Ray,
I have some concerns about the charcoal box. The idea of using 5mm sheet metal was generated to allow for the quick transfer of heat. However I am not sure if it will hold up to multiple uses as the excessive heat projected from the furnace stands at about 500C -700C. What is your take? What metal can I use that can provide quick heat transfer, hold the weight of 86 cubic feet of wood.
I really need guidance here.
Ava Zim, according to http://www.biocharretort.com/ it takes 4 hours to 8 hours, from lighting to shutdown. Then more time to wait for things to cool down, at least overnight. I usually load my barrel retort slowly during several days (Iām retired.), and cover it with a big tub. Then, I check the hourly weather forecast for wind direction and wind speed and humidity. Usually, I ignite at sunrise, or shortly before, when the grass if any) is coated with dew. A load of small branches is turned to a glowing bed of charcoal in 1.5 hours. If I use larger logs in the 3" to 4" diameter, it will need to burn for an additional hour (total = 2.5 hours). Then, I can cover the barrel and wait until the next day, or I can simply dump 20 gallons of rainwater into the charcoal. Since the holes around the bottom edge of the barrel are covered with clay, the water stays in the barrel and puts out the fire completely. When I first ignite the load, I add lots of small thorny brush such as mesquite and huisache (sweet acacia) to insure a good load of char on the very top, which is what burns any smoke rising from the larger wood inside the barrel. (My two barrel system has one barrel on top which acts as a big chimney. I throw paper balls and acacia into that top barrel to really get things going.)
I usually try to find scrap metal or rely on used barrels that I can simply replace when they burn out. The problem I have with local scrapyards is that they cut everything up into little hunks. The Keystone Pipeline uses 36" diameter pipe that has a wall thickness ranging from a bit less that 1/2" to almost 3/4" depending on where they are going to use it. Many people on this forum have built a Wayne Keith unit using 12" pipeline with wall thickness greater than 1/4", and even then have to go to great effort to insure it doesnāt burn out in the area around the input air nozzles. One of my neighbors was digging up an old 12" pipeline and selling it for scrap. He cut a couple of them to short lengths for me.
If all I had was 5mm sheet, I would probably stitch weld some angle iron to it, in the form of a frame, and expect it to burn out. Then, being cheap, I would try to patch it for a few more burnsā¦ Iāve even bolted some patches over some holes that developed in my 55 gallon oil drums. Perhaps someone else will offer an opinion.
Somebody suggested that I use Stainless Steel for the charcoal box. It will not rust or corrode under high temperatures I was told. What are your views?
Stainless would be nice! Stainless steels are generally more expensive than carbon steels. In my experience, they are harder to cut, requiring a plasma cutter or a high speed cut-off wheel in an angle grinder. Tig welding requires stainless rod and plenty of Argon inert gas. Some builders on this forum use stainless steel suspended on chain as a grate, and burn holes in it with a plasma cutter. I use 9" stainless cooking pots in the bottom half of my TLUD charcoal making stoves, but also use pieces of used steel stove pipe as sacrificial liners. Iāve gone though lots of liners, but never the stainless pot. Iām always on the look out for stainless scrap, but it is hard to find.
I always check the pots and pans aisle at the Goodwill for large dia and heavy SST items
Hello Ava,
I believe there are some āstainless steelsā that will rust depending on the chromium content. I found this out working QA at Bombardier. I also found this on line. It seems high temps aggravate the condition.
Pepe
