Talk:Column still

Robert Stein

I think it is important to include Robert Stein in the history of the column still as his model the patent still invented in 1827 was improved on by Coffey. —Preceding unsigned comment added by 59.167.231.150 (talk) 05:27, 29 February 2008 (UTC)

Stein's invention is now discussed in the article. I notice that you refer to his invention as "the patent still". Did he actually have a patent on it? (I thought that the term "patent still" came into common use because of a patent by Coffey, not Stein.) —BarrelProof (talk) 19:53, 29 May 2011 (UTC)

Boiling points

The last paragraph mentions that this still doesn't filter out higher boiling point contaminants. Is this true??? I thought methanol had a lower boiling point than alcohol66.64.248.162 (talk) 23:26, 21 July 2008 (UTC)

AFAIK methanol is an alcohol that is poisonous to humans. The alcohol found in various spirits is ethanol (Often? Solely?). See Ethanol and Methanol for properties, boiling points etc 59.95.26.31 (talk) 09:55, 23 December 2008 (UTC) Ferdi

The azeotrope is the 4% of ethanol-water compound. It has a lower BP than either of its parents. The BP of this azeotrope is lower than 78.37C. If an azeotrope is formed, it is always the first fraction. The first column of the Coffey still is now known as a reflux column. This type of still is used to make 96% pure ethanol. The hot distillate is then flavored and diluted with water. Gin and vodka are examples of such flavored spirits. There is little point in removing the azeotrope, via chemical drying, as water is later added in production. — Preceding unsigned comment added by 220.244.73.231 (talk) 23:27, 15 April 2014 (UTC)

It is possible that the original statement meant contaminants with higher volatility rather than those with higher boiling point it does not make sense and looks to have been removed.

You are correct in assuming that, all the methanol and any other more volatile products will distil off with the ethanol, some portion of water and other less volatiles will also be carried over. The more the process refluxes the less water and tails will be included to the azeotropic limit. The purer the distillate the less flavour components are included.

After 1908 the residual sugars in Sulfite process wood pulp were fermented and used to produce ethanol (in Germany, Italy, Sweden, Finland and perhaps elsewhere). At times this was targeted for human consumption. The distillation was done in multiple stages but continuously, a first stripping stage (to remove solids and the bulk of water) followed by a (column) rectifying stage to reach close to 95% prior to dehydration for fuel blending. For drinking and analytical use a further one or two refluxing fractionating stages (columns) were used to remove the fusels and recover the methanol.

The ratio of methanol to ethanol in distilled alcohol is similar to the original ferment as a first approximation. Ethanol is a common antidote to small doses of methanol and without the antidote it is very poisonous. Removing the methanol concentration at the start of a batch or in a later fractionating stage can eliminate the methanol but at this point there is little flavour left.

Idyllic press (talk) 15:10, 28 March 2017 (UTC)

Continuous still?

Why is there mention of a continuous still planted in the middle of an article on column stills? Confusing. Clarification needed.--69.122.62.231 (talk) 14:49, 3 December 2009 (UTC)

In informal use, the terms column still and continuous still are roughly synonymous, because the column still is the most well-known and widely-used way of performing distillation using a continuous process. See also the continuous distillation, fractional distillation, fractionating column, batch distillation, and pot still articles. This aspect seems to be treated somewhat differently in the article now than it was when the above comment was originally made – referring to continuous still as an "also known as" term for column still. I somewhat wonder whether this article and and some of those others (e.g., continuous distillation, fractional distillation, and fractionating column) should be merged. —BarrelProof (talk) 20:03, 29 May 2011 (UTC)

I think the informal use should be deprecated and the correct use should be indicated. A column still is a generic term for something with a tall hollow pipe or cylinder. In this context it implies a reflux column and used in a manner similar to a fractionating still. A pot still usually implies something that is batch processed traditionally not refluxing. A continuous still is usually of the column type and so usually of the refluxing type.

Fractionating can be done in time, temperature or space; in a gas chromatograph it is done in the time domain, in a pot still with temperature (cooler fore-shots are discarded) and in a continuous fractionating column it is done in space by taking the fractions off at different levels. Almost all distillation process are fractionating as the idea is to separate the raw material into fractions.

To recap, continuous means the raw material is pumped in and pot still means that it is done in batches. Column implies refluxing.

Idyllic press (talk) 14:27, 28 March 2017 (UTC)

Clearer explanation of the process

I'm afraid I can't fully grasp how the process works as the explanation in the text is unclear and sometimes ambiguous and possibly contrary to the diagram, which has a key but no explanation, including regarding which are wanted an which waste products.

The diagram lists the first stage as wash entering the rectifier but in the article text the rectifier (with a clearly incorrect link to the electrical device) is confusingly referred to as the second rather than the first column. The wash is shown descending the rectifier in a zig-zag or spiral but what is this achieving?

What is the "liquid out" at stage 3 in the diagram ((largely) condensed steam?) and is it a wanted or waste product?

When the alcohol vapour from stage 4 goes to the rectifier, what happens there? The article text states that "it circulates until it can condense at the required strength" but how does this come about? Are the "Most volatile components" removed at stage 6 of the diagram the desired end product? What are the "Recycled less volatile components" at stage 5 and are they recycled as they have a higher water content which can then be reduced further in recycling?

Why doesn't the addition of steam to the analyser simply further dilute the wash, defeating the object of the whole process?

The article states that "Column stills behave like a series of single pot stills, formed in a long vertical tube". Are we talking about the whole mechanism here, the analyser alone or something else? What is a bubble plate?

The link to analyser in the article text appears to be in need of disambiguation.

I potentially have some further points which require clarification but they are dependent on the answers to the above. Mutt Lunker (talk) 10:35, 29 May 2011 (UTC)

Because I could not find appropriate articles to link to for the rectifier and analyser terms, I simply removed the links and italicized the terms. I don't consider myself sufficiently knowledgeable to help with the other aspects of the above request for clarification. —BarrelProof (talk) 20:52, 29 May 2011 (UTC)

The image is abysmal. It has been drawn by someone who does not understand physics (pressure and gravity) and will not even work enough to explain the functions. The tiny logo above of the WikiProject Chemical and Bio Engineering is a much better fractionating column image and would then need the rectification column.

Idyllic press (talk) 14:14, 28 March 2017 (UTC)