RE: [Biochar] Fundamental facts about TLUDs

Hugh’s message (below) is a valuable evaluation and the a comparison about char-making options.

INFO ITEM:
To save this message for others to reference later (and because email messages are so short-lived even when archived with so many minor messages), I have sent this message to be saved at the “Eposts” (tab in the menu bar) at the www.drtlud.com<www.drtlud.com> website. I have been doing this since 2017 for SELECTED messages related to TLUD stoves (and some Biochar topics). There are over 200 saved messages there now. They are ordered only by date (most recent at the top of the list). I hope that someday this “collection” is useful. But there is no attempt to make it complete nor even easily searched. It is not a Blogsite.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD — Website: www.drtlud.com<www.drtlud.com/>
Email: psanders@ilstu.edu<mailto:psanders@ilstu.edu> Skype: paultlud
Phone: Office: 309-452-7072 Mobile & WhatsApp: 309-531-4434
Exec. Dir. of Juntos Energy Solutions NFP Go to: www.JuntosNFP.org<www.juntosnfp.org/>
Inventor of RoCC kilns for biochar and energy: See www.woodgas.com<www.woodgas.com>
Author of “A Capitalist Carol” (free digital copies at www.capitalism21.org<www.capitalism21.org/>)
with pages 88 – 94 about solving the world crisis for clean cookstoves.

From: main@Biochar.groups.io <main@Biochar.groups.io> On Behalf Of Hugh McLaughlin via groups.io
Sent: Sunday, September 13, 2020 8:48 PM
To: main@Biochar.groups.io
Subject: Re: [Biochar] Fundamental facts about TLUDs

Hello List,

Bill Knauss posted on another biochar group thread the video which describes “You can see from the video https://youtu.be/5Kfr4NRhJ0s that I made of the 350 gal TLUD back in 2012”.

I found the video almost a tutorial about how to do things right when it comes to Tluds. Highlighting some of the features that led to success:

1) Uniform feedstock. Tluds tolerate a wide range of feedstocks, but they have to be uniform around a set of characterisitics: moisture, shape and size (to get uniform vapor flow) and avoiding a set of particles much smaller than others (fines), because that leads to pressure drop instabilities.

2) Tall relative to the diameter (aspect ratio in Nerd-speak).

3) Separate and adjustable primary air supplies – one for each quadrant in this case. This allows re-balancing the migrating pyrolysis front if it drifts out of level.

4) Machinery to do the larger jobs of moving materials in and out.

In general, it is easier to control the primary air from below with a small fan than to try and balance the combination of primary and secondary air with a common stack. Some designs have the ability to restrict the secondary air, but there needs to be a large excess of secondary air with as much mixing and turbulence to burn the wood vapors as clean as possible – so inhibiting secondary air flows may be the wrong way to balance out a Tlud. As such, except for DIY and refugee designs, having a small fan and a rechargeable battery (or cell phone) are worth the cost and complexity.

Now I would like to bring forward a concept championed by Dr. Karl Frogner, which is distributed devices for thinly distributed feedstocks. In this concept, the device is easily accessed or constructed with local skills and materials. The device then travels to the feedstock and converts it to biochar and possibly local useful heat (cooking, warming inhabited spaces, making hot water for washing).

Using Frog’s approach, one does not aspire toward “bigger is better”, but rather targets the economic minimum for making the devices (as measured on a volume per capital cost including labor) and gets more of the units out there – not unlike scaling the stove model to consume available waste biomass supplies and making the primary goal the creation of biochar as the beneficial soil amendment and atmospheric carbon sink.

For example, let’s consider the challenge of converting 2 cubic yards (400 gallons) of feedstock into char. An Adam retort is one option, as is a version of Bill Knauss propane tank, and, using Frog’s approach, 8 Jolly Roger Ovens – each based on a 55-gallon drum as the fuel canister. Frog predicts, and I tend to agree, that the 8 JROs will outproduce the other options.

I was involved in a project this last year where we evaluated options for movable pyrolysis devices treating distributed feedstocks from almond and walnut production, of which there is a lot and more gets created every crop in a much large volume than the saleable nut meat. One platform took the JRO approach, envisioning multiple units that shared common resources, such as air bases to start the pyrolysis front and seal-able lids to quench the batch at the end of descending MPF to minimize the char losses.

Overall, I was convinced this approach has merit in some applications. The key was to fine tune the device to the feedstock properties and coordinate the activities to keep as much processor volume in char-making mode (active migrating pyrolysis front operation). Unfortunately, the virus shut all efforts down and it is unknown if and when the program will be resumed.

In closing, don’t buy a Tlud – build one. Start with an application and a fuel (wood pellets, chipped wood, acorns, shredded landscaping residues), and try out the variations of natural draft vs forced air, etc.

– Hugh McLaughlin

On Sunday, September 13, 2020, 4:38:13 PM EDT, Paul S Anderson <psanders@ilstu.edu<mailto:psanders@ilstu.edu>> wrote:

Tom,

Thank you for that VERY valuable summary of some important issues that will impact the larger RoCC kilns. We will be check such things when the units are operational. We will be looking to Biochar advocates for assistance at each location where a RoCC kiln could be used.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD — Website: www.drtlud.com<www.drtlud.com/>

Email: psanders@ilstu.edu<mailto:psanders@ilstu.edu> Skype: paultlud

Phone: Office: 309-452-7072 Mobile & WhatsApp: 309-531-4434

Exec. Dir. of Juntos Energy Solutions NFP Go to: www.JuntosNFP.org<www.juntosnfp.org/>

Inventor of RoCC kilns for biochar and energy: See www.woodgas.com<www.woodgas.com>

Author of “A Capitalist Carol” (free digital copies at www.capitalism21.org<www.capitalism21.org/>)

with pages 88 – 94 about solving the world crisis for clean cookstoves.

From: main@Biochar.groups.io<mailto:main@Biochar.groups.io> <main@Biochar.groups.io<mailto:main@Biochar.groups.io>> On Behalf Of Tom Miles via groups.io
Sent: Sunday, September 13, 2020 1:36 PMg
To: main@Biochar.groups.io<mailto:main@Biochar.groups.io>
Subject: Re: [Biochar] Fundamental facts about TLUDs

Air quality will be the primary limit on any of the mobile open stack devices like the RoCC or large flame cap kilns. EPA rules consider an enclosed fire of more than 2 tons per day (167 lb/hr) to be a waste incinerator so it requires what is called a special Title V permit. Permits will often limit the operating hours per day and the total tons per year of material that can be converted at a site in a given year. Multiple kilns will be considered as a single source. A typical mobile carbonizer permit might be 6-8 hours per day (or sunrise to sunset) and a maximum of 10,000 tons per year. They will also regulate the fuel type. Many locations do not require permits today as long as production is small (less than 10 MMBtuh fuel input, or about 1200 lbs/hour, which is the EPA threshold) and you are not in an Air Quality control district which typically can regulate emission down to about 2.5 MMBtuh (300 dry lbs/hr).

The primary concern is fine particulate, or PM 2., which affect health. You can see that our PM 2.5 emissions are off the charts in the west if you look at the maps at Purpleair The Air Quality Index scale goes to 500. At my house we are still at 350-400 even though we are well away from the fires. For comparison Normal, Illinois, where Paul is has an AQI of 23 currently.

Personnel safety and liability is also a concern, especially for large diameter units. Who holds the insurance certificate?

We could convert a lot of biomass to biochar and power if California and other states were to repeat the power generation contract incentives of the 1980s in which power purchase agreements at attractive prices were guaranteed for 10 years. At its peak California generated 965 MWe from about 13 million tons of wood waste, agricultural residues and waste urban wood in 66 facilities. There are about 23 direct-combustion biomass facility in operation with a capacity of 532 MW. This is a third of the facilities in operation (66) during the industries’ peak. It is now down to something like 4 million tons per year from biomass. Another 600-800 MWe is generated from Digester Gas (Anaerobic Digestion), Landfill Gas, and Municipal Solid Waste (MSW).

Tom

From: main@Biochar.groups.io<mailto:main@Biochar.groups.io> <main@Biochar.groups.io<mailto:main@Biochar.groups.io>> On Behalf Of Paul S Anderson
Sent: Sunday, September 13, 2020 10:44 AM
To: main@Biochar.groups.io<mailto:main@Biochar.groups.io>
Cc: Anderson, Paul <psanders@ilstu.edu<mailto:psanders@ilstu.edu>>
Subject: Re: [Biochar] Fundamental facts about TLUDs

Kirk,

You are certainly one of the most informed about combustion of TLUD gases. We thank you for your great efforts.

1. You largest TLUD is under 8 inches (20 cm) in diameter. You have not experienced the chaotic shifts that Hugh has mentioned, which are probably starting at diameters of 16 inches, and are more frequent at 24 inches (a 200 L barrel). And then become more serious as diameter go to 3 , 4, and 6 ft. So both you and Hugh are correct.

2. Your wrote:

A simple larger scale, cookie cutter design, perhaps prefabricated, biomass electrical power plant that uses pyrolysis and saves the char could make a commodity of all that dry wood that feeds the wild fires.

I suggest to exclude the electrical power plant from that sentence (because financially viable conversion of thermal energy to electricity requires quite large thermal power plants). Everything else in your sentence is precisely what I have been developing with the RoCC kiln technology. Currently there is one RoCC kiln in Butte county, with plans to be put to use in Paradise. 4-ft diameter. If you or others who are close enough want to visit it in action, let me know. Video of 4 minutes is at www.woodgas.com/resources<www.woodgas.com/resources> We would love to have more people in California / Oregon and other western states be involved. (also a 4 ft diameter unit being made in Pennsylvania and another in South Africa.)

But progress is slow because of Covid and funding to do the larger demonstration units to prove that the RoCC can grow larger (to accommodate more biomass). The objectives are, for California, to clear out substantial amounts of the excessive biomass, and to get the biochar to help offset the costs, and perhaps bury the biochar so that carbon dioxide REMOVAL (CDR) funds can be receive (someday, but not currently). Diameters of 10 ft and even 16 ft are discussed, but the largest being built now in Illinois is 6 ft diameter and 7 ft long. It will release many millions of BTUs per hour. It and larger ones need to be linked up with uses of that thermal energy (heating buildings, process heat, etc.)

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD — Website: www.drtlud.com<www.drtlud.com/>

Email: psanders@ilstu.edu<mailto:psanders@ilstu.edu> Skype: paultlud

Phone: Office: 309-452-7072 Mobile & WhatsApp: 309-531-4434

Exec. Dir. of Juntos Energy Solutions NFP Go to: www.JuntosNFP.org<www.juntosnfp.org/>

Inventor of RoCC kilns for biochar and energy: See www.woodgas.com<www.woodgas.com>

Author of “A Capitalist Carol” (free digital copies at www.capitalism21.org<www.capitalism21.org/>)

with pages 88 – 94 about solving the world crisis for clean cookstoves.

From: main@Biochar.groups.io<mailto:main@Biochar.groups.io> <main@Biochar.groups.io<mailto:main@Biochar.groups.io>> On Behalf Of Kirk Harris via groups.io
Sent: Sunday, September 13, 2020 11:12 AM
To: main@Biochar.groups.io<mailto:main@Biochar.groups.io>
Subject: Re: [Biochar] Fundamental facts about TLUDs

All,

There are some good insights in Hugh’s contribution.

1. TLUDs are not chaotic. The migratory pyrolysis front moves evenly downward. I have noted that there are variations in the exhaust gasses of the CO2 level, which is proportional to the power level, . Usually there is a high point early on which slowly reduces over time. I have assumed that the char has a rough surface, and so has more flow resistance then wood or pellets, slowing the gasses.

3. I have not run into this much unevenness as my largest fuel reactor chamber is 7.5 inches diameter. Having the MPF under the unburned fuel would mean very uneven migration. How it could become traditional combustion with restricted primary air confuses me.

4. How could it become a bonfire with limited primary air? The excess air needed to form a bonfire must be coming from above, and getting down through the char somehow. Or perhaps there is too much primary air. I am not quite sure how this would work. A bonfire needs lots of air.

I have wondered how an uneven migratory pyrolysis front, as Hugh described, behaves when it reaches the grate. It seems logical that some of the char would be burned in the area that first reaches the grate. This would of course decrease the amount of char produced, but how seriously I cannot say. The portion that is still pyrolyzing could possibly be producing more draft and so attract most of the primary air, reducing the burning of the char. If I understand Hugh, it seems logical that the larger the fuel chamber, the easier it would be to introduce unevenness in the pyrolysis front. It would probably then be better to use a smaller TLUD to heat a retort for making char, rather than trying to enlarge the TLUD fuel chamber. A fairly small TLUD would be needed to start the process, and begin pyrolyzing the wood and making wood gas, which can be burned to continue the process.

My interest in TLUDs over the last couple of years has been how to burn the wood gas as effectively as possible. Wood gas is a dirty gas, and I don’t know of any way to produce a cleaner burning gas directly from the pyrolysis front. Because of this, my efforts have been directed toward the wood gas burner system. The principle I have landed on is to rapidly burn the easy to burn gasses (CO, H2, CH4) in the wood gas, and concentrate that heat to crack the tars and other assorted long chain hydrocarbons. Then more secondary air is added to burn the newly cracked short chain flammable hydrocarbon gasses. This burns the wood gas very effectively, but leads to a fairly complicated burner system, and so might not be good to flair off the gasses produced in larger scale charcoal making. It might work for a biomass electrical power plant though.

There are lots of wild fires here in California, and heavy smoke. A simple larger scale, cookie cutter design, perhaps prefabricated, biomass electrical power plant that uses pyrolysis and saves the char could make a commodity of all that dry wood that feeds the wild fires. This could lead to the formation of commercial companies to gather the dry wood and sell it to the power plants. The first place to gather it is around evacuation routes, towns, and buildings. After this we could clear around fire roads and form safety zones where animals can find safety from a wild fire. I am imagining many such power plants placed from Washington state, through Oregon, into southern California and east to Colorado. They could produce a lot of biochar, sequester a lot of carbon, keep the air free of smoke, and reduce the need for fossil fuels.

Thank you Hugh for your insights,

I kind of changed the subject toward the end because the wild fires and smoke are on my mind right now.

Kirk H.

On 9/12/2020 6:36 PM, Hugh McLaughlin via groups.io wrote:

Dear list,

The basics of Tlud’s are well established, if not well organized. Let me share a few of my hunches, developed over the years:

1) Tlud’s are not chaotic. This means they follow the same path if started from the same starting point. This may seem obvious, but it is in fact a wonderful quality. It allows study and prediction of behavior. Lacking this, few studies will get far at predicting the future.

2) Tlud’s scale linearly, but become less stable as the many amplified variables become less deterministic. This is essentially academic gibberish, but it means that the scaled predictions are linear, but the results become less stable due to additional effects taking over.

3) For example, Tlud’s become less stable the bigger they are – in that the linear progression of the pyrolytic front in the z-axis become less stable in the x-y axis, leading to unstable (uneven) progression of the hot zone down the fuel stack. At some point, the flame zone expands under a section of fuel and the pyrolysis become unstable, resulting in traditional combustion of the fuel to ash.

4) Tlud’s make great stoves, due to relatively small scale and good heat transfer across the fuel bed. What is an acceptable temperature gradient across 150 mm become an unstable zone across 600 mm. At 2 meters, all stability is lost and the unit becomes a bonfire, not a controlled source of heat and biochar.

5) Significant instabilities in Tlud’s are observed at 200l vessels, and forced convection tends to exacerbate the imbalance. Bigger is only worse.

6) What Tlud’s do well they do brilliantly, beyond that, they are inferior to other designs.

I urge other to weigh in on the Tlud and it’s calling.

Regards,

Hugh McLaughlin, PhD, PE

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