Continuous plant · Distillation Lab

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Not to scale · drag to rotate · scroll to zoom · click a tray, a pump, a valve or an exchanger

Strength and temperature through the plant

Every stage from the base of the beer still to the top of the last rectifier. The wash is stripped on its way down the beer still; the vapor is enriched on its way up the rectifiers. The marks show where the feed lands and where spirit is drawn.

Fusel oil in the columns

Fusel oil is the higher alcohols of the wash: propanol, isobutanol and isoamyl alcohol. With no fusel oil draw it gathers in the 1st rectifier, where the liquid turns from weak to strong; the fusel oil draw, under the spirit draw, takes it off the tray you choose. When a tray's liquid holds a few percent of it and little alcohol, it would split into two liquids: a water-rich liquid and a fusel oil layer on top. Point at the map to read a tray; click it to select the tray.

Where each alcohol gathers

in the each in % of its own peak in the column · base to top · ▲ a draw

Where each alcohol goes now

per hour, and in % of what the wash brings

Heads in the columns

Heads are the most volatile congeners of the wash: methanol, acetaldehyde and ethyl acetate. In strong spirit acetaldehyde and ethyl acetate are several times more volatile than ethanol, so they rise to the top of the last rectifier and leave with the heads drawn from its condensate; the spirit is drawn a few trays lower, below them. Methanol is only a little more volatile than ethanol in strong spirit, and less in weak, so most of it stays with the spirit. Point at the map to read a tray; click it to select the tray.

Each column on its own: what it is, how it runs now and its trays over the run, the strength and the temperature (the key trays, or every tray). Point at a chart for every line's value at that moment.

Product strength

% vol at 20 °C, as drawn now

Flows

L/h at 20 °C

Losses in the effluent

% vol of alcohol leaving with the stillage

Beer feed

strength in, % vol

Alcohol balance

Energy

Heat exchangers

Duties and temperatures in the last time step. UA is the exchanger's conductance (W/K): its area times its heat transfer coefficient, sized for the design duties.

Calculation

Events

Model

Each tray is an equilibrium stage with a set efficiency, finite hold-up, weir overflow and metal that has to warm up, solved with the same ethanol–water NRTL tables as the batch lab. The heat exchangers are counterflow effectiveness–NTU models with a fixed UA and no hold-up. Mass and energy are booked exactly. With the pressure drop (Set up plant → Pressure) every tray boils at its own pressure: sieve trays, each adding its liquid, the vapor through its holes and a residual head, from the top down; there is no flooding or weeping. The foam carried over from the beer still is a set share of the vapor (an assumption), and the foam trap catches all of it.

The liquid model 6 congeners · fast, coarser (Set up plant) takes steps of up to 10 s instead of 2 s: about five times faster, so the plant keeps up at 1000×. The spirit and the losses stay the same, the fusel oil band sits up to about 0.4 tray higher, and the balances stay exact. At low speeds every model steps shorter, about a tenth of a second's worth of the plant at a time (0.1 s at 1×, 0.5 s at 5×, 1 s at 10×); from about 100× it takes its longest step.

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The summary report, snapshots and plant files carry the plant's notes.

What the plant is, how it was run and what came out: where the alcohol and the congeners went, every tank and the spirit drawn now, with a quality guide.

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Notes

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Feed pump—

Off800 L/h

Preheated in HX1—

The feed pump takes the wash from the tank up through the preheater HX1, where the top vapor warms it, onto the beer still's top tray. A cold feed condenses steam on that tray, so less but stronger vapor goes up; a hot feed sends more, weaker vapor up and needs less steam.

Live steam—

Off150 kW

Live steam is blown into the base. On its way down the trays the wash is stripped of its alcohol by the rising steam, and the spent wash, the effluent, is pumped out of the base: more trays or more steam leave less alcohol in it.

Foam carried over—

None10 % of the vapor

Supply—

2 °C40 °C

Condenser line HX4 → HX6 → HX5 → HX2—

Off4000 L/h

Effluent cooler HX3—

Off8000 L/h

One line runs through the product cooler HX4, the fusel cooler HX6 and the heads cooler HX5 on to the condenser HX2, another through the effluent cooler HX3. With too little water, or too warm, HX2 cannot condense all the vapor, and the rest leaves through its vent: alcohol lost to the air.

Heads draw—

Closed5 L/h

Spirit draw—

from tray

060 L/h

The heads draw takes the most volatile part of the top's condensate through its cooler HX5; the rest returns as reflux. The spirit is drawn a few trays below the top, through the product cooler HX4. A start-up runs on total reflux, the spirit valve closed, until the rectifiers are strong; then the valve is opened.

Fusel oil draw 1st rectifier—

from tray

Closed5 L/h

Fusel oil gathers in the 1st rectifier, where its liquid turns from weak to strong; the Fusel oil tab maps it, tray by tray. The draw takes it off a tray there through its cooler HX6. Draw from where most of it is, and no more than needed: the draw takes alcohol and water too, so lower the spirit draw by the alcohol it takes.

In a steady state the alcohol drawn equals the alcohol fed. Draws that take more than the feed brings let water climb the rectifier, and the spirit weakens; draws that take less let alcohol build up in the rectifiers.