Combined H2S and CO2 removal process for upgrading biogas
ESR 4.1 : Keren Jenifer Rajavelu
Supervisor : Prof. Dr. Martin Denecke
Natural Gas
Heating value = 39
CH4 = 85 - 95 % (mol)
CO2 = 0.2 - 1.5 % (mol)
H20 = 0
H2S = 1.1 to 5.0 ppm
Biogas from AD
Heating value = 23
CH4 = 60 - 70 % (mol)
CO2 = 30 - 40 % (mol)
H20 = 1 - 5 % (mol)
H2S = 0 - 4000 ppm
Growth of biogas
industry 25% renewable
energy target
Upgrading biogas from AD – What makes the
difference?
Corrosion in engines and
pipelines, extremely toxic
Constant increase in
global average
concentration of CO2 in
earth's atmosphere !!
Research Aim
Basic concept Material and Methods Results
This presentation covers
Research aim and Structure of presentation
• Development of energy efficient,
scalable processes for hydrogen
sulphide H2S and CO2 removal
• Testing of individual lab scale reactor
for both processes
• Combination, optimization and
interaction of two process
The main reaction principle involved
H2S + ½ O2 Sº + H2O
Reference Bacterial
species
Source of
energy
Electron
acceptor
Process
of
removal
Kim and
Chang et al.,
1991
Chlorobium
limicola
light CO2 anaerobic
Alcantata et
al., 2004
Thiobacillus Sulphur CO2 aerobic
Lee et al.,
1993
Acidithiobacill
us thiooxidans
Sulphur CO2 aerobic
Ma et al.,
2006
Thiobacillus
denitrificans
Sulphur or
thiosulphide
nitrate aerobic
Gadekar et
al., 2006
Thiomicrospor
a sp.
Carbon
source
nitrate anaerobic
Cardoso et
al., 2010
Thiobacillus
denitrificans
Sulphur or
thiosulphide
nitrate anaerobic
Son et
al.,2005
Acidithiobacill
us
ferrooxidans
Sulphur iron aerobic
Biological desulphurization of biogas or
H2S removal
FISH analysis using alpha –
proteobacteria probe showed more
stable population of sulphur oxidizing
bacteria
Design of biotrickling filter system for H2S removal
Design of reactor
(scrubbing column)
Design of other
components parts
(aeration column, piping
and hosing etc)
Design of
alarm system
Monitoring of
parameters automated
and manually
Parameter Unit Current
design
Clean gas concentration mg/m3 <10
Raw gas concentration g/m3 1000
Height of carrier material h
Column ratio h:d
m 0.6 m
>3/1
Pressure loss Pa/m
Gas flow rate Q m3/h 0.02 to 0.08
Retention time S 12 s – 150 s
Volume of trickle bed m3 0.0007
Design according to guideline VDI 3478 part 2
Results
Experimental conditions
Experiment [H2S]
ppm
[H2S] LR
(g S- H2S m-3.h-
1)
EBRT
(s)
1 1000 14.285 250
2 1000 28.571 126
3 1000 57.428 62
4 1000 85.713 43
Effect of EBRT, RE and Dissolved oxygen
during initial operation
RE = [(Cin – Cout)] * 100
RE
Removal efficiency
V
Reactor bed volume m3
Cin
pollutant inlet
concentration
g pollutant. m-3
Cout
pollutant outlet
concentration
g pollutant. m-3
Results
LR = [(Q biogas + Q Air IN . CIN] / V
LR Loading Rate g pollutant .m-
3.h-1
Q biogas+Q
Air IN
Total gas flow
rate
CIN Pollutant inlet
concentration
g pollutant .m -3
V Reactor bed
volume
m3
EBRT = V / (Q biogas + Q Air IN)
EBRT empty bed
residence time
S
V Reactor bed
volume
m3
Q biogas
+ Q Air IN
Total gas flow
rate
g pollutant .m -3
EC and RE versus H2S loading rate (LR)
Design of CO2 absorption with bottom ash
Design of absorption
reactor (better the
width, lower is the
pressure drop)
Feed in of bottom
ash with different
size fractions
Study of absorption
capacity
Experimental set up for CO2 removal using bottom ash
Results
Experimental conditions
Test no 1 2 3 4 5 6 7
Grain size 0 – 1
mm
0 – 1
mm
0 – 1 mm 0 – 2
mm
0 –
2mm
0 – 2
mm
0 – 1
mm
Liquid /Solid
ratio
0.05 0.1 0.2 0.4 0.2 0.2 0.2
Bottom ash (g) 400 400 400 300 300 200 10
Flow rate
(ml/min)
10 10 10 500 90 500 60
Gas
composition
(v%)
99.8 99.8 99.8 99.8 99.8 99.8 99.8
Breakthrough
time (min)
60 60 40 - 10 - -
CO2 uptake
(g/kg of
Bottom ash)
10.96 14.56
12.63 - - - -
pH 9.2 9.1 9.2 - - - -
High absorption capacity
pH of noncarbonated
bottom ash showed
11.2
Results
Breathrough curve of CO2 with bottom
ash
Comparison of CO2 absorption with
different L/s ratio
high absorption of CO2
Test no 1 2 3
Initial bottom ash
mass (g of WS)
423.60 436.84 476.02
Final bottom ash
mass (g of WS)
428.12 442.07 479.95
CO2 fixation using
mass balance
(g/400g of BA)
4.52 5.23 3.93
CO2 fixation using
gas analysis and
flow (g/400g of BA)
5.05 5.825 4.386
CO2 uptake (g/kg
of BA)
10.96 14.56 12.63
Mass balance and CO2 uptake for test
1, 2 and 3
CO2 Absorption capacity as a function of
time
Significant increase in weight after CO2
absorption
Simultaneous removal of CO2 and H2S
Combination and optimization of both processes
Thanks for listening
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n. 316838
Project coordinated by the QUESTOR Centre at Queen’s University Belfast www.qub.ac.uk/questor