[Stoves] Thick wood and MC in micro-gasifiers was Re: Smoke-free biomass pellet fueled stove

[Frank Shields]

Dear Crispin, 

<snip>

 

I was not specifically looking for the maximum total energy though of course
I have an interest in it. I am trying to track down the 'extra' energy that
lies between the missing char (burning wet fuel) and the energy needed to
dry the fuel. I was going to make a chart to post here showing the amount of
extra energy involved but have been travelling.

 

So how would you suggest doing this? I would think eliminating the secondary
air (and combustion) to be able to test the pyrolyzed gases formed (during
primary combustion) as they exit to determine the form the carbon is in (CO,
CO2, Particulate-C) would be useful info. Forget the hydrogen for now. Would
the change in increased volume of gas produced during primary combustion be
useful info?  That is; determining the (total amount of gas leaving the
secondary) - (the volume of air pumped in) = (the gas produced from the
fuel).

 

 

To put numbers on it, we often reach 2,000 ppm H2 in the stack when there is
plenty of O2 available, a healthy fire burning (wood under coal) and the
coal is igniting just fine. The H2(EF) which means the undiluted hydrogen
concentration reaches >15,000 ppm. It is very strange to watch a burning
coal+wood fire inside an enclosed stove that cannot ignite the hydrogen
emerging from that same fire. 

 

Not enough heat, hydrogen produced outside the Hot zone, some other chemical
reaction sucking up the available heat (evaporating water), test equipment
with a positive interference.  

 

 

One of the metrics we watch is the ratio of CO:CO2 as you would expect,
however we also watch the CO:H2 ratio. Both gases indicate poor combustion.
There is nearly always some H2 in the stack and when it goes high, it
becomes interesting. Even very late in a coke/charcoal fire there is some H2
present. Ditto for H2S and SO2 which move opposite, in concert

 

Every conventional explanation is that there is no water gas shift reaction
taking place, even though the conditions for it are present. This does not
add up. The reaction was deliberately created in gas plants, why should it
not take place when conditions are right in a stove?

 

Question that may seem unrelated: Does the ThermoWorks IR heat detector work
through glass to measure the heat on the other side? Most likely not but
being hopeful. I have a glass gasifier I use for experimenting. I can
arrange in several configurations and watch the flame front for doing such
experiments. I can burn or collect out-gas (tedlar bags) but have limiting
equipment to determine make-up. May be able to monitor CO2 real time and
filter through glass filters to determine particular carbon in outgas using
Leco CHN.     

 

But you talk about 'coal' along with biomass. Wonder how all that differs.
Can coal be used in a TLUD? 

 

<snip>

 

In very brief, the fuel consumed by a stove is the amount of raw fuel it
takes to perform some task assuming that the task is repeated, i.e. one of a
series of identical burns. The thermal efficiency overall is the task (work
done) divided by the heat potential of that quantity of raw fuel. When
applied to ordinary stoves the answer is pretty much the same as any water
boiling test, for example. However for char producing stoves where the char
mass is a significant fraction of the initial fuel, the fuel consumption and
thermal efficiency are significantly changed, often dramatically so. They
more or less match the real numbers observed in the field during, say, an
uncontrolled cooking test (UCT). The problem is at present the calculation
methods do not consider that stove would every produce large amounts of
charcoal so the calculated results are (erroneously) far from the real
values.

 

So it seems the Stove needs be:    ((WBT) + (biochar produced) = (wonderful
rating))

 

Regards

 

Frank

 

Frank Shields

Control Laboratories, Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

 <http://www.biocharlab> www.biocharlab.com

 

 

 

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