- the cooling source comes from a 6000L buried tank
That is awesome! I'm on well water and just send wast water down the drain. I'd love to have a buried tank to recirculate water.
- the diameter of the column, I will go with 89mm. so 3.5" or for the high 20:1 would be 1600mm
My VM is 3" and I get at least 3 to 3.25 LPH take-off rate at 2750W. I suspect 3.5" might be able to get a take-off rate around 4 LPH.
- the filling, what height do you recommend? SPP with copper mesh and stainless steel mesh?
SPP is so expensive and you'll need a lot for a 3.5" column. It's my understanding that most all SPP is made for 2" columns. I've seen one SPP that claims to be made for 3", but the wire diameter they use is smaller than what is typically recommended. I've always wanted to try SPP, but I tried properly sized Lava Rock and it has performed so well that I no longer have any interest in SPP. Lava Rock is inexpensive, readily available and easy to use.
For the type of design, I will perhaps go with a VM in the end, I have the possibility of having a 1"1/4 valve, do you think that this is sufficient?
1-1/4" gate valve should be fine. I use a 1" valve on my 3" and the valve is open 6 full turns while taking-off hearts. That means the valve is only partially open. If I used a larger (1-1/4") valve it would be open less, but will work fine. It's not so much about the size of the valve, but how much it needs to be open to give you the desired take-off rate. I know of at least one person on this forum that uses a 1-1/2" gate valve on a 3" VM.
- Heat the wash
- Harvest the heads up to 78°C
- Maintain the steam temperature at 78°C to harvest the hearts
With VM you can heat the boiler at 100% power. I heat-up at 5500W. Once up to temp, vapor will start to rise up the column. The reflux condenser should be turned on. Reduce power and operate at full reflux (gate valve closed) for 30 min to allow the column to stabilize/equalize. I reduce power to 2750W. Turn the product condenser on, barely crack open the gate valve and take-off foreshots slowly (smells like Acetone). Once you're into heads you can crack the gate valve open a bit more and continue taking-off heads a bit faster. Once you think you're out of heads and into hearts you can open the gate valve more. Keep taking-off hearts until tails arrive.
NOTICE I never mentioned any temperature. That's because temperature doesn't really mean anything. You will notice that the vapor temp at the top of the column will settle down once the column is equalized. You'll notice that the temp will rise a few 1/10ths degree in the beginning while removing foreshots, but the temp doesn't really mean anything and doesn't indicate cuts at all. You'll notice that the vapor take-off temp remains stable throughout the entire run through heads and hearts right up until the very end of the run. Once tails hits the vapor take-off temp will begin to rise a few 1/10th degree, doesn't drop and continues rising which indicates the run is over because you're into tails. At this point you should already be collecting in smaller jars so you don't get any tails in your hearts collection jars. VM is SUPER SIMPLE to operate. You'll love it.
- Play with the valve to have an output output of around 1L/min to have a good reflux rate
When you open the gate valve, that allows vapor to exit the still. The more the gate valve is open, the more vapor escapes therefore the higher take-off rate. You can tell what your take-off rate is by collecting in a glass graduated cylinder while timing it. 100% reflux means the gate valve is closed and 100% of the vapor is condensed by the reflux condenser. 90% reflux ratio means that 10% of the vapor is exiting the still and 90% is condensed by the reflux condenser.
