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
http://www.linkedin.com/groups?gid=1404717
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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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