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| Tekijä: | Khan, Nadir |
| Työn nimi: | Modelling of chemical reaction systems in polysulfide pulping |
| Julkaisutyyppi: | Diplomityö |
| Julkaisuvuosi: | 2015 |
| Sivut: | 13+62+8 Kieli: eng |
| Koulu/Laitos/Osasto: | Kemian tekniikan korkeakoulu |
| Oppiaine: | Process Systems Engineering (KE3004) |
| Valvoja: | Vuorinen, Tapani |
| Ohjaaja: | Fearon, Olesya |
| Elektroninen julkaisu: | http://urn.fi/URN:NBN:fi:aalto-201512165637 |
| Sijainti: | P1 Ark Aalto 3324 | Arkisto |
| Avainsanat: | polysulfide pulping polysaccharides yield modelling decomposition distribution stabilization |
| Tiivistelmä (eng): | Polysulfide pulping has shown great potential in terms of yield increase in comparison to normal kraft pulping. However, polysulfide chemistry itself is quite complex which makes it even more complicated when it is combined with wood chemistry. This makes polysulfide pulping a grey area, which requires investigation regarding polysulfide chemistry, and how it is linked with wood chemistry. This thesis work comprises of polysulfide chemistry modelling, and application of that chemistry in polysulfide pulping modelling. Modelling was done in VIC model which was built on Flowbat software. Before, carrying out modelling or simulations, mechanisms for the polysulfide species reactions with the wood components (cellulose, hemicelluloses) were described, after which VIC model was updated with polysulfide rearrangement (chemical equilibria between different polysulfide species) reactions, polysulfide degradation reactions, and reactions of polysulfide species with wood components. Polysulfide chemistry can be completely specified with the rearrangement reactions, degradation reactions, and the distribution of polysulfide species at the initial pulping conditions. However, rearrangement reactions are quite fast, and therefore, do not have a rate determining effect during polysulfide degradation reactions, and during oxidation reactions of polysaccharides by polysulfide. Hence, the rearrangement reactions were not considered in polysulfide chemistry modelling, and in polysulfide pulping modeling. Thus, Polysulfide chemistry was solely modelled with distribution of polysulfide species at the initial pulping conditions and with degradation chemistry of polysulfide species. Distribution of polysulfide species was calculated by the numerical iterative method in Matlab for each individual case or condition, after that this distribution was used in the Flowbat as the initial input for the polysulfide degradation and polysulfide pulping simulations. First, the polysulfide degradation model was successfully validated with the experimental data presented in literature. Secondly, the polysulfide pulping model was validated with published data. Some discrepancies were found in the initial trends, which were considered to be due to mass transfer, and high ion concentration at the start of the simulation. However, later part of the simulation started to follow the experimental trends. Since the kinetics for the polysulfide species reactions with the wood components were not available, kinetic parameters were adjusted manually. Therefore, the results were not perfectly accurate, and there were some convergence issues as well. Hence for more accurate results it is recommended to fit the experimental data in Kinfit software to find out the proper kinetics or experimentally find the kinetics for the polysulfide and wood components reactions. |
| ED: | 2016-01-17 |
INSSI tietueen numero: 52761
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