Bubble Cap Plates - what makes them so hard?

[LWTCS]

I don't need to have that fully sussed to get going..

Agreed for sure.

Just grappling with the question of whats better. The single cap? Or the multiple caps?

And I am most curious about how the volume of liquid within each chamber may or may not affect ABV.

I got a big ole single per chamber and I'm pulling 95.

Some calcs should help clear up some of the wondering.

[olddog]

OD my column is 3" - what size would you reckon for that? 1.25" riser? bigger?

Larry uses a 1/12"center tube (I think) for his 4" thump tower which after all is like a big single cap column, he has got his downcomers on the outside though. I personally think 1.25 should handle it with a 3"column.


OD

[LWTCS]

Larry uses a 1/12"center tube (I think) for his 4"

Yes that is correct. With the 2" cap. I used a single continuous 1.5 and installed inlet and outlet holes on either side of a blocker that diverts the vapor into the,,,,,,,I guess I would call it the bubble cap that is located at each thump chamber level.

Pic shows the arrangement. And of course the floor/plates are installed at the base of each 2" section.

[Manback]

Agreed for sure.

Just grappling with the question of whats better. The single cap? Or the multiple caps?

And I am most curious about how the volume of liquid within each chamber may or may not affect ABV.

I got a big ole single per chamber and I'm pulling 95.

Some calcs should help clear up some of the wondering.

I tried to come up with a way to easily adjust volume on the plates(ie move downcomers + risers) and there are obviously ways to do this (threads on the downcomer/riser) etc but they all, on closer inspection, become a hassle. However I guess as long as I get it tigged in right the first time it's all good. Theoretically..

Larry uses a 1/12"center tube (I think) for his 4"

Yes that is correct. With the 2" cap. I used a single continuous 1.5 and installed inlet and outlet holes on either side of a blocker that diverts the vapor into the,,,,,,,I guess I would call it the bubble cap that is located at each thump chamber level.

Pic shows the arrangement. And of course the floor/plates are installed at the base of each 2" section.

Mean set-up! Do you have a dephleg or you get 95 just charging it straight through?? Dephleg surely?

Cheers for the discussion guys. Should come away with good results.


Oh by the way, earlier I was talking about Bok heads.. I don't know why.. I'll just take product off the top plate I think.

[LWTCS]

Can't get out of the 80s without the dephleg

[loneswinger]

Manback,

You are planning to have the column in sections correct? So the plates will be welded to the column walls correct? If this is the case there will be no chance of vapor blowing past the plate which is good and you can probably get away with a fairly thick liquid level on each plate. With a thick layer of liquid, the distribution of holes that the vapor bubbles through is not as important as the chance that the bubbles condense in the liquid is greater, and the mixing should take care of itself. So I think you could get away with a single bubble cap and still have high efficiency plates. As to the liquid level, I remember seeing a number of no more than about 15% of the plate spacing, if I can find the reference I will send it your way. This will help ensure that your column will not flood and that entrained liquid won't contact the plate above.

-Loneswinger

[blind drunk]

LWCS says

Can't get out of the 80s without the dephleg

Is it a tasty and clean 80s?

bd

[LWTCS]

Is it a tasty and clean 80s?

The behavior with out the depheleg is much more like a conventional thumper in terms of product I would say. perhaps a bit less smearing than the single thumper. Recon it depends how you manage your runs.

But the dephleg does such a good job of compressing the heads. Additionally, I like to put her into reflux mode (after I collect heads) and let her cycle for a good long spell for esterfication.
Then I kill the dephleg and collect like a typical pothead run. Thats a yummy way.
Or I kill the dephleg after cycling,,then run it as a pothead run and as soon as I feel like I've collected the "cream"
I'll throw her back in to full reflux and wind the ABV back up and kepp the RR steep enough collect the rest as a nuetral (or the like).

So many ways to run this still. As previously mentioned,,,this still is not a one trick pony.

[Manback]

Manback,

You are planning to have the column in sections correct? So the plates will be welded to the column walls correct? If this is the case there will be no chance of vapor blowing past the plate which is good and you can probably get away with a fairly thick liquid level on each plate. With a thick layer of liquid, the distribution of holes that the vapor bubbles through is not as important as the chance that the bubbles condense in the liquid is greater, and the mixing should take care of itself. So I think you could get away with a single bubble cap and still have high efficiency plates. As to the liquid level, I remember seeing a number of no more than about 15% of the plate spacing, if I can find the reference I will send it your way. This will help ensure that your column will not flood and that entrained liquid won't contact the plate above.

-Loneswinger

Yes column will be in sections (maybe 5" + tri-clamp ferrules?). So I guess liquid level somewhere around 1/2"? And have the lowest point of the sight glasses about 5mm below the top of the liquid build-up?

Question: My risers need to be at least as high as the down-comers - right? Would these normally sit at the same level or slightly different?

Sorry if these questions are obvious, I just don't like diving in first without knowing what I'm roughly doing!

[olddog]

Question: My risers need to be at least as high as the down-comers - correct?

That's correct otherwise you will be getting liquid flowing back through the riser instead of the downcomer.


OD

[loneswinger]

OD is right, I have, however, seen them often drawn to be the exact same height though I don't know why. Maybe as an additional dump measure in case the down-comer gets backed up or something.

1/2" to 3/4" liquid level per 5" plate spacing sounds good in theory. The triclamps would be fantastic. Do you have a source in NZ?

-Loneswinger

[Manback]

I do for this time but it's a huge (and, truth be told, undeserved ) favour and unfortunately was a one-time deal, should hopefully have eleven 3" couplings sussed at a most reasonable rate! Off to buy a 4" one off the shelf today, see ya later 60NZD!

[Manback]

The downcomers will be either 1/2" or 5/8" so liquid backup shouldn't be too much issue with any luck. Time will tell tho.

[LWTCS]

you will be getting liquid flowing back through the riser instead of the downcomer

I thought the original design for the Humper would allow for draining back if the pot got too full. I was wrong.

I have a 2" inlet in to the humper and that liquid didn't not drain back,,,,,,,,,,,,Flooded the thumper and scared the shit out of me cuz the distillate stared shooting out the business end very very rapidly,,,,,and colored too I might add.

Might very well depend on how hard the unit is running.

No matter, better safe than sorry.