The thesis primarily focuses on the pressure influence on the reaction rate of char gasification using laboratory thermogravimetric analysis (TGA). It discusses also the gasification of char with a mixture of gasifying agents (CO2 + steam) under a pressure of 40 bar and temperatures up to 1100°C, which has not been reported in the literature to the best of found knowledge. The first section investigates the pressure impact on char gasification kinetics by varying the total and partial pressure of the gasifying agent. The second section investigates the effect of gasifying agent at 40 bar and combining the pyrolysis step in the investigation, which was done in-situ under inert atmosphere. Then, mixtures of the two gasifying agents were used for the gasification in separate experiments. The third section uses raw coal as material and gives attention to the char structure formed after the pyrolysis under the high pressure. The fourth section includes measurements for char characteristics during the gasification reaction and compares them with the reference char data performed previously in this research group under atmospheric pressure.:Abstract 1. Introduction 1 1.1 Scope of the thesis 1 1.2 Layout of the thesis 2 2. Literature Review 4 2.1 Background 4 2.2 Coal and gasification 5 2.2.1 Coal classification and characteristics 5 2.2.2 Introduction to gasification process 7 2.2.3 Coal Analysis 10 2.2.4 Pyrolysis 13 2.2.5 Gasification reactions 13 2.2.6 Mechanism of solid-gas reaction and Thermodynamic background 14 2.2.7 Regimes of gas-Solid Reactions 17 2.2.8 Summary 19 2.3 Effect of Pressure on gasification process 20 2.3.1 Advantages of high-pressure operation 20 2.3.2 Influence on the pyrolysis step 20 2.3.3 Effect of Pressure on coal swelling 21 2.3.4 Pressure influence on char morphology 23 2.3.5 Effect of pyrolysis pressure on char surface area 23 2.3.6 Effect on reaction order n 24 2.3.7 Summary 24 2.4 Pressure influence on char gasification reaction kinetics 24 2.4.1 Pressure influence on gasification reaction kinetics 25 2.4.2 Summary 27 2.5 Char gasification using gasifying agent mixtures 27 2.5.1 Mechanism 29 2.5.2 The role of the inhibition and the catalytic effect 29 2.5.3 Summary 32 2.6 Thermodynamic aspects and the estimation of the reaction rate 32 2.6.1 Background 32 2.6.2 Basic definitions of reaction rate 34 2.6.3 Intrinsic kinetic models 35 2.6.4 Theoretical models 36 2.6.5 Empiric Models 39 2.6.6 Intrinsic kinetic models expressed by CO2 concentration 40 2.6.7 Arrhenius Activation Energy 40 2.6.8 Differentiation of a polynomial fit data (Differential method): 41 2.6.9 Summary 43 3. Experimental Analysis 44 3.1 Thermogravimetry 44 3.2 Testing of the gas volume fraction and the total pressure influence on char gasification 45 3.2.1 Testing of the gas volume fraction influence 45 3.2.2 Testing of system pressure influence on char gasification 56 3.2.3 Discussion 65 3.3 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 65 3.3.1 Gasification with pure CO2 and H2O 66 3.3.2 Coal gasification using CO2 / H2O mixtures at high system pressure 87 3.3.3 Discussion 96 3.4 Pressure influence on coal gasification 100 3.4.1 Coal gasification under different system pressures 100 3.4.2 The effect of increasing pressure on coal morphology 104 3.4.3 Discussion 117 3.5 Influence of the pressure on the char properties during gasification 118 3.5.1 Discussion 129 4. General discussion 134 5. Conclusions 139 5.1 Significance of the findings 143 5.2 Recommendations 144 6. Appendix 146 6.1 Literature and Results 146 6.1.1 Conditions influence on gasification of the (a) temperature, (b) partial pressure 146 6.1.2 TGA-DMT 147 6.1.3 Testing of the gas volume fraction influence on coal gasification 148 6.1.4 Testing of system pressure influence on char gasification 150 6.1.5 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 152 6.1.6 Coal gasification under different pressures 162 6.1.7 Summary of gas mixture gasification studies 167 6.2 Figures Index 169 6.3 Tables Index 175 6.4 References 177

Syngas consisting mainly of a mixture of carbon monoxide, hydrogen and other diluents, is an important fuel for power generation applications since it can be obtained from both biomass and coal gasification. Clean coal technologies require stable and efficient operation of syngas-fired gas turbines. The trapped vortex combustor (TVC) is a relatively new gas turbine combustor concept which shows tremendous potential in achieving stable combustion under wide operating conditions with low emissions. In the present work, combustion of low calorific value syngas in a TVC has been studied using in-situ laser diagnostic techniques and numerical modeling. Specifically, this work reports in-situ measurements of mixture fraction, OH radical concentration and velocity in a single cavity TVC, using state-of-the art laser diagnostic techniques such as Planar Laser-induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV). Numerical simulations using the unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) approaches have also been carried out to complement the experimental measurements. The fuel-air momentum flux ratio (MFR), where the air momentum corresponds to that entering the cavity through a specially-incorporated flow guide vane, is used to characterize the mixing. Acetone PLIF experiments show that at high MFRs, the fuel-air mixing in the cavity is very minimal and is enhanced as the MFR reduces, due to a favourable vortex formation in the cavity, which is corroborated by PIV measurements. Reacting flow PIV measurements which differ substantially from the non-reacting cases primarily because of the gas expansion due to heat release show that the vortex is displaced from the centre of the cavity towards the guide vane. The MFR was hence identified as the controlling parameter for mixing in the cavity. Quantitative OH concentration contours showed that at higher MFRs 4.5, the fuel jet and the air jet stream are separated and a flame front is formed at the interface. As the MFR is lowered to 0.3, the fuel air mixing increases and a flame front is formed at the bottom and downstream edge of the cavity where a stratified charge is present. A flame stabilization mechanism has been proposed which accounts for the wide MFRs and premixing in the mainstream as well. LES simulations using a flamelet-based combustion model were conducted to predict mean OH radical concentration and velocity along with URANS simulations using a modified Eddy dissipation concept model. The LES predictions were observed to agree closely with experimental data, and were clearly superior to the URANS predictions as expected. Performance characteristics in the form of exhaust temperature pattern factor and pollutant emissions were also measured. The NOx emissions were found to be less than 2 ppm, CO emissions below 0.2% and HC emissions below 700 ppm across various conditions. Overall, the in-situ experimental data coupled with insight from simulations and the exhaust measurements have confirmed the advantages of using the TVC as a gas turbine combustor and provided guidelines for stable and efficient operation of the combustor with syngas fuel.

Erdöl und Erdgas liegen als flüssige Kohlenwasserstoffe in porösen Sedimentgesteinen im geologischen Untergrund vor. Um diese Kohlenwasserstoffe zu gewinnen, wird der Untergrund durch Tiefbohrungen zur Förderung erschlossen. Anschließend erfolgt die Förderung des Erdöls in drei Phasen: der Primär-, Sekundär- und Tertiärförderung. In der primären Phase wird Erdöl durch den Druck in der Lagerstätte gewonnen, in der sekundären Phase durch künstliche Aufrechterhaltung des Drucks und in der tertiären Phase durch technische Beeinflussung der strömungsmechanischen und thermodynamischen Eigenschaften des Erdöls. Dennoch verbleibt insbesondere bei Schweröllagerstätten ein Anteil von 45 bis 90 % des ursprünglich in der Lagerstätte vorhandenen Erdöls in der Lagerstätte. Aufgrund strömungsmechanischer und thermodynamischer Einschränkungen ist eine Gewinnung dieses Anteils technisch und/oder wirtschaftlich nicht möglich. Meist wird die Lagerstätte nach Abschluss der Förderung verfüllt und die übertägigen Anlagen zurückgebaut. Zugleich steigt weltweit der Bedarf an Energiequellen, insbesondere an solchen, die für die Dekarbonisierung und Umstellung auf umweltschonende Energien benötigt werden. Wasserstoff wird voraussichtlich als chemischer Energieträger der zukünftige Schlüsselrohstoff für die Energiewende sein. Diese Forschungsarbeit untersucht die Weiternutzung bzw. Erschließung ausgeförderter Erdöllagerstätten zur Wasserstoffgewinnungmittels thermischer Verfahren. Diese Verfahren orientieren sich an bereits etablierten Methoden für die übertägige Verfahrenstechnik. Durch das Verfahren wird die Lagerstätte mithilfe der Verbrennung des in dieser vorhandenen Restöls erhitzt und das entstehende Koks durch eine Wasserinjektion in Synthesegas umzuwandeln. Durch die hohen Temperaturen entsteht in der Lagerstätte eine Atmosphäre aus Wasserdampf, die zur Vergasung des Kokses führt. Das Gas wird durch die Wasserfront aus der Lagerstätte in die Produktionsbohrungen verdrängt und kann anschließend an der Oberfläche aufbereitet werden. Im Kontext der Lagerstättenprozesse entsteht nicht nur Wasserstoff, sondern auch weitere Verbrennungsprodukte wie Kohlenstoffmonoxid, Kohlenstoffdioxid, Sauergase und Kohlenwasserstoffgase. Diese werden verfahrenstechnisch aufbereitet und dampfreformiert in den obertägigen Anlagen. Zur Erfüllung der Anforderungen an blauen Wasserstoff ist die Reinjektion von Kohlenstoffdioxid erforderlich. In der Dissertation wird ein numerisches Berechnungsschema eingeführt und ausführlich getestet, um die lagerstättentechnische Simulation der thermischen Wasserstoffgewinnung durchzuführen. Anhand von Modelllagerstätten werden mithilfe dieses Schemas relevante Prozessparameter ermittelt und für die Übertragung auf die konkrete Lagerstättensimulation aufbereitet. Das Verfahren zur Wasserstoffförderung wird an einer antiklinalen Lagerstätte mit geostatistischer Heterogenität simuliert. Die Ergebnisse werden zur weiteren Auswertung bezüglich Integritätsfragen, Übertageanlagen sowie wirtschaftlicher und strategischer Aspekte herangezogen.

La diversification des sources d’énergies s’appuyant sur les énergies renouvelables doit contribuer à réduire la part des énergies fossiles dans la production d’électricité, en accord avec les directives européennes qui prévoient, pour la France de produire 21% de notre énergie à partir d’EnR en 2010.Les travaux rapportés dans ce mémoire s’attachent à l’industrialisation d’un procédé de gazéification de bois en vue de la production de chaleur et d’électricité. Des expériences de pyrolyse rapide de bois ont été menées sous diverses conditions expérimentales (densité de flux entre 0.9 et 6.3 MW/m², humidité entre 0 et 60%) pour comprendre et analyser les phénomènes fondamentaux impliqués lors de la gazéification du bois. Les divers produits (char, vapeurs et gaz) sont récupérés et analysés. Les résultats permettent de déterminer les rendements en chacun des produits pour différentes conditions expérimentales.La modélisation numérique du phénomène de pyrolyse du bois a ainsi été réalisée en se basant sur les données cinétiques fournies par la littérature puis comparée aux résultats expérimentaux. Même s’il n’y a pas concordance parfaite, les ordres de grandeur sont respectés. Ces modèles servent de base à la modélisation d’un réacteur de gazéification basé sur le réacteur DFB de Güssing incorporant la description hydrodynamique, la pyrolyse du bois, la gazéification du char et les réactions des vapeurs et des gaz. Ce modèle permet ainsi de déterminer l’efficacité du réacteur et ses différents paramètres opératoires.Mots clés : bois, pyrolyse, gazéification, processus élémentaires, modélisation, Güssing, énergies renouvelables, lit fluidisé circulant, génie des procédés / Diversification of energy sources based on renewable energies must contribute to reduce the share of fossil fuels in power generation, in agreement with the European directives which impose to France to generate 21% of its energy from renewable energies before 2010.The present work reported in this manuscript focus on the industrialization of a wood gasification process for the production of heat and electricity. Experiments of wood fast pyrolysis were performed under various experimental conditions (flux density between 0.9 and 6.3 MW/m2, moisture between 0 and 60%) for understanding and analysis of fundamental phenomena related to the gasification of wood. The various products (char, condensible vapours and gases) are recovered and analyzed. The results help to determine the yields of each of the products for various experimental conditions.The numerical modeling of wood pyrolysis phenomena has been achieved on the basis of kinetic data found through literature review and then compared to the experimental results. Even if there is no perfect agreement, orders of magnitude are respected. These models are used as a basis to develop a gasification reactor model for Güssing DFB reactor, including the hydrodynamics description, wood pyrolysis, char gasification, vapours and gases reactions. This model is used to determine the efficiency of the reactor and its various operating parameters

En raison de l'épuisement des combustibles fossiles et en raison de son coût croissant, les déchets ont été utilisés comme combustibles alternatifs dans les fours rotatifs à ciment pendant plusieurs années. Afin de répondre aux exigences de protection de l'environnement et de qualité du produit final, il est nécessaire de comprendre et de quantifier les différents processus intervenant dans le four. Dans le cadre de cette thèse, nous nous sommes intéressés à la substitution partielle des déchets (pneus usés et Refuse Derived Fuel « RDF ») et biomasse (résidus d’agriculture) dans les fours tournants de production de ciment à un taux de 50 % d’apport énergétique. Le présent projet de thèse a été financé par la République Démocratique Congo, porté par l’Université Kongo (UK), dans le cadre du renfoncement des capacités des universités congolaises. Les travaux de recherche ont été réalisés au sein du Laboratoire de Thermique, Energétique et Procédés (LaTEP) de l’Ecole Nationale Supérieure en Génie de Technologies Industrielles (ENSGTI)/Université de Pau et des Pays de l’Adour (France), dans le but d’étudier et de comprendre les phénomènes thermochimiques se déroulant dans les fours tournants de production de ciments, dans le cas de substitution partielle des combustibles fossiles par des combustibles alternatifs. Pour cela, un modèle mathématique à deux sous-modèles a été établi : - Le modèle monodimensionnel stationnaire du lit de solides et de l’enveloppe du four, caractérisé dans sa première partie par le mélange de la farine de ciment, de déchets et/ou biomasse, et de gaz, et alors que dans sa deuxième partie par les échanges thermiques. Le travail de modélisation est effectué à l'aide du langage de programmation Fortran 90 dans lequel sont implémentées les équations de conservations de la masse, des espèces et de l’énergie, l’équation de transport de la charge, ainsi que les équations algébriques. - Le modèle tridimensionnel instationnaire, repose sur l’utilisation de la mécanique des fluides numérique, et l’outil commercial Fluent a été retenu pour représenter les processus se déroulant au-dessus de la surface libre du lit.Le modèle complet est le couplage entre les deux sous modèles, étant donné les échanges qui s’y effectuent.Deux grands groupes de simulations ont été réalisés dans cette thèse : le cas monodimensionnel et le cas global (couplage Modèle 1D-Modèle 3D). Dans les deux situations, les simulations ont été effectuées dans le cas de fonctionnement au fuel lourd seul, puis dans celui du fonctionnement avec substitution partielle du combustible fossile par les combustibles alternatifs. Pour le modèle monodimensionnel, les simulations ont été effectuées en imposant les flux de chaleur dans la surface libre du lit et dans la paroi découverte. Alors que pour le modèle global, les simulations ont été effectuées en considérant les densités de flux de chaleur associées aux phénomènes physico-chimiques (combustion du fuel lourd, rayonnement, turbulence) se déroulant dans le volume de gaz situé au-dessus de la surface libre du lit.Les résultats ainsi obtenus nous ont permis de conclure sur l’importance de mener en amont une étude expérimentale dans un four tournant à l’échelle pilote afin de pouvoir disposer des ordres de grandeur des différents flux de chaleur au sein du four tournant. Les résultats obtenus nous ont également permis de nous rendre compte de la nécessité de disposer de la géométrie exacte (emplacement) du brûleur dans le four tournant. / Because of the depletion of fossil fuels and because of its increasing cost, waste has been used as alternative fuels in cement rotary kilns for several years. In order to fulfill the requirements of environmental protection and quality of the final product, it is necessary to understand and quantify the different processes occurring in the kiln.As part of this thesis, we focused on the partial substitution of waste (used tires and Refuse Derived Fuel "RDF") and biomass (agricultural residues) in rotary kilns producing cement at a rate of 50 % of energy supply. This thesis project was funded by the Democratic Republic of Congo, led by Kongo University (UK), as part of the capacity building of Congolese universities. The research work was carried out within the Laboratory of Thermal, Energy and Processes (LaTEP) of the National School of Engineering in Industrial Technologies (ENSGTI) /University of Pau, with the aim of to study and understand the thermochemical phenomena taking place in rotary kilns for the production of cement, in the case of partial substitution of fossil fuels by alternative fuels. For this, a mathematical model with two sub-models has been established:- The stationary one-dimensional model of the bed of solids and furnace casing, characterized in its first part by the mixing of cement flour, waste and / or biomass, and gas, and while in its second part by thermal exchanges. The modeling work is performed using the Fortran 90 programming language in which the conservation equations for mass, species and energy, the load transport equation, and the algebraic equations are implemented.- The unsteady three-dimensional model relies on the use of digital fluid mechanics, and the Fluent commercial tool has been retained to represent the processes taking place above the free surface of the bed.The complete model is the coupling between the two sub models, because of the exchanges that take place there.Two large groups of simulations have been realized in this thesis: the one-dimensional case and the global case (Model 1D-3D model coupling). In both situations, the simulations were carried out in the case of operation with heavy fuel oil alone, then in the case of operation with partial substitution of the fossil fuel by alternative fuels. For the one-dimensional model, the simulations were performed by imposing the heat flux in the free surface of the bed and in the exposed wall. Whereas for the global model, the simulations were performed considering the heat flux densities associated with physico-chemical phenomena (combustion of heavy fuel oil, radiation, turbulence) taking place in the volume of gas located above the free surface of the bed.The results thus obtained allowed us to conclude on the importance of carrying out an experimental study in a pilot scale furnace in order to be able to have orders of magnitude of the different heat flows within the rotating furnace. The results obtained also allowed us to realize the necessity to model the exact geometry (location) of the burner in the rotary kiln.

Encontrar soluções para a problemática dos resíduos e, em virtude da crescente demanda por energia, diminuir a dependência dos combustíveis fósseis têm constituído grandes desafios para os pesquisadores. O setor hospitalar é um potencial gerador dos chamados Resíduos de Serviços de Saúde (RSS) que também apresenta um alto consumo de energia em decorrência do seu período de funcionamento e de equipamentos que necessitam de infraestrutura adequada. Apesar de representarem uma pequena parcela perante o montante dos Resíduos Sólidos Urbanos (RSU), no Brasil, nem todos os geradores se preocupam com seu tratamento e destinação final. O emprego de tecnologias desenvolvidas para o tratamento desses resíduos com a possibilidade de recuperação energética deve ser avaliado. O Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HC-FMRP-USP) gera cerca de 1,9 ton/dia de RSS. Nesse contexto, o objetivo geral desta pesquisa foi avaliar a viabilidade legal, ambiental e econômico-financeira da implantação de um sistema próprio de tratamento de RSS no HCFMRP- USP para geração de energia. A metodologia foi estruturada em pesquisa exploratória, coleta de dados por meio de entrevistas semi-estruturadas com responsáveis pelo setor dos RSS no hospital, com pesquisadores da área da saúde, de escolas de engenharia, órgãos técnicos e indústrias fabricantes dos equipamentos; levantamento bibliográfico e análise de conteúdo. Para a avaliação econômico-financeira, foi empregada a avaliação custoefetividade. Estudos comparativos sobre os tipos de tratamento disponíveis e utilizados nacionalmente foram considerados. Assim, o processo que melhor se adequou ao sistema proposto foi o da incineração com tecnologia de gaseificação e combustão combinadas (GCC). Os resultados demonstraram que o sistema proposto está sob a égide da lei contemplando, inclusive, a Política Nacional de Resíduos Sólidos (PNRS), desde que mediante anuência do Conselho Gestor do campus da USP e de sua Comissão de Meio Ambiente, além do devido processo de licenciamento ambiental junto à CETESB e pré-análise dos RSS. Contudo, sob o aspecto ambiental há questões públicas e políticas sobre a aceitação de sua implantação no complexo hospitalar. Embora haja o emprego de avançada tecnologia, o equipamento avaliado necessita de instalação, manutenção e monitoramento adequados por profissionais capacitados para operá-los, a fim de se evitar possíveis danos às pessoas e ao meio-ambiente, para isso, os envolvidos devem agir com responsabilidade. Por fim, sob o aspecto econômico-financeiro houve um empate técnico entre os custos do tratamento realizado atualmente e os da proposta do investimento. Assim, esse último aspecto avaliado incidiu sobre o benefício implícito da decisão de se implantar ou não o processo. Portanto, considera-se a viabilidade da implantação de um sistema próprio para tratamento de RSS no HCFMRP-USP para geração de energia sob os três aspectos: legal, ambiental e econômicofinanceiro. / Finding solutions to the waste problem and reducing dependence on fossil fuels due to the growing demand for energy have become big challenges for researchers to deal with. Hospitals are large producers of Medical waste (MW) and also big energy consumers due to their long running hours and the running of equipment that demands adequate infrastructure. Despite accounting for a small share of all the Municipal Solid Waste (MSW) not all producers, in Brazil, are concerned about waste treatment and its final destination. The use of technologies developed with the aim of treating such waste in order to generate energy has to be assessed. The Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HCFMRP-USP) generates around 1.9 tons of waste per day. In this context, the general aim of this research program was to assess the legal, environmental and economic-financial feasibility of the implementation of a private system of biomedical waste treatment at HCFMRP-USP in order to generate energy. The method was structured in exploratory research, data gathering by means of semi-structured interviews with MW department staff at the hospital, with Health researchers, with Engineering College researchers, technical organizations and equipment manufacturers, besides bibliographic referencing and content analysis. Cost-effectiveness analysis was used for the economic-financial analysis. Comparative studies of the types of treatment available and used nationwide were taken into consideration. Thus, the process which best suited the proposed system was that of incineration by means of Gasification Combined Cycle (GCC). Results showed that the proposed system is under the support of Law and it also takes into consideration the National Policy for Solid Waste (NPSW), provided that it has the approval of the Director Council of the Administration of the campus of USP and of its Environment Committee as well as appropriate environmental licenses granted by CETESB and pre-analysis of MW. However, under the environmental aspect, there are public and political issues regarding the acceptance of this implementation in the hospital premises. Although there is the use of advanced technology, the equipment which was assessed needs to be installed, maintained and monitored adequately by professionals trained to operate it so as to avoid possible damage to humans and the environment. Staff involved must be responsible. Finally, under the economic-financial aspect there was a draw between the costs of the treatment conducted at present and those of the proposed investment. Therefore, this last aspect assessed prevailed over the implicit benefit of the decision on whether to implement the process or not. However, the feasibility of the implementation of a private MW treatment system at HC-FMRP-USP in order to generate energy is to be considered under the legal, environmental and economicfinancial aspects.

Im Rahmen dieser Arbeit werden Konzepte für Gasaufbereitung in Kombikraftwerken mit integrierter Wirbelschichtvergasung und CO2-Abtrennung untersucht (IGCC-CCS). Dabei stehen die Konvertierung von Kohlenmonoxid (CO-Shift) und die Einbindung dieses Prozeß-schrittes in ein IGCC-CCS-Kraftwerk im Mittelpunkt. Ziel der Arbeit ist die energetische und wirtschaftliche Bewertung von Konzepten zur CO2-Abtrennung für ein ab 2015 baubares, grundlastfähiges IGCC-CCS-Kraftwerk der 800-MW-Klasse. Dazu werden neben den bekannten konventionellen, mehrstufigen Konzepten der Rohgas- und Reingas-Shift weitere alternative Ansätze zur Steigerung des Anlagenwirkungsgrades sowie zur Senkung der spezifischen CO2-Emission verfolgt. Die Ergebnisse der mit Hilfe von ASPEN Plus und EBSILON Professional durchgeführten Prozesssimulationen werden im Vergleich zu Dampfkraftwerken neuester Bauart wirtschaftlich bewertet.

With the increasing global energy demand and the decreasing availability of good quality coals, a better understanding of the important properties that control the behaviour of low–grade coals and the subsequent chars in various utilisation processes, becomes pertinent. An investigation was therefore undertaken, to study the effects of chemical and physical properties imparted on chars during pyrolysis on the subsequent gasification reaction kinetics of typical South African inertinite–rich, high ash Highveld coals. An attempt was made at following these changes in the transition from coals to chars by a detailed characterisation of both the parent coals and the respective chars. These changes were determined using various conventional and advanced techniques, which included among others, carbon crystallite analysis using XRD and char carbon forms analysis using petrography. Three of the four original coals were characterised as Bituminous Medium rank C (coals B, C and C2), while coal D2 was found to be slightly lower in rank (Bituminous Medium rank D). The coals were rich in inertinites (> 54 vol. %, mmb with coal C2 having as high as 79 vol. %, mmb) and high in ash content (> 26.7 wt. %, db) and cabominerite and minerite contents (26 – 39 vol. %, mmb). The inertinitevitrinite ratios of the coals were found to range from 1.93 to 26.3. Characterization results show that both volatile matter and inherent moisture content decreased, while ash, fixed carbon and elemental carbon contents increased from coals to chars, indicating that the pyrolysis process was efficient. Elemental hydrogen, oxygen and nitrogen contents decreased, whereas total sulphur contents increased from coals to chars. This reveals that the total sulphur contained in the char samples was associated with the char carbon matrix and the minerals. Hydrogen–carbon and oxygen–carbon ratios decreased considerably from coals to chars showing that the chars are more aromatic and denser products than the original coals. Despite the fact that mineral matter increased from coals to chars, the relative abundance of the different mineral phases and ash components did not exhibit significant variation amongst the samples. The alkali index was, however, found to vary considerably among the subsequent chars. Petrographic analysis of the coals and char carbon forms analysis of the chars reveal that total reactive components (TRC) decrease while the total inert components (TIC) increase from coals to chars. The 0% gain in TIC observed in char C2 was attributed to its relatively high partially reacted maceral char carbon forms content. Total maceral reflectance shifted to higher values in the chars (4.43 – 5.28 Rsc%) relative to the coals (1.15 – 1.63 Rsc%) suggesting a higher structural ordering in the chars. Carbon crystallite analyses revealed that the chars were condensed (smaller in size) relative to the parent coals. Lattice parameters: interlayer spacing, d002, increased, while the average crystallite height, Lc, crystallite diameter, La, and number of aromatic layers per crystallite, Nave, decreased from coals to chars. Carbon aromaticity generally increased whereas the fraction of amorphous carbon and the degree of disorder index decreased from parent coals to the respective chars. Both micropore surface area and microporosity were observed to increase while the average micropore diameter decreased from coals to chars. This shows that blind and closed micropores were “opened up” during the charring process. Despite the original coal samples not showing much variation in their properties (except for their maceral content), it was generally observed that the subsequent chars exhibited substantial differences, both amongst themselves and from the parent coals. The increasing orders of magnitude of micropore surface area, microporosity, fraction of amorphous carbon and structural disorderliness were found to change in the transition, a good indication that the chars’ properties varied from that of the respective parent coals. Isothermal CO2 gasification experiments were conducted on the chars in a Thermax 500 thermogravimetric analyser in the temperature range of 900 – 950 °C with varying concentrations of CO2 (25 – 100 mol. %) in the CO2–N2 reaction gas mixture at ambient pressure (0.875 bar in Potchefstroom). The effects of temperature and CO2 concentration were observed to be in conformity with established trends. The initial reactivity of the chars was found to increase in the order: chars C2 < C < B < D2, with char D2 reactivity greater than the reactivity of the other chars by a factor > 4. Gasification reactivity results were correlated with properties of the parent coals and chars. Except for the rank parameter (the vitrinite reflectance), no significant trend was observed with any other coal petrographic property. Correlations with char properties gave more significant and systematic trends. Major factors affecting the gasification reactivity of the chars as it pertains to this investigation are: parent coal vitrinite reflectance, and: aromaticity, fraction of amorphous carbon, degree of disorder and alkali indices, micropore surface area, microporosity and average micropore diameter of the chars. The random pore model (chemical reaction controlling) was found to adequately describe the gasification reaction experimental data (both conversions and conversion rates). The determined activation energy ranged from 163.3 kJ·mol–1 for char D2 to 235.7 kJ·mol–1 for char B; while the order of reaction with respect to CO2 concentration ranged between 0.52 to 0.67 for the four chars. The lower activation energy of char D2 was possibly due to its lower rank, lower coal vitrinite reflectance and higher alkali index. The estimated kinetic parameters of the chars in this study correspond very well with published results in open literature. It was possible to express the intrinsic reactivity, rs, of the chars (rate of carbon conversion per unit total surface area) using kinetic results, in empirical Arrhenius forms. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

With the increasing global energy demand and the decreasing availability of good quality coals, a better understanding of the important properties that control the behaviour of low–grade coals and the subsequent chars in various utilisation processes, becomes pertinent. An investigation was therefore undertaken, to study the effects of chemical and physical properties imparted on chars during pyrolysis on the subsequent gasification reaction kinetics of typical South African inertinite–rich, high ash Highveld coals. An attempt was made at following these changes in the transition from coals to chars by a detailed characterisation of both the parent coals and the respective chars. These changes were determined using various conventional and advanced techniques, which included among others, carbon crystallite analysis using XRD and char carbon forms analysis using petrography. Three of the four original coals were characterised as Bituminous Medium rank C (coals B, C and C2), while coal D2 was found to be slightly lower in rank (Bituminous Medium rank D). The coals were rich in inertinites (> 54 vol. %, mmb with coal C2 having as high as 79 vol. %, mmb) and high in ash content (> 26.7 wt. %, db) and cabominerite and minerite contents (26 – 39 vol. %, mmb). The inertinitevitrinite ratios of the coals were found to range from 1.93 to 26.3. Characterization results show that both volatile matter and inherent moisture content decreased, while ash, fixed carbon and elemental carbon contents increased from coals to chars, indicating that the pyrolysis process was efficient. Elemental hydrogen, oxygen and nitrogen contents decreased, whereas total sulphur contents increased from coals to chars. This reveals that the total sulphur contained in the char samples was associated with the char carbon matrix and the minerals. Hydrogen–carbon and oxygen–carbon ratios decreased considerably from coals to chars showing that the chars are more aromatic and denser products than the original coals. Despite the fact that mineral matter increased from coals to chars, the relative abundance of the different mineral phases and ash components did not exhibit significant variation amongst the samples. The alkali index was, however, found to vary considerably among the subsequent chars. Petrographic analysis of the coals and char carbon forms analysis of the chars reveal that total reactive components (TRC) decrease while the total inert components (TIC) increase from coals to chars. The 0% gain in TIC observed in char C2 was attributed to its relatively high partially reacted maceral char carbon forms content. Total maceral reflectance shifted to higher values in the chars (4.43 – 5.28 Rsc%) relative to the coals (1.15 – 1.63 Rsc%) suggesting a higher structural ordering in the chars. Carbon crystallite analyses revealed that the chars were condensed (smaller in size) relative to the parent coals. Lattice parameters: interlayer spacing, d002, increased, while the average crystallite height, Lc, crystallite diameter, La, and number of aromatic layers per crystallite, Nave, decreased from coals to chars. Carbon aromaticity generally increased whereas the fraction of amorphous carbon and the degree of disorder index decreased from parent coals to the respective chars. Both micropore surface area and microporosity were observed to increase while the average micropore diameter decreased from coals to chars. This shows that blind and closed micropores were “opened up” during the charring process. Despite the original coal samples not showing much variation in their properties (except for their maceral content), it was generally observed that the subsequent chars exhibited substantial differences, both amongst themselves and from the parent coals. The increasing orders of magnitude of micropore surface area, microporosity, fraction of amorphous carbon and structural disorderliness were found to change in the transition, a good indication that the chars’ properties varied from that of the respective parent coals. Isothermal CO2 gasification experiments were conducted on the chars in a Thermax 500 thermogravimetric analyser in the temperature range of 900 – 950 °C with varying concentrations of CO2 (25 – 100 mol. %) in the CO2–N2 reaction gas mixture at ambient pressure (0.875 bar in Potchefstroom). The effects of temperature and CO2 concentration were observed to be in conformity with established trends. The initial reactivity of the chars was found to increase in the order: chars C2 < C < B < D2, with char D2 reactivity greater than the reactivity of the other chars by a factor > 4. Gasification reactivity results were correlated with properties of the parent coals and chars. Except for the rank parameter (the vitrinite reflectance), no significant trend was observed with any other coal petrographic property. Correlations with char properties gave more significant and systematic trends. Major factors affecting the gasification reactivity of the chars as it pertains to this investigation are: parent coal vitrinite reflectance, and: aromaticity, fraction of amorphous carbon, degree of disorder and alkali indices, micropore surface area, microporosity and average micropore diameter of the chars. The random pore model (chemical reaction controlling) was found to adequately describe the gasification reaction experimental data (both conversions and conversion rates). The determined activation energy ranged from 163.3 kJ·mol–1 for char D2 to 235.7 kJ·mol–1 for char B; while the order of reaction with respect to CO2 concentration ranged between 0.52 to 0.67 for the four chars. The lower activation energy of char D2 was possibly due to its lower rank, lower coal vitrinite reflectance and higher alkali index. The estimated kinetic parameters of the chars in this study correspond very well with published results in open literature. It was possible to express the intrinsic reactivity, rs, of the chars (rate of carbon conversion per unit total surface area) using kinetic results, in empirical Arrhenius forms. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Encontrar soluções para a problemática dos resíduos e, em virtude da crescente demanda por energia, diminuir a dependência dos combustíveis fósseis têm constituído grandes desafios para os pesquisadores. O setor hospitalar é um potencial gerador dos chamados Resíduos de Serviços de Saúde (RSS) que também apresenta um alto consumo de energia em decorrência do seu período de funcionamento e de equipamentos que necessitam de infraestrutura adequada. Apesar de representarem uma pequena parcela perante o montante dos Resíduos Sólidos Urbanos (RSU), no Brasil, nem todos os geradores se preocupam com seu tratamento e destinação final. O emprego de tecnologias desenvolvidas para o tratamento desses resíduos com a possibilidade de recuperação energética deve ser avaliado. O Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HC-FMRP-USP) gera cerca de 1,9 ton/dia de RSS. Nesse contexto, o objetivo geral desta pesquisa foi avaliar a viabilidade legal, ambiental e econômico-financeira da implantação de um sistema próprio de tratamento de RSS no HCFMRP- USP para geração de energia. A metodologia foi estruturada em pesquisa exploratória, coleta de dados por meio de entrevistas semi-estruturadas com responsáveis pelo setor dos RSS no hospital, com pesquisadores da área da saúde, de escolas de engenharia, órgãos técnicos e indústrias fabricantes dos equipamentos; levantamento bibliográfico e análise de conteúdo. Para a avaliação econômico-financeira, foi empregada a avaliação custoefetividade. Estudos comparativos sobre os tipos de tratamento disponíveis e utilizados nacionalmente foram considerados. Assim, o processo que melhor se adequou ao sistema proposto foi o da incineração com tecnologia de gaseificação e combustão combinadas (GCC). Os resultados demonstraram que o sistema proposto está sob a égide da lei contemplando, inclusive, a Política Nacional de Resíduos Sólidos (PNRS), desde que mediante anuência do Conselho Gestor do campus da USP e de sua Comissão de Meio Ambiente, além do devido processo de licenciamento ambiental junto à CETESB e pré-análise dos RSS. Contudo, sob o aspecto ambiental há questões públicas e políticas sobre a aceitação de sua implantação no complexo hospitalar. Embora haja o emprego de avançada tecnologia, o equipamento avaliado necessita de instalação, manutenção e monitoramento adequados por profissionais capacitados para operá-los, a fim de se evitar possíveis danos às pessoas e ao meio-ambiente, para isso, os envolvidos devem agir com responsabilidade. Por fim, sob o aspecto econômico-financeiro houve um empate técnico entre os custos do tratamento realizado atualmente e os da proposta do investimento. Assim, esse último aspecto avaliado incidiu sobre o benefício implícito da decisão de se implantar ou não o processo. Portanto, considera-se a viabilidade da implantação de um sistema próprio para tratamento de RSS no HCFMRP-USP para geração de energia sob os três aspectos: legal, ambiental e econômicofinanceiro. / Finding solutions to the waste problem and reducing dependence on fossil fuels due to the growing demand for energy have become big challenges for researchers to deal with. Hospitals are large producers of Medical waste (MW) and also big energy consumers due to their long running hours and the running of equipment that demands adequate infrastructure. Despite accounting for a small share of all the Municipal Solid Waste (MSW) not all producers, in Brazil, are concerned about waste treatment and its final destination. The use of technologies developed with the aim of treating such waste in order to generate energy has to be assessed. The Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HCFMRP-USP) generates around 1.9 tons of waste per day. In this context, the general aim of this research program was to assess the legal, environmental and economic-financial feasibility of the implementation of a private system of biomedical waste treatment at HCFMRP-USP in order to generate energy. The method was structured in exploratory research, data gathering by means of semi-structured interviews with MW department staff at the hospital, with Health researchers, with Engineering College researchers, technical organizations and equipment manufacturers, besides bibliographic referencing and content analysis. Cost-effectiveness analysis was used for the economic-financial analysis. Comparative studies of the types of treatment available and used nationwide were taken into consideration. Thus, the process which best suited the proposed system was that of incineration by means of Gasification Combined Cycle (GCC). Results showed that the proposed system is under the support of Law and it also takes into consideration the National Policy for Solid Waste (NPSW), provided that it has the approval of the Director Council of the Administration of the campus of USP and of its Environment Committee as well as appropriate environmental licenses granted by CETESB and pre-analysis of MW. However, under the environmental aspect, there are public and political issues regarding the acceptance of this implementation in the hospital premises. Although there is the use of advanced technology, the equipment which was assessed needs to be installed, maintained and monitored adequately by professionals trained to operate it so as to avoid possible damage to humans and the environment. Staff involved must be responsible. Finally, under the economic-financial aspect there was a draw between the costs of the treatment conducted at present and those of the proposed investment. Therefore, this last aspect assessed prevailed over the implicit benefit of the decision on whether to implement the process or not. However, the feasibility of the implementation of a private MW treatment system at HC-FMRP-USP in order to generate energy is to be considered under the legal, environmental and economicfinancial aspects.