Anoxic biogas biodesulfurization promoting elemental sulfur production in a Continuous Stirred Tank Bioreactor

Biological desulfurization of biogas has been extensively studied using biotrickling filters (BTFs). However, the accumulation of elemental sulfur (S) on the packing material limits the use of this technology. To overcome this issue, the use of a continuous stirred tank bioreactor (CSTBR) under anoxic conditions for biogas desulfurization and S production is proposed in the present study. The effect of the main parameters (stirring speed, N/S molar ratio, hydraulic residence time (HRT) and gas residence time (GRT)) on the bioreactor performance was studied. Under an inlet load (IL) of 100 g S-H2S m(-3) h(-1) and a GRT of 119 s, the CSTBR optimal operating conditions were 60 rpm, N/S molar ratio of 1.1 and a HRT of 42 h, in which a removal efficiency (RE) and S production of 98.6 +/- 0.4 % and 88 % were obtained, respectively. Under a GRT of 41 s and an IL of 232 g S-H2S m(-3) h(-1) the maximum elimination capacity (EC) of 166.0 +/- 7.2 g S-H2S m(-3) h(-1) (RE = 71.7 +/- 3.1 %) was obtained. A proportional-integral feedback control strategy was successfully applied to the bioreactor operated under a stepped variable IL.

Automated summary

The use of a continuous stirred tank bioreactor (CSTBR) under anoxic conditions for biogas desulfurization and S production was proposed. The optimal operating conditions were determined, resulting in high removal efficiency and sulfur production rates.