How do atmospheric and vacuum distillation units prevent naphthenic acid corrosion?
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Today a friend called to ask me about corrosion prevention using naphthenic acid for atmospheric and vacuum distillation units. The common methods used in our factory are as follows: 1. Reducing the flow rate in areas subject to high temperatures in order to minimize erosion corrosion. 2. Upgrading the material used in those high-temperature areas; basically, 316L material is used now. I’ve also heard that high-temperature corrosion inhibitors are used, but I’m not sure which companies use them Mixed effects? Are there any other methods of preservation?
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There are many manufacturers of corrosion inhibitors; you can find out by doing a search. Additionally, it’s important to make good use of the \"one removal and three injections\" method, as this can **reduce the need for naphthenic acid for corrosion protection**.
Adding high-temperature corrosion inhibitors can effectively prevent naphthenic acid corrosion, and Nanjing Petrochemical produces them.
The one-detach-three-injection process has little to do with naphthenic acid corrosion; however, oils with a high acid value are generally heavier and more difficult to desalt electrically.
Naphthenic acid corrosion is a type of high-temperature corrosion. To be honest, many high-temperature corrosion inhibitors used by Sinopec these days do not provide very effective protection; what’s really important is to do a good job in management!
In fact, corrosion does not occur in every high-temperature area; this is because naphthenic acid corrosion follows a boiling range distribution – most crude oils have a fraction with high acid values and high corrosivity at around 280 degrees, and another such fraction at around 400 degrees. For high-acid crude oil, it is best to feed it directly into secondary processing units such as hydrogenation, catalytic cracking, coking, etc., before proceeding with distillation.
Since the main temperature ranges where naphthenic acid causes severe corrosion are 220°C–280°C and 350°C–420°C, the best approach is to install 316L linings on the tower in these two temperature ranges and replace the internal components of the tower with 316L material. It is specifically noted that 304 material does not provide significant protection against naphthenic acid corrosion.
The corrosion inhibition effect of high-temperature corrosion inhibitors is not significant
Who said that? High-temperature corrosion inhibitors are very effective; if the effect is not noticeable, it is a problem with the inhibitor itself – it’s important to use the right solution for each situation. You can consult CNOOC Asphalt Co., Ltd., CNOOC Zhanjiang Fuel Oil Co., Ltd., CNOOC Taizhou, CNOOC Sichuan, and other refineries within the CNOOC group that process high-acidity Penglai 19-3 and Suizhong 36-1 crude oils. The manufacturer of high-temperature slow-release agents is a company based in Jinan, which is used by CNOOC’s systems. There are two reasons for the lack of noticeable effect: 1. The selected corrosion inhibitor is not appropriate ； 2. Over time, the concentration of the manufacturer’s corrosion inhibitor becomes insufficient. . . Of course, this can be controlled through factory inspections. :lol