Novel Agglomeration Strategy for Elemental Sulfur Produced during Biological Gas Desulfurization

Area of Science:

• Environmental Biotechnology
• Biogeochemistry
• Materials Science

Background:

• Biological desulfurization (BD) generates elemental sulfur (S), often with poor settleability.
• Sulfur crystal formation and agglomeration are critical factors influencing its separation.
• Understanding the mechanisms of sulfur crystallization in BD is essential for process optimization.

Purpose of the Study:

• To investigate a novel crystal agglomeration strategy for elemental sulfur (S) produced during biological desulfurization (BD).
• To elucidate the role of sulfide (HS⁻) and polysulfide (S²⁻) in sulfur crystal formation and morphology.
• To identify strategies for controlling sulfur particle size and improve settleability in BD.

Main Methods:

• Utilized a sulfide-rich, anoxic reactor to enhance nucleophilic dissolution of S by HS⁻ to S²⁻.
• Analyzed sulfur crystal size distribution and morphology using microscopy.
• Investigated the kinetics of sulfur formation from HS⁻ versus S²⁻.

Main Results:

• Enhanced S²⁻ formation led to uniformly sized sulfur crystal agglomerates (14.7 ± 3.1 μm).
• Minimal S²⁻ formation resulted in variable particle sizes (5.6 ± 5.9 μm) with both agglomerates and single crystals.
• Irregular agglomerates formed under enhanced S²⁻ conditions, attributed to disrupted crystal growth by (poly)sulfide dissolution.
• Sulfur formation from S²⁻ was approximately 5× faster than from HS⁻, promoting agglomeration.
• Sulfur crystal growth appeared to proceed via amorphous S globules.

Conclusions:

• The balance between sulfur dissolution and formation dictates the crystallization product in BD.
• Controlling S²⁻ formation is key to achieving uniform sulfur agglomerates and improving settleability.
• This strategy offers potential for preventing poor sulfur settleability in biological desulfurization processes.