[Stoves] When does a test end?

Wed Dec 15 12:11:00 CST 2010

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: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] 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/
Stoves at lists.bioenergylists.org
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists
.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20101216/3aa42a1c/attachment.html>