First VM Run - Partially Flooded Column / Fluidized Bed?

[werkkrew]

I am gearing up to do my very first attempt at a neutral on my new VM column in the next few weeks and I have been reading so much it's making my head spin. I have run a pot still many times and a 4 plate column a bunch, but never a true reflux / packed column setup.

The primary bits of my column are all 3" diameter, a 6" glass section and two 24" SS spools. My plan when I designed it was to run the sight glass above the packed column but below the tee for the VM valve so that I could watch the reflux. In terms of column packing my plan is to put a bit of copper mesh at the bottom and use 1/4" lava rock as the primary packing material. The copper mesh is to introduce copper into the vapor path as well as provide a way to hold up the lava rock.

In my reading I have seen many people mention running a "fluidized bed" or a partially flooded column, on purpose, as an optimal state of equilibrium in the column. Is this accurate for lava rock in a VM configuration?

If my packed column is 48" of SS, how can I know if the column is partially flooded when I can't see what's going on? Should I put the sight glass at the bottom so I can ensure there is a small pool of liquid at the bottom of the column or do I keep it at the top and look for the flooding at the top? My hearing isn't so good so the advice I have seen about "listening" to the column to know makes me nervous.

I was also planning to use a #10 mesh screen at the bottom to support the mesh / lava rock but I have read that the mesh screens "cause flooding" but now I'm not entirely sure that's a bad thing...If #10 mesh is still too fine, I would make an "X" or coarse grid of some sort myself as others have done.

Thanks!

[PLAYMP]

With 48 inches of packing you have a lot of room for "error" and really shouldn't have too much trouble pulling azeotrope, if you pack your sight glass for 6 extra inches even better. I don't think you need to worry too much about how much flooding is happening or not happening, especially the first time, even if it's an interesting theoretical discussion.

These instructions still work great and it was my bible the first time I ran a VM and had no idea what I was doing:

viewtopic.php?t=15508

The only major revision I've really implemented is that you don't really need let your column equalize for an hour. I basically just let my temp probe stabilize and wait an extra 5 minutes for good measure.

[werkkrew]

With 48 inches of packing you have a lot of room for "error" and really shouldn't have too much trouble pulling azeotrope, if you pack your sight glass for 6 extra inches even better. I don't think you need to worry too much about how much flooding is happening or not happening, especially the first time, even if it's an interesting theoretical discussion.

These instructions still work great and it was my bible the first time I ran a VM and had no idea what I was doing:

viewtopic.php?t=15508

The only major revision I've really implemented is that you don't really need let your column equalize for an hour. I basically just let my temp probe stabilize and wait an extra 5 minutes for good measure.

Yeah I have read that thread several times and I will have it open during my first run, it's an incredibly useful and informative post for sure.

[OtisT]

I never subscribed to the idea of running a column flooded. Regardless of how you run it, I don’t think you should create a bottleneck at the bottom of you column on purpose. Not sure how big a #10 filter is, but get one that is as open as possible.

If you want to flood a column do it the old fashioned way, with too much power.

[PLAYMP]

Good luck and enjoy. I think you will be surprised at how intuitive everything actually is once you actually start running. I definitely was.

[Setsumi]

For neutral, start with a clean ferment. run low wines that you stripped to 30% or higher. Dilute with water to 15 - 20%. I am not contesting a fluidized column but I think it is extreme to get there.

[kimbodious]

Sounds like a great well thought through design.

Be mindful that the copper pot scrubbers aren’t overly compressed if you are also using the to hold up the lava rock. If the pot scrubbers are too compressed they may hold up the return of the condensate to the boiler. The suggestion of a wire “X” sounds a good alternative.

Don’t put packing in the sight tower. You should have a clear free area of at least 6” between the top of the packing and the outflow. This allows the condensate to fall freely past the outflow. You don’t want to risk having low purity condensate spilling past or being blown out the outflow.

While I could run and maintain my CCVM reflux column with a fluidised bed on top of the packing, I really don’t believe the marginal increase in purity is worth the risk of flooding by trying to run the column that way. Now I back off the power ever so slightly and enjoy a much more relaxed run.

One last thing, consider insulating your column right up to the bottom of the sight tower.

[BrewinBrian44]

Running with the semi fluidized state is meant for SPP due to its unique characteristics. I’ve found that it works well for me, but I have SPP. I also did a ton of research about it to warrant giving it a try.

[Yummyrum]

I agree with concerns about compressing copper mesh . I had flooding issues using a seive style retainer . Ended up enlarging all the holes so its a copper web barely holding together .Then ended up
Using a layer of really big rocks on that to stop the smaller ones falling through the holes .

I also don’t subscrbe to deliberately running a flooded column . Like Kimbo , the stress is not worth the small gain . And to be honest , I didn’t find any really measurable improvement … but then I’ve never used SPP . Only rocks and scrubbers

[elbono]

Read through this thread if you haven't already. Opinions are varied on if this is good or bad or worth the effort. I look at it as maximizing power input which to a degree maximizes throughput at a particular reflux ratio. To me it isn't stressful but it does require more attention than running a bit lower on the power. I believe several people in that thread aren't running SPP.

You don't mention your power source but when I was running on gas a change in the breeze blowing on the boiler changed the height of the "boiling" layer on top of the packing. On electric I have insulation on the boiler and the level is much more stable. On gas there was no way I could hear anything above the burner roar. I haven't really tried on electric but I haven't noticed a change in the sound when running that way.

Put the sight glass between the packed column and the takeoff tee so you can see the top of the packing. I run my packing (SPP) just below the glass. I run a CCVM and need room for the RC to close my takeoff but more room will still give you more room for goofs while you're learning how it acts.

I never ran screen at the bottom but I can see it could prevent the falling liquid getting past rising vapor this wouldn't be anything like a fluidized layer, more like the reflux liquid running out the takeoff. I started with a X made from some scrap copper peices but it was a pain to get in place so I bent some 1.5mm stainless wire into a clover shape that deforms easily to get in place. Whatever you do make sure liquid can drain back to the boiler.

My advice is run it, make it fill the sight glass with bubbling vapor/liquid, run it with less power, act like a teenager with a new hotrod. Then pour everything back in boiler and act like an adult.

[Demy]

I use scrubbers, I'm not a fan of flooded columns... maybe as others say it only applies to SPP but maybe it's an extreme of things.

[Saltbush Bill]

In my reading I have seen many people mention running a "fluidized bed" or a partially flooded column, on purpose, as an optimal state of equilibrium in the column.

Ive always thought that it was a very small minority of people suggesting that semi flooded columns worked well.
As you can see from this post , the idea doesn't seem to be getting a lot of support.

[werkkrew]

In my reading I have seen many people mention running a "fluidized bed" or a partially flooded column, on purpose, as an optimal state of equilibrium in the column.

Ive always thought that it was a very small minority of people suggesting that semi flooded columns worked well.
As you can see from this post , the idea doesn't seem to be getting a lot of support.

Yeah it certainly seems that way, which is great because I wasn't really looking forward to trying to run it like that.