[Stoves] A photo of a lab test from Ulaanbaatar

[Crispin Pemberton-Pigott]

Dear Friends

 

I am circulating this as an into to the test methods applied in Mongolia
(and other places). It is a pretty good example of what the main
measurements look like.

 

The photo is of one of the two computer screens which side by side. On the
top left is the Digital Scale Capture Tool (DSC) available for $50 once off
payment to Jeremy fuzzychaos at gmail.com <mailto:fuzzychaos at gmail.com>  (as a
thank you).

 

On the left of the DSC screen is the mass from the scale per 10 seconds. On
the right is the (approx) calculated power in kW reported per minute. The
data is saved to disk each 10 seconds. Multiple copies of the DSC can be run
at the same time, one for each scale used.

 

Below the numbers screen is the average kW plot so far in blue and the
cumulative mass burned (also so far) curve in red.

 

Below that is the mass change detected by the scale per 10 seconds. The
value is shifted by the wind and moving fuel but overall as time passes, the
precision is high, about 1 part in 5000. The burn rate (green line) can be
seen to be declining towards zero as the fire burns out. 

 

There are 4 gas readings. This is the minimum if you want PM from a fire. On
the left is the CO2 level in the diluter. The other three are measured
directly from the stack (or hood). The CO is the concentration in the
chimney, in this case. The next CO2 is the CO2 in the chimney and is of
course higher than the CO2 in the diluter. The ratio between them is the
level of dilution, in this case it is 3.232:1. The PM measured in the
diluter is multiplied by the number 3.232 to give the equivalent of the
direct measure from the chimney (which might be too high to measure
directly). The dilution is variable with the turn of a knob.

 

The O2 on the right is the O2 in the chimney. 

 

Notice that the total of the O2 and CO2 on the right does not add up to
20.945%, the O2 concentration in the ambient air. This is because there is
H2 burning (from the fuel) and being turned into H2O. That H2O is not
measured on this screen and as you don't know what it is looking at this
picture, you can't tell if the equipment is working perfectly or not. Maybe
it is a measurement error, maybe it is diluted by water vapour (which it
is).

 

The CO is very low at 18 ppm. The value for EA is about 1.67 and Lambda is
therefore 2.67. 

 

2.67 x 18 ppm = 30. So the CO(EF) is 30 ppm, meaning that if there was no
dilution by air, the CO cell would read 30 instead of 18.

 

The CO/CO2 ratio is 18/(6.730 x 10,000) = 0.0002674 or 0.0266% (very good).

 

The 'modified combustion efficiency' is 

 

6.73/(6.73+18/10,000) = 0.9997 = 99.97%

 

The kW blue line for power is the running average from the beginning so the
value 11kW refers to the whole test as a whole.

 

The PM value will be multiplied again by Lambda (dilution) to get a
PM2.5(EF) value. This is the rating that the stove gets. 

 

Quick review:  PM reading x dilution in the diluter x dilution by excess air
= emission factor value. This is later multiplied by the mass burned x the
volume of gases produced by the fire based on the fuel analysis. The result
is the mass of PM (and by the same method the CO and any other gas) emitted
during the test.

 

Because the data is collected in real time, the stove can be tuned to find
the best operating parameters. Sections of the test can be analysed later to
create a plot of how the heat transfer efficiency, for example, changes with
power or fuel condition (etc).

 

Best regards

Crispin

 

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