Biogas Plants upgrading

• Air Products’ PRISM separators use proprietary hollow fiber membranes to selectively remove unwanted elements from biogas streams produced during the anaerobic digestion process. Thousands of tiny hollow fibers are spun from polymers in our state-of-the art production facility and assembled into durable and lightweight aluminum casings.
• When biogas is fed into the membrane separator under pressure, the unwanted gas molecules are selectively removed. This results in a purified stream of biomethane which is ready for industrial use and does not require secondary chemical scrubbing solutions.

Equipment List

PRISM membrane options for biogas upgrading

High methane recovery configuration

		Raw biogas IN	Biomethane OUT	Vent
Composition
Methane	mol%	55.0	98.0	0.3
Carbon Dioxide	mol%	45.0	2.0	99.7
Flow PB6050P3	nm³/hr	60.0	33.6	26.4
Flow PB4050P3	nm³/hr	23.0	13.0	10.0
Flow PB4030P3	nm³/hr	13.8	7.8	6.0
Pressure	barg	12.0	11.8	0.0

Power = 0.22 kW/nm³/hr raw biogas

Methane recovery = 99.8%

Low power configuration

		Raw biogas IN	Biomethane OUT	Vent
Composition
Methane	mol%	55.0	98.0	0.3
Carbon Dioxide	mol%	45.0	2.0	99.7
Flow PB6050P3	nm³/hr	120.0	63.3	56.7
Flow PB4050P3	nm³/hr	46.4	24.4	21.9
Flow PB4030P3	nm³/hr	28.0	14.7	13.2
Pressure	barg	12.0	11.8	0.0

Power = 0.15 kW/nm³/hr raw biogas

Methane recovery = 94%

Low capital configuration

		Raw biogas IN	Biomethane OUT	Vent
Composition
Methane	mol%	55.0	98.0	0.3
Carbon Dioxide	mol%	45.0	2.0	99.7
Flow PB6050P3	nm³/hr	350	176.8	173.2
Flow PB4050P3	nm³/hr	135.5	68.5	67.0
Flow PB4030P3	nm³/hr	81.6	41.2	40.4
Pressure	barg	12.0	11.8	0.0

Power = 0.17 kW/nm³/hr raw biogas

Methane recovery = 90%

Two stage system example

Biogas upgrading overview

Biogas is the production of methane from anaerobic digestion of farm wastes, manure, or municipal waste. Biogas contains high concentrations of carbon dioxide, hydrogen sulfide, and other impurities which need to be removed to make the methane commercially viable. The purified biomethane is used to generate heat and power, compressed for powering vehicles, or fed directly into the natural gas grid for resale.

PRISM® Membrane Separators for biogas upgrading (1).jpg

Competing technologies

The primary objectives of biogas upgrading systems are to remove carbon dioxide, hydrogen sulfide, water vapor, and oxygen. Membrane technology is one of several ways to separate methane from a biogas stream and each technology has distinct advantages and disadvantages.

Operations which have access to copious water, like a publicly owned treatment facility, may consider a water scrubbing tower as a viable technology. Alternatively, facilities with less access to water and limited capital resources, may find water scrubbing outside the scope of their project. This table lists some of the characteristics from different upgrading technologies.