[Stoves] Coal stoves

[Crispin Pemberton-Pigott]

Dear Anil

+++++
>Last week I was in Eastern India visiting the rural areas of West Bengal
and
Jharkhand states. I travelled in 300 kms radius of Kolkata. Most of these
areas were extremely polluted with smoke from coal stoves. The air was
difficult to breath and the eyes burnt with the smoke. 
+++++

I am working on exactly that problem.  Fortunately we have support from all
over to get something done here in Ulaanbaatar.

The basic requirements to make an improvement are:

1. A testing protocol that produces useful numbers for space heating (in our
case) including combustion efficiency, thermal efficiency, emissions factors
and stack loss. It is all but impossible to burn coal properly without a
chimney or a fan, one of the two.

2. A stove designer or trainer who can introduce very different, more modern
and cleaner burning technologies
3. Fuel assessment to see how cleanly the fuel can be burned so as to
provide a benchmark against which improved stoves can be rated.
4. Producer training and support to test new devices, both for emissions and
thermal performance and user acceptance.
5. Possibly fuel processing, be it sizing, grading, briquetting,
devolatilisation, semi-coking, drying (etc?).

The main challenge is to transform people from batch lighting and re-loading
to a 'little-by-little' (LBL) approach where the coal burns at a given rate
and is constantly refuelled by gravity or burns downwards in a cartridge.

Technologies suited to this are down-draft and side-draft stoves, or if they
are batch loaded, top lit updraft stoves like John Davies' packed bed
gasifier.

It is most likely that side draft stoves will in the long run be the
simplest to build and easiest to light and run.

Their emissions are determined by the combustion efficiency (which can be a
dramatic improvement) and sulphur content about which not much can be done
as it is in the fuel already.

We are fortunate here in that the local coals have very low sulphur content.
It is likely you are smelling unburned coal as much as you are smelling
sulphurous things.

One of the main polluters in Viet Nam and China is the bottom lit briquette
stove.  One way they can be improved is to have two types of briquettes: one
for lighting (higher volatiles) and ones for refuelling (more like
anthracite) so once the initial smoke plume is lower; there is not much
produced with adding a briquette.

There are about 300 years' worth of stove designs for coal, some of which
fall into the categories described above.

Regards
Crispin