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Could someone please put into 1st grade terms exactly how a continuous still works? I understand the pot still method, but every time I read about a continuous still I end up more confused than I started. http://www.straightbourbon.com/ubbthreads/images/icons/confused.gif
Well if I explain it it will be in the simplist terms , anyway here goes it is a column affair about 60 feet tall with a lot of plumbing steam pipes etc. the closet thing I think it reminds me of is the bubbling tower at a refinery, anyway the fermented mash is continiously being fed to it and the spent slops are carried away and of course the distilate is being removed. They say the Pot stills at L&g are made to run continous , I was disappointed when I heard that . We will see in Sept when the Straight Bourbon Bunch gets to tour there and maybe taste some of the still product!
You're right Jeff, the continuous column still is rather baffling. Just think of the column as a big piece of large diameter drain pipe standing on end. Inside are a number of plates 20 to 25 of them is fairly common. About two thirds of the way up the column is the feed tray (it's special plate with holes in it). Below the feed tray are the stripping plates or trays. These have holes in them too. The mash is pumped into the still via the feed tray and falls down the colum through the stripping trays. Live steam is is introduced to the still from the bottom and rises to meet the falling beer. The steam strips off the alcohol from the beer and together rise above the feed tray to the upper third of the still where there are usually four or five rectifying trays. These can be of several different designs, but the most common is the bubble cap tray. You have to see one of these puppys to really understand what it is and how it works. Each rectifying tray can be thought of as separate step in the distillation process as the alcohol content continues to rise as the steam and alcohol vapor continues to rise from tray to tray. The vapor comes off the column and is either condensed into low wine whiskey (singlings) and is then sent to the doubler or the vapor can go straight to the thumper to be doubled into high wines. Old Forester is a good example of a whiskey that has been thumped. Wild Turkey is doubled off in the more traditional arrangement. Each method has its merits. I hope this helps.
>Could someone please put into 1st grade terms exactly how a continuous
I'll start by reminding you that distillation separates things that have different
boiling points. Okay, now for the first graders explainiation:
Imagine a tall building, say, 20 stories high. The people that run the building
keep the first floor very hot, but as you climb the stairs, the building
gets cooler and cooler. There are people in the building, and if the floor
they're on is too hot for them, they go up a flight of stairs and sit there for a
while, and if they're decide it's too hot there, they go up another flight of stairs.
Sometimes, people are too cold, so they ride the escalator down until
it gets too hot and then they take the stairs up again.
It doesn't take long for people to find the floor that is perfect for them, so
most people at any given time are going to be happy, although you wouldn't
think so since you see a lot of people moving up and down, but it's true.
Since most people on any given floor are happy, you can use this building to
sort people continuously.
You push a bunch of random people into the building on the 5th floor,
and on the 12th floor, you take out people. Most people you take out
will be happy at the temperature that the 12th floor is at. Oh, and anyone
on the first floor or the 20th floor, you send them home to make more
room in the builing. Anyone on the first floor or the 20th floor is obviously
a wierdo you don't want around.
The temperature on any given floor is always the same. You have a
continuous flow of people in, and a continuous flow of people out.
That's my attempt at continuous distillation for first graders.
Great story. It made sense to me and I used to be a chemical engineering student.
Too much thinking for me. I'll just sip and enjoy. http://www.straightbourbon.com/ubbthreads/images/icons/wink.gif
If you understand pot stills, you understand the principle of distillation. That's step one. Here's how it is applied in a column still.
The still is a tall cylinder. The fermented mash enters near the top. Steam is introduced at the bottom. As the mash descends through the cylinder it meets perforated plates. The mash spreads out on the plate and gradually seeps through the perforations. Meanwhile, it is met by the rising steam, which grabs some of the alcohol and takes it in the opposite direction, up toward the top of the cylinder. As the mash descends, repeating this on sucessive plates, more and more of the alcohol is removed until it exits as virtually alcohol-free "spent" mash. Meanwhile, the alcohol-laden vapors are being directed out the top of the still to coils, where the vapor is cooled, which causes it to condense back into a liquid. This liquid is called "low wine." The low wine is then sent to a pot still for a second distillation, to separate more of the alcohol from the water. This liquid is called "high wine." It either goes directly into the barrel or, more commonly, is dilluted with water and then barreled.
You might ask, "why go through the second distillation to separate water and alcohol only to add more water back in?" The "water" in the first instance contains flavors from the mash that are considered undesirable. The water used for dillution is just water, no flavor.
Thanks Chuck, that explaination made the most sense to me http://www.straightbourbon.com/ubbthreads/images/icons/smile.gif But what are the benifits of this type of still over it's pot type cousin? Cost, time, etc...?
Cheaper to operate. Practical difference is continuous versus charge. Pot stills have to be emptied and "reloaded" each time they are used. Therefore, "batch size" is the capacity of the still. Continuous stills also have to be stopped and cleaned periodically, but they have a huge "batch size" compared to a charge (pot) still.
Also, bourbon is distilled from a fermented mash, a kind of grain slurry (think of thin oatmeal). In Scotland, the solids in the fermentate are separated from the liquid prior to distillation, so only liquid goes into the still. In other words, the process is different.
For the most part, malt whisky is the only whisky made in pot stills. What the Scots call "grain whisky," which is whisky made from anything other than 100% barley malt, is generally made in column stills, even in Scotland and Ireland.
In bourbon-making there are two distillation passes. The first is through a continuous (aka column, Cofey, patent) still. The second is through a pot (aka charge, alembic) still, which is classified as either a doubler or a thumper, depending on whether or not steam is used. These are not the glamorous copper teardrop-shaped pot stills you see in pictures. They are very plain-looking, but their function is the same.
Are continuous stills even partially self-cleaning? Or does all of the spent mash accumulate at the bottom?
I'm picturing the stoker coal furnace that was in our basement when I was a kid in southern Illinois. A worm gear at the bottom of the coal box forced coal into the furnace. All I had to do was keep the coal box full and occasionally remove the ash and clinkers from the fire box in the furnace.
I can imagine a similar worm gear arrangement to remove at least a majority of the spent mash from the bottom of the still.
I've heard folks either here at this forum or elsewhere state that bourbons undergoing primary distillation using pot stills retain more flavor and complexity than those distilled using continuous stills. Is that true and, if so, why?
(I'm assuming the respect that A.H. Hirsch has garnered here along with the anticipation of the new L&G product has quite a lot to do with the pot still production methods and their flavorful results.)
The spent (i.e., alcohol depleted) mash flows out of the still near the bottom. If it didn't, it would accumulate very quickly, defeating the whole purpose. The still has to be stopped periodically because the goop accumulates on everything inside the still. I believe the routine cleaning process is similar to backwashing. I saw a still at Jim Beam once that had been allowed to run much longer than normal, as an experiment. When it was opened, the caked-on spent mash was falling off in huge, black chunks. I asked the distiller what they learned from the experiment. "To not do it again," was his answer.
Pot still advocates make that claim pretty much across the board, not just for bourbon. With the exception of the Michter product, there has been so little pot distilled bourbon available, who can really say? Brown-Forman is gambling that it's true, or they went to a lot of trouble for nothing.
Thanks to everyone who helped clear up my foggy understanding of the continuous still. I think I've got it now. I am, however having trouble with the difference between a thumper and a doubler. I understand WHAT they do, just not exactly how a thumper works. If someone would be so kind as to enlighten me http://www.straightbourbon.com/ubbthreads/images/icons/grin.gif
I have trouble with this too, but I'll try. Both are used for the second distillation of the product of the beer still (i.e., low wines). Both are, technically, alembics or pot stills. The difference is that in a thumper, the low wines are introduced into the vessel as steam, i.e., the vapor coming off the beer still is not condensed. That's why it makes a thumping sound, as it hits the hotter steam in the vessel.
A doubler is more conventionally a pot still. Low wine vapor is condensed into a liquid and then steam is introduced to affect the second distillation.
I had it explained to me for the umpteenth time during the festival and I hope I got it right.
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