Wood gas generator construction details

The design we're building is called a "down-draft generator," and construction-wise, it can be described as a tank within a tank within a tank.


     A key goal for this stage of the project is to incorporate as much "off the shelf," or more accurately "out of the scrap pile," materials as possible. There's nothing wrong with making components from scratch if you need to, but no design of this level of complexity is likely to give optimal performance in its original form, so the first goal is to get an initial unit up and working as quickly, and cheaply, as possible and then "kaizen" from there.

     [kaizen - achieving a perfection of design through small, incremental improvements]

     For an outside shell, we're using an open-top 55 gallon drum. Inside of that is another 55 gallon drum that's been cut down, compressed and fastened together to create an inner wall that's about two inches smaller in diameter than the outside drum.

     The interior of the generator is a heat exchanger in which the heat from the exhaust gas cooks off the pyrolytic gas from the wood chips. One design goal is to keep most of the heat within the generator driving the initial pyrolytic phase of the conversion process, instead of heating up the environment around the generator.

     [pyrolysis - to break down a compound by heating it in an anaerobic atmosphere.]

     [anaerobic - having to do with an oxygen free environment.]

     In order to keep the reaction heat within the core of the gassifier, the space between the two drums will be filled with castable refractory insulation.