Process phase separation for methane enrichment

Report
PROCESS PHASE SEPARATION FOR
METHANE ENRICHMENT
using microorganisms
abilities for biogas upgrading
Flensburg, 12.09.2013
Torsten Stefan, B.Sc. Bioprocess Eng.
2
Table of Contents
1.
2.
3.
4.
5.
6.
Motivation
Idea and Theory
Experiments
Results
Future aspects
Summary
3
Motivation
component
formula
heat of
combustion
[kJ/Nm³]
Typical
fraction in
biogas [%]
methane
CH4
39819
45-70
hydrogensulfide
H2S
25336
<0,5
ammonia
NH3
17177
<0,001
hydrogen
H2
12750
0-1
carbon dioxide
CO2
0
25-55
Water
H2O
0
0-10
4
Separation of CO2 and CH4 mixtures
• Water or polyglycol scrubbers
• Amine scrubbers
• Membrane systems
• Cryogenic processes
Economically feasable in large scale (>1 MWel)
5
Biogas process
Polymeric molecules
Hydrolysis
Monomers
Acidogenesis
CO2, H2
H2S, NH3,
N2
Volatile fatty
acids
Acetogenesis
CO2, H2
Formic/acetic acid,
CO2, H2
digestate
Methanogenesis
CO2, CH4
6
Hydrolysis
Pictures:chemienet.info
7
Acidogenesis
  
→  ( )  +   +  
 
 
    →    +    +    +  
 
 
  
 
→   ()
 
 
  
→   
 
  
 
  
 
 
→    +   +  
 
→     +   +   

8
Acetogenesis
   +  +    →    + 
 
 
 ( )  +    →    + 
 
 
   +    →   +   + 
 
 
 () +   →   +   + 
 
 
   →   + 

 
9
Methanogenesis
  →  + 
  +    →   +  
 +   →  +  
  →  +   +   
 
   →   +  +   

10
Polymeric molecules
Biogas process
Gas Hydrolysis
composition
Intermediate
methane [%] Monomers
Carbon dioxide [%]
Formic acid
25
Acetic acid
50
75
Propionic acid
58,3
Butyric acid
62,5 Volatile fatty
41,7
acids
Valeric acid
65
Lactic acid
50
Ethanol
75
digestate
50
Acidogenesis
CO2, H2
H2S, NH3,
N2
37,5
35
Acetogenesis
Formic/acetic acid,
CO2, H2
Methanogenesis
50
CO2, H2
25
CO2, CH4
11
CO2 solubility in water
physical
chemical
CO2 solubility in water, 38°C
CO2 solubility in water, 38°C,
p(CO2)=0,3 bar
0.35
0.025
0.30
chem. Solubility [mol/L]
phy. Solubility [mol/L]
0.020
0.015
0.010
0.005
0.25
0.20
0.15
0.10
0.05
0.000
0.00
0
0.2
0.4
0.6
p(CO2) [bar]
0.8
1
3
4
5
6
pH [1]
7
8
9
12
Biogas process
Polymeric molecules
Hydrolysis
Monomers
Acidogenesis
CO2, H2
H2S, NH3,
N2
Volatile fatty
acids
Acetogenesis
CO2, H2
Formic/acetic acid,
CO2, H2
digestate
Methanogenesis
CO2, CH4
13
Experiments
14
Results
Substrate: Sugar-Cellulose-Mixture
15
Results
Substrate: Sour cheese whey
16
Results
Substrate: Pig-Manure
17
Results from Literature
Substrate: Soybean Processing Wastewater
Resource: Zhu, G.F. ; Li, J.Z. ; Wu, P. ; Jin, H.Z. ; Wang, Z.: The performance and phase separated characteristics of an
anaerobic baffled reactor treating soybean protein processing wastewater. In:Bioresource technology 99 (2008), Nr. 17, S.
8027–8033
18
Next steps
• Examine mixtures of manure and souring substrates
• Investigate semi-aerobic hydrolysis
• Upscaling to 200 L / 2 m³
• Proove applicability to STR cascades
19
Summary
• Phase separation uses natural sequenced biogas process for
•
•
•
•
•
methane enrichment
Methane fraction up to 85%
Relatively simple and cheap technology
Enhances energy storage capacity through higher methane
content
Applicable to STR cascades
Problems: slowly hydrolysible substrates and substrates with
high alkalinity in mono-fermentation

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