Abstract
Hydrogen generation from rapid hydrolysis of aluminum in sodium fluoride solution was investigated through a hydrolysis experiment. Rapid and instant hydrogen yield were observed using sodium fluoride as additive. The experimental results demonstrate that the increase of temperature and the amount of additives in a certain range will boost the hydrogen production. The amount of additives outside the range only has an effect on the rapid hydrolysis of the aluminum during the initial stage, but the total amount of hydrogen produced doesn’t increased significantly. Theoretical analysis of the effects of the mixing ratio and the temperature on the hydrogen production rates were performed using the shrinking core model and the kinetic model. The shrinking core model parameter a and k indicate the film change degree of porosity and thickness and the effect of time on the diffusion coefficient. the kinetic model is verified and the activation energy confirming hydrogen yield control by a molecular diffusion process. Correspondingly, mechanisms of Al corrosion in NaF solutions under low and high alkalinity were proposed, respectively.
Highlights
As a clean energy source, hydrogen occupies many advantages as high energy density abundant resource, and environment friendly
In order to comprehend the kinetic of the hydrogen generation procedure, kinetic model be used to obtain kex at different temperatures, and can calculate apparent activation energy by kex。Apparent activation energy is mainly used to explain the effect of temperature on hydrogen production
With the increased of additive to 3.0wt%, the time required for hydrogen generation was shortened, but the maximum hydrogen flow and hydrogen yield were almost no longer improved
Summary
As a clean energy source, hydrogen occupies many advantages as high energy density abundant resource, and environment friendly. The commonly used methods for removing the film and increasing the hydrogen yield rate are as follows: additives, such as the alkaline salts or other water-soluble inorganic salts, can cause local pitting on the surface of the membrane[7, 8]; mechanical cutting, such as ball milling with metal or metal salts with higher active aluminum content than aluminium, causes fracture on the oxide film on the surface of aluminium, and forming a potential difference between the water and the highly active metal to accelerate the removal of the oxide film; enhancing the reaction temperature and accelerating molecular diffusion to accelerate the density change of the film. In order to get a deeper insight into kinetics of the H2 generation process from Al particles in low and high alkaline solution, obtained results for experiments carried out with NaF additive are analyzed using two different models[12]. In addition to known parameters to be fitted, value of unknown parameters are substituted, the equation (7) is integrated into the parameter a, a express the change degree of film density and porosity. t is transformed into a function with Xb as the independent variable, and the original equation is transformed into the following equation (8)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
