By: Kris Bohm: Owner of Distillery Now Consulting LLC.
If you have a drink of bourbon from a well-known whiskey brand, chances are that whiskey was distilled on a continuous column still. When it comes to making whiskey and selecting the equipment for distilling it is wise to look to industry leaders and their choices can help guide your decisions. Distilleries that are selling millions of cases of bourbon and rye whiskey annually in countries all around the globe use continuous distillation equipment to make their whiskey and that type of still might be the best choice for you.
Most of the established distilleries in the southern United States made the decision decades or in some cases centuries ago to distill their whiskey on stills that are very different from the pot stills. While distillation of whiskey has its history firmly rooted in small batch distillation pot stills, the modern production of bourbon is a very different business from where it began centuries ago. The vast majority of whiskies you will find behind your local bar today were all distilled on continuous column stills. Whether it is bourbon, rye whiskey, Canadian or Irish whiskies there is a good chance that most of the bottles you’ll find were all made on a continuous column still. Together let’s explore a bit of history, operational theory and the economics of continuous stills. My goal with this article is to help you more carefully consider if a continuous column still is the right choice to make your whiskey.
The science of distillation is an ancient technology, with history pointing to the discovery of distilling occurring sometime in the first century AD. As knowledge of distillation and technology improved there are records of spirits being distilled for beverage in the 12th century by Latins. Up until the 1800s all distilling was done in batches on what was a known as simple pot still. The concept of continuous distillation first recorded in Europe in the early 1800s. Many variations of the design of continuous still were created during the 1800s. The first well documented continuous still was named the Coffey still after its inventor Aeneas Coffey. This still was reported to have been patented and built in 1830 and was made from wood, iron and copper. The Coffey Continuous still was found to be far more efficient than the traditional batch or pot still. The reason this still design was more efficient was that it uses less energy and labor to produce spirits. A big benefit of the Coffey still was that it could produce much larger quantities of spirits per hour than pot stills in a much smaller footprint. The Coffey still was recognized by distillers as a better choice of equipment to produce distilled spirits on an industrial scale. As continuous distillation grew in popularity through the 1800s many refinements were made to the original Coffey design, which set the continuous column still to be the equipment of choice for distilleries that needed to make large quantities of spirits.
Lets jump in and talk about the specifics of how continuous distillation works and how it differs from batch distillation. If you understanding of theory on batch distillation science, it is important to approach continuous distillation open minded as the operation and distillation theory is starkly different. The critically important concept one must accept when seeking to understand continuous distillation is the following.
Continuous Column Stills are NOT Pot Stills
The principles and physics that allow a continuous still to function and separate heads, hearts and tails are completely different from batch distillation.
Below is a breakdown of the steps from start to finish and the operating principles of a modern continuous column still. We will trace the 10 steps that occur in a continuous still which will take fermented distillers beer and turn it into spirits.
1) Beer is pumped from a tank called a beer well into the still and injected into the column above the stripping plates at a consistent and continuous flow rate.
2) As the beer is pumped through pipes to the still the beer first passes through a heat exchanger that preheats the liquid before it enters the column.
3) The preheated beer enters the column on the stripping plates and meets rising steam in the still which flash evaporates the alcohol out of the beer. The steam is directly injected into the base of the still.
4) The spirits that are extracted out of the beer are carried as hot vapor into the upper portion of the still. In the rectification portion of the still the spirit it is continuously rectified till it meets that target proof that is controlled by the still operator.
5) As the spirits are rectified in the still the proof increases which separates the tails and fusels with their higher boiling point that are left behind and concentrated on lower plates.
6) The spirits that the distiller wants to collect moves as hot vapor onto the condensers which continuously separates the heads from the hearts.
7) The heads and methanol which have a lower boiling point do not condense and remain vapor which is then is vented off the still at multiple condenser points.
8) The spirits (hearts) is condensed in the condensers, where it passes through the spirit safe and is then pumped to a spirit holding tank.
9) Thanks to gravity the water and solids of the beer slowly move down the stripping plates of the column to the bottom of the still.
10) By the time the beer exits the bottom of the column it has less than .05 percent alcohol remaining in it.
This summary of how a continuous still works is brief and bit simplified. There are pumps, processes and control valves that control cooling and flow to maintain equilibrium and balance in the operation of a continuous column still.
While continuous columns still are efficient and cost effective to operate, this does not mean they are inexpensive to operate. Let’s breakdown the inputs and outputs in the operation of a continuous still to consider the large scale at which they operate.
An 18” diameter continuous column still will distill on average 9 gallons per minute of beer. From a production perspective you can distill over 50,000 gallons of beer in a work week if the still is run 24 hours a day. In distilleries running continuous stills of this size they will often run a single shift per day and not 24/7. In that case a continuous column still being run for 8 hours a day 4 days a week will be distilling upwards of 16,000 gallons of beer per week. When this quantity of beer is distilled it can produce upwards of 45 full size barrels of whiskey per week. We will avoid the discussion here of exact cost as the price of the grains and barrels to produce these spirits can vary widely. Suffice to say the quantities of grain needed to make this much whiskey and the barrels to put it all in adds up to a sizable budget. When it comes to considering efficiency of labor my approach is to look how many labor hours it takes to make a barrel of whiskey. In my experience of operating a continuous still versus a pot still I have found it takes nearly 3 times as many labor hours to produce a barrel of whiskey on a pot still versus a continuous column still. When consideration of the difference in labor cost and energy efficiency is looked at it becomes obvious that a continuous column still is a smarter way to make large quantities of whiskey.
Pot stills are excellent for distilling small batches of spirits and also for distilleries that do not have the budget to produce spirits on an industrial level. On the other hand pot stills are not effective to produce spirits that are comparable in cost to produce as spirits made on a continuous still. One of the biggest hurdle young distilleries face as their sales increase is having the capacity to grow production to keep up with demand. A pot still is difficult to scale up. A continuous still is very easy to scale up production. If you are thinking about starting a distillery, we urge you to consider a continuous column still to make your spirits. The economics are too strong to ignore and the reduction in cost of production is critical to sustain your business as it grows.
Kris Bohm is the owner of Distillery Now Consulting. When Kris is not helping folks with continuous still he can be found pursuing adventures on two wheels and defending his beer mile record.
