Monday, April 28, 2008

North Americans Learn Waste to Energy Recycling

The schematic above shows an Indiana municipal waste to ethanol production plant due to begin construction this year and be completed within two years. The idea of turning garbage and waste into energy is catching on--even in the urban environment.
The gravity pressure vessel uses high transient pressure to work at higher transient temperatures in a fast reaction chamber. Higher transient temperatures enable the use of less acid to induce short interval very weak acid hydrolysis.

The first stage of the reaction chamber at the bottom of the gravity pressure vessel is wet oxidation providing only sufficient oxygen to react with organic debris dissolved in water which will use some of the lignin and other dissolved materials to provide exothermic heat to help sustain the process. It has been observed that slightly alkaline conditions also aid in dissolving portions of the lignin from the cell walls. Cellulose fibers are known to be refractory to short duration wet oxidation at these temperatures.

The second stage of the reaction zone reduces the pH condition to initiate de-polymerization of the cellulose using carbonic acid derived from later process fermentation steps, and supplemented using sulfuric acid or maleic acid in proportions at the operator’s discretion.

The reaction time is determined by the flow rate and distance between the point of acid injection and alkali quench, which is nominally engineered to be between one and ten seconds. The de-polymerized cellulosic materials are then cooled and depressurized by returning the fluids to the surface, and then cleaned and fermented to produce ethanol. __GCC
Several other current waste to energy projects are being implemented in Austin, Greenwood South Carolina, and Vancouber BC. Even Iraq is trying to get in on the act.



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