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Difference between revisions of "Gasification"
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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 reaction that take place during the oxidation phase are the following: | 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 reaction 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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<chem>C + 1/2O2-> CO</chem> ΔH = -111 kJ/mol (Partial oxidation) | <chem>C + 1/2O2-> CO</chem> ΔH = -111 kJ/mol (Partial oxidation) | ||
<chem>H2 + 1/2O2 -> H2O</chem> ΔH = -242 kJ/mol (Hydrogen combustion) | <chem>H2 + 1/2O2 -> H2O</chem> ΔH = -242 kJ/mol (Hydrogen combustion) | ||
The main product of this phase is the thermal energy, while the combustion product is a gas mixture of CO, CO<sub>2</sub> and water. | The main product of this phase is the thermal energy, while the combustion product is a gas mixture of CO, CO<sub>2</sub> and water. | ||
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Pyrolysis is the thermochemical decomposition of organic compounds. In particular, the cracking of chemical bonds takes place with the formation of three different fractions: a solid, a liquid and a gaseous fraction. The pyrolysis reaction takes place with a temperature in the range of 250-700°C. It is an endothermic reaction and, as in the drying step, the heat required comes from the oxidation process. The pyrolysis of organic material can be schematized with the following overall reaction: | Pyrolysis is the thermochemical decomposition of organic compounds. In particular, the cracking of chemical bonds takes place with the formation of three different fractions: a solid, a liquid and a gaseous fraction. The pyrolysis reaction takes place with a temperature in the range of 250-700°C. It is an endothermic reaction and, as in the drying step, the heat required comes from the oxidation process. The pyrolysis of organic material can be schematized with the following overall reaction: | ||
<chem>Biomass <=> H2 + CO + CO2 + CH4 + H2O + Tar + Char</chem> | |||
<chem>Biomass <=> H2 + CO + CO2 + CH4 + | |||
When the feedstock is made of biomass, since cellulose is its main component, in this reaction the biomass can be indicated with the chemical formula of cellulose (i.e., C<sub>6</sub>H<sub>10</sub>O<sub>6</sub>) | When the feedstock is made of biomass, since cellulose is its main component, in this reaction the biomass can be indicated with the chemical formula of cellulose (i.e., C<sub>6</sub>H<sub>10</sub>O<sub>6</sub>) | ||