[Gasification] CO2 recycling

[Ferruccio Pittaluga]

Dear all,
I have just read the following statements on a Jan 1942 paper by Torsten Kaelle (paper available at: http://www.hotel.ymex.net/~s-20222/gengas/kg_eng.html#fig6) referred to a coal gasifier for mobile applications:

"One could say, that the carbon-dioxide (CO 2 ) is the `fuel' from which producer gas, that is carbon monoxide (CO) is made. It could thus be considered a pure waste to generate carbon dioxide from charcoal, when the former ---as the final product of combustion in the motor---is available in sufficient quantities from the exhaust gases! It also goes without saying, that the larger portion of the CO 2 in the exhaust that can be reused for producing carbon monoxide, the more economically the gasifier operates, and the longer one can drive on the same amount of charcoal, and the cheaper the driving is. I therefore decided to mix a certain portion of the exhaust gases from the motor into the primary air. The combustion gases, passing from the combustion zone to the reduction zone will thereby contain more carbon dioxide than what corresponds to the consumed charcoal. The excess of heat will be consumed for reducing the excess CO 2 . If the portion of exhaust gases is small, the reaction will become complete and the producer gas becomes entirely free from CO 2 . In practice it is however better to let the producer gas contain one or two percent CO 2 . The heat value of the gas will not be significantly lowered by it, but it guarantees that all the heat is made useful. Further experiments showed, that the best effect was gained by an adding of about 17% CO 2  to the gasifier, which, under the condition that all of that was turned into CO, results in a significant saving of charcoal."

Has anyone got any experience on CO2 recycling within downdraft biomass gasifiers?
Many thanks.
Ferruccio Pittaluga

DIMSET/SCL - Savona Combustion Lab 
pittalug at unige.it