Modeling Hydrogen Generation from Hydroreactive Chemical Hydrides
Open Access
- Author:
- Hook, Michael
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Ali Borhan, Thesis Supervisor
Ali Borhan, Thesis Honors Advisor
Michael John Janik, Faculty Reader - Keywords:
- Chemical Hydrides
Hydrogen
Mathematical Model
Battery Cells
Dimensional Analysis - Abstract:
- Advancements in hydrogen generation and storage technology have resulted in an opportunity for increased usage of hydrogen as a renewable energy source due to its potential to provide greater energy density for fuel cell power systems as compared to current alternatives. One approach to generating hydrogen is through reaction of chemical hydrides with water. The aim of this research was to investigate the reaction of solid lithium hydride (LiH) and lithium aluminum hydride (LiAlH4) immersed in water via an experimental setup created to test variables including pellet size and orientation, water temperature, volume, water salinity, and system pressure. Simultaneous to physical experimentation, a mathematical model based on governing mass transfer and reaction equations was developed to predict hydrogen generation. Through data from initial testing with lithium hydride powder, the activation energy of the reaction and initial surface reaction rate constant were able to be determined, with values of 8684 J/mol and 0.133 mm/s respectively. Furthermore, single pellet reaction data was used alongside the created model to attain fitted values for a lumped rate constant and heat coefficient. Experimental data supported the hypotheses that elevated temperature contribute to a faster reaction. Pressure, salinity, and water volume were found to show no noticeable affect on tests with single pellets under this setup, while competing forces led to similar hydrogen generation per unit of initial surface area when additional pellets were added. Testing with LiAlH4, revealed that the reaction is suppressed in salt water. This is likely due to slower mass transfer because of a buildup of product oxide at the reacting surface. However, if salinity and temperature constrains can be overcome, LiAlH4 offers a greater hydrogen potential per volume of pellet. A summary of experimental results and the mathematical model will be presented. Current work is being done to refine the model in order to be able to predict an optimized pellet geometry for hydrogen generation at short time scales.