Large Amount Of Solvent Getting Stuck In My Closed Loop System.

[Pimpernickel]

I have a closed loop system with a 3'x18" material chamber with a cooling jacket around it. It reduces down to a 1 1/2" ball valve and I put some coffee filters in the reducer to stop any very small particles from getting through. I vacuum my loaded system down, place the collection chamber in an ice/salt bath, and put an isopropanol/dry ice bath in the cooling jacket then wrap with towels to try to insulate it. I'll fill with distilled butane until I get build a bit of pressure then I let it sit for 30-60 minutes. I open the valve and the solvent drops down into the collection chamber. After a minute or so I can let it sit there for 30 minutes and not get another drop of solvent, I can open the tank and run more solvent through and see about the same amount of solvent come out. I close the valve and finish the process but when I take the top of the column off for cleaning I'll always have 300-1000mL of solvent coming out of it. That's a very large amount. It's dangerous, makes a mess, and ruins my yield but I cannot figure out why it's not draining into the collection chamber, any ideas? The cooling jacket gets down to -109F (according to the cooling bath section of wikipedia, I can only measure to -59 with my thermometer) but that's well above the freezing point of butane, it can't be gelling at that temp can it?

 

[Fishmaster42]

i think its that coffee filter. i use the metal filter that came with the setup. i run a 3 x 18 pressure column. I freeze everything gas too. I crack the bottom valve let air out while i fill with tane when i see tan run out the end out count to three and close the valve and let it sit 5 mins then dump it. you can order stuff like that from. http://www.bestvaluevacs.com/

 

[Graywolf]

I have a closed loop system with a 3'x18" material chamber with a cooling jacket around it. It reduces down to a 1 1/2" ball valve and I put some coffee filters in the reducer to stop any very small particles from getting through. I vacuum my loaded system down, place the collection chamber in an ice/salt bath, and put an isopropanol/dry ice bath in the cooling jacket then wrap with towels to try to insulate it. I'll fill with distilled butane until I get build a bit of pressure then I let it sit for 30-60 minutes. I open the valve and the solvent drops down into the collection chamber. After a minute or so I can let it sit there for 30 minutes and not get another drop of solvent, I can open the tank and run more solvent through and see about the same amount of solvent come out. I close the valve and finish the process but when I take the top of the column off for cleaning I'll always have 300-1000mL of solvent coming out of it. That's a very large amount. It's dangerous, makes a mess, and ruins my yield but I cannot figure out why it's not draining into the collection chamber, any ideas? The cooling jacket gets down to -109F (according to the cooling bath section of wikipedia, I can only measure to -59 with my thermometer) but that's well above the freezing point of butane, it can't be gelling at that temp can it?

If you must filter, use a 1 micron sock filter, because a face filter blinds too fast.

 

[crocodile og]

IMHO you're getting back pressure from your collection pot because your material tube is colder than the collection pot itself because dry ice is colder than water ice.

When you add more butane it will overwhelm the gas pressure in the lower chamber but when allowed to stand the pressure from below stops the residual butane from seeping down for collection.

My bet is that if you use dry ice for the collection pot you will solve this issue.

 

[Graywolf]

Lowering the pot temperature will increase the pressure differential across the filter membrane, but the underlying issue is that the pores in the face filter work by plugging and once plugged, the filter becomes "blinded."

A 4" X 8" sock filter not only has more surface area, but it is a felt, which is a body filter, using its labyrinthine inner weave to trap the particles.

Another thing that can happen if the pool in the pot is above the bottom of the dip tube, is that pot head pressure can keep the column from draining. We solve that problem by drilling a 1/2" hole in the dip tube about half way up, facing away from the pump intake.

 

[crocodile og]

If the filter was clogged would that still allow liquid solvent through?

I went with pressure differential because Pimpernickel said that when he adds more solvent liquid passes through the filter.

 

[DjangoNugs]

Are you running the system actively with a pump? We were having the same problem so now we open the ball valve again after we start purging the butane from the collection chamber with the pump running. Once there's nothing dripping from the tube we take it off. We use 11micron qualitative filter paper and don't think that's caused is any problems like that. But I'm still figuring it all out myself.

 

[Graywolf]

If the filter was clogged would that still allow liquid solvent through?

I went with pressure differential because Pimpernickel said that when he adds more solvent liquid passes through the filter.

When a filter is clogged, its pores are blinded and it doesn't readily pass liquid.

More pressure will sometimes force more liquid through, but that soon further clogs the blinded filter as well. You need enough open pores for the amount of particles you are trapping, though we sometimes added fillers to help build filter cake on filter press membranes, which serve to prefilter the material before it reaches the filter face.

 

[DjangoNugs]

Yeah that makes me want to try it without the 11micron filter to see if it speeds up our process at all. Shit gets sludgy that's for sure. That's what they showed us at subzero when we bought the system and it works fine for them though...We, since my last response, have ceased to have this problem anymore the OP was speaking of until it started getting cold out. Tried a bunch of different things and then put the collection base in lukewarm water just to keep it room temperature and not let it freeze over. As soon as we did it the tube literally dropped all the remaining gas we knew had been stuck in the tube. This now leading me to believe it is better to keep the collection base at a more temperate degree and not freezing cold. You might could try that. Seemed to work for us. And the one other thing we changed was doing a dry recovery before putting the base in hot water for recollection so it can pull all that gas in the tube down before building up pressure from the heat...I'm still just speculating from my experiences. If anyone can correct me or reaffirm what I'm saying with good science I'm totally open to hearing all about it.

 

[DjangoNugs]

Hey pimpernickel You happen to figure this out yet? We thought we had but it still happens more than we would like. We've tried without the filters, we've tried cooling the base to the same temps as the tube, all to no avail. One buddy has the same cps tr21s as us and they just decided to spend 4K on a new pump hoping it works. Could that actually be the problem? All the gas falls out of the material column once the pressure gets in the negative numbers. I just don't see how 1lb of pressure could really hold up all that extra solvent. On the other hand I could see a more powerful pump could help get past this issue. Guess I'm curious as to whether people have this problem with other pumps too. Shits getting quite annoying. Anyone have any other thoughts?

 

[dabarino]

ever try filling your dry ice sleeve full of 150f hot water during your recovery to force butane out