Presentation given by Dr Hao Liu from University of Nottingham on "CO2 capture from NGCC Flue Gas and Ambient Air Using PEI-Silica Adsorbent" in the Capture Technical Session on Solid Adsorption at the UKCCSRC Biannual Meeting - CCS in the Bigger Picture - held in Cambridge on 2-3 April 2014

1. CO2 Capture from NGCC Flue Gas and
Ambient Air Using PEI-Silica Adsorbent
Dr Hao Liu, Dr Chenggong Sun, Dr Wenbin
Zhang, Prof Trevor Drage, Prof Colin Snape
UK CCSRC Annual Meeting, 3rd April 2014, University of Cambridge

2. Outline
 Background
 CO2 capture from NGCC flue gas using PEI-silica
adsorbent in a bubbling fluidized bed (BFB)
 material characterization
 working conditions
 experimental results
 Process simulation of a 550MWe NGCC power plant
integrated with PEI-SALT PCC
 CO2 capture from Ambient Air
 performance evaluation in the BFB reactor
 proposed “PEI-CFB air capture system”

3. HRSG & cooling
Background - Post-Combustion CO2 Capture
Why use solid sorbents instead of solvent?
Advantages
Challenges
 Less regeneration energy required
 Elimination of corrosion problems
 Less evaporation of solvent in the regenerator
 Optimal design to achieve high working capacity
 Consistent performance and high durability & stability
 Lack of experience of process design
NG feed
Gas Turbine
~
Air

4. Solid Adsorbents Looping Technology

5. Characteristics of the PEI-silica sorbents
polyethylenimine
2
+
Supporting substrates
 material: mesoporous silica
 BET surface area: 250 m2/g
 pore volumes: 1.7 cc/g
 mean pore diameter: 20 nm
PEI impregnation
 Wet impregnation method, by Sigma-Aldrich, UK
 PEI loading: 40 wt%
 Similar to the absorption of CO2 with amine solvents
 The reaction is reversible, allowing for the sorbents to be regenerated by
temperature, vacuum or pressure swing adsorption cycles.
Reaction mechanism
Average particle size ~ 250 mm

6. 20 30 40 50 60 70 80
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1SpecificHeatCp
(J/g.
o
C)
Temperature (
o
C)
product I
product II
Specific heat measurements of PEI-silica adsorbent
specific Heat (J/g.K)
1.5-1.9, by our
measurements
1.25, by Pirngruber
(2013)
1.926, by Yang (2009)
0.8-1.3, by Sjostrom
(2011)
Pirngruber, G. D. et al., International Journal of Greenhouse Gas Control, 14 (2013): 74-83
Yang, W. C. et al., Ind. Eng. Chem. Res., 48(2009): 341-351
Sjostrom, S. et al., Energy Procedia, 4(2011): 1584-1592

7. moisture
saturator
108mm
67mm
0.5m1.2m
Bubbling Fluidized Bed (BFB) reactor

8. CO2 Capture with NGCC Flue Gas - test conditions

9. Effect of CO2 concentration in flue gas
1 2 3
0
2
4
6
8
10
262524
232220
26
2524
2322
20
262524
2322 15% CO2
5% CO2
BreakthroughEqu.-Desorption
Capacities(wt%)
Equ.-Adsorption
20
Cycle ID#
Flue gas:
CO2, O2,
H2O,
balanced
with N2
Potential in low CO2-containing gas mixture application

10. Comparison of capacities for PC and NGCC flue gases
Simulated flue gas 1: from coal fired power plants (CO2 15%, O2 4%)
Simulated flue gas 2: from Natural Gas Combined Cycle (NGCC) power plants (CO2
5% and O2 12%)
No obvious oxidative
degradation has
been found even if
O2 level is increased
to 12% for 7 cycles
50 52 54 56 58 60
0
2
4
6
8
10
12
0
2
4
6
8
10
12
simulated flue
gas (NGCC)
simulated flue
gas (PC)
by adsorption
by desorption
breakthrough
Capacities(wt%)
Cycle ID
simulated flue
gas (NGCC)
Flue gases:
CO2, O2, H2O,
balanced with N2

11. Integration of PEI-SALT PCC into a 550MWe
NGCC power plant

12. Conceptual design of
PEI-Silica SALT system
o CFB riser as gas-solid
contactor and CO2 adsorber
o BFB as desorber to
regenerate solid sorbents
o Loop seal to return
sorbents back to CFB with
integrated heat exchanger
for heat recovery
o Cyclone to separate solid
sorbents from flue gas
o A mixture of CO2 and
steam is proposed as the
stripping gas

13. CO2 capture from ambient air
Adsorption
PEI loaded mass (kg) 0.96
CO2 concentration in Air (ppm) 398.6 (NOAA data)
Air flow rate (litre/min) 8
Adsorption temperature (degC) Room temperature
Desorption (conditions same as NGCC flue gas capture)
 Due to the limit of measurement range of current CO2 analyzer, CO2 concentration
in the adsorption stage can not be monitored;
 Total adsorbed mass can only be determined by desorption tests when adsorption
tests are finished;
 To find out the saturation time, adsorption tests have been set to be continuously
running for different periods of time. ( 4 / 5 / 6 / 7 / 10 days respectively);
total CO2 passing through BFB during test time
total CO2 released during desorption tests
a =
total adsorbed mass of CO2 during test time
loaded mass of PEI-silica sorbents
qad= (wt%)
qad has the same meaning as adsorption capacity if sorbents have been
saturated to reach equilibrium condition.
(%)

14. Total CO2 volume passing through the bed during adsorption, the
amount released during desorption and the CO2 capture rate ()
Batch A: Partially degraded sample Batch B: Fresh sample
Within a short gas-solid contact time of only 7.5 sec, the adsorbent
was capable of adsorbing almost all CO2 contained in the ambient air
before breakthrough
0 1 2 3 4 5 6
0
10
20
30
40
Run A-5
(10 days)
Run A-4
(7 days)
Run A-3
(6 days)
Run A-2
(5 days)
(%)
TotalCO2volume(litre,at1atmand20
o
C)
during adsorption
during desorption
Run A-1
(4 days)
(a)
0
20
40
60
80
100

0 1 2 3 4 5
0
10
20
30
40
50
60
70
Run B-4
(14 days)
Run B-3
(10 days)
Run B-2
(8 days)
(%)
TotalCO2volume(litre,at1atmand20
o
C)
during adsorption
during desorption
Run B-1
(6 days)
0
20
40
60
80
100

(b)

15. The ratio of adsorbed CO2 mass to the mass of bed material
 For PEI-B batch, the equilibrium adsorption capacity has decreased
from 11.1 wt% for the flue gas (15% CO2) capture case to around 7.3
wt% for air capture case.
 The capacity of 10.1 wt% of PEI-B for capturing a lower concentration
of CO2 (5%) from the simulated flue gas is also included for comparison.
1 2 3 4 5
0
2
4
6
8
10
qad
(wt%)
Run A-1
(4 days)
Run A-2
(5 days)
Run A-3
(6 days)
Run A-4
(7 days)
Run A-5
(10 days)
7.2 wt% for 15% CO2
flue gas adsorption
(a)
1 2 3 4
0
2
4
6
8
10
11.1 wt% for 15% CO2
flue gas adsorption
qad
(wt%)
Run B-1
(6 days)
Run B-2
(8 days)
Run B-3
(10 days)
Run B-4
(14 days)
10.1 wt% for 5% CO2
flue gas adsorption
(b)

16. Conceptual design of a PEI-silica solid sorbent based CFB system
for large scale air capture
Similar SALT design
with NGCC PCC system

17. DAC (APS, 2011)* Proposed PEI-CFB
Specifications
CO2 capture plant capacity (Mt/yr) 1 1
CO2 capture rate (%) 50 90
Air velocity (m/s) 2 5
Pressure drop through absorber/adsorber (Pa) 280 1592
Adsorber unit dimension (m) 12 (ø)  2.8 12 x 12 x 40
CO2 captured per unit (t-CO2/day) 8.3 40
Total number of units needed 330 68
Comparison of proposed PEI-CFB air capture system
with reference system (1) Design specifications
* Reference air capture system: APS (American Physical Society) report, Direct air
capture of CO2 with chemicals, A technology assessment for the APS panel on public
affairs. June 1, 2011. The DAC system operates with a sodium hydroxide solution
flowing counter-currently to the air flow.

18. DAC (APS, 2011)* Proposed PEI-CFB
Electricity (GJe/t-CO2) 1.8 3.4
Thermal Energy (GJt/t-CO2) 6.1 3.2
Total energy requirement (GJ/t-
CO2)
7.9 6.6
Operating cost associated with
electricity and thermal energy
($/t-CO2 captured)
81S1 81S1a 91S2 306S3 91 S1a 108S2 227S3
Avoided CO2 as a fraction of CO2
captured
0.7 S1 0.3 S1a 0.55 S2 1.0 S3 0.21 S1a 0.71 S2 1.0 S3
Operating cost associated with
electricity and thermal energy
($/t-CO2 avoided)
112 S1 261 S1a 164 S2 306 S3 425 S1a 152 S2 227 S3
Comparison of proposed PEI-CFB air capture system
with reference system (2) Energy and costs
S1: Electricity supplied by average power grid, thermal energy by combustion of natural gas with CO2 capture
S1a: Electricity supplied by average power grid, thermal energy by combustion of natural gas without CO2 capture
S2: Electricity supplied by Advanced NGCC with CCS, thermal energy by combustion of natural gas without CO2 capture
S3: Electricity supplied by wind power plants, thermal energy by advanced nuclear

19. Conclusions
 High performance of PEI-silica adsorbent for CO2 capture
from NGCC flue gas has been demonstrated in a
laboratory-scale BFB reactor with kg-scale adsorbent;
 Process simulation on a 550MWe NGCC plant integrated
with a PCC unit has shown that application of PEI-silica
adsorbent can save over 2% in efficiency penalty compared
to MEA, owing to the much lower regeneration heat
requirement;
 The potential of PEI-silica adsorbent in the application of
carbon capture from ambient air has been demonstrated
by the BFB tests and a “PEI-CFB air capture system” is
proposed for large scale application.

20. Thank for listening!
Any questions?
Contact email:
Liu.hao@nottingham.ac.uk
Acknowledgement
The authors wish to acknowledge the
financial support of UK EPSRC
(EP/J020745/1, EP/G063176/1).