Hydrocracking light and heavy naphtha failed corrosion testing
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Dear experts in hydrogenation, does the hydrocracking unit you work with often experience issues related to inadequate corrosion resistance of light and heavy naphtha? I’ve read several papers on hydrocracking recently, and in several cases the naphtha showed poor corrosion resistance. In such situations, process parameters are adjusted, such as reducing the distillation range or using desulfurization units for desulfurization. If you have encountered similar problems, please share how you handled them. I’d like to share some good experiences and methods with everyone.
Generally speaking, corrosion-related failures in weight stones are relatively rare; rather, it is the initial boiling point and dry point that are more likely to fail to meet the requirements. Moreover, in most cases, corrosion failures of the weight stones are caused by H2S; therefore, there is no need to install a special desulfurization unit. The issue can basically be resolved by adjusting the process operations in the preceding reaction section and the stripping tower. The reaction stage is primarily aimed at ensuring maximum desulfurization to achieve an optimal result; special attention must be paid to the desulfurization of alcohols. This way, it can be ensured that the subsequent distillation stage contains virtually no sulfur-containing substances other than H2S (referring here specifically to S in its liquid phase form) ； During the stripping stage of the fractionation section, it is only necessary to maintain a certain tower pressure and temperature so that H2S is not dissolved in the liquid phase of the heavy components; this should ensure that the corrosion resistance of these heavy components meets the required standards.
Reply to 1# zhg20051007: By adding an alkaline wash to remove hydrogen sulfide from the oil, there should be no issues with normal corrosion tests
Most of the problems arise with the post-refining process; thiols are usually to blame. Adjusting the distillation system doesn’t help in such cases, and if raising the temperature during post-refining still doesn’t work, the only solution is to use a desulfurization tank. Actually, the judgment is simple: hydrogen sulfide dissipates quickly. Take two samples – one is left to stand for 30 minutes while the other is analyzed immediately – and by checking the total sulfur content, you can determine the difference.
We are performing an additional alkali washing in front of the Calais desulfurization tower