Gian Claudio Faussone, October, 2011
The Italian group INSER has come up with a gasification process that they have patented as Circle Draft.
As described by them, the reactor vessel is composed of two chambers.
In the top chamber, the feedstock is pyrolysed and converted to charcoal (which is the yellow in the figure).
Then the charcoal descends into the lower vessel (grey in the figure) where it is gasified (generally with additional air) and a variable amount of steam or water.
The process requires that the feeder be sealed (so that additional air does not enter the pyrolysis zone) and it includes electric heaters in the top chamber to provide additional heat and compensate for wet fuels.
Pyrolysis syngas is captured from the top chamber (where air can reach 500 degrees C) and gasification syngas is captured from the bottom chamber ( 900 - 1000 degrees C) and both sets of syngas pass through charcoal (a primary filter) before they exit through the outlet. (Ash and slag are removed from the bottom).
For the detailed discussion and results of the project please see the attached scan of Mr. Faussone's presentation poster
Biomass Gasification with Circle Draft Process, and the INSER web site http://www.inser.it/