Building a Continuous Still for Stripping a Sugar Wash

[Lester]

Greetings folks.

Home-distilling is legal where I am.

I have a real need for a continuous stripper and don't yet have a set design to frabricate ATM so everything is still up in the air.

From the other topics on this forum I have been able to glean bits & pieces of info on how it will come together. Here's what I'm aiming for right now:

1. Small boiler 4~6 liters, with a passive overflow port
2. Loosely-packed SS scrubies for packing. This will get flushed with water after every 200 liters of wash has been stripped
3. Wash is gravity-fed near the top of the packing. A small aquarium pump is also being considered aside from gravity-feed.
4. A means for regulating the wash flow rate will be installed. Needle valve to be used during the initial trials
5. Liebig condenser for condensing the vapor & preheating the wash
6. Another Liebig at the boiler overflow for further preheating the wash


Design goals:
1. Stripping rate: >10 liters of distillate @ 43% ABV per hour, from a 10% ABV sugar wash. Vapor temp ~93 deg C.
2. Maximum heat utilization (low fuel consumption)
3. Should be able to run by itself with minimal adjustments on the fly
4. Spent Wash at the bottom of the column should be <1% ABV


Questions:
1. is a 3" x 3' column enough to strip the wash down to <1% ABV? I intentionally made it taller to give me a lot of leeway in adjusting for ABV at output & overflow, at high flow rates.
2. Is a 1" x 3' Liebig enough for the heat exchange expected?
3. Am I headed for disaster?


Sugar wash Recipe that I use:
For every 19 liters of wash......
White sugar - 4kgs
Panela - 0.5kg
Juice of 4 pcs Kalamansi
Active dry baker's yeast - 5 tbsp
Water to make 19 liters of wash
This wash ferments to dry in 6 days, minimal sediments, average temp here is now at 30~33 deg C; may need to use extra cooling during the hotter months of March~May

Thanks in advance for any inputs!

[Lester]

I thought I'd underscore the importance of fuel efficiency for this stripper.

If I am able to scavenge half of the energy I am putting in, it will effectively give me 33% more available power for stripping the wash, which in turn will result in shorter stripping times. Same heat input will result in more alcohol output for the same amount of time, simply because the heat is "re-used".

Being able to scavenge some of the heat provides a way around the apparent brick wall: It takes a finite amount of Power to vaporize a finite amount of alcohol.

[Doogie]

Q#2 - I would not really bother with the wash going thru the liebig - reason is 1) you may need a larger pump to get the wash thru it (if you go with a pump for charging the boiler, and you will have to use a pump for the liebig), and 2) I think the heat up of the liquid when you are already around 30' will be minimal (only 5-10') - so for the effort and cost of running it thru the liebig, it may not be worth it. Also, if you ever want to consider stripping something other than sugar wash, you run into a clogging issue.

You mention column and packing - neither would be required - you simply need a pot still - so if your discussion about the "column" is simply the riser for the pot still, then that is OK, but a full blown reflux column is not needed for stripping - and neither is the packing

You should factor in a liquid level gauge so you know exactly how much is in the pot. Relying on a passive output and hoping to add product at the correct rate could be problematic

[YHB]

Hi Lester

OK I'll go first.(not first -Doogie beat me to it)

I cannot get past why you want to use a column?

10 litres an hour - that is fast for a column,
43% ABV that is very low for a column.

You can get that ABV from a Pot and get that rate from a Pot by hitting it with enough heat.

Instead of a continuous column still, why not a Pot used continuously?

1) Strip a 10 (or what ever size you choose) litre "batch"
2) Use the waste heat from condenser to heat the next batch of wash
3) Dump depleted wash from boiler
4) Use waste heat from boiler backset to heat next "batch" of wash.
5) Add Hot wash to boiler.
6) Repeat

You could automate it as much as you like and with the right type of heat exchangers you should be able to save a lot of energy

Just my thoughts and no ultrasonic generators in sight.

[Lester]

Hello Doogie,

Thanks for your inputs.

You mentioned a pot still and by its very nature it is not a continuous still. I do have a pot still and have used it for stripping. I wanted a continuous still because.......

I mentioned fuel efficiency as one of the design goals and I think a properly-configured continuous still will beat a pot still by a very huge margin.

I can use a plunger-type pump (something like a syringe) driven by a solenoid to inoculate the column with a known wash volume periodically. Such positive-displacement pumps can easily force the wash through the liebig. It is not without its own problems though.

Liquid level gauge on the pot: That's a good point. Will consider it when building the boiler although there are other ways to get an alarm when the pot runs dry. An alarm is better cuz I don't have to keep an eye on the level. (I use a propane burner for my heat source so I don't really have a heating element that can scorch)

[Lester]

Hello Brian!

Why a column? Cuz that's where the magic takes place. The boiler can be wide & shallow holding a few liters of spent wash, the actual boiling of the wash takes place inside the column.

Will a 4" column get me 10 liters an hour? How about 2x of 4" columns? But that would need a lot of heat, right? That's why I wanted fuel efficiency. ABV requirement is not so high.

A pot still used continuously: I'd rather not do that! Looking for a more elegant solution here.

Thanks!

[Doogie]

Lester - my thoughts for the level gauge are to prevent overflowing the boiler. With a 4-6L pot the potential to overflow is great. Especially if the solenoid goes goofy.

But I think a pot still could work well also. My comments regarding the not running it thru the liebig are only because I think the effort to create it will not pay off quick enough. However an alternative, since you state that you are using a propane burner, you may want to consider a simple pump that circulates from your fermenter, around the outside of the pot and back to pre-heat your wash - there is a lot of wasted heat on the outside of the pot on a propane burner - maybe you can simply capture that wasted heat and with a simple copper loop around the pot, capture the heat that you are not considering.

Now, I cannot see you running a 4" column off a 4-6L pot ... I run a 2" column on a 50L pot and it works fine. it is kind of like a guy with a small pecker asking for XXL condoms ...

A pot still can go continuous ... continuous is simple action of adding more while subtracting spent wash plus produced low wines. A pot still could easily handle this with the mods you propose. The only reason for a column, IMO, is that your not really looking to strip wash, but produce final distillate for consumption.

Remember, elegance comes in many forms - big and pretty, or simple and efficient ...

[Lester]

Lester - my thoughts for the level gauge are to prevent overflowing the boiler. With a 4-6L pot the potential to overflow is great. Especially if the solenoid goes goofy.

I see your point now.

But I think a pot still could work well also. My comments regarding the not running it thru the liebig are only because I think the effort to create it will not pay off quick enough. However an alternative, since you state that you are using a propane burner, you may want to consider a simple pump that circulates from your fermenter, around the outside of the pot and back to pre-heat your wash - there is a lot of wasted heat on the outside of the pot on a propane burner - maybe you can simply capture that wasted heat and with a simple copper loop around the pot, capture the heat that you are not considering.

Yes that's a good point. My boiler is (somewhat) insulated and I do notice a 10~20 deg C temp rise within the chamber. The pot & stove are both enclosed in a small chamber.

Now, I cannot see you running a 4" column off a 4-6L pot ... I run a 2" column on a 50L pot and it works fine. it is kind of like a guy with a small pecker asking for XXL condoms ...

That's funny. Asian condoms come in one size fits all! Back on topic, that's what the overflow is for. The only purpose of the boiler is to generate steam to heat the column. I do have a 2" column on a 30-liter pot. It works fine too. But I want to go faster cuz I can't make enough now..... none left for me.

A pot still can go continuous ... continuous is simple action of adding more while subtracting spent wash plus produced low wines. A pot still could easily handle this with the mods you propose. The only reason for a column, IMO, is that your not really looking to strip wash, but produce final distillate for consumption.

yes but that will result in >1% ABV going to the drain.

Remember, elegance comes in many forms - big and pretty, or simple and efficient ...

You're absolutely right!

[Lester]

I see the need to post this link of the parent site:
http://homedistiller.org/equip/cont" onclick="window.open(this.href);return false;" rel="nofollow
.....almost the same except I don't have the rectifying section.

[Lester]

Here's something for the heavyweight number crunchers here on HD: Maritimer, Flyingdutchman, Edwin, etc.

A mythical still (a drawing on paper) With the wash (@ 30-deg C) going through the product condenser & overflow condenser for heat scavenging, before being fed into the column.

Let's say I have a fixed inoculation rate of 100ml/x amount of time, of 10% ABV wash. This goes into the packing and comes off as vapor at the top at 43% ABV (95-deg C from the phase diagram). The spent wash ends up in the boiler at <1% ABV, about 99.8-deg C temp.

After several inoculations the still is in steady state. We now take a snapshot of what's going on:
Distillate comes out at a fixed rate of 22ml/x time, consisting of 9.5ml EtOH & 12.6ml H2O = 43% ABV, 95-deg C temp
Boiler is overflowing at a fixed rate of 77.4ml/x time consisting of 0.5ml EtOH & 77.4 ml H20 = 0.6% ABV, 99.8-deg C temp
Wash is used for cooling the product & overflow condensers at rate = 100ml/x amount of time

All of the heat from the boiler overflow & distillate gets transferred to the wash, the condensers are 100% efficient in heat transfer. Insulation is likewise 100% efficient, zero heat lost inadvertently.

Questions:
1. What is the temp of the wash as it goes into the column? (Maritimer answered this already)
2. What is the temp of the distillate going into the collection jar?
3. What is the temp of the overflow as it hits the drain?
4. How much heat is used per inoculation?
5. Is there any excess heat and where did it go? There is no water cooling on this mythical still.

[Maritimer]

Hi Lester,

Let's assume this mythical still is VM (otherwise it's out of my ken).

2. What is the temp of the distillate going into the collection jar?

"Wash is used for cooling the product & overflow condensers at rate = 100ml/x amount of time."

If this is the only source of cooling, the still will produce more heat than the wash can take. There needs to be additional cooling for the product, but also for the reflux condenser.

So if there is additional cooling, the temperature of the product can be anything you want.

3. What is the temp of the overflow as it hits the drain?

Didn't you answer this? 99.8*C. Probably more because there is water in the boiler to create the steam. The ethanol in the boiler will also go into the column.

4. How much heat is used per inoculation?

With reflux, the key is the re in reflux. You will be condensing and then vapourizing over and over. So the amount of reflux will determine the amount of heat.

5. Is there any excess heat and where did it go? There is no water cooling on this mythical still.

As I showed in the calulations here: http://homedistiller.org/forum/viewtopi ... 0#p7149378 , the still, even in the pot still considered there, produces too much heat for the wash to condense.

M

[Edwin Croissant]

My first impressions:

4. A means for regulating the wash flow rate will be installed. Needle valve to be used during the initial trials
3. Should be able to run by itself with minimal adjustments on the fly

I think that you can use the boiling temperature to regulate your wash flow rate.

5. Liebig condenser for condensing the vapor & preheating the wash
6. Another Liebig at the boiler overflow for further preheating the wash

That is the right order, use the cold feed for condensing then use the heat from the bottoms for an extra boost
I think that you better not isolate your column for extra cooling.

1. Stripping rate: >10 liters of distillate @ 43% ABV per hour, from a 10% ABV sugar wash. Vapor temp ~93 deg C.

10% ABV feed will give you 54% distillate.
I am improving my calculation right now and I think that with a feed rate of 60 l/hour you get 10 l/hour 54% ABV distillate with 4,5 kW of power.

[Lester]

the still, even in the pot still considered there, produces too much heat for the wash to condense.

If there's too much heat then I can run this still using a tiny flame like that of a matchstick, yes? And perhaps the wash would vaporize inside the liebig, even before it hits the column? If the wash vaporizes then it takes a lot of heat with it. The wash's B.P. = 93-deg C while the vapor temp = 95-deg...... vapor is hotter than the wash by 2-deg C, but with less mass even after it condenses.

If that's not enough heat to boil the wash then the overflow adds even more heat, at 99.8-deg C.

So why would Edwin need this much power?

............. with 4,5 kW of power.

Didn't you answer this? 99.8*C. Probably more because there is water in the boiler to create the steam.

The overflowing liquid goes through a condenser before hitting the drain. The preheated wash coming from the product condenser is the coolant.

If the wash is boiling as it hits the packing then I only need to supply very little additional heat (maybe none?) from the boiler. So a matchstick flame should suffice?

There is no reflux condenser. The wash provides all the cooling for the packing, somewhat like reflux falling from the reflux condenser.

[Lester]

BTW I'm not saying this is a free energy system, not at all. But perhaps LHV of the wash needs to be added to the heat exchange equation of the condensers.

[Jacksonbrown]

I haven't read most of this but if it were me I'd look in to a TVR or MVR system.
Get rid of the boiler and use steam injection along with regen systems to suck every bit of heat energy out of the system.
Find a thermo guy that knows what he's talking about and pick his brain but the valving/flow control is what's going to hurt.
In a well designed system the only energy input could be the motors.

http://en.wikipedia.org/wiki/Vapor-comp ... vaporation

[Lester]

I got 2 pieces of 4" x 40" SS tubes from the scrapyard yesterday. Would make a nice continuous stripping column I think. I can simply seal off the bottom end, add an overflow port, then the lower portion can be the boiler. No need for a separate boiling pot.

[Lester]

I haven't read most of this but if it were me I'd look in to a TVR or MVR system.
Get rid of the boiler and use steam injection along with regen systems to suck every bit of heat energy out of the system.
Find a thermo guy that knows what he's talking about and pick his brain but the valving/flow control is what's going to hurt.
In a well designed system the only energy input could be the motors.

http://en.wikipedia.org/wiki/Vapor-comp ... vaporation

Thanks JB!

This is the first time I've heard of this MVR. Interesting.

I wonder if we can use a speaker in a resonant chamber. There will be pressure gradients in there for sure. Like in a 2-stroke engine's tuned pipe.

[Jacksonbrown]

Something else to think about.

http://en.wikipedia.org/wiki/Rising_film_evaporator

[Maritimer]

10% ABV feed will give you 54% distillate.

This is the immediate %ABV from a 10%ABV wash. When stripping, that is just the first "micro-distillation." After that, the %ABV of the wash decreases, so the %ABV of the vapour decreases. Think of stripping as making a lot of little distillations, each one adding to the total. In the end, the wash will be completely depleted. The sum of all these little distillations will result in about 29%ABV low wines. This has been calculated for all wash %ABVs here: http://homedistiller.org/forum/viewtopi ... 0#p7133969 .

If there's too much heat then I can run this still using a tiny flame like that of a matchstick, yes? And perhaps the wash would vaporize inside the liebig, even before it hits the column? If the wash vaporizes then it takes a lot of heat with it. The wash's B.P. = 93-deg C while the vapor temp = 95-deg...... vapor is hotter than the wash by 2-deg C, but with less mass even after it condenses.

There is a little problem here known as the second law of thermodynamics. One way to state it is that heat always flows from hot to cold. Another is that perpetual motion machines are impossible. The minimum energy requirement at standard temperature and pressure for a 10%ABV wash is that about 1/3 of the wash has to be vapourized. That requires adding enough energy to take the liquid to the vapour state--the latent heat of vapourization. You can't use the heat that has vapourized one gram of wash to vapourize another. If you could, you could build a perpetual motion machine.

M

[Jacksonbrown]

Of cause you can! (well almost) That's the point of recompression. The vapor temperature rises when compressed which gives you back your deltaT. You can even use multiple effects to do it a couple of times. Those laws are great arn't they
Of cause their are losses but we can certainly decreases a lot of inefficiencies and that seemed to be the main driver of the OP.

This has got me thinking now. Stilldragon sell cheep shell and tubes. How about something like this?

[Maritimer]

Please explain.

M

[Jacksonbrown]

The laws of thermodynamics or the P&ID?
Either way the links I put up should explain some.

A vacuum pump on the distillate side and a preheater in the feed tank might help things along too especially if the heat exchangers are of the shelf and not sized properly.
I'm incapable of the maths to size any of this stuff but I think the solution would look something like this if you want a truly efficient and genuinely continuous system.

[Jacksonbrown]

http://en.wikipedia.org/wiki/Multiple_effect_evaporator
Another concept
http://en.wikipedia.org/wiki/Multi-stag ... stillation

[Lester]

If you could, you could build a perpetual motion machine.

I did say this is NOT about free energy.

JB has alluded to one possible solution. Would be nice to run a still on <100 watts of power, for weeks on end.

Interesting how this thread has developed into several ideas.

[Lester]

...... How about something like this?

JB,

In your drawing, if you replaced the steam heat exchanger (left most column) with a packed column then that system represents EXACTLY what I have in mind.

Since it's a mythical still we can stretch the lengths of the condensers to what we think we need, then make use of the resulting thermal gradient along the length. Preheating perhaps? Sub-cooling?

And since it's mythical, the total mass of all the components is equal to 0 grams.

[Jacksonbrown]

I would leave the steam THE in as it's the heart of the system. If you wanted a column I'd put it on the vapour side and include a boka style head to raise the distillate abv.

The attached PID is a bit more like it. I added a recirc pump to the evaporator. You would just throttle the globe valve back till your spent wash has less than 1%abv


Not sure what you meant by the 'mythical' bits?!? I'm just putting some ideas out there. I can stop if you want.
All this stuff is basic chem eng. Nothing you're asking for is new in industry.

(PID edited, I had the product take off at the wrong point)

[Jacksonbrown]

http://video.geap.com/video/822743/gea- ... on-falling

This is a falling film not a rising film but similar concept.
Falling would be easier to design but harder to build but rising would be the opposite I guess. Maybe someone else knows more.

[NZChris]

I have run a four stage Weigand. Not the only four stage evaporater I've run. Noisy suckers. I can see that the idea could be adapted for stripping, but I'm not sure how you would go about collecting the vapor and creating the vacuum.

I'll watch the thread with interest, but I don't think I'll be designing one any time soon.

[Edwin Croissant]

10% ABV feed will give you 54% distillate.

This is the immediate %ABV from a 10%ABV wash. When stripping, that is just the first "micro-distillation." After that, the %ABV of the wash decreases, so the %ABV of the vapour decreases. Think of stripping as making a lot of little distillations, each one adding to the total. In the end, the wash will be completely depleted. The sum of all these little distillations will result in about 29%ABV low wines. This has been calculated for all wash %ABVs here: http://homedistiller.org/forum/viewtopi ... 0#p7133969 .

This is the difference between a simple distillation and continuous distillation.
With a simple (Rayleigh) distillation the still depletes during the run resulting in a decrease of the concentration and a average ABV of 29%. In a continuous stripper all the ethanol is evaporated by the produced steam when the feed flows down the column. At the feed entry there is 10% ABV feed boiling resulting in 54% vapor. This is only one part of the higher efficiency of continuous distillation. The other part is preheating the feed by running it through the condenser. You can do the last trick also with two stills, use the condenser of the working still to preheat the wash for the other one.

[Maritimer]

Hi Edwin,

I was thinking of my four-quadrant stripper. In it, the wash goes from one quadrant to the next, each time getting more and more depleted, so it really is a continuous pot still.

Getting 54%ABV from a 10%ABV wash in a continuous still is a very different view of things. I never understood (or even heard of) this point before.

In a continuous stripper all the ethanol is evaporated by the produced steam when the feed flows down the column. At the feed entry there is 10% ABV feed boiling resulting in 54% vapor.

The produced steam, when it meets the injected liquid wash, will heat it. It won't have enough heat to vapourize the water in the wash, but it can vapourize the ethanol because it has a lower LHV.

Vapour from a boiling 10%ABV wash is 54%ABV. When the wash is injected into the column, how do you arrive at the 54%ABV vapour when the amount of produced steam is arbitrary? Or does this work only for a specific amount of produced steam?

M