Method for separating bromine from gas field produced water by adopting hollow fiber membrane

Abstract

The invention belongs to the technical field of membrane separation-chemical absorption coupling separation, and particularly relates to a method for separating bromine from gas field produced water by adopting a hollow fiber membrane. The method comprises the following steps: (1) acidified and oxidized gas field produced water is conveyed to a hollow fiber membrane module through a centrifugal pump, passes through a tube pass of the hollow fiber membrane module and then flows back to the original place to form circulation of a raw material solution; and (2) conveying the absorption liquid to the same hollow fiber membrane module through a centrifugal pump, enabling the absorption liquid and the raw material liquid to flow back to the original position after passing through the shell pass of the hollow fiber membrane module, and forming circulation of the absorption liquid. The method is simple to operate, environment-friendly, low in energy consumption, high in yield and easy to industrialize. A bromine flux prediction model of the direct contact type membrane absorption process at low temperature is provided, and the model can predict the bromine flux of the direct contact type membrane absorption process under different process conditions, so that process optimization is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation - chemical absorption coupling separation, and specifically relates to a method for separating bromine from produced water in gas fields by using hollow fiber membranes. Background Art

[0002] Produced water in gas fields refers to a large amount of water generated during gas field exploitation. Currently, the treatment methods for produced water in gas fields are often precipitation, filtration, and then reinjection into the formation, etc. The gas field water in reinjection wells contains resources such as lithium, potassium, boron, and bromine, and has potential resource utilization value. Among them, bromine, as an important basic chemical raw material, is widely used in multiple fields such as the pharmaceutical industry, dye industry, and daily chemical industry. At the same time, as a chemical intermediate, bromine can be finely processed to obtain various final products such as bromohydrocarbons, bromoethers, bromoamines, and brominated flame retardants. The wide application of bromine - based products plays a crucial role in promoting the national economic development.

[0003] Multiple methods can be used to extract bromine, including steam distillation method, solvent extraction method, air blowing method, ion - exchange resin method, membrane separation method, etc. The steam distillation method has the advantages of simple process, convenient operation, less raw materials used, and being suitable for batch production, but it has many side reactions, reducing the bromine extraction rate. The solvent extraction method for extracting bromine has the advantages of small required equipment, simple operation, and low investment, but has high requirements for the extractant. When treating liquid materials with a low bromine content, both the steam distillation method and the solvent extraction method cannot meet the requirements. These two methods have high requirements for the raw material grade and usually extract bromine from liquid materials with a relatively high bromine content. The air blowing method is the main technical means for bromine production, but it requires large - scale equipment, high investment costs, and high energy consumption, and must be built in a centralized manner, which is not suitable for regions where bromine resources are relatively scattered. The ion - exchange resin method uses simple equipment and is not affected by seasonal climate, but subsequent processes such as resin regeneration are relatively complex, which limits its industrial application to a certain extent. The membrane separation method mainly includes gas - phase membrane method and liquid - phase membrane method. The liquid - phase membrane method has disadvantages such as entrainment loss, difficulty in continuous operation, and complex process, and is still in the experimental research stage. Extracting bromine by using the gas - phase membrane absorption method is an efficient bromine extraction method. It uses a hydrophobic microporous membrane to isolate the bromine - containing liquid material and the absorption liquid. After acidification and oxidation, the liquid material is filled with free bromine. These free bromines diffuse to the membrane interface, enabling bromine in the gas phase to pass through the membrane pores and be absorbed by the absorption liquid on the other side of the membrane, thereby realizing the separation and enrichment of bromine. The membrane absorption method has the advantages of simple operation, low energy consumption, and good scalability.

[0004] At present, chlorine gas is generally used as the oxidant for the raw material liquid in industry. However, due to the continuous strengthening of environmental protection measures, the danger of chlorine gas transportation, and the restricted use of chlorine gas in some areas rich in bromine, it is necessary to find an oxidant to replace chlorine gas. The membrane absorption method has high requirements for the permanent hydrophobicity, oxidation resistance, acid and alkali resistance of the membrane. At the same time, the hollow fiber membrane has a larger mass transfer specific surface area compared with the flat membrane. Therefore, selecting a suitable hollow fiber membrane material is the key to obtaining high flux and high yield. The commonly used membranes in current industrial applications, such as polypropylene membranes and polyvinylidene fluoride membranes, do not have the ability to resist oxidation and acid-base corrosion. Summary of the Invention

[0005] The object of the present invention is to: aiming at the problems existing in the background technology, such as the high requirements for the raw material grade of the steam distillation method and the solvent extraction method, the high investment cost, large equipment footprint, and high energy consumption of the air blowing method, and the complex process of the ion exchange resin method, to provide a method for separating bromine from the produced water of gas fields by using a hollow fiber membrane. In this method, sodium hypochlorite is used instead of chlorine gas as the oxidant, and a hollow fiber membrane module made of polytetrafluoroethylene membrane with excellent hydrophobicity, oxidation resistance, high temperature resistance, organic solvent resistance, and acid and alkali corrosion resistance is used for bromine separation. The method has the advantages of environmental protection, low energy consumption, high yield, etc.; to achieve the purpose of extracting bromine with low pollution, low energy consumption, high yield, and relatively simple process.

[0006] In order to achieve the above invention object, the technical solution of the present invention is as follows:

[0007] A method for separating bromine from the produced water of gas fields by using a hollow fiber membrane, the method comprising the following steps:

[0008] (1) The raw material liquid is transported to the hollow fiber membrane module by a centrifugal pump, and after passing through the tube side of the hollow fiber membrane module, it flows back to the original place to form a circulation of the raw material liquid.

[0009] (2) The absorbent liquid is transported to the same hollow fiber membrane module by a centrifugal pump, and after passing through the shell side of the hollow fiber membrane module, it flows back to the original place to form a circulation of the absorbent liquid.

[0010] This method also includes subsequent treatment of the absorbent liquid to achieve the purpose of separating bromine. The treatment of the absorbent liquid is prior art and will not be elaborated (for example, directly extracting the absorbent liquid after circulating for a period of time to obtain a mixed solution of sodium bromide and sodium bromate, adding acid for distillation, and obtaining liquid bromine finished product through steam blowing and condensation).

[0011] In the step (1), the raw material liquid is obtained by acidifying and oxidizing the produced water of gas fields, including the following steps: first, acidifying with H2SO4 solution to a pH between 2.00 and 2.25, and then oxidizing with sodium hypochlorite solution until the oxidation-reduction potential of the solution is 95 - 1080 mV to oxidize bromide ions to bromine.

[0012] As a preferred embodiment in the present application, in the step (1), the concentration of bromine in the raw material liquid is 50 - 8000 ppm, and the temperature is 30 - 80 °C.

[0013] As a preferred embodiment in the present application, the hollow fiber membrane module includes a membrane shell and hollow fiber membranes, wherein: the membrane material of the hollow fiber membranes is polytetrafluoroethylene, polyvinylidene fluoride, polypropylene or polyethylene.

[0014] As a preferred embodiment in the present application, for the hollow fiber membranes, the membrane pore size is 0.2 - 0.45 μm.

[0015] As a preferred embodiment in the present application, for the centrifugal pump, the set flow rate is 20 - 100 mL / min.

[0016] As a preferred embodiment in the present application, in the step (2), the absorption liquid contains a solvent that can undergo a reversible or irreversible chemical reaction with elemental bromine, including one of sodium bromide solution, sodium hydroxide solution, sodium carbonate solution or sodium formate solution; more preferably, it is sodium carbonate solution.

[0017] As a preferred embodiment in the present application, in the step (2), the concentration of the absorption liquid is 1 - 5 g / L.

[0018] As a preferred embodiment in the present application, in the method, the raw material liquid and the absorption liquid are in countercurrent / cocurrent.

[0019] As a preferred embodiment in the present application, the method further includes a process for predicting the bromine flux at low temperature, including the following steps:

[0020] S1, under different temperature conditions (low temperature), measure the initial bromine concentration C0 in the raw material liquid and the residual bromine concentration C in the raw material liquid after a certain time t t , and calculate the bromine flux J through the following formula:

[0021]

[0022] V is the volume of the raw material liquid, S is the effective membrane area, and M is the relative molecular mass of Br2;

[0023] S2, calculate the overall mass transfer coefficient K under different temperature conditions through the following formula:

[0024] J = KC0 × M × 10 3

[0025] S3, perform linear fitting according to the following formula, and regress the slope A and the intercept lnK0:

[0026]

[0027] T is the temperature;

[0028] S4. Use the equation obtained by fitting in S3 to calculate K under different temperature conditions, and substitute it into the equation in S2 to calculate the bromine flux.

[0029] Compared with the existing technologies, the beneficial effects of the present invention are as follows:

[0030] (1) The present invention uses the method of acidification and oxidation to treat the produced water from gas fields, and then completes the separation of bromine through two major steps of the circulation of the raw material liquid and the absorption liquid. The entire process flow is simple and easy to operate. The present invention uses sodium hypochlorite instead of chlorine as the oxidant of the raw material liquid, which has the characteristics of safety and environmental protection and meets the requirements of modern processes. The hollow fiber membrane used is an unmodified polytetrafluoroethylene membrane. Utilizing its excellent characteristics of acid resistance, alkali resistance, and oxidation corrosion resistance, the membrane absorption bromine extraction process is simple, green, has high operation reliability, low cost, and the membrane device occupies a small volume and is easy to industrialize.

[0031] (2) The present invention can effectively separate and recover bromine from the produced water of gas fields. Under the optimal process conditions of the raw material liquid temperature of 60 °C, the flow rates of the raw material liquid and the absorption liquid of 60 mL / min, the countercurrent flow of the raw material liquid and the absorption liquid, the raw material liquid concentration of 1000 ppm, and the absorption liquid concentration of 1 g / L, the bromine extraction rate can reach 93% when the process runs for 90 min.

[0032] (3) The coincidence degree between the bromine membrane flux prediction model and the experimental data in the present invention is relatively high, and it has the feasibility of practical application. Description of the Drawings

[0033] Figure 1 It is the yield curve in direct contact membrane absorption for Examples 1-4.

[0034] Figure 2 It is the flux diagram in direct contact membrane absorption for Examples 1-4.

[0035] Figure 3 It is the yield curve in direct contact membrane absorption for Examples 1 and 5-7

[0036] Figure 4 It is the flux diagram in direct contact membrane absorption for Examples 1 and 5-7.

[0037] Figure 5 It is the yield curve in direct contact membrane absorption for Examples 1 and 8-10

[0038] Figure 6 It is the flux diagram in direct contact membrane absorption for Examples 1 and 8-10.

[0039] Figure 7 For the yield curves of Example 1 and Examples 11 - 13 in direct contact membrane absorption

[0040] Figure 8 For the flux diagrams of Example 1 and Examples 11 - 13 in direct contact membrane absorption

[0041] Figure 9 For the yield curves of Example 1 and Example 14 in direct contact membrane absorption

[0042] Figure 10 For the flux diagrams of Example 1 and Example 14 in direct contact membrane absorption

[0043] Figure 11 For the yield curves of Example 1 and Examples 15 - 16 in direct contact membrane absorption

[0044] Figure 12 For the flux diagrams of Example 1 and Examples 15 - 16 in direct contact membrane absorption

[0045] Figure 13 For the yield curves of Example 1 and Examples 17 - 18 in direct contact membrane absorption

[0046] Figure 14 For the flux diagrams of Example 1 and Examples 17 - 18 in direct contact membrane absorption

[0047] Figure 15 For the overall mass transfer coefficient constant diagrams at different temperatures

[0048] Figure 16 For the comparison diagrams of the membrane flux experimental data and the fitting results of the prediction model at different temperatures

[0049] Figure 17 For the schematic diagram of the transfer of gaseous bromine in the inner membrane absorption process of hollow fiber membranes

[0050] Figure 18 For the schematic process flow diagram of separating bromine by direct contact membrane absorption using hollow fiber membranes, where 1 - constant temperature water bath, 2 - raw liquid bottle, 3 - pump, 4 - flow meter, 5 - thermometer, 6 - hollow fiber membrane module, 7 - absorption liquid bottle Detailed implementation manners

[0051] To make the above objects, methods, and advantages of the present invention more understandable, the following will describe in detail the specific implementation manners of the present invention with reference to specific embodiments

[0052] In the following description, many specific details are set forth in order to enable a person skilled in the art to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Persons skilled in the art may make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0053] Example 1:

[0054] In the produced water from a gas field with a bromine concentration of 1050 ppm to 1150 ppm, a 2.63 mol / L sulfuric acid solution was added dropwise until the pH = 2.00, and then a sodium hypochlorite solution was added dropwise until the redox potential reached 1040 mV, obtaining a raw material liquid with a bromine content of approximately 1000 ppm (the raw material liquid in the following examples was used as the experimental raw material liquid).

[0055] A hollow fiber membrane module was made using a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm bromine was preheated to 50 °C, the peristaltic pump was set at a flow rate of 60 mL / min, and it was pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it was pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material; a 1 g / L sodium carbonate solution was pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min, and after passing through the shell side of the membrane, it was pumped back into the absorption liquid storage tank to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid flowed countercurrently.

[0056] After 90 minutes of circulation, a bromine-rich absorption liquid was obtained. The absorption liquid was subjected to subsequent treatment to achieve the purpose of separating bromine; the treatment of the absorption liquid is prior art and will not be elaborated.

[0057] Example 2

[0058] The method was the same as that described in Example 1, except that the preheating temperature of the raw material liquid was changed to 30 °C. The specific operation was as follows:

[0059] A hollow fiber membrane module was made using a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm bromine was preheated to 30 °C, the peristaltic pump was set at a flow rate of 60 mL / min, and it was pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it was pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material; a 1 g / L sodium carbonate solution was pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min, and after passing through the shell side of the membrane, it was pumped back into the absorption liquid storage tank to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid flowed countercurrently.

[0060] After 90 minutes of circulation, a bromine-rich absorption liquid was obtained. The absorption liquid was subjected to subsequent treatment to achieve the purpose of separating bromine; the treatment of the absorption liquid is prior art and will not be elaborated.

[0061] Example 3

[0062] The method is the same as that described in Example 1, except that the preheating temperature of the raw material liquid is changed to 60°C. The specific operation is as follows:

[0063] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 60°C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0064] After 90 minutes of circulation, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0065] Example 4

[0066] The method is the same as that described in Example 1, except that the preheating temperature of the raw material liquid is changed to 70°C. The specific operation is as follows:

[0067] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 70°C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0068] After 90 minutes of circulation, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0069] Example 5

[0070] The method is the same as that described in Example 1, except that the flow rates of both the raw material liquid and the absorbent liquid are changed to 30 mL / min. The specific operation is as follows:

[0071] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50°C. The peristaltic pump is set at a flow rate of 30 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 30 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0072] After 90 minutes of circulation, a bromine-rich absorption solution is obtained. The absorption solution is subjected to subsequent treatment to achieve the purpose of separating bromine; the treatment of the absorption solution is prior art and will not be elaborated.

[0073] Example 6

[0074] The method is the same as that described in Example 1, except that the flow rates of the raw material liquid and the absorption liquid are both changed to 75 mL / min. The specific operation is as follows:

[0075] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm bromine is preheated to 50°C. The peristaltic pump is set at a flow rate of 75 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material; the 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 75 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid are in countercurrent flow.

[0076] After 90 minutes of circulation, a bromine-rich absorption solution is obtained. The absorption solution is subjected to subsequent treatment to achieve the purpose of separating bromine; the treatment of the absorption solution is prior art and will not be elaborated.

[0077] Example 7

[0078] The method is the same as that described in Example 1, except that the flow rates of the raw material liquid and the absorption liquid are both changed to 90 mL / min. The specific operation is as follows:

[0079] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm bromine is preheated to 50°C. The peristaltic pump is set at a flow rate of 90 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material; the 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 90 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid are in countercurrent flow.

[0080] After 90 minutes of circulation, a bromine-rich absorption solution is obtained. The absorption solution is subjected to subsequent treatment to achieve the purpose of separating bromine; the treatment of the absorption solution is prior art and will not be elaborated.

[0081] Example 8

[0082] The method is the same as that described in Example 1, except that the concentration of the raw material liquid is changed to 100 ppm. The specific operation is as follows:

[0083] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 100 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0084] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0085] Example 9

[0086] The method is the same as that described in Example 1, except that the concentration of the raw material liquid is changed to 4000 ppm. The specific operation is as follows:

[0087] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 4000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0088] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0089] Example 10

[0090] The method is the same as that described in Example 1, except that the concentration of the raw material liquid is changed to 7000 ppm. The specific operation is as follows:

[0091] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 7000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0092] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0093] Example 11

[0094] The method is the same as that described in Example 1, except that the concentration of the absorption liquid is changed to 0.1 g / L. The specific operation is as follows:

[0095] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 0.1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the recycling of the absorption liquid. The raw material liquid and the absorption liquid are in countercurrent flow.

[0096] After circulating for 90 minutes, a bromine-rich absorption liquid is obtained. The absorption liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorption liquid is prior art and will not be elaborated.

[0097] Example 12

[0098] The method is the same as that described in Example 1, except that the concentration of the absorption liquid is changed to 2 g / L. The specific operation is as follows:

[0099] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 2 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the recycling of the absorption liquid. The raw material liquid and the absorption liquid are in countercurrent flow.

[0100] After circulating for 90 minutes, a bromine-rich absorption liquid is obtained. The absorption liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorption liquid is prior art and will not be elaborated.

[0101] Example 13

[0102] The method is the same as that described in Example 1, except that the concentration of the absorption liquid is changed to 3 g / L. The specific operation is as follows:

[0103] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 3 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it is pumped back to the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0104] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0105] Example 14

[0106] The method is the same as that described in Example 1, except that the raw material liquid and the absorbent liquid are in co-current flow. The specific operation is as follows:

[0107] A hollow fiber membrane module is made of a polytetrafluoroethylene membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it is pumped back to the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in co-current flow.

[0108] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0109] Example 15

[0110] The method is the same as that described in Example 1, except that a hollow fiber membrane module is made of polyvinylidene fluoride (PVDF) membrane. The specific operation is as follows:

[0111] A hollow fiber membrane module is made of a 0.35 μm polyvinylidene fluoride membrane. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it is pumped back to the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0112] After circulating for 90 minutes, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is a prior art and will not be elaborated.

[0113] Example 16

[0114] The method is the same as that described in Example 1, except that a hollow fiber membrane module is made of polypropylene (PP) film. The specific operation is as follows:

[0115] A hollow fiber membrane module is made of a 0.35 μm polypropylene film. The raw material liquid containing 1000 ppm bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorption liquid. The raw material liquid and the absorption liquid are in countercurrent flow.

[0116] After circulating for 90 minutes, a bromine-rich absorption liquid is obtained. The absorption liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorption liquid is prior art and will not be elaborated.

[0117] Example 17

[0118] The method is the same as that described in Example 1, except that the absorption liquid is changed to sodium hydroxide solution. The specific operation is as follows:

[0119] A hollow fiber membrane module is made of a 0.45 μm polytetrafluoroethylene film. The raw material liquid containing 1000 ppm bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1 g / L sodium hydroxide solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back to the absorption liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorption liquid. The raw material liquid and the absorption liquid are in countercurrent flow.

[0120] After circulating for 90 minutes, a bromine-rich absorption liquid is obtained. The absorption liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorption liquid is prior art and will not be elaborated.

[0121] Example 18

[0122] The method is the same as that described in Example 1, except that the absorption liquid is changed to sodium bromide solution. The specific operation is as follows:

[0123] A hollow fiber membrane module is made of a 0.45-μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1 g / L sodium bromide solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back into the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0124] After 90 minutes of circulation, a bromine-rich absorbent liquid is obtained. The absorbent liquid is subjected to subsequent treatment to achieve the purpose of separating bromine. The treatment of the absorbent liquid is prior art and will not be elaborated.

[0125] Control Example 1

[0126] The method is the same as that described in Example 1, with the only difference being that when treating the raw material liquid, the pH is adjusted to 5. The specific operation is as follows:

[0127] 2.63 mol / L sulfuric acid solution is added dropwise to the produced water from gas fields at a certain concentration (1050 ppm - 1150 ppm) until the pH = 5, and then sodium hypochlorite solution is added dropwise to obtain the raw material liquid containing bromine.

[0128] A hollow fiber membrane module is made of a 0.45-μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min and pumped back into the absorbent liquid storage tank after passing through the shell side of the membrane to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow. Circulation is carried out for 90 minutes.

[0129] Since elemental bromine will hydrolyze to form corresponding bromides and hypobromites or bromates in alkaline or weakly acidic solutions, there is no elemental bromine in the raw material liquid. No elemental bromine passes through the membrane pores into the absorbent liquid after membrane absorption, and the reaction fails, with no yield and flux.

[0130] Control Example 2

[0131] The method is the same as that described in Example 1, with the only difference being that the pore size of the polytetrafluoroethylene membrane used is changed to 5 μm. The specific operation is as follows:

[0132] A hollow fiber membrane module was made using a 5-μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm of bromine was preheated to 50 °C. The peristaltic pump was set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it was pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1-g / L sodium carbonate solution was pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it was pumped back into the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid flowed countercurrently.

[0133] Due to the too large pore size of the membrane of the membrane module used, the reaction could not proceed at the beginning of the reaction due to membrane wetting, and the reaction failed, with no yield and flux.

[0134] Control Example 3

[0135] The method was the same as that described in Example 1, except that the temperature of the raw material liquid was changed to 0 °C. The specific operation was as follows:

[0136] A hollow fiber membrane module was made using a 0.45-μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm of bromine was cooled to 0 °C. The peristaltic pump was set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it was pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1-g / L sodium carbonate solution was pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it was pumped back into the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid flowed countercurrently. The cycle was carried out for 90 minutes.

[0137] Due to the too low temperature, a large amount of bromine could not be vaporized from the solution. Therefore, only a very small amount of bromine that could be ignored passed through the membrane pores into the absorbent liquid.

[0138] Control Example 4

[0139] The method was the same as that described in Example 1, except that the flow rates of the raw material liquid and the absorbent liquid were changed to 1000 mL / min. The specific operation was as follows:

[0140] A hollow fiber membrane module was made using a 0.45-μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm of bromine was preheated to 50 °C. The peristaltic pump was set at a flow rate of 1000 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it was pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. A 1-g / L sodium carbonate solution was pumped into the shell side of the hollow fiber membrane at a flow rate of 1000 mL / min. After passing through the shell side of the membrane, it was pumped back into the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid flowed countercurrently.

[0141] Due to the excessive flow rate, certain damage was caused to the membrane module and the membrane: the glue connecting the membrane module and the membrane became loose, resulting in the inability to isolate the tube side and the shell side, and the excessive impact force caused the membrane to be damaged, making the reaction unable to proceed, with no yield and flux.

[0142] Control Example 5

[0143] The method is the same as that described in Example 1, with the only difference being that the concentration of the raw material liquid is changed to 10 ppm. The specific operation is as follows:

[0144] A hollow fiber membrane module is made of a 0.45 μm polytetrafluoroethylene membrane. The raw material liquid containing 10 ppm bromine is preheated to 50 °C, the peristaltic pump is set at a flow rate of 60 mL / min, and it is pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material; a 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min, and after passing through the shell side of the membrane, it is pumped back to the absorption liquid storage tank to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid are in countercurrent flow. Cycle for 90 minutes.

[0145] Due to the extremely low content of elemental bromine in the raw material liquid, only a very small amount of elemental bromine that can be ignored enters the absorption liquid through the membrane pores at the end of the reaction.

[0146] Control Example 6

[0147] The method is the same as that described in Example 1, with the only difference being that the concentration of the absorption liquid is changed to 0 g / L. The specific operation is as follows:

[0148] A hollow fiber membrane module is made of a 0.45 μm polytetrafluoroethylene membrane. The raw material liquid containing 1000 ppm bromine is preheated to 50 °C, the peristaltic pump is set at a flow rate of 60 mL / min, and it is pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back to the raw material liquid storage tank to achieve the cyclic absorption of the raw material; a 0 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min, and after passing through the shell side of the membrane, it is pumped back to the absorption liquid storage tank to achieve the cyclic utilization of the absorption liquid; the raw material liquid and the absorption liquid are in countercurrent flow. Cycle for 90 minutes.

[0149] Since the absorption liquid side is deionized water, the absorption effect on bromine is very small and the solubility of elemental bromine in water is relatively low, so the yield and flux after the reaction are very low.

[0150] Control Example 7

[0151] The method is the same as that described in Example 1, with the only difference being that a hollow fiber membrane module is made of a polyethersulfone (PES) membrane.

[0152] A hollow fiber membrane module is made of a polyethersulfone membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it is pumped back into the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0153] Since the PES membrane used has poor hydrophobicity, the reaction cannot proceed due to membrane wetting at the beginning of the reaction, resulting in the failure of the reaction and no yield and flux.

[0154] Comparative Example 8

[0155] The method is the same as that described in Example 1, except that a hollow fiber membrane module is made of a polyacrylonitrile (PAN) membrane.

[0156] A hollow fiber membrane module is made of a polyacrylonitrile membrane with a pore size of 0.45 μm. The raw material liquid containing 1000 ppm of bromine is preheated to 50 °C. The peristaltic pump is set at a flow rate of 60 mL / min and pumped into the tube side of the hollow fiber membrane. After passing through the tube side of the membrane, it is pumped back into the raw material liquid storage tank to achieve the cyclic absorption of the raw material. The 1 g / L sodium carbonate solution is pumped into the shell side of the hollow fiber membrane at a flow rate of 60 mL / min. After passing through the shell side of the membrane, it is pumped back into the absorbent liquid storage tank to achieve the cyclic utilization of the absorbent liquid. The raw material liquid and the absorbent liquid are in countercurrent flow.

[0157] Since the PAN membrane used has poor hydrophobicity, the reaction cannot proceed due to membrane wetting at the beginning of the reaction, resulting in the failure of the reaction and no yield and flux.

[0158] The results of Examples 1 - 18 and Comparative Examples 1 - 8 are listed as follows, as shown in Table 1

[0159] Table 1 Comparison of the results of Examples 1 - 18 and Comparative Examples 1 - 8:

[0160]

[0161]

[0162] From Table 1, we can observe that the bromine recovery obtained by direct contact membrane absorption under the process conditions in Example 1 is significantly higher than that in Examples 2-18 and Comparative Examples 1-8. Therefore, for the method of separating bromine from produced water in gas fields using hollow fiber membranes provided by the present invention, the optimal process conditions are achieved when the membrane pore size of the polytetrafluoroethylene hollow fiber membrane is 0.45 μm, the raw material liquid temperature is 50 °C, the flow rates of the raw material liquid and the absorption liquid are 60 mL / min, the raw material liquid and the absorption liquid are in countercurrent flow, the raw material liquid concentration is 1000 ppm, and the absorption liquid concentration is 1 g / L. Under these conditions, the bromine recovery reached 92.96% in 90 min.

[0163] The membrane absorption process is a membrane separation technology driven by a concentration difference. Since the hollow fiber membrane material used in the experiment is hydrophobic, the raw material liquid and the absorption liquid will not mix with each other, water and solutes in ionic state cannot pass through the membrane pores, while volatile bromine can diffuse through the membrane pores to the other side of the membrane, thereby enabling absorption and enrichment. Membrane absorption essentially separates these two solutions by gas. According to the two-film theory, the mass transfer flux in the membrane absorption process is the product of the concentration difference of components on both sides of the membrane and the overall mass transfer coefficient:

[0164] N = K(C0 - C′ t )

[0165] The overall mass transfer coefficient at different temperatures can be calculated, where N is the mass transfer flux kmol / (m 2 ·h), K is the overall mass transfer coefficient m / h, C0 is the molar concentration of components in the raw material liquid mol / L, and C′ t is the concentration of components in the absorption liquid mol / L.

[0166] Then, using a mathematical expression with the same form as the Arrhenius equation:

[0167]

[0168]

[0169] The intercept lnK0 and the slope A can be calculated.

[0170] Based on the above theoretical derivation, the prediction model proposed in this patent is as follows:

[0171] The modeling process in the present invention is mainly used to predict the bromine flux of the direct contact membrane absorption process under different process conditions.

[0172] The prediction described above includes the following steps:

[0173] S1, perform membrane absorption to extract bromine from the raw material liquid. For different raw material liquid temperatures (at low temperatures), record the residual bromine concentration in the raw material liquid after a certain period of time respectively;

[0174] S2. In membrane absorption, the chemical reaction occurring on the absorbent side is rapid and irreversible. The resistance on the absorbent side can be neglected compared to the resistance of the entire process, i.e., C′ t = 0. Therefore, the equation can be simplified to

[0175] N = K(C0 - C′ t ) = KC0

[0176] S3. According to the initial bromine concentration C0 in the feed liquid and the residual bromine concentration C in the feed liquid after membrane absorption for a certain time t , calculate the bromine flux J

[0177]

[0178] Meanwhile

[0179] J = N × M × 10 3 = N × 160

[0180] where m is the total mass of bromine passing through the membrane in kg, S is the effective membrane area in m 2 , t is the reaction time in h, V is the volume of the feed liquid in L, and M is the relative molecular mass of Br2 in g / mol;

[0181] S4. Substitute the calculated bromine flux J into the equation

[0182] J = KC0 × 160

[0183] to obtain the value of K at different feed liquid temperatures;

[0184] S5. Substitute the overall mass transfer coefficient K at different temperatures and the corresponding feed liquid temperature T into the equation

[0185]

[0186] Plot a graph of lnK versus -1 / T. The slope of the resulting straight line is A, and the intercept of the straight line with the vertical axis is lnK0. Thus, obtain A and K0.

[0187] S6. According to the obtained A and K0, substitute them into the equation

[0188]

[0189] to calculate the overall mass transfer coefficient K value at the set temperature, and substitute it into the equation

[0190] J = KC0 × 160

[0191] According to the initial bromine concentration in the feed liquid and the set temperature, the bromine flux of the direct contact membrane absorption process at this temperature after a certain time can be predicted, thereby optimizing the process.

[0192] More specifically:

[0193] The residual bromine concentration after 10 minutes of liquid film absorption of 816 ppm raw material at 30 °C, 40 °C, and 50 °C was measured respectively, and the bromine fluxes J at different temperatures were calculated, which were J = 0.25073, 0.28696, 0.32320 kg / (m 2 ·h). Substitute into the equation:

[0194] J = KC0 × 160

[0195] Then the overall mass transfer coefficients K at 30 °C, 40 °C, and 50 °C can be calculated, which are K = 1.9204, 2.1979, 2.4755 m / h respectively. The lnK values at 30 °C, 40 °C, and 50 °C are 0.6525, 0.7875, 0.9064. Make a graph of the overall mass transfer coefficient versus temperature, as Figure 15 shown.

[0196] The linear correlation coefficient R between lnK and -1 / T can be obtained 2 = 0.99967, indicating that there is a linear relationship between lnK and -1 / T.

[0197] The slope of the fitting line in the graph of the overall mass transfer coefficient versus temperature function is A, and the intercept with the vertical axis is lnK0. A can be obtained as 1244.1 and K0 as 116.49.

[0198] Substitute A = 1244.1 and K0 = 116.49 into the equation

[0199]

[0200] Thus, the equation for the overall mass transfer coefficient of bromine in the direct contact membrane absorption process is obtained as:

[0201]

[0202] According to this equation, the membrane absorption bromine flux at 45 °C was predicted. From the above equation, the overall mass transfer coefficient K at 45 °C = 2.3335 m / h. Substitute it into the following equation:

[0203] J = KC0 × 160

[0204] When the raw material liquid concentration is 816 ppm, the bromine flux after 10 minutes of direct contact membrane absorption at 45 °C can be calculated as 0.30466 kg / (m 2 ·h).

[0205] A verification experiment was carried out on the direct contact membrane absorption process at 45 °C. The residual bromine concentration of the raw material liquid after membrane absorption was measured as 504 ppm, and the bromine flux was 0.30459 kg / (m 2·h), which is basically consistent with the predicted bromine flux, indicating that the predicted direct contact membrane absorption bromine flux at 45°C is relatively accurate. The experimental data of the membrane absorption flux at other temperatures when the raw liquid concentration is 816 ppm and the fitting results of the mathematical model are as Figure 16 shown. It can be seen that the predicted direct contact membrane absorption bromine flux is relatively accurate at low temperatures. As the temperature increases, the predicted bromine flux begins to deviate. Similarly, the bromine flux can be predicted under other temperature, concentration, and flow rate conditions, so as to optimize the process conditions.

[0206] In summary, a flux prediction model for this system at low temperatures for the direct contact membrane absorption bromine extraction process was proposed, and the bromine fluxes under other conditions were predicted. The model was verified to be relatively accurate through experiments, and the predicted bromine flux was in good agreement with the bromine flux in the experiments.

[0207] The above-described embodiments merely represent the specific implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application.

[0208] This background technology section is provided to generally present the context of the present invention. The work of the currently named inventors, to the extent described in this background technology section, and aspects of this section that do not constitute prior art at the time of filing this application are neither expressly nor impliedly admitted to be prior art of the present invention.

Claims

1. A method for separating bromine from produced water in gas fields using hollow fiber membranes, characterized in that, The method includes the following steps: (1) The raw material liquid is transported to a hollow fiber membrane module by a centrifugal pump, flows back to the original place after passing through the tube side of the hollow fiber membrane module, and forms a circulation of the raw material liquid; the raw material liquid is obtained by acidifying and oxidizing the produced water from gas fields. (2) The absorbent liquid is transported to the same hollow fiber membrane module by a centrifugal pump, flows back to the original place after passing through the shell side of the hollow fiber membrane module, and forms a circulation of the absorbent liquid.

2. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that, In step (1), the raw material liquid is obtained by acidifying and oxidizing the produced water from gas fields, and its preparation steps are as follows: first, the produced water from gas fields is acidified with an H2SO4 solution to a pH between 2.00 and 2.25; then, it is oxidized with a sodium hypochlorite solution until the oxidation-reduction potential of the solution is 95 - 1080 mV, oxidizing bromide ions to bromine.

3. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that, In step (1), the concentration of bromine in the raw material liquid is 50 - 8000 ppm, and the temperature is 30 - 80 °C.

4. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that, The hollow fiber membrane module includes a membrane shell and hollow fiber membranes, where: the membrane material of the hollow fiber membranes is a hydrophobic membrane, including polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or polyethylene.

5. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 4, characterized in that: The pore size of the membrane material is 0.2 - 0.45 μm.

6. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that: The flow rates of the centrifugal pumps through which the raw material liquid and the absorbent liquid pass are both 20 - 100 mL / min.

7. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that: In step (2), the absorbent liquid contains a solvent that can undergo a reversible or irreversible chemical reaction with elemental bromine, including any one of sodium bromide solution, sodium carbonate solution, sodium hydroxide solution, or sodium formate solution.

8. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that: In step (2), the concentration of the absorbent liquid is 1 - 5 g / L.

9. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that: The raw material liquid and the absorbent liquid are in a countercurrent / cocurrent state.

10. The method for separating bromine from produced water in gas fields using hollow fiber membranes according to claim 1, characterized in that, The method also includes a process for predicting the bromine flux at low temperatures, and the specific steps are as follows: S1. Measure the bromine concentration C0 of the initial raw material solution and the residual bromine concentration C of the raw material solution after a certain time t under different low-temperature conditions. t , and calculate the bromine flux J through the following formula: V is the volume of the raw material liquid, S is the effective membrane area, and M is the relative molecular mass of Br2; S2, calculate the overall mass transfer coefficient K under different temperature conditions through the following formula: J = KC0 × M × 10 3 S3, perform a linear fit according to the following formula, and regress the slope A and the intercept lnK0: T is the temperature; S4, use the equation obtained by fitting in S3 to find K under different temperature conditions, and substitute it into the equation in S2 to calculate the bromine flux.

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