Sciencemadness Discussion Board

Building a condenser - Input on approach

RogueRose - 7-6-2016 at 07:46

I have used a 12" Liebig condensor (8" of inner flow) and it seems to be much to small for my applications.

I'm planning on using this for alcohols and petroleum spirits and basically anything that won't corrode Cu or Al.

I am considering making the inner core (where the gas flows) out of copper tubing/pipe or thin walled alumimum tubing (I have 3/4" OD, .6875" ID x 36" length) Al tubing which should be good for heat transfer.

For the outer encasing I'm considering PVC/CPVC of adequate diameter to fit inner tubing. If I use copper inner tubing I can use copper outer tubing and soldering should be no problem for me. I can't do Al brazing, so it would be a Al/PVC mix if I went that route.


I'm thinking of a 24-30" condenser as IDK if I can really make it too big for what I'm planning on doing.

Is there a major drawback for either Cu or Al as the inner condensor tube as far as corrosion of general solvents (alcohols, toluene, xylene, acetone, etc)? The copper will be a thicker walled inner tube if that matters.

Any suggestions?

ficolas - 7-6-2016 at 07:55

Maybe this helps?
Handbook of corrosion data
It contains information about metals and their alloys and the corrosion of diferent substances, including copper and aluminium

I was looking at a similar table the other day looking for a material to use for the top of my magnetic stirrer

[Edited on 7-6-2016 by ficolas]

RogueRose - 7-6-2016 at 08:19

Quote: Originally posted by ficolas  
Maybe this helps?
Handbook of corrosion data
It contains information about metals and their alloys and the corrosion of different substances, including copper and aluminum

I was looking at a similar table the other day looking for a material to use for the top of my magnetic stirrer

[Edited on 7-6-2016 by ficolas]


Thank you for the helpful link. That showed a lot for my copper applications but was lacking severely in the aluminum. (In addition, my Al tube/pipe is probably almost 70 years old yet in pristiene condition - indoor climate controlled storage).


I think I'm leaning towards making one of each, maybe of different sizes. My question is whether 3/4" ID is too big and maybe needs a 1/4-3/8" pipe run through the middle to reduce volume and make gas move towards the outer cooled walls of the Cu or Al tube. Ideally I could run cooled water through the center pipe/shaft giving much greater cooling area.


On another note, does anyone know about condensers that have something like 10-30 12" pipes inside a box of pipe. The gasses flow down through all these 10-30 tubes while it is cooled with water flow in the box/pipe surrounding it.

Since none of the temps will be above 140F in the cooling water inside the condenser, is there anything I should know before building this?

Praxichys - 7-6-2016 at 08:58

All metals will contaminate your distillate to some degree. It just depends on what you plan to use the product for, and whether metals will affect the reaction. I would not recommend aluminum as even very slightly acidic solutions attack it to some degree, especially while hot. Alcohols also react with aluminum, slowly forming alkoxides. These are then hydrolyzed by any water present, eventually resulting in annoying flocs of aluminum hydroxides in the distilled product.

Despite the cost, I really recommend simply purchasing a larger glass condenser. Condensers are matched to the heat input at the boiling flask. If you are overwhelming your condenser, you can either get one with a larger surface area and cooling capacity, or turn the heat down. In my experience, if you are overwhelming a 12" liebig with things in the 60-80C boiling range, you are either heating much too aggressively or your condenser water is not circulating fast enough or is too warm to begin with. Try a little circulation pump in a bucket of ice water.

In lieu of purchasing a glass condenser, you can make a jacket around a piece of ordinary glass tube with a pair of double-bored corks and a bit of plastic pipe.

hissingnoise - 7-6-2016 at 09:56

Quote:
In lieu of purchasing a glass condenser, you can make a jacket around a piece of ordinary glass tube with a pair of double-bored corks and a bit of plastic pipe.

For condensers the glass must be borosilicate.

Dr.Bob - 7-6-2016 at 17:55

Aluminum is bad for chemistry, corrodes with many chemicals, as stated; copper has been used with ethanol for years. Glass is better, and while you can maybe make a condenser, they cost less than cleaning up a mess from other stuff. If you are only distilling ethanol, you can build or buy a specialized metal still, it has a high heat capacity, and requires pretty well designed equipment to purify well. But for most hydrocarbons, glass joints are better and safer, unless you make sure everything is sealed well, as leaks + hydrocarbons = fire.

Anything made of glass and plastic has the potential to leak or be dissolved from a leak, I don't think it is worth the risk and effort. You can buy larger condensers for $20-50, not that big of an investment.

RogueRose - 8-6-2016 at 00:17

Quote: Originally posted by Dr.Bob  
Aluminum is bad for chemistry, corrodes with many chemicals, as stated; copper has been used with ethanol for years. Glass is better, and while you can maybe make a condenser, they cost less than cleaning up a mess from other stuff. If you are only distilling ethanol, you can build or buy a specialized metal still, it has a high heat capacity, and requires pretty well designed equipment to purify well. But for most hydrocarbons, glass joints are better and safer, unless you make sure everything is sealed well, as leaks + hydrocarbons = fire.

Anything made of glass and plastic has the potential to leak or be dissolved from a leak, I don't think it is worth the risk and effort. You can buy larger condensers for $20-50, not that big of an investment.


Thanks for the suggestions I'll keep them in mind. I'll be find with copper and I am confident in my craftsmanship. Now the only issue is what size pipe to use. I have 1" ID for the outer and the choice of .5 or 3/4 as the vapor tube. The only possible problem I can see is that the 3/4 leaves little room to solder the water inlet ports and there is much less water in the condensor at all times (which shouldn't be too much of an issue as my pump is well above the needs and is turned down.

Any ideas on this issue?

Dr.Bob - 8-6-2016 at 03:49

The water only cools at the surface of the inner tube, so the outer tube need not be much larger. The flow is what controls the cooling power. And I often flow from top to bottom with the water, if under a large load, as then the coolest water is on top, right before the dist. head, and the water leaves the condenser as hot as possible.

But the conditions to distill ethanol well are very different than most hydrocarbons, which have much lower heat capacity, so you will need to heat the hydrocarbons slower, and they take less cooling to condense.

macckone - 8-6-2016 at 22:25

Condensors do not have to be borosilicate glass. But they do need to be very thin if they are not. Fluorescent tubes are usually a good diameter and designed for a moderate inner and outer temperature difference. However, copper is much better for non-acidic compounds if light copper contamination is not an issue. Copper will not shatter. For strong acids only glass will do and it needs to be good quality.

RogueRose - 9-6-2016 at 01:04

Thanks to all for the replies!

I have decided to go with the 3/4 but I am worried that it may be to wide and some gas might not hit the walls. So What I was thinking was putting a 1/2" OD copper tube capped on one end and placing it at the exit point of the condenser this will fit 2-4" into the condenser (capped end inside the condenser). This will make the gas move closer to the cooled condenser wall.

Since it is at the end of the condenser the gas should have decreased in volume a great deal so this insert shouldn't cause too much of a problem that I can see. It's temp shouldn't be much of a problem and I'd cool it if I could determine a good method.

Does anyone think this would be a bad idea or know if anyone has tried this before?