Heat exchangers are extremely common in the chemical industry, and their core function is to reduce the temperature during the operation of chemical equipment, prevent equipment from working at high temperatures, which can significantly extend the service life of the equipment, reduce the possibility of failure, and ensure that the equipment can continue to operate stably.
However, due to the generally corrosive nature of chemical raw materials, heat exchangers often struggle to escape corrosion when working for long periods of time in such a challenging environment. When corrosion becomes a serious problem, it can lead to leakage of fluid media in the heat exchanger, which not only poses a safety risk, but can also cause equipment failure, which in turn affects the production plan of the chemical company and causes economic losses. There are various causes of heat exchanger corrosion, including, but not limited to, physical wear, electrochemical reactions, and water-side corrosion of pipes.
Corrosion problems in heat exchangers
In the chemical production process, the corrosion problems faced by heat exchangers can be mainly divided into the following categories:
▍Corrosion problems caused by physical wear:
When a heat exchanger is in operation, its surface comes into contact with a variety of fluid media, including liquids, gases, bubbles, and solid particles. When these media flow at high speeds, they can scour the metal surface of the heat exchanger, resulting in corrosion products. At the same time, mechanical erosion can be combined with corrosion on the metal surface to accelerate the corrosion process.
▍Corrosion problems caused by electrochemical reactions:
During long-term use, the medium in the heat exchanger tube may flow unevenly or stagnate, resulting in the deposition of substances on the surface of the heat exchanger tube. These deposits can cause corrosion to metal surfaces along the direction of fluid flow. In addition, galvanic corrosion is characterized by inhomogeneity and unstable continuity, which can further exacerbate corrosion on metal surfaces.
▍Corrosion on the water side of the heat exchanger pipeline:
The main medium of the heat exchanger is usually water, and the water may contain a variety of impurities, such as dissolved gases, toxic and harmful substances, and low pH value, which are the main causes of water-side corrosion of heat exchanger pipes. Therefore, chemical companies need to pay special attention and take measures to prevent the occurrence of waterside corrosion.
In order to effectively deal with the corrosion problems faced by chemical heat exchangers, the following measures can be taken:
▍Use anticorrosive coatings:
Applying an anti-corrosion coating to the surface of the heat exchanger is an effective method of protection. This includes inorganic anti-corrosion coatings and metal anti-corrosion coatings such as electroplating, flame spraying, etc. These coatings provide a certain degree of isolation from direct contact between corrosive substances and the heat exchanger. After the coating has been applied, it is often baked at high temperatures to ensure that the coating adheres firmly to the surface of the heat exchanger for optimal corrosion protection.
▍Strengthen maintenance work:
Due to the long-term exposure of heat exchangers to corrosive environments, regular procedural inspections are essential. This helps to identify and deal with potential safety hazards in a timely manner, avoiding financial losses due to equipment failures. During the inspection, if any problems are found, they should be reported immediately and corresponding repair measures should be taken to prevent the problem from expanding during the operation of the equipment.
▍Regular cleaning and maintenance:
In order to ensure the proper operation of the heat exchanger and prolong its service life, regular cleaning and maintenance are key. This removes chemical deposits and microorganisms, reducing the potential for corrosion. Common cleaning methods include high-pressure water jet cleaning, chemical cleaning, and cleaning-in-place technologies. Enterprises should choose the appropriate cleaning method according to their specific situation to ensure the clean and efficient operation of the heat exchanger.
Through these measures, the corrosion rate of the heat exchanger can be significantly reduced, and its operating efficiency and safety can be improved, thus ensuring the continuity and stability of chemical production.
When a heat exchanger suffers from a severe or difficult blockage, chemical cleaning may no longer be a viable option. The disposal of the waste liquid generated after chemical cleaning is not only difficult but also relatively costly. In addition, if the cleaning process is not handled properly or the wrong cleaning agent is selected, it can lead to irreversible corrosion damage to the equipment.
Sponge ball cleaning technology, by regularly injecting sponge balls into the condenser inlet pipe, using water flow to send the sponge balls into the heat exchanger tube, and mechanically wiping the inner wall of the tube under pressure, this method can significantly reduce the downtime of the heat exchanger. However, this technique is suitable for a limited number of scenarios, mainly for the cleaning of heat transfer tubes in heat exchangers. In addition, using this technique requires frequent maintenance of the system, replacement of pellets, and checking for missing pellets, which can increase costs and potentially cause heat transfer pipe clogging.
High-pressure water cleaning technology is favored for its non-corrosive, non-polluting and non-damaging characteristics. Due to the use of water as the cleaning medium, high-pressure water cleaning has a low economic cost compared to other cleaning methods, and can be used in a wide range of scenarios, and can be used for many types of heat exchanger cleaning. When operating high-pressure water jet cleaning, the cleaning pressure can be adjusted according to the scale of the heat exchanger to avoid too high or too low pressure affecting the cleaning effect or causing damage to the heat exchanger equipment. Typically, a pressure washer of 50 to 70 Mpa is sufficient, but in some special cases, pressures of up to 140 Mpa or even 280 Mpa may be required. This flexibility and efficiency makes high-pressure water cleaning technology an effective choice for heat exchanger cleaning.
