For a full-cycle process, what are the requirements for the circulating oil?

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It is crucial in the operation of the vacuum distillation tower to prevent the recycled oil from carrying diesel components back into the cracking reactor; regular sampling of the recycled oil should be carried out along with tests using actual boiling point distillation to ensure that the diesel content is less than 3% by volume. As refineries process an increasing proportion of sulfur-containing and high-sulfur crude oils year by year, the sulfur content in the feedstock processed by hydrocracking units also rises. This accelerates corrosion in the distillation system, resulting in high levels of iron ions in the oil fed into the cracking reactors. Consequently, fouling (in the form of ferrous sulfide) builds up in the first bed of the cracking reactors, causing a rapid increase in pressure drop and an increased frequency of shutdowns for cleaning. The key to controlling Fe is to enhance the circulating hydrogen desulfurization system to address corrosion upstream. Additionally, the cracking reactor can use a large-pore-size Fe-removing protective agent, which is filled in stages together with the catalyst.