What are the reasons for severe corrosion in the maleic anhydride purification tower?
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Anhydride purification tower, made of 316L material; severe corrosion occurs in the tower above the maleic anhydride water feed inlet, and the chlorine content in the deionized water used for absorbing anhydride is less than 20 ppm. The normal corrosion rate of succinic acid is 0.05–0.5 mm/year. Is a high chloride ion content the cause of severe corrosion? Or other reasons? What is the corrosion situation of your purification towers at other domestic maleic anhydride manufacturers?
20 ppm is a relatively high concentration; corrosion at certain temperatures can be severe, and 316L material won’t be able to withstand it. Consider using a different material. It seems to have little to do with equipment manufacturing: lol
Thank you to the person above; if we install a reverse osmosis unit during the water treatment process, can that help reduce chloride ions?
Here, it is possible to consider using different materials for various parts of the tower: 316L can still be used for those parts that are not subject to corrosion, while N08367 (AL-6XN) or 2507 can be used for the parts where corrosion occurs; this should resolve any issues
316L is fine; it’s best to use materials that meet national standards. Additionally, welding should be carried out using 316 welding rods or plasma welding methods, so that the problems you mentioned won’t occur
Mainly because of its use in process water jackets, the chloride ion concentration rises significantly, leading to corrosion of the tray plates. There are two ways to mitigate the impact: 1. Use a large amount of fresh process water, and employ dilute acid water to be regularly discharged from the system ； 2. The trays above the acid feed port are made of titanium.
In the presence of chloride ions: it is not advisable to use 316L material, as corrosion will occur after 2–3 years, resulting in higher subsequent maintenance costs. Using titanium is possible, but the cost of the equipment is higher. For a long time, there has been a type of seawater-grade steel whose price is higher than that of 316L, but it has no maintenance costs. Another option is to use the SEBF industrial coating technology developed by the Chinese Academy of Sciences; applying this technology to ordinary steel yields excellent results, and it offers cost advantages. Dainai is also using this coating technology in order to reduce costs.
I don’t think the materials specified for the aforementioned towers are suitable. At present, I believe that 316L material is sufficient for the maleic anhydride purification towers. Manufacturers who have the capability or those planning to produce maleic anhydride can generally keep the same material; instead, they could consider using N08367 (AL-6XN) or 2507 material for the tower bottom during equipment fabrication, although this would increase costs significantly. For existing production facilities, I do not recommend making such changes as it would be a waste. I believe it is more important to improve the quality of the wastewater, to put effort into water treatment, and to raise the requirements regarding crude anhydride, washing water, and acidic water – in particular, parameters such as the concentration of acidic water must not be ignored
Due to its use in the process water jacket, the chloride ion concentration rises significantly, leading to corrosion of the tray. The other parts that are not corroded still use 316L, while the corroded areas use N08367 (AL-6XN) material or 2507.
The acid water has a low temperature and low concentration; add an acid water heater
Add a reverse osmosis unit; it is relatively inexpensive compared to replacing the equipment, and its operation is also simple.