1. Model

2. Advantages of Biological desulfurization

• No chemicals
• High efficiency on H2S removal
• Low operational costs
• 
  Efficiency and safety

3 The main reactions

1:H2S+2O2= H2SO4

2:H2S+1⁄2O2 =S+H2O

4.The Basic Process

The biogas and air are mixed with packing media flowing in a counter current with circulating water in a vertical column. The pack- ing media enlarges the contact surface area between the H2S in the gas flow, the nutrients in the water and the oxygen, also acting as a carrier for the bacteria. When limited quantities of oxygen are added to the biogas, specific aerobic bacteria such as Acidothiobacillus oxidise H2S into elemental sulphur and/or sulphuric acid (dependent on the environ- mental condition and oxygen concentration.) Oxygen is added to the gas as compressed air with an automatic control system adjusting the air flow in correlation with the biogas flow and oxygen concentration. Water and nutrients are automatically refreshed and sprayed on top of the media as required and heat can be added into the water circulation loop via a heat- exchanger to create the optimum temperature for the biological process.