Enhancement Of Hydrogen Generation Research Articles

Enhancement of hydrogen generation using nanoaluminum particles produced by a wire explosion process

Nanoaluminum particles were generated by a wire explosion process (WEP) in helium, argon, and nitrogen ambiences, by depositing energy equal to the vaporization energy of the conductor material volume. The size and shape of the generated nanoaluminum particles were analyzed using a transmission electron microscope (TEM). X‐ray diffraction (XRD) analysis was carried out to characterize the phase in nanoaluminum (Al) particles. Particle size distribution of the produced nano‐Al particles follows log‐normal distribution and the nanoparticles produced in helium were of smaller size compared to those produced in argon or nitrogen ambience. Hydrogen gas was generated on reacting aluminum nanoparticles with aqueous NaOH solution. It was observed that most of the oxides formed on reaction of Al and aqueous NaOH solution were bayerite at room temperature and boehmite at higher temperature. The formation of bayerite and boehmite was characterized using XRD and TEM studies. The reactions were also carried out at higher temperature to understand the hydrogen generation rate. Molarity of NaOH has a high influence on the rate of hydrogen generation. The rate constant of the reaction was calculated adopting the first order rate law for predicting the amount of hydrogen generation. Nickel (Ni) nanoparticles synthesized by WEP and copper sulfate (CuSO4) were used as catalysts and added to the reaction mixture of Al and aqueous NaOH solution to control the hydrogen generation rate. It was observed that the reaction rate of Al with NaOH medium has increased with the addition of CuSO4 and Ni nanoparticles due to the microgalvanic effect, thereby enhancing the hydrogen generation rate. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Study on the enhancement of hydrogen generation via biomass gasification in fluidizedbed reactors

In this study, solid biomass is gasified in fluidized-bed reactors, to investigate the effect of various means on syngas composition, especially for enhancing hydrogen content in the production gas. Conventionally, air is supplied to the reactor as gasification medium, which inevitably results in a high nitrogen content in the syngas. Alternatively, steam or oxygen-rich gas can be supplied to improve the syngas characteristics. On the other hand, a so-called “indirect gasification technology” realizes the whole conversion processes in dual reactors, for combustion and gasification, respectively; moreover, solid materials are circulated through two reactors, while gaseous streams in between are separated from each other. Hence, this system features the advantage of producing near nitrogen-free syngas in the gasifier, with air as oxidant in the combustor. Baseline experiments with various operating parameters, including air equivalence ratio (ER) and temperature, were firstly performed in a 30 kWth bubbling fluidized-bed gasifier; then, trial tests were conducted with the aforementioned operational and constructional factors. The preliminary test data show positive trends for the enhancement of hydrogen generation via biomass gasification. Further efforts will be pursued to establish a data base, which would be beneficial to extensive researches on clean energy and carbon abatement technologies.

A thermodynamic analysis of biogas partial oxidation to synthesis gas with emphasis on soot formation

A thermodynamic analysis of synthesis gas production via partial oxidation (POX) of biogas is performed in the present article. Chemical equilibrium calculations are conducted for partial oxidation of (CH4+CO2) mixtures based on Gibbs free energy minimization method emphasizing soot formation. Regarding precise evaluation of carbon dioxide effects on the reforming characteristics, the obtained results are compared with the experimental data. Furthermore, the effects of steam injection at the inlet of the reformer on the coking behavior and syngas production yield are studied. To investigate the effects of the equivalence ratio (ϕ), temperature and pressure, a broad parametric study is performed. The results reveal that the process temperature plays a pivotal role in enhancing the syngas production and soot abatement. It is also found that the pressure has an impractical effect on the syngas production yield, leading to the soot formation and decrease in both hydrogen and carbon monoxide yields. Furthermore, increasing the inlet CO2/CH4 makes the thermal reforming efficiency to rise at an equivalence ratio lower than 3. Meanwhile, increasing the steam to methane (S/C) ratio reduces carbon formation and enhances hydrogen production. Nonetheless, when the S/C ratio is larger than 2 at ϕ = 2.5 and 1 at ϕ = 3, the enhancement of hydrogen generation is minimized and even tends to become impractical. Therefore, near adiabatic and atmospheric condition at ϕ = 2.5–3 with S/C < 1 are recommended as the optimum operating routes for partial oxidation of biogas.

Enhancement of hydrogen generation using waste aluminum cans hydrolysis in low alkaline de-ionized water

In this study, hydrogen generation using hydrolyzed waste aluminum can in low alkaline aqueous solution is evaluated and the result is efficient in comparison with Al powders. Waste Al can was pretreated using a series of methods, such as paint removal in concentrated sulfuric acid and fragmented Al pieces in planetary ball milling, and then characterized with BET, XRD and SEM techniques. During hydrogen generation, low alkaline solution combined with elevating temperature and Ni or Ni/Bi additives in waste Al can-water hydrolysis system could achieve rapid hydrogen generation rate to 150 ml s−1 g−1 and total volume 1350 ml g−1. Moreover, planetary ball-milling of waste Al scraps could increase effective reactive area to improve generated hydrogen. The optimized results, which are attributed from micro-galvanic cell formation between Al/Ni closely contact, and accelerating reaction activity, are comparable with Al powders. In this report we successfully optimize the generated hydrogen efficiency of waste Al can base without high alkaline concentration which could cause environmental pollution and instrument damage problems.