The topic of master´s thesis is atmosferic gasification of biomass by the addition of oxygen and steam. The theoretical part is devoted to the description of biomass, process of gasification, kinds of gasification reactor and product gas. Further experiments are devised depending on the gasification medium and output temperature. In this case, the key aspect is the steam addition control. In the practical part, these experiments are performed in a fluidized bed reactor. Resulting values from samples of gas and tar are subsequently processed and evaluated.

Les déchets de bois et de plastiques sont des ressources prometteuses pour la production du gaz de synthèse (syngaz) par la pyro-gazéification grâce à leurs disponibilités et leurs caractéristiques énergétiques. Cependant, le syngaz issu de ces déchets peut contenir des teneurs élevées en chlorure d’hydrogène (HCl) qui est corrosif et toxique et qui doit donc être éliminé. Premièrement, les expériences de pyrolyse des mélanges de bois de peuplier et de plastiques ont mis en évidence l’influence des plastiques sur les produits obtenus. En effet, le HDPE et PS augmentent respectivement le pouvoir calorifique du syngaz et le rendement en huiles, tandis que le PVC augmente le rendement en char et le HCl dans le syngaz. Ensuite, les expériences de pyro-gazéification à l’échelle pilote ont montré que l’ajout de 1 % en masse de PVC dans un déchet de bois augmente la teneur en goudrons et HCl dans le syngaz par un facteur respectivement de 2 et 5,5, tandis que la concentration de chlore dans le char résiduel est 16 fois plus élevée. En parallèle, un model CFD a été développé pour simuler la pyro-gazéification du déchet de bois en couplant les phénomènes d’écoulement de fluides, transfert de masse et de chaleur, et les réactions chimiques. Ce modèle se compose des sous-modèles de séchage, pyrolyse, oxydation et gazéification du char. Les résultats de simulation sont en bon accord avec les données expérimentales obtenues par des expériences dans un gazéifieur à l’échelle pilote. En outre, les analyses de sensibilités du sous-modèle de la gazéification de char ont été réalisées. Finalement, une étude expérimentale a été conduite sur le traitement de HCl dans le syngaz. L’étude se concentre sur la valorisation de deux résidus solides industriels issus de la production de bicarbonate et carbonate de sodium. Leurs réactivités sont comparées avec celles de deux adsorbants commerciaux, NaHCO3 et Ca(OH)2. L’effet de la matrice gazeuse sur la performance des adsorbants est également examiné. Les résidus industriels ont un potentiel intéressant par rapport aux adsorbants commerciaux. Les résultats obtenus montrent des nouvelles approches pour la purification du syngaz généré par la gazéification des déchets de bois et de plastiques. / Wood and plastic waste are interesting feedstock for the production of syngas via pyro- gasification, mainly due to their abundant supply and good fuel properties. However, syngas derived from waste may contain significant amounts of hydrogen chloride (HCl), which is corrosive and toxic and must therefore be removed. In this work, co-pyrolysis experiments were first conducted in order to study the influence of mixing different plastics with wood samples on the pyrolysis products. It was found that HDPE and PS significantly increase the heating value and HCl content of the gas product respectively, while PVC increases the yield of char and HCl. Next, pilot-scale experiments were performed, which revealed that adding 1 wt% PVC to wood waste raises the content of tar and HCl in syngas by factors of 2 and 5,5 respectively, and also elevates the chlorine concentration in the char residue 16 time over the value obtained in the absence of PVC. In parallel, a CFD model was developed to simulate the pyro-gasification of wood waste by coupling fluid flow, heat and mass transfer, and chemical reactions. This model consists of drying, pyrolysis, oxidation and char gasification sub-models. The simulation results were in good agreement with experimental data obtained from the pilot-scale experiments. Furthermore, sensibility analyses on the char gasification sub-model were performed. Finally, an experimental study was conducted on the removal of HCl from syngas. The study focused on valorizing two industrial solid wastes generated from the process of sodium carbonate and sodium bicarbonate manufacture. Their HCl adsorption performance were compared to those of the commercial sorbents, NaHCO3 et Ca(OH)2. Moreover, the effect of gas matrix on their performance was studied. The industrial wastes showed potential for treating acid gas as compared to the commercial sorbents used. This opens up new approaches to the purification of syngas generated by the pyro-gasification of wood and plastic waste.

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Biomass to Liquids via Fischer-Tropsch synthesis (BTL-FT) is regarded as one of the most promising routes for providing alternative solution to growing demand for energy and environmental protection. In Chapter I, the development and key issues of BTL-FT process (especially Fischer-Tropsch synthesis) were reviewed and identified. In Chapter II, Mo/HZSM-5 catalyst was synthesized using Incipient Wetness Impregnation method and tested in nitrogen rich model bio-syngas. Different operation parameters (temperature, pressure, and GHSV) were tested to investigate their influence on the catalytic performance. Those parameters were found to affect the performance significantly. Liquid samples from conversion were mainly composed of C8 to C10 range hydrocarbons. The catalyst characterization revealed that molybdenum species were well distributed on the catalyst support, while dealumination, agglomeration and coke deposition were observed in spent catalyst. The top layer of the spent catalyst had the most coke deposition. A Three-Dimensionally Ordered Macro-porous (3DOM) Fe based Fischer-Tropsch catalyst was developed using a facile in-situ Nitrate Oxidation-PMMA templating technique in Chapter III. Several techniques (including SEM, BET, TPR, HRTEM, XRD, XPS, and DRIFTS) were combined to characterize the morphology, textural properties and microstructures of 3DOM Fe catalysts at different stages. The effects of bio-syngas composition on carbonaceous species formation, iron phase transformation and catalytic performance were investigated and correlated. A novel hybrid bio-refinery process co-converting biomass and natural gas into liquid fuels via FTS with a CO2 recycle loop was developed, modeled and simulated by using Aspen Plus in Chapter IV. The Aspen Plus model utilized experimental data from the 3DOM Fe catalyst. Economic analysis was performed on different scenarios based on the simulation results to determine profitability of the process. Results indicated that 102.65 t/h gasoline and 22.93 t/h diesel can be produced with the co-processing of 100.00 t/h biomass and 112.3 t/h natural gas using 307.78 t/h of recycled CO2 in the process simulation. The carbon conversion rate was estimated to be 81.23% for the hybrid process. Economic analysis revealed that the process can be profitable when using at least 10.00 t/h biomass and 11.23 t/h natural gas.

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Despite comprehensive studies addressing the chemical kinetics of butanol isomers, relevant uncertainties associated with the emissions of relevant pollutants persists. Also, a lack of chemistry knowledge of processes designed to produce biofuels limits their implementation at industrial scales. Therefore, the first objective of this thesis was to use cutting-edge kinetic theories to calculate rate constants of propen-2-ol, 1-pronenol, and vinyl alcohol keto-enol tautomerizations, which account for the production of the harmful carbonyl species. The second objective was to use the predictive capabilities of dynamic theories to reveal new chemistry of syngas oxy-combustion in supercritical CO2 and complexities of the zeolite dealumination, two processes involved in coal and biomass conversion. Rate constants computations considered transition state theory with variational effects, tunneling correction, and multistructural torsional anharmonicity. The study also included pressure effects by using and improving the system-specific quantum Rice-Ramsperger-Kassel/modified strong collision model. The atomistic simulations used ReaxFF force fields in hydrogen/oxygen/carbon monoxide/ carbon dioxide mixtures to represent the syngas system and an MFI zeolite with different water loading to model the dealumination. The results show that the studied assisted tautomerizations have much lower energy barriers than the unimolecular process. However, the “catalytic” effect is efficient only if the partner molecule is at high concentrations. Pressure effects are pronounced in the chemically activated tautomerizations, and the improved algorithm to compute pressure-dependent rate constants overcomes the initial difficulties associated with its application to C3 or larger molecules at temperatures above 800-1000 K. Reactive molecular dynamics simulations revealed the role of CO2 as an initiator in the syngas oxy-combustion and a new step involving the formation of formic acid. Those simulations for the zeolite dealumination process also showed that proton transfer, framework flexibility, and aluminum dislodging mediated by silicon reactions are complex dynamic phenomena determining the process. These aspects complement the dealumination theory uncovered so far and establish new paths in the study of water-zeolite interactions. Overall, the rate constants computed in this work reduce relevant uncertainties in the chemical kinetic mechanisms of alcohol oxidation, and the molecular dynamics simulations broaden the chemical knowledge of processes aimed at the utilization of alternative energy resources.

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