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Keywords:

  • mass transfer;
  • biogas desulfurization;
  • biotrickling filters;
  • jet-venturi;
  • venturi ejector;
  • diffuser

Abstract

BACKGROUND: Dissolved oxygen is a key parameter in the biological removal of gaseous H2S since sulfide-oxidizing bacteria convert H2S into elemental sulfur instead of sulfate under limiting dissolved oxygen concentrations. Elemental sulfur is insoluble in water and accumulates in the packing material in biotrickling filters, increasing the pressure drop and operating costs. A set of mass transfer tests was performed in a versatile pilot plant to supply the necessary oxygen for the biological oxidation of H2S. The plant can be operated with three different commercial gas–liquid contactor devices: a venturi ejector, a jet-venturi and a diffuser. The effects of different geometric and operating parameters have been tested for each device (including pressure rise and sulfate content to mimic real wastewater treatment plant conditions).

RESULTS: Results showed that the bioreactor pressure has a strong influence on the mass transfer characteristics of the three oxygenation devices. In addition, the ionic strength of the solution has a low influence on the mass transfer process.

The SOTE values obtained for the diffuser, jet-venturi and venturi ejector were 8.7%, 7.2% and 6.0%, respectively (pure water experiments), while SAE values were in the range 6.3–5.5 × 10−2, 4.1–4.8 × 10−1 and 3.1–3.7 × 10−1 kg O2 kW−1 h−1, respectively.

CONCLUSIONS: The jet-venturi offers the best oxygen transfer with lower power consumption compared with the diffuser and venturi ejector. The practical implementation of the most efficient aeration technology is possible from both technical and economical perspectives. Copyright © 2012 Society of Chemical Industry