Discusses cleaning up renewable natural gas from multiple sources to enable use for electricity production and transportation fuel use.

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Technologies
Processing 101: Gas Cleanup
Biogas to RNG Vehicle Fuelg
Jeff Cook
i @ iacrion@acrion.com

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Technologies
BioGas CompositionBioGas Composition
Digester and LFG
Methane (CH4) 45%- 65%
Carbon Dioxide(CO2) 30% -45%Carbon Dioxide(CO2) 30% 45%
Nitrogen (N2) 0% - 20%
Oxygen (O2) 0% - 2%Oxygen (O2) 0% 2%
Hydrogen Sulfide (H2S) from ppm’s to %’s
VOC’s (Si Cl F S) 100’s of ppm’sVOC s (Si,Cl,F,S) 100 s of ppm s
Water Saturated (2% to 6%)

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Technologies
These Aren’t Bank Deposits

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Technologies
CNG (gas @3600psi)
CARB
CNG
Pipeline Engine
Mf.
CH4 88% min # 65
CO2 1-2%CO2 1 2%
Inerts,
(N2,CO2)
1.5-4.5% 4% 16,100
BTU/lb LHV(N2,CO2) BTU/lb LHV
H2S 16 ppm 4 ppm
H2O Amb-10F 7 lb/MMscfO b 0
dew pt

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Technologies
LNG or LBM
Stored at BP of -260°F (-162°C)
Density 3 5 lb/galDensity 3.5 lb/gal
CO2 50 ppm
Water 1 ppm
Nitrogen 1%Nitrogen 1%

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TechnologiesLandfill LNG (-259°F)

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Technologies
Landfill Snow (d i 109°F)Landfill Snow (dry ice, -109°F)

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CO2 and VOC Removal Processes
• Condensation + Freezing of CO2
Membranes (CO2)• Membranes (CO2)
• Physical Absorption
• Chemical Absorption
• Pressure Swing Absorption (PSA)• Pressure Swing Absorption (PSA)
• Thermal Swing Absorption (TSA)

10. AcrionAcrion
Technologies CO2 Wash® Process
( ’ )
Refrigeration
CH4, CO2 (no VOC’s)
Refrigeration
Liquid CO2
(no VOC’s)(no VOC s)
Dry, Compressed Landfill Gas
with VOC’swith VOC s
Liquid CO2 and VOC’s

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Technologies
Membranes
Fast > Slow
H2>H2O>CO2>H2S>O2>N2 CH4H2>H2O>CO2>H2S>O2>N2,CH4
• Cellulose Acetate CO2/CH4=10
Spiral Wound Sheets
• Polyimide CO2/CH4=20• Polyimide CO2/CH4=20
Hollow Fiber,

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Technologies
Solvent Absorption
• PHYSICAL
Regeneration by Pressure Reduction,Regeneration by Pressure Reduction,
Vacuum and Stripping Gas
Water, Selexol, Methanol, ,
• CHEMICAL
Regeneration by Heating + Pressureg y g
Reduction
Amines (MEA)
Fouled by Oxygen and LFG Contaminants

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Technologies
Properties of Physical Solvents
Water Selexol MeOH
CO2 Solubility 0 56 3 63 13 5CO2 Solubility 0.56 3.63 13.5
V/V @T(C) 25 25 -25
CO2 CH4 14 3 15 2 19 6CO2:CH4 14.3 15.2 19.6
BP C 100 275 65
Sp Gr 1.0 1.03 0.79

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Solid Adsorption
• PSA (Pressure Swing)
Cycle time: 10’s of sec to 10’s ofCycle time: 10’s of sec. to 10’s of
min.
Vacuum Regeneration
• TSA (Thermal Swing)TSA (Thermal Swing)
Cycle time: hours
High temperature Regeneration

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Nitrogen Removal
• Address at Source ( e.g. Landfill)
PSA (N2 selective adsorbent)• PSA (N2 selective adsorbent)
• Cryogenic

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Conclusion
• All of the processes have been used
to produce RNG from biogasto produce RNG from biogas
• RNG Vehicle Fuel: high value
product
• Smaller Scale than Pipeline Projects

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LNG Fueling StationLNG Fueling Station