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

Paul Olivier paul.olivier at esrla.com
Sun Oct 16 01:25:41 CDT 2011


Tom,

But the temperature in the reactor is much higher than 350 C.
I have seen a sort of clinker in the biochar if I do not turn the fan off at
the end of a batch.
At what temperature does the vaporization of K take place?

Paul

On Sun, Oct 16, 2011 at 12:33 PM, Tom Miles Easystreet
<tmiles at trmiles.com>wrote:

> it exists in a form in which a portion will vaporize easily especially if
> chlorine is present. But at 350c you won't lose much from the char.
>
> T R Miles Technical Consultants Inc.
> tmiles at trmiles.com
> Sent from mobile.
>
> On Oct 15, 2011, at 10:25 PM, Paul Olivier <paul.olivier at esrla.com> wrote:
>
> 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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-- 
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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