A production system for the direct production of lithium carbonate and co-production of sodium chloride from brine

Abstract

This utility model relates to the field of lithium carbonate preparation technology from brine. To address the problems of complex processes, low resource recovery rates, and high production costs associated with existing direct brine lithium carbonate preparation processes, this utility model provides a production system for the direct preparation of lithium carbonate and co-production of sodium chloride from brine. The system includes a brine buffer unit, a first purification unit, a boron removal unit, a second purification unit, a first neutralization unit, a sodium precipitation unit, a lithium precipitation unit, and an alkali preparation unit. The brine buffer unit, the first purification unit, the boron removal unit, the second purification unit, the first neutralization unit, the sodium precipitation unit, and the lithium precipitation unit are connected sequentially. The alkali preparation unit is connected to the feed end of the lithium precipitation unit. This utility model enables the direct preparation of lithium carbonate and co-production of high-purity sodium chloride from brine, reducing the complex impurity removal and washing processes while fully utilizing the chlorine resources in the brine.

Description

Technical Field

[0001] This utility model relates to the field of brine preparation of lithium carbonate technology, and more specifically, to a production system for the direct preparation of lithium carbonate and co-production of sodium chloride from brine. Background Technology

[0002] Salt lake brine is a highly mineralized natural liquid mineral and an important source of lithium resources. It contains a large number of impurities, such as metallic elements like calcium, magnesium, and potassium, as well as natural sodium chloride, thus requiring a complex impurity removal process. In the impurity removal stage, chemical precipitation is usually used, which involves adding a specific precipitant to cause calcium ions to form insoluble compounds that precipitate and are thus separated from the brine. For example, the lime milk-soda ash method involves adding lime milk (Ca(OH)2) and soda ash (Na2CO3) to the brine. Calcium ions combine with carbonate ions to form calcium carbonate (CaCO3) precipitate. However, this precipitation process introduces new impurities, such as sodium ions, which is not conducive to the subsequent production of lithium carbonate, cannot fully utilize the resources in the brine, and is also inconvenient for wastewater treatment and discharge.

[0003] Based on the above description, there is an urgent need for a production system that can directly produce lithium carbonate from brine to improve resource utilization and reduce production costs. Utility Model Content

[0004] The purpose of this invention is to provide a production system for the direct production of lithium carbonate and sodium chloride from brine, aiming to solve the technical problems of complex processes, low resource recovery rates, and high production costs in the existing direct production of lithium carbonate from brine.

[0005] The embodiments of this utility model are achieved through the following technical solutions:

[0006] A production system for directly producing lithium carbonate and sodium chloride from brine includes a brine buffer unit, a first purification unit, a boron removal unit, a second purification unit, a first neutralization unit, a sodium precipitation unit, a lithium precipitation unit, and an alkali preparation unit; the brine buffer unit, the first purification unit, the boron removal unit, the second purification unit, the first neutralization unit, the sodium precipitation unit, and the lithium precipitation unit are connected in sequence; the alkali preparation unit is connected to the feed end of the lithium precipitation unit.

[0007] Preferably, the first purification unit includes a first mixing tank, a first reaction vessel, and a first filtration mechanism; the brine buffer unit and the first mixing tank are both connected to the feed end of the first reaction vessel; the discharge end of the first reaction vessel is connected to the feed end of the first filtration mechanism; and the discharge end of the first filtration mechanism is connected to the feed end of the boron removal unit.

[0008] Preferably, the second purification unit includes a second mixing tank, a second reaction vessel, and a second filtration mechanism; the discharge end of the boron removal unit and the second mixing tank are both connected to the feed end of the second reaction vessel; the discharge end of the second reaction vessel is connected to the inlet end of the second filtration mechanism; and the outlet end of the second filtration mechanism is connected to the first neutralization unit.

[0009] Preferably, the sodium precipitation unit includes a triple-effect evaporator, a concentrate buffer tank, and a cooling sodium precipitation centrifuge; the first neutralization unit is connected to the feed end of the triple-effect evaporator; the discharge end of the triple-effect evaporator is connected to the concentrate buffer tank; and the concentrate buffer tank is connected to the cooling sodium precipitation centrifuge.

[0010] Preferably, the liquid discharge end of the cooling sodium precipitation centrifuge is connected to the potassium precipitation unit; the slag discharge end of the cooling sodium precipitation centrifuge is connected to the first drying kiln.

[0011] Preferably, the lithium precipitation unit includes a lithium precipitation kettle, a lithium precipitation centrifuge, and a stirring and washing mechanism; the discharge end of the potassium precipitation unit is connected to the feed end of the lithium precipitation kettle; the discharge end of the lithium precipitation kettle is connected to the lithium precipitation centrifuge; the lithium precipitation centrifuge is connected to the feed end of the stirring and washing mechanism; and the alkali preparation unit is connected to the feed unit of the lithium precipitation kettle.

[0012] Preferably, the drain end of the agitation and washing mechanism is connected to the alkali preparation unit.

[0013] Preferably, the discharge end of the lithium-ion centrifuge is connected to a second neutralization unit; the second neutralization unit is sequentially connected to an evaporation unit and a centrifugation unit.

[0014] Preferably, the liquid discharge end of the centrifuge unit is connected to the boron removal unit; the slag discharge end of the centrifuge unit is connected to the second drying kiln.

[0015] Preferably, the slag discharge end of the potassium unit is connected to the first drying kiln.

[0016] The technical solution of this utility model embodiment has at least the following advantages and beneficial effects:

[0017] This invention removes various impurity metal ions from brine through multiple purification processes. It further removes boron from the brine through a boron removal unit, and then performs sodium precipitation and lithium precipitation after pH adjustment. Finally, it produces battery-grade lithium carbonate and also co-produces sodium chloride, thus realizing the extraction of lithium resources and the effective recovery of chlorine resources. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system connection of this utility model;

[0019] Figure 2for Figure 1 First partial schematic diagram;

[0020] Figure 3 for Figure 1 The second part of the diagram.

[0021] Icons: 1-Brine buffer unit, 2-First purification unit, 3-Boron removal unit, 4-Second purification unit, 5-First neutralization unit, 6-Sodium precipitation unit, 7-Lithium precipitation unit, 8-Alkali preparation unit, 9-Potassium precipitation unit, 10-Evaporation unit, 11-Centrifugation unit, 12-First drying kiln, 13-Second drying kiln, 14-Second neutralization unit. Detailed Implementation

[0022] The specific implementation method is described below with reference to the accompanying drawings.

[0023] Example 1

[0024] Please see Figures 1 to 3 This utility model provides the following technical solution: a production system for directly preparing lithium carbonate and co-producing sodium chloride from brine, which is suitable for situations where lithium carbonate is directly prepared from brine and sodium chloride is co-produced, and chlorine resources are recycled.

[0025] Specifically, such as Figures 1 to 3 As shown, a production system for directly producing lithium carbonate and co-producing sodium chloride from brine includes a brine buffer unit 1, a first purification unit 2, a boron removal unit 3, a second purification unit 4, a first neutralization unit 5, a sodium precipitation unit 6, a lithium precipitation unit 7, and an alkali preparation unit 8; the brine buffer unit 1, the first purification unit 2, the boron removal unit 3, the second purification unit 4, the first neutralization unit 5, the sodium precipitation unit 6, and the lithium precipitation unit 7 are connected in sequence; the alkali preparation unit 8 is connected to the feed end of the lithium precipitation unit 7.

[0026] In this embodiment, the brine buffer unit 1 includes multiple brine transfer tanks and brine buffer tanks. The brine transfer tanks and brine buffer tanks are connected. After the brine is transported to the plant, it is pumped from the brine transfer tanks to the brine buffer tanks for buffering. Then, it is further pumped into the first purification unit 2, where sodium sulfide and sodium hydroxide are used for precipitation and impurity removal. The purified liquid from the first purification unit 2 is then passed into the boron removal unit 3, where resin is used. The active groups on the resin exchange with boron ions in the solution, adsorbing the boron ions onto the resin and thus reducing the boron ion concentration in the solution (i.e., B ≤ 0.2%). (g / L); Further, the boron-removed liquid is passed into the second purification unit 4 for precipitation and impurity removal again. Then, the second purified liquid after filtration and purification in the second purification unit 4 is passed into the first neutralization unit 5 for pH adjustment. The filtrate is sent to the sodium precipitation unit 6 for sodium precipitation. Sodium chloride is separated from the filtrate in the form of crystals through the sodium precipitation unit 6, thereby realizing the utilization of heavy chlorine resources in the production system. At the same time, the introduced sodium ions are removed. After sodium precipitation, the separated liquid is further fed into the lithium precipitation unit 7. Soda ash is prepared through the alkali preparation unit 8 and pumped into the lithium precipitation unit 7 for the preparation of lithium carbonate.

[0027] This embodiment removes various impurity metal ions (such as calcium ions and magnesium ions) from the brine through multiple purification processes. Boron removal unit 3 further removes boron from the brine, and after pH adjustment, sodium precipitation and lithium precipitation are carried out. Finally, battery-grade lithium carbonate is produced, and sodium chloride is also produced in co-production, realizing the effective recovery of chlorine resources.

[0028] Specifically, such as Figure 2 As shown, the first purification unit 2 includes a first mixing tank, a first reaction vessel, and a first filtration mechanism; the brine buffer unit 1 and the first mixing tank are both connected to the feed end of the first reaction vessel; the discharge end of the first reaction vessel is connected to the feed end of the first filtration mechanism; and the discharge end of the first filtration mechanism is connected to the feed end of the boron removal unit 3.

[0029] In this embodiment, the first mixing tank is used to prepare sodium sulfate for the reaction. The first reaction vessel is connected to the brine buffer tank. The sodium sulfate and sodium hydroxide solution prepared in the first mixing tank are passed together into the first reaction vessel to react with the brine for impurity removal. The solution then passes through the first filtration mechanism to remove Ca. 2+ Mg 2+ Impurities such as Li2O and Ca2O are present; the first filtration structure includes a multi-stage plate and frame filter press; the specific process parameters of the first reaction vessel are Li2O ≥ 30 g / L and Ca2O ≥ 30 g / L. 2+ ≤3g / L, Mg 2+ ≤0.03g / L, SO4 2- ≤20g / L.

[0030] Specifically, such as Figure 3As shown, the second purification unit 4 includes a second mixing tank, a second reaction vessel, and a second filtration mechanism; the discharge end of the boron removal unit 3 and the second mixing tank are both connected to the feed end of the second reaction vessel; the discharge end of the second reaction vessel is connected to the inlet end of the second filtration mechanism; and the outlet end of the second filtration mechanism is connected to the first neutralization unit 5.

[0031] In this embodiment, the second mixing tank is used to prepare liquid alkali. The prepared liquid alkali is pumped into the second reaction vessel and reacted with the filtrate filtered by the first filtration structure. The filtrate is then further filtered by the second filter to remove impurities such as Ca2+ and Mg2+. The second filtration mechanism includes a multi-stage plate and frame filter press. The process parameters of the second reaction vessel are: Li2O ≥ 30 g / L, Ca2+ ≤ 0.1 g / L, Mg2+ ≤ 0.03 g / L, and pH value: 6-8.

[0032] In this embodiment, in the first neutralization unit 5, hydrochloric acid is used to adjust the pH value to about 7 so that the subsequent sodium precipitation unit 6 can be concentrated by evaporation using a triple-effect evaporator.

[0033] Specifically, such as Figure 3 As shown, the sodium precipitation unit 6 includes a triple-effect evaporator, a concentrate buffer tank, and a cooling sodium precipitation centrifuge; the first neutralization unit 5 is connected to the feed end of the triple-effect evaporator; the discharge end of the triple-effect evaporator is connected to the concentrate buffer tank; the concentrate buffer tank is connected to the cooling sodium precipitation centrifuge. The discharge end of the cooling sodium precipitation centrifuge is connected to the potassium precipitation unit 9; the slag discharge end of the cooling sodium precipitation centrifuge is connected to the first drying kiln 12.

[0034] In this embodiment, the filtrate filtered by the second filtration mechanism is further neutralized and calcium removed by the first neutralization unit 5. After calcium removal, it is further filtered by a plate and frame filter press. The filtered clear liquid is then passed into a triple-effect evaporator for evaporation and concentration, and the concentrated liquid is passed into a concentrated liquid buffer tank for buffering. Subsequently, the concentrated liquid is pumped into a cooling sodium precipitation centrifuge for cooling and sodium precipitation. After centrifugation, sodium chloride crystals are separated and transferred to the first drying kiln 12 for drying to prepare sodium chloride product. The separated clear liquid is further passed into the potassium precipitation unit 9 for further potassium precipitation. The potassium precipitation unit 9 includes a cooling potassium precipitation kettle and a cooling potassium precipitation centrifuge. That is, the mother liquor after sodium precipitation is cooled to a low temperature (such as below 20°C), and potassium chloride precipitates due to the decrease in solubility. The precipitated potassium chloride can be sent to the first drying kiln 12 to dry together with sodium chloride, which can further save production costs.

[0035] Specifically, such as Figure 3 As shown, the lithium precipitation unit 7 includes a lithium precipitation kettle, a lithium precipitation centrifuge, and a stirring and washing mechanism; the discharge end of the potassium precipitation unit 9 is connected to the feed end of the lithium precipitation kettle; the discharge end of the lithium precipitation kettle is connected to the lithium precipitation centrifuge; the lithium precipitation centrifuge is connected to the feed end of the stirring and washing mechanism; and the alkali preparation unit 8 is connected to the feed unit of the lithium precipitation kettle.

[0036] In this embodiment, the alkali preparation unit 8 includes an alkali preparation tank and a plate and frame filter press for filtering the alkali solution in the alkali preparation tank. The discharge end of the stirring and washing mechanism is connected to the alkali preparation unit 8, and the washing liquid after stirring is used as the alkali preparation solvent. The alkali solution is a sodium carbonate solution. The filtered alkali solution is pumped into the lithium precipitation kettle to react with the clear liquid after potassium precipitation and centrifugation. The reaction is carried out by heating and continuous stirring until the reaction is complete. After the reaction is completed, the temperature is kept warm.

[0037] In this embodiment, the process equipment parameters of the lithium precipitation reactor are as follows: EDTA (ethylenediaminetetraacetic acid, chelating agent, selectively chelates magnesium ions) addition amount: 1-1.5 m3 / reactor, feeding rate 1.5±0.2 m3 / h, reaction temperature ≥95℃, reaction time: 20-30 min, stirring frequency: 45-50 Hz, CO32-: 11-15 g / L.

[0038] In this embodiment, the process parameters of the lithium deposition centrifuge are as follows: primary dehydration time: 3-5 min, rinsing time: 5-8 min, secondary dehydration time: 8-10 min, Ca2+ ≤ 0.004 g / L, and moisture content ≤ 10%.

[0039] In this embodiment, the agitation and washing mechanism includes multiple agitation and washing tanks and multiple centrifuges, which repeatedly agitate and wash the precipitated lithium carbonate, and finally send it to the lithium carbonate drying kiln for finished product drying; wherein, the process equipment parameters of the agitation centrifuge are as follows: primary dehydration time: 3-5 min, rinsing time: 5-8 min, secondary dehydration time: 8-10 min, Ca2+≤0.004%, Na+≤0.03%, K+≤0.005%, SO42-≤0.06 g / L, and moisture ≤10%.

[0040] In this embodiment, the process parameters of the two-stage centrifuge are: dehydration time: 8-10 min, moisture content ≤10%; the process parameters of the first-stage washing kettle are: liquid-to-solid ratio: 10:1, stirring frequency: 47-50 Hz, stirring time ≥20 min, temperature ≥95℃; and the process parameters of the second-stage washing kettle are: stirring frequency: 47-50 Hz, stirring time ≥20 min, temperature ≥95℃.

[0041] In this embodiment, after multiple washing processes, the material is further centrifuged in a centrifuge, and then sent to a third drying kiln for drying, finally yielding battery-grade lithium carbonate.

[0042] Specifically, such as Figure 3 As shown, the discharge end of the lithium precipitation centrifuge is connected to the second neutralization unit 14; the second neutralization unit 14 is sequentially connected to the evaporation unit 10 and the centrifugation unit 11. The discharge end of the centrifugation unit 11 is connected to the boron removal unit 3; the slag discharge end of the centrifugation unit 11 is connected to the second drying kiln. The slag discharge end of the potassium precipitation unit is connected to the first drying kiln 12.

[0043] In this embodiment, the mother liquor separated by the lithium precipitation centrifuge is fed into the second neutralization unit 14. Since the pH value of the mother liquor after lithium precipitation is around 12, it is necessary to first use hydrochloric acid to adjust the pH value to 3-4 to remove carbonate ions in the liquid, and then add liquid alkali to restore it to neutral. Finally, it is sent to the evaporation unit 10 to avoid a large amount of lithium carbonate precipitating out during evaporation, which would lead to the loss of Li resources. Solid sodium chloride is obtained by separating through the evaporation unit 10 and the centrifugation unit 11. The evaporation unit 10 adopts an MVR evaporation system, the principle of which is that the crystallizer and the forced circulation evaporator combine to concentrate and separate the raw liquid through evaporation. The centrifugation unit 11 is composed of multiple centrifuges, which can be selected from filter centrifuges, sedimentation centrifuges, etc.

Claims

1. A production system for directly producing lithium carbonate co-producing sodium chloride from brine, characterized by: It includes a brine buffer unit (1), a first purification unit (2), a boron removal unit (3), a second purification unit (4), a first neutralization unit (5), a sodium precipitation unit (6), a lithium precipitation unit (7), and an alkali preparation unit (8); the brine buffer unit (1), the first purification unit (2), the boron removal unit (3), the second purification unit (4), the first neutralization unit (5), the sodium precipitation unit (6), and the lithium precipitation unit (7) are connected in sequence; the alkali preparation unit (8) is connected to the feed end of the lithium precipitation unit (7).

2. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 1, characterized by: The first purification unit (2) includes a first mixing tank, a first reaction vessel, and a first filtration mechanism; the brine buffer unit (1) and the first mixing tank are both connected to the feed end of the first reaction vessel; the discharge end of the first reaction vessel is connected to the feed end of the first filtration mechanism; the discharge end of the first filtration mechanism is connected to the feed end of the boron removal unit (3).

3. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 2, characterized by: The second purification unit (4) includes a second mixing tank, a second reaction vessel, and a second filtration mechanism; the discharge end of the boron removal unit (3) and the second mixing tank are both connected to the feed end of the second reaction vessel; the discharge end of the second reaction vessel is connected to the inlet end of the second filtration mechanism; and the outlet end of the second filtration mechanism is connected to the first neutralization unit (5).

4. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 3, characterized by: The sodium precipitation unit (6) includes a triple-effect evaporator, a concentrate buffer tank, and a cooling sodium precipitation centrifuge; the first neutralization unit (5) is connected to the feed end of the triple-effect evaporator; the discharge end of the triple-effect evaporator is connected to the concentrate buffer tank; and the concentrate buffer tank is connected to the cooling sodium precipitation centrifuge.

5. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 4, characterized in that: The liquid discharge end of the cooling sodium precipitation centrifuge is connected to the potassium precipitation unit (9); the slag discharge end of the cooling sodium precipitation centrifuge is connected to the first drying kiln (12).

6. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 5, characterized by: The lithium precipitation unit (7) includes a lithium precipitation kettle, a lithium precipitation centrifuge, and a stirring and washing mechanism; the discharge end of the potassium precipitation unit (9) is connected to the feed end of the lithium precipitation kettle; the discharge end of the lithium precipitation kettle is connected to the lithium precipitation centrifuge; the lithium precipitation centrifuge is connected to the feed end of the stirring and washing mechanism; and the alkali preparation unit (8) is connected to the feed unit of the lithium precipitation kettle.

7. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 6, characterized by: The drain end of the agitation and washing mechanism is connected to the alkali preparation unit (8).

8. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 6, characterized by: The discharge end of the lithium-ion centrifuge is connected to a second neutralization unit (14); the second neutralization unit (14) is connected in sequence to an evaporation unit (10) and a centrifugation unit (11).

9. The production system for directly producing lithium carbonate co-producing sodium chloride from brine according to claim 8, characterized by: The liquid discharge end of the centrifuge unit (11) is connected to the boron removal unit (3); the slag discharge end of the centrifuge unit (11) is connected to the second drying kiln (13).

10. The production system for directly preparing lithium carbonate and co-producing sodium chloride from brine according to claim 8, characterized in that: The slag discharge end of the potassium precipitation unit (9) is connected to the first drying kiln (12).

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