A system and method for obtaining concentrated lithium from gas field produced water

Abstract

The present application belongs to the field of gas field produced water treatment, and particularly relates to a system and method for obtaining concentrated lithium from gas field produced water. The system for obtaining concentrated lithium from gas field produced water comprises an oxidation mechanism, a liquid membrane mechanism and a concentration mechanism connected in sequence. The oxidation mechanism is used for oxidizing and degrading the produced water. The liquid membrane mechanism is used for selectively extracting lithium from the oxidized and degraded produced water. The concentration mechanism is used for concentrating lithium from the selectively extracted produced water. The system can effectively extract and concentrate lithium in the produced water, and improve the recovery rate of lithium in the produced water.

Description

Technical Field

[0001] This invention belongs to the field of gas field produced water treatment, specifically relating to a system and method for obtaining concentrated lithium from gas field produced water. Background Technology

[0002] As my country's strategic goal of "stabilizing oil production and increasing gas production" continues to advance, crude oil production is steadily rising, and natural gas production is accelerating. Consequently, the volume of produced water from oil and gas fields will also increase significantly during the development process. Currently, the total produced water volume is nearly 1 billion tons per year, and it is projected to increase by 10% by 2030. Produced water from gas fields is a byproduct of underground natural gas production. It has high mineralization and is rich in high-value-added components, including lithium, potassium, bromine, iodine, and boron. In some areas, the grade of produced water can reach the levels of deep-seated saline minerals, making it highly valuable for extraction and utilization. With the increase in produced water volume from gas fields, its overall resource potential is significant.

[0003] Currently, the primary treatment path for produced water from gas fields is reinjection, with a small amount discharged externally in some areas. Surface treatment technologies for produced water used for reinjection primarily target the removal of suspended solids, employing methods such as flotation and filtration. Surface treatment technologies for produced water used for discharge aim to remove sulfides, organic matter, and salts, mainly employing filtration, flotation, oxidation, and membrane separation. Currently, in the treatment of gas field produced water, high-value components such as lithium cannot be effectively extracted and utilized for resource recovery.

[0004] Lithium is the lightest metallic element in nature, primarily existing as hard rocks such as spodumene, lepidolite, and phosphogypsum, and also found in salt lake brines and deep underground brines. Lithium is widely used in important fields such as batteries, glass, and lubricants. With the development and application of new energy vehicles and energy storage technologies, lithium has received significant attention in the field of new energy materials, becoming an important strategic resource. Driven by the high-quality development of my country's new energy industry, lithium consumption is expected to grow rapidly.

[0005] Therefore, it is necessary to extract lithium from the extracted water.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] To achieve efficient extraction of lithium from produced water in gas fields, this invention provides a system and method for obtaining concentrated lithium from produced water. The system of this invention enables efficient extraction and concentration of lithium from produced water, thereby improving the lithium recovery rate.

[0008] This invention includes the following technical solutions:

[0009] The first aspect of the present invention provides a system for obtaining concentrated lithium from produced water from a gas field, comprising an oxidation unit, a liquid film unit, and a concentration unit connected in sequence.

[0010] The oxidation mechanism is used to oxidize and degrade the produced water;

[0011] The liquid film mechanism is used for lithium selective extraction from the oxidized and degraded produced water.

[0012] The concentration mechanism is used to concentrate lithium in the produced water after selective extraction.

[0013] Furthermore, the oxidation mechanism includes an oxidation reaction vessel.

[0014] Furthermore, the liquid film mechanism includes a stirred separation tank and a demulsifying tank, the oxidation mechanism is connected to the stirred separation tank, and the stirred separation tank is connected to the demulsifying tank.

[0015] Furthermore, the liquid film mechanism also includes a liquid film preparation device, which is connected to the stirred separation tank.

[0016] Furthermore, the concentration mechanism includes a membrane distillation reactor, a condensation collection tank, and a concentrated lithium storage tank; the demulsification tank is connected to the membrane distillation reactor, and the membrane distillation reactor is connected to the condensation collection tank and the concentrated lithium storage tank respectively; preferably, the upper end of the demulsification tank is connected to an emulsion membrane preparation device, and the lower end of the demulsification tank is connected to the membrane distillation reactor.

[0017] A second aspect of the present invention provides a method for obtaining concentrated lithium from produced water in a gas field, comprising the following steps:

[0018] Oxidative degradation of the extracted water;

[0019] Lithium-selective extraction was performed on the oxidized and degraded produced water.

[0020] Lithium concentration was performed on the produced water after selective extraction.

[0021] Furthermore, ozone is added to oxidize and degrade the extracted water.

[0022] Furthermore, a liquid membrane is added to perform lithium selective extraction treatment on the oxidized and degraded produced water; preferably, the volume ratio of the oxidized and degraded produced water to the volume of the liquid membrane is 0.1 to 5.

[0023] Furthermore, the method for preparing the liquid film is as follows:

[0024] Mix ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution;

[0025] Stirring at room temperature and pressure allows ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution to be homogenized and emulsified to obtain a liquid film.

[0026] Preferably, the volume ratio of ethyl acetate to trioctyl phosphate is 1-5, the volume ratio of trioctyl phosphate to sodium tetraphenylborate is 1-10, the volume ratio of organic solvent to sodium carbonate solution is 2-20, and the mass fraction ratio of ethyl acetate to surfactant is 10-100.

[0027] The organic solvents include ethyl acetate, trioctyl phosphate, sodium tetraphenylborate, and surfactants.

[0028] Furthermore, the surfactant has an HLB value of 3 to 6.

[0029] By adopting the above technical solution, the present invention has the following advantages:

[0030] 1. The system of the present invention can effectively extract and concentrate lithium in produced water, thereby improving the lithium recovery rate in produced water.

[0031] 2. This invention uses an oxidation pretreatment + liquid membrane selective extraction + membrane distillation concentration process to extract and concentrate lithium in gas field produced water, ultimately obtaining a near-saturated lithium carbonate solution.

[0032] 3. The oxidation mechanism of this invention can oxidize and degrade organic matter in produced water from gas fields, thereby reducing the interference of organic matter on subsequent lithium extraction and concentration processes. Using ozone in the gas-liquid enhancement device allows for more efficient and in-depth treatment of organic matter.

[0033] 4. In the preparation of the liquid membrane in this invention, trioctyl phosphate and ammonium tetraphenylborate are used as co-extractants, ethyl acetate is used as a diluent, sodium carbonate solution is used as the internal phase, and the surfactant is selected with an HLB value in the range of 3 to 6 to prepare a water-in-oil emulsion membrane. The prepared emulsion membrane has a selective extraction effect on lithium ions in gas field produced water, and the liquid membrane extraction method can complete extraction and back-extraction in one step.

[0034] 5. The liquid membrane demulsification of this invention adopts a heated demulsification method, with a demulsification temperature of 60-90℃. After heated demulsification, the lower lithium-containing aqueous phase has a certain temperature and can be directly introduced into the membrane distillation reactor for concentration. Since the membrane distillation reactor requires a certain temperature, this invention can effectively reduce the energy consumption required for heating.

[0035] 6. The freshwater produced by the membrane distillation reactor of this invention is recycled to the liquid membrane preparation device to supplement softened water, effectively reducing the amount of softened water required. The concentrated water produced by the membrane distillation reactor is the final near-saturated lithium carbonate solution, providing high-quality raw materials for the commercialization of lithium carbonate. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the system for obtaining concentrated lithium from produced water in a gas field, as described in an embodiment of the present invention.

[0038] In the attached diagram: 10 - Oxidation mechanism, 11 - Oxidation reaction vessel, 20 - Liquid film mechanism, 21 - Stirred separation vessel, 22 - Demulsifier, 23 - Liquid film preparation device, 30 - Concentration mechanism, 31 - Membrane distillation reactor, 311 - Reflux pipe, 312 - Outlet pipe, 313 - Inlet pipe, 314 - Concentrated lithium outlet pipe ， 32-Condensation collection tank, 33-Concentrated lithium storage tank, 40-Produced water storage tank. Detailed Implementation

[0039] The following description provides many different embodiments or examples for implementing various features of the invention. The elements and arrangements described in the specific examples below are only for concise expression of the invention and are merely examples, not intended to limit the invention.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a system for obtaining concentrated lithium from produced water from a gas field, such as... Figure 1 As shown, it includes an oxidation mechanism 10, a liquid film mechanism 20, and a concentration mechanism 30 connected in sequence;

[0043] The oxidation mechanism 10 is used to oxidize and degrade the produced water;

[0044] The liquid film mechanism 20 is used for lithium selective extraction from the oxidized and degraded produced water.

[0045] The concentration unit 30 is used to concentrate lithium in the extracted water after selective extraction.

[0046] Furthermore, the oxidation mechanism 10 includes an oxidation reaction vessel 11. The oxidation reaction vessel 11 can be selected from gas-liquid enhanced reactors such as a supergravity reactor, a venturi reactor, or a bubble column reactor.

[0047] Furthermore, the liquid film mechanism 20 includes a stirring separation tank 21 and a demulsifying tank 22, the oxidation mechanism 10 is connected to the stirring separation tank 21, and the stirring separation tank 21 is connected to the demulsifying tank 22.

[0048] Furthermore, the liquid film mechanism 20 also includes a liquid film preparation device 23, which is connected to the stirred separation tank 21.

[0049] Further, the concentration mechanism 30 includes a membrane distillation reactor 31, a condensation collection tank 32, and a concentrated lithium storage tank 33; the demulsification tank 22 is connected to the membrane distillation reactor 31, and the membrane distillation reactor 31 is connected to the condensation collection tank 32 and the concentrated lithium storage tank 33 respectively; preferably, the upper end of the demulsification tank 22 is connected to the emulsion membrane preparation device 23, and the lower end of the demulsification tank 22 is connected to the membrane distillation reactor 31.

[0050] Furthermore, the membrane distillation reactor 31 can be a plate-and-frame type or a hollow fiber type; the distillation membrane inside the membrane distillation reactor 31 is an organic hydrophobic membrane with a pore size of 0.01–0.5 μm. The material can be polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, or polyethersulfone.

[0051] It should be noted that all reaction vessels, devices and mechanisms in this invention are connected by pipelines. In order to improve the conveying efficiency, pumps can be installed in the pipelines.

[0052] Furthermore, a reflux pipe 311 is also provided. One end of the reflux pipe 311 is connected to the outlet pipe 312 of the membrane distillation reactor, and the other end is connected to the inlet pipe 313 of the membrane distillation reactor 31. The flow ratio of the reflux pipe 311 to the concentrated lithium outlet pipe 314 is 0.1 to 1.

[0053] Furthermore, the oxidation reaction tank 11 is connected to the produced water storage tank 40.

[0054] Example 2

[0055] This embodiment provides a method for obtaining concentrated lithium from produced water from a gas field, including the following steps:

[0056] Oxidative degradation of the extracted water;

[0057] Lithium-selective extraction was performed on the oxidized and degraded produced water.

[0058] Lithium concentration was performed on the produced water after selective extraction.

[0059] Furthermore, ozone is added to oxidize and degrade the extracted water. Preferably, the concentration of ozone is 10–150 mg / L, and the gas-liquid ratio is 0.5–5. Direct oxidation by ozone and indirect oxidative degradation by hydroxyl radicals remove major organic compounds from the water, including organic hydrocarbons, phenols, amines, and acids.

[0060] Furthermore, a liquid membrane is added to perform lithium selective extraction treatment on the oxidized and degraded produced water; preferably, the volume ratio of the oxidized and degraded produced water to the volume of the liquid membrane is 0.1 to 5.

[0061] Furthermore, the method for preparing the liquid film is as follows:

[0062] Mix ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution;

[0063] Stirring at room temperature and pressure homogenizes and emulsifies ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution to obtain a liquid film. Based on this, the liquid film has a selective effect on lithium ions, allowing lithium ions to pass through the liquid film unidirectionally.

[0064] Preferably, the volume ratio of ethyl acetate to trioctyl phosphate is 1-5, the volume ratio of trioctyl phosphate to sodium tetraphenylborate is 1-10, the volume ratio of organic solvent to sodium carbonate solution is 2-20, and the mass fraction ratio of ethyl acetate to surfactant is 10-100.

[0065] The organic solvents include ethyl acetate, trioctyl phosphate, sodium tetraphenylborate, and surfactants.

[0066] Preferably, the stirring time in liquid film preparation is 5 to 120 min.

[0067] Furthermore, the surfactant has an HLB value of 3 to 6.

[0068] Furthermore, when performing lithium selective extraction on the oxidized and degraded produced water, the liquid film is first mixed with the oxidized and degraded produced water and stirred to allow lithium ions in the oxidized and degraded produced water to enter the liquid film. The stirring time is 1–120 min, and after stirring, the mixture is allowed to stand for 30–180 min. Then, the liquid film and the lower layer of water are separated. The liquid film is then demulsified by heating at a temperature of 60–90°C for 5–60 min.

[0069] The method of this embodiment can be implemented using the system in embodiment 1. When using this system to execute the method of this embodiment, the devices therein can also be configured, specifically as follows:

[0070] The liquid film preparation device 23 is equipped with a stirrer, and the speed of the stirrer is set to 50-1500 rpm.

[0071] Based on Examples 1 and 2, the following are several examples of obtaining concentrated lithium:

[0072] Example 1

[0073] In this example, the influent is produced water from a gas field, with a COD of 215 mg / L, an initial lithium ion concentration of 39.1 mg / L, and a mineralization of 83 g / L. The volume of produced water to be extracted is 100 L. The ozone concentration in the oxidation system is 30 mg / L, and the gas-liquid ratio is 3. The total volume of the raw material for preparing the liquid membrane is 100 L, including 30 v / v% trioctyl phosphate, a trioctyl phosphate to ethyl acetate volume ratio of 0.2, a trioctyl phosphate to sodium tetraphenylborate volume ratio of 2, Span 80 surfactant with a mass of 2 wt.%, and a sodium carbonate solution concentration of 0.5 mol / L, with the sodium carbonate solution accounting for 15% of the total raw material volume. The agitator speed of the liquid membrane preparation device 23 is 600 rpm, and the preparation time is 15 min at room temperature and pressure. The residence time in the stirred separation tank 21 is 30 min, the demulsification temperature is 65℃, and the demulsification time is 35 min. The lithium ion concentration in the concentrated lithium storage tank 33 is 822 mg / L, and the concentration factor is 21 times.

[0074] Example 2

[0075] The feed water for this invention is produced water from a gas field, with a COD of 368 mg / L, an initial lithium ion concentration of 92 mg / L, and a mineralization of 103 g / L. The volume of produced water to be extracted is 50 L. The ozone concentration in the oxidation system is 80 mg / L, and the gas-liquid ratio is 5. The total volume of the raw material for preparing the emulsion membrane is 250 L, including 80 v / v% trioctyl phosphate, a trioctyl phosphate to ethyl acetate volume ratio of 0.8, a trioctyl phosphate to sodium tetraphenylborate volume ratio of 7, NP-10 surfactant (9 wt.%), and a sodium carbonate solution concentration of 4.5 mol / L, accounting for 40% of the total raw material volume. The stirrer in the membrane preparation device 23 rotates at 1500 rpm, and preparation is carried out at room temperature and pressure for 60 min. The residence time in the stirred separation tank 21 is 100 min, the demulsification temperature is 95℃, and the demulsification time is 50 min. The lithium ion concentration in the concentrated lithium storage tank 33 is 978 mg / L, and the concentration factor is 11 times.

[0076] Example 3

[0077] The feed water for this invention is produced water from a gas field, with a COD of 152 mg / L, an initial lithium ion concentration of 51 mg / L, and a salinity of 68 g / L. The volume of produced water to be extracted is 100 L. The ozone concentration in the oxidation system is 50 mg / L, and the gas-liquid ratio is 2. The total volume of the raw material for preparing the emulsion membrane is 50 L, including trioctyl phosphate at 35 v / v%, TOP to ethyl acetate at a volume ratio of 0.5, trioctyl phosphate to sodium tetraphenylborate at a volume ratio of 5, KC-23 surfactant at a mass of 5 wt.%, and sodium carbonate solution at a concentration of 2 mol / L, accounting for 25% of the total raw material volume. The stirrer in the membrane preparation device 23 rotates at 100 rpm, and preparation is carried out at room temperature and pressure for 100 min. The residence time in the stirred separation tank 21 is 180 min, the demulsification temperature is 80℃, and the demulsification time is 10 min. The lithium ion concentration in the concentrated lithium storage tank 33 is 876 mg / L, and the concentration factor is 17 times.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining concentrated lithium from produced water in a gas field, characterized in that, Includes the following steps: Ozone is added to oxidize and degrade the extracted water; Lithium-selective extraction treatment of the oxidized and degraded produced water was performed by adding a liquid membrane. Lithium concentration was performed on the produced water after selective extraction. The liquid film is prepared by: Mix ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution; Stirring at room temperature and pressure allows ethyl acetate, surfactant, sodium tetraphenylborate, trioctyl phosphate, and sodium carbonate solution to be homogenized and emulsified, resulting in a liquid film.

2. The method for obtaining concentrated lithium from produced water in a gas field according to claim 1, characterized in that, The volume ratio of the extracted water after oxidative degradation to the volume of the liquid film is 0.1 to 5.

3. A method for obtaining concentrated lithium from produced water in a gas field according to claim 2, characterized in that, The volume ratio of ethyl acetate to trioctyl phosphate is 1-5, the volume ratio of trioctyl phosphate to sodium tetraphenylborate is 1-10, the volume ratio of organic solvent to sodium carbonate solution is 2-20, and the mass fraction ratio of ethyl acetate to surfactant is 10-100. The organic solvents include ethyl acetate, trioctyl phosphate, sodium tetraphenylborate, and surfactants.

4. A method for obtaining concentrated lithium from produced water in a gas field according to claim 3, characterized in that, The surfactant has an HLB value of 3 to 6.

5. A system for obtaining concentrated lithium from produced water from a gas field, for implementing the method according to any one of claims 1-4, characterized in that, It includes an oxidation mechanism (10), a liquid film mechanism (20), and a concentration mechanism (30) connected in sequence. The oxidation mechanism (10) is used to oxidize and degrade the produced water; The liquid film mechanism (20) is used for lithium selective extraction from the oxidized and degraded produced water; The concentration unit (30) is used to concentrate lithium in the extracted water after selective extraction.

6. A system for obtaining concentrated lithium from produced water from a gas field according to claim 5, characterized in that, The oxidation mechanism (10) includes an oxidation reaction vessel (11).

7. A system for obtaining concentrated lithium from produced water from a gas field according to claim 5, characterized in that, The liquid film mechanism (20) includes a stirred separation tank (21) and a demulsifier (22), the oxidation mechanism (10) is connected to the stirred separation tank (21), and the stirred separation tank (21) is connected to the demulsifier (22).

8. A system for obtaining concentrated lithium from produced water in a gas field according to claim 7, characterized in that, The liquid film mechanism (20) further includes a liquid film preparation device (23), which is connected to the stirred separation tank (21).

9. A system for obtaining concentrated lithium from produced water from a gas field according to claim 7, characterized in that, The concentration mechanism (30) includes a membrane distillation reactor (31), a condensation collection tank (32), and a concentrated lithium storage tank (33); the demulsifier (22) is connected to the membrane distillation reactor (31), and the membrane distillation reactor (31) is connected to the condensation collection tank (32) and the concentrated lithium storage tank (33) respectively.

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