How to improve the cutting efficiency of a fractionation tower

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This post was last edited by cymlz0826 on 2017-10-13 at 14:36. As shown in the image, please forgive the poor quality of the drawing. This distillation tower does not have mid-stage reflux; the design team described it as half a distillation tower. There are two lines for extracting diesel, one at the 19th stage and another at the 29th stage. The problem now is that the cutting effect of diesel and residue oil is poor; there is too much residue oil. The lowest temperature during initial distillation is just over 110 degrees, while under better conditions it’s around 260/270/280 degrees. If this distillation column has a mid-stage recycle, can the cutting be done better? In winter, since it is necessary to control the freezing point and lower the temperature at the bottom of the tower, doesn’t that make separation even more difficult? If there is no external return flow, could increasing the amount of internal return flow be considered to enhance the cutting effect? Now, when we draw liquid from the side line, it is done in its entirety (there is no display of the liquid level in the collection tank, the valve is open at 100%, and the temperature at the outlet fluctuates greatly). We think it’s a dry plate). I’m wondering if it’s possible to control the amount of fluid drawn from layer 19, so that the oil can flow downward layer by layer through the overflow weir; wouldn’t this increase internal recirculation? Could this improve the distillation efficiency? Thereby enabling a more thorough separation of tail oil and diesel. It may affect the yield of diesel, but not by much. If this approach proves effective, once diesel and residue are properly separated, the temperature at the bottom of the tower can be increased appropriately. As the temperature at the bottom of the tower rises, the amount of oil vaporizing upward also increases. As long as there is sufficient overflow, it is entirely possible to increase the valve opening for extraction on the 19th level later on, provided that there is enough overflow available. Doing this also increases the oil holding capacity in the fractionation tower. Please analyze whether my idea is correct.