Characterization of hydride forming materials at subzero temperatures

GENTILE M. A.; BORZONE E.; BARUJ A.; MEYER G. O.

Río de Janeiro

Conferencia; 22nd World Hydrogen Energy Conference 2018; 2018

WHEC

Mountain areas with important snow accumulation present avalanche danger to both infrastructure and human life in scenarios such as road cleaning, mining and winter sport resorts. To minimize the risk associated with these random events, a usual practice is to perform controlled explosions at a convenient timing to promote smaller avalanches and prevent the build-up of dangerous situations. Hydrogen is sometimes used as fuel to produce such controlled detonations. Hydrogen is a clean fuel because the products of its reaction with oxygen are innocuous to the environment. The possibility of using hydride forming materials (HFM) in this kind of environment to store this hydrogen is a novel idea. HFM are attractive for safety reasons, as they offer high volumetric density storage of hydrogen at low pressure. Moreover, hydrogen pressure is almost constant during hydride formation (charge) and decomposition (discharge), facilitating the design of technological applications. In particular, we have contacted Catedral Alta Patagonia SA, a company managing an important ski resort, for designing a process and an equipment for hydrogen storage using HFM, and supplying it at an adequate pressure (over 100 kPa) at the environment temperature (down to -20°C). As most usual technological applications of HFM are designed to work at room temperature or higher, there is a lack of information about the HFM-hydrogen reaction at subzero temperatures.We propose to perform the hydrogen storage using HFM of the AB5 family. We present the characterization of samples prepared by melting in an arc furnace, with composition LaNi5, MmNi5 and MmNi5-xSnx (Mm: mischmetal). We studied the equilibrium and kinetics properties of the hydrogen absorption and desorption reaction in the temperature range from -24°C to 40°C. Partial substitution of Mm with La, or that of Ni with Sn, reduce the absorption equilibrium pressure down to 1000 kPa while maintaining the hydride decomposition pressure higher than 100 kPa. We determined the reaction enthalpy ΔH and entropy ΔS changes. The obtained results show that the use of these materials for the proposed application is feasible.