An Experimental Study of Spent Fuel Transport for On-Board Hydrogen Storage

Abstract

Ammonia borane (AB), a solid chemical under room temperatures, is a promising candidate material for on-board hydrogen storage. One of the major drawbacks that limit the use of this kind of materials is the difficulty to remove (transport) the spent fuels (reaction byproducts) out of the system. In the present study, a piston cylinder device was designed and used to study the spent fuel transport process and to find effective ways to improve the transportability of spent fuels. The piston, which has an area of 5.07 cm2, is designed to push out the spent fuel through a clear acrylic die, which has a diameter of 3.175 millimeters. The pushing force on the top of the piston is provided by compressed nitrogen gas. The piston/cylinder assembly is able to operate under a pressure of 30 bars, which gives a theoretical force of 1,520 N. The assembly can be mounted either vertically or horizontally. Experiments were carried out with sand surrogates and spent fuel of BmimCl (20 wt%) aided AB (80 wt%) thermolysis, which was conducted within the temperature range of 80°C to 120°C. A series of experiments with sands were conducted with different sand to oil weight ratios from infinite, 10:1, 7:1, 5:1, to 4:1. Results of the experiments with sand showed that the sand/oil mixture was extruded out from the piston/cylinder assembly when the mixture ratios were 5:1 and 4:1. The transportability of the 4:1 mixture is better than that of 5:1 mixture, indicated by the piston travel distance. Experiment also showed that the powder-like spent fuel could be moved out from the piston/cylinder assembly smoothly without any oil added. This study demonstrated that effective removal of AB spent fuel in hydrogen storage systems is possible. Considering that only a small amount of spent fuel sample was used, tests with more spent fuel need to be carried out to further support the present observation.