Crispin. Cc list
You say below re a perceived deficiency in TLUDS
"Cooking absolutely requires power control. A pyrolysis zone is
inherently set against such conditions. "
There has been considerable reporting on this list of the TDR (turn down
ratios) of TLUDs - and most have this capability. Power control seems to be
linearly related to primary air supply. often regarded as one of the major
benefits of TLUDs
What am I missing or not understanding in your "inherently" statement?
Ron
On Jun 10, 2013, at 10:02 AM, "Crispin Pemberton-Pigott"
<[email protected]> 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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