Again this is easily addressed by sayig that you want the char to be counted as 'not burnable'. I.e.
For a pyrolyser the definition of what is burnable can be the volatiles and some of the carbon. When the test ends is when the stove is still burning some of what you want burned (not the char). In cases where the stove is unable to burn the char, defining this point is not a problem. The main idea is that the stove starts, runs and is shut down when the burn is nearly done. The emissions during the test period are then calculated for the energy used in the process. If the yield is 20% char (which contains all the ash) then the calculation is adjusted appropriately and the finishing mass given at the beginning of the test. The big advantage of this approach is that emissions per task can be calculated from the test result, whereas the basic emissions cannot be calculated from an output given for a task because they are hidden by the calculations. Regards Crispin From: [email protected] [mailto:[email protected]] On Behalf Of Lloyd Helferty Sent: 16 December 2010 01:51 To: Discussion of biomass cooking stoves Subject: Re: [Stoves] When does a test end? 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 http://www.facebook.com/group.php?gid=42237506675 http://groups.google.com/group/biochar-ontario http://www.meetup.com/biocharontario/ http://grassrootsintelligence.blogspot.com www.biochar.ca Biochar Offsets Group: http://www.linkedin.com/groups?home= <http://www.linkedin.com/groups?home=&gid=2446475> &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 _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address Stoves mailing list 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/ [email protected] http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists .org
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