Currently there are different technologies for removing siloxanes from biogas systems: subcooling, adsorption on activated carbon/silica gel, graphite filters, certain types of resins and washing with certain reagents (e.g. methanol, sulfuric acid and hydrocarbon mixtures). Of these technologies, activated carbon appears to be among the most dominant in the industry.
The system consists of a minimum of two towers in series configuration, each having a bed of activated carbon. The gas travels through the carbon bed from bottom to top. Pressure drop through the bed and outlet concentrations are monitored to alert to a change in performance signaling the need to replace the carbon. The removal of water and VOC’s from biogas prior to an activated carbon unit significantly increases the activated carbon life and the system performance.