On-board Hydrogen Production Research Articles

Water neutrality and waste heat management in ethanol reformer - HTPEMFC integrated system for on-board hydrogen generation

On-board power generation for vehicular applications requires a compact, simplified and well-integrated fuel processor-fuel cell system. In the present paper, the integration of an ethanol reformer unit with a 50 kWe high temperature polymer electrolyte membrane (PEM) fuel cell is studied for potential automotive applications. A high-efficiency dual reformer system is used for on-board production of hydrogen from ethanol. Heat transfer equipment for recovery of water and effective utilization of waste heat has been incorporated into the integrated system. Detailed analysis using ASPEN simulations shows that gross system efficiencies of up to 39% can be achieved. Estimates of size, weight of the integrated system have been made to assess its suitability for application as auxiliary power units in automotive systems.

On-board hydrogen production for auxiliary power in passenger aircraft

This paper presents the potential of a method for on-demand hydrogen generation from the reaction of activated aluminum powder and water for commercial aircraft applications. The hydrogen produced on-board during flight can be used in a fuel cell to generate electric energy. Results of an investigation of the reaction between aluminum and urine show that, in addition to fresh water, the waste water available on-board the aircraft can be used for hydrogen generation. High reaction rates producing about 200–600 ml/min/g Al of hydrogen at a high yield of about 90% was demonstrated. The possibility to use the available waste water leads to high specific electric energy of up to about 850 Wh/kg. In addition, the aluminum–water reaction enables safe use of hydrogen. A comparison to the traditional hydrogen storage methods is also presented.

An efficient on-board metal-free nanocatalyst for controlled room temperature hydrogen production.

Positively charged functionalized carbon nanodots (CNDs) with a variety of different effective surface areas (ESAs) are synthesized via a cheap and time effective microwave method and applied for the generation of hydrogen via hydrolysis of sodium borohydride. To the best of our knowledge, this is the first report of metal-free controlled hydrogen generation. Our observation is that a positively charged functional group is essential for the hydrolysis for hydrogen production, but the overall activity is found to be enhanced with the ESA. A maximum value of 1066 ml g-1 min-1 as the turnover frequency is obtained which is moderate in comparison to other catalysts. However, the optimum activation energy is found to be 22.01 kJ mol-1 which is comparable to well-known high cost materials like Pt and Ru. All of the samples showed good reusability and 100% conversion even after the 10th cycle. The effect of H+ and OH- is also studied to control the on-board and on-demand hydrogen production ("on-off switching"). It is observed that H2 production decreases inversely with NaOH concentration and ceases completely when 10-1 M NaOH is added. With the addition of HCl, H2 production can be initiated again, which confirms the on/off control over production.

Liquid Organic Hydrogen Carriers (LOHCs): Toward a Hydrogen-free Hydrogen Economy.

The need to drastically reduce CO2 emissions will lead to the transformation of our current, carbon-based energy system to a more sustainable, renewable-based one. In this process, hydrogen will gain increasing importance as secondary energy vector. Energy storage requirements on the TWh scale (to bridge extended times of low wind and sun harvest) and global logistics of renewable energy equivalents will create additional driving forces toward a future hydrogen economy. However, the nature of hydrogen requires dedicated infrastructures, and this has prevented so far the introduction of elemental hydrogen into the energy sector to a large extent. Recent scientific and technological progress in handling hydrogen in chemically bound form as liquid organic hydrogen carrier (LOHC) supports the technological vision that a future hydrogen economy may work without handling large amounts of elemental hydrogen. LOHC systems are composed of pairs of hydrogen-lean and hydrogen-rich organic compounds that store hydrogen by repeated catalytic hydrogenation and dehydrogenation cycles. While hydrogen handling in the form of LOHCs allows for using the existing infrastructure for fuels, it also builds on the existing public confidence in dealing with liquid energy carriers. In contrast to hydrogen storage by hydrogenation of gases, such as CO2 or N2, hydrogen release from LOHC systems produces pure hydrogen after condensation of the high-boiling carrier compounds. This Account highlights the current state-of-the-art in hydrogen storage using LOHC systems. It first introduces fundamental aspects of a future hydrogen economy and derives therefrom requirements for suitable LOHC compounds. Molecular structures that have been successfully applied in the literature are presented, and their property profiles are discussed. Fundamental and applied aspects of the involved hydrogenation and dehydrogenation catalysis are discussed, characteristic differences for the catalytic conversion of pure hydrocarbon and nitrogen-containing LOHC compounds are derived from the literature, and attractive future research directions are highlighted. Finally, applications of the LOHC technology are presented. This part covers stationary energy storage (on-grid and off-grid), hydrogen logistics, and on-board hydrogen production for mobile applications. Technology readiness of these fields is very different. For stationary energy storage systems, the feasibility of the LOHC technology has been recently proven in commercial demonstrators, and cost aspects will decide on their further commercial success. For other highly attractive options, such as, hydrogen delivery to hydrogen filling stations or direct-LOHC-fuel cell applications, significant efforts in fundamental and applied research are still needed and, hopefully, encouraged by this Account.

Test bed for farm vehicle onboard hydrogen production system with microwave plasma

Abstract: Energy conservation and emission reduction are the focus worldwide. Farm vehicle engine would be more efficient if it is injected a little hydrogen during work, meanwhile, the emission of the vehicle would be decreased. Nowadays, there are many kinds of onboard hydrogen production methods, among which the microwave plasma method is regarded as the best. In order to develop an onboard hydrogen production system using microwave plasma, a new corresponding test bed was designed and developed in this research. The ethanol, water and air from the three supply pipelines were mixed and evaporated into gas mixture, and then the mixture was further created into hydrogen through microwave plasma reaction. In the test bed, a hydrogen production environment required for the reaction was provided, and hydrogen would come into being when the air was broken down by the plasma under the conditions of 0.1-0.7 atm. Furthermore, the reaction conditions could be controlled precisely, and real-time environmental data and spectral data could be collected during the hydrogen production. The experimental results showed that onboard hydrogen production could be achieved on this test bed, and the hydrogen amount produced could be adjusted to simulate real vehicle working conditions. In addition, the system is of rapid response, high precision and reliability, which can be applied in new products developments of the onboard hydrogen production system. Keywords: hydrogen production, test bed, microwave, plasma, farm vehicle, emission, steam reforming, partial oxidation DOI: 10.3965/j.ijabe.20160906.2112 Citation: Chen F E, Chen L H, Xie X, Li X, Y B Lan. Test bed for farm vehicle onboard hydrogen production system with microwave plasma. Int J Agric & Biol Eng, 2016; 9(6): 65－74.

Oxidative pyrolysis reforming of methanol in warm plasma for an on-board hydrogen production

To achieve on-board hydrogen production with high energy efficiency and low energy cost, the oxidative pyrolysis reforming (OPR) of methanol using air as an oxidant in a heat-insulated gliding arc plasma reactor is explored. Effects of dioxygen/methanol (O2/C) ratio, steam/methanol (S/C) ratio and specific energy input (SEI) on the OPR are investigated. The reaction rate ratio (α) of pyrolysis reforming to oxidative reforming in the OPR is deduced. The OPR of methanol strongly depends on the O2/C ratio, with which methanol conversion increases rapidly. In the OPR, methanol conversions occur mainly by the oxidative reforming (partial oxidation) at the O2/C ratios below 0.20, but by the oxidative reforming and the promoted pyrolysis reforming at the O2/C ratios above 0.20, which is confirmed by the enthalpy change for the overall reaction of OPR. Higher O2/C ratio results in higher energy efficiency and lower energy cost, however, higher S/C ratio or larger SEI leads to lower energy efficiency and higher energy cost. Under conditions of O2/C = 0.30, S/C = 0.5, SEI = 24 kJ/mol, energy efficiency of 74% and energy cost of 0.45 kWh/Nm3 with methanol conversion of 88% are achieved.

Hydrogen production via catalytic autothermal reforming of desulfurized Jet-A fuel

On-board hydrogen production via catalytic autothermal reforming is beneficial to vehicles using fuel cells as auxiliary power unit because it eliminates the challenges of hydrogen storage. As the primary fuel for both civilian and military air flight application, Jet-A fuel (after desulfurization) was reformed for making hydrogen-rich fuels in this study using an in-house-made Rh/NiO/K-La-Ce-Al-OX catalyst under various operating conditions. Based on the preliminary thermodynamic analysis of reaction equilibrium, important parameters such as ratios of H2O/C and O2/C were selected, in the range of 1.1–2.5 and 0.5–1.0, respectively. The optimal operating conditions were experimentally obtained at the reactor's temperature of 696 °C, which gave H2O/C = 2.5 and O2/C = 0.5, and the obtained fuel conversion percentage, hydrogen yield, and energy efficiency were 0.89, 1.44, and 0.65, respectively. In addition, a discussion of the molar fraction variation of CO and CO2 at different H2O/C, as well as the analysis of fuel conversion profile, leads to the finding of effective approaches for suppression of coke formation.

Enhancing the fuel economy and emissions performance of a gasoline engine-powered vehicle with idle elimination and hydrogen start

Idle elimination is a feasible way for reducing the fuel consumption and emissions at idle. The challenge for adopting idle elimination on gasoline engine is the high emissions during restart because rich mixtures have to be used at starting. This paper tries to start the engine with pure hydrogen at the restart for gasoline vehicles which adopt idle elimination. The investigation was done based on models built on AVL CRUISE. In the model, the vehicle was run under the New European Driving Cycle (NEDC). The hydrogen used on the vehicle was online produced and stored by an on-board hydrogen production and storage system. The energy for producing hydrogen is taken into account in the total fuel consumption. The simulation results showed that, with the adoption of gasoline start-idle elimination strategy, the vehicle fuel consumption during NEDC was reduced by 0.69L/100km, and NOx emissions were decreased by 5.5% compared with the original vehicle without idle elimination. However, HC and CO emissions at the restart were respectively increased by 87.5% and 18.1% for the gasoline vehicle due to the adoption of rich mixtures. Comparatively, with the adoption of hydrogen start-idle elimination strategy, the vehicle fuel consumption during NEDC was reduced by 0.79L/100km, HC and CO emissions were decreased by 70.8% and 13.6%, respectively. This shows a good capability of hydrogen combustion on reducing HC and CO emissions at the restart. However, NOx emissions were slightly increased by 7.9% under the hydrogen restart mode.

A high-efficiency, auto-thermal system for on-board hydrogen production for low temperature PEM fuel cells using dual reforming of ethanol

On-board reforming of liquid fuels is essential for improved driving range of fuel cell-powered vehicles. There is increasing demand for such vehicles to be fuelled from renewable energy sources. In the present paper, we propose an efficient reformer system for hydrogen production from ethanol. Reforming is an endothermic process, and high temperatures, well above the operating temperatures of PEM or equivalent fuel cells, are required for sufficient catalytic activity for reforming reactions. We use Co-Fe/ZnO catalyst to carry out the reforming at around 500 °C and a combustor of excess fuel as well as directly-fed ethanol to generate the high temperatures required for reforming. It is shown through simulations that introducing a second reformer to extract more hydrogen from the methane obtained from the first reformer improves the overall efficiency. ASPEN-based simulations show that the overall efficiency of an optimized dual reformer system can be as high as 48.47%.

Comparative efficiency and environmental impact assessments of a hydrogen assisted hybrid locomotive

The integration of more environmentally benign fuel options for mass transportation applications is a critical research initiative, particularly those that support and further development toward a hydrogen economy, a key target for future sustainability. The thermodynamic and environmental performances of a hydrogen assisted hybrid locomotive with ammonia-diesel co-fueling are comprehensively assessed through energy and exergy analyses, and impact assessment. Onboard hydrogen production via thermal ammonia decomposition (cracking) utilizes exhaust gases as a heat source, reducing the total diesel fuel consumption and increasing energy utilization of the fuel burned in the locomotive prime mover engine. The hybrid system performance is compared against a conventional diesel-electric locomotive through energy and exergy efficiencies, fuel consumption, and environmental impact to evaluate the viability of the hybrid locomotive as a clean rail transportation option.

Characteristics of hydrogen produced by pulsed discharge in ethanol solution

Hydrogen production from ethanol solution by pulsed high voltage spark discharge was investigated in this work. It is the first time that pulsed high voltage spark discharge in ethanol solution has been used for hydrogen production in the existing documents. A needle–plate reactor for on-board hydrogen production was also designed, which is small-scale and portable for automobiles. By optimizing the reaction conditions, the flow rate of hydrogen can reach 422mL/min at peak voltage=30kV, discharge frequency=30Hz, electrode distance=15mm, initial ethanol concentration=50%. It was also found that energy consumption of this method is about 1.69kWh/m3, which is better than most existing methods.

Hydrogen production from hydrocarbons over Rh supported on Ce-based oxides for automotive applications

On-board hydrogen production by reforming of fuel in the exhaust gas recirculation loop allows increasing the engine yield, thus decreasing the fuel consumption, and the formation of pollutants such as NOx. Various catalysts based on Rh supported on cerium-based oxides with alumina were prepared and characterized. Their catalytic performances were evaluated in the reforming of isooctane, chosen as model molecule, in the presence of a gas mixture of composition representative of the exhaust gas, i.e. H2O, CO2, O2 and N2. It was shown that the best performances in terms of hydrogen yield were obtained with the supports containing both ceria, in high amounts, and alumina, due to the high thermal stability of the support, the high metal dispersion and the limited sintering.

Applications of the Electrochemical Promotion of Catalysis in Methanol Conversion Processes

In this work, three possible applications of the phenomenon of electrochemical promotion of catalysis (EPOC) are demonstrated for methanol conversion processes: enhancement of the catalytic activity, modification of the catalytic selectivity and partial oxidation of the catalyst. For that purpose, a Ni catalyst film prepared via a physical vapour deposition technique was electrochemically promoted by K+ in different methanol conversion reactions for hydrogen production. Under methanol decomposition and steam reforming conditions, application of certain negative overpotentials and subsequent back-spillover of K+ promoter ions led to an increase in the Ni catalytic activity through electrophilic EPOC behaviour. On the other hand, under methanol partial oxidation conditions, the K+ ions caused a decrease in the catalytic selectivity toward H2 and CO while they favoured selectivity toward CO2 and H2CO. This effect was explained by an increase in the Ni oxidation state due to O2 activation induced by K+ ions, as shown by post-reaction X-ray diffraction analysis. All the potassium-induced effects were reversible between negative and positive polarizations. This shows the different possibilities of the EPOC phenomena on nickel catalysts in heterogeneous catalysis. Specifically, the in situ modification of catalytic activity and selectivity in methanol conversion reactions would be interesting for on-board hydrogen production processes, where the attenuation of catalyst deactivation and the control of metal oxidation state would also play a key role.

Design and packaging of a highly integrated microreactor system for high-temperature on-board hydrogen production

The development of miniaturized reactors that can operate at high temperatures independently is always of great interest for many applications, especially in the area of portable hydrogen production. Here we present such microreactor systems, made of glass, with integrated heating and fluidic features based on thick-film technology. Key considerations on design, fabrication and packaging of our systems to achieve a high-temperature operation (>500°C), a thermal decoupling over 400°C for the device in the use of standard electrical/fluidic connections, as well as a simple catalyst installation method, are described. Demonstration of these “plug-and-play” microreaction systems is shown with producing hydrogen on-board from catalytic partial oxidation of propane at about 550°C (achieving 85% conversion of propane and 46.8% of hydrogen yield). The energy efficiency in comparison of the power consumption of electrical heating with the estimated energy produced from reformates shows a negative balance in the system under 30sccm feed of fuel/air mixture, indicating that a sufficient feed rate of fuel/air mixture is required for the system to achieve optimal energy balance. At an adequate level of the feed rate, the CPOX carried in our systems can even reach a thermally self-sustaining manner without needs of the electrical heating, which have been illustrated in our application development in micro-fabricated microreactors and micro-scale solid oxide fuel cells.

High performance nickel–palladium nanocatalyst for hydrogen generation from alkaline hydrous hydrazine at room temperature

Room temperature synthesized highly active bimetallic Ni60Pd40 nanocatalyst with large surface area (150m2g−1) exerts 100% selectivity towards hydrogen generation (3 equivalents of gas in 60 min) from hydrous hydrazine under alkaline and ambient reaction conditions. This low noble metal content catalyst offers a new prospect for on-board hydrogen production system.

Hydrogen Storage Technologies for Transportation Application

The objective of this paper is to provide a brief overview of the possible onboard hydrogen storageoptions available today namely in fuel cell or ICE/electric hybrid vehicles. The issues associatedwith increasing the hydrogen volumetric densities via solid state materials storage and liquid carriersare the main focus with an overview of the current storage technologies. Possible onboard hydrogenproduction is discussed based on water splitting technologies.

Hydrogen by steam reforming of ethanol over Co–Mg incorporated novel mesoporous alumina catalysts in tubular and microwave reactors

Bio-ethanol is an excellent hydrogen carrier with a good potential to be used as a resource for on-board hydrogen production. In this work, a set of new Co incorporated mesoporous alumina (MA) catalysts, which were modified with Mg, were synthesized and tested in steam reforming of ethanol. Results proved that, the synthesis route of these materials had a highly significant effect on their catalytic performances. Co@Mg–MA and Co–Mg–MA catalysts, which were prepared by direct addition of Mg into the mesoporous alumina framework, gave the best performance in steam reforming of ethanol, with very high hydrogen yield values. This was concluded to be due to the presence of Co0 and CoO phases within the structures of these catalysts. However, Co–Mg@MA and Co@MA catalysts, which were prepared by the impregnation of Co/Mg or Co into mesoporous alumina, mainly catalyzed ethanol dehydration reaction to yield ethylene, rather than steam reforming. This was concluded to be due to the high Lewis acidity of these catalysts and the presence of cobalt aluminate phase in their structure. Activity tests of the synthesized catalysts were made both in a tubular reactor which was conductively heated and also in a focused-microwave system. Better energy utilization and more stable performance with much less coke formation were achieved in the focused-microwave reactor than the conventionally heated system.

Combining HC-SCR over Ag/Al2O3 and hydrogen generation over Rh/CeO2-ZrO2 using biofuels: An integrated system approach for real applications

We report on a high NOx reduction activity over Ag/Al2O3 catalysts, using hydrogen produced in a fuel reformer. The focus of the study is to evaluate the performance of a hydrocarbon selective catalytic reduction (HC-SCR) catalyst in real conditions. Initially, the catalytic materials for the fuel reformer (Rh/CeO2-ZrO2) and the HC-SCR (Ag/Al2O3) were evaluated in separate bench-scale reactor setups. These two setups were subsequently joined into an integrated bench-scale reactor setup with the aim to evaluate the influence of the reformate on the HC-SCR activity in a controlled environment. In the final phase of the study a 4wt.% Ag/Al2O3 catalyst doped with 100ppm(w) Pt was scaled up and tested in a pilot-scale reactor setup. The pilot-scale reactor setup enabled evaluation of the HC-SCR activity in real exhaust gases generated by a single cylinder engine (genset) together with a hydrogen-rich gas supplied from a fuel reformer. Commercial biodiesel (NExBTL) was used as reducing agent for the HC-SCR as well as fuel in the fuel reformer for both the bench-scale and pilot-scale experiments. This study gives an excellent link between evaluations of the catalytic materials, controlled bench-scale experiments and applied engine experiments, proving a viable concept for lean NOx reduction together with onboard hydrogen production. A NOx conversion of above 70% was reached at temperatures below 250°C, in bench-scale experiments when hydrogen produced in the fuel reformer is added.

Biogas upgrading for on-board hydrogen production: Reforming process CFD modelling

Hydrogen production through fuel reforming can be used to improve IC (internal combustion) engines combustion characteristics and to lower vehicle emissions. In this study, a computational fluid dynamics (CFD) model based on a detailed kinetic mechanism was developed for exhaust gas reforming of biogas to synthetic gas (H2 and CO). In agreement with experimental data, the reactor's physical and chemical performance was investigated at various O2/CH4 ratios and gas hourly space velocities (GHSV). The numerical results imply that methane reforming reactions are strongly sensitive to O2/CH4 ratio and engine exhaust gas temperature. It was also found that increasing GHSV results in lower hydrogen yield; since dry and steam reforming reactions are relatively slow and are both dependent on the flow residence time. Furthermore, the hot spot effect, which is associated to oxidation reforming reactions, was investigated for catalyst activity and durability.

The effect of reformer gas mixture on the performance and emissions of an HSDI diesel engine

Exhaust gas assisted fuel reforming is an attractive on-board hydrogen production method, which can open new frontiers in diesel engines. Apart from hydrogen, and depending on the reactions promoted, the reformate typically contains a significant amount of carbon monoxide, which is produced as a by-product. Moreover, admission of reformed gas into the engine, through the inlet pipe, leads to an increase of intake air nitrogen to oxygen ratio. It is therefore necessary to study how a mixture of syngas and nitrogen affects the performance and emissions of a diesel engine, in order to gain a better understanding of the effects of supplying fuel reformer products into the engine.In the current research work, a bottled gas mixture with H2 and CO contents resembling those of typical diesel reformer product gas was injected into the inlet pipe of an HSDI diesel engine. Nitrogen (drawn from a separate bottle) at the same volumetric fraction to syngas was simultaneously admitted into the inlet pipe.Exhaust analysis and performance calculation was carried out and compared to a neat diesel operation. Introduction of syngas + N2 gas mixture resulted in simultaneous reduction of the formation of NOx and smoke emissions over a broad range of the engine operating window. Estimation of the bottled carbon monoxide utilisation showed that by increasing either the load or the speed the admitted carbon monoxide is utilised more efficiently. As a general rule, CO2 emissions increase when the bottled carbon monoxide utilisation is approximately over 88%. Isolation of the H2 and N2 effect revealed that a CO diluted flame promotes the formation of smoke. When the intake air is enriched with syngas + N2, an increase of engine speed results in reduction of maximum pressure rise rate (dp/da). The effect of load on dp/da varies depending on engine speed. Finally, the engine is more fuel efficient when running on neat diesel.