阅读说明：本技术 一种碳酸锂生产系统及工艺 (Lithium carbonate production system and process ) 是由 张成勇 刘发贵 邢红 杨建育 马成功 张成胜 张荣子 保积龙 马汉晓 王文海 谢 于 2020-12-30 设计创作，主要内容包括：本发明公开一种碳酸锂生产工艺,包括：氯化锂溶液、碳酸钠溶液进入结晶器中初步结晶,生成碳酸锂晶核,得到浓度2％～6％的结晶料浆；所述结晶料浆进入浓密机中增稠,所述碳酸锂晶核继续结晶,得到浓度8％～20％的增稠料浆；所述增稠料浆经固液分离得到滤饼；所述滤饼经洗涤、干燥得到碳酸锂。本发明提供的碳酸锂生产工艺中,将碳酸锂的结晶过程分为两段,先在结晶器中生产碳酸锂晶核,碳酸锂晶核再在浓密机中进一步结晶长大,从而放缓结晶速度,便于控制结晶颗粒,减少杂质夹带,而且结晶器和浓密机可以连续进料和连续出料,产品质量、粒度稳定,所获碳酸锂产品中碳酸锂主含量可以达到99.0～99.40％。(The invention discloses a lithium carbonate production process, which comprises the following steps: the lithium chloride solution and the sodium carbonate solution enter a crystallizer for primary crystallization to generate lithium carbonate crystal nucleus to obtain crystallization slurry with the concentration of 2-6%; the crystallized slurry enters a thickener for thickening, and the lithium carbonate crystal nucleus is continuously crystallized to obtain thickened slurry with the concentration of 8-20%; carrying out solid-liquid separation on the thickened slurry to obtain a filter cake; and washing and drying the filter cake to obtain the lithium carbonate. In the lithium carbonate production process provided by the invention, the crystallization process of lithium carbonate is divided into two sections, lithium carbonate crystal nuclei are produced in the crystallizer firstly, and then are further crystallized and grown up in the thickener, so that the crystallization speed is slowed down, the crystallization particles are convenient to control, the impurity entrainment is reduced, the crystallizer and the thickener can continuously feed and continuously discharge materials, the product quality and the granularity are stable, and the main content of lithium carbonate in the obtained lithium carbonate product can reach 99.0-99.40%.)

1. A lithium carbonate production process, wherein the lithium carbonate production process comprises:

step S1, allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer (1) for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystal slurry with the concentration of 2% -6%, wherein the concentration of the lithium chloride solution is 15-30 g/l, the concentration of the sodium carbonate solution is 220-310 g/l, and the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1: 1.4-1.6;

step S2, thickening the crystallized slurry in a thickener (2), and continuously crystallizing the lithium carbonate crystal nucleus to obtain thickened slurry with the concentration of 8-20%;

step S3, carrying out solid-liquid separation on the thickened slurry to obtain a filter cake;

and step S4, washing and drying the filter cake to obtain lithium carbonate.

2. The lithium carbonate production process according to claim 1, wherein in step S1, the temperature of the crystallizer (1) is maintained at 75-90 ℃.

3. The lithium carbonate production process according to claim 2, wherein in step S1, while obtaining the crystallization slurry, a crystallizer overflow liquid is generated at the top of the crystallizer (1), and the crystallizer overflow liquid is returned to the crystallizer (1) after passing through the heat exchanger (3) so as to maintain the temperature of the crystallizer (1).

4. The lithium carbonate production process according to claim 1, wherein in step S1, stirring is performed at the time of primary crystallization, and the stirring is performed by upward stirring by an inclined blade.

5. The lithium carbonate production process according to claim 1, wherein in the step S2, thickened slurry is obtained, and simultaneously, thickener overflow liquid is generated at the top of the thickener (2) and enters a recovery device (4).

6. A lithium carbonate production system comprises a crystallizer (1), a thickener (2), a solid-liquid separation device (5), a washing device (6) and a drying device (7) which are connected in sequence;

the method comprises the following steps of (1) allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer (1) for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystallization slurry with the concentration of 2% -6%, allowing the crystallization slurry to enter a thickener (2), and continuously crystallizing the lithium carbonate crystal nuclei to obtain thickening slurry with the concentration of 8% -20%; the thickened slurry is processed by a solid-liquid separation device (5) to obtain a filter cake; the filter cake passes through the washing device (6) and the drying device (7) to obtain lithium carbonate;

crystallizer (1) includes outside-in suit's casing (11), shelters from a section of thick bamboo (12), a center section of thick bamboo (13) in proper order, form in a center section of thick bamboo (13) and supply lithium chloride solution with the mixing area (10) of mixed liquid is formed in the mixing of sodium carbonate solution, a center section of thick bamboo (13) with shelter from forming between a section of thick bamboo (12) and supply mixed liquid carries out the crystallization zone (20) that the crystallization formed the lithium carbonate crystal nucleus, shelter from a section of thick bamboo (12) with form clarification area (30) between casing (11).

7. The lithium carbonate production system according to claim 6, wherein the lithium carbonate production system further comprises a heat exchanger (3) connected with the crystallizer (1), a crystallizer overflow liquid is generated at the top of the crystallizer (1), and the crystallizer overflow liquid is returned to the crystallizer (1) after passing through the heat exchanger (3) so as to maintain the temperature of the crystallizer (1).

8. The lithium carbonate production system according to claim 6, wherein the lithium carbonate production system further comprises a recovery device (4) connected with the thickener (2), wherein a thickener overflow liquid is generated at the top of the thickener (2), and the thickener overflow liquid enters the recovery device (4) for recycling.

9. The lithium carbonate production system according to claim 6, wherein a stirrer (14) is provided in the crystallizer (1), and blades of the stirrer (14) are arranged obliquely.

Technical Field

The invention relates to the technical field of lithium carbonate production, in particular to a process for producing lithium carbonate by continuous reaction crystallization.

Background

In the technology for producing lithium carbonate by adsorbing and extracting lithium from brine with high magnesium-lithium ratio, old brine discharged in the production of potash fertilizer is subjected to the processes of lithium adsorption, lithium washing and desorption to obtain a high-concentration lithium chloride solution, and then the high-concentration lithium chloride solution and a soda solution are stirred to react and crystallize to generate lithium carbonate.

At present, in a common lithium carbonate reaction crystallization stage, a reaction kettle is adopted to obtain crystallization slurry, and the crystallization slurry is separated, washed, dried and packaged to obtain a lithium carbonate finished product. However, the reaction kettle is a batch reactor, the efficiency is low, a plurality of reaction kettle devices need to be arranged in large-scale production, each reaction kettle can cause unstable product quality and appearance due to problems of internal material distribution and crystal size control, particularly, the reaction and crystallization processes are completed in the reaction kettle at one time, and excessive agglomeration of crystal nuclei easily causes impurity entrainment, thereby affecting the overall quality of the lithium carbonate.

Disclosure of Invention

The invention aims to provide a lithium carbonate production system and a lithium carbonate production process, which are used for solving the problem that the product quality and the appearance are unstable due to different internal material distribution and crystal size control of a reaction kettle.

In order to achieve the above purpose, the invention provides the following technical scheme: a lithium carbonate production process, comprising:

step S1, allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystal slurry with the concentration of 2% -6%, wherein the concentration of the lithium chloride solution is 15-30 g/l, the concentration of the sodium carbonate solution is 220-310 g/l, and the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1: 1.4-1.6;

step S2, thickening the crystallized slurry in a thickener, and continuously crystallizing the lithium carbonate crystal nucleus to obtain thickened slurry with the concentration of 8-20%;

step S3, carrying out solid-liquid separation on the thickened slurry to obtain a filter cake;

and step S4, washing and drying the filter cake to obtain lithium carbonate.

According to one embodiment of the present invention, in step S1, the temperature of the crystallizer is maintained at 75-90 ℃.

According to an embodiment of the present invention, in step S1, while obtaining the crystallization slurry, a crystallizer overflow liquid is generated at the top of the crystallizer, and the crystallizer overflow liquid is returned to the crystallizer after passing through a heat exchanger to maintain the temperature of the crystallizer.

According to one embodiment of the present invention, in step S1, stirring is performed at the time of primary crystallization, and the stirring is performed by upward stirring by inclined blades.

According to one embodiment of the invention, in step S2, thickened slurry is obtained, and simultaneously, thickener overflow liquid is generated at the top of the thickener, and the thickener overflow liquid enters a recovery device.

The invention also provides a lithium carbonate production system, which comprises a crystallizer, a thickener, a solid-liquid separation device, a washing device and a drying device which are sequentially connected;

the method comprises the following steps of (1) allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystallization slurry with the concentration of 2% -6%, allowing the crystallization slurry to enter a thickener, and continuously crystallizing the lithium carbonate crystal nuclei to obtain thickening slurry with the concentration of 8% -20%; the thickened slurry is processed by a solid-liquid separation device to obtain a filter cake; the filter cake passes through the washing device and the drying device to obtain lithium carbonate;

the crystallizer comprises a shell, a shielding cylinder and a center cylinder which are sequentially sleeved from outside to inside, wherein a mixing area for mixing the lithium chloride solution and the sodium carbonate solution to form a mixed solution is formed in the center cylinder, a crystallization area for crystallizing the mixed solution to form lithium carbonate crystal nuclei is formed between the center cylinder and the shielding cylinder, and a clarification area is formed between the shielding cylinder and the shell.

According to an embodiment of the present invention, the lithium carbonate production system further comprises a heat exchanger connected to the crystallizer, wherein crystallizer overflow liquid is generated at the top of the crystallizer, and the crystallizer overflow liquid is returned to the crystallizer after passing through the heat exchanger so as to maintain the temperature of the crystallizer.

According to one embodiment of the invention, the lithium carbonate production system further comprises a recovery device connected with the thickener, wherein the top of the thickener generates thickener overflow liquid, and the thickener overflow liquid enters the recovery device for recycling.

According to one embodiment of the invention, an agitator is arranged in the crystallizer, and blades of the agitator are obliquely arranged.

Compared with the prior art, the lithium carbonate production system and the lithium carbonate production process provided by the invention have the following advantages:

in the lithium carbonate production process provided by the application, the crystallization process of lithium carbonate is divided into two sections, a lithium carbonate crystal nucleus is firstly produced in the crystallizer and then is further crystallized and grown up in the thickener, so that the crystallization speed is slowed down, the crystallization particles are convenient to control, the impurity entrainment is reduced, the crystallizer and the thickener can continuously feed and continuously discharge materials, the product quality and the granularity are stable, and the main content of lithium carbonate in the obtained lithium carbonate product can reach 99.0-99.40%.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. In the drawings:

fig. 1 is a schematic structural diagram of a lithium carbonate production system according to a preferred embodiment of the present invention;

fig. 2 is a flow chart showing steps of a lithium carbonate production process based on the lithium carbonate production system shown in fig. 1.

Reference numerals:

1 crystallizer, 11 shells, 12 shielding cylinders, 13 central cylinders, 14 stirrers, 10 mixing zones, 20 crystallization zones, 30 clarification zones, 2 thickeners, 21 rake racks, 3 heat exchangers, 4 recovery devices, 5 solid-liquid separation devices, 6 washing devices and 7 drying devices.

Detailed Description

The present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific examples described in the following embodiments of the present invention are merely illustrative of specific embodiments of the present invention and do not limit the scope of the invention.

The invention is further described with reference to the following figures and detailed description of embodiments.

As shown in fig. 1 and fig. 2, wherein fig. 1 is a schematic structural diagram of a lithium carbonate production system according to a preferred embodiment of the present invention; fig. 2 is a flow chart showing steps of a lithium carbonate production process based on the lithium carbonate production system shown in fig. 1.

This embodiment is a lithium carbonate production process, where the lithium carbonate production process includes:

step S1, allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer 1 for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystal slurry with the concentration of 2% -6%, wherein the concentration of the lithium chloride solution is 15-30 g/l, the concentration of the sodium carbonate solution is 220-310 g/l, and the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1: 1.4-1.6;

step S2, thickening the crystallized slurry in a thickener 2, and continuously crystallizing the lithium carbonate crystal nucleus to obtain thickened slurry with the concentration of 8-20%;

step S3, carrying out solid-liquid separation on the thickened slurry to obtain a filter cake;

and step S4, washing and drying the filter cake to obtain lithium carbonate.

In the lithium carbonate production process provided by the application, the crystallization process of lithium carbonate is divided into two sections, a lithium carbonate crystal nucleus is firstly produced in the crystallizer and then is further crystallized and grown up in the thickener, so that the crystallization speed is slowed down, the crystallization particles are convenient to control, the impurity entrainment is reduced, the crystallizer and the thickener can continuously feed and continuously discharge materials, the product quality and the granularity are stable, and the main content of lithium carbonate in the obtained lithium carbonate product can reach 99.0-99.40%.

The steps are explained in detail below.

In step S1, a lithium chloride solution and a sodium carbonate solution enter the crystallizer 1 for primary crystallization to generate a lithium carbonate crystal nucleus, and a crystallization slurry with a concentration of 2% to 6% and a crystallizer overflow liquid are obtained, the crystallization slurry is discharged from the bottom of the crystallizer 1, and the crystallizer overflow liquid is discharged from the top of the crystallizer 1.

The crystallizer 1 comprises a shell 11, a shielding cylinder 12 and a central cylinder 13 which are sequentially sleeved from outside to inside, wherein at least two of the shell 11, the shielding cylinder 12 and the central cylinder 13 are coaxially arranged. The coaxial arrangement makes the central axis of each barrel unified, and the effect is best, also is convenient for install.

In the transverse direction, three regions are formed among the housing 11, the shielding cylinder 12, and the central cylinder 13: a mixing area 10 for mixing the lithium chloride solution and the sodium carbonate solution to form a mixed solution is formed in the central cylinder 13, a crystallization area 20 for crystallizing the mixed solution to form lithium carbonate crystal nuclei is formed between the central cylinder 13 and the shielding cylinder 12, and a clarification area 30 is formed between the shielding cylinder 12 and the shell 11.

The lithium chloride solution and the sodium carbonate solution are directly added into the mixing zone 10 in proportion, and are fully mixed under the stirring action and then enter the crystallization zone 20.

The stirring is carried out by raising and stirring through the inclined blades. The upward form can form counter flow, which is beneficial to the mixing of two raw materials.

Specifically, a stirrer 14 is arranged in the crystallizer 1, the stirring speed is 55-65 rpm, namely 55-65 rpm, blades of the stirrer 14 are arranged in an inclined manner, the inclination angle of the stirring blades is calculated by considering the viscosity, specific gravity, solid content and the like of the solution, and then the rotation sequence (clockwise and anticlockwise) is selected to realize lifting or pressing.

In the upper part of the crystallization zone 20, lithium ions in the lithium chloride solution and carbonate ions in the sodium carbonate solution react first to combine to form lithium carbonate crystal nuclei, and in the lower part of the crystallization zone 20, lithium carbonate crystal nuclei collide with each other to crystallize and form crystals with smaller particles.

The clarification zone 30 is used to clarify the crystallizer overflow to reduce losses. Meanwhile, the overflow liquid of the crystallizer returns to the crystallizer 1 after passing through a heat exchanger 3 so as to maintain the temperature of the crystallizer 1. The temperature of the crystallizer 1 is kept at 75-90 ℃, namely the temperature of the primary crystallization is 75-90 ℃.

The heat exchanger 3 exchanges heat through steam, and the steam quantity of the heat exchanger 3 is interlocked according to the temperature change of the crystallizer 1, so that the automatic control and adjustment are convenient.

In step S2, the crystallized slurry enters the thickener 2 to be thickened, so as to obtain thickened slurry and thickener overflow liquid, the thickened slurry is discharged from the bottom of the thickener 2, and the thickener overflow liquid is discharged from the top of the thickener 2, and enters the recovery device 4 connected to the thickener 2 to be recycled. The concentration of lithium ions in the overflow liquid of the thickener is 1.0-3.0 g/l, and the concentration of sodium ions is 74-86 g/l.

The thickener 2 is provided with a rake rack 21, and the rotation speed of the rake rack 21 is 0.8-1 rpm, namely 0.8-1 rpm.

In step S3, the solid-liquid separation is performed by the solid-liquid separation device 5, and the solid-liquid separation device 5 is not limited to a centrifuge, a plate-and-frame filter press, or the like.

In step S4, washing and drying are respectively completed by the washing device 6 and the drying device 7, where the washing device 6 may be implemented by a general washing apparatus, and the drying device 7 may be implemented by a general drying apparatus.

As shown in fig. 1, the invention further provides a lithium carbonate production system, which comprises a crystallizer 1, a thickener 2, a solid-liquid separation device 5, a washing device 6 and a drying device 7, which are connected in sequence;

the method comprises the following steps of (1) allowing a lithium chloride solution and a sodium carbonate solution to enter a crystallizer 1 for primary crystallization to generate lithium carbonate crystal nuclei to obtain crystallization slurry with the concentration of 2% -6%, allowing the crystallization slurry to enter a thickener 2, and continuously crystallizing the lithium carbonate crystal nuclei to obtain thickening slurry with the concentration of 8% -20%; the thickened slurry is processed by a solid-liquid separation device 5 to obtain a filter cake; and the filter cake passes through the washing device 6 and the drying device 7 to obtain lithium carbonate.

The lithium carbonate production system still include with recovery unit 4 that the thickener is connected, the top of thickener 2 produces thickener overflow liquid, thickener overflow liquid gets into recovery unit 4 is with recycle.

The structure and function of each device are described in detail in the lithium carbonate production process, and are not described in detail herein.

Detailed description of the preferred embodiment 1

Lithium chloride solution and sodium carbonate solution enter the crystallizer 1 to obtain crystal slurry with the concentration of 2%, wherein the concentration of the lithium chloride solution is 18g/l, the concentration of the sodium carbonate solution is 220g/l, the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1:1.4, the reaction temperature of the crystallizer 1 is 85 ℃, and the stirring speed is 55 rpm; the crystallized slurry enters the thickener 2 for thickening to obtain thickened slurry with the concentration of 8%, wherein the speed of a rake frame 21 of the thickener 2 is 0.8 rpm; carrying out solid-liquid separation on the thickened slurry to obtain a filter cake; and washing and drying the filter cake to obtain the lithium carbonate. The main content of lithium carbonate in the obtained lithium carbonate product can reach 99.30 percent.

Specific example 2

Lithium chloride solution and sodium carbonate solution enter the crystallizer 1 to obtain crystallization slurry with the concentration of 6%, wherein the concentration of the lithium chloride solution is 24g/l, the concentration of the sodium carbonate solution is 290g/l, the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1:1.6, the reaction temperature of the crystallizer 1 is 76 ℃, and the stirring speed is 60 rpm; the crystallized slurry enters the thickener 2 for thickening to obtain thickened slurry with the concentration of 20%, wherein the speed of a rake frame 21 of the thickener 2 is 1 rpm; carrying out solid-liquid separation on the thickened slurry to obtain a filter cake; and washing and drying the filter cake to obtain the lithium carbonate. The main content of lithium carbonate in the obtained lithium carbonate product can reach 99.28 percent.

Specific example 3

Lithium chloride solution and sodium carbonate solution enter the crystallizer 1 to obtain crystallization slurry with the concentration of 3%, wherein the concentration of the lithium chloride solution is 30g/l, the concentration of the sodium carbonate solution is 220g/l, the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1:1.5, the reaction temperature of the crystallizer 1 is 75 ℃, and the stirring speed is 65 rpm; the crystallized slurry enters the thickener 2 for thickening to obtain thickened slurry with the concentration of 10%, wherein the speed of a rake frame 21 of the thickener 2 is 1 rpm; carrying out solid-liquid separation on the thickened slurry to obtain a filter cake; and washing and drying the filter cake to obtain the lithium carbonate. The main content of lithium carbonate in the obtained lithium carbonate product can reach 99.0%.

Specific example 4

Lithium chloride solution and sodium carbonate solution enter the crystallizer 1 to obtain crystallization slurry with the concentration of 4%, wherein the concentration of the lithium chloride solution is 15g/l, the concentration of the sodium carbonate solution is 310g/l, the volume ratio of the lithium chloride solution to the sodium carbonate solution is 1:1.4, the reaction temperature of the crystallizer 1 is 90 ℃, and the stirring speed is 62 rpm; the crystallized slurry enters the thickener 2 for thickening to obtain thickened slurry with the concentration of 15%, wherein the speed of a rake frame 21 of the thickener 2 is 0.9 rpm; carrying out solid-liquid separation on the thickened slurry to obtain a filter cake; and washing and drying the filter cake to obtain the lithium carbonate. The main content of lithium carbonate in the obtained lithium carbonate product can reach 99.40%.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim.