A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource

Abstract

The invention discloses a method for desalting and recycling high-salinity brine wastewater in oil and gas fields, which belongs to the technical field of environmentally friendly wastewater treatment, and comprises the following steps: removing floating oil, suspended matter and COD from wastewater by pre-treatment to obtain saline wastewater; concentrating the saline wastewater by a membrane distillation reactor to obtain concentrated wastewater; thermally evaporating the concentrated wastewater to respectively recover brine and water; the membrane distillation reactor comprises a separation membrane; the invention first concentrates the wastewater by membrane distillation, and then performs conventional distillation on the nearly saturated concentrated liquid, which can greatly reduce energy consumption; the separation membrane has an asymmetric hydrophilic and hydrophobic structure, and is prepared by using a polyvinyl fluoride material as a base hydrophobic membrane layer, and then spraying modified hydrophilic polyether ketone / sulfone on the contact surface of the high-salinity wastewater; the separation membrane has good separation flux and anti-salting performance.

Description

Technical Field

[0001] The invention relates to the technical field of environmentally friendly wastewater treatment, and in particular to a method for desalting and recycling high-salinity brine wastewater from oil and gas fields. Background Art

[0002] The petrochemical industry is a pillar industry of the country, covering multiple industries such as petroleum refining, organic chemical raw material manufacturing, chemical synthesis, dye manufacturing, organic pesticide manufacturing, etc., involving many products. The development of oil and gas fields will inevitably produce a large amount of petrochemical wastewater. Oil and gas field wastewater contains a large amount of organic matter, and the COD content is as high as thousands or even tens of thousands; after degrading COD by general physical and chemical methods, the wastewater still contains a large amount of Na, K, Cl and other ions, and its salt content greatly exceeds the standard of farmland irrigation water. If it is discharged directly, it will inevitably cause great pollution to rivers, lakes, drinking water and farmland, and even lead to a reduction in crop yields. Therefore, the treatment of such wastewater is very important for protecting the environment and realizing the recycling of water resources. However, the existing chemical treatment method is difficult to desalinate. Even if the salt in the wastewater is removed, new pollutants are generated, and it cannot be discharged directly. Although the simple distillation method can achieve the ideal desalination effect, the energy consumption is too high and the cost of wastewater treatment is high.

[0003] At present, the high-salt wastewater desalination technologies that have reached industrial-scale application mainly include "distillation" and "membrane separation". The distillation method includes multi-stage flash evaporation, multi-effect evaporation and compressed steam distillation. Although the distillation method can achieve the goal of zero emissions, it consumes huge energy and money, and also wastes resources; the membrane separation method uses a selectively permeable membrane as a filtration medium, and uses pressure difference, potential difference, osmotic pressure, etc. as a driving force to achieve the concentration of saline wastewater. Common membrane separation processes include microfiltration, ultrafiltration, reverse osmosis, electrodialysis, etc. For membrane technology, the main problem currently existing is membrane pollution.

[0004] Membrane distillation technology is a new separation technology that combines traditional thermal evaporation process with membrane separation technology. Its principle is to prevent waste liquid from penetrating the membrane pores in liquid form under the interception effect of hydrophobic microporous membrane, and only the volatile components penetrate the membrane pores under the promotion of the vapor pressure difference on both sides of the membrane, while the non-volatile components are intercepted, and finally the mixture is separated and purified, with the characteristics of high concentration multiple and low energy consumption. For high-salinity oil and gas field wastewater, membrane distillation technology is a good choice, among which the hydrophobic microporous membrane is the core component of the membrane distillation process, but due to the lack of high-throughput, anti-pollution, and heat-insulating membrane materials, the practical application of the membrane distillation process has been limited. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for desalting high-salinity brine wastewater in oil and gas fields and utilizing it as a resource.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0008] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0009] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0010] S3, thermally evaporating the concentrated wastewater to recover bittern and water respectively;

[0011] Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps:

[0012] (1) weighing polyvinyl pyrrolidone and dissolving it in deionized water, adding a nano-dispersion of polytetrafluoroethylene or polyvinylidene fluoride, stirring thoroughly to obtain a spinning solution, and electrospinning the spinning solution onto a ceramic fiber membrane or a receiving roller to obtain a hydrophobic membrane;

[0013] (2) Weighing 2,6-difluoro-2'-hydroxyacetophenone and 1-(4-bromophenyl)-3,5-diphenylbenzophenone respectively and dissolving them in N,N-dimethylformamide solvent, adding potassium carbonate, heating to 80-90° C. under a protective atmosphere and stirring and reflux reacting for 5-10 hours, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, and obtaining the modified monomer after recrystallization and purification;

[0014] (3) Weigh the modified monomer, 4,4′-difluorobenzophenone, and 4,4′-(hexafluoroisopropyl)diphenol respectively and dissolve them in a mixed solvent of toluene and sulfolane, add potassium carbonate, heat to 150-180° C. under a protective atmosphere, stir and reflux for reaction for 2-5 hours, remove water by azeotropy, and continue to stir and react at 200-210° C. for 4-8 hours. After the reaction is completed, cool the mixture, add deionized water to dilute the reaction system, separate the precipitate, wash it with hot deionized water and ethanol solvent in turn, dry it in vacuum, dissolve the precipitate in dichloromethane, add a dichloromethane solution of chlorosulfonic acid dropwise under ice cooling, stir and react at room temperature for 5-10 hours, wash it with an alkaline solution and deionized water in turn until it is neutral, and dry it in vacuum to obtain the first product;

[0015] (4) Weighing 2,5-di(4-pyridyl)-1,4-hydroquinone and 4,4′-difluorodiphenyl sulfone respectively and dissolving them in a mixed solvent of toluene and cyclopentane, adding potassium carbonate, heating to 150-180° C. under a protective atmosphere and stirring and reflux for 2-5 hours, removing water by azeotropy and continuing to stir and react at 200-210° C. for 4-8 hours, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, washing with hot deionized water and ethanol solvent in turn, and vacuum drying to obtain a second product;

[0016] (5) dissolving the first product in N,N-dimethylformamide solvent and filtering to obtain solution A; dissolving the second product in chloroform solvent and filtering to obtain solution B; spraying the solution A on the spinning surface of the hydrophobic membrane, drying, and then spraying the solution B on the spinning surface of the hydrophobic membrane, and drying again to obtain the product.

[0017] In some preferred embodiments, the thermal evaporation in step S3 is multi-stage flash evaporation, multi-effect evaporation or steam compression distillation.

[0018] In some preferred embodiments, the water vapor generated by the thermal evaporation in step S3 is used for heat exchange with the saline wastewater or concentrated wastewater in step S2.

[0019] In some preferred embodiments, the weight average molecular weight of the polyvinyl pyrrolidone in step (1) is 50,000-500,000, and its solubility concentration in deionized water is 0.04-0.1 g / mL.

[0020] In some preferred embodiments, the mass content of the polytetrafluoroethylene or the polyvinylidene fluoride in the nano-dispersion of step (1) is 50-70%, and the mass ratio of the polyvinyl pyrrolidone to the polytetrafluoroethylene or the polyvinylidene fluoride is 1:(9-12).

[0021] In some preferred embodiments, the mass ratio of the 2,6-difluoro-2'-hydroxyacetophenone to the 1-(4-bromophenyl)-3,5-diphenylbenzene and the potassium carbonate in step (2) is 1:(2-2.4):(0.7-0.9).

[0022] In some preferred embodiments, in step (3), the mass ratio of the modified monomer to the 4,4'-difluorobenzophenone, the 4,4'-(hexafluoroisopropyl)diphenol, and the potassium carbonate is 1:(1.45-1.6):(2.78-2.9):(1.25-1.35); the mass ratio of the precipitate to the chlorosulfonic acid is 1:(0.3-0.34).

[0023] In some preferred embodiments, the volume ratio of the toluene to the sulfolane in the mixed solvent of step (3) and step (4) is 1:(1.2-1.5).

[0024] In some preferred embodiments, the mass ratio of the 2,5-di(4-pyridyl)-1,4-hydroquinone to the 4,4′-difluorodiphenyl sulfone and the potassium carbonate in step (4) is 1:(1.2-1.34):(0.7-0.8).

[0025] In some preferred embodiments, the spraying amount of the first product and the second product on the spinning surface of the hydrophobic membrane in step (5) is 0.1-1 g / m 2 .

[0026] The beneficial effects of the present invention are:

[0027] The present invention provides a method for treating high-salinity wastewater by combining membrane distillation and thermal distillation. The wastewater is first concentrated by membrane distillation, and then the nearly saturated concentrated solution is subjected to conventional distillation, which can greatly reduce energy consumption. Aiming at the problem that the membrane distillation method lacks high-flux, anti-pollution and heat-insulating membrane materials, the present invention also provides a membrane distillation separation membrane, which has good separation flux and anti-salting performance. Specifically, the present invention uses polyvinyl fluoride material as a base hydrophobic membrane layer, sprays modified hydrophilic polyether ketone / sulfone on the contact surface of high-salinity wastewater, and obtains a separation membrane with an asymmetric hydrophilic and hydrophobic structure. The contact adsorption between the membrane and water molecules is changed by arranging a hydrophilic layer on the surface, thereby improving the separation flux. Furthermore, the present invention uses 2,6-difluoro-2 '-Hydroxyacetophenone and 1-(4-bromophenyl)-3,5-diphenylbenzene are used as raw materials, and the modified monomer is prepared by the substitution reaction of the bromine group on the alcohol hydroxyl group and polymerized, and then a negatively charged group is introduced into the side chain of the modified monomer by a sulfonation reaction to obtain a negatively charged polymer; the present invention also uses 2,5-di(4-pyridyl)-1,4-hydroquinone and 4,4'-difluorodiphenyl sulfone as monomers for polymerization to introduce a positively charged pyridine group into the side chain. As water molecules penetrate, the ion concentration on the membrane surface increases, and in a nearly saturated concentrated liquid system, salt is easily formed on the membrane surface to cause membrane failure. The present invention introduces a positively / negatively charged polymer on the membrane surface through modification, thereby improving the hydrophilicity and reducing its salt-forming performance. DETAILED DESCRIPTION

[0028] The present invention is further described in conjunction with the following examples.

[0029] Example 1

[0030] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0031] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0032] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0033] S3, subjecting the concentrated wastewater to multi-stage flash evaporation to recover brine and water respectively;

[0034] Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps:

[0035] (1) Weigh polyvinyl pyrrolidone and dissolve it in deionized water, add a nano-dispersion of polyvinylidene fluoride (60wt%), stir thoroughly to obtain a spinning solution, and electrospin the spinning solution on a receiving roller to obtain a hydrophobic membrane; the weight average molecular weight of the polyvinyl pyrrolidone is 100,000, and its solubility concentration in deionized water is 0.06g / mL. The mass ratio of the polyvinyl pyrrolidone to the polyvinylidene fluoride is 1:10, the feed rate of the electrospinning is 2mL / h, the spinning receiving distance is 15cm, and the electrospinning voltage is 17kV; the hydrophobic membrane has a thickness of 0.15mm, an average pore size of 0.19μm, and a porosity of 0.65;

[0036] (2) Weighing 2,6-difluoro-2'-hydroxyacetophenone and 1-(4-bromophenyl)-3,5-diphenylbenzene respectively and dissolving them in N,N-dimethylformamide solvent, adding potassium carbonate, heating to 85° C. under a protective atmosphere and stirring under reflux for 6 hours, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, and recrystallizing and purifying to obtain a modified monomer; the mass ratio of the 2,6-difluoro-2'-hydroxyacetophenone to the 1-(4-bromophenyl)-3,5-diphenylbenzene and the potassium carbonate is 1:2.2:0.8, and the recrystallization solvent is a mixed solvent of ethanol and chloroform (v / v=3 / 1);

[0037] (3) Weigh the modified monomer, 4,4′-difluorobenzophenone, and 4,4′-(hexafluoroisopropyl)diphenol respectively and dissolve them in a mixed solvent of toluene and sulfolane (v / v=2 / 3), add potassium carbonate, heat to 160°C under a protective atmosphere, stir and reflux for 3 h, remove water by azeotropic reaction, and continue to stir and react at 200°C for 5 h. After the reaction is completed, cool the mixture, add deionized water to dilute the reaction system, separate the precipitate, wash it with hot deionized water and ethanol solvent in turn, dry it in vacuum, and then The precipitate is dissolved in dichloromethane, and a dichloromethane solution of chlorosulfonic acid is added dropwise under ice water cooling, and then stirred for reaction at room temperature for 6 hours, and then washed with a 10% KOH aqueous solution and deionized water in sequence until neutral, and vacuum dried to obtain a first product; the mass ratio of the modified monomer to the 4,4'-difluorobenzophenone, the 4,4'-(hexafluoroisopropylidene)diphenol, and the potassium carbonate is 1:1.5:2.8:1.3; the mass ratio of the precipitate to the chlorosulfonic acid is 1:0.32;

[0038] (4) Weigh 2,5-di(4-pyridyl)-1,4-hydroquinone and 4,4'-difluorodiphenyl sulfone respectively and dissolve them in a mixed solvent of toluene and cyclopentane sulfone (v / v=3 / 4), add potassium carbonate, heat to 160°C under a protective atmosphere, stir and reflux for 3 h, remove water by azeotropy, and continue to stir and react at 200°C for 6 h. After the reaction is completed, cool the mixture, add deionized water to dilute the reaction system, separate the precipitate, wash it with hot deionized water and ethanol solvent in turn, and vacuum dry it to obtain a second product; the mass ratio of the 2,5-di(4-pyridyl)-1,4-hydroquinone to the 4,4'-difluorodiphenyl sulfone and the potassium carbonate is 1:1.25:0.75;

[0039] (5) The first product was dissolved in N,N-dimethylformamide solvent, and solution A was obtained after filtering; the second product was dissolved in chloroform solvent, and solution B was obtained after filtering; solution A was sprayed on the spinning surface of the hydrophobic membrane, and after drying, solution B was sprayed on the spinning surface of the hydrophobic membrane, and dried again; the spraying amounts of the first product and the second product on the spinning surface of the hydrophobic membrane were 0.2 and 0.28 g / m respectively. 2 .

[0040] In other embodiments, the water vapor generated by the thermal evaporation in step S3 is used for heat exchange with the saline wastewater or concentrated wastewater in step S2, which can further reduce energy consumption.

[0041] In other embodiments, the spinning solution can be electrospun onto a ceramic membrane, which can improve the mechanical properties of the separation membrane and reduce heat transfer on both sides of the separation membrane.

[0042] Example 2

[0043] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0044] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0045] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0046] S3, subjecting the concentrated wastewater to multi-stage flash evaporation to recover brine and water respectively;

[0047] Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps:

[0048] (1) Weigh polyvinyl pyrrolidone and dissolve it in deionized water, add a nano-dispersion of polytetrafluoroethylene (60wt%), stir thoroughly to obtain a spinning solution, and electrospin the spinning solution on a receiving roller to obtain a hydrophobic membrane; the weight average molecular weight of the polyvinyl pyrrolidone is 100,000, and its solubility concentration in deionized water is 0.06g / mL. The mass ratio of the polyvinyl pyrrolidone to the polytetrafluoroethylene is 1:10, the feed rate of the electrospinning is 2mL / h, the spinning receiving distance is 15cm, and the electrospinning voltage is 17kV; the hydrophobic membrane has a thickness of 0.15mm, an average pore size of 0.20μm, and a porosity of 0.65;

[0049] Steps (2) to (5) are the same as in Example 1.

[0050] Example 3

[0051] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0052] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0053] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0054] S3, subjecting the concentrated wastewater to multi-stage flash evaporation to recover brine and water respectively;

[0055] Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps:

[0056] (1) Weigh polyvinyl pyrrolidone and dissolve it in deionized water, add a nano-dispersion of polyvinylidene fluoride (60wt%), stir thoroughly to obtain a spinning solution, and electrospin the spinning solution on a receiving roller to obtain a hydrophobic membrane; the weight average molecular weight of the polyvinyl pyrrolidone is 100,000, and its solubility concentration in deionized water is 0.06g / mL. The mass ratio of the polyvinyl pyrrolidone to the polyvinylidene fluoride is 1:10, the feed rate of the electrospinning is 2mL / h, the spinning receiving distance is 15cm, and the electrospinning voltage is 17kV; the hydrophobic membrane has a thickness of 0.15mm, an average pore size of 0.19μm, and a porosity of 0.65;

[0057] (2) Weighing 2,6-difluoro-2′-hydroxyacetophenone and 1-(4-bromophenyl)-3,5-diphenylbenzene respectively and dissolving them in N,N-dimethylformamide solvent, adding potassium carbonate, heating to 85° C. under a protective atmosphere and stirring under reflux for 6 hours, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, and recrystallizing and purifying to obtain a modified monomer; the mass ratio of the 2,6-difluoro-2′-hydroxyacetophenone to the 1-(4-bromophenyl)-3,5-diphenylbenzene and the potassium carbonate is 1:2.2:0.8, and the recrystallization solvent is a mixed solvent of ethanol and chloroform (v / v=3 / 1);

[0058] (3) Weigh the modified monomer, 4,4'-difluorobenzophenone, and 4,4'-(hexafluoroisopropyl)diphenol respectively and dissolve them in a mixed solvent of toluene and sulfolane (v / v=2 / 3), add potassium carbonate, heat to 160°C under a protective atmosphere, stir and reflux for 3 h, remove water by azeotropic reaction, and continue to stir and react at 200°C for 5 h. After the reaction is completed, cool the reaction system, add deionized water to dilute the reaction system, separate the precipitate, wash it with hot deionized water and ethanol solvent in turn, and then vacuum dry it. The precipitate is dissolved in dichloromethane, and a dichloromethane solution of chlorosulfonic acid is added dropwise under ice water cooling, and then stirred for reaction at room temperature for 6 hours, and then washed with a 10% KOH aqueous solution and deionized water to neutrality, and vacuum dried to obtain a first product; the mass ratio of the modified monomer to the 4,4'-difluorobenzophenone, the 4,4'-(hexafluoroisopropylidene)diphenol, and the potassium carbonate is 1:1.5:2.8:1.3; the mass ratio of the precipitate to the chlorosulfonic acid is 1:0.32;

[0059] (4) dissolving the first product in N,N-dimethylformamide solvent and spraying it on the spinning surface of the hydrophobic membrane, and drying it to obtain a hydrophobic membrane; the amount of the first product sprayed on the spinning surface of the hydrophobic membrane is 0.2 g / m 2 .

[0060] Example 4

[0061] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0062] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0063] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0064] S3, subjecting the concentrated wastewater to multi-stage flash evaporation to recover brine and water respectively;

[0065] Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps:

[0066] (1) Weigh polyvinyl pyrrolidone and dissolve it in deionized water, add a nano-dispersion of polyvinylidene fluoride (60wt%), stir thoroughly to obtain a spinning solution, and electrospin the spinning solution on a receiving roller to obtain a hydrophobic membrane; the weight average molecular weight of the polyvinyl pyrrolidone is 100,000, and its solubility concentration in deionized water is 0.06g / mL. The mass ratio of the polyvinyl pyrrolidone to the polyvinylidene fluoride is 1:10, the feed rate of the electrospinning is 2mL / h, the spinning receiving distance is 15cm, and the electrospinning voltage is 17kV; the hydrophobic membrane has a thickness of 0.15mm, an average pore size of 0.19μm, and a porosity of 0.65;

[0067] (2) Weigh 2,5-di(4-pyridyl)-1,4-hydroquinone and 4,4′-difluorodiphenyl sulfone respectively and dissolve them in a mixed solvent of toluene and cyclopentane sulfone (v / v=3 / 4), add potassium carbonate, heat to 160°C under a protective atmosphere, stir and reflux for 3 h, remove water by azeotropy, and continue to stir and react at 200°C for 6 h. After the reaction is completed, cool the mixture, add deionized water to dilute the reaction system, separate the precipitate, wash it with hot deionized water and ethanol solvent in turn, and vacuum dry it to obtain a second product; the mass ratio of the 2,5-di(4-pyridyl)-1,4-hydroquinone to the 4,4′-difluorodiphenyl sulfone and the potassium carbonate is 1:1.25:0.75;

[0068] (5) dissolving the second product in chloroform solvent and spraying it on the spinning surface of the hydrophobic membrane, and drying it to obtain a hydrophobic film; the spraying amount of the second product on the spinning surface of the hydrophobic membrane is 0.28 g / m 2 .

[0069] Comparison example

[0070] A method for desalting high-salinity brine wastewater from oil and gas fields and utilizing it as a resource comprises the following steps:

[0071] S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater;

[0072] S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater;

[0073] S3, subjecting the concentrated wastewater to multi-stage flash evaporation to recover brine and water respectively;

[0074] Wherein, the membrane distillation reactor comprises a hydrophobic membrane, and the preparation method of the hydrophobic membrane comprises the following steps:

[0075] (1) Weigh polyvinyl pyrrolidone and dissolve it in deionized water, add a nano-dispersion of polyvinylidene fluoride (60wt%), stir thoroughly to obtain a spinning solution, and electrospin the spinning solution on a receiving roller to obtain the hydrophobic membrane; the weight average molecular weight of the polyvinyl pyrrolidone is 100,000, and its solubility concentration in deionized water is 0.06g / mL. The mass ratio of the polyvinyl pyrrolidone to the polyvinylidene fluoride is 1:10, the feed rate of the electrospinning is 2mL / h, the spinning receiving distance is 15cm, and the electrospinning voltage is 17kV; the hydrophobic membrane has a thickness of 0.15mm, an average pore size of 0.19μm, and a porosity of 0.65.

[0076] Experimental example

[0077] The separation performances of the separation membranes described in Examples 1-4 and the hydrophobic membrane described in the control example were tested and compared, and an air gap membrane distillation apparatus was used for simulated operation. The feed liquid and cooling water were circulated separately, and the effective evaporation area of ​​the membrane was 90% of the total membrane area. The feed liquids were 10wt%, 20wt%, and 26wt% sodium chloride solutions, respectively. The feed liquid temperature was 70°C, the cooling water temperature was 18°C, the feed liquid flow rate was 100mL / min, the operation time was 1h, the changes in the membrane interface morphology were observed, and the average membrane flux was calculated. The measurement results are as follows.

[0078]

[0079]

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for desalting high-salinity brine wastewater from oil and gas fields, characterized in that: The following steps are involved: S1. The wastewater is pre-treated to remove floating oil, suspended solids and COD to obtain saline wastewater; S2, concentrating the saline wastewater through a membrane distillation reactor to obtain concentrated wastewater; S3, thermally evaporating the concentrated wastewater to recover bittern and water respectively; Wherein, the membrane distillation reactor comprises a separation membrane, and the preparation method of the separation membrane comprises the following steps: (1) weighing polyvinyl pyrrolidone and dissolving it in deionized water, adding a nano-dispersion of polytetrafluoroethylene or polyvinylidene fluoride, stirring thoroughly to obtain a spinning solution, and electrospinning the spinning solution onto a ceramic fiber membrane or a receiving roller to obtain a hydrophobic membrane; (2) Weighing 2,6-difluoro-2'-hydroxyacetophenone and 1-(4-bromophenyl)-3,5-diphenylbenzophenone respectively and dissolving them in N,N-dimethylformamide solvent, adding potassium carbonate, heating to 80-90° C. under a protective atmosphere and stirring and reflux reacting for 5-10 hours, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, and obtaining the modified monomer after recrystallization and purification; (3) Weighing the modified monomer, 4,4'-difluorobenzophenone, and 4,4'-(hexafluoroisopropyl)diphenol respectively and dissolving them in a mixed solvent of toluene and sulfolane, adding potassium carbonate, heating to 150-180° C. under a protective atmosphere, stirring and reflux reacting for 2-5 hours, removing water by azeotropic means, and continuing to stir and react at 200-210° C. for 4-8 hours. After the reaction is completed, cooling, adding deionized water to dilute the reaction system, separating the precipitate, washing with hot deionized water and ethanol solvent in turn, vacuum drying, and then dissolving the precipitate in dichloromethane, adding a dichloromethane solution of chlorosulfonic acid dropwise under ice water cooling, stirring and reacting at room temperature for 5-10 hours, washing with an alkaline solution and deionized water in turn until neutral, and vacuum drying to obtain a first product; (4) Weighing 2,5-di(4-pyridyl)-1,4-hydroquinone and 4,4'-difluorodiphenyl sulfone respectively and dissolving them in a mixed solvent of toluene and cyclopentane, adding potassium carbonate, heating to 150-180° C. under a protective atmosphere and stirring and reflux for 2-5 h, removing water by azeotropy and continuing to stir and react at 200-210° C. for 4-8 h, cooling after the reaction is completed, adding deionized water to dilute the reaction system, separating the precipitate, washing with hot deionized water and ethanol solvent in turn, and vacuum drying to obtain a second product; (5) dissolving the first product in N,N-dimethylformamide solvent and filtering to obtain solution A; dissolving the second product in chloroform solvent and filtering to obtain solution B; spraying the solution A on the spinning surface of the hydrophobic membrane, drying, and then spraying the solution B on the spinning surface of the hydrophobic membrane, and drying again to obtain the product.

2. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1 is characterized in that: The thermal evaporation in step S3 is multi-stage flash evaporation, multiple-effect evaporation or steam compression distillation.

3. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1 is characterized in that: The water vapor generated by the thermal evaporation in step S3 is used for heat exchange with the saline wastewater or concentrated wastewater in step S2.

4. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: The weight average molecular weight of the polyvinyl pyrrolidone in step (1) is 50,000-500,000, and its solubility concentration in deionized water is 0.04-0.1 g / mL.

5. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: The mass content of the polytetrafluoroethylene or the polyvinylidene fluoride in the nano-dispersion in step (1) is 50-70%, and the mass ratio of the polyvinyl pyrrolidone to the polytetrafluoroethylene or the polyvinylidene fluoride is 1:(9-12).

6. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: In step (2), the mass ratio of the 2,6-difluoro-2'-hydroxyacetophenone to the 1-(4-bromophenyl)-3,5-diphenylbenzene and the potassium carbonate is 1:(2-2.4):(0.7-0.9).

7. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: In step (3), the mass ratio of the modified monomer to the 4,4′-difluorobenzophenone, the 4,4′-(hexafluoroisopropylidene)diphenol, and the potassium carbonate is 1:(1.45-1.6):(2.78-2.9):(1.25-1.35); the mass ratio of the precipitate to the chlorosulfonic acid is 1:(0.3-0.34).

8. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1 is characterized in that: The volume ratio of the toluene to the cyclopentane sulfone in the mixed solvent of step (3) and step (4) is 1:(1.2-1.5).

9. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: In step (4), the mass ratio of the 2,5-di(4-pyridyl)-1,4-hydroquinone to the 4,4′-difluorodiphenyl sulfone and the potassium carbonate is 1:(1.2-1.34):(0.7-0.8).

10. The method for desalting high-salinity brine wastewater from oil and gas fields as claimed in claim 1, characterized in that: Step (5) The spraying amount of the first product and the second product on the spinning surface of the hydrophobic membrane is 0.1-1 g / m 2 .

Images