What is the mechanical operation of Distillation?

Question

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Answer 1

The mechanics of distillation is the separation of two or more components of a mixture according to their different boiling points. A distillation process in a fractionation tower is that, the tower has a number of contacting devices.. e.g. Bubble Cap Trays. Each tray is, in effect, a single distillation process where the down-flowing liquid reflux is flowing across each tray at a specific temperature governed by the reflux rate, the temperature of the inlet liquid feed, the temperatue profile from the bottom to the top of the tower and the pressure of the system.
As down-flowing liquid flows across each tray, it contacts the rising vapours.
As stated, the temperature on each tray is controlled.
The down flowing cooler liquid will contain fractions with the same boiling point as the liquid on the tray and these will condense onto that tray.
Also, as the hotter vapour rises through the liquid, it too will have fractions the same as the liquid on the tray which will also condense. Any liquid on the tray that has a higher boiling point will be vapourised and join the rising hot vapour which is gradually cooling as it rises up the tower.
This process is continuing from tray to tray and gradually separates the components into the desired fractions at different levels of the tower. These are collected in 'Draw-off Pans' from where they are piped via coolers to storage.
The top vapour outlet is condensed and a portion is returned to the tower top as external reflux to control the tower top temperature and therefore the quality of the overhead product. The rest of the liquid is piped to coolers and storage.
Uncondensed gases will go to Fuel, other processes or to a flare system.
The heaviest 'Bottoms' product is also cooled, and sent to storage. Feed inlet from a furnace is temperature controlled, bottoms temperature is controlled by a 'Reboiler'.
All of these sections (and the tower pressure), under strict control results in the quality control of the products.

Answer 2

Distillation is a thermal process.

The only mechanical activity involved is that the fluid to be distilled may have to be mechanically pumped to the top of a distillation tower to be separated as it flows perforated trays down past an upcoming heated stream. As it goes down the component fractions that are evaporated are removed separately at specific (pre-calculated) levels of the distillation tower.