[Stoves] Briquette ignition in a Vesto Junior

Fri Aug 3 02:52:54 CDT 2012

Hi Crispin and stovers,

I've experimented with top-feed briquettes quite a bit and figured out a
few points:
- the gap around the briquette as you've also found out, needs to be there,
around 3-5mm allaround, if not, theres some kind of a choking smoke coming
out at sides and the fire doesn't seem to progress well
- i think its better to have more shorter briquettes than one or two long
ones, as the gap between the briquettes provides an extra air-pocket that
seems to help the fire going - i think its due to cold air escaping too
fast through the briquette making the fire too cold, while the gaps slow
down the process. I couldn't believe what a big difference that was,
especially in side-feed briquette stove. i was mainly all kins of
briquettes, from 3-5cm to 10-12cm, but stayed with around 5-7 cm
- now comparing the top or side-feed, i found quite a few reasons to
proceed with the latter, side feed: when you insert a briquette from the
top on an existing fire, there is a much bigger fluctuation in fire volume,
higher CO emissions and you have to lift the pot while doing it. The major
difference is that with the top feed, the cold briquette mass is instantly
all exposed to the fire, while in side-feed the briquette burns inside-out,
starting through the hole, which gives a much steadier flame volume and way
less smoke and CO emissions, also the briquette is always inserted where
the fire is the coldest - from the side.

Top feed was my first briquette stove in Malawi, with 16cm briquettes outer
diameter and cca 5cm hole. What did work much better than, was keeping the
fire going and manipulating the steady volume with few wood-sticks from
underneath, functioning pretty much the same as the 3-stone fire, which
locals were familiar with. the sticks were there just to regulate the
volume, not using much of them, while the briquette was the main fuel. This
helped a lot also if the briquettes are of worse quality or still a bit
wet. Also it was easier to persuade local people for using briquettes as it
was an easy-learning curve. if the briquettes were good and they acquired
the skill, then they would be able to drop the wood altogether

I haven't gone in this direction yet, but i'm sure that with some
air-supply regulations, it would be possible to improve the top-fed stove
as well!

I would be happy to hear about how the locals are satisfied with the stove
you're posting about and if the fire volume fluctuations is not a big
problem for them! Would be also great if you could post some photos of the
whole stove body

Regards,

-- 
*Rok Oblak, MAA *

rok.stoves at gmail.com
www.holeyroket.com

Gregorciceva ulica 5
4224 Gorenja vas
Slovenia

On Thu, Aug 2, 2012 at 10:02 PM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Briquette-Burning Friends****
>
> ** **
>
> George of the Jungle in the Gambia has provided some pretty interesting
> photos of the ignition and development of a fire in a Vesto Junior. The
> fuel is a hardwood sawdust bound by shredded, soaked typing paper. The fuel
> was made in a press designed by Richard Stanley.****
>
> ** **
>
> The important dimensions are that the combustion chamber is 125mm in
> diameter and the briquette is 110mm. They are about 75 mm high. Burning two
> at a time (it can stack 3) looks like this:****
>
> ** **
>
> [image: Description: cid:image009.jpg at 01CD70C7.93854540]****
>
> ** **
>
> [image: Description: cid:image010.jpg at 01CD70C7.93854540]****
>
> ** **
>
> [image: Description: cid:image011.jpg at 01CD70C7.93854540]****
>
> ** **
>
> [image: Description: cid:image012.jpg at 01CD70C7.93854540]****
>
> ** **
>
> [image: Description: cid:image013.jpg at 01CD70C7.93854540]****
>
> ** **
>
> [image: Description: cid:image014.jpg at 01CD70C7.93854540]****
>
> ** **
>
> The fire is a combination of a gas production zone with restricted primary
> air and a secondary air supply zone, with enough clearance around the
> briquette to prevent the outside of the fuel being kept away from the fire.
> If the briquette is tight in the chamber, it does not burn properly at a
> decent rate. Basically, it has to breathe.****
>
> ** **
>
> The flame space is sufficient to allow the combustion to be mostly
> completed before the hot gases hit the pot.****
>
> ** **
>
> George will report later on the burn rates, fuel savings and cooking
> efficiency.****
>
> ** **
>
> Regards****
>
> Crispin****
>
> ** **
>
> PS A Vesto Junior is a Vesto without an air controller. This project was
> designed around a humid tropical environment, locally produced biomass
> briquettes and a stove that will be largely manufactured locally to a
> specified design.****
>
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