VM Take-off rate for 3" 2200W Packed Column

[Dave022]

I am running my new 3" SPP packed column using VM as take-off and a 2200W keg boiler.

I am currently getting Over 96% out (which I am happy about) but it only runs at approx 400ml / hour.

This seems really low to me, am I wrong?

[The Stig]

To go beyond 95.6%, you’d need chemical drying agents (e.g., molecular sieves), which are rarely used in home setups due to safety and legality

[Dave022]

sorry fat fingers, over 95%...

[GrumbleStill]

Agree 100% - that’s a very low take off rate from a 3” - especially as you are using spp. You should be able to get 1.5 - 2 lph with a setup like that at 2200W.
Can you provide any more info on your rig eg column height, RC setup, takeoff valve size etc?

Cheers

[Dave022]

Hi thanks for the reply.

Column is 1120 mm high with 980 mm packed SPP. There is a hammerhead condenser on the top and a 1/2" takeoff below that controlled with a silicone tube and hoffman clamp direct to a standard liebig condenser. water control is seperate for both condensers.

[GrumbleStill]

Ok - Makes sense now.

The 1/2” offtake is way too small for a 3” VM. The amount of product you get / reflux ratio is dictated by the size of the of the offtake compared to size of the column above it. A 1.5” gate valve might be a better idea.

If that’s not an option, it might be worth considering switching to an LM design.

Cheers

[Dave022]

I am running another 10% sugar wash through this now, still the same issue. if I use 2200W I get 444ml / hr.

If I reduce water flow to reflux condenser then I increase flow but vapour escapes past the reflux condenser.

I have played with reduced power and water flow adjustments but can't seem to find a balance, is there a systematic approach I should be taking?

[Dave022]

Ok - Makes sense now.

The 1/2” offtake is way too small for a 3” VM. The amount of product you get / reflux ratio is dictated by the size of the of the offtake compared to size of the column above it. A 1.5” gate valve might be a better idea.

If that’s not an option, it might be worth considering switching to an LM design.

Cheers

Didn't see this reply before writing last comment. Well I could use a 3" to 1.5" reducing elbow at take-off, but the liebig condenser is only 1/2". Now I have a 1.5" to 1/2" reducer and could put a valve either at the 1.5" or 1/2" end; but is this going to help my situation?

[GrumbleStill]

Yeah, I can see how that could be an issue.

Could be a really good excuse to upgrade to a 2” shotty for your product condenser ;-)

Another approach could be go old school and reduce the whole column at the off take.

There’s a nice illustration of the concept in this post viewtopic.php?f=57&t=3117