[Stoves] Burning wet wood

[Paul Olivier]

See comments below.


On Thu, Jun 13, 2013 at 10:01 AM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Paul O****
>
> ** **
>
> *>*It is so inefficient to burn dirty coal or coal of a high moisture
> content.****
>
> ** **
>
> Please define a ‘dirty coal’. I have used many coals and they all made my
> hands dirty. I know you mean they burn badly in devices they are not suited
> for, right? coal
>

I worked for more than 20 years in coal preparation. I designed washers
that separated clean coal from dirty shale. I did not work with run-of-mine
coal, but what is referred to in the USA as gob piles. I worked in the
reclamation of abandoned mine lands. The separators that I designed
extracted a clean coal from a shale of a high ash content. If you say
"dirty coal" to someone in the industry, they will understand exactly what
you mean.

****
>
> ** **
>
> >Some say that there is no such thing as a bad fuels, just bad stoves. ***
> *
>
> ** **
>
> I can certainly say that from personal experience of designing coal stoves
> and advising coal stove designers.
>

Yes, there are fluidized bed gasifiers and rotary kiln gasifiers that can
handle just about anything. I once worked with Norman Bishop who had a lot
of experience in the direct reduction of iron ore. Norman designed a rotary
kiln gasifier powered by an oxy-fuel burner. This gasifier handle could
automobile shredder residue and car tires isolated by means of my dense
medium separators. But the cost of this gasifier at that time was 10
million US dollars. Not something that I could install in my kitchen.

> ****
>
> ** **
>
> >Just ask anyone in the coal industry if there is any such thing as a bad
> coal.****
>
> ** **
>
> Let us hear from them what a ‘bad coal’. I would like to know.
>

Every body in the trade can tell you what a bad coal is, and they usually
have a good idea of what is needed to prepare it into a good coal for a
specific purpose. There are almost no coals coming out of the ground that
must not be prepared.


> ****
>
> ** **
>
> >They will immediately point to many things that could make coal unfit
> for combustion. ****
>
> ** **
>
> Combustion in what? Good grief. If you build a device to burn anthracite
> and load lignite into it there will be all sorts of smoke and CO. If you
> put diesel into a gasoline engine you get a similar result – for very
> obvious reasons. Is anyone surprised?
>

You give examples that trivialize my central point. Coal must be prepared
for a specific end use, and not all coal can be used in every application
where coal is consumed.


> ****
>
> ** **
>
> >They will point to things such as moisture content, ash content, sulfur
> content, grindability, ash fusion temperature, grain size, MAF calorific
> value, volatile matter content, fixed carbon content and much more. ****
>
> ** **
>
> Those are all issues that can be addressed when designing a combustor.
>

But, Crispin, just about all coal must be prepared. Also there is extensive
blending going on. Combustors generally are not designed to handle
everything.


> When trying to make a short, hot, small, fan powered multi megawatt
> combustor, they are very careful to pick a coal to match exactly.
>

Yes, but to get the right coal to match exactly the design of the
particular combustor, extensive preparation is required. Often a lot of
blending takes place.

> ****
>
> ** **
>
> Europeans think they are really good at burning coal – centuries of
> experience, right? They bring their power station combustors to South
> Africa and show them off. They all fail. None of them work. Why? Lots of
> South Africans build coal burners that work really well. They also have
> years of experience: *designing combustors that work with their local
> coal! **Quelle surprise.*
>

Yes, but please do not tell me the South Africans do not do extensive coal
preparation. I worked with South African coal companies for many years.
These guys know their coal well, and they know how to prepare it.

> * *****
>
> ** **
>
> The new power station Eskom is building right now can burn coal with 40%
> ash. A European ‘coal expert’ will tell you that is a ‘lousy, unburnable
> coal’. It works fine if you have a clue what you are doing.
>

Yes, there are power stations designed to burn coal of a 40% ash. But often
they have little choice in doing so. The ash is inherent, even at the
lowest densities. I once worked in Serbia where at a 1.2 density the coal
had an ash content of about 35%. But at a 1.6 density the ash content was
65% and could not be burned. Still the Serbians were forced to do an
extensive preparation of their coal.

> ****
>
> ** **
>
> >Imagine how inefficient the coal industry would be if it had to design
> power stations around each type of bad coal presented to it.****
>
> ** **
>
> Imagine trying to design a biomass stove that was tuned to each type of
> fuel that happened to be available…oh wait…that is exactly what is
> happening on this list! What a surprise, again. Is that not exactly what
> you are doing?
>

Not at all. That is precisely what I am opposing. Crispin, I challenge you
to put coconut powder or fine sawdust into the best TLUD that you can
design. Then tell me if air is going to flow up through this fine biomass
in a uniform manner. Tell me that there will be minimal CO2 present in the
outgoing syngas. Also the device you design has to be small and easy to
use. It cannot occupy an entire corner of your kitchen, and no part of it
should be situated outdoors. Go for it.

However, if we pelletize the coconut dusk or the wood shaving, air flows up
through it in a uniform manner, and we have an incredibly simple reactor
that weighs less than 1.2 kg. It can be in continuous operation for up to
1.5 hours.


> ****
>
> ** **
>
> >If we prepare fuels correctly, designing stoves is so easy. ****
>
> Really? If you have unprepared fuel, but you know its characteristics
> really well, designing a stove to burn it cleanly is easy.
>

Ok, then show me a TLUD operating on loose coconut dust or fine sawdust.
There should be relatively little CO2 in the syngas, and it should be
relatively inexpensive. It should also make a uniform biochar. If you've
got such a device, I would be thrilled to promote it. Also it has to be
made of high quality materials, and it has to be in a price range that most
people can afford.

> ****
>
> Why do ethanol stoves stink? Have you ever smelled a Clean Cook stove?
> That is a highly prepared fuel. Everyone thinks designing an ethanol stove
> is really easy because ‘the fuel is clean’. Rubbish. There is no such thing
> as a ‘clean fuel’ and the proof is buy an ethanol stove and light it in a
> closed room. Measure the CO. Fuels do *not* a clean burn make, it is a
> match between the stove and the fuel and the operational method.
>

But some fuels like pellets are easy to gasify, whereas some fuels like
coconut dust are very, very difficult. Rarely do we come across any biomass
as uniform as the rice hull. Into this class I might also place the coffee
husk.


> ****
>
> >We focus far too much on designing stoves and surely not enough on
> preparing fuels. This is the big mistake that most funding organizations
> make in their promotion of clean cook stoves.****
>
> We do not focus enough on how to design good stoves and hope that
> preparing the fuel will compensate for our collective ignorance.
>
No, but we can make things infinitely complicated and expensive if we do
not prepare fuels correctly. Also, do not overlook the fact that it takes a
intelligence to prepare fuels correctly. We need intelligence in both fuel
preparation and stove design. There is nothing ignorant about those engaged
in fuel preparation. We sorely need their intelligence and expertise. To
overlook their contribution might end up making us look dumb and foolish.


> Commercial companies burn all sorts of things very well. Sometimes it
> involves fuel selection or preparation. But it always involves a careful
> balance of the combustor and the fuel properties.
>

Crispin, every coal that comes out of the ground is different from any
other coal, and every consumer of coal understands this. But without
minimal coal preparation, not a single power station could function
correctly. Sometimes the preparation is minimal, but there is always
preparation.

> ****
>
> The Japanese are burning kerosene with no flame at all. Eskom is burning
> coal with 40% ash. The Brits are burning car tires super clean and
> recovering the metals from the gas stream.
>
I understand all of this quite well. We put car tires in the 10 million
dollar gasifier that I had worked on with Norman Bishop. But are we to put
such gasifiers in our kitchens?


> The Mongolians are burning 30% moisture lignite with 50% volatiles cleaner
> than a Philips fan stove.
>
Ok, then put Mongolian coal, of a 30% moisture content and of all shapes
and sizes, into a TLUD, and tell me if you are going to get a beautiful
flame with no CO2 formation in the synas. If all you've got is such coal,
then I laud you for burning it. But I am not focusing on Mongolian coal,
but on the billions of tons of agricultural residues that abound right
across the face of our planet.


> Read the literature: all four are heavily criticised as being ‘dirty
> fuels’. There are thousands of negative references as people who have
> little idea what they are talking about parrot each other’s ignorance.
>
****
>
> Of course power stations are built to deal with the available coal types.
>
Yes, but every coal type is prepared, often time quite extensively.


> Just like a TLUD rice hull gasifier. It is a one-trick pony. Nothing wrong
> with that.
>
The TLUD works superbly on both rice hulls and coffee husk because these
materials are uniform and generally do not require preparation. When
hulled, coffee cherries and rice hulls are at a 12% moisture, and air flows
up through them within the reactor in a uniform manner. I venture to say
the TLUD will work well on most types of irregular biomass provided they
are properly prepared. This measn that the one stove could handle almost
any type of properly prepared biomass.

Thanks.
Paul Olivier


> ****
>
> Regards****
>
> Crispin****
>
> ** **
>
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-- 
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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