Problem with unqualified copper sheet corrosion in refined diesel?
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The diesel produced by our plant’s hydrofining unit suffers from insufficient removal of hydrogen sulfide, which results in copper sheet corrosion that does not meet the required standards. Does anyone with experience in this area know what level of hydrogen sulfide in diesel is necessary to ensure that copper sheet corrosion is within acceptable limits? What measures can be taken to solve it?
For copper sheet corrosion to be considered acceptable, the oil should also pass the Dr. test, that is, the content of active sulfur compounds such as hydrogen sulfide, thiols, and elemental sulfur in the oil should be below around 5 ppm! I don’t remember very clearly; you can look up the relevant standards! SH/T0174 Standard for Qualitative Determination of Thiol Compounds in Aromatics and Light Petroleum Products (Drabek Test) Last edited by tianleikkk on 2008-1-3 21:06]
If you can confirm that it is due to hydrogen sulfide, then the solution is to control the process parameters of the desulfurization tower in order to improve the efficiency of removing hydrogen sulfide. But there are other reasons for the unsatisfactory corrosion of diesel copper sheets, such as a high proportion of gasoline leading to overload in the distillation tower, poor quality of the oil produced due to high sulfur content, and leaks in the heat exchangers used for the product oil... Once the exact causes are identified, it becomes easier to resolve the problem: handshake
The refinement depth is insufficient. If light is considered from an operational perspective, it’s likely not feasible; pre-treatment steps should be added if necessary.
Stir the mixing tank several more times, and the corrosion level will meet the requirements.
There is currently controversy regarding the relationship between the corrosion level of copper sheets and hydrogen sulfide levels; it is generally believed that a hydrogen sulfide concentration of more than 1 ppm can lead to corrosion of copper sheets at a level greater than 1. The solution should be sought starting from what the original poster on the 3rd floor mentioned. If this problem is ultimately resolved, I hope the original poster can also explain it here.
The reason has been mentioned in the question: it is the high hydrogen sulfide content, which causes the copper sheets to corrode beyond acceptable levels； Analysis shows that the total sulfur content is only 80 ppm. We use the method of nitrogen stirring in a large tank. But this doesn’t solve the fundamental problem.
This problem exists with oil, and it also exists with liquefied gas
I also work at an oil refinery. The situation in our plant is as follows: the gasoline (naphtha) produced through coking has a copper corrosion value that is within acceptable limits and is neutral in nature; however, after hydrogenation, it becomes neutral again but its copper corrosion value is no longer within acceptable limits. Could it be due to an excessive level of thiol compounds, or is there some other reason? I would appreciate advice from those with more experience. The hydrogenation catalyst used in our factory is FH-98. This post was last edited by haike on 2008-1-13 at 14:00.]
Don’t you have a stripping tower in front of the distillation column there? If so, increasing the amount of stripping steam should yield better results. Additionally, increasing the water injection volume can also yield better results. If that still doesn’t work, then there’s only the option to reduce the quantity.
If the steam injection volume to your stripper is high and the temperature at the bottom of the tower is low, this may result in a higher water content in the diesel at the bottom of the tower. The presence of water increases the acidity of the diesel (sulfides have a higher solubility in water than in oil). If you conduct a copper sheet corrosion analysis by first filtering the sample through filter paper before carrying out the test, will the corrosion level be no more than grade 1? Secondly, by the time operation begins, the pre-sulfurization of the catalyst is complete; when its initial activity stabilizes or during the early stages of normal operation, some elemental sulfur (produced during pre-sulfurization) remains in the catalyst bed, which can cause the copper strips used in the production of diesel to become corroded and fail to meet quality standards. This issue resolves itself after the plant has been operating for some time.
9# Haike: During the hydrogenation process, sulfur compounds such as thioethers are ultimately converted into hydrogen sulfide; inadequate removal of hydrogen sulfide leads to copper sheets that do not meet the corrosion resistance requirements
Does a high steam volume cause a low temperature at the bottom of the stripping tower? Is it still caused by a small amount of steam? ?