[Stoves] When does a test end?

[Lloyd Helferty]

The only problem with using a "95% Rule" (The test ends when 95% of the 
combustion portion of the fuel has burned) is that when we are testing 
gasifier stoves like TLUD that are *designed to leave behind the 
"char"*, the mass of the fuel may never get down to 5% of the initial 
mass... so the emissions test may never actually "end" (officially)...  ;-)

   Lloyd Helferty, Engineering Technologist
   Principal, Biochar Consulting (Canada)
   www.biochar-consulting.ca
   603-48 Suncrest Blvd, Thornhill, ON, Canada
   905-707-8754; 647-886-8754 (cell)
      Skype: lloyd.helferty
   Steering Committee member, Canadian Biochar Initiative
   President, Co-founder&  CBI Liaison, Biochar-Ontario
     Advisory Committee Member, IBI
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Biochar Offsets Group: http://www.linkedin.com/groups?home=&gid=2446475


On 12/15/2010 11:42 AM, Crispin Pemberton-Pigott wrote:
>
> Dear Friends
>
> Of the age-old questions I when to end a stove test in order to 
> calculate the CO and PM emissions (which are the things usually 
> legislated).
>
> There has been little agreement in different US states and few other 
> countries outside Europe have anything at all. Stoves have very 
> different burning times, heat generating capacities, fuel loads, 
> burning properties, refuelling capabilities and purposes. What can we 
> do that will make comparisons fair and possible?
>
> So, here follows a proposal which seems to work in practise.
>
> The test is started at the time of ignition.
>
> The test ends when 95% of the combustion portion of the fuel has 
> burned, leaving 5%.
>
> The combustible portion is the non-moisture, non-ash portion of the 
> fuel as received (meaning as it is used in the stove).
>
> When the fuel is weighed, say 5 kg, and either set aside or loaded 
> into the stove, the total amount is noted and the moisture content 
> calculated, for example at 15% = 750 g. That means there is 4250 g of 
> dry fuel there.  Then subtract the ash portion, say it was 3% of the 
> initial mass = 30 g. Final number is 4250-30 = 4220. That is the mass 
> of 'things which can burn'. 95% of that is 4220 x .95 = 4009 g.
>
> All the moisture is expected to be gone. So if the whole stove is 
> mounted on a scale the mass change will be burnables + moisture = 
> 4009+750 = 4759. One the scaled mass has dropped 4759 g the test is over.
>
> Then the emissions are calculated based on the MJ of heat 
> theoretically generated (using LHV as received).
>
> If a scale is not used, then the mass burned can be determined by 
> weighing the fuel as it is use, fuel remaining or anything else that 
> shows when 95% of the fuel is gone. Typically this is late in the 
> dying fire stage so it is a bit easier then it perhaps sounds.
>
> When do test a stove that includes refuelling or a number of 
> refuellings, the same calculation applies. It seems to work very well, 
> gives results representative of real life and normally has a test time 
> that is less than a working day.
>
> It is offered a test method for rating the emissions of any type of 
> testing from water boiling to 24/7 space heating.
>
> Regards
>
> Crispin
>
>
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