An experimental and modeling study on the reactivity of extremely fuel-rich methane/dimethyl ether mixtures

Chemical reactions in stoichiometric to fuel-rich methane/dimethyl ether/air mixtures (fuel air equiva- lence ratio φ=1–20) were investigated by experiment and simulation with the focus on the conversion of methane to chemically more valuable species through partial oxidation. Experimental data from dif- ferent facilities were measured and collected to provide a large database for developing and validating a reaction mechanism for extended equivalence ratio ranges. Rapid Compression Machine ignition delay times and species profiles were collected in the temperature range between 660 and 1052 K at 10 bar and equivalence ratios of φ= 1–15. Ignition delay times and product compositions were measured in a shock tube at temperatures of 630–1500 K, pressures of 20–30 bar and equivalence ratios of φ= 2 and 10. Ad- ditionally, species concentration profiles were measured in a flow reactor at temperatures between 473 and 973 K, a pressure of 6 bar and equivalence ratios of φ= 2, 10, and 20. The extended equivalence ratio range towards extremely fuel-rich mixtures as well as the reaction-enhancing effect of dimethyl ether were studied because of their usefulness for the conversion of methane into chemically valuable species through partial oxidation at these conditions. Since existing reaction models focus only on equivalence ratios in the range of φ= 0.3–2.5, an extended chemical kinetics mechanism was developed that also covers extremely fuel-rich conditions of methane/dimethyl ether mixtures. The measured ignition delay times and species concentration profiles were compared with the predictions of the new mechanism, which is shown to predict well the ignition delay time and species concentration evolution measure- ments presented in this work. Sensitivity and reaction pathway analyses were used to identify the key reactions governing the ignition and oxidation kinetics at extremely fuel-rich conditions

Mixture Risk Assessment of Complex Real-Life Mixtures—The PANORAMIX Project

Humans are involuntarily exposed to hundreds of chemicals that either contaminate our environment and food or are added intentionally to our daily products. These complex mixtures of chemicals may pose a risk to human health. One of the goals of the European Union’s Green Deal and zero-pollution ambition for a toxic-free environment is to tackle the existent gaps in chemical mixture risk assessment by providing scientific grounds that support the implementation of adequate regulatory measures within the EU. We suggest dealing with this challenge by: (1) characterising ‘real-life’ chemical mixtures and determining to what extent they are transferred from the environment to humans via food and water, and from the mother to the foetus; (2) establishing a high-throughput whole-mixture-based in vitro strategy for screening of real-life complex mixtures of organic chemicals extracted from humans using integrated chemical profiling (suspect screening) together with effect-directed analysis; (3) evaluating which human blood levels of chemical mixtures might be of concern for children’s development; and (4) developing a web-based, ready-to-use interface that integrates hazard and exposure data to enable component-based mixture risk estimation. These concepts form the basis of the Green Deal project PANORAMIX, whose ultimate goal is to progress mixture risk assessment of chemicals.Horizon 2020 research and innovation programme, the Green Deal project PANORAMIX Grant Agreement No. 10103663

Flexible energy conversion and storage via high-temperature gas-phase reactions: The piston engine as a polygeneration reactor

Piston engines are typically considered devices converting chemical energy into mechanical power via internal combustion. But more generally, their ability to provide high-pressure and high-temperature conditions for a limited time means they can be used as chemical reactors where reactions are initiated by compression heating and subsequently quenched by gas expansion. Thus, piston engines could be “polygeneration” reactors that can flexibly change from power generation to chemical synthesis, and even to chemical-energy storage. This may help mitigating one of the main challenges of future energy systems – accommodating fluctuations in electricity supply and demand. Investments in devices for grid stabilization could be more economical if they have a second use. This paper presents a systematic approach to polygeneration in piston engines, combining thermodynamics, kinetics, numerical optimization, engineering, and thermo-economics. A focus is on the fuel-rich conversion of methane as a fuel that is considered important for the foreseeable future. Starting from thermodynamic theory and kinetic modeling, promising systems are selected. Mathematical optimization and an array of experimental kinetic investigations are used for model improvement and development. To evaluate technical feasibility, experiments are then performed in both a single-stroke rapid compression machine and a reciprocating engine. In both cases, chemical conversion is initiated by homogeneous-charge compression-ignition. A thermodynamic and thermo-economic assessment of the results is positive. Examples that illustrate how the piston engine can be used in polygeneration processes to convert methane to higher-value chemicals or to take up carbon dioxide are presented. Open issues for future research are addressed

Validity of the Livengood & Wu correlation and theoretical development of an alternative procedure to predict ignition delays under variable thermodynamic conditions

A theoretical study about the autoignition phenomenon has been performed in this article. The hypotheses of the Livengood & Wu integral have been revised, concluding that the critical concentration of chain carriers is not constant. However, its validity under engine conditions has been justified. Expressions to characterize the temporal evolution of the concentration of chain carriers, as well as the critical concentration of active radicals and the ignition delay, have been obtained starting from the Glassman s model. A new expression to predict ignition delays under variable conditions has been developed and the results obtained with this expression have been compared with those obtained from the Livengood & Wu integral. Two different fuels have been studied: isooctane (as a gasoline surrogate) and n-heptane (as a diesel fuel surrogate). The new method to predict ignition delays under variable conditions has shown, in general, better results than the classic Livengood & Wu integral, but the inability of the Glassman s model to reproduce the negative temperature coefficient regime should be improved in future works.The authors would like to thank different members of the CMT-Motores Termicos team of the Universitat Politecnica de Valencia for their contribution to this work. The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lopez-Pintor (Grant FPU13/02329). This work was partly founded by the Generalitat Valenciana, Project PROMETEOII/2014/043.k.Desantes Fernández, JM.; López Sánchez, JJ.; Molina Alcaide, SA.; López Pintor, D. (2015). Validity of the Livengood & Wu correlation and theoretical development of an alternative procedure to predict ignition delays under variable thermodynamic conditions. Energy Conversion and Management. 105:836-847. https://doi.org/10.1016/j.enconman.2015.08.013S83684710

Design of synthetic EGR and simulation study of the effect of simplified formulations on the ignition delay of isooctane and n-heptane

[EN] A method to create synthetic mixtures that simulate the Exhaust Gas Recirculation (EGR) of an internal combustion engine, using O2, N2, CO2, H2O and Ar, has been designed. Different simplifications of this synthetic EGR have been validated in order to reproduce ignition delays. To do this, a parametric study has been carried out with CHEMKIN. The ignition delay of each simplified mixture and the ignition delay of the complete mixture have been simulated for different initial pressures, temperatures, equivalence ratios, oxygen mass fractions and for two different fuels, isooctane and n-heptane. The results obtained with each simplification have been compared with the results obtained with the complete EGR, and based on this comparison the errors in ignition delay have been calculated. The behavior of the errors in ignition delay with the variation of the different parameters of the simulations has been studied. In summary, it can be seen that the relative error increases with temperature and decreases with pressure, equivalence ratio and oxygen mass fraction. Finally, the limit oxygen mass fractions for the use of each simplification have been obtained. Based on these results, it can be concluded that the only gas that can be obviated to keep the error in ignition delay under 1% is ArThe authors would like to thank different members of the CMT-Motores Termicos team of the Universitat Politecnica de Valencia for their contribution to this work. The authors would also like to thank the Spanish Ministry of Education for financing the PhD. Studies of Dario Lepez-Pintor (Grant FPU13/02329). This work was partly founded by the Generalitat Valenciana, project PROMETEOII/2014/043.Desantes, J.; López, JJ.; Molina, S.; López Pintor, D. (2015). Design of synthetic EGR and simulation study of the effect of simplified formulations on the ignition delay of isooctane and n-heptane. Energy Conversion and Management. 96:521-531. https://doi.org/10.1016/j.enconman.2015.03.003S5215319

A walk in the PARC:developing and implementing 21st century chemical risk assessment in Europe

Current approaches for the assessment of environmental and human health risks due to exposure to chemical substances have served their purpose reasonably well. Nevertheless, the systems in place for different uses of chemicals are faced with various challenges, ranging from a growing number of chemicals to changes in the types of chemicals and materials produced. This has triggered global awareness of the need for a paradigm shift, which in turn has led to the publication of new concepts for chemical risk assessment and explorations of how to translate these concepts into pragmatic approaches. As a result, next-generation risk assessment (NGRA) is generally seen as the way forward. However, incorporating new scientific insights and innovative approaches into hazard and exposure assessments in such a way that regulatory needs are adequately met has appeared to be challenging. The European Partnership for the Assessment of Risks from Chemicals (PARC) has been designed to address various challenges associated with innovating chemical risk assessment. Its overall goal is to consolidate and strengthen the European research and innovation capacity for chemical risk assessment to protect human health and the environment. With around 200 participating organisations from all over Europe, including three European agencies, and a total budget of over 400 million euro, PARC is one of the largest projects of its kind. It has a duration of seven years and is coordinated by ANSES, the French Agency for Food, Environmental and Occupational Health & Safety

Internationalizationof Read-Across as a Validated New Approach Method (NAM) for Regulatory Toxicology

Read-across (RAx) translates available information from well-characterized chemicals tothe substance for which there is a toxicological data gap. The OECD is working on case studies to probe general applicability of RAx, and several regulations (e.g. EU-REACH) already allow this procedure to be used to waive new in vivotests. The decision to prepare a review on the state of the art of RAx as a tool for risk assessment for regulatory purposes was taken during a workshop with international experts in Ranco, Italy in July 2018. Three major issues were identified that need optimisation to allowa higher regulatory acceptance rate of the RAx procedure: (i) the definition of similarity of source and target, (ii) the translation of biological/toxicological activity of source to target, in the RAx procedure, and (iii) how to deal with issues of ADMEthat may differ between source and target. The use of new approach methodologies (NAM) was discussed as one of the most important innovations to improve the acceptability of RAx. At present, NAM data may be used to confirm chemical and toxicological similarity. In the future, the use of NAM may be broadened to fully characterize the hazard and toxicokinetic properties of RAx compounds. Concerning available guidance, documents on Good Read-Across Practice (GRAP) and on best practices to perform and evaluatethe RAx process were identified. Here, in particular the RAx guidance, being worked out by the European Commission’s H2020 project EU-ToxRisk, together with many external partners with regulatory experience, is given

Setting the stage for next-generation risk assessment with non-animal approaches: the EU-ToxRisk project experience

In 2016, the European Commission launched the EU-ToxRisk research project to develop and promote animal-free approaches in toxicology. The 36 partners of this consortium used in vitro and in silico methods in the context of case studies (CSs). These CSs included both compounds with a highly defined target (e.g. mitochondrial respiratory chain inhibitors) as well as compounds with poorly defined molecular initiation events (e.g. short-chain branched carboxylic acids). The initial project focus was on developing a science-based strategy for read-across (RAx) as an animal-free approach in chemical risk assessment. Moreover, seamless incorporation of new approach method (NAM) data into this process (= NAM-enhanced RAx) was explored. Here, the EU-ToxRisk consortium has collated its scientific and regulatory learnings from this particular project objective. For all CSs, a mechanistic hypothesis (in the form of an adverse outcome pathway) guided the safety evaluation. ADME data were generated from NAMs and used for comprehensive physiological-based kinetic modelling. Quality assurance and data management were optimized in parallel. Scientific and Regulatory Advisory Boards played a vital role in assessing the practical applicability of the new approaches. In a next step, external stakeholders evaluated the usefulness of NAMs in the context of RAx CSs for regulatory acceptance. For instance, the CSs were included in the OECD CS portfolio for the Integrated Approach to Testing and Assessment project. Feedback from regulators and other stakeholders was collected at several stages. Future chemical safety science projects can draw from this experience to implement systems toxicology-guided, animal-free next-generation risk assessment.publishe