title: Multi-injection moving bed reactors in Cu-Cl cycle hydrolysis for hydrogen production
Creators: name: Broders, Jenna M.
Publisher: name: Memorial University of Newfoundland
publisherIdentifier: https://ror.org/04haebc03
publisherIdentifierScheme: ROR
Year: 2024

description: Hydrogen as an energy source has emerged as a promising solution for addressing energy demands while reducing carbon emissions. It has become a focal point of research and innovation in the pursuit of sustainable and clean energy sources. There are several methods of hydrogen production, with thermochemical water splitting through the Copper- Chlorine (Cu-Cl) cycle gaining momentum as a carbon neutral production technique with readily available resources. A significant challenge for large-scale implementation of the Cu-Cl cycle is the endothermic gas-solid hydrolysis reaction, which requires a large amount of steam in excess of stoichiometry to achieve favourable solid conversion, reducing process efficiency. In this thesis, investigation of the hydrolysis reaction is presented to enhance the understanding of the reaction limitations as well as identify scenarios which improve conversion and minimize steam requirements. Employing the established ideal operating conditions, this thesis aims to develop a kinetic model for a novel reactor design – downdraft multi-injection moving bed reactors (MBR). A detailed literature review highlights current work on techniques that increase CuCl₂ conversion and reduce steam to copper ratios (SCR), side reactions and by-products, as well as explores the various types of reactors for the hydrolysis phase. Applying the established operating ranges and side reactions from the literature, a phase equilibrium simulation is generated to discern conditions that will improve solid conversion and mitigate side reaction progression. From the set of simulations, an ideal temperature of 375℃, pressure of 1 bar, and a molar SCR of 10:1, were utilized to model the behaviour of a downdraft multi-injection MBR through reactors in series. This simulation demonstrated a 17% increase in CuCl₂ conversion when compared to a single injection reactor at the same conditions, indicating the viability of an MBR approach to the hydrolysis stage. In terms of steam reduction techniques, a gas recirculation configuration was explored to recycle the unreacted outlet steam. Due to the increasing concentration of HCl gas with every recycle, this configuration requires additional processing to reduce the concentration of HCl. Building on the results from the phase equilibrium MBR simulation, reaction rates and kinetics were introduced to generate a more realistic predictive model of the hydrolysis reaction in downdraft multi-injection MBR conditions. A comparison to a fixed bed reactor at the same conditions was performed. A 23.4% increase in CuCl₂ solid conversion was observed. Applying the same conditions as those used in the phase equilibrium model resulted in a total conversion of 61.1%. Through a sensitivity analysis at varying reactor lengths, injection spacing and steam injection amounts, a maximum conversion of 66.5% was achieved. The sensitivity analysis also demonstrated the importance of reactor design on reaction progression, emphasizing the need to investigate different reactor scenarios to identify conditions for the best conversion and product yield. Overall, this research demonstrated the promising feasibility of the MBR reactor design for the hydrolysis reactor, with the ability to obtain higher solid conversion at lower SCR.