A system and method for removing iron and sulfur from offshore oilfield wastewater

Abstract

The application discloses a kind of offshore oilfield sewage iron stabilizing and sulfur removing system and method.The system includes two pipelines connected with flow pipeline, two pipelines are equipped with main valve, two main valves are connected with the two ends of micro-bubble generator through high-pressure hose, micro-bubble generator suction inlet is connected with swing joint tee suction connector through check valve, swing joint tee suction connector one spare end is connected with ozone generator through ball valve, swing joint tee suction connector another spare end is connected with reagent tank through ball valve.The application generates micro-bubble by inhaled ozone gas, inhaled iron ion stabilizer reacts with ferrous ion in production sewage to form complex iron catalyst;Through micro-bubble ozone and complex iron catalyst, hydrogen sulfide is rapidly reacted to generate sulfur, sulfate and other substances, to achieve the purpose of oilfield sewage iron stabilizing and sulfur removing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a seawater oilfield sewage iron stabilization and sulfur removal system and method. BACKGROUND

[0002] The produced liquid of each platform of the offshore oilfield group has complex components, and the produced liquid of some oil-water wells causes pipe column corrosion and exceeds the content of ferrous ions and hydrogen sulfide due to the presence of sulfate-reducing bacteria. During the treatment process of the seawater oilfield sewage on the platform, hydrogen sulfide is easy to react with ferrous ions to form ferrous sulfide precipitate, causing the water body to turn black, and the deposited ferrous sulfide scale blocks the sewage process pipeline, affecting the normal production of the oilfield. Hydrogen sulfide accumulates in the sewage process, and hydrogen sulfide is dissolved in the production water, corrodes steel and equipment, and is easy to volatilize into the air in the production water, affecting the safety of the operating personnel. Therefore, it is necessary to use a corresponding device or method to remove sulfur from the seawater oilfield sewage containing sulfur. The current common methods for removing sulfur from seawater are as follows:

[0003] (1) Install a large gas stripping desulfurization tower. According to Henry's principle, when nitrogen or natural gas is used for gas stripping, hydrogen sulfide can be effectively removed. However, due to the limited space on the offshore platform, it is not suitable to install a large gas stripping desulfurization tower for sulfur removal equipment;

[0004] (2) Use strong oxidizing agents such as hydrogen peroxide or chlorine dioxide to remove hydrogen sulfide in production sewage. However, hydrogen peroxide has poor stability and is not easy to store, and is prone to explosion. Chlorine dioxide has strong corrosion and is easy to cause pipeline corrosion and perforation;

[0005] (3) Use desulfurizing agents such as lye, triazine, and organic amine. The dosage of the reagent is large, which can reduce the content of hydrogen sulfide in seawater oilfield sewage, but it is easy to cause water body scaling, and cannot stabilize iron ions and reduce the production of ferrous sulfide scale.

[0006] In addition, the existing patent literature also describes a method for removing sulfur from seawater. For example, the oilfield sewage hydrogen sulfide treatment device disclosed in Chinese Utility Model Patent CN205133217U discloses an oilfield sewage hydrogen sulfide treatment device. The device uses the method of sodium hypochlorite electrolysis to remove sulfur. The device has low desulfurization cost, simple operation, obvious desulfurization effect, and high practical value in the removal and treatment of hydrogen sulfide in oilfield sewage containing sulfur. However, the device has the problem of excessive oxidation, which can easily cause corrosion of metal pipelines, and cannot stabilize iron ions to solve the problem of black water.

[0007] For example, the utility model discloses CN208545230U a kind of oilfield sewage desulfurization treatment device discloses a kind of oilfield sewage hydrogen sulfide treatment device.The device uses aeration oxidation, physical filtration and ozone sterilization three methods to combine and carry out desulfurization treatment to oilfield sewage.The device is low in desulfurization cost, easy to operate, obvious in desulfurization effect, with very high practical value in oilfield sulfur-containing sewage hydrogen sulfide removal treatment.But the device uses aeration water tank and desulfurization tower, and the land area is large, and active carbon needs to be replaced regularly.

[0008] In summary, it is of great significance to develop a miniaturized offshore oilfield sewage iron stabilizing and desulfurization system and method for the above problems. SUMMARY

[0009] To solve the problems of excessive hydrogen sulfide content, excessive iron ions, black water body and ferrous sulfide scale blockage in offshore oilfield production wastewater, the present application provides an offshore oilfield sewage iron stabilizing and desulfurization system and method. The system occupies small space, is easy to install and operate, and has low cost. The method uses process water pressure to mix ozone and iron ion stabilizer through a micro-bubble generator for physical and chemical reactions in the process pipeline, which can reduce the hydrogen sulfide content of offshore oilfield sewage, reduce ferrous sulfide deposition, and meet the requirements of offshore oilfield sulfur-containing sewage treatment.

[0010] In a first aspect, the present application provides an offshore oilfield sewage iron stabilizing and desulfurization system, which is realized by the following technical solutions.

[0011] An offshore oilfield sewage iron stabilizing and desulfurization system comprises two pipelines connected with a process pipeline, and main valves are arranged on the two pipelines. The two main valves are connected with two ends of a micro-bubble generator through high-pressure hoses. A suction inlet of the micro-bubble generator is connected with a swing joint three-way suction connector through a check valve. One spare end of the swing joint three-way suction connector is connected with an ozone generator through a ball valve, and the other spare end of the swing joint three-way suction connector is connected with a reagent tank through a ball valve.

[0012] Further, one end of the high-pressure hose is a 2-inch external thread male joint, and the thread is a tapered pipe thread. The other end is a 1502 oil nut female joint.

[0013] Further, the two ends of the micro-bubble generator are 2-inch 1502 oil nut male joints. The top of the suction inlet of the micro-bubble generator is an external thread joint.

[0014] Further, the two ends of the micro-bubble generator are 2-inch 1502 oil nut male joints. The top of the suction inlet of the micro-bubble generator is an external thread joint.

[0015] Further, the two ends of the micro-bubble generator are 2-inch 1502 oil nut male joints. The top of the suction inlet of the micro-bubble generator is an external thread joint.

[0016] Further, the screw threads at both ends of the ball valve are 4-split double internal thread structure, and the screw threads are all conical pipe threads.

[0017] Further, the ball valve is provided with a quick connector at the connecting end of the medicine tank, and the quick connector is connected with the medicine tank through a hose.

[0018] In a second aspect, the application provides a method for stabilizing iron and removing sulfur in offshore oilfield sewage, which is realized by using the following technical scheme.

[0019] A method for stabilizing iron and removing sulfur in offshore oilfield sewage, which uses the offshore oilfield sewage iron stabilization and sulfur removal system, and comprises the following steps.

[0020] S1. Close the flow main valve on the flow pipeline, and open the first main valve and the second main valve;

[0021] S2. Open the first ball valve, and oxygen is introduced into the ozone generator to generate ozone;

[0022] S3. Add an iron ion stabilizer to the medicine tank, open the second ball valve, adjust the flow of the iron ion stabilizer according to the production sewage flow, and keep the concentration of the iron ion stabilizer at 40-80 ppm;

[0023] S4. The ozone, iron ion stabilizer and sewage enter the micro-bubble generator at the same time, the sewage is treated by the micro-bubble generator and then enters the flow pipeline, and the sewage continuously performs the iron stabilization and desulfurization reaction in the micro-bubble generator and the flow pipeline.

[0024] Further, the ozone output of the ozone generator is 50-200 g / h.

[0025] Further, the iron ion stabilizer is selected from one or more of sodium nitrilotriacetate, EDTA-2Na, citric acid, sodium citrate, ammonium citrate, polyacrylic acid sodium, iminobutane acid sodium salt, iminodisuccinic acid tetrasodium salt, diethylenetriamine pentaacetic acid penta sodium salt, and glutamic acid N, N-diacetic acid tetrasodium salt.

[0026] The application has the following beneficial effects.

[0027] 1. The application uses ferrous ions in production sewage to generate complex iron catalysts by using iron ion stabilizers, stabilizes iron ions, improves the utilization rate of ozone and the efficiency of removing hydrogen sulfide, and saves desulfurization time.

[0028] 2. The ozone used in the method is easy to prepare and decomposes quickly in water without secondary pollution.

[0029] 3. The system has a small volume, can perform physical and chemical reactions in the flow pipeline, and occupies a small amount of platform deck space.

[0030] 4. The application can reduce the dosage of triazine sulfur removal agent, reduce the cost of oilfield production, and the sulfur removal method is green, environmentally friendly and simple. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the seawater sewage iron stabilizing and sulfur removal system of the application.

[0032] Among them, 1. Process main valve; 2. First main valve; 3. Second main valve; 4. Micro-bubble generator first oil nipple joint; 5. Micro-bubble generator second oil nipple joint; 6. Micro-bubble generator body; 7. Micro-bubble generator suction port; 8. One-way valve; 9. Union tee suction joint; 10. First ball valve; 11. Second ball valve; 12. Ozone generator; 13. Agent tank; 14. First high-pressure hose; 15. Second high-pressure hose. DETAILED DESCRIPTION

[0033] The application will be further described below in conjunction with examples.

[0034] The experimental methods used in the following examples are conventional methods unless otherwise specified; The materials, reagents, etc. used in the following preparation examples and examples can be obtained from commercial channels unless otherwise specified.

[0035] As shown in Figure 1 A seawater sewage iron stabilizing and sulfur removal system, including two main valves, namely first main valve 2 and second main valve 3 (2-inch internal thread pressure ball valve, pressure: 64 kg); Two 2-inch high-pressure hoses, namely first high-pressure hose 14 and second high-pressure hose 15 (pressure-resistant 35 MPa, one end is a 2-inch external thread joint, the other end is a 1502 female thread oil nipple joint); A micro-bubble generator (both ends are 2-inch 1502 male thread oil nipple joints), the micro-bubble generator body 6 is made of 304 stainless steel material, the pressure is 6.3 MPa, the micro-bubble generator suction port 7 is a 4-inch external thread structure, which can generate a negative pressure of 90 KPa or more, and can suck ozone and iron ion stabilizer; A one-way valve 8 (4-inch, external thread to internal thread); A union tee suction joint 9 (4-inch, external and internal thread joints); Two ball valves, namely first ball valve 10 and second ball valve 11 (4-inch, double internal thread); An ozone generator 12; An agent tank 13.

[0036] The two main valves of the application are 2-inch double internal thread joints, one end of which is connected to one end of the 2-inch high-pressure hose.

[0037] One end of the 2-inch high-pressure hose of the application is connected to the main valve through the thread joint and sealed with thread joint tape; The other end of the high-pressure hose is a 1502 oil nipple joint female end, which is connected to the 1502 oil nipple joint male end at both ends of the micro-bubble generator body 6.

[0038] The micro-bubble generator body 6 is 481 cm long, and the two ends of the body are 2-inch 1502 public oil nut joint, that is, the first oil nut joint 4 of the micro-bubble generator and the second oil nut joint 5 of the micro-bubble generator, which are connected to the female oil nut joint of the 2-inch high-pressure hose. The 4th micro-bubble generator suction port 7 of the ozone or iron ion stabilizer is arranged on the micro-bubble generator body 6, the top of the 4th suction port is a male thread structure (the thread is a conical pipe thread), the male thread of the 4th suction port is connected to the female thread of the one-way valve 8. The oil nut head from the middle to one end of the 4th suction port is 344 cm long, the oil nut head from the middle to the other end of the 4th suction port is 137 cm long, and the thread top of the 4th suction port is 76 cm long from the generator body to the middle.

[0039] The two ends of the one-way valve 8 are 4th threads, the flow direction is from the male thread to the female thread, and the threads are conical pipe threads. The female thread end is connected to the male thread of the micro-bubble generator suction port, and the male thread end is connected to the female thread of the live tee joint. The thread connection is sealed by using thread tape.

[0040] The live tee suction joint is a 4th male thread, which is made of 304 stainless steel. The female thread end of the 4th female thread of the tee is connected to the male thread of the one-way valve 8, and the male thread end of the 4th male thread of the tee is connected to two 4th ball valves, respectively. The thread connection sealing is sealed by using thread tape.

[0041] The two 4th ball valves are made of 304 stainless steel, one end of each is connected to the 4th male thread of the tee, the other end of the first ball valve 10 is connected to the ozone generator 12, and the other end of the second ball valve 11 can be equipped with a 1 / 2" quick connector with good sealing performance and connected to a hose to extract the iron ion stabilizer. The thread connection sealing is sealed by using thread tape.

[0042] The ozone generator 12 uses an oxygen tank or an oxygen generator as an oxygen source, and the ozone output is 200 g / h.

[0043] The iron ion stabilizer is selected from one or more of sodium nitrilotriacetate, EDTA-2Na, citric acid, sodium citrate, ammonium citrate, polyacrylic acid sodium, iminobutane acid sodium salt, iminodisuccinic acid tetrasodium salt, diethylenetriamine pentaacetic acid pentasodium salt, and glutamic acid N, N-diacetic acid tetrasodium salt. The iron ion stabilizer prepared from the above-mentioned materials is a light yellow transparent liquid, the density is 1.35 g / cm 3 , the iron ion chelating capacity is greater than 50 mg / g, and the pH value of 1% aqueous solution is 11.7.

[0044] The mechanism of the present application for stabilizing iron and removing hydrogen sulfide is as follows:

[0045] (1) A part of the dissolved ozone in water directly reacts with the dissolved hydrogen sulfide in water to generate sulfur, and the reaction formula is as follows:

[0046] 3H2S(g)+O3(g)→3H2O+3S↓

[0047] (2) Ferrous ions in the production wastewater react with the ferric ion stabilizer (Ln) to form a divalent ferric ion complex, as shown in the following reaction formula:

[0048] Fe 2+ +Ln - →Fe 2+ Ln

[0049] The complex structure is as follows (taking EDTA as an example):

[0050]

[0051] (3) The reaction of ferrous ions with ozone generates a complexed iron catalyst with oxidizing properties, as shown in the following reaction formula:

[0052] 6Fe 2+ Ln + O3(g) + 3H2O → 6Fe 3+ Ln+6OH -

[0053] Fe 3+ +Ln - →Fe 3+ Ln

[0054] (4) The complex of ferric ions reacts with dissolved H2S in wastewater in a redox reaction to produce elemental sulfur and ferrous ion complexes. The reaction formula is as follows:

[0055] Fe 3+ Ln + H₂S → Fe 2+ Ln+S↓+2H +

[0056] (5) The complex of ferrous ions generated in reaction (4) undergoes a redox reaction (3) with ozone to generate ferric ion complex, thus realizing the regeneration of the complexed iron catalyst, and the reaction continues.

[0057] Example 1

[0058] A method for iron stabilization and desulfurization of wastewater from offshore oil fields includes the following steps:

[0059] (1) Press Figure 1 The system is shown to be installed into the bypass of the offshore oilfield wastewater process pipeline, and connected to ozone and iron ion stabilizer through the suction connector 9 of the tee.

[0060] (2) Close the main process valve 1 on the process pipeline, and open the first main valve 2 and the second main valve 3;

[0061] (3) Open the first ball valve 10, and oxygen is introduced into the ozone generator, with an ozone output of 200g / h;

[0062] (4) Open the second ball valve 11, the medicine tank 13 adds the iron ion stabilizer, and adjusts the size according to the production sewage flow, and keeps the iron ion stabilizer concentration to be 50ppm;

[0063] (5) The ozone, the iron ion stabilizer and the sewage (the sewage quality is as shown in Table 1) enter the micro-bubble generator body 6 simultaneously, and the sewage continuously carries out the iron stabilizing and desulfurization reaction in the micro-bubble generator 6 and the following flow pipeline.

[0064] Table 1: Sewage quality

[0065] Test item Value pH (25°C) 8.02 Salinity, mg / L 34875 SRB bacteria count (cells / mL) 2500 Total iron, mg / L 12.1 Sewage turbidity, NTU 68.2 Suspended solids content, mg / L 16.8 Sewage hydrogen sulfide content, ppm 62.5

[0066] Comparative Example 1

[0067] Using the ozone oxidation process, no iron ion stabilizer is added. The sewage and ozone are directly introduced into the micro-bubble generator, wherein the ozone concentration is the same as that in Example 1, and the sewage is the same as that in Example 1.

[0068] Comparative Example 2

[0069] Using the hydrogen peroxide oxidation process, no iron ion stabilizer is added, and hydrogen peroxide is added to the medicine tank, and the effective concentration of hydrogen peroxide is 10ppm. The sewage and hydrogen peroxide are directly introduced into the micro-bubble generator, wherein the sewage is the same as that in Example 1.

[0070] Comparative Example 3

[0071] The flow main valve 1 is opened, and the first main valve 2 and the second main valve 3 are closed. The sewage is not added with any medicine, and the sewage is the same as that in Example 1.

[0072] The indicators of the production sewage treated in Example 1 and Comparative Examples 1-3 are detected, and the detection results are as shown in Table 2.

[0073] Table 2

[0074] Test item Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Sewage turbidity, NTU 3.71 10.61 8.62 68.2 Suspended solids content, mg / L 2.2 16.4 11.4 16.8 Sewage hydrogen sulfide content, ppm 0.2 10.2 6.5 62.5

[0075] As shown in the above table, after the sewage of the offshore oilfield is treated by the method of the present application, the water body is relatively clean and transparent, and the turbidity, the suspended substance content and the hydrogen sulfide content of the sewage can be significantly reduced.

[0076] The present application can carry out desulfurization treatment on the hydrogen sulfide in the production sewage of the offshore oilfield, does not need to introduce iron source, stabilizes the ferrous ion in the production sewage, improves the hydrogen sulfide removal efficiency, and carries out the desulfurization reaction in the sewage flow pipeline, does not occupy the platform deck space, has good treatment effect, high ozone utilization rate, simple process flow, easy operation, good economic benefit, and is beneficial to industrial application.

[0077] The embodiments of the present application are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, and thus: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A wastewater stabilization and desulfurization system for offshore oilfields, characterized in that, It includes two pipes connected to the process pipeline, and each pipe is equipped with a main valve, including a first main valve (2) and a second main valve (3). The two main valves are connected to the two ends of the microbubble generator through high-pressure hoses. The inlet of the microbubble generator is connected to the tee fitting through a one-way valve. One of the unused ends of the tee fitting is connected to the ozone generator through a first ball valve (10). The other unused end of the tee fitting is connected to the reagent tank through a second ball valve (11). The reagent tank contains an iron ion stabilizer.

2. The system for removing iron and sulfur from offshore oilfield wastewater according to claim 1, characterized in that, One end of the high-pressure hose is a 2-inch male external thread connector with tapered pipe thread, and the other end is a 1502 oil-sealed female thread connector.

3. The system for removing iron and sulfur from offshore oilfield wastewater according to claim 1, characterized in that, The microbubble generator has 2-inch 1502 oil-filled male connectors at both ends; the top of the microbubble generator inlet has an external thread structure.

4. The system for removing iron and sulfur from offshore oilfield wastewater according to claim 1, characterized in that, The one-way valve has 4-point threads at both ends, with the outer thread flowing into the inner thread. All threads are tapered pipe threads. The inner thread end connects to the suction port of the microbubble generator, and the outer thread end connects to the union tee suction connector.

5. The system for removing iron and sulfur from offshore oilfield wastewater according to claim 1, wherein The union tee suction connector has 4-point external and internal threads, and the threads are all tapered pipe threads.

6. The offshore oilfield wastewater iron stabilization and desulfurization system according to claim 1, characterized in that, The ball valve has a 4-point double internal thread structure at both ends, and the threads are all tapered pipe threads.

7. The offshore oilfield wastewater iron stabilization and desulfurization system according to claim 1, characterized in that, The ball valve is equipped with a quick connector at the connection end with the medicine tank, and the quick connector is connected to the medicine tank through a hose.

8. A method for iron stabilization and desulfurization of wastewater from offshore oilfields, characterized in that: The offshore oilfield wastewater iron stabilization and desulfurization system according to any one of claims 1-7 includes the following steps: S1. Close the main process valve (1) on the process pipeline, and open the first main valve (2) and the second main valve (3). S2. Open the first ball valve (10) and oxygen is introduced into the ozone generator (12) to produce ozone; S3. Add iron ion stabilizer to the reagent tank (13), open the second ball valve (11), adjust the iron ion stabilizer flow rate according to the production wastewater flow rate, and keep the iron ion stabilizer concentration at 40-80ppm; S4. Ozone, iron ion stabilizer and wastewater enter the microbubble generator at the same time. After being treated by the microbubble generator, the wastewater enters the process pipeline. The wastewater continuously undergoes iron stabilization and desulfurization reaction in the microbubble generator and process pipeline.

9. A method for iron stabilization and desulfurization of wastewater from offshore oilfields according to claim 8, characterized in that: The ozone generator has an ozone output of 50-200 g / h.

10. A method for iron stabilization and desulfurization of wastewater from offshore oilfields according to claim 8, characterized in that: The iron ion stabilizer is selected from one or more of the following: sodium triacetate, EDTA-2Na, citric acid, sodium citrate, ammonium citrate, sodium polyacrylate, sodium iminosuccinate, tetrasodium iminodisuccinate, pentasodium diethylenetriaminepentaacetate, and tetrasodium N,N-diacetate of glutamate.

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