[Stoves] Heat / cook stove - proposed design

[ajheggie at gmail.com]

On Tuesday 10 January 2012 06:23:29 Andrew C. Parker wrote:
> On the subject of backfires in stoves doing surprising things, I am
> pretty   sure I have mentioned it before, but, in Richard Hill's
> document describing his stick-wood fired furnace, he mentions that
> during prototyping he experienced, "explosions strong enough to lift a
> twenty-pound cast-refractory charging door."  So, yes, by all means do
> be careful.

I have direct experience and remember the bruises when I stupidly 
unfastened the refractory fire brick and steel door (for the manual ash 
scraper) because I wondered why the 500kW boiler was smoking and failing 
to ignite, the depression from the ID fan sucked in enough air  past the 
loose door as I removed it to reach the glowing char to cause a 
deflagration...

The reason was simple the software had been changed and the stoker was 
still running whilst the igniter was still blowing, moving the embers 
such that they were hot enough to pyrolyse surrounding material but were 
disturbed before they could get any one bit up to the autoignition point. 
The firebox was full of pyrolysis offgas just waiting to be ignited.

Another story I have probably told here: early in my career as a tree 
feller we hand loaded much smaller lorries than now. One of these was run 
by an undertaker in Oxford and the driver, whose name I forget after 35 
odd years, had a wood stove which he loaded up before work and left 
damped down. One rainy day he came home and decided to gee the fire up, 
he opened the stove door and this sudden air movement allowed air in and 
smoke out, again causing a deflagration which set fire to his anorak. 
Unfortunately he gasped in the flames and though he got himself to 
hospital he died a few days later fromm the lung damage.

AJH