Distillation

In distillation, alcohol is separated from the other parts of beer by boiling. The gas that comes off of boiling has a higher alcohol percentage than the liquid that didn't boil, but it's not pure alcohol. So a distillation tower has a series of stages where liquid is boiled. The gas goes up, and the liquid drips down.

So a distillation tower has higher and higher proof liquid as you go up. You put the beer into near the middle of the tower, where the proof matches the beer's proof. The top half, with the higher proof, is called the "rectifier". The lower half, with the low grade liquid, is called the "stripper".

The beer drips down through the stripper and the alcohol evaporates. That alcohol, along with water that also evaporated, moves up out of the stripper into the rectifier. The beer with its alcohol stripped out is called "whole stillage".

In the rectifier, the alcohol and water vapor condenses and boils again. At the very top of the rectifier, 98% pure alcohol vapor exits the distillation tower. At the bottom of the stripper, almost no alcohol is left.

Here's a picture of the distillation tower that was already set up when we bought the plant:

The tower on the left is the stripper, the other is the rectifier. The shiny outer surface you see covers the insulation to reduce wasted heat. The two vertical black pipes connecting them are so that the liquid from the rectifier can be pumped back up to the top of the stripper, and the vapor from the stripper can be sent to the bottom of the rectifier.

Another view of the original pair of stripper (on left) and rectifier. The access ports are to clean the distillation trays.

A stripper / rectifier pair at the plant, ready to be assembled. The original pair is in the background to the left.  The vertical towers are in the background of the above picture.

This is a view of one of the trays inside the above pair of towers.  The mushroom shaped objects are "bubble caps". The fluid flows over the side "downcomers" to the left and right, down to the next layer below this one. The vapor comes up through the bubble caps.

The above distillation tower was originally at a plant in New Hampshire. Here's a (bad) picture of the facility before we took it apart.

Another view of the New Hampshire site. The distillation towers are in center of the picture, towards the top left.