Powdery desulphurization substance for binding hydrogen sulfide in biogas plants
General
Production and use of biogas became more important since the implementation of the “Renewable Energy Sources Act” (EEG). Biogas is produced by anaerobic conversion of biomass. In addition to the main components methane and carbon dioxide biogas often contains hydrogen sulfide which has to be removed before use to prevent odor and corrosion problems. Different desulphurization technologies can be applied such as the dosage of oxygen, the addition of iron salts, subsequent removal with fixed-bed absorbers based on iron hydroxide, flue gas scrubber or biological oxidation of hydrogen sulfide.
Das Problem
The dosage of aerial oxygen into the fermentation chamber often has only minor effect on the formation of hydrogen sulfide but leads to a dilution of the biogas and thus to a reduced calorific value. On the other hand downstream desulfurization technologies require high capital investment. Furthermore the formation for hydrogen sulfide in the bioreactor is not prevented although the inhibiting effect of this gas on methane production is well known. The dosage of highly acidic iron salts leads to precipitation of sulfide. The disadvantages of this method are the reduction of the buffering capacity of the fermentation substrate and the requirements for storage and handling of iron salts due to their water hazard class restrictions.
The solution
Specifically to solve the problems mentioned above HeGo Biotec GmbH developed a desulfurization reagent based on iron hydroxide. The precipitation of hydrogen sulfide in the fermenter can be described by the following chemical reaction:
Procedure
Microscopic view of methanosarcina acetivorans
The iron hydroxide contained in FerroSorp® DG binds the hydrogen sulfide immediately during formation. In a first reaction the trivalent iron is reduced under anaerobic conditions to divalent iron. Thereby hydrogen sulfide can already be oxidized to elemental sulfur. In a subsequent reaction divalent iron reacts with hydrogen sulfide forming finely dispersed iron sulfide which is reflected in a blackening of the fermenting residue. Using FerroSorp® DG no additional anions are introduced into the substrate. The in FerroSorp® DG contained calcium compounds increase the buffer capacity of the fermentation substrate and thus counteract acidification.
Coprecipitation of trace elements with hydrogen sulfide is reliably prevented. Thus methanogenesis can proceed uninhibited resulting in optimal biogas yield and high methane levels.
Application
FerroSorp® DG can be added easily to the fermenting substrate in the receiving station. FerroSorp® DG is classified as “not hazardous to waters”. Due to its chemical properties it can be considered as safe. There are no specific regulations concerning storage and handling of FerroSorp® DG.
Advantages at a glance
- Highly active reagent for hydrogen precipitation in biogas plants
- Optimum yield of biogas with high methane content
- Effective protection against acidification of the fermenting substrate by increasing the buffer capacity
- Cost effective compared to downstream hydrogen sulfide removal techniques due to higher biogas yield.
- Easy to apply
- No increase in salinity of the fermenting substrate
- No impairment of the fermenting residue considering material recycling and waste management
Brochure FerroSorp® DG [75 KB]