阅读说明：本技术 一种利用氧化镁降低盐湖卤水镁锂比的方法 (Method for reducing magnesium-lithium ratio of salt lake brine by using magnesium oxide ) 是由 张勇 桑子容 韩培林 李陇岗 权彩兄 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种利用氧化镁降低盐湖卤水镁锂比的方法,包括以下步骤：S1：在盐湖老卤中,加入含氧化镁矿产物,得到混合溶液A；S2：向混合溶液通入氯化氢-蒸汽体,得到混合溶液B；S3：将混合溶液B固液分离,并将液体进行结晶、离心后分离,得到MgCl_2·6H_2O和滤液；S4：将MgCl_2·6H_2O用饱和MgCl_2溶液洗涤,回收洗涤后的MgCl_2·6H_2O,并将洗涤液加入S2的混合溶液B中；S5：检测S3滤液中的镁锂浓度,若满足镁锂质量比小于3,则收集该滤液,否则再循环。充分利用了低价矿物和工业废弃物,方便的制得了含镁缺水前驱物,通过缺水前驱物的加入,化学吸附卤水中的游离水,迫使老卤中的氯化镁结晶,从而实现了老卤镁锂比的降低。(The invention discloses a method for reducing the magnesium-lithium ratio of salt lake brine by using magnesium oxide, which comprises the following steps: s1: adding a magnesium oxide-containing ore product into old brine of a salt lake to obtain a mixed solution A; s2: introducing hydrogen chloride-steam into the mixed solution to obtain a mixed solution B; s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl 2 •6H 2 O and a filtrate; s4: mixing MgCl 2 •6H 2 Saturated MgCl for O 2 Washing the solution and recovering the washed MgCl 2 •6H 2 O, adding the washing solution into the mixed solution B of the S2; s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium to lithium is less than 3, and otherwise, recycling. Fully utilizes low-price minerals and industrial wastes, and conveniently prepares magnesium-containing vacancyThe water precursor is added to chemically adsorb free water in the brine and force magnesium chloride in the old brine to crystallize, so that the reduction of the ratio of magnesium to lithium in the old brine is realized.)

1. A method for reducing the magnesium-lithium ratio of salt lake brine by using magnesium oxide is characterized by comprising the following steps:

s1: adding a magnesium oxide-containing ore product into old brine of a salt lake to obtain a mixed solution A;

s2: introducing hydrogen chloride-steam into the mixed solution A to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution, and adding the washing solution into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium to lithium is less than 3, and adding the filtrate into the mixed solution B of S2 to repeat the circulating operation if the mass ratio of magnesium to lithium is not more than 3.

2. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 1, is characterized in that: the mass ratio of magnesium to lithium in the salt lake old brine in S1 is 3-120: 1.

3. the method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 1, is characterized in that: the magnesium oxide-containing ore product in S1 is one or two of industrial waste residue and raw ore.

4. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 1, is characterized in that: the hydrogen chloride-vapor in S2 is a mixed gas of hydrogen chloride and water vapor.

5. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 3, is characterized in that: the raw ore is one or two of brucite ore, serpentine ore and magnesite.

6. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 3, is characterized in that: the industrial waste residue is solid waste obtained after magnesium-containing mineral is calcined and decomposed.

7. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 4, is characterized in that: the mass fraction of hydrogen chloride is > 45%.

8. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 1, is characterized in that: and auxiliary agents can be added into the mixed solution A and the mixed solution B, and the addition amount is 0.1-1% of the mass of the salt lake old brine.

9. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 8, is characterized in that: the auxiliary agent is one or more of fatty alcohol polyoxyethylene ether sodium carboxylate, octadecyl trimethyl ammonium chloride and polyacrylamide.

10. The method for reducing the magnesium-lithium ratio of the salt lake brine by using the magnesium oxide, according to claim 1, is characterized in that: the magnesium oxide-containing ore product and the hydrogen chloride-steam are directly from the industrial product of lithium extraction by a calcined water leaching method.

Technical Field

The invention belongs to the technical field of lithium extraction from brine, and particularly relates to a method for reducing the magnesium-lithium ratio of salt lake brine by using magnesium oxide.

Background

The salt lake is a salinization water body, generally refers to lake with lake water salinity w (NaCleq) >3.5% (more than sea water average salinity), and also includes dry salt lake with surface brine, which is composed of salt deposition and intergranular brine, wherein the brine contains a large amount of sodium, potassium, magnesium, lithium, chlorine, sulfur and other elements, and is one of the important raw materials for extracting lithium element at present.

A plurality of salt lakes exist in China, wherein the Qinghai salt lake region is the most abundant lake region of the salt lake resources in China, the airing condition is good, but the magnesium-lithium ratio of the salt lake resources is high, and great difficulty is brought to the enrichment and separation of lithium; although the amount of the original halogen magnesium lithium reaches 1577:1 although the amount of the original halogen magnesium lithium is the largest in the Carlo salt lake, the lithium ion concentration is low; the reserve of east tai gilel salt lake is minimum, but the magnesium-lithium ratio is minimum, and is 35.2:1 (18: 1 for old brine); the west Ginell salt lake is similar to the east Taiwan, and the ratio of magnesium to lithium is 61: 1; the ratio of magnesium to lithium in Yienden salt lake is 90.5:1 (old brine is 51: 1); and secondly, the magnesium-lithium ratio of the large chadan salt lake is 134:1 (the old brine is 92: 1).

In the prior art, different extraction methods are generally adopted in the lithium extraction technology of salt lake brine according to the molar ratio of magnesium and lithium elements in the brine, and for brine with low lithium content and high magnesium-lithium ratio, a solvent extraction method, an adsorption method, a salting-out method and a calcination water leaching method can be adopted. Wherein, the solvent extraction method has high requirement on the acid corrosion resistance of equipment, the acid-base consumption is high, and the raffinate organic phase residue pollutes the surrounding environment of the salt lake; the adsorption method consumes high power and water, the content of lithium in the eluent is low, and the production stability is poor; HCl gas generated by a calcination water leaching method has high corrosivity, high energy consumption and excessive byproduct amount; the technical process of the salting-out method is carried out under a closed condition, the total recovery yield of lithium is low, and the practical application is difficult; for brine with high lithium content and low magnesium-lithium ratio, an evaporation crystallization separation method and a precipitation method are generally adopted, wherein the precipitation method is divided into two steps of salt field evaporation concentration and precipitation separation, and the evaporation concentration is a process of gradually and naturally evaporating and concentrating brine through salt field solarization and separating high-concentration lithium-containing brine, but the production period of the process is long (15-30 days), the influence of natural conditions is large, and the production efficiency is low.

In the development process of extracting lithium from salt lake brine, the search for a technology for reducing cost, reducing environmental pollution and improving efficiency and recovery rate is still a topic of interest, so that the search for an advantageous technique for extracting lithium from salt lake brine is of great significance. In the process of extracting lithium, the lithium extraction process of the brine with high magnesium-lithium ratio needs to consume more manpower and material resources, and the cost of the brine with low magnesium-lithium ratio in the process of extracting lithium is relatively low. The natural salt lake in nature has high magnesium-lithium ratio, which brings great difficulty to the enrichment and separation of lithium, therefore, the development of the method for reducing the magnesium-lithium ratio of the salt lake brine with low cost, environmental friendliness and high efficiency can greatly reduce the difficulty of lithium extraction.

The Chinese patent with the publication number of CN110342553A discloses a method for reducing the ratio of magnesium to lithium in a salt lake by auxiliary crystallization and salt drying, wherein magnesium salts are directly added into brine, but the magnesium salts have larger dosage and more expensive unit price, thereby causing a larger cost problem; meanwhile, in the industry of extracting lithium by a large amount of calcining water leaching method in the areas around salt lakes, the emission of waste gas containing magnesium oxide waste and hydrogen chloride is large, so that not only is a certain resource waste caused, but also a certain environmental damage is caused.

Disclosure of Invention

The invention aims to provide a method for reducing the magnesium-lithium ratio of salt lake brine by using magnesium oxide, which indirectly adds magnesium oxide waste and hydrogen chloride waste gas step by step to further form a water-deficient precursor and reduces the magnesium-lithium ratio of brine by chemical adsorption.

The invention discloses a method for reducing the magnesium-lithium ratio of salt lake brine by using magnesium oxide, which comprises the following steps:

s1: adding a magnesium oxide-containing ore product into old brine of a salt lake to obtain a mixed solution A;

s2: introducing hydrogen chloride-steam into the mixed solution A to obtain a mixed solution B;

s3: carrying out solid-liquid separation on the mixed solution B, crystallizing and centrifuging the liquid, and then separating to obtain MgCl2.6H2O and filtrate;

s4: washing MgCl2.6H2O with saturated MgCl2 solution, and adding the washing solution into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium to lithium is less than 3, and adding the filtrate into the mixed solution B of S2 to repeat the circulating operation if the mass ratio of magnesium to lithium is not more than 3.

Further, the mass ratio of magnesium to lithium in the salt lake old brine in S1 is 3-120: 1.

further, the magnesium oxide-containing ore product in S1 is one or both of industrial waste slag and raw ore.

Further, the hydrogen chloride-vapor in S2 is a mixed gas of hydrogen chloride and water vapor.

Further, the raw ore is one or two of brucite ore, serpentine ore and magnesite.

Further, the industrial waste residue is solid waste obtained after magnesium-containing mineral is calcined and decomposed.

The calcination water leaching method can generate a large amount of HCl gas and MgO-containing waste residues in the process of extracting lithium, on one hand, the generation of the HCl gas can corrode equipment, and on the other hand, the HCl gas can pollute the environment when being discharged into the environment. The invention provides a method for reducing the magnesium-lithium ratio of salt lake brine, which solves the problems that a byproduct hydrochloric acid generated by a calcining water immersion method corrodes equipment and pollutes the environment, and solves the problems of long period and high cost in the evaporation and concentration process of the salt lake brine, and pollutants are not introduced in the production. The method improves the application value of the by-product generated by the calcining water immersion method, and has the advantages of environmental friendliness, low cost and high efficiency.

Of course, the invention can also adopt raw ore containing magnesium oxide to carry out step-by-step reaction addition, such as brucite ore, serpentine ore and magnesite, the market price of which is about 100 yuan/ton, and effectively provides a magnesium source with lower cost, thereby reducing the cost of industrial process.

Further, the mass fraction of hydrogen chloride is > 45%.

Furthermore, an auxiliary agent can be added into the mixed solution A and the mixed solution B, and the addition amount is 0.1-1% of the mass of the old brine in the salt lake.

Furthermore, the auxiliary agent is one or more of fatty alcohol polyoxyethylene ether sodium carboxylate, octadecyl trimethyl ammonium chloride and polyacrylamide.

The magnesium chloride hexahydrate crystal particles are enlarged, solid-liquid separation is facilitated, and the crystallization auxiliary agent enables the magnesium chloride hexahydrate crystals to be crystallized more perfectly, so that the entrainment of the magnesium chloride hexahydrate crystals to lithium liquid is reduced.

The method indirectly introduces the waste residue containing magnesium oxide and the water vapor containing HCl into the brine, and the specific chemical reaction equation is as follows: MgO +2HCl = MgCl₂+ H2O, on the other hand HCl in water and Mg in brine²⁺Salt with MgCl₂In the form of MgCl₂Crystallizing the mixed solution to obtain MgCl₂•6H₂Coarse crystal of O and large amount of Mg in bittern²⁺With MgCl₂•6H₂The O coarse crystals are taken out, the process not only effectively utilizes the magnesium oxide waste residues and HCl-containing waste gases generated by a calcining water leaching method, but also reduces the magnesium-lithium ratio of the salt lake brine; and in MgCl₂•6H₂In the process of generating O coarse crystals, water molecules are taken out in the form of crystal water, and brine is further concentrated; MgCl produced₂•6H₂The O crystal is calcined to obtain MgO, the MgO can be further recycled, no impurity is introduced into the salt lake, the production process is simple, and the equipment investment is low. On the other hand, Mg²⁺The saturated solution is obtained into needle-shaped MgCl in the process of natural evaporation crystallization₂•6H₂O, difficult to separate from brine, and Mg added²⁺Salt can induce the production of a large amount of particulate MgCl₂•6H₂O, particulate MgCl₂•6H₂O is easy to separate from brine by means of sedimentation.

The invention has the beneficial effects that:

(1) the low-price minerals and industrial wastes are fully utilized, the magnesium-containing water-deficient precursor is conveniently prepared (no special or complex equipment is added), and the free water in the brine is chemically adsorbed by adding the water-deficient precursor, so that the magnesium chloride in the old brine is forced to be crystallized, and the reduction of the magnesium-lithium ratio of the old brine is realized.

(2) According to the invention, through the addition of the auxiliary agent, the magnesium chloride hexahydrate crystal particles are enlarged, solid-liquid separation is facilitated, and meanwhile, the crystallization auxiliary agent enables the magnesium chloride hexahydrate crystal to be crystallized more perfectly, so that the entrainment of the magnesium chloride hexahydrate crystal to lithium liquid is reduced.

(3) The industrial waste (the industrial waste residue containing magnesium oxide and the waste gas containing hydrogen chloride) is low in price, the production cost is reduced, and meanwhile, the utilization rate of the industrial waste is improved.

Drawings

FIG. 1 is a process flow diagram of the invention for reducing the magnesium-lithium ratio of salt lake brine;

FIG. 2 is a diagram showing the effect of crystallization after addition of an auxiliary according to the present invention;

FIG. 3 is a graph showing the effect of crystallization without addition of an auxiliary according to the present invention.

Detailed Description

The invention will be further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, various changes or modifications of the present invention may be made by those skilled in the art, and equivalents may fall within the scope of the claims of the present application. The proportions in the examples of the invention are by weight.

Example 1

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 59: 1, directly adding industrial waste residue containing magnesium oxide generated in the lithium extraction industry by a calcination water leaching method to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Example 2

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 43: 1 adding industrial waste residue containing magnesium oxide generated in the lithium extraction industry by a calcination water leaching method to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Example 3

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 18:1 adding industrial waste residue containing magnesium oxide generated in the lithium extraction industry by a calcination water leaching method to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: solid-liquid separation is carried out on the mixed solution B, and the liquid is separated after crystallization and centrifugation,to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Example 4

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 59: 1, directly adding brucite ore to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Example 5

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 59: 1, directly adding magnesite to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Example 6

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 120: 1, directly adding serpentine ore to obtain a mixed solution A;

s2: introducing industrial waste gas (hydrogen chloride-steam gas) generated in the lithium extraction industry by a calcination water leaching method into the mixed solution to obtain a mixed solution B;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S2;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S2 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Comparative example 1

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 59: 1, directly adding Mg2+ salt to directly obtain a mixed solution B;

s2: hydrogen chloride-steam gas does not need to be introduced;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂The lithium entrained in the O enters the washing liquid and the washing liquid is added to the S1 in the mixed solution B;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S1 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Comparative example 2

S1: in salt lake brine, wherein the mass ratio of magnesium to lithium in the brine is in the range of 59: 1, directly adding Mg2+ salt to directly obtain a mixed solution B;

s2: hydrogen chloride-steam gas does not need to be introduced;

s3: separating solid from liquid of the mixed solution B, crystallizing and centrifuging the liquid, and separating to obtain MgCl₂•6H₂O and a filtrate;

s4: mixing MgCl₂•6H₂Saturated MgCl for O₂Washing the solution to obtain MgCl₂•6H₂Lithium carried in the O enters a washing solution, and the washing solution is added into the mixed solution B of S1;

s5: and detecting the concentration of magnesium and lithium in the S3 filtrate, collecting the filtrate if the mass ratio of magnesium and lithium is less than 3, or adding the filtrate into the mixed solution B of S1 for repeated circulating operation, and finally obtaining the standard-reaching solution.

Evaluation: in conclusion, it can be seen that the solid waste obtained after the calcination and decomposition of the minerals containing magnesium chloride is used as a magnesium source and added into the brine to reduce the magnesium-lithium ratio, the additional cost is not required to be increased, and only a pipeline for conveying the raw materials is required to be built in the early stage; the brucite ore/magnesite and serpentine are used as magnesium sources to be added into brine, and only a small amount of raw ore is consumed to obtain standard-reaching liquid; in the comparative example, magnesium salt is directly added as a magnesium source, although HCl-containing waste gas is not required to be introduced, the chemical reagent is high in price, so that the method provided by the invention has a great cost advantage compared with a method for reducing the magnesium-lithium ratio by directly adding the magnesium source under the condition of obtaining the same benefit.

The embodiments of the present invention have been described above by way of example, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the application of the present invention shall fall within the scope of the patent of the present invention.