Oilfield produced water for steam injection boiler feed water treatment system

Abstract

The application relates to the technical field of sewage treatment, and discloses an oilfield produced water used for steam injection boiler feed water treatment system, which comprises a multistage oil removal unit, a fine treatment unit and a high-pressure reverse osmosis unit.The multistage oil removal unit is provided with a first primary inlet and a first final water outlet, is used for receiving produced water through the first primary inlet, and carries out multistage oil removal and suspended matter removal treatment on the produced water; the fine treatment unit is provided with a second primary inlet and a second final water outlet, the second primary inlet is communicated with the first final water outlet, is used for receiving output water output by the multistage oil removal unit through the second primary inlet, and carries out multistage filtration to carry out deep oil removal and suspended matter removal treatment; the high-pressure reverse osmosis unit is communicated with the second final water outlet, is used for receiving output water output by the fine treatment unit, and carries out impurity removal treatment, wherein the impurities include salts. In this way, the oil content and the suspended matter content can be reduced to the maximum, and the desalination rate can be improved.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, for example to an oilfield produced water treatment system for steam injection boiler feedwater. Background Technology

[0002] Oilfield produced water reused in steam injection boilers must meet stringent water quality standards, such as total hardness ≤0.1 mg / L, total iron ≤0.05 mg / L, and oil content ≤0.1 ppm. Traditional "air flotation + sand filtration + ion exchange" processes achieve a desalination rate of less than 95% when treating high-salinity (TDS>30,000 mg / L) wastewater.

[0003] The relevant technology uses a solution of "CAF vortex air flotation + multi-media filtration + ordinary RO" to treat the produced water. However, due to RO membrane oil contamination and Cl⁻ residue exceeding 500 ppm, the heat exchange tubes perforated in a short period of time, significantly increasing maintenance costs.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0006] This disclosure provides an oilfield produced water treatment system for steam injection boiler feedwater to improve oil removal and desalination efficiency.

[0007] In some embodiments, the oilfield produced water is used in a steam injection boiler feedwater treatment system, comprising: a multi-stage oil removal unit having a first primary inlet and a first secondary outlet, for receiving produced water through the first primary inlet and performing multi-stage oil and suspended solids removal treatment on the produced water; a fine treatment unit having a second primary inlet and a second secondary outlet, the second primary inlet being connected to the first secondary outlet, for receiving the produced water output from the multi-stage oil removal unit through the second primary inlet and performing multi-stage filtration for deep oil and suspended solids removal treatment; and a high-pressure reverse osmosis unit, the inlet of which is connected to the second secondary outlet, for receiving the produced water output from the fine treatment unit and performing impurity removal treatment, wherein the impurities include salt.

[0008] In some embodiments, the multi-stage oil removal unit includes: an air flotation device, the inlet of which serves as the first-stage inlet; a coalescing oil separator, the inlet of which is connected to the outlet of the air flotation device; and an activated filter, the inlet of which is connected to the outlet of the coalescing oil separator, the outlet of which serves as the first-stage outlet. The air flotation device, the coalescing oil separator, and the activated filter sequentially perform oil and suspended solids removal treatment on the produced water.

[0009] In some embodiments, the air flotation device adopts a high-efficiency dissolved air cyclone microbubble flotation device; the coalescing oil remover adopts a horizontal structure or a vertical structure, wherein the internal components of the horizontal structure are combined with packing, and the internal components of the vertical structure are combined with coalescing filter elements.

[0010] In some embodiments, the multi-stage oil removal unit further includes: a wastewater collection and settling tank, the inlet of which serves as the first primary inlet, and the outlet of which is connected to the inlet of the air flotation device, so as to physically separate the produced water by settling and initially isolate floating oil, scum and solid sediments.

[0011] In some embodiments, the fine treatment unit includes: an ultrafilter, the inlet of which serves as the second first-stage inlet; and an activated medium filter, the inlet of which is connected to the outlet of the ultrafilter, the outlet of which serves as the second final-stage outlet; the ultrafilter and the activated medium filter sequentially perform progressive deep oil and suspended solids removal treatment on the effluent from the multi-stage oil removal unit.

[0012] In some embodiments, the ultrafilter is a silicon carbide ceramic membrane ultrafilter.

[0013] In some embodiments, the high-pressure reverse osmosis unit includes a first-stage deionization process device, wherein the reverse osmosis membrane is an HPRO membrane; or, the high-pressure reverse osmosis unit includes: a concentrated brine reverse osmosis device, the inlet of which is connected to the outlet of the second final stage; and an electro-deionization device, the inlet of which is connected to the outlet of the concentrated brine reverse osmosis device.

[0014] In some embodiments, the device further includes: a desiliconization device, the inlet of which is connected to the first final stage outlet, the outlet of which is connected to the second first stage inlet, and the inlet of which is provided with a first on / off valve controlled by a controllable switch; a bypass branch connected between the first final stage outlet and the second first stage inlet, the bypass branch being provided with a second on / off valve controlled by a controllable switch; by controlling the opening or closing of the first on / off valve and the second on / off valve, the desiliconization device is selectively controlled to receive the effluent from the multi-stage oil removal unit and perform desiliconization treatment.

[0015] In some embodiments, the oilfield produced water used in the steam injection boiler feedwater treatment system further includes: a pure water collection and storage tank, the inlet of which is connected to the outlet of the high-pressure reverse osmosis unit, for storing or discharging the produced water processed by the high-pressure reverse osmosis unit; a sludge tank, the inlet of which is connected to the sludge outlet of the multi-stage oil removal unit, for collecting the sludge deposited by the multi-stage oil removal unit; and a waste liquid collection tank, the inlet of which is connected to the waste liquid outlets of the multi-stage oil removal unit, the fine treatment unit, and the high-pressure reverse osmosis unit, for collecting sludge, scum, and concentrated brine.

[0016] In some embodiments, the oilfield produced water used in the steam injection boiler feedwater treatment system further includes: an SDI detection module, located at the first final stage outlet, for detecting the SDI content of the final stage produced water of the multi-stage oil removal unit, thereby dynamically adjusting the dosage of the water purification agent.

[0017] The oilfield produced water used in the steam injection boiler feedwater treatment system provided in this embodiment can achieve the following technical effects: The first inlet of the multi-stage oil removal unit receives the produced water. The second inlet of the fine treatment unit is connected to the first outlet of the multi-stage oil removal unit, and the inlet of the high-pressure reverse osmosis unit is connected to the second outlet of the fine treatment unit. First, the produced water undergoes preliminary multi-stage oil and suspended solids removal treatment by the multi-stage oil removal unit. Then, the produced water from the multi-stage oil removal unit undergoes deep multi-stage oil and suspended solids removal treatment by the fine treatment unit. Finally, the produced water from the fine treatment unit undergoes impurity removal treatment, such as desalination, by the high-pressure reverse osmosis unit. In this way, multi-stage preliminary and deep oil removal maximizes the reduction of oil and suspended solids content. Furthermore, since preliminary and deep oil removal occur before desalination in the high-pressure reverse osmosis unit, it reduces the occurrence of oil fouling and clogging of the reverse osmosis membrane. Additionally, the high-pressure reverse osmosis unit utilizes high-pressure reverse osmosis membrane technology to improve the desalination rate.

[0018] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of an oilfield produced water treatment system for steam injection boilers provided in an embodiment of this disclosure; Figure 2 This is a schematic diagram of the oilfield produced water treatment system for steam injection boiler feedwater, provided in the embodiments of this disclosure, in practical application.

[0020] Figure label: 10. Multi-stage oil removal unit; 11. Air flotation device; 12. Coalescing oil separator; 13. Activated media filter; 14. Wastewater collection and settling tank; 20. Fine treatment unit; 21. Ultrafiltration unit; 22. Activated media filter; 30. High-pressure reverse osmosis unit; 40. Silicon removal device; 41. First shut-off valve; 50. Bypass branch; 51. Second shut-off valve; 60. Pure water collection tank; 70. Steam generator; 80. Sludge tank; 90. Waste liquid collection tank. Detailed Implementation

[0021] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0022] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0023] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0024] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0025] Unless otherwise stated, the term "multiple" means two or more.

[0026] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0027] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0029] Combination Figure 1 As shown in the figure, this disclosure provides an oilfield produced water treatment system for steam injection boiler feedwater. The system includes a multi-stage oil removal unit 10, a fine treatment unit 20, and a high-pressure reverse osmosis unit 30. The multi-stage oil removal unit 10 consists of multiple oil removal devices and has a first primary inlet and a first secondary outlet. It is understood that the inlet of the primary oil removal device serves as the first primary inlet, and the outlet of the secondary oil removal device serves as the first secondary outlet. The fine treatment unit 20 consists of multiple membrane pretreatment devices and has a second primary inlet and a second secondary outlet. It is understood that the inlet of the primary membrane pretreatment device serves as the second primary inlet, and the outlet of the secondary membrane pretreatment device serves as the second secondary outlet.

[0030] The first inlet receives the produced water, and the multi-stage oil removal unit 10 performs multi-stage oil and suspended solids removal treatment on the produced water. The second inlet is connected to the outlet of the first final stage, and the fine treatment unit 20 receives the product water output from the multi-stage oil removal unit 10 after high-efficiency oil removal, and performs deep oil and suspended solids removal treatment on the product water. The inlet of the high-pressure reverse osmosis unit 30 is connected to the outlet of the second final stage to receive the product water output from the fine treatment unit 20 after deep filtration, and removes impurities from the product water, such as dissolved inorganic salts, organic matter, microorganisms, heavy metals, borosilicates, etc.

[0031] The oilfield produced water system provided in this embodiment is used for steam injection boiler feedwater treatment. The first inlet of the multi-stage oil removal unit 10 receives the produced water, the second inlet of the fine treatment unit 20 is connected to the first outlet of the multi-stage oil removal unit 10, and the inlet of the high-pressure reverse osmosis unit 30 is connected to the second outlet of the fine treatment unit 20. First, the produced water undergoes preliminary multi-stage oil and suspended solids removal treatment by the multi-stage oil removal unit 10. Then, the produced water from the multi-stage oil removal unit 10 undergoes deep multi-stage oil and suspended solids removal treatment by the fine treatment unit 20. Finally, the produced water from the fine treatment unit 20 undergoes impurity removal treatment, such as desalination, by the high-pressure reverse osmosis unit 30. In this way, multi-stage preliminary oil removal and multi-stage deep oil removal maximize the reduction of oil content and suspended solids. Simultaneously, the preliminary and deep oil removal are performed before the desalination treatment in the high-pressure reverse osmosis unit 30, which can reduce the occurrence of oil fouling and clogging of the reverse osmosis membrane. Meanwhile, the high-pressure reverse osmosis unit 30 adopts high-pressure reverse osmosis module technology, which can improve the desalination rate.

[0032] Optionally, the multi-stage oil removal unit 10 includes: a carbon flotation unit (CFU) 11, a coalescing oil separator (CFC) 12, and an activated carbon filter (KMF) 13. The CFU 11 serves as the first-stage oil removal unit, with its inlet serving as the first-stage inlet, receiving the produced water. The CFU 11 removes oil and suspended solids from the produced water. The coalescing oil separator 12 serves as an intermediate-stage oil removal unit, with its inlet connected to the outlet of the CFU 11. The produced water from the CFU 11 enters the coalescing oil separator 12 for deep oil and suspended solids removal. The activated carbon filter 13 serves as the final-stage oil removal unit, with its inlet connected to the outlet of the coalescing oil separator 12. The produced water from the coalescing oil separator 12 enters the activated carbon filter 13 for fine oil and suspended solids removal. The outlet of the activated carbon filter 13 serves as the first-stage outlet, which is then connected to the second-stage inlet of the fine treatment unit 20. Thus, the air flotation device 11, the coalescing oil separator 12, and the activated filter 13 constitute a three-stage oil removal unit, which sequentially removes oil and suspended solids from the produced water.

[0033] Optionally, a single-stage centrifugal pump is installed at the inlet of the air flotation device 11 for pressurization.

[0034] Optionally, the air flotation device 11 may employ a high-efficiency dissolved air cyclone microbubble flotation device (CDFU), a shallow air flotation device (DAF), or a vortex air flotation device (CAF).

[0035] Optionally, the coalescing oil separator 12 adopts a horizontal or vertical structure. The horizontal structure uses internal components combined with packing, while the vertical structure uses internal components combined with a coalescing filter element. Optionally, the coalescing filter element can be replaced with a stainless steel + activated fiber hybrid filter element with a pore size of less than or equal to 30 μm.

[0036] Optionally, the multi-stage oil removal unit 10 also includes a wastewater collection and settling tank 14. The wastewater collection and settling tank 14 is located upstream of the air flotation unit 11, serving as the first-stage oil removal device. Its inlet receives the produced water as the first-stage inlet, and after more than 12 hours of physical settling separation, most of the floating oil, scum, and solid sediment are removed. The outlet of the wastewater collection and settling tank 14 is connected to the inlet of the air flotation unit 11, allowing the stagnant water from the middle section of the wastewater collection and settling tank 14 to enter the air flotation unit 11. Accordingly, the air flotation unit 11 becomes an intermediate-stage oil removal device. Thus, the wastewater collection and settling tank 14, the air flotation unit 11, the coalescing oil separator 12, and the activated carbon filter 13 constitute a four-stage oil removal unit.

[0037] Optionally, the sewage collection and settling tank 14 is a domed tank.

[0038] Optionally, the fine treatment unit 20 includes an ultrafilter 21 and an activated carbon filter 22. The ultrafilter 21 serves as the first-stage membrane pretreatment device, with its inlet serving as the second first-stage inlet, which is then connected to the outlet of the activated carbon filter 13. The effluent from the activated carbon filter 13 enters the ultrafilter 21 for deeper oil, colloid, and suspended solids removal. The activated carbon filter 22 serves as the final-stage membrane pretreatment device, with its outlet serving as the second final-stage outlet. The inlet of the activated carbon filter 22 is connected to the outlet of the ultrafilter 21, and the effluent from the ultrafilter 21 enters the activated carbon filter 22 for more thorough oil and suspended solids removal. Thus, the ultrafilter 21 and the activated carbon filter 22 constitute a two-stage fine treatment unit, sequentially and thoroughly removing oil and suspended solids from the effluent output from the multi-stage oil removal unit 10.

[0039] Optionally, the ultrafilter 21 is a silicon carbide ceramic membrane ultrafilter (SiC-UF).

[0040] The activated media filter 22 is officially called the hydrophilic and oleophobic activated media ultrafine filter (AAF). Its working filtration speed can reach 18m / h, which is more than twice that of conventional media filters.

[0041] Optionally, the high-pressure reverse osmosis unit 30 includes a primary deionization process device, whose reverse osmosis membrane is an HPRO (High Pressure Reverse Osmosis) membrane. Alternatively, the high-pressure reverse osmosis unit 30 includes a two-stage deionization process device, specifically a series-connected brine reverse osmosis (SWRO, Sea Water Reverse Osmosis) device and an electrodeionization (EDI) device. The inlet of the brine reverse osmosis device is connected to the outlet of the second final stage, and the inlet of the electrodeionization device is connected to the outlet of the brine reverse osmosis device. The combination of the SWRO and EDI devices is suitable for water quality with TDS < 50000 mg / L.

[0042] Optionally, the HPRO membrane unit operates at a water temperature of less than 35 ℃, with a short-term maximum of 40 ℃.

[0043] Optionally, the inlet of the high-pressure reverse osmosis unit 30 is equipped with a multi-stage high-pressure centrifugal pump for pressurization.

[0044] Optionally, the oilfield produced water treatment system for steam injection boiler feedwater also includes a desiliconization device 40 and a bypass branch 50. The desiliconization device 40 is connected between the multi-stage oil removal unit 10 and the fine treatment unit 20. Specifically, the inlet of the desiliconization device 40 is connected to the outlet of the first final stage, i.e., the outlet of the activated filter 13. The outlet of the desiliconization device 40 is connected to the inlet of the second primary stage, i.e., the inlet of the ultrafilter 21. Simultaneously, the inlet of the desiliconization device 40 is equipped with a first shut-off valve 41, which can be opened or closed under the control of a controller. The bypass branch 50 is connected between the first final stage outlet and the second primary stage inlet. Specifically, the two ends of the bypass branch 50 can be connected to the pipelines connected to the inlet and outlet of the desiliconization device 40, respectively. Simultaneously, the connection point between the bypass branch 50 and the pipeline connected to the inlet of the desiliconization device 40 is located upstream of the first on-off valve 41. Thus, the opening and closing of the first on-off valve 41 does not affect the flow of produced water into the bypass branch 50. The bypass branch 50 is equipped with a second on-off valve 51, which can be opened or closed under the control of the controller. In this way, by controlling the opening or closing of the first on-off valve 41 and the second on-off valve 51, the desiliconization device 40 can be selectively controlled to receive the produced water from the multi-stage oil removal unit 10 and perform desiliconization treatment.

[0045] Optionally, when the silicate concentration in the effluent of the multi-stage oil removal unit 10 exceeds a concentration threshold, the first on-off valve 41 is opened while the second on-off valve 51 is closed, allowing the silicate removal device 40 to treat the effluent for silicate removal. When the silicate concentration in the effluent of the multi-stage oil removal unit 10 is less than or equal to the concentration threshold, the first on-off valve 41 is closed while the second on-off valve 51 is opened, allowing the effluent to bypass the silicate removal device 40 and directly enter the fine treatment unit 20. Optionally, the concentration threshold is 3 mg / L.

[0046] Optionally, the oilfield produced water treatment system for steam injection boilers also includes a pure water collection and storage tank 60 (BT). The inlet of the pure water collection and storage tank 60 is connected to the outlet of the high-pressure reverse osmosis unit 30 (connected to the outlet of the primary deionization process equipment, or connected to the outlet of the electro-deionization equipment) to receive the produced water processed by the high-pressure reverse osmosis unit 30 for storage or final output. Optionally, the outlet of the pure water collection and storage tank 60 is connected to the inlet of a steam generator (SG) 70, which supplies steam to the boiler system according to actual demand.

[0047] Optionally, the oilfield produced water treatment system for steam injection boiler feedwater also includes a sludge tank 80. The wastewater collection and settling tank 14, air flotation device 11, coalescing oil separator 12, and activated filter 13 of the multi-stage oil removal unit 10 are all equipped with sludge outlets, and the inlet of the sludge tank 80 is connected to these sludge outlets to collect the sludge settled in the multi-stage oil removal unit 10.

[0048] Optionally, the oilfield produced water treatment system for steam injection boiler feedwater also includes a waste liquid collection tank 90. ​​The wastewater collection and settling tank 14, the air flotation device 11, the coalescing oil separator 12, the activated media filter 13, the ultrafiltration unit 21, the activated medium filter 22, and the high-pressure reverse osmosis unit 30 are all equipped with waste liquid outlets. The inlet of the waste liquid collection tank 90 is connected to these waste liquid outlets to collect waste liquids such as sludge, scum, and concentrated brine discharged from the multi-stage oil removal unit 10, the fine treatment unit 20, and the high-pressure reverse osmosis unit 30.

[0049] Optionally, the oilfield produced water treatment system for steam injection boiler feedwater also includes an SDI (Silt Density Index) detection module. The SDI detection module is located at the first final stage outlet, i.e., the outlet of the activated filter 13, and is used to detect the SDI content of the final stage produced water from the multi-stage oil removal unit 10, thereby dynamically adjusting the dosage of the water purification agent (e.g., PAC, polyaluminum chloride). Optionally, the initial increment of the water purification agent is 5 ppm to 10 ppm, and when SDI > the index threshold, the increment is gradually increased by 50% in a gradient manner. Optionally, the index threshold is set to 3.

[0050] Combination Figure 2 As shown, in specific implementation, the oilfield produced water used in the steam injection boiler feedwater treatment system includes: 1) Four-stage oil removal unit: a) Wastewater sedimentation device 101:1000m 3 After the domed tank is left to stand for 12 hours or more, the floating oil is separated by gravity (the oil content is reduced from 10,000 mg / L to 300 mg / L). b) High-efficiency dissolved air cyclone microbubble flotation device (CDFU) 102: adopts jet dissolved air cyclone microbubble flotation separation technology (gas pressure 0.4 MPa) for demulsification flotation and oil removal (oil content reduced from 300 mg / L to 45 mg / L, suspended solids reduced from 200 mg / L to 30 mg / L); c) Coalescing oil separator (CFC) 103: Three-stage combined functional packing physical demulsification and oil removal (oil content reduced from 45 mg / L to 10 mg / L, suspended solids reduced from 30 mg / L to 10 mg / L). d) Activated Filter Media (KMF) 104: A composite filter media of quartz sand and activated carbon modified with nano-coating (particle size 0.6 mm to 1.2 mm, layer height 1.5 m) adsorbs colloidal oil (oil content 10 mg / L reduced to 2 mg / L, suspended solids 10 mg / L reduced to 2 mg / L).

[0051] A three-stage synergistic process for oil and suspended solids removal, consisting of jet dissolved air cyclone, physical coalescence demulsification, and active adsorption by nano-coating.

[0052] 2) Fine processing unit: a) Silicon carbide ceramic membrane ultrafiltration (SiC-UF) 105: made of silicon carbide, with a pore size of 0.1 μm, capable of retaining micron-sized particles (oil ≤1 ppm, suspended solids ≤0.5 ppm, SDI<3). b) Hydrophilic and oleophobic activated media ultrafine filter (AAF) 106: Activated alumina filter media modified with nano-coating (particle size 0.4 mm to 0.8 mm, layer height 1.2 m) provides final oil, suspended solids, and iron removal (oil ≤ 0.1 ppm, suspended solids ≤ 0.1 ppm, Fe ≤ 0.02 mg / L), serving as the final barrier to ensure RO feed water meets standards.

[0053] The silicon carbide ceramic membrane SiC-UF (oil resistant) and the hydrophilic and oleophobic active medium ultrafine filter AAF (iron and manganese removal) form a dual barrier.

[0054] 3) Anti-fouling high-pressure reverse osmosis unit (HPRO) 107: a) The EPR8040HRLE-SW membrane (99.8% desalination rate, TDS tolerance >40000 mg / L, operating pressure 6000 kPaG) was used. b) Protection mechanism: Inlet water temperature is less than 35 ℃ (as guaranteed by the circulating cooling system).

[0055] Chemical cleaning triggered: membrane pressure difference increased by 15% (pH=2 citric acid solution).

[0056] Scale inhibitor dosage: Hydroxyethylidene diphosphonic acid (HEDP), concentration 2 ppm.

[0057] 4) Key Control Points: a) Add deoxygenating agent (sodium bisulfite, controlled dissolved oxygen less than or equal to 0.05 mg / L) to the CDFU inlet; b) Online monitoring of KMF outlet SDI, dynamically adjusting PAC dosage (5 ppm to 10 ppm).

[0058] The system also includes: a pure water collection and storage tank (BT) 108, a steam boiler 109, a waste liquid collection tank 110, and a sludge tank 111. A wastewater lift pump 112 is connected between the wastewater settling device 101 and the high-efficiency dissolved air cyclone microbubble flotation device 102. A multi-stage high-pressure centrifugal booster pump 113 is connected between the hydrophilic and oleophobic active media ultrafine filter 106 and the high-pressure reverse osmosis device 107.

[0059] The main process flow codes for the above system are as follows: Produced water V-001 → P-100 (1) (diversion rate 97%), Produced water P-100 → V-002 (2) (diversion rate 100%), Produced water V-002 → V-003 (3) (diversion rate 97%), Produced water V-003 → V-004 (4) (diversion rate 97%), Produced water V-004 → V-005 (5) (diversion rate 99%), Produced water V-005 → V-006 (6) (diversion rate 90%), Produced water V-006 → P-200 (7) (diversion rate 99%), Produced water P-200 → V-007 (8) (diversion rate 100%), Produced water V-007 → V-008 (9) (diversion rate 45%), Produced water V-008 → Steam boiler (10) (diversion rate 100%).

[0060] The material balance sheet for the main process flow is as follows:

[0061] The process flow codes for the above system are as follows: Oily scum V-001 → V009 (A) (diversion percentage 1%–3%), Oily scum V-002 → V009 (B) (diversion percentage 1%–3%), Oily scum V-003 → V009 (C) (diversion percentage 1%–3%), Oily scum V-004 → V009 (D) (diversion percentage 0.5%–1%), Oily scum V-005 → V009 (E) (diversion percentage 10%), Oily scum V-006 → V009 (F) (diversion percentage 0.5%–1%), Concentrated brine V-007 → V009 (G) (diversion percentage 55%–65%), Oily sludge V-001 → V010 (a) (diversion percentage 0.1%–1%), Oily sludge V-002 → V010 (b) (Diversion ratio 0.1% to 0.5%), oily sludge V-003 → V010 (c) (Diversion ratio 0.1% to 0.3%).

[0062] The material balance sheet for the secondary main process flow is as follows:

[0063] This new process can treat various types of produced water from oil fields to meet the feedwater quality standards for steam boilers.

[0064] The foregoing description and accompanying drawings fully illustrate embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. Embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A system for treating produced water from oilfields for use as feedwater in steam injection boilers, characterized in that, include: The multi-stage oil removal unit has a first-stage inlet and a first-stage outlet, and is used to receive produced water through the first-stage inlet and perform multi-stage oil and suspended solids removal treatment on the produced water. The fine treatment unit has a second primary inlet and a second final outlet. The second primary inlet is connected to the first final outlet and is used to receive the effluent output from the multi-stage oil removal unit through the second primary inlet and perform multi-stage filtration for deep oil and suspended solids removal. A high-pressure reverse osmosis unit, the inlet of which is connected to the outlet of the second final stage, is used to receive the product water output from the fine treatment unit and perform impurity removal treatment, wherein the impurities include salt.

2. The oilfield produced water treatment system for steam injection boilers according to claim 1, characterized in that, The multi-stage oil removal unit includes: An air flotation device, wherein the inlet of the air flotation device is used as the first primary inlet; A coalescing oil separator, the inlet of which is connected to the outlet of the air flotation device; An activated filter media, wherein the inlet of the activated filter media is connected to the outlet of the coalescing oil separator, and the outlet of the activated filter media serves as the first final stage outlet; The air flotation device, the coalescing oil remover, and the activated filter media sequentially perform oil and suspended solids removal treatment on the produced water.

3. The oilfield produced water treatment system for steam injection boilers according to claim 2, characterized in that, The air flotation device is a high-efficiency dissolved air cyclone microbubble flotation device. The coalescing oil separator adopts a horizontal or vertical structure, wherein the internal components of the horizontal structure are combined with packing, and the internal components of the vertical structure are combined with coalescing filter elements.

4. The oilfield produced water treatment system for steam injection boilers according to claim 2, characterized in that, The multi-stage oil removal unit also includes: A wastewater collection and settling tank is provided, with its inlet serving as the first primary inlet. The outlet of the wastewater collection and settling tank is connected to the inlet of the air flotation device to physically separate the produced water through settling, thus initially isolating floating oil, scum, and solid sediments.

5. The oilfield produced water treatment system for steam injection boilers according to claim 1, characterized in that, The fine processing unit includes: An ultrafilter, wherein the inlet of the ultrafilter serves as the second primary inlet; An activated medium filter, wherein the inlet of the activated medium filter is connected to the outlet of the ultrafiltration device, and the outlet of the activated medium filter serves as the outlet of the second final stage. The ultrafiltration unit and the activated carbon filter sequentially perform deep oil and suspended solids removal treatment on the effluent from the multi-stage oil removal unit.

6. The oilfield produced water treatment system for steam injection boilers according to claim 5, characterized in that, The ultrafilter is a silicon carbide ceramic membrane ultrafilter.

7. The oilfield produced water treatment system for steam injection boilers according to claim 1, characterized in that, The high-pressure reverse osmosis unit includes a primary deionization process device, and its reverse osmosis membrane is an HPRO membrane. or, The high-pressure reverse osmosis unit includes: A concentrated brine reverse osmosis device, wherein the inlet of the concentrated brine reverse osmosis device is connected to the outlet of the second final stage; An electro-deionization device, wherein the inlet of the electro-deionization device is connected to the outlet of the concentrated brine reverse osmosis device.

8. The oilfield produced water used in the steam injection boiler feedwater treatment system according to any one of claims 1 to 7, characterized in that, Also includes: A silicon removal device, wherein the inlet of the silicon removal device is connected to the outlet of the first final stage, the outlet of the silicon removal device is connected to the inlet of the second first stage, and the inlet of the silicon removal device is provided with a first on / off valve controlled by a switch. A bypass branch is connected between the first final stage outlet and the second first stage inlet, and the bypass branch is equipped with a second on / off valve with a controlled switch. By controlling the opening or closing of the first on / off valve and the second on / off valve, the desiliconization device can be selectively controlled to receive the effluent from the multi-stage oil removal unit and perform desiliconization treatment.

9. The oilfield produced water used in the steam injection boiler feedwater treatment system according to any one of claims 1 to 7, characterized in that, Also includes: A pure water collection and storage tank, the inlet of which is connected to the outlet of the high-pressure reverse osmosis unit, is used to store or output the water produced by the high-pressure reverse osmosis unit. A sludge tank, the inlet of which is connected to the sludge outlet of the multi-stage oil removal unit, is used to collect the sludge deposited by the multi-stage oil removal unit; The waste liquid collection tank has its inlet connected to the waste liquid outlet of the multi-stage oil removal unit, the fine treatment unit, and the high-pressure reverse osmosis unit to collect sludge, scum, and concentrated brine.

10. The oilfield produced water used in a steam injection boiler feedwater treatment system according to any one of claims 1 to 7, characterized in that, Also includes: An SDI detection module is installed at the first final stage outlet to detect the SDI content of the final stage effluent from the multi-stage oil removal unit, thereby dynamically adjusting the dosage of the water purification agent.

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