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Injecting hydrogen into the natural gas network to reduce CO2 emissions in the EU residential sector is considered a critical element of the zero CO2 emissions target for 2050. Burning natural gas and hydrogen mixtures has potential risks, the main one being the flame flashback phenomenon that could occur in home appliances using premixed laminar burners. In the present study, two-dimensional transient computations of laminar CH4- + air and CH4 + H-2 + air flames are performed with the open-source CFD code OpenFOAM. A finite rate chemistry based solver is used to compute reaction rates and the laminar reacting flow. Starting from a flame stabilized at the rim of a cylindrical tube burner, the inlet bulk velocity of the premixture is gradually reduced to observe flashback. The results of the present work concern the effects of wall temperature and hydrogen addition on the flashback propensity of laminar premixed methane-hydrogen-air flames. Complete sequences of flame dynamics with gradual increases of premixture velocity are investigated. At the flame flashback velocities, strong oscillations at the flame leading edge emerge, causing broken flame symmetry and finally flame flashback. The numerical results reveal that flashback tendency increase with increasing wall temperature and hydrogen addition rate. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hidrojen teknolojileri araştırmaları; hidrojenin petrol rafinerilerinde, çelik üretimi ve kimyasal üretim gibi sanayi üretiminde ve çeşitli kaynaklarla yakıt elde edilmesinde kullanılması, güç kaynağı olarak sistemi güçlendirmesi, suyun elektrolizi yoluyla elde edilmesi, enerji taşıyıcısı olarak sisteme dahil olması, depolama, taşıma ve ulaşım, havacılık ve uzay, evsel kullanım, risk ve güvenlik sorunları konularının etkileştiği bir araştırma alanıdır. Toplumsal gerçekliğe ve doğanın kendisine içkin olan bu karmaşık yapı, hidrojen teknolojileri araştırmalarının disiplinlerarası bir yaklaşımla ele alınmasını gerekli kılmaktadır. Bu nedenle çalışmanın amacı, hidrojen araştırmalarının disiplinlerarası bu yapısında toplumsal bilimler alanlarının rolünü ve katkısını belirlemektir. Bu amaçla ilgili kavramlar yardımıyla hidrojen teknolojileri araştırmaları alanında 1975-2021 yılları arasında Web of Science (WoS) Sosyal Bilimler Atıf Endeksinde dizinlenmiş 379 makale analiz edilmiştir. Çalışmanın sonuçlarına göre son 10 yılda hidrojen teknolojileri araştırmaları alanında yayın sayısı ve atıf sayısı hızla artmaktadır. Yayınların yarısından fazlasının birden fazla yazarlı olması, bu alanda yazarlar arasındaki etkileşim ve işbirliğinin yoğun olduğunu göstermektedir. Hidrojen teknolojileri alanındaki bu araştırmalar, “Teknik ve Sistemsel Bağlam”, “Enerji taşıyıcı olarak Hidrojen”, “Politik Arkaplan”, “Ulaşım ve Davranışsal Faktörler” ve “Altyapı ve Tasarım” olarak isimlendirilen beş tematik kümede toplanmıştır ve bu kümelerin birleşimini bütüncül bir toplumsal-teknik sistem olarak ele almak mümkündür. Anahtar kelime analizi, zaman geçtikçe alandaki araştırmaların toplumsal boyutlarının ve etkilerinin daha detaylı incelendiğini göstermektedir. Tematik konu haritası ise, hidrojen teknolojileri sisteminin bir bütün olarak tüm boyutlarıyla ele alındığı göstermektedir., Hydrogen technologies research is an area where various research areas interact with each other such as the use of hydrogen in oil refineries, industrial production such as steel production and chemical production and obtaining fuel from various sources, strengthening the system as a power source, obtaining water through electrolysis, inclusion in the system as an energy carrier, storage, transportation, aviation and space, risk and security issues. This complex structure, which is immanent to social reality and nature itself, requires hydrogen technologies research to be handled with an interdisciplinary approach. Therefore, the study aims to determine the role and contribution of social science fields in this interdisciplinary structure of hydrogen technologies research. For this purpose, 379 articles indexed in the Web of Science (WoS) Social Sciences Citation Index between 1975-2021 in the field of hydrogen technologies research were analyzed with the help of related keywords. According to findings, the number of publications and citations in the field of hydrogen technologies research has been increasing rapidly in the last 10 years. The fact that more than half of the publications have more than one author shows that the interaction and cooperation between the co-authors in this field are intense. Studies in the field of hydrogen technologies are gathered in five thematic clusters named as “Technical and Systemic Context”, “Hydrogen as an Energy carrier”, “Political Background”, “Transportation and Behavioral Factors” and “Infrastructure and Design”, combining these clusters into a holistic socio-technical system. Keyword analysis shows that as time passes, the social dimensions and effects of research in the field are examined in more detail. The thematic topic map, on the other hand, shows that the hydrogen technologies system as a whole is handled with all its dimensions.

International audience; Model-free and model-fitting kinetic approaches were used to investigate the hydrothermal carbonization (HTC) of avocado stone. The total solid mass yield was used to estimate the kinetic parameters and reaction mechanism. The results obtained show that the HTC process for avocado stones could be divided into four temperature zones. Up to 160 °C, the initial induction period where the reaction rate is relatively slow. The second zone (160 to 200 °C) corresponds to the maximum decomposition rate. The third zone between 200 and 220 °C corresponds to the stabilization zone; in this zone, the total solids yield is practically constant, and finally, the polymerization zone, between 220 and 250 °C, where an increase in total solid yield was observed. The kinetic parameters and reaction mechanism were determined in two temperature zones, from 150 to 210 °C and 210 to 250 °C. In the first zone, the decomposition of avocado stone during the HTC process followed a random nucleation reaction mechanism (Avrami-Erofeev-1) with the activation energy of 87.84 ± 3.28 kJ/mol. In contrast, in the second zone, it followed a first-order reaction model, and the activation energy was 230.96 ± 28.84 kJ/mol. Analysis of PAHs with gas chromatography-mass spectrometry showed that the number of PAHs in the hydrochar increases with an increase in temperature from 190 to 250 °C. The 3–4 rings PAHs were dominant in the hydrochars prepared at temperatures between 230 and 250 °C, while two rings were largely prevalent in the hydrochar obtained at low temperatures.

This study focused on the analysis of the pyrolytic behavior of four lignocellulosic biomasses: avocado stone (AS), Agave salmiana bagasse (AB), cocoa shell (CS), and α-cellulose (CEL). According to the triplet kinetics analysis, the order of pyrolytic decomposition was AS AB CEL CS. The AS was dominated by a second-order reaction, while AB followed a 2D diffusion-Valensi model. On the other hand, the pyrolysis of CS starts with an nth-order reaction and ends random nucleation model, and CEL was dominated by one-dimensional diffusion and first-order reaction. Thermodynamic studies reveal that the difference between the activation energy versus enthalpy change was6.5 kJ/mol for all biomasses, thus showing the ease of pyrolysis reaction of these biomasses. Furthermore, the AS and AB showed that the reactions are close to thermodynamic equilibrium and stability, whereas CS and CEL indicated high reactivity.