Germany
Interaction of Hydrogen Jets with Hot Surfaces of Various Sizes and Temperatures
Sep 2019
Publication
The formation of hydrogen jets from pressurized sources and ignition has been studied by many projects also when hitting hot devices. In the paper presented at the conference 2 years ago the ignition was caused by glow plug a “point like source” at various temperatures distances of igniter and source and source pressures. In continuation of that work ignition now occurred by 1 or 3 platelets of size 45 x 18 mm at a temperatures of 1223 K. When hitting these hot platelets the resulting flame explosions and flame jets show interesting characteristics in contrast to the point like ignition where the explosions drifts downstream with the jet. Parameters of the experiments vary in initial pressure of the tubular source (10 20 and 40 MPa) distance between the nozzle and the hot surface (3 5 and 7 m) and temperature of the hot surface (1223 K). The initial explosions stabilize already at the stagnation point or the wake of the hot platelets. Furthermore flames propagate upstream and downstream depending on the pressure of the hydrogen reservoir and the distance. The achieved flame velocities vary strongly from 30 to 240 m/s. With all investigated hydrogen pressures strong reactions v > 40 m/s occur at platelet distances of 3 and 5 m. The higher values are mainly achieved with jets with 40 MPa pressure at 3 m distance. In these cases the initial explosion contours show irregular shapes. Various effects are found like explosion separation further independently initiated explosions and two parallel flame jets upstream as well as downstream.
Is Direct Seawater Splitting Economically Meaningful?
Jun 2021
Publication
Electrocatalytic water splitting is the key process for the formation of green fuels for energy transport and storage in a sustainable energy economy. Besides electricity it requires water an aspect that seldomly has been considered until recently. As freshwater is a limited resource (<1% of earth's water) lately plentiful reports were published on direct seawater (around 96.5% of earth's water) splitting without or with additives (buffers or bases). Alternatively the seawater can be split in two steps where it is first purified by reverse osmosis and then split in a conventional water electrolyser. This quantitative analysis discusses the challenges of the direct usage of non-purified seawater. Further herein we compare the energy requirements and costs of seawater purification with those of conventional water splitting. We find that direct seawater splitting has substantial drawbacks compared to conventional water splitting and bears almost no advantage. In short it is less promising than the two-step scenario as the capital and operating costs of water purification are insignificant compared to those of electrolysis of pure water.
Initial Assessment of a Fuel Cell—Gas Turbine Hybrid Propulsion Concept
Jan 2022
Publication
A fuel cell—gas turbine hybrid propulsion concept is introduced and initially assessed. The concept uses the water mass flow produced by a hydrogen fuel cell in order to improve the efficiency and power output of the gas turbine engine through burner steam injection. Therefore the fuel cell product water is conditioned through a process of condensation pressurization and revaporization. The vaporization uses the waste heat of the gas turbine exhaust. The functional principles of the system concept are introduced and discussed and appropriate methodology for an initial concept evaluation is formulated. Essential technology fields are surveyed in brief. The impact of burner steam injection on gas turbine efficiency and sizing is parametrically modelled. Simplified parametric models of the fuel cell system and key components of the water treatment process are presented. Fuel cell stack efficiency and specific power levels are methodically derived from latest experimental studies at the laboratory scale. The overall concept is assessed for a liquid hydrogen fueled short-/medium range aircraft application. Block fuel savings of up to 7.1% are found for an optimum design case based on solid oxide fuel cell technology. The optimum design features a gas turbine water-to-air ratio of 6.1% in cruise and 62% reduced high-level NOx emissions.
Development of a Model Evaluation Protocol for CFD Analysis of Hydrogen Safety Issues – The SUSANA Project
Oct 2015
Publication
The “SUpport to SAfety aNAlysis of Hydrogen and Fuel Cell Technologies (SUSANA)” project aims to support stakeholders using Computational Fluid Dynamics (CFD) for safety engineering design and assessment of FCH systems and infrastructure through the development of a model evaluation protocol. The protocol covers all aspects of safety assessment modelling using CFD from release through dispersion to combustion (self-ignition fires deflagrations detonations and Deflagration to Detonation Transition - DDT) and not only aims to enable users to evaluate models but to inform them of the state of the art and best practices in numerical modelling. The paper gives an overview of the SUSANA project including the main stages of the model evaluation protocol and some results from the on-going benchmarking activities.
Dynamic Simulation of Different Transport Options of Renewable Hydrogen to a Refinery in a Coupled Energy System Approach
Sep 2018
Publication
Three alternative transport options for hydrogen generated from excess renewable power to a refinery of different scales are compared to the reference case by means of hydrogen production cost overall efficiency and CO2 emissions. The hydrogen is transported by a) the natural gas grid and reclaimed by the existing steam reformer b) an own pipeline and c) hydrogen trailers. The analysis is applied to the city of Hamburg Germany for two scenarios of installed renewable energy capacities. The annual course of excess renewable power is modelled in a coupled system approach and the replaceable hydrogen mass flow rate is determined using measurement data from an existing refinery. Dynamic simulations are performed using an open-source Modelica® library. It is found that in all three alternative hydrogen supply chains CO2 emissions can be reduced and costs are increased compared to the reference case. Transporting hydrogen via the natural gas grid is the least efficient but achieves the highest emission reduction and is the most economical alternative for small to medium amounts of hydrogen. Using a hydrogen pipeline is the most efficient option and slightly cheaper for large amounts than employing the natural gas grid. Transporting hydrogen by trailers is not economical for single consumers and realizes the lowest CO2 reductions.
On Capital Utilization in the Hydrogen Economy: The Quest to Minimize Idle Capacity in Renewables-rich Energy Systems
Oct 2020
Publication
The hydrogen economy is currently experiencing a surge in attention partly due to the possibility of absorbing variable renewable energy (VRE) production peaks through electrolysis. A fundamental challenge with this approach is low utilization rates of various parts of the integrated electricity-hydrogen system. To assess the importance of capacity utilization this paper introduces a novel stylized numerical energy system model incorporating the major elements of electricity and hydrogen generation transmission and storage including both “green” hydrogen from electrolysis and “blue” hydrogen from natural gas reforming with CO2 capture and storage (CCS). Concurrent optimization of all major system elements revealed that balancing VRE with electrolysis involves substantial additional costs beyond reduced electrolyzer capacity factors. Depending on the location of electrolyzers greater capital expenditures are also required for hydrogen pipelines and storage infrastructure (to handle intermittent hydrogen production) or electricity transmission networks (to transmit VRE peaks to electrolyzers). Blue hydrogen scenarios face similar constraints. High VRE shares impose low utilization rates of CO2 capture transport and storage infrastructure for conventional CCS and of hydrogen transmission and storage infrastructure for a novel process (gas switching reforming) that enables flexible power and hydrogen production. In conclusion all major system elements must be considered to accurately reflect the costs of using hydrogen to integrate higher VRE shares.
Hydrogen-related Challenges for the Steelmaker: The Search for Proper Testing
Jun 2017
Publication
The modern steelmaker of advanced high-strength steels has always been challenged with the conflicting targets of increased strength while maintaining or improving ductility. These new steels help the transportation sector including the automotive sector to achieve the goals of increased passenger safety and reduced emissions. With increasing tensile strengths certain steels exhibit an increased sensitivity towards hydrogen embrittlement (HE). The ability to characterize the material's sensitivity in an as-delivered condition has been developed and accepted (SEP1970) but the complexity of the stress states that can induce an embrittlement together with the wide range of applications for high-strength steels make the development of a standardized test for HE under in-service conditions extremely challenging. Some proposals for evaluating the material's sensitivity give an advantage to materials with a low starting ductility. Despite this newly developed materials can have a higher original elongation with only a moderate reduction in elongation due to hydrogen. This work presents a characterization of new materials and their sensitivity towards HE.
This article is part of the themed issue ‘The challenges of hydrogen and metals’.
Link to document download on Royal Society Website
This article is part of the themed issue ‘The challenges of hydrogen and metals’.
Link to document download on Royal Society Website
Hydrogen Scaling Up: A Sustainable Pathway for the Global Energy Transition
Nov 2017
Publication
Deployed at scale hydrogen could account for almost one-fifth of total final energy consumed by 2050. This would reduce annual CO2 emissions by roughly 6 gigatons compared to today’s levels and contribute roughly 20% of the abatement required to limit global warming to two degrees Celsius.
On the demand side the Hydrogen Council sees the potential for hydrogen to power about 10 to 15 million cars and 500000 trucks by 2030 with many uses in other sectors as well such as industry processes and feedstocks building heating and power power generation and storage. Overall the study predicts that the annual demand for hydrogen could increase tenfold by 2050 to almost 80 EJ in 2050 meeting 18% of total final energy demand in the 2050 two-degree scenario. At a time when global populations are expected to grow by two billion people by 2050 hydrogen technologies have the potential to create opportunities for sustainable economic growth.
“The world in the 21st century must transition to widespread low carbon energy use” said Takeshi Uchiyamada Chairman of Toyota Motor Corporation and co-chair of the Hydrogen Council. “Hydrogen is an indispensable resource to achieve this transition because it can be used to store and transport wind solar and other renewable electricity to power transportation and many other things. The Hydrogen Council has identified seven roles for hydrogen which is why we are encouraging governments and investors to give it a prominent role in their energy plans. The sooner we get the hydrogen economy going the better and we are all committed to making this a reality.”
Achieving such scale would require substantial investments; approximately US$20 to 25 billion annually for a total of about US$280 billion until 2030. Within the right regulatory framework – including long-term stable coordination and incentive policies – the report considers that attracting these investments to scale the technology is feasible. The world already invests more than US$1.7 trillion in energy each year including US$650 billion in oil and gas US$300 billion in renewable electricity and more than US$300 billion in the automotive industry.
“This study confirms the place of hydrogen as a central pillar in the energy transition and encourages us in our support of its large-scale deployment. Hydrogen will be an unavoidable enabler for the energy transition in certain sectors and geographies. The sooner we make this happen the sooner we will be able to enjoy the needed benefits of Hydrogen at the service of our economies and our societies” said Benoît Potier Chairman and CEO Air Liquide. “Solutions are technologically mature and industry players are committed. We need concerted stakeholder efforts to make this happen; leading this effort is the role of the Hydrogen Council.”
The launch of the new roadmap came during the Sustainability Innovation Forum in the presence of 18 senior members of the Hydrogen led by co-chairs Takeshi Uchiyamada Chairman of Toyota and Benoît Potier Chairman and CEO Air Liquide and accompanied by Prof. Aldo Belloni CEO of The Linde Group Woong-chul Yang Vice Chairman of Hyundai Motor Company and Anne Stevens Board Member of Anglo American. During the launch the Hydrogen Council called upon investors policymakers and businesses to join them in accelerating deployment of hydrogen solutions for the energy transition. It was also announced that Woong-chul Yang of Hyundai Motor Company will succeed Takeshi Uchiyamada of Toyota in the rotating role of the Council’s co-chair and preside the group together with Benoit Potier CEO Air Liquide in 2018. Mr Uchiyamada is planning to return as Co-chairman in 2020 coinciding with the Tokyo Olympic and Paalympic Games an important milestone for showcasing hydrogen society and mobility.
You can download the full report from the Hydrogen Council website here
On the demand side the Hydrogen Council sees the potential for hydrogen to power about 10 to 15 million cars and 500000 trucks by 2030 with many uses in other sectors as well such as industry processes and feedstocks building heating and power power generation and storage. Overall the study predicts that the annual demand for hydrogen could increase tenfold by 2050 to almost 80 EJ in 2050 meeting 18% of total final energy demand in the 2050 two-degree scenario. At a time when global populations are expected to grow by two billion people by 2050 hydrogen technologies have the potential to create opportunities for sustainable economic growth.
“The world in the 21st century must transition to widespread low carbon energy use” said Takeshi Uchiyamada Chairman of Toyota Motor Corporation and co-chair of the Hydrogen Council. “Hydrogen is an indispensable resource to achieve this transition because it can be used to store and transport wind solar and other renewable electricity to power transportation and many other things. The Hydrogen Council has identified seven roles for hydrogen which is why we are encouraging governments and investors to give it a prominent role in their energy plans. The sooner we get the hydrogen economy going the better and we are all committed to making this a reality.”
Achieving such scale would require substantial investments; approximately US$20 to 25 billion annually for a total of about US$280 billion until 2030. Within the right regulatory framework – including long-term stable coordination and incentive policies – the report considers that attracting these investments to scale the technology is feasible. The world already invests more than US$1.7 trillion in energy each year including US$650 billion in oil and gas US$300 billion in renewable electricity and more than US$300 billion in the automotive industry.
“This study confirms the place of hydrogen as a central pillar in the energy transition and encourages us in our support of its large-scale deployment. Hydrogen will be an unavoidable enabler for the energy transition in certain sectors and geographies. The sooner we make this happen the sooner we will be able to enjoy the needed benefits of Hydrogen at the service of our economies and our societies” said Benoît Potier Chairman and CEO Air Liquide. “Solutions are technologically mature and industry players are committed. We need concerted stakeholder efforts to make this happen; leading this effort is the role of the Hydrogen Council.”
The launch of the new roadmap came during the Sustainability Innovation Forum in the presence of 18 senior members of the Hydrogen led by co-chairs Takeshi Uchiyamada Chairman of Toyota and Benoît Potier Chairman and CEO Air Liquide and accompanied by Prof. Aldo Belloni CEO of The Linde Group Woong-chul Yang Vice Chairman of Hyundai Motor Company and Anne Stevens Board Member of Anglo American. During the launch the Hydrogen Council called upon investors policymakers and businesses to join them in accelerating deployment of hydrogen solutions for the energy transition. It was also announced that Woong-chul Yang of Hyundai Motor Company will succeed Takeshi Uchiyamada of Toyota in the rotating role of the Council’s co-chair and preside the group together with Benoit Potier CEO Air Liquide in 2018. Mr Uchiyamada is planning to return as Co-chairman in 2020 coinciding with the Tokyo Olympic and Paalympic Games an important milestone for showcasing hydrogen society and mobility.
You can download the full report from the Hydrogen Council website here
The Impact of Hydrogen Admixture into Natural Gas on Residential and Commercial Gas Appliances
Jan 2022
Publication
Hydrogen as a carbon-free fuel is commonly expected to play a major role in future energy supply e.g. as an admixture gas in natural gas grids. Which impacts on residential and commercial gas appliances can be expected due to the significantly different physical and chemical properties of hydrogen-enriched natural gas? This paper analyses and discusses blends of hydrogen and natural gas from the perspective of combustion science. The admixture of hydrogen into natural gas changes the properties of the fuel gas. Depending on the combustion system burner design and other boundary conditions these changes may cause higher combustion temperatures and laminar combustion velocities while changing flame positions and shapes are also to be expected. For appliances that are designed for natural gas these effects may cause risk of flashback reduced operational safety material deterioration higher nitrogen oxides emissions (NOx) and efficiency losses. Theoretical considerations and first measurements indicate that the effects of hydrogen admixture on combustion temperatures and the laminar combustion velocities are often largely mitigated by a shift towards higher air excess ratios in the absence of combustion control systems but also that common combustion control technologies may be unable to react properly to the presence of hydrogen in the fuel.
Can Industry Keep Gas Distribution Networks Alive? Future Development of the Gas Network in a Decarbonized World: A German Case Study
Dec 2022
Publication
With the growing need for decarbonization the future gas demand will decrease and the necessity of a gas distribution network is at stake. A remaining industrial gas demand on the distribution network level could lead to industry becoming the main gas consumer supplied by the gas distribution network leading to the question: can industry keep the gas distribution network alive? To answer this research question a three-stage analysis was conducted starting from a rough estimate of average gas demand per production site and then increasing the level of detail. This paper shows that about one third of the German industry sites investigated are currently supplied by the gas distribution network. While the steel industry offers new opportunities the food and tobacco industry alone cannot sustain the gas distribution network by itself.
Sector Coupling Potential of Wind-based Hydrogen Production and Fuel Cell Train Operation in Regional Rail Transport in Berlin and Brandenburg
Jan 2021
Publication
As the transport sector is ought to be decarbonized fuel-cell-powered trains are a viable zero-tailpipe technology alternative to the widely employed diesel multiple units in regional railway service on non-electrified tracks. Carbon-free hydrogen can be provided by water-electrolysis from renewable energies. In this study we introduce an approach to assess the potential of wind-based hydrogen for use in adjacent regional rail transport by applying a GIS approach in conjunction with a site-level cost model. In Brandenburg about 10.1 million train-km annually could be switched to fuel cell electric train operation. This relates to a diesel consumption of appr. 9.5 million liters today. If fuel cell trains would be employed that translated to 2198 annual tons hydrogen annually. At favorable sites hydrogen costs of approx. 6.40 €/kg - including costs of hydrogen refueling stations - could be achieved. Making excess hydrogen available for other consumers would further decrease hydrogen production costs.
Safety Concept of Nuclear Cogeneration of Hydrogen and Electricity
Oct 2015
Publication
There is a significant potential for nuclear combined heat and power (CHP) in quite a number of industries. The reactor concepts of the next generation would be capable to open up in particular the high temperature heat market where nuclear energy is applicable to the production processes of hydrogen (or liquid fuels) by steam reforming or water splitting. Due to the need to locate a nuclear facility near the hydrogen plant an overall safety concept has to deal with the question of safety of the combined nuclear/industrial system by taking into account a qualitatively new class of events characterized by interacting influences. Specific requirements will be determined by such factors as the reactor type the nature of the industrial process the separation distances of the industrial facility and population centers from the nuclear plant and prevailing public attitudes. Based on the Japanese concept of the GTHTR300C nuclear reactor for electricity and hydrogen cogeneration theoretical studies were conducted on the release dispersive transport and explosion of a hydrogen cloud in the atmosphere for the sake of assessing the required minimum separation distance to avoid any risk to the nuclear plant's safety systems. In the case of sulfur-iodine water splitting the accidental release of process intermediates including large amounts of sulfur dioxide sulfur trioxide and sulfuric acid need to be investigated as well to estimate the potential risk to nuclear installations like the operators' room and estimate appropriate separation distances against toxic gas propagation. Results of respective simulation studies will be presented.
Influence of Microstructural Morphology on Hydrogen Embrittlement in a Medium-Mn Steel Fe-12Mn-3Al-0.05C
Aug 2019
Publication
The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite achieving an extraordinary balance of mechanical properties and alloying cost. In the present work two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve comparable mechanical properties with different microstructural morphologies. One heat treatment was merely austenite-reverted-transformation (ART) annealing and the other one was a successive combination of austenitization (AUS) and ART annealing. The distinct responses to hydrogen ingression were characterized and discussed. The UFG martensite colonies produced by the AUS + ART process were found to be detrimental to ductility regardless of the amount of hydrogen which is likely attributed to the reduced lattice bonding strength according to the H-enhanced decohesion (HEDE) mechanism. With an increase in the hydrogen amount the mixed microstructure (granular + lamellar) in the ART specimen revealed a clear embrittlement transition with the possible contribution of HEDE and H-enhanced localized plasticity (HELP) mechanisms.
Linking Ab Initio Data on Hydrogen and Carbon in Steel to Statistical and Continuum Descriptions
Mar 2018
Publication
We present a selection of scale transfer approaches from the electronic to the continuum regime for topics relevant to hydrogen embrittlement. With a focus on grain boundary related hydrogen embrittlement we discuss the scale transfer for the dependence of the carbon solution behavior in steel on elastic effects and the hydrogen solution in austenitic bulk regions depending on Al content. We introduce an approximative scheme to estimate grain boundary energies for varying carbon and hydrogen population. We employ this approach for a discussion of the suppressing influence of Al on the substitution of carbon with hydrogen at grain boundaries which is an assumed mechanism for grain boundary hydrogen embrittlement. Finally we discuss the dependence of hydride formation on the grain boundary stiffness
The Curious Case of the Conflicting Roles of Hydrogen in Global Energy Scenarios
Oct 2019
Publication
As energy systems transition from fossil-based to low-carbon they face many challenges particularly concerning energy security and flexibility. Hydrogen may help to overcome these challenges with potential as a transport fuel for heating energy storage conversion to electricity and in industry. Despite these opportunities hydrogen has historically had a limited role in influential global energy scenarios. Whilst more recent studies are beginning to include hydrogen the role it plays in different scenarios is extremely inconsistent. In this perspective paper reasons for this inconsistency are explored considering the modelling approach behind the scenario scenario design and data assumptions. We argue that energy systems are becoming increasingly complex and it is within these complexities that new technologies such as hydrogen emerge. Developing a global energy scenario that represents these complexities is challenging and in this paper we provide recommendations to help ensure that emerging technologies such as hydrogen are appropriately represented. These recommendations include: using the right modelling tools whilst knowing the limits of the model; including the right sectors and technologies; having an appropriate level of ambition; and making realistic data assumptions. Above all transparency is essential and global scenarios must do more to make available the modelling methods and data assumptions used.
Tetrahydroborates: Development and Potential as Hydrogen Storage Medium
Oct 2017
Publication
The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative hydrogen is widely regarded as a key element for a potential energy solution. However differently from fossil fuels such as oil gas and coal the production of hydrogen requires energy. Alternative and intermittent renewable energy sources such as solar power wind power etc. present multiple advantages for the production of hydrogen. On the one hand the renewable sources contribute to a remarkable reduction of pollutants released to the air and on the other hand they significantly enhance the sustainability of energy supply. In addition the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of renewable energy sources. In this regard hydrogen storage technology is a key technology towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen solid-state storage is the most attractive alternative from both the safety and the volumetric energy density points of view. Because of their appealing hydrogen content complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review the progresses made over the last century on the synthesis and development of tetrahydroborates and tetrahydroborate-based systems for hydrogen storage purposes are summarized.
Healthy Power: Reimagining Hospitals as Sustainable Energy Hubs
Oct 2020
Publication
Human health is a key pillar of modern conceptions of sustainability. Humanity pays a considerable price for its dependence on fossil-fueled energy systems which must be addressed for sustainable urban development. Public hospitals are focal points for communities and have an opportunity to lead the transition to renewable energy. We have reimagined the healthcare energy ecosystem with sustainable technologies to transform hospitals into networked clean energy hubs. In this concept design hydrogen is used to couple energy with other on-site medical resource demands and vanadium flow battery technology is used to engage the public with energy systems. This multi-generation system would reduce harmful emissions while providing reliable services tackling the linked issues of human and environmental health.
Critical Materials for Water Electrolysers at the Example of the Energy Transition in Germany
Feb 2021
Publication
The present work aims to identify critical materials in water electrolysers with potential future supply constraints. The expected rise in demand for green hydrogen as well as the respective implications on material availability are assessed by conducting a case study for Germany. Furthermore the recycling of end‐of‐life (EoL) electrolysers is evaluated concerning its potential in ensuring the sustainable supply of the considered materials. As critical materials bear the risk of raising production costs of electrolysers substantially this article examines the readiness of this technology for industrialisation from a material perspective. Except for titanium the indicators for each assessed material are scored with a moderate to high (platinum) or mostly high (iridium scandium and yttrium) supply risk. Hence the availability of these materials bears the risk of hampering the scale‐up of electrolysis capacity. Although conventional recycling pathways for platinum iridium and titanium already exist secondary material from EoL electrolysers will not reduce the dependence on primary resources significantly within the period under consideration—from 2020 until 2050. Notably the materials identified as critical are used in PEM and high temperature electrolysis whereas materials in alkaline electrolysis are not exposed to significant supply risks.
Development of a Flashback Correlation for Burner-stabilized Hydrogen-air Premixed Flames
Feb 2022
Publication
With a growing need for replacing fossil fuels with cleaner alternatives hydrogen has emerged as a viable candidate for providing heat and power. However stable and safe combustion of hydrogen is not simple and as such a number of key issues have been identified that need to be understood for a safe design of combustion chambers. One such issue is the higher propensity of hydrogen flames to flashback compared to that for methane flames. The flashback problem is coupled with higher burner temperatures that could cause strong thermal stresses in burners and could hinder their performance. In order to systematically investigate flashback in premixed hydrogen-air flames for finding a global flashback criteria in this study we use numerical simulations as a basic tool to study flashback limits of slit burners. Flashback limits are found for varying geometrical parameters and equivalence ratios and the sensitivity of each parameter on the flashback limit and burner temperatures are identified and analyzed. It is shown that the conventional flashback correlation with critical velocity gradient does not collapse the flashback data as it does not take into account stretch induced preferential diffusion effects. A new Karlovitz number definition is introduced with physical insights that collapses the flashback data at all tested conditions in an excellent manner.
Hydrogen Storage: Thermodynamic Analysis of Alkyl-Quinolines and Alkyl-Pyridines as Potential Liquid Organic Hydrogen Carriers (LOHC)
Dec 2021
Publication
The liquid organic hydrogen carriers (LOHC) are aromatic molecules which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum coal processing and wood preservation or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems provided they have favorable thermodynamic properties which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected evaluated and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines calculated using the quantum-chemical G4 methods agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.
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