Pyramid Resource Center-Green Energy Center

Flory, Paul, D.

Solid Waste Authority of Central Ohio (SWACO)

关键词: Natural Gas;    Methane;    Combustion;    Decay;    Oxygen;   

DOI  :  10.2172/1023754
RP-ID  :  DOE/06GO86012
RP-ID  :  FG36-06GO86012
RP-ID  :  1023754

美国|英语

来源: UNT Digital Library

【 摘 要 】

There are currently over 3,500 USA/Canadian landfills listed by the EPA/EC and like numbers in Europe that are producing methane-rich landfill gas (LFG). This gas is typically made up of 50-percent methane (CH4), 35-percent carbon dioxide (CO2), and 2 to 25% nitrogen and oxygen (N2 & O2), plus dozens of dilute contaminants. LFG is classified as a renewable fuel, because it is generated via biological decay of municipal solid waste, a constant byproduct of human activity. To date, most LFG has been allowed to escape into the atmosphere. On account of its high CH4 content, LFG may contribute to climate change, as CH4 is one of the most harmful greenhouse gases with 21 times the global warming potential of CO2. Of the landfills that collect LFG, most simply flare it. In the past decade, some landfills have begun to use LFG for electricity generation or for direct combustion as low Btu gas. Very few landfills upgrade LFG to high Btu gas. A patented CO2 WashTM process developed by Acrion Technologies Inc., and licensed to Firm Green Inc. shows promise as an economically and environmentally sustainable process to recover energy and prevent pollution from landfills. The CO2 WashTM has already been proven at lab-scale. It upgrades LFG, which consists of 50% methane (CH4) + 35% carbon dioxide (CO2) + 2 to 25% nitrogen + oxygen (N2+O2), 1 to 2% water vapor, and dozens of contaminants (which total a few hundred to a few thousand parts per million). CH4, which by itself has an energy content of 1,012 British thermal units (Btu) per standard cubic foot (SCF), is the only component in LFG that contributes to its energy content, which is therefore about 400-550 Btu/SCF. Accordingly, raw LFG is usually referred to as medium-Btu gas. To be salable, it is necessary to remove essentially all the components besides CH4, while keeping the vast majority of the revenue producing CH4. This is high-Btu gas, yielding 850 to 1,000 Btu/SCF. The CO2 WashTM process upgrades LFG to about 930 Btu/SCF, and reduces the contaminants to levels that make it salable as a vehicle fuel in the form of compressed natural gas (CNG).