Fractionating tower without mid-stage reflux
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Our plant’s distillation column does not have a mid-stage reflux; according to the designer, this is considered half a distillation column, with two side streams – one taken from stage 19 and the other from stage 29. What are the advantages of this design? What is the difference in operation from a full distillation column? How is the freezing point of this type of diesel controlled?
Our unit is equipped with mid-stage reflux; diesel is extracted at layer 19, and naphtha at layer 29. Mid-stage extraction is used to remove excess heat to generate steam. Only the internal return flow is a factor to be adjusted; other products have a significant impact.
In a fractionating column without mid-stage reflux, the heat within the column cannot be removed, which causes the heavier components to move upward. As a result, the product becomes heavier, the separation efficiency is poor, and the load on the column top increases
When the load on the distillation tower is not high, mid-stage reflux is not considered
1. The oil from layer 19 of the distillation tower is heavier, while the oil from layer 29 is lighter. Mixing these two types of oil gives you the oil you want. If you prefer a heavier oil, increase the flow rate from layer 19 and decrease it for layer 29; do the opposite if you want a lighter oil. This allows for better control over the quality of the oil products. 2. If there is mid-stream reflux, it becomes quite difficult to fully control the temperature of each layer as well as the quality of the oil