Hotspot issues in the pre-hydrogenation reactor of gasoline hydrogenation units
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The gasoline hydrogenation pre-hydrogenation reactor is a fully liquid-phase hydrogenation reactor, designed as a single reactor bed with a hydrogen-to-oil ratio of 5-10. At high hydrogen-to-oil ratios, hot spots appear in the lower part of the bed; as the hydrogen-to-oil ratio is reduced, these hot spots gradually disappear. Is the hydrogen-to-oil ratio related to hot spots?
One is uneven catalyst packing, and the other is the exothermic reaction of monoene saturation. Lowering H will reduce monoene saturation, thereby decreasing heat release and eliminating hot spots.
Hot spots are mainly caused by channeling in the bed layer, and increasing circulation has little effect on suppressing hot spots.
The hot spot disappears when the hydrogen-to-oil ratio is reduced; it appears only when the hydrogen-to-oil ratio is increased
This indicates that gully flow is not yet severe. It also shows that the hydrogen-to-oil ratio cannot be lower than a certain value.
I agree with the opinion from the second floor: the saturation of dienes is an exothermic reaction, which causes the catalyst to react too rapidly in certain areas. The heat generated reaches the conditions necessary for the reaction of monenes. With hydrogen present, the monenes participate in this reaction, resulting in local hot spots. If the circulation ratio is reduced, there will not be enough hydrogen, and the monenes will not react excessively, thereby eliminating those local hot spots. Was it right or not?
Hotspots are supposed to not disappear; they just weaken. A higher hydrogen-to-oil ratio will further accentuate the hot spots.