[Stoves] TLUD Oven paper updated

[Marquitusus]

Hi Julien and all,
You have mentioned the problem with temperature control, and the solution: turning down the primary air.
Yes. It is possible in theory, but in the practice it is not easy to built a TLUD stove with primary air control. Almost for me! It is what I'm trying to do now: testing any sliding little doors or other methods. It is my poor tinsmith skills I guess!
Would you say that the solution to this is to build a TLUD-oven unit that is designed to use only pellets as fuel, and use a TLUD of sufficient depth to pyrolyze for two hours? Yes, this is what I think would be the best. Changing the reactor in the middle of a baking process can be challenging for a baker when you have a lot of loaves of bread you have to manage! Pellets or any other well working fuel.
I find that 30 cm of softwood pellets lasts about that long, and there is a slight reduction in power output over time. I also think 30cm of pellets would last this long, but since now I have found challenging building a TLUD stove with a reactor of more than 20cm in length, because lack of primary air draft. This normally leads to little power and the extinguish of the flame due to too much distance between the combustion zone and the pyrolisis front. As Crispin has suggested a lot of times, some early secondary air  near the fuel bed should do the trick. I wonder when I will have time to try this...
About measuring temperature in an oven with a thermocouple, I answer in the next mail

Thanks!
Marc

Date: Mon, 2 Feb 2015 17:20:37 -0500
From: winter.julien at gmail.com
To: stoves at lists.bioenergylists.org
Subject: [Stoves] TLUD Oven paper updated

Hi Marc;
Thanks for your paper on baking with a TLUD.  There is a lot we can learn from your experience.
You have mentioned the problem with temperature control, and the solution: turning down the primary air.
You have also mentioned a problem with duration of temperature, with about 2 hours being best.  Would you say that the solution to this is to build a TLUD-oven unit that is designed to use only pellets as fuel, and use a TLUD of sufficient depth to pyrolyze for two hours?  I find that 30 cm of softwood pellets lasts about that long, and there is a slight reduction in power output over time.  Otherwise, if using nut shells, would it be possible to have a second TLUD to exchange with the first when pyrolysis is complete?
You may be aware that measuring air temperature with a thermocouple is prone to some inaccuracy due to radiant energy exchange between the thermocouple and the environment.  In your case, since the walls of the oven heat up, the error may not be of practical consequence ... but it is something you may want to check into.
A radiation shield can be used to improve the accuracy of thermocouple measurements in air.  I need to solve this problem myself.  At the moment, I am considering inserting a K-type thermocouple probe into a thin-walled stainless steel tube with openings at both ends, such as described here:http://www.msm.cam.ac.uk/utc/thermocouple/pages/ThermocouplesInGasTurbines.html
Perhaps someone else has some suggestions?
Thanks again for the informative paper.
Cheers,Julien.
(ps: Gmail's spelling checker has a sense of humor.  It wants to change "pyrolyze" into "paralyze".  Good thing I did a little proof-reading.)
-- 
Julien Winter
Cobourg, ON, CANADA



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