Ken & Mark, the experience that I am relating had no science in it at all.
The Generator was started at around 4pm and ran until lights out at 10pm, a
matter of 6 hours a day. There was never any regularity or steady state
conditions to measure.. If for any reason there was a heavy load then the
engine governor opened up and it dragged more gas and the gasifier
delivered more and everything got hotter. The 'Daisy Chain. as Mark
called it had a degree of self regulation, and we always ran it with a
good deal of reserve power potential. I would suspect if we tried to get too
close to the point of maximum efficiency and optimum conditions we would
have had to start throwing extra load in and out of the sytem to maintain a
tigher balance. and steady state conditions. I am sure that there was also
a measure of drying that happened as the wood hopper cooled down
during the night after the evenings run. But Heh, the wood was free, it
was gathered every day by a work party of school boys with bush knives who
went down the road to an old derserted airfield from WW2 and came home
with 5 poles of Leucaena scrub and pushed them into an automatic docking
saw which dropped the nuggets into a wheelbarrow which they ran up a ramp
and tipped their contribution into the open top of an old 2000 gallon water
tank on a stand, which had a cone shape made for the bottom with a
manually operated slide. The bottom of the hopper was high enough to push
in another wheel barrow underneath and take out a load of dried wood and
wheel it up another ramp to tip it into the top of the gasifier, whivh did
have a lid.. I can't quite remember the timing of the regular filling the
gasifier but it was one of those regular monotonuous jobs which Island
folks seem to love and would have had me with a book proped .up on the side
of the hopper.
Ken C.
----- Original Message -----
From: "Ken Boak" <[email protected]>
To: "Discussion of biomass pyrolysis and gasification"
<[email protected]>
Sent: Sunday, December 19, 2010 10:47 PM
Subject: Re: [Gasification] Drying fuel with IC exhause and
otherpleasures...
KenC,
Thanks for your description of your drying fuel experiences.
It's my understanding that the hot exhaust does two things:
1. It provides the heat to drive the moisture out of the structure of the
wood
2. It provides a transport mechanism to carry the liberated water vapour
out
of the drying vessel
To confirm the physics of this we need a chart showing the saturated gas
figures for nitrogen (or air) for temperatures from 100C to 700C, showing
the quantity of water which can be held in saturation for a specific
volume
of the exhaust gas at certain temperatures. The hotter the gas, the more
water can be held in saturation.
If the exhaust emerges from the manifold at 400C, and it is not saturated,
then it will remove moisture and cool to the point where it becomes fully
saturated and an equilibrium will be reached.
The saturated exhaust will then find its way out of the vessel, taking its
water load with it.
A new volume of non-saturated exhaust will be emitted from the engine to
replace it.
Over the course of time, the dividing boundry line between dry wood and
wet
wood will move slowly away from the exhaust manifold and towards the
exhaust
drying vessel outlet.
The drying vessel should be placed on a slope, so that condensed water
vapour on the cool vessel walls on startup has the opportunity to drain
away.
Ken B.
On 19 December 2010 07:28, Ken Calvert <[email protected]> wrote:
Mark, sure you can watch the condensation from an engine ticking over,
and which you have probably just started, but I challenge you to bore a
hole in the floor of your car and point a IR beam thermometer down on the
exhaust pipe when you are doing >80mph. You wouldn't be worrying about
relative humidity then.
Its apples with apples, not iceblocks out of the frig!
Ken C.
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