A cleaning system for a sour water stripping column and a method of cleaning a sour water stripping column

Abstract

The application discloses a cleaning system of a sewage stripping tower and a method for cleaning the sewage stripping tower, wherein the cleaning system of the sewage stripping tower comprises an olefin separation device, a waste alkali delivery pump is arranged on the olefin separation device, the waste alkali delivery pump is provided with an outlet guide, a sewage stripping tower is provided with a feed pump, the feed pump is provided with an inlet guide, a connecting pipeline is connected with the outlet guide of the waste alkali delivery pump at one end and connected with the inlet guide of the feed pump at the other end, and the connecting pipeline is used for introducing waste alkali liquid generated by the olefin separation device into a feed system of the sewage stripping tower, so that the waste alkali liquid is subjected to a saponification reaction with oil wax type pollutants attached to a tower tray surface in the sewage stripping tower, and the oil phase is removed. The scheme of the application utilizes waste alkali liquid generated by the device as a cleaning medium, can clean the sewage stripping tower, and realizes resource utilization of the waste alkali liquid. Meanwhile, the cleaning process is carried out in a normal operation state, and offline shutdown is not needed, so that production interruption and economic loss are avoided.

Description

Technical Field

[0001] This application generally relates to the field of wastewater treatment technology in olefin production processes. More specifically, this application relates to a cleaning system for a wastewater stripping tower; further, this application also relates to a method for cleaning a wastewater stripping tower using the wastewater stripping tower cleaning system. Background Technology

[0002] Methanol-to-olefins (MTO) technology is one of the mainstream processes for producing important basic chemical raw materials such as ethylene and propylene from coal or natural gas. In an MTO unit, the wastewater stripping tower is the core equipment of the wastewater treatment unit. Its main function is to strip unreacted oxygen-containing compounds (such as methanol and dimethyl ether) and oxygen-containing compounds generated during the reaction (mainly aldehydes and ketones) from the water and return them to the reactor for reprocessing, while ensuring that the purified process water meets the requirements for discharge or reuse.

[0003] In actual production, side reactions inevitably occur in the reaction system of the MTO unit, generating a certain amount of large molecular hydrocarbons. These hydrocarbons enter the water washing system with the reaction gas, where they mix with impurities such as oil and wax, and a small amount of catalyst powder carried in the washing water, and then enter the wastewater stripping tower together. Under the high-temperature conditions inside the stripping tower, the above mixture gradually adheres to and deposits on the surface of the trays, forming a dense layer of oil and wax. This layer has strong adhesion and hydrophobicity, and is difficult to remove by conventional water rinsing.

[0004] The oil and wax buildup on the tray surface causes a series of technical problems: First, the effective throughput of the tray decreases, and the gas and liquid flow channels narrow, leading to a continuous increase in the tower pressure differential. This increased pressure differential not only increases energy consumption but also significantly reduces the stripping effect, making it difficult to consistently meet the oxygen content standards in the purified water. Second, with prolonged operation, the tray blockage worsens, eventually causing the wastewater stripping tower to malfunction and requiring offline manual cleaning. According to actual operational statistics, existing MTO units require at least two offline cleanings per year for their wastewater stripping towers. Each cleaning requires the unit to operate at reduced load or undergo partial shutdown, resulting in significant economic losses. Third, during offline cleaning, the purified water cannot be properly treated, and the discharged purified water quality frequently exceeds standards, easily leading to environmental accidents. Furthermore, manual tray cleaning requires operators to enter the tower, posing high safety risks, and is labor-intensive and costly.

[0005] To address the aforementioned issues, a common approach is to periodically perform preventative offline cleaning of the wastewater stripping tower. However, this requires interrupting the unit's operation, affecting production continuity. Another approach is to optimize upstream reaction processes to reduce the generation of oily and waxy byproducts. However, this involves modifying the reaction system, resulting in significant investment, a long development cycle, and limited effectiveness. Another approach attempts to add chemical dispersants or scale inhibitors to the wastewater stripping tower to suppress the deposition of oil and wax on the tray surfaces. However, this increases operating costs, and the introduction of chemical agents may adversely affect subsequent water treatment units.

[0006] In view of this, there is an urgent need to provide a cleaning system and method for cleaning wastewater stripping towers, so as to effectively remove oil and wax contaminants adhering to the surface of the tower trays without affecting subsequent water treatment units, and extend the operating cycle of the wastewater stripping tower. Summary of the Invention

[0007] In order to at least solve one or more of the technical problems mentioned above, this application proposes a cleaning system and method for cleaning wastewater stripping towers that can effectively remove oil and wax contaminants adhering to the surface of the trays and extend the operating cycle of the wastewater stripping tower.

[0008] In a first aspect, this application provides a cleaning system for a wastewater stripping tower, comprising:

[0009] An olefin separation unit is equipped with a waste alkali transfer pump, which has an outlet drain; a wastewater stripping tower is equipped with a feed pump, which has an inlet drain; and a connecting pipeline, one end of which is connected to the outlet drain of the waste alkali transfer pump, and the other end is connected to the inlet drain of the feed pump. The connecting pipeline is used to introduce the waste alkali solution generated by the olefin separation unit into the feed system of the wastewater stripping tower, so that the waste alkali solution reacts with the oil and wax contaminants attached to the surface of the trays in the wastewater stripping tower to remove the oil phase.

[0010] In some embodiments, a control valve is provided on the connecting pipeline for adjusting the injection flow rate of waste alkali solution.

[0011] In some embodiments, the connecting pipeline is further provided with a one-way valve, which is used to prevent the material in the wastewater stripping tower from flowing back into the olefin separation unit.

[0012] In some embodiments, the system further includes a pH monitoring device and a controller. The pH monitoring device is installed in the purified water outlet pipeline of the wastewater stripping tower or inside the tower to monitor the pH value of the purified water in real time. The controller is electrically connected to the pH monitoring device and the control valve to automatically adjust the opening of the control valve according to the feedback signal from the pH monitoring device.

[0013] In some embodiments, the feed pump inlet of the wastewater stripping tower is also connected to a settling tank, which is used to perform settling pretreatment on the feed entering the wastewater stripping tower to separate some of the oil, wax and solid impurities carried in the feed.

[0014] In some embodiments, a filter is provided between the outlet of the waste alkali transfer pump of the olefin separation unit and the connecting pipeline to remove solid impurities from the waste alkali solution.

[0015] In some embodiments, the purified water outlet pipeline of the wastewater stripping tower is connected to a purified water pump, which is used to transport the purified process water to subsequent processes or a reuse system.

[0016] In some embodiments, the outlet of the waste alkali delivery pump of the olefin separation unit is connected to multiple connecting pipelines, which are respectively connected to the inlet drains of the feed pumps of multiple sets of wastewater stripping towers.

[0017] In a second aspect, this application provides a method for cleaning a wastewater stripping tower using the aforementioned cleaning system, comprising the following steps: starting the waste alkali external pump of the olefin separation unit; opening the outlet drain valve of the waste alkali external pump and the inlet drain valve of the wastewater stripping tower feed pump; injecting the waste alkali solution into the feed system of the wastewater stripping tower through the connecting pipeline; and causing the waste alkali solution to undergo a saponification reaction with the oil and wax contaminants adhering to the surface of the trays in the wastewater stripping tower, thereby removing the oil phase.

[0018] In some embodiments, during the injection of waste alkali solution, the pH value of the purified water is monitored in real time, and the injection volume of waste alkali solution is adjusted according to the pH value.

[0019] The wastewater stripping tower cleaning system described above utilizes the waste alkaline solution generated by the device itself as the cleaning medium, eliminating the need for additional chemical agents and achieving resource utilization of the waste alkaline solution, thus reducing wastewater treatment costs. Simultaneously, the cleaning process is carried out during the normal operation of the wastewater stripping tower, eliminating the need for offline shutdown and avoiding production interruptions and economic losses caused by offline cleaning. By removing the oil and wax buildup on the tower tray surface online, the tower tray throughput is restored, the tower pressure differential is reduced, and the stripping effect and purified water quality are ensured. This significantly extends the operating cycle of the wastewater stripping tower and reduces the labor intensity and operational safety risks associated with manual cleaning. Attached Figure Description

[0020] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein: Figure 1A schematic diagram of the cleaning system of the wastewater stripping tower according to an embodiment of this application is shown.

[0021] In the diagram: 100, the cleaning system of the wastewater stripping tower; 101. Olefin separation unit; 102. Wastewater stripping tower; 103. Connecting pipelines; 104. Feed pump; 105. Waste alkali external transfer pump; 106. Purified water pump; 107. Settling tank. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0024] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0025] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0026] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] like Figure 1As shown, in some embodiments, this application provides a cleaning system 100 for a wastewater stripping tower, comprising: an olefin separation unit 101 equipped with a waste alkali transfer pump 105, the waste alkali transfer pump 105 having an outlet drain; a wastewater stripping tower 102 equipped with a feed pump 104, the feed pump 104 having an inlet drain; and a connecting pipeline 103, one end of the connecting pipeline 103 being connected to the outlet drain of the waste alkali transfer pump 105, and the other end being connected to the inlet drain of the feed pump 104, and used to introduce the waste alkali liquid generated by the olefin separation unit 101 into the feed system of the wastewater stripping tower 102, so that the waste alkali liquid undergoes a saponification reaction with the oil and wax contaminants attached to the surface of the trays in the wastewater stripping tower 102, thereby removing the oil phase.

[0028] In this application, the wastewater stripping tower cleaning system 100 includes an olefin separation unit 101, a wastewater stripping tower 102, and connecting pipelines 103. Specifically, the olefin separation unit 101 is equipped with a waste alkali external pump 105, which has an outlet drain. During operation, the olefin separation unit 101 generates waste alkali liquid, which mainly originates from the waste alkali washing system of the olefin separation unit and is used to remove acidic gases from the cracked gas. Therefore, the waste alkali liquid contains alkaline substances such as sodium hydroxide. These alkaline substances have strong saponification capabilities and can undergo saponification reactions with oily substances.

[0029] The wastewater stripping tower 102 is equipped with a feed pump 104, which has an inlet drain. The wastewater stripping tower 102 is the core equipment of the wastewater treatment unit in a methanol-to-olefins plant. Its main function is to strip unreacted oxygen-containing compounds and those generated during the reaction from the water and return them to the reactor for reprocessing, while ensuring that the purified process water meets discharge or reuse requirements. In actual operation, due to side reactions in the reaction system, large molecular hydrocarbons generated enter the water washing system with the reaction gas. These hydrocarbons mix with impurities such as oil and wax, and a small amount of catalyst powder carried in the wash water, and then enter the wastewater stripping tower 102 together. Under the high-temperature conditions inside the stripping tower, this mixture gradually adheres to and deposits on the surface of the trays, forming an oil and wax caking layer. This leads to tray blockage, increased tower pressure differential, and decreased stripping efficiency, severely affecting the long-term stable operation of the wastewater stripping tower 102.

[0030] To address the aforementioned issues, this application introduces the waste alkaline solution generated by the olefin separation unit 101 into the feed system of the wastewater stripping tower 102 via a connecting pipeline 103. Specifically, one end of the connecting pipeline 103 is connected to the outlet drain of the waste alkaline external pump 105, and the other end is connected to the inlet drain of the feed pump 104. During system operation, the waste alkaline solution, after being pressurized by the waste alkaline external pump 105, enters the connecting pipeline 103 through the outlet drain, and then enters the feed system of the wastewater stripping tower 102 through the inlet drain of the feed pump 104, ultimately entering the tower along with the feed material. Once inside the wastewater stripping tower 102, the waste alkaline solution comes into full contact with the oily and waxy contaminants adhering to the surface of the tower trays under the high-temperature environment. Because the waste alkaline solution contains alkaline substances such as sodium hydroxide, these alkaline substances undergo a saponification reaction with the oily and waxy contaminants, converting the water-insoluble oily substances into water-soluble carboxylates and glycerol. As the saponification reaction proceeds, the oil and wax slab that was originally firmly attached to the surface of the tray gradually softens, decomposes, and falls off the surface of the tray. The detached reaction products are carried away with the liquid phase flow in the tower, thereby achieving online removal of oil and wax contaminants from the surface of the tray.

[0031] This application's solution utilizes the waste alkaline solution generated by the device itself as the cleaning medium, eliminating the need for additional chemical agents and achieving resource utilization of the waste alkaline solution, thus reducing wastewater treatment costs. Simultaneously, the cleaning process is carried out under normal operating conditions of the wastewater stripping tower 102, eliminating the need for offline shutdown and avoiding production interruptions and economic losses caused by offline cleaning. By removing the oil and wax buildup on the tower tray surface online, the tower throughput is restored, the tower pressure differential is reduced, and the stripping effect and purified water quality are ensured. This significantly extends the operating cycle of the wastewater stripping tower 102 and reduces the labor intensity and operational safety risks associated with manual cleaning.

[0032] In one specific implementation, a control valve is provided on the connecting pipeline 103 for adjusting the injection flow rate of the waste alkali solution.

[0033] In this application, to further optimize the injection control of waste alkali solution, a control valve is installed on the connecting pipeline 103 to regulate the injection flow rate of waste alkali solution. During actual operation, the content of oily and waxy pollutants in the feed of the wastewater stripping tower 102 is not constant but varies with fluctuations in the upstream reaction conditions. When side reactions intensify, the amount of macromolecular hydrocarbons and oily and waxy substances entering the wastewater stripping tower 102 increases, accelerating the accumulation of deposits on the tower tray surface. In this case, it is necessary to appropriately increase the injection volume of waste alkali solution to ensure that the saponification reaction can completely remove the oily and waxy crust on the tower tray surface. Conversely, when the upstream conditions are stable and the oily and waxy content in the feed is low, excessive injection of waste alkali solution will not only waste alkaline resources but may also affect the normal stripping process within the wastewater stripping tower 102, and even lead to an increase in the pH value of the purified water, affecting the water quality compliance for discharge.

[0034] Therefore, this application installs a control valve on the connecting pipeline 103 to control the injection flow rate of waste alkali solution by adjusting the valve opening. Operators can adjust the opening of the control valve according to the operating parameters of the wastewater stripping tower 102, such as the tower pressure difference trend and the purified water quality analysis results, to match the waste alkali solution injection volume with the degree of oil and wax contamination within the tower.

[0035] In one specific implementation, the connecting pipeline 103 is also provided with a one-way valve, which is used to prevent the material in the wastewater stripping tower 102 from flowing back into the olefin separation unit 101.

[0036] In this application, to prevent backflow of materials and potential safety accidents, a one-way valve is installed on the connecting pipeline 103. This one-way valve prevents materials in the wastewater stripping tower 102 from flowing back into the olefin separation unit 101. Those skilled in the art will understand that under abnormal operating conditions, such as an unexpected shutdown of the waste alkali delivery pump 105 causing a sudden drop in outlet pressure, the pressure on the wastewater stripping tower 102 side may be higher than that on the olefin separation unit 101 side, causing the materials inside the tower to flow backwards along the connecting pipeline 103. The materials in the wastewater stripping tower 102 contain oxygen-containing compounds, oils, waxes, and catalyst powder. If they flow back into the olefin separation unit 101, they may contaminate the product, clog equipment, disrupt the water balance, and seriously affect the stable operation of the unit. Therefore, this application installs a one-way valve on the connecting pipeline 103, utilizing its one-way flow characteristic to ensure that the medium can only flow from the olefin separation unit 101 to the wastewater stripping tower 102. When a backflow trend occurs, the one-way valve automatically closes, cutting off the reverse channel, effectively preventing material backflow, and ensuring the safe and stable operation of the unit.

[0037] In one specific implementation, the system further includes a pH monitoring device and a controller. The pH monitoring device is installed in the purified water outlet pipeline of the wastewater stripping tower 102 or inside the tower, and is used to monitor the pH value of the purified water in real time. The controller is electrically connected to the pH monitoring device and the control valve, and is used to automatically adjust the opening degree of the control valve according to the feedback signal from the pH monitoring device.

[0038] In this application, to achieve precise control of the waste alkali injection volume, the system also includes a pH monitoring device and a controller. The pH monitoring device is installed in the purified water outlet pipeline of the wastewater stripping tower 102 or inside the tower, and is used to monitor the pH value of the purified water in real time; the controller is electrically connected to the pH monitoring device and the control valve, and is used to automatically adjust the opening degree of the control valve according to the feedback signal from the pH monitoring device.

[0039] Those skilled in the art will understand that the main components of waste alkali solution are alkaline substances such as sodium hydroxide, and its injection volume directly affects the pH value of the purified water. If the injection volume is insufficient, the saponification reaction will be incomplete, and the removal of oil and wax from the tray surface will be ineffective; if the injection volume is too large, it may cause the pH value of the purified water to rise, exceeding the discharge standards and causing an environmental accident. Therefore, using the pH value of the purified water as a control indicator to achieve closed-loop control of the waste alkali solution injection volume is crucial to ensuring the cleaning effect and water quality compliance.

[0040] In practice, the pH monitoring device collects the pH value of the purified water in real time and transmits the detection signal to the controller. The controller has preset upper and lower pH ranges and compares the received real-time pH value with the preset range. When the real-time pH value is lower than the preset lower limit, it indicates that the amount of waste alkali injected is insufficient, and the controller sends an opening command to the control valve to increase the amount of waste alkali injected; when the real-time pH value is higher than the preset upper limit, it indicates that the amount of waste alkali injected is too large, and the controller sends a closing command to the control valve to reduce the amount of waste alkali injected; when the real-time pH value is within the preset range, the controller maintains the current opening degree of the control valve.

[0041] The proposed solution utilizes the aforementioned closed-loop control method, enabling the system to automatically adjust the amount of waste alkali solution injected based on changes in the pH value of the purified water, ensuring that the pH value remains stable within the target range. This automatic control mode not only guarantees the full progress of the saponification reaction and effectively removes oil and wax contaminants from the surface of the trays, but also avoids the risk of water quality exceeding standards due to lag or inaccuracy in manual adjustments, thereby improving the system's automation level and operational reliability.

[0042] In one specific implementation, the inlet of the feed pump 104 of the wastewater stripping tower is also connected to a settling tank 107, which is used to perform settling pretreatment on the feed entering the wastewater stripping tower 102 to separate some of the oil, wax and solid impurities carried in the feed.

[0043] In the scheme of this application, the inlet of the feed pump 104 of the sewage stripping tower is also connected to a settling tank 107. The settling tank 107 is used to perform settling pretreatment on the feed entering the sewage stripping tower and separate out some of the oil, wax and solid impurities carried in the feed.

[0044] Those skilled in the art will understand that in a methanol-to-olefins (MTO) unit, the feed to the wastewater stripping tower mainly comes from wash water and condensate from the compressor section of the olefin separation unit. Due to side reactions in the reaction system, the generated large molecular hydrocarbons enter the wash system with the reaction gas, mixing with impurities such as oil, wax, and small amounts of catalyst powder carried in the wash water, and then enter the feed system of the wastewater stripping tower. If these impurities enter the tower directly, they will adhere to and deposit on the surface of the trays, accelerating tray blockage and affecting the stripping effect and operating cycle.

[0045] To address the aforementioned issues, this application incorporates a settling tank before the feed pump inlet. The feed material first enters the settling tank, where the density difference between oil, wax, solid impurities, and water allows for initial separation under gravity. The less dense oil and wax substances float to the surface, while the denser solid particles sink to the bottom. The relatively clean aqueous phase in the middle layer is then pumped into a wastewater stripping tower for further treatment. An oil collection trough or skimming device can be installed at the top of the settling tank to periodically remove the floating oil and wax; a drain outlet can be installed at the bottom to periodically remove the deposited solid impurities.

[0046] In some embodiments, the diameter of the connecting pipeline 103 is 10-30 mm. The selection of the diameter of the connecting pipeline 103 has a significant impact on the injection flow control of waste alkali solution and the stability of system operation. Taking into account process requirements, ease of operation, and economy, the diameter of the connecting pipeline 103 is 10-30 mm, preferably 20 mm.

[0047] In one specific implementation, a filter is provided between the outlet of the waste alkali transfer pump 105 of the olefin separation unit 101 and the connecting pipeline 103 to remove solid impurities from the waste alkali solution.

[0048] In this application, to ensure the cleanliness of the waste alkali solution and the reliability of system operation, a filter is installed between the outlet of the waste alkali external pump 105 of the olefin separation unit 101 and the connecting pipeline 103. This filter is used to remove solid impurities from the waste alkali solution. Those skilled in the art will understand that the waste alkali solution generated by the olefin separation unit 101 may contain small amounts of solid impurities, including metal fragments from equipment corrosion, welding slag residue from construction, and precipitates generated from the reaction. If these impurities enter the connecting pipeline 103 directly without treatment, it may cause the control valves to become clogged or jammed, or the valves to malfunction, or they may deposit on the trays of the wastewater stripping tower 102, exacerbating the blockage and affecting the cleaning effect.

[0049] Therefore, this application includes a filter installed between the outlet of the waste alkali transfer pump 105 and the connecting pipeline 103. The waste alkali solution, after being pressurized by the waste alkali transfer pump 105, enters the filter, where solid impurities are removed by the filter screen. The cleaned waste alkali solution then enters the connecting pipeline 103 and is transported to the wastewater stripping tower 102. Additionally, a drain valve is installed at the bottom of the filter to facilitate the periodic discharge of trapped impurities.

[0050] In one specific implementation, the purified water outlet pipeline of the wastewater stripping tower 102 is connected to a purified water pump 106, which is used to transport the purified process water to subsequent processes or a reuse system.

[0051] In the scheme of this application, the purified water outlet pipeline of the wastewater stripping tower 102 is connected to a purified water pump 106, which is used to transport the purified process water to the subsequent process section or the reuse system.

[0052] Those skilled in the art will understand that the wastewater stripping tower 102, as the core equipment of the wastewater treatment unit in a methanol-to-olefins plant, primarily functions to strip unreacted oxygen-containing compounds and those generated during the reaction from the water and return them to the reactor for reprocessing, while ensuring that the purified process water meets discharge or reuse requirements. The purified water after stripping has reduced its oxygen content to within acceptable limits and can be reused as process makeup water in the production system, or further treated to meet discharge standards.

[0053] In the actual process flow, the purified water collected from the bottom or side of the wastewater stripping tower 102 is led out through the purified water outlet pipeline, on which a purified water pump 106 is installed to provide power for the transportation of the purified water. After pressurizing the purified water, the purified water pump 106 delivers it to a designated destination according to the design requirements of the unit. Common destinations include: as makeup water for the quench tower, as washing water for the scrubbing tower, as pretreatment water for the boiler feedwater system, or as transported to a wastewater treatment plant for advanced treatment.

[0054] In one specific implementation, the connecting pipeline 103 is also equipped with a flow meter and a pressure gauge for real-time monitoring of the injection flow rate and pressure of the waste alkali solution.

[0055] In this application, to achieve real-time monitoring of the waste alkali injection process, a flow meter and a pressure gauge are installed on the connecting pipeline 103 to monitor the injection flow rate and pressure of the waste alkali, respectively. Those skilled in the art will understand that flow rate is a key parameter affecting the saponification reaction effect. By reading the waste alkali flow rate in real time through the flow meter, operators can control the flow rate within a reasonable range based on changes in tower pressure differential and water quality analysis results, combined with control valves, ensuring cleaning effectiveness while avoiding over-injection. Pressure is an important basis for judging the system's operating status. Monitoring the injection pressure through the pressure gauge can promptly detect problems such as filter blockage, valve malfunction, or pump abnormal operation, preventing excessive pressure leading to leakage risks or insufficient pressure preventing successful injection.

[0056] This application enables real-time monitoring of the waste alkali injection process by installing flow meters and pressure gauges, providing operators with operational data support, facilitating timely parameter adjustments and equipment status assessment, and improving the system's operability and operational safety.

[0057] In one specific implementation, the outlet of the waste alkali transfer pump 105 of the olefin separation unit 101 is connected to multiple connecting pipelines 103, which are respectively connected to the inlet drains of the feed pumps 104 of multiple sets of wastewater stripping towers 102.

[0058] In the scheme of this application, in order to improve the utilization efficiency of waste alkali liquid and the system integration, the outlet of the waste alkali external pump 105 of the olefin separation unit 101 is connected to multiple connecting pipelines 103, which are respectively connected to the inlet drain of the feed pump 104 of multiple sets of sewage stripping towers 102.

[0059] Those skilled in the art will understand that in large-scale methanol-to-olefins (MTO) plants, multiple wastewater stripping towers 102 are typically configured and operate in parallel. Each tower faces the problem of tray clogging and requires online cleaning. Setting up a separate waste alkali supply system for each tower would increase the number of equipment and raise investment costs. To address this, this application adopts a centralized supply and decentralized injection method. Multiple parallel connecting pipelines 103 are installed at the outlet of the waste alkali external pump 105, each pipeline independently connected to the inlet drain of the corresponding wastewater stripping tower's feed pump 104. Each pipeline can be independently equipped with control valves and other instruments to achieve independent control of the waste alkali injection volume for a single tower. Operators can adjust the waste alkali injection volume of each branch pipeline according to the operating status of each tower, such as changes in tower pressure differential, to achieve differentiated cleaning control.

[0060] Through the above configuration, this application enables a single waste alkali supply system to simultaneously serve multiple wastewater stripping towers 102, improving equipment utilization, reducing investment costs, and making operation more flexible, thereby achieving optimal resource allocation.

[0061] In some embodiments, this application provides a method for cleaning a wastewater stripping tower 102 using the aforementioned wastewater stripping tower cleaning system 100, comprising the following steps: starting the waste alkali external pump 105 of the olefin separation unit 101; opening the outlet drain valve of the waste alkali external pump 105 and the inlet drain valve of the wastewater stripping tower 102 feed pump 104; injecting waste alkali solution into the feed system of the wastewater stripping tower 102 through the connecting pipeline 103; allowing the waste alkali solution to undergo a saponification reaction with the oil and wax contaminants adhering to the surface of the trays in the wastewater stripping tower 102, thereby removing the oil phase. During the waste alkali solution injection process, the pH value of the purified water is monitored in real time, and the injection volume of waste alkali solution is adjusted according to the pH value.

[0062] In this application, the method for online cleaning using the aforementioned wastewater stripping tower 102 cleaning system includes the following steps: First, the waste alkali external pump 105 of the olefin separation unit 101 is started to provide power for conveying the waste alkali solution. After the waste alkali external pump 105 is running normally, the waste alkali solution is drawn from the waste alkali washing system of the olefin separation unit 101 and prepared to be transported to the wastewater stripping tower 102. Second, the outlet drain valve of the waste alkali external pump 105 and the inlet drain valve of the feed pump 104 of the wastewater stripping tower 102 are opened to connect both ends of the connecting pipeline 103. After the two valves are opened, the waste alkali solution enters the connecting pipeline 103 through the outlet drain of the waste alkali external pump 105, and then enters the feed system of the wastewater stripping tower 102 through the inlet drain of the feed pump 104, finally entering the tower along with the feed of the wastewater stripping tower 102. Subsequently, the waste alkali solution comes into full contact with the oil and wax contaminants adhering to the surface of the tower trays inside the wastewater stripping tower 102. The alkaline substances such as sodium hydroxide in the waste alkaline solution undergo a saponification reaction with oil and wax contaminants, converting water-insoluble oily substances into water-soluble carboxylates and glycerol. This causes the oil and wax caking layer to detach from the surface of the tray and be carried away with the liquid phase flow in the tower, thereby achieving online removal of the oil phase from the tray.

[0063] It is worth noting that the pH value of the purified water is monitored in real time throughout the entire process of waste alkali injection, and the injection volume of waste alkali is dynamically adjusted according to changes in pH. The pH value of the purified water is a key indicator of whether the waste alkali injection is appropriate: if the pH value is too low, it indicates that the amount of waste alkali injected is insufficient, the saponification reaction is incomplete, and the control valve needs to be opened wider to increase the injection volume; if the pH value is too high, it indicates that the amount of waste alkali injected is too large, which may affect the water quality compliance, and the control valve needs to be closed wider to reduce the injection volume. Through this closed-loop control method, the pH value of the purified water is maintained within the target range, ensuring both sufficient saponification reaction and stable compliance of the purified water quality.

[0064] The method provided in this solution is implemented under normal operating conditions of the wastewater stripping tower 102, requiring no offline shutdown, and is simple, safe, and reliable to operate. By injecting waste alkali solution online to remove oil and wax contaminants from the tower trays, the tower throughput can be effectively restored, the tower pressure differential reduced, the operating cycle of the wastewater stripping tower 102 extended, the frequency and labor intensity of manual cleaning reduced, and the waste alkali solution can be utilized as a resource, thus reducing environmental disposal costs.

[0065] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A cleaning system (100) for a wastewater stripping tower, characterized in that, include: An olefin separation unit (101) is provided with a waste alkali transfer pump (105), and the waste alkali transfer pump (105) is provided with an outlet drain. Wastewater stripping tower (102), on which a feed pump (104) is provided, the feed pump (104) having an inlet drain; and A connecting pipeline (103) is provided, one end of which is connected to the outlet drain of the waste alkali transfer pump (105), and the other end is connected to the inlet drain of the feed pump (104). The pipeline is used to introduce the waste alkali liquid generated by the olefin separation unit (101) into the feed system of the wastewater stripping tower (102), so that the waste alkali liquid reacts with the oil and wax contaminants attached to the surface of the tray in the wastewater stripping tower (102) to remove the oil phase.

2. The cleaning system according to claim 1, characterized in that, The connecting pipeline (103) is equipped with a control valve for adjusting the injection flow rate of waste alkali solution.

3. The cleaning system according to claim 2, characterized in that, The connecting pipeline (103) is also equipped with a one-way valve, which is used to prevent the material in the sewage stripping tower (102) from flowing back into the olefin separation unit (101).

4. The cleaning system according to claim 2, characterized in that, The system also includes a pH monitoring device and a controller. The pH monitoring device is installed in the purified water outlet pipeline or inside the wastewater stripping tower (102) to monitor the pH value of the purified water in real time. The controller is electrically connected to the pH monitoring device and the control valve and is used to automatically adjust the opening of the control valve according to the feedback signal from the pH monitoring device.

5. The cleaning system according to any one of claims 1-4, characterized in that, The feed pump (104) of the wastewater stripping tower is also connected to a settling tank (107) at its inlet. The settling tank (107) is used to perform settling pretreatment on the feed entering the wastewater stripping tower (102) to separate some of the oil, wax and solid impurities carried in the feed.

6. The cleaning system according to any one of claims 1-4, characterized in that, A filter is provided between the outlet of the waste alkali external pump (105) of the olefin separation unit (101) and the connecting pipeline (103) to remove solid impurities in the waste alkali solution.

7. The cleaning system according to any one of claims 1-4, characterized in that, The purified water outlet pipeline of the wastewater stripping tower (102) is connected to a purified water pump (106), which is used to transport the purified process water to subsequent processes or a reuse system.

8. The cleaning system according to any one of claims 1-4, characterized in that, The outlet of the waste alkali transfer pump (105) of the olefin separation unit (101) is connected to multiple connecting pipelines (103), which are respectively connected to the inlet drain of the feed pump (104) of multiple sets of sewage stripping towers (102).

9. A method for cleaning a wastewater stripping tower (102) using a cleaning system (100) of any one of claims 1 to 8, characterized in that, Includes the following steps: Start the waste alkali transfer pump (105) of the olefin separation unit (101); Open the outlet drain valve of the waste alkali transfer pump (105) and the inlet drain valve of the feed pump (104) of the wastewater stripping tower (102); Waste alkaline solution is injected into the feed system of the wastewater stripping tower (102) through the connecting pipeline (103); The waste alkaline solution undergoes a saponification reaction with the oil and wax contaminants attached to the tray surface in the wastewater stripping tower (102), thereby removing the oil phase.

10. The method according to claim 9, characterized in that, During the injection of waste alkali solution, the pH value of the purified water is monitored in real time, and the injection volume of waste alkali solution is adjusted according to the pH value.

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