Corrosion in the distillation product cooler

Could the leakage start from the shell side, which could possibly be due to corrosion caused by the chilled brine?

The device for reinforcing and alkalinizing after the compressor removes water; more corrosion inhibitors are added to the brine, which **reduces** equipment leakage

Does your high-boiling tower corrode? If there is no corrosion, check the water at 0 degrees

Cooled with 6-degree water; it’s not saltwater, it’s corrosion on the vinyl chloride material side

If it is corrosion on the material side, attention should be paid to the composition of the material. Vinyl chloride is a neutral medium and does not affect stainless steel (304 stainless steel should be used! ) It causes corrosion. From the perspective of the process flow, the components in vinyl chloride that may cause corrosion to stainless steel are mainly OH- and CL-. Under the operating conditions of the final product condenser, the corrosion caused by OH- should be mild; I believe that it is primarily CL- that causes corrosion. I wonder what the vinyl chloride water removal process is at the company on the first floor? If there is no solid alkali dryer, the possibility of CL levels exceeding the limit is very high. Although the purification unit is equipped with an alkali scrubber, since the distillation system (except for the solid-removing alkali dryer) does not have the capability to treat CL-, the presence of CL- ion corrosion in the subsequent distillation system indicates that the treatment effect of the preceding units was poor. During the production process, it is necessary to pay attention to the CL- content in the final vinyl chloride monomer, as this has a significant impact on upstream control, equipment corrosion prevention, and polymerization quality.

The key issue is still the poor water removal performance of your system. If water is not removed using an alkaline desiccant dryer or a water separator, and proper sedimentation and separation of water are not achieved, it can easily lead to corrosion of the distillation equipment.

It is mainly caused by the moisture contained in vinyl chloride

Chloroethylene hydrolyzes to acidic substances that corrode stainless steel (intergranular corrosion) to a much greater extent than ordinary carbon steel; therefore, water should be removed as much as possible during the distillation of chloroethylene. In the presence of water, changes in temperature are a key factor in the hydrolysis of vinyl chloride. It is unwise to use stainless steel equipment for the final condenser when it is not possible to ensure water removal, due to the presence of reboilers and condensers.

Our system causes corrosion on the 0-degree saline side. It has not appeared on the vinyl chloride side.

Our factory has a solid-alkali dryer before feeding into the low tower, but corrosion still occurs, and the moisture content in the final product remains high. What is your setup for using solid-alkali dryers, and what level of moisture removal can it achieve?

Carbon steel is a better choice; stainless steel is prone to pinhole corrosion. It’s of course better to remove as much water as possible.

These days, there are usually two sets: one is used for water removal in the gas phase before the total condenser, and the other is installed before the monomer tank after the finished product; the results so far are quite good!

It is mainly due to the high moisture content of the monomer. New collectors have been introduced in the industry to replace water separators, and it is said that they work quite well.

In our factory, when using liquid-solid alkali drying, there are sometimes difficulties in discharging the waste fluid, and the carryover of liquid alkali affects subsequent processes. I wonder what levels the moisture content and acid level of the monomer reach after using solid alkali drying