Long-distance concentrated brine conveying graded pressurization anti-corrosion control system

Abstract

The application discloses a long-distance concentrated brine conveying grading pressurization anti-corrosion control system and belongs to the technical field of concentrated brine pipeline conveying. The system comprises a long-distance conveying pipeline composed of pipeline materials resistant to concentrated brine corrosion, a relay pump station arranged every 15-20 kilometers along the pipeline, a variable frequency speed regulating pump group and a scale inhibitor injection device arranged in the relay pump station, a segmented differential scale prevention coating coated on the inner wall of the pipeline and a distributed leakage monitoring sensor network arranged along the pipeline. The application systematically proposes a full series of corrosion resistant pipeline materials list suitable for long-distance conveying of high-concentration brine in view of the strong corrosiveness and easy scaling characteristics of the high-concentration brine, and the list covers more than twenty types of materials. The single pump lift and the pipeline pressure grade are reduced through grading pressurization, the scaling is delayed through the double scale prevention mechanism of the scale prevention coating and the scale inhibitor injection, and the leakage points are found in time through the distributed leakage monitoring. A waste heat recovery device can be arranged at the end of the pipeline, and the conveying waste heat is used for a downstream mineral extraction process.

Description

Technical Field

[0001] This invention belongs to the field of concentrated brine pipeline transportation technology, specifically relating to a system for graded pressurization, corrosion prevention control, segmented internal wall anti-scaling coating, leakage monitoring and waste heat recovery in the process of transporting concentrated brine produced by coastal seawater desalination plants across regions to inland desert areas via long-distance pipelines. Background Technology

[0002] Transporting concentrated brine from coastal desalination plants over long distances to inland deserts for resource utilization is an innovative solution to address marine pollution from concentrated brine discharge and to achieve resource recovery. However, this transportation process faces several technical challenges: First, there is the strong corrosiveness of concentrated brine. The salinity of concentrated brine is typically 4%-7%, which has an extremely strong electrochemical corrosive effect on metal pipes. Although carbon steel pipes are inexpensive, their corrosion rate in concentrated brine environments is extremely high, often resulting in severe perforation within a few years, with maintenance costs far exceeding the initial investment. Secondly, there are energy consumption and safety issues related to long-distance transportation. The transportation distance of concentrated brine can reach tens to hundreds of kilometers. If a single pump is used for high-pressure transportation, not only will the investment in the pumping station be huge, but the pipeline will also have to withstand extremely high pressure. Once a leak occurs, the high-pressure jet will cause a serious environmental accident. Thirdly, there are limitations in the selection of pipeline materials. In existing technologies, when selecting materials for concentrated brine transport pipelines, engineers are often limited by existing technical biases and tend to consider only one or a few materials. Fourthly, there is the problem of scaling on the inner walls of pipelines. Concentrated brine contains high concentrations of calcium and magnesium ions, and a scale layer as thin as 2 mm can increase pipeline transport energy consumption by approximately 15%-25%. Current technologies for addressing scaling mainly include regular pigging and the addition of chemical scale inhibitors, but neither effectively slows down scaling at its source. Chemical dosing alone cannot fundamentally solve the problem of calcium and magnesium scale adhesion to the pipe wall—scale inhibitors can only chelate scale ions or alter the crystal structure in solution, but cannot prevent the deposition of already formed microcrystals on the pipe wall. Fifth, there is the lag in leak detection. Traditional pipeline leak detection relies on manual inspections or calculations of the difference between inlet and outlet flow rates, making it difficult to achieve immediate detection and precise location of leaks. Sixth, there is a waste of waste heat. During the long-distance transportation and pumping of concentrated brine, the water temperature gradually increases, and this waste heat is wasted in traditional solutions. Summary of the Invention

[0003] The purpose of this invention is to provide a long-distance concentrated brine transportation staged pressurization and corrosion prevention control system. I. A complete series of corrosion-resistant pipe material systems This invention systematically presents a comprehensive list of corrosion-resistant pipe materials suitable for long-distance transportation of high-concentration brine, covering more than twenty categories of materials. Those skilled in the art should understand that any pipe material employing at least equivalent corrosion resistance and suitable for transporting concentrated brine with a salinity ≥4%, including but not limited to composite pipes with thermoplastic plastics such as HDPE, PVC, PP, and PVDF as the lining or matrix and fiber-reinforced materials (such as carbon fiber, glass fiber, and aramid fiber) as the reinforcing layer, combined with the anti-scaling coating and graded pressurization scheme of this invention, should fall within the protection scope of this invention. II. Special anti-scaling coating for inner walls This invention discloses an anti-scaling coating formulation specifically for pipelines containing high-calcium and high-magnesium concentrated brine. Epoxy resin, as the base resin, provides adhesion and chemical corrosion resistance; PTFE micropowder imparts extremely low surface energy and strong hydrophobicity to the coating; nano-silica fills the micropores; silane coupling agent prevents filler agglomeration; and graphene forms a labyrinth effect to extend the permeation path. Although epoxy resin is the preferred matrix resin, any technical solution that uses a film-forming resin with equal or lower surface energy (including but not limited to polyurethane resin, silicone resin, acrylic resin, fluorocarbon resin, etc.) to replace epoxy resin and is compounded with low surface energy fillers such as PTFE micro powder to form a hydrophobic and anti-scaling coating is an equivalent solution of the present invention and should fall within the protection scope of the present invention. Even if the inner wall of the pipe is coated with a common anti-corrosion coating based on epoxy resin or the like but without the addition of low surface energy fillers, as long as the coating is objectively used on the inner wall of a pipe that transports concentrated brine, and together with the injection of scale inhibitors, it constitutes a technical solution to delay scaling, it still utilizes the core concept of this invention—delaying scaling through the dual mechanism of coating and scale inhibitors, and should fall within the protection scope of this invention. Coating application method: Sandblast the inner wall of the pipe to Sa 2.5 grade; mix the components in proportion and degas under vacuum; after adding the curing agent, apply by high-pressure airless spraying or centrifugal casting; cure at room temperature or with heat. Dry film thickness 200-500μm. Coating performance indicators: adhesion ≥5MPa; water contact angle ≥95°; no bubbling, peeling, or swelling after continuous immersion in concentrated brine with salinity of 5%-25% and temperature of 20-70°C for 365 days; the amount of calcium and magnesium scale deposited on the surface is reduced by more than 60% compared with uncoated pipes. III. Segmented Differentiated Coating Strategy The upstream pipeline transports primary concentrated brine, which contains residual scale inhibitors, organic matter, and a high concentration of calcium and magnesium ions. It requires a complete composite coating formulation with a dry film thickness of 200-500 μm. The downstream pipeline transports high-purity sodium chloride concentrated brine that has undergone membrane concentration treatment. The core task of scale prevention is to prevent sodium chloride crystals from adhering. Therefore, the downstream pipeline only needs to be coated with a hydrophobic coating with extremely low surface energy—a pure PTFE coating or a mixed coating of PTFE and epoxy resin, with a dry film thickness of 100-200μm. The material cost is only 30%-40% of that of the upstream composite coating. The segmented differentiated coating strategy is the optimal technical solution of this invention. Even if competitors use a uniform coating throughout the entire section, or only use a coating in one section while leaving another section uncoated, as long as their technical solution includes the core feature of the anti-scaling coating on the inner wall of this invention, it should still fall within the protection scope of this invention. IV. Dual Anti-scaling Mechanism This invention employs a dual anti-scaling mechanism of "inner wall anti-scaling coating + anti-scaling agent injection". The inner wall anti-scaling coating reduces the surface energy of the pipe wall, making it difficult for scale-forming ions and micro-crystals to adhere, thus fundamentally delaying scaling at its source. Anti-scaling agent injection serves as an auxiliary measure; the synergistic effect of these two mechanisms achieves an overall anti-scaling efficiency of over 90%. V. Staged pressurization system A relay pumping station is installed every 15-20 kilometers along the pipeline, equipped with variable frequency speed-regulating pump sets that automatically adjust the speed according to real-time pressure and flow rate. The above numerical ranges are preferred ranges and not strict limitations on the scope of protection. Any technical solution that substantially employs a staged pressurization scheme but makes only non-substantial adjustments to the spacing between pumping stations should fall within the scope of protection of this invention. VI. Leakage Monitoring Device Fiber optic sensors are distributed along the pipeline to detect leaks in real time. Any device capable of detecting pipeline leaks in real time, regardless of the technical principle used (including but not limited to fiber optic sensing, acoustic sensing, flow difference analysis, pressure wave monitoring, etc.) and whether or not it has a location function, should fall within the protection scope of this invention as long as it substantially achieves real-time leak detection of concentrated brine delivery pipelines. VII. Waste Heat Recovery Device (Preferred Solution) A waste heat recovery device can be installed at the pipeline outlet, and the recovered heat can be used for the downstream bromine extraction unit. Even without a waste heat recovery device, the delivery system, which includes an anti-scaling coating on the inner wall, staged pressurization, and leak monitoring, constitutes an independent invention in itself. Split Avoidance Statement

[0004] Those skilled in the art should understand that separating the above-mentioned technical features into different legal entities or geographical regions does not change the fact that it operates collaboratively as a complete system. Any act of circumventing the scope of protection of this invention by splitting the system, subcontracting services, or other means shall be considered equivalent infringement. Detailed Implementation

[0005] Example 1: 40km concentrated brine transport system – segmented coating scheme This embodiment focuses on a concentrated brine pipeline approximately 40 kilometers long, running from a coastal desalination plant to an inland desert terminal. The concentrated brine has a salinity of approximately 5.8% and a flow rate of approximately 30,000 m³ / h. Front-end piping (0-25 km): DN800 HDPE pipe. Inner wall coated with a composite anti-scaling coating: 50 parts bisphenol A epoxy resin, 12 parts PTFE micro powder, 5 parts nano-silica, 1 part graphene, 2 parts silane coupling agent, 1 part silicone defoamer, and 20 parts polyamide curing agent. Sandblasted to Sa 2.5 grade, high-pressure airless spraying, cured at room temperature for 48 hours, dry film thickness 300-400 μm. Membrane concentration unit (25 km away): High-pressure reverse osmosis increases brine concentration from 5.8% to approximately 20%. Downstream piping (25-40 km): DN800 PVC-U pipes are used. The inner wall is coated with a simplified anti-scaling coating: pure PTFE emulsion spraying, dry film thickness 150μm, water contact angle ≥105°. Intermediate pumping stations: One station is set up at the 15km mark of the first section and another at the 32km mark of the second section. Each station is equipped with a variable frequency speed-regulating centrifugal pump, and the flow-through components are made of 2205 duplex stainless steel. Injection of scale inhibitor: Organophosphonate scale inhibitor, injection concentration 2-5 mg / L. Leakage monitoring: Distributed fiber optic temperature sensing cables are laid throughout the line. A sudden drop in temperature of 2-5°C is detected within 5 seconds after a leak, with a positioning accuracy of ±5 meters. Waste heat recovery: A shell-and-tube heat exchanger is installed at the outlet end, and the heat is used to preheat the feed brine of the downstream bromine extraction unit, saving about 15,000 tons of heating steam per year. Five years of operational verification: The front-end composite coating reduced calcium and magnesium scale by 68%; the back-end simplified coating reduced sodium chloride crystal adhesion by 85%. Example 2: Coating Formulation Variant – Polyurethane Matrix The film-forming resin of the anti-scaling coating on the front section of the pipeline is polyurethane resin instead of epoxy resin, which is suitable for pipeline sections with large temperature differences and is an equivalent solution of the present invention. Example 3: Coating Formulation Variant – Fluorocarbon Resin Matrix The film-forming resin of the anti-scaling coating on the front-end pipeline is fluorocarbon resin, with a water contact angle ≥110°, which is an equivalent solution of the present invention. Example 4: Basic Conveying System Without Waste Heat Recovery The pipeline outlet does not have a waste heat recovery device, but it still includes the core features of an inner wall anti-scaling coating, graded pressurization, and leak monitoring, forming an independent long-distance concentrated brine delivery system. The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A long-distance concentrated brine transportation staged pressurization and corrosion-resistant control system, characterized in that, include: A long-distance transmission pipeline, with its inlet end connected to the concentrated brine output interface of a coastal desalination plant and its outlet end extending to a terminal facility in an inland desert area, is constructed using pipe materials resistant to concentrated brine corrosion. An anti-scaling coating is applied to the inner wall of the long-distance transmission pipeline. At least two intermediate pump stations are spaced along the long-distance transmission pipeline for graded pressurization of the concentrated brine within the pipeline. Corrosion and scale prevention devices are installed within the long-distance transmission pipeline and / or the intermediate pump stations to delay corrosion and scaling on the inner wall of the pipeline. Leakage monitoring devices are distributed along the long-distance transmission pipeline for real-time detection of pipeline leaks.

2. The system according to claim 1, characterized in that, The pipeline material resistant to concentrated salt water corrosion includes at least one of the following materials: fiber reinforced plastic (FRP) pipes; high-density polyethylene (HDPE) pipes; polyvinyl chloride (PVC) pipes, including rigid polyvinyl chloride (PVC-U) pipes and chlorinated polyvinyl chloride (PVC-C) pipes; polypropylene (PP) pipes, including homopolymer polypropylene (PP-H) pipes, block copolymer polypropylene (PP-B) pipes and random copolymer polypropylene (PP-R) pipes; polyvinylidene fluoride (PVDF) pipes; acrylonitrile-butadiene-styrene (ABS) engineering plastic pipes; polyethylene (PE) pipes, including medium-density polyethylene (MDPE) pipes and cross-linked polyethylene (PEX) pipes; polybutene (PB) pipes; and steel-reinforced plastic composite pipes, including steel-reinforced polyethylene (PE) composite pipes and steel wire. Reinforced plastic composite pipes; perforated steel-reinforced polyethylene composite pipes; bimetallic composite pipes, including stainless steel-lined composite pipes and metallurgical composite bimetallic pipes; plastic-lined steel pipes, including polytetrafluoroethylene (PTFE), polyethylene (PE), and polypropylene (PP)-lined steel pipes; rubber-lined steel pipes; fiberglass-lined steel pipes; enamel-lined steel pipes; fiberglass reinforced plastic (RPMP) pipes; centrifugally cast glass fiber reinforced plastic pipes (Hobas pipes); stainless steel pipes, including 304, 316, 316L, 2205, and 2507 super duplex stainless steel pipes; duplex stainless steel composite pipes; titanium and titanium alloy pipes; nickel-based alloy pipes, including Hastelloy and Monel alloy pipes; and ceramic-lined composite steel pipes.

3. The system according to claim 1, characterized in that, The anti-scaling coating on the inner wall is composed of the following raw materials in parts by weight. Composition: Epoxy resin: 40-60 parts; Polyamide curing agent: 15-25 parts; Polytetrafluoroethylene (PTFE) micro powder: 8-15 parts; Nano silica: 3-8 parts; Silane coupling agent: 1-3 parts; Graphene or graphene oxide: 0.5-2 parts; and Organosilicon defoamer: 0.5-1.5 parts; wherein, the epoxy resin is at least one of bisphenol A type epoxy resin or bisphenol F type epoxy resin; the particle size of the PTFE micro powder is 1-10 μm; and the particle size of the nano silica is 10-50 nm.

4. The system according to claim 3, characterized in that, The construction method of the inner wall anti-scaling coating includes the following steps: Step A: Sandblasting or shot blasting the inner wall of the pipe to remove the surface oxide layer and oil stains, so that the surface roughness of the inner wall reaches Ra 5-15μm; Step B: Mixing epoxy resin with PTFE micro powder, nano silica, graphene, silane coupling agent and defoamer in proportion, stirring and degassing under vacuum conditions to obtain the coating main agent; Step C: Adding polyamide curing agent to the coating main agent, stirring evenly, and then coating it onto the inner wall of the pipe by high-pressure airless spraying or centrifugal casting; Step D: After coating, curing at room temperature for 24-48 hours, or heating and curing at 60-80°C for 4-8 hours to form an anti-scaling coating with a dry film thickness of 200-500μm.

5. The system according to claim 3 or 4, characterized in that, The long-distance transmission pipeline is divided into a front-end pipeline and a rear-end pipeline, depending on the water quality of the transmission medium. The inlet of the front-end pipeline is connected to the concentrated brine output interface of the coastal desalination plant, and its outlet is connected to the inlet of a membrane concentration unit located in an inland desert area. The concentrated brine transported in the front-end pipeline is primary concentrated brine that has not undergone subsequent membrane concentration treatment and contains residual scale inhibitors, organic matter, calcium and magnesium ions, and suspended solids from the seawater desalination process. The inlet of the rear-end pipeline is connected to the concentrated brine outlet of the membrane concentration unit, and its outlet... The pipeline extends downstream to a mineral extraction unit or a salt-producing pond. The concentrated brine transported in the downstream pipeline is a high-purity sodium chloride concentrated brine that has been treated by the membrane concentration device. The inner wall of the upstream pipeline is coated with a first anti-scaling coating, which adopts the composition formula described in claim 3. The inner wall of the downstream pipeline is coated with a second anti-scaling coating, which is a pure polytetrafluoroethylene (PTFE) coating or a mixed coating of PTFE and epoxy resin. The dry film thickness of the second anti-scaling coating is 100-200 μm.

6. The system according to claim 3 or 4, characterized in that, The inner wall anti-scaling coating achieves the following performance indicators: adhesion to the pipe substrate ≥5MPa (tested according to ASTM D4541 pull-off method); water contact angle ≥95°; after continuous immersion in concentrated brine with a salinity of 5%-25% and a temperature of 20-70°C for 365 days, the coating shows no blistering, peeling, or swelling; under the above conditions, the amount of calcium and magnesium scale deposited on the coating surface is reduced by more than 60% compared to the inner wall of the pipe without coating.

7. The system according to claim 2, characterized in that, Different sections of the long-distance pipeline use different types of pipe materials resistant to concentrated salt water corrosion, or a combination of multiple pipe materials resistant to concentrated salt water corrosion, depending on the transmission pressure, terrain conditions, and corrosive environment.

8. The system according to claim 1, characterized in that, The relay pumping station is set up every 15-20 kilometers along the long-distance transmission pipeline. Each relay pumping station is equipped with a variable frequency speed control pump set, which automatically adjusts the pump speed according to the real-time pressure and flow of the pipeline.

9. The system according to claim 1 or 2, characterized in that, The corrosion and scale prevention device includes: an anti-corrosion coating applied to the inner wall of the pipeline in contact with concentrated brine; and a scale inhibitor injection device disposed in the relay pump station for quantitatively injecting scale inhibitor into the pipeline.

10. The system according to claim 1 or 2, characterized in that, The leakage monitoring device includes: a distributed fiber optic temperature sensor or a distributed acoustic wave sensor, laid along the outer wall or inside the pipeline of the long-distance delivery pipeline, for real-time monitoring of abnormal temperature or acoustic wave signals along the pipeline; and a central monitoring terminal, connected to the distributed fiber optic temperature sensor or the distributed acoustic wave sensor, for determining that a leak has occurred when a sudden drop in temperature or an abnormal acoustic wave is detected, and for further locating the leak point.

11. The system according to claim 1, characterized in that, It also includes a waste heat recovery device, which is installed at the outlet end of the long-distance transport pipeline to recover the ambient heat and pumping friction heat absorbed by the concentrated brine during the long-distance transport process; the heat recovered by the waste heat recovery device is used to provide a heat source for the bromine extraction unit in the downstream mineral extraction process.

12. The system according to claim 1, characterized in that, The total length of the long-distance pipeline is between 10 kilometers and 200 kilometers, and it extends from the coastal area to the inland desert area along the elevation gradient, with an elevation difference between 50 meters and 1,500 meters.

13. The system according to claim 1, characterized in that, The diameter of the long-distance transmission pipeline is between DN400 and DN1200.

14. The system according to claim 1, characterized in that, The design service life of the long-distance transmission pipeline shall not be less than 30 years.