Distillers Grains & Evaporation

Distillers Grains and Evaporation

Thin Stillage, Syrup and Condensate

After the beer column, whole stillage is separated. The wet cake goes to the dryer; the thin stillage goes to the evaporators, is concentrated to syrup, and is blended back with the cake to make distillers grains. Each of those steps has heat exchange around it, and the stream changes character as it goes.

Concentration changes the duty. Thin stillage entering the evaporator train and syrup leaving it are not the same fluid. Viscosity climbs, the transfer coefficient falls and the fouling rate rises with the solids content. A unit sized at the dilute end will underperform at the concentrated end, which is the most common disappointment on this part of the plant.

Free-flow is usually the answer. The stream carries fibre. A wide unobstructed channel passes it, and the pack opens for mechanical cleaning rather than relying on chemical circulation alone. The surface area penalty is real and it is worth paying.

Condensate is the clean side of the same process. Evaporator condensate is a recoverable low-grade heat stream and it is comparatively clean, so it takes a standard plate selection. Recovering it into process water or CIP make-up is usually straightforward once someone looks for it.

Size at the Concentrated End. The single most useful thing you can send for this duty is the range rather than a design point. Thin stillage at the front of the evaporator train and syrup at the back differ enough in viscosity and fouling behaviour that a selection made for one will not serve the other.

Where a unit has to work across the range, it gets sized against the hard end. That costs surface area, and it is the difference between a unit that holds its duty through the campaign and one that is cleaned more often than the schedule allows.