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Coal fired IGCC power plant design offers huge potential for future power generation in terms of raw fuel availability, efficiency and, most importantly, flexibility. Pressurized entrained flow gasification is considered one of the best options in current gasification technology thanks to its compactness, reliability, and fuel flexibility. Since it is not affordable to perform investigations directly in an industrial setting, it is therefore of fundamental importance to study the gasification behavior of fuels in pilot-plant scale and lab-scale test rigs that provide boundary conditions comparable to large scale facilities. This dissertation provides experimental measurements of process parameters such as fuel conversion and fuel particle temperature at conditions relevant to industrial process and aims to produce valuable data that can then be fed into analytical modeling and simulation tools. PART I of this thesis is focuses on the experimental activities carried out in order to investigate the gasification behavior of solid fuels during gasification at high temperature and high pressure. Set-ups used in this work, include a pressurized and an atmopsheric entrained flow reactors, thermogravimetric analyzers and a wire mesh reactor. Different aspects of the gasification process are investigated in this thesis. Pressure and temperature influence are investigated during devolatilization and gasification experiments. The work’s novelty is assured by the investigation of reactant partial pressure influence with CO2, H2O and a mixture of both, which is performed in the entrained flow reactors at high temperature and at high pressure.. Reactant partial pressure influence is also investigated at lower temperatures in TGAs. Several experiments with char samples produced in the entrained flow reactors are carried out with pure reactants in order to retrieve intrinsic kinetic data. Mixed gasification atmosphere experiments are compared with literature m, Mit Kohle betriebene IGCC-Kraftwerke zeigen großes Potential für die künftige Stromerzeugung bezüglich Brennstoffverfügbarkeit, Effizienz und insbesondere Flexibilität. Aufgrund der Kompaktheit, Zuverlässigkeit und Brennstoffflexibilität wird die Flugstromvergasung unter Druck als eine der besten Optionen der verfügbaren Vergasungstechnologien angesehen. Die Umwandlung eines festen Brennstoffes in ein Synthesegas ist ein komplexer Prozess. Da es finanziell nicht möglich ist, die Untersuchungen im industriellen Maßstab durchzuführen, ist es erforderlich, das Vergasungsverhalten von Brennstoffen in Pilotanlagen und Laborversuchen unter industrienahen Betriebsbedingungen zu untersuchen. Diese Dissertation beinhaltet experimentelle Messungen von Prozessparametern, wie beispielsweise Brennstoffumsatz und Partikeltemperaturen, unter industrierelevanten Bedingungen, mit dem Ziel, nützliche Daten als Grundlage für analytische Modelle und Simulationen bereitzustellen. TEIL I dieser Arbeit beschäftigt sich mit den Experimenten, die durchgeführt wurden, um das Vergasungsverhalten fester Brennstoffe bei hohen Temperaturen und Drücken zu untersuchen. Den Kern des experimentellen Aufbaus bildet der Pressurized High Temperature Entrained Flow Reactor (PiTER), welcher Temperaturen von bis zu 1600 °C bei einem Druck von bis zu 2,0 MPa als Versuchsbedingungen ermöglicht. Weitere Anlagen, die in dieser Arbeit verwendet wurden, sind ein atmosphärischer Flugstromreaktor, thermogravimetrische Analysatoren (TGA) und ein Drahtnetzreaktor. In dieser Arbeit werden verschiedene Aspekte des Vergasungsprozesses diskutiert. Druck- und Temperatureinflüsse wurden während Pyrolyse- und Vergasungsexperimenten untersucht. Die Neuheit der Arbeit wird durch die Untersuchung des Partialdruckeinflusses von CO2, H2O und einer Mischung aus beiden Reaktanten gewährleistet. Diese Experimente wurden in Flugstromreaktoren bei hohen Temperaturen und hohen Drücken durchgeführt. Der Einfluss des Partialdruckes de

Coal fired IGCC power plant design offers huge potential for future power generation in terms of raw fuel availability, efficiency and, most importantly, flexibility. Pressurized entrained flow gasification is considered one of the best options in current gasification technology thanks to its compactness, reliability, and fuel flexibility. Since it is not affordable to perform investigations directly in an industrial setting, it is therefore of fundamental importance to study the gasification behavior of fuels in pilot-plant scale and lab-scale test rigs that provide boundary conditions comparable to large scale facilities. This dissertation provides experimental measurements of process parameters such as fuel conversion and fuel particle temperature at conditions relevant to industrial process and aims to produce valuable data that can then be fed into analytical modeling and simulation tools. PART I of this thesis is focuses on the experimental activities carried out in order to investigate the gasification behavior of solid fuels during gasification at high temperature and high pressure. Set-ups used in this work, include a pressurized and an atmopsheric entrained flow reactors, thermogravimetric analyzers and a wire mesh reactor. Different aspects of the gasification process are investigated in this thesis. Pressure and temperature influence are investigated during devolatilization and gasification experiments. The work’s novelty is assured by the investigation of reactant partial pressure influence with CO2, H2O and a mixture of both, which is performed in the entrained flow reactors at high temperature and at high pressure.. Reactant partial pressure influence is also investigated at lower temperatures in TGAs. Several experiments with char samples produced in the entrained flow reactors are carried out with pure reactants in order to retrieve intrinsic kinetic data. Mixed gasification atmosphere experiments are compared with literature m, Mit Kohle betriebene IGCC-Kraftwerke zeigen großes Potential für die künftige Stromerzeugung bezüglich Brennstoffverfügbarkeit, Effizienz und insbesondere Flexibilität. Aufgrund der Kompaktheit, Zuverlässigkeit und Brennstoffflexibilität wird die Flugstromvergasung unter Druck als eine der besten Optionen der verfügbaren Vergasungstechnologien angesehen. Die Umwandlung eines festen Brennstoffes in ein Synthesegas ist ein komplexer Prozess. Da es finanziell nicht möglich ist, die Untersuchungen im industriellen Maßstab durchzuführen, ist es erforderlich, das Vergasungsverhalten von Brennstoffen in Pilotanlagen und Laborversuchen unter industrienahen Betriebsbedingungen zu untersuchen. Diese Dissertation beinhaltet experimentelle Messungen von Prozessparametern, wie beispielsweise Brennstoffumsatz und Partikeltemperaturen, unter industrierelevanten Bedingungen, mit dem Ziel, nützliche Daten als Grundlage für analytische Modelle und Simulationen bereitzustellen. TEIL I dieser Arbeit beschäftigt sich mit den Experimenten, die durchgeführt wurden, um das Vergasungsverhalten fester Brennstoffe bei hohen Temperaturen und Drücken zu untersuchen. Den Kern des experimentellen Aufbaus bildet der Pressurized High Temperature Entrained Flow Reactor (PiTER), welcher Temperaturen von bis zu 1600 °C bei einem Druck von bis zu 2,0 MPa als Versuchsbedingungen ermöglicht. Weitere Anlagen, die in dieser Arbeit verwendet wurden, sind ein atmosphärischer Flugstromreaktor, thermogravimetrische Analysatoren (TGA) und ein Drahtnetzreaktor. In dieser Arbeit werden verschiedene Aspekte des Vergasungsprozesses diskutiert. Druck- und Temperatureinflüsse wurden während Pyrolyse- und Vergasungsexperimenten untersucht. Die Neuheit der Arbeit wird durch die Untersuchung des Partialdruckeinflusses von CO2, H2O und einer Mischung aus beiden Reaktanten gewährleistet. Diese Experimente wurden in Flugstromreaktoren bei hohen Temperaturen und hohen Drücken durchgeführt. Der Einfluss des Partialdruckes de

Coal devolatilization, as first step in thermochemical processes involving solid fuels, has been targeted in plenty of CFD investigations: despite the variety of models that were developed to define the rate of the process and the amount of volatile matter released, not all of them are suitable for CFD simulations of large-scale coal combustors. Empirical models ensure both simplicity and feasibility, but not full reliability for all coal types and operating conditions. CFD modeling results for coal conversion during devolatilization in an entrained flow reactor and oxy-conditions are presented and compared to experimental data. A benchmark assessment of one-step models on the accuracy of the volatile yield prediction is then performed. It is shown that the heating rate strongly influences the devolatilization process and its modeling, not only in terms of rate but also in terms of yield, which differs significantly from the proximate analysis value. This indicates the need for a model able to predict the variation of coal volatile yield with temperature and heating rate, in addition to the kinetic model., SCOPUS: ar.j, info:eu-repo/semantics/published

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The promising properties of torrefied biomass provide a valid co-firing option for large percentage biomass utilization in existing coal-fired boilers. Torrefied biomass is expected to have a better combustion stability than raw biomass and similar to that of coal. The present work will characterizes the oxidation properties of torrefied biomass char and compare with that of raw biomass char. The studied two chars are produced from raw and torrefied biomass in an Isothermal Plug Flow Reactor (IPFR) at high temperature and high heating rate, a sufficient residence time is applied for the completion of the high temperature devolatilization. Char oxidation tests are carried out in the IPFR by varying temperature, oxygen concentration and residence time. The reactivity of two studied chars are analyzed and compared with referenced biomass char and coal char, and the impact of torrefaction on char reactivity is also discussed in this paper. Finally, the char oxidation kinetic parameters are determined using a parameter optimization method, and the obtained kinetics are examined by comparing the experimental and predicted mass conversions., QC 20150227

Flameless combustion is a novel combustion technology able to ensure high combustion efficacies with low pollutant emissions thanks to the dilution of reactants, usually achieved through recirculation of combustion products. The technology has been successfully applied in several processes and has been found to be able to handle a large variety of fuels, including low grade fuels, industrial by-products and hydrogen. Further development of this innovative combustion technology would benefit of Computational Fluid Dynamics (CFD) tools; however, modelling flameless combustion is much more challenging than conventional flames, because of the strong coupling between turbulent mixing and chemical kinetics. In particular the chemical kinetics plays a fundamental role, even though there no common opinion on the degree a mechanism can be reduced. Some useful works may be found on flameless burners fed with methane, but there is lack of information on different fuels. The present work describes the numerical modelling of an ethylene jet flame issuing in a hot coflow burner, emulating flameless combustion and fully characterised in literature, with the scope of investigating the potential for chemistry reduction in the context of flameless combustion. A Principle Component/Variable Analysis is used to investigate the most important species in the chemical mechanism and subsequently a dimension reduction technique based on the Rate-controlled constrained-equilibrium (RCEE) principle is applied to the detailed mechanism to be coupled to the CFD code, in order to make simulations more affordable. Results indicated that the use of Principle Component/Variable Analysis leads to a good choice of the variables to be retained as results with the reduced scheme were found to be consistent with those obtained with the full mechanism., SCOPUS: ar.k, info:eu-repo/semantics/published

Torrefied biomass is a coal-like fuel that can be burned in biomass boilers or co-fired with coal in co-firing furnaces. To make quantitative predictions regarding combustion behavior, devolatilization should be accurately described. In this work, the devolatilization of three torrefied biomasses and their parent material were tested in an isothermal plug flow reactor, which is able to rapidly heat the biomass particles to a maximum temperature of 1400 degrees C at a rate of 10(4) degrees C/s, similar to the conditions in actual power plant furnaces. During every devolatilization test, the devolatilized biomass particles were collected and analyzed to determine the weight loss based on the ash tracer method. According to the experimental results, it can be concluded that biomass decreases its reactivity after torrefaction, and the deeper of torrefaction conducted, the lower the biomass reactivity. Furthermore, based on a two-competing-step model, the kinetic parameters were determined by minimizing the difference between the modeled and experimental results based on the least-squares objective function, and the predicted weight losses exhibited a good agreement with experimental data from biomass devolatilization, especially at high temperatures. It was also detected that CO and H-2 are the primary components of the released volatile matters from the devolatilization of the three torrefied biomasses, in which CO accounts for approximately 45-60%, and H-2 accounts for 20-30% of the total volatile species., QC 20140305

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In this work, the flame characteristics of torrefied biomass were studied numerically under high-temperature air conditions to further understand the combustion performances of biomass. Three torrefied biomasses were prepared with different torrefaction degrees after by releasing 10%, 20%, and 30% of volatile matter on a dry basis and characterized in laboratory with standard and high heating rate analyses. The effects of the torrefaction degree, oxygen concentration, transport air velocity, and particle size on the flame position, flame shape, and peak temperature are discussed based on both direct measurements in a laboratory-scale furnace and CFD simulations. The results primarily showed that the enhanced drag force on the biomass particles caused a late release of volatile matter and resulted in a delay in the ignition of the fuel-air mixture, and the maximum flame diameter was mainly affected by the volatile content of the biomass materials. Furthermore, oxidizers with lower oxygen concentrations always resulted in a larger flame volume, a lower peak flame temperature and a lower NO emission. Finally, a longer flame was found when the transport air velocity was lower, and the flame front gradually moved to the furnace exit as the particle size increased. The results could be used as references for designing a new biomass combustion chamber or switching an existing coal-fired boiler to the combustion of biomass., QC 20131004