Water treatment system for ship dual-fuel main engine and exhaust gas recirculation system comprising same

Abstract

The invention provides a brand-new water treatment system for a dual-fuel main engine of a ship. The water treatment system comprises a tubular membrane module box, a pressurizing circulating pump, a CIP automatic backwashing chemical bin and an instrument pipe valve, the tubular module box adopts a double-membrane combined system, a polyvinylidene fluoride (PVDF) hollow fiber membrane is adopted for primary filtration, and a silicon carbide ceramic membrane is adopted for deep filtration. Through a brand new designed tubular membrane module box, a polyvinylidene fluoride (PVDF) hollow fiber membrane and a silicon carbide ceramic membrane are combined for application, a double-membrane system solves the problem of multiple pollutants in ship dual-fuel main engine wastewater treatment, and comprehensive removal of emulsified oil, suspended particles, heavy metal ions and soluble organic matters is realized. Compared with a single-membrane system, the treatment efficiency and the stability of the system are improved through combination of double membranes, the cleaning frequency and the maintenance cost are remarkably reduced, and a more economical, efficient and reliable solution is provided for ship wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of ship exhaust gas and wastewater treatment, and in particular to a ship dual-fuel main engine water treatment system and an exhaust gas recirculation system comprising the same. Background Art

[0002] As the International Maritime Organization (IMO) has tightened its regulations on the emission of nitrogen oxides (NOx) from ships, the shipping industry is constantly seeking effective emission reduction technologies to ensure that they meet international standards. Among them, exhaust gas recirculation (EGR) technology, as one of the most effective means to reduce nitrogen oxide emissions, has gradually been widely used on ship main engines. The basic principle of EGR technology is to reintroduce part of the exhaust gas into the combustion chamber, thereby reducing the combustion temperature and reducing the content of nitrogen oxides formed at high temperatures. However, the application of the exhaust gas recirculation system brings a series of challenges, especially oil stains, carbon particles and other impurities in the exhaust gas. If these impurities are not handled in a timely and effective manner, they will not only pollute the recirculated gas, but also accumulate inside the equipment, causing system corrosion, pipeline blockage and other problems, thereby affecting the operating efficiency and life of the exhaust gas recirculation system. In order to solve these problems, the water treatment system, as an important part of the exhaust gas recirculation system, plays a key role. By washing and filtering the exhaust gas, the water treatment system can effectively remove impurities in the exhaust gas, ensure the smooth operation of the system, and reduce the risk of equipment damage. Therefore, the reliability of the exhaust gas recirculation system depends to a large extent on the performance of the water treatment system.

[0003] In the EGR system, the water treatment system is a crucial link. Its main task is to purify the wastewater from the exhaust gas scrubber to ensure that the water recycled back to the system reaches the required cleanliness standards. This not only helps to extend the service life of the system equipment, but also meets the strict requirements of the International Maritime Organization for ship emissions. In particular, Resolution 307 (73) adopted by the MEPC (Marine Environment Protection Committee) clearly stipulates the discharge standards for wastewater. According to the resolution, the oil content in the wastewater discharged by ships shall not exceed 15ppm, and the turbidity of the water must be less than 50NTU (turbidity units). In order to achieve this goal, the wastewater treatment system must have an efficient oil-water separation function and be able to effectively remove impurities such as emulsified oil and carbon powder particles in the exhaust gas.

[0004] Dual-fuel engines use liquefied natural gas (LNG) and traditional heavy fuel oil (HFO) or diesel (MDO) as fuel, and are currently a widely used power technology. Compared with single-fuel engines, the exhaust gas produced by dual-fuel engines after combustion is more complex. This results in pollutants in the exhaust gas not only including oil stains and carbon particles, but also sulfides, nitrogen oxides, incompletely burned hydrocarbons and other acidic substances. The water treatment system needs to have stronger multifunctional processing capabilities to effectively remove these diverse pollutants.

[0005] In addition, in the dual-fuel main engine system, the exhaust gas recirculation and water treatment systems consume a certain amount of energy. In order to reduce the overall energy consumption of the ship, the water treatment system needs to maintain low energy consumption while efficiently removing pollutants. This requires that the water treatment technology must be both efficient and energy-saving during the treatment process.

[0006] Silicon carbide ceramic membrane (SiC membrane) is a new type of high-performance filtration material that has been widely used in the treatment of ship dual-fuel engine wash water, especially for the treatment of highly polluted, alkaline and chemically strong wastewater. Companies such as LiqTech and Ovivo have developed patented technologies based on SiC ceramic membranes specifically for wash water treatment systems. These systems can effectively treat pollutants in ship wash water, such as suspended particles, heavy metals and hydrocarbons, ensuring that the wastewater is not discharged directly into the ocean after filtration.

[0007] However, the pore size of silicon carbide ceramic membranes is usually small, which makes them less efficient in treating large particle pollutants. If wastewater containing more large particle pollutants is directly treated, the silicon carbide membrane is easily contaminated quickly, resulting in reduced system operating efficiency and increased cleaning frequency. In addition, due to its small pore size, it usually needs to be operated at a higher pressure (10-15 bar) to ensure that water flows through the membrane and achieves effective filtration, which significantly increases energy consumption when treating large volumes of wastewater. Summary of the invention

[0008] The purpose of the present invention is to provide a new water treatment system for dual-fuel main engines of ships, which has stable equipment working performance, high treatment efficiency, low energy consumption, and can effectively treat diverse pollutants.

[0009] In order to solve the above technical problems, the present invention provides a new water treatment system for dual-fuel main engines of ships, which includes a tubular membrane module box, a booster circulation pump, a CIP automatic backwashing medicine tank and instrument pipe valves; the tubular module box adopts a double membrane combination system, the primary filtration adopts polyvinylidene fluoride (PVDF) hollow fiber membrane, and the deep filtration adopts silicon carbide ceramic membrane.

[0010] Wherein, the PVDF hollow fiber membrane and the silicon carbide ceramic membrane are both designed as standardized modular units and embedded in a tubular membrane module box.

[0011] The PVDF hollow fiber membrane unit and the silicon carbide ceramic membrane unit are arranged in series in sequence. The PVDF hollow fiber membrane unit is placed at the front end of the tubular membrane module box as a primary filter, and the silicon carbide ceramic membrane is placed at the rear end of the tubular membrane module box as a depth filter.

[0012] The PVDF hollow fiber membrane unit is designed as a graded porous membrane structure, specifically including an outer large pore layer and an inner small pore layer. The pore size of the outer large pore layer is designed to be 0.3-0.6 μm, and the pore size of the inner small pore layer is designed to be 0.1-0.3 μm.

[0013] The silicon carbide ceramic membrane group unit is composed of a support layer and an active filter layer. The support layer adopts a honeycomb structure design, with a porosity of 40-60% and a pore size of 50-100μμm, ensuring that at high flow rates, large particles in the wastewater can pass through the support layer smoothly without causing pressure damage to the membrane.

[0014] Among them, the active filter layer is designed as a single-layer active filter layer, and adopts a gradient pore size design. From the outer layer to the inner layer, the pore size gradually decreases from 0.05μm to 0.01μm, and the filtration accuracy is improved through graded filtration.

[0015] Among them, the booster circulation pump is connected to the tubular membrane module box, and the pre-treated wastewater is pressurized and sent into the tubular membrane module box. After filtration, the clean water flows to the outlet, and the concentrated pollutants are discharged through the concentrated water outlet. The CIP automatic backwashing medicine tank transports the cleaning agent to the tubular membrane module box through the pipeline to clean the membrane surface regularly.

[0016] Among them, the water treatment system for the dual-fuel main engine of the ship can also include a filter press unit and a tubular membrane module box mud discharge unit. The tubular module box mud discharge unit is connected to the tubular module box through a pipeline. The pollutants retained after membrane filtration, especially solid particles and sludge, are discharged centrally through the mud discharge unit. The sludge retained after membrane filtration is discharged centrally. The filter press unit is connected to the tubular module box mud discharge unit.

[0017] The present invention also provides an exhaust gas recirculation (EGR) system for a dual-fuel main engine ship, which comprises: an exhaust gas cleaning system, an EGC circulating water system, a pH neutralizer dosing system and the above-mentioned water treatment system;

[0018] The exhaust gas cleaning system is used to clean the recirculated exhaust gas to remove particulate matter and sulfide therein;

[0019] The EGC circulating water system is used to treat and cool the circulating water in the EGR system to ensure the water temperature and water quality during the exhaust gas cleaning process.

[0020] The present invention also provides a method for treating the above-mentioned ship dual-fuel main engine exhaust gas washing wastewater, which comprises:

[0021] In the first step, the wastewater enters the booster circulation pump through the pipeline, and after being pressurized to 5-8 bar, it enters the PVDF hollow fiber membrane unit;

[0022] In the second step, the wastewater after primary filtration flows to the silicon carbide ceramic membrane unit, where the pressure is further increased to 10-15 bar for deep filtration;

[0023] In the third step, the effluent is discharged through pipes, and the concentrated wastewater and pollutants are intercepted and discharged through a dedicated discharge port.

[0024] Beneficial Effects of the Invention

[0025] The present invention uses a newly designed tubular membrane module box, including a polyvinylidene fluoride (PVDF) hollow fiber membrane and a silicon carbide ceramic membrane. The double membrane system solves the problem of multiple pollutants in the treatment of wastewater from dual-fuel main engines of ships, and achieves comprehensive removal of emulsified oil, suspended particles, heavy metal ions and soluble organic matter. Compared with a single membrane system, the dual membrane combination not only improves the treatment efficiency and stability of the system, but also significantly reduces the cleaning frequency and maintenance costs, providing a more economical, efficient and reliable solution for ship wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 An exhaust gas recirculation (EGR) system for a dual-fuel main engine ship of the present invention;

[0027] Figure 2 A schematic diagram of the structure of the water treatment system of the present invention;

[0028] Figure 3 A schematic diagram of the tubular module box structure of the water treatment system of the present invention. DETAILED DESCRIPTION

[0029] The water treatment system for the dual-fuel main engine of a ship provided by the present invention mainly includes a tubular membrane module box, a booster circulation pump, a CIP automatic backwashing medicine tank and instrument pipe valves. The booster circulation pump is connected to the tubular membrane module box, and the pre-treated wastewater is pressurized and sent into the tubular membrane module box. After filtration, the clean water flows to the water outlet, and the concentrated pollutants are discharged through the concentrated water outlet. The CIP automatic backwashing medicine tank transports the cleaning agent to the tubular membrane module box through a pipeline, and regularly cleans the membrane surface to prevent membrane clogging and extend the service life of the membrane.

[0030] The tubular membrane module box is the core filtration unit of the water treatment system. It uses internal pressure multi-stage cross-flow filtration technology to separate pollutants in the water through the selective permeability of the membrane. The membrane module can effectively filter suspended particles, heavy metal ions, dissolved organic matter and other pollutants to ensure that the water quality meets the discharge standards.

[0031] Considering the drawbacks of using silicon carbide ceramic membrane alone, the present invention proposes to use a dual membrane system, using polyvinylidene fluoride (PVDF) hollow fiber membrane for primary filtration, taking advantage of its good hydrophilicity to remove emulsified oil, suspended particles and most organic pollutants in wastewater. These pollutants account for a large proportion of ship wastewater, and PVDF membrane can effectively remove such large particle pollutants and oils through its microfiltration characteristics (pore size 0.05-0.1μm), making subsequent treatment steps easier.

[0032] The deep filtration uses silicon carbide ceramic membrane, which has extremely high chemical corrosion resistance and mechanical strength, and can treat heavy metal ions, fine particles and dissolved organic matter in ship wastewater under high pressure. In particular, the pore size range of silicon carbide membrane is small (0.01-0.05μm), which can further remove dissolved pollutants that PVDF membrane cannot retain.

[0033] Compared with single membrane technology, the combination of dual membranes not only improves filtration efficiency, but also reduces membrane pollution and cleaning frequency, thereby reducing system maintenance costs and operating energy consumption.

[0034] The PVDF hollow fiber membrane and the silicon carbide ceramic membrane are designed as standardized modular units, embedded in the membrane module box. When the membrane performance is attenuated or damaged, the corresponding membrane unit can be quickly replaced without stopping the entire membrane system. Each membrane unit operates independently, and the system can freely configure the number and type of membrane modules according to the different pollutant concentrations of the wastewater.

[0035] The PVDF hollow fiber membrane unit and the silicon carbide ceramic membrane unit are arranged in series in sequence. The PVDF hollow fiber membrane unit is placed at the front end of the membrane module box as a primary filter, and the silicon carbide ceramic membrane is placed at the rear end of the membrane module box as a depth filter.

[0036] A single PVDF hollow fiber membrane unit and the silicon carbide ceramic membrane unit can be connected in series through pipelines to form a membrane assembly, and multiple membrane assemblies can be placed in parallel in a membrane assembly box through pipelines. Alternatively, multiple PVDF hollow fiber membrane units can be connected in parallel through pipelines, and multiple silicon carbide ceramic membrane units can be connected in parallel through pipelines according to needs. The parallel-connected PVDF hollow fiber membrane unit group and silicon carbide ceramic membrane unit group are connected in series through pipelines and installed together in a module box.

[0037] The outlet of the PVDF hollow fiber membrane unit is connected to the inlet of the silicon carbide membrane unit through a pipe to ensure the continuity of water flow between the two membrane units. Each membrane unit is designed with independent inlet and outlet, and its pressure and flow rate can be controlled separately.

[0038] The PVDF hollow fiber membrane group unit is designed as a graded porous membrane structure, which can achieve multifunctional filtration, specifically including an outer large-pore layer and an inner small-pore layer. The pore size of the outer large-pore layer is designed to be 0.3-0.6μm, which is used for preliminary filtration of large suspended particles and emulsified oil. This layer effectively intercepts large particles while ensuring high flux of water flow. The pore size of the inner small-pore layer is designed to be 0.1-0.3μμm, which is used to remove fine particles and larger oil molecules. The pollutant burden is further reduced through graded filtration in the middle layer.

[0039] It is further preferred that nanomaterials (such as graphene oxide or titanium dioxide nanoparticles) are coated on the surface of the PVDF hollow fiber membrane, which can significantly enhance its hydrophilicity and anti-pollution properties. Through this nano-modification technology, the adhesion of oils and organic matter to the membrane surface can be reduced, thereby improving the flux and service life of the membrane.

[0040] The silicon carbide ceramic membrane unit consists of a support layer and an active filter layer. The support layer adopts a honeycomb structure design, and the porosity is maintained at 40-60%, which reduces the pressure drop and ensures that the wastewater can be evenly distributed on the membrane surface and smoothly flow through the entire membrane assembly. The support layer is made of coarse-porous silicon carbide material with a pore size of 50-100μm, ensuring that large particles in the wastewater can pass through the support layer smoothly at high flow rates without causing pressure damage to the membrane.

[0041] The active filter layer is the core part of the silicon carbide ceramic membrane, which is used to efficiently remove fine particles, dissolved organic matter and heavy metal ions in wastewater. The active filter layer is designed as a single-layer active filter layer with a pore size range of 0.01-0.05μm, which is mainly used to remove fine suspended particles and dissolved pollutants. According to the specific conditions of the wastewater, the pore size range can be adjusted to meet different filtration needs.

[0042] Further preferably, the active filter layer adopts a gradient pore size design, where the pore size gradually decreases from 0.05 μm to 0.01 μm from the outer layer to the inner layer, thereby improving the filtration accuracy through graded filtration.

[0043] The method for preparing the active filter layer with a gradually varying pore size comprises:

[0044] The first step is to select and classify silicon carbide ceramic powder. Select silicon carbide ceramic powder of 0.01μm-0.05μm. Through screening technology, ensure that the size of each layer of powder is consistent, and divide it into two layers of powder. The outer layer powder is preferably 0.03-0.05μm, and the inner layer powder is preferably 0.01-0.03μm.

[0045] The second step is powder accumulation and stratification. The outer layer of large-sized powder is accumulated on the substrate. After homogenization treatment, the layer thickness is ensured to be consistent. On the basis of the outer layer, fine-grained silicon carbide powder is accumulated to form the inner filter layer.

[0046] The third step is sintering. After the second step of stacking, the product is sintered at a temperature of 1800-2200°C for 2-6 hours. The sintering process usually needs to be carried out in an inert atmosphere such as argon or in a vacuum environment.

[0047] The fourth step is post-processing, which includes optional polishing. The outer layer can be polished to reduce the roughness of the membrane surface and improve the smoothness of the water flow channel.

[0048] Further preferably, the silicon carbide ceramic membrane unit may also be subjected to surface modification technology. By physically and chemically modifying the surface of the silicon carbide membrane, its hydrophilicity and anti-pollution ability may be improved, and the frequency of membrane cleaning may be reduced.

[0049] The internal pressure cross-flow booster membrane filtration provided by the present invention is the core technology of the entire water treatment system. Its principle is that by applying high pressure in the membrane assembly, the wastewater flows laterally along the membrane surface under the action of high pressure, and small molecules (such as water molecules) and dissolved pollutants in the water pass through the membrane into the clean water side, while large particles and suspended matter are retained on the wastewater side.

[0050] The use of internal pressure cross-flow booster membrane filtration technology has obvious advantages in treating water used by dual-fuel main engines, especially in treating complex and variable wastewater components, including:

[0051] 1. Efficient pollutant separation

[0052] Internal pressure cross-flow booster membrane filtration effectively removes suspended particles, grease, heavy metal ions and dissolved organic pollutants in wastewater through the selective permeability of the membrane. These pollutants are often present in the wastewater of dual-fuel main engines, especially the waste gas scrubbing water contains a large amount of sulfur oxides, tiny particles and oil residues.

[0053] By applying internal pressure, pollutants in the wastewater can be forced to pass through the membrane surface, resulting in more efficient separation. Internal pressure enhances the dynamics of membrane filtration, enabling the treatment of high concentrations of suspended solids and pollutants.

[0054] The wastewater produced by the dual-fuel main engine has complex composition and large fluctuations in content. Internal pressure membrane filtration can quickly adapt to different water qualities and maintain a stable treatment effect.

[0055] 2. Cross-flow filtration reduces membrane fouling

[0056] Cross-flow filtration offers important advantages over conventional “dead-end filtration”, particularly in preventing membrane surface fouling and clogging.

[0057] During the cross-flow filtration process, wastewater does not pass through the membrane directly, but flows laterally along the membrane surface. This design greatly reduces the deposition of particulate matter on the membrane surface, prevents the membrane surface from being quickly blocked by pollutants, and extends the service life of the membrane.

[0058] Cross-flow filtration can effectively delay the accumulation of pollutants on the membrane surface and reduce the frequency of membrane cleaning, thereby reducing downtime and maintenance costs, which is crucial to the continuous operation of ships.

[0059] 3. Suitable for high pressure environment and improve filtration efficiency

[0060] Internal pressure booster membrane filtration technology can work under high pressure, which is particularly beneficial for ship systems that need to treat large amounts of wastewater. The wastewater generated by dual-fuel main engines is large in volume and contains high concentrations of pollutants, so efficient filtration technology is required to treat it.

[0061] Pressure filtration allows wastewater to flow through the membrane surface more quickly while maintaining a high permeability. This not only allows for the treatment of larger volumes of wastewater, but also effectively separates pollutants with smaller solubility, making the treated water cleaner.

[0062] Internal pressure boost filtration is able to treat complex wastewater components, such as fine particles and dissolved contaminants in exhaust scrubber water, which are difficult to treat with other conventional filtration technologies.

[0063] 4. Reduce energy consumption

[0064] Although the system relies on a high-pressure pump to provide pressure during the filtration process, its efficient cross-flow filtration mode reduces the overall energy consumption of the system. By improving filtration efficiency and reducing membrane surface fouling, the technology can achieve better treatment results at lower energy consumption.

[0065] Compared with traditional filtration systems, cross-flow filtration can effectively avoid membrane clogging and reduce energy waste under high flow rate and high pressure conditions. This efficiency-energy consumption balance is particularly important in ship systems because energy resources on ships are limited.

[0066] Furthermore, an ultrasonic vibration device is provided on the surface of the silicon carbide membrane group unit to generate vibrations on the membrane surface regularly to reduce membrane contamination, extend the service life of the membrane and reduce the frequency of CIP in-situ cleaning. Preferably, the ultrasonic frequency is between 20-40kHz, which can be automatically adjusted according to the degree of membrane contamination. The self-cleaning cycle is automatically started every 24 hours and lasts for 5-10 minutes each time. On the one hand, the ultrasonic vibration device greatly reduces the adhesion of deposits on the membrane surface and improves the filtration flux; on the other hand, it extends the service life of the membrane and reduces the cleaning downtime and the use of chemicals.

[0067] The water treatment system for the dual-fuel main engine of the ship can also include a filter press unit and a tubular membrane module box mud discharge unit. The tubular module box mud discharge unit is connected to the tubular module box through a pipeline. The pollutants retained after membrane filtration, especially solid particles and sludge, are discharged through the mud discharge unit. The sludge retained after membrane filtration is discharged in a centralized manner. The filter press unit is connected to the tubular module box mud discharge unit. The filter press unit further processes the sludge by pressing and dehydrating to form a mud cake for easy transportation.

[0068] The present invention also provides an exhaust gas recirculation (EGR) system for a dual-fuel main engine ship, which comprises: an exhaust gas cleaning system (EGC), a pH neutralizer dosing system and the above-mentioned water treatment system;

[0069] The exhaust gas cleaning system EGC is used to clean the recirculated exhaust gas to remove particulate matter and sulfide therein;

[0070] The water treatment system is used to treat wastewater generated after exhaust gas cleaning, and achieves comprehensive removal of emulsified oil, suspended particles, heavy metal ions and soluble organic matter.

[0071] The exhaust gas cleaning system EGC further comprises an EGC scrubber, an EGC circulating water cooler, an EGC circulating water pump and an EGC circulating water tank;

[0072] The EGC circulating water cooler is used to cool the circulating water used in the exhaust gas cleaning process;

[0073] The EGC circulating water pump is used to drive the cooled water into the EGC washing tower for cleaning;

[0074] The EGC circulating water tank is used to store circulating water for cleaning exhaust gas.

[0075] The pH neutralizer dosing system is closely connected to the EGR wastewater storage tank. After the wastewater passes through the water treatment system, the pH value may be acidic. The pH neutralizer system is used to adjust the pH to ensure that the discharge meets environmental protection standards.

[0076] The present invention also provides a method for treating the above-mentioned ship dual-fuel main engine exhaust gas washing wastewater, which comprises:

[0077] In the first step, the wastewater enters the booster circulation pump through the pipeline, and after being pressurized to 5-8 bar, it enters the PVDF hollow fiber membrane unit;

[0078] In the second step, the wastewater after primary filtration flows to the silicon carbide ceramic membrane unit, where the pressure is further increased to 10-15 bar for deep filtration;

[0079] In the third step, the effluent is discharged through pipes, and the concentrated wastewater and pollutants are intercepted and discharged through a dedicated discharge port.

[0080] The booster circulation pump provides sufficient pressure to ensure that the wastewater maintains a high flow rate in the tubular membrane module box, thereby forming a "cross-flow filtration" effect. Unlike traditional dead-end filtration, cross-flow filtration allows a portion of the wastewater to flow along the membrane surface instead of directly passing through the membrane, which reduces the accumulation of pollutants on the membrane surface and extends the service life of the membrane. The booster pump is usually made of corrosion-resistant materials (such as stainless steel) and has high efficiency and long life. The pump design must ensure that the pressure in the system is stable enough to avoid membrane damage or reduced filtration efficiency due to pressure fluctuations.

[0081] The CIP automatic backwashing tank is used to store the chemicals required for cleaning, and to transport the cleaning solution to the membrane assembly through pipes when the system needs to be cleaned and maintained. The CIP tank can regularly remove pollutants accumulated on the membrane surface, restore the filtration performance of the membrane, and prevent membrane clogging and performance degradation. It is made of corrosion-resistant materials and is equipped with a precise metering system that can control the amount of cleaning agent. Usually, CIP systems use acidic or alkaline cleaning agents, which are selected according to the nature of the contaminants (such as mineral deposits, grease, etc.). The system also includes a set of automated control programs to ensure that the cleaning process is safe, effective and controllable.

[0082] The cleaning frequency of PVDF membrane is every 200 hours, and the cleaning frequency of silicon carbide membrane is every 300 hours. The pollutants attached to the membrane surface are effectively removed by low-concentration chemical cleaning agents combined with reverse water flow.

[0083] Instruments, pipes and valves are the control and monitoring units of the entire water treatment process, which are used to ensure the stable operation of the filtration system. Instruments are mainly used to monitor key parameters such as water flow, pressure, temperature, pH value, etc., and pipes and valves are used to adjust water flow and chemical delivery to ensure that the system can operate normally under various working conditions. It mainly includes sensors, pressure gauges, flow meters, thermometers, automatic control valves, manual valves, etc. The sensor will feed back various key data to the control system. The operator can adjust the system through these instrument data, or the system will automatically adjust to ensure that the system operates stably and efficiently under different working conditions. Pipes and valves work together with the control system to achieve operations such as flow regulation, pressure control and chemical delivery, thereby optimizing the water treatment effect and extending the life of the equipment.

[0084] The oil content of the effluent water of the water treatment system for the dual-fuel main engine of the ship provided by the present invention meets the working conditions of the oil content alarm (that is, the oil content is lower than 15PPM) and the effluent turbidity is lower than 30NTU.

[0085] The following embodiments and drawings are used to describe the implementation modes of the present invention in detail, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0086] like Figure 1 As shown, the present invention provides an exhaust gas recirculation (EGR) system for a dual-fuel main engine ship, which comprises: an exhaust gas cleaning system EGC, a pH neutralizer dosing system 11 and a water treatment system 13; the exhaust gas cleaning system further comprises an EGC scrubber 14, an EGC circulating water cooler 1, an EGC circulating water pump 2, an EGC circulating water tank 3, a wastewater storage tank 4, a pH analyzer 7, a liquid level transmitter 8 and a high-level switch 9; after the exhaust gas is discharged from the dual-fuel main engine, it enters the exhaust gas cleaning system EGC, and is cleaned by the circulating water provided by the circulating water pump 2. After the cooling water is cooled by the EGC circulating water cooler 1, the cooling water is cooled by the EGC circulating water cooler 1 and then is cooled by the EGC circulating water cooler 1. The circulating water tank 3 refluxes to form a closed circulating cooling system. The wastewater generated during the exhaust gas cleaning process flows into the EGR wastewater storage tank 4 to wait for further treatment. During the treatment process, the pH analyzer 7 is used to measure the pH value of the wastewater to ensure that it meets the treatment requirements. The liquid level transmitter 8 is used to detect the water level of the wastewater storage tank 4 to prevent overflow or too low. The high-level switch 9 serves as an emergency alarm device when the water level is too high. The wastewater storage tank 4 is directly connected to the water treatment system 13. The wastewater is transported to the water treatment system 13 by a water pump. Before transportation, the pH analyzer 7 measures the pH value of the wastewater to ensure the effectiveness of the treatment process.

[0087] The pH neutralizer dosing system 11 is closely connected to the wastewater storage tank 4. After the wastewater passes through the water treatment system, the pH value may be acidic. The pH neutralizer system 11 is used to adjust the pH to ensure that the discharge meets environmental protection standards. Sodium hydroxide alkali solution is added to the pH neutralizer system 11.

[0088] like Figure 2 As shown, the water treatment system 13 includes a tubular membrane module box 15, a booster circulation pump 16, a CIP automatic backwashing medicine bin 17, instrument pipe valves, a filter press box 18, a mud discharge box 5 and a clean water tank 10. The booster circulation pump 16 is connected to the tubular membrane module box 15, and the wastewater in the wastewater storage tank 4 is pressurized and sent to the tubular membrane module box. In this process, the primary filter 19 performs pretreatment. After being filtered by the tubular module box 14, the clean water flows to the clean water tank 10, and the concentrated pollutants are discharged to the mud discharge box 5 through the concentrated water outlet. The CIP automatic backwashing medicine bin 17 transports the cleaning agent to the tubular membrane module box 15 through a pipeline, and regularly cleans the membrane surface to prevent membrane clogging and extend the service life of the membrane.

[0089] The water treatment system 13 also includes an oil-water monitoring sensor 6 for monitoring the oil content in the treated water to ensure that the oil content in the water does not exceed the standard, and then stores the oil in the clean water storage tank 10 through the valve 12.

[0090] like Figure 3 As shown, the specific structure of the tubular module box 15 adopts a dual membrane system, and the primary filtration adopts a polyvinylidene fluoride (PVDF) hollow fiber membrane 20, which uses its good hydrophilicity to remove emulsified oil, suspended particles and most organic pollutants in the wastewater. These pollutants account for a large proportion of ship wastewater, and the PVDF membrane can effectively remove such larger particle pollutants and oils through its microfiltration characteristics (pore size 0.05-0.1μm), making the subsequent treatment steps easier.

[0091] The deep filtration uses silicon carbide ceramic membrane 21, which has extremely high chemical corrosion resistance and mechanical strength, and can treat heavy metal ions, fine particles and dissolved organic matter in ship wastewater under high pressure. In particular, the pore size range of silicon carbide membrane is small (0.01-0.05μm), which can further remove dissolved pollutants that PVDF membrane cannot retain.

[0092] A single PVDF hollow fiber membrane unit and the silicon carbide ceramic membrane unit can be connected in series through pipelines to form a membrane assembly, and multiple membrane assemblies can be placed in parallel in a membrane assembly box through pipelines. Alternatively, multiple PVDF hollow fiber membrane units can be connected in parallel through pipelines, and multiple silicon carbide ceramic membrane units can be connected in parallel through pipelines according to needs. The parallel-connected PVDF hollow fiber membrane unit group and silicon carbide ceramic membrane unit group are connected in series through pipelines and installed together in a module box.

[0093] The PVDF hollow fiber membrane group unit is designed as a graded porous membrane structure, specifically including an outer large pore layer and an inner small pore layer. The pore size of the outer large pore layer is designed to be 0.3-0.6 μm, and the pore size of the inner small pore layer is designed to be 0.1-0.3 μm.

[0094] The silicon carbide ceramic membrane group unit is composed of a support layer and an active filter layer. The support layer adopts a honeycomb structure design, with a porosity of 40-60% and a pore size of 50-100μm, ensuring that large particles in the wastewater can pass through the support layer smoothly at high flow rates without causing pressure damage to the membrane. The active filter layer is designed as a single-layer active filter layer with a gradient pore size design. From the outer layer to the inner layer, the pore size gradually decreases from 0.05μm to 0.01μm, and the filtration accuracy is improved through graded filtration.

[0095] All of the above are primary implementations of this intellectual property and do not set limitations on other forms of implementation of this new product and / or new method. Those skilled in the art will use this important information and modify the above content to achieve similar implementations. However, all modifications or transformations based on the new product of this invention belong to the reserved rights.

[0096] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A water treatment system for a dual-fuel main engine of a ship, characterized in that: It includes a tubular membrane module box, a booster circulation pump, a CIP automatic backwashing medicine bin and instrument pipe valves; the tubular module box adopts a double membrane combination system, polyvinylidene fluoride (PVDF) hollow fiber membrane is used for primary filtration, and silicon carbide ceramic membrane is used for deep filtration.

2. The water treatment system for a dual-fuel main engine of a ship according to claim 1, characterized in that: The PVDF hollow fiber membrane and the silicon carbide ceramic membrane are both designed as standardized modular units and embedded in a tubular membrane module box.

3. The water treatment system for a dual-fuel main engine of a ship as claimed in claim 1 or 2, characterized in that: The PVDF hollow fiber membrane unit and the silicon carbide ceramic membrane unit are arranged in series in sequence. The PVDF hollow fiber membrane unit is placed at the front end of the tubular membrane module box as a primary filter, and the silicon carbide ceramic membrane is placed at the rear end of the tubular membrane module box as a depth filter.

4. The water treatment system for a dual-fuel main engine of a ship according to claim 3, characterized in that: The PVDF hollow fiber membrane group unit is designed as a graded porous membrane structure, specifically including an outer large pore layer and an inner small pore layer. The pore size of the outer large pore layer is designed to be 0.3-0.6 μm, and the pore size of the inner small pore layer is designed to be 0.1-0.3 μm.

5. The water treatment system for a dual-fuel main engine of a ship as claimed in claim 3 or 4, characterized in that: The silicon carbide ceramic membrane group unit is composed of a support layer and an active filtration layer. The support layer adopts a honeycomb structure design, with a porosity maintained at 40-60% and a pore size of 50-100 μm, ensuring that at a high flow rate, large particles in the wastewater can pass through the support layer smoothly without causing pressure damage to the membrane.

6. The water treatment system for a dual-fuel main engine of a ship according to claim 5, characterized in that: The active filter layer is designed as a single-layer active filter layer, and adopts a gradient pore size design. From the outer layer to the inner layer, the pore size gradually decreases from 0.05 μm to 0.01 μμm, and the filtration accuracy is improved through graded filtration.

7. The water treatment system for a dual-fuel main engine of a ship according to claim 1 or 2, characterized in that: The booster circulation pump is connected to the tubular membrane module box, and the pre-treated wastewater is pressurized and sent into the tubular membrane module box. After filtration, the clean water flows to the water outlet, and the concentrated pollutants are discharged through the concentrated water outlet. The CIP automatic backwashing medicine tank transports the cleaning agent to the tubular membrane module box through the pipeline to clean the membrane surface regularly.

8. The water treatment system for a dual-fuel main engine of a ship according to claim 1 or 2, characterized in that: The water treatment system for the dual-fuel main engine of a ship may also include a filter press unit and a tubular membrane module box mud discharge unit. The tubular module box mud discharge unit is connected to the tubular module box through a pipeline. The pollutants retained after membrane filtration, especially solid particles and sludge, are discharged centrally through the mud discharge unit. The filter press unit is connected to the tubular module box mud discharge unit.

9. An exhaust gas recirculation (EGR) system for a dual-fuel main engine ship, characterized in that: include: Exhaust gas cleaning system EGC, pH neutralizer dosing system and the above-mentioned water treatment system; The exhaust gas cleaning system EGC includes an EGC scrubber, an EGC circulating water cooler, an EGC circulating water pump and an EGC circulating water tank; The EGC circulating water cooler is used to cool the circulating water used in the exhaust gas cleaning process; The EGC circulating water pump is used to drive the cooled water into the EGC washing tower for cleaning; The EGC circulating water tank is used to store circulating water for cleaning exhaust gas.

10. The method for treating wastewater using the water treatment system for a dual-fuel main engine of a ship according to claim 1 or 2, characterized in that: include: In the first step, the wastewater enters the booster circulation pump through the pipeline, and after being pressurized to 5-8 bar, it enters the PVDF hollow fiber membrane unit; In the second step, the wastewater after primary filtration flows to the silicon carbide ceramic membrane unit, where the pressure is further increased to 10-15 bar for deep filtration; In the third step, the effluent is discharged through pipes, and the concentrated wastewater and pollutants are intercepted and discharged through a dedicated discharge port.

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