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Absorption of a water solution in sodium hydroxide enhances the water’s absorption. Sodium hydroxide reacts with hydrogen sulphide to form sodium sulphide or sodium hydrogen sulphide. Both are insoluble, and this method is not generative.
Scrubbing is considered to be more suitable process that can also be used for the selective removal of hydrogen sulphide.Scrubbing is considered for the simultaneous carbon dioxide and hydrogen sulphide removal in order to meet the fuel demand for biogas quality.
Methane is an inflammable gas: A common gas compressor poses fire hazards, since the auto-ignition temperature of biogas is 537 °C. Leakage and excessive temperature rise can be fatal. Hermetically sealed reciprocating compressors can be used, but they need extensive cooling systems.
Due care during operation must be done so as not to allow the temperature to rise above safe limits.
Low-Pressure Storage of Biogas :Floating gas holders on the digester form a low-pressure storage option for biogas systems. These systems typically operate at pressures up to 10-inch water column (less than 2 psi).
Floating gas holders can be made of steel, fiberglass, or a flexible fabric.
A separate tank may be used with a floating gas holder for the storage of the digestate and also storage of the raw biogas.
Medium-Pressure Storage of Cleaned Biogas
Biogas can also be stored at medium pressure between 2 and 200 psi.
To prevent corrosion of the tank components and to ensure safe operation, the biogas must first be cleaned by removing H2S.
Next, the cleaned biogas must be slightly compressed prior to storage in tanks.
