Pretreatment device for oilfield produced water

Abstract

The invention discloses an oilfield produced water pretreatment device and relates to the technical field of sewage desulfurization. A sewage inlet pipeline and a pH value adjusting pipeline are arranged on the upper portion of the gas stripping tower, the pH value adjusting pipeline is connected with a pH value adjusting dosing device, an exhaust pipeline is arranged on the top of the gas stripping tower and connected with a dissolving tank, a nitrogen backflow pipeline is arranged on the top of the dissolving tank, and a nitrogen backflow pump is arranged on the nitrogen backflow pipeline. The nitrogen reflux pipeline enters the lower part of the gas stripping tower after passing through a nitrogen reflux pump. The method has the beneficial effects that nitrogen capable of refluxing is adopted as gas stripping gas, safe production is guaranteed while desulfurization is carried out, the usage amount of the nitrogen is small, the operation cost is low, removed H2S and the nitrogen are separated in the dissolving tank, the nitrogen is refluxed, an H2S dissolving solution enters the reaction tank, sulfur dioxide is added for reaction to generate elemental sulfur and water, clear water is refluxed and reused, and the production cost is reduced. And the desulfurized sewage is subjected to aeration for iron removal and air flotation for impurity removal, so that a pretreatment index is reached.

Description

Technical Field

[0001] The invention relates to the technical field of sewage desulfurization, and in particular to an oilfield produced water pretreatment device. Background Art

[0002] In the process of oil and gas extraction, it is necessary to remove sulfur and iron from wastewater through pretreatment to facilitate further treatment. Positive pressure gas stripping is often used to remove sulfur-containing wastewater. After passing through the pH adjustment device, the sulfur-containing wastewater enters the gas stripping tower and meets the gas stripping gas entering the bottom of the gas stripping tower. The gas stripping gas strips the hydrogen sulfide in the wastewater. For high-sulfur wastewater, air is used as gas stripping. The free hydrogen sulfide in the wastewater and the oxygen in the air are prone to explosion, which poses certain safety hazards. Summary of the invention

[0003] In order to solve the safety problem existing in the existing sewage desulfurization, the present invention provides an oilfield produced water pretreatment device.

[0004] The technical scheme provided by the present invention is: an oilfield produced water pretreatment device, comprising a gas stripping tower, a sewage inlet pipeline and a pH value adjustment pipeline are arranged at the upper part of the gas stripping tower, the pH value adjustment pipeline is connected to the pH value adjustment and dosing device, an exhaust pipeline is arranged at the top of the gas stripping tower, the exhaust pipeline is connected to the dissolving tank, the exhaust pipeline enters from the top of the dissolving tank and extends to the bottom of the dissolving tank, a nitrogen reflux pipeline is arranged at the top of the dissolving tank, a nitrogen reflux pump is arranged on the nitrogen reflux pipeline, the nitrogen reflux pipeline enters the lower part of the gas stripping tower after passing through the nitrogen reflux pump, a dissolved liquid overflow pipeline is arranged on one side of the dissolving tank, the dissolved liquid overflow pipeline is connected to the top of the reaction tank, the upper part of the reaction tank is a cylindrical container, the lower part of the reaction tank is a conical tube with a reduced diameter, a discharge valve is arranged at the lower part of the reaction tank, a clean water reflux pipeline is arranged on one side of the upper part of the reaction tank, a clean water reflux pump is arranged on the clean water reflux pipeline, and the end of the clean water reflux pipeline is connected to the upper part of the dissolving tank; A sulfur dioxide dosing pipeline is connected to the overflow pipeline of the dissolved liquid, and the sulfur dioxide dosing pipeline is connected to the sulfur dioxide dosing device; A sewage outflow pipe is provided at the bottom of the air stripping tower, and the sewage outflow pipe is connected to the top of the aeration tower. An aeration fan is provided at the bottom of the aeration tower.

[0005] The outlet of the aeration tower is connected to the flotation tank by a pipeline.

[0006] The discharge valve includes a feed pipe, which is connected to the bottom of the reaction tank. A cylinder sleeve is provided at the lower part of the feed pipe, a piston is provided in the cylinder sleeve, the piston and the cylinder sleeve are connected through three sealing rings, a material storage ring groove is processed between the two sealing rings on the right side of the piston, and a discharge pipe is provided at the lower part of the cylinder sleeve. When the material storage ring groove of the piston is located at the feed pipe position, the piston is provided with sealing rings on both sides of the feed pipe, and when the material storage ring groove is located at the discharge pipe position, the piston is provided with sealing rings on both sides of the feed pipe; The cylinder sleeve is fixedly connected with an electric push rod, which is connected with the piston through a rigid plate. The telescopic trajectory of the electric push rod is the same as the moving trajectory of the piston.

[0007] The nitrogen reflux pipeline is provided with a one-way valve and a flowmeter at the rear end of the nitrogen reflux pump, the sewage inlet pipeline is provided with a flowmeter, the clean water reflux pipe is provided with a one-way valve at the rear end of the clean water reflux pump, the dissolved liquid overflow pipeline is provided with a flowmeter, and the dissolved liquid overflow pipeline is connected in series with a static mixer after being connected to the sulfur dioxide dosing pipeline; The nitrogen return pipe is connected with a nitrogen supplement pipe beside the rear end of the one-way valve, and the clean water return pipe is connected with a clean water supplement pipe beside.

[0008] The beneficial effects of the present invention are as follows: the present invention uses refluxed nitrogen as stripping gas, which ensures safe production while desulfurizing, uses less nitrogen, has low operating costs, and removes H 2 S and nitrogen are separated in the dissolving tank, nitrogen is refluxed, H 2 The S solution enters the reaction tank, and sulfur dioxide is added to react to generate elemental sulfur and water. The clean water is refluxed for repeated use, and elemental sulfur is recycled. The wastewater after desulfurization is aerated to remove iron and air flotation to remove impurities to meet the pretreatment indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Attached Figure 1 It is a schematic diagram of the structure of the present invention; Attached Figure 2 It is a structural schematic diagram of the discharge valve in the present invention; Attached Figure 3 It is a working diagram of the discharge valve in the present invention.

[0010] In the figure: 1- air stripping tower, 2- dissolution tank, 3- reaction tank, 4- sulfur dioxide dosing device, 5- pH value adjustment dosing device, 6- aeration tower, 7- air flotation tank, 8- nitrogen reflux pipeline, 9- sewage inlet pipeline, 10- pH value adjustment pipeline, 11- exhaust pipeline, 12- clean water reflux pipeline, 13- dissolved liquid overflow pipeline, 14- sulfur dioxide dosing pipeline, 15- nitrogen reflux pump, 16- clean water reflux pump, 17- aeration fan, 18- sewage outflow pipeline, 19- nitrogen supplement pipeline, 20- clean water supplement pipeline, 21- discharge valve, 22- feed pipe, 23- cylinder sleeve, 24- piston, 25- discharge pipe, 26- electric push rod, 27- rigid plate, 28- material ring groove. DETAILED DESCRIPTION

[0011] like Figures 1 to 3As shown, an oilfield produced water pretreatment device comprises a gas stripping tower 1, a sewage inlet pipe 9 and a pH value adjustment pipe 10 are arranged on the upper part of the gas stripping tower 1, the pH value adjustment pipe 10 is connected to the pH value adjustment dosing device 5, an exhaust pipe 11 is arranged on the top of the gas stripping tower 1, the exhaust pipe 11 is connected to the dissolving tank 2, the exhaust pipe 11 enters from the top of the dissolving tank 2 and extends to the bottom of the dissolving tank 2, a nitrogen reflux pipe 8 is arranged on the top of the dissolving tank 2, a nitrogen reflux pump 15 is arranged on the nitrogen reflux pipe 8, and a nitrogen The reflux pipe 8 enters the lower part of the gas stripping tower 1 after passing through the nitrogen reflux pump 15. A dissolved liquid overflow pipe 13 is provided on one side of the dissolving tank 2. The dissolved liquid overflow pipe 13 is connected to the top of the reaction tank 3. The upper part of the reaction tank 3 is a cylindrical container. The lower part of the reaction tank 3 is a conical tube with a reduced diameter. A discharge valve 21 is provided at the lower part of the reaction tank 3. A clean water reflux pipe 12 is provided on one side of the upper part of the reaction tank 3. A clean water reflux pump 16 is provided on the clean water reflux pipe 12. The end of the clean water reflux pipe 12 is connected to the upper part of the dissolving tank 2. A sulfur dioxide dosing pipeline 14 is connected to the overflow pipeline 13 of the dissolved liquid, and the sulfur dioxide dosing pipeline 14 is connected to the sulfur dioxide dosing device 4; A sewage outflow pipe 18 is provided at the bottom of the stripping tower 1 , and the sewage outflow pipe 18 is connected to the top of the aeration tower 6 , and an aeration fan 17 is provided at the bottom of the aeration tower 6 .

[0012] The operation process of the present invention is that the sulfur-containing sewage enters the gas stripping tower 1 from the sewage inlet pipe 9, and at the same time, the pH adjuster in the pH adjustment dosing device 5 enters the gas stripping tower 1 through the pH adjustment pipe 10, and the pH value of the sulfur-containing sewage is adjusted to 4.5-6. The gas in the sulfur-containing sewage is dissolved and ionized in the sulfur-containing sewage, exists in the form of ions, and reaches ionization equilibrium. By adjusting the concentration of H+, ionization is suppressed, and sulfide is converted into gaseous H 2 S, nitrogen enters from the bottom of the stripping tower 1, and the nitrogen gas mixes with the sulfur-containing wastewater to remove H 2 S takes out, nitrogen and H 2 The mixed gas of S enters the dissolving tank 2, which is filled with clean water. 2 S is dissolved in clean water, and nitrogen flows out from the top of the dissolving tank 2, and is pressurized by the nitrogen reflux pump 15 and enters the bottom of the stripping tower 1 again for recycling; H 2 The S solution enters the reaction tank 3 through the solution overflow pipe 13, and sulfur dioxide, sulfur dioxide and H are added at the same time. 2 S reacts to produce sulfur and water, and the reaction formula is: 2H 2 S+SO 2 =3S=2H 2 O The sulfur generated by the reaction is deposited at the bottom of the reaction tank 3, and the supernatant is returned to the dissolution tank 2 through the clean water return pipe 12 for recycling; The desulfurized wastewater enters the aeration tower 6 for aeration to remove the iron in the wastewater. 2 Oxidized F 3 , which can remove iron and remove residual H 2 S is oxidized and further desulfurized.

[0013] The outlet of the aeration tower 6 is connected to the flotation tank 7 by a pipeline. Most of the suspended solids and oil are removed from the sewage through the flotation tank 7. The suspended solids and oil in the effluent water are less than 10 mg / L, meeting the pretreatment standard. The present invention uses refluxed nitrogen as stripping gas, which ensures safe production while desulfurizing, uses less nitrogen, has low operating costs, and removes H 2 S and nitrogen are separated in dissolving tank 2, nitrogen is refluxed, and H 2 The S solution enters the reaction tank 3, and sulfur dioxide is added to react to generate sulfur and water. The clean water is refluxed for reuse, and the elemental sulfur is recycled. The wastewater after desulfurization is aerated to remove iron and air flotation to remove impurities, thus meeting the pretreatment indicators.

[0014] The discharge valve 21 includes a feed pipe 22, which is connected to the bottom of the reaction tank 3. A cylinder sleeve 23 is provided at the lower part of the feed pipe 22, and a piston 24 is provided in the cylinder sleeve 23. The piston 24 and the cylinder sleeve 23 are connected through three sealing rings. A material storage ring groove 28 is processed between the two sealing rings on the right side of the piston 24. A discharge pipe 25 is provided at the lower part of the cylinder sleeve 23. When the material storage ring groove 28 of the piston 24 is located at the position of the feed pipe 22, the piston 24 is provided with sealing rings on both sides of the feed pipe 22. When the material storage ring groove 28 is located at the position of the discharge pipe 25, the piston 24 is provided with sealing rings on both sides of the feed pipe 22. An electric push rod 26 is fixedly connected to the cylinder sleeve 23, and the electric push rod 26 is connected to the piston 24 through a rigid plate 27. The telescopic trajectory of the electric push rod 26 is the same as the moving trajectory of the piston 24. Such a structure ensures that the liquid in the reaction tank 3 will not flow out when unloading or not unloading. The electric push rod 26 is opened at a fixed time, and the material ring groove 28 moves to the top of the discharge pipe 25. The sulfur in the material ring groove 28 falls into the discharge pipe 25, and the sulfur settled in the reaction tank 3 is discharged for recycling.

[0015] The nitrogen reflux pipe 8 is provided with a check valve and a flow meter at the rear end of the nitrogen reflux pump 15, the sewage inlet pipe 9 is provided with a flow meter, and the two flow meters can detect the gas-water ratio, the clean water reflux pipe 12 is provided with a check valve at the rear end of the clean water reflux pump 16, and the dissolved liquid overflow pipe 13 is provided with a flow meter, and the dissolved liquid overflow pipe 13 is connected in series with a static mixer after being connected to the sulfur dioxide addition pipe 14; The nitrogen reflux pipe 8 is connected to a nitrogen supplement pipe 19 at the rear end of the one-way valve, and the clean water reflux pipe 12 is connected to a clean water supplement pipe 20. When the flow rate of the solution overflow pipe 13 becomes smaller, clean water is supplemented.

Claims

1. An oilfield produced water pretreatment device, comprising a gas stripping tower (1), characterized in that: A sewage inlet pipe (9) and a pH value adjustment pipe (10) are provided at the top of the gas stripping tower (1), the pH value adjustment pipe (10) is connected to the pH value adjustment dosing device (5), an exhaust pipe (11) is provided at the top of the gas stripping tower (1), the exhaust pipe (11) is connected to the dissolution tank (2), the exhaust pipe (11) enters from the top of the dissolution tank (2) and extends to the bottom of the dissolution tank (2), a nitrogen reflux pipe (8) is provided at the top of the dissolution tank (2), a nitrogen reflux pump (15) is provided on the nitrogen reflux pipe (8), and the nitrogen reflux pipe (8) passes through a nitrogen reflux pump (15) to discharge the nitrogen reflux pump. After the flow pump (15), the liquid enters the lower part of the stripping tower (1); a dissolving liquid overflow pipe (13) is provided on one side of the dissolving tank (2); the dissolving liquid overflow pipe (13) is connected to the top of the reaction tank (3); the upper part of the reaction tank (3) is a cylindrical container; the lower part of the reaction tank (3) is a conical tube with a reduced diameter; a discharge valve (21) is provided at the lower part of the reaction tank (3); a clean water return pipe (12) is provided on one side of the upper part of the reaction tank (3); a clean water return pipe (12) is provided with a clean water return pump (16); and the end of the clean water return pipe (12) is connected to the upper part of the dissolving tank (2); A sulfur dioxide dosing pipeline (14) is connected to the overflow pipeline (13) of the dissolved liquid, and the sulfur dioxide dosing pipeline (14) is connected to the sulfur dioxide dosing device (4); A sewage outflow pipe (18) is provided at the bottom of the air stripping tower (1), and the sewage outflow pipe (18) is connected to the top of the aeration tower (6), and an aeration fan (17) is provided at the bottom of the aeration tower (6).

2. The oilfield produced water pretreatment device according to claim 1, characterized in that: The outlet of the aeration tower (6) is connected to the flotation tank (7) via a pipeline.

3. The oilfield produced water pretreatment device according to claim 1, characterized in that: The discharge valve (21) comprises a feed pipe (22), the feed pipe (22) is connected to the bottom of the reaction tank (3), a cylinder sleeve (23) is provided at the lower part of the feed pipe (22), a piston (24) is provided in the cylinder sleeve (23), the piston (24) and the cylinder sleeve (23) are connected by three sealing rings, a material storage ring groove (28) is processed between two sealing rings on the right side of the piston (24), a discharge pipe (25) is provided at the lower part of the cylinder sleeve (23), when the material storage ring groove (28) of the piston (24) is located at the position of the feed pipe (22), the piston (24) is provided with sealing rings on both sides of the feed pipe (22), and when the material storage ring groove (28) is located at the position of the discharge pipe (25), the piston (24) is provided with sealing rings on both sides of the feed pipe (22); The cylinder sleeve (23) is fixedly connected to an electric push rod (26), which is connected to the piston (24) via a rigid plate (27), and the telescopic trajectory of the electric push rod (26) is the same as the moving trajectory of the piston (24).

4. The oilfield produced water pretreatment device according to claim 1, characterized in that: The nitrogen reflux pipeline (8) is provided with a check valve and a flow meter at the rear end of the nitrogen reflux pump (15), the sewage inlet pipeline (9) is provided with a flow meter, the clean water reflux pipe (12) is provided with a check valve at the rear end of the clean water reflux pump (16), the dissolved liquid overflow pipeline (13) is provided with a flow meter, the dissolved liquid overflow pipeline (13) is connected in series with a static mixer after being connected to the sulfur dioxide addition pipeline (14), the nitrogen reflux pipeline (8) is connected with a nitrogen supplement pipeline (19) at the rear end of the check valve, and the clean water reflux pipeline (12) is connected with a clean water supplement pipeline (20).

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