Secondary membrane treatment equipment and methods for wastewater from ship exhaust gas recirculation systems

Abstract

This application relates to the field of marine wastewater treatment technology, and more specifically to a secondary membrane treatment device and method for wastewater from a marine exhaust gas recirculation system. The device includes a primary circulation filtration module and a secondary circulation filtration module. This invention achieves a higher overall raw water concentration by performing secondary filtration on top of the primary circulation filtration module's initial concentration. Compared to using only primary filtration, this reduces the contaminant concentration on the membrane within the primary circulation filtration module, effectively lowering the risk of membrane fouling and thus reducing the membrane replacement frequency. Furthermore, although the concentration of contaminants in the concentrate treated by the membrane in the secondary circulation filtration module is higher, the overall treated water volume is smaller, resulting in a lower membrane replacement frequency in the secondary circulation filtration module. This achieves the advantages of secondary filtration, reducing membrane clogging risk, and extending membrane lifespan.

Description

Technical Field

[0001] This invention relates to the field of ship wastewater treatment technology, and more specifically, to a secondary membrane treatment device and method for wastewater from a ship exhaust gas recirculation system. Background Technology

[0002] The Intelligent Controlled Exhaust Gas Recirculation (ICRE) system, also known as the ICRE system, primarily generates wastewater from two sources: 1. Cooling and scrubbing wastewater generated during the main engine exhaust gas scrubbing process in the cooling tower; 2. Cleaning water from the ICRE main engine air cooler. This wastewater is often acidic and contains carbon powder and unburned oil, with oil content reaching up to 45 ppm and turbidity reaching 625 NTU. This fails to meet IMO (International Maritime Organization) standards and results in direct discharge into seawater. The challenge in treating this type of wastewater lies in its relatively simple composition: high oil content but low turbidity, while carbon powder can aid in oil removal to some extent.

[0003] Current methods for treating ICER system wastewater mainly include air flotation and membrane filtration. Air flotation for ICER system wastewater treatment typically involves adding demulsifiers, flotation, and sludge removal. However, when the wastewater has a high oil content, the treatment effect of air flotation equipment often falls short of expectations. Membrane filtration for ICER system wastewater treatment typically includes pretreatment and membrane filtration. In actual operation, higher feed concentrations significantly increase the rejection rate, but contaminants also tend to accumulate more quickly on the membrane surface, leading to a reduction in membrane pore size and affecting the membrane's stable flux. Therefore, in practical applications, a balance must be struck between higher rejection rates and higher stable flux to achieve a higher concentration ratio and thus improve treatment efficiency.

[0004] However, existing membrane treatment equipment can typically only achieve a concentration ratio of about 20 times for oily wastewater. Referring to the patent document (CN113979566A), oily wastewater is purified using only a single-stage membrane filtration module. To ensure treatment efficiency, a high concentration ratio is chosen. As the concentration ratio reaches its limit, such as increasing from 20 times to 100 times, the concentration of pollutants that the membrane module can withstand is 5 times higher than before. Pollutants are very likely to clog the membrane surface, causing the clean water output of the membrane treatment equipment to drop rapidly in a short period of time. If it cannot be effectively cleaned, the membrane needs to be replaced, which is costly.

[0005] Therefore, there is a need for a secondary membrane treatment device and method for wastewater from a ship exhaust gas recirculation system that reduces the risk of membrane clogging and extends the service life of the membrane when the wastewater is concentrated in the same way. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a secondary membrane treatment device for wastewater from a ship exhaust gas recirculation system. This device treats oily wastewater from the system and includes: a wastewater lifting device for feeding the oily wastewater; a primary circulating membrane module connected to the lifting device for generating a first-proportion treated liquid; a clear water tank and a sludge tank connected to the primary circulating membrane module; and a secondary circulating membrane module connected to both the sludge tank and the clear water tank. The secondary circulating membrane module includes: a concentrate flushing module connected to the clear water tank and the primary circulating membrane module; a dual-purpose exhaust / liquid pipe connected to the sludge tank and the primary circulating membrane module; and a secondary circulating filtration module connected to the clear water tank for treating the first-proportion treated liquid into a second-proportion treated liquid. The concentration ratio of the second-proportion treated liquid is greater than that of the first-proportion treated liquid.

[0007] In one embodiment of the present invention, the concentrate flushing module includes: a backflush pump, a first backflush pipe, a second backflush pipe, and a third backflush pipe; the first backflush pipe is connected to the clear water tank and the inlet of the backflush pump respectively; the outlet of the backflush pump is connected to the second backflush pipe; and the third backflush pipe is connected to the second backflush pipe and the primary circulating membrane module respectively.

[0008] In one embodiment of the present invention, the secondary circulation filtration module includes: a secondary membrane cylinder, a secondary circulation pump, a second circulation pipe, a secondary clean water pipe, a fourth backwash pipe, and a sludge discharge pipe; the second circulation pipe connects the secondary membrane cylinder, the secondary circulation pump, and the sludge bin in series; the secondary clean water pipe is connected to both the second circulation pipe and the clean water bin; the fourth backwash pipe is connected to the ends of the secondary clean water pipe and the second backwash pipe that are away from the backwash pump; and the sludge discharge pipe is connected to the second circulation pipe located between the secondary circulation pump and the secondary membrane cylinder.

[0009] In one embodiment of the present invention, it further includes: a clean water discharge pipe assembly and an oil content detection device; the oil content compliant discharge pipe and the oil content excessive discharge pipe in the clean water discharge pipe assembly are both connected to the second backflushing pipe; the oil content detection device is located between the clean water discharge pipe assembly and the second backflushing pipe.

[0010] In one embodiment of the present invention, it further includes: a freshwater pipe, an acidic reagent tank, and an alkaline reagent tank; one end of the freshwater pipe is connected to the primary circulating membrane module and the sludge tank, and the other end is connected to the sludge tank; the acidic reagent tank and the alkaline reagent tank are respectively connected to the primary circulating membrane module and the sludge tank.

[0011] In one embodiment of the present invention, a wastewater treatment method for a ship exhaust gas recirculation system is also provided, which can be applied to the wastewater secondary membrane treatment equipment in any of the above embodiments. The wastewater treatment method includes: controlling a wastewater lifting device to send oily wastewater into a primary circulating membrane module and venting the air in the primary circulating membrane module; controlling the primary circulating membrane module to perform a first treatment on the oily wastewater to obtain a first proportion treatment liquid, the first proportion treatment liquid including a first clean water and a primary concentrate; controlling a backwash pump to mix a portion of the first clean water and the primary concentrate and then introduce it into a sludge tank; controlling the secondary circulating membrane module to produce a second proportion treatment liquid; the second proportion treatment liquid including a second clean water and a secondary concentrate, the secondary concentrate being transported to a ship sludge storage tank, and determining whether the clean water tank meets a first condition; if so, the second clean water being transported to the secondary circulating membrane module, and backwash water being transported to the sludge tank; controlling a freshwater pipe, an acidic reagent tank, and an alkaline reagent tank to perform chemical cleaning on the primary and secondary circulating membrane modules.

[0012] In one embodiment of the present invention, the wastewater lifting device is controlled to send oily wastewater into a primary circulating membrane module and vent the air in the primary circulating membrane module, and the primary circulating membrane module is controlled to perform a first treatment on the oily wastewater to obtain a first proportioned treatment liquid, the first proportioned treatment liquid including a first clean water and a primary concentrate, including: opening the inlet valve and setting a predetermined time for opening the first shut-off valve, and venting the air in the primary circulating membrane module through the exhaust-liquid dual-purpose pipe, after which the first shut-off valve is closed; controlling the first product water valve to open to introduce the oily wastewater into the primary circulating membrane module and activating the primary circulating membrane module to produce the first clean water and the primary concentrate; introducing the first clean water into the clean water tank and controlling the primary concentrate to circulate in the primary circulating membrane module; controlling the backwash pump to mix a portion of the first clean water and the primary concentrate and then introduce it into the sludge tank, including: controlling the first shut-off valve to open and activating the backwash pump to introduce a portion of the clean water in the clean water tank into the primary circulating membrane module to mix with the primary concentrate and then introduce it into the sludge tank.

[0013] In one embodiment of the present invention, the production of a second proportioned treated liquid is controlled by a secondary circulating membrane module; the second proportioned treated liquid includes a second clean water and a secondary concentrate, the secondary concentrate is transported to a sludge storage tank in the ship's hold, and it is determined whether the clean water tank meets a first condition, including: filtering the first proportioned treated liquid to obtain the second clean water and the secondary concentrate; introducing the second clean water into the clean water tank, and transporting the secondary concentrate to the sludge storage tank in the ship's hold; obtaining the liquid level height in the clean water tank, and determining whether the liquid level height meets the first condition.

[0014] In one embodiment of the present invention, controlling the freshwater pipe, the acidic reagent tank, and the alkaline reagent tank to perform chemical cleaning on the primary and secondary circulating membrane modules includes: controlling the freshwater pipe to perform a first freshwater flush on the inlet main pipe and the sludge tank; controlling the alkaline reagent tank to perform an alkaline flush on the primary circulating membrane module and the sludge tank; controlling the freshwater pipe to perform a second freshwater flush on the inlet main pipe and the sludge tank; controlling the acidic reagent tank to perform an acidic flush on the primary circulating membrane module and the sludge tank; and controlling the freshwater pipe to perform a third freshwater flush on the inlet main pipe and the sludge tank.

[0015] In one embodiment of the invention, the alkaline agent in the alkaline agent compartment comprises 3%-10% sodium hydroxide, 1%-5% triethanolamine, 3%-15% sodium octanoate and 0.5%-5% fatty alcohol polyoxyethylene ether.

[0016] By adopting the technical solution of the present invention, the following technical effects can be achieved:

[0017] (1) Compared with using only primary filtration, the secondary filtration provided in this application reduces the concentration of pollutants on the membrane in the primary circulating filtration module, effectively reducing the risk of contamination of the membrane in the primary circulating filtration module, thereby extending the service life of the membrane in the primary circulating filtration module; in addition, although the concentration of contaminants in the concentrate treated by the membrane in the secondary circulating filtration module is higher, the overall water volume treated is small, only 5% of the oily wastewater, and the required concentration ratio is relatively low. This makes the risk of membrane contamination in the secondary circulating filtration module lower and the replacement frequency less frequent, resulting in a significant reduction in the overall cost of use compared with the prior art. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The figure shows a schematic diagram of the structure of a secondary membrane treatment device for wastewater in a ship exhaust gas recirculation system according to this application from a certain angle;

[0020] Figure 2 The figure shows a schematic diagram of the structure of a secondary membrane treatment device for wastewater in a ship exhaust gas recirculation system according to this application, which removes the primary circulation filter module and the primary circulation pump.

[0021] Figure 3 The figure shows a schematic diagram of the structure of a secondary membrane treatment device for wastewater in a ship exhaust gas recirculation system according to this application, when removing the primary circulation filter module, primary circulation pump, inlet pipe assembly, and freshwater pipe.

[0022] Figure 4 The diagram shows the structure of a freshwater pipe at a certain angle.

[0023] Figure 5 The diagram shows a structural schematic of the two-stage circulating filter module from another angle;

[0024] Figure 6 The diagram illustrates the logic block diagram of the wastewater treatment method of the ship exhaust gas recirculation system of this application.

[0025] Explanation of reference numerals in the attached figures:

[0026] 10. Primary circulating membrane module; 101. Inlet pipe assembly; 1011. Main inlet pipe; 10111. Inlet valve; 10112. Inlet flow meter; 1012. Inlet branch pipe; 102. Primary circulating filtration module; 1021. Primary membrane cartridge; 1022. Primary circulating pump; 1023. First circulation pipe; 10231. First pressure gauge; 103. Clean water pipe assembly; 1031. Clean water branch pipe; 1032. Clean water... Main pipe; 10321, Second pressure gauge; 1033, First product water valve; 20, Clean water tank; 30, Sludge tank; 301, Fresh water to sludge pipe; 3011, Fifth shut-off valve; 40, Secondary circulation membrane module; 401, Concentrate flushing module; 4011, Backflush pump; 4012, First backflush pipe; 4013, Second backflush pipe; 4014, Third backflush pipe; 4015, Primary backwash valve; 402, Exhaust / liquid dual-purpose pipe; 4021, First shut-off valve; 403, Secondary circulating filtration module; 4031, Secondary membrane cartridge; 4032, Secondary circulating pump; 4033, Secondary circulating pipe; 40331, Third pressure gauge; 40332, Fourth shut-off valve; 4034, Secondary clean water pipe; 40341, Secondary product water flow meter; 40342, Secondary product water valve; 40343, Fourth pressure gauge; 4035, Fourth backwash pipe; 4036, Sludge discharge pipe. Pipes; 40361, Sludge Flow Meter; 40362, Secondary Sludge Discharge Valve; 50, Clean Water Discharge Pipe Assembly; 501, Oil Concentration Compliance Discharge Pipe; 5011, Second Shut-off Valve; 502, Oil Concentration Excess Discharge Pipe; 503, Oil Concentration Detection Device; 601, Fresh Water Pipe; 6011, Third Shut-off Valve; 602, Acidic Chemical Tank; 603, Alkaline Chemical Tank; 70, Drain Pipe Assembly; 701, Main Drain Pipe; 702, Branch Drain Pipe. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] See Figure 1 , Figure 1The figure shows a schematic diagram of the structure of a secondary membrane treatment device for wastewater in a ship exhaust gas recirculation system according to this application, viewed from a certain angle; combined with Figures 2 to 5 A secondary membrane treatment device for wastewater from a ship exhaust gas recirculation system is disclosed. This device treats oily wastewater from the system and includes: a wastewater lifting device for feeding the oily wastewater, a primary circulation membrane module 10, a clear water tank 20, a sludge tank 30, and a secondary circulation membrane module 40. The primary circulation membrane module 10 is connected to the wastewater lifting device to generate a first proportion of treated liquid. The clear water tank 20 is connected to the primary circulation membrane module 10. The secondary circulation membrane module 40 is connected to the sludge tank 30. The first-stage circulating membrane module 40 is connected to the clear water tank 20 and the first-stage circulating membrane module 10. The second-stage circulating membrane module 40 includes a concentrate flushing module 401, an exhaust liquid dual-purpose pipe 402, and a second-stage circulating filtration module 403. The concentrate flushing module 401 is connected to the clear water tank 20 and the first-stage circulating membrane module 10. The exhaust liquid dual-purpose pipe 402 is connected to the sludge tank 30 and the first-stage circulating membrane module 10. The second-stage circulating filtration module 403 is connected to the clear water tank 20 and is used to treat the first proportion treatment liquid into a second proportion treatment liquid. The concentration ratio of the second proportion treatment liquid is greater than that of the first proportion treatment liquid.

[0029] The wastewater lifting device is used to send oily wastewater from the raw water tank into the primary circulating membrane module 10. The wastewater lifting device is further implemented as a wastewater pump.

[0030] Furthermore, the wastewater secondary membrane treatment equipment also includes: a clean water discharge pipe assembly 50, which is connected to the concentrate flushing module 401.

[0031] Furthermore, such as Figure 1 and Figure 2 As shown, the primary circulating membrane module 10 includes an inlet pipe assembly 101, a primary circulating filtration module 102, and a clean water pipe assembly 103. The two ends of the inlet pipe assembly 101 are connected to the wastewater lifting device and the primary circulating filtration module 102, respectively. The primary circulating filtration module 102 generates a first proportioned mixed liquid of oily wastewater.

[0032] Based on specific operational conditions, oily wastewater generated by the ship's exhaust gas recirculation system is collected by a wastewater lifting device and pumped into the system. Subsequently, the oily wastewater enters the primary circulation membrane module 10 for preliminary separation. Here, the oily wastewater undergoes circulation filtration within the primary circulation membrane module 10, separating into a majority of clean water and a small portion of concentrated liquid, i.e., the first proportion of treated liquid. Most of the clean water is directed to a clean water tank, and the small portion of concentrated liquid is directed to a sludge tank 30. Then, a portion of the concentrated liquid is directed to the secondary circulation membrane module 40 for further treatment. In the secondary circulation membrane module 40, a portion of the concentrated liquid is recirculated and filtered. The second proportion of the treated liquid is concentrated at a much higher concentration than the first proportion of the treated liquid. During this process, the concentrated liquid flushing module 401 periodically uses clean water from the clean water tank 20 to backwash or chemically clean the primary circulating membrane module 10 to remove oil and contaminants adhering to the membrane surface, restore membrane flux, and ensure the continuous and stable efficiency of the primary treatment. The gas and concentrated liquid are safely discharged through the exhaust liquid dual-purpose pipe 402. Finally, the second proportion of the treated liquid, which has reached the preset concentration ratio, generated by the secondary circulating membrane module 40 is discharged from the system.

[0033] The first proportion of the treatment solution includes 95% clean water and 5% primary concentrate.

[0034] The second proportion of the treatment solution, based on the 5% primary concentrate, produces 80% purified water and 20% secondary concentrate.

[0035] For ease of understanding, specifically, assuming that the oily wastewater fed into the primary circulating filtration module 102 by the wastewater lifting device is 3000L, then after this 3000L of oily wastewater is circulated multiple times in the primary circulating filtration module 102, 2850L of clean water and the remaining 150L of primary concentrate will be produced. It should also be noted that the oily wastewater flows into the primary circulating filtration module 102 along the inlet pipe assembly 101, and after multiple circulations, the produced clean water flows into the clean water tank 20 through the clean water pipe assembly 103.

[0036] The system includes a clear water tank 20 and a sludge tank 30 for storing and transferring clear water and concentrate. The two ends of the clear water pipe assembly 103 are connected to the primary circulation filtration module 102 and the clear water tank 20, respectively. The clear water produced by the primary circulation filtration module 102 is sent into the clear water tank 20, and the sludge tank 30 is used for transferring concentrate.

[0037] The secondary circulation membrane module 40 specifically includes: a concentrate flushing module 401, an exhaust liquid dual-purpose pipe 402, and a secondary circulation filtration module 403. The two ends of the concentrate flushing module 401 are connected to the clear water tank 20 and the primary circulation membrane module 10, respectively. The two ends of the exhaust liquid dual-purpose pipe 402 are connected to the sludge tank 30 and the primary circulation filtration module 102, respectively. The secondary circulation membrane module 40 is connected to the sludge tank 30 and the clear water tank 20, respectively. 5% of the primary concentrate flows into the secondary circulation filtration module 403. The secondary circulation filtration module 403 produces 80% of the primary concentrate as clear water and 20% as secondary concentrate, and the concentration ratio of the oily wastewater reaches 100 times.

[0038] It should be noted that when 5% of the primary concentrate circulates within the primary circulating filtration module 102 for a predetermined time and the influent flow rate reaches a set value, 5% of the raw water volume of clean water is extracted from the clean water tank 20 through the concentrate flushing module 401 and sent into the primary circulating filtration module 102. This causes the primary concentrate to be sent into the exhaust and liquid dual-purpose pipe 402 and flows into the sludge tank 30. Subsequently, through the second circulating filtration module, the primary concentrate in the sludge tank 30 flows into the secondary circulating filtration module 403, circulating multiple times, producing 80% of the primary concentrate volume of clean water and 20% of the secondary concentrate. Taking the above assumed data as an example, 150L of primary concentrate, after being filtered by the secondary circulating filtration module 403, produces 120L of clean water and 30L of secondary concentrate. Subsequently, the produced clean water is sent into the clean water tank 20, and the produced secondary concentrate is discharged to the external ship sludge tank 30.

[0039] In addition, the clean water discharge pipe assembly 50 is connected to the concentrate flushing module 401. It should be noted that when the clean water in the clean water tank 20 reaches the predetermined height, the clean water in the clean water tank 20 is extracted through the concentrate flushing module 401 and sent into the clean water discharge pipe assembly 50. Depending on whether the oil content meets the standard, it is decided whether to discharge it into the seawater or let it flow back into the raw water tank for filtration.

[0040] In summary, this application, by setting up a primary circulating filtration module 102 and a secondary circulating filtration module 403, can ultimately produce 99% clean water and 1% concentrate from oily wastewater. In the prior art, due to the use of only primary filtration, achieving a 100-fold raw water concentration ratio (i.e., obtaining 99% clean water and 1% concentrate from oily wastewater) requires a significant increase in the water production capacity of the membrane in the primary circulating filtration module 102. Furthermore, because the membrane rejection rate is significantly increased, pollutants easily and quickly accumulate on the membrane surface, forming blockages, leading to frequent replacements. Additionally, the high rated flux of the primary circulating filtration module 102 results in high replacement costs, further increasing the overall operating cost of the equipment. In this application, the primary circulating filtration module 102 achieves a raw water concentration ratio of 20 times, and the secondary circulating filtration further increases the overall raw water concentration ratio to 100 times. Compared to using only primary filtration, this significantly reduces the contamination load on the membrane within the primary circulating filtration module 102. The pollutant concentration is reduced by 5 times, effectively reducing the risk of contamination of the membrane in the primary circulating filtration module 102, thereby reducing the replacement frequency of the membrane in the primary circulating filtration module 102. In addition, although the concentration of pollutants in the concentrate treated by the membrane in the secondary circulating filtration module 403 is higher, the overall volume of water treated is small, only 5% of the oily wastewater volume, and the concentration ratio is also relatively low, only 5 times. This makes the risk of contamination of the membrane in the secondary circulating filtration module 403 low, and the replacement frequency is also low. This achieves a clever balance between the retention rate and stable flux of the overall membrane module. With a raw water concentration ratio of 100 times, the overall operating cost is significantly reduced compared to the prior art, rather than simply stacking membrane filtration modules. At the same time, compared to the 20 times raw water concentration ratio membrane modules in the prior art, this application reduces the volume of concentrated sludge by at least 80% by increasing the raw water concentration ratio to 100 times, reducing the area occupied by sludge storage in the ship's hold, thereby improving the ship's endurance.

[0041] Furthermore, such as Figure 1 and Figure 2As shown, the primary circulating filtration module 102 includes two primary membrane cartridges 1021, a primary circulating pump 1022, and a first circulating pipe 1023 connecting the primary membrane cartridges 1021 and the primary circulating pump 1022 in series. The inlet pipe assembly 101 includes an inlet main pipe 1011 and an inlet branch pipe 1012. The two ends of the inlet main pipe 1011 are respectively connected to the middle section of the inlet branch pipe 1012 and the wastewater lifting device. The two ends of the inlet branch pipe 1012 are respectively connected to the first circulating pipe 1023 located between the two primary membrane cartridges 1021. The clear water pipe assembly 103 includes two clear water branch pipes 1 031 and the main water pipe 1032, each stage membrane cylinder 1021 has a main water pipe 1031 connected to its side wall. One end of the main water pipe 1032 is connected to the main water tank 20, and the other end of the main water pipe 1032 is connected to the two main water pipes 1031. The end of the main water pipe 1032 near the main water tank 20 is equipped with a first water production valve 1033. The main water inlet pipe 1011 is equipped with an inlet valve 10111 and an inlet flow meter 10112. The first circulation pipe 1023 is equipped with a first pressure gauge 10231, and the main water pipe 1032 is equipped with a second pressure gauge 10321.

[0042] It should be noted that after the oily wastewater is lifted by the wastewater lifting device, it is sent to the main clean water pipe 1032, and then sent to two clean water branch pipes 1031 along the main clean water pipe 1032. By positioning the outlet ends of the two clean water branch pipes 1031 between the two primary membrane cells 1021, the oily wastewater treated by the two primary membrane cells 1021 is balanced, ensuring that the wastewater quality contacted by the two primary membrane cells 1021 is similar. This also ensures that the degree of fouling of the membranes in the two primary membrane cells 1021 is relatively similar during long-term operation, avoiding the situation where one primary membrane cell 1021 treats most of the oily wastewater while the other primary membrane cell 1021 treats a small portion, thus preventing one primary membrane cell 1021 from being subjected to excessive fouling. The first-stage membrane cylinder 1021 is severely contaminated and cannot be used normally, while the other first-stage membrane cylinder 1021 is less contaminated and can still be used normally, thus improving the overall service life of the equipment. In addition, when the oily wastewater flows into the first circulation pipe 1023 through the clear water branch pipe 1031, the oily wastewater is made to flow in the first circulation pipe 1023 by the first-stage circulation pump 1022. When the oily wastewater flows through the first-stage membrane cylinder 1021, it filters out clear water and discharges it from the two clear water branch pipes 1031. After being collected, it flows along the clear water main pipe 1032 to the clear water tank 20, achieving a clear water production of 95% of the oily wastewater. It should be noted that at this time, the first-stage concentrate with 5% oily wastewater is still flowing in the first circulation pipe 1023. The total amount of oily wastewater entering the first circulation pipe 1023 is accumulated and read by the inlet flow meter 10112. The selective opening and closing of the inlet main pipe 1011 and the end of the clean water main pipe 1032 near the clean water tank 20 is realized by the inlet valve 10111 and the first product water valve 1033. The water pressure of the first circulation pipe 1023 is detected by the first pressure gauge 10231, and the water pressure of the clean water main pipe 1032 after the membrane is detected by the second pressure gauge 10321. The difference between the two is used to realize the real-time detection of the blockage of the first-stage membrane cylinder 1021.

[0043] Furthermore, the concentrate rinsing module 401 includes: a backflush pump 4011, a first backflush pipe 4012, a second backflush pipe 4013, and a third backflush pipe 4014; the first backflush pipe 4012 is connected to the clear water tank 20 and the inlet of the backflush pump 4011 respectively; the outlet of the backflush pump 4011 is connected to the second backflush pipe 4013; and the third backflush pipe 4014 is connected to the second backflush pipe 4013 and the primary circulation membrane module 10 respectively.

[0044] Furthermore, a first-stage backwash valve 4015 is provided on the third backwash pipe 4014, and a first shut-off valve 4021 is provided at the end of the exhaust liquid dual-purpose pipe 402 near the sludge tank 30.

[0045] Specifically, the two ends of the first backwash pipe 4012 are connected to the clean water tank 20 and the inlet of the backwash pump 4011, respectively. The outlet of the backwash pump 4011 is connected to the second backwash pipe 4013. The two ends of the third backwash pipe 4014 are connected to the second backwash pipe 4013 and the clean water main pipe 1032, respectively. The third backwash pipe 4014 is equipped with a first-stage backwash valve 4015. The exhaust liquid dual-purpose pipe 402 is equipped with a first shut-off valve 4021 at the end near the sludge tank 30.

[0046] It should be noted that by operating the backwash pump 4011, 5% of the clean water containing oily wastewater flows from the clean water tank 20 into the first backwash pipe 4012, and after passing through the backwash pump 4011, it flows sequentially along the second backwash pipe 4013, the third backwash pipe 4014, and the clean water main pipe 1032 into the first circulation pipe 1023. At this time, the first shut-off valve 4021 is opened, and the primary concentrate flows into the sludge tank 30 along the exhaust liquid dual-purpose pipe 402. In addition, by setting the primary backwash valve 4015, the selective opening and closing of the third backwash pipe 4014 is achieved.

[0047] Furthermore, the secondary circulation filtration module 403 includes: a secondary membrane cylinder 4031, a secondary circulation pump 4032, a second circulation pipe 4033, a secondary clean water pipe 4034, a fourth backwash pipe 4035, and a sludge discharge pipe 4036; the second circulation pipe 4033 is connected in series with the secondary membrane cylinder 4031, the secondary circulation pump 4032, and the sludge chamber 30; the secondary clean water pipe 4034 is connected to the second circulation pipe 4033 and the clean water chamber 20 respectively; the fourth backwash pipe 4035 is connected to the end of the secondary clean water pipe 4034 and the second backwash pipe 4013 away from the backwash pump 4011 respectively; the sludge discharge pipe 4036 is connected to the second circulation pipe 4033 located between the secondary circulation pump 4032 and the secondary membrane cylinder 4031.

[0048] Furthermore, the sludge discharge pipe 4036 is equipped with a sludge discharge flow meter 40361 and a secondary sludge discharge valve 40362, the secondary clean water pipe 4034 is equipped with a secondary product water flow meter 40341 ​​and a secondary product water valve 40342, the fourth backwash pipe 4035 is equipped with a secondary backwash valve, the second circulation pipe 4033 is equipped with a third pressure gauge 40331, the secondary clean water pipe 4034 is equipped with a fourth pressure gauge 40343, and the second circulation pipe 4033 is located on the side of the sludge discharge pipe 4036 away from the secondary circulation pump 4032 and is also equipped with a fourth shut-off valve 40332.

[0049] Specifically, the second circulation pipe 4033 is connected in series with the secondary membrane cylinder 4031, the secondary circulation pump 4032, and the sludge bin 30. The two ends of the secondary clear water pipe 4034 are connected to the second circulation pipe 4033 and the clear water bin 20, respectively. The two ends of the fourth backwash pipe 4035 are connected to the secondary clear water pipe 4034 and the end of the second backwash pipe 4013 away from the backwash pump 4011, respectively. The sludge discharge pipe 4036 is connected to the second circulation pipe 4033 located between the secondary circulation pump 4032 and the secondary membrane cylinder 4031. The sludge discharge pipe 4036 is equipped with a sludge discharge flow meter 40361 and a secondary sludge discharge valve 40362. The secondary clear water pipe 4034 is equipped with a secondary permeate flow meter 40341 ​​and a secondary permeate valve 40342. The fourth backwash pipe 4035 is equipped with a secondary backwash valve. The second circulation pipe 4033 is equipped with a third pressure gauge 40331. (Refer to...) Figure 5 The secondary clean water pipe 4034 is equipped with a fourth pressure gauge 40343, and the second circulation pipe 4033 is located on the side of the sludge discharge pipe 4036 away from the secondary circulation pump 4032 and is also equipped with a fourth shut-off valve 40332.

[0050] It should be noted that after the primary concentrate flows into the sludge tank 30, the secondary circulation pump 4032 is activated and the secondary sludge discharge valve 40362 is closed. The primary concentrate then continuously passes through the secondary membrane cylinder 4031, the sludge tank 30, and the secondary circulation pump 4032 along the second circulation pipe 4033, continuously producing 80% of the primary concentrate's volume of clean water. The reading is accumulated through the secondary permeate flow meter 40341. When the reading of the secondary permeate flow meter 40341 ​​reaches the target, the secondary permeate valve 40342 is closed and the secondary sludge discharge valve 40362 is opened. The secondary circulation pump 4032 continues to operate, and the reading is accumulated through the sludge discharge flow meter 40361 until the remaining 20% ​​of the primary concentrate's volume of secondary concentrate passes through the sludge discharge pipe 4036 and is discharged along the sludge discharge pipe 4036 to the external ship sludge storage tank.

[0051] Furthermore, such as Figure 2 As shown, the wastewater secondary membrane treatment equipment also includes: a clean water discharge pipe assembly 50 and an oil detection device 503; the oil discharge pipe 501 that meets the oil content standard and the oil discharge pipe 502 that exceeds the oil content standard in the clean water discharge pipe assembly 50 are both connected to the second backflushing pipe 4013; the oil detection device 503 is located between the clean water discharge pipe assembly 50 and the second backflushing pipe 4013.

[0052] Furthermore, a second shut-off valve 5011 is provided on both the oil separation standard discharge pipe 501 and the oil separation excess discharge pipe 502.

[0053] Specifically, the clean water discharge pipe assembly 50 includes an oil-compliant discharge pipe 501 and an oil-excess discharge pipe 502, both of which are connected to the second backflushing pipe 4013. The wastewater secondary membrane treatment equipment of the ship exhaust gas recirculation system also includes an oil detection device 503, which is located between the clean water discharge pipe assembly 50 and the second backflushing pipe 4013. Both the oil-compliant discharge pipe 501 and the oil-excess discharge pipe 502 are equipped with a second shut-off valve 5011.

[0054] It should be noted that when the clean water in the clean water tank 20 reaches the predetermined water level, the backwash pump 4011 operates, causing the clean water to flow along the first backwash pipe 4012, the backwash pump 4011, the second backwash pipe 4013, and through the oil separation detection device 503. If the oil content of the clean water meets the standard, the clean water is discharged along the oil separation standard discharge pipe 501; if the oil content of the clean water does not meet the standard, the clean water is discharged along the oil separation excess discharge pipe 502 to the ship's raw water tank; the second shut-off valve 5011 enables the selective opening and closing of the oil separation standard discharge pipe 501 and the oil separation excess discharge pipe 502.

[0055] Furthermore, such as Figures 2 to 4 As shown, the wastewater secondary membrane treatment equipment also includes: a freshwater pipe 601, an acidic reagent tank 602, and an alkaline reagent tank 603; one end of the freshwater pipe 601 is connected to the primary circulating membrane group 10 and the sludge tank 30, and the other end is connected to the sludge tank 30; the acidic reagent tank 602 and the alkaline reagent tank 603 are respectively connected to the primary circulating membrane group 10 and the sludge tank 30.

[0056] Furthermore, a third shut-off valve 6011 is provided at one end of the freshwater pipe 601 near the main inlet pipe 1011, and a fifth shut-off valve 3011 is provided on the freshwater-to-sewage pipe 301.

[0057] Specifically, the secondary membrane treatment equipment for wastewater in the ship's exhaust gas recirculation system includes a freshwater pipe 601, an acidic reagent tank 602, and an alkaline reagent tank 603. One end of the freshwater pipe 601 is connected to the main inlet pipe 1011 and the freshwater-to-sludge pipe 301 in the primary circulation membrane module 10, respectively. The other end of the freshwater-to-sludge pipe 301 is connected to the sludge tank 30. The acidic reagent tank 602 and the alkaline reagent tank 603 are connected to the dosing ports on the first circulation pipe 1023 and the sludge tank 30, respectively, via flexible hoses. Figure 4 A third shut-off valve 6011 is provided at one end of the freshwater pipe 601 near the main inlet pipe 1011, and a fifth shut-off valve 3011 is provided on the freshwater sewage pipe 301.

[0058] It should be noted that fresh water is introduced through fresh water pipe 601, and acidic agent is introduced into the first circulation pipe 1023 through acidic agent tank 602. The fresh water and acidic agent are mixed in the first circulation pipe 1023 and the impurities of the fouling membrane are removed by acid washing. Alkaline agent is introduced into the first circulation pipe 1023 through alkaline agent tank 603. The fresh water and alkaline agent are mixed in the first circulation pipe 1023 and the oil in the membrane is removed by alkaline washing.

[0059] In addition, such as Figure 3 As shown, the wastewater secondary membrane treatment equipment of the ship exhaust gas recirculation system also includes an empty pipe assembly 70, which includes an empty main pipe 701 and an empty branch pipe 702. The two ends of the empty branch pipe 702 are connected to the empty main pipe 701 and the first circulation pipe 1023, respectively. The empty main pipe 701 is connected to the clear water tank 20, the sludge tank 30, the acidic reagent tank 602, and the alkaline reagent tank 603.

[0060] Furthermore, the present invention also provides a wastewater treatment method for a ship exhaust gas recirculation system, which can be applied to the wastewater secondary membrane treatment equipment described in any of the above claims. The wastewater treatment method includes:

[0061] S1: Control the wastewater lifting device to send oily wastewater into the primary circulating membrane module and vent the air in the primary circulating membrane module, and control the primary circulating membrane module to perform the first treatment on the oily wastewater to obtain a first proportion of treated liquid, the first proportion of treated liquid including first clean water and primary concentrate.

[0062] S2: Control the backwash pump to mix part of the first clean water and the first-stage concentrate and then introduce it into the sludge tank;

[0063] S3: Control the secondary circulating membrane module to produce the second proportion of treated liquid; the second proportion of treated liquid includes the second clean water and the secondary concentrate. The secondary concentrate is transported to the sludge storage tank in the ship's hold, and it is determined whether the clean water tank meets the first condition.

[0064] S4: If so, the second clean water is delivered to the secondary circulating membrane module, and the backwash water is delivered to the sludge tank;

[0065] S5: Control the freshwater pipe, acidic chemical tank, and alkaline chemical tank to perform chemical cleaning on the primary and secondary circulating membrane modules.

[0066] Based on the specific working conditions, the wastewater lifting device is activated to pump the oily wastewater into the primary circulating membrane module 10, while simultaneously venting the air from the membrane module to ensure stable system operation. Subsequently, the primary circulating membrane module 10 is controlled to perform the first treatment of the oily wastewater, initially separating it to obtain a first proportion of treated liquid. The backwash pump 4011 is further controlled to mix a portion of the first clean water produced from the first treatment with the primary concentrate, and the mixture is introduced into the sludge tank 30 for temporary storage. A secondary filtration operation is then performed, and air is simultaneously vented from the primary circulating membrane module 10, while the oily wastewater is introduced into the primary circulating membrane module 10. Then, the secondary circulating membrane module 40 performs further treatment on the sludge from the sludge tank 30, producing a second clean water and a higher concentration secondary concentrate. The final secondary concentrate is then transported to the ship's sludge storage tank for final disposal. Simultaneously, the system detects the water level or quality in the clear water tank 20 to determine whether it meets the preset first condition. If the clear water tank 20 meets the first condition, the system performs two operations: first, it sends the second clear water back to the secondary circulating membrane module 40 for internal circulation or dilution to optimize the secondary treatment effect; second, it initiates the flushing procedure, sending backwash water to the sludge tank 30, which may be used to flush the tank walls or dilute the concentrate in the tank. Finally, the control system coordinates the fresh water pipe 601, the acidic reagent tank 602, and the alkaline reagent tank 603 to sequentially perform chemical cleaning on the primary circulating membrane module 10 and the secondary circulating membrane module 40 to remove membrane fouling and ensure the long-term treatment efficiency of the system.

[0067] Furthermore, the wastewater lifting device is controlled to send oily wastewater into the primary circulating membrane module and to purge the air from the primary circulating membrane module. The primary circulating membrane module is also controlled to perform a first treatment on the oily wastewater to obtain a first proportioned treated liquid. The first proportioned treated liquid includes a first purified water and a primary concentrate, comprising:

[0068] Open the inlet valve and set the first shut-off valve to open for a predetermined time. Expel the air from the primary circulating membrane module through the exhaust-liquid dual-purpose pipe. After the predetermined time, the first shut-off valve closes.

[0069] The first product water valve is opened to introduce oily wastewater into the first-stage circulating membrane unit, and the first-stage circulating membrane unit is put into operation to produce first-stage clean water and first-stage concentrate.

[0070] The first clean water is introduced into the clean water tank, and the first-stage concentrate is controlled to circulate in the first-stage circulating membrane module;

[0071] The backwash pump mixes a portion of the first-stage clean water and the first-stage concentrate before introducing it into the sludge tank, including:

[0072] The first shut-off valve is opened and the backwash pump is activated to introduce some of the clean water in the clean water tank into the primary circulating membrane module to mix with the primary concentrate, and then into the sludge tank.

[0073] Specifically, the inlet valve 10111 is opened, and the first shut-off valve 4021 is opened for a predetermined time, venting air from the primary circulating membrane module 10 through the exhaust-liquid dual-purpose pipe 402. After the predetermined time, the first shut-off valve 4021 is closed. Then, the first product water valve 1033 is opened, and the primary circulating pump 1022 is activated, delivering 95% of the clean water from the oily wastewater to the clean water tank 20 through the primary circulating filtration module 102, while the 5% concentrate continues to circulate within the primary circulating filtration module 102. If the cumulative reading of the inlet flow meter 10112 reaches a set value, the primary backwash valve 4015 and the first shut-off valve 4021 are opened. The system closes the inlet valve 10111 and the first product water valve 1033, shuts off the wastewater lifting device, operates the primary circulation pump 1022 at low power, and activates the backwash pump 4011. A small amount of clean water in the clean water tank 20 is sent to the primary circulation filtration module 102 and mixed with 5% concentrate to form a first proportion of treated liquid, which then flows to the sludge tank 30. Subsequently, the secondary filtration operation is performed simultaneously, as well as the air is discharged from the primary circulation membrane module 10 and wastewater is introduced into the primary circulation membrane module 10. This ensures that both the primary circulation filtration module 102 and the secondary circulation filtration module are running at the same time, and the secondary circulation pump 4032 is activated.

[0074] Furthermore, the secondary circulating membrane module is controlled to produce a second proportion of treated liquid; the second proportion of treated liquid includes a second clean water and a secondary concentrate. The secondary concentrate is transported to the sludge storage tank in the ship's hold, and it is determined whether the clean water tank meets the first condition, including:

[0075] The first proportion of the treated liquid is filtered to obtain a second clean water and a secondary concentrate.

[0076] The second clean water is introduced into the clean water tank, and the secondary concentrate is transported to the sludge storage tank in the ship's hold.

[0077] Obtain the liquid level in the clear water tank and determine whether the liquid level meets the first condition.

[0078] Specifically, the secondary sludge discharge valve 40362 is closed first, and the secondary product water valve 40342 is opened, allowing 80% of the clean water filtered from the primary concentrate to be sent into the clean water tank 20. At the same time, the secondary circulation pump 4032 operates, producing 80% of the primary concentrate's volume of clean water and 20% of the secondary concentrate through the secondary circulation filtration module 403. When the cumulative flow of the secondary product water flow meter 40341 ​​reaches the set value, the secondary sludge discharge valve 40362 is opened, and the secondary product water valve 40342 and the fourth shut-off valve 40332 are closed, allowing the secondary concentrate to be transported along the sludge discharge pipe 4036 to the external ship sludge tank 30. When the cumulative reading of the sludge discharge flow meter 40361 reaches the set value, the secondary sludge discharge valve 40362 is closed, and then it is determined whether the liquid level in the clean water tank 20 is greater than the first specified height.

[0079] Further, the second clean water is delivered to the secondary circulating membrane module 40, and the backwash water is delivered to the sludge tank 30. Specifically, this includes: after the liquid level in the clean water tank 20 is greater than the first specified height, the backwash pump 4011 and the secondary circulating pump 4032 operate, and the primary backwash valve 4015, the secondary sludge discharge valve 40362 and the secondary product water valve 40342 are closed. Clean water is then sent along the first backwash pipe 4012 and the second backwash pipe 4013 into the fourth backwash pipe 4035, and along the secondary clean water pipe 4034 into the secondary circulating filter module 403. Finally, the backwash water is sent into the sludge tank 30. After the cumulative reading of the secondary product water flow meter 40341 ​​reaches the set value, the backwash pump 4011 and the secondary circulating pump 4032 stop operating, the secondary backwash valve is closed, and then step S1 is executed.

[0080] Furthermore, if the liquid level in the clear water tank 20 reaches the second designated height, the backflush pump 4011 will operate and send the clear water to the second backflush pipe 4013. The clear water will be detected by the oil separation detection device 503. If the oil separation meets the standard, the clear water will be discharged to the outside of the hull along the oil separation standard discharge pipe 501. If the oil separation exceeds the standard, the clear water will be discharged to the raw water tank along the oil separation excess discharge pipe 502.

[0081] In addition, if the liquid level in the clear water tank 20 drops to the third specified height, the backwash pump 4011 will stop working.

[0082] Furthermore, the freshwater pipes, acidic chemical tanks, and alkaline chemical tanks are used to perform chemical cleaning on the primary and secondary circulating membrane modules, including:

[0083] Control the freshwater pipe to perform the first freshwater flush on the main inlet pipe and sludge bin;

[0084] The alkaline reagent tank is used to flush the primary circulating membrane module and sludge tank with alkaline water.

[0085] Control the freshwater pipe to perform a second freshwater flush on the main inlet pipe and sludge bin;

[0086] The acidic reagent tank is used to flush the primary circulating membrane module and sludge tank with acid water.

[0087] Control the freshwater pipe to perform a third freshwater flush on the main inlet pipe and sludge bin.

[0088] Chemical rinsing includes fresh water rinsing, alkaline rinsing, and acid rinsing. A first fresh water rinsing is performed before alkaline rinsing, a second fresh water rinsing is performed after alkaline rinsing and before acid rinsing, and a third fresh water rinsing is performed after acid rinsing.

[0089] Specifically, during step S1, the difference between the values ​​of the first pressure gauge 10231 and the second pressure gauge 10321 exceeds a specified value, i.e. Figure 6If the transmembrane pressure difference exceeds the standard, the primary circulating filter module 102 will be cleaned with chemicals. If the value of the second pressure gauge 10321 exceeds the specified value during step S2, the primary circulating filter module 102 will be cleaned with chemicals. If the value of the secondary product water flow meter 40341 ​​is lower than the specified value during step S3, the secondary circulating filter module 403 will be cleaned with chemicals. If the value of the fourth pressure gauge 40343 exceeds the specified value during step S4, the secondary circulating filter module 403 will be cleaned with chemicals.

[0090] Furthermore, the freshwater pipe 601, acidic chemical tank 602, and alkaline chemical tank 603 are controlled to perform chemical cleaning on the primary circulating membrane module 10 and the secondary circulating membrane module 40. Specifically, this includes performing primary chemical flushing and secondary chemical flushing on the primary circulating membrane module 10 and the secondary circulating membrane module 40.

[0091] S51: When performing chemical cleaning on the primary circulating filtration module 102, specifically, firstly, open the first shut-off valve 4021 to vent the primary circulating membrane module 10. After a predetermined time, close the inlet valve 10111, the first shut-off valve 4021, the first product water valve 1033, and the fifth shut-off valve 3011, and open the third shut-off valve 6011 to allow fresh water to enter through the fresh water pipe 601 and send the fresh water into the primary circulating filtration module 102. Simultaneously, activate the primary circulating pump 1022 to achieve chemical cleaning of the primary circulating filtration module 102 before alkaline washing. The process begins with a fresh water rinse at 02. Then, the alkaline agent in the alkaline agent tank 603 is pumped into the primary circulating filter module 102 via a dosing pump, and fresh water is introduced into the primary circulating filter module 102 to mix with the alkaline agent for alkaline washing. After alkaline washing, a fresh water rinse is repeated. Next, the acidic agent in the acidic agent tank 602 is pumped into the primary circulating filter module 102 via a dosing pump and mixed with fresh water for acid washing. After acid washing, fresh water is introduced into the primary circulating filter module 102 again to rinse it.

[0092] S52: When cleaning the secondary circulating filter module 403 with chemicals, close the secondary product water valve 40342, the secondary sludge discharge valve 40362, and the third shut-off valve 6011, and open the fourth shut-off valve 40332 and the fifth shut-off valve 3011 to allow fresh water to enter the fresh water pipe 601 and be sent to the sludge tank 30. Also, operate the secondary circulating pump 4032 to complete the fresh water rinsing of the secondary circulating filter module 403 before alkaline washing. Subsequently, the alkaline chemicals in the alkaline chemical tank 603 are sent to the secondary circulating filter module 403 through the dosing pump, and fresh water is introduced into the secondary circulating filter module 403 to mix with the alkaline chemicals for alkaline washing. After alkaline washing, repeat the fresh water rinsing once more. Then, the acidic chemicals in the acidic chemical tank 602 are sent to the secondary circulating filter module 403 through the dosing pump and mixed with fresh water for acid washing. After acid washing, fresh water is introduced into the secondary circulating filter module 403 again to clean it.

[0093] Furthermore, the alkaline reagent components in alkaline reagent compartment 603 include 3%-10% sodium hydroxide, 1%-5% triethanolamine, 3%-15% sodium octanoate and 0.5%-5% fatty alcohol polyoxyethylene ether.

[0094] More specifically, in the wastewater treatment method of the ship's exhaust gas recirculation system, during step S1, the inlet valve 10111 is opened, and the first shut-off valve 4021 is opened for a predetermined time. Air is then discharged from the primary circulation membrane module 10 through the exhaust-liquid dual-purpose pipe 402. After the predetermined time, the first shut-off valve 4021 is closed, the first product water valve 1033 is opened, and the primary circulation pump 1022 is activated. 95% of the clean water from the oily wastewater is then transported to the clean water tank 20 through the primary circulation filter module 102. It should be noted that at this time, the 5% concentrate is still present. The water circulates in the primary circulating filter module 102. If the cumulative reading of the inlet flow meter 10112 reaches the set value, step S2 is executed, and the primary backwash valve 4015 and the first shut-off valve 4021 are opened, while the inlet valve 10111 and the first product water valve 1033 are closed. The wastewater lifting device is shut off, the primary circulating pump 1022 is operated at low power, and the backwash pump 4011 is activated. A small amount of clean water in the clean water tank 20, specifically clean water with 5% oily wastewater content, is sent to the primary circulating filter module 102 and mixed with the 5% oily wastewater. The primary concentrate is mixed and flows to the sludge tank 30; then step S3 is implemented simultaneously with step S1, and both the primary circulating filter module 102 and the second circulating filter module are running at the same time, causing the secondary circulating pump 4032 to operate. In step S3, the secondary sludge discharge valve 40362 is closed first, and the secondary product water valve 40342 is opened, allowing 80% of the clean water filtered from the primary concentrate to be sent to the clean water tank 20. When the cumulative flow of the secondary product water flow meter 40341 ​​reaches the set value, the secondary sludge discharge valve 40362 opens, and... The secondary permeate valve 40342 and the fourth shut-off valve 40332 are closed, allowing the secondary concentrate to be transported along the sludge discharge pipe 4036 to the external sludge tank 30. When the accumulated reading of the sludge discharge flow meter 40361 reaches the set value, the secondary sludge discharge valve 40362 is closed. Then, it is determined whether the liquid level in the clear water tank 20 is greater than the first specified height. Once the liquid level in the clear water tank 20 exceeds the first specified height, step S4 is executed. After step S4 is completed, steps S1-S4 are repeated until the liquid level in the clear water tank 20 reaches the specified height, at which point step S5 is executed. It should be noted that sometimes, or during step S1, the liquid level in the clear water tank 20 reaches the specified height; in this case, step S5 is executed simultaneously during the execution of steps S1 to S2.

[0095] In addition, in step S1, the preferred dynamic constant flow rate of the oily wastewater is 3 m³ / h to 12 m³ / h, and the preferred flow velocity of the oily wastewater circulating in the primary circulating filtration module 102 is 3 m / s to 5 m / s; in step S4, the preferred flow velocity of the primary concentrate circulating in the secondary circulating filtration module 403 is 6 m / s.

[0096] In summary, the wastewater secondary membrane treatment equipment and treatment method of the ship exhaust gas recirculation system based on the embodiments of this application have been clarified. It provides secondary filtration for the wastewater secondary membrane treatment equipment and treatment method of the ship exhaust gas recirculation system, and has advantages such as reducing the risk of membrane clogging and extending the service life of the membrane when the wastewater is concentrated at the same level.

[0097] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A wastewater treatment method for a ship exhaust gas recirculation system, characterized in that, The ship exhaust gas recirculation system includes a secondary membrane treatment device for wastewater, which is used to treat oily wastewater from the ship exhaust gas recirculation system. The secondary membrane treatment device includes: Wastewater lifting equipment used to feed oily wastewater; A primary circulating membrane module, which is connected to the wastewater lifting device, is used to generate a first proportion of treated liquid. The system includes a clear water tank and a sludge tank, with the clear water tank connected to the primary circulating membrane module. Oily wastewater is circulated and filtered within the primary circulating membrane module, separating it into a majority of clear water and a small portion of concentrated liquid, which is the first proportion of treated liquid. The majority of the clear water is introduced into the clear water tank, and the small portion of concentrated liquid is introduced into the sludge tank. A secondary circulating membrane module, wherein the secondary circulating membrane module is connected to the sludge tank and the clear water tank; the secondary circulating membrane module comprises: The concentrate rinsing module is connected to the clear water tank and the primary circulating membrane module; The exhaust liquid dual-purpose pipe is connected to the sludge bin and the primary circulating membrane module; A secondary circulating filtration module, connected to the clear water tank, is used to process the first proportion of the treated liquid into a second proportion of the treated liquid; the concentration ratio of the second proportion of the treated liquid is greater than that of the first proportion of the treated liquid. The wastewater treatment method includes: The wastewater lifting device is controlled to send oily wastewater into the primary circulating membrane module and to vent the air in the primary circulating membrane module. The primary circulating membrane module is also controlled to perform a first treatment on the oily wastewater to obtain a first proportion of treated liquid, which includes a first clean water and a primary concentrate. The backwash pump is controlled to mix a portion of the first clean water and the first-stage concentrate and then introduce it into the sludge bin; The secondary circulating membrane module is controlled to produce the second proportion of treated liquid, that is, the secondary circulating membrane module performs deep treatment on the mixed liquid from the sludge tank to produce the second proportion of treated liquid, which includes a second clean water and a secondary concentrate with a higher concentration; the secondary concentrate is transported to the ship's sludge storage tank, and it is determined whether the clean water tank meets the first condition; If so, the second clean water is delivered to the secondary circulating membrane module, and the backwash water is delivered to the sludge bin; The freshwater pipe, acidic reagent tank, and alkaline reagent tank are used to clean the primary and secondary circulating membrane modules with chemicals.

2. The wastewater treatment method according to claim 1, characterized in that, The control system directs the wastewater lifting device to feed oily wastewater into the primary circulating membrane module and vents the air from the primary circulating membrane module. It also controls the primary circulating membrane module to perform a first treatment on the oily wastewater to obtain a first-proportion treated liquid. The first-proportion treated liquid comprises a first purified water and a primary concentrate, including: Open the inlet valve and set the first shut-off valve to open for a predetermined time, and discharge the air in the primary circulating membrane module through the exhaust-liquid dual-purpose pipe. After the predetermined time, the first shut-off valve closes. The first product water valve is opened to introduce oily wastewater into the primary circulating membrane module, and the primary circulating membrane module is put into operation to produce the first clean water and the primary concentrate. The first clean water is introduced into the clean water tank, and the first-stage concentrate is controlled to circulate in the first-stage circulating membrane module; The control backwash pump mixes a portion of the first clean water and the first-stage concentrate before introducing it into the sludge tank, including: The first shut-off valve is opened and the backwash pump is activated to introduce a portion of the clean water in the clean water tank into the primary circulating membrane module to mix with the primary concentrate, and then into the sludge tank.

3. The wastewater treatment method according to claim 2, characterized in that, The second proportion of the treated liquid is produced by controlling the secondary circulating membrane module to perform deep treatment on the mixed liquid from the sludge tank, and the second proportion of the treated liquid includes a second clean water and a secondary concentrate with a higher concentration. The secondary concentrate is transported to the ship's sludge storage tank, and it is determined whether the clear water tank meets the first condition, including: The first proportion of the treatment solution is filtered to obtain the second purified water and the secondary concentrate. The second clean water is introduced into the clean water tank, and the secondary concentrate is transported to the sludge storage tank in the ship's hold; Obtain the liquid level in the clear water tank and determine whether the liquid level meets the first condition.

4. The wastewater treatment method according to claim 3, characterized in that, The control freshwater pipe, acidic reagent tank, and alkaline reagent tank perform chemical cleaning on the primary circulating membrane module and the secondary circulating membrane module, including: The freshwater pipe is controlled to perform a first freshwater flush on the main inlet pipe and the sludge bin; The alkaline reagent tank is controlled to perform alkaline water flushing on the primary circulating membrane module and the sludge tank; The freshwater pipe is controlled to perform a second freshwater flush on the main inlet pipe and the sludge bin; The acidic reagent tank is controlled to perform acid flushing on the primary circulating membrane module and the sludge tank; The freshwater pipe is controlled to perform a third freshwater flush on the main inlet pipe and the sludge bin.

5. The wastewater treatment method according to claim 4, characterized in that, The alkaline reagent in the alkaline reagent compartment comprises 3%-10% sodium hydroxide, 1%-5% triethanolamine, 3%-15% sodium octanoate, and 0.5%-5% fatty alcohol polyoxyethylene ether.

6. A secondary membrane treatment device for wastewater from a ship exhaust gas recirculation system, characterized in that, The wastewater secondary membrane treatment equipment can be used with the wastewater treatment method as described in any one of claims 1 to 5; The concentrated liquid flushing module includes: a backflush pump, a first backflush pipe, a second backflush pipe, and a third backflush pipe; The first backflush pipe is connected to both the clear water tank and the inlet of the backflush pump. The outlet of the backflush pump is connected to the second backflush pipe; The third backflush tube is connected to the second backflush tube and the first-stage circulating membrane module.

7. The wastewater secondary membrane treatment equipment according to claim 6, characterized in that, The secondary circulation filtration module includes: a secondary membrane cylinder, a secondary circulation pump, a second circulation pipe, a secondary clean water pipe, a fourth backwash pipe, and a sludge discharge pipe; The second circulation pipe connects the secondary membrane cylinder, the secondary circulation pump, and the sludge bin in series. The secondary clean water pipe is connected to the second circulation pipe and the clean water tank, respectively. The fourth backflush pipe is connected to the secondary clean water pipe and the end of the second backflush pipe that is away from the backflush pump, respectively. The sludge discharge pipe is connected to the second circulation pipe located between the secondary circulation pump and the secondary membrane cylinder.

8. The wastewater secondary membrane treatment equipment according to claim 7, characterized in that, It also includes: a clean water discharge pipe assembly and an oil separation detection device; Both the oil-compliant discharge pipe and the oil-excess discharge pipe in the clean water discharge pipe group are connected to the second backflush pipe. The oil separation detection device is located between the clean water discharge pipe group and the second backflushing pipe.

9. The wastewater secondary membrane treatment equipment according to claim 7, characterized in that, It also includes: freshwater pipes, acidic reagent tanks, and alkaline reagent tanks; One end of the freshwater pipe is connected to the primary circulating membrane module and the sludge tank, and the other end is connected to the sludge tank. The acidic reagent tank and the alkaline reagent tank are respectively connected to the primary circulating membrane module and the sludge tank.

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