The experimental analysis of an autothermal gasoline reformer for use in an auxiliary power unit was undertaken. The development of these auxiliary power units has the potential to create positive economical and environmental benefits. It will provide the necessary energy and heating while utilizing a fuel with a well established infrastructure. Autothermal reforming is a process in which both oxygen and steam are combined with a hydrocarbon fuel over a catalyst bed in order to produce a hydrogen rich gas stream. This process utilizes an exothermic partial oxidation reaction to promote the hydrogen efficient, endothermic steam reforming reaction. The main goals of this study were to design and test the operating conditions of a new autothermal reformer and to determine an operational envelope for the reactor. Furthermore, the data collected was used to validate a numerical model of the reactor that would assist in the development of future compact autothermal reformers. A compact autothermal reformer has been designed with the capability to produce detailed wall and centerline temperature profiles during operation. During the experimental phase of this project, a strong relationship between the main input variables (the oxygen to carbon and steam to carbon ratios) and the performance characteristics of the reactor was found. For the range of experimental conditions tested, the highest molar percent of hydrogen in the reformate for a gas hourly space velocity of 20,000h-1 was found at an oxygen to carbon ratio of 1.0 and a steam to carbon ratio of 2.0. Performance characteristics used for the reactor were the lower heating value, the percent hydrogen yield and fuel conversion, and were found to have maximum values of 46.0%, 47.6% and 67.7% respectively. Carbon deposition on the catalyst bed was found to be significant under certain operating conditions, but had a very small effect on the final conditions of the ATR. The computational fluid dynamics model was shown to have fairly accurate predictions for the temperature profiles as well as the reformate compositions when compared to the experimental data. A number of recommendations have been made to the experimental and numerical studies. It is likely that if employed in future testing, they would improve the overall performance of the compact autothermal reformer. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2008-04-23 17:14:46.198

The development of an auxiliary power unit (APU) capable of providing climate control and electricity in long haul trucks is of significant interest due to the expected economic and environmental benefits. A potentially efficient and environmentally friendly APU design is one based on the use of an autothermal fuel reformer that converts on-board truck fuel to a hydrogen rich gas that directly fuels a solid oxide fuel cell unit. To assist in the development of such a unit a numerical study of the autothermal reforming of iso-octane in a compact tubular reactor has been undertaken. This was done to determine the reactor performance and the factors that potentially influence its performance. Variations in the wall thermal conductivity, the catalyst thermal conductivity, the catalyst porosity, the conditions of the inlet reactant gas, and the effectiveness factor of the chemical reaction mechanism have been studied to determine their effects on the performance of the reformer. It has been found that higher thermal conductivities of the outer wall and in the catalyst region gave increased dry hydrogen yield and fuel conversion. The study of the effects of inlet species concentration ratios indicated that maximum hydrogen yield was obtained with an oxygen-to-fuel ratio between 1.0 and 1.15 and a steam-to-fuel ratio of approximately 3.0. Results obtained with various inlet species temperatures and bed porosities showed only small changes in the reformer performance. While the results obtained here do provide useful information about the performance of the autothermal reformer, the model used has been re-assessed and it is recommended that an improved model be used in future work. In particular, the assumed effectiveness factors for all of the chemical reactions occurring in the catalyst region need to be improved. This was highlighted by the fact that a brief study indicated a very strong dependence of the reformer product gas composition on the effectiveness factor. This indicates that while the present model is able to predict trends in the reformer performance, it is limited in its accuracy due to the fact that the effectiveness factor used is only approximately known. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2007-08-31 13:22:27.466

This thesis reports the outcome of a simulation study that examines the feasibility of using hydrogen peroxide as an alternative oxidant in the autothermal reforming (ATR) of diesel. The primary objective is to compare hydrogen peroxide's performance against conventional oxidants in reforming, focusing on product distribution and three pivotal process properties: diesel conversion, hydrogen production, and ethylene generation. The study further investigates the influence of the heat of decomposition on the performance and reaction routes of different oxidants. Additionally, a comparative analysis is conducted on the reforming performance in different reformer configurations, specifically contrasting a combined-reformer-configuration with a catalytic-reformer configuration. The ANSYS Chemkin-Pro is utilized to understand the potential benefits and challenges of the proposed approached. A reduced chemical mechanism of N-heptane/Toluene reforming as a surrogate for diesel, combined with a detailed surface reaction mechanism of propene on a three-way Pt/Rh catalyst are used in this study. It is found that the use of hydrogen peroxide as an oxidant demonstrated a complete fuel conversion and 183% higher hydrogen yield when compared with conventional oxidants. It also led to a 12% lower generation of ethylene, a precursor for coke formation. The catalytic-reformer configuration showed superior performance over the combined-reformer-configuration in terms of hydrogen yield. The insights from this study offer valuable perspectives on the feasibility and efficiency of using hydrogen peroxide as an alternative oxidant in the ATR of diesel, paving the way for potential advancements in the field.

A numerical study was carried out to improve the design of an autothermal reformer for the onboard production of hydrogen to be used in fuel-cell- powered auxiliary power units (APU) to provide heating and electricity in long haul trucks when they are at rest. The development of these auxiliary power units is based upon the use of power generated by solid oxide fuel cell (SOFC) system, instead of from a conventional gasoline engine. The present work was undertaken to improve the design of a prototype autothermal fuel reformer that had been developed by the Fuel Cell Research Centre (FCRC) at Queen’s University to convert liquid hydrocarbon truck fuel to a hydrogen rich product gas. In this development work and in the previous work iso-octane (C8H18) has been used as a surrogate fuel. Using this surrogate of gasoline, the reformer was simulated using various inlet steam/carbon (H2O/C), oxygen/carbon (O/C) molar ratios and gas-hourly-space-velocity (GHSV). In the reformer considered the reforming process is carried out in a compact tubular reactor with a centerline thermocouple tube using a 2% Pt-ZrCe based catalyst with a local porosity of 0.6. During the initial simulations, it was observed that near the start of the catalyst region there were large temperature gradients due to an exothermic partial oxidation reaction. In order to reduce the temperature gradients and facilitate heat transfer by conduction along the reformer, the central thermocouple tube was replaced with a central solid rod. The effects of variations in the thermal conductivity of central solid rod, of the reactor wall, of the catalyst bed, of the inert porous material near the inlet and the outlet of the catalyst bed, of the gas hourly space velocity, of the effectiveness factor of the chemical reaction mechanism on the performance of the reactor were studied. The results so obtained were analyzed to determine potential design improvements that would increase the hydrogen output. The results were compared with the previous numerical and experimental results obtained in the previous studies of the reformer and found to be in good agreement with the general trends of the temperature profiles as well as the outlet molar concentrations of product species. After the analysis and evaluation of all the results, it was found that by replacement of central thermocouple tube with central solid rod made of high conductivity material and by using material for inert porous region at the outlet that had a thermal conductivity equal to that of the catalyst bed led to more even temperature profiles within the catalyst region. It was also found that the hydrogen molar percentage output could be increased by approximately more than 25% and that the length of the reactor could be reduced by 20mm by incorporating these changes in the reformer design. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-03-09 12:14:27.627

The depletion of fossil fuels together with growing environmental concerns have created incitement for developing a more energy-efficient and environmentally-friendly vehicle fleet. The development towards cleaner heavy-duty vehicles started already in the 80’s with the introduction of emission legislations. Initially, engine optimization was enough for reaching the legislated levels of emissions. However, at present engine optimization is not enough but exhaust aftertreatment has become an essential part of heavy-duty vehicles, in order to meet the emission standards. Today, the total emissions are targeted which means that there is an interest in decreasing the idling emissions as well as the emissions during operation. To reduce the overall emissions several states in the USA have introduced idling legislations. Due to the limitations in idling time alternative solutions for power generation during rests are requested. A possible alternative is a fuel cell auxiliary power unit, combining a fuel cell with a fuel reformer (FC-APU).  The focus of this thesis is the development of the fuel reformer for an FC-APU, in which the hydrogen to the fuel cell is generated from diesel in a high-temperature catalytic process. The produced hydrogen can also be used in other heavy-duty vehicle applications i.e. selective catalytic reduction of NOx (HC-SCR), where addition of hydrogen is essential for reaching high conversion at low temperatures. The effect of using hydrogen from a fuel reformer in HC-SCR is included in this work. The catalytic material development is focused on developing promoted materials with lower rhodium content but with catalytic activity comparable to that of materials with higher rhodium content. This includes evaluation and extensive characterization of both fresh and aged promoted materials. The work also includes reactor design where a micro reactor with multiple air inlets is evaluated. This work has contributed to increased knowledge of catalytic materials suitable for reforming of diesel. By changing the support material from the traditionally used alumina to ceria-zirconia, increased H2 yield was achieved. In addition, the ceria-zirconia supported material was less prone to coke. By promoting the material with cobalt or lanthanum it was possible to decrease the rhodium content by 2/3 with enhanced catalytic performance. It was also discovered that promotion with lanthanum decreased the tendency for coking even further. Additionally, the lanthanum-promoted material had higher thermal stability as well as a stable highly dispersed rhodium phase. Furthermore, the work has contributed to an increased knowledge concerning the fuel reformer’s effect on HC-SCR. The work displays clear evidence of benefits with using hydrogen-rich gas from a fuel reformer instead of pure hydrogen. The benefits are derived from the content of low molecular weight hydrocarbons present in the hydrogen-rich gas, which are strong reducing agents increasing the NOx reduction. This finding proves that fuel reforming in combination with HC-SCR is a viable option for NOx abatement. / <p>QC 20150202</p>

The present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150 degrees C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of >80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.

Fuel cell is one of the most promising clean energy and alternative energy technologies due to its advantages of low emissions and high efficiency. One application of the fuel cell technology is onboard auxiliary power units (APUs) for power generation in aircrafts, ships, and automobiles. In order to supply hydrogen or syngas for the fuel cell APUs, onboard fuel processing technology was proposed to convert hydrocarbon fuels into syngas through reforming reactions. Two major tasks need to be completed in onboard fuel processing technology. Firstly sulfur compounds have to be removed from hydrocarbon fuels because sulfur can cause reforming catalyst deactivation and fuel cell electrodes poisoning problems. Secondly hydrogen and carbon monoxide shall be produced by reforming of hydrocarbon fuels at a high energy conversion efficiency. This dissertation focused on onboard fuel processing of Jet-A fuel to produce hydrogen and syngas for solid oxide fuel cell (SOFC) APUs. Jet-A fuel was studied because it is the logistic fuel commonly used for civilian airplanes and military heavy duty trucks. Ultra-deep adsorptive desulfurization of Jet-A fuel from over 1,000 ppmw to below 50 ppmw, and autothermal reforming of n-dodecane as a Jet-A fuel surrogate as well as the real desulfurized Jet-A fuel to produce syngas have been systematically investigated in the present study. For the adsorptive desulfurization of Jet-A fuel, a novel NiO-CeO₂/A1₂O₃-SiO₂ adsorbent was proposed and prepared in-house for experimental tests. The sulfur adsorption kinetic characteristic and isotherm at equilibrium were studied in batch tests, and the dynamic desulfurization performance of the adsorbent was investigated in fixed bed tests. Fixed bed tests operation conditions including liquid hourly space velocity (LHSV), adsorbent particle size, and fixed bed dimensions were optimized to achieve the highest adsorbent sulfur adsorption capacity. For the reforming of Jet-A fuel, autothermal reforming (ATR) method was employed and a bimetallic NiO-Rh catalyst was synthesized for the ATR reactions. A lab-scale 2.5 kWt autothermal reforming system including the reformer and balance-of-plant was designed, fabricated, integrated and tested. The reforming system performances at various operation conditions were compared. Reformer operation temperature, steam to carbon ratio and oxygen to carbon ratio, as well as pre-heating temperatures for fuel, air and steam were optimized based on system energy conversion efficiency, H₂ selectivity and COₓ selectivity.

L'hydrogène pourrait jouer un rôle prépondérant dans le domaine de l'énergie dans les années à venir. De nos jours, la production d'hydrogène provient majoritairement de ressources fossiles. En vue de l'impact néfaste de l'utilisation de ressources fossiles sur l'environnement, produire de l'hydrogène à partir de ressources renouvelables présente un grand intérêt. Dans cette étude, le reformage autotherme du biogaz, une source renouvelable de méthane, a été étudié sur des catalyseurs au nickel à 700°C et à pression atmosphérique. Cette étude porte sur un biogaz modèle composé à 60% de méthane et 40% de dioxyde de carbone mis en présence d'oxygène et de vapeur d'eau dans les proportions : 42% H2O, 14% CH4, 9% CO2, 7% O2 dilués dans l'argon. Dans un premier temps, un criblage de catalyseurs au nickel a été réalisé grâce à un montage composé de 6 réacteurs parallèles. L'outil a permis de montrer qu'un catalyseur bimétallique NiRh supporté sur un spinelle de magnésium était actif et très stable, montrant une conversion totale du méthane après 200h de réaction. L'équivalent de ce catalyseur sans Rh s'est désactivé après seulement 2h de réaction. Notre étude a démontré que cette désactivation était causée par la formation du spinelle de nickel, NiAl2O4. Cette formation est une conséquence des hautes températures présentes dans la zone de combustion qui induisent un désordre dans la structure cristalline du support et permettent, en présence de NiO, la diffusion de ions Ni2+ dans les lacunes du support. Enfin, une étude cinétique a été menée sur des catalyseurs structurés. Un modèle cinétique a été développé, permettant également de décrire le profil de désactivation causée par la perte de sites actifs / Hydrogen is expected to play an increasingly important role in the energy sector in the years to come. Nowadays, hydrogen is mainly produced from fossil fuels. The extensive use of fossil fuels is unsustainable and therefore, hydrogen production from renewable sources is of great interests. Autothermal reforming of biogas, a renewable source of methane, was studied over nickel catalysts at 700°C and at atmospheric pressure. This study focused on model biogas composed of 60% methane and 40% carbon dioxide, reacting with oxygen and steam respecting the composition: 42% H2O, 14% CH4, 9% CO2, 7% O2 diluted in argon. First and foremost, a screening of different catalyst compositions was carried out with a six parallel-flow reactor set-up. This high-throughput technology showed that a NiRh bimetallic catalyst supported on magnesium spinel was active and very stable, still fully converting methane after 200 hours of reaction. On the other hand, its noble-metal free equivalent deactivated after only 2 hours. Our study showed that deactivation was caused by the formation of nickel spinel NiAl2O4. Its formation is a consequence of the exothermicity of the combustion reaction taking place at the catalyst inlet. The high temperatures induce a disorder in the crystal structure of the support and, in presence of NiO, Ni2+ ions can then diffuse into the vacancies of the support. The inactive NiAl2O4 phase is formed. Finally, a kinetic study was performed on structured catalysts. A kinetic model was developed, which also allowed the description of the deactivation profile caused by the loss of active sites

Le reformage autothermique, dans lequel une oxydation air carburant permet d’initier les réactions de formation d’hydrogène à partir de carburant et d’eau, semble une voie prometteuse pour la synthèse d’hydrogène à bord de navires. Son application au diesel, carburant majoritairement utilisé dans le secteur maritime, bien que moins bien connue académiquement que celle du méthane, permet une opérabilité du vaisseau sur l’ensemble du globe. Cependant les réacteurs associés sont particulièrement sujets au dépôt de carbone, néfaste pour leur durabilité, et requièrent alors une attention toute particulière au niveau des zones de mélange lors de leur conception. Dans les cas d’écoulements fortement tridimensionnels, une approche RANS couplée à un schéma cinétique décrivant les espèces gazeuses, est le plus souvent utilisée. Ce schéma consiste alors soit en un nombre succint de réactions empiriques, au risque de se montrer peu précis sur les niveaux de polluants, ou au contraire en des schémas d’une cinquantaine d’espèces issus de la réduction automatique de schémas complets, qui restent cependant trop lourds à utiliser lors d’une phase de conception. L’objectif de la thèse est alors de proposer une méthodologie pour décrire l’impact d’une géométrie sur les niveaux de polluants compatibles avec les outils habituellement utilisés dans le milieu industriel. Ainsi, la description du couplage chimie-écoulement est réalisée par le biais des logiciels Fluent R et de la suite Chemkin R de ANSYS R . Après une analyse de la chimie du reformage autothermique du diesel, une méthode de génération de schémas globaux d’une di-zaine d’espèces à partir d’un schéma détaillé est proposée. Elle est, par la suite appliquée avec succès à l’oxydation partielle du n-dodécane. Le schéma estalors utilisé dans la première simulation réactive de reformeur auto-thermique avec injection de diesel liquide réalisée à ce jour. Malgré les difficultés de validation dûes au manque de données experimentales et aux limitations des logiciels imposés, les résultats obtenus sont encourageants. / Autothermal reformers use fuel-air oxidation to ensure production of hydrogen from fuel and water on-board. The use of diesel instead of better-known methan, permits the ships to be refuelled all around the world. These systems show strong sensitivity to carbon deposit which reduces their lifetime. Good knowledge of the fuel air mixing is thus required. Academic description of such tridimensional systems usually relies on the application of a RANS simulation coupled with gaseous chemical kinetics mechanism. These mechanisms can then consist on a few empirical reactions, or at the opposite, on quite large schemes, with more than 50 species derived automatically from big detailled schemes. The resulting description is then not enough precise, or at the opposite too computationally expensive to be used during design process. This thesis thus aims to develop an industrial compatible methodology to describe the impact of design geometry on pollutant formation. ANSYS software such as Fluent and Chemkin are then used to perform the simulation. An original method of limited size mechanism derivation from larger chemical scheme is proposed. It is succesfully applied to the generation of a partial oxidation mechanism of n-dodecane, from the results of diesel reforming chemical analysis. The resulting scheme is then applied on theliquid injection diesel autoreformer reactive simulation. Even if validation difficulties result from the lack of experimental data and limitations of the softwares, it remains the first simulation of this kind in the litterature, to our knowledge. Promising results are obtained.

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