[Stoves] TLUD Oven paper updated

[Paul Anderson]

Marc,       A reply to an older message.    see below

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/3/2015 1:47 AM, Marquitusus wrote:
> 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!
For primary air control, try a tube or thin pipe into the area under the 
grate.   Near the outer end of the pipe, cut down half-way a slit (use a 
hack saw).   Into the slit you can slide a thin piece of metal that is a 
barrier that closes inside the pipe and has an upper piece that you can 
hold.   Make several of the barriers, and into them put different 
numbers of small holes (2 mm maybe) so that there are different amounts 
of air that can pass the barrier (plus what air leaks past.).
>
> /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.
If the baker has a second TLUD unit, ignite it and insert it promptly 
when the initial unit has finished the pyrolysis.   Repeat as many times 
as needed.   This should not impact the bread at all.

Paul

>
> /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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