[Stoves] Limiting factor for secondary burn?

[frank]

Dear Crispin, and stovers,

I have a new O2 detector and a CO2 meter.

A few more questions, if you don't mind.
1) what should the small fuel look like after the primary burn (I have 
not set up for the secondary burn yet)?  Should the sticks look like 
sticks - only black?
2) should the glow move up the pri. fuel body (BLUD) because the 
structure of the fuel is maintained (only black) or should the fuel drop 
down due to additional breakdown?
3) Is the goal to have the tar go into the sec. burn? or is it better to 
trap it in the fuel body and keep it away (only letting the lighter vol. 
organics go into the sec. burn)?
4) It you get tar in the pri. burn is that indication of a burn that is 
too hot?
5) stupid question - is the tar in the wood there and able to be solvent 
extracted - or does it develop during the burn?
6) the smoke I see from the pri. burn is a pure white cloud, sometimes 
yellow. Is that my goal?
7) It would seem the tars going through the fuel (up draft or down 
draft) would accumulate ahead of the burn and the burn would be 
different from start to finish.
8) I was surprised how much tar I got from cardboard(?) and for any fuel 
testing that will need to be blanked out.

I really like working with this glass shell. You can see what the burn 
is doing and have complete control with the compressed air.  A number 11 
stopper fits the top and you can bore all types of holes  in the top. 
Cleans up nicely in a furnace using an Orton 022 pyrometric bar.
Also the corrugated cardboard (the paper removed from one side and 
rolled) works great for starting the fire. A match will get it to glow 
long enough to adjust the air, a very even distribution of fire to start 
the small fuel placed on top because of all the tubes.

I feel like I know nothing!
Thanks for all your help.

Frank


 








Crispin Pemberton-Pigott wrote:

>Dear Frank
>
>You are really on the right track.  Impressive.
>
>It will be difficult to match practise with theory if you do not have a 
>meter for at least one important measurement.
>
>The most important is O2.  You can get one cheap, and you need it.  From the 
>O2 reading in undiluted exhaust, you can determine the excess air which is 
>the most important factor in heat transfer efficiency.
>
>Even if you know what the air flow should be, it is not determined by the 
>hole sizes.  It is determined by what happens to flow through them and that 
>is dependant on draft which is variable.  Trying to guess what is in the 
>exhaust gases is hopeless.
>
>What the CO is and the particulates are, you can leave to others, but you do 
>have to know if you are putting in too much air while still in development.
>
>If you have a meter that gives you 'Excess Air' it is fine, but they cost a 
>lot more and are only really doing math for you, not testing something 
>different.
>
>O2 that is NOT present has been burned.  The better your stove, the less O2 
>in the exhaust.  The more air you don't have going in the more likely you 
>are to get a hot burn.
>
>At some point, choking off more air reduces O2 still further, but creates 
>masses of smoke (from not enough air).  It is now at the difficult point. 
>Once you have the excess air down to about 100%, you enter the territory 
>where you can increase the CO and particulates with further choking.  This 
>is not a hard and fast rule, but you get the idea.  There are limits. 
>Increasing the excess air a lot can often increase the CO and partculate 
>production because the fire is cooled by all that unneeded air.  That is the 
>condition of an open fire.
>
>I am really impressed with your progress in understanding this.
>
>Best regards
>Crispin
>
>----- Original Message ----- 
>
>  
>
>>I noticed that the primary burn seems to have a narrow window regarding
>>the amount of air to keep the burn glowing. Too little and the burn ... 
>>    
>>
>
>
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>
>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com