Notes from Windward: #67
TLUD Gasifier Update
The type of gasifier we'll be using to fire the pizza oven is called a TLUD (pronounced "tea lud") with the initials standing for Top Lit Up Draft. This particular unit was fabricated from a twenty-gallon propane tank nestled inside of a 40 gallon water tank. For a gasification article from Volume 66 of the Notes, Click Here.
With the TLUD standing on its head, the space between the inner tank and the outer shell was filled with perlite (a form of puffed rock) as an insulator, with the gap sealed with a bit of fiber glass insulation.
Then the bottom cover was bolted in place, and the air inlet piping attached before the TLUD was returned to its up-right position.
The next pic shows the TLUD's top in place with the safety chains attached.
The interior of the TLUD was filled with wood chips, compressed air was fed into the bottom, and a fire kindled on top of the wood chips.
Once the wood chips were buring nicely, the TLUD's lid was replaced, generating smoke out the flare tube.
The next pic shows the wood gas being burned.
Having demonstrated that our TLUD produces burnable gas, we shut off the incoming air and allowed the pyrolysis to stop. The next day we opened the TLUD and found a nice bed of charcoal covering the top of the woodchips. At the TLUD gets up to its operating temperature, this layer plays a key role in the generation of useful gas in that glowing char reduces the pyrolytic gas (a stew of all sorts of organic compounds) to producer gas (carbon monoxide and hydrogen).
In order to get a better seal, we added some braided glass caulking to the joint between the TLUD's lid and its main body.
The next night's test show that the caulking was effective, and that the next step would be to work on improving the burner. The burner shown here was actually designed to work with propane, and the TLUD's burner needs to be somewhat different because of the different flame propagation speeds, and the amount of air needed to fully combust the wood gas.
Notes From Windward - Index - Vol. 67