Development and demonstration of a deployable apparatus for generating hydrogen from the hydrolysis of aluminum via sodium hydroxide

Emergency and backup power is often enabled through the use of petrochemical based fuels and combustion-based generator systems, and while reliable, these backup power systems fail when petrochemical supplies are disrupted due to refinery, oil outages, or transportation delays. Fuel cells in some cases can serve as a backup to these traditional generators, but they also are fuel-limited to supplies of available energy sources. Recent work conducted in our laboratories focused on the development of a “backup” emergency hydrogen generation system that could be employed when existing energy stockpiles have failed or depleted. Specifically, aluminum metal can be used to generate hydrogen for fuel cells via hydrolysis with sodium hydroxide. In this paper, we summarize the engineering work to produce a deployable aluminum to hydrogen generator which is capable of producing 3.75 kg of hydrogen per day from scrap aluminum feedstocks. The generator was built upon an aircraft deployable pallet, allowing for hydrogen to be generated remotely in cases of power and fuel outages.     

Molten salt-enhanced production of hydrogen by using skimmed hot dross from aluminum remelting at high temperature

The skimmed hot dross generated in secondary production of aluminum contains high amount of metallic aluminum and also the potential heat. An innovative process for hydrogen generation using skimmed hot dross from aluminum remelting industry is proposed in this work. The reaction behavior between skimmed dross and water steam in terms of hydrogen evolution variation at high temperature is studied. The results show that the inherent salts in the dross could accelerate the hydrogen generation at temperature region of 600–850 °C by dissolving the amorphous and γ-Al₂O₃ product layer in water steam atmosphere. The maximum aluminum conversion degree was found to be more than 60%, and the hydrogen evolution rate was over 60 cm³ g^?1 min^?1 when skimmed dross with 30 wt% Al was used in non-isothermal test. The mechanism related to the texture responding of alumina layer with different amount of salts additives and temperatures is discussed.     

Hydrolytic reaction of waste aluminum foils for high efficiency of hydrogen generation

Hydrolyzed waste aluminum foil in low alkaline aqueous solution and concomitant additives are evaluated to generate hydrogen gas. The result of hydrogen generation using wasted Al foil is efficient in comparison with traditional Al powder. A polythene film coated on waste Al foil was removed by immersing into nitric acid for 5 h prior to hydrolyzed reaction. Low alkaline solution (0.75 M NaOH) combined with Bi additives at elevating temperature (70 °C) in waste Al foil-water hydrolysis system enable to increase hydrogen generation rate to 30 ml s^?1 g^?1 and total volume 1300 ml g^?1. The optimized result is attributed to the micro-galvanic cell formation between Al/Bi and removing hydroxide on Al foil surface by alkaline solution. In this report we develop low cost and waste recovery by hydrolyzing waste Al foil. High efficiency of hydrogen generation is achieved by low alkaline concentration and reducing activation energy. Al oxidation mechanism is explained by the linear-parabolic growth model and polarization curves indicate that corrosion potential of Al foils did not abruptly degrade and the corrosion capability with reliability were verified.     

Kinetic performance of hydrogen generation enhanced by AlCl3 via hydrolysis of MgH2 prepared by hydriding combustion synthesis

Magnesium hydride (MgH₂) is a very promising hydrogen storage material and it has been paid more and more attention on the application of supplying hydrogen on-board because the theoretical hydrogen yield is up to 1703 mL/g when it reacts with water. However, the hydrolysis reaction is inhibited rapidly by the passivation layer of Mg(OH)₂ formed on the surface of MgH₂. This paper reports that high purity MgH₂ (～98.7 wt%) can be readily obtained by the process of hydriding combustion synthesis (HCS) and the hydrogen generation via hydrolysis of the as-prepared HCSed MgH₂ can be dramatically enhanced by the addition of AlCl₃ in hydrolysis solutions. An excellent kinetics of hydrogen generation of 1487 mL/g in 10 min and 1683 mL/g in 17 min at 303 K was achieved for the MgH₂-0.5 M AlCl₃ system, in which the theoretical hydrogen yield (1685 mL/g) of the HCSed product was nearly reached. The mechanism of the hydrolysis kinetics enhancement was demonstrated by the generation of a large amounts of H⁺ from the Al³⁺ hydrolysis and the pitting corrosion (Cl^?) of the Mg(OH)₂ layer wrapped on the surface of MgH₂ even at a low temperature. In addition, the apparent activation energies for the MgH₂ hydrolysis in the 0.1 M AlCl₃ and 0.5 M AlCl₃ solutions are decreased to 34.68 kJ/mol and 21.64 kJ/mol, respectively, being far superior to that of reported in deionized water (58.06 kJ/mol). The results suggest that MgH₂ + AlCl₃ system may be used as a promising hydrogen generation system in practical application of supplying hydrogen on-board.     

The development of a PEMFC hybrid power electric vehicle with automatic sodium borohydride hydrogen generation

This paper describes the development of a hybrid Proton Exchange Membrane Fuel Cell (PEMFC) electric vehicle consisting of a 3 kW PEMFC, PV arrays, secondary battery sets, and a chemical hydrogen generation system. We first integrate a hybrid PEMFC electric vehicle and design power management strategies. The on-board hydrogen generation system can provide sufficient hydrogen for continuous operation of the PEMFC, and the performance tests demonstrate the effectiveness of the integrated system in providing sustainable power for driving. We then use Matlab/SimPowerSystem? to develop a simulation model and adjust the model parameters using experimental data. The results indicated that the model can effectively predict system responses and can be used for performance evaluation. We also use the simulation model to estimate the mileage and costs of the developed electric vehicle, and we discuss the impacts of component sizes on system costs and travelling ranges.     

Study of hydrogen production and storage based on aluminum–water reaction

The rate and yield of hydrogen production from the reaction between activated aluminum and water has been investigated. The effect of different parameters such as water–aluminum ratio, water temperature and aluminum particle size and shape was studied experimentally. The aluminum activation method developed in-house involves 1%–2.5% of lithium-based activator which is diffused into the aluminum particles, enabling sustained reaction with tap water or sea water at room temperature. Hydrogen production rates in the range of 200–600 ml/min/g Al, at a yield of about 90%, depending on operating parameters, were demonstrated. The work further studied the application in proton exchange membrane (PEM) fuel cells in order to generate green electric energy, demonstrating theoretical specific electric energy storage that can exceed batteries by 10–20 folds.     

A small-scale and portable 50 W PEMFC system that automatically generates hydrogen from a mixture of Al,CaO, NaOH and sodium CMC in water without external power supply

The production of hydrogen from water under kinetic control is studied using a hydrophobic pouch filled with a mixture of aluminum, calcium oxide, water-soluble alkaline sodium CMC (Carboxymethylcellulose), and sodium hydroxide particles. NaOH particles easily absorb moisture from the air. Thus, CaO is added to protect NaOH from melting. To control the hydrogen generation rate, the aluminum powder is shaped into the spherical solids (M1) and irregular pellets (M2) using the alkaline sodium CMC. The hydrogen-generating pouch is prepared before hydrogen generation rate test. Results show that the best recipe for the range test is 40 wt% M1, 48 wt% M2, and 12 wt% mixed powder including NaOH, CaO and NaHCO₃, because of its greater stability and high hydrogen concentration. The best ratio of the aluminum powder and alkaline sodium CMC in three tests is 95 wt% to 5 wt%. The reaction of the pouch and water produces an on-board hydrogen supply for a polymer electrolyte membrane fuel cell (PEMFC) that can remain stable for 5 h or more, without requiring the addition of energy. This pouch has been applied in small-scale to large-capacity hydrogen generators for the PEMFC. Furthermore, this pouch has been used successfully to develop a 50 W portable hydrogen PEMFC generator.     

Wind energy–hydrogen storage hybrid power generation

In this theoretical investigation, a hybrid power generation system utilizing wind energy and hydrogen storage is presented. Firstly, the available wind energy is determined, which is followed by evaluating the efficiency of the wind energy conversion system. A revised model of windmill is proposed from which wind power density and electric power output are determined. When the load demand is less than the output of the generation, the excess electric power is relayed to the electrolytic cell where it is used to electrolyze the de‐ionized water. Hydrogen thus produced can be stored as hydrogen compressed gas or liquid. Once the hydrogen is stored in an appropriate high‐pressure vessel, it can be used in a combustion engine, fuel cell, or burned in a water‐cooled burner to produce a very high‐quality steam for space heating, or to drive a turbine to generate electric power. It can also be combined with organic materials to produce synthetic fuels. The conclusion is that the system produces no harmful waste and depletes no resources. Note that this system also works well with a solar collector instead of a windmill. Copyright © 2001 John Wiley & Sons, Ltd.     

Dynamic process of hydrogen and heat generation from reaction of Al–Li alloy powders and water vapor at moderate temperatures

As one of the alternative clean fuels, aluminum is suitable for generating hydrogen and power via metal hydrolysis. The reaction process characteristics were studied in a cylindrical reactor with 5 g of Al–Li alloy powder as fuel at moderate temperatures. The test performed good results with 1,130 mL/g alloy of H₂ yield, 86% of the reaction efficiency, and 54.5% of usable heat ratio. The dynamic change of temperature distribution was measured by 12 thermocouples in the reactor, and the maximum was not beyond 892°C. On the basis of the temperature characteristics, the reaction propagation speed was calculated and in the range of 0.57–0.95 mm/s. Moreover, the micromorphology and ingredients presented obvious differences between top product and bottom product, which was resulted from water vapor diffusion. The reaction of Al–Li alloy and steam was determined by both water vapor diffusion and heat transfer, which led to the distinct temperature trends near the vapor inlet, away from the vapor inlet, on the top and at the bottom. On the basis of the results, a mild and controllable hydrogen generation can be achieved at moderate temperatures by optimizing vapor inlet arrangement.     

Recommendations for ammonia borane composite pellets as a hydrogen storage medium

The perspective of this study describes a new concept for ammonia borane (NH₃BH₃, AB) in the form of pellet composited with CoB catalyst to use as a hydrogen storage medium. For the purpose of this, hydrogen storage capacity and physical-chemical properties of composite pellet are examined and tested to investigate effects of specified environmental conditions by exposing pellets in temperature from 22 °C to 80 °C in a long period of time (1 day–4 months). A statistical strategy is provided to detail the investigation for significant differences between holding conditions and their interactions. These results suggest that the changing in holding time is more important than the temperature. The general point of view, there is no change in hydrogen storage properties when the composite pellets held at low temperature about 22 °C for 3 months, and the same trend is also preserved when the composites are kept at the higher temperature for a week. It is concluded that the composite pellets shown performance at hydrogen storage with easy handling and controlled hydrogen generation for on-board energy applications.     

Portable water-using H2 production materials converted from waste aluminum

This study investigates the feasibility of using waste aluminum as a substitute to pure aluminum for preparing portable water-using hydrogen production materials by gas atomization process. The H₂ production performances of waste aluminum H₂ production materials in different reaction conditions considering reaction temperature, reaction aqueous solution and water adding method were investigated. The results show that such materials can achieve a high Al/H₂ conversion and a stable H₂ flow rate for practical fuel cell electricity generation. In addition, the recycling of activation agents and Al(OH)₃ can be realized.     

Assessment of sugarcane bagasse gasification in supercritical water for hydrogen production

Sugarcane bagasse is one of the major resources of agricultural biomass waste in the world. In this work, supercritical water gasification characteristics of sugarcane bagasse were investigated. The effect of temperature (600–750 °C), concentration (3–12 wt%), residence time (5–20 min) and catalysts (Raney-Ni, K₂CO₃ and Na₂CO₃) on bagasse gasification were studied. A kinetic study on the non-catalytic and Na₂CO₃ catalytic bagasse gasification was conducted to describe the kinetic information of the bagasse gasification reaction. The results showed that a higher reaction temperature, a lower bagasse concentration and a longer residence time could favor the gasification of bagasse, leading to a higher hydrogen yield. Bagasse was nearly completely gasified at 750 °C without using any catalyst and the carbon gasification efficiency could reach up to 96.28%. The addition of employed catalysts remarkably promoted the bagasse gasification reactivity. The maximum hydrogen yield (35.3 mol/kg) was achieved at 650 °C with the Na₂CO₃ loading of 20 wt%. The experimental data fitted well with a homogeneous model based on a Pseudo-first-order reaction hypothesis. The kinetic study showed that Na₂CO₃ catalyst could lower the activation energy E_a of bagasse gasification from 117.88 kJ/mol to 78.25 kJ/mol.     

Liquid organic hydrogen carriers (LOHCs) in the thermochemical waste heat recuperation systems: The energy and mass balances

This paper is presented a concept of thermochemical recuperation of waste heat based on hydrogen extraction from liquid organic hydrogen carriers (LOHC), on the example of methylcyclohexane-toluene system. The advantages of this concept is described, for example, a possibility to use a moderate low temperature of waste heat for generation high-exergy “green” hydrogen fuel. To understand the effect of operating parameters on the energy and mass balance, the thermodynamic analysis was performed. The chemical system for hydrogen generation was analyzed via Gibbs free energy minimization method. The thermodynamic analysis was conducted under various operating conditions: temperature of 100–400 °C, pressure of 1–4 bar. Aspen HYSYS software was used for the energy and mass conservation analysis. Sankey diagram for the energy flows is depicted. The results showed that the maximum energy efficiency the thermochemical waste heat recuperation system have in the temperature range above 300–350 °C. In this temperature range, the effect of pressure on the energy balance is negligible and it is recommended for the thermochemical recuperation system to use LOHC with a pressure of 1.5–2 bar. Based on the analysis, it was concluded that the temperature potential of waste heat for about 300–350 °C is enough for the investigated concept. An analysis of a mass balance showed that the decreasing in condensation temperature leads to a significant increasing in the share of condensed toluene from toluene-hydrogen mixture after a reactor. If temperature of a hydrogen-toluene mixture of 20 °C at pressure above 2 bar about 96% of toluene can be condensed after the first condenser.     

An onboard hydrogen generator for hydrogen enhanced combustion with internal combustion engine

Hydrogen enhanced combustion (HEC) for internal combustion engine is known to be a simple mean for improving engine efficiency in fuel saving and cleaner exhaust. An onboard compact and high efficient methanol steam reformer is made and installed in the tailpipe of a vehicle to produce hydrogen continuously onboard by using the waste heat of the engine for heating up the reformer; this provides a practical device for the HEC to become a reality. This use of waste heat from engine enables an extremely high process efficiency of 113% to convert methanol (8.68 MJ) for 1.0 NM of hydrogen (9.83 MJ) and low cost of using hydrogen as an enhancer or as a fuel itself. The test results of HEC from the onboard hydrogen production are presented with 2 gasoline engine vehicles and 2 diesel engines; the results indicate a hike of engine efficiency in 15–25% fuel saving and a 40–50% pollutants reduction including 70% reduction of exhaust smoke. The use of hydrogen as an enhancer brings about 2–3 fold of net reductions in energy, carbon dioxide emission and fuel cost expense over the input of methanol feed for hydrogen production.     

Supercritical water gasification of food waste: Effect of parameters on hydrogen production

Food waste is a type of municipal solid waste with abundant organic matter. Hydrogen contains high energy and can be produced by supercritical water gasification (SCWG) of organic waste. In this study, food waste was gasified at various reaction times (20–60 min) and temperatures (400 °C-450 °C) and with different food additives (NaOH, NaHCO₃, and NaCl) to investigate the effects of these factors on syngas yield and composition. The results showed that the increase in gasification temperature and time improved gasification efficiency. Also, the addition of food additives with Na⁺ promoted the SCWG of food waste. The highest H₂ yield obtained through non-catalytic experiments was 2.0 mol/kg, and the total gas yield was 7.89 mol/kg. NaOH demonstrated the best catalytic performance in SCWG of food waste, and the highest hydrogen production was 12.73 mol/kg. The results propose that supercritical water gasification could be a proficient technology for food waste to generate hydrogen-rich gas products.     

Aluminum composites with bismuth nanoparticles and graphene oxide and their application to hydrogen generation in water

The bismuth nanoparticles modified graphene oxide composites (Bi-NPs@GO) and bismuth nanoparticles (Bi-NPs) were prepared by a hydrothermal method. The activated aluminum/bismuth nanoparticles Bi-NPs@GO/Al and Bi-NPs/Al were prepared. Their hydrolysis reaction performance were studied. The experimental results show that the composite of aluminum and Bi-NPs@GO can react rapidly with water. The 4-h milled Bi-NPs@GO/Al composite shows better hydrogen generation performance and reacted with tap water even at 0 °C. The Bi-NPs@GO/Al composite exhibits high hydrogen generation rate at room temperature. The enhancement of aluminum hydrolysis in the composite may be due to that the addition of nano-scale Bi and graphene oxide.     

Investigation on PEM water electrolysis cell design and components for a HyCon solar hydrogen generator

Hydrogen as a secondary energy carrier promises a large potential as a long term storage for fluctuating renewable energies. In this sense a highly efficient solar hydrogen generation is of great interest especially in southern countries having high solar irradiation. The patented Hydrogen Concentrator (HyCon) concept yields high efficiencies combining multi-junction solar cells with proton exchange (PEM) membrane water electrolysis. In this work, a special PEM electrolysis cell for the HyCon concept was developed and investigated. It is shown that the purpose-made PEM cell shows a high performance using a titanium hybrid fiber sinter function both as a porous transport layer and flow field. The electrolysis cell shows a high performance with 1.83 V at 1 A/cm² and 24 °C working under natural convection with a commercially available catalyst coated membrane. A theoretical examination predicts a total efficiency for the HyCon module from sunlight to hydrogen of approximately 19.5% according to the higher heating value.     

A review on hydrogen generation,explosion, and mitigation during severe accidents in light water nuclear reactors

Progress of severe accident (SA) can be divided into core degradation and post core meltdown. An important phenomena during severe accidents is the hydrogen generation from exothermal reaction between oxidation of core components, and molten core concrete interaction (MCCI). During the severe accidents, a large amounts of hydrogen is produced, deflagrated and consequently the containment integrity is violated. Therefore, the main objectives of this study is to highlight the source of hydrogen production during SA. First, a thorough literature review and main sources of hydrogen production, hydrogen reduction systems are introduced and discussed. Based on the available results, the amount of produced hydrogen in a typical pressurized water reactor (PWR) and a boiling water reactor (BWR) are estimated to be 1000 and 4000 kg, respectively during in-vessel phase. The average rate of hydrogen production is about 1 kg/s during reflooding of a degraded core. Also, about 2000 kg hydrogen is produced during MCCI for a PWR. The lower and upper range of hydrogen required to initiate combustion is 4.1 and 74 vol percent, respectively. In this paper a review is provided of what has been done in the literature with regard to hydrogen generation in severe accidents of nuclear power plants. In addition, the review identifies the literature gaps and underlines the need of developing a systematic hydrogen management strategy. A hydrogen management strategy is proposed in order to maintain the containment integrity against the probable combustion or hydrogen explosion loads.     

Controlled hydrogen generation by reaction of aluminum/sodium hydroxide/sodium stannate solid mixture with water

Aluminum/water reaction system has gained considerable attention for potential hydrogen storage applications. In this paper, we report a new aluminum-based hydrogen generation system that is composed of aluminum/sodium hydroxide/sodium stannate solid mixture and water. This new system is characterized by the features as follows: the combined usage of sodium hydroxide and sodium stannate promoters, the use of solid fuel in a tablet form and the direct use of water as a reaction controlling agent. The factors that influence the hydrogen generation performance of the system were investigated. The optimized system exhibits a favorable combination of high hydrogen generation rate, high fuel conversion, rapid dynamic response, which makes it promising for portable hydrogen source applications.     

Production of useful energy from solid waste materials by steam gasification

A steam gasification processes is an energy conversion pathway through which organic materials are converted to useful energy. In spite of the high energy content in organic waste materials, they have been mostly disposed of in landfills, which causes harmful environmental issues such as methane emissions and ground water pollution and contaminations. In this sense, organic solid waste materials are regarded as alternative resources for conversion to useful energy in the steam gasification process. In this study, three types of waste materials – municipal solid waste (MSW), used tires and sewage sludge – were used to generate syngas through the gasification process in a 1000 °C steam atmosphere. The syngas generation rates and its chemical compositions were measured and evaluated over time to determine the characteristics and dynamics of the gasification process. Also, carbon conversion, and mass and energy balances are presented which demonstrates the feasibility of steam gasification as a waste conversion pathway. The results show that the syngas contains high concentrations of H₂, around 41–55% by volume. The syngas generation rate was found to depend on the carbon content in the feedstock regardless of the types of input materials. Comparing to the hydrogen production from water splitting that requires extremely high temperatures at around 1500 °C, hydrogen production by steam gasification of organic materials can be regarded as equally effective but requires lower system temperatures. Copyright © 2016 John Wiley & Sons, Ltd.