A method of pretreating gas field water

Abstract

The application discloses a pretreatment method of gas field water, which comprises the following steps: gas stripping of the gas field water to obtain gas phase and liquid phase, wherein the volume ratio of the gas field water to the stripping gas is 1:8-20; returning the gas phase to the previous step after dry desulfurization; adding the liquid phase into a dissolved air water floatation after oxidative desulfurization and oil-water separation by biomass modified cotton sponge; performing oxidation treatment on the water phase after oil-water separation, then performing sedimentation treatment, and performing filtration treatment on the water phase after solid-liquid separation; removing sulfur and reducing COD by gas stripping and oxidation; treating the hydrogen sulfide gas generated by the gas stripping by dry desulfurization; recycling the desulfurized gas; removing suspended solids, high-valence metal ions with valence of two or more, colloids, organic matters, bacteria and microorganisms by a ceramic ultrafiltration membrane filter and a ceramic nanofiltration membrane filter.

Description

Technical Field

[0001] This invention relates to the field of sulfur-containing waste treatment technology in natural gas extraction, and specifically to a pretreatment method for gas field water. Background Technology

[0002] Natural gas has become an important component of my country's energy consumption. Natural gas extraction generates gas field water, which requires harmless treatment and resource utilization. Currently, the valuable resources contained in my country's gas field water are mainly inorganic salts (potassium chloride, sodium chloride) and some high-value elements (such as lithium ions, bromide ions, etc.). The extraction of these valuable resources requires pretreatment to remove impurities. Simultaneously, pretreatment is also the primary step in the reinjection, reuse, and compliant discharge of gas field water. Because my country has many sulfur-containing gas fields, the resulting gas field water contains a large amount of hydrogen sulfide. The desulfurization process requires pH adjustment to convert sulfur ions in the gas field water into hydrogen sulfide, which not only complicates the process but also poses a risk of corrosion to storage tanks. Therefore, finding an economical, scientific, reasonable, and efficient pretreatment technology is particularly important. Summary of the Invention

[0003] The technical problem this invention aims to solve is that in the desulfurization process of gas field gas containing a large amount of hydrogen sulfide, pH adjustment is needed to convert sulfur ions in the gas field water into hydrogen sulfide. This not only increases the complexity of the process but also poses a risk of corrosion to the storage tanks. The goal is to provide a pretreatment method for gas field water that combines gas stripping and oxidation for desulfurization and COD reduction. Dry desulfurization is used to treat the hydrogen sulfide-containing gas generated during gas stripping, and the desulfurized gas is reused. Further suspended solids are removed using ceramic ultrafiltration and ceramic nanofiltration membrane filters, along with divalent and higher valence metal ions, colloids, organic matter, bacteria, and microorganisms.

[0004] This invention is achieved through the following technical solution:

[0005] A method for pretreatment of gas field water, the pretreatment method comprising:

[0006] Gas field water is stripped to obtain gas phase and liquid phase. The volume ratio of gas field water to stripping gas used in the stripping is 1:8 to 20.

[0007] After dry desulfurization in the gas phase, return to the previous step;

[0008] After liquid phase oxidation and desulfurization, dissolved gas water flotation is added, followed by oil-water separation through biomass-modified cotton sponge.

[0009] The aqueous phase after oil-water separation is oxidized, then settled, and after solid-liquid separation, the aqueous phase is filtered.

[0010] The beneficial effects of this invention are:

[0011] 1. In the process of desulfurization by air stripping, there is no need to convert sulfur ions in the degassing field water into hydrogen sulfide by adjusting the pH with acid. The remaining sulfur ions are oxidized in the subsequent advanced oxidation process, which simplifies the desulfurization process and avoids the risk of corrosion of the water storage tank.

[0012] 2. The pretreated gas field water has a hydrogen sulfide content ≤1mg / L, a suspended solids content ≤1mg / L, an oil content ≤1mg / L, and a COD ≤50mg / L, which meets the requirements of the water intake process for extracting valuable resources. That is, the water can be recycled for the extraction of natural gas, thus saving water resources.

[0013] 3. The hydrogen sulfide gas generated from gas stripping desulfurization is reintroduced into the gas stripping step after being subjected to dry desulfurization. The elemental sulfur generated by dry desulfurization can be used for process applications.

[0014] 4. Using biomass-modified cotton sponge for oil-water separation results in water with low oil content, which is beneficial for the recycling of the aqueous phase.

[0015] 5. The entire pretreatment process uses a small amount of chemical reagents, resulting in low cost. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0017] Figure 1 This is a flowchart illustrating the pretreatment process of gas field water in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a fixed-bed reaction in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0020] Because my country has many sulfur-containing gas fields, the resulting gas field water contains large amounts of hydrogen sulfide, and safety issues exist during the treatment process. Therefore, finding an economical, scientific, reasonable, and efficient pretreatment technology is particularly important.

[0021] In the process of realizing this invention, the inventors discovered that existing gas field water pretreatment generally consists of coagulation and flocculation units, filtration units, oxidation units, and softening units, which mainly remove suspended solids, reduce COD, and precipitate high-valence metal ions that are prone to scaling.

[0022] The pretreatment section of Chinese Patent 201611175024.6 includes a pre-sedimentation tank unit, a coagulation sedimentation unit, a sand filtration unit, and a UF system. The coagulation sedimentation unit alone requires the addition of agents such as aluminum sulfate, polyaluminum chloride, ferric chloride, ferrous sulfate, and magnesium carbonate. Moreover, the treated water sample still contains a large amount of organic matter, color, hardness, etc.

[0023] Although Chinese patent 201810812821.3 can obtain relatively high-quality pretreated water, the process is complicated, including adding coagulant, flocculant and descaling agent first, then adding bactericide, and then sand filtration, activated carbon filtration and ultrafiltration treatment.

[0024] Chinese Patent 202010931741.7 provides a wastewater gas stripping desulfurization system and process. The system includes a pH adjustment device, a gas stripping device, and a negative pressure device. Its main process is to adjust the pH to convert sulfur in the gas field water into hydrogen sulfide, and then remove the hydrogen sulfide by negative pressure gas stripping.

[0025] Chinese Patent 201910960352.4 provides a method and system for desulfurizing high-sulfur wastewater from oil and gas fields. The main method involves adjusting the pH to convert sulfur in the gas field water into hydrogen sulfide, and then using natural gas or nitrogen for gas stripping at a pressure of 150-200 kPa.

[0026] In summary, current gas field water treatment methods have at least the following problems:

[0027] 1. The desulfurization stripping process requires pH adjustment to convert sulfur ions in the gas field water into hydrogen sulfide, which not only increases the process complexity but also poses a risk of corrosion to the storage tanks.

[0028] 2. The treated water quality cannot meet the requirements of some valuable resource extraction processes (such as the requirements of hydrogen sulfide content ≤1mg / L, suspended solids content ≤1mg / L, oil content ≤1mg / L, and COD ≤100mg / L for many lithium and bromine extraction processes).

[0029] 3. Gas stripping desulfurization does not consider how to handle hydrogen sulfide-containing gases or how to reuse them;

[0030] 4. The sediment produced by the hardening process is difficult to settle quickly and easily clogs the filtration system.

[0031] To address the above problems, this invention provides a pretreatment method for gas field water, such as... Figure 1 As shown, the preprocessing methods include:

[0032] S1. Gas stripping is performed on the gas field water to obtain gas phase and liquid phase. The volume ratio of gas field water to the gas stripping gas used in the gas stripping is 1:8 to 20.

[0033] S2. After dry desulfurization in the gas phase, return to the previous step;

[0034] S3. After liquid phase oxidation and desulfurization, dissolved gas water flotation is added, followed by oil-water separation through biomass-modified cotton sponge.

[0035] S4. The aqueous phase after oil-water separation is oxidized, then settled, and the aqueous phase after solid-liquid separation is filtered.

[0036] In this invention, in step S1, the gas stripping process can be a conventional gas stripping method in the art, such as depressurized gas stripping or atmospheric gas stripping. The gas used in the gas process can be a conventional gas in the art, such as air, purified natural gas, nitrogen, etc. This step is mainly to remove hydrogen sulfide gas from the gas field gas.

[0037] In this invention, in step S2, "dry desulfurization" refers to the contact between a solid desulfurizing agent and a hydrogen sulfide-containing gas, where the reaction with the hydrogen sulfide fixes the sulfur in the hydrogen sulfide within the solid desulfurizing agent. The gas phase is then returned to step S1, achieving both gas stripping and hydrogen sulfide treatment. Dry desulfurization can be carried out in a fixed bed. The fixed bed has a height of 6 cm and an inner diameter of 1.5 cm. The fixed bed is filled with a modified electric arc furnace dust adsorbent with a particle size of 1–1.5 mm. The reaction pressure in the fixed bed during the desulfurization process is 101–200 kPa.

[0038] In step S2, the gas phase is mixed with vaporized water before entering the solidification bed. The mixed gas exiting the fixed bed is condensed by condensate water, and the gas phase is then dried before returning to step S1. Figure 2 As shown.

[0039] The modified electric arc furnace dust adsorbent can be prepared by the following steps:

[0040] A1. Mix and grind the electric arc furnace dust agglomerates with a particle size greater than 0.5 mm with a solvent, dry them, and then crush and screen them to obtain particles with a particle size of 1.0 to 1.5 mm.

[0041] A2. The particles are heat-treated to obtain the modified electric arc furnace dust adsorbent.

[0042] The grinding process is carried out using conventional grinding equipment, such as a ball mill. The grinding time is generally 3 to 5 hours. The temperature used in the drying process is generally 70 to 90°C, such as 75°C, 83°C, 88°C, etc.

[0043] The solvent content ranges from 20wt% to 40wt%, for example: 25wt%, 32wt%, 36wt%, 39wt%, etc. The solvent is generally water.

[0044] The temperature during heat treatment is generally 500-700℃, such as 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, etc.; it is generally carried out in an oxygen-containing atmosphere, such as air.

[0045] In step S3, oxidative desulfurization mainly employs inorganic desulfurization, and the oxidants involved include, but are not limited to, at least one of hypochlorite, persulfate, and ferrate. Hypochlorite, persulfate, and ferrate can be their respective potassium or sodium salts.

[0046] In step S3, the dissolved air water refers to supersaturated water formed by dissolving air into water to the maximum extent in the shortest time.

[0047] In step S3, the biomass-modified cotton sponge mainly adsorbs oil to achieve oil-water separation. During the process, oil and sludge can be scraped off simultaneously, allowing the biomass-modified cotton sponge to continuously adsorb oil.

[0048] Biomass-modified cotton sponge can be prepared by the following steps:

[0049] H1. Stearamine and paraformaldehyde were mixed at 50°C to 80°C in the presence of an organic solvent to obtain a mixture;

[0050] H2. Add biomass phenols to the mixture and react at 100-120℃ for 3-8 hours, then add alkaline solution and separate to obtain biomass monomers;

[0051] H3. Carbonize the biomass monomers at 80–300℃, and then react them in an anaerobic environment at 500–700℃ for 3–7 hours to obtain biomass carbon balls;

[0052] H4. Immerse biomass carbon pellets in stearic acid;

[0053] H5. Immerse the cotton sponge in the biomass carbon ball solution for 10-20 minutes, then dry and solidify.

[0054] In step H1, the molar ratio of stearylamine to paraformaldehyde is generally 1–3:2–7, for example, 1:2, 2:5, or 3:7, etc. The reaction temperature can be 55℃, 60℃, 65℃, 68℃, 72℃, 77℃, etc.

[0055] In step H1, the organic solvent is typically dimethyl sulfoxide, N,N-dimethylformamide, or ethanol.

[0056] In step H2, the biomass phenol is generally diphenyl ether, anisole, or rose ether. The reaction temperature can be 105℃, 108℃, 110℃, 113℃, 115℃, 118℃, etc. The precipitate obtained after adding an alkaline solution is dried to obtain biomass monomers; the drying process is generally carried out in a vacuum environment.

[0057] In step H3, the carbonization temperature is generally 80–300°C, preferably 150–230°C, and more preferably 180–200°C. The temperature gradient during carbonization is generally 50–100°C.

[0058] In step H3, the oxygen-free environment can be an inert gas atmosphere or a nitrogen atmosphere, such as an argon atmosphere.

[0059] In step H4, the biomass carbon balls are treated with stearic acid, which gives them hydrophobic properties, enabling them to absorb oil. Cotton sponges are used primarily to reduce weight, allowing them to float on the water surface and effectively absorb oil.

[0060] In step S3, the biomass-modified cotton sponge is typically placed at the water outlet.

[0061] In step S4, the oxidant used in the oxidation treatment includes at least one of Fenton oxidant, ferrate, and ozone, preferably Fenton oxidant and ozone. The Fenton oxidant mainly consists of a chelating agent, a ferrous salt, and hydrogen peroxide, wherein the hydrogen peroxide content in the hydrogen peroxide is generally around 30 wt%. The mass ratio of the chelating agent, ferrous salt, and hydrogen peroxide is 1:(15-25):(15-45). The chelating agent includes, but is not limited to, at least one of aminocarboxylates, hydroxycarboxylates, and organophosphates.

[0062] In step S4, the sedimentation treatment mainly employs coagulants and flocculants. The coagulants include, but are not limited to, at least one of polyaluminum chloride, polyaluminum sulfide, polyaluminum magnesium silicate, polyferric chloride, polyaluminum ferric chloride, and polyferric sulfate; the dosage is generally 200-600 mg / L. The flocculant is cationic polyacrylamide and its derivatives, with a viscosity-average molecular weight of 20 million ± 1 million, and a dosage of 1-4 mg / L.

[0063] In step S4, the filtration process includes sequentially performing a rotary drum precision filter with a filtration accuracy of 10–20 μm, a ceramic ultrafiltration membrane filter with a membrane pore size of 0.01–0.1 μm, and a ceramic nanofiltration membrane filter with a membrane pore size of 0.005–0.007 μm. This removes divalent and higher valence metal ions, colloids, organic matter, bacteria, microorganisms, etc.

[0064] Table 1. Water quality of four gas field waters (except for pH, which is dimensionless, and SRB, which is units / mL, all other water quality indicators are in mg / L).

[0065] Gas field water <![CDATA[Ca 2+ ]]> <![CDATA[K + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Na + ]]> <![CDATA[Ba 2+ ]]> <![CDATA[Li + ]]> <![CDATA[Sr 2+ ]]> <![CDATA[Cl - ]]> <![CDATA[Br - ]]> TDS sulfides COD Petroleum ammonia nitrogen TSS SRB pH A 1917 2781 309.6 30960 1163.2 146.7 200 48047.1 212.7 <![CDATA[8.69×10 4 ]]> 8.32 177 13.7 249 282 <![CDATA[1.5×10 4 ]]> 7.64 B 3975 2074 801.4 28560 471.2 124.82 472 54019.5 326.6 <![CDATA[10.30×10 4 ]]> 152 385 49.3 205 397 <![CDATA[110×10 2 ]]> 7.45 C 2023.0 3475.0 233.8 35460.0 1806.0 90.0 1414.0 67694 543 <![CDATA[11.32×10 4 ]]> 327 1025 66.0 308 456 <![CDATA[7.5×10 4 ]]> 6.54 D 2076.0 2409.0 524.3 27700.0 1303.0 60.7 993.7 49390 391 <![CDATA[8.53×10 4 ]]> 343 1320 43.2 397 660 <![CDATA[110×10 4 ]]> 5.91

[0066] Example 1

[0067] Gas field water A was used for pretreatment, and the treatment steps are as follows:

[0068] S1. Air stripping is used to perform atmospheric pressure air stripping on water A in the gas field. The volume ratio of air to water in the gas field is 10:1, and the volume of air stripping is calculated according to standard conditions.

[0069] S2. The hydrogen sulfide-containing gas generated in step S1 is introduced into the solidified bed for desulfurization treatment. The height of the fixed bed is 6cm and the inner diameter is 1.5cm. The fixed bed is filled with modified electric arc furnace dust adsorbent. The particle size of the modified electric arc furnace dust adsorbent is 1-1.5mm. The reaction pressure of the fixed bed during the desulfurization process is 101-130KPa.

[0070] S3. The gas after desulfurization treatment in step S2 is re-entered into the gas stripping step in step S1.

[0071] S4. Add sodium persulfate to the gas field water after gas stripping in step S1 for oxidative desulfurization. The amount of sodium persulfate added is 120 mg / L.

[0072] S5. Dissolved air water is introduced into the gas field water that has undergone oxidation and desulfurization in step S4. Dissolved air flotation is carried out by air. The dissolved air water is the air in the air tank that enters the dissolved air tank through the jet device and dissolves in the water at a pressure of 0.35MPa. The volume ratio of dissolved air water to gas field water is 1:100.

[0073] S6. In step S5, a scraper is used to remove floating oil and scum from the front end of the water outlet.

[0074] S7. The water treated in step S6 is overflowed into the advanced oxidation unit, where 0.015 mg / L disodium ethylenediaminetetraacetate, 0.3 mg / L ferrous sulfate, and 1.5 mg / L hydrogen peroxide (30% mass concentration) are added, and 0.5% ozone (the volume percentage of ozone in the gas field water under standard conditions) is introduced for advanced oxidation.

[0075] S8. Pump the water treated in step S7 into the cyclone flocculation sedimentation system. Add 200 mg / L polyaluminum chloride and 2 mg / L cationic polyacrylamide with a viscosity-average molecular weight of 20 million ± 1 million sequentially through the pipe mixer before entering the system. Let the water settle in the cyclone sedimentation system for 30 minutes.

[0076] S9. The water treated in step S8 overflows into the intermediate water tank. The water in the intermediate water tank is pumped to the filtration system and filtered sequentially through a rotary drum precision filter with an accuracy of 20μm and a ceramic ultrafiltration membrane filter with a membrane pore size of 0.05μm.

[0077] S10. Pump the water treated in step S9 into a ceramic nanofiltration membrane filter with a membrane pore size of 0.005μm to remove divalent and higher valence metal ions, colloids, organic matter, bacteria, microorganisms, etc.

[0078] After treatment steps S1 to S10, the water quality of the gas field was significantly improved. The comparison of water quality before and after treatment is shown in Table 2.

[0079] Table 2 Comparison of water quality before and after treatment A in gas field water (except for pH, which is dimensionless, and SRB, which is units / mL, all other water quality indicators are in mg / L).

[0080]

[0081] Example 2

[0082] Gas field water (B) was used for pretreatment, and the treatment steps are as follows:

[0083] S1. Nitrogen gas stripping is used to perform atmospheric pressure gas stripping on gas field water B. The volume ratio of nitrogen gas to gas field water used for gas stripping is 15:1, and the volume of gas stripping gas is calculated according to standard conditions.

[0084] S2. The hydrogen sulfide-containing gas generated in step S1 is introduced into a fixed bed identical to that in the example for desulfurization treatment, with a reaction pressure of 150-160 kPa.

[0085] S3. The gas after desulfurization treatment in step S2 is re-entered into the gas stripping step in step S1.

[0086] S4. Add sodium hypochlorite to the gas field water after gas stripping in step S1 for oxidative desulfurization. The amount of sodium hypochlorite added is 100 mg / L.

[0087] S5. Dissolved air water is introduced into the gas field water that has undergone oxidation and desulfurization in step S4. Dissolved air flotation is carried out by air. The dissolved air water is the air in the air tank that enters the dissolved air tank through the jet device and dissolves in the water at a pressure of 0.35MPa. The volume ratio of dissolved air water to gas field water is 2:100.

[0088] S6. In step S5, a scraper is used to remove floating oil and scum from the front end of the water outlet.

[0089] S7. The water treated in step S6 is overflowed into the advanced oxidation unit, where 0.03 mg / L sodium gluconate, 0.7 mg / L ferrous chloride, and 1.4 mg / L hydrogen peroxide (30% mass concentration) are added, and 1% ozone (the volume percentage of ozone in the gas field water under standard conditions) is introduced for advanced oxidation.

[0090] S8. Pump the water treated in step S7 into the cyclone flocculation sedimentation system. Add 250 mg / L polyaluminum chloride and 2.5 mg / L cationic polyacrylamide with a viscosity-average molecular weight of 20 million ± 1 million sequentially through the pipe mixer before entering the system. Let the water settle in the cyclone sedimentation system for 40 minutes.

[0091] S9. The water treated in step S8 overflows into the intermediate water tank. The water in the intermediate water tank is pumped to the filtration system and filtered sequentially through a rotary drum precision filter with an accuracy of 15μm and a ceramic ultrafiltration membrane filter with a membrane pore size of 0.07μm.

[0092] S10. Pump the water treated in step S9 into a ceramic nanofiltration membrane filter with a membrane pore size of 0.007μm to remove divalent and higher valence metal ions, colloids, organic matter, bacteria, microorganisms, etc.

[0093] After treatment steps S1 to S10, the water quality of the gas field was significantly improved. The comparison of water quality before and after treatment is shown in Table 3.

[0094]

[0095] Example 3

[0096] Pretreatment using gas field water (C) is performed, and the treatment steps are as follows:

[0097] S1. The gas field water C is subjected to negative pressure gas lifting using purified natural gas. The negative pressure gas lifting operating pressure is -30kPa. The volume ratio of purified natural gas to gas field water used for gas lifting is 18:1. The gas lifting volume is calculated according to standard conditions.

[0098] S2. The hydrogen sulfide-containing gas generated in step S1 is introduced into a fixed bed for desulfurization treatment.

[0099] S3. The gas after desulfurization treatment in step S2 is re-entered into the gas stripping step in step S1.

[0100] S4. Add potassium ferrate to the gas field water after gas stripping in step S1 for oxidative desulfurization. The amount of potassium ferrate added is 120 mg / L.

[0101] S5. Dissolved air water is introduced into the gas field water that has undergone oxidation and desulfurization in step S4. Dissolved air flotation is carried out by air. The dissolved air water is made by air entering the dissolved air tank through a jet device and dissolving in water at a pressure of 0.35 MPa. The volume ratio of dissolved air water to gas field water is 4:100.

[0102] S6. In step S5, a scraper is used to remove floating oil and scum from the front end of the water outlet.

[0103] S7. The water treated in step S6 overflows into the advanced oxidation unit, where 0.05 mg / L sodium ethylenediaminetetramethylene phosphate, 0.75 mg / L ferrous nitrate, 2.0 mg / L hydrogen peroxide (30% mass concentration), and 100 mg / L potassium ferrate are added, and 0.5% ozone (the volume percentage of ozone in the gas field water under standard conditions) is introduced for advanced oxidation.

[0104] S8. Pump the water treated in step S7 into the cyclone flocculation sedimentation system. Add 200 mg / L polyaluminum ferric chloride and 2.5 mg / L cationic polyacrylamide with a viscosity-average molecular weight of 20 million ± 1 million sequentially through the pipe mixer before entering the system. Let the water settle in the cyclone sedimentation system for 45 minutes.

[0105] S9. The water treated in step S8 overflows into the intermediate water tank. The water in the intermediate water tank is pumped to the filtration system and filtered sequentially through a rotary drum precision filter with an accuracy of 10μm and a ceramic ultrafiltration membrane filter with a membrane pore size of 0.05μm.

[0106] S10. Pump the water treated in step S9 into a ceramic nanofiltration membrane filter with a membrane pore size of 0.007μm to remove divalent and higher valence metal ions, colloids, organic matter, bacteria, microorganisms, etc.

[0107] After treatment steps S1 to S10, the water quality of the gas field was significantly improved. The comparison of water quality before and after treatment is shown in Table 4.

[0108] Table 4. Comparison of water quality before and after C treatment in the gas field (except for pH, which is dimensionless, and SRB, which is units / mL, all other water quality indicators are in mg / L).

[0109]

[0110] Example 4

[0111] Gas field water (D) is used for pretreatment, and the treatment steps are as follows:

[0112] S1. The gas field water D is subjected to negative pressure gas lifting using air lifting. The negative pressure gas lifting operating pressure is -35kPa. The volume ratio of purified natural gas to gas field water used for gas lifting is 12:1. The gas lifting volume is calculated according to standard conditions.

[0113] S2. The hydrogen sulfide-containing gas generated in step S1 is introduced into a fixed bed for desulfurization treatment.

[0114] S3. The gas after desulfurization treatment in step S2 is re-entered into the gas stripping step in step S1.

[0115] S4. Add sodium hypochlorite and sodium persulfate to the gas field water after gas stripping in step S1 for oxidative desulfurization. The amount of sodium hypochlorite added is 50 mg / L, and the amount of sodium persulfate added is 50 mg / L.

[0116] S5. Dissolved air water is introduced into the gas field water that has undergone oxidation and desulfurization in step S4. Dissolved air flotation is carried out by air. The dissolved air water is made by air entering the dissolved air tank through a jet device and dissolving in water at a pressure of 0.35 MPa. The volume ratio of dissolved air water to gas field water is 3:100.

[0117] S6. In step S5, a scraper is used to remove floating oil and scum from the front end of the water outlet.

[0118] S7. The water treated in step S6 is overflowed into the advanced oxidation unit, where advanced oxidation is carried out by adding 0.015 mg / L diethylenetriaminepentamethylphosphonate, 0.015 mg / L disodium ethylenediaminetetraacetate, 0.6 mg / L ferrous sulfate, and 1.2 mg / L hydrogen peroxide (30% mass concentration).

[0119] S8. Pump the water treated in step S7 into the cyclone flocculation sedimentation system. Add 300 mg / L polyaluminum chloride and 2 mg / L cationic polyacrylamide with a viscosity-average molecular weight of 20 million ± 1 million sequentially through the pipe mixer before entering the system. Let the water settle in the cyclone sedimentation system for 25 minutes.

[0120] S9. The water treated in step S8 overflows into the intermediate water tank. The water in the intermediate water tank is pumped to the filtration system and filtered sequentially through a rotary drum precision filter with an accuracy of 20μm and a ceramic ultrafiltration membrane filter with a membrane pore size of 0.07μm.

[0121] S10. Pump the water treated in step S9 into a ceramic nanofiltration membrane filter with a membrane pore size of 0.005μm to remove divalent and higher valence metal ions, colloids, organic matter, bacteria, microorganisms, etc.

[0122] After treatment steps S1 to S10, the water quality of the gas field was significantly improved. The comparison of water quality before and after treatment is shown in Table 5.

[0123] Table 5. Comparison of water quality before and after treatment D in the gas field (except for pH, which is dimensionless, and SRB, which is units / mL, all other water quality indicators are in mg / L).

[0124]

[0125] As shown in Tables 2-5, the pretreatment method for gas field gas disclosed in this invention separates hydrogen sulfide from other sulfur-containing substances for processing. Hydrogen sulfide is removed from the gas field gas via gas stripping, unlike existing methods that rely on pH adjustment. After hydrogen sulfide extraction, a fixed-bed desulfurization process is performed to remove hydrogen sulfide from the gas phase, enabling the recycling of the stripped gas and preventing environmental pollution. This is significantly different from existing technologies and avoids the risk of storage tank corrosion. Most importantly, the pretreated gas field water, in addition to being recyclable, meets the requirements for valuable resource extraction feedwater (hydrogen sulfide content ≤1 mg / L, suspended solids content ≤1 mg / L, oil content ≤1 mg / L, COD ≤50 mg / L), which is completely different from existing technologies (which do not report on the extraction of valuable resources from gas field water). The sulfur obtained in the fixed-bed desulfurization process can also be utilized, avoiding waste or environmental pollution. The coupled filtration process of ceramic ultrafiltration membrane filter and ceramic nanofiltration membrane filter achieves physical hardening removal, avoiding the problems of difficult-to-settle sediments and easy clogging of the filtration system caused by chemical precipitation hardening removal, which is conducive to continuous pretreatment.

[0126] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of pretreating gas field water, characterized by, The pretreatment method comprises: The gas field water is subjected to gas stripping to obtain a gas phase and a liquid phase, and the volume ratio of the gas field water to the stripping gas used for the gas stripping is 1:8-20; The gas phase is returned to the previous step after dry desulfurization; After the liquid phase is subjected to oxidative desulfurization and then air flotation after adding dissolved air, the oil-water separation is performed by using the biomass modified cotton sponge; The water phase after the oil-water separation is subjected to oxidation treatment, and then is subjected to sedimentation treatment, and then is subjected to solid-liquid separation, and then the water phase is subjected to filtration treatment; The preparation of the biomass modified cotton sponge comprises: Stearic amine and paraformaldehyde are mixed at a molar ratio of 1-3:2-7 in the presence of an organic solvent at 50-80 DEG C to obtain a mixed solution; Biomass phenol is added to the mixed solution and reacted at 100-120 DEG C for 3-8 hours, and then a basic solution is added to obtain biomass monomers by separation; The biomass monomers are carbonized at 80-300 DEG C, and then reacted in an oxygen-free environment at 500-700 DEG C for 3-7 hours to obtain biomass carbon spheres; The biomass carbon spheres are immersed in stearic acid; The cotton sponge is immersed in the biomass carbon sphere solution for 10-20 minutes, dried and solidified.

2. The method of claim 1, wherein the gas field water is pretreated by, The biomass phenol comprises at least one of diphenyl ether, anisole and rose ether.

3. The method of claim 1, wherein the gas field water is pretreated by adding a coagulant to the gas field water. The carbonization temperature gradient in the carbonization process is 50-100 DEG C.

4. The method of claim 1, wherein the gas field water is pretreated by adding a coagulant to the gas field water. The molar ratio of the stearic amine to the paraformaldehyde is 1:2, 2:5 or 3:

7.

5. The method of pretreating gas field water of claim 1, wherein, The filtration treatment comprises a drum-type precision filter with a precision of 10-20 microns, a ceramic ultrafiltration membrane filter with a membrane pore size of 0.01-0.1 microns and a ceramic nanofiltration membrane filter with a membrane pore size of 0.005-0.007 microns, which are sequentially arranged.

6. The pretreatment method of gas field water according to claim 1, characterized by, In the dry desulfurization, a modified electric arc furnace dust adsorbent is used, and the reaction is carried out in a fixed bed, and the reaction pressure is 101-200 KPa.

7. The method of pretreating gas field water according to claim 6, wherein, The preparation of the modified electric arc furnace dust adsorbent is as follows: Electric arc furnace dust agglomerates with a particle size greater than 0.5 mm and a solvent are mixed and ground according to a solvent proportion of 20wt%-40wt%, and then dried, and then crushed to obtain particles with a particle size of 1.0-1.5 mm; The particles are heat-treated in an oxygen-containing atmosphere at 500-700 DEG C to obtain the modified electric arc furnace dust adsorbent.

8. The method of pretreating gas field water of claim 1, wherein, The oxidant used in the oxidation treatment comprises at least one of a Fenton oxidant, a ferrate and ozone; The Fenton oxidant comprises a chelating agent, a ferrous salt and hydrogen peroxide, and the mass ratio of the chelating agent, the ferrous salt and the hydrogen peroxide is 1:15-25:15-45.

9. The method of pretreating gas field water of claim 1 wherein, The coagulant comprises at least one of polyaluminum chloride, polysulfur aluminum chloride, polysilicate aluminum magnesium, polymeric ferric chloride, polyaluminum ferric chloride and polymeric ferric sulfate; and the flocculant is cationic polyacrylamide and its derivatives, and the viscosity-average molecular weight is 19-21 million.

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