Boiler temp control

Distillation methods and improvements.

Moderator: Site Moderator

Post Reply
timbit1985
Novice
Posts: 7
Joined: Fri Sep 20, 2013 3:39 pm

Boiler temp control

Post by timbit1985 »

Hey,
I do industrial and commercial controls for heating, cooling and ventilation for work. A natural extension to my work is making diy controllers at home out of micro-controllers. I've successfully made a few different PID temperature controllers for various nerdy applications.

I'm interested in making a small 2" diam fractionating still to mess around with controls systems. I'm aiming for 95% ABV ethanol. My objective is not meant to make a system to set and forget (that sounds insanely dangerous) but to combine 2 of my loves together. Electronics and good booze, if I were to make an semi-automated still, I would want to be monitoring it during operation.

A few things i'm considering:
-Thermoprobes to measure the following.
-Boiler liquid temp.
-Temp in the column at the take off (is that what you call the point at which you remove the distillate?)
-Distillate temperature in the collection vessel.
-Condenser water in and water out temperature.
- PI control of either the boiler or condensate temperature at the take off.
- PI control of the condenser water.
-Condenser flow sensor.
-Alarm and manual reset for dangerous overtemp and coil water flow failure.

I have a couple of questions for you.

In a fractionating still:

1) Would there be advantage in holding the beer at a particular temperature to vaporize various compounds? I.e instead of boiling the liquor, hold it around 45C to force off the methanol then ramp the temperature up to 76C (or whatever the temp for ethanol is).

2) Would it be better to control the vapour temperature at the point the distilled fluid exits the still? If so, why? Would it be a function of speed? I could see option 1 being quite slow.

3) Does the TD across the water cooled condenser coil have an impact on the quality of the product? From my experience a 10F TD across water cooled condensing coils is a good number to shoot for. Should I even both looking at TD?

At this point, building a still is just a wet dream, but i'd very much appreciate input into the value of measuring and controlling the above values.
rumbuff
Swill Maker
Posts: 248
Joined: Sat Mar 03, 2012 11:09 pm

Re: Boiler temp control

Post by rumbuff »

Hi again timbit, I just replied to your welcome post. Looking over this post it seems that you need a little bit more research. You're on the right track, but some of this will be easier to understand if you see a still run, or try it first. As to your questions,

1. The boiling point is determined by the composition of the liquids in the pot, there's no point trying to control the liquid temperature.

2. The vapour temperature is determined by the composition of the vapour. In a reflux still, you can control how many redistilations are happening, and that has an effect on the purity, and therefore the temp.

3. The TD doesn't matter. As long as the input is cold enough to condense without causing shock cooling, and the output won't scald anybody, it doesn't matter. You might have to make the condenser larger, but you'll use less water.


As to the other stuff, some of them matter, some of them don't, but that'll get clear when you read up some more
olddog
retired
Posts: 3618
Joined: Fri Jan 16, 2009 6:16 pm
Location: WEST OZ

Re: Boiler temp control

Post by olddog »

This might help http://coppercustomstillcomponents.com. ... f=77&t=194" onclick="window.open(this.href);return false;" rel="nofollow


OD
OLD DOG LEARNING NEW TRICKS ......
Maritimer
Rumrunner
Posts: 716
Joined: Sun Jul 01, 2012 6:09 am
Location: Nova Scotia, Canada

Re: Boiler temp control

Post by Maritimer »

Hi timbit,

I'm using microcontroller to control my still. The most important factor to control is power to the boiler.

Here is my thread about my microcontroller-controlled power supply. Look toward the end to see discussion about Bresenham's algorithm. http://homedistiller.org/forum/viewtopi ... 1#p7023135

Here is a design for a safe VM still that I concocted with cholme:
http://homedistiller.org/forum/viewtopi ... 5#p7085290

And if you decide to build a VM still, here is my plan for measuring the reflux ratio in real time: http://homedistiller.org/forum/viewtopi ... 2#p7020450
http://homedistiller.org/forum/viewtopi ... 0#p7023905

It's great not to feel that paranoia that they do in the States. I like to go to the local brewshop and discuss distilling with the salespeople and occasionally with other customers.

If you'd like to get into detailed discussions, please PM me.

M
timbit1985
Novice
Posts: 7
Joined: Fri Sep 20, 2013 3:39 pm

Re: Boiler temp control

Post by timbit1985 »

Hey cool link. Your rr formula seems similar to a formula I often use. Btu=gpm x 499.8 x delta t.

499.8 being a constant including sensisble heat of water, density, and time.

All I know, is that I frequently use it to estimate secondary refrigerant flow rates through glycol lines. I don't see why you couldn't plug in the appropriate numbers for ethanol. Nice link and info thanks!
Post Reply