Thumpers

Myles

OK lets open a discussion by throwing in a hand grenade.

Despite what you may have heard previously, many thumpers are not actually used to increase the ABV of the product. Its just that this seems to have been latched onto as the main reason for using one. Sorry folks but it just isn't acurate.

Admitedly they will do that, but in many cases it is incidental. The real purpose often tends to be flavour modification. Either to increase, or to decrease the flavour, but we can get to that later. Lets also leave what you put into the thumper to start with to later.

So how do they work?

Simply put there is a mass and energy transfer out of the primary boiler and into the secondary boiler - the thumper. Yes, a thumper is a true parasitic boiler, and it is heated by the primary boiler.
Naturally what actually occurs, happens in phases, and is 'not quite so simple' as stated just above.

You really do need to think about what a thumper does in phases, because it actually does different things at different points in the run. Lets start with the simplest version. Add enough plain water to the thumper to cover the end of the vapour injector.

Phase 1

Your primary boiler starts producing vapour. This is a mixture of different volatiles determined by the contents of the boiler charge. These all have a boiling point higher than the temperature of the thumper charge. Result is that virtually all of these vapours will condense into the thumper charge. The volume of the thumper charge increases. The temperature also increases, because the condensing vapour releases energy. Your thumper is probably LOUD. This is caused by the violently collapsing bubbles.

Phase 2

Your boiler is now warmed up and contains a higher volume of charge. It is most likely a lot quieter, expecially if your vapour injector has been modified to include a diffuser to make smaller bubbles. So what happens now?
Your boiler is producing a mixture of volatile vapours, these now hit a hot liquid. Some of them are going to tend to condense into liquid because their boiling point is still higher than the liquid temperature. Some others are likely to get through the liquid. NONE of them do anything absolute, there is no 100% condensation, just tendencies.

So some of the vapour from the boiler gets through the thumper - but the composition has changed - it contains more of the lower boiling point headsy components.

Phase 3

The thumper charge has heated up enough that it actually starts to produce its own vapour. Some of this is from agitation by the vapour bubbling through it, and some is from the thumper charge actually boiling. Importantly the composition of the liquid in the thumper is different to the composition of the liquid in the primary boiler. That means the two vapour streams ALSO have different compositions.
So the vapour released from the thumper charge, mixes with the vapour from the boiler (that just sneaked through the thumper charge). The end result is a vapour produced by the thumper. That vapour is very different from the vapour produced by the primary boiler AT THAT MOMENT IN TIME. It will have a different composition and a higher ABV.

The thumper tends to hold back the lighter higher boiling point, components so it compresses the heads cuts.

Things continue this way through most of the run. The vapour produced by your primary boiler is constantly changing, as is the vapour produced by the thumper. The two boilers in combination are behaving just like a normal pot still, only a slightly more efficient one.

Lets jump towards the end of the run.

Phase 4

Your primary boiler charge is now alcohol depleted. It is producing a vapour with a very low ABV, and can be considered to be steam. This is now directly heating the thumper charge. Most of the volatiles produced by the thumper now, are being boiled off from the volatiles that remain in the thumper charge. The effect is that the tails are also compressed so you get a bigger hearts phase.

The thumper is still a pot still, so you still need to find the 'sweet spot' power level. Your best option is to find the sweet spot for your primary boiler, without the thumper. Then add in the thumper, and from that starting power level you can experiment with power management to get your run parameters as you wish them to be.

That's long enough for any first post. :>

Moonshine

Bravo, @Myles! :-bd

Makes me want to build a thumper right away. First question that comes to mind:

Is there any point in pre-heating the thumper with an own power source (electrical immersion heater in the thumper) or use it purely passive?

Myles

@Moonshine you can heat a thumper, it just depends what you wish to acheive. As I suggested above thumpers can actually be used for different reasons. You just need to keep in mind your reason for using the thumper in the first place. It is possible to use a thumper in such a way that you end up NOT doing what you had intended!!

Myles

Thumper # 1 - Thick Mash

Probably the first use of a thumper. You can't distill a thick mash with direct heat without burning it. Solution, put it in a thumper. Fill the boiler with water and distill the mash with steam injection.

An old, old, OLD method - but still valid today.

Lloyd

So how is a thumper different from a plate?
Thumper, plate, same benefit.
Both are one "theoretical plate" or one distillation.

A thumper can hold more volume because it is designed to do so while a plate is not.
It is not practical to have 6 or 10 thumpers but 6 or 10 plates is normal.

Your thumper description could easily be translated into how a plate functions during a run.

Myles

@Lloyd absolutely correct. The only significant difference between a thumper and a plate is how you use them. To be continued :))

Myles

Thumper # 2 - Worm Condenser Protection

Another equally old application. Pot stills have a tendency to puke or eject foam, especially when directly heated on open flame. Adding a thumper containing water is one way to clean up the vapour stream. Puking or even foaming into a worm condenser can lead to blockages. In this application a thumper is a safety device.

Myles

Caribean Rum. This traditional method uses a pot still with 2 thumpers. One thumper is charged with diluted heads, the other thumper is charged with diluted tails. Those aren't the names used, but in effect that is what they are.

Reason, flavour edit, enhancement. The vapour carries over some flavour components from the heads and tails into the product. Why dilute? Well the heads and tails also contain some nasty flavours. Some of them are water soluble so diluting holds them back, and lets you pick up the ones you want.

Adding in additional flavour is easier to do in a thumper than on a plate. Its not really much different in principle to the GB4. You can put botanicals on the plates, but it is probably more convenient to have them in a secondary component in the vapour path.

Myles

Thumper # 3 - Flavour Modification

Slightly different to the above rum scenario. This involves deliberately putting things in the vapour path. Fruit pulp, molasses, crystal malt, unfermented mash. Virtually anything you can think of.

Myles

Thumper # 4 - ABV Increase

Its like a plate but most likely not as efficient as a plate. If this is your intention - use a plate!!

Lloyd

Sorry, not trying to distract from the understanding of thumpers but rather trying to put them into modern context.
Long before plates were available there were pot stills later "doublers" or thumpers came into being.

Henry the Moonshiner had no other choice but a pot still back in the day but as he got edumacated he was able to construct a thumper. He could neither conceive of nor construct a bubble plate column so he used the technology that he had available to him at the time.

Fast forward to modern times where plated stills are simple to acquire and pot stills with thumpers are antiquated. Am I missing something here?

I swear I'm not being trite, just trying to understand. Each plate is basically an inline thumper and its easy and cheap to stack many, or just one, into a column.

Is a thumper, in light of these modern advances, even worthwhile?
Surges, foaming, etc have already been mitigated.

If its just sometime to get back to the good ole days than that's cool but I'm not yet convinced it is worthwhile.

Convince me.

grim

Exploit inefficiency?

Myles

The 1 thing that you can do with a thumper that you can't do with a plate is the flavour enhancement. Yes you can do some of that with the GB4, but there are some things you can't put in a gin basket. Well possibly not yet.

The other thing is the reboiler issue. We haven't mentioned that option yet.

captainshooch

Thank you for posting @myles , very interesting :-bd

Unsensibel

@Myles said: Caribean Rum.... Adding in additional flavour is easier to do in a thumper than on a plate. Its not really much different in principle to the GB4. You can put botanicals on the plates, but it is probably more convenient to have them in a secondary component in the vapour path.

That's an interesting thought! Has anyone ever tried making a gin by putting a sieve on top of the RC and make gin in a one pass distillation on let's say a 4-plate set-up? Yes, you would loose some flavor to the heads but otherwise seems feasible.

CothermanDistilling

Making Gin in one pass from the mash would be classified 'Distilled Gin' in the US, and I think it would be wonderful, but crazy difficult to do without making a whole bunch of mistakes... (if you did it from neutral, it would be Redistilled Gin in the US, but still Distilled Gin in the EU).

See the Big Gin Thread for more..

Myles

@Sadi has been putting anise on plates in his CD. There is a lot of overlap between plates and thumpers, but it is not a full overlap.

You can't add liquids to a plate and keep them there. :D

FloridaCracker

Guess I got into the distilling thing way after the thumper went bye bye and I never quite understood the concept. Does the vapor from the boiler bubble through the liquid in the thumper?

Unsensibel

@FloridaCracker Yeah, pretty much except thumper usually has a pipe going in the liquid with the resulting bubbles being rather large

popcorn

I love a thumper

luckyliqueur

@Myles said: ... a diffuser to make smaller bubbles.

Can you show me some of these diffusers . . . . are they like brass gas jets or more DIY than that?

(nice article . . worthy of a Wikipedia entry . . . . is there gonna be a SD editorial team working to produce a new encyclopedic manual :D )

Sadi

@Moonshine said:

Is there any point in pre-heating the thumper with an own power source (electrical immersion heater in the thumper) or use it purely passive?

I have tried that Moonshine. One has to be very carefull though, even a little heat can be too much and can dry the thumper. I was trying to manage the level of liquid in the thumper. Then I found that in my case the level did not raise much and gave up. Insulation helps though.

I used thumpers a lot with my previous setup. As my setup was all glass, it was interesting to watch what was going on. I used it for my anise infusions to start with, then figured putting anise in the column was better for my product. I have tried some options as @Myles described for brandies and whiskeys, then again later I used some kind of plates/(inline thumpers) without a downcomer to get similar results.

There is something that I cannot name clearly that draws me towards the thumper. Currently, I am working on it using our modular parts. Exploiting inefficiencies seems interesting.

Nice post Myles. Thank you. :-bd

Cheers.

Sadi

Hmm. I will try one perforated plate with a bubble cap instead of a downcomer tomorrow. What do you think?

Myles

@Sadi just because of what you are trying to do I think you will be better off with the perforated plate. Because you have a layer of anise above the plate you will disrupt the vapour path from the cap and I think you will have much more even vapour distribution from the perforations. Try it though to see.

@luckyliqueur I have tried a variety of diffusers In pot and keg based thumpers.

This one just used a reduced T with an extra hole drilled pointing straight down to the base of the pot.

Because my latest thumper was keg based

and I wanted to be able to remove the vapour injector for cleaning I used a different method.

I soldered a cap into the end of the injector tube to leave 4 thin (about 2mm x 10mm long) horizontal slots and added a 1/4" hole in the centre of the cap. No picture unfortunately so you will have to use your imagination. A copper disc with 4 tabs bent up at 90 degrees and soldered to the inside of the tube.

The last thumper is very LOUD untill the charge heats up, and then it settles to a barely audible fizz. That compression fitting has no depth stop, so the injector goes straight through to the base of the thumper. The difuser has to be flush with the outer daimeter of the injector to get through the fitting. The valve is just there as a refil port to pre charge with a bit of water.

Myles

30 litre keg Thumper, with leveling feet and drain.

googe

Your a machine Myles!, always loved that 4 legged one!.

Moonshine

@Myles' work is pure ART! :-bd

Myles

:\"> Carefull, or hat will not fit due to big head. ;)

luckyliqueur

Thanks @Myles.

I luv the 30 litre keg Thumper with the tripod legs.

You're an inspiration as always.

Myles

Thumper # 5 - Reboiler

OK I admit this is where it gets a bit unconventional.

For as long as there have been distillation columns, some folks have been using reboilers. The normal "industrial" approach is a steam heated coil in the column base to re-heat the column bottoms. The other typical approach is to pump the column bottoms into an external heater and re-inject the vapour back into the column to mix with the vapour stream from the boiler.

It has always been acknowledged that returning column bottoms back to the boiler has been thermo-dynamically flawed. It is an energy waste on several levels.

Simple perhaps, but not efficient. Within the brewing community there have been many approaches tried to find a solution.

One of the most common is the boiler in boiler concept. The column is mounted directly onto the boiler and the base of the column is actually internal to the boiler. This is a true reboiler, because the contents of the reboiler will always have a lower boiling point than the contents of the primary boiler.
Of course it isn't that easy or everyone would be doing it. To get it to work you really need the reboiler to be copper. The thermal transfer through stainless steel is not really condusive to heating the reboiler by immersing it in the wash in the main boiler.

Option 2. Stick a heat source under the reboiler. Also used in the vapour reflux concept with packed columns. (Instead of having your dephlegmator condensate returned to the top of the column you return it to the bottom of the column)

I haven't made up my mind yet, about the vapour reflux concept. I can see the theory in my mind, I just haven't done enough runs to get conclusive results. It might be one of these issues where there are many ways to get to the same end point. Which is better?

Using an independently heated secondary boiler brings in all sorts of control issues. Many folks might not want that level of complication.

That FINALLY brings me to my end point. Sorry about the long post. Use of a parasitic reboiler under a side mounted column.

For me this is a good compromise option. Well insulated, this will be an effective reboiler and you might not (dependent on your cappacity) even need an overflow to the primary boiler.
You save energy on two counts. You don't unnecessarily dilute your boiler charge, and you reboil the column bottoms.
You don't need a secondary power source.

If you really HAVE to push it a bit further, put a calendria inside the chamber below the column and circulate your boiling wash through it to heat the column bottoms. I don't think it neccesary personally.

I honestly can't see why this thumper option isn't the first choice option for any side mounted column. However, you now know my opinion so you can at least concider the idea. Good luck. ;)

This is a pot still with a thumper mounted packed column, but the principle is the same.

My own dash is going to be thumper mounted. :D

CothermanDistilling

ding light bulb of potentially stupid/potentially awesome idea....

I love the thought of using the inside of the boiler as the heat source to vaporize bottoms....