Blackening of hydrocracking tail oil
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After the hydrogenation unit has been in operation for some time, the tail oil gradually turns black. What is the reason for this?
It’s not entirely clear whether it turns black – are there black particles suspended in it, or does it turn completely black? If it is a full-range distillation, the color will change when the content of polycyclic aromatic hydrocarbons in the tail oil exceeds 100 ppm, though it remains in the yellow to orange-red range. If it passes through somewhere else, the cracked products are transparent, so they shouldn’t turn black either. Keep an eye on it. See what other masters have to say