[Stoves] why does coffee husk biochar smell like urine?

Paul Olivier paul.olivier at esrla.com
Sat Oct 15 22:25:41 PDT 2011


Tom,

I am not sure if I understand all that you are saying here.
I thought that the potassium compounds melt at 350 C and vaporize at
substantially higher temperatures.
If most of the K stays in the char, then it does not vaporize at 350 C.
Is this correct?

Paul

On Sun, Oct 16, 2011 at 11:00 AM, Tom Miles <tmiles at trmiles.com> wrote:

> The actually exists as KOH and vaporize starting at about 350 and
> increasing in greater proportions as you increase temperature. Once it
> vaporizes it condenses quickly with chlorine or sulfur, if present. Only
> when it is hot enough (750 C or higher) will it begin to melt, especially If
> it is present with silica in a ratio of about 1:2. Husk silica is more
> resistant than straw silica to alkali silicate formation. I would think the
> most of the K will stay in the char. If you get K volatilization you will
> see it where you burn the gas. Over time you’ll get agglomeration of very
> fine (submicron like cigarette smoke) particles that we call an alkali fume.
> At such low fuel rates you’re not likely to see anything for some time.
> ****
>
> ** **
>
> Using the rice husk as a pilot fuel for the coffee husk makes a lot of
> sense. You’ll get a clean gas and a rich husk char. ****
>
> ** **
>
> Tom****
>
> ** **
>
> *From:* stoves-bounces at lists.bioenergylists.org [mailto:
> stoves-bounces at lists.bioenergylists.org] *On Behalf Of *Paul Olivier
> *Sent:* Saturday, October 15, 2011 5:17 PM
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] why does coffee husk biochar smell like urine?****
>
> ** **
>
> Frans,
>
> When subjected to temperatures greater than 350 C,
> are you saying that K2O melts but does not vaporize?
> Are you saying that we end up with melted K2O?
> If the original coffee husks contains 36% to 38%
> then the final biochar must contain at least twice that amount.
> If this is correct, then coffee husk biochar must be quite valuable,
> not only as a soil amendment but also as a fertilizer.
> Surely this cannot be right.
>
> The coffee husk contains some sort of oily substance
> that begins to volatilize at temperatures as low as 170 C.
> When gasified it produces a lot of black soot.
> I tried many burner designs in the last few weeks to get rid of the soot
> and to turn orange flames into blue.
> Supplying hot premixed secondary air does not effectively consume this
> soot.
> Sometimes it makes things worse.
>
> A few days ago I cheated.
> I mixed coffee husks and rice hulls in equal volumes.
> (Note that the coffee husk has a bulk density of 180 kg/m3,
> while the rice husk has a bulk density of about 100 kg/m3.)
> The flame at the base was blue and white.
> This is the first time I saw the color white in the gasification of coffee
> husks.
> As the flame rose, it split into two parts:
> one part vertical and the other part more horizontal.
> The vertical part was blue/white and the more horizontal part was orange.
> But there were no streaks of black within the orange part of the flame and
> no visible soot.
>
> The gasifier that I used looked like this:
>
> http://dl.dropbox.com/u/22013094/150%20Gasifier%20Drawings%20PDF/001%20-%20150%20Gasifier%20Assembly.pdf
> Note the burner design:
> it is a Belonio burner with two rings of burner holes, together with a
> burner housing.
> This burner design gives by far the best result.
> Secondary air is sucked up between the housing and the burner.
> It then moves from vertical to horizontal,
> and from here it hits the two rings of holes that are offset from one
> another.
>
> The best result, of course, is with 100% rice husks.
> With the current burner design, the flame is totally blue right from the
> very beginning.
>
> When I mixed rice hulls with coffee husks (half/half by volume),
> not only does most of the soot disappear,
> but the burn is quite consistent and steady from beginning to end.
>
> Paul
>
> ****
>
> On Sun, Oct 16, 2011 at 5:35 AM, Frans Peeters <peetersfrans at telenet.be>
> wrote:****
>
> Dear Paul ,****
>
>  ****
>
>    I did many times fusions with pure KOH .****
>
> At 350° C it melts and is very aggesive to dissolve ceramics Al2O3 and SiC
> powders . (Diamond recup. )****
>
> It is verry verry  hygroscopic and the hydroxyde airosols with water in the
> air gives your nose sense alcalic .****
>
> Your brain makes the link to urine . but not the real potasium make it .**
> **
>
> It goes not into gas  but sputers airosols has a special creep effect out
> of   a creuset .! Even after cooling .****
>
> Also a battery  and fuel cel with KOH . It creeps in a isolated conductor
> for 20 cm after years ,and destroys manny apparati .****
>
> KOH Is colourless but Nickel gives  yellow.salts .****
>
> It does not become K2O2 becouse to destroy SiC we must ad Na2O2 to oxydize
> the carbide .****
>
> Potasium is to measure with flame spectro 440 um purple colour in a
> hydrogen flame . (Sodium =yellow . Cupper =green Sr =red****
>
> Sorry ,I drink no coffe !            But have a friend who drinks pee ….**
> **
>
>  ****
>
> Regards****
>
> Frans****
>
>  ****
>
>  ****
> ------------------------------
>
> *Van:* stoves-bounces at lists.bioenergylists.org [mailto:
> stoves-bounces at lists.bioenergylists.org] *Namens *Paul Olivier
> *Verzonden:* zaterdag 15 oktober 2011 9:07
> *Aan:* Discussion of biomass cooking stoves
> *CC:* Will Rutherford; loren cardeli; CHRISTA ROTH
> *Onderwerp:* [Stoves] why does coffee husk biochar smell like urine?****
>
>  ****
>
> Christa,
>
> Do you have any idea why coffee husk biochar smells like urine?
>
> I just read that coffee husks contain 36% to 38% K2O.
> This supposedly accounts for the low melting point of its ash.
> That its ash has a low melting point makes sense to me,
> since, if I leave the fan on a bit too long after the gasification cycle is
> finished,
> I see a stony yellowish/white ash at the bottom of the reactor.
>
> How is this possible that coffee husks could have so much K2O?
> What happens to the K2O when it is subjected to heat?
> I see that K2O has a melting point > 350C.
> If subjected to heat does it turn into K2O2 or even KO2?
> At what point does it turn into a gas?
>
> Does the presence of K2O account for its urine smell?
> What does this urine smell mean with regard to the value of coffee husk
> biochar?
> Would coffee husk biochar be rich in potassium?
>
> Paul
> --
> Paul A. Olivier
> 27C Pham Hong Thai Street
> Dalat
> Vietnam****
>
>
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> ****
>
>
>
>
> --
> Paul A. Olivier PhD
> 27C Pham Hong Thai Street
> Dalat
> Vietnam
>
> Louisiana telephone: 1-337-447-4124 (rings Vietnam)
> Mobile: 090-694-1573 (in Vietnam)
> Skype address: Xpolivier
> http://www.esrla.com/****
>
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-- 
Paul A. Olivier PhD
27C Pham Hong Thai Street
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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