[Stoves] SEET Lab in Ulaanbaatar running again in its new home

[Frank Shields]

Dear Crispin,

 

<snip>

>Is the height where the inside-outside heat standard or site specific? 

 

It is site-specific but as the intended audience is in gers (yurts) the
height is very constant. It is about 2.7 metres from the floor. The chimney
is typically 3 metres long and sits on the top of the stove so depending on
the stove height, the amount of chimney poking into the sky is about 1
metre. Generally speaking all stoves have chimneys that are too large in
diameter. That is interesting.

 

You say to large in diameter. Based on the need for faster gas flow?

 

 

>The compressor taking in CO2 free air is making the dilution? 

 

The compressor compresses air. It is filtered to 0.01 µm and put through a
CO2 and water vapour adsorber, filtered again and then sued in the diluter.
It is very simple and effective. The dew point is -100 F. The CO2 is <1 ppm.
The O2 is much higher, about 33% which was interesting to see.

 

All this seems unnecessary to me. The amount of CO2 in the room air must be
insignificant to what is going up the stack. Same as to moisture. Perhaps
particles are a problem so in-air should be filtered.   

 

>What is used to scrub the CO2 from the air? 

 

I think it is a metal matrix of some kind. It does not get used up. There
are two units and they are cycled. One breathes with ‘wash air’ or ‘sweep
gas’ as it is termed. The other is under pressure for 30 seconds.

Very interesting. I am thinking it may be a Teflon membrane where when the
gas is pressurized the CO2 goes through the membrane more than the O2 or
N2(?) and swept away on the other side. It would be interesting to know how
this works.  

 

The CO2 produced is measured real time(?) using IR detection? 

 

Yes. Two channels in parallel, one for the stack and one for the diluter.

 

Don’t see how this can work. Measure the CO2 before diluter in the stack and
after the diluter in the stack and you can get the dilution (mixing required
I would think). The CO2 concentration from combustion goes up and down a lot
so the two measurements before and after must be synchronized perfectly to
determine the dilution rate. Then we have the constant changing in gas flow
up the stack would vary enough to make this synchronizing a problem.  As I
have mentioned in the past we need some type of segregate standard gas to
introduce into the primary dilution air at a constant rate to do this.
Mercury is the only one I can think of and that is very toxic. But it can be
detected at very low concentrations and scrubbed using S-treated activated
carbon so not as toxic as one would seem when used in lab conditions (but I
would not want to use it). If we can come up with a segregate standard we
can come up with a very accurate means of gas analysis. Without it I see
problems.      

 

 

If CO2 is produced at varying concentrations as the fuel combusts how is it
used as a measure of air dilution? 

 

The CO2 in the stack is measured. Whatever the CO2 in the diluter is at the
time is compared with the stack concentration and a mathematical correction
is made to consider that some of the stack CO2 (and therefore a % of the
diluter CO2) came from the ambient air. Stack/Diluter = dilution factor.

 

We run the dilution between 4 and 300 with 10 being typical.

 

It has to be high enough (using dry air) to prevent condensation (formation
of fog) in the sample so the particle does not think it is PM. This is
calculated based on the moisture content of the fuel and the hydrogen
content that forms moisture when burned. The system can deal with 140 gm of
water vapour per cubic metre of gases. That is a humidity ratio (by mass) of
about 13%.

 

It would seem that there is enough moisture in the outside air and the
combustion gas to create the fog. That it is more the change in temperature
(lowering) that creates the fog than the moisture in the gas. Pre-heating
the dilution air is the answer to preventing fog and not dry air.  

 

Thanks

 

Frank

 

Thanks 

 

Frank Shields

 

BioChar Division

Control Laboratories, Inc. 

42 Hangar Way

Watsonville, CE  95076

 

(831) 724-5422 tel

(81) 724-3188 fax

 <mailto:frank at biocharlab.com> frank at biocharlab.com

www.controllabs.com

 

 

 

Regards

Crispin

 

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