Two-stage hydrocracking

The feedstock for the second stage consists mainly of two components: fresh feed (oil that has not been converted in the first stage) and recycled feed (oil that has passed through the second stage once or multiple times without being converted). Generally, requirements are set for the feedstock used in the entire system; however, when problems do arise, they usually occur first in the first-stage reactor, such as coking. Although the operations in the first-stage reactor and the distillation system can affect the ratio between fresh feed and recycled feed, it is still best to maintain stability in the amount of feed supplied to the second stage. This prevents fluctuations in the operation of the reaction-related parameters (heater fuel flow, cold hydrogen flow, fresh hydrogen flow) and in product quality, which can be caused by changes in the cutting point of the circulating oil. I only have a slight understanding of it – as a reference for attacks

What about the boiling range of the second-stage material? ? ?

Is the target product section the naphtha in the middle of the distillation tower? If the naphtha has a high dry point and acceptable density, won’t it proceed to Stage 2 where it further deteriorates?