How to prevent corrosion in regular first-line and regular top circulation
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We are processing naphthenic heavy crude oil, and the low-temperature corrosion is quite serious. There is process anti-corrosion in the Chang-1 and Chang-top circulation. There were not many pipeline perforations in the Chang-1 before. There were also valve perforations and heat exchanger perforations in the Chang-1 circulation. We replaced 304 stainless steel, but the corrosion is still serious. Can you please tell me how CNOOC performs process anti-corrosion on the Chang-line and Chang-top circulation? Can neutralizing corrosion inhibitor be added to the Chang-line?
Reply 1# 448610880 It is best to upgrade the material and add corrosion inhibitors, but the modification cost is high, especially the operating cost.
Reply 2# linweihua6 We have already reached 304 stainless steel. Do we still need to upgrade to 316L stainless steel? We all use it in high-temperature parts.
We have a corrosion inhibitor injection process here, but the effect is not good. We can't spare some equipment and pipe fittings that are prone to problems now.
Reply 3# 448610880 316L is fine, it is best to use 317H directly
This Haiyou, if I guess correctly, we should be colleagues in the same system. Let’s communicate if we have the opportunity. Let me answer your question first: 1. First of all, it is useless to add corrosion inhibitors and pipeline upgrades for the first-line and top-circulation corrosion problems, which is a waste of money. 2. These two corrosions are caused by water in the upper part of the atmospheric tower. They are mainly low-temperature chloride ion corrosion. The pipelines were upgraded to stainless steel, which rotted faster. 3. The best way: First, the operation is to increase the load on the upper part of the normal pressure tower as much as possible, so that the water vapor is cooled in the condensation area of the volatilization line at the top of the tower, reducing the phenomenon of water in the tower and delaying the corrosion rate. ； The second is to consider technical transformation to remove the condensed water in the top circulation, control the phenomenon of water in the atmospheric tower, move the corrosion parts up to the outside of the tower, and then do anti-corrosion work at the top of the tower. Suggestions for reference!
Reply 6# cn2009 What is the chlorine content in crude oil? What is the chloride ion content in normal line? In how many chloride ion environments is stainless steel allowed to be used? In what temperature range does chloride ion corrode stainless steel more severely?
I strongly agree with the original poster, naphthenic acid will not corrode below 250 degrees. Installing a dewatering device at the inlet of the pump can also solve the problem.
Reply 8# karamay Just saw it. . . First of all, I would like to thank this friend for supporting my point of view. Secondly, let me briefly answer a few questions raised by the moderator. I have not analyzed the chloride ion content in crude oil and normal oil, and I have no data to provide. What I said above is chlorine corrosion caused by water in the oil. As for the chloride ions in sewage, The analysis data is high and low, with the high above 200 mg/l. The normal temperature of the first line is around 160 degrees, and the normal temperature of the top loop is around 110 degrees. I would like to ask if this environment will cause chloride ions to be sensitive to stainless steel.
Reply 8# karamay What is the full name of the dehydration device at the pump outlet? How can I find such a device online? I have never come across such a device before. Thank you.
Reply 10# 448610880 There is no one specializing in selling this thing. You can use an automatic dehydrator. I made a dehydration tank myself. The residence time is designed to be about 10 minutes. In order to solve the problem of salt formation, we installed one in the catalytic fractionation tower. in addition: We detected chlorine in the dehydration at the top of the coking fractionation tower, and the highest level was over 7,000. The coking unit directly processes acid-containing heavy oil and is a combined fractionation tower.