Reflux problem in catalytic fractionation towers
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Through calculation, the difference between the enthalpy at the bottom of the feed fractionation tower and the enthalpy of the gas phase in the diesel extraction stage is greater than the amount of heat removed by external reflux; in other words, a portion of the heat is removed through the vaporization caused by internal reflux. However, the diesel extraction stage of the catalytic fractionation column is a full extraction tray; the liquid phase on the lower trays has no internal reflux apart from the mid-section reflux. If there is any internal reflux, is its composition diesel? In that case, not all of the liquid phase in the full extraction tray can be extracted, and a portion of it will flow back as internal reflux to the lower trays. I’m not sure if it’s a calculation error or something else; I hope everyone can help me figure it out. Thank you
I don’t know what the original poster used to calculate it. As far as I know, when using software for calculations (such as ASPEN), even if full extraction is applied, there still needs to be a certain amount of internal reflux; otherwise it will lead to a dry plate condition, resulting in the failure of the entire column to converge.
Part of the liquid phase in the full extraction tray overflows and flows back as an internal reflux to the lower trays
It shouldn’t be completely drawn out; there should be a small amount of liquid left, and the software just omits that part for you.
There is backflow; the minimum backflow level is controlled in order to obtain more waste heat from the middle section