Biogas desulfurization using autotrophic denitrification process

Area of Science:

• Environmental Engineering
• Biotechnology
• Chemical Engineering

Background:

• Biogas production from chicken manure generates hydrogen sulfide (H2S), a corrosive and toxic gas.
• Effective biogas desulfurization is crucial for its utilization and environmental protection.
• Autotrophic denitrification offers a potential biological solution for H2S removal.

Purpose of the Study:

• To evaluate an autotrophic denitrification process for biogas desulfurization.
• To assess the performance of an upflow fixed bed reactor (UFBR) for sulfide removal.
• To compare the process using sodium sulfide versus H2S scrubbed from biogas.

Main Methods:

• A laboratory-scale UFBR was operated for 105 days.
• The reactor was fed with either sodium sulfide or H2S and nitrate.
• The sulfur to nitrogen (S/N) ratio was maintained at 2.5 mol/mol.

Main Results:

• Feeding with sodium sulfide at pH 7.7 achieved 95% sulfide and 90% nitrate removal but caused reactor clogging.
• Feeding with H2S scrubbed from biogas at pH 8-9 yielded 98% sulfide and 97% nitrate removal.
• H2S removal as elemental sulfur exceeded 95% without operational issues, allowing effluent reuse.

Conclusions:

• Autotrophic denitrification in an UFBR is effective for biogas desulfurization.
• Operating at a higher pH (8-9) with H2S scrubbing prevents elemental sulfur accumulation and clogging.
• This method enables efficient H2S removal and potential reuse of reactor effluent.