CN215756474U - Device for continuously producing lithium chloride from lithium-rich brine in salt lake - Google Patents
Device for continuously producing lithium chloride from lithium-rich brine in salt lake Download PDFInfo
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Abstract
The utility model provides a device for continuously producing lithium chloride from lithium-rich brine in a salt lake. The above-mentioned device includes: a continuous buffer homogenization unit; the continuous magnesium removal unit is provided with a buffer homogenized brine inlet and a magnesium removal brine outlet of the continuous buffer homogenized unit, the buffer homogenized brine inlet is connected with the buffer homogenized brine outlet, and the continuous magnesium removal unit is used for removing magnesium ion impurities in buffer homogenized brine discharged from the buffer homogenized brine outlet to obtain magnesium removal brine; the multi-effect falling-film evaporator is provided with a magnesium-removing brine inlet and a concentrated brine outlet, and the magnesium-removing brine inlet is connected with the magnesium-removing brine outlet; the single-effect evaporation crystallizer is provided with a concentrated brine inlet and a lithium chloride crystallization outlet, and the concentrated brine inlet is connected with the concentrated brine outlet; the continuous drying unit is connected with the lithium chloride crystal outlet; and the centrifugal separation unit is arranged on a pipeline connected with the continuous drying unit and the lithium chloride crystal outlet. The device can effectively separate the lithium chloride in the lithium-rich brine of the salt lake by a shorter process.
Description
Technical Field
The utility model relates to the technical field of lithium salt production, in particular to a device for continuously producing lithium chloride from lithium-rich brine in a salt lake.
Background
The salt lake lithium-rich brine is one of the main raw materials for extracting lithium at present, accounts for 66% of the world lithium resource reserves, and the other is granite pegmatite type lithium ore. The lithium-containing salt lakes are classified into 3 types of carbonate, sulfate (sodium sulfate, magnesium sulfate, etc.) and chloride, which are distributed very unevenly, mainly in south america andes (argentina, bolivia, chile), chinese tibetan plateau and north america, nevada. The salt lake lithium-rich brine is a main source of basic lithium salt required by the lithium battery new energy industry at present and in the future, is also a main process raw material of each salt lake lithium extraction enterprise, links up the original brine, the potassium fertilizer production and the lithium carbonate production, and is developed for years, so that the lithium-rich brine in the salt lake region is mature in production, and the large-scale stable production can be basically realized.
Salt lake lithium-rich brine extraction (precipitation) lithium domestic production enterprises are mainly focused on Qinghai-Tibet plateau, wherein the Chaodia basin is taken as a main part, and the primary (salt) lake-I (production) process is basically adopted. At present, because salt lake areas are mostly located in the gobi abdominal region, the recruitment is difficult, the personnel quality is overall low, and the enterprise products are single (only lithium carbonate), if lithium chloride solution in lithium-rich brine can be used for directly preparing lithium chloride, and continuous production is realized, the product types and the risk resistance of the salt lake lithium extraction enterprise can be increased, the product quality can be further stabilized through a continuous process, and the economic benefits of the enterprise are improved. However, the production product of the lithium-rich brine in the salt lake is mainly lithium carbonate at present, and a process for directly producing lithium chloride is not available.
The existing reports of producing lithium chloride from the lithium-rich brine in the salt lake are less: chinese patent application CN108358221A discloses a process for preparing lithium chloride by using magnesium sulfate subtype salt lake brine, Chinese patent application CN108264067A discloses a new process and equipment for producing lithium chloride by using salt lake brine, Chinese patent application CN108264066A discloses a new process for producing high-purity lithium chloride by using salt lake brine, and the like. However, the above processes have disadvantages, such as the introduction of additional auxiliary chemical materials, "lower alcohols", or low purity.
SUMMERY OF THE UTILITY MODEL
The utility model mainly aims to provide a device for continuously producing lithium chloride from salt lake lithium-rich brine, which solves the problems that in the prior art, the lithium chloride produced from the salt lake lithium-rich brine needs auxiliary low-carbon alcohol chemical reagents or has low purity and the like.
In order to achieve the above object, according to one aspect of the present invention, there is provided an apparatus for continuously producing lithium chloride from a lithium-rich brine in a salt lake, comprising: the continuous buffer homogenizing unit is provided with a salt lake lithium-rich brine inlet and a buffer homogenizing brine outlet; the continuous magnesium removal unit is provided with a buffering and homogenizing brine inlet and a magnesium removal brine outlet, the buffering and homogenizing brine inlet is connected with the buffering and homogenizing brine outlet, and the continuous magnesium removal unit is used for removing magnesium ion impurities in the buffering and homogenizing brine discharged from the buffering and homogenizing brine outlet to obtain magnesium removal brine; the multi-effect falling-film evaporator is provided with a magnesium-removing brine inlet and a concentrated brine outlet, and the magnesium-removing brine inlet is connected with the magnesium-removing brine outlet; the single-effect evaporation crystallizer is provided with a concentrated brine inlet and a lithium chloride crystallization outlet, and the concentrated brine inlet is connected with the concentrated brine outlet; the continuous drying unit is connected with the lithium chloride crystal outlet and is used for drying the lithium chloride crystal discharged from the lithium chloride crystal outlet; and the centrifugal separation unit is arranged on a pipeline connected with the lithium chloride crystal outlet of the continuous drying unit.
Further, the continuous magnesium removal unit comprises: the sodium hydroxide solution storage tank and the conveying device are used for supplying the sodium hydroxide solution; the precipitation reaction device is provided with a buffer homogenized brine inlet, a precipitator inlet and a precipitated slurry outlet, the precipitator inlet is connected with the sodium hydroxide solution storage tank and the conveying device, and the precipitation reaction device is used for performing precipitation reaction on magnesium ion impurities on the buffer homogenized brine and the sodium hydroxide solution; the continuous settling tank is provided with a precipitation slurry inlet, an overflow liquid outlet and a bottom flow outlet, and the precipitation slurry inlet is connected with the precipitation slurry outlet; the primary continuous filtering device is provided with an underflow inlet and a primary filtering liquid outlet, and the underflow inlet is connected with the underflow outlet; the second-stage continuous filtering device is provided with a first-stage filtrate inlet, an overflow liquid inlet and a magnesium removal brine outlet, wherein the first-stage filtrate inlet is connected with the first-stage filtrate outlet, and the overflow liquid inlet is connected with the overflow liquid outlet.
Further, the first-stage continuous filtering device adopts a vacuum belt filter or a vertical filter press; the secondary continuous filtering device adopts a precision filter.
Further, the precipitation reaction device comprises a plurality of magnesium precipitation grooves which are arranged in series, a baffle plate is arranged in each magnesium precipitation groove, an atomization device is arranged in each magnesium precipitation groove, the atomization device is connected with a sodium hydroxide solution storage tank and a conveying device, and the atomization device is used for adding the sodium hydroxide solution in an atomization mode.
Further, the device also comprises a magnesium slag receiving device, the first-stage continuous filtering device is also provided with a first slag outlet, the second-stage continuous filtering device is also provided with a second slag outlet, and the magnesium slag receiving device is respectively connected with the first slag outlet and the second slag outlet.
Further, the magnesium slag receiving device is also provided with a magnesium slag outlet, and the magnesium slag outlet is connected with the first-stage and/or second-stage magnesium precipitation tank and is used for returning part of magnesium slag as crystal seeds to the precipitation reaction process.
Further, the apparatus further comprises: the flocculant supply device is connected with the continuous settling tank and is used for supplying flocculant to the continuous settling tank; and a filter aid supply device connected with the bottom of the continuous settling tank and used for supplying the filter aid to the continuous settling tank.
Further, the multi-effect falling-film evaporator adopts a three-effect or four-effect falling-film evaporator.
Furthermore, in the multi-effect falling-film evaporators, the first and second-effect falling-film evaporators are made of TA10 material, and the rest are made of TA2 material; in the single-effect evaporation crystallizer, an evaporator is made of TA10 material, and a crystallizer is made of TA2 material.
Furthermore, the device also comprises an automatic control unit which is respectively connected with the continuous buffer homogenizing unit, the continuous magnesium removing unit, the multiple-effect falling film evaporator, the single-effect evaporation crystallizer and the continuous drying unit and is used for carrying out automatic control on the continuous buffer homogenizing unit, the continuous magnesium removing unit, the multiple-effect falling film evaporator, the single-effect evaporation crystallizer and the continuous drying unit.
The utility model provides a device for continuously producing lithium chloride from salt lake lithium-rich brine, which firstly utilizes a continuous buffer homogenizing unit to buffer and homogenize the salt lake lithium-rich brine, and can remove part of solid impurities. The salt lake brine has high magnesium content, the removal of impurities magnesium and the separation of magnesium and lithium are crucial to the production of lithium chloride in the salt lake, and the magnesium ion impurities can be effectively removed through the continuous magnesium removal unit. According to the characteristics of lithium chloride materials, namely the boiling point of lithium chloride rises and is quickly improved along with the increase of the concentration, anions (sodium, potassium, boron) and the like in the magnesium-removing brine are greatly removed, the investment, maintenance, operation cost and the like of evaporation equipment are comprehensively considered, the evaporation concentration of the lithium chloride in the lithium-rich brine of the salt lake is divided into two sections, namely the magnesium-removing brine is close to a lithium chloride saturated solution, a multi-effect falling film evaporator is adopted, the evaporator is high in evaporation intensity, high in heat transfer coefficient, low in energy consumption and stable in operation, is suitable for remote areas of the salt lake, a single-effect forced circulation evaporation crystallizer is adopted, and finally qualified lithium chloride products are produced.
In short, the device provided by the utility model can be used for more effectively separating the lithium chloride in the salt lake lithium-rich brine by a shorter flow on the basis of not adding low-carbon alcohol and the like, and the obtained lithium chloride has higher purity.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the utility model and, together with the description, serve to explain the utility model and not to limit the utility model. In the drawings:
FIG. 1 is a schematic structural diagram of an apparatus for continuously producing lithium chloride from a lithium-rich brine in a salt lake according to an embodiment of the utility model; and
fig. 2 shows a schematic flow chart of a method for continuously producing lithium chloride from a lithium-rich brine in a salt lake according to an embodiment of the utility model.
Wherein the figures include the following reference numerals:
10. a continuous buffer homogenization unit; 20. a continuous magnesium removal unit; 21. a sodium hydroxide solution storage tank and a conveying device; 22. a precipitation reaction device; 23. a continuous settling tank; 24. a first stage continuous filtration device; 25. a secondary continuous filtration device; 30. a multi-effect falling film evaporator; 40. a single-effect evaporative crystallizer; 50. a continuous drying unit; 60. a centrifugal separation unit; 70. a continuous conveying device; 80. and (7) packaging the units.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Interpretation of terms:
1. liquid lithium ore: lithium chloride (LiCl) equivalent concentration reaches more than 150mg/L lithium-containing brine, including salt lake brine and well brine, and the lithium content of liquid lithium ore is converted into lithium chloride.
2. Lithium-rich brine: lithium-rich brine produced from liquid lithium ore processing is used to extract lithium salt compounds.
3. And (3) lithium deposition: adding precipitant to precipitate lithium from the solution as solid lithium salt.
4. Basic lithium salt: industrial grade lithium carbonate, industrial grade lithium hydroxide monohydrate, and industrial grade lithium chloride.
As described in the background art, the production of lithium chloride from the lithium-rich brine in the salt lake in the prior art has the problems of needing an auxiliary low-carbon alcohol chemical reagent, or having low purity and the like.
In order to solve the problem, the utility model provides a device for continuously producing lithium chloride from salt lake lithium-rich brine, which comprises a continuous buffer homogenizing unit 10, a continuous magnesium removing unit 20, a multi-effect falling-film evaporator 30, a single-effect evaporation crystallizer 40, a continuous drying unit 50 and a centrifugal separation unit 60, as shown in figure 1; the continuous buffer homogenizing unit 10 is provided with a salt lake lithium-rich brine inlet and a buffer homogenizing brine outlet; the continuous magnesium removal unit 20 is provided with a buffer homogenized brine inlet and a magnesium removal brine outlet, the buffer homogenized brine inlet is connected with the buffer homogenized brine outlet, and the continuous magnesium removal unit 20 is used for removing magnesium ion impurities in the buffer homogenized brine discharged from the buffer homogenized brine outlet to obtain magnesium removal brine; the multi-effect falling-film evaporator 30 is provided with a magnesium-removing brine inlet and a concentrated brine outlet, and the magnesium-removing brine inlet is connected with the magnesium-removing brine outlet; the single-effect evaporation crystallizer 40 is provided with a concentrated brine inlet and a lithium chloride crystallization outlet, and the concentrated brine inlet is connected with the concentrated brine outlet; the continuous drying unit 50 is connected with the lithium chloride crystal outlet and is used for drying the lithium chloride discharged from the lithium chloride crystal outlet. The centrifugal separation unit is arranged on a pipeline connected with the continuous drying unit and the lithium chloride crystal outlet.
The device firstly utilizes the continuous buffer homogenizing unit to buffer and homogenize the lithium-rich brine in the salt lake, and can remove part of solid impurities. The salt lake brine has high magnesium content, and the removal of magnesium impurity and the magnesium-lithium separation are crucial to the production of lithium chloride in the salt lake. According to the characteristics of lithium chloride materials, namely the boiling point of lithium chloride rises and is quickly improved along with the increase of the concentration, anions (sodium, potassium, boron) and the like in the magnesium-removing brine are greatly removed, the investment, maintenance, operation cost and the like of evaporation equipment are comprehensively considered, the evaporation concentration of the lithium chloride in the lithium-rich brine of the salt lake is divided into two sections, namely the magnesium-removing brine is close to a lithium chloride saturated solution, a multi-effect falling film evaporator is adopted, the evaporator is high in evaporation intensity, high in heat transfer coefficient, low in energy consumption and stable in operation, is suitable for remote areas of the salt lake, a single-effect forced circulation evaporation crystallizer is adopted, and finally qualified lithium chloride products are produced. And the centrifugal separation unit is used for centrifugally separating lithium chloride crystal solids precipitated from the supersaturated solution after evaporation and concentration, and sending the lithium chloride crystal solids into the continuous drying unit for drying.
In short, the device provided by the utility model can be used for more effectively separating the lithium chloride in the salt lake lithium-rich brine by a shorter flow on the basis of not adding low-carbon alcohol and the like, and the obtained lithium chloride has higher purity.
In order to remove magnesium more effectively, in a preferred embodiment, as shown in fig. 1, the continuous magnesium removal unit 20 includes a sodium hydroxide solution storage tank and delivery device 21, a precipitation reaction device 22, a continuous settling tank 23, a primary continuous filtration device 24, a secondary continuous filtration device 25; the sodium hydroxide solution storage tank and conveying device 21 is used for supplying a sodium hydroxide solution; the precipitation reaction device 22 is provided with a buffer homogenized brine inlet, a precipitator inlet and a precipitated slurry outlet, the precipitator inlet is connected with the sodium hydroxide solution storage tank and the conveying device 21, and the precipitation reaction device 22 is used for performing precipitation reaction on magnesium ion impurities on the buffer homogenized brine and the sodium hydroxide solution; the continuous settling tank 23 is provided with a precipitation slurry inlet, an overflow liquid outlet and a bottom flow outlet, and the precipitation slurry inlet is connected with the precipitation slurry outlet; the first-stage continuous filtering device 24 is provided with an underflow inlet and a first-stage filtrate outlet, and the underflow inlet is connected with the underflow outlet; the second-stage continuous filtering device 25 is provided with a first-stage filtrate inlet, an overflow liquid inlet and a magnesium removal brine outlet, wherein the first-stage filtrate inlet is connected with the first-stage filtrate outlet, and the overflow liquid inlet is connected with the overflow liquid outlet.
In the actual operation process, the sodium hydroxide solution enters the precipitation reaction device 22 to react with the buffered homogenized brine to produce magnesium hydroxide slag. The precipitated slurry can be continuously precipitated after entering the continuous settling tank 23, the supernatant overflows to form overflow liquid, the underflow enters the primary continuous filtering device 24 for primary filtering, and the primary filtered liquid and the overflow liquid enter the secondary continuous filtering device 25 for further filtering, so as to obtain the magnesium-removing brine.
In a preferred embodiment, the primary continuous filtration device 24 employs a vacuum belt filter or a vertical filter press; the two-stage continuous filtration device 25 employs a precision filter. The vacuum belt filter can be a horizontal vacuum belt filter, the filtering precision of the precision filter is 3-5 mu m, and the magnesium hydroxide slag can be removed as fully as possible through the two-stage filtering.
In order to make the precipitation reaction more fully proceed and promote the magnesium ion impurities to be more fully precipitated, in a preferred embodiment, the precipitation reaction device 22 comprises a plurality of magnesium precipitation tanks arranged in series, baffle plates are arranged in the magnesium precipitation tanks, and the magnesium precipitation tanks are provided with atomization devices which are connected with a sodium hydroxide solution storage tank and a conveying device 21, and the atomization devices are used for adding the sodium hydroxide solution in an atomized form. Therefore, the sodium hydroxide solution can be uniformly added into the magnesium precipitation tank through the atomization device, and fully contacts and reacts with the buffering homogenized brine. And a plurality of magnesium precipitation grooves are arranged in series, and baffle plates are arranged in the magnesium precipitation grooves, so that the reaction can be continuously carried out, the magnesium removal effect is further improved, the continuous magnesium precipitation reaction is conveniently carried out, and the continuous feeding and discharging are realized. When actually setting up, set up the inlet in the magnesium groove and deposit the thick liquids export, the top sets up the overflow mouth, and the overflow mouth of last one-level links to each other with the inlet of next one-level, can make the thick liquids that precipitate constantly from each deposit thick liquids export discharge and with subsequent continuous settling tank 23 deposit thick liquids import and link to each other in the continuous operation process, the inlet in the magnesium groove is promptly for buffering homogenization brine import in the first order.
In a preferred embodiment, the apparatus further comprises a magnesium slag receiving device, the primary continuous filtering device 24 further comprises a first slag outlet, the secondary continuous filtering device 25 further comprises a second slag outlet, and the magnesium slag receiving device is respectively connected with the first slag outlet and the second slag outlet. More preferably, the magnesium slag receiving device is also provided with a magnesium slag outlet which is connected with the first-stage magnesium precipitation tank and/or the second-stage magnesium precipitation tank and is used for returning part of magnesium slag as seed crystals to the precipitation reaction process. Therefore, the magnesium hydroxide slag is used as the crystal seed to return to the precipitation reaction, so that the magnesium hydroxide precipitate can be promoted to grow on the surface of the crystal seed to form agglomerated magnesium hydroxide with a certain particle size, and the subsequent filtering removal is facilitated.
For the purpose of further enhancing the effect of magnesium removal, in a preferred embodiment, the above apparatus further comprises a flocculant supply means and a filter aid supply means, the flocculant supply means being connected to the continuous settling tank 23 for supplying a flocculant to the continuous settling tank 23; a filter aid supply means is connected to the bottom of the continuous settling tank 23 for supplying filter aid to the continuous settling tank 23. Thus, the flocculating agent is favorable for flocculation and agglomeration of the magnesium slag in the precipitated slurry and accelerates the settling velocity. A filter aid is further added to the continuous settling tank 23 to assist in the magnesium slag filtration. Preferably, the continuous settling tank 23 comprises an overflow tank and an underflow tank, the overflow tank is arranged above the underflow tank and is communicated with the underflow tank, the underflow tank is internally provided with a stirring device, the flocculating agent supply device is connected with the overflow tank, and the filter aid supply device is connected with the underflow tank. In the actual operation process, the stirring device in the underflow groove is opened, and the underflow is sent to the subsequent one-stage continuous filtering device 24 for one-stage filtering at a certain stirring speed. The above-mentioned precipitation slurry can be continuously fed into the continuous settling tank 23 by a pump to be subjected to a settling treatment. In addition, in order to reduce the equipment investment and achieve the purposes of corrosion prevention and wear resistance, it is preferable that the continuous settling tank 23 has a non-metallic lining.
Preferably, the multi-effect falling-film evaporator 30 employs a three-effect or four-effect falling-film evaporator. Preferably, in the multi-effect falling-film evaporator 30, the first and second-effect falling-film evaporators are made of TA10, and the rest are made of TA 2; in the single-effect evaporative crystallizer 40 (i.e. the single-effect central circulation forced evaporative crystallizer), the evaporator is made of TA10 material, and the crystallizer is made of TA2 material. It should be noted here that the materials of the evaporators of the multi-effect falling-film evaporator 30 and the single-effect evaporative crystallizer 40 mainly refer to a heater (heat exchanger) and a circulating pipe. Preferably, the apparatus further comprises a preheater disposed between the magnesium removal brine inlet of the multi-effect falling-film evaporator 30 and the concentrated brine outlet of the continuous magnesium removal unit 20, for preheating the magnesium removal brine.
In a preferred embodiment, the above apparatus further comprises an automatic control unit (DCS system) electrically connected to the continuous buffer homogenizing unit 10, the continuous magnesium removing unit 20, the multi-effect falling film evaporator 30, the single-effect evaporative crystallizer 40, and the continuous drying unit 50, respectively, for automatically controlling each of them. Like this, can pass through the operation of each device of automatic control unit control, greatly reduced human cost improves production efficiency.
Preferably, a centrifugal separation unit 60 and a continuous conveying device 70 connected in sequence are further disposed on the connecting pipeline between the continuous drying unit 50 and the single-effect evaporative crystallizer 40, and are used for centrifugally separating lithium chloride crystalline solids precipitated from the supersaturated solution after evaporation concentration, and then conveying the lithium chloride crystalline solids to the continuous drying unit 50. Further preferably, the separated mother liquor outlet of the centrifugal separation unit 60 is connected with the magnesium removal brine inlet of the multi-effect falling-film evaporator 30. The separated mother liquor of the centrifugal separation unit 60, which still contains lithium chloride and is close to saturation, is returned to the evaporation system so as to further recover the lithium chloride therein. In actual operation, the condensate of the multi-effect falling-film evaporator 30 and the single-effect evaporative crystallizer 40 can also be used for preparing a sodium hydroxide solution or entering a boiler.
Preferably, the automatic control unit is also electrically connected to the centrifugal separation unit 60 and the continuous conveying device 70 for automatic control thereof.
More preferably, the apparatus further comprises a packaging unit 80 connected to the outlet of the drying unit 50 for packaging the dried lithium chloride crystals for sale and transportation.
Further, for the continuous buffer homogenizing unit 10, it is preferable to: particularly, the device is a closed buffer tank or a buffer tank, so that secondary pollution to brine is avoided; the seepage-proofing arrangement is carried out to prevent valuable elements from losing; preferably, a diversion weir is arranged in the buffer tank or the buffer groove, and the retention time of the lithium-rich brine in the salt lake is prolonged while the lithium-rich brine in the salt lake is stored in the buffer tank or the buffer groove, so that the purposes of naturally settling trace solids, homogenizing and stabilizing the later-stage production are achieved; a certain gradient is considered at the bottom of the buffer pool or the buffer tank, so that the trace solid in the brine can be cleaned regularly. During the specific implementation, the storage period can be properly prolonged or the storage capacity can be increased according to the stable supply capacity and the investment condition of raw materials of each enterprise.
According to another aspect of the utility model, the utility model provides a method for continuously producing lithium chloride from salt lake lithium-rich brine, namely Li in the salt lake lithium-rich brine+15-25 g/l of Mg2+The concentration is 4-6 g/l，Cl-The concentration is 100-130 g/l, one or more of impurity elements Na, K and B are also included as shown in figure 2, and the method comprises the following steps: s1, continuously buffering and homogenizing the lithium-rich brine in the salt lake to obtain buffered and homogenized brine; s2, continuously removing magnesium from the buffered and homogenized brine to obtain magnesium-removed brine; s3, carrying out multi-effect falling film evaporation treatment on the magnesium-removed brine to obtain concentrated brine; s4, carrying out single-effect evaporation crystallization treatment on the concentrated brine to obtain lithium chloride crystals; and S5, continuously drying the lithium chloride crystal to obtain the lithium chloride product.
The method firstly carries out buffer homogenization on the lithium-rich brine in the salt lake, and can remove part of solid impurities. The salt lake brine has high magnesium content, and the removal of magnesium impurity and the magnesium-lithium separation are crucial to the production of lithium chloride in the salt lake. According to the characteristics of lithium chloride materials, namely the boiling point of lithium chloride rises and is quickly improved along with the increase of the concentration, anions (sodium, potassium, boron) and the like in the magnesium-removing brine are greatly removed, the investment, maintenance, operation cost and the like of evaporation equipment are comprehensively considered, the evaporation concentration of the lithium chloride in the lithium-rich brine of the salt lake is divided into two sections, namely the magnesium-removing brine is close to a lithium chloride saturated solution, a multi-effect falling film evaporator is adopted, the evaporator is high in evaporation intensity, high in heat transfer coefficient, low in energy consumption and stable in operation, is suitable for remote areas of the salt lake, a single-effect forced circulation evaporation crystallizer is adopted, and finally qualified lithium chloride products are produced.
In conclusion, the method provided by the utility model can be used for more effectively separating the lithium chloride in the salt lake lithium-rich brine by a shorter flow on the basis of not adding low-carbon alcohol and the like, and the obtained lithium chloride has higher purity.
In order to make the precipitation reaction more fully proceed and promote more fully precipitation of magnesium ion impurities, in a preferred embodiment, step S2 includes: s21, mixing the buffered homogenized brine with a sodium hydroxide solution, and carrying out a precipitation reaction of magnesium ion impurities to obtain a precipitation slurry; s22, introducing the precipitation slurry into a continuous settling tank for continuous settling treatment to obtain overflow liquid and underflow; s23, performing primary continuous filtration treatment on the underflow to obtain primary filtrate; and S24, carrying out secondary continuous filtration treatment on the primary filtrate and the overflow liquid together to obtain the magnesium-removing brine.
In the actual treatment process, besides lithium ions, magnesium ions and chloride ions, the salt lake lithium-rich brine also contains a small amount of impurity ions such as Na, K, B and the like, but the effect of the treatment process is not influenced.
More preferably, the precipitation reaction is carried out in a plurality of magnesium precipitation tanks which are arranged in series, wherein the magnesium precipitation tanks are provided with baffle plates and provided with atomization devices; in step S21, the sodium hydroxide solution is atomized by an atomization device and added to the magnesium precipitation tank, and contacts and reacts with the buffered homogenized brine. Thus, the sodium hydroxide solution can be sprayed into the magnesium precipitation tank in a mist form through the atomization device, and fully contacts and reacts with the buffering homogenized brine. And a plurality of magnesium precipitation grooves are arranged in series, and baffle plates are arranged in the magnesium precipitation grooves, so that the reaction can be continuously carried out, the magnesium removal effect is further improved, the continuous magnesium precipitation reaction is conveniently carried out, and the continuous feeding and discharging are realized.
In a preferred embodiment, the mass concentration of the sodium hydroxide solution is 30-40%, the excess coefficient of the sodium hydroxide solution in the precipitation reaction process is less than 1.05, and the temperature of the precipitation reaction is 55-65 ℃; preferably, the pH value of the precipitation reaction is 11-13. The excess factor is the ratio of the amount of sodium hydroxide actually added to the theoretically required amount, based on the theoretically required amount of sodium hydroxide and magnesium ions for the reaction, and preferably the excess factor of the sodium hydroxide solution during the precipitation reaction is < 1.05 and >1, preferably 1.05. Under the process condition, the precipitation reaction of magnesium ions is more sufficient, and the magnesium removal effect is better. Preferably, in the process of adding the sodium hydroxide solution, the adding speed of the sodium hydroxide is controlled and slowly added, and the adding speed is controlled according to the amount of magnesium ions, so that the magnesium hydroxide can slowly grow up, and the formation of microcrystals is avoided as much as possible. Preferably, during the actual adding process, the sodium hydroxide solution is continuously added according to the molar ratio of the chemical reaction, and the adding speed is controlled to be in accordance with the excess coefficient when the molar number of the magnesium ions enters the molar number per unit time.
In a preferred embodiment, the first continuous filtration treatment produces a first portion of the residue and the second continuous filtration treatment produces a second portion of the residue; the method further comprises the following steps: the first part of filter residue and the second part of filter residue form magnesium slag; and returning part of the magnesium slag as seed crystal to the precipitation reaction process. Therefore, the magnesium hydroxide slag is used as the crystal seed to return to the precipitation reaction, so that the magnesium hydroxide precipitate can be promoted to grow on the surface of the crystal seed to form agglomerated magnesium hydroxide with a certain particle size, and the subsequent filtering removal is facilitated.
More preferably, in step S22, the continuous sedimentation treatment process includes: adding a flocculating agent into the continuous settling tank to flocculate the settled slurry; filter aid is added to the bottom of the continuous settling tank. Thus, the flocculating agent is favorable for flocculation and agglomeration of the magnesium slag in the precipitated slurry and accelerates the settling velocity. A filter aid is further added to the continuous settling tank 23 to assist in the filtration of the magnesium slag. Preferably, the flocculating agent is anionic polyacrylamide, and the addition amount of the flocculating agent is preferably 100-250 mg/kg relative to the precipitation slurry; preferably, the filter aid is diatomaceous earth; more preferably, the addition amount of the filter aid is 0.5-1 wt% of the amount of the magnesium slag in the precipitation slurry.
In a preferred embodiment, in step S23, the one-stage continuous filtration process is performed using a vacuum belt filter or a vertical filter press; in step S24, the secondary continuous filtration process is performed using a precision filter, preferably, the precision filter has a filtration precision of 3 to 5 μm. Thus, the two-stage filtration mode is matched with each other, so that the magnesium removal effect can be further improved.
Preferably, in step S3, the multi-effect falling film evaporation treatment adopts a three-effect or four-effect falling film evaporator; preferably, the final lithium chloride concentration in the multi-effect falling film evaporation treatment process is controlled to be 45-50%, and the evaporation temperature is controlled to be 155 +/-10 ℃. Thus, the key concentration is the saturation concentration, and the evaporation efficiency is higher. More preferably, in step S4, the single-effect evaporative crystallization treatment employs a single-effect evaporative crystallizer; preferably, in the single-effect evaporation crystallization treatment process, the concentration of lithium chloride at the end point of evaporation is controlled to be 53%, the evaporation temperature is 165 +/-10 ℃, and the crystallization temperature is controlled to be 95-105 ℃. Under these conditions, the solubility of lithium chloride can be reduced as much as possible, and lithium chloride can be precipitated by evaporation and crystallization. More preferably, in the single-effect evaporation crystallization treatment process, the rotation speed of the crystallizer is controlled to be 10-20 r/min, and the vapor pressure of the crystallization liquid surface is controlled to be 500-600 mmHg. This is beneficial to avoid the formation of hydrated lithium chloride and finally the wet lithium chloride product is obtained. And continuously drying the wet lithium chloride product at the temperature of more than 160 ℃ to obtain the anhydrous lithium chloride product.
In the actual operation process, the magnesium removal brine is preferably preheated before being subjected to multi-effect falling film evaporation treatment, wherein the preheating temperature can be 80-90 ℃, so that the crystallization efficiency is further improved.
Preferably, the method further comprises controlling the performing of the steps S1 to S4 by an automatic control system. Therefore, full-automatic production can be realized through remote online control, and the continuity and stability of the production process are ensured; the method has the advantages that the current situation that each workshop section needs frequent intervention of operators in the traditional production is changed, and the industrial level is improved.
Preferably, before the continuous drying, the method further comprises the step of centrifuging and continuously conveying the lithium chloride crystals, and mother liquor obtained by centrifuging can be returned to the multi-effect falling-film evaporation treatment process. More preferably, the above process further comprises the step of packaging the lithium chloride product for sale and transport after continuous drying.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the utility model as claimed.
Example 1
In a certain salt lake lithium extraction enterprise, a semi-industrialized test is carried out by adopting the device shown in figure 1 of the utility model, and the lithium-rich brine comprises the following raw materials:
| element(s) | Li+ | Mg2+ | Cl- | Na+ |
| Concentration (g/L) | 15～20 | 8 | 100 | 1.9 |
And (3) naturally settling and buffering the lithium-rich brine in a continuous buffering and homogenizing unit, and carrying out continuous magnesium removal treatment on the buffered and homogenized brine in continuous magnesium removal equipment. Specifically, the lithium-rich brine after the buffering homogenization treatment is continuously introduced into three continuous magnesium precipitation tanks which are connected in sequence, and each magnesium precipitation tank is provided with an atomizing device for adding 30 wt% of sodium hydroxide aqueous solution into each magnesium precipitation tank for continuous magnesium removal. During the magnesium removal, the temperature was 55 ℃, the excess coefficient of the sodium hydroxide aqueous solution was 1.04, and the system pH was 13, to obtain a precipitation slurry. Continuously pumping the precipitation slurry into a continuous settling tank for continuous settling separation, adding 200mg/kg of anionic polyacrylamide serving as a flocculating agent during the continuous settling separation, and adding diatomite accounting for 1% of the amount of the residue serving as a filter aid to obtain underflow and overflow liquid; and performing primary continuous solid-liquid separation on the bottom flow in a vacuum belt filter to obtain primary filtrate and magnesium slag, performing continuous fine filtration on the overflow liquid and the primary filtrate in a precision filter, wherein the filtration precision is 3-5 mu m, so as to obtain magnesium-removed brine and magnesium slag, and returning the two magnesium slag parts as crystal seeds to the step of continuous magnesium removal treatment.
The method comprises the steps of continuously feeding magnesium-removed brine into a triple-effect falling-film evaporator for preconcentration, controlling the end point concentration to be 50% and the evaporation temperature to be 165 ℃ to obtain a nearly saturated solution, then continuously feeding the nearly saturated solution into a single-effect evaporation crystallizer, specifically adopting a single-effect central circulation forced evaporation crystallizer, controlling the evaporation temperature to be 175 ℃ and the evaporation end point lithium chloride to be 53%, then crystallizing at 95 ℃, ensuring the rotation speed of the crystallizer to be 20 r/min and the micro-negative pressure state of 500mmHg of vapor pressure of a crystallization liquid surface, avoiding forming hydrated lithium chloride, and finally obtaining a wet lithium chloride crystal product. And (3) conveying lithium chloride solid obtained by centrifuging a wet lithium chloride crystal product by a centrifuge to a drying unit, and returning mother liquor obtained by centrifuging to the triple-effect falling-film evaporator. In the actual operation process, the condensate of the three-effect falling-film evaporator and the single-effect evaporation crystallizer is used for preparing a sodium hydroxide solution or enters a boiler.
The whole lithium extraction process flow can be continuously controlled remotely through a DCS system without manual field operation, and the obtained lithium chloride product is stable in quality and qualified in batches through random detection of the quality of the lithium chloride product. Specifically, the produced lithium chloride can meet the quality standard of GB/T10575-2007 first-grade products and above, and the yield is more than 93%.
Example 2
In a certain salt lake lithium extraction enterprise, a semi-industrialized test is carried out by adopting the device shown in figure 1 of the utility model, and the lithium-rich brine comprises the following raw materials:
| element(s) | Li+ | Mg2+ | Cl- | Na+ |
| Concentration (g/L) | 15～20 | 8 | 100 | 1.9 |
And (3) naturally settling and buffering the lithium-rich brine in a continuous buffering and homogenizing unit, and carrying out continuous magnesium removal treatment on the buffered and homogenized brine in continuous magnesium removal equipment. Specifically, the lithium-rich brine after the buffering homogenization treatment is continuously introduced into three continuous magnesium precipitation tanks which are connected in sequence, and each magnesium precipitation tank is provided with an atomizing device for adding 30 wt% of sodium hydroxide aqueous solution into each magnesium precipitation tank for continuous magnesium removal. The temperature during the magnesium removal was 65 ℃, the excess factor of the aqueous sodium hydroxide solution was 1.05, and the pH of the system was 11, to obtain a precipitation slurry. Continuously pumping the precipitation slurry into a continuous settling tank for continuous settling separation, adding 250mg/kg of anionic polyacrylamide as a flocculating agent during the continuous settling separation, and adding diatomite accounting for 0.5% of the amount of the residue as a filter aid to obtain underflow and overflow liquid; and performing primary continuous solid-liquid separation on the bottom flow in a vacuum belt filter to obtain primary filtrate and magnesium slag, performing continuous fine filtration on the overflow liquid and the primary filtrate in a precision filter, wherein the filtration precision is 3-5 mu m, so as to obtain magnesium-removed brine and magnesium slag, and returning the two magnesium slag parts as crystal seeds to the step of continuous magnesium removal treatment.
Continuously feeding the magnesium-removed brine into a triple-effect falling-film evaporator for preconcentration, controlling the end point concentration to be 45% and the evaporation temperature to be 155 ℃ to obtain a nearly saturated solution, then continuously feeding the nearly saturated solution into a single-effect evaporation crystallizer, specifically adopting a single-effect central circulation forced evaporation crystallizer, controlling the evaporation temperature to be 165 ℃ and the evaporation end point lithium chloride to be 53%, then crystallizing at 105 ℃, ensuring the rotation speed of the crystallizer to be 10 r/min and the micro-negative pressure state of the vapor pressure of the crystallization liquid surface to be 600mmHg, avoiding the formation of hydrated lithium chloride, and finally obtaining a wet lithium chloride crystal product. And (3) conveying lithium chloride solid obtained by centrifuging a wet lithium chloride crystal product by a centrifuge to a drying unit, and returning mother liquor obtained by centrifuging to the triple-effect falling-film evaporator. In the actual operation process, the condensate of the three-effect falling-film evaporator and the single-effect evaporation crystallizer is used for preparing a sodium hydroxide solution or enters a boiler.
The whole lithium extraction process flow can be continuously controlled remotely through a DCS system without manual field operation, and the obtained lithium chloride product is stable in quality and qualified in batches through random detection of the quality of the lithium chloride product. Specifically, the produced lithium chloride can meet the quality standard of GB/T10575-2007 first-grade products and above, and the yield is more than 94%.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
this application adopts the system of carrying lithium of salt lake brine, and this system is including the continuous magnesium equipment that removes, continuous evaporation crystallization equipment and the continuous drying equipment that connect gradually. The integrated lithium extraction system can achieve continuous production, so that the labor intensity is obviously reduced, the product difference caused by manual control subjective distinction is reduced, the quality stability of products is improved, the product cost is reduced, and the batch qualification of lithium chloride products is improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The device for continuously producing lithium chloride from lithium-rich brine in a salt lake is characterized by comprising the following components:
the continuous buffer homogenizing unit (10) is provided with a salt lake lithium-rich brine inlet and a buffer homogenizing brine outlet;
the continuous magnesium removal unit (20) is used for removing magnesium ion impurities in the buffered and homogenized brine discharged from the buffered and homogenized brine outlet, the continuous magnesium removal unit (20) is provided with a buffered and homogenized brine inlet and a magnesium removal brine outlet, and the buffered and homogenized brine inlet is connected with the buffered and homogenized brine outlet;
the multi-effect falling-film evaporator (30) is provided with a magnesium-removing brine inlet and a concentrated brine outlet, and the magnesium-removing brine inlet is connected with the magnesium-removing brine outlet;
the single-effect evaporation crystallizer (40) is provided with a concentrated brine inlet and a lithium chloride crystallization outlet, and the concentrated brine inlet is connected with the concentrated brine outlet;
the continuous drying unit (50) is connected with the lithium chloride crystal outlet and is used for drying the lithium chloride crystal discharged from the lithium chloride crystal outlet; and
and the centrifugal separation unit (60) is arranged on a pipeline connecting the continuous drying unit (50) and the lithium chloride crystal outlet.
2. The apparatus for continuously producing lithium chloride from the lithium-rich brine in the salt lake according to claim 1, wherein the continuous magnesium removal unit (20) comprises:
a sodium hydroxide solution storage tank and delivery device (21) for supplying a sodium hydroxide solution;
a precipitation reaction device (22) for performing a precipitation reaction of the magnesium ion impurities on the buffered homogenized brine and the sodium hydroxide solution, wherein the precipitation reaction device (22) is provided with a buffered homogenized brine inlet, a precipitant inlet and a precipitated slurry outlet, and the precipitant inlet is connected with the sodium hydroxide solution storage tank and conveying device (21);
the continuous settling tank (23) is provided with a precipitation slurry inlet, an overflow liquid outlet and an underflow outlet, and the precipitation slurry inlet is connected with the precipitation slurry outlet;
a primary continuous filtration device (24) having an underflow inlet and a primary filtrate outlet, the underflow inlet being connected to the underflow outlet;
the second-stage continuous filtering device (25) is provided with a first-stage filtering liquid inlet, an overflow liquid inlet and a magnesium removal brine outlet, wherein the first-stage filtering liquid inlet is connected with the first-stage filtering liquid outlet, and the overflow liquid inlet is connected with the overflow liquid outlet.
3. The device for continuously producing the lithium chloride from the salt lake lithium-rich brine according to claim 2, wherein the primary continuous filtering device (24) adopts a vacuum belt filter or a vertical filter press; the two-stage continuous filtering device (25) adopts a precision filter.
4. The device for continuously producing lithium chloride from the lithium-rich brine in the salt lake according to claim 2, wherein the precipitation reaction device (22) comprises a plurality of magnesium precipitation tanks arranged in series, baffles are arranged in the magnesium precipitation tanks, and the magnesium precipitation tanks are provided with atomization devices which are connected with the sodium hydroxide solution storage tank and the conveying device (21), and the atomization devices are used for adding the sodium hydroxide solution in an atomized form.
5. The apparatus for continuously producing lithium chloride from the lithium-rich brine in the salt lake according to claim 4, wherein the apparatus further comprises a magnesium slag receiving device, the primary continuous filtering device (24) further comprises a first slag outlet, the secondary continuous filtering device (25) further comprises a second slag outlet, and the magnesium slag receiving device is respectively connected with the first slag outlet and the second slag outlet.
6. The device for continuously producing lithium chloride from the salt lake lithium-rich brine as claimed in claim 5, wherein the magnesium slag receiving device is further provided with a magnesium slag outlet, and the magnesium slag outlet is connected with the first-stage and/or second-stage magnesium precipitation tank and is used for returning part of magnesium slag as seed crystals to the precipitation reaction process.
7. The apparatus for continuously producing lithium chloride from the lithium-rich brine in the salt lake according to any one of claims 2 to 6, wherein the apparatus further comprises:
-a flocculant supply device connected to the continuous settling tank (23) for supplying flocculant to the continuous settling tank (23);
a filter aid supply means connected to the bottom of said continuous settling tank (23) for supplying filter aid to said continuous settling tank (23).
8. The plant for continuously producing lithium chloride from the salt lake lithium-rich brine according to any one of claims 1 to 6, wherein the multi-effect falling-film evaporator (30) is a three-effect or four-effect falling-film evaporator.
9. The device for continuously producing lithium chloride from the lithium-rich brine in the salt lake according to claim 8, wherein in the multiple-effect falling-film evaporator (30), the first and second-effect falling-film evaporators are made of TA10, and the rest are made of TA 2; in the single-effect evaporation crystallizer (40), an evaporator is made of TA10 material, and a crystallizer is made of TA2 material.
10. The apparatus for continuously producing lithium chloride from the salt lake lithium-rich brine according to any one of claims 1 to 6, further comprising an automatic control unit, which is respectively connected with the continuous buffer homogenizing unit (10), the continuous magnesium removal unit (20), the multi-effect falling-film evaporator (30), the single-effect evaporation crystallizer (40) and the continuous drying unit (50) for automatically controlling each of them.
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