Author: Pablo Diaz Gomez Maqueo Publisher: ISBN: Category : Languages : en Pages :
Book Description
"This thesis presents the experimental study of non-thermal plasmas applied to methane reforming at atmospheric pressure. The resulting hydrogen-containing gas is studied as a potential fuel additive to increase chemical reactivity in gas turbine engine conditions. Reactivity control is proposed as a fuel flexibility technology for low calorific fuels and as a mean to operate in low emission conditions such as lean premixed combustion.The experimental section of the thesis is focused on the characterization of pulsed-powered non-thermal discharge plasmas as fuel reformers. The experimental reactor consists of a pin to plane plasma chamber designed to be optically accessible and to isolate the reacting gases from the surrounding air. The applied voltage pulse duration is on the order of 100 ns to prevent thermalization of the plasma channel and to decouple thermal energy from excitation energy delivered by the discharge. When a voltage pulse is applied to the pin electrode, two stable regimes are identified: a diffuse regime with a plasma that occupies most of the inter-electrode volume, and a filamentary regime with constricted spark-like filaments. The first regime operates at a maximum energy per pulse of 1.3 mJ with negligible conversion efficiency. On the contrary, the filamentary regime reaches a maximum energy per pulse of 13.9 mJ with conversion and energy efficiencies of 26.3 % and 19.7 % respectively. Both regimes have gas temperatures estimated to be near 500 K, and there is no correlation with respect to the energy per pulse. The results suggest that the more energetic filamentary regime is not heating the gas, but rather delivering the energy towards better conversion efficiencies.To study the individual contributions of reactant temperature, pulse repetition frequency, and energy per pulse on the reforming performance of the reactor, a new high voltage pulser was developed and a preheating system capable of reaching 800 K was added. Temperature estimations show that varying the energy per pulse has a minimal effect on the temperature of the gas, while increasing the frequency heats the gas up to 777 K. Increasing reactant temperature is shown to have a negligible effect, while increasing the pulse repetition frequency has the strongest effect on conversion and energy efficiency. Additionally, the best performance is observed in partial oxidation, reaching a maximum conversion efficiency of 68.2 % and an energy efficiency of 31.5 %.The obtained results demonstrate the applicability of nanosecond repetitively-pulsed discharges as methane reformers. Capable of producing mixtures with up to 29.7 % hydrogen, these discharges can be used to increase chemical reactivity in gas turbine engine conditions as shown by the numerical simulations. This conversion is not dependent on the reactant temperature, but rather on the total amount of energy deposited by the discharge. Additionally, increasing the repetition frequency of the discharge seems to have the largest increase in efficiency, pointing towards future optimization of plasma-assisted fuel reforming technologies." --
Author: Sreekar Parimi Publisher: ISBN: Category : Languages : en Pages :
Book Description
Utilization of natural gas in remote locations necessitates on-site conversion of methane into liquid fuels or high value products. The first step in forming high value products is the production of ethylene and acetylene. Non-thermal plasmas, due to their unique nonequilibrium characteristics, offer advantages over traditional methods of methane reforming. Different kinds of non-thermal plasmas are being investigated for methane reforming. Parameters of these processes like flow rate, discharge size, temperature and other variables determine efficiency of conversion. An efficient process is identified by a high yield and low specific energy of production for the desired product. A study of previous work reveals that higher energy density systems are more efficient for methane conversion to higher hydrocarbons as compared to low energy density systems. Some of the best results were found to be in the regime of warm discharges. Thermal equilibrium studies indicate that higher yields of ethylene are possible with an optimal control of reaction kinetics and fast quenching. With this idea, two different glow discharge reactor systems are designed and constructed for investigation of methane reforming. A counter flow micro plasma discharge system was used to investigate the trends of methane reforming products and the control parameters were optimized to get best possible ethylene yields while minimizing its specific energy. Later a magnetic glow discharge system is used and better results are obtained. Energy costs lower than thermal equilibrium calculations were achieved with magnetic glow discharge systems for both ethylene and acetylene. Yields are obtained from measurements of product concentrations using gas chromatography and power measurements are done using oscilloscope. Energy balance and mass balances are performed for product measurement accuracy and carbon deposition calculations. Carbon deposition is minimized through control of the temperature and residence time conditions in magnetic glow discharges. Ethylene production is observed to have lower specific energies at higher powers and lower flow rates in both reactors. An ethylene selectivity of 40% is achieved at an energy cost of 458MJ/Kg and an input energy cost of 5 MJ/Kg of methane.
Author: Annemie Bogaerts Publisher: MDPI ISBN: 3038977500 Category : Technology & Engineering Languages : en Pages : 248
Book Description
Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, methane conversion into higher hydrocarbons or oxygenates. It is also widely used for air pollution control (e.g., VOC remediation). Plasma catalysis allows thermodynamically difficult reactions to proceed at ambient pressure and temperature, due to activation of the gas molecules by energetic electrons created in the plasma. However, plasma is very reactive but not selective, and thus a catalyst is needed to improve the selectivity. In spite of the growing interest in plasma catalysis, the underlying mechanisms of the (possible) synergy between plasma and catalyst are not yet fully understood. Indeed, plasma catalysis is quite complicated, as the plasma will affect the catalyst and vice versa. Moreover, due to the reactive plasma environment, the most suitable catalysts will probably be different from thermal catalysts. More research is needed to better understand the plasma–catalyst interactions, in order to further improve the applications.
Author: Nikolay Britun Publisher: BoD – Books on Demand ISBN: 1789848407 Category : Science Languages : en Pages : 88
Book Description
Low-temperature non-equilibrium gaseous discharges represent nearly ideal media for boosting plasma-based chemical reactions. In these discharges the energy of plasma electrons, after being received from the electromagnetic field, is transferred to the other degrees of freedom differently, ideally with only a small part going to the translational motion of heavy gas particles. This unique property enables the important application of non-equilibrium plasmas for greenhouse gas conversion. While the degree of discharge non-equilibrium often defines the energetic efficiency of conversion, other factors are also of a great importance, such as type of discharge, presence of plasma catalysis, etc. This book is focused on the recent achievements in optimization and understanding of non-equilibrium plasma for gas conversion via plasma modeling and experimental work.
Author: D.M. Bibby Publisher: Elsevier ISBN: 0080960707 Category : Technology & Engineering Languages : en Pages : 759
Book Description
This proceedings volume comprises the invited plenary lectures, contributed and poster papers presented at a symposium organised to mark the successful inauguration of the world's first commercial plant for production of gasoline from natural gas, based on the Mobil methanol-to-gasoline process. The objectives of the Symposium were to present both fundamental research and engineering aspects of the development and commercialization of gas-to-gasoline processes. These include steam reforming, methanol synthesis and methanol-to-gasoline. Possible alternative processes e.g. MOGD, Fischer-Tropsch synthesis of hydrocarbons, and the direct conversion of methane to higher hydrocarbons were also considered.The papers in this volume provide a valuable and extremely wide-ranging overview of current research into the various options for natural gas conversion, giving a detailed description of the gas-to-gasoline process and plant. Together, they represent a unique combination of fundamental surface chemistry catalyst characterization, reaction chemistry and engineering scale-up and commercialization.
Author: JianHua Yan Publisher: Springer ISBN: 9811036594 Category : Technology & Engineering Languages : en Pages : 107
Book Description
This book provides an overview of hydrogen production from renewable resources such as ethanol using plasma or plasma-catalytic technologies. Further, it presents a balanced and comprehensive treatment of the core principles, novel plasma reactors and diagnostics, as well as state-of-the-art plasma energy applications. It brings together technological advances and research on plasma generators and their application in hydrogen production, including plasma-assisted alcohol reforming technology, plasma-catalytic alcohol reforming technology, the alcohol reforming mechanism, models of alcohol reforming for hydrogen production, the energy balance of hydrogen production from ethanol, and a comparison of alcohol reforming assisted by different plasma treatment systems. As such, it offers a valuable reference guide for scientists, engineers and graduate students in the fields of energy and environment, plasma physics and chemistry.
Author: Flora Uwadiegwu Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Topics on conversion and utilization of methane and carbon dioxide are imperative as they tackle global warming effects from the two greenhouse gases (GHGs). Non-thermal plasma processes have been proposed as an efficient means to reform both gases as they have the advantage of realizing thermodynamically unfavorable reactions due to their unique non-equilibrium properties. Non-thermal processes also overcome the drawback of the high temperature required by conventional catalytic processes. In this work, an AC dielectric-barrier discharge (DBD) was used for the activation of methane and carbon dioxide to produce syngas. The effect of operating parameters such as CH4/CO2 mole ratio and feed gas flow rate on the performance of the plasma process were investigated in terms of the conversion of feed gas, product selectivity and energy conversion efficiency. The results show that the energy efficiency using a DBD is comparable with other dielectric-barrier discharges and even slightly higher but still relatively lower than that of the gliding arc primarily due to its smaller discharge volume." --
Author: Pablo Diaz Gomez Maqueo
Author: Sreekar Parimi
Author: Annemie Bogaerts
Author: Nikolay Britun
Author: D.M. Bibby
Author: Yun Yang
Author: Helen J. Gallon
Author: JianHua Yan
Author: Luca Lietti
Author: Flora Uwadiegwu