Upgrading landfill gas using a high pressure water absorption process

The upgrading of landfill gas (methane 54.2 ± 2.0%, carbon dioxide 42.1 ± 2.4% and nitrogen 3.7 ± 1.2%) was studied with a pilot-scale high pressure water absorption system consisting of absorption, desorption and gas drying units. The gas was upgraded in two phases and with two absorption columns operating in sequence in pressures up to 180 bar, and with initial pressures of 8 and 10 bar. This type of high pressure process, where water is used for increasing the gas pressure, does not need a separate compression unit to produce the gas pressure required by gas vehicles. Product gas with a methane contents ranging from 83.0% to 92.1% was achieved with differing process parameters, the carbon dioxide and nitrogen content of the product gas ranged from 4.4% to 6.3% and 2.5% to 7.4%, respectively. Hydrogen sulphide was removed from the raw landfill gas with over 99% efficiency. To conclude the used high pressure gas absorption technique is capable for upgrading landfill gas to 87.9 ± 2.0% methane content.