Active Vs passive recovery speed

This is ultimately what I wanted to bring to the table . . . My perspective was while passive was generally overall faster, it still had major costs that were not making it overall more efficient. While I love the passive system style and sound (or lack thereof) What are the tradeoffs in overall energy cost vs speed/noise & pump maintenance?

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we are dealing with hundreds of cfm gas flow.
multiple giant corken/blackmer compressors are a very bulky solution to try and keep up.

there is no comparison between some tubes and a silly pair of pistons and checkvalves.

we have a few energy efficiency tricks that really push our ice capabilities. (also insulation.)

conventional extractors have a loooong way to go for speed + efficiency improvements.

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Hundreds of cfm and a couple gas compressors are bulky? Sure you got your math right?:joy:

Passive is not faster. The bulk transfer stage at the high point in bell curve is only time the pump wont increase speed. But these pumps are flow thru so you could literally shut them off and the pressure would flow thru them. At all other points running the gas compressor will aid recovery times. And youre not accounting for the recovery of solvent in your material vessel. That is where the biggest gains active has over passive.

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Can one of you passive gurus actually explain how this works on a batch system?

If you have a passive batch system running with a single solvent tank and you run a column or an entire rack of columns simultaneously into the collection pot and begin recovery, how do you then inject the next column or rack full of columns while the first is still recovering back into the same tank you injected from?

What I’m gathering is if you’re using a single solvent tank on a passive system you need to wait for recovery to be completed and remove heat from the collection before applying pressure assist to the tank and injecting the second column.

The other option I can see is you have to use a separate cold tank for recovery while you inject from the first like soxhlet has described. You then need valves and hoses to deal with switching everything around and it still sounds difficult to inject while recovering.

I think @MrRandy got it right:

This is why you see some people using “hybrid systems” to get the best of both worlds.

If you follow Bhogart on IG you can see that they have one setup with separate vapor paths for the active and passive sides requiring the operator to deal with switching back and forth. I’m sure they eek out the best of both worlds that way, but again, the system complexity and steps added to the SOP aren’t worth it IMO.

A simple bypass line around the pump in any active system could accomplish the same thing but if the pump is sized correctly and freely flows through its valves allowing a degree of bypass, why bother? Having to open and close the bypass valve is just one more opportunity for a mistake to happen.

Like I’ve said before, even if you can achieve the absolute fastest recovery rate possible with a direct passive recovery setup on a batch system, you can still get extremely fast, highly similar rates with an active setup with a lot less headaches, a simpler system design and simpler operational procedures that will probably allow you to get through more material in a work day.

I think a lot of people don’t understand that pumps like a TR21 or CMEPOL are very undersized for our purposes and it requires several of them at minimum to be worthwhile.

Some of you guys laugh and jest about trying to have a simple system design. I believe simpler is better if the results are the same or highly similar. Don’t forget I’m talking specifically about batch systems. I think people add unneeded complexity to inflate their own ego and sense of self-importance. In my systems, I avoid “jangles” and complicated designs as much as possible.

IMO all a batch system needs to have is one solvent tank with liquid and vapor ports, a pressure assist tank, pump and however you want to setup and connect columns/collection pot. Having to add other tanks with more valves, lines and steps in the SOP in the name of a minor increase in recovery rate doesn’t make sense to me.

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You need to understand the flow physics pumping/sucking the low density butane causes choking in the orifice of the pump (from supersonic flow).

These issues are best explained in two of my insta posts:

https://www.instagram.com/p/B4ZTOKch4Vl/

https://www.instagram.com/p/B4ZPTjJBT2l/

Hence why I am a proponent of using passive for everything, even large scale.

If you take a look at the specs of the systems we offer you will see the electric refrigeration is hugely more cost effective than CO2/LN2, and provides all the needed energy to pre-chill the solvent and do recovery (3 loops total on our flagship model: https://www.greenprocess.solutions/2020/01/13/2-5-4-ton-refrigeration-system-spec-sheet-quote/).

The extractor needs to correctly designed for all of this to work, obviously.

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Have you guys seen the posts on Bhogart’s IG of their hybrid recovery system? I think they’re on to something.




They have it setup with dedicated valves and heat exchangers for each leg which requires the operator to manually switch between the active and passive legs.

I’m thinking you could add a one-way check valve with 5-10 PSI cracking pressure to the passive leg, remove the control valves and just feed both legs into the same heat exchanger and not have to worry about switching between them.

This is pretty much an active recovery setup with a bypass and check valve around the pump.

When the differential pressure between the collection and solvent tanks is above the cracking pressure of the check valve, the passive leg will operate automatically when needed and the recovery pump can operate continuously.

I think this design offers max efficiency but I personally don’t have too much time on my system when the tank pressures would operate the passive leg so I’m not sure if the added complexity maxes sense for a small increase in efficiency.

What do you all think about this design?

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Can anyone point me at the maths for how many BTUs (or other more appropriate unit of measure) to calculated how much heat energy I have to dump in a CLS water bath to keep my water temp up to @120F. I’m running a passive system.

The system is:
4"x48" material column
1/2" JIC hose to
6"x36" fully jacketed dewax spool w/ 3 - 6" filter plates at bottom
1/2" JIC hose to
12"x12" shatter platter (not jacketed) in waterbath (non circulating :-1:)
1/2" JIC hose to 3x12 spool of mol seives to 1/2" hose to 120lb recovery/injection tank with internal condenser coil and full jacket.

Solvent is Isobutane pure 99.something percent instrument grade (usually), just switched gas suppliers, used to get it from Matheson before they stopped selling it last year. but always iso, no blends.

I’m running LN2 through the jacket on the recovery tank and outside for now, because of the massive ▲T the hot water bath is cooling too fast and I’m not getting enough vapor pressure to move as fast as I should be able to.

I do not own this machine, I just started running it for a friend, it is pretty janky right now, I’m working on getting a jacketed base and a jacketed material spool as well as trying to design a chiller that uses LN2 to chill a thermal exchange fluid (I am considering methanol as it is cheap, has good thermal transfer properties and is easily pumped at -100C) still looking into safety on this issue…

So I’m in need of the maths that ultimately calculate how many watts I have to my heater needs to keep water hot. or even just the math for how much heat is being moved per rate of evaporation.

Thanks in advance for everyone in this community, I’ve spent 60-80hrs researching in the last month or so and this site has been a fundamental part and it’s members have provided wonderful insight and info on how to operate well at almost any scale.

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It s not ISO butane but won t differ to much I asume

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Have you done this yet? I wanna see

There you go !

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Thanks, that’s a nice spreadsheet of some of the values I need.
I’m looking more for the formulas I need to use to calculate how much heat I need to add or how many btus of heat need to be removed from the system including the latent heat from phase change and loss of efficiency to the environment

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Simple math is what I use
I know the volume I need to evaporate
So that times their liquid and vapor enthalpy is the amount of heat I need to ad at my desired pressure /temp
I know the heat transfer numbers on my jackets and coils so I know there rates
I don t know my losses to surroundings
But I add 20% for insulated jackets and piping

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Add another recovery line

That’s exactly what I was looking for, the abstract calculations (simple math) to start narrowing in on what is a complex issue with many variables.

One of my biggest challenges is that there are no temp probes anywhere in the system, so I’ll have to use a non contact thermometer and guess.

honestly I could just buy an electric home water heater and a boiler circulator as I’m sure that there is more than enough heat energy in a unit that size. I’m more interested in figuring out how to calculate the basic overall energy gains and losses in the system because the owners have a much poorer understanding of physics than they believe and I’m just some guy with ass-burgers (that’s what I call HFA) and no degrees… but I can assure you that I understand far more about how all this shit works.
Math is a good language to show people how things actually work in my experience.

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Temp and pressure are directly linked
The vapor pressure is a perfect indication of the temperature within

I am going to do this, I looked into the rate that i should be able to move gas at through a 1/2" line vs dual vs 1.5" hardline… seem that this isn’t my main issue currently as even with one 1/2" line the possible throughput was insane like “30lbs/min” or something way outside of current realworld parameters in this case. It is a good solution however I would have to add an external coil as the current setup has an internal coil in the solvent tank :thinking:

excellent point. I assume that I can tweak that once I know how much pressure is being lost due to evap when I can measure how fast the collection pot is losing mass

I use a modulating butane/propane heater of 32kw on a 240L collection pot
Even with a jacket and internal coil I had isseus to keep the 12cfm corken fed and 45psi in the pot
I solved this with welding a ss coil to a 6" >1 1/2" endcap with two 3/8 ports
The coils entry and exit for water
This I placed at the botom of my collection pot and use the 1 1/2" as connection to my honeypot
I manage to ad an additional 6 kw of heat to my solvent

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O one more thing the circulation pump is on a temp controles switch so when things go haywire on the boiler the pump shuts water circulation

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