Thermodynamic study of regenerative barium-based materials towards barium sulfide for catalytic sulfur dioxide reduction

Abstract

Flue gas with high SO2 content presents a series of human health and environmental problems, which prompted Flue Gas Desulfurization (FGD) technologies widely utilised in industries. However, the conventional FGD using absorbents or adsorbents could generate secondary sulfur-containing pollutants. Thus, a regenerative FGD reaction system that eliminates secondary pollutants while recovering valuable S has been researched. Ba-based materials, viz. Ba(OH)2, BaCO3 and BaO as the precursors, are involved in a regenerative BaS/BaSO4 reaction system of this research. Current thermodynamic study via minimization of Gibbs free energy explored the feasibility of BaS production from these Ba-based materials and reviewed its potential in SO2 reduction to S. Formation of BaS from Ba-based materials was feasible but the yield depends strongly on the temperature and sulfidizing agent used. Compared to BaCO3-systems, Ba(OH)2- and BaO-systems showed better performance in BaS synthesis due to their high equilibrium conversion, even at temperatures< 773 K. Besides, H2S is a better sulfidizing agent for BaS synthesis due to higher BaS yield (maximum 99%). Synthesis routes of different Ba-systems were confirmed by their respective Keq profiles. The feasibility of BaS catalyst in SO2 reduction to S was proven by the excellent SO2 reducing activity and high S yield (100%) at 273 – 1173 K with S8 and S2 as major products. BaS regeneration via H2 was also validated by high BaS yield (100%) at 473 – 1273 K.