Odin on Whiskey Column Design (2)

Introduction

This post continues where the last one stopped. Please read the first post on column design first. Better still, read the two posts prior to that, on boiler design as well.

I finished the first post on column design with a statement that needs further explanation: fruit brandy columns are not ideal for whiskey making. Let’s dive in deeper.

Fruit brandy column lay-out

Fruit brandy columns usually have a wide, broad column, completely made out of copper. Most of the time they do not sit directly on top of the boiler, but on top of an onion like structure called a helmet. Inside the column, there are usually 4, 5, or even 6 bubble cap plates. Near the top of the column you find the so-called dephlagmator. On top of that there may be an additional copper catalyst. After that some horizontal tubing that connects the column to the product cooler. Here’s where gasses get transfered from column to be cooled down to product.

Catalyst

The catalyst is a section near the top of the fruit brandy column filled with copper packing. It is there to deal with unwanted sulfur compounds. Fruit brandy ferments create lots of sulfer, that’s why a catalyst is needed.

Dephlagmator

The dephlagmator is a sort of column cooler. It is a section where the gasses that travel upwards go through tubes that are cooled with water. As a result part of the gasses condense and drop back onto the bubble cap plates.

Bubble cap plates

The bubble cap plates are filled with condensated gasses that fall down from the dephlagmator. The rising gasses, from the boiler or from the plate below, now have to travel through this liquid bath. In this way each plate, with liquids on top of them, effectively performs one distillation.

Wide copper column

The wide column ensures relative low vapour speeds. The column is made out of copper so it can help clean up sulfuric compounds.

What fruit brandy distillers look for

As we did with whiskey, we need to ask ourselves what a fruit brandy column needs to do in order to support the Master Distiller’s wish to make fine fruit brandy. Again, as with whiskey, the answer is easy: the fruit brandy column needs to help harvest the right tastes.

What the right taste components are for a fruit brandy? That’s easy to answer too. Contrairy to a whiskey, that get’s most of its taste and character from (early) Tails smearing into Hearts, a fruit brandy gets it’s taste mostly from Heads smearing into Hearts.

With the Tree Metaphore in mind we can easily envision this: fruity tastes come over in the first parts of the run. During Heads. So … for a great fruit brandy the column needs to facilitate the smearing of Heads into Hearts.

Not much good can be found in Tails, when you are making a fruit brandy, so a well designed fruit brandy column makes sure Tails don’t come over.

The last thing a fruit brandy column is designed to do, is to clean up sulfurs. Sulfuric compounds are formed in abundance during fruit fermentation. They make the drink undrinkable. Fortunately, copper reacts with sulfur and sorta neutralizes it.

How this design favours fruit brandy making

The onion or helmet on top of the boiler (and situated below the actual column) does three things. Remember that high rpm spinner fruit brandy stills use? And how they throw the pulp high into the gas bed? The helmet creates extra head space, so the pulp (or grains, when a fruit brandy still is used for whiskey making) flying around does not enter the actual column.

The second thing the helmet does is create a buffer for turbulence. The turbulence is caused by the narrow boiler design and fast spinning agitator. The helmet sits well above that so that most of the turbulence created in the boiler gets a chance to subside, prior to entering the column.

Thirdly, the helmet functions as an expansion chamber, slowing vapour speed down.

The column, sitting on top of the helmet, is fed with low vapour speed gasses. The wide fruit brandy column design makes sure vapour speeds stay low during the entire distillation run.

Why slow vapour speeds help the fruit brandy distiller? Remember that big, heavy molecules need a lot of speed, when we want them to come over in the final product? Well, Ethanol needs much less energy to be distilled. And the Headsy fractions, like Methanol and Ethyl Acetate, need even less energy.

This is the really important part. Pay attention, please, here we go …

It is the lower vapour speeds that favour the separation of Headsy tastes and allow a fruit distiller to smear them in a controlled way into Hearts! 

They need the low vapour speeds to ensure that at the beginning of a run more (and more pure) Heads come over. Due to the fact that they use relatively inefficient dephlagmators that can usually only cool down part of the gasses, higher vapour speeds would smear in too much Ethanol, making good cuts for Fores and Heads more difficult. The lack of total column control means they are left with no other option than to slow vapour speeds down as much as possible.

But … low vapour speeds mean no Tails come over, right? Right! But that is of no concern to the fruit brandy distiller. In a fruit brandy distilate the Tails only cause off tastes and problems. It is a major concern when you want to make whiskey or rum, though …

In fact, apart from the low vapour speeds, even the water baths on top of the bubble cap plates, and their respective temperatures (ABV-related, off course), prevent the smearing of Tails into Hearts. Tails get trapped and accumulate in on the lower plates.

Low vapour speeds and copper are the key to fruit brandy distillation. The low vapour speed allows the distiller to work with Heads, while not having to worry about Tails. The copper takes care of the sulfur rich fruit brandy washes.

Instead of a narrow column, a wide column is better. Lower vapour speeds again. And efficiency isn’t very important. In fact, an efficient still, with insulated column will decrease the amount of passive reflux that helps fill the bubble cap trays. And the nett energy gain, caused by augmented energy efficiency, will increase instead of reduce vapour speeds.

Oh, and last but not least, fruit brandy stills have a lot of plates. The alcohol needs to come off at a rather high ABV, in order to give the fruit brandy Master Distiller the capability to (1) Harvest a good Heads faction, while (2) still being able to get rid of unwanted Fores. Remember that the Heads and Fores factions are much more volatile and also much smaller than the Tails faction.

This is quite critical. Fruit brandy does not age as long as whiskey does. Neither do (unwanted, overconcentrated) Fores and Heads faction age out as well as early Tails do. The fruit brandy maker therefore needs more control. Because the 1860 technology does not provide total column management systems, he needs to have the extra plates and higher ABV to improve control.

And why it isn’t the best when making whiskey

We concluded in the previous post that a still designed for whiskey making should be efficient and have a rather narrow column. The narrow column creates the vapour speeds needed to carry over early Tails. The efficiency of the still makes it possible to use power management as an effective means to influence vapour speeds even more. More power in for more smearing, less power in for less smearing.

Fruit brandy stills don’t promote higher vapour speeds, so if smearing early Tails into Hearts is your goal, as it is when making whiskey … you will have a hard task at hand.

Most distillers that use fruit brandy equipment for whiskey making have to re-run their Tails again and again (I know one distillery that re-uses Tails five times!), just to get sufficient amounts of Tails associated congeners over in their final product.

Fruit brandy columns are made from copper and uninsulated. Copper radiates off increadible amounts of energy into the distilling room. That’s the second problem.

Even if you wanted to enforce higher vapour speeds by adding more power, most of that power just translates to more energy losses rather than higher vapour speeds. And even if you can circumvent that by for instance insulating the column … the additional gasses would just start throwing the water beds on top of the plates in the air, thus creating vapour channeling, where huge amounts of Tails can suddenly overwhelm both the system and your drink.

Third problem? Copper is expensive in two ways: to buy and to run. Yes it serves a goal when making fruit brandy, by keeping sulfurs under control, but grain washes only procuce limited amounts of sulfur.

Copper is much more expensive to buy. And it is much more expensive to run, due to energy losses. An expensive and inefficient fruit brandy still means your whiskey’s cost price will be higher. Well, explain that to your shareholders, now that Craft Distillers too are faced with more and more intense price competition!

There’s yet another challenge, when you want to use a fruit brandy still to make whiskey. Fruit brandy stills have too many plates. Whiskey needs just two or three distillations, not four or five. There are three problems associated with redistilling whiskey too much:

  1. Capital investment and cost price: you buy more plates than you need;
  2. The taste will become thinner with each distillation cycle;
  3. High ABV new make whiskey spirit … needs to be watered down right away!

Whiskey needs barrel ageing. And barrel ageing takes place at around 60%. So, as long as the whiskey is distilled in such a way that proper cuts can be made, usually twice, let’s try to keep our Hearts cut as close to the 60% as possible. Why? Easy. If we have to water an 80% new make down to 60% … we dilute away around a quart of the total taste potential. When making whiskey, you are after taste. You want to harvest taste, not dilute it!

And that’s the third reason why whiskey made in a fruit brandy still is so often thin in taste. A recap:

  1. No Maillard Reaction in the boiler;
  2. Low vapour speeds and liquid baths on plates effectively block early Tails smearing into Hearts;
  3. High ABV new make spirit needs to be diluted right away.

Conclusions

Great whiskey can be “found” where early Tails smear into Hearts. Whiskey distillation therefore benefits from an efficient still combined with a narrow column for high vapour speeds. The high vapour speed helps getting over early Tails. An efficient still allows you to control that process by means of power management.

The very popular fruit brandy stills are not ideal, when you are in the persuit of making great whiskey, because they are designed to harvest Headsy rather than Tails related congeners. Because of low vapour speeds, too many distillation cycles, and indirectly fired boilers, the whiskey tends to come over tasting thin.

More?

Yes, for sure. Next post will be about how we apply the “lessons learned” and “vision shared” into our product designs. And maybe a fourth post after that? Yes, on brandy, rum and vodka.

http://www.istill.eu

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