[Stoves] Improving Thermal Efficiency (TARP-VE)

Frank Shields frank at compostlab.com
Tue Jun 5 11:38:30 CDT 2012


Stovers,

 

It seems testing for pm seems pointless in some ways in that don't they form
based on cooling temperatures change in air flow and moisture content etc.?
So depending on 'snap shot' in time and location they will differ in size
and problem. Since pm is from organics larger than CO or CO2 having
potential to form particles we should focus on a measure of complex organics
left over leaving the stack. Thinking pulling gas into a tube that re-heats
and oxidizes, comparing CO2 before and increase after, to determine pm
potential. Why spend so much time and interest in pm measuring when its
formation  is so elusive? 

 

Frank

 

 

Frank Shields

Control Laboratories, Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

 <http://www.biocharlab/> www.biomasslab.com

 

 

 

 

 

 

 

 

 

From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin
Pemberton-Pigott
Sent: Tuesday, June 05, 2012 8:58 AM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] Improving Thermal Efficiency (TARP-VE)

 

Dear Dean

 

There are two levels of collection depending on who wants what. We are using
a Dusttrak DRX which can measure up to 150 milligrammes per cubic metre. It
measures and reports PM 1.0, 2.5, 4.0 and 10 simultaneously. It is a light
scattering instrument that can measure down to PM0.1. We also have in JHB a
GRIMM 180 aerosol monitor which covers 0.125 to 32 microns in 32 channels.

 

In order to collect data from much higher concentrations, the exhaust stream
from the stove is captured (or sampled directly from the chimney) and
diluted using dry air to get the humidity below the condensation point so as
to avoid measuring condensed water droplets as particles. This dilution also
considers what the PM level is at the time. It is not a fixed dilution - it
can be adjusted at will by an operator. As a result it can cover a range of
2 million to 1 in concentration. LBNL just built a copy of it and said it
work right off the bat. 

 

Gravimetric confirmation can be provided when someone really wants the info.
Deep quartz filters are preferred because they are far easier to work with
and the concentrations tend to be high, and the scale needed is not in the
same class as that required for IAQ work. Both Profs Annegarn and Lodoysamba
have many years experience with outdoor air measurements so we can set up
for anything people want to know. 

 

We have always been concentrating on stove development and avoiding
certification (many difficult issues) so the setup is aimed at real time
measurements so as to find sweet spots and develop them. I don't have a lot
of confidence in light scattering especially or small sizes where the
detection efficiency is low. There are good machines around which can detect
over 1 billion particles per cubic centimeter and characterise the size and
shape simultaneously but budget becomes an issue. A stove development lab
just doesn't need that kind of detail.

 

The big issues for anything using a hood (which we use for small stoves) is
the condensation of moisture at low dilution rates because it is reported as
PM. Really clean stoves produce so little that the temptation to reduce the
dilution leads to problems. That assumes of course that the sample is
properly dried / condensed. Condensed particles are probably dominant in
terms of health effects. To get the particles to condense and keep the
moisture in vapour form is the core challenge.

 

We have managed to cope with PM up to 17 grammes per cubic metre (O2
factored to 0%). The was measured during the operation of an 'improved
stove' that was promoted having never been tested.

 

As you probably know, we are using a carbon mass balance method of
determining the volume of emissions (scale and diluted sample) so there is
normally no hood involved. Even when there is, we do not capture the whole
volume of emissions, only a sample + the mass burned. This is quite
different from the EPA and PEMS hood method. I can't really comment on the
overall accuracy comparison, but the no-hood method copes better I think
with moisture in the stack and can handle massive doses of PM early followed
by very low levels later.

 

Regards

Crispin

 

Dear Crispin,

How are you measuring PM in your experiments these days: light scattering,
pump and filter, or something else?

Best,

Dean

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