Removal of sulfur hexafluoride in molten-tin bubble column reactors: Kinetics parameter identification and scale-up studies

Abstract

This study presents the degradation of sulfur hexafluoride (SF6), which is a greenhouse gas emitted from semiconductor industry, in a molten metal bubble column reactor (MMBCR) using tin. Experiments were conducted in a bench-scale MMBCR ranging from 468 °C to 668 °C using a mixture of N2 and 1000 ppm SF6 to estimate reaction kinetic parameters, where high-value solid product (SnS and SnF2) used in solar-cell devices were produced. A one-dimensional MMBCR model integrating reaction kinetics, axial dispersion, and heat transfer was formulated to investigate hydrodynamics and the performance of three pilot-scale multitubular MMBCRs at a feed flow rate of 300 LPM. At 650 °C, the SF6 removal efficiencies (η) of the pilot-scale MMBCRs with 80, 60, and 40 tubes at the same height (=0.5 m) and diameter (=0.1 m) were 85 %, 83 %, and 82 %, respectively. The pilot-scale MMBCR featuring 80 tubes exhibited the highest η owing to a low axial dispersion coefficient and high residence time. This study provides useful insights and guidelines for the design and upscaling of SF6 degradation processes utilizing MMBCRs in the semiconductor industry.