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Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (4)
- 9 Komponentensicherheit (4)
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- 3 Gefahrgutumschließungen; Energiespeicher (3)
- 3.5 Sicherheit von Gasspeichern (3)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (3)
- 2.2 Prozesssimulation (2)
- 2.1 Sicherheit von Energieträgern (1)
- 4 Material und Umwelt (1)
Sensor systems are widely used in hydrogen technologies. The lecture presents requirements and properties of sensor systems and shows application examples of these technologies for safety and process control for hydrogen technologies. The focus is on gas sensors as well as sensors for pressure, temperature and gas flow. These systems are applied, among other things, for monitoring and control of operating conditions, indication of hazardous conditions and triggering of alarms.
Introduction of H2Safety@BAM
(2021)
This contribution for the Open Forum of the 8th HSN Symposium introduces the SensRef activities of the Competence Centre H2Safety@BAM.
The testing of gas and humidity sensors is essential for the application of sensing devices. The testing determines properties of an investigated humidity sensor or gas sensor. In testing, the sensor property is the observed response of a sensing system to an input stimulus in comparison to a reference within a test procedure. This tutorial is structured into six chapters. The first chapter is about basics of hygrometry and gas sensing. It includes definitions, sensor classification, overview of application categories, as well as construction and functional principles. The chapter on requirements of deployed sensors focus on stability, response time, cross-sensitivity, electrical and mechanical requirements, and other. The sensing performance is characterised by determinations of parameters like accuracy, repeatability, detection limits (low and high), and response/recovery time. The description of testing signals on specified qualitative and quantitative characteristics, and the adequately estimated measurement uncertainty is the content of the analysis chapter. All chapters contain examples of testing procedures from testing/calibration labs for hygrometers and gas sensors which are essential for implementation into quality management systems.
Um die Absorption von Wasserstoff und dessen Verhalten in den Werkstoffen beim Einsatz unter Druck-H2 sowie die H- abhängigen Materialeigenschaften zu definieren, entwickelt die BAM mit ihrer langjährigen Erfahrung adäquate Prüfkonzepte, die einsatzrelevante Bedingungen und reale Beanspruchungen (Temperatur, Wasserstoff und mech. Beanspruchung) hierarchisch berücksichtigen. Der Vortrag gibt eine Einführung in das Thema von wasserstoffunterstützen Materialschäden durch die Problematik der Einspeisung von Wasserstoff in bestehende Erdgasnetze. Ferner wird auf die Hochdruck-Infrastruktur (sowie H2-Tankstellen) und die Entwicklung von Prüfkonzepten für die Gasinfrastruktur unter Druckwasserstoffbeaufschlagung eingegangen.
Increasing environmental problems with conventional energy technology are stimulating the demand for alternative energy solutions. With air quality reaching catastrophic levels in large cities worldwide, Fuel Cell Electric Vehicles offer the ideal combination of clean power with the amenities of electric drives. Hydrogen use on vehicles, nevertheless, also raises some issues about safe handling. As fuel cells and hydrogen applications, including vehicles, approach technological maturity, developing their business cases becomes crucial in introducing them to the consumer markets.
The Joint European Summer School JESS 2021 addresses these issues by offering high quality graduate level courses on selected topics of vehicle technology, innovation & business development, safe handling of hydrogen, and modelling. This series of summer schools has been ongoing since 2004 and targets an audience of university students (MSc and PhD levels) and post-doctoral researchers. We also welcome more experienced researchers and engineers wishing to expand their general knowledge, for instance, to suit a newly acquired position or collect credits for Continuous Professional Development (CPD). The course content is tailored to the needs of a diverse audience: newcomers to the field, experienced students, and young professionals working at the forefront of fuel cell and hydrogen applications.
Despite its contribution to tackling climate change by lightweight design, growing CFRP production also results in a global waste generation of 62 kt/a. Accordingly, the energy-intensive production process of carbon fibers (CF) necessitates sustainable recycling solutions.
Herein we will give an overview of current recycling processes, discuss their limitations and present a novel approach for safe treatment of CF unsuitable for material recovery . Our project CF Pyro examines feedstock recycling in pyrometallurgical processes, focusing on reactivity of CF, process stability and prevention of hazardous WHO fiber release. Besides fundamental experimental breakthroughs, their broader impact on circular economy will be presented.
Martensitic 9% Cr steels like P91 and P92 show susceptibility to delayed hydrogen assisted cracking depending on their microstructure. In that connection, effective hydrogen diffusion coefficients are used to assess the possible time-delay. Limited data on room temperature diffusion coefficients reported in literature vary widely by several orders of magnitude (mostly attributed to variation in microstructure). Especially P91 weld metal diffusion coefficients are rare so far. For that reason, electrochemical permeation experiments had been conducted using P92 base metal and P91 weld metal (in as-welded and heat-treated condition) with different thicknesses. From the results obtained, diffusion coefficients were calculated using to different methods, time-lag, and inflection point. Results show that, despite microstructural effects, the sample thickness must be considered as it influences the calculated diffusion coefficients. Finally, the comparison of calculated and measured hydrogen concentrations (determined by carrier gas hot extraction) enables the identification of realistic diffusion coefficients.
This study gives an overview on the important field of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the different technological field of hydrogen generation, storage, transport and use. In addition, the emerging field of additive manufacturing is included. Finally, some remarks are given for necessary changes in the standardization and its challenges.
Introduction: Homogenously catalyzed reactions in multiphase systems, as they are used for example for the hydroformylation or reductive amination, offer a promising approach to produce base chemicals from renewable resources. The organic and gaseous educts react with the catalyst, which is designed to be soluble in water to provide a good separation from the likewise organic products. In the resulting gas/liquid/liquid systems, the reaction is controlled through interfacial and transport phenomena. These processes fail for long chained olefins – e.g. vegetable oils and fats – because of their low solubility in water. Therefore, surfactants can be added as an emulsifier to form micellar emulsion systems (MES) [1], increase reaction speed [2] and facilitate phase separation [3]. These systems form up to three liquid phases, depending on temperature and composition. For fast reactions, the gas/liquid mass transfer plays an important role. Due to the multiple phases present, the dispersion conditions of the particles and the resulting mass transfer are complex.
Methods: In this work, the mass transfer in MES is investigated. For simplicity, only the non-reactive material system without catalyst consisting of water, dodecane and the non-ionic surfactant Marlophen NP8 was investigated. Hydrogen was applied as gas phase. The phase behavior of the MES was characterized using settling experiments and by measuring the conductivity of the emulsions [4]. The mass transfer experiments were conducted in two different setups employing the dynamic pressure method.
In a pressurized stirred tank reactor, the mass transfer performance of the whole MES was determined under the complex dispersion conditions and a variety of different system parameters by measuring the volumetric mass transfer coefficient (kLa). The specific transfer area (a) was determined measuring gas hold-up and using optical endoscope measurements [5] to record bubble sizes. The non-spherical bubbles were analyzed with a trained convolutional neural network [6].
Using a falling film capillary in a closed pressurized system [7], the mass transfer of the single phases appearing in MES were quantified. The phases were removed and investigated separately after the settling experiments. A gravity-driven laminar flow with well-defined transfer area was established along the capillary and by measuring the pressure drop over time the mass transfer coefficient (kL) could be calculated.
Results: The mass transfer coefficients of hydrogen in the single phases of the micellar emulsion system covered a broad range. The kL of the aqueous phase was similar to pure water, while the third, bi-continuous phase forming in MES had very small kL values due to its high viscosity. The mass transfer coefficient of the organic phase was found to be far higher than of the aqueous phase.
In the stirred tank reactor, different phases formed the continuous phase in the whole MES mixture for the temperature range investigated. The fastest mass transfer was found for a continuous aqueous phase below 87 °C. At higher temperatures, a phase inversion occurred, and the organic phase became continuous. The high kL of the organic phase measured in the falling film contactor did not translate directly to a higher kLa in the stirred tank reactor as the value dropped compared to an aqueous continuous phase present. The change in continuous phase were found to affect the drop and bubble sizes in the system. For an organic continuous phase, the Sauter mean diameter of the bubbles were larger and the transfer area smaller, which was the main reason for the reduced kLa.
This work describes the effects of catalyst layers (CLs) consisting of hydrophobic PTFE on the performance and water management of PEM fuel cells. Catalyst inks with various PTFE contents were coated on Nafion membranes and characterized using contact angle measurements, SEX-EDX, and mercury porosimetry. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were conducted under varying operating conditions for the prepared materials. At dry conditions, CLs with 5 wt.% PTFE were advantageous for cell performance due to improved membrane hydration, whereas under humid conditions and high air flow rates CLs with 10 wt.% PTFE improved the performance in high current density region. Higher PTFE contents (⩾20 wt.%) increased the mass transport resistance due to reduced porosity of the CLs structure. Operando neutron radiography was utilized to study the effects of hydrophobicity gradients within CLs and cathode microporous layer (MPLC) on liquid water distribution. More hydrophobic CLs increased the water content in adjacent layers and improved performance, especially at dry conditions. MPLC with higher PTFE contents increased the overall liquid water within the CLs and GDLs and escalated the water transfer to the anode side. Furthermore, the role of back-diffusion transport mechanism on water distribution was identified for the investigated cells.