System and method for separating lithium in oilfield brine

Abstract

The invention provides a system and method for separating lithium in oil field brine, and the system comprises an extraction unit which is used for carrying out extraction and phase separation on the oil field brine and an extraction system, the main extraction agent is prepared from at least one of 1-hexyl-3-butylimidazole hexafluorophosphate, 1-hexyl-3-butylimidazole bis (trifluoromethanesulfonimide) salt, 1-octyl-3-butylimidazole hexafluorophosphate, and 1-octyl-3-butylimidazole bis (trifluoromethanesulfonimide) salt; the main extraction agent is prepared from at least one of the following components: 1-hexyl-3-butylimidazole hexafluorophosphate, 1-hexyl-3-butylimidazole bis (trifluoromethanesulfonimide) salt; the elution unit is communicated with the extraction unit and is used for mixing and eluting the organic phase obtained by the extraction unit and an eluent to obtain a water phase and an organic phase; and the reverse extraction unit is communicated with the elution unit and is used for mixing the organic phase obtained by the elution unit with a reverse extraction solution and performing reverse extraction to obtain an organic phase and a water phase, and the water phase is a lithium-containing solution. According to the method, the specific ionic liquid extraction agent is used for extracting the lithium in the oil field brine, acid and alkali are not needed to regulate the pH value, an emulsification phenomenon is avoided in the extraction process, and the extraction rate and the total recovery rate of the lithium ions are relatively high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield brine resource development. Specifically, the present application relates to a system and method for separating lithium from oilfield brine. BACKGROUND

[0002] Lithium resources are one of the scarce emerging mineral resources and an important raw material for the new energy automobile industry. Through deep underground brine regional exploration, deep brine coexisting with oil and gas contains abundant lithium resources. Oilfield brine is also called oilfield water. Broadly speaking, oilfield water refers to underground water in the oilfield area, including oil layer water and non-oil layer water. In a narrow sense, oilfield water refers to underground water in the oilfield area directly connected with the oil layer. The extraction of lithium from unconventional brine (oilfield brine and geothermal brine) at home and abroad has basically only completed small-scale experiments and preliminary technical evaluation. The extraction of lithium from oilfield brine in China has just started, and there is an urgent need for oilfield brine lithium extraction technology. To fully exploit and utilize lithium resources, it is necessary to efficiently and selectively extract lithium from oilfield brine containing high concentrations of competitive ions. At present, there have been a large number of studies and reports on the separation and extraction of lithium from high magnesium-lithium ratio systems in salt lake brine, but in calcium chloride type oilfield brine, the concentrations of sodium, potassium, magnesium, and calcium competitive ions are very high, and the problems of high sodium-lithium ratio, high potassium-lithium ratio, and high calcium-lithium ratio need to be solved.

[0003] At present, the effective methods for extracting lithium from oilfield brine include adsorption and solvent extraction, etc. The extraction method is one of the most promising methods for brine lithium extraction. The composition of salt lake brine is different from that of oilfield brine. Oilfield brine in China is characterized by high calcium, sodium, and potassium, and is mostly alkaline. At present, the crown ether extraction system has low selectivity and low lithium loading for high lithium-magnesium ratio and lithium-sodium ratio brine. Although the tributyl phosphate-iron trichloride-kerosene extraction system has been successfully applied to salt lake brine, Fe 3+ It is easy to precipitate under alkaline conditions, and the water phase of the brine requires weak acidity, which is not suitable for the extraction of oilfield brine under alkaline conditions.

[0004] Ionic liquids have the advantages of almost no volatilization, non-toxicity, and environmental protection, and are a good solvent and easy to recover. In addition, ionic liquids as main extractants have achieved high lithium extraction rate and selectivity from high magnesium-lithium ratio salt lake brine.

[0005] A synergistic solvent extraction method for separating lithium and magnesium from high magnesium-lithium ratio salt lake brine using an ionic liquid / trioctyl phosphate is disclosed in Chinese Patent Application No. 202310475637.5. The method uses trioctyl phosphate as an extractant, ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([HOEMIM][Tf2N]) as a synergistic extractant, and (water) as a stripping agent to form an extraction system. After extraction, stripping, and deep magnesium removal, lithium carbonate is prepared. This method uses ionic liquids as the main extractant for efficient extraction and separation of lithium from salt lakes. The ionic liquids are suitable for magnesium-lithium separation but have weak separation effect on sodium and potassium ionic liquids.

[0006] Therefore, further research is needed in the field to separate lithium from oilfield brine. SUMMARY

[0007] The main purpose of the present application is to provide a system and method for separating lithium from oilfield brine. The method is used for the extraction of lithium from oilfield brine, with high extraction rate and high selectivity.

[0008] To achieve the above purpose, the present application provides a system for separating lithium from oilfield brine, comprising:

[0009] An extraction unit for extracting and separating phases of oilfield brine and an extraction system, wherein the extraction system comprises a main extractant, and the main extractant comprises at least one of 1-hexyl-3-butylimidazolium hexafluorophosphate, 1-hexyl-3-butylimidazolium bis(trifluoromethylsulfonyl) imidate, 1-octyl-3-butylimidazolium hexafluorophosphate, and 1-octyl-3-butylimidazolium bis(trifluoromethylsulfonyl) imidate;

[0010] An elution unit in communication with the extraction unit to mix and elute the organic phase obtained from the extraction unit with an eluent, thereby obtaining an aqueous phase and an organic phase;

[0011] A stripping unit in communication with the elution unit to mix and strip the organic phase obtained from the elution unit with a stripping agent, thereby obtaining an organic phase and an aqueous phase, wherein the aqueous phase is a lithium-containing solution.

[0012] The system for separating lithium from oilfield brine according to the present application further comprises a pretreatment unit in communication with the extraction unit, wherein the pretreatment unit comprises a ultrafiltration device and a nanofiltration device connected in sequence.

[0013] The system for separating lithium from oilfield brine according to the present application further comprises a post-treatment unit in communication with the stripping unit to mix and separate phases of the organic phase obtained from the stripping unit, and the organic phase obtained from the post-treatment unit is recycled as the extraction system.

[0014] The system for separating lithium in oilfield brine, wherein the post-processing unit further comprises a resin impurity removal device, and the aqueous phase obtained by the back extraction unit is subjected to the resin impurity removal device to remove impurities, so as to obtain a lithium-containing solution.

[0015] The system for separating lithium in oilfield brine, wherein the extraction unit comprises a centrifugal dispersion reactor, the elution unit comprises a centrifugal dispersion reactor, and the back extraction unit comprises a centrifugal dispersion reactor.

[0016] To achieve the above-mentioned purpose, the application further provides a method for separating lithium in oilfield brine, comprising:

[0017] Step 1, the oilfield brine is subjected to extraction and phase separation with an extraction system, wherein the extraction system comprises a main extractant, and the main extractant comprises at least one of 1-hexyl-3-butylimidazole hexafluorophosphate, 1-hexyl-3-butylimidazole bistrifluoromethylsulfonimidate, 1-octyl-3-butylimidazole hexafluorophosphate and 1-octyl-3-butylimidazole bistrifluoromethylsulfonimidate.

[0018] Step 2, the organic phase obtained in step 1 is mixed with an eluent to perform elution, so as to obtain an aqueous phase and an organic phase.

[0019] Step 3, the organic phase obtained in step 2 is mixed with a back extraction liquid to perform back extraction, so as to obtain an organic phase and an aqueous phase, wherein the aqueous phase is a lithium-containing solution.

[0020] The method for separating lithium in oilfield brine, wherein the oilfield brine is subjected to ultrafiltration treatment to remove oil and suspended solids and nanofiltration treatment to remove divalent cations before being subjected to extraction and phase separation with the extraction system.

[0021] The method for separating lithium in oilfield brine, wherein the organic phase obtained in step 3 is mixed with an acid liquid to perform phase separation, and the obtained organic phase is recycled as the extraction system; and / or, the aqueous phase obtained in step 3 is subjected to resin impurity removal to remove impurities, so as to obtain a lithium-containing solution.

[0022] The method for separating lithium in oilfield brine, wherein the extraction system further comprises a synergistic extractant, and the synergistic extractant is a trialkyl phosphine oxide, wherein the alkyl group has 1-10 carbons; and the molar ratio of the main extractant to the synergistic extractant is 1-4:4-1.

[0023] The method for separating lithium in oilfield brine, wherein the eluent is a 0.5-1.5 mol / L hydrochloric acid aqueous solution, the back extraction liquid is a 3-5 mol / L hydrochloric acid aqueous solution, the volume ratio of the oilfield brine to the extraction system in step 1 is 5:1-1:5, and the volume ratio of the back extraction liquid to the organic phase obtained in step 2 is (1-5):(1-60).

[0024] Advantages of the present application:

[0025] The present application adopts specific ionic liquid extractant for extracting lithium in oilfield brine, without adding acid and alkali to regulate pH value, without emulsification phenomenon and third phase in the extraction process, and the ionic liquid as a green solvent has high stability, non-flammability, almost no volatility and other characteristics, green and environmental protection. The system and method can improve the extraction rate of lithium ions in oilfield brine to more than 95%, and the total recovery rate of lithium is more than 90%. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a schematic diagram of the system for separating lithium in oilfield brine in an embodiment of the present application.

[0027] Among them, the reference signs:

[0028] 1 extraction unit

[0029] 2 elution unit

[0030] 3 stripping unit DETAILED DESCRIPTION

[0031] The technical solution of the present application is described in detail below, the following embodiments are implemented on the premise of the technical solution of the present application, and the detailed implementation process is given, but the protection scope of the present application is not limited to the following embodiments, and the structure or experimental method without specific conditions in the following embodiments is usually according to the conventional conditions.

[0032] The present application provides a system for separating lithium in oilfield brine, please see Figure 1 , comprising an extraction unit 1, an elution unit 2 and a stripping unit 3.

[0033] The extraction unit is used for extraction and phase separation of oilfield brine and extraction system, the extraction system includes a main extractant, the main extractant includes at least one of 1-hexyl-3-butyl imidazole hexafluorophosphate, 1-hexyl-3-butyl imidazole bis-trifluoromethanesulfonamide salt, 1-octyl-3-butyl imidazole hexafluorophosphate, 1-octyl-3-butyl imidazole bis-trifluoromethanesulfonamide salt;

[0034] The elution unit is in communication with the extraction unit to mix and elute the organic phase obtained from the extraction unit with the eluent, to obtain the water phase and the organic phase;

[0035] The stripping unit is in communication with the elution unit to mix and strip the organic phase obtained from the elution unit with the stripping liquid, to obtain the organic phase and the water phase, wherein the water phase is a lithium-containing solution.

[0036] The oilfield brine of the present application refers to the general oilfield brine, including the underground water of the oil layer and the non-oil layer in the oilfield region. The oilfield brine of the present application is not particularly limited, for example, the oilfield brine contains Li + , Na + , Ca 2+ , Mg 2+ .

[0037] In an embodiment, the extraction unit comprises a centrifugal dispersion reactor, and the oilfield brine and the extraction system are extracted and phase-separated in the centrifugal dispersion reactor to obtain an organic phase (oil phase) or an aqueous phase. The centrifugal dispersion reactor of the present application is not particularly limited, and the conventional centrifugal dispersion reactor in the art can be used.

[0038] In an embodiment, the extraction system further comprises a co-extraction agent. The main extraction agent is at least one of 1-hexyl-3-butyl imidazole hexafluorophosphate ([HMIM][PF6]), 1-hexyl-3-butyl imidazole bistrifluoromethanesulfonimidate ([HMIM][TF2N]), 1-octyl-3-butyl imidazole hexafluorophosphate ([OMIM][PF6]), 1-octyl-3-butyl imidazole bistrifluoromethanesulfonimidate ([OMIM][TF2N]). The co-extraction agent is a trialkyl phosphine oxide, wherein the alkyl group has 1-10 carbons, specifically, can have 2 carbons, 3 carbons, 4 carbons, 5 carbons, 6 carbons, 7 carbons, 8 carbons, 9 carbons, etc., and specifically can be tri-n-octyl phosphine oxide (TRPO), tributyl phosphine oxide (TBPO).

[0039] In an embodiment, the molar ratio of the main extraction agent to the co-extraction agent is 1-4:4-1, and the volume ratio of the oilfield brine to the extraction system is 5:1-1:5, preferably 1:2, in other words, the volume ratio of the organic phase to the aqueous phase obtained after extraction and phase separation is 5:1-1:5.

[0040] In a specific embodiment, the extraction unit further comprises two pumps for delivering the oilfield brine and the extraction system into the centrifugal dispersion reactor, and the rotation speed of the pumps is 200-400 rpm. After 10-20 min, the organic phase and the aqueous phase are obtained, wherein the organic phase is the extraction phase and the aqueous phase is the raffinate phase.

[0041] In an embodiment, the elution unit comprises a centrifugal dispersion reactor, i.e., the elution unit is provided with another centrifugal dispersion reactor, and the organic phase separated from the extraction unit and the eluent are mixed and phase-separated in the centrifugal dispersion reactor to obtain the organic phase and the aqueous phase. In another embodiment, the elution unit comprises two pumps, and the organic phase separated from the extraction unit and the eluent are delivered into the centrifugal dispersion reactor through the two pumps, and after 10-20 min, the organic phase and the aqueous phase are obtained.

[0042] In an embodiment, the eluent is 0.5-1.5 mol / L hydrochloric acid aqueous solution. The amount of the eluent is not particularly limited in the present application, and can be adjusted as needed.

[0043] In an embodiment, the stripping unit comprises a centrifugal dispersion reactor, i.e. the stripping unit is provided with a centrifugal dispersion reactor, the organic phase obtained from the elution unit and the stripping solution are fed into the centrifugal dispersion reactor, mixed, and separated into an organic phase and an aqueous phase, the organic phase containing the main extractant and the co-extractant, and the aqueous phase being a lithium-containing solution, such as a lithium chloride-containing solution.

[0044] In another embodiment, the stripping unit comprises two pumps, the organic phase obtained from the elution unit and the stripping solution are fed into the centrifugal dispersion reactor through the two pumps, extracted, and separated into an organic phase and an aqueous phase after 10-20 min.

[0045] In yet another embodiment, the stripping solution is 3-5 mol / L hydrochloric acid aqueous solution. The volume ratio of the stripping solution to the organic phase obtained from the elution unit is (1-5):(1-60), and further (1-5):(1-50).

[0046] In an embodiment, the system for separating lithium from oilfield brine in the present application further comprises a pretreatment unit, which is in communication with the extraction unit, and the pretreated oilfield brine is fed into the extraction unit; the pretreatment unit comprises an ultrafiltration device and a nanofiltration device connected in sequence. The ultrafiltration device is used to preliminarily remove oil and suspended solids in the oilfield brine, and the nanofiltration device is used to retain divalent cations.

[0047] In another embodiment, the ultrafiltration membrane used in the ultrafiltration device is UEOS503, the membrane material is polysulfone (PS), the molecular weight cut-off is 5000-8000 Dalton, and the membrane surface area is 1-2 m 2 , for example 1.5 m 2 , the applicable pH range is 2-13, the operating temperature range is 5-45℃, and the operating pressure range is 0-0.15 MPa. After the oilfield brine passes through the ultrafiltration device, the oil content is ≤10 mg / L, and the solid suspended solids are ≤10 mg / L.

[0048] In yet another embodiment, the nanofiltration membrane used in the nanofiltration device is DL, the molecular weight cut-off is 150-300, the rejection rate is 98%, the operating pressure is <4 MPa, the temperature is <50℃, the effective pH is 3-9, and the effective membrane area is 0.38 m 2 . In an embodiment, after the oilfield brine passes through the nanofiltration device, the Na + concentration is less than 80 g / L, the Ca 2+ concentration is less than 0.05 g / L, and the Mg 2+less than 0.05 g / L. In another embodiment, the concentration of Li + about 200 mg / L.

[0049] In one embodiment, the system for separating lithium from oilfield brine of the present application further comprises a post-treatment unit in communication with the stripping unit to mix the organic phase obtained from the stripping unit with an acid solution and to separate the phases, and the organic phase obtained from the post-treatment unit is recycled to be used as the extraction system. The post-treatment unit of the present application is mainly used for the regeneration of the primary extractant, for example, comprising a separation device. In one embodiment, the acid solution herein is an aqueous hydrochloric acid solution with a concentration of 2-6 mol / L. The present application does not particularly limit the amount of the organic phase obtained from the stripping unit and the acid solution, which can be selected as needed.

[0050] In one embodiment, the post-treatment unit further comprises a resin impurity removal device, and the aqueous phase obtained from the stripping unit is subjected to the resin impurity removal device to remove impurities to obtain a lithium-containing solution. In another embodiment, the resin is LSC-500 chelating resin, which can further remove calcium and magnesium ions in the aqueous phase, and the reaction temperature is 65°C. After the aqueous phase is subjected to the resin impurity removal device, the concentration of Li + 5-10 g / L, Ca 2+ , Mg 2+ <10 mg / L.

[0051] The present application also provides a method for separating lithium from oilfield brine, which can use the system for separating lithium from oilfield brine described above, comprising:

[0052] Step 1, the oilfield brine is subjected to extraction and phase separation with an extraction system, and the extraction system comprises a primary extractant, and the primary extractant comprises at least one of 1-hexyl-3-butyl imidazole hexafluorophosphate, 1-hexyl-3-butyl imidazole bistrifluoromethylsulfonamide salt, 1-octyl-3-butyl imidazole hexafluorophosphate, and 1-octyl-3-butyl imidazole bistrifluoromethylsulfonamide salt;

[0053] Step 2, the organic phase obtained from Step 1 is mixed with an eluent to elute to obtain an aqueous phase and an organic phase;

[0054] Step 3, the organic phase obtained from Step 2 is mixed with a stripping solution to strip to obtain an organic phase and an aqueous phase, and the aqueous phase is a lithium-containing solution.

[0055] The present application is directed to oilfield brine, extraction system, etc., which has been described in detail above and will not be repeated here. The related methods described in the above system for separating lithium from oilfield brine are also applicable.

[0056] In an embodiment, before the oilfield brine is extracted with the extraction system and phase separation, the oilfield brine is sequentially subjected to ultrafiltration treatment to remove oil and suspended solids, and nanofiltration treatment to remove divalent cations.

[0057] In an embodiment, the organic phase obtained in step 3 is mixed with an acid solution and phase separated, and the obtained organic phase is recycled as the extraction system; and / or, the aqueous phase obtained in step 3 is subjected to resin impurity removal to remove impurities to obtain a lithium-containing solution.

[0058] The ion liquid extraction system of the present application has a high lithium extraction rate in weak alkaline oilfield brine, does not need to add acid or base to regulate pH value, has no emulsification phenomenon and third phase in the extraction process, and the lithium ion extraction rate can reach 95% or more, and the total lithium recovery rate is 90% or more. In addition, the present application uses a centrifugal dispersion reactor to extract lithium in oilfield brine, which can further improve the extraction efficiency of lithium element. Furthermore, the present application can reduce the influence of calcium and magnesium on lithium ions by setting a pretreatment process of membrane separation to remove organic matter, calcium and magnesium ions and other heavy metal ions in the brine. In summary, the process of the present application is simple, easy to control, continuous in operation, high in reliability, and high in automation degree; the process of the present application can effectively separate and recover lithium from lithium-containing oilfield brine, and the lithium chloride solution obtained by back extraction has high purity of lithium chloride and less impurities, which can be used to prepare lithium bicarbonate and lithium hydroxide products.

[0059] The technical solutions of the present application will be further described in detail below through specific examples.

[0060] Raw material source: oilfield brine from a certain oilfield, the content of each metal in the oilfield brine is shown in the following table.

[0061] Component Li Mg Ca Na K Content mg / L 201.6 1367.03 14012.06 83352.63 4830.16

[0062] Evaluation and analysis method: the metal content is detected by inductively coupled plasma optical emission spectrometer (ICP-OES).

[0063] Example 1:

[0064] (1) After the oilfield brine is subjected to an ultrafiltration device to remove oil and suspended solids, the brine is introduced into a nanofiltration device to intercept divalent cations, and the oilfield brine obtained after pretreatment has a Li + concentration of 200 mg / L, a Na + concentration of 83.35 g / L, a Ca 2+ concentration of less than 0.05 g / L, and a Mg 2+ concentration of less than 0.05 g / L.

[0065] (2) Organic phase preparation: tributylphosphine oxide and ion liquid [HMIM][TF2N] are mixed, and the molar ratio of the two is 1:1.

[0066] (3) At 25°C, the organic phase and the pretreated oilfield brine are pumped into the first centrifugal dispersion reactor at a flow rate of 50 mL / min (1:1 in volume) to perform the extraction reaction, and the raffinate (aqueous phase) and the loaded organic phase (oil phase) are obtained by phase separation.

[0067] (4) The 1.5 mol / L hydrochloric acid solution is used as the washing liquid, which is pumped into the second centrifugal dispersion reactor, and the loaded organic phase of step (3) is pumped into the second centrifugal dispersion reactor, the washing liquid and the organic phase are in a volume ratio of 1:1, and the washing is performed in the reactor, and the washing raffinate (aqueous phase) and the washed organic phase (oil phase) are obtained by phase separation.

[0068] (5) The 4 mol / L hydrochloric acid solution is used as the stripping liquid, which is pumped into the third centrifugal dispersion reactor, and the washed organic phase (oil phase) of step (4) is pumped in, the stripping liquid and the washed organic phase are in a volume ratio of 1:20, and the stripping is performed in the centrifugal dispersion reactor, and the lithium chloride solution is obtained by phase separation.

[0069] (6) After the lithium chloride solution is removed by the LSC-500 chelating resin, ICP-OES detection is performed, the lithium extraction rate is 95.8%, the recovery rate is 91.5%, Li + The concentration of Ca 2+ , Mg 2+ is less than 10 mg / L.

[0070] Extraction rate

[0071] Recovery rate

[0072] C ini(aq) is the ion concentration of the pretreated oilfield brine, V ini(aq) is the volume of the pretreated oilfield brine; C eq(aq) is the ion concentration of the aqueous phase obtained by extraction, V eq(aq) is the volume of the aqueous phase obtained by extraction.

[0073] is the ion concentration of the untreated oilfield brine, is the volume of the untreated oilfield brine; C fin(aq) is the ion concentration of the final lithium solution, V e(aq) is the volume of the final lithium solution.

[0074] Example 2:

[0075] (1) The oil field brine is filtered by an ultrafiltration device to remove oil and suspended solids, and then the brine is introduced into a nanofiltration device to intercept divalent cations, so that the oil field brine obtained by pretreatment contains Li + at a concentration of 200 mg / L, Na + at a concentration of 83.35 g / L, Ca 2+ at a concentration of less than 0.05 g / L, and Mg 2+ at a concentration of less than 0.05 g / L.

[0076] (2) Organic phase preparation: tributylphosphine oxide and ionic liquid 1-hexyl-3-butyl imidazole hexafluorophosphate ([HMIM][PF6]) are mixed, and the molar ratio of the two is 1:2.

[0077] (3) At 25°C, the organic phase and the pretreated oil field brine are pumped into a centrifugal dispersion reactor at flow rates of 100 mL / min and 50 mL / min, respectively (at this time, the volume ratio is 2:1) to perform an extraction reaction, and the raffinate (aqueous phase) and the loaded organic phase (oil phase) are obtained by phase separation.

[0078] (4) A 1.0 mol / L hydrochloric acid solution is used as a washing liquid, which is pumped into a second centrifugal dispersion reactor, and the loaded organic phase is pumped into the second centrifugal dispersion reactor, and the volume ratio of the washing liquid to the organic phase is 1:1, so that the two are washed in the reactor, and the washing raffinate (aqueous phase) and the washed organic phase (oil phase) are obtained by phase separation.

[0079] (5) A 5 mol / L hydrochloric acid solution is used as a stripping liquid, which is pumped into a third centrifugal dispersion reactor, and the washed organic phase (oil phase) is pumped in, and the volume ratio of the stripping liquid to the organic phase is 1:40, so that the two are stripped in the centrifugal dispersion reactor, and the lithium chloride solution is obtained by phase separation.

[0080] (6) After the lithium chloride solution is removed by LSC-500 chelating resin, ICP-OES detection is performed, the lithium extraction rate is 94.2%, the recovery rate is 90.4%, Li + at a concentration of 7.8 g / L, Ca 2+ at a concentration of less than 10 mg / L, and Mg 2+ at a concentration of less than 10 mg / L.

[0081] Example 3:

[0082] (1) The oil field brine is filtered by an ultrafiltration device to remove oil and suspended solids, and then the brine is introduced into a nanofiltration device to intercept divalent cations, so that the oil field brine obtained by pretreatment contains Li + at a concentration of 200 mg / L, Na + at a concentration of 83.35 mg / L, Ca 2+ at a concentration of less than 0.05 g / L, and Mg 2+ at a concentration of less than 0.05 g / L.

[0083] (2) Organic phase preparation: Tri-n-octylphosphine oxide was dissolved in the ionic liquid 1-octyl-3-butylimidazolium bis(trifluoromethanesulfonamide) salt ([OMIM][TF2N]) at a molar ratio of 4:1.

[0084] (3) At 25°C, the organic phase and the pretreated brine were pumped into the centrifugal dispersion reactor (volume ratio of 1:5) by a horizontal flow pump at flow rates of 25 mL / min and 125 mL / min, respectively, to carry out the extraction reaction and obtain the raffinate (aqueous phase) and the loaded organic phase (oil phase) by phase separation.

[0085] (4) Using 0.5 mol / L hydrochloric acid solution as washing liquid, pump it into the second centrifugal dispersion reactor and pump the loaded organic phase into the second centrifugal dispersion reactor. The volume ratio of washing liquid to organic phase is 1:1, so that the two are washed inside the reactor and the washing liquid (aqueous phase) and washing organic phase (oil phase) are obtained by phase separation.

[0086] (5) Using 2 mol / L hydrochloric acid solution as the back-extraction liquid, pump it into the third centrifugal dispersion reactor and pump in the washing organic phase (oil phase). The volume ratio of the back-extraction liquid and the organic phase is 1:10, so that the two are back-extracted inside the centrifugal dispersion reactor and the lithium chloride solution is obtained by phase separation.

[0087] (6) After impurity removal from the lithium chloride solution using an LSC-500 chelating resin, ICP-OES analysis showed a lithium extraction rate of 76.5% and a recovery rate of 80.4%. + The concentration was 5.9 g / L, Ca 2+ Mg 2+ Concentration <10mg / L.

[0088] Example 4:

[0089] (1) After removing oil and suspended solids from the oilfield brine using an ultrafiltration device, the brine is passed through a nanofiltration device to retain divalent cations. The Li in the oilfield brine obtained after pretreatment is... + Concentration of 200 mg / L, Na + The concentration was 83.35 g / L, Ca 2+ Concentration less than 0.05 g / L, Mg 2+ Concentration less than 0.05 g / L;

[0090] (2) Organic phase preparation: Tri-n-octylphosphine oxide was dissolved in the ionic liquid 1-octyl-3-butylimidazolium hexafluorophosphate ([OMIM][PF6]) at a molar ratio of 1:4.

[0091] (3) The organic phase and the pretreated brine were pumped into the centrifugal dispersion reactor at a flow rate of 100 mL / min and 25 mL / min, respectively, at 25°C (the volume ratio was 4:1) to carry out the extraction reaction, and the raffinate (aqueous phase) and the loaded organic phase (oil phase) were obtained by phase separation.

[0092] (4) The washing liquid was pumped into the second centrifugal dispersion reactor, and the loaded organic phase was pumped into the second centrifugal dispersion reactor, and the volume ratio of the washing liquid and the organic phase was 1:1, so that the washing liquid and the organic phase were washed in the reactor, and the washing raffinate (aqueous phase) and the washed organic phase (oil phase) were obtained by phase separation.

[0093] (5) The stripping liquid was pumped into the third centrifugal dispersion reactor, and the washed organic phase (oil phase) was pumped in, and the volume ratio of the stripping liquid and the organic phase was 1:60, so that the stripping liquid and the organic phase were stripped in the centrifugal dispersion reactor, and the lithium chloride solution was obtained by phase separation.

[0094] (6) After the lithium chloride solution was removed by LSC-500 chelating resin, ICP-OES detection was carried out, the lithium extraction rate was 90.5%, the recovery rate was 86.4%, Li + concentration was 8.2g / L, Ca 2+ , Mg 2+ concentration was less than 10mg / L.

[0095] Comparative Example 1:

[0096] (1) After the oil field brine was treated by an ultrafiltration device to remove oil and suspended solids, the brine was passed through a nanofiltration device to retain divalent cations, and the pretreated oil field brine had a Li + concentration of 200mg / L, Na + concentration of 83.35g / L, Ca 2+ concentration of less than 0.05g / L, Mg 2+ concentration of less than 0.05g / L;

[0097] (2) Organic phase preparation: tri-n-octylphosphine oxide was dissolved in ionic liquid 1-vinyl-3-ethylimidazole dibutyl phosphate salt, and the molar ratio of the two was 1:4.

[0098] (3) The organic phase and the pretreated brine were pumped into the centrifugal dispersion reactor at a flow rate of 100 mL / min and 25 mL / min, respectively, at 25°C (the volume ratio was 4:1) to carry out the extraction reaction, and the raffinate (aqueous phase) and the loaded organic phase (oil phase) were obtained by phase separation.

[0099] (4) with 1.0 mol / L hydrochloric acid solution as the washing liquid, pumping it into the second centrifugal dispersion reactor, and pumping the loaded organic phase into the second centrifugal dispersion reactor, the volume ratio of the washing liquid and the organic phase being 1:1, so that the two are washed in the reactor, and the washing residue (aqueous phase) and the washed organic phase (oil phase) are obtained by phase separation.

[0100] (5) with 6 mol / L hydrochloric acid solution as the stripping liquid, pumping it into the third centrifugal dispersion reactor, and pumping the washed organic phase (oil phase) into the third centrifugal dispersion reactor, the volume ratio of the stripping liquid and the organic phase being 1:60, so that the two are stripped in the centrifugal dispersion reactor, and the lithium chloride solution is obtained by phase separation.

[0101] (6) after the lithium chloride solution is removed by LSC-500 chelating resin, ICP-OES detection is adopted, the lithium extraction rate is 70.5%, the recovery rate is 66.4%, Li + The concentration of Ca 2+ , Mg 2+ is >10 mg / L.

[0102] Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and modifications should all belong to the protection scope of the claims of the present application.

Claims

1. A system for separating lithium from oilfield brine, the system comprising: The method comprises the following steps: An extraction unit is used for extracting and separating phases of oilfield brine and an extraction system, wherein the extraction system comprises a main extractant, and the main extractant comprises at least one of 1-hexyl-3-butylimidazole hexafluorophosphate, 1-hexyl-3-butylimidazole bistrifluoromethylsulfonamide, 1-octyl-3-butylimidazole hexafluorophosphate and 1-octyl-3-butylimidazole bistrifluoromethylsulfonamide; An elution unit is in communication with the extraction unit, so as to mix and elute the organic phase obtained by the extraction unit with an eluent, and obtain a water phase and an organic phase; A stripping unit is in communication with the elution unit, so as to mix and strip the organic phase obtained by the elution unit with a stripping agent, and obtain an organic phase and a water phase, wherein the water phase is a lithium-containing solution.

2. The system for separating lithium from oilfield brine according to claim 1, wherein, The method further comprises a pretreatment unit in communication with the extraction unit, wherein the pretreatment unit comprises an ultrafiltration device and a nanofiltration device connected in sequence.

3. The system for separating lithium from oilfield brines of claim 1, wherein, The method further comprises a post-treatment unit in communication with the stripping unit, so as to mix and separate phases of the organic phase obtained by the stripping unit with an acid solution, and the organic phase obtained by the post-treatment unit is recycled as the extraction system.

4. The system for separating lithium from oilfield brines according to claim 3, wherein, The post-treatment unit further comprises a resin impurity removal device, and the water phase obtained by the stripping unit passes through the resin impurity removal device to remove impurities and obtain the lithium-containing solution.

5. The system for separating lithium from oilfield brines of claim 3, wherein, The extraction unit comprises a centrifugal dispersion reactor, the elution unit comprises a centrifugal dispersion reactor, and the stripping unit comprises a centrifugal dispersion reactor.

6. A method of separating lithium from oilfield brine, characterized in that, The method comprises the following steps: Step 1: Extracting and separating phases of oilfield brine and an extraction system, wherein the extraction system comprises a main extractant, and the main extractant comprises at least one of 1-hexyl-3-butylimidazole hexafluorophosphate, 1-hexyl-3-butylimidazole bistrifluoromethylsulfonamide, 1-octyl-3-butylimidazole hexafluorophosphate and 1-octyl-3-butylimidazole bistrifluoromethylsulfonamide; Step 2: Mixing and eluting the organic phase obtained in step 1 with an eluent, and obtaining a water phase and an organic phase; Step 3: Mixing and stripping the organic phase obtained in step 2 with a stripping agent, and obtaining an organic phase and a water phase, wherein the water phase is a lithium-containing solution.

7. The method of claim 6, wherein the method further comprises the step of, Before the oilfield brine is extracted and separated with the extraction system, the oilfield brine is subjected to ultrafiltration treatment to remove oil and suspended solids, and is subjected to nanofiltration treatment to remove divalent cations.

8. The method of claim 6, wherein the method further comprises, The method further comprises the following steps: mixing and separating phases of the organic phase obtained in step 3 with an acid solution, and recycling the obtained organic phase as the extraction system; and / or, removing impurities from the water phase obtained in step 3 by a resin to obtain a lithium-containing solution.

9. The method of claim 6, wherein the method is characterized by, The extraction system further comprises a synergistic agent, and the synergistic agent is a trialkyl phosphine oxide, wherein the alkyl group has 1-10 carbons; and the molar ratio of the main extractant to the synergistic agent is 1-4:4-1.

10. The method of claim 6, wherein the method is characterized by, The eluent is a 0.5-1.5 mol / L hydrochloric acid aqueous solution, the stripping agent is a 3-5 mol / L hydrochloric acid aqueous solution, the volume ratio of the oilfield brine to the extraction system in step 1 is 5:1-1:5, and the volume ratio of the stripping agent to the organic phase obtained in step 2 is (1-5):(1-60).

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