the proportion of the total amount of loss on heating up to 550° C. was defined as the heating loss component.

The yield of the obtained lithium carbonate powder was 74.4%, the average particle size was 47 μm, and the weight loss component on heating was 0.092%.

Example 1 Using the same crystallization tank as used in Reference Example 1, a purified lithium hydroxide aqueous solution with a concentration of 5.2% by weight was poured into the crystallization tank from the 201 aqueous solution feeder, and the liquid temperature was raised to 80°C while stirring. The temperature rose to . Average particle size 43μ from lithium carbonate powder inlet
m, 1 liter of lithium carbonate powder with heating loss component 0°073%
65g was added and thoroughly stirred to disperse in the aqueous solution.

While maintaining the liquid temperature at 80° C. and stirring sufficiently, carbon dioxide gas was continuously supplied to the tank at a flow rate of 2.21 per minute for 4 hours.

The recovery rate of lithium carbonate powder was 70.2%, and the average particle size was 5.
The heating loss component of 28ml was 0.052%.

Reference Example 2, Example 2 Using the same crystallization tank as Reference Example 1, crystallization and recovery were performed in the same manner as Reference Example 1 and Example 1, except that the liquid temperature and the amount of lithium carbonate powder added were changed. .

Reference example 2 120 0 Example 2 1
00 180 Reference example 2 B1.3 4
5 0.049 Example 2 76.7 48
0. OL3 Example 3 Using the same crystallization tank as used in Reference Example 1, a lithium carbonate aqueous solution with a concentration of 1.1% by weight was poured into the crystallization tank from the 2 (l) aqueous solution feeder, and the same crystallization tank as that used in Example 1 was added. 63 g of the same lithium carbonate powder was added, and the liquid temperature was raised to 90° C. while stirring thoroughly.

While thoroughly stirring and maintaining the liquid temperature at 90° C., the mixture was evacuated from the exhaust port and water was evaporated over 4 hours until the liquid amount reached approximately 1071 kg, thereby precipitating lithium carbonate.

The obtained lithium carbonate slurry was separated and dried in the same manner as in Reference Example 1, except that it was washed with 80° C. hot water.

Yield of lithium carbonate powder is 67.7%, average particle size is 66
μm, and the heating loss component was 0.071%.

Example 4 The same crystallization tank as used in Reference Example 1 was used. Add 89g of the same lithium carbonate powder, stir thoroughly, and bring the liquid temperature to 90%.
The temperature was raised to ℃.

While maintaining the liquid temperature at 90° C., argon gas was introduced from the gas inlet at a rate of 0.81 per minute, and lithium carbonate was crystallized while expelling carbon dioxide gas produced by decomposition of lithium hydrogen carbonate. Crystallization time was approximately 2.5 hours.

The obtained lithium carbonate slurry was separated, washed and dried in the same manner as in Reference Example 1.

Lithium carbonate powder with an average particle size of 51 μm and a heating loss component of 0.058% was obtained in a yield of 77.0%.

Comparative Examples 1 to 4 Lithium carbonate was prepared in the same manner as in the example except that the same crystallization tank as used in the reference example was used, lithium carbonate powder was not added, and the temperature of the lithium compound aqueous solution was set as follows. Crystallization was performed.

Comparative Example 4 14.0% Formic Acid 30 4 Lithium Aqueous Solution The yield, average particle size, and heating loss components of the obtained lithium carbonate powder were as follows.

Claims (4)

[Claims] (1) When obtaining lithium carbonate powder by crystallization from an aqueous solution containing a lithium compound, lithium carbonate 10 is produced in advance by crystallizing lithium carbonate powder in the aqueous solution.
A method for producing lithium carbonate powder, which comprises adding 5 to 100 parts by weight per 0 parts by weight, and crystallizing the aqueous solution by heating it to 70°C or higher. (2) A method for producing lithium carbonate powder according to claim 1, characterized in that lithium carbonate powder is precipitated while blowing carbon dioxide into a lithium hydroxide aqueous solution containing a lithium compound. (3) A method for producing lithium carbonate powder according to claim 1, characterized in that lithium carbonate powder is precipitated by concentrating a lithium carbonate aqueous solution containing a lithium compound and having a saturated concentration or less. (4) Production of lithium carbonate powder according to claim 1, characterized in that lithium carbonate powder is precipitated by desorbing carbon dioxide from an aqueous lithium hydrogen carbonate solution containing a lithium compound. Method