Advice needed: Dephlegmator cooling capacity and plumbing

[wrathskellar]

Greetings folks,

After a few years now running a simple pot still, and a few months prior to that with a Nixon-Stone, I've just acquired a 4" modular 6 bubble-plate still. It came with tubing, wye connectors, and valves for both the reflux and product condensers, but the plumbing parts are all really cheap and I'd like to upgrade them and make some improvements on the system. I have questions about how to design the plumbing system, and I know there are a lot of unknowable variables that limit the ability to conclusively answer. But I'd like to avoid making mistakes that would result in buying a bunch of fittings and valves and stuff more than once to arrive at a working system. So I'm asking for your experience with similar equipment ...

I want to stick with flexible opaque polyurethane tubing, but get somewhat better quality connectors and valves. Based on my reading here, there's a few other mods I'd like to make too. (diagram below) Also, since it's hard to find metric fittings in the US, I want to replace the metric tubing that came with the still with tubing sized in good ol' American inches. Along with that, I'm trying to avoid steel fittings. Plastic push-connect fittings look like the best option for ease of assembly / disassembly, reconfiguration, cost and weight considerations, etc. There are both cheap and decent quality push-connect components available and I'd like to stick with better quality stuff.

Most of the problems I've encountered in designing this have been around the question of the amount of water flow I'll need at full reflux. The dephlegmator is 4" dia x 8" L, and made up of six 15mm ID vapor tubes, and will be fed by garden hose, adapted down to the tubing. The still was supplied with 12mm OD / 8 mm ID tubing, so I figure that's considered sufficient.

So I guess my first question is what tube size is suited to this still? I'm thinking 3/8", but that might be dependent on power input so I should add here that I'm gas fired, and the best I can do is guess at power input levels. I'm running on a 15.5 gal beer keg as a boiler. Also, 3/8" tubing has a 1/4" ID, which is rather smaller than the 8mm ID I was supplied with. I could step up to 1/2" tubing, but then you run into the second problem ...
... which is sourcing a decent quality, plastic body needle valve for reflux control. McMaster-Carr has these:

https://www.mcmaster.com/7781k42

which look like a good option, but they only accommodate 1/4 and 3/8 OD tubing. And assuming 3/8 OD / 1/4" ID is enough flow for full reflux, will that valve pass enough fluid when wide open? I'm struggling to wrap my head around flow coefficients, but it looks to me like its max flow rate is .4 GPM (its flow coefficient). Or am I way off base? (That seems likely at this point, as my head is spinning trying to parse the physics of fluid dynamics.)

I'm happy to take suggestions for flow control valves. Finding push-connect valves has been hard, so I might have to compromise and use a couple metal NPT adapters to make something work.

Ok, so assuming 3/8" tube is sufficient, and the valve is fine, another problem is that the coolant water supply also feeds an impressive garden and lawn, and its irrigation needs. Sprinklers are constantly turning on and off through the day, which will affect the flow rate of coolant, which will result in constant fiddling with the needle valve to keep things in equilibrium. To avoid this, I'm thinking a simple flow regulator of the sort used in drip irrigation systems might help if placed before the reflux condenser inlet. But what flow rate would I need at full reflux? Again, this brings up a bunch of questions I don't know how to answer: how much heat am I putting into the system? How efficient is the dephlegmator? What temp is the water? And so on. Generally speaking though, with similarly sized stills, is 1 GPM enough? Closer to 5? 10? What's your experience?

And lastly, I plan on adding a bypass valve to the outlet side of the dephlag, so I can quickly put the system into full reflux. I'm thinking a simple quarter turn ball valve will do here.
Thoughts?

[still_stirrin]

....After a few years now running a simple pot still, and a few months prior to that with a Nixon-Stone, I've just acquired a 4" modular 6 bubble-plate still. It came with tubing, wye connectors, and valves for both the reflux and product condensers, but the plumbing parts are all really cheap and I'd like to upgrade them and make some improvements on the system....I want to stick with flexible opaque polyurethane tubing, but get somewhat better quality connectors and valves...the question of the amount of water flow I'll need at full reflux.

The dephlegmator is 4" dia x 8" L, and made up of six 15mm ID vapor tubes, and will be fed by garden hose, adapted down to the tubing. The still was supplied with 12mm OD / 8 mm ID tubing, so I figure that's considered sufficient....might be dependent on power input so I should add here that I'm gas fired, and the best I can do is guess at power input levels. I'm running on a 15.5 gal beer keg as a boiler....So I guess my first question is what tube size is suited to this still?

Whew, a lot of background info there (thanks)...I’d say don’t use less than 1/2”ID for the plumbing.

A 4” plate will require a lot of power to run and you’ll need to remove that heat from the system. If you use anything smaller than 1/2”, the flow pressure drop could be significant when operating in reflux and you’ll have a hard time keeping it stable. Garden hose is typically 1/2” ID (5/8” OD) and I wouldn’t use anything smaller.

With flow control valves on the discharge from the deflag and product condenser, you can easily regulate the flow slower if needed. But you can’t make it greater if the hoses and fittings are too small ID. Also, depending on your water source, your inlet pressure may fluctuate too, especially if it is sympathetic to an irrigation system or household plumbing. You’ll need a steady flow (at a uniform pressure) to manage the CM (coolant managed) reflux still.

...Ok, so assuming 3/8" tube is sufficient, and the valve is fine, another problem is that the coolant water supply also feeds an impressive garden and lawn, and its irrigation needs. Sprinklers are constantly turning on and off through the day, which will affect the flow rate of coolant, which will result in constant fiddling with the needle valve to keep things in equilibrium.

To avoid this, I'm thinking a simple flow regulator of the sort used in drip irrigation systems might help if placed before the reflux condenser inlet.

But what flow rate would I need at full reflux? Again, this brings up a bunch of questions I don't know how to answer: how much heat am I putting into the system? How efficient is the dephlegmator? What temp is the water? And so on. Generally speaking though, with similarly sized stills, is 1 GPM enough? Closer to 5? 10? What's your experience?

How big is your gas burner? That will determine how much heat you can put into the system. And again, the 4” 6-plate column will require a lot of heat to keep loaded. So, the flowrate demand could be as high as 5 gpm depending on the temperature of the water. And bear in mind too that with a high flowrate, the pressure drop through your plumbing will affect the flow’s stability. So, keeping the piping large diameter will minimize flow loss in the network as the velocity will be slower.

...And lastly, I plan on adding a bypass valve to the outlet side of the dephlag, so I can quickly put the system into full reflux. I'm thinking a simple quarter turn ball valve will do here.

Sure, a bypass would help you balance the flow. But as indicated already, don’t undersize your piping or valves.

Good luck with the new system.
ss

[LWTCS]

As per your diagram, I wouldn't recommend merging your discharge. At least not immediately.
You'll want to have a visual indicator of your usage. The clear tube will help you evaluate your flow rates. But you'll also want to collect the individual discharge to get a handle on usage.

Make sure you get some quality hose that won't soften with higher temps. Doing so will shut down flow.

[Demi]

I'm a big ol noob here, so if someone else contradicts the following, go with their advice, maybe even read it as a question instead of a suggestion, since it seems like you already know much more than I do. That said:

Controlling reflux flow (or any irrigation flow) on the output side builds up pressure in condenser in my limited experience. For me, it blew the hoses off, and required a changing of pants. The input flow won't allow pressure to escape backwards, and limiting the flow out gives it nowhere to go if it exceeds available throughput. On this setup I can't imagine you would ever run low enough flow for this to happen, but just food for thought. Is there an advantage to controlling flow on the output side? Maybe this only happens if it's completely closed?

[This Old Fart]

The valves referenced below have a max temp of 140f, is this a problem?

which is sourcing a decent quality, plastic body needle valve for reflux control. McMaster-Carr has these:

https://www.mcmaster.com/7781k42

[LWTCS]

I'm a big ol noob here, so if someone else contradicts the following, go with their advice, maybe even read it as a question instead of a suggestion, since it seems like you already know much more than I do. That said:

Controlling reflux flow (or any irrigation flow) on the output side builds up pressure in condenser in my limited experience. For me, it blew the hoses off, and required a changing of pants. The input flow won't allow pressure to escape backwards, and limiting the flow out gives it nowhere to go if it exceeds available throughput. On this setup I can't imagine you would ever run low enough flow for this to happen, but just food for thought. Is there an advantage to controlling flow on the output side? Maybe this only happens if it's completely closed?

Controlling flow on the output side prevents syphoning. Also allows the shell to be optimally filled.

[wrathskellar]

A 4” plate will require a lot of power to run and you’ll need to remove that heat from the system. If you use anything smaller than 1/2”, the flow pressure drop could be significant when operating in reflux and you’ll have a hard time keeping it stable. Garden hose is typically 1/2” ID (5/8” OD) and I wouldn’t use anything smaller.

That seems ... huge, at least relative to what was provided with the still (8mm ID), and what I've seen in pics of similar systems. And it introduces a whole set of problems with sourcing: 1/2" ID tubing seems to all be of the soft variety and only compatible with barbed fittings, and 1/2" flow control valves are approaching the $100 range. Reading here on running similar plated columns seems to imply that (at least during product take-off) reflux water flow is minimal ("a trickle" is how I've seen it described). Of course there's a whole variety of factors that influence that, and I won't know what's needed until I run the thing.

How big is your gas burner? That will determine how much heat you can put into the system. And again, the 4” 6-plate column will require a lot of heat to keep loaded. So, the flowrate demand could be as high as 5 gpm depending on the temperature of the water.

The burner is pretty generic, but a fairly powerful, double-banjo, and can bring a 12 gallon charge of 10% wash to a boil in about 35-40 minutes. Running the pot still (2" dia x 18" tall), it's hard to adjust down far enough for a spirit run, or a single-run brandy/whiskey. It will blow out in the slightest breeze when take-off rate is reduced to a pencil-lead stream. Considering the new column is larger in surface area, and taller, I'll definitely be running at higher power levels, but I doubt I'll need (want?) to run the burner full bore while refluxing or during product take-off. I'm sure there's some math somewhere to estimate all this, but that's pretty far out of my lane. Reading here shows folks with PID-controlled elements running around 1500 watts IIRC, after heating up at full power.

Thanks a bunch for the discussion. I learn something every time I hang out here

[wrathskellar]

The valves referenced below have a max temp of 140f, is this a problem?

which is sourcing a decent quality, plastic body needle valve for reflux control. McMaster-Carr has these:

https://www.mcmaster.com/7781k42

Yep, I noticed that too. I have no idea if that's a problem. Water output temp is going to be highly dependent on input temp, power input, condenser efficiency, etc, etc. FWIW, the valves that came with the still look a lot like the valves sold by StillDragon, so I figure it's not that big of a deal.

Looking at high-temp flow adjustment valves though and we're into metal bodies, and $150+

[still_stirrin]

... 1/2" flow control valves are approaching the $100 range...

Not in the big box store....you can get a 1/2” brass valve with a stainless ball for about $10. What are you looking for?

... The burner is pretty generic, but a fairly powerful, double-banjo, and can bring a 12 gallon charge of 10% wash to a boil in about 35-40 minutes. Running the pot still (2" dia x 18" tall), it's hard to adjust down far enough for a spirit run, or a single-run brandy/whiskey. It will blow out in the slightest breeze when take-off rate is reduced to a pencil-lead stream...

BTU’s??? What’s the power potential? And don’t forget, a 4” 6-plate column will require a lot more boiler heat than a 2” x 18” tall packed column. Probably 4 to 5 times more power just to keep it running.

...pretty far out of my lane.... Reading here shows folks with PID-controlled elements running around 1500 watts IIRC, after heating up at full power....

Well, the 1.5kW input is for a 2” packed column.

In fact, that’s about the power input I use when running the reflux column, a 39” tall 2” ID, glass marble packed combination LM/VM head. And I have a concentric reflux condenser and a 24” long shotgun product condenser, both of which are supplied with a garden hose and the water throughput regulated by ball valves on the condensers’ outputs. Again, I valve the condenser discharge thereby keeping the condensers pressurized to the “source pressure” to ensure that the flow won’t “cavitate” through the condenser as the pressure (due to flow) drops....basic hydraulic engineering.

Bottomline, if you plumb with tubing (or hoses) that are too small in diameter and they have flow pressure drop at the desired flow rates necessary to cool your condensers, then you’ll struggle with heat management and operation of your still. It is wiser to size the hoses and fittings big enough to pass MORE water flow than you’ll need and then regulate it DOWN to where you’ve balanced the heat transfer.

If you’re worried about the “pressure side” of the water source blowing hoses apart, then use reinforced hoses and proper hose clamps. Vinyl hoses will soften at water temperatures approaching boiling, so reinforcement is highly suggested. My big box store has clear vinyl hoses with nylon reinforcement weaving imbedded so it will handle elevated temperatures without failure. If you’re worried beyond that, then plumb with copper tubing or even the CSST, corrugated stainless steel tubing. It’s only YOUR money!

But...you can do it however you want.

You don’t have to heed my advice, as I am only a mechanical design engineer who has designed heat exchangers for oil and gas production platforms. And, I have worked as a licensed plumber plumbing residential and commercial buildings before returning to college for my BSME degree. Also, I have worked commercially for years in a local brewpub brewing beers for the community.
ss

[wrathskellar]

... 1/2" flow control valves are approaching the $100 range...

Not in the big box store....you can get a 1/2” brass valve with a stainless ball for about $10. What are you looking for?

Something with somewhat greater precision than a bog standard garden hose spigot valve. After all this is a CM still, and fine, repeatable adjustment is going to be important. Also, preferably something lighter weight than brass or steel, as it will be supported primarily by the coolant lines themselves and their attachments to the condensers. Another requirement is the ability to quickly and easily break down the setup. I don't have a permanent place for the still, so it will be cleaned, disassembled into larger parts, and stored in a tote until next time. Hence, some quick disconnect plumbing system is preferred over pipe thread, at least in the places where it needs to be broken down.

... The burner is pretty generic, but a fairly powerful, double-banjo, and can bring a 12 gallon charge of 10% wash to a boil in about 35-40 minutes. Running the pot still (2" dia x 18" tall), it's hard to adjust down far enough for a spirit run, or a single-run brandy/whiskey. It will blow out in the slightest breeze when take-off rate is reduced to a pencil-lead stream...

BTU’s??? What’s the power potential? And don’t forget, a 4” 6-plate column will require a lot more boiler heat than a 2” x 18” tall packed column. Probably 4 to 5 times more power just to keep it running.

No idea what the BTU rating on the burner is. Making a guess based on what's available on the market today, I'd SWAG around 60k BTU.

...pretty far out of my lane.... Reading here shows folks with PID-controlled elements running around 1500 watts IIRC, after heating up at full power....

Well, the 1.5kW input is for a 2” packed column.
In fact, that’s about the power input I use when running the reflux column, a 39” tall 2” ID, glass marble packed combination LM/VM head.

I was mistaken, it's closer to 3-4kW as a consensus for 4" bubble plate stills. Using my complete lack of knowledge and an online calculator, it looks like that's about 13,500 BTU, or just around 25% of the burner at full bore. If I were a math-talking guy, I'd calculate the amount of coolant at 60 deg F I'd need through a condensor of the dimensions I have, to reduce the X deg F vapor flowing at Y fps through the condenser by Z deg F. I'd add 20% for a fudge factor, and then I'd match that flow rate to plumbing component dimensions. Sure, I could just run the garden hose straight to the condenser inlet and use the valve on the side of the house for my cooling management, but I think there are better solutions.

Bottomline, if you plumb with tubing (or hoses) that are too small in diameter and they have flow pressure drop at the desired flow rates necessary to cool your condensers, then you’ll struggle with heat management and operation of your still.

Hence my suggestion to use a flow regulator on the inlet side of the RC. Wouldn't that at least reduce, if not eliminate the problem of pressure drops, assuming it's adequately sized for whatever volume of coolant I need at full reflux?

[NineInchNails]

I have a 3" dephlegmator and I use 1/4" John Guest/Sharkbite fittings, 1/4" hose and a tiny brass needle valve. Running one 5500W at approx 30% power during a spirit run, my water comes out at around 165F. I've only ran this about 4 or 5 times, but no signs of degradation or failure. Flow is very slow. I find I get stable operation by using a small aquarium pump in a 5 gal bucket with a mini float valve to keep it full. I connect the pump to the 1/4" line running to the dephlegmator. Connecting it to the faucet is very frustrating for me as the pressure is not stable enough to run consistent.

When I first started running and learning the dephleg & bubble cap plates, I was inputting too much power and I was driving condensate above the dephleg and flooding the riser. At first I didn't understand what was happening until I shut the power off and saw all the condensate rush down through the sight glass.

[NineInchNails]

I've been doing a very long spirit run today and my fittings are holding up just fine, but the clear 1/4" tubing is degrading significantly on the output side of the dephlegmator. Polypropylene tubing has a higher temp rating. I'll be sourcing some ASAP to replace the polyethylene tubing.

[RC Al]

Sounds like your going to be running just off tap water?
I strongly recommend a small pump fed off a reservoir fed by a ball cock (pretty much a toilet cistern) to help you remove pressure fluctuation problems from sharing water with a household.

It would seem that you are not taking into account using your product condenser in pot still mode when you would be running flat out with your gas

When your looking at comparing gas to power you need to account for losses, im pretty sure im only getting 30 odd % of my power into my wash currently even with a basic shroud

If you want some better than garden quality quick release fittings, have a look at cam locks

Here is my set up on the outlet of my pc - it could be run with the clear tubing as you want just fine, what is there is the cheap irrigation plastic tube and barb fittings in oz 19mm - 3/4" (most likely around 5/8 equiv in usa) combined with 1" plastic bsp fittings, its supported and arranged so that heat wont cause any kinking with the super thin hoses and the tee pieces take any load or strains. I haven't even gotten around to adding all the clamps yet, zero issues after a few runs so far - this is my 3rd go at plumbing this one

The output from the pc is on the bottom right feeding the valve manifold and the air trap/relief above
The bottom blue valve is a 3/8" ss needle valve
The Top red one is a 1" gate valve - I had to go bigger than the 3/4 for the cheap big box valve to keep the bore size the same as the tubing

[NineInchNails]

My solution was to use this mini float valve in a 5 gal bucket and an aquarium pump to feed water to the dephlegmator. I tap 1/4" threads into the float valve and screw a John Guest/Sharkbite fitting into it. There are valves that connect to tubing, but I prefer John Guest quick disconnect. With high temps you need polypropylene tubing though. I found 100' for $15 on Amazon. Polyethylene degrades quickly if you get up to around 160F.

[wrathskellar]

I have a 3" dephlegmator and I use 1/4" John Guest/Sharkbite fittings, 1/4" hose and a tiny brass needle valve. Running one 5500W at approx 30% power during a spirit run, my water comes out at around 165F. I've only ran this about 4 or 5 times, but no signs of degradation or failure. Flow is very slow. I find I get stable operation by using a small aquarium pump in a 5 gal bucket with a mini float valve to keep it full. I connect the pump to the 1/4" line running to the dephlegmator. Connecting it to the faucet is very frustrating for me as the pressure is not stable enough to run consistent.

Any guesses what the flow rate to your dephlag is when running in full reflux?

[NineInchNails]

I have a 3" dephlegmator and I use 1/4" John Guest/Sharkbite fittings, 1/4" hose and a tiny brass needle valve. Running one 5500W at approx 30% power during a spirit run, my water comes out at around 165F. I've only ran this about 4 or 5 times, but no signs of degradation or failure. Flow is very slow. I find I get stable operation by using a small aquarium pump in a 5 gal bucket with a mini float valve to keep it full. I connect the pump to the 1/4" line running to the dephlegmator. Connecting it to the faucet is very frustrating for me as the pressure is not stable enough to run consistent.

Any guesses what the flow rate to your dephlag is when running in full reflux?

Flow rate depends on your power input and how you built the dephlag. If it's bigger and has more tubes then you'll need a very slow flow rate in comparison to a smaller one with less tubes. I've been considering installing a thermowell in the water output so I can keep an eye on it and try to dial in on my ideal temp rather than flow rate and see how that works for me. As long as I run at a consistent power, it should be accurate & repeatable. All you have to do is start out with full flow/reflux then start dialing it down until you find your ideal flow rate & % reflux. You'll get the hang of it.

[wrathskellar]

Flow rate depends on your power input and how you built the dephlag. If it's bigger and has more tubes then you'll need a very slow flow rate in comparison to a smaller one with less tubes. I've been considering installing a thermowell in the water output so I can keep an eye on it and try to dial in on my ideal temp rather than flow rate and see how that works for me. As long as I run at a consistent power, it should be accurate & repeatable. All you have to do is start out with full flow/reflux then start dialing it down until you find your ideal flow rate & % reflux. You'll get the hang of it.

Yep, that's what i figure, but in the process of sizing the plumbing parts (tubing, valves, flow regulator, etc), I'm looking to get a general idea of what I'll need to accommodate. When you run, say 10 gallons of 10% ABV wash, do you find you need closer to 1 gallon/minute of cooling to the dephlag at full reflux? 5 gallons? 10?

[NineInchNails]

Flow rate depends on your power input and how you built the dephlag. If it's bigger and has more tubes then you'll need a very slow flow rate in comparison to a smaller one with less tubes. I've been considering installing a thermowell in the water output so I can keep an eye on it and try to dial in on my ideal temp rather than flow rate and see how that works for me. As long as I run at a consistent power, it should be accurate & repeatable. All you have to do is start out with full flow/reflux then start dialing it down until you find your ideal flow rate & % reflux. You'll get the hang of it.

Yep, that's what i figure, but in the process of sizing the plumbing parts (tubing, valves, flow regulator, etc), I'm looking to get a general idea of what I'll need to accommodate. When you run, say 10 gallons of 10% ABV wash, do you find you need closer to 1 gallon/minute of cooling to the dephlag at full reflux? 5 gallons? 10?

I haven't collected my dephleg water before to determine how much water it uses. I just send it down the drain. Temp of the water makes a bit of difference too. I will collect in a drum one of these days and determine my rate, but that would only be useful for my dephleg at the power I run with 55F well water.

I use a little pump with a 1/2" outlet. I use a plastic barbed fitting, approx 1/2" thicker wall clear vinyl tubing to feed my dephlag. Cheap, thin wall tubing can kink rather easily. I ordered 100' of polypropylene 1/4" OD hose $15 on Amazon to connect to the tiny brass needle valve for flow control on the outlet of the dephleg. You could use 3/8" instead of 1/4", but I don't think it's really necessary.

Since I'll have all that polypropylene tubing, I'll be re-plumbing it to my shotgun and reflux coil for convenience. I used to use 1/2" PEX. 1/4" will be a LOT more convenient and easier to use.

[wrathskellar]

Since I'll have all that polypropylene tubing, I'll be re-plumbing it to my shotgun and reflux coil for convenience. I used to use 1/2" PEX. 1/4" will be a LOT more convenient and easier to use.

I've been considering PEX, as it's cheap, and easy to find, while being compatible with push-connect fittings and has good heat tolerance. What did you find inconvenient about PEX? Is it too stiff?

[NineInchNails]

Since I'll have all that polypropylene tubing, I'll be re-plumbing it to my shotgun and reflux coil for convenience. I used to use 1/2" PEX. 1/4" will be a LOT more convenient and easier to use.

I've been considering PEX, as it's cheap, and easy to find, while being compatible with push-connect fittings and has good heat tolerance. What did you find inconvenient about PEX? Is it too stiff?

The 1/2" fittings are expensive. 1/2" PEX is significantly more rigid and cumbersome than smaller dia polypropylene tubing. I used PEX swivel crimp connections that you can screw on & off with your fingers and it just became a pain in the ass. Push disconnect 1/2" fittings are even more expensive. I had to install hooks in the trusses to hang the PEX hoses where needed and to stow the hoses out of the way when not in use. Takes too darn long to connect & disconnect where smaller, lighter and more flexible polypropylene hoses are much much easier & quicker to use. I'm absolutely thrilled to ditch the 1/2" PEX and replace it with small tubing.

When running high psi tap water, it's super convenient using small tubing on my reflux coil and shotgun condenser. When specifically running water to my dephleg, I use a pump, 1/2" vinyl tubing, float valve and a small needle valve. That makes the flow consistent, perfectly stable and really easy to adjust the flow rate in comparison to higher psi from the tap (which surges).