A method for extracting lithium from high-sodium oilfield brines

Abstract

This invention discloses a method for extracting lithium from oilfield brine with high sodium chloride content. The method includes the following steps: (1) using evaporation and crystallization to precipitate sodium chloride from the oilfield brine with high sodium chloride content, obtaining a lithium-enriched mother liquor; (2) adding hydrochloric acid to the lithium-enriched mother liquor to adjust the pH, and introducing chlorine gas to convert bromide ions in the solution into bromine gas, obtaining a bromine by-product and a debromine-removed mother liquor; (3) adding liquid alkali to the debromine-removed mother liquor, and using an adsorbent to adsorb and desorb the lithium element in the solution, obtaining a lithium chloride solution. The method of this invention can make full use of by-products to increase economic benefits and significantly reduce costs. The production process does not require the use of large amounts of acid and alkali. Only pH adjustment and the use of a small amount of hydrochloric acid and sodium hydroxide are needed to recover bromine by-products and lithium chloride, etc. Moreover, the hydrochloric acid and liquid alkali neutralize to generate sodium chloride in the subsequent process, which is consistent with the original composition of the brine, has no environmental pollution, and can be directly returned to the oilfield.

Description

Technical Field

[0001] This invention relates to the field of oilfield brine resource development and comprehensive utilization technology, and to a method for extracting lithium from oilfield brine with high sodium chloride content. Background Technology

[0002] Currently, lithium extraction technology from oilfield brine in China is in its initial stage, and various technologies face numerous challenges in large-scale industrial application. Existing research primarily focuses on the traditional evaporation and concentration followed by sodium carbonate precipitation for lithium extraction.

[0003] CN108584995A discloses a method for the comprehensive extraction of lithium, potassium, and boron from oilfield brine. The process includes: pretreatment; evaporation and crystallization to precipitate sodium salts to obtain sodium extraction mother liquor; evaporation and crystallization of the sodium extraction mother liquor to precipitate potassium salts to obtain potassium extraction mother liquor; purification of the potassium extraction mother liquor with lime milk and Glauber's salt to obtain purified potassium extraction mother liquor; addition of hydrochloric acid or sulfuric acid to the purified potassium extraction mother liquor to obtain crude boric acid and crude lithium-containing mother liquor; evaporation and concentration of the crude lithium-containing mother liquor, followed by chelation or adsorption purification to obtain refined lithium-rich mother liquor; and alkali precipitation and washing of the refined lithium-rich mother liquor to obtain crude lithium carbonate. This process applies salt field technology and chemical separation methods to the separation and extraction of lithium, potassium, and boron resources from oilfield brine.

[0004] CN101007642A discloses a method for producing lithium carbonate from oilfield brine. The process flow of this method includes removing ammonium magnesium from lime water, removing calcium from sodium sulfate, removing water by evaporation, removing calcium from oxalic acid, precipitating lithium with soda ash, and washing the product with crude lithium salt. The process conditions are as follows: the volume ratio of raw brine to quicklime is 100:10-30, the mass ratio of ammonium magnesium removal brine to sodium sulfate is 100:15-38, the specific gravity of the brine at the evaporation endpoint is 1.25-1.30, the mass ratio of lithium-rich brine to oxalic acid is 100:0.3-1.5, and the mass ratio of lithium extraction brine to soda ash is 100:5-20.

[0005] However, existing technologies do not make full use of by-products, resulting in low economic efficiency. Moreover, the large amount of acid or alkali used not only increases costs but also leads to difficulties in post-processing and is environmentally unfriendly. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a method for extracting lithium from oilfield brine with high sodium chloride content.

[0007] In this invention, "high sodium chloride oilfield brine" refers to oilfield brine with a sodium chloride concentration greater than 15% and less than 26%, such as 16%, 18%, 20%, 25%, etc.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for extracting lithium from oilfield brine with high sodium chloride content, the method comprising the following steps:

[0010] (1) Sodium chloride in oilfield brine with high sodium chloride content is precipitated by evaporation crystallization to obtain lithium-enriched mother liquor;

[0011] (2) Add hydrochloric acid to the mother liquor after lithium enrichment to adjust the pH to acidic conditions to obtain a bromine-containing solution. Pass the bromine-containing solution and chlorine gas into the reaction vessel to convert the bromide ions in the bromine-containing solution into bromine gas, and obtain bromine by-product and bromine-removed mother liquor.

[0012] (3) After adding sodium hydroxide to the bromine removal mother liquor, the lithium element in the solution is adsorbed and desorbed to obtain a lithium chloride solution.

[0013] In one embodiment, the bromine byproduct is bromine, with the chemical formula Br2, which is a liquid at room temperature.

[0014] Oilfield brine is characterized by its high oil content, which severely impacts subsequent adsorption efficiency and leads to loss of adsorbent activity. Furthermore, due to the high sodium chloride content (nearly saturation) and low lithium concentration in oilfield brine, sodium chloride precipitates more readily than lithium chloride during lithium extraction, making traditional evaporation, concentration, and crystallization processes ineffective for separation and extraction. The method of this invention selectively adsorbs and extracts lithium chloride, significantly reducing the influence of sodium chloride on the lithium extraction process.

[0015] In the method of the present invention, sodium chloride is obtained by evaporation and crystallization in step (1), and lithium element in the mother liquor is enriched, which is beneficial to the subsequent extraction of lithium element. In step (2), hydrochloric acid is used to adjust the pH to acidic conditions and chlorine gas is used in combination, which can convert bromide ions in the solution into bromine byproducts. Moreover, the use of hydrochloric acid can neutralize sodium hydroxide in subsequent steps and convert it into sodium chloride.

[0016] In the method of this invention, the pH needs to be adjusted to acidic conditions to avoid alkaline substances consuming chlorine gas and generating impurities.

[0017] The method provided by this invention can extract lithium from oilfield brine with high sodium chloride and low lithium content. The process makes full use of by-products to increase economic benefits and significantly reduce costs. The production process does not require the use of large amounts of acid and alkali. Only pH adjustment and the use of a small amount of hydrochloric acid and sodium hydroxide are needed to recover bromine by-products and lithium chloride. Moreover, hydrochloric acid and sodium hydroxide neutralize to generate sodium chloride in the later process. The elemental composition of the mother liquor after lithium extraction remains basically unchanged and is consistent with the original composition of the brine. It does not pollute the environment and can be directly returned to the oilfield. No new substances need to be added in the front-end process.

[0018] The method of this invention can efficiently extract lithium from oilfield brine, and has the advantages of simple operation, strong applicability, full extraction of by-products, high economic benefits, significant reduction in production costs, high bromine yield and lithium extraction efficiency, with a comprehensive yield of over 70%, reducing resource waste. Furthermore, the adsorption-exchange process in this invention is a room-temperature reaction, reducing equipment requirements. Bromine yield refers to the proportion of bromine in the bromine by-products to the total bromine content in the brine. Lithium extraction efficiency refers to the proportion of lithium adsorbed by the adsorbent to the total lithium content in the brine. Total brine refers to the high-sodium chloride oilfield brine in step (1). Comprehensive yield refers to the proportion of lithium in the final product (e.g., lithium carbonate) to the total lithium content in the brine.

[0019] The present invention does not limit the form in which sodium hydroxide is added; it can be in solid or liquid form. Liquid sodium hydroxide is also called liquid alkali.

[0020] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0021] Preferably, the method further includes a pretreatment step, which includes: extracting high-sodium chloride oilfield brine from the bottom layer and filtering it through an ultrafiltration membrane to remove organic impurities.

[0022] Preferably, step (1) includes: evaporating the water in the high sodium chloride oilfield brine to remove 50%-80% (e.g., 50%, 52%, 55%, 57%, 60%, 65%, 70%, 75% or 80% of the water), removing the sodium chloride, and obtaining the mother liquor enriched with sodium chloride and lithium.

[0023] Preferably, the lithium concentration in the lithium-enriched mother liquor is between 100 ppm and 300 ppm, such as 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 200 ppm, 220 ppm, 240 ppm, 260 ppm, 280 ppm, or 300 ppm. The lithium concentration is based on the total mass of the lithium-enriched mother liquor.

[0024] Preferably, in step (2), the pH is adjusted to 2-3, such as 2, 2.3, 2.6 or 3.

[0025] Preferably, the volume of chlorine gas introduced is 100 to 150 times the volume of the bromine-containing solution introduced, for example, 110, 115, 120, 125, 130, 135, 140, 145, or 150 times.

[0026] Preferably, the chlorine gas is introduced at a rate of 9 m / s. 3 / h -15m 3 / h, for example, 9m 3 / h, 10m 3 / h、11m 3 / h、12m 3 / h、13m 3 / h, 14m 3 / h or 15m 3 / h etc.

[0027] Preferably, the bromine-containing solution is introduced at a rate of 0.06 m. 3 / h -0.15m 3 / h, for example 0.06m 3 / h, 0.07m 3 / h, 0.08m 3 / h, 0.1m 3 / h, 0.12m 3 / h, 0.13m 3 / h, 0.14m 3 / h or 0.15m 3 / h etc.

[0028] Preferably, in step (3), sodium hydroxide is added to make the pH of the solution after the reaction 7.

[0029] Preferably, the adsorbent in step (3) is columnar, and the type of adsorbent is selected from at least one of aluminum-based adsorbents, manganese-based adsorbents, or titanium-based adsorbents.

[0030] Preferably, the method in step (3) further includes separating the adsorbent containing lithium and returning the resulting lithium-extracted mother liquor to the oil field.

[0031] Preferably, the desorption method includes: washing the lithium element in the adsorbent containing the lithium element with water to obtain a lithium chloride solution.

[0032] Preferably, the concentration of the lithium chloride solution is 300ppm-500ppm, such as 300ppm, 325ppm, 350ppm, 375ppm, 400ppm, 450ppm, or 500ppm. The concentration of the lithium chloride solution refers to the mass content of lithium chloride based on the total mass of the lithium chloride solution.

[0033] As a preferred embodiment of the method of the present invention, the method further includes a step of purifying the lithium chloride solution, the purification step including: passing the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane and a nanofiltration membrane for filtration to obtain a purified lithium chloride solution.

[0034] Lithium chloride solutions can be filtered through ultrafiltration membranes to remove large molecular impurities, through reverse osmosis membranes to enrich low-content lithium elements, and through nanofiltration membranes to remove divalent and trivalent metal ion impurities such as calcium, magnesium, and iron.

[0035] Preferably, the method further includes evaporating, concentrating, and crystallizing the lithium chloride purification solution to obtain a lithium chloride product.

[0036] Preferably, the method further includes evaporating and concentrating the lithium chloride purification solution, adding sodium carbonate solution, separating, and obtaining lithium carbonate product.

[0037] As a further preferred embodiment of the method described in this invention, the method includes the following steps:

[0038] S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer and filters it through an ultrafiltration membrane to remove organic impurities, thus obtaining pretreated oilfield brine.

[0039] Among them, the sodium chloride mass fraction of oilfield brine with high sodium chloride and low lithium content is greater than 15% and less than 26%, the COD value is 1500ppm-100000ppm (e.g., 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 8000ppm, 10000ppm, 12000ppm, 15000ppm, 20000ppm, 25000ppm, 30000ppm, 35000ppm, 400000ppm, 45000ppm, 50000ppm, 60000ppm, 70000ppm, 80000ppm or 100000ppm, etc.), and the lithium ion concentration is <100ppm (e.g., 90ppm, 85ppm, 80ppm, 75ppm, 70ppm, 65ppm, 60ppm, 55ppm, 50ppm, 40ppm or 30ppm, etc.).

[0040] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 50%-80% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor. The lithium concentration in the lithium-enriched mother liquor is 100ppm-300ppm.

[0041] S3 adds hydrochloric acid to the mother liquor after lithium enrichment to adjust the pH to 2-3, and obtains a bromine-containing solution. The bromine-containing solution and chlorine gas are introduced into the reaction vessel to convert the bromide ions in the bromine-containing solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain a bromine byproduct and a bromine-removed mother liquor.

[0042] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0043] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0044] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0045] S6 evaporates, concentrates, and crystallizes the lithium chloride purification solution to obtain the lithium chloride product;

[0046] Alternatively, the lithium chloride purification solution can be evaporated and concentrated, then sodium carbonate solution can be added and separated to obtain the lithium carbonate product.

[0047] In one embodiment, the evaporation concentration is 10%-20%, such as 10%, 12%, 14%, 15%, 17%, 18%, or 20%.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with existing technologies, the present invention has the following beneficial effects:

[0050] (1) The method provided by the present invention can extract lithium from oilfield brine with high sodium chloride and low lithium content. The process makes full use of by-products to increase economic benefits and significantly reduce costs. The production process does not require the use of large amounts of acid and alkali. Only pH adjustment and the use of a small amount of hydrochloric acid and sodium hydroxide are needed to recover bromine by-products and lithium chloride. In addition, hydrochloric acid and sodium hydroxide neutralize to generate sodium chloride in the later process. The elemental composition of the mother liquor after lithium extraction remains basically unchanged and is consistent with the original composition of the brine. It does not pollute the environment and can be directly returned to the oilfield. No new substances need to be added in the front-end process.

[0051] (2) The method of the present invention can efficiently extract lithium from oilfield brine. It has the advantages of simple operation, strong applicability, full extraction of by-products, high economic benefits, significant reduction in production costs, and high lithium extraction efficiency. The overall yield can reach more than 70%, reducing resource waste. At the same time, in the method of the present invention, the adsorption exchange process is a room temperature reaction, which reduces the requirements for equipment. Attached Figure Description

[0052] Figure 1 This is a schematic flowchart of a method for extracting lithium from oilfield brine with high sodium chloride content, provided by one embodiment of the present invention. Detailed Implementation

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0054] This invention provides a method for extracting lithium from oilfield brine with high sodium chloride content. A schematic flowchart is shown below. Figure 1 The method includes the following steps:

[0055] S1 extracts high-sodium chloride oilfield brine from the bottom layer and filters it through an ultrafiltration membrane to remove organic impurities, thus obtaining pretreated oilfield brine.

[0056] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 50%-80% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor. The lithium concentration in the lithium-enriched mother liquor is 100ppm-300ppm.

[0057] S3 adds hydrochloric acid to the mother liquor after lithium enrichment to adjust the pH to 2-3, and obtains a bromine-containing solution. The bromine-containing solution and chlorine gas are introduced into the reaction vessel to convert the bromide ions in the bromine-containing solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain a bromine byproduct and a bromine-removed mother liquor.

[0058] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0059] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0060] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0061] S6 evaporates, concentrates, and crystallizes the lithium chloride purification solution to obtain the lithium chloride product;

[0062] Alternatively, the lithium chloride purification solution can be evaporated and concentrated, then sodium carbonate solution can be added and separated to obtain the lithium carbonate product.

[0063] In this embodiment of the invention, the composition of oilfield brine with high sodium chloride has two typical index values, as shown in Sample 1 and Sample 2 in Table 1. The mass fraction of sodium chloride in the oilfield brine shown in Sample 1 is 23.5%, and the COD value is 1900 ppm; the mass fraction of sodium chloride in the oilfield brine shown in Sample 2 is 22.5%, and the COD value is 1600 ppm.

[0064] Table 1

[0065]

[0066] Example 1

[0067] This embodiment provides a method for extracting lithium from oilfield brine with high sodium chloride content, the method comprising the following steps:

[0068] S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer (the composition is shown in Sample 1 in Table 1), filters it through an ultrafiltration membrane to remove organic impurities, and obtains pretreated oilfield brine.

[0069] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 80% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor, in which the lithium concentration is 275 ppm.

[0070] S3 adds hydrochloric acid to the lithium-enriched mother liquor to adjust the pH to 3, obtaining a bromine-containing solution. The bromine-containing solution and chlorine gas are then introduced into the reaction vessel at a rate of 11 m / s. 3 The rate of bromine-containing solution flow is 0.1 m / h. 3 / h, the chlorine gas is introduced in a volume 110 times that of the bromine-containing solution, converting bromide ions in the solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain bromine byproducts and bromine removal mother liquor.

[0071] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0072] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0073] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0074] S6 evaporates, concentrates, and crystallizes the lithium chloride purification solution to obtain the lithium chloride product.

[0075] Example 2

[0076] This embodiment provides a method for extracting lithium from oilfield brine with high sodium chloride content, the method comprising the following steps:

[0077] S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer (the composition is shown in Sample 1 in Table 1), filters it through an ultrafiltration membrane to remove organic impurities, and obtains pretreated oilfield brine.

[0078] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 70% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor, in which the lithium concentration is 180 ppm.

[0079] S3 adds hydrochloric acid to the lithium-enriched mother liquor to adjust the pH to 3, obtaining a bromine-containing solution. The bromine-containing solution and chlorine gas are then introduced into the reaction vessel at a rate of 11 m / s. 3 The rate of bromine-containing solution flow is 0.1 m / h. 3 / h, the chlorine gas is introduced in a volume 110 times that of the bromine-containing solution, converting bromide ions in the solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain bromine byproducts and bromine removal mother liquor.

[0080] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0081] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0082] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0083] S6 evaporates and concentrates the lithium chloride purification solution, adds sodium carbonate solution, and separates to obtain lithium carbonate product.

[0084] Example 3

[0085] This embodiment provides a method for extracting lithium from oilfield brine with high sodium chloride content, the method comprising the following steps:

[0086] S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer (the composition is shown in Sample 1 in Table 1), filters it through an ultrafiltration membrane to remove organic impurities, and obtains pretreated oilfield brine.

[0087] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 60% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor, in which the lithium concentration is 135 ppm.

[0088] S3 adds hydrochloric acid to the lithium-enriched mother liquor to adjust the pH to 3, obtaining a bromine-containing solution. The bromine-containing solution and chlorine gas are then introduced into the reaction vessel at a rate of 11 m / s. 3 The rate of bromine solution flow is 0.1 m / h. 3 / h, the chlorine gas is introduced in a volume 110 times that of the bromine-containing solution, converting bromide ions in the solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain bromine byproducts and bromine removal mother liquor.

[0089] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0090] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0091] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0092] S6 evaporates, concentrates, and crystallizes the lithium chloride purification solution to obtain the lithium chloride product.

[0093] Example 4

[0094] This embodiment provides a method for extracting lithium from oilfield brine with high sodium chloride content, the method comprising the following steps:

[0095] S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer (composition see Sample 2 in Table 1), filters it through an ultrafiltration membrane to remove organic impurities, and obtains pretreated oilfield brine.

[0096] S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 50% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor, in which the lithium concentration is 110 ppm.

[0097] S3 adds hydrochloric acid to the lithium-enriched mother liquor to adjust the pH to 3, obtaining a bromine-containing solution. The bromine-containing solution and chlorine gas are then introduced into the reaction vessel at a rate of 11 m / s. 3 The rate of bromine-containing solution flow is 0.1 m / h. 3 / h, the chlorine gas is introduced in a volume 110 times that of the bromine-containing solution, converting bromide ions in the solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain bromine byproducts and bromine removal mother liquor.

[0098] S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field.

[0099] After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution.

[0100] S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

[0101] S6 evaporates and concentrates the lithium chloride purification solution, adds sodium carbonate solution, and separates to obtain lithium carbonate product.

[0102] Example 5

[0103] The difference from Example 1 is that hydrochloric acid was added to adjust the pH to 1.

[0104] Example 6

[0105] The difference from Example 1 is that hydrochloric acid was added to adjust the pH to 5.

[0106] Example 7

[0107] The difference from Example 1 is that the chlorine gas flow rate is 15m³. 3 / h.

[0108] Example 8

[0109] The difference from Example 1 is that the chlorine gas flow rate is 9m³. 3 / h.

[0110] Comparative Example 1

[0111] The difference from Example 1 is that hydrochloric acid is not added, and the pH value of the system is 8-10.

[0112] The system contains alkaline substances, consumes more chlorine gas, and generates impurities.

[0113] Comparative Example 2

[0114] The difference from Example 1 is that the order of steps S2 and S3 is reversed.

[0115] test:

[0116] The bromine extraction rate was obtained by detecting the bromine content before and after bromine extraction, and the lithium yield of the adsorption section was obtained by detecting the lithium content before and after lithium adsorption extraction. The overall lithium yield was obtained by detecting and calculating the ratio of the final produced lithium to the input lithium. The results are shown in Table 2.

[0117] Table 2

[0118]

[0119] Note: The lithium adsorption section yield refers to the lithium extraction rate in step S4.

[0120] (1) As shown in Table 2, the method of the present invention can efficiently extract lithium from oilfield brine. It has the advantages of simple operation, strong applicability, full extraction of by-products, high economic benefits, significant reduction in production costs, high bromine yield and high lithium extraction efficiency. The overall yield can reach more than 70%, reducing resource waste. At the same time, in the method of the present invention, the adsorption exchange process is a room temperature reaction, which reduces the requirements for equipment.

[0121] (2) Compared with Example 1, in Example 2, the amount of water evaporated by sodium precipitation is slightly smaller. The concentrations of bromine and lithium in the remaining solution after evaporation are lower than those in Example 1. The lower the concentration, the less favorable it is for the efficiency of bromine extraction by blowing gas and the lower the efficiency of lithium extraction by adsorption, resulting in a lower yield of bromine and lithium than in Example 1.

[0122] (3) Compared with Example 1, in Example 3, the amount of water evaporated by sodium precipitation is slightly smaller, and the concentrations of bromine and lithium in the remaining solution after evaporation are lower than those in Example 1. The lower the concentration, the less favorable it is for the efficiency of bromine extraction by blowing gas and the lower the efficiency of lithium extraction by adsorption, resulting in a lower yield of bromine and lithium than in Example 1.

[0123] (4) Compared with Example 1, in Example 4, the amount of water evaporated by sodium precipitation is small, and the concentrations of bromine and lithium in the remaining solution after evaporation are lower than those in Example 1. The lower the concentration, the less favorable it is for the efficiency of bromine extraction by blowing gas and the lower the efficiency of lithium extraction by adsorption, resulting in a lower yield of bromine and lithium than in Example 1.

[0124] (5) Compared to Example 1, the solution in Example 5 has a lower pH, which reduces the amount of chlorine dissolved in water, affecting the rate and efficiency of the reaction between chlorine and bromine, and ultimately reducing the yield of bromine. At the same time, a large amount of acid will damage the lithium adsorbent, affecting its adsorption capacity and reducing the yield of lithium.

[0125] (6) Compared with Example 1, the pH of the solution in Example 6 is higher. After the chlorine dissolves, it is easy to react with the alkaline salts in the solution, which affects the reaction efficiency with bromine and reduces the yield of bromine.

[0126] (7) In Example 7, compared to Example 1, the chlorine gas flow rate was increased from 11m³. 3 / h increased to 15m 3 / h, the yield of bromine and lithium elements is not affected, but it will cause excessive waste of chlorine when used in production.

[0127] (8) In Example 8, compared to Example 1, the chlorine gas flow rate was reduced from 11m³. 3 / h decreased to 9m 3 The reduced chlorine usage per hour led to a decrease in the efficiency of the bromine reaction, thus reducing the bromine yield.

[0128] (9) In Comparative Example 1, the chlorine gas introduced first reacts with the alkaline substances in the solution, generating impurities and reducing the reaction efficiency with bromine, resulting in a decrease in bromine yield and an increase in chlorine consumption.

[0129] (10) In Comparative Example 2, bromine was extracted before sodium precipitation and evaporation, resulting in low bromine content in the solution and significantly reducing the bromine yield.

[0130] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for extracting lithium from oilfield brine with high sodium chloride content, characterized in that, The concentration of sodium chloride in the high-sodium-chloride oilfield brine is greater than 15% and less than 26%, and the COD value is 1500ppm-100000ppm. The method includes the following steps: (1) Evaporate the water in the oilfield brine with high sodium chloride to remove 50%-80% of the water, and take out the sodium chloride to obtain the mother liquor enriched with sodium chloride and lithium. (2) Add hydrochloric acid to the mother liquor after lithium enrichment to adjust the pH to acidic conditions to obtain a bromine-containing solution. Pass the bromine-containing solution and chlorine gas into the reaction vessel to convert the bromide ions in the bromine-containing solution into bromine gas, and obtain bromine by-product and bromine-removed mother liquor. (3) After adding sodium hydroxide to the bromine removal mother liquor, the lithium element in the solution is adsorbed and desorbed to obtain a lithium chloride solution.

2. The method according to claim 1, characterized in that, The method further includes a pretreatment step, which includes: extracting high-sodium chloride oilfield brine from the bottom layer and filtering it through an ultrafiltration membrane to remove organic impurities.

3. The method according to claim 1, characterized in that, The lithium concentration in the mother liquor after lithium enrichment is 100ppm-300ppm.

4. The method according to claim 1, characterized in that, In step (2), adjust the pH to 2-3.

5. The method according to claim 1, characterized in that, The volume of chlorine gas introduced is 100 to 150 times the volume of the bromine-containing solution introduced.

6. The method according to claim 1, characterized in that, The chlorine gas was introduced at a rate of 9m. 3 / h -15m 3 / h.

7. The method according to claim 1, characterized in that, The bromine-containing solution was introduced at a rate of 0.06 m / s. 3 / h-0.15m 3 / h.

8. The method according to claim 1, characterized in that, In step (3), sodium hydroxide is added to make the pH of the solution after the reaction 7.

9. The method according to claim 1, characterized in that, In step (3), the adsorbent is columnar, and the type of adsorbent is selected from at least one of aluminum-based adsorbents, manganese-based adsorbents, or titanium-based adsorbents.

10. The method according to claim 1, characterized in that, The method in step (3) further includes separating the adsorbent that adsorbs lithium elements and returning the resulting lithium-extracted mother liquor to the oil field.

11. The method according to claim 1, characterized in that, The desorption method includes: washing the lithium element out of the adsorbent containing the lithium element with water to obtain a lithium chloride solution.

12. The method according to claim 11, characterized in that, The concentration of the lithium chloride solution is 300ppm-500ppm.

13. The method according to claim 11, characterized in that, The method further includes a step of purifying the lithium chloride solution, which includes: filtering the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution.

14. The method according to claim 13, characterized in that, The method further includes evaporating, concentrating, and crystallizing the lithium chloride purification solution to obtain a lithium chloride product.

15. The method according to claim 13, characterized in that, The method further includes evaporating and concentrating the lithium chloride purification solution, adding sodium carbonate solution, separating, and obtaining lithium carbonate product.

16. The method according to claim 1, characterized in that, The method includes the following steps: S1 extracts oilfield brine with high sodium chloride and low lithium content from the bottom layer and filters it through an ultrafiltration membrane to remove organic impurities, thus obtaining pretreated oilfield brine. Among them, the mass fraction of sodium chloride in oilfield brine with high sodium chloride and low lithium content is greater than 15% and less than 26%, the COD value is 1500ppm-100000ppm, and the lithium ion concentration is <100ppm. S2 uses an MVR evaporator to evaporate the water in the oilfield brine, removing 50%-80% of the water. The precipitated sodium chloride is then removed by a centrifuge to obtain a lithium-enriched mother liquor. The lithium concentration in the lithium-enriched mother liquor is 100ppm-300ppm. S3 adds hydrochloric acid to the mother liquor after lithium enrichment to adjust the pH to 2-3, and obtains a bromine-containing solution. The bromine-containing solution and chlorine gas are introduced into the reaction vessel to convert the bromide ions in the bromine-containing solution into bromine gas. The bromine gas escaping from the surface is collected by blowing air to obtain a bromine byproduct and a bromine-removed mother liquor. S4 adds liquid alkali to the bromine removal mother liquor, and the liquid alkali reacts with hydrochloric acid. The pH of the solution after the reaction is 7. The resulting solution is circulated through an adsorption column, and lithium elements are adsorbed onto the adsorption column. The resulting lithium-extracted mother liquor is returned to the oil field. After the adsorption column is saturated, lithium is washed out with water to achieve desorption and obtain a lithium chloride solution. S5 filters the lithium chloride solution sequentially through an ultrafiltration membrane, a reverse osmosis membrane, and a nanofiltration membrane to obtain a purified lithium chloride solution. S6 evaporates, concentrates, and crystallizes the lithium chloride purification solution to obtain the lithium chloride product; Alternatively, the lithium chloride purification solution can be evaporated and concentrated, then sodium carbonate solution can be added and separated to obtain the lithium carbonate product.

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