[Stoves] Jatropha fruit as fuel?

Fri Jan 25 04:12:25 CST 2013

Dear Bjarne,

Do you notice any tar deposits in the hollow part of the upper stove 
part; i.e., between the outer wall and the wall of the gas-combustion area?

regards,
Ronald von Vermindertenerkältungssymptome    :D

On 25.01.2013 08:20, Bjarne Laustsen wrote:
> Dear Crispin
>
> The secondary air enter into the combustion through 3 rows of holes in 
> the bottom part of the internal chimney in the top part of the stove. 
> We have designed this internal chimney to have a height allowing the 
> gasses to burn without going over the top of the stove. So the flame 
> will not reach the pot if the stove is operated in the right way.
>
> We have earlier tried to bring in the secondary air closer to the fuel 
> bed, however it was not very successful. For me to see it is necessary 
> to have a separation of of the fuel bed and the burning of the volume 
> where the gasses are burnt if you operate gasification stove, else it 
> does not work satisfactory.
>
> The burning of the gases in the internal chimney gives heat enough to 
> keep the pellets hot enough to release the gasses so that is not a 
> problem.
>
> A problem with this separation of the two is that in strong winds the 
> flames can be blown out, if this happens the stove stops operating and 
> a lot of smoke will develop. This is not a big problem here as most 
> households cook in sheltered places, so we have not got complains on 
> that. The stove can also get started again if a light match are 
> dropped down into the internal chimney, this will get the gases to 
> burn again.
>
> Yours
> Bjarne Laustsen
>
>
>
> On 1/24/2013 5:04 PM, Crispin Pemberton-Pigott wrote:
>> Dear Bjarne
>>
>> It is now clear - there are two sections of the stove - a gas making 
>> unit
>> and a mixing/burning unit.
>>
>> I am still missing one critical piece of information: where does the
>> secondary air enter the upper unit? It seems to have all the basic 
>> parts in
>> place.
>>
>> There is a feature, not in the positive sense, that man gasifiers 
>> have which
>> is to separate the gas burning from the fuel bed. There is no essential
>> reason for doing this. It actually introduces two new problems that 
>> should
>> not be there which are: separating the radiated heat from the 
>> underside of
>> the flame from fuel bed and the addition of the problems related to the
>> flame going out and not re-lighting.
>>
>> Thus, where you add the secondary air is critical. It can prevent both
>> problems. It would be unfortunate if you were spending money and 
>> effort to
>> create a problem that should not be there.
>>
>> I did not realise without the photos that you had a removable upper 
>> section.
>> The photos helped a lot in clearing that up. If the secondary air were
>> pushed into the gas at the top of the fuel containing section and the 
>> plate
>> with the triangular holes were not present, what happens? If there 
>> was the
>> same top round disk placed at the top if the fuel container - or 
>> better, at
>> the bottom of the upper unit so it is removable - it would push the
>> secondary air into the gas near enough to the fuel to help keep it 
>> hot. The
>> 'disk' could have any of a number of complex shapes to promote 
>> mixing, but
>> the point is that the secondary air should not be added near the top 
>> because
>> it means the flames will be running against the pot spoiling the CO 
>> and PM
>> burn. That is why I am asking about where (am perhaps how) the 
>> secondary air
>> is introduced.
>>
>> The stove looks quite strong.
>>
>> Regards
>> Crispin
>>
>>
>> Dear Crispin
>> Here is some pictures of the Jiko Bomba casification cookstove.
>> The first shows the two part of the stove with pellet as fuel in the 
>> firebox
>> before fire is lit.
>> Second show the stove burning.
>> The third the same, in the end of the gasification.
>> The forth shows the charcoal stage where the pellets remains as glowing
>> carbon. A pot can be put on top of the bottom part of the stove, 
>> there are
>> three supports for that.
>>
>> Yours
>> Bjarne Laustsen
>>
>>
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>
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