The atmospheric pressure column reduces the overlap between Constant 1 and Constant 2

It shows that the temperatures you two set weren’t controlled properly; overlapping occurs simply because nothing is pressing down from above and nothing is steaming from below.

First, we need to consider what kind of raw materials are used by Unit 1 and Unit 2 for their downstream processes. If both are used to produce diesel, then the degree of overlap between them is not a concern. However, if Unit 1 is used to produce aviation fuel or as a raw material for molecular sieves, it becomes necessary to control the parameters related to Unit 1. Controlling these parameters ensures that a high degree of overlap does not lead to any problems. Secondly, if the overlap between stream 1 and stream 2 is significant, then separation and extraction need to be taken into consideration. Atmospheric distillation columns are generally designed for fuel use; in other words, the three distillation side streams of such columns are usually evenly distributed, and it can be assumed that their theoretical number of theoretical plates is similar, as is their separation precision. Between the first distillate and the second distillate, there is only the middle distillate; in other words, the three main factors affecting the overlap between the first and second distillates are the first distillate, the second distillate, and the middle distillate. You can start from these three perspectives. If there is a stripping tower on the secondary line, adjustments can also be made starting from that stripping tower.

Adjust the mid-section reflux, and adjust the vapor in the secondary stripping tower