Reduced pressure reflux
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The first stage of the vacuum distillation column has two types of reflux: one returns directly to the packing below the extraction point on stage 1 after being extracted from there, while the other is cooled through a heat exchange system before returning to the packing above the extraction point on stage 1. I would like to ask the teachers: what is the function of each of these two reflux processes, and how are they used? Thank you!
What returns to the packing at the bottom of the extraction port is the internal reflux of the tower, which serves the purpose of distillation. The upper part is a cold return stream, which serves for heat exchange
Thank you! Thank you so much! Teacher, could you explain end-backflow in more detail?
In general, crude oil vacuum distillation towers make use of packed columns quite often; in particular, the trays above the fourth vacuum stage are all packed beds. Each of these packed beds is equipped with a liquid redistributor. Thus, the liquid extracted from the first vacuum stage, after heat exchange, is directed to one path – which is equivalent to using the reflux from the middle stage of the first vacuum stage for heat absorption – and then sent to the liquid redistributor of the second vacuum stage before returning to the tower； The remainder is then cooled by a cooler and divided into two streams: one stream returns to the top of the vacuum distillation tower to serve as a cooling reflux and control the temperature at the tower top (since vacuum distillation involves creating a vacuum, there is very little oil in the reflux tank), while the other stream is used as the product to be exported from the plant. Now you understand, right?
Our newly installed pressure reduction tower is just as you described: the pump outlet feeds directly beneath the packing without going through any heat exchange. However, it’s not clear how the flow is distributed inside the tower; the product coming out at the primary outlet is light diesel. The old tower only has a cold reflux stream that consists of wax oil. This thermal backflow backwashing seems to serve a distillation function; I’m a beginner – let’s learn from each other*.