[Stoves] Thick wood and MC in micro-gasifiers was Re: Smoke-free biomass pellet fueled stove

[Tom Reed]

Dear Crispin, Paul and Aul:

The water-gas reaction

            C + H2O ===> CO + H2
DH.    420.                 280.    280. 
DH (delta H, but my I pad has no delta symbol), the heat produced by the reaction  is -(560-420) 
=. -140 kJ/(12 g of C).  In other words you would have to add 140 g of heat (plus enough heat to reach reaction temperature) to make the reaction go.  

<><><>

My memory is that I dried wood chips in a 230 F oven for several hours, then prepared 7 bags of equal weight chips (100 g ?) and added enough water to each bag to bring total weight to 5,10,15, 20, 25, 30 % moisture, and then let the bags sit for a few days to equilibrate the water and chips.  I then burned each sample until only charcoal remained (flame color changed fro yellow to blue) in our WoodGas battery blown stove. 

I was delighted to find 30,25,20,15,10,5 and 1% charcoal remaining.  From this it seemed obvious that each lowest layer of charcoal, in order to ignite the subsequent layer of chips below it, had to be partially burned in order to remove the water from the next layer of wood chips in order to ignite it.  Dry wood burns; wet wood won't.  

Since that experiment in my Denver lab, I have moved twice and would have difficulty finding my original notebook.  But the experiments made so much sense, that I am sure the above description is in essence correct.  

Onward...

Tom Reed


Thomas B Reed 
280 Hardwick Rd
Barre, MA 01005

508 353 7841

On Nov 12, 2012, at 9:10 AM, Paul Anderson <psanders at ilstu.edu> wrote:

> Dear Andrew,        with copies to Tom and Morgan
> 
> I am sending a copy of this reply to Tom Reed <tombreed2010 at gmail.com> .  This is the only email address he now uses, in case anyone else wants to note it down.
> 
> Tom did those experiments with known moisture a few years ago. Perhaps he still has the notes.   I think it was not prepared as a formal report.  I believe he said it was nearly linear, with about 0% char when MC reached 30%.
> 
> 150mm diameter is beyond anything I have ever tried.   I marvel when the 70 mm branches pyrolyzed all the way through in the experiments done by my Ugandan associates.   There is a photo of the loaded fuel in the Quad TLUD in the report of test results by CREEC on the Quad stove  (see the report at    www.drtlud.com  ).   Thickness (diameter) increases the length of time of the operation of the stove (quite logically).   Jackson, the CREEC technician, did a great job with having 3 different sizes of the same wood in the three different runs.     But we do not have funding for running repeated tests to get sufficient replications.
> 
> The issues include being too thick so that the pyrolysis gases are too slow / too little to sustain a good flame at the upper combustion part of the TLUD.
> 
> I hope that CSU can put that into their computer model.   And I hope that CSU will write something to the Stove Listserv or tell us where they are writing something.   So far they hold the biggest pot of funding for research about micro-gasifiers, except for the big companies like Philips (and what BP did in the past).
> 
> Paul
> 
> Paul S. Anderson, PhD  aka "Dr TLUD"
> Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
> Website:  www.drtlud.com
> 
> On 11/12/2012 5:53 AM, ajheggie at gmail.com wrote:
>> [Default] On Sun, 11 Nov 2012 20:01:02 -0600,Paul Anderson
>> <psanders at ilstu.edu> wrote:
>> 
>>> Crispin and all,
>>> 
>>> I think that the char being created in a TLUD  is not hot enough to
>>> cause the water gas reaction.
>> I take this view too, and even if it were hot enough the endothermy of
>> the reaction would limit it.
>> 
>> If this phenomena is important to us, e.g we want to maximise char
>> retention, then it's worth knowing the optimum fuel moisture content.
>> Also I had found there was a limit to the size of particle that could
>> be thoroughly charred. I found I could not successfully scale up a
>> tlud device to chare 150mm cross section longs which I hade carefully
>> dried. What I never got round to trying, as I lost the farm workshop
>> due to redevelopment, was seeing if such logs would char if embedded
>> in smaller material.
>> 
>> I no longer have a useful tlud device that will consistently produce
>> measurable results but it may be worth doing some runs with oven dried
>> wood chips which have been then re wetted with the correct amount of
>> water to give samples of 0-25%mc wwb and weigh the char produced when
>> lit with the same amount of liquid fuel. I would especially like to
>> see the results when fed with primary air maintained at a constant
>> flow.
>> 
>> AJH
>> 
>> _______________________________________________
>> Stoves mailing list
>> 
>> to Send a Message to the list, use the email address
>> stoves at lists.bioenergylists.org
>> 
>> to UNSUBSCRIBE or Change your List Settings use the web page
>> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>> 
>> for more Biomass Cooking Stoves,  News and Information see our web site:
>> http://www.bioenergylists.org/
>> 
>