Effect of sulfide on morphology and particle size of biologically produced elemental sulfur from industrial desulfurization reactors

We investigated the effect of polysulfide formation on properties of biologically produced elemental sulfur (S8) crystals, which are produced during biological desulfurization (BD) of gas. The recent addition of an anoxicsulfidic reactor (AnSuR) to the BD process resulted in agglomerated particles with better settleability for S8 separation. In the AnSuR, polysulfides are formed by the reaction of bisulfide (HS-) with S8 and are subsequently oxidized to S8 in a gas-lift reactor. Therefore, sulfur particles from the BD are shaped (i.e. morphology and particle size) both by formation and dissolution. We assessed the reaction of HS- with S8 particles in anoxic, abiotic experiments in a batch reactor using two S8 samples from industrial BD reactors. Under these conditions, the sulfur particle surface became coarser and more porous, and in addition the smallest particles disappeared. Agglomerates initially fell apart but were reformed at a later stage. Moreover, we found different observed polysulfide formation rates for each S8 sample, which was related to the initial morphology and size. Our findings show that particle properties can be controlled abiotically and that settleability of S8 is increased by increasing both the HS--S8 ratio and retention time.

Automated summary

The effect of polysulfide formation on biologically produced elemental sulfur crystals was investigated, showing that polysulfides formed in the AnSuR reactor improved settleability of S8 particles. Anoxic, abiotic experiments revealed that sulfur particles became coarser and more porous, with smaller particles disappearing and agglomerates initially breaking apart but later reforming. Different observed polysulfide formation rates for each S8 sample were found to be related to the initial morphology and size. Increasing HS--S8 ratio and retention time were shown to increase settleability of S8 particles.