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 <[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 > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ >
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