Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 229

Bio-oxidation (biological oxidation) is one of the most used methods of desulfurization, based on injection of a small amount of air (2 to 8% v/v) into the raw gas stream. This way, the hydrogen sulfide is biologically oxidized either to solid free sulfur or to liquid sulfurous acid (H₂SO₃):

In practice, the precipitated sulfur is collected and added to the storage tanks where it is mixed with digestate, in order to improve the fertilizer properties of digestate. Biological desulfurization is frequently carried out inside the digester, and, for this kind of desulfurization, oxygen and Sulfobacter oxydans bacteria must be present, to convert hydrogen sulfide into elementary sulfur, in the presence of oxygen. Typically, Sulfobacter oxydans is present inside the digester (does not have to be added) as the anaerobic digester substrate contains the necessary nutrients for their metabolism. In the process, the air is injected directly in the headspace of the digester and the reactions occur in the reactor headspace, on the floating layer (if existing) and on reactor walls. Due to the acidic nature of the products, there is the risk of corrosion. The process is dependent of the existence of a stable floating layer inside the digester, and the process often takes place in a separate reactor.

Chemical desulfurization of gas streams can take place outside of digester, using a base (usually sodium hydroxide). Another chemical method to reduce the content of hydrogen sulfide is to add commercial ferrous solution (Fe²⁺) to the feedstock. Ferrous compounds bind sulfur in an insoluble compound in the liquid phase, thereby preventing the production of gaseous hydrogen sulfide.

See also: Biofiltration, Bioscrubbing, Gas Cleaning – Biological Methods Gas Processing, Gas Treating.