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Дисертації з теми "Char de gazéification":
Morin, Mathieu. "Gazéification de la biomasse en double lit fluidisé circulant : étude des réactions élémentaires de gazéification et de combustion du char et de reformage des goudrons." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0089/document.
The thermochemical conversion of biomass at high temperature (>700°C) in Fast Internally Circulating Fluidized Bed (FICFB) is a promising alternative route to fossil fuels (oil, coal) to produce syngas which can be used in several applications. The aim of the present work is to develop methodologies as well as theoretical and experimental tools for determining the intrinsic kinetic of biomass transformations (biomass pyrolysis, char gasification and combustion, cracking and reforming of tars). Firstly, a fluidized bed reactor has been designed and built at the Laboratory of Chemical Engineering (LGC). This reactor can operate for temperatures between 20 and 1000°C with a well-defined gas supply (N2, O2, H2, H2O and tars). A sampling and analysis gas system enables the continuous quantification of the non-condensable gases and tars molar fractions. A hydrodynamic and thermal study enabled the determination of the operating conditions for each experimental study. Secondly, the char gasification and combustion was performed in the fluidized bed reactor. The influence of the operating conditions (temperature and compounds partial pressure) led to the modelling of the different solid transformation kinetics. Besides, in the case of char combustion, a reaction scheme was proposed and the kinetic obtained in the fluidized bed was compared to that obtained in a thermogravimetric analyzer. Finally, a study on the tar reforming in a fluidized bed reactor highlighted the effect of the reactive atmosphere on the reaction scheme of toluene conversion over olivine and char
Abdelaal, Ali Hassan Ali. "Industrial char recoveries in the perspective of circular economy in the wood gasification industry." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2023. http://www.theses.fr/2023IMTA0369.
Several biomass gasification chars, generated from pilot and commercial scale gasifiers, were studied in order to identify possible uses. The chars were produced in the region of South Tyrol with woodchips and pellets as feedstock. The as-received chars were heterogeneous. It was observed that simple mechanical sieving led to the identification of higher-quality char than the original material. The sieved char had a surface area of 1454 against 647 m2.g−1 for the mixture. The char performance as an adsorbent in water treatment was studied with ibuprofen and paracetamol. The maximum batch adsorption capacity obtained were 297.4 and 323.0 mg.g−1 towards ibuprofen and paracetamol, respectively, which is equivalent to the adsorption capacity of commercial activated carbons. To facilitate the use of powder char in fixed bed columns, beads with chitosan hydrogel were produce. The catalyst proprieties were studied through the tar reforming at both lab and pilot scales. The lab tests were carried out with a synthetic tar mixture with 3 chars. The highest removal efficiency achieved was 54% at 650°C, increase to 72% with steam. Despite showing an excellent performance, it was not possible to use the best-performing char in the pilot scale study due to its powder nature. At the pilot scale, removal efficiency reaches 68% to nearly 100% when steam was used. This work shows that the best-performing char as adsorbent or as catalyst was the same
Guizani, Chamseddine. "Effects of CO2 on the biomass pyro-gasification in High Heating Rate and Low Heating Rate conditions." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2014. http://www.theses.fr/2014EMAC0010/document.
The present work deals about the effects of CO2 enriched atmospheres on biomass pyrolysis and char gasification reactions in High Heating Rate (HHR) and Low Heating Rate (LHR) conditions, at the biomass particle level. In the first part, we studied the effects of CO2 on the high temperature fast pyrolysis reaction and evaluate its effects on the pyrolysis rate, on the gas yield as well as on the char properties including chemical composition, texture and reactivity at 850°C. We focused also on the effects of CO2 on the HHR-char gasification reaction when injected as a co-reactant with steam. We studied the mixed atmosphere gasification reaction in CO2 and H2O for different atmosphere compositions. Finally, we imagined a hypothetical case of a pure CO2 operating gasifier. The case of a pure CO2 pyrogasification process was tackled experimentally and theoretically by numerical modelling with aim to provide pyrolysis and gasification characteristic reaction times, and to understand the unfolding of the global CO2 pyro-gasification reaction. In the second part, we were interested on the issue of LHR-char gasification in the presence of CO2 with two principal objectives: on one hand, providing reactivity data for practical gasification operations and on the other hand, understanding the gasification reaction mechanisms (in CO2, H2O and their mixtures) at the level of the char basic structural units (BSU). We examined the influence of particle size on the single atmosphere gasification in CO2 and H2O using the Thiele modulus approach. We also studied the effects of temperature and particle size on the char gasification in mixed atmosphere of CO2 and steam at 900°C. We also had a focus on the issue of cyclic atmosphere gasification and studied the effects of a prior CO2 gasification on the char reactivity towards H2O and vice versa. To further understand the char gasification mechanisms in single and mixed atmospheres of CO2 and H2O, we opted to monitor the evolution of the chemical, structural and textural char properties along the gasification in CO2, H2O and their mixtures. Deep char characterization were performed on small LHR-char particles partially gasified at 20%, 50% and 70% of conversion in CO2, H2O and their mixtures. These characterisations are of high interest as they shed light on the unfolding of the gasification reaction in CO2, H2O and their mixtures
Teixeira, Gabriel. "Gazéification de charbon de granules de bois : comportement thermochimique et mécanique d’un lit fixe continu." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0010/document.
Multi-stage gasification of biomass leads to the production of a clean synthetic gas that can easily be used for electrical and/or thermal energy. However, optimization of these processes in terms of conversion yield and flexibility regarding the type of biomass is a major industrial challenge. To that end, a key stage of the process was specifically studied in this thesis: char gasification in a continuous fixed bed reactor. Granulation is the solution proposed for making use of low density or small particle-size biomasses. The performance of two wood chars – made from wood chips and pellets – was studied at the same time using experimental and numerical tools. Experiments were first conducted in a very highly instrumented pilot reactor, reproducing this zone of the process. The profiles measured, namely temperature, gas composition, bed density and particle velocity formed a unique database revealing reactor performance. A very reactive zone under 5 cm thick was thus located at the top of the bed, or even significant compaction leading to a drop in particle velocity, in a ratio of 8. Granular char gasification led to the same final conversion rates and synthetic gas compositions as for the chars derived from wood chips. A numerical model of the study zone was then developed, based on solving conversion equations combined with reaction kinetics, using COMSOL software. Taking into account bed compaction and the apparent kinetics of the heterogeneous reactions on a particle scale in the reaction source terms were two specificities of the model. It enabled satisfactory reproduction of the profiles of the physical magnitudes measured, for various operating conditions and for the two charsstudied. Use of this model is already providing new and complementary experimental information; it will eventually make it possible to optimize the industrial process
Collard, François-Xavier. "Nouvelles stratégies catalytiques pour la gazéification de la biomasse : influence de métaux imprégnés sur les mécanismes de pyrolyse." Compiègne, 2012. http://www.theses.fr/2012COMP2022.
The very promising development of the use of biomass for biofuel production by gasification is slowed down owing to too high tar concentration in the gas produced by this process. Recent works showed that, when impregnated in biomass, metals display catalytic activity that results in a significant decrease in the production of the primary tars, during the pyrolysis step, which precedes the oxidation reactions. The main aim of this work was to assess the effect of impregnated metals on pyrolysis mechanisms and on the tar yield of this step. The reactivity of the metal-doped char produced, during the oxidation reactions, was also evaluated. The study of the influence of iron and nickel on the pyrolysis conversion of the main polymers that form biomass (i. E. Cellulose, xylan and lignin) and of biomass samples showed that impregnated metals mainly catalyzed the mechanisms of char formation. This phenomenon inhibited the depolymerization and fragmentation reactions, which are responsible for most tar formation. When impregnated in the amorphous phase of the polysaccharides, nickel also promoted some depolymerization reactions. This result explains the bigger decrease in tar production obtained with iron than with nickel. However, nickel was more efficient in limiting the production of molecules containing a benzene ring and to catalyze the secondary reactions of volatile compounds. During gasification tests, the conversion of the iron-doped char revealed problems of deactivation of the metal catalyst, which led to a decrease in the reaction rate of the oxidation reaction. On the contrary, the catalytic activity of nickel was stable and made possible the oxidation reactions of char at 600 °C with CO2 and at 500 °C with steam. These findings show that the approach which consists in impregnating biomass with metals, allows considering the implementation of gasification processes at low temperature, which could limit the tar problem and could improve the energy conversion efficiency of these processes
Authier, Olivier. "Etude découplée des phénomènes physicochimiques impliqués dans les réacteurs de gazéification de la biomasse. Application au cas d'un lit fluidisé double." Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL015N/document.
Among the biomass gasification technologies, the dual fluidized bed gasifier may be used to produce a methane-rich syngas. Analysis of all the physicochemical phenomena involved inside the gasifier is difficult because they all occur simultaneously. In this thesis, the main chemical reactions are decoupled and studied independently one of each other at the scale of original laboratory facilities in thermal conditions close to those encountered in the gasifier. Intraparticular reactions of biomass pyrolysis and gas/solid reactions (char-steam gasification and catalytic thermal cracking of vapors on olivine) are carried out with an image furnace. Experiments related to gas-phase vapors thermal cracking are performed inside a continuous self stirred tank reactor. All the products formed by the reactions are recovered and analyzed. Mass balance closures are achieved accurately. Controlling steps of each reaction are discussed on the basis of a characteristic times analysis. Kinetic parameters are determined according to both processes modelings and optimizations from the experimental results. Different ways of possible methane formation and consumption mechanisms are identified and discussed. The gasifier is modelled by considering a single-particle model (primary pyrolysis reactions), secondary reactions, solids and gas-phase hydrodynamics and transfers. Finally, the decoupling methodology is validated from the comparison of model results with measurements performed at the 8 MW Güssing gasifier (Austria)
Gordillo, Ervin David. "Etude des transferts de chaleur et de masse dans des procédés de vapogazéification de char de biomasse innovants (solaire - nucléaire)." Thesis, La Rochelle, 2011. http://www.theses.fr/2011LAROS347.
The possibility of producing syngas from carbon compounds other than coal or oil would allow countries lacking energy resources to move toward energy independence. The steam gasification is a process that could help to this predisposition, producing a hydrogen-rich gas from carbon-rich materials (e.g. biomass char) and steam. Since gasification is an endothermic process, the energy source is the first concern to be addressed in the gasifierdesign. If we want it to not contribute to global warming, the energy source and carbon must remain renewable.Until now, engineers designed gasifiers thinking about uniformity of properties within the reactor, it simplifies the variables modeling and control, however, with innovative heat sources and the possibility to use only steamfor gasification, it can be concluded that a temperature gradient enhances the hydrogen production, thus the syngas quality is improved. The new gasification technologies therefore require the understanding of transport phenomena to apply this advantage in order to improve the syngas production and quality. Three reactor typesare modeled as part of this work, it is shown that there is a lack of firm criteria to choose the reaction device according to the resources, consequently, the reactors performance could be diminished if the energy source is not properly used. The theory of the temperature gradient is built based on the main results and it is a simple toolto help the engineer to make decisions that will improve the fuel gas production
Adamon, Gildas David Farid. "Modélisation de la cinétique de gazéification étagée de la biomasse tropicale : cas des balles de riz et des rafles de maïs." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2354/document.
The gasification tests in this study were carried out using an instrumented installation equipped with a fixed bed reactor using carbon dioxide and water steam, as reagents. In this study, we considered the stepped gasification process. In addition, the ten-year resource availability study allowed us to select two agricultural residues, taking into account their availability over time, the absence of nutritional conflict and their physicochemical characteristics… At the end of this study, two agricultural residues were selected: rice husks and corn cobs. The pyrolysis of these two biomasses was carried out in a muffle furnace at a temperature of 450 °C for a residence time of 45 minutes. A mathematical model based on the Newton method has been proposed to estimate the coke yield of rice husk and corn cobs as a function of temperature, for a fixed residence time. We also carried out a physicochemical characterization of these two agricultural residues as well as their pyrolysis cokes. Several pyrolysis tests have also been carried out in ATG in order to determine the real order of the decomposition reactions by pyrolysis, of these two biomasses, as a function of temperature. For the gasification tests, they were carried out on the pyrolysis coke of the two retained biomasses, using an installation equipped with a fixed-bed reactor on the one hand, and by thermogravimetric analysis of another hand. Several kinetic models (VRM, SCM and RPM) were used to model the gasification reaction kinetics of rice husk and corn cobs with carbon dioxide and water steam. It appears that the RPM model is the most suitable of the three models studied to best simulate the gasification reaction of char from rice husk and corn cobs under the operating conditions studied in this study. Thus, the activation energies obtained are respectively 165.8 kJ/mol and 152.9 kJ/mol with carbon dioxide and water steam for rice husk while the exponential factor varies from 2595.4 s-1 to 3473.4 s-1 with respective values of the structural parameter Ψ = 3.8 for the Boudouard reaction and Ψ = 2.16 for the water steam gasification. However, the activation energies obtained for corn cobs are 114.4 kJ/mol and 105.5kJ/mol respectively with carbon dioxide and water steam while the exponential factor varies from 13.9 s-1 to 18.3 s-1 with respective values of the structural parameter Ψ = 12.3 for the Boudouard reaction and Ψ = 8.68 for the water steam gasification
Freysz, Valerian. "Contribution à la modélisation d’un gazeifieur de biomasse : application à un gazeifieur allothermique solaire pour la production de gaz de synthèse." Thesis, La Rochelle, 2016. http://www.theses.fr/2016LAROS009/document.
This work focuses on the modeling of biomass gasification in a solar fixed bed reactor. We developed and validated different modules to compute physical problems associated with such gasifier (finite volume, thermodynamic equilibrium, view factor, radiosity, evolution of the mesh, etc.). The reactor is then modeled, and results are compared to experimental measurements for its validation. These results suggest that for the operating conditions encountered in this reactor, the evolution of the heating rate and the ash concentration may influence the kinetics of the beech wood gasification. A study of the reactor by assuming thermodynamic equilibrium is conducted and shows that this approach should be used with caution for the studied temperature range. Parametric study of an air-air exchanger between the output and input gas is proposed. It shows that the addition of an inert gas can be interesting from an energy point of view in such conditions. Finally, a solar absorber suited to the reactor is modeled and validated in order to assess the sensitivity of the complete system
Demarthon, Romain. "Modélisation et simulation d’un étage haute température pour la purification d’un gaz chargé en goudrons et en particules carbonées par assistance plasma." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3001/document.
In order to contest to the high world demand for primary energy, the Europlasma group developed a new process, called CHO-Power, to enhance the thermochemical potential of a mixture of urban waste and biomass residues. One of the characteristics of this process is the use of a high temperature reactor assisted by a plasma torch for tar and soots thermal cracking. The aim of this study to improve the knowledge of the global reaction mechanism involved during the thermal treatment of gas. In this context, a pilot plant reactor was designed and built on the Europlasma Research and Development Center. During this work, the reaction pathway used to represent tars cracking at high temperature has been enhanced. Coupled to a computational fluid Dynamics Software, allow simulating the complex processes occurring within the reactor (aeraulics, reaction, and heat transfer). Two major changes were made to the simplified kinetic model previously used: the modeling of a discrete and reactive phase to take into account the possible particle gasification of carbonaceous residues and the addition of new reaction pathways to enhance the modeling of the formation of soot and its precursors. The comparison between the experimental and numerical values will validate or not the global reaction scheme and will give important information about the next evolution of the tar degradation scheme