Experimental assessment of a combined plasma/catalytic system for hydrogen production via partial oxidation of hydrocarbon fuels

A combined reformation system, which includes both auto-thermal catalytic and non-equilibrium plasma units, is studied experimentally. The system is assessed for the practical application of hydrogen production via reforming of liquid gasoline-like fuels. The catalyst has been previously used for reforming of different types of hydrocarbons, demonstrating good performances in terms of hydrogen production for temperatures as high as 800°C. In this work, a non-equilibrium plasma source is coupled to the catalytic unit. A pulsed corona reactor is used as a non-equilibrium plasma source at atmospheric pressure. The performances of combined reformation system are characterized experimentally in terms of hydrogen yield and electric power consumption. Hydrogen conversion and byproduct composition are determined and quantified with respect to power consumption, reactor temperature, input reactant composition, and configuration of the experimental setup.     

Recent advances in cleaner hydrogen productions via thermo-catalytic decomposition of methane: Admixture with hydrocarbon

A continuous increase in the greenhouse gases concentration due to combustion of fossil fuels for energy generation in the recent decades has sparked interest among the researchers to find a quick solution to this problem. One viable solution is to use hydrogen as a clean and effective source of energy. In this paper, an extensive review has been made on the effectiveness of metallic catalyst in hydrocarbon reforming for CO_X free hydrogen production via different techniques. Among all metallic catalyst, Ni-based materials impregnated with various transition metals as promoters exhibited prolonged stability, high methane conversions, better thermal resistance and improved coke resistance. This review also assesses the effect of reaction temperature, gas hour space velocity and metal loading on the sustainability of thermocatalytic decomposition TCD of methane. The practice of co-feeding of methane with other hydrocarbons specifically ethylene, propylene, hydrogen sulphide, and ethanol are classified in this paper with the detailed overview of TCD reaction kinetics over an empirical model based on power law that has been presented. In addition, it is also expected that the outlook of TCD of methane for green hydrogen production will provide researchers with an excellent platform to the future direction of the process over Ni-based catalysts.     

Life cycle assessment of hydrogen fuel production processes

The use of hydrogen as an alternative fuel is gaining more and more acceptance as the environmental impact of hydrocarbons becomes more evident. A life cycle assessment study has been carried out to investigate the environmental aspects of hydrogen production. Production by natural gas steam reforming and production upon renewable energy sources are examined. Hydrogen is selected as a future alternative fuel because of the absence of CO₂ emissions from its use, its high-energy content and its combustion kinetics. A very large number of environmental burdens result from the operation of the different hydrogen production routes. A complete and accurate identification and quantification of the environmental emissions has been attempted. The use of wind, hydropower and solar thermal energy for the production of hydrogen are the most environmental benign methods. The benefits and the drawbacks of the competing hydrogen production systems are presented.     

Production of renewable hydrogen from aqueous-phase reforming of glycerol over Pt catalysts supported on different oxides

Aqueous-phase reforming of oxygenated hydrocarbons for hydrogen production presents several advantages as feed molecules can be easily found in a wide range of biomass, there is no need for its vaporization and the process allows thorough exploitation of the environmental benefits of using hydrogen as an energy carrier. The use of glycerol in particular is motivated due to its availability as a consequence of increasing biodiesel production worldwide. In this contribution, the performance of Pt-based catalysts supported on different oxides (Al₂O₃, ZrO₂, MgO and CeO₂) is studied on glycerol reforming. All catalysts led to a hydrogen-rich gas phase. However, a good potential activity with high production of hydrogen and low concentration of undesired hydrocarbons was accomplished over the catalysts supported on MgO and ZrO₂. The high electron donating character of such oxides indicates the influence of the nature of the support in catalytic performance for glycerol reforming.     

On the outlook for solar thermal hydrogen production in South Africa

Global warming and tightening environmental legislation is putting pressure on divesting from fossil fuel in the energy sector, with the transport sector likely to see the biggest changes. Current alternative energy sources are electric vehicles and hydrogen. Conventional hydrogen production technologies are fossil fuel based, emitting significant amounts of CO₂ into the atmosphere. This paper explores various ways to integrate solar thermal technologies into hydrogen production to generate carbon free hydrogen in South Africa. South Africa's abundant solar resource indicates that the country may become a significant player in the hydrogen market. However, the high capital cost associated with solar thermal energy put solar thermal hydrogen at a price disadvantage against conventional production technologies. Significant market penetration for solar thermal hydrogen is not expected within the next decade, but cost reduction due to improved manufacturing techniques and larger manufacturing volumes might close the gap in the long term.     

Optimization of hydrogen production by Chemical-Looping auto-thermal Reforming working with Ni-based oxygen-carriers

Chemical-Looping auto-thermal Reforming (CLRa) is a new process for hydrogen production from natural gas that uses the same principles as Chemical-Looping Combustion (CLC). The main difference with CLC is that the desired product is syngas (H₂ + CO) instead of CO₂ + H₂O. For that, in the CLRa process the air-to-fuel ratio is kept low to prevent the complete oxidation of the fuel. The major advantage of this technology is that the heat needed for converting CH₄ to syngas is supplied without costly oxygen production and without mixing of air with carbon containing fuel gases.An important aspect to be considered in the design of a CLRa system is the heat balance. In this work, mass and heat balances were done to determine the auto-thermal operating conditions that maximize H₂ production in a CLRa system working with Ni-based oxygen-carriers. It was assumed that the product gas was in thermodynamic equilibrium at the exit of the air- and fuel-reactors and the equilibrium gas compositions were obtained by using the method of minimization of the Gibbs free energy of the system. It was found that to reach auto-thermal conditions the oxygen-to-methane molar ratio should be higher than 1.20, which means that the maximum H₂ yield is about 2.75 mol H₂/mol CH₄. The best option to control the oxygen-to-methane molar ratio is to control the air flow fed to the air-reactor because a lower air excess is needed to reach auto-thermal conditions.     

From biomass to electricity through integrated gasification/SOFC system-optimization and energy balance

In this paper the integrated process of biomass gasification and a solid oxide fuel cell (SOFC) was studied in terms of thermodynamics. The study is based on an ongoing project intending to develop an innovative sustainable technology with high efficiency. According to some assumptions, the energy balance revealed that the process can be auto-thermal. Furthermore, and due to the utilization of the hydrogen content of steam utilized in the reforming stage, the overall efficiencies to electrical power could reach very high levels.     

Performance comparison of autothermal reforming for liquid hydrocarbons,gasoline and diesel for fuel cell applications

This paper discusses the reforming of liquid hydrocarbons to produce hydrogen for fuel cell applications, focusing on gasoline and diesel due to their high hydrogen density and well-established infrastructures. Gasoline and diesel are composed of numerous hydrocarbon species including paraffins, olefins, cycloparaffins, and aromatics. We have investigated the reforming characteristics of several representative liquid hydrocarbons. In the case of paraffin reforming, H₂ yield and reforming efficiency were close to thermodynamic equilibrium status (TES), although heavier hydrocarbons required slightly higher temperatures than lighter hydrocarbons. However, the conversion efficiency was much lower for aromatics than paraffins with similar carbon number. We have also investigated the reforming performance of simulated commercial diesel and gasoline using simple synthetic diesel and gasoline compositions. Reforming performances of our formulations were in good agreement with those of commercial fuels. In addition, the reforming of gas to liquid (GTL) resulted in high H₂ yield and reforming efficiency showing promise for possible fuel cell applications.     

Polysilanes: The grail for a highly-neglected hydrogen storage source

The hydrogen economy is a proposed system of delivering energy using hydrogen for engines and fuel cells. Otherwise, hydrogen, in comparison to hydrocarbons, is quite difficult to store or transport with current technology since it possesses a good energy density by weight, but a poor energy density by volume requiring a large tank to store at high pressure and low temperature. In this context, polysilanes constitute a neglected hydrogen storage source. We present a general catalyzed environmentally friendly, rapid and safe hydrogen production from organosilane hydrogen carriers' derivatives by reacting with water. The reaction is successful with a wide range of silane derivatives in quantitative yield of H₂ gas and could be used for daily life applications due to its modest cost, easy approach for implementing and limitation of greenhouse gas liberation.     

Simulation of high temperature thermal energy storage system based on coupled metal hydrides for solar driven steam power plants

Concentrating solar power plants can achieve low cost and efficient renewable electricity production if equipped with adequate thermal energy storage systems. Metal hydride based thermal energy storage systems are appealing candidates due to their demonstrated potential for very high volumetric energy densities, high exergetic efficiencies, and low costs. The feasibility and performance of a thermal energy storage system based on NaMgH₂F hydride paired with TiCr_1.6Mn_0.2 is examined, discussing its integration with a solar-driven ultra-supercritical steam power plant. The simulated storage system is based on a laboratory-scale experimental apparatus. It is analyzed using a detailed transport model accounting for the thermochemical hydrogen absorption and desorption reactions, including kinetics expressions adequate for the current metal hydride system. The results show that the proposed metal hydride pair can suitably be integrated with a high temperature steam power plant. The thermal energy storage system achieves output energy densities of 226 kWh/m³, 9 times the DOE SunShot target, with moderate temperature and pressure swings. In addition, simulations indicate that there is significant scope for performance improvement via heat-transfer enhancement strategies.     

Integrated fossil fuel and solar thermal systems for hydrogen production and CO2 mitigation

In most current fossil-based hydrogen production methods, the thermal energy required by the endothermic processes of hydrogen production cycles is supplied by the combustion of a portion of the same fossil fuel feedstock. This increases the fossil fuel consumption and greenhouse gas emissions. This paper analyzes the thermodynamics of several typical fossil fuel-based hydrogen production methods such as steam methane reforming, coal gasification, methane dissociation, and off-gas reforming, to quantify the potential savings of fossil fuels and CO₂ emissions associated with the thermal energy requirement. Then matching the heat quality and quantity by solar thermal energy for different processes is examined. It is concluded that steam generation and superheating by solar energy for the supply of gaseous reactants to the hydrogen production cycles is particularly attractive due to the engineering maturity and simplicity. It is also concluded that steam-methane reforming may have fewer engineering challenges because of its single-phase reaction, if the endothermic reaction enthalpy of syngas production step (CO and H₂) of coal gasification and steam methane reforming is provided by solar thermal energy. Various solar thermal energy based reactors are discussed for different types of production cycles as well.     

LCA evaluation for the hydrogen production from biogas through the innovative BioRobur project concept

BioRobur is a project aimed to produce hydrogen from biogas through an auto-thermal reforming (ATR) process, in which innovative catalytic systems are used to promote the ATR reactions involved in the process for the conversion of biogas into syngas. A detailed LCA study of hydrogen production from biogas ATR using the BioRobur technology has been performed. LCA analysis has been also conducted for other two conventional processes for the production of hydrogen from biogas: the steam reforming and water hydrolysis (a biogas-fueled Internal Combustion engine (ICE) followed by an Electrolyser). A comparison between these technologies has been made from both the environmental and the energetic viewpoints. The LCA has demonstrated that BioRobur is the most environmentally friendly of considered processes. Moreover, the ICE plus Electrolyser has resulted to be the because of the very large amount of biogas needed for the least efficient process, due to the low conversion yield of biogas into energy of the ICE.     

Simulation of hydrogen thermal desorption and stability titanium hydrides TiHx

Hydrogen behavior in metals and alloys is of great importance since the hydrogen-metal systems used for absorption of nuclear radiation in thermonuclear energy production. Titanium hydride (TiH²) employed widely as a material for hydrogen storage due to its high capacity for hydrogen isotopes.The hydrogen thermal desorption of titanium hydrides with different concentrations is studied by density functional theory methods for determining the cohesion energy of H in TiH_x as a function of the hydrogen concentration, and stability TiH_x sample with high-level H is determined. For macro-kinetic simulation of hydrogen behavior in TiH_x we use the open hydrodynamic package OpenFOAM. Using such simulations, we can model the hydrogen thermal desorption under the action of an ion beam.     

Hydrogen from solar energy,a clean energy carrier from a sustainable source of energy

Solar energy is going to play a crucial role in the future energy scenario of the world that conducts interests to solar-to-hydrogen as a means of achieving a clean energy carrier. Hydrogen is a sustainable energy carrier, capable of substituting fossil fuels and decreasing carbon dioxide (CO₂) emission to save the world from global warming. Hydrogen production from ubiquitous sustainable solar energy and an abundantly available water is an environmentally friendly solution for globally increasing energy demands and ensures long-term energy security. Among various solar hydrogen production routes, this study concentrates on solar thermolysis, solar thermal hydrogen via electrolysis, thermochemical water splitting, fossil fuels decarbonization, and photovoltaic-based hydrogen production with special focus on the concentrated photovoltaic (CPV) system. Energy management and thermodynamic analysis of CPV-based hydrogen production as the near-term sustainable option are developed. The capability of three electrolysis systems including alkaline water electrolysis (AWE), polymer electrolyte membrane electrolysis, and solid oxide electrolysis for coupling to solar systems for H₂ production is discussed. Since the cost of solar hydrogen has a very large range because of the various employed technologies, the challenges, pros and cons of the different methods, and the commercialization processes are also noticed. Among three electrolysis technologies considered for postulated solar hydrogen economy, AWE is found the most mature to integrate with the CPV system. Although substantial progresses have been made in solar hydrogen production technologies, the review indicates that these systems require further maturation to emulate the produced grid-based hydrogen.     

MCFC-based marine APU: Comparison between conventional ATR and cracking coupled with SR integrated inside the stack pressurized vessel

In the present work the implementation of MCFCs as auxiliary power units on-board large vessels, such as cruising, passengers or commercial, ships was investigated. The MCFC stack was designed to supply 500 kW_e and was fed with diesel oil undergoing a reforming process. The system modelling of the plant was performed in steady-state and aimed at assessing the power efficiency for different reforming strategies, process configurations and constituting items thermal integrations. The code Matlab/Simulink was used to this end. Two major fuel processing strategies were examined: “auto-thermal reforming” and “inside vessel steam reforming”. The latter consisted of a pre-reforming unit in which the liquid fuel underwent a catalytic cracking in mild conditions; subsequently, the resulting gas mixture made of light hydrocarbons was mixed with steam and fed into a steam reformer inside the MCFC stack vessel, where conversion to syngas occurred. Due to the high temperature (650 °C) exothermic level of MCFC, the stack was compatible with a syngas steam reforming production thermally self sustained. This allowed to increase the global electrical efficiency from 32.7% (for the ATR-based system) up to 44.6%. The process was then designed aiming at increasing the overall efficiency by thermally integrating the outlet flue gases with the pre-heating section. This lead to efficiencies equal to 39.1% and 50.6% for the “auto-thermal reforming” and “inside vessel steam reforming”, respectively. Finally, the process was upgraded from an auxiliary power unit (APU) to a combined heat and power unit (CHP), since the residual heat in the flue gases was recovered for heating purposes (sanitary water production) and the demineralised water recirculation was implemented to reduce the water make-up and the process environmental footprint.     

Investigation on the effect of temperature on photothermal glycerol reforming hydrogen production over Ag/TiO2 nanoflake catalyst

Photothermal reforming of biomass-derived hydrocarbons is an efficient approach to generate renewable hydrogen driven by solar. However, the current understanding of the general thermal effect on hydrogen production is limited since the photothermal and thermal radiation from solar is difficult to separate. Herein, an experimental study is carried out by synthesizing a series of photothermal catalysts composed of Ag nanoparticles supported on TiO₂ nanoflake (TNF). The structure of the Ag/TNF was examined by XRD, XPS, and HRTEM, respectively. The local temperature rise of the Ag/TNF was detected during the photothermal reforming reaction of the aqueous bio-glycerol, and its influence on H₂ yield was analyzed. By introducing different weight ratios of Ag nanoparticles on TNF, the equilibrium temperature was obviously increased due to the localized surface plasmon resonance (LSPR) effect and dynamic balance between LSPR and heat dissipation was found. It was observed that increasing the weight ratio of Ag particles could result in an increased temperature and lower hydrogen yields. In fact, such photothermal reforming hydrogen production was a synergistic effect between photogenerated-electrons and phonons. Therefore, precisely regulating the photothermal effect by controlling the metal nanoparticles loading to achieve proper thermal balance and high catalytic activity is one effective countermeasure to enhance hydrogen production.     

Gas and liquid phase fuels desulphurization for hydrogen production via reforming processes

The present work focuses on the development of efficient desulphurization processes for multi-fuel reformers for hydrogen production. Two processes were studied: liquid hydrocarbon desulphurization and H₂S removal from reformate gases. For each process, materials with various chemical compositions and microporous structures were synthesized and characterized with respect to their physicochemical properties and desulphurization ability. In the case of liquid phase desulphurization, the adsorption of sulphur compounds contained in diesel fuel under ambient conditions was studied employing as sorbents, zeolite-based materials, i.e. NaY, HY and metal ion-exchanged NaY and HY, as well as a high-surface area activated carbon (AC), for three different diesel fuels with sulphur content varying between 5 and 180 ppmw. Among all sorbents studied, AC showed the best desulphurization performance followed by cerium ion-exchanged HY. The gas phase desulphurization experiments involved the evaluation of zinc-based mixed oxides, synthesized by non-conventional (combustion synthesis) techniques on high steam content reformate gas mixtures.     

Biogas upgrading using ionic liquid [Bmim][PF6] followed by thermal-plasma-assisted renewable hydrogen and solid carbon production

The use of hydrogen as clean energy has attracted significant attention because conventional industrial hydrogen production processes show negative environmental impact, require intensive energy, and/or are dependent on natural gas. The main objective of this study is to develop an innovative and environment-friendly hydrogen production process utilizing biogas as an alternative to natural gas. Ionic liquid [Bmim][PF₆] shows high potential for the replacement of aqueous amine solutions for CO₂ absorption and are employed for biogas upgrading, while thermal plasma (TP), which is beneficial for converting electrical energy to chemical energy, is employed for the simultaneous production of clean “turquoise” hydrogen and solid carbon. In addition, an intercooler is used to improve CO₂ removal in the absorber. Heat and power integration are employed to enhance the performance of the upgrading process and thermal-plasma-assisted hydrogen production. All simulations were conducted using Aspen Plus V10.0 software. The simulated results show that the solid carbon production from biomethane increases compared to that in the proposed base case. The savings in both the heater used to preheat the TP reactor and the third flash drum are 100%, while the saving in power consumption in the compression section is 62.0%. Furthermore, sensitivity is investigated to determine the effect of biomethane composition on the performance of the proposed configuration.     

Effects of nanofluids on the photovoltaic thermal system for hydrogen production via electrolysis process

In this study the photovoltaic hybrid thermal system has been fabricated for an effective increase in production of electric output. Further the PV/T system also designed to produce the hydrogen from the water through electrolysis process. Several studies reported drastic reduction in the electric output due to high cell temperatures. Nevertheless, these effects are reduced by introduction of the nanoparticles. This study also examines the nanofluids MWCNT and Fe₂O₃ as the passive cooling agent for higher electric output production without any major energy loss. The nanoparticles are dispersed in the water at the optimum fashions to increase the thermal and electrical efficiency of the system. Both MWCNT and Fe₂O₃ nanofluids were passed to the hybrid system at the flow rate of 0.0075 kg/s and 0.01 kg/s. The highest electrical output and thermal efficiency has been obtained at 12.30 P.M. With regard to the production of hydrogen, the maximum productions were observed from 12.15 P.M. to 13.00 P.M.. Implementation of this method compensates the energy loss with superior electrical output compared to previous conventional method. By compelling the results, 0.01 kg/s subjected to be efficient on the electricity production and the hydrogen generation. Further, employing the electrolyzer as the attached to the hybrid system produces the hydrogen, which can be stored for future use as the promising source of energy.