How to control corrosion at the top of the atmospheric tower in atmospheric and vacuum distillation units

You can refer to the paper on atmospheric and vacuum distillation corrosion at http://bbs.hcbbs.com/thread-1658036-1-1.html. Generally, three processes are involved: electrodesalination, water injection, and the addition of neutralizing agents and corrosion inhibitors. The main approach is to prevent corrosion through process controls, with material selection serving as a supplementary measure. For pipeline materials, carbon steel is most commonly used; however, 1Cr13 composite steel and 2205 double-phase steel are also employed in some cases. For the air cooler tube bundles, 316 can be chosen, or higher-grade materials such as 825 and 625 can also be used.

Corrosion at the top of atmospheric pressure towers is a long-standing problem, mainly caused by chemical corrosion and electrochemical corrosion. The selection and use of additives, especially corrosion inhibitors, is a key approach; material upgrades such as the use of stainless steel pipeline equipment or titanium alloy heat exchanger tubes are also effective. Additionally, online corrosion monitoring helps to keep track of the locations and rates of corrosion.

Generally, a neutralizing and corrosion-inhibiting agent is added to the overhead distillate line to maintain a pH level of 6–9; strict monitoring is required to ensure that the concentration of iron ions in acidic water does not exceed 3 mg/l. If the overhead condenser uses air cooling, the material of the air-cooling tubes can be upgraded (it seems to be an aluminum alloy)

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Thank you for the reply from above; I hope everyone can provide more suggestions

The main processes include electrodialysis, water injection, injection of corrosion inhibitors and neutralizing agents, etc. Additionally, there is the selection of materials for equipment such as heat exchangers

Our factory is currently facing the problem of acidic water emulsification during top cutting. After investigation, it was found that the neutralizing and corrosion-inhibiting agents were causing emulsification, but replacing them with products from different manufacturers did not resolve the issue completely. Do you have products that do not cause emulsification? How do you address this problem?

Note: The high-temperature corrosion inhibitor, the general corrosion inhibitor, and the injected liquid keep the pH at around 7 only

Inject ammonia water, inject slow-release agent, inject water

In our plant, corrosion in the atmospheric pressure towers is particularly severe. The main reason for this is the poor quality of the crude oil; originally, the three electric desalination tanks were not able to remove enough salt from the crude oil. An additional, larger electric desalination tank was later added, which helped to improve the situation. A large amount of salt accumulates at the top, causing significant scaling; most of the top-side heat exchangers leak, which severely affects product quality. The seals on the top-side circulation pumps often fail, and valves cannot be closed properly. Additionally, corrosion leads to perforations in the top-side air coolers. A series of problems arise as a result. Later, we changed the material of the top circulation heat exchanger, washed the atmospheric pressure tower regularly, and added an external flushing line for the normal line as well as a regular flushing line with deoxygenated water for the top circulation pump. By controlling the top circulation rate and, at the same time, to manage corrosion at the top, the top temperature is increased (since our crude oil is heavy, the temperature cannot be as high as in some refineries); in addition, a top heat exchanger is used to raise the top temperature and prevent corrosion caused by low-temperature water solubility. The processes for injecting water, ammonia, and corrosion inhibitors have been modified, with strict control over the amount and concentration of these substances injected. Through a series of such measures, it is possible to keep the level of iron ions in acidic water under control.