Novel sulfur looping scheme to convert H2S to H2 using Ni3S2 supported over ZrO2: Thermodynamic, kinetic, and comparative system analyses

Abstract

The conventional H2S abatement technology is facing challenges related to the low energy efficiency and loss of the product value due to steam generation. To overcome these challenges, an efficient process concept is required to upgrade H2S into high-value H2. Herein, we perform system evaluation on a novel two-step sulfur looping (SL) scheme that utilizes Ni3S2 supported over ZrO2 as a sulfur carrier which can be regenerated in the presence of CO2, and compared to the state-of-the-art Claus process. Both steps of SL – sulfidation and regeneration, are investigated through a combination of ASPEN-based analysis and thermogravimetric experiments to determine the optimum fixed-bed operating conditions. The advantages of the SL scheme over the Claus process are substantiated through process analysis which shows ~19% higher energy and ~8% higher exergy efficiency. Furthermore, for >99% H2S conversion, the SL scheme achieves 2.4% higher sulfur yield compared to the Claus process. The superior performance can be attributed to the production of H2 while eliminating the high temperature oxidation furnace and the air separation unit. The findings of this study provide system-level insights through combined thermodynamic and kinetic aspects and lay out the framework for the potential scale-up of an innovative H2S to H2 conversion technology.