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ventilation for pot still and sizing pressure release valve

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Very misleading demo. Sulfur hexafluoride has a density of 6.12 g/L, versus air at 1.23 g/L and ethanol vapor at 1.50 g/L. You're going to have a VERY hard time floating a boat on a tub of ethanol vapor. And even with sulfur hexafluoride's extreme density, it STILL fully mixes with air eventually. It is the most potent greenhouse gas ever tested - 24,000 X more so than CO2. It's effectively banned in Europe.

 

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3dog, I'm not suggesting the use of sulfur hexafluoride in anyway and I'm not suggesting a "boat" will float in ETOH vapors. Some people just need help visualizing things and many believe if something is "heavier than air" your still "wouldn't work". In a perfect scenario with no air or surface movement, which is impossible, if ethanol vapors were being pumped in the bottom of the pot they would push the oxygen out just as water would if you were filling it through the bottom of the pot. 

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Agreed iskiebaedistillery but that visualization really has little to do/compare with still operations. Ethanol vapor will not behave like the sulfur hexafluoride did. Ethanol vapor is so close to air in density that natural currents, temperature variations, and even basic entropic mixing rapidly blends the gases.

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Ive always had an issue with pop offs. One you are doing something very wrong. Two you are releasing a ton of vapor into the air next to an open flame, most the time. The safest thing I have seen was a 5 psi pop off while using electric controller from schnappstills with explosion proof contactors and an alarm to notify of high temps. Both being used as emergency shut off. Plus a large exhaust fan in the gable. Best option NEVER walk away form your still, and keep an eye on temp. Pressure is created by heat. Heat is read in temp. Raising temp= raising pressure. Obviously if you still reaches 213F you have a MAJOR ISSUE!

 

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replying to Moonshiner 11

6 hours ago, Moonshiner11 said:

One you are doing something very wrong

I don't understand why you have an issue, the only reason any safety device is needed is for when something goes wrong, usually when not expected. Hopefully the safety device never needs to operate
 

7 hours ago, Moonshiner11 said:

Two you are releasing a ton of vapor into the air next to an open flame,

Please read previous page on this thread. I said safety valves should release the vapour to a safe place outside. Yes, you could have a problem if released inside.

I will probably cause a bit of disagreement here, but an open flame close to the release of a relatively small continuous flammable vapour is actually a safety device, it consumes the vapour before it builds to an explosive level. Research the reason for flare stacks at oil refineries and oil wells.

7 hours ago, Moonshiner11 said:

Raising temp= raising pressure

ONLY in a solid sealed container. A correctly operating still is open to atmosphere so raising temperature does not increase the pressure in the still. The pressure will only increase if the still has a fault that blocks the outlet, AND the condenser is not condensing the vapour as fast as it is being produced.

7 hours ago, Moonshiner11 said:

Obviously if you still reaches 213F you have a MAJOR ISSUE!

Every day my still reaches 213F in the pot, it is one indication that all the alcohol has probably all boiled off. It is not an ISSUE

Pure water boils at about 212F, depending on the altitude.

Water that contains "salts" can boil at well over 212F. Sea water boils at roughly 220F. I assume there is enough salt in my pot to increase the boiling point by 1F

If I didn't turn the heat off the pot temperature will gradually increase as water boils off and the salt concentration increases.

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Moonshiner 11

Pressure relief safety devices are very important.  Every still in every distillery should have pressure relief safety devices on the inner boilers and jackets.  We are now starting to put them on our columns as well, just for the sake of safety redundancy.  Safety devices on the inner boilers and columns should be 5psi and they should be of the correct capacity for the boiler size, and of course everyone knows, or should know that the vapor from pressure relief safety devices, that are on inner boilers and columns should be routed to a safe area to the exterior of the building. 

Please tell me a little about the Jason Schnapp heating systems and panels.  Are they NEMA4X?  Do they have all UL listed components? Do the control panels meet the NEC 409 requirements? 

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We installed 2 floorsweeping vents that flank our still with ceiling vents plumbed into the same explosion proof exhaust fan above the system. We don't run the still without the negative pressure from the venting turned on. Frankly we never turn it off. 

Pressure relief valves are a critical safety device and I can't imagine a still running without one. Where the industry has fallen into trouble was with equipment producers using relief valves that were rated for high pressure systems. This, in effect, made the valves just for show to pass regulations. The welds and joints in most stills wont last past 40 psi, so a relief valve higher than that is pointless. I believe this is the main contributing factor to the Silver Trail explosion last year. They had packing that clogged the vapor line and thus pressurized their kettle and the relief valve was rated at something obscene like 150 psi. Most typical stills should never have system pressures much higher than the solution's vapor pressure which is minute in the scheme of a pressure system. Everyone should check their stills for relief valves (both pressure and vacuum). 

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I have a lingering engineering question. Valves have been beat to death. I don't think ventilation has been.

Why do all of these ventilation systems rely on negative pressure and venting through an explosion proof fan?

I would assume we could remove the same amount of air/fumes from a building with positive pressure (fan blowing in on one end of the building) and vents at the far end (exhausting air).

My logic sees this as safer, less expensive and just as effective.

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Not sure if this is the reason, but a lot of buildings have forced air for heat. Its not running 100% of the time, so if it was positive pressure then the ethanol vapors could be forced through the ducts. Obviously, if you just had exhaust ventilation directly from the distillery to the atmosphere and radiant hot water heat, then I could see it working.

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Heat? In the distillery? Only in Minnesota...:rolleyes:

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On 10/6/2015 at 1:50 PM, glisade said:

Alcohol vapor is not heavier than air when it is hot...otherwise your still wouldn't work.

Actually, this is not entirely correct. The hot vapors rise in the still because the condenser creates a lower pressure (slight vacuum) and the vapors travel from the higher pressure where the vapors are generated in the pot to the top. Even at 200'F (above its atmospheric boiling point) ethanol vapors are 20% heavier than air. Ethanol vapors will fairly quickly mix with air, although they will still tend to seek the floor.

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On 9/28/2016 at 1:06 PM, Falling Rock said:

Why do all of these ventilation systems rely on negative pressure and venting through an explosion proof fan?

iskiebaydistillery has the right idea. By using negative pressure ventilation, you prevent any flammable ethanol vapors from traveling from the origin to other parts of the building that are not designed for the hazardous location - primarily electrical. If your distillery is in a separate building, positive pressure ventilation will definitely work and save the cost of the XP fan.

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This is a 2 inch pressure/ vacuum release on my still. I turned heat off at end of run and left condenser water on. A slight vacuum develops in the still and air quickly enters and prevents still collapsing. Over pressure vents the other way if for instance cooling water not turned on. I recently saw a still that collapsed after turned off and hatch left closed. Air could not enter parrot fast enough to overcome the vacuum. It was re-built then a few months later the base buckled and split when another operator forgot to turn condenser water on and pressure increased because vapour could not escape through the condenser fast enough. Very dangerous situation. That still now fixed and has a similar water column safety.

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This is why we have always put vacuum relief valves on all of our still pot and mash tun inner boilers.  Everyone should have them on their fully enclosed storage tanks as well.  Vacuum is a force of nature, not to be screwed with.  http://www.teachertube.com/video/railroad-tank-car-vacuum-implosion-258883

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