Cleaning method applied to graphite heat exchanger
By combining ultrasonic thickness gauge and citric acid cleaning solution with high-pressure water flushing, the problem of incomplete cleaning of graphite heat exchangers was solved, achieving efficient cleaning and improved corrosion resistance, thus extending the equipment's lifespan.
Patent Information
- Application Number
- CN202610209849.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-13
- Publication Date
- 2026-04-10
AI Technical Summary
Traditional mechanical cleaning methods are insufficient to completely remove fouling from graphite heat exchangers, leading to equipment damage and reduced heat transfer efficiency. Furthermore, these devices are susceptible to shock and high-pressure fluctuations, shortening their lifespan.
An ultrasonic thickness gauge is used to detect the thickness of the dirt. A cleaning solution containing citric acid and corrosion inhibitor is prepared for internal circulation cleaning. Combined with high-pressure water flushing and passivation treatment, a protective film is formed.
It improves descaling efficiency, enhances the corrosion resistance and heat transfer efficiency of graphite heat exchangers, extends equipment service life, and reduces operating costs.
Smart Images
Figure CN121829209A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of heat exchanger cleaning, and particularly relates to a cleaning method applied to a graphite heat exchanger. BACKGROUND
[0002] The graphite heat exchanger is a kind of corrosion-resistant heat exchange equipment widely used in chemical industry, pharmaceutical industry, electroplating industry, metallurgy industry and the like, and is especially suitable for the scene where the heat transfer medium is strong acid, has outstanding corrosion resistance, high thermal conductivity and excellent stability. Although the graphite heat exchanger has excellent corrosion resistance, it is relatively brittle and is not resistant to impact and high pressure fluctuation. If not cleaned regularly, damage is easily caused due to dirt accumulation and blockage, the service life of the equipment is shortened, and the operation cost is increased.
[0003] The traditional mechanical cleaning is difficult to clean the graphite heat exchanger thoroughly. The mechanical cleaning relies on physical force to remove dirt, but for the graphite heat exchanger which is relatively weak in material, it is easy to cause scratches or damage to the pipe wall, and stubborn dirt and deposits located at complex positions cannot be cleaned, resulting in incomplete cleaning and reduced heat transfer efficiency. SUMMARY
[0004] The purpose of the present application is to solve the problems in the prior art and provide a cleaning method applied to a graphite heat exchanger.
[0005] The technical scheme is a cleaning method applied to a graphite heat exchanger, comprising the following steps: S1. Detecting dirt, detecting the dirt thickness of the graphite heat exchanger by an ultrasonic thickness gauge, the ultrasonic thickness gauge emitting high-frequency sound waves to the pipe wall or sheet of the graphite heat exchanger, the high-frequency sound waves propagating inside the graphite heat exchanger, the high-frequency sound waves being reflected when encountering the interface between the dirt layer and the base material, the thickness of the dirt layer being calculated by measuring the time difference from emission to reception of the echo wave, combined with the propagation speed of the high-frequency sound waves, and isolating the positions that do not need to be cleaned; S2. Preparing a cleaning solution, the cleaning solution being prepared according to the following mass percentage: 99-99.5% of citric acid and 0.5-1% of corrosion inhibitor, and being prepared using deionized water or softened water to avoid the calcium and magnesium ions in the water from reacting with the citric acid in advance; the citric acid powder is slowly added into the water while stirring until completely dissolved; the acidity of the cleaning solution is detected by pH test paper; S3. Internal circulation cleaning, the prepared cleaning solution is injected into the graphite heat exchanger, and the circulating pump is used for low-pressure internal circulation flow; the outlet pipe of the circulating pump is connected to the cleaning solution inlet of the graphite heat exchanger, and the cleaning solution recovery pipe is connected to the outlet of the graphite heat exchanger, forming a circulation path from bottom to top; S4. Empty the cleaning liquid, and discharge the cleaned cleaning liquid through the drain pipe. The water is discharged from the top of the graphite heat exchanger, and gradually discharged downward until all the water in the graphite heat exchanger is discharged; S5. Pure water flushing. Connect the pure water supply pipeline to the inlet of the graphite heat exchanger, and connect the outlet to the drainage system. The graphite heat exchanger is flushed with pure water, so that the interior of the graphite heat exchanger is free of cleaning liquid and residual; S6. High-pressure flushing. The inlet and outlet of the graphite heat exchanger are connected to the high-pressure water pipe. The water flow output by the high-pressure water pipe flushes the interior of the graphite heat exchanger. The flushing is performed in a root-by-root manner, so that each graphite pipe is flushed. The discharge at the outlet is checked. When the dirt is completely discharged, the high-pressure pipe is closed; S7. Removing residual moisture. The power supply of the graphite heat exchanger and the connection of the process pipeline are disconnected, and the graphite heat exchanger is ensured to be in a complete stop state. All materials, cooling liquid or heating medium in the graphite heat exchanger are emptied. The interior of the graphite heat exchanger is dried by a drying tool, and there is no residual moisture; S8. Forming a protective film on the surface of the graphite. The grease, dust and oxides on the surface of the graphite heat exchanger are removed before passivation treatment. The surface of the graphite is passivated by a passivation agent to form a protective film.
[0006] Further improvements of the present application are that, in step S3, the duration of the low-pressure internal circulation flow of the circulating pump is 2-4 hours.
[0007] Further improvements of the present application are that, in step S3, the temperature of the low-pressure internal circulation flow of the circulating pump is 40-60 degrees Celsius.
[0008] Further improvements of the present application are that, in step S5, the water pressure of the pure water flushing is 10-15 MPa.
[0009] Further improvements of the present application are that, in step S6, the water pressure of the high-pressure water pipe is 20-30 MPa.
[0010] Further improvements of the present application are that, in step S7, the drying tool includes a hair dryer.
[0011] Further improvements of the present application are that the hair dryer is integrated with a temperature sensor and a humidity sensor.
[0012] Further improvements of the present application are that the passivation agent includes potassium permanganate.
[0013] Compared with the prior art, the cleaning method applied to the graphite heat exchanger provided by the present application at least achieves the following beneficial effects: The present application prepares the cleaning solution by mixing citric acid and corrosion inhibitor, the hydrogen ions in the citric acid react with the alkaline substances such as calcium carbonate and magnesium hydroxide in the dirt to generate soluble calcium citrate, carbon dioxide and water, thereby dissolving the dirt; the carboxyl and hydroxyl groups in the citric acid molecules form stable water-soluble complexes with metal ions such as calcium, magnesium and iron, preventing the ions from re-depositing, thereby improving the dirt removal efficiency; the added corrosion inhibitor can inhibit the slight corrosion of the graphite heat exchanger metal parts by the citric acid, the corrosion inhibitor can form a protective film on the metal surface to isolate the metal matrix from the corrosive environment, thereby blocking the electrochemical corrosion process; the high-pressure flushing forms a high-speed jet flow, directly impacting the dirt on the surface of the graphite heat exchanger, instantaneously generating a huge kinetic energy to make the dirt layer fall off, thereby improving the heat transfer efficiency, reducing the operation cost and prolonging the service life of the equipment. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 The flow chart of the cleaning method applied to the graphite heat exchanger according to the present application. DETAILED DESCRIPTION
[0015] Various exemplary embodiments of the present application will now be described in detail. It should be noted that the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way limiting to the scope of the present application and its applications or uses.
[0016] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as if the techniques, methods, and apparatus were discussed in detail herein. Any examples discussed herein should be understood to be illustrative only and not restrictive. Thus, other examples of the exemplary embodiments could have different values.
[0017] Reference Figure 1 A cleaning method applied to a graphite heat exchanger, comprising the following steps: S1. Detecting dirt, detecting the dirt thickness of the graphite heat exchanger by an ultrasonic thickness gauge, the ultrasonic thickness gauge emits high-frequency sound waves to the tube wall or sheet of the graphite heat exchanger, the high-frequency sound waves propagate inside the graphite heat exchanger, the high-frequency sound waves are reflected when encountering the interface between the dirt layer and the base material, the thickness of the dirt layer is calculated by measuring the time difference from the emission to the reception of the ultrasonic waves, combined with the propagation speed of the high-frequency sound waves, and the parts that do not need to be cleaned are isolated; S2. Prepare the cleaning solution according to the following mass percentages: 99-99.5% citric acid and 0.5-1% corrosion inhibitor. Use deionized water or softened water to avoid premature reaction between calcium and magnesium ions in the water and citric acid. Slowly add the citric acid powder to the water while stirring until completely dissolved. Use pH test paper to test the acidity of the cleaning solution. S3. Internal circulation cleaning: Inject the prepared cleaning solution into the graphite heat exchanger, and the circulation pump performs low-pressure internal circulation; connect the outlet pipe of the circulation pump to the cleaning solution inlet of the graphite heat exchanger, and connect the cleaning solution recovery pipe to the outlet of the graphite heat exchanger to form a bottom-up circulation path. S4. Drain the cleaning fluid. Discharge the cleaning fluid through the drain pipe. When draining, start from the top of the graphite heat exchanger and gradually move downwards until all the water in the graphite heat exchanger is drained. S5. Pure water rinsing: Connect the pure water supply pipeline to the inlet of the graphite heat exchanger and the outlet to the drainage system. Rinse the graphite heat exchanger with pure water to ensure that there is no cleaning fluid or residue inside the graphite heat exchanger. S6. High-pressure flushing: Connect the inlet and outlet of the graphite heat exchanger to the high-pressure water pipe. The water flow output from the high-pressure water pipe flushes the inside of the graphite heat exchanger. Use a flushing method to flush each graphite tube one by one, so that each graphite tube is flushed. Check the discharge at the outlet. When all the dirt is discharged, close the high-pressure pipe. S7. Remove residual moisture, disconnect the power supply and process piping of the graphite heat exchanger to ensure it is completely stopped, drain all materials, coolant or heating medium from the graphite heat exchanger, and use a drying tool to dry the inside of the graphite heat exchanger to ensure no moisture remains, thus avoiding corrosion caused by residual moisture. S8. A protective film is formed on the graphite surface. Before passivation treatment, grease, dust and oxides on the surface of the graphite heat exchanger are removed. The graphite surface is then passivated with a passivating agent to form a protective film.
[0018] In step S3, the circulation pump performs low-pressure internal circulation for 2-4 hours; in step S3, the temperature of the circulation pump during low-pressure internal circulation is 40-60 degrees Celsius; in step S5, the water pressure for pure water rinsing is 10-15 MPa; in step S6, the water pressure in the high-pressure water pipe is 20-30 MPa, achieving efficient cleaning while reducing water consumption; in step S7, the drying tool includes a blower gun, which generates a strong airflow to quickly dry the moisture in the graphite heat exchanger, shortening the drying time; the blower gun integrates a temperature sensor and a humidity sensor, which can automatically adjust the airflow and temperature according to environmental conditions to achieve precise drying; in step S8, the passivating agent includes potassium permanganate, which provides oxygen atoms, which react with carbon atoms on the graphite surface to generate stable oxides, forming a protective film and improving corrosion resistance.
[0019] In summary, this invention provides a cleaning method for graphite heat exchangers. A cleaning solution is prepared by combining citric acid and a corrosion inhibitor. Hydrogen ions in the citric acid react chemically with alkaline substances such as calcium carbonate and magnesium hydroxide in the dirt, generating soluble calcium citrate, carbon dioxide, and water, thereby dissolving the dirt. The carboxyl and hydroxyl groups in the citric acid molecules form stable water-soluble complexes with metal ions such as calcium, magnesium, and iron, preventing ion redeposition and thus improving descaling efficiency. The added corrosion inhibitor inhibits the slight corrosion of the graphite heat exchanger's metal components by citric acid. The inhibitor forms a protective film on the metal surface, isolating the metal substrate from the corrosive environment and thus blocking the electrochemical corrosion process. High-pressure scouring creates a high-speed jet that directly impacts the dirt on the graphite heat exchanger surface, instantly generating enormous kinetic energy and causing the dirt layer to detach. This invention first softens the dirt through chemical cleaning and then peels it off through physical high-pressure scouring, improving cleaning efficiency, heat transfer efficiency, and reducing operating costs.
[0020] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. A cleaning method for graphite heat exchangers, characterized in that, Includes the following steps: S1. Detecting fouling: The thickness of fouling in the graphite heat exchanger is detected by an ultrasonic thickness gauge. The ultrasonic thickness gauge emits high-frequency sound waves into the tube wall or plate of the graphite heat exchanger. The high-frequency sound waves propagate inside the graphite heat exchanger. When the high-frequency sound waves encounter the interface between the fouling layer and the substrate, they are reflected. By measuring the time difference between the ultrasonic wave emission and the received echo, and combining it with the propagation speed of the high-frequency sound waves, the thickness of the fouling layer is calculated, and the parts that do not need to be cleaned are isolated. S2. Prepare the cleaning solution according to the following mass percentages: 99-99.5% citric acid and 0.5-1% corrosion inhibitor. Use deionized water or softened water to avoid premature reaction between calcium and magnesium ions in the water and citric acid. Slowly add the citric acid powder to the water while stirring until completely dissolved. Use pH test paper to test the acidity of the cleaning solution. S3. Internal circulation cleaning: Inject the prepared cleaning solution into the graphite heat exchanger, and the circulation pump performs low-pressure internal circulation; connect the outlet pipe of the circulation pump to the cleaning solution inlet of the graphite heat exchanger, and connect the cleaning solution recovery pipe to the outlet of the graphite heat exchanger to form a bottom-up circulation path. S4. Drain the cleaning fluid. Discharge the cleaning fluid through the drain pipe. When draining, start from the top of the graphite heat exchanger and gradually move downwards until all the water in the graphite heat exchanger is drained. S5. Pure water rinsing: Connect the pure water supply pipeline to the inlet of the graphite heat exchanger and the outlet to the drainage system. Rinse the graphite heat exchanger with pure water to ensure that there is no cleaning fluid or residue inside the graphite heat exchanger. S6. High-pressure flushing: Connect the inlet and outlet of the graphite heat exchanger to the high-pressure water pipe. The water flow output from the high-pressure water pipe flushes the inside of the graphite heat exchanger. Use a flushing method to flush each graphite tube one by one, so that each graphite tube is flushed. Check the discharge at the outlet. When all the dirt is discharged, close the high-pressure pipe. S7. Remove residual moisture, disconnect the power supply and process piping of the graphite heat exchanger to ensure it is completely stopped, drain all materials, coolant or heating medium from the graphite heat exchanger, and use a drying tool to dry the inside of the graphite heat exchanger to ensure no moisture remains. S8. A protective film is formed on the graphite surface. Before passivation treatment, grease, dust and oxides on the surface of the graphite heat exchanger are removed. The graphite surface is then passivated with a passivating agent to form a protective film.
2. The cleaning method for graphite heat exchangers according to claim 1, characterized in that, In step S3, the circulation pump performs low-pressure internal circulation for 2 to 4 hours.
3. The cleaning method for graphite heat exchangers according to claim 1, characterized in that, In step S3, the temperature at which the circulating pump performs low-pressure internal circulation is 40–60 degrees Celsius.
4. The cleaning method for graphite heat exchangers according to claim 1, characterized in that, In step S5, the water pressure for pure water rinsing is 10-15 MPa.
5. The cleaning method for graphite heat exchangers according to claim 1, characterized in that, In step S6, the water pressure in the high-pressure water pipe is 20-30 MPa.
6. The cleaning method for a graphite heat exchanger according to claim 1, characterized in that, In step S7, the drying tool includes a hair dryer.
7. A cleaning method for graphite heat exchangers according to claim 6, characterized in that, The blow gun integrates a temperature sensor and a humidity sensor.
8. The cleaning method for a graphite heat exchanger according to claim 1, characterized in that, In step S8, the passivating agent includes potassium permanganate.