Dry Desulfurization Tower

The most commonly used dry desulfurization method is iron oxide desulfurization. Hydrogen sulfide in biogas is removed through chemical reactions on the surface of solid iron oxide. The lower the flow rate of biogas in the desulfurization tower and the longer the contact time, the more thorough the reaction will be. At normal temperature, biogas passes through the desulfurizer bed. The hydrogen sulfide in the biogas reacts with active iron oxide. Then, the desulfurizer containing sulfides comes into contact with the oxygen in the biogas. When water is present, the iron sulfides are converted back into iron oxide and elemental sulfur. This desulfurization regeneration process can be repeated multiple times until most of the pores on the surface of the iron oxide desulfurizer are covered with sulfur or other impurities and lose their activity. After a period of use, the desulfurizer needs to be replaced. The ineffective desulfurizer that has been replaced can be regenerated.

The desulfurization reaction is:

Fe2O3·H2O+3H2S→Fe2S3·H2O+3H2O

The regeneration reaction is:

Fe2S3·H2O+1.5O2→Fe2O3·H2O+3S

The regenerated desulfurizer can still be used, but the regeneration reaction is slower than the desulfurization reaction. In order to ensure the full regeneration of the desulfurizer, the above two processes are often carried out separately in engineering practice.