nanoparticle-enhanced capture of carbon-dioxide … co2 capture introduction objectives materials...

Nanoparticle-enhanced CO2

capture

Introduction

Objectives

Materials andMethods

G-L Systems andnanofluids

Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian

Parametersaffecting EpCorrelation ofresults

Conclusions

Acknowledgments

Nanoparticle-enhanced capture ofcarbon-dioxide with amine solvents

Srinivas Komati, Syam Sundar and A. K. [email protected]

Department of Chemical Engineering, IIT Bombay.Powai, Mumbai 400076, INDIA.

Symposium on the Global energy future

(IIT Bombay) Nanoparticle-enhanced CO2 capture Oct 04, 2010 1 / 20


capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Outline

1 IntroductionObjectives

2 Materials and MethodsGas-liquid systems and nanofluids

NanoparticlesCharacterization

Experimental apparatusExperiments: Regimes and Hydrodynamic conditions

3 ResultsDiffusion is FickianParameters affecting Ep

Correlation of results

4 Conclusions

5 Acknowledgments



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Introduction

Introduction

• Proven and currently practiced processes for CO2 capturein power generation from coal are based on gas absorption:

• Conventional plants - chemical absorption based on amine(MEA/MDEA/hindered amines) solvents

• Gasification - physical absorption (Selexol/Rectisolprocesses)

• The gas-liquid mass transfer step is an importantdeterminant of the rate at which CO2 can be captured,and hence, of equipment size. Intensification of this step istherefore of interest.



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Introduction

Why nanoparticles?

• Literature claims anomalous effects of nanoparticles ontransport rates in heat transport and momentum transport.

• Effect of nanoparticles on mass transport: Literaturesuggests an enhancement in rates, but is not conclusive –

• convective mass transport:• often studied in bubbling equipment, and interpreted in

terms of an overall effect on the rate – effect on kL isdifficult to assess.

• Particles of Fe3O4, CuO, Al2O3, SiO2, Cu and Au, ofdifferent sizes (10 to 200 nm) and in differentconcentrations (< 1 to 40%w) have been used.

• conflicting results – results of different groups difficult tocompare.

• Molecular transport: Limited data; qualitative and difficultto interpret.

— if proven, could have potential in the CO2 capturecontext!



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Introduction Objectives

Objectives of the present study

The objectives stem from the need —

• for systematic studies and to unify results from the fewsuch studies which exist in the literature—

• conduct studies in model contactors and model systems;compare effects in different contactors

• interpret the observations using the established theories ofinterphase transport

• Establish and validate a basis for process design.

— also to examine the systems relevant to CO2 capture.

• to distinguish the effect from those that fine particles areknown to cause in gas-liquid transport,

• Use well characterized particles so that enhancements dueto the grazing effect can be calculated



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Materials and Methods G-L Systems and nanofluids

Gas-liquid systems studied and absorption regimes

Absorption of CO2 in –

• Water: Physical absorption.

• Methyldiethanolamine(MDEA) solutions: slow → fasttransition, and Fast reaction regimes

• Monoethanolamine(MEA) solutions: Instantaneousreaction regime.



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments


Nanoparticles and their characteristics

• Magnetic Iron oxide: ferrofluids: Liquid phase co-precipitationfollowed by stabilization by various means —

L: stabilized by Lauric acid: Size 7-13 nm (average 10.1nm);Stable for short times in tert-amines; not verystable in primary and secondary amines.

T: stabilized by TMAOH: Size 10-35 nm (average 21.1 nm);better stability than L.

P: stabilized by grafted polymer: Size 10-16 nm (average 13.2nm); excellent stability.

• Gold colloid: Made from HAuCl4; broad size distribution(12-250 nm; average 110 nm).

• Silica: Sigma-Aldrich; broad size distribution (6-240 nm;average 110 nm); also Ludox HS-40 (14.7 nm) and LudoxSM-30 (11.3 nm).



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments


Particle and system characterization

• Particle size, its distribution and stability:

• DLS• TEM• XRD and Debye-Scherrer equation• BET

• Reactivity of the particles towards the solute.

• Solubility of the gas (for CO2).

• Specific surface: BET.

• Surface tension (in the presence of P nanoparticles).



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Materials and Methods Apparatus

Apparatus – Wetted wall column

• Known hydrodynamics; conforms to penetration theory precepts.

• short contact times (order of a sec); dead-end operation.

Experimental setup

Wetted wall



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Materials and Methods Apparatus

Apparatus – Liquid filled capillary

• Unsteady state absorption into quiescent liquid.

• (See figure) Shrinkage of gas slug A gives the rate of masstransfer.

• Long contact times (tens of minutes).



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Materials and Methods Experiments

Experiments: Systems, regimes and Hydrodynamicconditions

The systems, apparata and literature results allow a study under –

• different hydrodynamic conditions, and

• different levels of diffusion limitations.

Apparatus System Regime NanoparticlesWWC CO2 − MDEA Slow→ Fast Fe3O4(L,T,P)

FastCO2 − MEA Instantaneous Fe3O4(L,T,P)

O2 − dithionite Slow→ Fast Fe3O4(P)Capillary CO2 − water Physical Fe3O4(P); Au; Silica

CO2 − MEA Instantaneous Fe3O4(P)Stirred cell O2 − water Physical Fe3O4

Olle et al, 2006Bubble column CO2 − MDEA Instantaneous Fe3O4(L,T)

Rajagopal et al, 2007



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Results

Enhancement Ep due to nanoparticles

• From the measured absorption rates, using the theory ofmass transfer with chemical reaction, the physical masstransfer coefficient kL is calculated.

• Between WWC and capillary, a range of contact times(hence kL values) can be obtained.

• The values in the presence (kL,p) and absence (kL) ofnanoparticles are compared to define an EnhancementFactor Ep due to particles:

%Ep =

(k0l ,p

k0l

)× 100



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Results Diffusion is Fickian

Is the diffusion in nanofluids Fickian?

Capillary: Fickian diffusion into a stagnant fluid —

L1 − L2 =

[2

√DA

π

c∗A

cG

]E√

t =EkLc∗

A

ScG

— square root dependence of (L1 − L2) on time.

Figure: (a) Fe3O4; CO2 −MEA Figure: (b) Gold, phys. absorp.



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Results Parameters affecting Ep

Ep: Effect of particle hold-up and size

Size and hold-up matter —(different fluids in WWC)

but so does the depth ofdiffusion! (P: Capillary)



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Results Correlation of results

A normalized particle size . . . and a correlation

• It is the particle size dp in relation to the depth ofpenetration of solute λ that is of importance!

• Penetration theory: penetration depth with reaction√DAtcE

dp

λ=

kLdpE

DA= Shm

– a modified Sherwood number!

• Processing the data to seek a correlation between Ep interms of ε and Shm gives:

Ep = 1.519ε0.17Sh−0.16m



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments


Results for Fe3O4 – this work

Conditions: 0.02% < ε < 1%; 4× 10−6 < Shm < 1.8× 10−3



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments


Results: Comparison for Fe3O4 with literature

— data are from Olle et al., I&EC Research, 45,4355, 2006.(IIT Bombay) Nanoparticle-enhanced CO2 capture Oct 04, 2010 17 / 20


capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments


Results: Comparison for other nanoparticles

Figure: (a) Wide PSD (10-250nm) gold and silica

Figure: (b) Ludox HS-40 (14.7nm) and SM-30 (11.3 nm).



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Conclusions

Conclusions

• Nanoparticles in suspension enhance lliquid phase mass transfercoefficients. This work establishes this across several gas-liquidsystems, regimes, in the presence and absence of reaction, andin the presence and absence of flow, for several types ofnanoparticles.

• Extant theories for the effect of fine particles do not explain theenhancements (large and inconsistent values of solutepartitioning on nanoparticles required to fit the data).

• The extent of enhancement depends on particle holdup andparticle size in relation to the depth of penetration in anycircumstance.

• The results suggest that the nanoparticles influence moleculartransport rates.

• Taylor dispersion studies to measure liquid phase diffusivitiesand validation in a bubbling type contactor are in progress.



capture

Introduction

Objectives



Nanoparticles

Characterization

Apparatus

Experiments

Results

Diffusion isFickian


Conclusions

Acknowledgments

Acknowledgments

Acknowledgments

• Financial assistance:• Newreka (Pvt.) Ltd.• Ministry of Human Resource Development’s Thrust area

funding.• C3U


nanoparticle-enhanced capture of carbon-dioxide … co2 capture introduction objectives materials...

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