@The_Lone_Stiller It’s just a regular diptube setup. Like the standard lab glass ones. Nothing special, LOL.
The collection pot and discrete column recovery attach at the top. The valve is for vaccing it down. The inlet to the pump is off to the side. The 3/4" diptube extends down to about 3" from the bottom.
My thinking is that gravity plus the widening of the piping (slows velocity) at the bottom helps trap oil.
I am considering adding another identical trap in series with this one because they’re pretty cheap and it’s good insurance for protecting the Corken which isn’t cheap in the slightest. A single trap has worked fine so far but I also keep a good amount of headspace in my collection pot.
Adding some type of internal baffling inside the collection pot has also crossed my mind but the the trap is working fine for me so I’ll probably just stick with that.
I run propane at about -40C so the vapor is around that temperature (definitely lower than ambient) coming out of the pot. The body of the separator will definitely get cold and condense/freeze atmospheric moisture on the bottom half during longer runs.
The propane vapors won’t condense inside the separator because there is no mechanism to remove heat from them back below the boiling point. The lines to the separator and the lower half of the separator itself get cold because they are transferring heat into the vapors, further warming them and discouraging condensation.
It doesn’t really make sense to me to add any extra heat to the separator because I’ll just have to remove it again in the post-compressor heat exchanger. Heat is only added to the liquid phase in the collection pot. Once it’s converted to vapor I want to keep its temperature as low as possible within reason to save dry ice.
Sorry it took me so long to respond, I have had a lot to deal with lately.
@GroovyOctopusLabs The diptube is made by using what’s called a “bored through fitting”. This is just a normal double ferrule compression fitting (ie Swagelok tube fitting) that has had the inner ridge removed to allow a tube to slide all the way through the fitting instead of seating like a typical tube stub would.
You can order most Swagelok fittings like this by adding -BT to the end of the ordering number, check their catalog. In my case I ordered a cheap fitting from another company and had the ridge machined out at my local shop.
The one pictured below with a 1.5" triclamp and 1/2" compression fitting is $20 at brewershardware but you’d need to get it machined. (edit: The linked fitting may indeed be bored-through already from brewershardware, I’m not sure.)
Also, the diptube design I’m using is not the only possible design for this application but was very easy/cheap to put together. You can see how once you have the bored-through fitting to make the diptube you can design all kinds of things that would work.
The main idea in my experience is just to have a vapor path that is highly convoluted but at the same time not too restrictive like some of the large, unnecessary mol sieve columns. Lots of possible design choices that are both effective and easy to clean.
Here are a couple pics of version 2.0 of the liquid/vapor separator.
It’s just two identical diptube traps hooked in series (or ATM as I like to say).
The single trap I was using before worked great. When I took it apart to clean you could see oil residue up to about 18" from the bottom of the trap, the rest was pretty clean. The diptubes extend down to about 3" from the bottom of the traps.
The overall height of one of the traps is about 42"(107cm).
I still noticed some very slight residue on the outlet fitting of the trap after 2.5 months of hard use so I decided to add the second one. I probably shouldn’t wait so long to clean it, but you know how it can be.
The trap is true 3/4" minimum orifice the entire way through, which is my goal (including valve orifices) for the vapor path on my new system.
In addition to the trap I make sure to never fill my collection pot above 50-60% to avoid unnecessary flinging of oil droplets as much as possible.
Also, I’m still NOT using any molsieve anywhere on my system and I haven’t had any issues in years.
The vapor from the collection pot/columns enters the trap in the upper right, goes down the diptube then up and out to the left, then down the second diptube and back up and out to the compressor.