An on-line cleaning system for plate heat exchangers of a leachate MBR system

Abstract

This application discloses an online cleaning system for plate heat exchangers in a leachate MBR system. The system includes a cleaning tank storing acidic cleaning agent, which is connected to the heat exchanger via an outlet pipe and a return pipe. The outlet pipe is equipped with a shut-off valve to separate an acidic section and a mixing section. The acidic section is connected to a cleaning pump and valves. Connecting pipes include first and second connecting pipes for flushing the acidic and mixing sections, connecting the outlet pipe to the main water supply pipe and equipped with corresponding flushing valves. An alkaline agent tank is connected to the mixing section and is equipped with an alkaline pump and an outlet valve. A waste liquid pipe connects the plate heat exchanger outlet pipe to a waste liquid pool, with a switching valve between the two connection points. The monitoring module includes a DCS system and various connected sensors. The DCS system is also connected to the pumps and valves. This system enables accurate prediction of scaling, adopts appropriate cleaning methods for different degrees of scaling, and also achieves the recycling of cleaning solution, reducing agent consumption and the amount of scale-containing wastewater generated, reducing environmental pollution, lowering operating costs, reducing on-site manual operation, and reducing labor intensity and labor costs.

Description

Technical Field

[0001] This application belongs to the field of heat exchanger cleaning technology, specifically an online cleaning system for plate heat exchangers in a leachate MBR system. Background Technology

[0002] In the leachate MBR system of waste-to-energy plants, plate heat exchangers are key heat exchange equipment, and their operating efficiency directly affects the stability of the entire system. Currently, the industry commonly uses mechanical tower circulating cooling water to provide cooling medium for plate heat exchangers. However, during long-term circulation, due to evaporation and concentration, the concentration of minerals such as calcium and magnesium ions in the water continuously increases. When saturation is reached, hard calcified deposits easily form on the surface of the heat exchanger plates.

[0003] In existing technologies, cleaning of plate heat exchangers mainly relies on offline disassembly and cleaning. This involves stopping operation and disassembling the equipment when scale buildup reduces heat exchange efficiency, requiring manual cleaning of each heat exchange plate. This method has significant drawbacks: Calcified deposits become hard and require repeated scraping with high-strength tools for manual cleaning; cleaning a single heat exchanger typically takes over 48 hours, making it difficult to thoroughly remove scale from crevices; manual cleaning is costly; and there is a risk of secondary damage such as scratches on heat exchange plates and damage to gaskets, increasing equipment maintenance costs. During offline cleaning, the nitrification liquid in the MBR system cannot cool down properly, leading to a decrease in biochemical reaction efficiency. In severe cases, this may force a reduction in the treatment load, affecting leachate treatment progress. During disassembly, residual nitrification liquid inside the heat exchanger is directly exposed to the air, releasing malodorous gases containing ammonia and hydrogen sulfide, which does not meet pollutant emission requirements and may cause pollution to surrounding water bodies and soil.

[0004] Furthermore, existing technologies lack a scaling early warning mechanism. Operators can only judge the scaling situation by observing changes in the temperature difference between the heat exchanger inlet and outlet. Cleaning is often only carried out when the heat exchange efficiency drops by more than 30%, resulting in serious energy waste. At the same time, traditional offline cleaning cannot achieve the recycling of cleaning agents, which not only increases the consumption of agents but also generates a large amount of scale-containing wastewater, which is difficult to treat. Utility Model Content

[0005] To address the aforementioned problems in the existing technology, this application provides an online cleaning system for plate heat exchangers in a leachate MBR system. Through intelligent monitoring, automated cleaning processes, and closed-loop circulation design, it achieves efficient cleaning of plate heat exchangers and stable system operation.

[0006] To achieve the above objectives, this application adopts the following technical solution: an online cleaning system for plate heat exchangers in a leachate MBR system, comprising: A cleaning tank is used to store acidic cleaning agent. The cleaning tank outlet pipe and the cleaning tank return pipe are connected to the plate heat exchanger inlet pipe and the plate heat exchanger outlet pipe. A shut-off valve is installed on the cleaning tank outlet pipe, which divides the tank into an acidic section and a mixing section. A cleaning pump, a cleaning pump inlet valve, and a cleaning pump outlet valve are installed on the acidic section. A cleaning tank return valve is installed on the cleaning tank return pipe. The connecting pipe includes a first connecting pipe for rinsing the acidic section and a second connecting pipe for rinsing the mixed section. The first and second connecting pipes are connected to the water outlet pipe of the cleaning tank and the water supply main pipe at both ends of the shut-off valve, and are equipped with a first flushing valve and a second flushing valve respectively. An alkaline reagent tank is used to store alkaline cleaning agents. It is connected to the mixing section with the connection point located behind the second connecting pipe. An alkaline pump and an alkaline outlet valve are installed accordingly. Waste liquid pipe is used to connect the outlet water pipe of plate heat exchanger to waste liquid tank. The connection point is located in front of the connection point of the return water pipe of cleaning tank and a switching valve is installed between the two connection points. The monitoring module includes a DCS system and a pH sensor, conductivity meter, pressure gauge, vortex flow meter, and differential pressure transmitter connected to the DCS system. The pH sensor and conductivity meter are installed on the inlet and outlet pipes of the plate heat exchanger. The pressure gauge is installed on the inlet and outlet pipes of the plate heat exchanger and connected to the differential pressure transmitter. The vortex flow meter is installed at the inlet of the heat exchanger. The DCS system is also connected to various pumps and valves within the system.

[0007] The return water pipe of the cleaning tank is connected in series with a precision filter and an ion exchange column for the regeneration of the cleaning solution.

[0008] An infrared thermal imager is installed on the outside of the shell of the plate heat exchanger. The infrared thermal imager is used to acquire the surface temperature distribution data of the heat exchange plates and transmit it to the DCS system.

[0009] The cleaning tank and the alkaline agent tank are equipped with liquid level sensors and electric heating rods, respectively, and the liquid level sensors and electric heating rods are connected to the DCS system.

[0010] A pressure buffer tank is installed on the water outlet pipe of the cleaning tank located at the rear end of the cleaning pump outlet valve.

[0011] The beneficial effects of this application are: This application provides an online cleaning system for plate heat exchangers in a leachate MBR system. Through an intelligent monitoring and early warning module, it achieves accurate prediction of heat exchanger scaling conditions, allowing for advance planning of cleaning work and preventing a significant drop in heat exchange efficiency due to severe scaling. This effectively reduces energy waste and improves system operational stability. The system employs a tiered cleaning mode and a cleaning fluid regeneration device, which not only improves cleaning efficiency and allows for appropriate cleaning methods for different levels of scaling, but also enables the recycling of the cleaning fluid, reducing reagent consumption and the generation of scale-containing wastewater, thus reducing environmental pollution and lowering operating costs. Closed-loop control and remote operation and maintenance functions ensure the normal operation of the MBR system during the cleaning process, while also enabling remote monitoring, fault diagnosis, and automatic repair reporting, greatly improving operation and maintenance efficiency, reducing manual on-site operations, and lowering labor intensity and labor costs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the online cleaning system for plate heat exchangers in this application; 1—Nitrification tank; 2—Plate heat exchanger; 2-1—Heat exchanger inlet pipe; 2-2—Heat exchanger outlet pipe; 3—Mechanical pressure tower; 4—Mechanical pressure tower inlet valve; 5—Mechanical pressure tower outlet valve; 6—Circulating cooling water pump; 7—Nitrification circulating pump; 8—Cleaning tank; 8-1—Cleaning tank return water pipe; 8-2—Cleaning tank outlet water pipe; 9—Cleaning pump; 10—Cleaning pump inlet valve; 11—Cleaning pump outlet valve; 12—Vortex flow meter; 13—Differential flow meter 14—Pressure transmitter; 15—Cleansing tank return water valve; 16—First flushing valve; 17—Second flushing valve; 18—First connecting pipe; 19—Second connecting pipe; 20—Stop valve; 21—Precision filter; 22—Ion exchange column; 23—Alkaline reagent tank; 24—Alkaline pump; 25—Alkaline outlet valve; 26—Waste liquid pipe; 27—Waste liquid valve; 28—Waste liquid pool; 29—Switching valve; 30—Make-up water header. Detailed Implementation

[0013] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0014] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0015] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0016] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0017] like Figure 1 As shown, an online cleaning system for plate heat exchangers in a leachate MBR system includes a cleaning tank, connecting pipes, an alkaline reagent tank, a waste liquid pipe, a DCS system, and various detection devices. The nitrification tank 1 is connected to the plate heat exchanger 2 via pipes, and a nitrification circulation pump 7 is installed on the connecting pipes to improve the activity of microorganisms in the nitrification liquid through cooling circulation. The plate heat exchanger 2 and the mechanical tower 3 are connected via the plate heat exchanger inlet pipe 2-1 and the plate heat exchanger outlet pipe 2-2 to form a circulation loop. A mechanical tower inlet valve 4 and a mechanical tower outlet valve 5 are installed on the corresponding pipes. A circulating cooling water pump 6 is installed on the plate heat exchanger inlet pipe 2-1, and the mechanical tower 3 provides circulating cooling water to the plate heat exchanger 2. An infrared thermal imager is installed on the exterior of the plate heat exchanger 2 shell to acquire surface temperature distribution data of the heat exchange plates and transmit it to the DCS system.

[0018] During operation, plate heat exchangers in leachate MBR systems generate various types of contaminants due to the characteristics of the water quality. Calcium and magnesium ions in the circulating cooling water easily form calcified precipitates such as carbonates. These substances are alkaline and require acidic cleaning agents to dissolve them. Other potential contaminants include system makeup water (such as organic matter introduced by the mechanical tower makeup water), microbial growth on the inner walls of pipes (such as bacterial metabolic products), and the infiltration of trace amounts of external oil, forming a composite scale layer of "calcified layer + organic matter / biofilm". Simple acid washing cannot penetrate the organic coating layer and is insufficient to fully react with the internal calcified precipitates. Alkaline cleaning agents are needed to emulsify the organic matter, disrupt the biofilm structure of the biofilm, and peel off the outer coating of the composite scale layer, creating conditions for subsequent acid washing and ensuring complete removal of the calcified precipitates. Therefore, two cleaning tanks are required to address these issues separately. Furthermore, after acid cleaning, acidic substances may remain on the surface of the pipes and heat exchange fins. This residual acid can corrode the stainless steel and other metal materials of the heat exchanger, potentially leading to pipe leaks and heat exchange fin damage in the long term. The residual acid on the cooling water side needs to be neutralized to neutral by adding alkaline cleaning agent in an alkaline cleaning tank, thereby fundamentally eliminating the risk of acid corrosion and extending the service life of the equipment.

[0019] The cleaning tank 8 is used to store acidic cleaning agent. It is connected to the plate heat exchanger inlet pipe 2-1 and outlet pipe 2-2 via the cleaning tank outlet pipe 8-2 and return pipe 8-1. A shut-off valve 20 is installed on the cleaning tank outlet pipe 8-2, dividing it into an acidic section and a mixing section. The acidic section is equipped with a cleaning pump 9, a cleaning pump inlet valve 10, and a cleaning pump outlet valve 11. A cleaning tank return valve 15 is installed on the cleaning tank return pipe 8-1. A precision filter 21 and an ion exchange column 22 for cleaning solution regeneration are connected in series on the cleaning tank return pipe 8-1. A pressure buffer tank is installed on the cleaning tank outlet pipe 8-2, located downstream of the cleaning pump outlet valve 11, to control instantaneous pressure fluctuations within a threshold value, stabilizing the cleaning pump outlet pressure and preventing damage to the equipment due to pressure fluctuations.

[0020] The connecting pipes include a first connecting pipe 18 for rinsing the acidic section and a second connecting pipe 19 for rinsing the mixed section. A first flushing valve 16 is installed on the first connecting pipe 18, with its outlet connected to the cleaning tank outlet pipe 8-2 at the front end of the shut-off valve 20, and its inlet connected to the water supply header 30. A second flushing valve 17 is installed on the second connecting pipe 19, with its outlet connected to the cleaning tank outlet pipe 8-2 at the rear end of the shut-off valve 20, and its inlet connected to the water supply header 30. The shut-off valve 20 switches between cleaning fluid return and waste liquid discharge, ensuring that the acidic cleaning fluid returns normally to the cleaning tank 8, and that the alkaline cleaning waste liquid or flushing water is smoothly discharged into the waste liquid pool 28, avoiding cross-contamination.

[0021] The alkaline reagent tank 23 stores alkaline cleaning agents and is connected to the mixing section, with the connection point located behind the second connecting pipe 19. An alkaline pump 24 and an alkaline dispensing valve 25 are installed on the connecting pipe. Electric heating rods and level sensors are installed inside the cleaning tank 8 and the alkaline reagent tank 23. The electric heating rods are used to increase the temperature of the cleaning solution in winter, improving the reactivity of the cleaning agents and enhancing the cleaning effect. The level sensor is used to detect the remaining amount of cleaning agent and remind the user to replenish the solution. The control signal is connected to the DCS system.

[0022] Waste liquid pipe 26 is used to connect the plate heat exchanger outlet pipe 2-2 to the waste liquid pool 28. The connection point is located in front of the connection point of the cleaning tank return water pipe 8-1, and a switching valve 29 is installed between the two connection points. A waste liquid valve 27 is installed on the waste liquid pipe 26. The switching valve 29 prevents waste liquid from flowing to the rear end of the plate heat exchanger outlet pipe 2-2.

[0023] The DCS system and online cleaning system testing equipment are connected to various pumps and valves within the online cleaning system. This connection is used to receive data from the testing equipment and transmit control signals to control the operation of the online cleaning system. The system testing equipment includes a pH sensor, conductivity meter, pressure gauge 14, vortex flow meter 12, and differential pressure transmitter 13. The pH sensor and conductivity meter are installed on the inlet pipe 2-1 and outlet pipe 2-2 of the plate heat exchanger. Pressure gauge 14 is installed on the inlet pipe 2-1 and outlet pipe 2-2 of the plate heat exchanger and connected to the differential pressure transmitter 13; the vortex flow meter 12 is installed on the pipe located at the heat exchanger inlet.

[0024] When the differential pressure transmitter 13 detects that the inlet and outlet pressure difference of the plate heat exchanger rises above the threshold, and the vortex flow meter 12 shows a decrease in flow rate, combined with the conductivity meter detecting that the conductivity of the circulating water exceeds the threshold (excessive calcium and magnesium ion concentration), it is determined to be calcification and scaling. At this time, an acidic cleaning agent is activated. The acidic cleaning agent can react with metal ions such as calcium and magnesium, dissolving the calcified precipitates and restoring the heat exchanger's heat exchange efficiency. After acidic cleaning, the residual acid solution must be neutralized with an alkaline cleaning agent (such as sodium bicarbonate solution) to prevent acidic substances from corroding the heat exchanger's metal pipes.

[0025] When an infrared thermal imager detects an abnormally high localized temperature on the surface of a plate heat exchanger fins, accompanied by a slow increase in differential pressure, indicating biofilm buildup, an alkaline cleaning agent is used. The alkaline cleaning agent disrupts the biofilm structure, promoting the removal of the biofilm. When dealing with a complex scale layer consisting of calcification and organic matter, an alkaline cleaning agent is first used to emulsify the grease and other organic matter, followed by an acidic cleaning agent to dissolve the calcification layer, thus improving the cleaning effect.

[0026] The DCS system continuously monitors changes in the inlet and outlet water quality of the plate heat exchanger using a pH sensor and conductivity meter. When the conductivity or pH value exceeds a set threshold, a scaling warning is triggered. Pressure gauge 14 and differential pressure transmitter 13 monitor the inlet and outlet pressures and differential pressure in real time. Combined with flow data from vortex flowmeter 12, the system accurately determines the degree of scaling in the heat exchanger. An infrared thermal imager scans the surface temperature distribution of the heat exchange plates, and the data is transmitted to the DCS system. Temperature differences are used to locate severely scaled areas and areas where biofilm accumulates, providing a basis for cleaning. Liquid level sensors in the cleaning tank 8 and alkaline chemical tank 23 monitor the remaining chemical levels in real time. When the levels fall below a threshold, the DCS system issues a replenishment reminder. Temperature sensors monitor the chemical temperature, and in winter, the electric heating rod automatically activates to ensure chemical activity.

[0027] An automated cleaning process for plate heat exchangers in a leachate MBR system: Acidic cleaning process: The DCS system controls the opening of the cleaning pump inlet valve 10, cleaning pump outlet valve 11, shut-off valve 20, cleaning tank return water valve 15, and switching valve 29, and closes the mechanical tower outlet valve 5, waste liquid valve 27, and alkaline liquid outlet valve 25. The cleaning pump 9 sends the acidic cleaning agent in the cleaning tank 8 to the plate heat exchanger 2 via the cleaning tank outlet pipe 8-2. The cleaned liquid is then processed through the cleaning tank return water pipe 8-1, precision filter 21, and ion exchange column 22 before flowing back to the cleaning tank 8, achieving recycling.

[0028] Alkaline cleaning process: The DCS system controls the closure of shut-off valve 20, cleaning pump-related valves, and switching valve 29, and opens alkaline pump 24, alkaline outlet valve 25, and waste liquid valve 27. The alkaline agent enters plate heat exchanger 2 through the mixing section, and the cleaning waste liquid is discharged into waste liquid pool 28 through waste liquid pipe 26.

[0029] Rinsing process: After acid cleaning, close the relevant valves of the cleaning pump and the shut-off valve 20, open the first flushing valve 16, and flush the acid section with water from the water supply header 30 through the first connecting pipe 18, flushing the residual acid back to the cleaning tank 8; for alkaline cleaning or when the mixing section and plate heat exchanger 2 need to be rinsed, close the shut-off valve 20 and open the second flushing valve 17, and let the water flow through the second connecting pipe 19 into the mixing section, the plate heat exchanger inlet pipe 2-1, the plate heat exchanger 2, and the plate heat exchanger outlet pipe 2-2, and finally discharge it into the waste liquid pool 28 through the waste liquid pipe 26. Repeat the rinsing process multiple times to ensure no chemical residue.

[0030] The DCS system automatically controls the opening and closing of pumps and valves based on data from various sensors, achieving automated operation of the cleaning process. It records data such as cleaning time, chemical consumption, differential pressure changes, and flow recovery for each cleaning cycle, generating a cleaning report to provide a basis for optimizing cleaning cycles and parameters. When equipment malfunctions, abnormal liquid levels, or parameters exceeding limits are detected, the DCS system immediately issues an alarm and takes corresponding protective measures, such as closing relevant valves and stopping pump operation, to ensure system safety.

[0031] Finally, it should be noted that in this document, relationships such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "include," "contain," or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0032] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0033] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An online cleaning system for plate heat exchangers in a leachate MBR system, characterized in that, include: A cleaning tank is used to store acidic cleaning agent. The cleaning tank outlet pipe and the cleaning tank return pipe are connected to the plate heat exchanger inlet pipe and the plate heat exchanger outlet pipe. A shut-off valve is installed on the cleaning tank outlet pipe, which divides the tank into an acidic section and a mixing section. A cleaning pump, a cleaning pump inlet valve, and a cleaning pump outlet valve are installed on the acidic section. A cleaning tank return valve is installed on the cleaning tank return pipe. The connecting pipe includes a first connecting pipe for rinsing the acidic section and a second connecting pipe for rinsing the mixed section. The first connecting pipe and the second connecting pipe are connected to the water outlet pipe of the cleaning tank and the water supply main pipe at both ends of the shut-off valve, and a first flushing valve and a second flushing valve are installed accordingly. An alkaline reagent tank, used to store alkaline cleaning agents, is connected to the mixing section with the connection point located behind the second connecting pipe, and is equipped with an alkaline pump and an alkaline outlet valve. Waste liquid pipe is used to connect the outlet water pipe of the plate heat exchanger to the waste liquid pool. The connection point is located in front of the connection point of the return water pipe of the cleaning box and a switching valve is provided between the two connection points. The monitoring module includes a DCS system and a pH sensor, conductivity meter, pressure gauge, vortex flow meter, and differential pressure transmitter connected to the DCS system. The pH sensor and conductivity meter are installed on the inlet and outlet pipes of the plate heat exchanger. The pressure gauge is installed on the inlet and outlet pipes of the plate heat exchanger and connected to the differential pressure transmitter. The vortex flow meter is installed at the inlet of the heat exchanger. The DCS system is also connected to various pumps and valves within the system.

2. The online cleaning system for plate heat exchangers in a leachate MBR system as described in claim 1, characterized in that, A precision filter and an ion exchange column for regenerating the cleaning solution are connected in series on the return water pipe of the cleaning tank.

3. The online cleaning system for plate heat exchangers in a leachate MBR system as described in claim 1, characterized in that, An infrared thermal imager is installed on the outside of the shell of the plate heat exchanger. The infrared thermal imager is used to acquire the surface temperature distribution data of the heat exchange plates and transmit it to the DCS system.

4. The online cleaning system for plate heat exchangers in a leachate MBR system as described in claim 1, characterized in that, The cleaning tank and the alkaline agent tank are respectively equipped with a liquid level sensor and an electric heating rod, and the liquid level sensor and the electric heating rod are connected to the DCS system.

5. The online cleaning system for plate heat exchangers in a leachate MBR system as described in claim 1, characterized in that, A pressure buffer tank is installed on the water outlet pipe of the cleaning tank located at the rear end of the outlet valve of the cleaning pump.

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