[Stoves] Between PM 2.5 and PM 10

[Jonathan P Gill]

Crispin,

Even with the most cursory experience, it is very clear that a TLUD with a variable speed fan will have a power range. The turn down from full on is reasonable, if not as great as a modern gas stove in the privileged world.

Extract CO2 from the atmosphere!

On Jun 10, 2013, at 12:02 PM, Crispin Pemberton-Pigott <crispinpigott at gmail.com> wrote:

> Dear Julien
>  
> I think it is important to emphasize that just because a TLUD burns really cleanly, it is not necessary to use that method in order to a) burn just as clean, b) to burn pellets, c) to make char if desired.
>  
> Despite the early raving about the high quality of TLUD emissions, this is not always the case. TLUD are quite capable of produce high tar emissions with poor combustion. Alternative designs like crossdraft and downdraft stoves are quite capable of producing very low emissions. In all three designs the critical factors are the same: heating of the fuel slowly to dry it and create gases, a hot zone to break down the gases into mostly CO and H2 and water vapour, a hot combustion zone with limited excess air, a heat exchange zone where the completed burn passes to the pot (etc).
>  
> TLUD's are one way to get that nice set of features, if they are built correctly. Many are not, but are still better than an open fire or a dreadful 'box with a chimney'.
>  
> I appreciate the enthusiasm for the TLUD as an easy solution but it brings a number of problems many users do not want to face: producing or using small fuel particles (strong resistance to fuel preparation in Indonesia) and the (almost) inability to be refuelled for continuous operation (4 hour burns are common).
>  
> TLUD's are also very fuel dependent in terms of size, moisture, species and the minimum power level to work properly. It is not a technology that solves all our problems. Notice that Paul A and Paul are both very clear about how to get wood or rice hulls or other fuels to 'burn properly' and that does not make the fire controllable, it just makes it clean. Cooking absolutely requires power control. A pyrolysis zone is inherently set against such conditions. That is why TLUD coal stoves make such great space heating appliances: continuous heat at constant power with at least some measure of controllability. But they only cook at high power, basically.
>  
> Regards
> Crispin
>  
> +++++++
>  
> Dear Crispin;
>  
> Thanks for your excellent response to the issue of untrafine particles and the article by Just, Rogak and Kandlikar (2013).  That TLUDs have a strong secondary gas fire is a very important distinction from many
> other stove designs.   The ability of a stove to handle a variety of
> fuel qualities is also an issue, because, as we all know, the rate of heat production and the temperature of the flaming pyrolysis affects the nature and temperature of gases entering the secondary gas fire.
> We may find that in area of high human population density, pellet fuels are way-and-above the best option for low-emissions of particulate matter.  Hopefully, there can be a market for biochar to offset the cost of pellets.  That were soil scientists (me) come in.
>  
> Speaking of pollution being relative, my parents lived in London, England during 1930-1950.  A lot of coal was burned for heating and cooking.  The particle emissions produced nuclei for water vapor to condense resulting in the infamous London fog.  It was at times so dense that bus conductors had to get off the bus and walk in front to show drivers the way.  The people of London simply assumed that it was normal that your window curtains and the white marble of buildings turned back.  When Londoners switched to using more gas and electricity, the famous fog went away.
>  
> Julien.
>  
> --
> Julien Winter
> Cobourg, ON, CANADA
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