Landfill Gas Treatment

More than 100 nonmethane organic compounds (NMOCs) have been identified in the landfill gas (LFG) so far. Specific contaminants which present a hindrance to the LFG utilization for energy production, are hydrogen sulfide, hydrogen halides, and silicon containing compounds. During the combustion process, hydrogen sulfide and halogenated compounds form corrosive acids like H₂SO₃, HCl, and HF. The silicon containing compounds, like volatile methylsiloxanes, are converted into silicates and micro-crystalline quartz dust, which are both sources of PM 2.5 air pollution. In some instances, these particles build-up in the boiler tubes and combustion chambers, causing equipment failures and necessitating increased maintenance. There is a need to remove these contaminants before one can utilize the LFG. Traditionally trace constituents in landfill gas are removed by adsorption or absorption techniques. The adsorption system normally consists of a dehydration process and a series of adsorbent beds. The adsorbents used to remove gaseous contaminants typically include activated carbon and silica gel. Another approach for the removal of gaseous siloxanes is physical absorption using high boiling organic solvents. Installations for NMOCs absorption include both spraying towers and packed columns. This approach is based on the ability of one compound to solubilize another compound.