Online cleaning method for heat exchanger of methanol-to-olefin device
Through the combination of online cleaning methods and chemical cleaning agents, the problem of heat exchanger scale in methanol-to-olefin device is solved, and the equipment is efficient, economical and production stability is achieved.
Patent Information
- Application Number
- CN202510651998.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-20
- Publication Date
- 2025-07-18
AI Technical Summary
In the methanol-to-olefin device, the heat exchanger is fast and the scale is often formed, resulting in poor heat exchange effect, affecting production stability and efficiency.
The online cleaning method is adopted, and the heated condensate is connected to the heat exchanger process side and the circulating water side for rinsing and back-blowing, respectively, and combined with trisodium phosphate and citric acid for alkali washing and pickling washing to remove dirt.
It realizes flexible and safe online cleaning, extends the equipment life, reduces cleaning costs, maintains the heat transfer efficiency and production stability of the heat exchanger, and improves production efficiency and economic benefits.
Smart Images
Figure CN120333221A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of methanol-to-olefins, and in particular, to an online cleaning method for heat exchangers in a methanol-to-olefins device. Background Art
[0002] The methanol-to-olefins (MTO) device is a process for producing low-carbon olefin products mainly composed of ethylene and propylene using methanol as a raw material. Liquid-phase methanol takes heat in the reactor, is heated by a methanol-purified water heat exchanger and a methanol-condensate heat exchanger, vaporizes in a methanol-steam heat exchanger and a methanol-stripping gas heat exchanger, and the vaporized gaseous methanol is superheated in a methanol-reaction gas heat exchanger and enters the reactor in a gaseous form. In the reactor, the gaseous methanol produces a reaction gas mainly composed of ethylene and propylene under the action of a catalyst. The reaction gas exits the reactor, enters the quench water washing system after the catalyst fines carried are recovered by a cyclone separator; in the quench water washing system, the reaction gas is cooled and sent to the downstream olefin separation unit for purification; some oxides and water in the reaction gas are condensed in the water washing tower and enter the sewage stripping tower, the oxides in the water are recovered and sent back to the reactor for recycling, and at the same time, qualified purified water is sent to the sewage treatment unit.
[0003] In the related art, since the methanol-to-olefins device was put into operation, there has been a phenomenon that the heat exchangers in the water system scale quickly and have a large amount of scale, resulting in poor heat exchange effect. Coupled with the dual effects of the continuous rise in temperature and high load, the heat extraction pressure of the heat exchangers in the water system is relatively large. Summary of the Invention
[0004] In order to solve the above technical problem that the heat exchangers scale quickly and have a large amount of scale, resulting in poor heat exchange effect, this application proposes an online cleaning method for heat exchangers in a methanol-to-olefins device.
[0005] In view of this, this application proposes an online cleaning method for heat exchangers in a methanol-to-olefins device, including: isolating the heat exchanger from the methanol-to-olefins production system and discharging the internal medium of the heat exchanger; on the process side of the heat exchanger, connect condensate in a top-down manner for online flushing until there are no visible impurities in the drained liquid; on the circulating water side of the heat exchanger, introduce heated condensate in a top-down manner for online circulating cleaning; open the exhaust port above the process side and add a first volume of condensate, connect plant air to the lower end interface of the process side, and blow the condensate in the heat exchanger in a bottom-up manner. After a preset time, close the plant air and discharge the condensate inside the heat exchanger.
[0006] In some realizable ways, after discharging the condensate inside the heat exchanger, the method further includes: on the process side of the heat exchanger, adding a set amount of trisodium phosphate and a dispersant into the heat exchanger, and adding a second volume of condensate; opening the exhaust port above the process side, connecting the lower end interface of the process side to the plant air, and using the bottom-in and top-out method to backflush the condensate inside the heat exchanger, and introducing condensate into the circulating water side in the top-in and bottom-out manner to heat the process side, and discharging the solution inside the heat exchanger after a first predetermined time to complete the caustic cleaning treatment of the heat exchanger.
[0007] In some realizable ways, after completing the caustic cleaning treatment of the heat exchanger, the method further includes: on the process side of the heat exchanger, adding a preset amount of citric acid and a dispersant into the heat exchanger, and adding a third volume of condensate; opening the exhaust port above the process side, connecting the lower end interface of the process side to the plant air, and using the bottom-in and top-out method to backflush the condensate inside the heat exchanger, and introducing condensate into the circulating water side in the top-in and bottom-out manner to heat the process side, and discharging the solution inside the heat exchanger after a second predetermined time to complete the pickling treatment of the heat exchanger.
[0008] In some realizable ways, after completing the pickling treatment of the heat exchanger, the method further includes: on the process side of the heat exchanger, introducing condensate in the top-in and bottom-out manner for on-line flushing until no visible impurities are discharged from the drain.
[0009] In some realizable ways, when performing the caustic cleaning treatment on the heat exchanger, the pH value range of the mixture of trisodium phosphate, dispersant and condensate is: 9.8 to 10.2; when performing the pickling treatment on the heat exchanger, the pH value range of the mixture of citric acid, dispersant and condensate is: 4.8 to 5.2.
[0010] In some realizable ways, the steps of isolating the heat exchanger from the methanol-to-olefins production system and discharging the internal medium of the heat exchanger specifically include: closing the inlet valves and outlet valves on the process side and the circulating water side of the heat exchanger to isolate the heat exchanger from the system; opening the high-point exhaust valve and the low-point drain valve on the process side and the circulating water side to discharge the internal medium of the heat exchanger.
[0011] In some realizable ways, the temperature range of the heated condensate is: 175°C to 185°C.
[0012] In some realizable ways, the preset time is 24 hours to 72 hours.
[0013] In some realizable ways, the condensate is the liquid formed after the heat exchanger is cooled, and the temperature of the condensate is 128°C to 132°C.
[0014] In some realizable ways, the pressure range of the plant air is 0.7 MPa to 0.85 MPa.
[0015] Compared with the prior art, the present application has the following technical effects:
[0016] The online cleaning method of the heat exchanger of the methanol-to-olefins device provided by the present application is relatively flexible, and the time can be manually controlled; the online cleaning is safer and there is no need to disassemble and assemble the heat exchanger; the online cleaning better protects the equipment, there is no need to disassemble and assemble the heat exchanger and high-pressure water flushing, and the equipment has a longer service life; the online cleaning can effectively control the offline cleaning cost of the heat exchanger and bring considerable economic benefits.
[0017] The additional aspects and advantages of the present application will become apparent in the following description section or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:
[0019] Figure 1 The flow diagram showing the online cleaning method of the heat exchanger of the methanol-to-olefins device in an embodiment of the present application;
[0020] Figure 2 The structural diagram showing the heat exchanger of the methanol-to-olefins device in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] In order to more clearly understand the above objects, features and advantages of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments may be combined with each other.
[0022] Many specific details are set forth in the following description in order to fully understand the present application. However, the present application may be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.
[0023] The following refers to Figure 1 and Figure 2 to describe the online cleaning method of the heat exchanger of the methanol-to-olefins device according to some embodiments of the present application.
[0024] As Figure 1 and Figure 2 shown, the present application proposes an online cleaning method of the heat exchanger of the methanol-to-olefins device, including the following steps:
[0025] S202: Isolate the heat exchanger from the methanol-to-olefins production system and discharge the internal medium of the heat exchanger;
[0026] S204: On the process side of the heat exchanger, condensate is introduced for on-line flushing in the up-inlet and down-outlet manner until no visible impurities are found in the drained liquid.
[0027] S206: On the circulating water side of the heat exchanger, heated condensate is introduced for on-line circulating cleaning in the up-inlet and down-outlet manner; the exhaust port above the process side is opened, and condensate of the first volume is added. The lower-end interface of the process side is connected to plant air, and the condensate inside the heat exchanger is back-blown in the down-inlet and up-outlet manner. After a preset time, the plant air is closed, and the condensate inside the heat exchanger is drained.
[0028] The on-line cleaning method for the heat exchanger of the methanol-to-olefins device provided by this application can make full use of the flow characteristics and thermal energy effect of the condensate to perform on-line cleaning of the heat exchanger by introducing condensate for on-line flushing in the up-inlet and down-outlet manner on the process side of the heat exchanger and introducing heated condensate for on-line circulating cleaning in the up-inlet and down-outlet manner on the circulating water side. Further, the condensate of the first volume can fill the internal space of the condenser. After the condenser is filled with condensate, plant air is connected to the lower-end interface of the process side. The plant air can provide the power to agitate the condensate, enabling the condensate to come into full contact with the scale on the inner wall of the heat exchanger. The flowing condensate will continuously touch and impact the scale, causing the scale to loosen and dissolve in the condensate, and then be discharged from the heat exchanger along with the condensate.
[0029] Compared with the traditional off-line cleaning, the on-line cleaning method provided by this application is more flexible, the time can be manually controlled, the on-line cleaning is safer, and there is no need to disassemble and assemble the heat exchanger. By performing timely and effective on-line cleaning of the heat exchanger, the dirt accumulated inside the heat exchanger can be removed in time, and the heat transfer efficiency and heat exchange performance of the heat exchanger can be maintained stable. It helps to maintain the stability of process parameters such as temperature and pressure during the production process of the methanol-to-olefins device, reduce production fluctuations caused by the decline in the performance of the heat exchanger, and provide a reliable guarantee for the stable operation of the device. After the cleaning is completed, the heat exchanger can quickly return to the normal working state, effectively reducing the production interruption time caused by the heat exchanger cleaning, ensuring the high-efficiency continuous production of the device, and improving the overall production efficiency.
[0030] The on-line cleaning method for the heat exchanger of the methanol-to-olefins device provided by this application does not require the heat exchanger to be disassembled from the device for cleaning, can effectively control the cost of off-line cleaning of the heat exchanger, and brings considerable economic benefits.
[0031] In some embodiments provided by the present application, after discharging the condensate inside the heat exchanger, the method further includes: on the process side of the heat exchanger, adding a set amount of trisodium phosphate and a dispersant into the heat exchanger, and adding a second volume of condensate; opening the exhaust port above the process side, connecting the lower end interface of the process side to plant air, and using the bottom-in and top-out method to backflush the condensate inside the heat exchanger, and introducing condensate in the top-in and bottom-out manner on the circulating water side to heat the process side, and discharging the solution inside the heat exchanger after a first predetermined time to complete the caustic washing treatment of the heat exchanger.
[0032] In this embodiment, trisodium phosphate has strong alkalinity and can react with oil stains, organic impurities, etc. on the inner wall of the process side of the heat exchanger through saponification reaction to convert them into water-soluble substances, thereby effectively removing stubborn dirt that is difficult to remove by rinsing. The dispersant can reduce the surface tension between dirt particles, prevent them from re-aggregating and depositing, ensure that the dirt is evenly dispersed in the solution, further enhance the cleaning effect, make the internal channels of the heat exchanger cleaner, and restore the high-efficiency heat transfer performance.
[0033] Through the combined action of bottom-in and top-out plant air backflushing and introducing heated condensate in the top-in and bottom-out manner on the circulating water side, the airflow generated by the backflushing can agitate the solution, enabling trisodium phosphate and the dispersant to fully contact the inner wall of the heat exchanger. At the same time, heating can increase the chemical reaction rate and the solubility of dirt, achieving a full-scale cleaning of all corners and complex structures inside the heat exchanger, avoiding cleaning dead corners, and ensuring the consistency and reliability of the cleaning quality.
[0034] Under appropriate concentrations and operating conditions, the trisodium phosphate solution has relatively low corrosivity to the metal material of the heat exchanger, and the dispersant can form a protective film on the metal surface, reducing the direct contact between the solution and the metal and reducing the possibility of corrosion. At the same time, the gentle backflushing operation and heating method will not cause excessive mechanical impact and thermal stress on the inner wall of the heat exchanger, thereby protecting the structural integrity of the heat exchanger and extending the service life of the equipment.
[0035] After the caustic washing treatment, the internal channels of the heat exchanger are unobstructed, and the heat transfer efficiency is significantly improved. It can transfer heat to or take heat away from the process medium more stably, maintain the stability of process parameters such as temperature and pressure during the production process of the methanol-to-olefins plant, reduce production instability factors caused by fluctuations in the performance of the heat exchanger, and ensure the efficient and continuous production of the plant.
[0036] In actual applications, after adding about 25 Kg of trisodium phosphate, 100 Kg of dispersant and filling up the condensate on the process side, connect the bottom-in and top-out to plant air for backflushing, and connect the top-in and bottom-out on the circulating water side to the heated condensate to heat the process side, and discharge the solution inside the heat exchanger after no less than 24 hours.
[0037] In some embodiments provided by the present application, after the caustic cleaning treatment of the heat exchanger is completed, the method further includes: on the process side of the heat exchanger, adding a preset amount of citric acid and a dispersant into the heat exchanger, and adding a third volume of condensate; opening the exhaust port above the process side, connecting the lower end interface of the process side to plant air, and performing backwashing on the condensate in the heat exchanger in a bottom-up manner, and introducing the condensate into the circulating water side in a top-down manner to heat the process side. After a second predetermined time, the solution in the heat exchanger is drained to complete the pickling treatment of the heat exchanger.
[0038] In this embodiment, as an acidic medium, citric acid can chemically react with inorganic scales such as metal oxides and water scales remaining after caustic cleaning, dissolve them into soluble substances, and thoroughly remove stubborn scales that are difficult to remove by caustic cleaning. The dispersant can prevent the scale from precipitating and reattaching, evenly disperse the scale in the solution, ensure that the dirt on all parts of the inner wall of the heat exchanger is effectively removed, achieve deep purification, and restore the high-efficiency heat transfer performance of the heat exchanger.
[0039] Under appropriate concentrations and operations, the citric acid solution has low corrosivity to the metal material of the heat exchanger, and the protective film formed by the dispersant can further reduce the corrosion risk. Gentle backwashing and heating operations avoid causing mechanical damage and excessive thermal stress to the inner wall of the heat exchanger, protect the structural integrity of the equipment, extend the service life, and reduce the maintenance cost and production interruption caused by equipment damage. After pickling treatment, the inside of the heat exchanger is clean, and the heat transfer efficiency is stable, which helps to accurately control process parameters such as temperature and pressure in the production of the methanol-to-olefins plant, reduce production fluctuations, ensure the high-efficiency and continuous operation of the plant, improve the product purity and quality, reduce the reject rate, and enhance the economic benefits of the enterprise.
[0040] In actual applications, after adding about 10 Kg of citric acid, 100 Kg of dispersant and filling the condensate on the process side, backwashing is performed by connecting plant air in a bottom-up manner, and the condensate after heating is introduced into the circulating water side in a top-down manner to heat the process side. After no less than 24 hours, the solution inside the heat exchanger is drained.
[0041] In some embodiments provided by the present application, after the pickling treatment of the heat exchanger is completed, the method further includes: on the process side of the heat exchanger, connecting the condensate in a top-down manner for on-line flushing until no visible impurities are discharged from the drain.
[0042] In this embodiment, reaction products, incompletely reacted citric acid, dispersants and other impurities will remain in the heat exchanger after pickling. By adopting the on-line flushing method of condensate with upward inlet and downward outlet, with the help of the gravity and flow scouring force of the condensate, the residual impurities in all corners of the heat exchanger can be quickly flushed out completely, ensuring that the inside of the heat exchanger is clean and free of dirt, and avoiding the adverse effects of impurities on the equipment operation and product quality in subsequent production. Timely removal of residual impurities can prevent them from redepositing on the inner wall of the heat exchanger to form dirt, maintain the high-efficiency heat transfer performance of the heat exchanger, ensure the stability of process parameters, reduce production failures caused by equipment performance fluctuations, reduce the equipment maintenance frequency and cost, and extend the service life of the heat exchanger.
[0043] In some embodiments provided by the present application, when the heat exchanger is subjected to caustic washing treatment, the pH value range of the mixed solution of trisodium phosphate, dispersant and condensate is: 9.8 to 10.2; when the heat exchanger is subjected to pickling treatment, the pH value range of the mixed solution of citric acid, dispersant and condensate is: 4.8 to 5.2.
[0044] In this embodiment, during caustic washing, the trisodium phosphate mixed solution with a pH value between 9.8 and 10.2 has a suitable alkalinity and can fully react with oil stains, organic impurities, etc. in the heat exchanger through saponification and other reactions, converting them into soluble substances for efficient removal. The dispersant can prevent the secondary deposition of dirt and ensure thorough cleaning. During pickling, the citric acid mixed solution with a pH value between 4.8 and 5.2 has a moderate acidity and can fully react and dissolve with inorganic scales such as metal oxides and water scales. The dispersant evenly disperses the scale substances to achieve deep scale removal and restore the high-efficiency heat transfer performance of the heat exchanger. Within this pH range, the acid and caustic washing mixed solutions have little corrosiveness to the metal material of the heat exchanger, will not damage the equipment structure due to excessive corrosion, ensure the integrity of the equipment, extend the service life, and reduce the maintenance cost and production interruption caused by equipment damage. Precise pH value control can stabilize the cleaning effect, avoid equipment performance fluctuations caused by incomplete cleaning or over-cleaning, maintain the stability of parameters such as temperature and pressure in the methanol-to-olefins production process, and ensure continuous and efficient operation of production.
[0045] In actual applications, the chemical dosage is based on the pH value after the condensate is filled to the full. The pH value of the caustic washing liquid medicine is about 10, and the pH value of the pickling liquid medicine is about 5.
[0046] In some embodiments provided by the present application, the step of isolating the heat exchanger from the methanol-to-olefins production system and discharging the internal medium of the heat exchanger specifically includes: closing the inlet valves and outlet valves on the process side and the circulating water side of the heat exchanger to isolate the heat exchanger from the system; opening the high-point exhaust valves and low-point drain valves on the process side and the circulating water side to discharge the internal medium of the heat exchanger.
[0047] In this embodiment, by closing the inlet and outlet valves on the process side and the circulating water side, the heat exchanger can be quickly and reliably completely isolated from the methanol-to-olefins production system, cutting off the flow path of the medium between the heat exchanger and the system, avoiding mutual contamination of the cleaning liquid and the production medium during subsequent cleaning operations, preventing possible dangerous chemical reactions, and ensuring the safety of the entire production system and personnel.
[0048] Opening the high-point exhaust valve and the low-point drain valve can effectively discharge the medium in the heat exchanger, simultaneously release the internal pressure, prevent equipment damage and explosion risks caused by sudden pressure increase due to temperature changes during cleaning, and also avoid excessive overflow of the medium during cleaning, reducing environmental pollution and safety threats.
[0049] In some embodiments provided by the present application, the temperature range of the heated condensate is: 175°C to 185°C.
[0050] In this embodiment, during the cleaning process, the circulating water side is cleaned with heated condensate at a specific temperature (175°C to 185°C). While cleaning, the heat exchanger can be heated using the heated condensate. After being heated, the heat exchanger can effectively dissolve and peel off dirt, improving the cleaning effect.
[0051] In a preferred embodiment, the condensate is heated to 180°C, and the heated condensate is introduced into the circulating water side in a top-in and bottom-out manner to heat the process side.
[0052] In some embodiments provided by the present application, the preset time is 24 hours to 72 hours.
[0053] In this embodiment, the ventilation preset time of general plant air is controlled between 24 hours and 72 hours. Depending on the type of heat exchanger, the time for introducing plant air is also different. For heat exchangers that are prone to fouling or where the fouling is not easily shed, a longer time of plant air introduction is required to ensure the cleaning effect.
[0054] In some embodiments provided by the present application, the condensate is the liquid formed after the heat exchanger is cooled, and the temperature of the condensate is 128°C to 132°C.
[0055] In this embodiment, the heat exchanger includes a low-pressure steam heat exchanger and a very-low-pressure steam heat exchanger. The low-pressure steam heat exchanger refers to the bottom reboiler of the sewage stripper in the methanol-to-olefins production system, and the very-low-pressure steam heat exchanger refers to the methanol vaporizer. The condensate at 128°C to 132°C has relatively high heat energy, which can accelerate the reaction between the chemical cleaning agent and the dirt in the heat exchanger, enhance the dissolution ability of stubborn impurities such as oil stains and water scales, improve the cleaning efficiency and effect, and shorten the cleaning time.
[0056] High temperature enhances the fluidity of the condensate and increases the scouring force, which can more thoroughly remove the dirt in the dead corners and complex structures inside the heat exchanger, ensure the cleanliness inside the heat exchanger, and restore the high-efficiency heat transfer performance.
[0057] In a preferred embodiment, the temperature of the condensate is 130 °C.
[0058] In some embodiments provided by the present application, the pressure range of the plant air is 0.7 MPa to 0.85 MPa.
[0059] In this embodiment, the pressure of the plant air is 0.7 MPa to 0.85 MPa. The plant air within this pressure range can generate sufficient air flow power, which can fully stir the condensate, accelerate its chemical reaction with the dirt, make the condensate fully contact with the scale on the inner wall of the heat exchanger. The moving condensate will continuously touch and impact the scale, loosen the scale, dissolve it into the condensate, and then be discharged from the heat exchanger with the condensate, improving the cleaning efficiency and quality.
[0060] In actual applications, according to the actual operation status, a combination of offline maintenance and online cleaning of the heat exchanger can be adopted. The online cleaning method of this heat exchanger is more suitable for the situation where there is oil sludge on the shell side and the tube side is relatively clean.
[0061] 1. Online cleaning is more flexible and the time can be manually controlled.
[0062] 2. Online cleaning is safer and there is no need to disassemble and assemble the heat exchanger.
[0063] 3. Online cleaning better protects the equipment. There is no need to disassemble and assemble the heat exchanger and perform high-pressure water flushing, so the equipment has a longer service life.
[0064] 4. Although the cleaning effect of online cleaning is not as thorough as offline cleaning, it is more economical, and the cleaning effect can maintain about 50 - 80% of that of offline cleaning.
[0065] 5. The expected annual economic benefit is 885,000 yuan / year.
[0066] According to the actual operation situation, currently the key points of online cleaning of the heat exchangers in the water system are the water-cooled coolers (E1204A - F), water-cooled coolers (E1205A - H), hydrocyclone water-cooled coolers (E1207AB), and purified water-cooled coolers (E1209A - C).
[0067] Specifically, E1204 is normally cleaned 3 rounds (18 times) per year. After using on-line cleaning, it is cleaned offline 2 rounds (12 times), saving 6 times. The cost of single offline maintenance is 60,000 yuan, and the cost of single on-line cleaning is about 0.5 ten thousand yuan, generating an economic benefit of 330,000 yuan. E1205 is normally cleaned 3 rounds (12 times) per year. After using on-line cleaning, it is cleaned offline 2 rounds (8 times), saving 4 times. The cost of single offline maintenance is 75,000 yuan, and the cost of single on-line cleaning is about 0.5 ten thousand yuan, generating an economic benefit of 280,000 yuan; E1207 is normally cleaned 3 rounds (6 times) per year. After using on-line cleaning, it is cleaned offline 2 rounds (4 times), saving 2 times. The cost of single offline maintenance is 60,000 yuan, and the cost of single on-line cleaning is about 0.5 ten thousand yuan, generating an economic benefit of 110,000 yuan; E1209 is normally cleaned 3 rounds (9 times) per year. After using on-line cleaning, it is cleaned offline 2 rounds (6 times), saving 3 times. The cost of single offline maintenance is 60,000 yuan, and the cost of single on-line cleaning is about 0.5 ten thousand yuan, generating an economic benefit of 165,000 yuan. The total annual economic benefit is about 33 + 28 + 11 + 16.5 = 885,000 yuan.
[0068] The following is a detailed description according to two methods: with chemical addition and without chemical addition. The specific operation steps are as follows:
[0069] 1) Mode without chemical addition:
[0070] 1. Completely cut off the heat exchanger and drain the water;
[0071] 2. Connect the condensate to be directly discharged from the upper part to the lower part on the process side until it is visually clean;
[0072] 3. Connect the condensate to be heated from the upper part to the lower part on the circulating water side. After the process side is filled with condensate, connect the plant air for back blowing from the lower part to the upper part. After a period of time, drain the liquid on the process side. Repeat this step until the drained liquid on the process side is visually clean;
[0073] 4. After cleaning is completed, the heat exchanger is put on standby.
[0074] 2) Mode with chemical addition:
[0075] 1. Completely cut off the heat exchanger and drain the water;
[0076] 2. Connect the condensate to be directly discharged from the upper part to the lower part on the process side until it is visually clean;
[0077] 3. Connect the condensate to be heated from the upper part to the lower part on the circulating water side. After the process side is filled with condensate, connect the plant air for back blowing from the lower part to the upper part. After a period of time, drain the liquid on the process side. Repeat this step until the drained liquid on the process side is visually clean;
[0078] 4. Alkaline cleaning: Add about 25 Kg of trisodium phosphate and 100 Kg of dispersant to the process side. After filling the process side with condensate, connect the plant air for back blowing from the lower part to the upper part. Connect the condensate from the upper part to the lower part on the circulating water side to heat the process side. After no less than 24 hours, drain the chemical solution;
[0079] 5. Pickling: Add about 10 Kg of citric acid and 100 Kg of dispersant to the process side. After filling up the condensate, blow it back with plant air in a bottom-in and top-out manner. For the circulating water side, connect it in a top-in and bottom-out manner to the condensate to heat the process side. After no less than 24 hours, drain the liquid medicine; (This step is used as appropriate)
[0080] 6. After draining all the liquid medicine, connect the process side in a top-in and bottom-out manner to directly drain the condensate until it is visually clean;
[0081] 7. After the cleaning is completed, the heat exchanger is put on standby.
[0082] Precautions:
[0083] 1. The above operations shall be carried out in sequence. If there is a problem in a certain step, please check it in time.
[0084] 2. Do not operate the opening and closing of all valves forcefully. In case of valve leakage, you can try to open and close it repeatedly.
[0085] 3. The dosage of the added medicine is based on the pH after filling with water. The pH of the configured caustic cleaning liquid medicine is about 10, and the pH of the pickling is about 5; If splashed by the liquid medicine, clean it in time.
[0086] 4. Pay attention to operating the accompanying heat condensate slowly to prevent scalding.
[0087] 5. In case of leakage of the rubber hose, replace it in a timely manner according to the specific situation.
[0088] 6. Clean the pneumatic diaphragm pump in time after each use to prevent blockage caused by long-term accumulation.
[0089] In this application, the term "a plurality" means two or more, unless otherwise clearly defined. Terms such as "installed", "connected", "connected to", "fixed" and other terms should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific situation.
[0090] In the description of this specification, the description of terms such as "an embodiment", "some embodiments", "specific embodiments" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.
[0091] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.
Claims
1. An on-line cleaning method for a heat exchanger of a methanol-to-olefins device, characterized in that, Including: Isolate the heat exchanger from the methanol-to-olefins production system and discharge the internal medium of the heat exchanger. On the process side of the heat exchanger, introduce condensate for on-line flushing in a top-in and bottom-out manner until there are no visible impurities in the drained liquid. On the circulating water side of the heat exchanger, introduce heated condensate for on-line circulating cleaning in a top-in and bottom-out manner; open the exhaust port above the process side and add a first volume of condensate, connect the lower end interface of the process side to plant air, and blow back the condensate in the heat exchanger in a bottom-in and top-out manner. After a preset time, close the plant air and discharge the condensate inside the heat exchanger.
2. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to claim 1, wherein, After discharging the condensate inside the heat exchanger, the method further includes: On the process side of the heat exchanger, add a set amount of trisodium phosphate and a dispersant into the heat exchanger, and add a second volume of condensate. Open the exhaust port above the process side, connect the lower end interface of the process side to plant air, and blow back the condensate in the heat exchanger in a bottom-in and top-out manner. On the circulating water side, introduce condensate in a top-in and bottom-out manner to heat the process side. After a first predetermined time, drain the solution inside the heat exchanger to complete the caustic washing treatment of the heat exchanger.
3. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to claim 2, wherein, After completing the caustic washing treatment of the heat exchanger, the method further includes: On the process side of the heat exchanger, add a preset amount of citric acid and a dispersant into the heat exchanger, and add a third volume of condensate. Open the exhaust port above the process side, connect the lower end interface of the process side to plant air, and blow back the condensate in the heat exchanger in a bottom-in and top-out manner. On the circulating water side, introduce condensate in a top-in and bottom-out manner to heat the process side. After a second predetermined time, drain the solution inside the heat exchanger to complete the pickling treatment of the heat exchanger.
4. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to claim 3, wherein, After completing the pickling treatment of the heat exchanger, the method further includes: On the process side of the heat exchanger, introduce condensate for on-line flushing in a top-in and bottom-out manner until there are no visible impurities in the drained liquid.
5. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to claim 4, characterized in that, When performing the caustic washing treatment of the heat exchanger, the pH value range of the mixture of trisodium phosphate, dispersant and condensate is: 9.8 to 10.
2. When performing the pickling treatment of the heat exchanger, the pH value range of the mixture of citric acid, dispersant and condensate is: 4.8 to 5.
2.
6. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to any one of claims 1 to 5, characterized in that, The step of isolating the heat exchanger from the methanol-to-olefins production system and discharging the internal medium of the heat exchanger specifically includes: Close the inlet valve and outlet valve on the process side and circulating water side of the heat exchanger to isolate the heat exchanger from the system. Open the high-point exhaust valve and low-point drain valve on the process side and circulating water side to discharge the internal medium of the heat exchanger.
7. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to any one of claims 1 to 5, characterized in that, The temperature range of the heated condensate is: 175°C to 185°C.
8. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to any one of claims 1 to 5, characterized in that, The preset time is 24 hours to 72 hours.
9. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to any one of claims 1 to 5, characterized in that, The condensate is the liquid formed after the heat exchanger is cooled, and the temperature of the condensate is 128°C to 132°C.
10. The online cleaning method of the heat exchanger of the methanol-to-olefins device according to any one of claims 1 to 5, characterized in that, The pressure range of the plant air is 0.7 MPa to 0.85 MPa.