Cleaning a still

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User: ClaireG

Hello

Im trying to clean the condenser on our still at school, and its proving to be a very very very long task. Currently Im squirting 6M HCl into the top of the condenser, but as soon as it reacts with the limescale, it bubbles and pushes the acid back out. 2 days in, and 5 coils cleaned (with another 15 coils to go) im getting rather annoyed. Has anyone got any tips at all, to make this go a little quicker.

Thanks, from a very frustrated chemistry technician
 

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User: Jyeardly

firstly use a lower strength acid 1 or 2 molar
the last time I did this I set up a drip system from a 2l bottle an let it run
Now in Scotland so the water is nice and soft and scale is a ad memory
 

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User: ClaireG

Thank you very much, I will try a 1M acid tomorrow. How exactly did you set up a drip system, if you don't mind explaining :)
 

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User: Jyeardly

an old plastic acid bottle push a pin in near the bottom and remove
cover the small hole left with tape
fill the bottle with acid and screw on the top
over a sink remove the tape and slowly unscrew the cap till the desired flow rate is achieved
set up above the coil and use a funnel to direct the drips
(I set the coil in a large bin to catch any spillage)

good luck
 

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User: dwood

We've used citric acid in the past (5M) which doesn't seem to bubble up as much as HCl when in contact with limescale. We now take the still apart and soak the glass coil and element sleeve in an acid bath. It is much easier to remove all the scale this way.
 

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User: marilyn

Hello

I too use citric acid. I make sure that the water in the still is very hot. Then I add citric acid solid. Once the fizzing subsides I turn on the still briefly to start the re-fizzing. Before I do all this however, I do remove the tower and place an old tea towel over the opening so any bubble froth that might want to escape can't. This method only takes 1 hour to complete. I think that this is quite good seeing that our water is very hard. Try it, and see if it works for you.
 

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User: spikydog

i descale ours three times a year , with 2m HCL , yes the secret is not so strong acid as it makes its way back out the flask!! then rinse with plenty of water , the job takes 15 minutes of my time , if its got a lot of limescale build up i just clean it as and when...... :0)
 

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User: Nadya

Does the coil come out shiny again? The one we have got discloured and dark, so I stopped the process just in case the metal gets corroded.
 

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User: 23skidoo

10% Formic Acid i use like another poster suggested and we have 'hard water' In Lincolnshire.
 

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User: 007

We follow the CLEAPSS guidelines and use Ethanoic acid, ours is nice and shiny, didn't take very long to clean, and neutralised pretty quickly afterwards too.
 

TechZoe

the boss technician lady
Just resurrecting this thread to say don't use citric acid if you're in a very hard water area and you haven't cleaned the still for a while. Turns out calcium citrate is virtually insoluble in water :( Any ideas what to do to get rid of it ? Keep flushing with water, or react with ... ?! The still is like this http://www.timstar.co.uk/wa17601-d4000-distinction-water-still-bibby.html and the boiler at the bottom is approx 1/3 full with white solid; I'm worse off now than before I started !
 
I've always used 10% methanoic acid to clean my still after being told to do this when I first started as a Technician some years ago - sorry can't recall where or who the information came from - probably should check! And we are also in a hard water area.
 
Hi TechZoe
I have the same type of still as you. I try to dismantle it once a term and remove the element to clean and attempt to scrape as much as I can from the inside of the still using a bent spoon. Not very technical but gets the worst out without damaging the glass. The element I loosen what I can. I try to avoid using any acid in it as purchasing a new element is costly. This is the link to the PDF for the maintenance of this type of still.

http://www.stuart-equipment.com/adminimages/W4000(1).pdf
 
Just resurrecting this thread to say don't use citric acid if you're in a very hard water area and you haven't cleaned the still for a while. Turns out calcium citrate is virtually insoluble in water :( Any ideas what to do to get rid of it ? Keep flushing with water, or react with ... ?! The still is like this http://www.timstar.co.uk/wa17601-d4000-distinction-water-still-bibby.html and the boiler at the bottom is approx 1/3 full with white solid; I'm worse off now than before I started !
I've always used 10% methanoic acid to clean my still after being told to do this when I first started as a Technician some years ago - sorry can't recall where or who the information came from - probably should check! And we are also in a hard water area.
For de-scale we use 100 ml of tap water to which 100 ml of concentrated hydrochloric acid (30% -36 % w/v) as added.:rolleyes:;)
 

TechZoe

the boss technician lady
I've always used 10% methanoic acid to clean my still after being told to do this when I first started as a Technician some years ago - sorry can't recall where or who the information came from - probably should check! And we are also in a hard water area.
For de-scale we use 100 ml of tap water to which 100 ml of concentrated hydrochloric acid (30% -36 % w/v) as added.:rolleyes:;)
2M HCl works for me.

Thank you for the replies. I've chucked some 2M HCl in and it seems to be doing the trick. We usually use HCl, but it seems to turn the glass sheath of the element yellow; so I decided to try something weaker. The manual says to use formic acid, but we haven't got much so I thought citric would be worth a try - I won't try that again !

Hi TechZoe
I have the same type of still as you. I try to dismantle it once a term and remove the element to clean and attempt to scrape as much as I can from the inside of the still using a bent spoon. Not very technical but gets the worst out without damaging the glass. The element I loosen what I can. I try to avoid using any acid in it as purchasing a new element is costly. This is the link to the PDF for the maintenance of this type of still.

http://www.stuart-equipment.com/adminimages/W4000(1).pdf
Thanks Casey; I do have the manual and it says to use formic acid; which is in short supply here + ordering ban meant I decided to try something different :rolleyes: Unfortunately we have already had to replace the element once (after about a year) which was painfully expensive ! I also can't dismantle the still as the tap from the mains water supply is slightly broken and you can't turn the flow off completely. I can only descale the boiler effectively by detaching the tube that runs from the condenser coil to the boiler and redirecting it down a hosepipe into the sink, otherwise the acid gets too diluted before it has a chance to work ! The caretaker assures me he will replace the tap next time he drains the mains tank - however he's been saying this for the last year, and it hasn't happened yet ...
 
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