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Investigation
of the Thermal Decomposition of |
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D. Merz, H. Geisert, J. Vehlow Forschungszentrum Karlsruhe, Institut für Technische Chemie Bereich Thermische Abfallbehandlung, 76021 Karlsruhe
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Investigation
of the Thermal Decomposition of |
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D. Merz, H. Geisert, J. Vehlow Forschungszentrum Karlsruhe, Institut für Technische Chemie Bereich Thermische Abfallbehandlung, 76021 Karlsruhe
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A HGF project has been launched to develop strategies for primary-side nitrogen oxide reduction in municipal solid waste (MSW) incineration. This implies a detailed knowledge of the major primary N-containing products released from the pyrolysis and gasification zone of the fuel bed. As a first step, screening tests using model substances for the N-carriers in various waste fractions (e.g. proteins from food waste, yard/garden waste and textiles; Polyamide and Polyurethane from the plastic fraction) are performed in laboratory to identify such species. Even the thermolysis of simple model substances results in a complex gaseous product mixture. A selective analytical method has to be applied in order to concentrate on the major reaction products and to minimize the analytical effort in view of the high number of process parameters like temperature, heating rate, oxygen content, humidity, etc.. The coupling of TG and FTIR represents an efficient tool for this study. Identifying the functional groups of the substances involved in the gas mixture, FTIR allows the chemical classification of the gases, even if the vibrational bands cannot be assigned to the individual chemical compounds due to the complexity of the mixture. Gelatin was selected as one model species for proteins. In air atmosphere the DTG curve of gelatin shows two extrema (at 300 °C and at 500-600 °C). The FTIR spectra suggests CO2 being a major gasification product at both temperatures, whereas NH3 is mainly contributing at the lower temperature with smaller release at the higher range only. In inert atmosphere (pyrolysis conditions) one single mass loss step is found which comprises simultaneous release of CO2 and NH3 at 300 °C. This indicates that the amino acids are subject to deamination and decarboxylation in this TG stage. At the flank (450 °C) of the same DTG extreme the release of CH-compounds and of species with the functional groups C-OH and C=O is observed. Further information on the FTIR spectra is expected to result from the analyses using TG-MS, TG-GC, and GC-MS.
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