A gas phase steady-state distribution device for flotation machines used in oilfield produced water treatment

Abstract

This invention discloses a gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment, comprising a water distribution main pipe, a slag scraper, an inclined plate, and a sludge scraper installed inside the flotation machine casing; a release device is provided at the inlet of the water distribution main pipe, and a water distribution branch pipe is connected to the water distribution main pipe, which in turn is connected to a water distribution branch pipe, which is also connected to a second release device; the outer wall of the flotation machine casing has a slag discharge port, a sludge discharge port, and a water outlet; the flotation machine inner cavity, a reflux pump, a dissolved air tank, and the first release device are connected in sequence. The beneficial effects of this invention are: improved gas-phase rising flow pattern, enhanced ability of bubbles to carry oil droplets and impurities, resulting in effluent water quality meeting design requirements, significantly improved treatment efficiency, and a substantial reduction in residence time and equipment size.

Description

Technical Field

[0001] This invention relates to the field of dissolved air flotation treatment technology for oilfield produced water, and particularly to a gas phase steady-state distribution device for a flotation machine used in oilfield produced water treatment. Background Technology

[0002] Flotation is a process in which air is dissolved in water in the form of tiny bubbles. These bubbles adhere to suspended oil droplets and impurities in the water, and because their density is less than that of water, they float to the surface, forming a scum layer that separates from the water. Flotation has advantages such as large processing capacity, strong adaptability, and high separation efficiency, and is widely used in oilfield produced water treatment. Currently, commonly used flotation processes include dissolved air flotation, vortex flotation, and induced flotation, among which dissolved air flotation is the most widely used. Dissolved air flotation involves dissolving air in water under pressure to create a supersaturated state, then reducing the pressure to atmospheric pressure, causing the air to precipitate and be released into the water as tiny bubbles, thus achieving flotation. Traditional dissolved air flotation (DAF) devices include a dissolved air release zone, a separation zone, and a sedimentation zone, which are separated by guide plates. The sedimentation zone is equipped with inclined plates. On the one hand, as bubbles with oil droplets and impurities adhere to them float to the surface, the unstable flow pattern causes disturbances in the water flow, resulting in some of the oil droplets and impurities adhering to the bubbles falling off. On the other hand, due to the influence of the flow pattern, the upward trajectory of the bubbles is irregular and spiral-shaped, which increases the time it takes for the bubbles to float to the liquid surface compared to a straight upward trajectory, thereby reducing the processing efficiency.

[0003] The main competitors in this technical field are oil and gas field companies and specialized technology companies. As flotation is a crucial step in the oilfield produced water treatment process, these competitors have been dedicated to researching high-efficiency, low-cost flotation alternatives. Currently published patent applications, such as "A Multi-Space High-Efficiency Separation Closed-Loop Air Flotation Device for Oilfield Produced Water" (application number: 202310629668.1), are similar in principle to this invention. The solution is to provide a multi-space high-efficiency separation closed-loop air flotation device for oilfield produced water. The air flotation tank contains multiple vertically placed, parallel partition plates that divide the tank into multiple tank spaces. These partitions restrict the upward trajectory of air bubbles. Produced water inlets are located at the body of each tank space, air outlets are located at the top of each tank space, and water outlets are located at the bottom of each tank space. The competitor's technical solution involves modifying the flotation machine structure, using partition plates to restrict the upward trajectory of bubbles. The main drawbacks are: first, the location and number of partition plates are limited by the flotation machine's shape, and the modification work is extensive; second, the varying distances the water travels to each tank cause flow deviations, affecting the treatment effect; and third, interference between the upward trajectories of bubbles still exists within each tank. This invention optimizes and improves upon these shortcomings. Summary of the Invention

[0004] To address the problem of irregular bubble trajectories in oilfield produced water leading to easy detachment of adhering substances and long floating times, this invention provides a gas phase steady-state distribution device for flotation machines used in oilfield produced water treatment. This device makes the bubble trajectories approximately straight, improving bubble carrying capacity, shortening bubble floating time, and thus improving the efficiency of dissolved air flotation treatment.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a gas phase steady-state distribution device for flotation machine used in oilfield produced water treatment, comprising a water distribution main pipe, a slag scraper, an inclined plate, and a sludge scraper installed inside the flotation machine shell; a release device is provided at the inlet of the water distribution main pipe, a water distribution branch pipe is connected to the water distribution main pipe, a water distribution branch pipe is connected to the water distribution branch pipe, and a release device is connected to the water distribution branch pipe; the outer wall of the flotation machine shell is provided with a slag discharge port, a sludge discharge port, and a water outlet; the flotation machine inner cavity, a reflux pump, a dissolved gas tank, and the release device are connected in sequence.

[0006] Furthermore, the slag scraper is located above the water distribution main.

[0007] Furthermore, the first water distribution branch pipe, the second water distribution branch pipe, and the third water distribution branch pipe are distributed on both sides of the main water distribution pipe in sequence from near to far.

[0008] Furthermore, the first, second, and third water distribution branch pipes become progressively shorter.

[0009] Furthermore, the water distribution branch pipes are evenly spaced and distributed in parallel.

[0010] Furthermore, the slag discharge port and water outlet are located on the upper part of the outer wall of the flotation machine shell.

[0011] Furthermore, the slag discharge port and water outlet are located above the water inlet.

[0012] Furthermore, the sludge discharge port is located at the bottom of the outer wall of the flotation machine casing.

[0013] Furthermore, the water distribution main is located above the inclined plate.

[0014] Furthermore, the inclined plate is located above the sludge scraper.

[0015] The beneficial effects of this invention are: it improves the flow pattern of rising gas phase, enhances the ability of bubbles to carry oil droplets and impurities, not only ensuring that the effluent quality meets the design requirements, but also significantly improving the treatment efficiency, residence time, and equipment size.

[0016] This invention is applicable to all oilfield produced water treatment fields employing flotation processes, including but not limited to the treatment of light oil produced water for production water injection, the treatment of heavy oil produced water for reuse in steam injection boilers, the discharge of heavy oil produced water that meets standards, and the treatment of unconventional oil and gas fracturing flowback fluid and produced water. Besides using traditional reagent dosing methods, it can also be implemented without reagents, significantly reducing operating costs. Therefore, this invention has broad application prospects. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a top view of the water distribution pipe;

[0020] Figure 3 This is an isometric drawing of the water distribution pipe;

[0021] Figure 4 This is a schematic diagram of a partial structure of the water distribution pipe.

[0022] The components are: 1. Inlet; 2. Releaser 1; 3. Main water supply pipe; 4. Branch water supply pipe; 5. Sludge scraper; 6. Sludge discharge port; 7. Inclined plate; 8. Sludge scraper; 9. Sludge discharge port; 10. Outlet; 11. Return pump; 12. Dissolved air tank; 13. Branch water supply pipe; 14. Releaser 2. Detailed Implementation

[0023] The following will be combined with the appendix Figure 1-4 The technical solutions of the present invention have been clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0025] In the description of this invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used only for distinction and should not be construed as indicating or implying relative importance.

[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Example 1

[0028] A gas phase steady-state distribution device for a flotation machine used in oilfield produced water treatment includes a water distribution main pipe 3, a slag scraper 5, an inclined plate 7, and a sludge scraper 8 installed inside the flotation machine shell; a release device 2 is provided at the inlet 1 of the water distribution main pipe 3; a water distribution branch pipe 13 is connected to the water distribution main pipe 3; a water distribution branch pipe 4 is connected to the water distribution branch pipe 13; and a release device 2 14 is connected to the water distribution branch pipe 4; a slag discharge port 6, a sludge discharge port 9, and a water outlet 10 are provided on the outer wall of the flotation machine shell; the flotation machine inner cavity, a reflux pump 11, a dissolved air tank 12, and the release device 2 are connected in sequence.

[0029] The air flotation process generally consists of the following four steps: First, coagulants and flocculants are added to the produced water to agglomerate fine suspended particles and oil droplets into hydrophobic particles or large flocs; second, as many tiny, uniform bubbles as possible are generated and evenly distributed throughout the equipment; third, a good combination of bubbles and oil droplets or bubbles and floc particles is formed; fourth, the combination floats to the surface and separates from the water as scum, while the heavier flocs settle to the bottom and separate as sludge. Due to its high oil removal efficiency and short residence time, air flotation is widely used in various oil and gas fields.

[0030] Example 2

[0031] A gas-phase steady-state distribution device for a flotation machine used in oilfield produced water treatment includes a water distribution main pipe 3, a slag scraper 5, an inclined plate 7, and a sludge scraper 8 installed inside the flotation machine casing. A release device 2 is installed at the inlet 1 of the water distribution main pipe 3. A water distribution branch pipe 13 is connected to the water distribution main pipe 3, and a water distribution branch pipe 4 is connected to the water distribution branch pipe 13. A second release device 14 is connected to the water distribution branch pipe 4. A slag discharge port 6, a sludge discharge port 9, and a water outlet 10 are provided on the outer wall of the flotation machine casing. The flotation machine cavity, a reflux pump 11, a dissolved air tank 12, and the release device 2 are connected in sequence. The slag scraper 5 is located above the water distribution main pipe 3, the water distribution main pipe 3 is located above the inclined plate 7, and the inclined plate 7 is located above the sludge scraper 8. A first water distribution branch pipe, a second water distribution branch pipe, and a third water distribution branch pipe are distributed at intervals from near to far on both sides of the water distribution main pipe 3. The first, second, and third water distribution branch pipes decrease in length sequentially. The water distribution branch pipes 4 are evenly spaced and parallel to each other. The sludge discharge port 6 and the water outlet 10 are located on the upper part of the outer wall of the flotation machine shell. The sludge discharge port 6 and the water outlet 10 are located above the water inlet 1. The sludge discharge port 9 is located at the bottom of the outer wall of the flotation machine shell.

[0032] With relatively mature dissolved air flotation (DAF) technologies, one of the keys to improving the processing efficiency of DAF technology is process control. This involves ensuring both the collision and adhesion of bubbles with oil droplets and impurities, and maintaining the stability of the bubble-oil droplet-impurity aggregate to prevent desorption. This invention is applicable to three dissolved air flotation processes: full-process DAF, partial DAF, and partial reflux DAF.

[0033] For partial dissolved air flotation and partial recirculation dissolved air flotation, the raw water / recirculation water containing dissolved gas is first mixed with the raw water containing undissolved gas, and then the mixture enters the flotation machine. The purpose is to evenly disperse the dissolved gas in the raw water. The entire process of dissolved air flotation can meet the above requirements without modification.

[0034] Two inlets 1 are provided along the length of the flotation machine. Raw water containing dissolved gas enters the flotation machine through the two inlets 1 and flows in the order of water distribution main pipe 3 → water distribution branch pipe 13 → water distribution branch pipe 4. Finally, the dissolved gas is released through the release device 2 14 evenly distributed on the water distribution branch pipe 4.

[0035] The arrangement of water distribution main pipe 3, water distribution branch pipe 13, and water distribution branch pipe 4 requires that the distance from the water inlet 1 to the release device 2 14 at the end of each water distribution branch pipe 4 be basically equal. The purpose is to ensure that the head loss of each pipeline is equal and to avoid flow deviation.

[0036] The water distribution branch pipes 4 are evenly distributed along the length of the flotation machine, and the release devices 2 14 on each water distribution branch pipe 4 are evenly distributed along the width of the flotation machine. The purpose is to achieve a uniform distribution of all release devices 2 14 on the entire plane of the flotation machine.

[0037] After the raw water passes through the release device 214, a large number of tiny bubbles are released and float to the surface with the water flow. Since there is no guide or obstruction, the trajectory of the bubbles is approximately straight. Therefore, the time for the bubbles to float can be greatly shortened, and the attached substances are not easy to fall off, thus greatly improving the separation efficiency.

[0038] Due to the significantly improved separation efficiency, the residence time can be shortened by more than one-third compared to traditional flotation machines, and the separation zone height H can also be reduced by more than one-third.

[0039] The sedimentation zone is equipped with inclined plates 7. Small oil droplets agglomerate into large oil droplets and float to the surface, where they are removed by the slag scraper 5. Small particles agglomerate into large particles and settle to the bottom, where they are removed by the sludge scraper 8.

[0040] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims. Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the features in the embodiments disclosed in the present invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment, characterized in that, The system includes a water distribution main pipe (3), a slag scraper (5), an inclined plate (7), and a sludge scraper (8) installed inside the flotation machine housing; a release device (2) is provided at the inlet (1) of the water distribution main pipe (3); a water distribution branch pipe (13) is connected to the water distribution main pipe (3); a water distribution branch pipe (4) is connected to the water distribution branch pipe (13); a release device (2) is connected to the water distribution branch pipe (4); a slag discharge port (6), a sludge discharge port (9), and a water outlet (10) are provided on the outer wall of the flotation machine housing; the flotation machine inner cavity, a reflux pump (11), a dissolved air tank (12), and a release device (2) are connected in sequence.

2. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The slag scraper (5) is located above the water distribution main pipe (3).

3. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The water distribution main pipe (3) has a first water distribution branch pipe, a second water distribution branch pipe, and a third water distribution branch pipe distributed on both sides from near to far.

4. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 3, characterized in that, The first, second, and third water distribution branch pipes become progressively shorter.

5. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 4, characterized in that, The water distribution branch pipes (4) are equally spaced and parallel to each other.

6. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The slag discharge port (6) and water outlet (10) are located on the upper part of the outer wall of the flotation machine shell.

7. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The slag discharge port (6) and water outlet (10) are located above the water inlet (1).

8. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The sludge discharge port (9) is located at the bottom of the outer wall of the flotation machine shell.

9. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The water distribution main pipe (3) is located above the inclined plate (7).

10. The gas-phase steady-state distribution device for flotation machines used in oilfield produced water treatment according to claim 1, characterized in that, The inclined plate (7) is located above the sludge scraper (8).

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