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TRANSCRIPT
Absorptive Technologies for Carbon Capture for the Iron &
Steel sector
A.K. Suresh Indian Institute of Technology Bombay
Mumbai, India – 400 076
19/10/14 A.K. Suresh | IIT Bombay 2/21
Contents
Contents
l CO2 emissions and the Iron & Steel sector l Absorptive Technologies for CO2 capture
l Some strategies to improve the economics of CCS in
the industry
l Conclusions
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CO2 Emissions & the Steel sector
Emissions – Steel sector
Industry
CO2 emissions [million tons] Reference India World#
Steel 144.4* [~8.4 %]
~2980.1* [~9.1 %]
World Steel Association 2011
Overall 1725.7 32578.6 EIA 2011
• Iron and Steel: the largest emitter of CO2 in the manufacturing sector –
• Energy intensive nature of the industry • Reliance on fossil carbon for fuel & reductants • Size of the industry
Source: Pro$iles, No. 12(1), IEA Clean Coal Centre, Feb 2012 4/21
Source apportionment
Emissions -Steel sector
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CO2 concentrations: Steel vs other sectors
Emissions -Steel sector
Source of flue gas CO2 concentration (%) Pulverized coal power plant 13-15
NGCC power plant 3-9
IGCC power plant using coal slurry 7 Steam reformer 8 Petrochemical plant 7 Steel mill 25 Cement plant 30
• CO2 concentration the gas stream influences the choice of capture technology
Source: Lee and Sircar (2008)
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Absorption technologies for CO2 capture
Absorption Technologies
u Fairly mature; Physical and Chemical solvents; choice of technology depends on Ø Solvent capacity for CO2 Ø Rate of absorption Ø Cost in terms of energy requirement and efficiency penalty
u Possibilities for innovation – Ø Newer solvents, more efficient hardware Ø Use of waste products of the industry for capture and
recycling Ø Novel strategies for process intensification
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Absorption: Physical vs Chemical
Absorption Technologies
Physical Absorption Chemical Absorption Based on solubility of CO2 in solvent – works better at high pCO2
Based on reaction of CO2 with the solvent – can work at low pCO2, but capacity limited by reactant
Regeneration is by pressure swing – less energy intensive
Regeneration by increasing temperature – energy intensive
Tolerant to oxides and other impurities Forms stable salts with oxides
Solvents: Rectisol, Selexol etc. Solvents: Alkanolamines, NH3 etc.
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Absorption Technologies
Absorption Technologies
Physical
Chemical
l Fluor Econamine (MEA) l MHI KS-1, KS-2 (Hindered amines) l Chilled Ammonia (NH3) l Shell Carbonate (K2CO3) l Others
l Rectisol (Methanol) l Selexol (PEG derived ethers) l Others
Low Regeneration energy vapor pressure byproduct formation viscosity corrosion rate
High Absorption capacity Absorption rate Thermal and Chemical stability
Desired:
Feasible for higher than 15% CO2 Rectisol gives higher loading than chemical solvents for pCO2> 4 atm
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Solvent Characteristics
Absorption Technologies
Source: Pandurean et al (2013), Bailey & Feron (2005)
Property Unit Rectisol Selexol MEA DEA MDEA
Concentration % Wt - - 30 40 50 Molecular Weight g/g mole 32 280 61.09 105.14 119.17 pH , 20 ºC - - - 12.1 11.0 11.5 Vapor press., 20 ºC mmHg 125 0.00073 0.36 0.01 0.10 Abs. Viscosity, 20 ºC cP 0.6 5.8 24.1 380 101 Typical loading mole/mole - - 0.3 0.3-0.7 0.45 Heat of absorption MJ/kg of CO2 - - 2.0 1.5 1.3
Rate constant, 25 ºC m3/kmole.s - - 7600 1500 5
Chemical solvents: MDEA/hindered amines better in terms of energy Physical solvents may be competitive for high pCO2
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EfViciency Penalty
Energy/efficiency cost
Source: Goto et al (2013)
l Cost of electricity can increase significantly. l Regeneration energy is clearly high for Econamine FG+ (MEA) compared to
CANSOLV (tertiary) or KS-1 (hindered); physical solvents attractive from this perspective
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Steel Industry wastes – Potential carbon capture agents
Strategies -1
Solid/Liquid Waste Qty (kg/t)
Capture Potential+ (kg/t)
Source of generation
Blast furnace slag 340-421 100-124 Blast furnace BF flue dust 28 0.7 Blast furnace LD* slag 200 78.6 Steel melting shop LD sludge 15-16 1.1-1.2 Steel melting shop Flyash - - Power plant
Source: B.Das et al (2007) *LD: Linz-Donawitz + Based on CaO content
Sequestration/recycle potential : About 9-10% of the CO2 generated
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Slag carbonation routes
Strategies -1
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Additional possibilities Strategies -1
§ Use of alkaline wastewaters as physical solvents
§ Use of extraction agents which can leach Ca from silica matrix
§ Use of phenolic wastewater from coke oven – § Precipitation of Ca § Recovery of phenol and recycle of lime
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Process intensiVication with nanoparticles
Strategies -2
l OBSERVATION: l Nanoparticles in suspension enhance mass transfer rates in gas-
liquid mass transfer
l MECHANISM: l A microconvection effect caused by the Brownian motion of
nanoparticles (?) l A correlational approach provides a design basis.
l IMPLICATIONS: l Would favorably influence rate in absorption as well as desorption!
Mass transfer in nanoVluids Studies in model apparatus
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Wetted wall column
Absorption capillary
Systems: Gas : CO2 Particles: Fe3O4, SiO2, TiO2 Solvents: Water
MEA, MDEA
Observations: § Enhancement in rate § Extent depends on ü Basic mass transfer rate ü Relative size of particle to
solute penetration depth ü Density of particles ü Volumetric hold-up
Strategies -2
15/21
u = u(Re p ,Sh,ε )
Mass transfer in nanoVluids Explaining the observations
19/10/14 A.K. Suresh | IIT Bombay
§ Brownian motion of nanoparticles a net advective motion in the direction of transfer;
Correlation of results:
Re p =dpvBrownρ p
µSh =
klrxndpD
=(klEc )dp
D ε = particle vol fraction
Strategies -2
16/21
Mass transfer in nanoVluids Test of the correlation in a packed bed
19/10/14 A.K. Suresh | IIT Bombay
Strategies -2
6.0E-05
8.0E-05
1.0E-04
1.2E-04
1.4E-04
1.6E-04
0 0.001 0.002 0.003 0.004 0.005
Exp
t. kl
(m/s
)
ε Volume fraction of NP
L=227 ml/min
L=146 ml/min
L=304
Results from physical absorption studies (12 nm silica):
17/21
Mass transfer in nanoVluids A design basis
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Strategies -2
10
1
kl ×104
18/21
Mass transfer in nanoVluids A design basis (e.g. silica in water)
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Strategies -2
10
19/21
Summing up
19/10/14 A.K. Suresh | IIT Bombay
§ Economics of CCS – a deterrent for deployment
§ Steel industry wastes offer possibilities to capture CO2 and recycle adjuvants
§ Use of novel strategies to improve rates of absorption and recovery of CO2 have shown promise
Conclusions
Acknowledgments
19/10/14 A.K. Suresh | IIT Bombay
§ Doctoral students § Ratnesh Khanolkar (Nanofluids work) § Raghavendra Ragipani (Steel slags etc).
§ Funding received § CCCU funding to develop the nanofluids
strategy § Jindal (JSW) support for exploring
applications to steel industry
Acknowledgments