[Stoves] personal pollution monitors (Andrew)

[Andrew Heggie]

On 27 December 2016 at 01:34, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

> ‎I was a bit taken aback by this idea. The lowest PM I have measured with wood pellets as a fuel definitely didn't have a fan. Huh.

The wood pellets imported for power stations, which previously only
burned coal, are crushed back to dust and then blown into the furnace.

Good pellets don't create sparks in my fan induced room heater and it
is sparks that burn out to flyash.

In the big wood chip boilers one could see sparks blown off the fire
bed which is why the fuel specification was for low fines. There is a
lot of turbulence in the  furnaces of these wood chip boilers from
both forced primary and secondary air and an induced draft fan after
the heat exchanger.


>
> . My perception/ idea is that the BC is not always 'burned out' but is not formed in the first place if the gasification process is 'good'. To achieve this it is not necessary to create a high energy content gas, but a burnable gas with carbon already divided as much as possible, preferably CO.

Yes I can understand this as the Products of Incomplete Combustion are
formed in the secondary flame, get that right and no PICs but if the
combustion chamber is quenched by heat losses losses through the walls
then the temperature falls and PICs are more likely. As you know low
combustion temperatures are also caused by high excess air and damp
wood.
>
> The bark retention info is interesting, to think that they think that far ahead is good.

Crispin this latter was my speculation from seeing videos of short
rotation single stem hardwoods being harvested, it would need further
research to find the actual reasons.

Andrew