[Stoves] Comments about T-LUDs: Close combustion

[Alex and Christine English]

On 8 Oct 2006, at 12:15, Paul S. Anderson wrote:


Hi Paul,

> At the risk of being too general in these statements below, Paul replies:
> 
> 1.  The closer the combustion to the gas creation, the emissions are cleaner.

No, what I wrote was:

"Well the latter senario appears to yeild significant reductions
in emissions, comparable to systems with greater and more 
destinct separation between the zones of fuel and burnout. "

The comma between emissions and comparable means "aproximately equal".
The issue  isn't distance, but retaining a rich and consistant enough supply of 
unburned fuel  to sustain a vigorous, concentrated  and hot reaction with and 
appropriate amount of air.

It used to be said that flames from biomass fuels should not see cooled surfaces and 
have a long, 2 seconds or more, "retention time" before exiting to heat exchange 
surfaces. This method is still used and has its ad and disad..vantages. 

Time, Temperature and Turbulence has long been the mantra for clean combustion.

A properly set up gasifier, two stage or close coupled combustor allows the operator to 
reduce excess air ( the most intimate of cool "surfaces") and increase turbulence and 
temperatures over the whole zone of final burn out. The "Time" factor or retention time 
then deminishes in importance and you are operating similarly to a liquid or gasous 
fuel burner. 

A very experience opperator once told me that " its all about fuel pile management".

I take that to mean that if you can't create a large hot oxygen starved zone in 
the fuel pile you will have difficulty getting a complete burnout afterwards without 
a long insulated retention chamber.

Regards,

Alex