Reusing Carbon after Polishing Spirits


You can reuse your carbon by washing it, and heating it up so that it will release any of the trapped fusels. Les explains ...
    I have now reused my cabon which I use in the stainless steel filtering column as described in Gerts manual 4 times with excellent results.I am using 1 kilo which I boil for approx 30 minutes then rinse several times with cold water. Because I am fortunate to live in the sub tropics I place the carbon on a steel tray to a depth of 4 mm and leave in the sun until dry. The end result is nice shiney carbon no smell whatsoever. This product could be reusable for a long time.I generally run 8 litres of 45-50% through the filter each run.
FizzyNick adds ..
    The physical and chemical properties of carbon work in our favour and mean that you have nothing to fear in heating it in an oven. Thanks to the carbon atom having a strong covalent bond (x4) it is very stable under normal conditions. The oven will never reach a high enough temperature to even start to effect it. The heating of the carbon should allow for the disappation of the built-up cogeners in pores of the granules or powder. Due to the fact that the nasty alcohol molecules will be released over a period of hours there is an almost nil probability of an explosion due to alcohol vapour build up. If you have a fan assisted oven this is even better as it will help to circulate the alcohol being released more evenly.

    The bottom line is you could heat the carbon at top setting on your fan assisted oven for a year and still be in no danger. Wouldn't like to see the bill for the electricity though :)

    As far as steam is concerned [from a domestic steam-cleaner] I do not think that would work. The alcohol molecules need to be vapourised from the fissures of the carbon. Water molecules (steam) would not do any more good than actually boiling the carbon in a pan of water as they would not necessarily displace the alcohol from the fissures.
Note that this is simply a "cleaning" of the dirty carbon - you are not reactivating it fully back to its prior state. Smudge writes ...
    Whilst its true carbon is activated by contact with steam, don't think you can do it yourself while you're boiling the jug for a coffee:

    GRANULATED CARBON ACTIVATION
    Most Carbon is activated using steam. Activation is also accomplished using chemicals. Wood based carbons steam activation involves a two step process, carbonization and activation. Carbonization occurs in an oxygen deficient environment at high temperatures, 700 degree Celsius. Activation of carbon occurs by using steam where temperature of the carbon is raised to 1800 degrees.

    REACTIVATED CARBON
    Reactivating carbon is a simple process where the spent carbon is thermally reactivated . Reactivation occurs a temperatures between 1400-1700°F where ether volatile organics or oxidized off forming CO2 and water. The non volatile organic compounds are carbonized to form char. In the final phase of the process steam is used to reactivate the carbon. Approximately 80-90% by dry weight of the carbon is recovered in this process. The remainder is made up with virgin carbon. Reactivated carbon performs exactly the same in adsorptive capabilities as virgin carbon.

    Information courtesy of www.onionenterprises.com
Mike writes of his technique for cleaning carbon for reuse ..
    I think you will find that the extreme heat procedures you read about concerning commercial reactivation of carbon are not necessary in a hobby situation. I regularly treat my carbon after use, and find that it serves me very well. Rather than calling it "reactivation", it is perhaps better to describe the process as "cleaning", as "activation" really means treating raw carbon so that it has a suitable internal structure with a very large surface.
    Try this:
    • Wash used carbon in plenty of running water to get rid of all external rubbish. I do this simply by rinsing under a tap with the carbon in a sieve.
    • Then boil it in an open pan of water for around quarter of an hour. This will get rid of the bulk of the volatiles. If you want to do a really thorough wash, carry on by boiling it up in an ordinary pressure cooker for 10 minutes. This will get rid of even more than open air boiling.
    • Finally, strain off all the carbon and rinse under a tap for a minute, then spread it all out on a wide baking tray covered in ordinary baking foil (saves rusting the tray!).
    • Shove that in the kitchen oven to dry slowly at around 160C/320F, making sure that you periodically open the oven door to vent the smelly steam that comes off.
    It takes time to drive all the water off, but organic molecules still held inside the carbon will come off with the steam quite readily at this low temperature. Don't try heating at the highest temperature your oven is capable of .. not only is it unnecessary, you will also run the risk of ending up with a pile of gray ash! Try it. I think you will find that it's more than adequate.
Peter describes his microwave technique ..
    before i go through it i will say microwaving charcoal can be VERY DANGEROUS! I got the idea of microwaveing it after reading that carbon can reach extremely high temperatures in a microwave. You can get carbon crucibles for melting steel and silver. So it reaches well above 1000C. I thought this would be ideal to burn off and residual nasties stuck in the carbon and also to sterilise it.

    I get my carbon in a plastic filter from work. I cut the filter open with and dump the dirty carbon into a 40litre container and fill it with hot water in my shower. I let it settle and decant the dirty water. I repeat this until the water is clear, usually 4 times. I then boil it up in a pressure cooker to really clean it and sterilise it. I then drain it off rinse again and put it in a pyrex lasagne type container. I microwave it on full for 5 mins at a time stirring it after each 5 mins. After about 20 mins it is dry but keep a close eye on it. I then microwave it for 40 seconds at a time stirring each time. it looks dry but after a while it starts to gives off dry vapours again.

    It gets extremely hot so a pyrex dish is essential. it is important to stir to prevent hot spots. Once i didnt stir for a while and when i did stir it was glowing red in the middle! after about 10 blasts at 40 seconds the vapors stop coming off and i then stop and let it cool overnight. the vapours have a choking smell and are a bit like smoke since they are "dry" but they dont stink the room or anything.

    How much ? I didnt weigh it but it looks 500g judging from the 1 kilo bags i used to get. The microwave is 800W, but microwaves do vary in efficiency. Mine seems to heat small cups of water faster than my last 800W maybe it has hot spots or something. I would go very slowly your first time maybe 2 mins at a time until appears totally dry. When it is dry it just falls off the spoon like sand. if you cant leave it in the microwave to cool down (incase "she" finds it) be very careful where you leave it. I took it out once and put it on some newspaper and the paper started to smoke! it works very well when recharged, but i always put lots in each gallon jar anyway.
Mike warns about using a microwave :
    Carbon is a good conductor of electricity, so microwave radiation is readily absorbed. However, high voltages are generated across the gaps between the granules. Sparks result when the voltage jumps across these gaps. Air is a good insulator, so this sparking will readily occur when the carbon is dry, for the voltages can be very high indeed. Strong eddy currents in the carbon heat the granules as it does have some resistance, so plenty of heat is generated, usually ending up with the carbon igniting.

    It's slightly different when the carbon is wet. Water is generally considered to be a good conductor, but that is only because it can readily dissolve salts that disassociate in solution into electrically charged ions, and these carry the current. Water that has been through the distilling process has no salt content, and any salts present in the carbon/water mix will generally be those lingering on after the manufacturing process. The water separating the carbon granules is therefore a fairly good insulator and sparking will also be experienced, usually with generation of a bit of hydrogen and oxygen as the water is broken down by electrolysis. The heat generated will initially go towards heating and vaporizing the water, so keeping the carbon below its ignition point. However, when all that water has boiled off, the dry carbon will then heat up - as before - and ignite. One "interesting" side effect you might notice if treating damp carbon in a microwave is that you can end up with an explosion, for that dampness may well contain a goodly proportion of alcohol if you haven't first washed the carbon thoroughly. The atmosphere in the microwave can quickly reached critical proportions with the oxygen in the air, and a spark is a tried and true way of igniting that mix! You can even get the same effect in an ordinary oven from a red-hot heating element if the carbon still has a lot of alcohol left in it ... ending up with a muffled thump and the oven door blowing open!! (Been there, done that, and would be wearing the T-shirt if it hadn't been scorched!)

    Moral? Do NOT dry carbon in a microwave oven as the risks of fire or even explosion are too great, and wash carbon thoroughly in lots of clean water before drying in an ordinary oven ... keeping the oven door slightly open to vent any flammable gases that will almost certainly be given off, as no amount of ordinary sluicing in water will get rid of all the alcohols deep inside the carbon granules. Proof that they are indeed still there will become more than evident to your nose as they are vaporized ... so keep the kitchen windows wide open if you don't want the whole house to reek of congeners!


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