hydrogen sulphide which gets adsorbed cannot be subjected to recycling, and so, it
must be removed before the addition of biogas into the column (Zhao et al. 2010).
Low energy requirement, ease of operation, equipment compactness and low investment cost are the major advantages of this method (Augelletti et al. 2017). About
96–98% methane is generated, and about 4% is lost in the off-gas (Bauer et al.
2013a; Ryckebosch et al. 2011; Angelidaki et al. 2018).
Pressure swing adsorption technology is advantageous only if:
• The plant capacity is small/medium.
• No compression is required.
• Recovered methane is utilised for other purposes (Report 2012).
9.3.4 Membrane Separation Methods
Membrane separation methods are developed for landfill gas upgrading. It is based
on the property of permeability of the membranes that are mostly made of polymeric
materials such as cellulose acetate (Baker 2012)/polyimide/polysulfone/
polydimethylsiloxane (Report 2012). Membrane selection is very important for
separation efficiency. The membranes are stacked like hollow fibres. Through the
membranes, water, carbon dioxide and ammonia are highly permeable, oxygen and
hydrogen sulphide are moderately permeable, and methane and nitrogen are slightly
permeable. The penetration of the gas is based on the concentration gradient of
permeate, its chemical affinity and the size of the molecules (Petersson and
Wellinger 2009). The transport of the gases takes place during the generation of
pressure differences on both sides of the membranes (Scholz et al. 2013).
Membrane separation method process can be done in two ways: dry (gas/gas
separation) or wet (gas/liquid separation). In dry process, mainly polymeric
membranes are used for high specificity, and the rate of permeation depends upon
the membrane type and sorption coefficient (Baker 2012). The sorption coefficient is
based on the condensability of the molecules. Large molecules are highly condensable. Moreover, the methane gets attached to the membrane side. There are four
types of configurations in the dry method. They are two-stage with a recirculation
loop, single stage, three-stage with sweep biogas stream and two-stage with sweep
biogas stream (Makaruk et al. 2010). In wet process, the membrane separates the
liquid, and the gas feed and the gas molecules undergo diffusion process (Angelidaki
et al. 2018).
The advantages of membrane technology include requirement of low skilled
labour and less maintenance, and the disadvantages include high membrane cost,
membrane damage and degradation (Scholz et al. 2013).
Membrane technology is advantageous only if:
• It adapts the flexible partial load behaviour.
• The methane can be reutilised.
• It adapts to small or medium plant capacity.
252
B. S. Dhanya et al.
must be removed before the addition of biogas into the column (Zhao et al. 2010).
Low energy requirement, ease of operation, equipment compactness and low investment cost are the major advantages of this method (Augelletti et al. 2017). About
96–98% methane is generated, and about 4% is lost in the off-gas (Bauer et al.
2013a; Ryckebosch et al. 2011; Angelidaki et al. 2018).
Pressure swing adsorption technology is advantageous only if:
• The plant capacity is small/medium.
• No compression is required.
• Recovered methane is utilised for other purposes (Report 2012).
9.3.4 Membrane Separation Methods
Membrane separation methods are developed for landfill gas upgrading. It is based
on the property of permeability of the membranes that are mostly made of polymeric
materials such as cellulose acetate (Baker 2012)/polyimide/polysulfone/
polydimethylsiloxane (Report 2012). Membrane selection is very important for
separation efficiency. The membranes are stacked like hollow fibres. Through the
membranes, water, carbon dioxide and ammonia are highly permeable, oxygen and
hydrogen sulphide are moderately permeable, and methane and nitrogen are slightly
permeable. The penetration of the gas is based on the concentration gradient of
permeate, its chemical affinity and the size of the molecules (Petersson and
Wellinger 2009). The transport of the gases takes place during the generation of
pressure differences on both sides of the membranes (Scholz et al. 2013).
Membrane separation method process can be done in two ways: dry (gas/gas
separation) or wet (gas/liquid separation). In dry process, mainly polymeric
membranes are used for high specificity, and the rate of permeation depends upon
the membrane type and sorption coefficient (Baker 2012). The sorption coefficient is
based on the condensability of the molecules. Large molecules are highly condensable. Moreover, the methane gets attached to the membrane side. There are four
types of configurations in the dry method. They are two-stage with a recirculation
loop, single stage, three-stage with sweep biogas stream and two-stage with sweep
biogas stream (Makaruk et al. 2010). In wet process, the membrane separates the
liquid, and the gas feed and the gas molecules undergo diffusion process (Angelidaki
et al. 2018).
The advantages of membrane technology include requirement of low skilled
labour and less maintenance, and the disadvantages include high membrane cost,
membrane damage and degradation (Scholz et al. 2013).
Membrane technology is advantageous only if:
• It adapts the flexible partial load behaviour.
• The methane can be reutilised.
• It adapts to small or medium plant capacity.
252
B. S. Dhanya et al.