Numerical Modeling of High-Pressure Partial Oxidation of Natural Gas

High-Pressure Partial Oxidation (HP-POX) of natural gas is one of the techniques in the synthesis gas production by non-catalytic reforming. On the path to emissions reduction, all operating facilities must be optimized to satisfy environmental regulations. In a rapidly changing economic and political environment, technological development from lab-scale to demo-scale, and industrial-scale is no longer feasible. Therefore, new research and design methods must be applied. One of such methods commonly used in science and industry is numerical modeling, which utilizes Computational Fluid Dynamics (CFD), Reduce Order Models (ROMs), kinetic, and equilibrium models. The CFD models provide details about flow field, temperature distribution, and species conversion. However, the computational effort required to conduct such calculations is significant. The computationally expensive CFD models cannot be effectively used in the reactor optimization. Herewith, other modeling techniques utilizing kinetic and equilibrium models do not provide necessary details for process optimization and can only be used for adjustments of boundary conditions, investigation of specific processes occurring in the reactor, or development of sub-models for CFD. A numerical investigation was conducted to validate existing CFD models against benchmark experiments. The results reveled that the CFD model is sensitive to modeling parameters, when simulating complex flows where turbulence-chemistry interaction occurs. Moreover, it was shown that the results sensitivity increases along with the oxidizer/fuel inlet velocities ratio. Based on the conducted experiments, the CFD model validation resulted in definition of the modeling parameters suitable for modeling of HP-POX of natural gas. Based on the validated CFD model, a ROM for HP-POX of natural gas was developed. The model assumes that the reactor consists of several zones characterized by specific conversion processes. Moreover, the model considers inlet streams dissipation upon the injection, and includes several optimization stages that allows model adjustments for any reactor geometry and boundary conditions. It was shown that the developed ROM can reproduce global reactor characteristics at non-equilibrium conditions unlike other ROMs, kinetic, or equilibrium models. Moreover, the validation against CFD results showed that the ROM can correctly account for the \gls{rtd} in the reactors of different geometries and volumes without extensive additional optimization. Finally, new experiments were designed and conduced at semi-industrial HP-POX facility at TU Bergakademie Freiberg. The experiments aimed to study the influence of different oxidizer/fuel velocities ratios on the reactants mixing and process characteristics at high operating pressures. The high velocity difference between oxidizer and fuel was achieved by injection of High-Velocity Oxidizer (HVO). The experiments showed no significant influence of the HVO on the global reactor characteristics and overall species conversion process. However, the numerical analysis of the experimental results demonstrated that the oxidation zone is affected by the oxidizer inlet velocity, and becomes less efficient in the fuel conversion when the oxidizer/fuel inlet velocities ratio is increased. In summary, a sophisticated numerical model validation was conducted and sensitivity of the numerical results to the modeling parameters was carefully studied. The novel natural gas conversion technique was experimentally studied. Based on the conducted experiments and numerical evaluation a ROM was developed. The ROM is capable of producing high accuracy results and greatly decreases the computational effort and time needed for reactor development and optimization

Generation of (synthetic) influent data for performing wastewater treatment modelling studies

The success of many modelling studies strongly depends on the availability of sufficiently long influent time series - the main disturbance of a typical wastewater treatment plant (WWTP) - representing the inherent natural variability at the plant inlet as accurately as possible. This is an important point since most modelling projects suffer from a lack of realistic data representing the influent wastewater dynamics. The objective of this paper is to show the advantages of creating synthetic data when performing modelling studies for WWTPs. This study reviews the different principles that influent generators can be based on, in order to create realistic influent time series. In addition, the paper summarizes the variables that those models can describe: influent flow rate, temperature and traditional/emerging pollution compounds, weather conditions (dry/wet) as well as their temporal resolution (from minutes to years). The importance of calibration/validation is addressed and the authors critically analyse the pros and cons of manual versus automatic and frequentistic vs Bayesian methods. The presentation will focus on potential engineering applications of influent generators, illustrating the different model concepts with case studies. The authors have significant experience using these types of tools and have worked on interesting case studies that they will share with the audience. Discussion with experts at the WWTmod seminar shall facilitate identifying critical knowledge gaps in current WWTP influent disturbance models. Finally, the outcome of these discussions will be used to define specific tasks that should be tackled in the near future to achieve more general acceptance and use of WWTP influent generators

Development of a High Intensity Neutron Source at the European Spallation Source: The HighNESS project

The European Spallation Source (ESS), presently under construction in Lund, Sweden, is a multidisciplinary international laboratory that will operate the world's most powerful pulsed neutron source. Supported by a 3M Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) is now underway to develop a second neutron source below the spallation target. Compared to the first source, located above the spallation target and designed for high cold and thermal brightness, the new source will provide higher intensity, and a shift to longer wavelengths in the spectral regions of cold (2 /- 20 {\AA}), very cold (VCN, 10 /- 120 {\AA}), and ultra cold (UCN, > 500 {\AA}) neutrons. The core of the second source will consist of a large liquid deuterium moderator to deliver a high flux of cold neutrons and to serve secondary VCN and UCN sources, for which different options are under study. The features of these new sources will boost several areas of condensed matter research and will provide unique opportunities in fundamental physics. Part of the HighNESS project is also dedicated to the development of future instruments that will make use of the new source and will complement the initial suite of instruments in construction at ESS. The HighNESS project started in October 2020. In this paper, the ongoing developments and the results obtained in the first year are described.Comment: 10 pages, 10 figures, 14th International Topical Meeting on Nuclear Applications of Accelerators, November 30 to December 4, 2021, Washington, D

Managing the Uncertainty Associated with Hydrogen Gas Hazards and Operability Issues in Nuclear Chemical Plants

The complex and diverse nature of reprocessing and decommissioning operations in existing nuclear chemical plants within the UK results in a variety of challenges. The challenges relate to the quantified risk from hydrogen explosions and how best to manage the associated uncertainties. Several knowledge gaps in terms of the Quantified Risk Assessment (QRA) of hydrogen hazards have been identified in this research work. These include radiolytic hydrogen explosions in sealed process pipes, the failure of ventilation systems used to dilute radiolytic hydrogen in process vessels, the decision uncertainty in installing additional hydrogen purge systems and the uncertainty associated with hold-up of hydrogen in radioactive sludges. The effect of a subsequent sudden release of the heldup hydrogen gas into a vessel ullage space presents a further knowledge gap. Nuclear decommissioning and reprocessing operations also result in operational risk knowledge gaps including the mixing behaviour of radioactive sludges, the performance of robotics for nuclear waste characterisation and control of nuclear fission products associated with solid wastes. Bayesian Belief Networks (BBNs) and Monte Carlo Simulation (MC) techniques have been deployed in this research work to address the identified knowledge gaps. These techniques provide a powerful means of uncertainty analysis of complex systems involving multiple interdependent variables such as those affecting nuclear decommissioning and reprocessing. Through the application of BBN and MC Simulation methodologies to a series of nuclear chemical plant case studies, new knowledge in decommissioning and reprocessing operations has been generated. This new knowledge relates to establishing a realistic quantified risk from hydrogen explosions and nuclear plant operability issues. New knowledge in terms of the key sensitivities affecting the quantified risk of hydrogen explosions and operability in nuclear environments as well as the optimum improvements necessary to mitigate such risks has also been gained

Scalable and non-intensive routes to silicon for lithium-ion battery anodes

Silicon has been highlighted as a promising anode material in lithium-ion batteries due to its step change in capacity verses conventional graphite. The cycling of silicon anodes within a lithium-ion battery (LIB) leads to degradation and capacity fade due to the 280% volume change of silicon. Many avenues of silicon synthesis have been explored to produce nanostructures which can withstand this change in volume. Magnesiothermic Reduction (MgTR) of silica to silicon shows significant promise over other syntheses in scalability, economic and environmental aspects for producing porous silicon nanostructures. The problem with MgTR is a lack of understanding regarding the pore evolution of porous silicon based on reduction parameters and precursor material, which in turn limits predictive design for desired applications. Here we show for the first time that the pore structure of porous silicon is strongly related to the interconnectivity of silicon crystallites. We show that the MgTR is a thermodynamically driven equilibria which determines the purity of the silicon product. Higher temperatures also cause sintering of silicon nanocrystallites. We show that it is the interconnectivity of these crystallites determine the pore size and distribution within porous silicon. These findings apply to a wide variety of porous silica precursors and we show this mechanism is true for the introduction of pores into nonporous quartz after MgTR. Further, we show that by exploiting this mechanism, mesoporous silicon can be produced which has excellent promise for LIB applications with a capacity of 2170 mAh/g after 100 cycles. As a second section of the thesis, we focused on the use of silica directly in LIBs. The use of silica has potential advantages over other silicon based active materials, upon reduction with lithium silicon is produced and contained within a supporting structure of inactive material. However, there is no detailed understanding of how the lithium-silica reduction reaction progresses and the chemical nature of the products. Here we develop a new method to effectively monitor the rate of electrochemical reduction of silica and propose a mechanistic understanding of this process. In addition, and for the first time, we characterise the existence of elemental silicon in the reduced structures. Our proposed mechanism is based upon the initial insulating nature of the silica active material and how electronic conduction pathways are formed in the reduced material. We apply the principles of this mechanism to reduce the length of the electrochemical reduction reaction to 13 hour compared with 400 hour reduction times reported in the literature. The findings herein provide a significant step change and hence can be taken forward to design optimal materials for LIB applications. These results strongly support the potential for reduction in silicon costs for LIB in both economic and environmental terms as well as for a reverse engineering approach to design specific porous silicon and silica for desired applications

Student Research Colloquium Proceedings 2009

2009 Student Research Colloquium proceedings include the following: a schedule of the day\u27s events, acknowledgement of research sponsors, the day\u27s program, conference presentation abstracts, student presenter index, research sponsor index, planning committee, poster and paper presentation judges, registration desk, sponsors, and donors, map of Atwood Memorial Center. Keynote address on greenhouse gases, global demand for energy, and tomrorow\u27s technology to address these issues given by Dr. Sean Garrick, Associate Professor, Department of Mechanical Engineering, University of Minnesota. Sustainability Panel Discussion panelists: Dr. Anthony Akubue, Professor, Environmental and Technological Studies, St. Cloud State University; Dr. Sean Garrick, Associate Professor, Mechanical Engineering, University of Minnesota; Valerie Knopp, Assistant Director of Financial Aid, Offices of Scholarships and Financial Aid, St Cloud State University; Teresa A. Lamo-Nelson, Doctoral Candidate, Higher Education Administration, St. Cloud State University; Angela Olson, Assistant Professor, Aviation, St. Cloud State University; Dr. Tracy E. Ore, Associate Professor/Coordinator, Sociology and Anthropology/St Cloud State University Community Garden, Dr. Mitch Bender (Moderator), Associate Professor, Environmental and Technological Studies, St Cloud State University

Workshop on Applications of Phase Diagrams in Metallurgy and Ceramics

A workshop was held to assess the current national and international status of phase diagram determinations and evaluations for alloys, ceramics, and semiconductors; to determine the needs and priorities, especially technological, for phase diagram determinations and evaluations; and to estimate the resources being used and potentially available for phase diagram evaluation. Highlights of the workshop, description of a new poster board design used in the poster sessions, lists of attendees and demonstrations, the program, and descriptions of the presentations are included