[Stoves] Pressed biofuel - and Fire balls. Testing

[Richard Stanley]

Frank,

Recent studies and recent less formal tests tell us that the  
configuration of the fuel is as important as the content burned in  
bulk even densified in bulk .

A one Joel Chaney at Nottingham University in the UK did an  
interesting assessment of combusiton of the hollow core briquette  
studfyingg particularly the effect of the hole on combustion. As  
well, and long prior to this, Kobus Venter in South Africa has been  
assessing various ways of creating low cost insulation for biomass  
combustion. A one Rok Oblak is working on optimising practicality for  
the user with his research on stove design up in Vancouver with a  
special side-feed configuration in coordination with the side feed  
experts at Approvecho. He will be (or already has?)    presenting/ed/  
his work at the Ethos Conference. We have also seen tests that were  
both optimistic with the right configuration and pessimistic out of  
Southern Oregon University and now Boise State through  Owen McDougal  
(Chem Prof) and his understudy, Seth Edimiller. We have observed  
participated in countless other, on-site tests within the user  
communities where we got it right or failed miserably--until we  
begain to learn what wa really happening with (at least) the  hollow  
core form of biomass bq.

What we have learned form much of this is that– for the third world  
cookstove user at least– one wants to expend only the minimum energy  
necessary to heat the surface area to assure a clean and relatively  
smoke free start of combustion.  Where we simply dump in a whole  
hollow core briquette or for that matter a solid one, and try to  
ignite it we, are seeing, effectively most of the initial energy  
being used just to heat up the mass ..


While this minimum-combustion exposure-relative-to-total-fuel-load   
approach may not make much of a difference, once you have a mass of  
burning fuel which can quickly absorb the addition of fresh  
combustibles,   it is critical to the local cook stove operator who  
usually only requires the heat for  for short durations (say ~one  
hour +/- 15 min) with need for a relativley quick and smoke-free  
startup. Thus, beyond absolute chemical properties we are facing the  
challenge of "use properties" eh ?

Ok, with that bit I receed to lurker status ..Its just to "kindle"  
your awareness and possible exchange with these other colleagues as  
you pursue your research and testing too.

Regards Richard Stanley

www.legacyfound.org

.
On Jan 5, 2009, at 10:25, frank wrote:

> Hi Jeff,
> You are talking about samples 12 (small) and 13 (large) paper balls.
> The method I am using for calculating out the results is prone to  
> error because it makes assumption as to some of the values and uses  
> oxygen to make up the difference.
> Also I ran low on samples # 5, 12 and 13 so could not run the  
> carbon data in duplicate as I did with the others and used less  
> than the amount of sample I like to use.
>
> This is the process.
> 1) Sample dried to get water.
> Dry sample
> 2) Dried sample heated to 550 to get total Ash
> 3) Ash treated with acid and washed filtered to get (A) carbonate  
> and soluble ash (B) non-sol ash.
> 4) Total Carbon determined on the dried sample.
> 5) Dried Sample  heated to 400 deg C without air to get Char + Ash.
> 6) Assume 6% hydrogen in the ash free organic matter fraction
> Char + Ash
> 7) Determine fixed carbon in char + ash
> 8) Determine fixed carbon in char (subtract ash)
>
>
> From all these numbers we can get:
> water
> volatile matter at 400 deg C. (CHNO)
> hydrogen is 6% of vol matter
> volatile carbon at 400 deg c  (total - fixed carbon)
> volatile matter (HNO) (volatile C - volatile matter)
> Total ash - soluble ash = non-sol ash
> Oxygen is what is needed to make it 100%
>
> So I work from both ends; dry sample and char fraction, to  
> determine all the values. That means all the carbon data and ash  
> data must be accurate.   It also means the hydrogen must be close  
> to 6% of  volatile organic fraction. Notice #9 has some negative  
> results perhaps because the ash had some carbon still left. Sample  
> like # 15 took a -long- time and lots of work to get all the  
> organic carbon removed from the ash at 500 deg + O2. Testing  
> materials made from mixes of different things like wood, char,  
> carbonates etc is tricky so I found out I must have larger samples  
> to work with, do the work in (at least) triplicate and treat each  
> one as individual to make sure the values I get to work with are  
> accurate. I think looking at the oxygen value calculated to make  
> everything add to 100% will be the clue as to how well the test  
> worked. Your sample #12 has Oxygen at 65.5% much higher than the  
> others so I suspect the volatile organic carbon should have been  
> higher. Also volatile carbon should be about 50% of total volatile  
> matter for biomass  (not sure about paper) so that is another  
> indication this number may be low.
> So I think #9 and # 12 may not be good numbers. Also sample size  
> used  was smaller than I would have liked for # 5 and 13.
> The particle density was done by the sand method.  I will need to  
> have a larger sample size to get bulk density - from four to twenty  
> liters of material.
>
> So I learned a lot from these samples.
>
>
> How I suggest we can use this data:
> 1) Will this fuel work in a char producing gasifier?  High volatile  
> carbon - low fixed carbon indicates it is.
> 2) How much fuel is needed (volume and weight) to boil a needed  
> quantity of water - based on HHV bulk density value.
> etc.
>
> Thanks for any suggestions
> Frank
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> Jeff Davis wrote:
>
>> Hi Frank,
>>
>> I didn't think that the size of the fuel would change the LHV. For
>> example the small paper fireballs are 7.3 MJ/kg and the large paper
>> fireballs are 14.6 MJ/kg (LHV). Maybe I had something mixed in  
>> with the
>> paper.
>>
>>
>> Thanks,
>>
>>
>>
>> Jeff
>>
>>
>> On Wed, 2008-12-31 at 17:17 -0800, frank wrote:
>>
>>> Greetings,
>>>
>>> Its late and I am going home but wanted to get these lab reports   
>>> to you in case you can get some time to go over them and advise  
>>> me.  They are re-tests of pressed biomass from  Richard Stanley  
>>> and Fire Balls from Jeff Davis sent me to experiment with.   I  
>>> would need to get additional sample to complete the size  
>>> distribution and Packing density values  on the right side of the  
>>> report.
>>>
>>> Have a great new years everyone.
>>>
>>> Frank
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
> -- 
> Frank Shields
> Soil Control Lab
> 42 Hangar way
> Watsonville, CA  95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> frank at compostlab.com
> www.compostlab.com
>
>