[Bioconversion] Veg Lister - torrified woodcips

Tue Nov 7 03:36:53 CST 2006

Ken & list,

First step is to experiment by passing the exhaust gases directly through
the woodchips to pick up the volatiles in the exhaust gas stream.  It will
then be a case of identifying the main constituents of the exhaust gas
mixture to see whether it is still of any value to feed back through the
incandescent zone of a gasifier.  It's still going tobe around 80% nitrogen,
with the other 20% made up from a mix of CO2, CO, CH4, H2O, ethane, ethene,
acetylene, phenols, formic acid, acetic acid, methanol and so on in trace
amounts.  It's going to contain more chemical  calorific value than the
diesel exhaust, but at a lower temperature.    I am looking at the diesel
exhaust generally as a transport mechanism for delivering thermal energy and
gaseous reactants to the torrefier and gasifier.  There is also a hope that
final passing the exhaust through incandescent charcoal will reduce some of
the undesirable compounds and odours in the exhaust gas stream - veg oil
burns with a very distinct odour, and not necessarily to the taste of the
neighbours!

I imagine the torrifier/dryer as a separate unit to the gasifier. In this
way it would be possible to torrefy a batch of woodchips, without
interfering with the charge currently running in the gasifier.

My current  batch size is limited to around 100 litres of woodchips at a
time weighing around 25kg depending on the moisture content.  A batch of
this size is intended to keep the 3kW Lister generator dual fuelled for a
daily shift of around 10 hours.

Ken

----- Original Message ----- 
From: "Ken Basterfield" <ken at basterfield.com>
To: "'Discussion of biological conversion to fuels and chemicals'"
<bioconversion at listserv.repp.org>
Sent: Tuesday, November 07, 2006 9:20 AM
Subject: Re: [Bioconversion] Veg Lister - torrified woodcips

> Ken,
> I presume that you will torrify the wood chips indirectly with the exhaust
> gases if it is intended to recirculate the voltalies into the hearth of
the
> gasifier?
>
> Have you any thoughts on the heat exchanger design? And what sort of
volumes
> would you be processing at a time.
>
> The rest I agree is very exciting, particulerly the Diesel dual fuelling
> which seems to help solve the gas variabilty control problem.
>
> Must get on and complete my Fluidyne gasifier.
> Ken
>
>
>
> I've stopped 48,061 spam and fraud messages. You can too!
> Free trial of spam and fraud protection at
> http://www.cloudmark.com/sig/?rc=f4n4hl
>
> -----Original Message-----
> From: bioconversion-bounces at listserv.repp.org
> [mailto:bioconversion-bounces at listserv.repp.org] On Behalf Of Ken Boak
> Sent: 07 November 2006 09:09
> To: Discussion of biological conversion to fuels and chemicals
> Subject: Re: [Bioconversion] Veg Lister - torrified woodcips
>
>
> Rex & List,
>
> A simple experiment can be done using a propane torch, and introducing
> propane into the air intake of the diesel engine.
>
> Provided that the engine governor is working and maintaining a fixed
speed,
> it will be noticed that the governor acts to close the rack on the
injection
> pump, thereby reducing the fuel (veg oil) injected.
>
> Details on the Ankur Scientific gasifier site, suggest that the quantity
of
> pilot fuel can be reduced to about 20%, when wood gas is introduced in
this
> manner.  As the calorific value of the gas is likely to be variable in
> nature, the governor will adjust the position of the injector pump rack to
> compensate.
>
> Wood gas should be mixed with air in approximately 50% ratio, using some
> sort of a mixing valve.  It should be remembered that the gasifier is
> relying on the suction from the engine to draw air through and gas out.
The
> mixing valve should ensure that the correct air ratios can be maintained
for
> efficient gasification.
>
> On the 6hp Lister, the IP rack has sufficient travel to completely cut off
> the fuel supply, so closing down to 20% injection should not be a problem.
>
> The whole question of running a gasifier with a diesel engine in dual fuel
> mode is a very exciting one, particularly when it forms part of a combined
> heat and power system, that has to cope with varying electrical and
thermal
> loads.   In Northern climates where the heat required might approach 10
> times the electricity requirement, this presents an interesting concept,
> where the gasifier can be used to provide additional thermal output when
> needed.
>
> It should be remembered that the diesel engine rejects approximately 1/3rd
> of its heat energy via its exhaust. Efficient utilisation of this heat is
> key to maintaining overall system efficiency.
>
> As the exhaust gases are emitted at approximately 300 to 400 C, they are
of
> the right temperature range to initiate the drying and torrefaction of the
> woodchips, prior to them being pyrolised.
>
> Torrefaction is generally done by heating the biomass to around 250 to 300
C
> and maintaining it at these temperature for between 30 and 60 minutes.
> Torrefaction serves to drive off the volatiles, and reduce the internal
> water content of the fuel, resulting in approximately 30% mass loss, but
> only 10% energy loss, thus the energy density of the fuel is increased
from
> around 19MJ/kg  to 22MJ/kg.  The 10% of energy loss driven off with the
> volatiles can be recouperated by circulating the torrefaction gases back
> through the incandescent charcoal bed. These volatiles will be further
> cracked and this will reduce the overall tar content in the final
pyrolisis
> gases - which is a good thing if you are wanting to run an IC engine.
>
> Torrefaction alters the mechanical nature of the wood, making it more
> friable and brittle. This means that it is easier to process, and using a
> mechanical grater system such as proposed in the Kalle gasifier of 1943,
> torrefied wood could be ground within the gasifier to porduce smaller
> particle sizes - and thus more efficient gasification.
>
> Torrified wood is a stable substance and can be stored without
re-absorption
> of water and the risk of the mosisture content rising, such that would
occur
> with wood or charcoal.  Torrefied wood is a more homogenous fuel, and if
> produced from chips of the right particle size could provide an
alternative
> fuel for woodstoves and possibly pellet stoves
>
> As only 10% of the energy content is lost in the torrefaction process, it
is
> a far better fuel for barbeques compared with charcoal, and is easier
> toignite and burns with less initial smoke because the volatiles have
> already been partly driven off.
>
> So the hot exhaust of the Lister could be used to produce batches of
> torrified woodchips, which could either be used immediately within the
> gasifier,  or allowed to cool, stored and used much later for barbeque or
> heating fuel.
>
> There is approximately 2.5 to 3kW of thermal energy available in the
exhaust
> of the Lister whilst running at full output.  Whilst mostly consisting of
> hot nitrogen, there is CO2, CO, H2O and some excess air O2. There will be
> some carbon particulates (soot) and possibly some unburnt fuel. All of
these
> could be returned into the incandescent reduction zone of the gasifier for
> further utilisation.
>
> Any thoughts,
>
>
> Ken
>
>
>
>
> ----- Original Message ----- 
> From: "Zietsman, Rex" <Rex at Process.co.za>
> To: <bioconversion at listserv.repp.org>
> Sent: Tuesday, November 07, 2006 4:33 AM
> Subject: [Bioconversion] Veg Lister
>
>
> > Ken,
> >
> >
> >
> > Sorry for the slow brain... If I understand you correctly, the
> > governor will cut back the veg oil feed to the engine based on engine
> > speed. I am assuming that the fuel injection pump rack can cut back
> > that far when gas is being introduced. If so, it is a great win. The
> > trick then is to get a link between the governor and the gas feed such
> > that the veg oil contribution is about 20%. As you say, if there is no
> > gas available at the time, the fuel injection pump rack will
> > automatically be controlled by the governor to provide all the energy.
> > This is a particularly clever way of running a Lister.
> >
> >
> >
> > Rex
> >
> > _______________________________________________
> > Bioconversion mailing list
> > Bioconversion at listserv.repp.org
> > http://listserv.repp.org/mailman/listinfo/bioconversion_listserv.repp.
> > org
>
>
> _______________________________________________
> Bioconversion mailing list
> Bioconversion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/bioconversion_listserv.repp.org
>
> ______________________________________________
> This email has been scanned by Netintelligence
> http://www.netintelligence.com/email
>
>
> _______________________________________________
> Bioconversion mailing list
> Bioconversion at listserv.repp.org
> http://listserv.repp.org/mailman/listinfo/bioconversion_listserv.repp.org