[Stoves] Charcoal stove design

[Paul Anderson]

Stovers,

That website (below) goes to products pages.   If I remember correctly, 
the ETHOS presentation was a PowerPoint and had diagrams of air flows to 
focus the air onto the char pieces.   But I do not know where that 
presentation can be seen.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 9/18/2013 8:55 PM, Alex English wrote:
> AT ETHOS a few years back (2010 I think), Bryan Wilson gave an 
> excellent presentation on an improved combustion charcoal stove. The 
> ETHOS website doesn't seem to have a link for it.
> I believe this is the the one,
> http://www.envirofit.org/products/?sub=cookstoves&pid=12
>
> Alex
>
>
>
> On 18/09/2013 5:37 AM, Saastamoinen Jaakko wrote:
>>
>> Dear Frank and Crispin,
>>
>> the main DIRECT product in the reaction of carbon with oxygen is CO 
>> but also some CO2 is directly formed. CO that is formed can be 
>> oxidized to CO2 (CO+½O2=CO2) at high enough temperatures in the 
>> vicinity of carbon particle or in later stage in the gas flow. So 
>> there are different zones along the gas flow in carbon particle layer 
>> when air (or gas) is flowing upwards through it:
>>
>> I)Zone where exothermic reaction C+½O2=CO takes place (but some CO2 
>> is also formed). Here the gas temperature is rather low because it is 
>> close to the inlet and the gas has not heated up enough. So CO is not 
>> burning well.
>>
>> II)Zone where the gas temperature becomes high enough so that also 
>> the exothermic reaction CO+½O2 =CO2 (enhanced by H2O) takes place in 
>> the gas. This leads to even higher local temperature along the gas 
>> flow so that exothermic reactions (C+½O2=CO and CO+½O2=CO2) take 
>> place at even higher rate. Here also the endothermic reaction 
>> CO2+C=2CO takes place because the char temperature is high enough. 
>> This rrwaction adjust the temperature level preventing it to increase 
>> very high. Then at the location, where all oxygen is consumed, the 
>> gas temperature and CO2 concentration reach the maximum values.
>>
>> III)After that the carbon reacts with CO2 producing carbon monoxide 
>> in endothermic gasification reaction CO2+C=2CO. The gas is cooled due 
>> to this endothermic reaction. If the layer is very thick, the gas is 
>> cooled to a temperature at which the reaction rate C+CO2=2CO becomes 
>> very low.
>>
>> So some conclusions:
>>
>> 1.For a thin layer, there is only zone I producing CO.
>>
>> 2.For thicker layer (zone II), the exit gas contains much CO2 and 
>> some CO. The exit gas is hot and CO may be burned introducing 
>> (preheated) secondary air. The exit gas is hottest if the thickness 
>> of the layer is just in the  intermediate transfer regime from zone 
>> II to III.
>>
>> 3.For a thick layer, the gas contains much CO and some CO2. Its 
>> temperature is low and it is difficult to burn CO without highly 
>> preheated secondary air.
>>
>> The reaction CO+½O2=CO2 can take place also in the other direction. 
>> This reverse reaction (dissociation) of carbon dioxide is not 
>> significant at temperatures <1800 K.
>>
>> Regards
>>
>> Jaakko
>>
>> *From:*Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On 
>> Behalf Of *Frank Shields
>> *Sent:* 18. syyskuuta 2013 0:55
>> *To:* 'Discussion of biomass cooking stoves'
>> *Subject:* Re: [Stoves] Charcoal stove design
>>
>> *Dear Crispin,*
>>
>> **
>>
>> *So the CO2 > CO is endothermic. But still needs carbon. As I see it 
>> the only difference is the temperature changing as the gases move 
>> around the pot. Wondering if the reading could be affected by 
>> temperature? Perhaps amount of gas entering the instrument or 
>> something? Interesting. Could hydrogen react with one of the oxygen 
>> in CO2 making water leaving CO? *
>>
>> **
>>
>> *Frank*
>>
>> **
>>
>> *From:*Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On 
>> Behalf Of *Crispin Pemberton-Pigott
>> *Sent:* Tuesday, September 17, 2013 2:01 PM
>> *To:* 'Discussion of biomass cooking stoves'
>> *Subject:* Re: [Stoves] Charcoal stove design
>>
>> My conclusion is the CO splits endothermically. It does not happen in 
>> stoves with high EA.
>>
>> Crispin
>>
>> *Dear Crispin,*
>>
>> **
>>
>> *<snip>*
>>
>> I found that directly above the middle of a good stove (under the 
>> pot) there is zero CO -- I was amazed. But nearer the edges there is 
>> more.
>>
>> */[Frank >] How is that possible? I thought going from CO2 > CO could 
>> only occur be in a bed of char. This is very strange. /*
>>
>> *//*
>>
>> */Regards/*
>>
>> *//*
>>
>> */Frank/*
>>
>>
>>
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>
>
>
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