[Gasification] CO2 recycling

Fri Oct 5 21:24:39 EDT 2007

Jim ,

The loaded down draft gasifier, uses a considerable amount of
calories in bringing about the desired reactions needed to make gas.

Let us assume an unconventional arrangement for extracting
gas from biomass.

We have a sealed container loaded with “fuel” It is
supported by a radial heater taken from a cooking range , this being the
“grate”

Immediately above, and annularly disposed around this grate,
is a circular hollow doughnut some 4” in height with an outer diameter of say
14”.

This doughnut is a non resonant reaction chamber, having, an
off set inlet connected to a wave guide, being fed from a domestic microwave oven
magnetron.  

. The inner lining of the “doughnut” is insulated with a
dielectric insulating material. This annular enclosure will retain the plasma.  

Initially,  we will bring
the grate up to red heat by externally providing current.  This will cause the fuel to vaporize, and
pass through the reaction chamber.

At this point, the RF is turned on. Igniting the volatile gasses
within the reaction chamber, together with the metered control of steam

the reformation process in this high temperature plasma can perform all of the
desirable reactions we require to synthesize our gas requirements.

The heat generated within the doughnut will be conducted to
the fuel within its annular space. Eliminating the requirement for further
power to the grate.

In order to control the high temperature within the reaction
chamber, a controlled amount of H2O will be added to the plasma, this will be
cracked. 

The system is sealed; there is no down draft of air. The gas
is the product of cracked water together with the fuel being gasified by plasma.

The heat generated in the reaction zone will destroy the
complex compounds responsible for tar etc. much of the biomass will be reduced
to carbon, which in itself is a microwave absorbent.

I particularly liked the grape in the micro wave oven
experiment, where the pip carbonizes and the juice turns to hydrogen and
oxygen. 

 http://www.youtube.com/watch?v=vb6WCkC0K1I&feature=PlayList&p=A5B4897404F34F8B&index=7

Now comes the energy cost of obtaining this reaction.

First and fore most, none of the “fuel” we are converting to
gas will be used for the breakdown or preparation of pyrolisis for reaction
zones. There need be no “input gas” such as oxygen or nitrogen.

The water added to the reaction zone will provide the needed
oxygen and hydrogen.

The reaction is going to be carbon hungry.

The fuel needs to be brought up to temperature fast, the
required heat will be provided by the engine exhaust, and the processed gas,
together with the radiated heat from the reaction chamber, these heat gradients
will assist in the pyrolization process.

The exhaust CO2 could provide some of the needed heat and carbon
to the process.

This gasifier, Generator and engine will have to be a combo
for math analyses. 

AT least 1.5 kw, to run the gasifier plasma.

Let’s say the output of our engine puts out 10kw of work. That
means there is at least 20kw of heat which can be added to the raw biomass in
the gasifier.

The reaction chamber will be running a 5000+ K, The
conducted heat from this insulated chamber will be at least 1000 deg and in
contact with the fuel.

It is difficult to control the out put of the magnetron. Most
systems use the digital approach, OFF & ON. I am still researching this.

One last word for those who feel plasma gasification is
science fiction.

It is already here. An electrode less plasma is just one
jump ahead.

GF

-----Original Message-----
From: jim mason <jimmason at whatiamupto.com>
To: Discussion of biomass pyrolysis and gasification <gasification at listserv.repp.org>
Sent: Thu, 4 Oct 2007 3:40 pm
Subject: Re: [Gasification] CO2 recycling

gf, your musings on plasma and microwave gasfication are very
interesting.  i look forward to seeing how these schemes might work
out re the realities of energy input and output.  thermodynamics is a
relentless master.  there is no duping the king of the castle, now
matter how clever our dancing.  nontheless, please continue.  can we
in any way define and divide some of the experiments here towards
faster answers?

co2 recycling is clearly interesting to the degree that we have
adequate heat in the char zone.  such is harder in biomass gasfiiers
for the reasons doug elaborated.  note also that the endothermic
energy required to reduce co2 is greater than that for h2o.  this is
an oft forgotten fact.  i do not have the chart in front of me, but i
remember it taking about 20% less energy to reduce water thermally
than carbon dioxide.  the resulting fuel hydrogen fuel is more
attractive for engine situations, as it will support higher rpm, given
the faster flame front of hydrogen.

so all other things being equal (which they are not), it is better to
inject steam to partake of "excess" heat in the char zone, than
recycle co2 into the char zone.  note that most ICs also have a waste
heat stream in the form of  hot water and/or steam.

either way, it is deceptive to think of either h2o or co2 as fuel.
both are the end products of combustion.  they both have elements that
if separated or reformed, can again be fuel, but doing so requires an
addition of energy, which is exactly what you are trying to get out.
you can't get more energy out of these molecules than what you pack
in.

the potential "free energy" here is the waste from the internal
combustion engine.  as we are working with a gasification system that
requires process heat, the waste heat from the engine is useful for
us.  we can essentianlly increase the thermal efficiency of the engine
by recycling its waste heat for drying, pyrolysis and blast preheating
in the gasifier.  thus reducing fuel consumption.  note that IC
exhaust heat is not high enough to directly heat a char zone.  but it
is high enough for all the other zones.

integrating all these systems is one of the very low hanging fruits in
the world of small scale gasification.  contemporary sensors and
embedded control makes it much more easy than back in kalle's days.
nonetheless, kalle was on to most all the right ideas and
opportunities in small scale gasification.  i'm trying to continue
from where he left off.

jim

On 10/3/07, Daniel Chisholm <dmc at danielchisholm.com> wrote:
> On Tue, 2007-02-10 at 22:27 -0400, gfwhell at aol.com wrote:
> > ... CO2 as "recyclable" ... seems to have been missed by most.
> > The addition of steam in the proximity of hot carbon is about all that
> > is needed to produce CO.+H2
> > Maintaining the  temperature is crucial for this reaction which is,in
> > itself,  endothermic. I have been researching the possibility of
> > providing the additional heat necessary to maintain this reaction
> > which will allow the hot exhaust gas from an engine to be returned for
> > recycling. I believe it will be possible to eliminate much of the
> > nitrogen entirely from the reaction zone.. For some years now,  gases
> > have been refined and processed with the use of microwave plasma. the
> > temperature of which can reach 10000K,.
>
> Just be sure that your process makes sense when operating under the
> following rules:
>
> 2 - heat flows from high temperature to lower temperature (so the heat
> in a 400-600C engine exhaust gas stream won't flow into an 800-900C
> reaction zone - but it can be used to preheat incoming reactants)
>
> 3 - non-thermal energy is more valuable than thermal energy, typically
> by a factor of 3X-7X.  (So any electricity, shaft power, etc that your
> process uses must produce more than 3X-7X as much heat in the end, in
> order for your process to be profitable).
>
>
>
>
>
> --
> - Daniel
> Fredericton, NB  Canada
>
>
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>

-- 
--------------------------------------------------------------------------------
jim mason
website: www.whatiamupto.com
current project: mechabolic (http://www.mechabolic.org)
announce list: http://lists.spaceship.com/listinfo.cgi/icp-spaceship.com

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