Comparison of Flame Cap (FC or Open Cavity) Kiln and

Rotatable Covered Cavity (RoCC) Kiln Technologies

A Presentation at the 3rd Biochar Workshop

Butte College, Oroville, CA 27 – 28 February 2020

Paul S. Anderson, PhD Email: psanders@ilstu.edu

Woodgas Pyrolytics, Inc. www.woodgas.com

RoCC kiln

• 4-foot diameter, 5-foot long.

• Shortly after ignition.

• 27 February 2020

• Berkeley Olive Grove, Oroville, CA.

Farm-scale Char Production: Affordable 4C Kilns for

Quarter-Ton to One-Ton of Biochar Per Workday

Presentation on 1 July 2019 by

Paul S. Anderson, PhD ( psanders@ilstu.edu )

US Biochar Initiative Conference, Ft. Collins, Colorado

Several slides are taken or modified from an earlier presentation. [ See drtlud.com/resources and woodgas.com/resources ]

Review of Sizes for Pyrolytic Biomass Reduction & Biochar Production• Based on input of biomass per day

• Small 1 kg to 1 ton input• Retort: Regular and Adam Retort

• TLUD (Top-Lit UpDraft): Stoves and barrels

• Flame cap or cavity kiln: Cone; pyramid; trough; Kon Tiki

• Medium Missing size for 1 t to 20 t input

• Large 20 ton to 200 t/day (20 t/hr x 10 hr)• Air curtain: By Air Burner Co. and

ROI Carbonator 500 (Approx. $150 K to $600 K)

• Heated screw and Rotary kilns: (Installations from $300 K to $1.2 million)

• Furnaces that have char in the ashes.

The Challenges: To have Medium-size facilities with clean emissions, safety and biochar

• A full review would take all the available time and still be incomplete.

Small = flame cap || Large = air curtain

Exposed flames and || High volume of air

possible emissions. || has much combustion.

BOTH feature the use of air to "cover" the top to control emissions.

Note the missing middle for medium size char production technology.

• A fundamental issue: When the volume (pile) of biomass gets to be large, the biomass and char partially insulate and isolate the biomass in the center.

• Without sufficient air (with O2), there is not sufficient heat, so pyrolysis slows or even stops.

Review of "Flame Cap" kiln technology• Kelpie Wilson, Hans-Peter Schmidt & others have provided great explanations:

• https://greenyourhead.typepad.com/wilson_biochar_associates/Flame-Kilns.html

• https://www.biochar-journal.org/en/ct/39 (Kon Tiki design.)

• Two major principles and major features of flame cap pyrolysis:• The flame of burning gases above the biomass prevents (mostly) the entrance of air with

oxygen from reaching downward the created hot charcoal.

• The walled structure is where charcoal becomes buried under successive layers of biomass being pyrolyzed.

• Product names have referenced the shape of the walled structure: • Japanese cone kiln Pyramid kiln Trough kiln Trench kiln Pit kiln Barrel kiln (upright).

• Also, for specific designs: Oregon kiln Kon-Tiki pyrolyzer & Moxham kiln.

• All rely on a lower space, a cavity, for the collection of charcoal (w/o air entrance).

•A proposed additional inclusive name is "cavity kilns".There are numerous topless or uncovered or open cavity kilns. (see next)

Flame Cap or Open Cavity Kilns• Flame cap kiln is a cavity kiln with an open top:

• Cone, pyramid, trough, barrel/tube (vertical), trench/pit, etc.

• None have features to facilitate re-exposure of once-covered fuel.

• The cavities where charcoal collects remain relatively cool.

• There is less stress on the metal than from the higher temperatures of burning charcoal.

Covered Cavity Kiln• In 2014, after one attempt with a half barrel,

Anderson left a top on his cavity, creating a "covered cavity kiln".

• Provisional Patent Application but not pursued. Released into public knowledge in 2015.

• Named: Clean Controlled Covered Cavity (4C) kiln.

• Five of the 4C kilns were built and used occasionally by Anderson and Doug McCarty.

• Encouraging results for biochar but too labor intensive. Insufficient reasons to launch a product.

• No known replications by anyone.

Anderson 4C Kiln – Barrel (55 gallon = 0.2 m3 ) : For Farm and Forest Pyrolytic Biomass Reduction and Biochar Production

http://www.drtlud.com/wp-content/uploads/2019/01/4C-Kiln-for-CHAB-2019-01-23.pdf

YIMBY = Yes In My Back Yard

I have never had a complaint about smoke release. I have been quite careful to keep the flame cap burning.

Advantages of Covered Cavity Kilns • Lower emissions:

• Less influence of winds.

• More time keeping combustion gases concentrated.

• Door facilitates control of direction and volume of entering air.

• Controlled exit of emissions via chimneys.• Allows for monitoring with instruments to control operations.

• Controlled (channeled) exit of heat• Facilitates finding uses of the heat.

• Facilitates using the heat to pre-dry incoming fuel.

• Reduces risks of sparks and starting wildfires.

• Char extraction options instead of tipping or shoveling.

• Can be scaled larger more easily. (to be discussed).

• Good quality char. (see next). (The only testing thus far.)

Char quality: Test results of char from Anderson 4C kiln

Based on our testing it looks like excellent char. The ash is 10% so reporting on an ash-free basis it brings the carbon much higher in this natural fraction. The butane activity is a mid-ranged based on typical findings on dry wt basis. -- Frank Shields Oct. 2014

Disadvantages of Cavity Kilns, both open-top and covered

• Fuel input is gradual and frequent and requires presence and attention of the user.

• Possible incomplete charring if the biomass fuel becomes buried between incoming biomass and the bed of produced char that is cooling.

• Lack of control of internal temperatures, resulting from

**** Lack of control of air flows.****

• [Note: We will deal with these problems.]

Larger-size attempts with 4C kiln technology

210 gallon 0.8 m3 (above)

http://www.drtlud.com/wp-content/uploads/2019/01/4C-Kiln-for-CHAB-2019-01-23.pdf

275-gallon 1.0 m3

http://www.drtlud.com/wp-content/uploads/2019/01/4C-Kiln-for-CHAB-2019-01-23.pdf

Anderson 4C Kiln – Large Tank (4x6x8 ft) (1200 gallon or 4.5 m3 or 6 yd3 )

First public demonstration was held on Friday 19 July 2019 in Goodfield, Illinois at a meeting of the Illinois Biochar Group (IBG). Above: Fabrication

underway of a 4x6x4 ft test unit with ~2.4 m3

capacity.

Biochar was produced and therefore it was successful, but not sufficient to justify further work with this type of design. It was too labor intensive, awkward to use, and too hot to approach for necessary functions for mixing and extraction.

TWO innovations for the Anderson kilns:• Why two? Because the first one is deficient by itself.

• Covered Cavity Kiln (1st innovation, 2014) has three deficiencies found in all flame cap cavity kilns. • Fuel input is still gradual and requires attention of the user.

• Possible incomplete charring if the biomass fuel becomes buried.

• Lack of control of air flows.

• Rotatable Covered Cavity (RoCC) Kiln (2nd innovation, 2019) shows how to solve these problems:• Facilitate fuel delivery and with possible automation.

• Assure complete charring of the biomass.

• Attain better control over the air flows, emissions and availability of heat.

• Have (nearly) continuous operations as well as batch operations.

• Be sufficiently low cost with low maintenance and low labor requirements.

• Be able to scale to much larger sizes and volumes.

Solutions• Tumbling of the biomass is possible if the kiln is rotated when needed.

• Let gravity do the work of mixing and exposing the torrefied biomass.

• Rotation of 240o is possible because it is a covered cavity.

• Remove the door; have an open portal that goes to different positions for different purposes.

• Fuel loading by horizontal shelf or vertical drop (incl. bins and hoppers).

• Unloading downward. Let gravity do the work.

• Moveable grate (prongs/fingers) to help select what is discharged. Door to cover portal is possible for special cases, including 360o rotation.

• Separate the chimneys from the kiln; place them on a detached hood.

• Utilize standardized materials, such as corrugated steel pipe (CSP) that has many diameters and plenty of length.

This allows for additional benefits

• Scale from < 2-ft to > 16-ft diameters, and lengths appropriate for the biomass and desired throughput.

• Be either portable or stationary.

• Is compatible for addition of sensors and air control.

• Have directional control of the emitted gases and heat which can provide additional value.

• The operators are less exposed to direct fire and radiant heat.

Introductory images of two RoCC Kilns

• There are MANY improvements that cannot be seen in these initial images. Do not replicate what is shown here.

• See RoCC Kiln Manual at woodgas.com/RoCCand contact Paul Anderson for assistance.

• 3-foot diameter, 4-foot long. India >>>>

• 4-foot diameter, 5-foot long.

• 28 February 2020; Shortly after ignition.

• Berkeley Olive Grove, Oroville, CA. >>>>>>>

The front side is under the hood and has the horizontal shelf for feeding fuel.

SUMMARY:•The Rotatable Covered Cavity (RoCC) kiln technology and devices help fill the massive gap in size and cost options for small and medium biochar operations such as for farms, woodlots, and places generating “refuse” biomass.

•Possible scale-up to very large sizes. This will depend on need, financing and engineering.

Original: Paul S. Anderson 2019-03. Text changes and color added 2020-03.

1. Include numerous non-monetary benefits.2. Any one benefit could be sufficient justification. Attaining two benefits (or 3 or 4) is possible w/ awesome results.3. If possible, find uses for the heat from pyrolysis. 4. The charcoal (biochar) can have more value than the 30% increase in created heat from burned charcoal.5. Biomass disposal by pyrolysis can be less expensive than if sent to landfill or burned to ash. 6. Biochar into soil is stable Carbon Dioxide Removal (CDR) plus available energy (BC&E).

Multiple Profit Centers from

Pyrolysis

Pyrolytic Devices and Technologies

Charcoal ProductsBiochar into soilChar gasificationFuel, filter, etc.

Thermal EnergyApplications of heat

Replace fossil fuels

Biomass DisposalAvoid landfillFire protectionAir quality

OtherBenefits ChemicalsCarbon OffsetsClimate benefits

Economics of RoCC Pyrolysis• The smaller units can be manually operated by one person.

• Larger units could have automated loading/unloading.

• Financial feasibility is impacted by costs of biomass feedstock, labor, equipment, value of the char produced, and value of heat and by-products.

• There are many business models.• Dr. Anderson has patent pending status on the RoCC process and basic components.

• It is time for others to become involved!!• Sponsors, investors, licensees, researchers, corporations, agencies are welcome.

• Geographic territories can be allocated to those who facilitate progress.

Contact: Paul S. Anderson, PhD Email: psanders@ilstu.edu

Phone: 309-452-7072 Woodgas Pyrolytics, Inc. www.woodgas.com

Table of sizes of RoCC Char makers (Version 2020-03-08; Draft still in need of refinement; Some rounding.)

(Based on cylinders; Extrapolations from Column B; Estimated variability of +/- 50%)

A B C D E FSize >>>>

Issue (below) 55 gallon (Barrel) ~140 < 180 gallon 464 gallon (4x5 ft)

(8 barrels) (1.7 m3)750 gallon (4x8 ft)( 14 barrels)

1500 gallon(~ 20 barrels)

a Dimensions (Diameter x Length)

(D) 2 x 3 ft = 9 ft3 3 x 4 ft (28 ft3)(210 gal)

4 x 5 ft (62 ft3)(464 gal)

4 x 8 ft = 100 ft3(2.8 m3)

4 x 16 ft= 200 ft3(~5.6 m3)

b Fuel input (kg/hr)(extrapolation from Col B)

~25 kg ~50 lbs(~3 - ~2.5 kg/ft3/hr)

~84 kg/hr 180 - 200 kg/hr 250 – 300 kg ( Quarter ton )

500 kg 1000 lbs( Half ton )

c Char output (kg/hr @ 20% yield) [ CO2e reduction per hour]

5 kg 1 wheelbarrow (WB) [ 18 kg ]

~16 kg/hr[ 58 kg ]

40 kg[ 146 kg ]

50 kg[ ~ 183 kg ]

100 kg [ 366 kg ]

d Thermal energy output as 70% of total (30% remains in char)12 MJ/kg/hr 8 BTU/lb/hr

300 MJ83 kW-h

284 K BTU

Almost 1 M BTU(Under EPA interest threshold)

2400 MJ666 kW-h

2.3 M BTU

3000 MJ830 kW-h

2.8 M BTU

6000 MJ1660 kW-h

5.6 M BTUef

A (repeated) F ( with new units) G I J K

Size >>>> Issue (below)

1500-gallon 200 ft34x16 ft; 5x10 ftf; 6x7 ft

3000-gallon 400 ft3 11.3 m3

7500-gallon 1000 ft3 28 m3 = 20 ft container

15,000 gal 2000 ft356 m3 = 40 ft container

30 K gallon 4000 ft3113 m3 (RR tank car)

a Diameter / Length 4 x 6 x 8ft = 200 ft3(~5.6 m3)

6 x 14 ft or 7 x 10 ft8 x 8 ft

8 x 20 ft10 x 13 ft 12 x 9 ft

12 x 18 ft 14x 13 ft16 x 10 ft

10 x 52 ft (RR tank car) 16 x 20 ft

b Fuel input (estimate per hr)(extrapolation from Col B)

500 kg( Half ton )

1000 kg ~ One ton per hour

2.5 tons per hour 5 tons per hour(~3 - ~2.5 kg/ft3/hr)

~10 tons/hr

c Char output ( w/ 20% yield)[ CO2e reduction per hour ]

100 kg[ 0.36 t ]

200 kg/hr[ 0.73 t ]

500 kg/hr[ 1.8 t ]

1 t/hr[ 3.6 t ]

Estimate 2 tons/hour[ 7.2 t/hr ]

d Thermal energy output as 70% of total (30% remains in char)12 MJ/kg 8 K BTU/lb

6 GJ Gigajoules1.66 MW-h

5.6 M BTU

12 GJ Gigajoules3 MW-h

10 M BTU

30 GJ8 MW-h

28 M BTU

60 GJ16 MW-h

57M BTU

~120 GJ 33 MW-h

114 M BTUef