Landfill gas upgrading with countercurrent water wash

Area of Science:

• Chemical Engineering
• Environmental Science
• Renewable Energy

Background:

• Landfill gas (LFG) is a renewable energy source, primarily composed of methane and carbon dioxide.
• Upgrading LFG to a higher methane concentration is crucial for its utilization as a vehicle fuel.
• Conventional LFG upgrading processes often require high capital costs and specific operational parameters.

Purpose of the Study:

• To investigate a pilot-scale countercurrent absorption process for upgrading landfill gas.
• To evaluate the effectiveness of water as an absorbent under varied operational conditions.
• To determine optimal parameters for producing high-energy content gas suitable for vehicle fuel.

Main Methods:

• A pilot-scale countercurrent absorption and desorption system was employed.
• Water was used as the absorbent in an absorption column with a 3:1 height-to-diameter ratio.
• The effects of pressure (10-30 bar), gas flow rate (50-100 l/min), and water flow rate (5-10 l/min) were systematically studied.

Main Results:

• Methane content in the product gas reached over 90% under optimized conditions (e.g., >20 bar pressure with 10 l/min water flow, or 30 bar with 5 l/min water flow).
• Carbon dioxide content was reduced to 3.2%-4.8%, and nitrogen remained between 6%-7%.
• Hydrogen sulfide was effectively removed to below detection limits, and methane content in exhaust gas increased with pressure.

Conclusions:

• The pilot-scale gas upgrading process using countercurrent absorption with water is effective for producing high-energy content gas (>90% methane) from landfill gas.
• The process, utilizing a non-conventional column geometry and optimized pressure/flow rates, shows promise for producing viable vehicle fuel.
• Further optimization and scale-up could enhance the economic feasibility of landfill gas utilization.