[Stoves] FW: Bottom-loaded, continuous-running TLUDs

[Anderson, Paul]

Stovers,

Another selected side discussion to post now to the whole Stoves Listserv.   I am not doing any editing.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>       Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com>

From: Julien Winter <winter.julien at gmail.com>
Sent: Thursday, November 8, 2018 11:24 AM
Subject: Re: Bottom-loaded, continuous-running TLUDs

Hi Norm;

Thanks for the pdf.   Very interesting.  It refreshes my memory from last January.

You make a good point about falling embers for my diagram of a continuous TLUD.   Embers could fall into the below the primary air.  Although oxygen-limited, there could be enough oxygen in the fuel to support smoldering.  That may not be a problem if the fuel supply rate is fast enough.   Another option is a horizontal gasifier.  Injecting primary air at the bottom of the tube may make the flaming pyrolysis more even.  In a sense that becomes more like a moving grate gasifier, but with fuel being pushed rather than being pulled by a moving grate.

I too sieved my wood chips of fines before I used them in a 8 inch TLUD.   I use hardware cloth, so the screen size was about 8 mm.

Cheers,
Julien.

On Thu, Nov 8, 2018 at 12:05 PM Norman Baker <ntbakerphd at gmail.com<mailto:ntbakerphd at gmail.com>> wrote:
Julien;

I too have seen some very hot temperatures in our large TLUDs. Controlling the primary air to 10% (at the moment for an experimental standard for comparisons between TLUD versions) largely stopped that problem. In the PowerPoint attached, we actually saw the metal getting red-hot and starting to droop in the combustor.

I am beginning to think porosity which is a measure of airflow needs to be carefully considered in TLUD function. Because of the fines and sawdust in commercially available wood chips, I built a two woodchip sifters. Now we have two sizes of wood chips to work with and they are definitely different in the way they perform in the identical TLUD. Now that I have version 19 and it seems to operate quite well, I will be running it side-by-side with version 16 using the smaller chips. I am not terribly good with numbers and definitely am not a physicist, but I think someone with the expertise should take a look at the porosity of wood chips. The Wikipedia link seems to be a good starting point - https://en.wikipedia.org/wiki/Porosity. There is a student at Evergreen State College who promised to do some calculations, but has not.

I don't think you have seen our version 16 TLUD. I have attached the PowerPoint presentation prepared for a year and a half ago at ethos. It is rough and not what I would consider presentable, but it will help you understand what we are doing.

Norm
[Image removed by sender.] Ring of Fire – Feb 2017 Current Version.pptx<https://drive.google.com/file/d/1NT4-jj_Nn4a9mwbLIVK-WcESiiRmNHfe/view?usp=drive_web>Error! Filename not specified.

On Thu, Nov 8, 2018 at 8:47 AM Julien Winter <winter.julien at gmail.com<mailto:winter.julien at gmail.com>> wrote:
Hi Norm;

I ran a fair number trials (ca 50) of 8-inch diameter TLUD trials with wood chips to  measure reactor temperature profiles.   I had a fair bit of trouble with the migratory pyrolysis fire (MPF) running down the side-walls of the TLUD.   Then I put a series of flat rings (ca 1 inch wide with a 6 inch aperture) up into the fuel bed to act as fire blocks on the side-walls.  That forced the MPF  down the middle of the fuel bed, and I got more typical TLUD performance.

I too have see fire transmitted downward by falling embers in fuel beds with large voids.  In cases where there are wood pieces, the MPF doesn't really exist, but it is possible to to get good primary air flow in the fuel bed to prevent conversion to an updraft gasifier.   Where there is large pore space, a very strong draft can develop in the fuel bed, pulling primary air, and the void-space temperature can rise to 1200 °C.  The gas flame above is good enough to flash-fry a small goat.

Cheers,
Julien.

On Thu, Nov 8, 2018 at 11:36 AM Norman Baker <ntbakerphd at gmail.com<mailto:ntbakerphd at gmail.com>> wrote:
Jarod

Read Julian's idea.



On Thu, Nov 8, 2018 at 8:18 AM Julien Winter <winter.julien at gmail.com<mailto:winter.julien at gmail.com>> wrote:
Hi All;

I am just back from walking the dog, and wipped-off a quick diagram for a continuous TLUD.   Plug-flow fuel, with primary air injected not too far down (e.g. 15-20 cm) down from the char surface.   If the fuel supply is air-tight, then primary air is properly controlled.

Attached.

Julien.

On Thu, Nov 8, 2018 at 8:57 AM Dean Still <deankstill at gmail.com<mailto:deankstill at gmail.com>> wrote:
Hi Julien,

I'm going to be experimenting with bottom lit gasifiers to try to find continuously fed combustion (upside down TLUD).

Can anyone send a suggestion?

For the TLUD Summit: If we have ten TLUDs Tuesday morning after ETHOS we can do hot start tests to boil with 15 minute simmer and get all tests done by Tuesday evening. Then have a great data based discussion to start our iterations on Wednesday, Thursday, Friday. I hope that Friday we can write up statements of what works well to help the wider TLUD community.

Best,

Dean

On Thu, Nov 8, 2018 at 8:22 AM Julien Winter <winter.julien at gmail.com<mailto:winter.julien at gmail.com>> wrote:
Hi All;

As I was eating my excellent breakfast of Marmite on toast, it occurred to me that bottom-loaded TLUDs could face a potential problem.

TLUDs  with a fairly well-filled fuel bed, such as pellets, depend on a flaming pyrolytic front (FPF) to work properly.  If ever you have worked with wood chips, you will have experienced what will happen if the channelizes, or follows the source of the primary air down the sidewalls of the reactor.  You will get a fire across the bottom grate, and the TLUD converts to an updraft gasifier ;  very smoky.

Over time, that situation may develop with TLUDs being fed pellets from the bottom of the reactor, especially if the new pellets are not uniformly introduced across the surface of the grate.

For a continuously-running gasifier and char-maker, we may find ourselves moving back to some version of the moving-grate gasifier.  Alex English, 200 km east of me, did some work on those once.  Starting in the 1940s, 'TLUDs' were used in combustion science labs to study moving-grate gasifiers.

Marmite is not as good as Vegamite, but it will do.

Cheers,
Julien

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