Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: julianf on June 28, 2013, 01:24:26 PM
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My spirit hydrometer has just turned up.
Its calibrated to ethanol at 20c.
The 'virgin' meth i just tested came out at 99% at around 15c ish (outside temp).
I have confidence that the sample tested was close to pure (ie 99.99%), so i would assume that the 1% deviation is due to equipment, calibration, temperature etc.
I then tested a sample of reclaimed, and that read 96% on the scale. Under my assumption that the previous 1% deviation is due to equipment calibration, rather than an impure reference sample, this would give a purity on the reclaimed to be between 96% and 97%. Ie probably 3% water.
Im now wondering which stage of the 2stage process to use the reclaimed in.
In S1, there are loads of other 'unknowns' anyhow. Also the reclaimed will never be the total amount on S1 (due to the reclaimed total from the last batch never being as large as the S1 dose) - however, at present i have a load of reclaimed, and very little virgin.
When do you use your reclaimed?
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I've used reclaimed that was 96% before. Made the methoxide up with virgin meth, put that in and let it process a bit, then added the reclaimed working on the assumption that the glyc created in the initial part of the reaction would help with the water.
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If you want to check the graduations are the expected distance apart on your hydrometer, a 100ml measuring cylinder is good for this. Put in 100ml Meth, pop in the hydrometer, add 1ml of water - should float up by 1%.
My ethanol hydrometer (which goes up to 99%) sinks entirely when put into virgin Meth, though it bobs up if 1ml water is added. So if I'm testing reclaimed and I see it sink, then I'm happy it's good to re-use without worry.
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Interestingly (for me) ive just fount the correction chart for my hydrometer.
As mentioned, its calibrated at 20c. I was testing at more like 15c. The chart states that, at 85%+, at 15c, 1% should be added to the read out. Which, specific density errors between ethanol and methanol aside, would tie in with the 99% reading that i got from my 'virgin' sample.
I would therefore be happy to assume my recovered to be 97%, however, when im feeling keen, i will do as you say, and test by adding water to a 100% sample.
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I get a regular 98% reading on my Spirit Hydrometer for reclaimed methanol.
I use the reclaimed in stage 1, ASM first, reclaimed and top up with virgin to required volume.
I prefer to use virgin for stage 2.
I once used reclaimed methanol for stage 2 that was distilled off of stage 1, I was very short of methanol at the time and it worked a treat.
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I then tested a sample of reclaimed, and that read 96% on the scale. Under my assumption that the previous 1% deviation is due to equipment calibration, rather than an impure reference sample, this would give a purity on the reclaimed to be between 96% and 97%. ie probably 3% water.
That would probably be right for your reclaimed Julianf....so long as you've generated it yourself.
A word of warning though for people who buy reclaimed methanol is any impurity could be anything and should not be assumed as being water. Reclaimed methanol is recovered from all sorts of chemical processes.
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Take the water out? If its just water in it use a molecular sieve
Explanation of them here
http://www.bio.umass.edu/microscopy/mol_sieves.htm (http://www.bio.umass.edu/microscopy/mol_sieves.htm)
Have got the molecular seive just got to buy the hydrometer and try it when I get a chance
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Recovered meth is often polluted with FAME , I'm guessing that won't do a molecular sieve much good?
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Recovered meth is often polluted with FAME , I'm guessing that won't do a molecular sieve much good?
Don't know will find out :) Was going to wash after use in IPA they are made of ceramic I believe
Need to get a hydrometer could you recommend a source? Seen them on eBay but could I get one locally from a wine making suppliers or something? What size am I looking for?
Anyone got a link?
Ta very much ;D
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1 x Stevenson Reeves Spirit Hydrometer / Alkohometer 0-100% (alchometer) = £4.29
1 x Glass Trial Jar (glass trial jar) = £5.75
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Sub-Total: £10.04
Shipping: £2.00
Total: £12.04
http://www.balliihoo.co.uk
The trial jar is cheaper than getting one off ebay, however, its base is small, so its not that stable.
If that's a problem for you, there's one on ebay that i was otherwise going to buy - i can look up the item number for you later.
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You have a pm..........message me back and I may have a solution to your problems.....
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Just so that Nathan can read this......y hv..........mssg m bck nd my hv sltn t yr prblms :D ;)
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Nige you spelt "Your" worng its UR as opposed to YR ;D ;D ;D
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1 x Stevenson Reeves Spirit Hydrometer / Alkohometer 0-100% (alchometer) = £4.29
1 x Glass Trial Jar (glass trial jar) = £5.75
------------------------------------------------------
Sub-Total: £10.04
Shipping: £2.00
Total: £12.04
http://www.balliihoo.co.uk
The trial jar is cheaper than getting one off ebay, however, its base is small, so its not that stable.
If that's a problem for you, there's one on ebay that i was otherwise going to buy - i can look up the item number for you later.
Thanks for that :)
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Nige you spelt "Your" worng its UR as opposed to YR ;D ;D ;D
just goes to show how old I am....I'm just not down with the kidz ;D
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text speak....it's just for knobs. That's why I cant do it. everything has to be grammatically correct. Some have the gift....some dont..........I know you read them
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I'm just not down with the kidz ;D
You're far too tall to be doing with anyone young or old.
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yp ur prbbly rite
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LOL..... PMSL M8
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1 x Stevenson Reeves Spirit Hydrometer / Alkohometer 0-100% (alchometer) = £4.29
1 x Glass Trial Jar (glass trial jar) = £5.75
------------------------------------------------------
Sub-Total: £10.04
Shipping: £2.00
Total: £12.04
http://www.balliihoo.co.uk
The trial jar is cheaper than getting one off ebay, however, its base is small, so its not that stable.
If that's a problem for you, there's one on ebay that i was otherwise going to buy - i can look up the item number for you later.
Got it through today thanks
My reclaimed seems to be 99% could that be right? Did the test at 20C ???
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Sounds a little too good to me ... are you using ASM?
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Sounds a little too good to me ... are you using ASM?
Yes ASM when I did the demeth my PID wasnt working properly i discovered >:( so I used the temp gauge on the front of the processor, didnt want to push the temp up any more than necessary so only took it to just under 80C.
Reasoned that Methanol boils at 64.7C so as my processor is well insulated, temp at the head would still be high. I could hear it vaporizing in the head and it was running out the condenser so I thought that was high enough. Maybe not being near boiling point of water helped?
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With ASM may be it's possible, but the likely hood is that your virgin methanol was only 99% in the first place, so to have recovered methanol with the same purity is unlikely. I've only once checked methanol purity since I started using ASM and that only because I suspected the process I was using introduced water and indeed it did ... it was off scale on my hydrometer!
The acid test will be if it processes OK in the next batch ... my guess is that it will.
You reasoning regarding water and methanol separation is logical, but I'm afraid it doesn't work as easily as that. Water and methanol are miscible and as such are very difficult to separate. Several of us tried at length to do it with a GL, but regardless of how carefully you control the temperature the methanol will never be pure enough to reuse. It is possible but you need several stages of reflux and to be honest just isn't economical at the scale we work at.
Best bet is to dry the oil very well, use ASM sparingly and then recover the methanol before doing any water washing.
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Got it through today thanks
My reclaimed seems to be 99% could that be right? Did the test at 20C ???
Sounds about right Dave, been getting those sort of readings since I started using asm.
I did 10 batches in a row continually using all the reclaimed topped up with virgin and the 11th reclaim measured 98%.
As for the temperature, the higher you go the more methanol can be distilled out of the bio, purity doesn't seem to change.
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Now that is interesting gents. With ASM being a "dry" catalyst it could be worth dipping my toes into recovering again.
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With ASM may be it's possible, but the likely hood is that your virgin methanol was only 99% in the first place, so to have recovered methanol with the same purity is unlikely. I've only once checked methanol purity since I started using ASM and that only because I suspected the process I was using introduced water and indeed it did ... it was off scale on my hydrometer!
The acid test will be if it processes OK in the next batch ... my guess is that it will.
You reasoning regarding water and methanol separation is logical, but I'm afraid it doesn't work as easily as that. Water and methanol are miscible and as such are very difficult to separate. Several of us tried at length to do it with a GL, but regardless of how carefully you control the temperature the methanol will never be pure enough to reuse. It is possible but you need several stages of reflux and to be honest just isn't economical at the scale we work at.
Best bet is to dry the oil very well, use ASM sparingly and then recover the methanol before doing any water washing.
If i had the time / energy required (and, more importantly, did not want to spend it doing somthing else!) i would try a colum, as high as possible, filled with marbles from the toy shop.
If / when i ever get sorted, id like to build a still running from solar. Id just dump all the glyc etc in it, and leave it. Come back to get the methanol, which, for me, is the most expensive part of the process.
A 54mm copper pipe may do. Possibly even soil and vent?
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I forget what percentage you can get up to with ethanol from standard distillation alone, but its certainly not 100%.
I seem to recall that its then dried with benzene or something?
Wikipedia to the rescue -
(this is for ethanol)
Distillation
Ethylene hydration or brewing produces an ethanol–water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation can concentrate ethanol to 95.6% by volume (89.5 mole%). This mixture is an azeotrope with a boiling point of 78.1 °C, and cannot be further purified by distillation. Addition of an entraining agent, such as benzene, cyclohexane, or heptane, allows a new ternary azeotrope comprising the ethanol, water, and the entraining agent to be formed. This lower-boiling ternary azeotrope is removed preferentially, leading to water-free ethanol.[39]
Vapor-liquid equilibrium of the mixture of Ethanol and Water (incl. azeotrope), composition given in molefractions
At pressures less than atmospheric pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures, and at pressures less than 70 torr (9.333 kPa), there is no azeotrope, and it is possible to distill absolute ethanol from an ethanol-water mixture. While vacuum distillation of ethanol is not presently economical, pressure-swing distillation is a topic of current research. In this technique, a reduced-pressure distillation first yields an ethanol-water mixture of more than 95.6% ethanol. Then, fractional distillation of this mixture at atmospheric pressure distills off the 95.6% azeotrope, leaving anhydrous ethanol at the bottoms.
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Sounds about right Dave, been getting those sort of readings since I started using asm.
I did 10 batches in a row continually using all the reclaimed topped up with virgin and the 11th reclaim measured 98%.
As for the temperature, the higher you go the more methanol can be distilled out of the bio, purity doesn't seem to change.
Thanks Jim I am not going mad then :)
With ASM may be it's possible, but the likely hood is that your virgin methanol was only 99% in the first place, so to have recovered methanol with the same purity is unlikely.
Picture speaks a thousand words, what do you read it as?
I know there is a little Bio in there but Tony said this is normal I think
(http://i250.photobucket.com/albums/gg244/zukenstein/Bio/first/percentreclaim_zps7724c936.jpg) (http://s250.photobucket.com/user/zukenstein/media/Bio/first/percentreclaim_zps7724c936.jpg.html)
Best bet is to dry the oil very well, use ASM sparingly and then recover the methanol before doing any water washing.
Thanks for the advice that is exactly what I am doing, nice to have it confirmed :)
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I've never seen that with any methanol I've recovered.
Are you sure it's bio? Bio is miscible with methanol. Will it mix?
Bio has an sg of between 8.6 - 9 and methanol 7.91, so significant quantities could adversely effect the reading.
I can't remember further back in the post, but is the hydrometer reading up to 100% alcohol (it's not clear from the photo), if so they are not the most accurate indicators, but should be adequate for our use. Personally I wouldn't hang my hat on the reading being very accurate, but it should be a good indication that the methanol is OK to re-use.
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I must get round to finishing this page, but if you look here ... http://www.biopowered.co.uk/wiki/Testing_methanol_purity you can see the difference between an alcohol hydrometer and a laboratory version.
The scale on my lab. hydrometer probably represents around 3-4% over it's full length (that's just a guess but you get the idea).
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I think there should maybe be mention of calibration with a 'known' good sample.
In which case, it does not really matter too much what the scale etc. is - what matters is if the sample tested reads the same as the known good.
(and, as tony suggested, further calibration can be done by adding water to the sample)
I guess the thing im trying to get across is, so long as the hydrometer floats, and changes level etc. it does not matter so much what the marks inside say, so long as its calibrated by us on purchase.
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I've never seen that with any methanol I've recovered.
Are you sure it's bio? Bio is miscible with methanol. Will it mix?
Bio has an sg of between 8.6 - 9 and methanol 7.91, so significant quantities could adversely effect the reading.
I can't remember further back in the post, but is the hydrometer reading up to 100% alcohol (it's not clear from the photo), if so they are not the most accurate indicators, but should be adequate for our use. Personally I wouldn't hang my hat on the reading being very accurate, but it should be a good indication that the methanol is OK to re-use.
Bit misleading that pic the meth has a brown tinge to it all the way through how the camera is it makes it look like a layer on top there isn't its all the same colour.
Yes it does read up to 100% I know it's not lab grade but if it says 98-99% as Jim says his does and it's ok since I am using one of his processors I will use it.
In fact I have just completed the first stage with about 6 litres of it, 10/90 says 2ml drop out so good so far fingers crossed :)