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GEK Kit Operation Manual

Page history last edited by jay@... 12 years ago

return to How to Build and Run the GEK Gasifier 

Rev 4.3 Updated"041112

GEK Kit Operation Manual

Version 3.5-4.x

Basic GEK & TOTTI, Level III & IV Kits 


Table of Contents

I. Notes about Safety 

II. Recommended Tools

III. Assembly Prerequisites

IV. FiIlter Media 

V. Adding Charcoal to the Reactor 

VI. Feedstock Requirements and Filling the Hopper

VII. Double Check & Cold Test

 VIII. Manometer and Thermocouples

IX. Operating the GEK: Start Up and Shutdown

X. Maintenance


I. Notes about Safety 


Before you start, and whenever you run a gasifier, please remember the following . . . 

Please wear safety goggles at all times while operating the PowerPallet or the GEK Gasifier. 


Review the health guidelines of carbon monoxide:

A gasifier is a dangerous thermo-chemical device.  Like most useful tools, it will do damage if used incorrectly.   A gasifier purposely generates carbon monoxide and other dangerous volatile organic gases as an interim step before combustion of the gas in a flare or engine.   Carbon monoxide is colorless, odorless, and will quickly colonize your hemoglobin, leaving no sites left for oxygen to land.  Acute exposure to carbon monoxide can be harmful or fatal.  Exposure to other VOCs is similarly problematic.  (In short, it is somewhat like smoking cigarettes, just exponentially worse.)


Always use a gasifier outdoors, and with extensive ventilation.  Always stay out of the smoke and/or produced gas before it is combusted.  Know that this is NOT typical campfire smoke.  Do NOT treat it as if it were.  The carbon monoxide concentrations in gasifier gas are higher than in other "smokes".  You can get in trouble quickly, usually before you realize it. 


Always have a fast reacting carbon monoxide meter in the area where you are working.  Ideally, hang one on a tether around your neck.  Carbon monoxide meters are included in your kit, if not they are available at more hardware stores in the smoke detector section.



Do not run the GEK Gasifier or PowerPallet without filter media in the gas filter. Lack of filter media in the gas filter can allow a large volume of wood gas and air mixture. Large volumes of near stoichiometric mixture can pose a danger of explosion. 



II. Recommended Tools and Materials:

  1. Biomass 
    • It is important to use feed stock within the requirements of the system. Please refer to the biomass feed stock requirements outlined here:
    • Please note that using feed stocks outside of the range of characteristics outlined above can lead to very difficult or long start up times. While the flare burns off the CO and hydrogen, long and difficult start ups can produce an incombustible gas with high CO concentrations- to remedy this, there is a connection for the option to flare these gases with propane between in the intermediate. 
    • Feed stock characteristics outside of this range can also cause bridging across the reduction bell or in the hopper. Longer sections can also jam or immobilize the auger.  


  1. Highly recommended tools and materials include:  
    • two 1/2'' or 13mm wrench or socket drivers
    • suggested: hand held drill  
    • two hand held propane torches
    • 2-5 oz of diesel or gasoline
    • squirt bottle 
    • box fan or other active ventilation 
    • safety glasses
    • ear protection
    • gloves for touching hot surfaces
    • pliers
    • step stool or ladder 
    • long stick ~4' (metal or wooden)
    • water or colored fluid 
    • bucket
    • <1/2'' screen for sifting
    • <1.5'' screen for sifting
    • air compressor capable of 6-8 cfm at 90-120psi 
    • motor oil (if you have the Filter Foam Disks) or towel, fabric, other disposable fine filter
    • caulking gun
    • scissors


III.  Assembly Prerequisites

  • These instructions assume you have completed the Fabrication Instructions (if you welded your own, Level III) as well as the Assembly Instructions (if you bought the Level IV).
  • Try starting up without the hopper first, this will be easier to manage preliminary runs. 


IV. Filter Media

Warning! Lack of filter media in the reactor can allow for the volume to fill with a stoichiometric mixture of gas and air which can allow potential for explosion. Never run the GEK or PowerPallet systems with an empty gas filter. 

  • Make sure the filter housing is filled with charcoal media following the chart below marked in inches from the top of the Gas Filter lid.  
  • Other materials can be used, however only use organic material that does not have any volatile portion that can withstand temperatures up to 150C.  
  • Make sure that the fine dust does not make it into your filter, any very fine particulates will overwhelm your final filters and can possibly make it into your engine. If you are not running an engine, this will not be a problem as it will just burn up in the flare.  (Some people will wash the charcoal with water to separate the finer materials)




  1. Place the Perf Disk on the support bolts at the bottom of the filter.
  2. Fill the first 2'' of space with ~1'' dia. charcoal.  
  3. Fill the rest of the gas filter with charcoal between 1/2''-1/16th'' up to the top.
  4. If you have the Filter Foam Disks, save room at the top to add these. Place the Coarse Foam (65dpi) first and then the second Fine Foam (45dpi) on the top. Make sure that the filter lid does not compress the foam filters.
  5. If you do not have the Filter Foam Disks, use an organic mesh cloth (cloth, t-shirt, or rag works very well) to completely cover the top of the media. Make sure the cloth covers the bulk to the edges so that the small bulk media particles do not escape with the gas stream. 
  6. Next place the second Perf Disk on top of the filter media. 
  7. Attach the Filter Barrel Lid.  


  • Most of the GEK kits do not come with the Filter Foam Disks. However if you are using these Filter Foam Disks, dip them in an oil like clean motor oil or the like and squeeze out the excess. These filters work by efficiency trapping small particles using the oil surface. 
    • We are starting to phase in the Filter Foam Disks. If you do not have these, you may use any organic fabric such as a cloth to provide filtering for the finer particulates. If this was not included in your kit and you would like to purchase them from us, contact for ordering information. 


V. Adding Charcoal to the Reactor 

  • Fill the bottom of the reactor, as well as inside the reduction bell, and on top of the ash grate with charcoal. Fill the reduction bell, then spin your ash grate, this will pull the charcoal into the space under your reactor, reapeat until it wont fill any more. Use chunks of about .5" -  1" cross section.  No dust, as that will foul the reduction on start.  Fill all the way up to about 4 inches below the Reactor Lid. Make sure the charcoal fully filling all the lower spaces and nooks and crannies. Shake the Ash Grate vigorously to allow the charcoal to settle into the Reactor. If you need to use a long stick to jam the charcoal down into the Ash Grate and below the Reduction Bell.
  • USE REAL WOOD CHARCOAL!  It is important that you start with real wood charcoal, not Kingsford or the like, which is mostly pressed coal dust.  Get some charcoal from your fireplace or firepit, or mesquite BBQ charcoal.  Make sure the charcoal is fully pyrolysed.  To the degree that you use imcompletely pyrolysed charcoal, you will get tar on start up.  To the degree you use wet charcoal, you will have steam on start up.  Charcoal is very hydroscopic so it is likely your charcoal will be wetter than you imagine.  Such is OK as it will vaporize off quickly.  You will see this as white smoke at the beginning of the start.



VI. Feedstock Requirements and Filling the Hopper

  1. Feed stock requirements

We promote your experimentation with all kinds of feed stocks with our systems, however we have noted that outside of these requirements of the feed stock may require some additional components, filters, or reactor design. If you have questions about your feed stock, please send an email to with the following information: particle size distribution, moisture content, species, a picture, and your end use of the gasifier; and we will send you advice on your proposed feed stock according to your use. 

    • Generally the feed stock requirements for the v4.3 and earlier are as follows:
      • 0.5 - 1.5'' particle size 
      • <15% moisture content by dry weight (for initial start)
      • <25% moisture content by dry weight (once the system is up to temperature)
      • Low volatile content (higher volatile content fuels that contain heavier saps or resins, such as pine cones, tend to create heavier tars that can clog the system and require more frequent break down and maintenance).
      • No coal, brown coal, peat, plastics, or tires (some feed stocks contain compounds that create substances that are not only difficult on the system but the Gas Filter may not be designed to handle it. This could result in dangerous emissions and produce some acids (sulfuric acid or hydrochloric acid) that tend to eat up the inside of the equipment if not filtered appropriately).
      • No fine saw dust or other fine material (if the packing characteristic is such that there is little void space, the flow rate of the wood gas will limited through the Reactor. Finer material is best in fluidized or active bed gasifier designs).
      • Larger slivers or particle sizes can cause bridging over the Reduction Bell or jam the Auger. 



More on the GEK Forum:


     2. Filling the Hopper

    • When filling the hopper, use the step stool to pour in the feed stock from the top. If you have another hopper or auger feed system, you may consider adapting on to the hopper or drying bucket to service the GEK system.
    • The Hopper lid can be opened for under 30 seconds to refill while the gasifier is running. You will want to do this quickly and be sure to not stick your head into the hopper and take a giant breath! While there may be CO in the Hopper, generally risk of exposure at this point is very low due to the suction of air wanting to enter the system.
    • Be sure to wipe any chips off of the lid before sealing the lid down. Make sure you get a good air tight seal every time you reattach the lid. 


VII. Double Check & Cold Test

Before lighting, always double check everything! It is much easier to trouble shoot the preliminaries before the gasifier gets hot. 

  1. Gaskets and Seals
    •  Durning assembly every single flange and connection should be sealed, there should be no metal flanges touching each other without sealing. The ejector venturi pulls a vacuum on the system which pulls air through the air nozzles inside the reactor. If seals are leaking, the reaction will be compramised leading to failed runs and leaking of wood gas (namely carbon monoxide) will occur out of unsuspected places in the system during shut down. 




     2. Cold Test 

  • Open the air inlet cap on the reactor, open the valve to the swirl burner, and close the air pre-mix valve. Turn on the air compressor (or fan), does the manometer quickly respond (you should be able to pull 5 inches of water easily before its lit)? If not, do not try to light the GEK Reactor, instead double check: 
    1. Air Inlet cap: Is the Air Inlet cap still on?
    2. Check the Manometer: If the Manometer is still not responding, check to see if the manometer is hooked up correctly. Are there two different channels- One connected to the Reactor giving the difference between the outside pressure and the reactor, and the second channel is connected to the filter giving the differential reading for outside pressure and filter pressure. 
    3. All seals in place: Any leaking downstream in the system will bypass the suction needed for the air nozzles. Sealing is very important: check: bottom plate of the reactor, bottom of the reduction bell, top of the gas cowling, reactor lid, reactor lid port cover, cyclone flange, mason jar connection, cyclone tube plate, filter housing, filter housing lid, ash port, lid port, hopper flange, hopper lid, drying bucket, grate shaker etc.
    4. All bungs/openings are plugged/capped: There are several places where there are holes that need to be plugged: large bung on the side of the gas cowling, thermocouple port on the top of the reactor, any ports on the lid, the gas out sampling port on the gas cowling right before the cyclone, the three ports on the filter housing (one is populated with the manometer), the port at the bottom of the reactor (where the manometer face plate is located).
    5. Open all gas valves: There are two valves on the top of the ejector venturi assembly. There is one that is a port for the gas take off, this should be closed at start up. The other routes to the swirl burner, this one should be open. The purpose of the flare is to start up the reactor and flare off the tarry gasses during the time it takes the reactor to get up to the temperatures it takes to crack the tars. It is possible after a run that wood tars will condense on the gate valve making it harder to open, with the same amount of torque you gave it previously it feels open when it could be closed. Double check this when it is relevent.
    6. All seals in place: Any leaking downstream in the system will bypass the suction needed for the air nozzles. Sealing is very important: check: bottom plate of the reactor, bottom of the reduction bell, top of the gas cowling, reactor lid, cyclone flange, mason jar connection, cyclone tube plate, filter housing, filter housing lid, ash port, top port.
    7. Open/close proper gas valves: There are two valves on the top of the ejector venturi assembly. There is one that is a port for the gas take off, this should be closed at start up. The other routes to the swirl burner, this one should be open. The purpose of the flare is to start up the reactor and flare off the tarry gasses during the time it takes the reactor to get up to the temperatures it takes to crack the tars. It is possible after a run that wood tars will condense on the gate valve making it harder to open, with the same amount of torque you gave it previously it feels open when it could be closed. Double check this when it is relevent.
    8. Manometer responding? Yes? Great!


VIII. Manometer and Thermocouples

  1. Manometer
    • Fill up the manometer with water up to the zero mark. We add a couple drops of of something colored so that it is more visible.
    • Be sure to get all of the bubbles out. This is easier to disconnect the ends of the manometer from the reactor and filter port temporarily so that the bubbles can escape.




     2. Thermocouples


    • There are several places that we have added ports so that thermocouples can be placed in significant places through out the system. We have found that the top and bottom of reduction temperatures to be of significant importance and will tell a lot about how the reactor is running:


      • Top of reduction temperature: The new stainless steal 11'' hourglass reduction bell has a thermocouple port in the top of reduction temperature can slide into the instrument. Thread the thermocouple through the smooth threadless port down through the top of the reactor. Be sure to secure and protect the thermocouple so that it is not in the way of the flow of biomass through the reactor.Be sure to seal up the port so that no air is able to enter.  
      • Bottom of reduction temperature: The cap on the close nipple of the manometer can be ameded to be a port for a thermocouple. A thermocouple at this location will clear the bottom of the reaction chamber inside the gas cowling. Be careful when placing a thermocouple at this location: If the thermocoule seems to jam, move it around a little so that it will slide in between the gas lines. Place the thermocouple one inch inside the edge of the reduction bell, any further can block the flow of charcoal in this region.

    • Test your thermocouples. Are do they respond to a flare? Are they reading the right temperature?

IX. Operating the GEK: Start up and Shutdown

Saftey! Be aware, and remember protective eye equipment, when dealing with the combustion of fuels there is always a potential of explosions.

  1. Air Flow
    • Connect the air compressor to the Ejector Venturi. 
    • Open the compressed air valve on the Ejector Venturi. This is the 1/4" valve where the air line connects. Set the pressure drop across the reactor to about 1''H2O.
  2. Ignition 
    • Leave the Air Inlet port closed for now.  
    • Squirt in about 2oz of liquid fuel into the lighting port for lighting the Reactor.
    • Light with a propane torch holding it about an inch from the inlet so as to provide oxygen for the propane torch. Make sure that the air is flowing into the reactor to be careful of potential back fire, or puffs from this port. You may need to keep the torch there for a minute or two.
    • When the temperature of the starts to rise, open the 1'' Air Inlet port.
    • When the Reactor is at about 100C, close the cap on the ignition port when Reactor is lit.
    • The temperatures should start climbing from here. If not, open the ignition port carefully add more liquid fuel, and apply the propane torch again. 
  3. Flare
    • Within a few seconds of lighting, gas will come out of the flare. At first this may not be a combustible gas until the Reactor bed gets up to temperature.
    • As soon as you see the smoke in the flare, place the second propane torch over this smoke to burn off any potential CO and particulates.   
    • If this initial uncombustible gas is a concern, a propane connection can also be introduced just before the flare using a pumbing T. The propane can be introduce to the flare to burn off any gasses, then turned off after the Reactor has warmed up. There is a port that comes with the Ejector Venturi for this purpose.
  4. Sustained Flare
    • After a few minutes the T_tred and T_bred temperatures will read above 400-500C and the gas produced will be able to hold a flare, at this point you may discontinue using the propane torch or pilot.  Adjust the oxygen mixture on the flare to transition from a propane to wood gas flare (this is the 3/4" valve on your Ejector). 
    • Keep the propane torch nearby in case the flare goes out and you need to relight it quickly. 
    • Remember do not breathe the gas when it is unburned.  After it is burned it is very clean.
    • Notes on Flare Dynamics:
      • When the O2 valve is closed too far, the flare does not have enough oxygen and it will rise up out of the flare stack. Because there may not be enough oxygen to competely combust the carbon monoxide and hydrogen, there could be some carbon monoxide being released near the flare that has not combusted. As you open the O2 valve, the flare will pull back into the flare stack. All of the woodgas should be combusting before halfway along the flare stack. This ensures a complete combustion.
      • When the O2 valve is opened the ejector will be pulling air through this port which will lower the vacuum that it pulls on the rest of the system. Notice that when the O2 valve is opened, the manometer will indicate that the pressure drop across the reactor (and the filter) lowers. Make sure that you are staying in range of the proper pull rate. You may need to increase the flow across the ejector to make up for this difference.
  5. Proper Gas Pull Rates and Ranges
    • For starters, we suggest running the reactor at about 5"H2O vacuum, as read on the GEK manometer.  This is a good pull rate that will most likely bring you up into the correct temperature range to ensure tar is cracked.
    • As for ongoing running, here's the range of gas pull rates you can explore, and where the "out of bounds" thresholds are to be found.  Remember this is the reactor only.  You can expect to see another 2-5"H2O with the reading after the filter.

10+ Overpull

8 Maximum

6 Good

5 Ideal

4 Good

2 OK

1 Minimum

0-1 Underpull

  • Overpull creates a mess of soot and weak gas
  • Underpull creates a mess of tars and richer gas




     6. Filter

    • The manometer is your first indication that the filter media may be clogged.
    • If the filter media is working properly, generally there will be a 2-4 inch of water difference between the two of them.




    • If the reactor and filter pressure have a larger difference between them, it might be best to change your filter media.




     7. Note rate of fuel consumption

    • All biomass is different. Check the fuel level every few minutes through the fill port until you get a feel for how quickly it lowers.   Do not let it go more than halfway to the nozzles before you refill. Without a hopper or auger filling option attached, the Reactor will likely need more fuel every 5-10 minutes for the 3'' bell, and much shorter for the 4''bell.Nonetheless, when first learning how the GEK runs, you should experiment without the hopper.


     8. Shut down

      • Close the Flare valve (the valve in between the Ejector and the Gas Filter. 
      • Place the 1'' cap on the Air Inlet.
      • Close the air compressor needle valve and the air premix valve.
    • DO NOT let the gasifier run out of feed stock while continuing to allow air inside the reactor. The consequence of this will increase the temperatures in the reactor to 1000C or above and combustion can migrate to your cyclone and even the gas filter. The indication that you have run out of fuel is if the auger motor is running continuously without adding any feed stock to the reactor, and the lid of the reactor becomes hotter than 400C. (You may add a thermocouple at the lid or add an LED in line with the auger circuit- or logic with a timer and alarm to detect the auger duty cycle). 
      • Combustion occurs because the reactor is designed to allow a ratio of air into the vessel that is proportional to the wood chips in the vessel. When the amount of wood chips decrease, there is an increase in the O2/wood chips (air/fuel) ratio. This swings the reaction from partial combustion (gasification) to complete combustion. 

     9. Ponder

    • Try and break it.  Figure out how and why it works.  Change the fuels.  Change all the internals around.  Make it better.  Send us your pictures and videos so we can ponder the mysteries of biomass thermal conversion together and tell others what you did. Enjoy!


X. Maintenance


WARNING: Before opening the GEK system when cold, connect the compressor up to the Ejector, open the Flare Valve, place the propane torch in the swirl burner and increase the flow from the air compressor. Purge the wood gas out of the system for a few minutes before opening the system to do maintenance. We have never had issues with CO exposure during the running of the gasifier, it is usually when it is cold and not running that people may become casual and forget that the unit still contains wood gas even when the system is cold and its been well after the last run. <BE AWARE>


  • Maintenance and the GEK:
    • Before starting the GEK make sure of the following:
      • Cyclone jar is empty
      • Gas Filter is not clogged
      • Charcoal is about 4'' from the top of the Reactor Lid.
      • You are able to turn all valves to the fully open and closed position 
      • make sure the manometer is working (we have seen users lay the tubing against the Reactor surface and melt the manometer- make sure you don't do this!). 
    • The frequency of the full break down and maintenance of the GEK will be most dependent on what feed stock you are using. Break down the gasifier after about 10-15 cycles (start up and shutdown) to service the unit. Feed stocks with a lot of resin or sap, higher moisture contents, and more time spent in lower temperature ranges will increase the frequency of maintenance needed for the GEK. You will want to check it out first after this first run of cycles, you may be able to go longer till the next break down for maintenance, but we suggest to check it sooner to become more familiar with how your feed stock and use and scenario is interacting with the equipment. 
  1. Reactor
    • Air Lines
      • Slide the Reactor out of the Gas Cowling and check the Air Lines.
      • Use a wire brush to scrape the soot and tars off of the lines.  
      • Check for cracks 
    • Reduction Bell
      • Check for corrosion 
    • Air Nozzles 
      • check for corrosion 
  2. Gas Lines
    • Use a long pole or bottle brush and clean the insides of the gas lines. 
  3. Cyclone
    •  Empty Cyclone Condensate Jar
    • Clean out the Cyclone and scrape the walls of any tars or soot.  
  4. Gas Filter
    • Filter Foam Disks
      • To clean, wash in soapy warm water.
      • Make sure they are completely dry before adding more oil.
      • Squeeze out the excess and pack back into the filter
    • Bulk Filter Media
      • The spent media mostly consists of wood tar and water.
      • Dry this bulk out and add it at the max 10% or so back into your feed stock to give it a second pass (there is still energy in the tars, but don't overwhelm the system by adding too much.

     5. Reassemble the GEK

    • Make sure all seals are in tact and will keep a good air tight seal. While most of the gaskets and sealants can be found commonly at hardware stores, you can purchase a pack of seals, tapes, sealants, and insulation from us. For pricing information contact 


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