Does the size of the copper tubing inside the condenser have a bearing on how much methanol you'd recover??? Wondering if I can use the 3/8" tubing I already have as opposed to buying somne 1/2"????

hi vaman4215

The cross sectional area or 'doorway size' which the methanol is allowed to escape thru is the key factor, as it will determine back-pressure in your still.

The diameter of exit should at least be big enough that your still doesn't build up too much pressure. Small diameter will mean you will need to safely limit your power input. If it can't get out quick enough, you may have a problem on your hands.

The area of cold copper the vapor can condense onto is the another key factor.

If you reduce the diameter of pipe, you should increase the length, to maintain enough area for the vapour to condense onto, provided the diameter is large enough to allow safe pressure in the still.

But, too much length of narrow tube will further restrict the free flow of vapour out the still, so this is to be avoided.

The faster you make vapour, the faster you must be able to get it out the still and condense it.

Vapour production rate depends on several things, most importantly ...

1. Heat power input to the still
2. Concentration of methanol in the still

So, your rate of vapour production will be at its highest near the beginning, and will be affected by how much heat power you put into it.


More than necessary is generally better than not enough when it comes to both length and diameter in a condenser, as in certain other things in life

quote:

More than necessary is generally better than not enough when it comes to both length and diameter in a condenser, as in certain other things in life

So then size does matter .............

I have a small still and process about 10 litres at a time or so. The outlet goes from 1/2" into a 1/4" soft copper tube that is coiled into the condenser, 10ft of it surrounded by the water jacket. My heat is supplied by a 240V heating element run on 110V and the methanol streams but not excessively, more of a quick drip or shallow stream at times.
This set up has worked well for me, but then I also make soap at the same time so the volume is intentional to reflect that aspect of recovery.
I dunno about a larger volume still but I would be very apt to follow Graham's advice.

I think I'll just go ahead and invest in some 1/2 tubing then or 3/4 if the price is right....Would rather be safe than sorry, especially where methanol is concerned...I kinda figured it'd be too small,but one never knows till they ask the veterans of BD...Thanks guys.

ok. so I go aginst the grain here..but

the pipe feeding my reflux column is 3/4" iron pipe

reflux column is 2" copper pipe packed with stainless steel scrub pads

the condenser.. is connnected to the top of the column with 10' of 3/8" copper tube.

the condenser is 3/8" copper tube that was part of an AC unit. and its fan cooled. no water

heating is 4500w using a 240 element

temp control is done by the pot and head temp.

I'm working on some photos if I can merge them into one. I'll post it.

I agree, if the column/condenser cannot remove the excess heat from the vapor fast enough it won't work properly( poor purity and vapor coming out). not enough heat and it'll either not work or work very slow. my doesn't work at all if I try running on 120V.

-dkenny

I made my condensor useing 3" inch copper pipe for the outer shell. Internal tubes were made from copper also.Center tube was 1" with (8) 3/8" copper tubes around the perimeter. These tubes were held inplace by two brass disc drilled and reamed to accept the 1" and 3/8" copper pipe. I made the whole internal tube assembly 42" long and the external 3" pipe 48" long. I Believe this will allow for plenty of vapor flow and zero back pressure.
Joe.D

If you are concerned that 3/8 may be too small and you have enough of the tubing you should run two lines in parallel. This will solve the length/back pressure issue and allow you to use materail that you already own.

-Jim