drmiller100 wrote: ↑Sun Mar 20, 2022 6:04 pm
Imagine a different paradigm.
What if rather than boiling ALL the water repeatedly we inject boiling beer mid point in the column so that ONLY pure water dripped off the bottom of the column into the boiler.
What reflux rate would this require?
Easy peasy. In a McCabe-Thiele method the "quality" or "q" of the feed is about the energy needed (or subtracted) to/from the feed to to get it just into vapor phase divided by the vaporization heat need to get it from BP to vapor. This determines the slope 'm' of the q-line as q/(q-1).
For a feed just at it's boiling point, q=1, and m=infinity; so a vertical line.
For a totally vaporized feed just at the BP, q=0, and slope = 0; so a horizontal line.
Like this for a hot liquid feed, producing neutral spirits (95%ABV),
neutral spirits, 10%ABV liquid feed
And this for your vapor feed for same ABV%.
neutral spirits, 10%ABV vapor feed
The green line is the q-line.
The good news for vapor-feed is that the number of theoretical plates need drops from 14 to 8!!
The very very bad news is that the practical reflux ratio increases from 4.05 to 38!! Yes, you need to reflux 80% in the liquid-feed case, and 97.5% in the vapor feed case. The fewer plates separate product very nicely, but only b/c you are refluxing and overflowing very high ABV stuff.
When the light-blue operating line gets close to the diagonal. then reflux and energy req's go high.
Imagine if you run a 72 plate reflux column on top of a pot still. First we run it at 95 percent etoh. Then We run it 80 percent. Which requires more energy? The answer is the column will only take so much energy before flooding out regardless of percent at the top.
Half-right, half-wrong.
The heat energy-in creates an (almost) fixed amount of vaporization (on a molar basis) and a mol of either H2O or EtOH occupy a very similar volume in vapor phase (at any given temp & pressure). So energy-in is proportional to vapor flow rate (it's ~5% less vapor flow at the cooler top, where vapor is more dense).
Flooding occurs at a vapor flow rate (therefore an energy-in rate) where the updraft causes misty liquid droplets to flow upward, which ruins the separation. Every column has a nearly fixed limit on energy in before flooding.
The thing you are missing is that your 95% column REQUIRES more reflux to operate than the 80% condition (I assume you meant ABV). You can put identically the same power into either, but you'll get 80% product out at a faster rate. So the 95% operates for a longer time, taking more power.
The number of plates is only relevant IF they form equilibrium stages, and that won't happen w/o reflux.
*IF* your system has sufficient plates (and 72 is way excessive) then you can control the distillate based on the reflux. More reflux = higher ABV product. Lower reflux = lower ABV product. Zero reflux = one plate separation only. It's just that simple.
Your 95%ABV product (0.8281 mf) requires a minimum reflux ratio of 2.69, so up to 27.1% of that vapor is available as product.
Your 80%ABV product (0.5211mf) requires a minimum reflux ratio of 1.27, so up to 44.1% of the vapor can be collected as product.
The 80%ABV product appears 1.6 times faster (molar basis of product) than the 95%ABV product.
Even the ethanol take-off rate is about 2.5% faster for the 80%ABV.
Stevea you never got back to me about latent heat of vaporization. Do you understand what that is?
Do you?
Last edited by stevea on Mon Mar 21, 2022 4:35 am, edited 1 time in total.
Let me say that none of this is very obvious at first glance. There is a fair bit of complexity in a column still or continuous still. The reflux to energy relationship is pretty simple. The reflux to product ABV is complex. The number of plates needed vs some reflux amount isn't so clear. That there is actually a minimum amount of reflux needed , despite an arbitrary number of plates is non-obvious. I have a mental picture now for most of this, but the feed-quality q-line stuff impact on number of plates and reflux still baffles me. I've no intuition yet on that.
drmiller100 wrote: ↑Sun Mar 20, 2022 6:10 pm
My still is continuous. It requires enough reflux to ensure the temperature gradient so the top of the column is colder than the bottom.
Any rectification column (of a given height with a given packing) needs the same reflux given mash ABV and given product ABV, whether its batch or continuous feed
Stevea I believe is saying it is for example 80% reflux required if you have 10% feed and taking off ~96% product. Whether or not those 10% feed vapors enter the rectification column from a big batch pot kettle or injected into the top of a stripping column below.
To take off 2 gallons of etoh per hour you must inject 20 gallons of 10% wash per hour and inject enough heat to vaporize ~100 gallons of water in the bottom boiler, and take away enough heat to reflux 80 gallons per hour at the top of the column.
A 3800w heating element in water does not vaporize that much steam.
Let me correct a major misunderstanding. To get azeotrope(97+%ABV) from a 10%ABV feed requires ~81% of vapor to be refluxed in practice. So you have to vaporize ~5 MOL at the bottom of still to get 1 MOL of product.
But the vaporization amount to product ratios are in MOLs not volume or gallons.
Also its mols of bottom vapor to mols of product (not feed).
2 gallons of azeotrope is ~148.8 mols (about 15.6mol of water and 133 mol of EtOH).
To get that you need to vaporize an *about* 5x that many MOLS of mostly water at the bottom of the still. So ~744 mol of water .
744 mol of water is 29.5 lbs of water or 3.55 gallons.
You must vaporize ~3.5gal of bottoms water or steam to get 2 gallons of azeotrope product.
In different units,
You must vaporize 750 mol of water to get 150 mol of azeotrope.
==
>> Any rectification column (of a given height with a given packing) needs the same reflux given mash ABV and given product ABV, whether its batch or continuous feed
Not exactly. When your pot/batch still is at 10%ABV and simmering, and the column above is equal to the rectification section of a continuous still, then the reflux required is very similar (a little lower) compared to the continuous case. As your pot boils off ethanol to lower ABV - then you must increase reflux to keep the same product ABV. At some point you will either have insufficient plates to collect product OR you will have a reflux ratio so high you will be getting negligible product at a high energy cost.
It doesn't intrinsically require energy to separate etoh from h20. It isn't endothermic or expthermic.
Thank you all for your interest.
My still does work. I will totally admit I have had to rationalize some of the results and it took a lot of failures to get it to work. And I do still have problems.
Like I need a positive displacement pump that doesn't mind soluble solids and isn't much affected by changes in back pressure.
>> It doesn't intrinsically require energy to separate etoh from h20. It isn't endothermic or expthermic.
Yes it certainly does! The mixing is exothermic. https://pubs.acs.org/doi/pdf/10.1021/je60034a008
The peak value is about 780 Joule/mol around 40%ABV. That should raise the temperature by about 9C or 16F.
That's not a lot of energy compared to vaporization, but you DO have to supply that energy to separate them.
For positive displacement pumps for solids. Moyno-type and Netzche work very well, but are expensive and typically large. Rotary-lobe pumps are again great, but expensive. Diaphragm pumps work OK, but are 'pulse-y'. I wish someone made something in this range of sizes.
drmiller100 wrote: ↑Mon Mar 21, 2022 7:44 am
Funny. When you mix hooch with water to drunk it certainly doesn't get warm or cold.
Yes it does. Take some 95% abv from a reflux run and proof it down to 30%. You'll feel the container get warm. Not hot, it's not going to boil, but it does get warm.
"I have a potstill that smears like a fresh plowed coon on the highway" - Jimbo
drmiller100 wrote: ↑Mon Mar 21, 2022 7:44 am
Funny. When you mix hooch with water to drunk it certainly doesn't get warm or cold.
Yes it does. Take some 95% abv from a reflux run and proof it down to 30%. You'll feel the container get warm. Not hot, it's not going to boil, but it does get warm.
drmiller100 wrote: ↑Mon Mar 21, 2022 7:44 am
Funny. When you mix hooch with water to drunk it certainly doesn't get warm or cold.
Yes it does. Take some 95% abv from a reflux run and proof it down to 30%. You'll feel the container get warm. Not hot, it's not going to boil, but it does get warm.
Huh. I never noticed this. Thanks!!!
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
drmiller100 wrote: ↑Mon Mar 21, 2022 7:44 am
Why does it require 80 percent reflux rate? In my continuous still pure water drips into the boiler
stevea wrote: ↑Mon Mar 21, 2022 5:17 am
To get that you need to vaporize an *about* 5x that many MOLS of mostly water at the bottom of the still.
Ok, if you are collecting about 1 MOL per hour, 5 MOL per hour must be going up the column. You imply the energy to vaporize 5 MOL per hour must come from the boiler. HOWEVER, there was something else neglected. 4 MOL from the column fall back down into the boiler. AKA Energy returning to the bottom tank that doesn't come from your heating element. This way of thinking leads me back towards what drmiller100 is saying, the energy input is only to vaporize/lift the quantity of ethanol you are taking off (*PLUS the enthalpy of mixing you noted above, plus the other losses we mentioned heat in product, heat down the drain, heat into the room). Not 5x vaporization because reflux.
At the top of the column, Reflux Condensor causes ethanol to condense to a liquid, and fall until it meets a rising vapor slightly below, reflux happens mixing happens and some vapors go up and some liquid falls down the column even further, repeating what just happened. Isn't the bottom boiler just the very bottom of a column, with some vapors being driven upward as the bottom boiler absorbs energy (latent heat of vaporization) from condensing vapors above falling down due to reflux
stevea wrote: ↑Mon Mar 21, 2022 1:15 am
We agree that the theoretical heat add is about 0.5 kW-hour per gallon of feed. That's about 6 cents per gallon of feed for electric ENERGY in my area. If inefficiency doubles or triples that ENERGY cost, it's still a "don't care" price item.
For fuel, Thats 60 cents per gallon cost. Double or triple that is a pretty big deal, if product is for fuel. Paying double or triple in electricity makes sense for 1 gallon of drinking alcohol, if it gets the right blend of trace compounds in the product.
I'm really curious how a still design focused on fuel production would look, compared to drinking product stills which are more discussed.
Last edited by football29 on Mon Mar 21, 2022 1:45 pm, edited 1 time in total.
football29 wrote: ↑Mon Mar 21, 2022 10:42 am
HOWEVER, there was something else neglected. 4 MOL from the column fall back down into the boiler. AKA Energy returning to the bottom tank that doesn't come from your heating element. This way of thinking leads me back towards what drmiller100 is saying, the energy input is only to vaporize/lift the quantity of ethanol you are taking off (*PLUS the enthalpy of mixing you noted above, plus the other losses we mentioned heat in product, heat down the drain, heat into the room). Not 5x vaporization because reflux.
No, the reflux already has lost most of its energy while condensing.
I still don't fully understand how the still we are talking about works. I attempted to draw my understanding based on the video in the very first post. One thing I'm not sure about, is very close to where the mash is injected, there are 2 others hose connections that I don't know what they are.
"Three heat exchangers" are mentioned but I only see two. Is there another heat exchanger after the bottom drain heat exchanger that preheats the feed INSIDE the column??
football29 wrote: ↑Mon Mar 21, 2022 1:32 pm
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I still don't fully understand how the still we are talking about works. I attempted to draw my understanding based on the video in the very first post. One thing I'm not sure about, is very close to where the mash is injected, there are 2 others hose connections that I don't know what they are.
"Three heat exchangers" are mentioned but I only see two. Is there another heat exchanger after the bottom drain heat exchanger that preheats the feed INSIDE the column??
Firefox.jpg
I tried running 3 of the 5/16 tube to inject beer into the column. It didn't work any better than one injection point.
One heat e changer is the condenser. Beer comes from the barrel, through the pump, up to the condenser. The condenser is 5/16 copper wound in a coil. Beer is heated from 70 ish F up to 120 ish.
Then beer comes down to the next heat exchanger which is directional. This uses overflow/waste from the boiler.
When it is all rolling well the beer will start boiling at this point as it is injected into the column.
I think of the bottom of the column top of the boiler as an exchanger. Probably isn't thougb.though.
No one has ever mentioned the two different sizes of the column.
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
drmiller100 wrote: ↑Mon Mar 21, 2022 3:34 pm
No one has ever mentioned the two different sizes of the column.
I see the top of the column is slightly narrower than the bottom, at least from the outside.
Is this an intentional design feature or just the material you had? What does it tapering down the diameter of the column do? Increase vapor velocity?
4000 watts is pretty good for 3 inch reflux column with marbles.
3 inch rectifier with 20 gph is too much and it floods badly.
So where I inject beer on down is 4 inch. Until the bottom of the marbles I went back to 3 inch. Local muffler shop can't bend 4 inch.
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
LWTCS wrote: ↑Sun Mar 20, 2022 7:43 am
Football wrote:
"So reflux cost energy because it reduces rate of product take off,,,"
It also raises the abv.
You have to think in proof gallons.
And then you have to identify which "efficiency" needs to be exploited the most. Usually labor hours will be the priority.
*IF* you want higher ABV product off a column, then you *MUST* add energy via reflux to separate against entropy - NO EXCEPTION. no dispute here.
*IF* you want optimal proof-gallons (the most ethanol) - then you should learn to drink 10% ABV grist-y wash. {no one rational does that}. I do not understand the point of this comment?
We agree that labor is a huge factor in the trade-offs. OTOH I doubt that running a borosilicate tube and ceramic plate column takes any more labor and should have considerably higher throughput, lower height and operate at lower power. let's see the design
Sorry stevea, the ability to save/recover 100,000 btu on a system that would otherwise use 600,000 btu is a significant ROI in any financial market space.
Obviously we do not at all envision the same process flow.
I think you misread my intentions. The OPs claim about energy efficiency flies in the face of all known ChemE practice - by a large factor. It's extremely likely to be wrong. And I certainly OUTLINED the lower limits of energy reqs for ANY distillation based only on fundamental theory.
This isn't about saving every last cent on energy - its about understanding the factual limits, AND understanding HOW to create efficient distillation. If you have a GOOD REASON to squander energy for some greater cause - especially flavor quality - then I am very interested. If you want to squander energy b/c you don't understand the design parameters, then you are just acting from ignorance or tradition. I strongly suspect you'll need about double the energy and perhaps 50% more practical plates. That sounds 'not smart' unless you get something good in return. I have no idea what you mean by this at all.
We agree that the theoretical heat add is about 0.5 kW-hour per gallon of feed. That's about 6 cents per gallon of feed for electric ENERGY in my area. If inefficiency doubles or triples that ENERGY cost, it's still a "don't care" price item. The bigger problem is the instantaneous POWER (energy per unit time) and cooling and the number of plates. If you can cut your power needs in half and make a still 30% shorter, that's a win. totally agree. My understanding is that Adam (Stumpy) has been able to lower operating costs by 30%. I have no reason to believe his calculations are not at the very least reasonably close to accurate.
My main point is that until we understand how distillation "works" and what is optimal, we have no basis to evaluate trade-offs. I'd like to understand what is near-optimal, and then make JUDICIOUS trade-offs from there.
... This is just not true. Feed beer at the 10th plate of a 10 plate beer stripper and you don't need one bit of forced reflux to enrich from 10% to 50% .
Yes it is true. Examine the McCabe-T diagram posted above. Find 10% ABV = 0.032 mol fraction on the X-axis, then go UP and see this intersects the VLE curve at 0.25mf on the Y-axis; and 0.25mf = 53% ABV. What you have described (10%ABV liquid to 50% ABV vapor) IS one plate of separation - just as I said. ah, I certainly did not do a good job of contextualizing my thought process.
When comparing batch to continuous outcomes, ( since this is I assume why we are discussing continuous distillation)the 50% ABV works to be sure. But the batch version of the chart is only a snap shot completely predicated upon a 10% beer. With batch distillation that 50% distillate at that particular plate value goes away very quickly as alcohol is rendered out of the system. The aggregate abv of any typical " balls to the wall" strip run would not be 50%. And if it were, there would be a bunch of alcohol remaining in the kettle with out a few more plates and forced reflux. Therefore my thinking is that with respect to continuous distillation, a 50% low wines off of the beer column is very enriched and in that context not at all the product of a single plate count for a commensurate volume and run speed done with a batch system. Certainly I may have drifted too far off topic trying to make a point if you hand cuff your self to the snap shot illustrated on that chart.?
Stripper comment:
Much of the alcohol flashes early. But some alcohol does make it's way further down the column to at some point flash. This is the catalyst that enriches the beer column with no reflux notwithstanding the continuous beer feed of 10%. Ah!! The beer feed.
I really don't get your terminology, nor explanation. 'FLASH' distillation is a very real thing (involves lowering pressure to instantaneously boil-off a fraction of feed) , but definitely NOT happening here, nor in an isobaric(common) still, Your 'point flash' means little to me - explain. by flashing, I mean the point when the miscible liquid solution of water and alcohol is vaporized. It is not uncommon terminology. It is generic terminology.
In a stripper your plates are operating between the VLE curve and the "stripping operating line" which is actually pretty easy to derive from theory as a straight line on a McCabe-T diagram.
In an isolated stripper (no overflow from rectification, which changes the op-line), with feed near it's boiling point, it takes a very large number of plates to get product vapor that is fully "one plate better" than the feed (say 10%ABV to 53% ABV). however you can get very close with a modest number of plates.
My description would be that the feed at the top plate absorbs high enthalpy, lower ABV vapor from below and this causes an exchange the released higher ABV vapor product. The next plate down loads with partially depleted overflow wash from above, and it too absorbs higher enthalpy, lower ABV vapor from below and ... I've a McCabe-Thiele spreadsheet, and I converted the values to ABV% so in such a stripper we see ...
(yeah - a little rounding error in conversions.)
The MOST effective plates on a molar basis are plates 3,4,5, NOT the top plate as you seem to have suggested. wut? Are you referring to me? I suggested no such thing. Anyone with any practical experience knows that the distance from 10% to 90% is far closer than the distance from 91% to 95%. And 94% to 95% is especially far,,,figuratively speaking.
The explanation is clear if you examine a McCabe-T with a stripper operating line drawn in. The bottom plates don't vaporize a lot of mols of EtOH b/c the wash is too depleted and low ABV at the bottom. The top plates also don't extract as many mols of EtOH b/c the vapor from below is already near the VLE limit. IOW The 50.27%ABV vapor from plate2 can't do very much depletion from a 10%ABV feed at plate1, which has a VLE limit of 53%ABV.
BTW - it's true that you can add more stripping plates and lose less EtOH at the bottom at essentially no energy cost. I think I misunderstood the calculation in Miller's "Whisky Science ..' book.Well adding dwell time gives the alcohol more opportunity to flash. There's that (generic) flash word again. Achieve a 212 F or more discharge temp and its fine. Yes higher temps are possible with grain in solids since you question that previously.
Less white board and more practical application please.
If we don't understand this very-basic white-board (theory), then we CAN'T understand the concepts, and we CAN'T see the obvious truths & errors. You made two gaffes here. You didn't see that 10%ABV=>50%ABV vapor is one theoretical separation plate; that's about reading a VLE curve. You didn't (seem to) see that the effectiveness of plates (stripper or rectification) is related, in a McCabe-T to the vertical height of the stair-steps AND that those steps become small when constrained by the stripper operating line. Only in the past few months after manually constructing some McCabe-T diagrams did the huge importance of the q-line, and the two operating lines dawn on me. It incidentally explains the energy needed to drive a continuous still, and the peculiar issue of minimum required reflux to get a target separation. well, I did try to explain my thought process above.
Distillation involves the application of ENERGY to reverse (locally) ENTROPY, so it's intrinsically a strange, complex beast. I don't think I'm competent to design a good practical still until I understand how it actually works. Monkey-see, monkey-do isn't a design process, and it gives you zero insight into how to make improvements. on the otherhand, taking experienced, practical application can help you steer clear of reinventing the wheel.
I WILL get around to a practical design once I puzzle-out how to make effective stripper plates that can tolerate some yeast and maybe grist. perfs and a wier is a good place to start.
i wonder both theoretically and observationally, to what extent the injected beer "starts to boil" as it passes through the bottom drain heat exchanger, or is it still a liquid that is raised closer to its boiling temperature.
Most of what I read about continuous stills sounds like people are measuring maybe ~80C feed injection temperature, but 10% ABV boils at 91C, so hot liquid but not a vapor.
drmiller100 wrote: ↑Mon Mar 21, 2022 4:11 pm
4000 watts is pretty good for 3 inch reflux column with marbles.
3 inch rectifier with 20 gph is too much and it floods badly.
So where I inject beer on down is 4 inch. Until the bottom of the marbles I went back to 3 inch. Local muffler shop can't bend 4 inch.
I compute ~2300 watts to make 1 gph of steam, 4000w makes less than 2 gph of steam, starting from water already at 100c. Where does 20 gph come from?
drmiller100 wrote: ↑Mon Mar 21, 2022 4:11 pm
4000 watts is pretty good for 3 inch reflux column with marbles.
3 inch rectifier with 20 gph is too much and it floods badly.
So where I inject beer on down is 4 inch. Until the bottom of the marbles I went back to 3 inch. Local muffler shop can't bend 4 inch.
I compute ~2300 watts to make 1 gph of steam, 4000w makes less than 2 gph of steam, starting from water already at 100c. Where does 20 gph come from?
Are you factoring the boiling point of a 10% beer? Or the boiling point of water?
Also it does appear that Doug is using "spent" beer as his steam vapor source? This does give any remaining alcohol down low on the column a bit more opportunity to flash compared to live steam injection.
Therefore if a measure of alcohol is in the lower section of the column, it will surely impact the efficiency.
That is probably a good thing as long as there is enough dwell time to ensure that all the alcohol has flashed off before being discharged as effluent.
Easy to evaluate by monitoring the discharged effluent temps. Anything 212F or over is fine.
The system perhaps starts up with a bit of wonk. But with a few minutes of tail chasing probably dials itself right in.
LWTCS wrote: ↑Wed Mar 23, 2022 3:54 pm
Are you factoring the boiling point of a 10% beer? Or the boiling point of water?
Using boilting point of water. since it sounds like everyone agrees the bottom should be 99%+ water if things are right, otherwise alcohol is going down the drain.
So using water heat of vaporization, and with the stated 4000 watts, 1.68 gallons/hour of steam should be generated at the bottom of the column from that heat input.
Per Stevea's explanation of ChemE theory*, and using the 10% ABV beer feed assumption, 1.68 gallons/hour of steam at the bottom equates to .94 gallons/hour of ethanol vapor at the top, but 80% must come back down the column again as reflux, so the product take off rate from 4000 watts is .19 gallons/hour, if the product is azeo.
Or is there something about the ChemE theory* that doesn't apply to a fuel still of the design, but only to drinking product designs?
I'm not sure if the feed comes in as beer vapors that ADD to the steam from the boiler going up, or if the feed comes in as beer liquid that condenses some of the rising steam and gives off enriched vapors. So I'm not sure if you add flowrates or subtract them but nowhere does boiler evaporation + beer injection rates equal 20 gph that i can see, based on the theory stated in this thread and the given heating element of 4000watts.
That's a good question.
Thats a stevea question really. He likes to run the numbers.
As a practical matter, once the still finds its path to steady state however, the boiling point of a 10% ABV at the injection point becomes the driver. EDIT:Yeah let me take that back. As a practical matter I use a target low wines vapor temp as the driver. Others have used the bottoms discharge temp as the driver. Though I do feel bottoms discharge temps are not close enough to the spirit to get a feel for final profile/ outcome. Prolly crazy talk cuz I can't sipher bout moles and such.
There is a difference between start up costs vs running costs. Cost more to initiate phase change than it does to maintain phase. Think pump curve.
drmiller100 wrote: ↑Mon Mar 21, 2022 4:11 pm
4000 watts is pretty good for 3 inch reflux column with marbles.
3 inch rectifier with 20 gph is too much and it floods badly.
So where I inject beer on down is 4 inch. Until the bottom of the marbles I went back to 3 inch. Local muffler shop can't bend 4 inch.
I compute ~2300 watts to make 1 gph of steam, 4000w makes less than 2 gph of steam, starting from water already at 100c. Where does 20 gph come from?
Directional
Heat
Exchanger
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
Pump in small amount like 2gph of beer maybe it works. Pump in 20 gph of beer, I think you would have cold beer going down the drain and the 2nd heat exchanger would stop heating your incoming beer to boiling point.
LWTCS wrote: ↑Mon Mar 21, 2022 5:59 pm
*IF* you want optimal proof-gallons (the most ethanol) - then you should learn to drink 10% ABV grist-y wash. {no one rational does that}. I do not understand the point of this comment?
Maximal "proof gallons"= max ethanol. So if you drink wash you don't have the losses at the bottom. No one (I hope) is seeking actual maximal proof-gallons w/o considering quality.
We agree that labor is a huge factor in the trade-offs. OTOH I doubt that running a borosilicate tube and ceramic plate column takes any more labor and should have considerably higher throughput, lower height and operate at lower power. let's see the design
Not yet complete. Imagine a 2" borosilcate tube w/ some packing better than marbles; small pall rings maybe.
I have no idea what you mean by this at all.
I mean the losses aren't an extra 1/6th but perhaps double.. Also that this requires more plates as the plates are less efficient.
totally agree. My understanding is that Adam (Stumpy) has been able to lower operating costs by 30%. I have no reason to believe his calculations are not at the very least reasonably close to accurate.
Yes, I had an email exchange w/ Stumpy early-on. He lowered energy by 30% COMPARED TO WHAT ? HOW? He didn't lower it below the theoretical lower bound. I *suspect* you are comparing batch to continuous; which i wasn't addressing. Miller, "Whisky Science ..." calculates that batch uses ~3.5x the amount of heat energy as continuous. So 30% seems underwhelming.
When comparing batch to continuous outcomes, ( since this is I assume why we are discussing continuous distillation)the 50% ABV works to be sure. But the batch version of the chart is only a snap shot completely predicated upon a 10% beer. With batch distillation that 50% distillate at that particular plate value goes away very quickly as alcohol is rendered out of the system. The aggregate abv of any typical " balls to the wall" strip run would not be 50%. And if it were, there would be a bunch of alcohol remaining in the kettle with out a few more plates and forced reflux. Therefore my thinking is that with respect to continuous distillation, a 50% low wines off of the beer column is very enriched and in that context not at all the product of a single plate count for a commensurate volume and run speed done with a batch system. Certainly I may have drifted too far off topic trying to make a point if you hand cuff your self to the snap shot illustrated on that chart.?[/u][/b]
Totally unclear where you are going with this. I was only discussing continuous. Yes, batch ops are less energy efficient for the reasons you state.
Stripper comment:
Much of the alcohol flashes early. But some alcohol does make it's way further down the column to at some point flash. This is the catalyst that enriches the beer column with no reflux notwithstanding the continuous beer feed of 10%. Ah!! The beer feed.
I really don't get your terminology, nor explanation. 'FLASH' distillation is a very real thing (involves lowering pressure to instantaneously boil-off a fraction of feed) , but definitely NOT happening here, nor in an isobaric(common) still, Your 'point flash' means little to me - explain. by flashing, I mean the point when the miscible liquid solution of water and alcohol is vaporized. It is not uncommon terminology. It is generic terminology.
Not common where I'm reading. https://en.wikipedia.org/wiki/Flash_evaporation
To 'flash' is to cause a sudden evaporation by pressure reduction.
You are describing evaporation at the bubble point - boiling-off by heat at a constant pressure.
(yeah - a little rounding error in conversions.)
The MOST effective plates on a molar basis are plates 3,4,5, NOT the top plate as you seem to have suggested. wut? Are you referring to me? I suggested no such thing. Anyone with any practical experience knows that the distance from 10% to 90% is far closer than the distance from 91% to 95%. And 94% to 95% is especially far,,,figuratively speaking.
You said "Much of the alcohol flashes early", which isn't accurate. That first plate offers little EtOH to the vapor stream, compared to the 5th plate. Compare the difference in ABV.vap for the relativity constant amount (volume or mols) of vapor.
... Achieve a 212 F or more discharge temp and its fine. Yes higher temps are possible with grain in solids since you question that previously.
When you boil a pot of water at 1atm pressure - then adding more heat does NOT raise the temp above 100C; instead it causes more boil-off. Solids make no difference. The same thing applies in your still. If your bottoms is liquid above 100C, it' only possible b/c the pressure is higher (** well if you had a LOT of ionic solubles, salt, in the water the temp is SLIGHTLY higher). Claims of 220F bottoms is only plausible if the still base is ~2.5psig, which suggests other problems. If that were true, then when the bottoms were discharged to 1atm, it would immediately FLASH (correct use of term) causing the liquid fraction to immediately reach 212F. [this principle is used in flash-distillation units].
Distillation involves the application of ENERGY to reverse (locally) ENTROPY, so it's intrinsically a strange, complex beast. I don't think I'm competent to design a good practical still until I understand how it actually works. Monkey-see, monkey-do isn't a design process, and it gives you zero insight into how to make improvements. on the otherhand, taking experienced, practical application can help you steer clear of reinventing the wheel.
No offense intended to anyone - but by reading a little, I will avoid blunders like choosing large marbles for packing, or blowing air over a column to waste excess energy. Does anyone think the boka' plates are anything like an effective plate ? These choices point to fundamental misunderstandings about theory. Yes - there are a huge number of practical issues that have no good answers w/o experimentation or reading of others experience. I *hope* to use water at ~15psig(2atm absolute) and 120C to reboil column bottoms Can I transfer enough heat with reasonable HX ? Will fouling be a major problem ?
I WILL get around to a practical design once I puzzle-out how to make effective stripper plates that can tolerate some yeast and maybe grist. perfs and a wier is a good place to start.
Good points, But why not a packed column for both rectification & striping ? Maybe filter the grist out.
Wrt plates I was just reading a nice industry article that suggests much smaller sieve plate holes (2 or 3mm) reduces entrainment. The weir determines the plate liquid depth, and .... there are calculations. I *usually* see that designated plate spacing is typically much larger than these small systems allow, and flooding is the issue, ... which suggests packing.
Pump in small amount like 2gph of beer maybe it works. Pump in 20 gph of beer, I think you would have cold beer going down the drain and the 2nd heat exchanger would stop heating your incoming beer to boiling point.
II pump 20 gallons of beer per hour, and
I preheat it to 125 degrees in the condenser
And I pull 2 gph of etoh
That leaves 18 gph of 212 water coming out the boiler.
You don't think 18 gallons of 212 can heat up 20gph to 190 or so?
This image calls it a counter flow heat exchanger. If space isn't a limitation it is really efficient and if flows are similar the fluids basically exchange temperature.
LWTCS wrote: ↑Wed Mar 23, 2022 3:54 pm
Are you factoring the boiling point of a 10% beer? Or the boiling point of water?
Using boilting point of water. since it sounds like everyone agrees the bottom should be 99%+ water if things are right, otherwise alcohol is going down the drain.
So using water heat of vaporization, and with the stated 4000 watts, 1.68 gallons/hour of steam should be generated at the bottom of the column from that heat input.
Per Stevea's explanation of ChemE theory*, and using the 10% ABV beer feed assumption, 1.68 gallons/hour of steam at the bottom equates to .94 gallons/hour of ethanol vapor at the top, but 80% must come back down the column again as reflux, so the product take off rate from 4000 watts is .19 gallons/hour, if the product is azeo.
Or is there something about the ChemE theory* that doesn't apply to a fuel still of the design, but only to drinking product designs?
I'm not sure if the feed comes in as beer vapors that ADD to the steam from the boiler going up, or if the feed comes in as beer liquid that condenses some of the rising steam and gives off enriched vapors. So I'm not sure if you add flowrates or subtract them but nowhere does boiler evaporation + beer injection rates equal 20 gph that i can see, based on the theory stated in this thread and the given heating element of 4000watts.
Strangely enough latent heat of vaporization suggests it takes about three times as much energy to vaporize a pound of water as it does etoh.
One more time. The 4000 watts goes towards heat losses, warming some water (one btu per pound per degree) and lifting etoh vapors from the top of the column to the condenser.
I don't vaporize 20 gph. I distill 2 gph of etoh.
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
drmiller100 wrote: ↑Thu Mar 24, 2022 6:47 pm
I have a lot of respect for lwtcs as he has DONE things. And writing a compliment to a moderator may help when rude attacking someone else in the next sentence?
Stevea can take his theoretical bullshit and go somewhere else. Cannot attack the thoughts so attack the thinker?
drmiller100 wrote: ↑Thu Mar 24, 2022 6:47 pm
I have a lot of respect for lwtcs as he has DONE things. And writing a compliment to a moderator may help when rude attacking someone else in the next sentence?
Stevea can take his theoretical bullshit and go somewhere else. Cannot attack the thoughts so attack the thinker?
Irony.
What do you think of my words on latent heat of vaporization? Do you use Mol ratios in your distillation?
Have you run a still?
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
