[Stoves] Tar characterization
Paul Anderson
psanders at ilstu.edu
Sun Nov 13 12:43:49 CST 2016
Dear Paul M., (and Tami and all)
It is great to see you and your team putting serious inquiry and
instrumentation to the task of understanding TLUD characteristics, in
this case, about the nature of the pyrolytic gases BEFORE the secondary
combustion.
You wrote:
> Because a TLUD is more more uncontrolled than an industrial gasifier,
That is a safe statement because industrial gasifiers are much larger,
easier to control, and much much more expensive (with instruments
controls, etc.) for a few units whereas the TLUDs can be many thousands
of units. So, I agree with your statement.
Where I respectfully "disagree" is with the implied assumption that
there will be considerable variability between TLUD stoves. I
hypothesize that with a specific TLUD stove model and a specific
appropriate fuel and operation in the same way, there will be
considerable consistancy in the pyrolytic gases.
I do not have instrumentation or skilled personnel to check that
hypothesis, so I am delighted that you are considering to do that task.
*********** (What is below is known to Paul M. and others, but is
written here for general readers and students ****
Consider a known TLUD (example is the Champion TLUD by Servals of
Chennai, India, which are available for purchase in Australia, USA,
Europe and some other places, mainly thanks to Australian Paul Taylor
for promotion of distribution).
Consider "standard" pellets, as are widely available because of the
"pellet stove business" for heating, not for cooking. Great fuel,
appropriate for use in the testing.
Consider setting several (3 or 4??) standard "tasks" or operation-modes
(after reasonable time for ignition):
A. Moderate power, with BOTH a measured, metered flow of primary air,
AND the same flow but regulated only with simple control of primary
air. "Same" will be seen as equal fire power because that is set by the
primary air flow (when the other variables are controlled.).
B. High power.
C. Low power.
Collecting samples of the pyrolytic gases will not disrupt the
operations of the stove. Sufficient number of samples are taken,
compared, and the results can be known and reported.
*******************
I hope that you will do this. Perhaps others might. Good to have
replications by different places. But what I request is that IF such
work is being undertaken, please say so to this Stove Listserv so that
we can be sure that AT LEAST ONE RESEARCH TEAM does do some variation of
this work.
Of course there can be additional studies with a change of the stove or
using some other fuel.
But let us remember that even though the TLUD stoves are small compared
to the larger gasifiers, there could be ten-thousand of the same stove
model in an area with most households using basically the same type of
fuel with very similar cooking practices. The research being discussed
could be quite useful for those households and eventually some millions
that will be in similar situations.
TLUD stove technology research has moved into the sophisticated
laboratories. We know that TLUD stoves work well; now we want to
understand better and also find ways to improve their operations.
Thank you (and all) for doing research on TLUD micro-gasification.
Paul A.
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 11/12/2016 11:21 PM, Paul Medwell wrote:
> Hi Frank,
>
> Personally, I'd like a little more fidelity than a TGA and
> ultimate/proximate analysis (but without necessarily going too
> detailed). I think some interesting models of a TLUD could be
> developed with a bit better understanding of the incoming flow
> composition to the combustion zone. The gasification process is not my
> area of expertise: I'd need to speak with my colleagues about what
> they can measure, beyond the "normal" stuff. Because a TLUD is more
> more uncontrolled than an industrial gasifier, I just don't know what
> sort of starting range of species we expect to see.
>
> Cheers,
> Paul
>
> On 13/11/2016 3:26 PM, Frank Shields wrote:
>> Stoves,
>>
>> All we really need is to characterize the fuel. The moisture is an
>> easy one. Ash is an easy one. Particle size and shape is an easy two.
>> The organic fraction is what we need to work on. I’m thinking we need
>> to develop a Table of the flammable volatiles being released from the
>> Standard Combustion Chamber (SCC) using a specific biomass at
>> different temperatures when operated to simulate for a specific stove
>> type. Flammability measured per the O2 feed into that heated tube
>> (mentioned before) and measuring temperature increase or CO2 exiting.
>> So we have a specific biomass (or a representative biomass) and heat
>> in the combustion chamber using controlled heating coils and
>> controlled air flow and measure the flammability of the gasses
>> leaving. Perhaps end up with a table like this:
>> Moisture %
>> Size distribution range and uniformity coefficient
>> Size shape
>> Ash %
>> Total volatile matter % dw
>> Flammability at 450 deg. C
>> Flammability at 550 deg. C
>> Flammability at 650 deg. C
>>
>> Once we start testing and with suggestions from others I am sure we
>> will change the above as we learn more as what tests are such they
>> are shown to effect the combustion process. Any specific biomass
>> will have their own reading from the above tests. When testing stoves
>> the above results of the fuel used is reported along with the results.
>>
>> Readings of a specific nature like measuring the chemicals released
>> that change all the time means nothing. It is only the flammability
>> of the released gases thats important. And, perhaps, the pattern of
>> this flammability as temperatures in the combustion chamber or air
>> flow change.
>>
>> Each different design of a stove tested using a single fuel (single
>> mapping of flammability and characteristics) will result in different
>> degrees of success based on cooking. So it is the job of the stove
>> designer to optimize success using a fuel he/she specifics based on
>> the above tests. The fuels stay the same and the stoves modified to
>> work with a fuel. That stove can be marketed in places where that
>> fuel is available.
>>
>> I don’t see this being that hard. A local fuel that is close to the
>> established mapping that works best for Pauls TLUD (for example) can
>> be modified to fit using equipment sent to them to do the job. Dry,
>> chip, split or clean - whatever is needed. Low temperature may just
>> be interested in temperatures to 550c while Rockets need the mapping
>> up to higher temperatures.
>>
>> So no expensive or special equipment needed for testing. Only a lot
>> of research using a Standard Chamber and operated to simulate a stove
>> type. Someone needs to design and build the combustion chamber.
>>
>>
>> Regards
>>
>> Frank
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>> On Nov 12, 2016, at 7:58 PM, Paul Medwell
>>> <paul.medwell at adelaide.edu.au> wrote:
>>>
>>> Hi Tami,
>>>
>>> Thanks for the detailed response.
>>>
>>> The answer to your question is "the more we can have the better".
>>> Realistically, it would be too easy to end up with too much
>>> information and just become overwhelmed. Even if it were possible to
>>> obtain full speciation measurements of the pyrolysis/gasification
>>> products, it probably isn't practicable to use. For example, in the
>>> case of gaseous turbulent combustion there is already too much of a
>>> compromise needed for methane combustion: detailed kinetic
>>> mechanisms are often too large for CFD...obviously the problem
>>> becomes much worse for other fuels. There is a huge amount of work
>>> in the area of kinetic mechanism reductions (mainly for engine
>>> fuels), but detailed kinetics of tars seems out of the question any
>>> time soon.
>>>
>>> In the first instance, it would be interesting to see a plot of the
>>> mass spectrum of the pyrolysis/gasification products in a TLUD
>>> (before the secondary air inlets) for different operating
>>> conditions. It would also be nice to know the global C/H ratio. We
>>> are in the process of getting a new GC/MS, but only to 300 amu.
>>> We'll wait and see how that goes. The long-term plan is to include
>>> this in a model of the system, as well as subsequent experiments of
>>> the specific details of soot production in the combustion zone.
>>> However, this is all work to be done in the future.
>>>
>>> Cheers,
>>> Paul
>>>
>>>
>>> On 13/11/2016 6:52 AM, Bond, Tami C wrote:
>>>> Hi Paul, and all,
>>>>
>>>> Sorry that I have not been keeping up with Stoves discussions….
>>>>
>>>> We have fussed a bit with trying to characterize the organic matter
>>>> emitted from wood combustion.
>>>>
>>>> What kind of characterization do you want? Full speciation is
>>>> well-nigh impossible. But one needs to start with the question of
>>>> what you want to know and why?
>>>> The problem is that this stuff is complex chemically and doesn’t
>>>> take well to matching with standards.
>>>>
>>>> Brief summary of what I know:
>>>> - GC/MS is really hard for characterization because it is poor at
>>>> identifying compounds that are large (molecular weight) and polar.
>>>> Wood organics are both. You’ll get the light organic material, but
>>>> that’s a very small fraction of the emissions. You can get into
>>>> derivatization of the emissions before GC/MS and that may get you a
>>>> little more. See all Jamie Schauer’s, Wolfgang Rogge’s work. Most
>>>> of it ends up being classified as “UCM” (unresolved complex mixture).
>>>> - FTIR— have tried a little. Although it nominally gives you
>>>> functional groups, and occasionally you can see differences between
>>>> one kind of wood or burning condition and another, it’s not very
>>>> quantitative. Plus there are a lot of overlaps between the
>>>> interesting functional groups, so you can’t distinguish some of them.
>>>> - 1NMR— kind of like FTIR— you can sort of see functional groups
>>>> and that’s about it.
>>>> - UV-Vis— used for humic matter (and some “tar” isn’t far off
>>>> that)— Again not quantitative, rather just gives a sense of how
>>>> strong an absorber it is. You won’t see any structure as you do in
>>>> UV-Vis of individual compounds. There are so many compounds that
>>>> the entire spectrum smooths out.
>>>> —> From our UV-Vis work we found that most of the stuff
>>>> dissolves in methanol, not hexane not water. (Chen & Bond, Atmos
>>>> Chem Physics 2010, open access)
>>>> - 13CNMR— which can get at the carbon skeleton rather than
>>>> functional groups… tough. You need HUGE sample sizes and they don’t
>>>> stay suspended because anything concentrated enough to measure
>>>> wants to precipitate. We ended up using DCM, I think— I’d have to
>>>> check. And then, the result was not all that interesting: we again
>>>> couldn’t distinguish the unsaturated bonds, e.g. aromatic vs
>>>> conjugated but linear bonds.
>>>> - LC/MS— expensive and full of artifacts— I’ve never gotten into
>>>> it. Too expensive and haven’t seen the benefit, although I’d be
>>>> interested if someone tried.
>>>>
>>>> The question, again, is what you want to know and why. If it’s some
>>>> kind of physical property of the emissions, you’d be better off
>>>> measuring that.
>>>>
>>>> Tami
>>>>
>>>>
>>>>
>>>>> On Sep 2, 2016, at 12:22 PM, Paul Medwell
>>>>> <paul.medwell at adelaide.edu.au> wrote:
>>>>>
>>>>> Dear Philip,
>>>>>
>>>>> Thanks for another great suggestion.
>>>>>
>>>>> This is also something that is planned. As part of an unrelated
>>>>> project we have been looking at this: we are still in the process
>>>>> of finding a solvent that has a collection yield, that doesn't
>>>>> interfere with (or gives an interference profile that we can
>>>>> correct for) and that OH&S will let us have. Fortunately, for the
>>>>> cookstove work there are fewer constraints than the other project
>>>>> (which is limited to sampling extremely low flowrates). We'll find
>>>>> a solution and share it.
>>>>>
>>>>> Cheers,
>>>>> Paul
>>>>>
>>>>
>>>>
>>>>
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>>
>>
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