[Stoves] Saving the WBT

[Frank Shields]

Dear Crispin, Ron, and all,

 

When I now think about all this it all seems so simple and obvious as the
way to do it. Not sure if others are following me in my thinking. 

All we need to do is have all start with the same Energy from a biomass and
use that as a baseline when comparing stoves. Oven dry weight energy value
minus the char in the pipe. When burning wet (real) biomass we just report
that in the 6 Box reporting sheet so a lower (or higher if the water
reaction) results can be explained.   

 

When the fuel is wet we have all that FREE energy from the catalyst that
will evaporate it IN the stove body. In fact, if one puts a cup of water in
a stove the evaporated steam hitting the pot will increase the water
temperature in the pot. Unless the steam lowers the temperature of the
secondary, or otherwise interferes with the secondary combustion, it will
add to the energy heating the water. It cost nothing to evaporate the water.


 

As for coal: I have not thought how this would work and know little about
burning coal. I would think it much like adding char to a rocket stove?
There being little secondary combustion and the stove body getting very
hot(?) 

 

In my own mind I think this is what really happens in the real world and it
seems clear to me this is the direction we should go. And if we can make it
work it would simplify stove testing immensely.  

 

Regards

 

Frank

 

 

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

 

 

 

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Crispin Pemberton-Pigott
Sent: Monday, August 19, 2013 1:45 PM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] Saving the WBT

 

Dear Frank

 

It is a difficult question to answer. Do you want the actual energy
available from a particular piece of wood or the heat theoretically
available, or what it would be if it was dry?

 

If the fuel is moist, then the gasification or the volatiles energy has to
evaporate that moisture to get it out of the way. Unfortunately the amount
of gas you can make from a bit of wood literally changes with the moisture
level because the moisture is involved in the chemistry of what happens in
the processes.

 

With respect to coal, I was not even about to get a carbon content of the
'volatiles' let alone an energy figure. 

 

I suspect you are not going to get a good answer, and whatever answer you
get is not going to be very useful in a real world problem.

 

Regards

Crispin

 

 

 

Dear Stovers,

 

 

I am trying to determine the best way to calculate the energy in the Natural
Volatiles. The sample we place in the iron pipe of the oven dried biomass we
can test or 'look up' the energy value. In the char remaining after 450c
deg. (char-ash) we can give that a value of 34.78 kJ/g. Then for the total
NV in the fuel we just subtract the total biomass from the char energy
remaining. All done in the pipe. Then use the energy calculated from the
increase temperature of the water to determine efficiency. 

 

I am still wondering what to do with the moisture in the fuel. Any
suggestions?

It is like the NV fraction but with possible varying results. As Alex
reminded me in his writings there is the water-reaction that can increase
the energy output or the LHV stealing energy from the NV. So depending on
the stove and operator working the catalyst to control the internal body
temperature the water can be a plus or minus.  My thinking now is to just
use the dry NV value as the total energy of the biomass. Like playing golf.
You have a par 5 and you can go above or below depending on your day. The
dry NV value is the value we use and we go above or below 100% efficiency
depending on how good the stove and operator controls the catalyst and if
water is included in with the biomass. 

 

>From the replies it's a bit hard to tell but it seems we are mostly all in
agreement. : )

 

Regards

 

Frank

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20130819/bd974b18/attachment.html>