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ventilation for pot still and sizing pressure release valve

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Hi guys,

Alcohol vapour is heavier than air so I believe it would sink in a distillery situation if a failure of equipment were to occur. Does everyone install ventilation specifically for operating their stills? What's the best solution. Would an alcohol vapour detection device suffice?

I have a simple 180 litre copper pot still that needs a pressure release valve and vacuum release. Any tips on sizing a valve for this size of a still and where to get them?

Cheers,

Pádraic

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Our State fire code guy had us install exhaust vans above the still. Don't ask why since you already know that alcohol vapor is heavier than air. I haven't seen one installed in other distilleries but that doesn't make it right or wrong. I believe it depends on the inspector.

Our fire and building inspector was fine with 15 psi relief valves. (jacketed still) You can get them at your local plumbing shops.

I haven't seen one on a pot still, again with apparently packing columns to much or overfilling the pots can happen, then you will have a major issue.

But i would get with your local and state fire code.

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Thank you for the response @Williamsburg Distillery. I appreciate the feedback. I prefer to be armed with information before approaching these guys as they can take a very conservative route if they don't know all the facts.

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Alcohol vapor is not heavier than air when it is hot...otherwise your still wouldn't work. Which is why it might be a good idea to have good ventilation above your stills in case of a leak and make sure the exhaust fans are brushless i.e. explosion proof.

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I have used Stranahan's as an example before...they have knee walls around the stills and blending tanks, vents sucking air at floor level and just above the tanks.

post-8489-0-22616400-1444156919_thumb.jp

post-8489-0-73626300-1444157026_thumb.jp

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Guys I really appreciate all the feedback and advice. I will be installing a stainless steel hood above the still and an extraction system to vent any potential vapours.

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Guys I really appreciate all the feedback and advice. I will be installing a stainless steel hood above the still and an extraction system to vent any potential vapours.

Our fire guy asked for an exhaust hood as well, but insists that it be suppressed - you might hear the same thing from your guy.

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,,,,,,,,,,,,

Our fire and building inspector was fine with 15 psi relief valves. (jacketed still) You can get them at your local plumbing shops.

I haven't seen one on a pot still, again with apparently packing columns to much or overfilling the pots can happen, then you will have a major issue.

But i would get with your local and state fire code.

Relief valves have been discussed recently on another thread, please read if you haven't already.

I think Williamsburg has the 15 psi on his steam circuit, not on the pot where the boiling alcohol and mash is.

In my opinion these 15 psi plumbing shop valves could be dangerous on the pot because it could give the operator a false sense of security. They are pretty well useless if the still is trying to puke

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Cheers Pete. I have read that thread but let's say a still was trying to puke as you put it, is there a device/ mechanism that I can allow it to do so?

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1.jpg

Cheers Pete. I have read that thread but let's say a still was trying to puke as you put it, is there a device/ mechanism that I can allow it to do so?

I am not qualified to recommend anything specific but

BURST DISCS of correct pressure and diameter to allow a quick release of pressure.

POP TOP release valves. These open completely as soon as they reach the set pressure.

U tube of water, a longer and bigger version of those found under kitchen sink. (see image below)

All must be safely vented outside.

Simple spring loaded valves might be OK for clean vapor or water but they quickly clog if there are any solids.

photo.JPG

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Cheers Pete. I have read that thread but let's say a still was trying to puke as you put it, is there a device/ mechanism that I can allow it to do so?

YES! An old remedy for this was called a "Slobber Box." A Thumper without being precharged.

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"Slobber box" what a great descriptive name.

I imagine that would work very well as long as the pipe from the still was large enough to avoid too much back pressure

If the top of the "slobber box" was removable then the "slobber" could be bucketed back to the still after it settled down.

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Keys to preventing a still from "puking" are; control the heat better and ventilate your parrot. You can be sophisticated and put a cold finger in the lyne arm, but the first two suggestions are what matters.

Oh, and yes, folks. Ethanol vapor, or a bulk of the flammable vapor from a still's production is LIGHTER than air.

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We have continuous ventilation at low rate over the still, exhausted with heat exchanger. This also keeps general odor build up to a minimum. And we have a high rate exhaust fan in the room at the ceiling that can be used when there is a significant release of ethanol or any other vapor or odor or particulates.

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The authorities are starting to get tougher on new distilleries in Tasmania

The easiest and cheapest way to satisfy much of their concerns is to have enough forced ventilation = Bluestar

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The question of whether a gas is lighter or heavier than air has several implications in the alcoholic beverage industry, and there is quite a bit of misinformation and misunderstanding around.

The first factor to bear in mind is that gases mix very easily i.e. they are miscible. If you discharge pure ethanol vapor into air it will quickly mix with the air and you should assume that it is evenly distributed throughout the room. The danger is not confined to the floor area. The gases will not layer out according to their molecular weights. Mixing gases is just like mixing liquid alcohol into liquid water. The fact that liquid ethanol is lighter than liquid water does not cause the liquid alcohol to float to the top of the water. It will happen with oil in water because the oil is not miscible in water, but ethanol and water are perfectly miscible and you can leave a bottle of vodka on the shelf for 10 years and the ethanol will not float to the top. Gases are also perfectly miscible and will not layer out.

On the other hand, you do get accidents caused by layering of gases. I have seen cases of people asphixiated by carbon dioxide. But this was caused by very cold CO2 being formed by vaporization from dry ice blocks stored in a pit. The CO2 vapor was generated very slowly and because of the extreme cold it just sat in the pit. To get layering the gas has to be very gently discharged and generally there are large temperature differences that cause bulk density differentials.

Theoretically, ethanol vapor is heavier than air all the way up to about 190 degrees C (370 F) under equal pressures. But this only applies to gases that are kept apart. As soon as they mix they stay mixed and will not separate into layers based on the theoretical pure densities.

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So would you say that a knee wall isn't going to make a difference?

The question of whether a gas is lighter or heavier than air has several implications in the alcoholic beverage industry, and there is quite a bit of misinformation and misunderstanding around.

The first factor to bear in mind is that gases mix very easily i.e. they are miscible. If you discharge pure ethanol vapor into air it will quickly mix with the air and you should assume that it is evenly distributed throughout the room. The danger is not confined to the floor area. The gases will not layer out according to their molecular weights. Mixing gases is just like mixing liquid alcohol into liquid water. The fact that liquid ethanol is lighter than liquid water does not cause the liquid alcohol to float to the top of the water. It will happen with oil in water because the oil is not miscible in water, but ethanol and water are perfectly miscible and you can leave a bottle of vodka on the shelf for 10 years and the ethanol will not float to the top. Gases are also perfectly miscible and will not layer out.

On the other hand, you do get accidents caused by layering of gases. I have seen cases of people asphixiated by carbon dioxide. But this was caused by very cold CO2 being formed by vaporization from dry ice blocks stored in a pit. The CO2 vapor was generated very slowly and because of the extreme cold it just sat in the pit. To get layering the gas has to be very gently discharged and generally there are large temperature differences that cause bulk density differentials.

Theoretically, ethanol vapor is heavier than air all the way up to about 190 degrees C (370 F) under equal pressures. But this only applies to gases that are kept apart. As soon as they mix they stay mixed and will not separate into layers based on the theoretical pure densities.

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I think you will find the knee wall shown above at Stranahan's is for containing a liquid spill, not vapor

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My experience/understanding is in line with PeteB's, i.e. the wall is there to retain liquid spills and generally keep the main floor dry. If the ethanol vapor were gently "poured" behind the knee wall the concentration of ethanol would be higher there, but would mix quickly. The main thrust of my argument is not to deny that lower areas might have higher concentrations of ethanol at some stage, but rather to say that you should not regard higher areas as safe. You should assume that the vapors will spread throughout the room and regard the entire volume as potentially flammable.

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Re: Stranahans -- the kneewall is for containment as they are an H3 not an F1. This was part of a discussion at the last ADI conference.

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Floor level ventilation isn't as useful in a room where ethanol vapor being leaked from a still is a potential concern. Gasses discharged from the still will be both hot, thus rising, and agitated, if not by general airflow from movement then from convection created by the hot equipment, thereby mixing as meercat suggested. They are, however, being used in barrel aging rooms, as the ethanol vapor slowly leaks and can stratify in the less frequented rooms. This is more of an insurance issue at the moment but expect to hear more about it as the regulating bodies turn more of their attention to us.

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On November 14, 2015 at 3:34 AM, meerkat said:

The question of whether a gas is lighter or heavier than air has several implications in the alcoholic beverage industry, and there is quite a bit of misinformation and misunderstanding around.

The first factor to bear in mind is that gases mix very easily i.e. they are miscible. If you discharge pure ethanol vapor into air it will quickly mix with the air and you should assume that it is evenly distributed throughout the room. The danger is not confined to the floor area. The gases will not layer out according to their molecular weights. Mixing gases is just like mixing liquid alcohol into liquid water. The fact that liquid ethanol is lighter than liquid water does not cause the liquid alcohol to float to the top of the water. It will happen with oil in water because the oil is not miscible in water, but ethanol and water are perfectly miscible and you can leave a bottle of vodka on the shelf for 10 years and the ethanol will not float to the top. Gases are also perfectly miscible and will not layer out.

On the other hand, you do get accidents caused by layering of gases. I have seen cases of people asphixiated by carbon dioxide. But this was caused by very cold CO2 being formed by vaporization from dry ice blocks stored in a pit. The CO2 vapor was generated very slowly and because of the extreme cold it just sat in the pit. To get layering the gas has to be very gently discharged and generally there are large temperature differences that cause bulk density differentials.

Theoretically, ethanol vapor is heavier than air all the way up to about 190 degrees C (370 F) under equal pressures. But this only applies to gases that are kept apart. As soon as they mix they stay mixed and will not separate into layers based on the theoretical pure densities.

Very good post meerkat! You did a good job describing the situation. There is a misconception out there, that is, if ethanol were heavier than air, your still wouldn't work. However, as ethanol goes from liquid to vapor form, it displaces the air pushing the air out. Imagine these vapors being produced at the surface of your wash inside the still, and building up slowly eventually making their way through the system. In an open air environment, however, it mixes very easily as you stated. The heavy gas in the tank in this video shows it clearly: 

 

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