CFD-DEM modelling of liquid-solid-gas flow in rotary drums and an application in solar panel leaching

Rotary drums play a crucial role in various chemical processes including drying, mixing, and reactions. An in-depth study of the fluid dynamics and particulate interactions inside the rotary drum is pivotal for design refinement and efficiency improvement. Considering the inherent presence of gases and the typically nonspherical nature of particles in the rotary drums, this thesis developed an unresolved reactive superquadric computational fluid dynamics-discrete element method (CFD-DEM) coupled with the volume of fluid (VOF) to describe the complex behaviours of liquid-nonspherical-particle-gas flow. Then, it is particularly applied to the application of the silver leaching process in a rotary drum - a crucial step in the recycling of end-of-life crystalline silicon (c-Si) photovoltaic modules. After the introduction in Chapter 1 and the literature review in Chapter 2, 1) In Chapter 3, the CFD-DEM-VOF model is developed to describe the liquid-solid-gas flow and mixing in a rotary drum by considering inter-particle collisions, inter-phase interactions, and interface morphology. A smoothing method is used to link the quantities between the particle and computational grids, allowing the fine grids to resolve flow details such as the gas-liquid interface position and curvature. After model validations, the typical mixing behaviours of liquid-solid-gas flow in a rotary drum are studied. The effects of liquid presence and rotating speed on particle-scale behaviours (e.g., repose angle, active-passive zone depth, solid residence time and contact force chain) and the time-evolved mixing performance (e.g., mixing index and axial dispersion) are studied. The work sheds light on the process optimization of multiphase flow in rotary drums. 2) Given the nonspherical nature of particles in many rotary drum applications, Chapter 4 studies the transportation mechanism of chip-like particles in a particle-liquid rotary drum by the CFD-DEM approach where particle morphology is described by a superquadric method. After model validations, the particle-scale information (e.g., active-passive interface, mixing, dispersion, orientation, and force) under different rotating speeds is analysed. The fundamental study sheds light on the design and optimization of rotary drums for many mixing processes where nonspherical particles are involved. 3) Considering the gas existence in many rotary drums with nonspherical particles, Chapter 5 develops an unresolved CFD-DEM-VOF coupling framework, featuring a superquadric method to model the liquid-nonspherical particle-gas flow and a so-called “ghost domain” algorithm to improve the parallelization efficiency. The model is applied to two cases – cuboid particle sedimentation and dambreak formation. This research introduces an innovative computational approach for simulating systems containing gas, nonspherical particles, and liquid. It demonstrates a potential to analyse interactions between particles and fluids in the unresolved framework. 4) Chapters 6 and 7 address an urgent need - photovoltaic panel recycling, by focusing on optimising silver (Ag) recovery. In Chapter 6, we introduce a novel rotary perforated drum leaching reactor (RPDLR) as a scalable solution, benchmarking its performance against conventional beaker leaching. The effects of the reactor scale and the configurations on Ag conversion during leaching are experimentally investigated by applying two scales’ leaching beaker systems (solid/liquid ratio of 2 g/0.04 L and 250 g/5 L) and the RPDLR (solid/liquid ratio of 250 g/ 5 L), respectively. Comparative studies of N-type and P-type solar cells within the RPDLR reveal distinct leaching behaviours, analysed through SEM-EDS to elucidate the Ag conversion patterns. This study not only confirms the effectiveness of the RPDLR but also highlights its capacity to achieve high Ag recovery rates, highlighting its potential for industrial-scale photovoltaic recycling. 5) Further, Chapter 7 develops a reactive CFD-DEM-VOF coupling framework and applies it to simulate internal hydrodynamics and leaching performance in a rotary drum leaching reactor. The complex inter-phase interaction, intense rotation boundary and leaching involvement are considered simultaneously in the rotary drum with the co-existence of gas, nonspherical solar panels (solid) and leaching acid (liquid). After model validations, the particle-scale information (e.g., distribution, motion and Ag conversion) under different HNO3 concentrations is analysed. As a result, this thesis develops an unresolved reactive superquadric CFD-DEM-VOF model tailored for exploring the complex dynamics of liquid-nonspherical particle-gas reacting flow and provides great insights into optimizing rotary drum designs for enhanced efficiency in Ag recovery processes from end-of-life PV modules.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2024

Author dc:creator

• Tang, Xinxin ; https://orcid.org/0009-0006-8770-508X

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/30559

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/103239