Shotgun reflux condenser for a 3" column

[sergiolis]

Hi guys,
I've just built a 3" Bokakob to make basically neutral spirit. My heat element is 5500W and my packing is SPP. So looking at this table
( http://pracowniametaloplastyczna.pl/en/advices" onclick="window.open(this.href);return false;" rel="nofollow ) I will have to work at about 4600W. I trust this table because I was working nicely with a 2" column at 2700W
I built a dimroth reflux condenser but looks like it is not able to knock down more than 4000W.

Anyway as I have a 12" SS spool tube I'm thinking to build a Shotgun.
Using 15mm OD copper tube I could build a 12x12" lenght in a 3" ID (72mm). Setting 5000w in the calculator estimates about 2.75m of 15mm tube and If I build this condenser I would have 3.6m
This is my idea, but I would like to know if I'm on the good track.

[der wo]

As I wrote in the other thread, I don't have practical experience with dimensioning shotgun dephlegmators. But unfortunately no one answers, so I try:

The parent site calculator gives you not the right results for reflux condensers. Reflux condensers can be noticeable smaller than product condensers.
BTW you have to type in the inner diameter. 13mm, not 15mm. This results at 5000W in 3.04m. So perhaps you need 2m. Your plan is oversized. But it looks very symmetrical with 3 tubes in the middle and 9 besides. So I would go for it.

But perhaps look in other builds, what other members have written. Google search shotgun perhaps.

Here products from stilldragon:
3 Inch dephlegmator:
https://www.stilldragon.eu/en/condenser ... mator.html" onclick="window.open(this.href);return false;" rel="nofollow
3 Inch product condenser:
https://www.stilldragon.eu/en/condenser ... enser.html" onclick="window.open(this.href);return false;" rel="nofollow
Unfortunately they write no maximum wattage... the most important number. But you can see the size difference between reflux and product cooler. And both are much smaller than your design.
Perhaps you find info in the stilldragon forum. Or ask there.

[SilverBullet]

My 3 inch column dephlegmator condenser only has five, half inch tubes, 6 inches in length. I can only use a trickle of water, I mean a trickle. Any more and it's in 100% reflux. Hope that helps

[Saltbush Bill]

In my opinion you are over thinking and over complicating things..a 3 inch bok packed with copper mesh will run quite nicely at about 2400w.
Using SPP you may be able to use more power ...but I doubt the amounts you are suggesting

[sergiolis]

Hi Saltbush,
As far as I know SPP works different. You can increase the power much more than when you are using other packings. I will quote Odin:

"The more power you throw at your column, the more reflux you create. The more reflux you create, the wetter the conditions are in which the SPP has to do its job, making it ever more efficient. Until you push it too much and create actual column flooding"

More power means more redistillations, so better separation. In practice it means you can increase your take-off considerably without losing the equilibrium, but to do that you need power. As I said I was working with a 2" column packed with SPP at 2700W and easily a take-off about 40-45 ml/min.
der wo is working at 2800W, Odin too....
I don't know exactly what power will be ideal for my new 3" column because you need experience with your rig and I just run it once dealing with a Feints run.
I hope someone experienced with SPP in 3" column will contribute with some suggestions...
Anyway I noticed that my dimroth reflux condenser was overwhelmed at about 4000W so I'm trying to build a condenser able to work easily at 5000W. Maybe oversized but easy-handling.
Hi SilverBullet, could I ask you at what power are you working?
der wo I've searched a lot here in HD and in google too but I couldn't find a specific response for such power. And as you said I didn't find any answer talking about a maximum wattage between 4500-5000W but I will continue to seek and I will try to ask in SD forum too.
Thanks a lot

[der wo]

der wo is working at 2800W

2600W!

[SilverBullet]

Hi SilverBullet, could I ask you at what power are you working

I use propane on that set up. Not much help to you there but after I'm up and running, I do have the heat turned down low.

[sergiolis]

Thanks Silver, I will insist on my search...

[sergiolis]

Finally I found some hints that tell me my dephlegmator will do the job:

Re: Variable Coolant Height Dephlegmator
Postby myles » Fri May 11, 2012 9:24 pm

Thanks rock, yes I had picked up on the variable height capability. That cavitation in the lines is interesting, most of my condensers run on full pressure ( 1 bar) input with flow control on the output, but the dephlegmator is probably going to be the other way round.

I agree completely about the bottom of the condenser reservoir acting like a cold finger. I was going to include a conventional cold finger at one point and combine it with a big coil, but the shotgun will be an interesting build and I haven't done one yet. Have to keep the skills improving.

In case anyone is evaluating the design, the calculator on the home site gives for a 1/2" jacketed tube a power capacity of 55 watts per inch with in / out temperatures of 15 and 20 degrees. I did a quick search and came up with 2 quoted sets of dephlegmator performance figures.

6" long by 7 of 1/2" tubes that can handle 3kw - this is equivalent to 71 watts per inch
6" long by 13 of 1/2" tubes that can handle 7.2 kW - this is equivalent to 92 watts per inch

Now obviously there are lots of undisclosed variables, but an average gives you close to 73 watts per inch. Therefore as a ballpark estimate I reccon 75 watts per linear inch (for 1/2" tube) would be close enough to get anyone started.



Postby Sungy » Fri May 11, 2012 11:10 pm

My 3 inch diameter 7 tube shot gun is 6 inch long with another 3 inch section. Never used the 2nd section yet. Just the first 6" will knock down every thing I throw at it. I have a modified MK5500 setup. 240 volt x 24.5 Amps = 5880 watts. 5880 watts / 42 inches = 140 watts per inch for me. Water temp was 23'C at the time if that helps. It was accidental that this data was created but useful.

LET'S DO IT!!!

[sergiolis]

I finished the deplhegmator. In the Bokakob configuration it will be fed with water from the liebig.But I have a question...
I think if I connect the hose at the top of the dephleg (counterflow) water will flow at the bottom and the dephleg will not be full of water.
Should I connect water in at the bottom of the dephleg?

[still_stirrin]

Raise a loop of the outflow hose above the inflow hose. That will fill the deflag with water and keep it full (until you're ready to drain it).

Gravity....it's not just a good idea....it's the law!
ss

[cranky]

This is the first I have seen this thread but I can't help commenting on it.

A lot of people think of reflux condensers as the same in different columns but in my personal experience you cannot think of the reflux condenser on top of a boka the same as a reflux condenser on a CM. The two, while working similar, don't do the same thing. A boka RC needs to be overkill because you need to cool everything and make it fall back down before it reaches the top of the condenser but on a CM if some vapor makes it past the RC it's no big deal and will likely condense before it makes it to the bend and fall back to the condenser. I've made a boka with a shotgun and it takes more than people who use CMs think it should. I now run a slightly larger than 3 inch flute and 3.5 inch CM. The flute has a dimroth much like the one pictured in the original post. Mine is about 8 inches long and has no problem knocking down everything my 5500W element can throw at it. I have the advantage of my dimroth being in a sight glass so I can see exactly how it works. I can also see that the vapor gets pretty close to the top before it fully condenses at full power but I don't believe anybody would ever need to run that much wattage to run reflux on a 3". My packed CM has a 6 inch shotgun on top and also has no trouble knocking down everything at full power but I cannot say there isn't some vapor making it past before it falls back to the condenser and back to the column, because I have no sight glass above the RC. I can tell you the shotgun on top of my boka was calculated as overkill and in theory should have been able to handle the power but in practice due to vapor speed and what not it could blow vapor and sometimes cool liquid right out the top and that isn't a good thing. My point here is that although in theory there is no difference between theory and practice in practice there is. Now granted my Boka was 1.5" diam so the vapor speed in it may have been faster than a larger diam column but my advice is, if you are using a shotgun at the kind of power you are talking about, keep a mirror handy and check frequently to see that you are actually condensing everything and not blowing things right out the top.

I also don't think it really matters which way the cold water enters the condenser. On my CM it goes in through the bottom and out the top and does fine. Some people insist it needs to go in from the top but my belief is that the cold water will go to the bottom anyway and with a boka you want to cool things as fast as you can to keep vapor as far from the top as possible.

Just my 2 cents.

[kimbodious]

Cranky, you make a great point! You can blow vapour up and out past the biggest RC if the speed is high enough.

[sergiolis]

Wow! still_stirrin that's a very simple solution that a hopeless at physics like me could not picture it Really thanks for the advice. Sorry about my ignorace, now another stupid question: Do I need to maintain the loop the whole run or once is full of water it is enough?

Great advices cranky, As you say my RC supposedly is overkill. It is 11" long x 12 tubes (13mm ID). But my idea was to work peacefully. Anyway at the moment everything are suppositions but I think i'll be working at least about 4000W because SPP works better with power. So that's why I wanted a beast condenser
... But you are right a mirror will help me to know what is going on.
I have some concerns about air inside the water jacket... I will try first the hose loop and if I have some issues I will connect water in at the bottom of the dephleg.
I don't know exactly why but it was quite difficult to seal it completely.... I was making some test connecting the dephleg to tap water and when I blocked water out I realized that with the water pressure there were some pinholes. I think is completely sealed now. Besides that, it won't be subjected to a such pressure.... But if you think it is a serious issue and must be guaranteed a perfect seal I will try to check it 100%...

Thank you guys, I really appreciatted your help ..

[der wo]

Wow! still_stirrin that's a very simple solution that a hopeless at physics like me could not picture it Really thanks for the advice. Sorry about my ignorace, now another stupid question: Do I need to maintain the loop the whole run or once is full of water it is enough? ... I have some concerns about air inside the water jacket... I will try first the hose loop and if I have some issues I will connect water in at the bottom of the dephleg.

Probably you will hear it, bubbles in the jacket and hose will make a sound, especially when playing with the water flow. And if your hose is transparent, you can see, if there is water or air.

I don't know exactly why but it was quite difficult to seal it completely.... I was making some test connecting the dephleg to tap water and when I blocked water out I realized that with the water pressure there were some pinholes. I think is completely sealed now. Besides that, it won't be subjected to a such pressure.... But if you think it is a serious issue and must be guaranteed a perfect seal I will try to check it 100%...

This would ruin the run. Not only, that your distillate gets diluted, inside the jacket probably is full of flux and copper compounds... I would check the shotgun before every run (fill it with a bit water, close one water connection with a finger and blow into the other. Now you should hear any pinholes).

[sergiolis]

Thanks der wo,
I did the blow test succesfully!
It weights 2.355 Kg!!!!!

[cranky]

That looks like it should do a fine job

As far as leaks, it all depends on where they are. The connection to one of my valves has a slight leak that I haven't fixed yet. It's not a big deal since it doesn't get near any distillate but if it was where cooling water got into the distillate, I would make sure I was confident it doesn't leak.

The reason I made that big long post above was that people often think about putting shotguns on top of bokas, myself included, and hopefully when someone doing research on this subject stumbles across this thread they will understand what they are facing. I don't pretend to know everything going on or why but the reason I mention the vapor speed being an issue is that when you reduce the diam of something the vapor speed goes up. You are reducing the area of your column from 28.27 sq. in. to 9.42 sq. in. which I think essentially creates a sort of venturi causing vapor speed to go up tremendously, but like I said, I don't really understand a lot of the whys, I just know what happened when I did it and wanted to get the word of caution in there. In truth I think you are going to find yourself running quite a bit less power than you anticipate, depending on just how pure you want things, but an abundance of caution and overkill are good things in this hobby.

One other thing I found was with the boke (anything really) is that I don't like running my reflux condenser through my product condenser. The reason is it winds up preheating your RC water and can effect controlling your reflux. I personally like keeping my PC and RC on different pumps so I can control them individually.

[sergiolis]

Hi cranky, I understand your theory about vapour speed and I will test its capacity. But I think that in general people use shotguns even for 4" columns so they must be quite effective and they should hold quite power too... Let's see, maybe small pieces of ss scrubbers at the top into the tubes could help to keep vapours inside.
Separated lines for cooling different condensers sounds great and probably it will be a further step in my configuration...
I need to test this thing before saying too much silly things I will comment soon on the result.
As this still will be mainly to make neutral I'm trying to work close to its maximum efficiency... And it's just a supposition but if I was working in a 2" column at 2700W, 4000w in a 3" column I think it's not a crazy idea... who knows!
Thank you very much for your encouraging comments!

[cranky]

Hi cranky, I understand your theory about vapour speed and I will test its capacity. But I think that in general people use shotguns even for 4" columns so they must be quite effective and they should hold quite power too... Let's see, maybe small pieces of ss scrubbers at the top into the tubes could help to keep vapours inside.
Separated lines for cooling different condensers sounds great and probably it will be a further step in my configuration...
I need to test this thing before saying too much silly things I will comment soon on the result.
As this still will be mainly to make neutral I'm trying to work close to its maximum efficiency... And it's just a supposition but if I was working in a 2" column at 2700W, 4000w in a 3" column I think it's not a crazy idea... who knows!
Thank you very much for your encouraging comments!

They are just cautionary words mostly for the benefit of others. Just keep an eye on the top of that thing

But I think that in general people use shotguns even for 4" columns so they must be quite effective and they should hold quite power too.

That's what I was talking about when I said

A lot of people think of reflux condensers as the same in different columns but in my personal experience you cannot think of the reflux condenser on top of a boka the same as a reflux condenser on a CM.

It's easy to think of a condenser as just a condenser but a PC does a different job than an RC in a slightly different way and different columns also use RCs in different ways. A short shotgun works fine in a CM because it doesn't matter if some gets past, eventually you have to run it all past it anyway but a boka is different because you need it to condense everything all the time so they require different ways of thinking about condensers. I'm all for what you are doing and think what you have will work just fine and I know you will figure out how to run it just fine. I just wanted to caution you to keep an eye on it just in case.

[sergiolis]

Hi cranky I will definitely do it and honestly I think you have given me some good advices.
Next week I will know how much vapour squeeze that thing and I will comment

[cranky]

I'm interested in seeing how well it does compared to my CM. I just checked my post about my numbers on my CM. Unfortunately I don't keep notes on power but my takeoff speed was a quart every 15 minutes at 94%. I cant get my CM above that, unlike my Boka. I was probably running at about 14 Amps, which is where I seem to like to run, I have no idea how much that translates to in wattage.

[sergiolis]

it depends on your voltage.
W= V·I

[cranky]

it depends on your voltage.
W= V·I

Therein lies the problem, I read my voltage at the switch so it does little more than tell me the switch is turned on. When I had it hooked up after the controller the voltage varies as power is turned down. In truth those things mean very little to me since I run pretty much by sight rather than numbers, the meter is only there to look pretty and tell me I do have power.

[RedwoodHillBilly]

it depends on your voltage.
W= V·I

Therein lies the problem, I read my voltage at the switch so it does little more than tell me the switch is turned on. When I had it hooked up after the controller the voltage varies as power is turned down. In truth those things mean very little to me since I run pretty much by sight rather than numbers, the meter is only there to look pretty and tell me I do have power.

If you are using a type of volt ammeter that uses a current transformer (the doughnut that goes over 1 wire to your element) connect the voltage measurement before your SSVR and the xfmr on the element wire. The current measurement will average out and you can calculate power as P = E * I

If this is too much, don't worry about it, and just remember numbers that work for you.

[cranky]

it depends on your voltage.
W= V·I

Therein lies the problem, I read my voltage at the switch so it does little more than tell me the switch is turned on. When I had it hooked up after the controller the voltage varies as power is turned down. In truth those things mean very little to me since I run pretty much by sight rather than numbers, the meter is only there to look pretty and tell me I do have power.

If you are using a type of volt ammeter that uses a current transformer (the doughnut that goes over 1 wire to your element) connect the voltage measurement before your SSVR and the xfmr on the element wire. The current measurement will average out and you can calculate power as P = E * I

If this is too much, don't worry about it, and just remember numbers that work for you.

I don't really worry about it.

[RedwoodHillBilly]

I don't really worry about it.

Right on brother, do what works for you.

[sergiolis]

I made this rustic scale to measure my power, so nothing to say...

[cranky]

I made this rustic scale to measure my power, so nothing to say...

potenciómetro web.jpg

Looks pretty good to me.
On that scale I probably run around the 2200-2640 area.

[sergiolis]

I was at 2700W with a 2" column packed with SPP... Let's see what I get with the 3"...

[sergiolis]

S.O.S.
I need help!!!
The shotgun doesn't work. At about 2600w vapours are scaping...
I build this condenser because supposedly is one of the most effective but is working at lower efficiency that my dimroth...
I had to stop the run.
I don't know what to do now.
I can't deduce where is the problem. It is bigger than the average I've seen here.
The only issue I can figure it out is too much vapour surface for the amount of water surface, but I'm really stuck.