Charcoal Gasifier

Basics

• There are some advantages with using charcoal (rather than wood) for gasification (section taken from: Troy Martz Gasifier). These may include:
  • Sufficiently drying wood/biomass to an appropriate water content % takes days. Charcoal can be made and used in mere hours.
  • The byproduct of charcoal sizing (anything under 1/16th of an inch) just happens to be perfectly sized for biochar...what a great byproduct to have
  • We don’t have to worry about tar! Thus, filtration in the down line is relegated to ash and dust…easily done.
  • Pure carbon is a perfect catalyst for the reduction process… You never really get 100% there with biomass.
  • We eliminated “pyrolysis” from the problem we’re trying to solve, so the gasifier design becomes infinitely more flexible than the “Imbert” design
  • We can scale gas production with the same system by merely swapping out a single nozzle size – we can go from 2kW to 50kW with the same machine!
  • Yes, charcoal has less BTU’s, but we can also utilize those BTU’s by capturing and using that heat with a smart charcoal retort design
  • Charcoal gasifiers have the potential to produce far more powerful gas flow than biomass gasifiers... Cracking steam is the key.

Troy Martz Gasifier - gasifies charcoal

Existing DIY/OS Designs

Greenhill Forge (YouTube Channel) 's Design

• A Video by the YouTube Channel "Greenhill Forge" Titled "Building a Simple Gasifier: FREE Engine Fuel from Charcoal" ( ~25 Minute Watch )
  • • Need to check with them if it's okay, but they have some GREAT infographics ~3:54
    • Also 0:55 Safety Note was Apt
      • "If you decide to experiment with gasification, please remember that it is LITERALLY a Carbon Monoxide making machine, and it can be extremely dangerous, so make sure you know what you are doing and do it safely
      • Uncertain on if SynGas has any Methane in it, but minor mistake / that may be an unintentional product infrequently mentioned in giant plant designs etc
      • I know Wood Gas / Pyrolysis Gas does tend to contain all sorts of gas species

Design Overview

• It is a Crossdraft Gasifier

Notes Taken by User: Eric while (re-)watching the video

• Made largely of welded together steel
• Uninsulated (Unlike the current OSE Design which uses a Fire Brick Hearth)
• It was made using a CNC Plasma Cutter , thus Files exist somewhere
• Intermittent Fillet Welds were used
• A Truncated U Shape is made over the Ash Grate to confine the reaction to a narrower space (presumably to follow the zone interacting with the air, almost the inverse of the "Dead Man" in Blast Furnaces )
• Oversized Inlet and Outlet Pipes (No exact dimensions mentioned)
• Only a linear (forward and backward) Ash Shaker , will be interesting to see if that will clog up or not
  • Largely depends on the Ash Content of the Charcoal , and the Hardness of the Shaker Grate? (ie can it grind up + "eat" the Bottom Ash / Clinker )
    • In terms of Design for Cleaning , making that part easily accessible may be worthwhile)
• Hinged Lid Reinforced with Square Tubing, and has a Gasket + Spring Latch
• Adhesive Fire Rope mentioned as a Gasket Material
• 3 Thermocouples "Stabbed In" (After being predrilled) and sealed with RTV Silicone
  • A more robust solution may be warranted for LONG TERM use (ie if/WHEN a probe fails, and needs replaced etc), but for an experimental setup this is fine
• It then goes to a Cyclonic Filter
• Neat Gas Flare made using a standard Soup Can and Steel Tubing
  • As per that Landfill Gas paper, probably the Chandelier Type? (Double Check This)
• Need to check an older video (with their albeit far more novel Charcoal Retort]] , but it seems this design DOES use Screened Charcoal
  • Seems to be a Trommel of Welded Wire Mesh, akin to that used for fencing
• Exhaust Blower On + a Blowtorch put in the inlet for start
  • 10-30 Second Startup until Self Sustaining Flare Flame
• Fuel Tank Removed from Engine, Engine Adapted to Drill Engine Starter , Fuel Line Capped Off, Carburetor / Throttle Body/ Fuel Assembly left in place as an easier experimental setup for that, dedicated replacement can be done later down the line
• A standard T-Fitting and Butterfly Valve (Neat DIY/OS Design using PVC Pipe made) is made for regulating Air-Fuel Mixture
  • Flashback Arrestors / Explosion Proofing, or at least Leak Monitoring may be warranted on this side, has my safety spidey senses tingling a bit
• An Air Filter Sponge is used, some sort of 3D Printed / CNC Milled adapter to either the standard String Trimmer/Chainsaw Filters, or a larger filter (Could be identical to HVAC and/or Car+Truck etc for Parts Reduction + Making Stockpiles of Spare Parts Inventory more useful etc) would probably be a better end goal solution
• A Sawdust Air Filter made from a Open Head Plastic Drum (30 Gallon Maybe?) is used AFTER the Blower/Flare Stack, but before the engine
  • CAN work, but leaves one to wonder on Blower Durability, most are air cooled, and as with Vacuum Cleaner Pre-Motor Filters keeping a blower as clean as possible is best practice
    • Frequent Enough Removal + Servicing could PROBABLY suffice, and again this is an experimental setup, not a power plant!, still just documenting thoughts
• They noted Corrosion in the Heart, possibly due to an Oversized Reduction Zone (Thus syngas flowing by not doing anything, cooling down/condensing + causing corrosion)
  • Syngas Filtration / Syngas Upgrading including Water Vapor Removal is worth investigating
  • Having a Thermometer-Hydrometer (Assuming they can be operated in an Atmosphere of Syngas, and do so without exploding etc) inline may aid in troubleshooting
• ALL IN ALL great design!

Thoughts/Ideas On It

• I'll have to go check out the OSE Design; they look similar in overall form, but may have different internals and whatnot
• Materials Science nerd me wonders if having it be CO-rich, Hydrogen -lean would be beneficial for Leak Detection + Reducing Hydrogen Embrittlement etc
  • Granted the adding water/steam basically turns Waste Heat into "Free" Power, right?
  • Granted it would add to Ash Content / clogging issues and POTENTIALLY add all sorts of problems, but using this as a way to Evaporate/Destroy Greywater etc would be neat (Although assuming Freshwater isn't scarce locally it shouldn't be that big of a deal
  • Exhaust Gas Water Recovery would be interesting to look into as well, if using a Rocket Mass Heater type mechanism to cool exhaust gas + a basic Dehumidifier (ESPECIALLY a Rotary Desiccant Wheel Dehumidifier )
  • Granted more parasitic load there eric!
• MORE SENSORS
  • Granted Intrinsically Safe / Explosion Proof Concerns there
  • Also, as with many Modern Cars etc, this can lead to an issue of "What would have been "business as usual" before (No sensor, but operating fine), is now a repair need (Sensor Broken/Faulty->Please Troubleshoot)
    • LUCKILY with Design for Repair / Design for Cleaning and all that, it SHOULD be a matter of remove it + put a new sensor from the spare bin in
      • Also how much does each temp probe cost etc 10-40USD maybe, above that it starts getting a bit much
      • Granted all relevant on how giant/important of aa build it will be/how long they last for ("Buy Once, Cry Once. Buy Cheap, Buy Twice " etc)
• I do think a Fire Brick / Refractory Lining would help. Designing it such that it slides in and is held in by slots, or is Interlocking Bricks would be nice for a Design for Repair / Design for Cleaning perspective (ie don't grab an SDS Drill / turn the whole thing to rubble/scrap metal, just remove the sacrificial layer and resume
  • I still haven't found a Refractory Material i LOVE from an Appropriate Materials perspective, but Firebrick / some rated mortar etc isn't HORRIBLE (again, need to check out the OSE Design)
• In terms of Charcoal Size, would powder/1cm chunks work well, or no?
  • Thinking More Surface Area = More Gas, granted do larger chunks/pellets help with air flow, anything smaller would be too clogging?
• A Rotary Airlock or other means to Refill While Running would also be nice
  • A "Knife Gate" and airtight lid may work a la those Wood Chip Boilers
• Some means to view Fuel Level (Short of it burns X Liters of Charcoal per Hour, thus we should add another bucket in an hour" type Dead Reckoning would be nice )
  • A Sapphire Watch Glass Based Sight Glass (ie one port up top, one just above the hot zone/one in the hot zone, keep it above the line and you're good)

Internal Links

• Gasifier 3D CAD (For OSE’s Latest Design)
• Compressed Fuel Gas
• Troy Martz Gasifier - gasifies charcoal
• Biomass to Fuel
• The Biochar Economy and Kon-Tiki Kiln

External Links

• "Small wood and charcoal gasifiers for operation of internal combustion engines"
• An Instructable by "fjrgjgr" Titled "Charcoal Powered Generator - Gasifier"
• A Permies . com Forum Post on Charcoal Gasification
• The Bioenergylists Page on Charcoal Gasifier Designs