Hydrogen-water isotope exchange in a trickle bed column by process simulation and 3D computational fluid dynamics modelling

• Main Author: Aldehani, Mohammed
• Other Authors: Aiouache, Farid
• Published: Lancaster University 2016
• Subjects: 621.48
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695907

Hydrogen is the most abundant chemical element in the universe and exists under three isotopic forms: protium, deuterium and tritium. Protium is commonly used in a variety of industries including electronics, metallurgy, chemistry and petrochemistry. Deuterium and tritium have taken more roles in both civil and defence nuclear industries and biomedical sciences. Today water treatment systems at nuclear sites remove many contaminating debris isotopes, with the exception of tritium. This is because tritiated waters have traditionally been particularly difficult and expensive to treat while they can spread easily if they escape into the environment. The topic of separation and purification of tritium and deuterium has a considerable value. Among the numerous separation methods of hydrogen isotopes, H2-H2O liquid catalytic exchange has attracted interest because of its mild operating conditions, high efficiency, limited corrosion and toxicity. The method of hydrogen-water liquid catalytic exchange has many possible applications such as; producing and upgrading heavy water, producing light water and removing tritium from light and heavy waters for recycling to fusion reactors or for low level nuclear deposits. This thesis presents the hydrogen-water isotope exchange reaction that is taking place co-currently and counter-currently through a trickle bed column. Numerical simulations were performed by process design and fluid flow modelling. The missing physical properties of deuterium, and particularly of tritium isotopologues in gaseous and water forms, were predicted and validated with existing literature data. Moreover, suitable operating parameters were approached allowing isotopic exchange to be performed under favourable performance. Intrinsic fluid flow studies by 3D modelling offered more understanding of various underlying phenomena taking place at the local scale and provided identification of main hydrodynamic characteristics in a trickle bed reactor including trends of pressure drop, liquid holdup and catalyst wetting efficiency. The activity of the catalytic process in terms of rate of conversion was discussed through the effect of operating conditions and was validated by a comparison with experimental data and literature.