steady take off rate

[adamOVD]

I am getting a rush of spirit from my parrot, then it slows way down, then surges, then slows down over and over, and I am trying to stabilize my take off rate. It happens whether i am running it with a pot still head or a column head and whether I am running water to the deph. or not. It's more pronounced with the column head, and I can see the plates stack more before the surge, and empty more after the surge. Some runs are worse than others, and it seems to get worse at the end of the run.                 

I'm running one of Paul's Bain Marie stills with water in the jackets, and controlling the heat input to the kettle with digital solid state power regulators into 4 elements. Heads are homemade, column still has plates with downcomers. I've tried turning power off to single elements and running full power to fewer elements instead of using the regulators, and running things at all different settings. Running more power to the pot and more cooling to the deph. definitely helps keep the plates stacked, but doesn't completely eliminate the problem.  Tried using fermcap even though I have plenty of head space in the pot and don't see much foaming.

Could my agitator be running too fast? Would leaving the jackets partially empty help anything?

Really appreciate all the advise I've received here on the forum. Maybe I' m asking too much with this one, but tried everything I can think of, and would appreciate any pointers.

[PeteB]

I have had a similar problem with an alembic, ie. no plates and no parrot.

If the boiling slowed for a moment then cold air would enter the still through the outlet and momentarily cool the internal vapour causing a slight vacuum which sucks in more air then the air heats and expands and rushes back out carrying extra spirit. Once the air had finished expanding the outflow would stop for a moment and a bit of cold air would enter and the cycle would repeat.

Does your parrot empty itself during these pulses or is there a vacuum brake where air can get in?  Install a parrot with higher volume that fixed my problem.

 

 

[Patio29Dadio]

Quote

I am getting a rush of spirit from my parrot, then it slows way down, then surges, then slows down over and over. 

Any problem with variable water pressure, or changes to water temp going to your dephlegmator?   Oops... never mind... I re-read and you say it happens without water to your pre-condenser.   Sounds like a question for Paul Hall... guessing it is in your Baine Marie heating... maybe too much water?

[adamOVD]

32 minutes ago, PeteB said:

Does your parrot empty itself during these pulses or is there a vacuum brake where air can get in?  Install a parrot with higher volume that fixed my problem.

 

Its not so bad that my parrot empties. It does have a surge breaker, but I can't see running without it as I do get air escaping though it during the run. I'll mess around with sealing them when they aren't needed to see if anything changes.

Ill also try running with the jackets partially empty. Paul has told me they had good success running them 60% full. Maybe with steam condensing on the walls of the upper jackets the heat throughout the pot will be more even.

Thanks for the replies. Any more tips would be much appreciated.

[Southernhighlander]

Hi Adam,

I haven't had those complaints from anyone else,  of course that doesn't mean that no one else has had the problem.  Lets try and diagnose it.

 How long has it been doing that?

Is it a 105 gallon standard series still or a 100 gallon pro series?

 How many gallons are in the pot? 

Did you get your heating system from me?

Did you get your columns, condenser and parrot from me?

Did you buy the vfd with your agitator and if not did you buy your own?

Are you running a solenoid valve on your deflegmator cooling water?

What kind of coolant control valves are you using?

How many plates do you have?

How is your deph plumbed , can you show us a picture?

How is your final condenser plumbed?

Do you run coolant from your final condenser to the dephlegmator or are they plumbed separately?

Are you using one of our thermostatic valves?

How much water do you have in the jacket?

do you have a float switch or some other device adding water to the jacket during the run?

What is the temp of the water or steam in the jacket?

How much water do you evaporate out of the jacket during the run?

 

Thank you.

 

[adamOVD]

 Hey Paul, thanks for reaching out.

How long has it been doing that?

Doesn't happen every time, but has been  since set up

Is it a 105 gallon standard series still or a 100 gallon pro series?

105

 How many gallons are in the pot? 

Sometimes 105, sometimes 70, sometimes 85

Did you get your heating system from me?

Did you get your columns, condenser and parrot from me?

Only got the boiler from you. We built the rest.

Did you buy the vfd with your agitator and if not did you buy your own?

No VFD, off or on.

Are you running a solenoid valve on your deflegmator cooling water?

What kind of coolant control valves are you using?

Condensers are plumbed separately. Just running cold water to them through a ball valve. 1/4" on the deph, 1/2 on the PC

How many plates do you have?

it's modular, but I usually run 5.

How is your deph plumbed , can you show us a picture?

How is your final condenser plumbed?

Do you run coolant from your final condenser to the dephlegmator or are they plumbed separately?

See above, ill send pictures of everything later.

Are you using one of our thermostatic valves?

No

How much water do you have in the jacket?

Ive been filling to the top of the sight glass.

do you have a float switch or some other device adding water to the jacket during the run?

None just fill it in the beginning.

What is the temp of the water or steam in the jacket?

Usually hold it around 205 until the end of the run. I'm at about 4,000 ft elevation. Running 4 220 elements at 60-68% after heat up.

How much water do you evaporate out of the jacket during the run?

I don't evaporate a noticeable amount until I hit tails. Evaporate 1/4- 1/3 out of the jackets by the end of the run depending on how deep I run into the tails.

 

[Southernhighlander]

Does it surge with 105 gallons in it?

What is the diameter of your column, line arm and the diameter and length of your dephlegmator and final condenser?

Try running with the jacket 60% full, with everything else remaining the same and let us know what happens.  

[adamOVD]

It does. Maybe not as bad. Column and deph. Are 6". Deph. Is 1' long shotgun style. Final condenser is 4" diameter, 3' long. Lyne arm is 2".

Will give it a go. Probably not going to do another run until next Monday though.

[Southernhighlander]

Okay I have rethought things.  Fill the pot to the normal level and after you run out the heads crank the heat up to 214 and compensate for the extra heat with coolant flow to the dephlegmator.  Keep and eye on the sight gauge and make sure that the water in the jacket does not get less than 20%

[Southernhighlander]

Good job on building your column and condenser.  Looks nice.  If running at 214 doesn't work to your satisfaction, later on you might try adding 40% glycol to your water and set your temp on 218F,  The boiling point is 220.  Of course if you are crash cooling mash with the jacket you can't use the glycol unless you set things up for that, which might not be that big of a deal.  

[adamOVD]

Thanks Paul, guess I should've just emailed you.

Still fill the jackets to 60%?

Ill try putting more heat into the jacket, but I am at 4000 ft elevation, so boiling temps are slightly lower. I'd like to avoid putting oil or glycol in the jackets so I can cool with them as you mentioned, but also because I fill them with 185f water when I start to cut back on heat up time.

[adamOVD]

What about running the vent pipe for the jackets into a blow off bucket to get a slight back pressure? Is that not safe?

[Southernhighlander]

No fill it 90%.  If you bring it up to a boil then the jacket temp will even out and it probably won't surge anymore but you will put a lot of water vapor in the air and boil the water out of the jacket fairly quickly, but I think that you will have enough to do the run. 

As far as a pipe in a bucket. 27.7" of water column creates 1 psi.  It does not matter how wide the water column is.   Water column works the same down as up.  So if you put a 27.7" pipe down into 27.7" of water you will be pushing water column down and back up and you can get 2 psi.  If the vessel is taller you will gain more pressure, however the top of the water column should be at least 3 or 4 inches below the top of your liquid level. 2.17 psi will give you 219 F steam at sea level.   This is perfectly legal because you are not closing the system (heating system/jacket)

Another thing that you can do is to use 40% glycol and 60% water and pump out the water glycol moisture when you crash cool in the jacket and then pump it back in afterwords but you cannot do that with oil.

The weird thing is, my baine maries with my electrical heating system and columns etc do not surge even when running water in the jacket, so it is possible that it has something to do with your column, condenser, controller or parrot, since those are not mine.

[meerkat]

Below the tapered section at the bottom of the condenser there is a tee with a 90 degree elbow on it.  Is this a vent that is always open?  If it is a vent and the surging is significant I would expect liquid to come out here during the surges - or is the flow during the surges not that much more than during the slow times?  Any feel for the ratio between the maximum and minimum flows?

Are the surges enough to cause the parrot to overflow?  Does the flow out of the parrot ever stop completely during the slow part of the cycle?

Do you see bubbles coming to the surface of the parrot during the surges?

[Southernhighlander]

53 minutes ago, meerkat said:

Below the tapered section at the bottom of the condenser there is a tee with a 90 degree elbow on it.  Is this a vent that is always open?  If it is a vent and the surging is significant I would expect liquid to come out here during the surges - or is the flow during the surges not that much more than during the slow times?  Any feel for the ratio between the maximum and minimum flows?

Are the surges enough to cause the parrot to overflow?  Does the flow out of the parrot ever stop completely during the slow part of the cycle?

Do you see bubbles coming to the surface of the parrot during the surges?

That is his burp tube.  It is there to prevent burping, which some people call surging.    i put them on all of my stills. No liquid will ever burp out of the burp tube or the parrot with the burp tube in place.  His problem is not the burping of liquid.  His problem is that he is getting uneven output.  It will run slow and then fast.  

[adamOVD]

@meerkat Yeah, I rigged up the "burp tube" because sometimes I get a lot of uncondensable gas escaping. Think it happens when there is a lot of yeast in the pot. I'm sure that doesn't help the inconsistent the flow rate, but I don't think it is the cause of it, as it happens whether gas escapes or not. I'm going to cap it off whenever it seems unneeded in case @PeteB is right and cold air is being sucked in through it. I also have small vent holes in the parot.

The rush of spirits is never so great it would push spirits out of the T, or even the vent holes of the parrot. The flow rate when fast is about 2 or 3 times faster then when it is slow. I can still get through my runs, but it makes making my cuts a lot more difficult, and keeps the plates from stacking consistently through the run.

[Southernhighlander]

I have burp tubes on all of my stills and none of them have inconsistent flow rates like yours.  At least not that I know of.  The burp tube has nothing to do with it.  Can you send me a picture of your plates?

[meerkat]

@Southernhighlander and @adamOVD - I agree 100% on the need for the "burp tube". I always install them, although I always include a 3 or 4 ft vertical riser from the elbow. But even with the riser I have seen liquid gushing from the vent. The venting of uncondensible gases is critical and I have seen operators on continuous plants using the smell from these vents as an indication of the operation of the column.

I would be very careful about blanking it off. PeteB's concern about sucking air into the condenser is valid, but I have found this to only happen when the condenser is significantly oversized or the water is unusually cold.

In my experience this cycling of the product rate is caused by either bad piping design around the condenser, or by cycling of the heat input in the boiler. I suppose it could be caused by the plates but I have never seen that and it seems to be happening here whether the plates are installed or not.

Most of the cycling cases I have come across have been caused by condenser piping design and that was the motivation for my questions. @vsaks had exactly this problem last year. But from the photo you have supplied and the answers to the questions I think in this case the problem is not around the condenser.

Unfortunately most of my experience on the heating side has been with thermosiphon reboilers and I have never used a bain marie boiler. Cycling can definitely occur with an oversized thermosiphon reboiler so in view of the elimination of the condenser piping and the plates as suspected causes I would concentrate on the heating side.

 

[Southernhighlander]

Meerkat,

 

You should always run a vent tube from the burp tube to the outside of the building.  If your condenser goes down and your burp tube is not vented to the outside you could have a really dangerous situation on your hands.  It states this in my safety manual. 

 

I like to look at things from all different directions, but I think that once Adam fallows my recommendations the problem will be solved.

During testing of my finished designs we never had any problems with surging or major flow inconsistencies, were we built the entire still including the heating system column and condensers.  We have around 160 baine marie stills in distilleries in the USA and a few others around the world. I have myself created over 60 different still designs with the largest being over 5,000 gallons.  I have also designed ethanol, propane and butane extraction systems for removing oil from plant material for the pharmaceutical and nutraceutical industries.  We are currently installing a vacuum distilling system in NY that will process  up to 12,000 lbs of plant material per day.  

[meerkat]

@Southernhighlander I have no doubt that you can build a complete bain marie-based system. The problem in this situation could be mismatched components.  Is the column being used the same diameter that you would install on this boiler?  Are the plates the same design?  Are the power and positioning of the agitator as per your design?  Is the heating power what you would use?

@adamOVD It would be useful if you could find some other parameter that is cycling at the same frequency as the product flow, as this could indicate the cause.  For example, can you measure the amps to the agitator?  If the agitator is causing a vortex the entrained vapor might be interfering with the heat transfer from the shell and causing the cycling.  Does the temperature in the jacket vary?  Can you measure the pressure in the boiler?  Does it cycle?  I am pulling things out of the air here, but you need to measure whatever you can and try to find something that is cycling in sync with the production rate.

[Southernhighlander]

4 minutes ago, meerkat said:

@Southernhighlander I have no doubt that you can build a complete bain marie-based system. The problem in this situation could be mismatched components.  Is the column being used the same diameter that you would install on this boiler?  Are the plates the same design?  Are the power and positioning of the agitator as per your design?  Is the heating power what you would use?

@adamOVD It would be useful if you could find some other parameter that is cycling at the same frequency as the product flow, as this could indicate the cause.  For example, can you measure the amps to the agitator?  If the agitator is causing a vortex the entrained vapor might be interfering with the heat transfer from the shell and causing the cycling.  Does the temperature in the jacket vary?  Can you measure the pressure in the boiler?  Does it cycle?  I am pulling things out of the air here, but you need to measure whatever you can and try to find something that is cycling in sync with the production rate.

At this point it is best if Adam fallows my recommendations. If they don't work we can then move forward and check some other things.

[adamOVD]

Here's one of the plates. I agree that the burp tube probably isn't the problem, but it literally takes two seconds to put a cap on it and eliminate it as a possible problem.

Hopefully it is a surge boiling problem, caused by the limited heat transfer intrinsic to a bain Marie still, running at a higher altitude??, and my own inexperience running a still. I think Paul's got me on the right track though. Thanks for all the input. I'm excited to tell you how the run goes on Monday, but I am cooking, bottling and bartending till then. Thanks again for all the input.

[ViolentBlue]

Hi Adam

the surging you are experiencing I think may be caused by the condenser. the style of condenser you have needs a fairly high flow rate to cool properly, so you are most likely having very cold water hitting very hot vapor, this will create a vacuum/pressure cycle that while similar to "chuffing" has a much longer cycle time

as for solutions,turn down your water flow to the condenser till it stops, your distillate will probably come out hot if left like this, but turn the cooling water up slowly till you find a point of equilibrium between surging and warm distillate. On a larger system suffering from this same issue, a vacuum break can be added to the top of condenser.

one other more costly option would be to swap out your condenser for a more efficient inverted flow multi tube condenser, if you are not recirculating your cooling water, this will save you a lot of water down the drain.

[adamOVD]

Thanks @ViolentBlue I'll play with that as well. That would help explain why it only does it intermittently. Whenever I run too much water, or the take off rate slows or gets hotter at the end of the run. I'll be more diligent in holding the spirit in the parrot at a set temp.

Just to be 100% sure, you are talking about the final product condenser. Not the dephlemator right?

[adamOVD]

After a great deal of thought, I am almost certain @ViolentBlue is correct about the condenser being the source of the problem.. Ever piece of the puzzle fits perfectly. 

I've read in other posts about very cold water causing surging, but it all kinda went over my head, as many other ideas were also being talked about at the same time. I think i finally get it now though.

The massive cloud of heated vapor hits my over-sized condenser, which due to it being a somewhat simple and inefficient design, I am running too much cooling water to. The vapor quickly shrinks down to a small quantity of liquid, creating a vacuum that sucks the vapor out of the column and a the same time lowers the boiling temperature, making the surging even worse. That continues until the surging vapor heats up the condenser enough that everything equalizes, and then the whole cycle starts again.

Feel free to correct me if I am wrong. Can't thank everyone enough for all the feedback, fairly certain I can get things dialed in for the next run. Hopefully this helps some else out down the road as well.