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Difference between revisions of "Gasification"
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=== Gasification process === | === Gasification process === | ||
The principal reactions of the gasification are endothermic and the necessary energy for their occurrence is granted by the oxidation of part of the organic material, through an allo-thermal or an auto-thermal phase. In the auto-thermal process, the gasifier is internally heated through partial combustion, while in the allo-thermal process the energy required | The principal reactions of the gasification are endothermic and the necessary energy for their occurrence is granted by the oxidation of part of the organic material, through an allo-thermal or an auto-thermal phase. In the auto-thermal process, the gasifier is internally heated through partial combustion, while in the allo-thermal process the energy required for the gasification is supplied externally. Considering the auto-thermal system, gasification can be seen as a sequence of several stages. The main steps of the gasification process are: | ||
# Oxidation (exothermic stage) | # Oxidation (exothermic stage) | ||
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==== Oxidation ==== | ==== Oxidation ==== | ||
The partial oxidation of the feedstock is necessary to obtain the thermal energy required for the endothermic stages of the process in order to maintain the operative temperature at the required value. The oxidation phase is carried out in near oxygen free conditions in order to oxidize only part of the feedstock. The main | The partial oxidation of the feedstock is necessary to obtain the thermal energy required for the endothermic stages of the process in order to maintain the operative temperature at the required value. The oxidation phase is carried out in near oxygen free conditions in order to oxidize only part of the feedstock. The main reactions that take place during the oxidation phase are the following: | ||
<chem> C + O2 -> CO2</chem> ΔH = -349 kJ/mol (Char combustion) | <chem> C + O2 -> CO2</chem> ΔH = -349 kJ/mol (Char combustion) | ||
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==== Drying ==== | ==== Drying ==== | ||
During the drying phase, the moisture contained in the feedstock is evaporated. The amount of heat required is | During the drying phase, the moisture contained in the feedstock is evaporated. The amount of heat required is proportional to the feedstock moisture content. Generally, the heat required derives from the other stages of the process. | ||
==== Pyrolysis ==== | ==== Pyrolysis ==== | ||