Corrosion in the distillation unit of the styrene plant?
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Corrosion in the vacuum line of the styrene product tower in the distillation unit of the styrene plant? The pH value of the hot well fluid at night is 4; what causes the corrosion?
Is it carbonic acid (CO2) corrosion caused by the previous system? Also, please check the composition of the inhibitor to see if there is any acidic medium present
Reply to 2# WSL01218: The system was checked beforehand; the pH was 7.2. We are using DNBP from Jilin Jiuxin and true polymerization inhibitors from NALCO. I checked the technical specifications for DNBP, and it states that the free acid content is less than or equal to 0.02%. Could an expert help find a solution?
An additive that neutralizes ammonia (Nalco) also needs to be added in the distillation tower.
Reply to 4# WSL01218: Regarding the method of adding ammonia, it cannot be considered due to the lack of experience in this area within the industry. We conducted analyses and found it to be nitrate; we thought it was due to the decomposition of DNBP. However, when the manufacturer arrived and tried to carry out the decomposition under the same vacuum and temperature conditions, no decomposition products were produced, which is causing us a lot of trouble now. The corrosion caused by vacuuming in our styrene product tower is quite severe. I hope colleagues will share their opinions for discussion. We are still exploring at the moment.
It was analyzed as nitrate; I’ve heard of it for the first time. The corrosion issues I’m aware of are mainly related to the acidity in the dehydrogenation liquid. Our plant has been monitoring the pH value of the aqueous phase in the condensate from the crude styrene tower; it’s currently around 6.5. It is acidic corrosion in the dehydrogenation liquid; therefore, organic ammonia needs to be added, and many plants both domestically and internationally are doing so.
This nitrate was detected in the laboratory using mass spectrometry. The corrosion occurs mainly in the separation tower for residue oil; I suspect it is caused by DNBP present in the residue oil, or by the decomposition of NALCO’s synergistic anti-polymerization agents, but I’m not sure, as I don’t know if other plants experience this issue as well.
Analysis of the causes of corrosion in styrene distillation unit equipment and research on countermeasures; please check out this article: http://bbs.hcbbs.com/thread-1196190-1-1.html
Could it be that after the pickling of crude styrene, the neutralization was incomplete, and residues were carried into the distillation tower?
Acidic corrosion caused by water in the feed can be addressed by adding a corrosion inhibitor