Biomethane upgrading from biogas
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Biomethane – upgrading from biogas
Presenter: Lê Khắc Duyên
Ho Chi Minh city University of Technology (HCMUT)
Contents
2
1. Introduction and overview
2. Biogas upgrading technologies
3. Costs of biogas upgrading
4. Conclusions
Introduction and overview
3
Biomethane
AdvantagesDefinition
Producing
Application
s
Introduction and overview
4
Definition of biomethane
Biomethane is biogas that has been upgraded to around 95%
methane
Green gas
Advantages of biomethane
Local and temporal decoupling of production and utilization
Storage capability
Flexibility regarding several utilization paths: electricity (combined
with full utilization of heat); heat (combined with power or in
natural gas burners); vehicle fuel (for natural gas vehicles); and
primary product for the chemicals industry
Introduction and overview
5
Producing biomethane
Sewage waste
Agricultural manures
Food waste from domestic or commercial premises
Garden or horticultural wastes
Three stages to the production of biomethane
Pre-treatment
Digestion
Upgrading
Holsworthy biogas plant in
Devon in the UK
Introduction and overview
6
Applications of biomethane
Electricity (combined with full utilization of heat)
Heat (combined with power or in natural gas burners)
Vehicle fuel (for natural gas vehicles)
Primary product for the chemicals industry
Usage of biogas (Source: Tragner et al. 2008)
Introduction and overview
7
Introduction and overview
8
Overview of numbers of plants and raw biogas upgrading capacities in
Europe as of December 2011 (Copyright: Fraunhofer IWES, 2012)
Introduction and overview
9
Upgrading capacity of European biogas upgrading plants in the period
1987–2011 related to raw biogas (Copyright: Fraunhofer IWES, 2012)
Biogas upgrading technologies
10
Typical composition of biogas [1]
Component Chemical symbol Concentration
Methane CH4 50 – 70 %-vol
Carbon dioxide CO2 25 – 45 %-vol
Water vapour H2O 2 – 7 %-vol
Oxygen O2 <2 %-vol
Nitrogen N2 <2 %-vol
Ammonia NH3 <1 %-vol
Hydrogen H2 <1 %-vol
Hydrogen sulphide H2S 20 – 20000 ppm
ppm – parts per million; %-vol – Volumetric percentage
Biogas upgrading technologies
11
Basic flow diagram of biogas upgrading
Biogas upgrading technologies
12
Overview of possible biogas upgrading
technologies for CO2 removal
(Copyright: Fraunhofer IWES, 2012)
Biogas upgrading technologies
13
Schematic illustration of different combinations of biogas cleaning processes
and biogas upgrading processes (adapted from Schmuderer, 2010)
Pressure swing adsorption (PSA)
14
Process scheme of the pressure swing adsorption process
(Copyright: Fraunhofer IWES, 2012)
Pressure swing adsorption (PSA)
15
Using activated carbon, zeolites or carbon molecular sieves
Low temperatures (5 to 35oC) and high pressures (4 to 7 bar)
Besides CO2, other molecules such as H2S, NH3 and H2O can be co-adsorbed
H2O and H2S are removed before
Methane concentrations in the biomethane flow are >96%
The electricity demand varies from 0.16 to 0.35 kWhel/mn3 raw gas
One plant operator reported an average specific electricity demand of 0.23
kWhel/mn3 for an operation pressure of 5.4 bar, methane concentrations in the
product gas of 96–97%
Pressure swing adsorption (PSA)
16
Pressure swing adsorption plant (copyright: Fraunhofer IWES)
Water scrubber
17
Process scheme of water scrubber process (Copyright: Fraunhofer IWES, 2012)
Water scrubber
18
Based on the reversible absorption by physical bonding
forces (van der waals force)
Low temperatures (5–10oC) and high pressures (4–8 bar)
CO2 and other acidic (e.g. H2S) and basic (e.g. NH3) gas
components are absorbed
Methane concentrations in the biomethane flow are
>96%
The electricity demand of the process varies from 0.20 to
0.30 kwhel/mn3 raw gas
Water scrubber
19
Water scrubber plant (Copyright: Fraunhofer IWES)
Physical absorption by organic solvents
20
Process scheme of physical absorption (using organic solvents)
(Copyright: Fraunhofer IWES, 2012)
Physical absorption by organic solvents
21
Increased absorption rates for CO2
The parallel absorption of CO2, H2S and H2O
Pressure of~6–7 bar, temperature of 10–20oC
CH4 concentrations in the product gas flow are in the
range 93–98%
The electricity demand varies from 0.23 to 0.33
kWhel/mn3 raw biogas
Solubility in cmn3 /(gbar) of selected gases at 25oC in tetraethylene glycol dimethyl
ether (Genosorb® 1753)
Physical absorption by organic solvents
22
Genosorb® scrubber plant (Copyright: Fraunhofer IWES)
Chemical absorption by organic solvents
23
Process scheme of chemical absorption (using organic solvents)
(Copyright: Fraunhofer IWES, 2012)
Chemical absorption by organic solvents
24
CO2 and H2S are chemically bound to an organic
scrubbing agent
Alkanolamine solutions: monoethanolamine (MEA),
diethanolamine (DEA), methyldiethanolamine (MDEA),…
Pressure (~50–150 mbar), temperatures from 106 to
160oC
Methane concentrations in the product gas flow are~99%
The electricity demand varies from 0.06 to 0.17
kwhel/mn3 related to raw biogas
Chemical absorption by organic solvents
25
Amine scrubber plant (Copyright: Fraunhofer IWES)
