[Stoves] Jatropha and its future

[Crispin Pemberton-Pigott]

Dear Roger

 

>I am curious if this "log" was an extruded or pressed product. 

It is a pressed/extruded log (same thing) using no binder save the lignin in
the material. The diameter is about 110 mm and the length about 250/300mm -
will check.

The colour is 'pine' so I would say, golden.

>.The moisture content is known to be about 8%. 

It varies with storage. The production process dries the wood almost
completely (hot) and it picks up some moisture after that.

>It is approx 8500 btu/lb, 

That would be 8500 x 1055 x 2.2046 (lbs/kg) = 19.8 MJ per kg which is
definitely a 'dried' energy content.

With 8% moisture it is about 17 MJ/kg for typical hardwood.

>.and gives a burn time of up to 12 hours (in our stove) 

It is important that you express this burn time together with a kW rating
(or BTU if you can work that out instead).

A couple of contributors explained this before but here is a repeat:

8500 BTU's / lb in the 2.2 kg log.

That is 8500 x 1055 x 2.2 = 43,493,000 Joules total heat content (43.4 MJ)

One Watt is 1 joule per second of energy.

12 hours = 12 x 60 minutes x 60 seconds = 43,200 seconds.

43,493,000 Joules / 43,200 seconds = 1007 Watts average heat output on a
continuous basis. That is the same as saying 'the power output is 1 kW'
average.

>Funny thing is I get more smoke at a higher heat output than the medium to
lower end. 

That has to do with the availability of secondary air and the combustion
environment (including its physical size).

>Estimated [heat] output at 27,000 high, 5,000 btu low output. 

Per what? Per hour? Per day? It is not clear. 5000 BTU's is 5.275 MJ. If
that was per hour, it is 1.465 kW. The 27,000 = 7.9 kW. If it takes 12 hours
to burn the log, (and in fact there is still some coals left) it averages 1
kW heat output average.

An earlier point I was making about Mongolian space heating is that the
homes need between 4 and 12 kW on a continuous basis. We would need to burn
at about your 'medium' power level continuously to keep the place warm. The
largest stoves we work with in homes are 20 kW, equivalent to about 1.3 kg
of wood per hour (depending on the moisture content).

Any stove sold there has to be able to cook a 16 inch diameter wok, and to
boil 9 litres of water (in the wok) in less than 1.5 hours from ignition (or
it won't be considered at all for the programme). Some stoves can boil it in
30 minutes, but 90 is the upper limit. Mass production facilities are
available. It has to retail under $150.

Good luck with the EPA testing and alla that. Please keep us informed about
how it goes.

Crispin

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