Closed loop system... Could use a few pointers

We extract at low temperatures using a closed loop system, and chilled butane. If you pack the columns and then freeze them to below 0F and place your recovery tank in a denatured alcohol/dry ice bath, you can push/pull the butane through the material with the recovery pump down to about -50C.

We had to upsize our supply hoses to 3/8" and limit column height.

It does take more butane and more time to extract at low temperatures, but time is relative when you compare those few additional minutes to the total process time.

We are currently building prototype heat exchangers for experimentation purposes, including a short counter flow heat exchanger using liquid N2, to chill room temperature butane to -50C in a short distance, so as to allow the rest of the system to deal with easier to pump ambient temperature liquid butane.

As some of ya'll know, a counter flow heat exchanger is a tube within a tube, and coolant is pumped through the outside tube, while the liquid to be cooled is pumped through the inside tube, or vice versa, because it will work either way.

Twitch. said:

you cant unless you have a subzero extractor, i have already called every single close loop company everyone says if you try to get the column that cold the valves will fail.... I have looked into it because, I believe the retarded low temps I get my stuff to is what gives me such a clean product

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PTFE is what most folks use for low temperature applications, and it retains its resilience as low as -273C, but does require more clamping pressure because it starts out pretty resistant to compression.

Butterfly valves don't work in this application, and we use 3 piece ball valves with PTFE seats and seals, which can have seat and packing gland compression adjusted.

We use all high pressure clamps at low temperature for the same reason, and all our hoses are stainless over braided PTFE. The clamps are torqued to 50 inch pounds.

I asked reps about packing the column and then placing it in a deep freezer, they all suggested not to that the valves could or would fail.....but your saying you pack yalls columns and freeze them? can you explain a little more

We clamp a blank end cap on a column and pack it first with a few commercial coffee filters and then material, and then coffee filters, with another end cap.

Those go in a -4F chest freezer for 24 hours or so before running.

The valves are not in the freezer but see the chilled butane from the storage tank, which has been soaking in alcohol and dry ice.

We flood from the bottom until it over flows and then rinse from the top. It typically takes twice to three times as long.