Biologically produced elemental sulfur clogging induced by thiols in gas biodesulfurization systems

Abstract

The gas bio-desulfurization process involves the biotic oxidation of hydrogen sulfide (H2S) into hydrophilic and usable sulfur, which possesses favorable settleability, facilitating its separation and recovery from the bioreactor. Nonetheless, in thiol-containing gas bio-desulfurization systems, elemental sulfur is prone to aggregating and adhering to packings, pipes, pumps, and valves, leading to sulfur clogging and impeding the operation of the BDS process. This study systematically investigates the underlying mechanisms of sulfur agglomeration and clogging. A suite of analytical techniques, including laser diffraction, scanning electron microscopy (SEM), electrophoretic light scattering (ELS), X-ray diffraction (XRD), and sessile drop method, were employed to analyze the sulfur clogging phenomenon. The results reveal that the presence of thiols is a primary contributor to sulfur agglomeration and clogging. Thiols are commonly found in natural gas, biogas, and landfill gas and have a lowering effect on the surface hydrophilicity of sulfur particles, making them more hydrophobic and exacerbating sulfur aggregation. The accumulation of more agglomerated and less hydrophilic sulfur particles on packings and pipes leads to sulfur clogging. It occurs due to the nucleophilic S8 dissolution that promotes polysulfide formation and removes the hydrophilic biomacromolecules on the particle surface, making the sulfur particles more prone to aggregation. This study represents a pioneering effort to illuminate the mechanism behind sulfur clogging and attribute it to thiols, offering valuable insights for addressing the industrial challenge of sulfur clogging and expanding the application scope of gas bio-desulfurization.