Re: GAS-L: Re: Pellet stove and Pelletizing Switch Grass

["*.English" <english@adan.kingston.net>]

> On Sun, 21 Jan 2001 16:50:15 -0500, Alex wrote:

> Where do you think it differs from a second generation stove then?

Andrew,
I am unsure what you mean by "a second generation stove". Perhaps 
Phase Two EPA. I have yet to actually see one burning. The people who 
have, say that its flame is very different from other pellet stoves. 
I think, but I am not sure, that the top fed version, may be the 
first stove to have no under fuel air supply. All the air comes in 
above the fuel. That doesn't necessarily mean that there is no air 
contacting the fuel as the air could drop down. What exactly 
happens, I don't know, however it appears as though this is how ash 
slagging and fly ash is avoided. 

> I am intrigued by the differences in particulates in the flue gases
> between understoked and over stoked pellet stoves

Could you point me to this reference. I looked for it, but did not 
find it.
 
> What about the talk of controlling pyrolysis temperature in the lower
> part of the combustion chamber (I hardly think is deserves the label
> of gasifier, it looks like an updraught device not far removed from a
> bonfire)? If the temperature is kept too low the bottom part of the
> fire merely pyrolises the material falling onto it in the combustion
> product of the charcoal. If the charcoal layer is deep enough (20
> particle diameters using Tom Reeds rule of thumb) and hot enough (and
> it looks hot enough in mine) then the pyrolysis takes place in a flow
> of largely nitrogen and CO.

What's in a name? It could be called a close-coupled gasifier based 
on the conceptually air starved fuel. It is supposed to operate with 
a very shallow fuel bed.

> I would be interested to know if anyone
> has monitored the CO:CO2 ratio in the offgas from the top down stove
> prior to the secondary flame. 

I could do this with a little dilution to bring the CO into the
instrument's range  and a lot of filtering of condensibles.

> And a major attribute of a pellet system to my mind is that it can be
> switched off to conserve fuel. A problem with conventional stoves
> seems to be that being batch loaded fuel is wasted after cooking is
> finished 

Not necessarily. I have stopped the top down process before 
completion buy shutting down primary air. After letting it cool there 
was an untouched layer of fresh pellets in the bottom, covered of 
course with charcoal pellets with only a thin layer (<2 cm) of brown 
pellets inbetween.

> 
> Joacim made a very relevant point on the energy account, in general it
> is not yet feasible to use biomass as the source for generating the
> motive power to make the pellet.

I understand what he is getting at. We need an affordable efficient 
one hundred horsepower pellet fired heat engine and use for the waste 
heat. Then its full steam ahead.

I think REAP is claiming that the pelleting can be done with biomass 
energy using the  currently under utilized steam power capacity from 
bagasse  at existing sugar mills. 

I wonder if pellets could be a heat  battery helping to store any 
unused power production during fluctuations supply and demand. 
How fast can these machines start and stop.

What I am hearing now is that pellet demand is very close to out  
pacing supply in North America thanks to  current oil and gas heating 
cost. They seem to be holding the price steady, but quality is less 
consistent.  It has been their mantra that pellets are the only fuel 
which hasn't seen a price rise in ten years. 

Alex


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