Charcoal Making Outdoor Cookstove (TLUD)
Wikipedia definition: A top-lit updraft gasifier (also known as a TLUD) is a micro-kiln used to produce charcoal, especially biochar, and heat for cooking. ... A TLUD gasifier takes it further from a rocket stove in more efficient way of smoke-free, highly efficient combustion of the fuel. My Rocket Stove (not a TLUD) is made of a concrete mixture of sand/crushed glass/perlite/and charcoal fines mixed with Portland Cement. It works very well for simmering a pot of beans. (I have since painted it black with latex paint.) The major drawback, in my opinion, is that it burns the wood to ash, and does not make charcoal.
This Blog Post will show the Charcoal Making Stove that has evolved on my patio over the last dozen years. In the beginning, I constructed very small stoves from bean and coffee cans. (TinCanium). and even purchased a Stainless Steel Campstove designed by Tom Reed.
This was a very good fan assisted stove that I used until it finally burnt out, as shown in the photo below:
My attempts to repair it with an air conditioner accumulator were not very successful.
I moved on to the 2008 Champion TLUD stove that Paul Anderson describes in plans available online. http://www.drtlud.com/?resource=prt09320
Using a discarded Freon container, I built a version of that stove that worked well for many years. It is still the best stove in my collection for making a large batch of Pita Breads, as I describe in this eight year old YouTube Video: https://youtu.be/JOuoE2KAbQI
Be sure to expand the description for more information, and to Donna's website for the detailed recipe and technique. (It is very difficult to make the breads develop pockets.)
Martin Payne attended a Stove Workshop and purchased a pair of the Anderson designed flat-pack Quad stoves which we assembled. Photo:
The Quad Stove makes charcoal, and it is easy to dump the charcoal at the end of the cooking session by just lifting the bottom part of the stove and dumping. It can be temperamental, and doesn't hold enough fuel to do any serious cooking or water heating.
Meanwhile, I purchased two more Tom Reed Woodgas stoves and gave one to each of our children. Also purchased a Bio-lite TEG powered motorcycle camping stove, which I used a few times and re-sold on eBay. (It was too small!)
Purchased a really inexpensive Chinese Stainless Steel Campstove, but it also was too small, and practically useless unless you wanted to heat a 4 ounce cup of tea. I experimented with trying to collect charcoal from the Rocket Stove, but really wanted a stove that would produce significant amounts of charcoal.
After a decade of making a room full of experimental stoves, and actually using them several times a week, I'll describe what I have been using for the last two years, and am very satisfied with the power level and lack of any smoke in normal operation, and the fact that it will hold enough fuel for a maximum of 90 minutes of high power cooking. One criteria was that it be made entirely of "obtanium" or recycled materials. First (and most important) is the grate, which needs to be almost indestructible, because as the fuel pyrolyizes, starting at the top and working down to the grate, you end up with a pile of 2000 degree glowing charcoal that will absolutely destroy materials it contacts if additional forced air is added with a small blower. Normally, the char is dumped as soon as there are no more flames, meaning the wood has been converted to charcoal, but if you are cooking rice or beans, and need a bit more time, it is easy to turn on the blower and consume some of the charcoal to finish the cooking process. A grate made from a 10" worn-out carbide sawblade or a small cast iron frying pan will work. (The frying pan will outlast the sawblade.)
Finally, after burning a hole in the grate, I turned to the frying pan solution:
A stainless pot with a 9" diameter is used to hold the grate. Use a Harbor Freight angle grinder with a thin cut-off blade to remove the teeth from the sawblade, or alternatively put it in a strong vise and knock the teeth off with a heavy duty hammer.
Cut a 2" hole in the lower edge of the pot, and insert a piece of pipe with slots cut in the bottom edge, like this: Use the angle grinder, then punch the middle into the pipe.
Cut a hole in the pot, leaving fingers that can be wrapped around the slotted pipe and covered with a strip of tin and a hose clamp.
The pipe should stick out of the side of the pot no more than an inch or two, and it should run all the way to the opposite side of the pot, with the notches facing down.
Next, use two pieces of regular 6" diameter 24" long stove pipe bolted to each other and placed into the 9" pot. Bolt them to the pot, after putting the grate (skillet) in place. (This allows dumping of the charcoal without having the grate fall out.) Measure the height of the pot with pipe as it stands on the ground, and cut a section from a water heater tank that high, plus 1/2".
To get a better understanding, here is one of my earlier builds (from June of 2013) shown as a YouTube slide show: https://youtu.be/vHms7E0VAio Be sure to read the description under the video.
A layer of old tin roofing is inserted into the water heater tank to provide some insulation, with some fiberglass inserted between the two. I leave this stove out on the patio, covered so water does not get into it and saturate the fiberglass insulation. However, Mice do like to take up housekeeping, until I start loading the stove, and then they move out, or else.
Since that slide show/video in 2013, I have made some improvements in that I no longer use the throttle at the bottom, nor do I use the bricks supporting the pot. The bricks were not very stable, and were replaced with a metal oil change pan filled with a casting of perlite, crushed glass, sand, charcoal, and Plaster. I had an old used pan, but here is a photo of a new one:
Here is the finished product.
and (making Naan in a cast iron Wok).
Underneath the drip pan assembly is a sheet of steel cut from the top of a 55 gallon steel drum. The steel has a 4" diameter hole (a restriction), so when you cast the material in the drip pan, use a grapefruit juice can filled with rocks to create this hole in the cast material. (Just leave the can in place as it will burn out in a few years.) Cut the hole in the bottom of the drip pan once the material has set up. Just cut crosses with the angle grinder/cut-off wheel and bend them up.
The drip pan assembly is heavy and holds the steel lid tight against the edges of the water heater cylinder.
Fuel:
Load the stove for a cooking session by placing charcoal brands (piece of wood not entirely converted to charcoal) on the grate, followed by slices of mesquite or oak hardwood, with a handful of paper/cardboard slices/ then some more hardwood, and near the top use a softwood like cedar or pine, with a layer of paper/cardboard slices. Sprinkle a bit of alcohol on top of the paper, throw in a match, and install the covers, bricks and pot holder grill. A 90 minute burn is about the maximum that can be obtained. Use less fuel for a shorter burn, or use more paper/cardboard and softwood fuel which will burn faster and hotter. One trick is to use a bit of dry small charcoal pieces on top of the paper. All fuel needs to be very dry.
Use a 12 volt computer fan and a motorcycle battery blowing into the primary air hole at the bottom of the stove to insure plenty of air for starting. Also use air at the very end as the pyrolysis front encounters the charcoal brands at the bottom. Failure to do this might result in plenty of unburned smoke! I have heard a TLUD stove also called a "smoke burning stove". There is the 1/2" inch gap under the lid between the edges of the stove pipe that supplies secondary air for burning the smoke. The 4" restriction forces a sort of mixing action of the flames. If desired, a few holes can be drilled into the stove pipe every 6" from the top down to the center, as in the design of the Peko Pe Norwegian grass burning stove. http://www.drtlud.com/2014/05/26/peko-pe-grass-cooker-handbook/
At the end of the cooking session, there will just be a bed of char at the bottom of the stove, and no flames are left. Remove the top, and take out the stovepipe/pot combination (using heavy welding gloves) and dump the char into a large container of water to extinguish it. Later, dump off the water, and spread the char out to dry. By volume, the char should be at least 25% by volume of the original feedstock.
The charcoal made this way can add up to a significant amount. Look at this pile!
Cooking outside means the house is not heated by the stove and the air conditioning system doesn't have to work as hard. (We are in the Sub-Tropics, defined as less than 30 degrees North Latitude.)
There is no mess on the indoor pretty stove to clean up.
Water can be heated for washing dishes and cleaning up afterwards.
Excess fuel, after cooking, can be used to heat water for killing fire ants by pouring boiling water into the mounds, after probing the mound to find the area where the little white "eggs" are located.
Tomatoes can be boiled and reduced to half volume. We have been freezing this sauce, but this year we are telling ourselves we must put them in canning jars to leave more space in the freezer.
This Blog Post will show the Charcoal Making Stove that has evolved on my patio over the last dozen years. In the beginning, I constructed very small stoves from bean and coffee cans. (TinCanium). and even purchased a Stainless Steel Campstove designed by Tom Reed.
I moved on to the 2008 Champion TLUD stove that Paul Anderson describes in plans available online. http://www.drtlud.com/?resource=prt09320
Using a discarded Freon container, I built a version of that stove that worked well for many years. It is still the best stove in my collection for making a large batch of Pita Breads, as I describe in this eight year old YouTube Video: https://youtu.be/JOuoE2KAbQI
Be sure to expand the description for more information, and to Donna's website for the detailed recipe and technique. (It is very difficult to make the breads develop pockets.)
Meanwhile, I purchased two more Tom Reed Woodgas stoves and gave one to each of our children. Also purchased a Bio-lite TEG powered motorcycle camping stove, which I used a few times and re-sold on eBay. (It was too small!)
Purchased a really inexpensive Chinese Stainless Steel Campstove, but it also was too small, and practically useless unless you wanted to heat a 4 ounce cup of tea. I experimented with trying to collect charcoal from the Rocket Stove, but really wanted a stove that would produce significant amounts of charcoal.
After a decade of making a room full of experimental stoves, and actually using them several times a week, I'll describe what I have been using for the last two years, and am very satisfied with the power level and lack of any smoke in normal operation, and the fact that it will hold enough fuel for a maximum of 90 minutes of high power cooking. One criteria was that it be made entirely of "obtanium" or recycled materials. First (and most important) is the grate, which needs to be almost indestructible, because as the fuel pyrolyizes, starting at the top and working down to the grate, you end up with a pile of 2000 degree glowing charcoal that will absolutely destroy materials it contacts if additional forced air is added with a small blower. Normally, the char is dumped as soon as there are no more flames, meaning the wood has been converted to charcoal, but if you are cooking rice or beans, and need a bit more time, it is easy to turn on the blower and consume some of the charcoal to finish the cooking process. A grate made from a 10" worn-out carbide sawblade or a small cast iron frying pan will work. (The frying pan will outlast the sawblade.)
A stainless pot with a 9" diameter is used to hold the grate. Use a Harbor Freight angle grinder with a thin cut-off blade to remove the teeth from the sawblade, or alternatively put it in a strong vise and knock the teeth off with a heavy duty hammer.
Cut a 2" hole in the lower edge of the pot, and insert a piece of pipe with slots cut in the bottom edge, like this: Use the angle grinder, then punch the middle into the pipe.
Next, use two pieces of regular 6" diameter 24" long stove pipe bolted to each other and placed into the 9" pot. Bolt them to the pot, after putting the grate (skillet) in place. (This allows dumping of the charcoal without having the grate fall out.) Measure the height of the pot with pipe as it stands on the ground, and cut a section from a water heater tank that high, plus 1/2".
To get a better understanding, here is one of my earlier builds (from June of 2013) shown as a YouTube slide show: https://youtu.be/vHms7E0VAio Be sure to read the description under the video.
A layer of old tin roofing is inserted into the water heater tank to provide some insulation, with some fiberglass inserted between the two. I leave this stove out on the patio, covered so water does not get into it and saturate the fiberglass insulation. However, Mice do like to take up housekeeping, until I start loading the stove, and then they move out, or else.
Since that slide show/video in 2013, I have made some improvements in that I no longer use the throttle at the bottom, nor do I use the bricks supporting the pot. The bricks were not very stable, and were replaced with a metal oil change pan filled with a casting of perlite, crushed glass, sand, charcoal, and Plaster. I had an old used pan, but here is a photo of a new one:
Underneath the drip pan assembly is a sheet of steel cut from the top of a 55 gallon steel drum. The steel has a 4" diameter hole (a restriction), so when you cast the material in the drip pan, use a grapefruit juice can filled with rocks to create this hole in the cast material. (Just leave the can in place as it will burn out in a few years.) Cut the hole in the bottom of the drip pan once the material has set up. Just cut crosses with the angle grinder/cut-off wheel and bend them up.
The drip pan assembly is heavy and holds the steel lid tight against the edges of the water heater cylinder.
Fuel:
Use a 12 volt computer fan and a motorcycle battery blowing into the primary air hole at the bottom of the stove to insure plenty of air for starting. Also use air at the very end as the pyrolysis front encounters the charcoal brands at the bottom. Failure to do this might result in plenty of unburned smoke! I have heard a TLUD stove also called a "smoke burning stove". There is the 1/2" inch gap under the lid between the edges of the stove pipe that supplies secondary air for burning the smoke. The 4" restriction forces a sort of mixing action of the flames. If desired, a few holes can be drilled into the stove pipe every 6" from the top down to the center, as in the design of the Peko Pe Norwegian grass burning stove. http://www.drtlud.com/2014/05/26/peko-pe-grass-cooker-handbook/
At the end of the cooking session, there will just be a bed of char at the bottom of the stove, and no flames are left. Remove the top, and take out the stovepipe/pot combination (using heavy welding gloves) and dump the char into a large container of water to extinguish it. Later, dump off the water, and spread the char out to dry. By volume, the char should be at least 25% by volume of the original feedstock.
The charcoal made this way can add up to a significant amount. Look at this pile!
Cooking outside means the house is not heated by the stove and the air conditioning system doesn't have to work as hard. (We are in the Sub-Tropics, defined as less than 30 degrees North Latitude.)
There is no mess on the indoor pretty stove to clean up.
Water can be heated for washing dishes and cleaning up afterwards.
Excess fuel, after cooking, can be used to heat water for killing fire ants by pouring boiling water into the mounds, after probing the mound to find the area where the little white "eggs" are located.
Tomatoes can be boiled and reduced to half volume. We have been freezing this sauce, but this year we are telling ourselves we must put them in canning jars to leave more space in the freezer.
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