Regarding the passivation issue of the solvent portion
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While investigating the on-site process, I noticed that there was a pipeline leading from the outlet of the solvent regeneration tower’s reflux pump directly to the air cooler. The technician said it was a passivation line, designed to prevent ferrous sulfide from catching fire during shutdown periods. I would like to ask what the passivation medium used for the tower is, and how it can be determined when the passivation process is complete I hope fellow sailors can give some advice!
1. Shutdown passivation is used to prevent the formation of ferrous sulfide; this serves both to protect the equipment and to protect those who enter the equipment. 2. I have seen two instances where equipment was damaged due to the spontaneous combustion of ferrous sulfide, with wrinkles appearing on the casing (creep? ), the first incident was relatively severe; subsequently, 2 meters of the equipment’s cylinder was replaced. The second incident was less serious, and the equipment is still in use. 3. I have seen situations where smoke suddenly appeared inside equipment – in a catalytic distillation tower, not one in our workshop. While performing maintenance work from a distance at a higher elevation, I happened to witness that moment: suddenly, thick smoke rose from the manhole located in the upper middle part of the catalytic distillation tower. Fortunately, no one suffered from suffocation – it turned out that the person who was in the middle part of the tower had just come out, while there were still people at the bottom. 4. The ferrous sulfide passivator is kept secret by the manufacturer; it is acidic in nature, with a pH value of around 4 in its aqueous solution. After the reaction is complete, the pH should be neutral; otherwise, it means the reaction has not been completed or insufficient amount of the substance was added.