Method and system for coupling electrolytic treatment of oilfield produced water with desulfurization of natural gas

Abstract

The invention relates to the technical field of solid waste treatment, in particular to a method and system for coupling electrolysis treatment of oilfield produced water with natural gas desulfurization. The method comprises the following steps: introducing decontaminating produced water containing hypochlorous acid ions into sulfur-containing natural gas, so that the hypochlorous acid ions in the decontaminating produced water fully react with hydrogen sulfide in the sulfur-containing natural gas, and then carrying out solid-liquid separation to respectively obtain desulfurized natural gas and elemental sulfur; decontaminated produced water containing hypochlorous acid ions generated after electrolysis of oilfield produced water is adopted as a natural oxidation desulfurizer, so that the sulfur element in hydrogen sulfide is oxidized to form elemental sulfur, the hypochlorous acid ions are reduced into chloride ions and water, meanwhile, desulfurized natural gas is discharged out of a system, and then the elemental sulfur can be separated from the water in a solid-liquid separation mode. According to the method, the cost of removing the sulfur element in the sulfur-containing natural gas can be effectively reduced, and meanwhile, environmental pollution caused by adopting a hydrogen sulfide treatment reagent can be avoided.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste treatment, and particularly to a method and system for coupling electrolytic treatment of produced water from oilfields with natural gas desulfurization. Background Art

[0002] Most of the sulfur elements in natural gas exist as reducing H2S. H2S is a highly toxic gas with a typical rotten egg smell. When burned in the air, it will produce SO2 and cause serious environmental pollution. At the same time, H2S will also corrode pipelines, instruments and other equipment and reduce their service life. Therefore, removing hydrogen sulfide and organic sulfides in natural gas can not only avoid equipment corrosion and catalyst poisoning, improve the service life of equipment, but also produce high-quality natural gas products, and more importantly, avoid sulfur pollution problems in subsequent natural gas applications.

[0003] At present, a variety of methods have been developed to remove hydrogen sulfide gas from natural gas: such as dry desulfurization methods using activated carbon, molecular sieves and membranes as separation media; chemical absorption methods using alkanolamines such as methyl ethylene glycol, monoethanolamine and diethanolamine as absorbents; physical absorption methods using solvents such as methanol, propylene carbonate and polyethylene glycol dimethyl ether, etc. However, the above methods all use special hydrogen sulfide treatment reagents, which makes the cost of hydrogen sulfide treatment relatively high, and media such as methanol and alkanolamines are toxic themselves. Once leaked, it will bring serious environmental pollution problems. Summary of the Invention

[0004] The present application provides a method and system for coupling electrolytic treatment of produced water from oilfields with natural gas desulfurization to solve the technical problems of high cost and environmental pollution in removing hydrogen sulfide from natural gas in the prior art.

[0005] In a first aspect, the present application provides a method for coupling electrolytic treatment of produced water from oilfields with natural gas desulfurization, the method comprising:

[0006] Introducing decontaminated produced water containing hypochlorite ions into sulfur-containing natural gas to allow the hypochlorite ions in the decontaminated produced water to fully react with hydrogen sulfide in the sulfur-containing natural gas, and then performing solid-liquid separation to obtain desulfurized natural gas and elemental sulfur respectively.

[0007] Optionally, the mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:1 to 100.

[0008] Optionally, the mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:50 to 100.

[0009] Optionally, the mass concentration of the hypochlorite ions ≤ 1%.

[0010] Optionally, the mass concentration of the hypochlorite ions is 0.5% to 1%.

[0011] Optionally, the concentration of hydrogen sulfide in the sulfur-containing natural gas is ≥ 500 ppm.

[0012] Optionally, the concentration of hydrogen sulfide in the sulfur-containing natural gas is 500 ppm to 1000 ppm.

[0013] Optionally, the method further includes:

[0014] Purify the produced water from the oilfield, and then perform electrolysis to obtain decontaminated produced water containing hypochlorite ions.

[0015] Optionally, the chemical oxygen demand of the decontaminated produced water is ≤ 15.

[0016] Optionally, the electrolysis time is 1 h to 5 h.

[0017] Optionally, the chemical oxygen demand of the produced water from the oilfield is 2500 to 3500.

[0018] In a second aspect, the present application provides a system for coupling electrolysis treatment of produced water from an oilfield with natural gas desulfurization. The system is adapted to the method described in the first aspect. The system includes:

[0019] An electrolysis unit, which includes a produced water delivery pipeline, an electrolytic cell, and a decontaminated produced water output pipeline. The produced water delivery pipeline is connected to the water inlet of the electrolytic cell, and one end of the decontaminated produced water output pipeline is connected to the water outlet of the electrolytic cell;

[0020] A spraying unit, which includes a sulfur-containing gas delivery pipeline, a desulfurized gas delivery pipeline, a spraying part, and a mixed liquid discharge pipeline. The sulfur-containing gas delivery pipeline is connected to the gas inlet of the spraying part, the desulfurized gas delivery pipeline is connected to the gas outlet of the spraying part, the other end of the decontaminated produced water output pipeline is connected to the liquid inlet of the spraying part, and the feed port of the mixed liquid discharge pipeline is connected to the discharge port of the spraying part.

[0021] Optionally, the system further includes a solid-liquid separation unit, and the feed port of the solid-liquid separation unit is connected to the discharge port of the mixed liquid discharge pipeline.

[0022] Optionally, the sulfur-containing gas delivery pipeline is arranged below the decontaminated produced water output pipeline.

[0023] Optionally, the desulfurized gas delivery pipeline is arranged at the top of the spraying part, and the mixed liquid discharge pipeline is arranged at the bottom of the spraying part.

[0024] Optionally, the spraying part further includes a spraying pipeline, the spraying pipeline is connected to the liquid outlet end of the decontaminated produced water output pipeline, and the spraying pipeline is arranged below the desulfurized gas delivery pipeline.

[0025] Optionally, the spraying part further includes a liquid collecting tray, which is arranged between the sulfur-containing gas conveying pipeline and the mixed liquid discharging pipeline, so as to form a reaction space between the liquid collecting tray and the spraying pipeline.

[0026] Optionally, the liquid collecting tray is provided with a through mixed liquid outlet, so as to form a mixed liquid storage space between the liquid collecting tray and the feed port of the mixed liquid discharging pipeline.

[0027] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0028] A method for coupling electrolytic treatment of oilfield produced water and natural gas desulfurization provided by an embodiment of the present application uses the decontaminated produced water containing hypochlorite ions generated after electrolysis of oilfield produced water as a natural oxidative desulfurization agent, and uses hypochlorite ions to oxidize hydrogen sulfide in sulfur-containing natural gas, so that the sulfur element in hydrogen sulfide is oxidized to form elemental sulfur, while hypochlorite ions are reduced to chloride ions and water. At the same time, the desulfurized natural gas is discharged from the system, and the elemental sulfur can be separated from the water by solid-liquid separation. In the above method, no special hydrogen sulfide treatment reagent needs to be added during the whole treatment process, and only the difference in different phases needs to be used to directly separate the desulfurized natural gas and the chloride ion-containing solution after the reaction. Therefore, the cost of removing sulfur elements from sulfur-containing natural gas can be effectively reduced, and at the same time, environmental pollution caused by using hydrogen sulfide treatment reagents can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a schematic flow chart of a method for coupling electrolytic treatment of oilfield produced water and natural gas desulfurization provided by an embodiment of the present application;

[0032] Figure 2 It is a detailed schematic flow chart of a method for coupling electrolytic treatment of oilfield produced water and natural gas desulfurization provided by an embodiment of the present application;

[0033] Figure 3 It is a logical schematic diagram of a system for coupling electrolytic treatment of oilfield produced water and natural gas desulfurization provided by an embodiment of the present application;

[0034] Figure 4 Schematic diagram of the reaction principle of the diaphragm-free electrolytic cell provided by the embodiment of the present application;

[0035] Figure 5 Schematic diagram of the structure of the spraying unit provided by the embodiment of the present application;

[0036] Among them, 1 - electrolysis unit, 11 - produced water delivery pipeline, 12 - electrolytic cell, 13 - decontaminated produced water output pipeline, 2 - spraying unit, 21 - sulfur-containing gas delivery pipeline, 22 - desulfurized gas delivery pipeline, 23 - spraying part, 231 - spraying pipeline, 232 - liquid collection tray, 233 - mixed liquid outlet, 24 - mixed liquid discharge pipeline, 3 - solid-liquid separation unit. Specific embodiments

[0037] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0039] The creative thinking of the present application is:

[0040] Currently, the diaphragm-free electrolytic cell shown in Figure 4 is used to electrolyze and integrate the produced water to achieve the electrolytic decontamination of the produced water and the production of hydrogen. However, due to the large amount of Cl - in the produced water, a large amount of Cl - is oxidized at the anode side during electrolysis using the diaphragm-free electrolytic cell to produce Cl2, and the produced Cl2 further reacts with OH - generated at the cathode side to form strongly oxidizing ClO - , and ClO - can further oxidize organic matter. However, when the organic matter content in the produced water is not sufficient to completely consume ClO - , the excess ClO - will affect the various indicators of the produced water. Therefore, to ensure that the various indicators of the produced water meet the standards, measures should be taken to completely consume ClO - .

[0041] H2S can react with NaClO to generate elemental sulfur, and the reaction principle is as follows:

[0042] H2S + NaClO = NaCl + S↓ + H2O;

[0043] Wherein S precipitates in the form of an element.

[0044] Therefore, in this application, for the first time, the decontaminated oilfield produced water containing NaClO produced by electrolyzing the oilfield produced water is used as a desulfurization reagent for natural gas. Without using external desulfurization reagents, it has low cost and can be widely applied, showing great commercial application prospects.

[0045] As Figure 1 shown, an embodiment of this application provides a method for coupling electrolytic treatment of oilfield produced water and desulfurization of natural gas. The method includes:

[0046] S1. Introduce the decontaminated produced water containing hypochlorite ions into the sulfur-containing natural gas, so that the hypochlorite ions in the decontaminated produced water react fully with hydrogen sulfide in the sulfur-containing natural gas, and then perform solid-liquid separation to obtain desulfurized natural gas and elemental sulfur respectively.

[0047] It should be noted that in order to make the decontaminated produced water containing hypochlorite ions contact the sulfur-containing natural gas fully, the introduction method can be spray atomization, ultrasonic atomization, or pressure atomization. Generally, the above-mentioned various introduction methods make the decontaminated produced water form micron-sized droplets, and the droplets have a good specific surface area at the micron level. Therefore, they can contact the gas molecules in the sulfur-containing natural gas fully and react on the surface of the droplets, so that elemental sulfur can be obtained.

[0048] It should be noted that the solid-liquid separation can be carried out by centrifugation, vacuum filtration, or pressure filtration.

[0049] In some optional embodiments, the mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:1 - 100.

[0050] In the embodiments of this application, by defining the specific mass ratio of the sulfur-containing natural gas to the decontaminated produced water, there can be enough hypochlorite ions in the decontaminated produced water to react completely with hydrogen sulfide in the sulfur-containing natural gas, so that the hypochlorite ions in the hypochlorite ions are converted into chloride ions, and at the same time, the sulfur ions in hydrogen sulfide are converted into elemental sulfur. Subsequently, the desulfurized natural gas and chloride ions after the reaction are directly separated by the differences in different phases, so that the sulfur element in the sulfur-containing natural gas can be removed at low cost and the environmental pollution caused by the hydrogen sulfide treatment reagents in the prior art can be avoided.

[0051] In some optional embodiments, the mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:50 - 100.

[0052] In the embodiments of the present application, further limiting the specific mass ratio of the sulfur-containing natural gas to the decontaminated produced water can further ensure that there is sufficient hypochlorite ion in the decontaminated produced water to completely react with hydrogen sulfide in the sulfur-containing natural gas, and the hypochlorite ion in the hypochlorite ion is converted into chloride ion, while the sulfur ion in hydrogen sulfide is converted into elemental sulfur. In this way, sulfur elements in the sulfur-containing natural gas can be removed at low cost, and environmental pollution caused by hydrogen sulfide treatment reagents in the prior art can be avoided.

[0053] The mass ratio of the sulfur-containing natural gas to the decontaminated produced water can be 1:50, or 1:60, or 1:70, or 1:80, or 1:90, or 1:100.

[0054] In some alternative embodiments, the mass concentration of the hypochlorite ion ≤ 1%.

[0055] In the embodiments of the present application, limiting the specific mass concentration of the hypochlorite ion can ensure that there is sufficient hypochlorite ion in the decontaminated produced water to completely react with hydrogen sulfide in the sulfur-containing natural gas, and the hypochlorite ion in the hypochlorite ion is converted into chloride ion, while the sulfur ion in hydrogen sulfide is converted into elemental sulfur. In this way, sulfur elements in the sulfur-containing natural gas can be removed at low cost, and environmental pollution caused by hydrogen sulfide treatment reagents in the prior art can be avoided.

[0056] In some alternative embodiments, the mass concentration of the hypochlorite ion is 0.5% - 1%.

[0057] In the embodiments of the present application, further limiting the specific mass concentration of the hypochlorite ion can further ensure that there is sufficient hypochlorite ion in the decontaminated produced water to completely react with hydrogen sulfide in the sulfur-containing natural gas, and the hypochlorite ion in the hypochlorite ion is converted into chloride ion.

[0058] The mass concentration of the hypochlorite ion can be 0.5%, or 0.55%, or 0.60%, or 0.65%, or 0.70%, or 0.75%, or 0.80%, or 0.85%, or 0.90%, or 0.95%, or 1.00%.

[0059] In some alternative embodiments, the concentration of hydrogen sulfide in the sulfur-containing natural gas ≥ 500 ppm.

[0060] In the embodiments of the present application, the specific concentration of hydrogen sulfide in the sour natural gas is limited, so that there is enough hydrogen sulfide in the sour natural gas to react completely with the hypochlorite ions in the decontaminated produced water, and the sulfur ions in the hydrogen sulfide are converted into elemental sulfur, and at the same time, the hypochlorite ions in the hypochlorite ions are converted into chloride ions, which can remove the sulfur element in the sour natural gas at a low cost and avoid the environmental pollution caused by the hydrogen sulfide treatment reagents in the prior art.

[0061] In some optional embodiments, the concentration of hydrogen sulfide in the sour natural gas is 500 ppm to 1000 ppm.

[0062] In the embodiments of the present application, the specific concentration of hydrogen sulfide in the sour natural gas is limited, so that there is enough hydrogen sulfide in the sour natural gas to react completely with the hypochlorite ions in the decontaminated produced water, and the sulfur ions in the hydrogen sulfide are converted into elemental sulfur, and at the same time, the hypochlorite ions in the hypochlorite ions are converted into chloride ions, which can remove the sulfur element in the sour natural gas at a low cost and avoid the environmental pollution caused by the hydrogen sulfide treatment reagents in the prior art.

[0063] like Figure 2 As shown, in some optional implementations, the method further includes:

[0064] S101. Purify the produced water from the oil field and then electrolyze it to obtain decontaminated produced water containing hypochlorite ions.

[0065] In the embodiment of the present application, by purifying the produced water from the oil field, larger sediments can be removed, and then by electrolysis, not only can the chloride ions in the decontaminated produced water be converted into hypochlorite ions, but the chemical oxygen demand of the produced water can also be effectively reduced by electrolysis, thereby facilitating the subsequent acquisition of discharged produced water with qualified indicators.

[0066] It should be noted that the purification treatment can use flocculants to treat floating impurities and insoluble matter in the oilfield produced water, and then remove the sediment through filtration to obtain relatively pure oilfield produced water.

[0067] In some optional embodiments, the chemical oxygen demand of the decontaminated produced water is ≤15.

[0068] In the embodiments of the present application, the specific chemical oxygen demand of the decontaminated produced water is limited, so that it can be clarified that the decontaminated produced water before the reaction contains a small amount or no other oxidizing substances except hypochlorite ions. Therefore, there can be sufficient hypochlorite ions in the decontaminated produced water to react completely with the hydrogen sulfide in the sour natural gas, so that the hydrogen sulfide in the sour natural gas can be effectively converted into elemental sulfur, thereby avoiding a large amount of other oxidizing substances reacting with hydrogen sulfide and affecting the desulfurization effect of the natural gas.

[0069] In some alternative embodiments, the electrolysis time is 1 h to 5 h.

[0070] In the embodiments of the present application, by defining the specific electrolysis time, the chloride ions in the produced wastewater can be completely converted into hypochlorite ions, and at the same time, other non-hypochlorite oxidizing ions can be effectively removed by electrolysis, thereby reducing the chemical oxygen demand of the produced water and facilitating the complete reaction of the hypochlorite ions in the produced water with hydrogen sulfide in the sour natural gas.

[0071] The electrolysis time can be 1 h, or 1.5 h, or 2.0 h, or 2.5 h, or 3.0 h, or 3.5 h, or 4.0 h, or 4.5 h, or 5.0 h.

[0072] In some alternative embodiments, the chemical oxygen demand of the produced water from the oilfield is 2500 to 3500.

[0073] In the embodiments of the present application, by defining the specific chemical oxygen demand of the produced water from the oilfield, most of the produced water from the oilfield can be covered. If the chemical oxygen demand of the produced water from the oilfield is too high, the electrolysis time can be appropriately increased or a reducing agent can be added in advance to treat the produced water from the oilfield.

[0074] The chemical oxygen demand of the produced water from the oilfield can be 2500, or 2550, or 2600, or 2650, or 2700, or 2750, or 2800, or 2850, or 2900, or 2950, or 3000, or 3050, or 3100, or 3150, or 3200, or 3250, or 3300, or 3350, or 3400, or 3450, or 3500.

[0075] As Figure 3 shown, based on a general inventive concept, the present application provides a system for coupling electrolytic treatment of produced water from an oilfield with natural gas desulfurization. The system is adapted to the method, and the system includes:

[0076] An electrolysis unit 1, the electrolysis unit 1 includes a produced water delivery pipeline 11, an electrolytic cell 12, and a decontaminated produced water output pipeline 13. The produced water delivery pipeline 11 communicates with the water inlet of the electrolytic cell 12, and one end of the decontaminated produced water output pipeline 13 communicates with the water outlet of the electrolytic cell 12;

[0077] The spraying unit 2, the spraying unit 2 includes a sulfur-containing gas delivery pipeline 21, a desulfurized gas delivery pipeline 22, a spraying section 23 and a mixed liquid discharge pipeline 24. The sulfur-containing gas delivery pipeline 21 communicates with the air inlet of the spraying section 23. The desulfurized gas delivery pipeline 22 communicates with the air outlet of the spraying section 23. The other end of the decontaminated produced water output pipeline 13 communicates with the liquid inlet of the spraying section 23. The feed inlet of the mixed liquid discharge pipeline 24 communicates with the discharge outlet of the spraying section 23.

[0078] This system is implemented based on the above method. The specific steps of the method can be referred to the above embodiments. Since this system adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated here one by one.

[0079] It should be noted that the electrolytic cell 12 can adopt, for example, Figure 4 the diaphragm-free electrolytic cell 12 as shown.

[0080] The spraying section 23 can adopt, for example, Figure 5 the spray tower as shown.

[0081] The specific working process of the above system is as follows: The produced water delivery pipeline 11 transports the flocculated oilfield produced water into the electrolytic cell 12. After complete electrolysis, it is then input into the spraying section 23 through the decontaminated produced water output pipeline 13. Then, sulfur-containing natural gas is input into the spraying section 23 through the sulfur-containing gas delivery pipeline 21. After the reaction in the spraying section 23 is complete, the desulfurized gas is discharged from the spraying unit 2 through the desulfurized gas delivery pipeline 22. At the same time, the formed mixed liquid containing elemental sulfur is discharged from the system through the mixed liquid discharge pipeline 24 for subsequent treatment.

[0082] In some optional embodiments, the system further includes a solid-liquid separation unit 3. The feed inlet of the solid-liquid separation unit 3 communicates with the discharge outlet of the mixed liquid discharge pipeline 24.

[0083] In the embodiments of the present application, by introducing the solid-liquid separation unit 3, the mixed liquid containing elemental sulfur can be treated, so that elemental sulfur and produced water can be separated. The produced water can be directly discharged later, and elemental sulfur can be sold as a by-product.

[0084] It should be noted that the solid-liquid separation unit 3 can adopt a centrifuge, or a vacuum filter, or a plate and frame filter press, or a solid-liquid separation system composed of a centrifuge, a vacuum filter and a plate and frame filter press.

[0085] In some optional embodiments, the sulfur-containing gas delivery pipeline 21 is arranged below the decontaminated produced water output pipeline 13.

[0086] In the embodiment of the present application, the distribution position of the sulfur-containing gas transmission pipeline 21 relative to the decontaminated produced water output pipeline 13 is defined. Since the sulfur-containing natural gas diffuses upward in the spraying part 23, and the decontaminated produced water flows downward due to gravity, setting the sulfur-containing gas output pipeline below the sulfur-containing gas transmission pipeline 21 can cause the sulfur-containing natural gas and the decontaminated produced water to form a countercurrent. This can not only increase the contact area between the sulfur-containing natural gas and the decontaminated produced water, but also increase the contact reaction time between them, enabling the hypochlorite ions in the decontaminated produced water to react completely with the hydrogen sulfide in the sulfur-containing natural gas.

[0087] In some alternative embodiments, the desulfurized gas transmission pipeline 22 is provided at the top of the spraying part 23, and the mixed liquid discharge pipeline 24 is provided at the bottom of the spraying part 23.

[0088] In the embodiment of the present application, by designing the layout positions of the desulfurized gas transmission pipeline 22 and the mixed liquid discharge pipeline 24, since the aforementioned natural gas diffuses from the bottom to the top of the spraying part 23, and the decontaminated produced water flows from the top to the bottom, the mixed liquid containing elemental sulfur formed after the reaction between the hypochlorous acid in the decontaminated produced water and the hydrogen sulfide in the sulfur-containing natural gas will gather at the bottom of the spray tower due to gravity, thus facilitating subsequent solid-liquid separation treatment.

[0089] In some alternative embodiments, the spraying part 23 further includes a spraying pipeline 231, the spraying pipeline 231 communicates with the liquid outlet end of the decontaminated produced water output pipeline 13, and the spraying pipeline 231 is provided below the desulfurized gas transmission pipeline 22.

[0090] In the embodiment of the present application, by refining the spraying pipeline 231 that functions as a spray in the spraying part 23 and defining the distribution of the spraying pipeline 231, after the hypochlorous acid in the produced water and the hydrogen sulfide in the sulfur-containing natural gas react completely, the desulfurized natural gas and the produced water can be directly separated and discharged from the system through the provided desulfurized gas transmission pipeline 22. Furthermore, the desulfurized natural gas and the chlorine ion-containing solution after the reaction can be directly separated by utilizing the differences in different phases.

[0091] In some alternative embodiments, the spraying part 23 further includes a liquid collecting tray 232, the liquid collecting tray 232 is provided between the sulfur-containing gas transmission pipeline 21 and the mixed liquid discharge pipeline 24, so as to form a reaction space between the liquid collecting tray 232 and the spraying pipeline 231.

[0092] In the embodiment of the present application, by arranging a liquid collecting tray 232 at the bottom of the spraying part 23, since the liquid collecting tray 232 is arranged between the sulfur-containing gas conveying pipeline 21 and the mixed liquid discharging pipeline 24, it can block the downward diffusion of the sulfur-containing gas conveying pipeline 21, so that a reaction space with sufficient volume can be formed between the spraying pipeline 231 and the liquid collecting tray 232 for the produced water and the sulfur-containing natural gas, thereby enabling the reaction between hypochlorous acid in the produced water and hydrogen sulfide in the sulfur-containing natural gas to be complete.

[0093] In some alternative embodiments, the liquid collecting tray 232 is provided with a through mixed liquid outlet 233, so as to form a storage space for the mixed liquid between the liquid collecting tray 232 and the feed port of the mixed liquid discharging pipeline 24.

[0094] In the embodiment of the present application, by opening a through mixed liquid outlet 233 on the liquid collecting tray 232, the produced water mixed liquid containing elemental sulfur can be discharged in real time through the mixed liquid outlet 233, avoiding the accumulation of the produced water in the spraying tower, which affects the entry of the sulfur-containing natural gas into the spraying tower, and enabling the reaction between hypochlorous acid in the produced water and hydrogen sulfide in the sulfur-containing natural gas to be complete.

[0095] The following further elaborates the present application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0096] Example 1

[0097] The initial COD of the untreated oilfield produced water is 3000, where the NaCl concentration is 1 wt%, the H2S concentration in the sulfur-containing natural gas is 1000 ppm. The oilfield produced water is first subjected to flocculation treatment, and then the produced water is introduced into the diaphragm-free electrolytic cell 12 for electrolysis. The residence time of the produced water in the electrolytic cell 12 is 2 h;

[0098] Subsequently, the sulfur-containing natural gas and the electrolyzed produced water are introduced into the spraying tower, and the gas-liquid mass ratio in the spraying tower is controlled to be 1:50. It is measured that the COD of the produced water at the outlet of the electrolytic cell 12 is 15, and the H2S concentration of the natural gas at the outlet of the spraying tower is 0.

[0099] Example 2

[0100] The initial COD of the untreated oilfield produced water is 3000, where the NaCl concentration is 0.5 wt%, the H2S concentration in the sulfur-containing natural gas is 1000 ppm. The oilfield produced water is first subjected to flocculation treatment, and then the produced water is introduced into the diaphragm-free electrolytic cell 12 for electrolysis. The residence time of the produced water in the electrolytic cell 12 is 5 h;

[0101] Subsequently, the sulfur-containing natural gas and the electrolyzed produced water from the oilfield are introduced into the spray tower, and the gas-liquid mass ratio in the spray tower is controlled to be 1:50. The COD of the produced water at the outlet of the electrolyzer 12 is measured to be 15, and the H2S concentration of the natural gas at the outlet of the spray tower is 0.

[0102] Example 3

[0103] The initial COD of the untreated produced water from the oilfield is 2600, where the NaCl concentration is 1 wt%, the H2S concentration in the sulfur-containing natural gas is 1000 ppm. The produced water from the oilfield is first subjected to flocculation treatment, and then the produced water is introduced into the diaphragm-free electrolyzer 12 for electrolysis. The residence time of the produced water in the electrolyzer 12 is 1 h.

[0104] Subsequently, the sulfur-containing natural gas and the electrolyzed produced water from the oilfield are introduced into the spray tower, and the gas-liquid mass ratio in the spray tower is controlled to be 1:100. The COD of the produced water at the outlet of the electrolyzer 12 is measured to be 15, and the H2S concentration of the natural gas at the outlet of the spray tower is 0.

[0105] In summary, a method for coupling the electrolytic treatment of produced water from an oilfield with natural gas desulfurization provided by the embodiments of the present application uses the decontaminated produced water containing hypochlorite ions generated after electrolyzing the produced water from the oilfield as a natural oxidative desulfurization agent, so that the sulfur element in hydrogen sulfide is oxidized to form elemental sulfur, and the hypochlorite ions are reduced to chloride ions and water. Only the difference in different phases needs to be used to directly separate the desulfurized natural gas and the chloride ion-containing solution after the reaction. Therefore, the cost of removing the sulfur element in the sulfur-containing natural gas can be effectively reduced, and at the same time, environmental pollution caused by using hydrogen sulfide treatment reagents can be avoided.

[0106] At the same time, this method can simultaneously achieve the harmless treatment of the produced water from the oil and gas field and the desulfurization of natural gas without adding specific external desulfurization reagents. The cost is low, it can be applied on a large scale, and it has great commercial application prospects.

[0107] At the same time, a system for coupling the electrolytic treatment of produced water from an oilfield with natural gas desulfurization provided by the embodiments of the present application only needs to introduce a spray unit 2 (spray tower) in the stage of desulfurizing the sulfur-containing natural gas. The overall system structure is simple and the cost is low.

[0108] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0109] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the figures. Additionally, in the description of the specification of the present application, the terms "comprising", "including", etc. mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B may be singular or plural. In this text, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one (item) of the following", or similar expressions refer to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0110] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for coupling the electrolytic treatment of oilfield produced water with natural gas desulfurization, characterized in that, The method includes: Introducing decontaminated produced water containing hypochlorite ions into the sulfur-containing natural gas, so that the hypochlorite ions in the decontaminated produced water fully react with hydrogen sulfide in the sulfur-containing natural gas, and then performing solid-liquid separation to obtain desulfurized natural gas and elemental sulfur respectively.

2. The method according to claim 1, wherein The mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:1 to 100.

3. The method according to claim 2, wherein The mass ratio of the sulfur-containing natural gas to the decontaminated produced water is 1:50 to 100.

4. The method according to claim 1, wherein The mass concentration of the hypochlorite ions ≤ 1%.

5. The method according to claim 4, wherein The mass concentration of the hypochlorite ions is 0.5% to 1%.

6. The method according to claim 1, characterized in that, The concentration of hydrogen sulfide in the sulfur-containing natural gas ≥ 500 ppm.

7. The method according to claim 6, wherein The concentration of hydrogen sulfide in the sulfur-containing natural gas is 500 ppm to 1000 ppm.

8. The method according to claim 1, characterized in that The method further includes: Purifying the oilfield produced water, and then performing electrolysis to obtain decontaminated produced water containing hypochlorite ions.

9. The method according to claim 8, wherein The chemical oxygen demand of the decontaminated produced water ≤ 15.

10. The method according to claim 8, characterized in that, The time of the electrolysis is 1 h to 5 h.

11. The method according to claim 8, characterized in that, The chemical oxygen demand of the oilfield produced water is 2500 to 3500.

12. A system for coupling electrolytic treatment of produced water in oilfields with natural gas desulfurization, characterized in that, The system is adapted to the method according to any one of claims 1-11, and the system includes: An electrolysis unit (1), the electrolysis unit (1) includes a produced water delivery pipeline (11), an electrolytic cell (12) and a decontaminated produced water output pipeline (13), the produced water delivery pipeline (11) communicates with the water inlet of the electrolytic cell (12), and one end of the decontaminated produced water output pipeline (13) communicates with the water outlet of the electrolytic cell (12); A spraying unit (2), the spraying unit (2) includes a sulfur-containing gas delivery pipeline (21), a desulfurized gas delivery pipeline (22), a spraying part (23) and a mixed liquid discharge pipeline (24), the sulfur-containing gas delivery pipeline (21) communicates with the gas inlet of the spraying part (23), the desulfurized gas delivery pipeline (22) communicates with the gas outlet of the spraying part (23), the other end of the decontaminated produced water output pipeline (13) communicates with the liquid inlet of the spraying part (23), and the feed port of the mixed liquid discharge pipeline (24) communicates with the discharge port of the spraying part (23).

13. The system according to claim 12, wherein, The system further includes a solid-liquid separation unit (3), and the feed port of the solid-liquid separation unit (3) communicates with the discharge port of the mixed liquid discharge pipeline (24).

14. The system according to claim 12, wherein The sulfur-containing gas delivery pipeline (21) is arranged below the decontaminated produced water output pipeline (13).

15. The system according to claim 12, wherein, The desulfurized gas delivery pipeline (22) is arranged at the top of the spraying part (23), and the mixed liquid discharge pipeline (24) is arranged at the bottom of the spraying part (23).

16. The system according to claim 12, wherein The spraying part (23) further includes a spraying pipeline (231), the spraying pipeline (231) communicates with the liquid outlet end of the decontaminated produced water output pipeline (13), and the spraying pipeline (231) is arranged below the desulfurized gas delivery pipeline (22).

17. The system according to claim 16, wherein The spraying part (23) further includes a liquid collecting tray (232), the liquid collecting tray (232) is arranged between the sulfur-containing gas delivery pipeline (21) and the mixed liquid discharge pipeline (24), so as to form a reaction space between the liquid collecting tray (232) and the spraying pipeline (231).

18. The system according to claim 17, wherein The liquid collecting tray (232) is provided with a penetrating mixed liquid outlet (233), so as to form a mixed liquid storage space between the liquid collecting tray (232) and the feed inlet of the mixed liquid discharge pipe (24).

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