What pump for bokakob double coil?

[fishhawk357]

I am in the process of building a bokakob mini still and am just about done with it. I only need to drill the thermometer hole and solder the 1/4 inch tube for it. I have, after 3 attempts, been able to make the double helix coil. My problem is that my pump wont pump enough water through the coil. It is just a pond pump. I need a pump that wont break the bank but still be able to pump at a decent rate. Anyone have any suggestions? Thanks in advance for any help.

[glassman]

i use a sump pump from home d. desent head and pressure. but i'm also pumping thru 3/8 tubing. gman

[gunnaknow]

Do you really need a pump? I thought that you could hook the tubing up to the tap and that the mains pressure would push the water around. I've just bought 1.5" copper pipe and now feel disheartened because at no point did the bokakob design explain that a pump was needed. I'm thinking about abandoning the whole project now because it just seems like one expense after another when building a reflux still. Do I really need a pump if I make a reflux still??

[Dmad]

Gunnaknow, you don't need to have a recirculation pump to run a reflux still. You can simply attach it to the tap or the hose and it should provide adequate enough flow.

[As-Ol-Joe]

Lowe's has a variety of ponds pumps. They range from $19 to about $54 with head pressures to about 6 feet. I use the small one and recirculate my water using ice to keep the bucket cool. It only takes about 5 gallons of ice for an eight hour run.

[HookLine]

No, you do not need a pump, you can hook it straight up to the tap. That is how I do it. Pumps are only used in recycling systems, in places where water is limited.

(EDIT: Dmad beat me to it.)

Almost all of the expenses in any kind of still are upfront, once it is made the running costs are very low.

At the risk of disappointing you a little further, 2" is a much better size for a column. 1.5" runs very slow.

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fishhawk357

The problem you have run into is that the standard 'double helix' coil only has one pathway for the water, the water flows down one coil and back up the other. This means it has quite high back pressure and low flow rates, and most of the readily available pumps cannot handle that.

One solution is to make a coil condenser with 2 (or more) parallel coils and a centre return tube, like this one, or this one. It has at least half the back pressure and can handle at least twice the flow rates.

Hawke made a 3 coil version, check this thread.

This kind of design is more suitable for a pump. Ask Rudi how well it works, he uses it with a pump recirculating system.

[As-Ol-Joe]

I use a recirculating system because my sewer rate is twice as high as my water rate. I have to pay for my water 3 times. It makes more sense for me than having the tap run for 8 hours.

[tracker0945]

I use a cheap marine bilge pump ($20) and it pumps plenty for my double coil Bok Mini.
There are many ways of getting around any problem.
Cheers

[gunnaknow]

Gunnaknow, you don't need to have a recirculation pump to run a reflux still. You can simply attach it to the tap or the hose and it should provide adequate enough flow.

No, you do not need a pump, you can hook it straight up to the tap. That is how I do it. Pumps are only used in recycling systems, in places where water is limited.

OK, thanks guys. That puts my mind at rest.

Almost all of the expenses in any kind of still are upfront, once it is made the running costs are very low.

At the risk of disappointing you a little further, 2" is a much better size for a column. 1.5" runs very slow.

I actually bought 1.65" pipe so it hopefully won't be too slow. By my calculations, using pi, 1.65" offers 20% more area than 1.5" and 32% less area than 2". Although these figures don't exclude the walls, so it's approximate. I only want enough for personal uses so I think 1.65" should be a good inbetween size for me.

[absinthe]

hookline I'm surprised your using running water in Oz.. i recycle everything i can gray water and cooling water.. (i fill the bath up for the stripping run and when I'm finished i pull out the pump add a lil more hot water and have a bath .. then she goes on the garden)

[jmd445]

Using the double coil as shown here-- http://homedistiller.org/wiki/index.php/Image:19_ ... oil-1-.jpg" onclick="window.open(this.href);return false;" rel="nofollow --where do you vent the pressure if the top of the column is capped?

[Husker]

It is very easy to drill a couple small holes (2 at 3/8" should be enough), into the top of the cap.

[HookLine]

Using the double coil as shown here-- http://homedistiller.org/wiki/index.php/Image:19_ ... oil-1-.jpg" onclick="window.open(this.href);return false;" rel="nofollow --where do you vent the pressure if the top of the column is capped?

hookline I'm surprised your using running water in Oz.

Fair point.

But I live in the far tropical north, and we have shitloads of water... no drought up here, our already high and reliable average annual rainfall is actually increasing! I also catch the used coolant water in large plastic barrels, and after it has cooled down I throw it on the fruit trees. It doesn't go to waste.

But I am probably moving to the much drier SE Qld/northern NSW area in a couple of years, and if that happens I will definitely be going to a recirculating system.

[duds2u]

Hook,
By the time you get to move down here Anna will make sure we can only use air cooled condensers.

[Hawke]

That tripple I built will knock down the space shuttle with very little flow
Man, I wish I'd found the Boka design before I built my valved reflux, could have saved a bunch of money.

You might be able to cut the transition at the bottom of your coils and add the center return to it. Then the smaller pump would probably work ok.

[nutmg1]

I tried the pump in a 32 gallon bucket.

I started with 6 frozen 2 liters. The Ice couldn't keep the water cold, especially on a reflux spirit run. It’s my understanding that you want the water running as slow as you can and still knocking down the vapor. Thus the water output is as hot as you can get it.

What temp does the water need to be to knock down the eho? Maybe I am thinking it needs to be colder than it really does? I'm at high elevation and our water comes out of the hose really cold this time of year.

How much water do you need in the reservoir? I had about 25 gallons. I couldn’t find any info on this on the parent site.

[Hawke]

Anything below the boiling point will condense the product. The warmer it is, the more flow required. As long as you don't have vapor escaping it's good.
Luckily, I'm on a well, I just water the lawn while I'm stillin'

[nutmg1]

Anything below the boiling point will condense the product. The warmer it is, the more flow required. As long as you don't have vapor escaping it's good.
Luckily, I'm on a well, I just water the lawn while I'm stillin'

That's good to know. Its a little dark in my garage and the top of the condenser is about 9 feet off the ground. I spend a lot of time standing on a ladder with my hand over the condenser trying to figure out if vapor is coming out.

I'll try the pump again on my next run.

[HookLine]

nutmg1

There is another way to do it. Stick a thermometer in the top inch or so of the coil. If it reads significantly below the vapour point of ethanol (78.4ºC), then there is no ethanol vapour coming out, it is all being condensed.

That is how I do it. (I set my thermometer alarm to 50ºC.)

You do need to make sure the end of the probe (where the reading is actually taken from) is not touching the coils (ie the cooling surfaces), as that can skew the reading.

[rad14701]

An alternative to climbing a ladder and using your hand to check for escaping vapors would be to use an old discarded cosmetics or signal mirror mounted at a 45 degree angle at the top of the column... Simply looking up and maybe shining a light at the mirror for signs of condensation on the mirrors surface should tell the tale... And if it is mounted an inch or so above the column there should never be an issue of the mirror getting too warm to give an accurate indication...

[Rudi]

Fishhawk357,
I use a pond pump in a 200l drum for my reflux and pot still.The reflux condensor is a true double concentric parallel wind with a 1/2" inch return line down the centre. I can run both stills without adding ice or top up water.
The top layer of water in the drum gets hot but as you run your hand down the drum it gradually gets cooler towards the bottom where the pump is.

If you run a closed circuit with your recirculating system with all the air purged there will be a net lift of 0 this means the head on you pump is not so important.The water coming down pulls the water going up. If you have some time do a search Pinto explained it somewhere. I originally built a 12" long double concentric continuous counterwind
. The small pump I have would only push a dribble through it.The pump pushes a good flow through the new condensor (the second pic in Hooks post). The pump is only a small pond pump it cost around $30 at Bunnings.

Rudi
edit; added Mr Anal's corrections

[fishhawk357]

Thanks for all the replies, I have already built another coil. This time I used a 3/4 pipe for winding and only made a single coil with the return running up the center. Flow is much better. I ran the still today with water to test it out and it worked real nice. I let the steam build up till it was really rushing out the output tube then turned on the water. It stopped the steam but the water was coming out really hot. To hot to drink. My cooliong bucket got hot quick also. Its only 5 gallons. I hope it works well with distillate at a lower temp, only one way to find out. I'll try to run it this weekend if I get a chance. It did show promise with water though.

[HookLine]

At the risk of being called a pedant...

A true double helix is one of these, with two coils of the same size interwoven between each other. (The centre tube is irrelevant to it being a double helix.)

A coil wind like mine and Rudi's is probably best described as a double concentric parallel wind, and Hawkes' 3 coil condenser as a triple concentric parallel wind.

The kind of double coil that is common here and is (incorrectly) called a 'double helix' is probably best described as a double concentric continuous counterwind.

Okay, the pedant has now left the building.

[Oaty]

I had been reading all this about how large a reservoir I would need with rapt attention. Then, it struck me! I've got a swimming pool out back! Duh!!!

[fishhawk357]

Hookline, you got me thinking. My original coil was a continuous double coil. My new one is a single coil. All I have to do, in theory, Is make another single coil and then interweave them and find a way to connect them without creating to much bulk as I built the 1.5 before I learned that the 2 would be more efficient. I already have several failed coils from previous attempts that I may be able to salvage. Thanks for the info and pics.

[HookLine]

You're welcome. I find this part of still design very interesting, a nice mix of thermodynamics and fluid dynamics.

Have fun experimenting, and let us know how it turns out.