[Stoves] Blown charcoal is the base of maintained good wood-burning

[Boll, Martin Dr.]

Excuse, that I changed the topic from:

Re: [Stoves] scoping out a practical solid fuel stove igniter

I think the discussion is now more in direction of maintaining fire, or re-igniting, than on a first starting fire.


Dear Crispin and topic-interested,

The solution Crispin proposes with the small secondary air-holes has a big advance, which I want to clear out very simply, but basic.

-but first I give the additional result of my very simple tests told some days ago: A piezo-spark does not light some very-light-cotton cloud, containing (spark-incended) motor-fuel.
It needs the "very fitting fuel-air-ratio". ( I should have been reminding the not starting lawn-mower. - simple tip,I was told: "put the engine for half an hour into the sunshine!"-- and that was right! )

Reason for stoves: We need a   __real big__  "spark" because we normally,- in out-blown stoves-, have no ideal gas-air-ratios; not in mixture not in ratio . -Had we these ideal in proportion and mixture, the flame was not blown out;- I guess, it was the admired and seldom seen blue flame. - But better is a real flame.

I think, to return to the very old-fashioned fire starting-mode is the safest, simplest and most manageable way.

 The low self-ignition temperature of charcoal, is simple to maintain. ( 300°C ; but charcoal-gasification is not below 400-600°C, * P.S. ) Charcoal burns properly (during some time) just beside some fresh air,  ( one cannot blow it out under most conditions )
 The high self-ignition temperature of woodsmoke is higher, (otherwise the smoke would not exist, but self-ignite) ( start about 400°C sure above 550°C, * P.S. )
My own can-burn-observations are, that a dark red color does not fit to reignite smoke, so I guess, that, to be safe, the temperature must be above the charcoal-gasification temperature, which is, compared by the rates of wikipedia above the self-incending temperature of wood-gas. 
- Out of that I followed: The C in gas-form is burning and maintains, or re-ignites the woodgas-flame. -I guess, It is at least the 730°C, bright red, slightly orange ( in terms of Tom's given scale)

I smile about myself, because it took years for me to get that "really" aware; -So much aware, that I came, for me,  to the simplest and most rational conclusion, that there is no stable burn below the self-ignition-temperature of all burning "stuff". 
 

 The normal surrounding air -without draft- maintains glow of charcoal, but not/never maintains -during some time (under that condition)- the self-ignition-temperature of smoke.

I state for myself roughly as one of basic facts for wood-burning: Blown charcoal is the base of maintained good wood-burning.

So I say simply :  "Blow the glow!"

Here I repeat my question I former asked: "What locally speed of air is minimal needed to get that glow-temperature (guessed: bright red, silghtly orange) on the surface of charcoal, to maintain a woodgas-flame?

( I had to look to the very interesting and important contribution of Tom (Reed) on this list about color and temperature; a basic knowledge I have to remind)
And happy, I found it!:  http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/2013-November/007676.html

For quick information I had asked before big G and found:  http://de.wikipedia.org/wiki/Glut_(Lichtausstrahlung)   (You will certainly have no difficulties to understand few words in "neighbour"-dialect German) 


Crispin, how about putting some charcoal as the base of the fuel-load by a stack-burning stove, in order to end without smoke?
- Or is the smoke-amount to less-concentrated to burn?
- The higher glow-temperature on top of the surface of superficial charcoal-layer of the TLud by the small air-holes maintains the self-ignition temp. of the smoke.
So the concept, always to have  secondary-air-holes (some!, not many!!; and small-enough but not bigs!) ) just above the (in that burning moment!) upper charcoal-layer would be at least one of the best solutions. 
-Nature never "squeezes out a lemon to the very-rest", as we want to do to perfect something! Cannot we loose a tiny little bit of charcoal to get rid of a lot of unburnt smoke; -which gives then some additional heat and latter PM?

Special regards to low-tech-friends and
Kind Regards to all

Martin

* P.S. Mentioned temperatures out of:
 http://www.hs-owl.de/fb8/fileadmin/download_autoren/sonnenberg_andreas/Rodehutskors.pdf



<Message: 3
<Date: Sat, 12 Jul 2014 08:22:33 +0700
<From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
<To: "'Discussion of biomass cooking stoves'"
	<stoves at lists.bioenergylists.org>
<Subject: Re: [Stoves] scoping out a practical solid fuel stove igniter
<Message-ID: <COL401-EAS138AE5A6D7B76DDD50591A6B1080 at phx.gbl>
<Content-Type: text/plain; charset="utf-8"
<
<Dear Kirk
<
<
<I appreciate that you are working on a common TLUD need and are willing to share what you can discover. Flameouts are a common problem particularly at the end when there is still a <possibility of there being significant smoke from the remnant volatiles.
<
<
<One of the activities noticeable at a TLUD convention is inventors tossing just-struck matches into a smoke bomb to re-establish the flame.
<
<
<My own cure, after creating enough smoke to hide my embarrassed face, was to conduct the combustion of the gases as close as possible to the upper surface of the fuel.
<
<
<This turned out to pretty much solve the problem because the secondary air entrance is low enough to the fuel that it keeps the top hot. This is not in line with many designs which have a gas <burning zone that is away from the fuel. In my current view the move down burns some of the char and the payback is a product people are willing to use because the flame is reliable.
<
<
<There is a new stove which was designed in Mongolia and produced in China that was submitted to the UB-CAP lab for testing which has what I consider the ?right? approach. The fuel bed is <about 320mm deep which is typical of the breed. The secondary air is provided through very small holes (maybe 4 or 5mm diameter) around the ceramic combustion chamber. They are at least <125mm below the top of the fuel, were the available space to be completely filled. The secondary air is preheated to a high degree and limited in volume by a restricted entrance. 
<
<
<It is extremely clean-burning. It has no controls at all ? it just runs and burns out. The PM2.5 reduction against the baseline is over 99%. 
<
<
<I have used the same approach and recommend it. Secondary air should not be spread out over the fuel chamber, not vertically at least. It should be lower than the fuel top when ignited as it <serves little purpose right at the beginning. The fuel shrinks considerably as it burns and drops to uncover the ports which are not blocked in the meanwhile, they allow air to enter, but later they <are clear of the fuel.
<
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<In the end the flame is hot enough to brighten and maintain a hot upper surface that resists the flameout at the tail end.
<
<
<Regards
<
<Crispin
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