CO2NET Lectures on Carbon Capture and Storage€¦ · CO2NET Lectures on Carbon Capture and Storage...

CO2NET Lectures on Carbon Capture and Storage

1. Climate Change, Sustainability and CCS2. CO2 sources and capture3. Storage, risk assessment and monitoring4. Economics5. Legal aspects and public acceptance

Prepared by Utrecht Centre for Energy research

Contents lecture 2:CO2 sources and capture

• CO2 sources• CO2 capture/decarbonisation routes• Separation principles• CO2 capture technologies in power cycles +

consequences on the power cycle• Comparison of different CO2 capture technologies• CO2 transport

CO2 emissions from fossil fuel use

Source: IEA WEO 2004

0

4000

8000

12000

16000

20000

power industry transport residential +services

othersectors

CO

2 em

issi

ons

(Mt/y

r)

20302002

CO2 emissions industry and power

Source: IEA GHG 2002a

Total: 13.44 Gt/y in 2000.

CO2 emissions by region


CO2 source distribution

Source: IEA GHG 2002b

Scale CO2 emissions


Purity CO2 sources

• Ammonia 100%• Hydrogen 10-100%• Ethylene oxide 100%• Gas processing 100%• Cement 15-30%• Iron and steel 15%• Ethylene 10-15%• Refineries 3-13%• Power 3-15%

CO2 sources and capture

• CO2 capture targets: large, stationary plants.• Power production

– Large sources, representing large share total emissions

• Industrial processes– Large sources, some emitting pure CO2

• Synthetic fuel production (Fischer-Tropsgasoline/diesel, Dimethyl ether (DME), methanol, ethanol)– Target sources in future?

Power plants

• Pulverised coal plants (PC) • Natural gas combined cycle (NGCC) • Integrated coal gasification combined

cycle (IGCC)• Boilers fuelled with coal, natural gas, oil

and biomass

Pulverised coal plant (PC)

Source: TVA

Natural gas combined cycle(NGCC)

HRSG

Gas turbine Steam turbine

compressor

Flue gas

Fuel

Air

CombustionChamber

Integrated coal gasification combined cycle (IGCC)

Source: Gottlicher, 2004

Power plant overview

1600-170043-45 (up to 52%)250-350IGCC

500-70055-58 (up to 65%)100- 500NGCC1000-125040-46 (up to 50%)500 –1000PC

Capital cost (€/kWe)

Efficiency (% LHV)

Capacity (MWe)

Plant

(efficiencies forecasted for 2010-2020)

CO2 emission + concentration

CO2 emission factors: coal 95 kg/GJ natural gas 56 kg/GJ

0.0

0.1

0.2

0.3

0.40.5

0.6

0.7

0.8

0.9

PC NGCC IGCC

CO

2 em

issi

on (k

g/kW

h)

min max

[CO2]=12-15% [CO2]=3-4%

Contents


consequences on the power cycle• Comparison of different CO2 capture

technologies• CO2 transport

Post-combustion capture

Separation of CO2 from mainly N2 in flue gas from combustion process (end-of-pipe)

energy conversion CO2 capture

flue gas

power

air

fuel

CO2

exhaust

Pre-combustion capture

Conversion of fossil fuels in syngasand separation of CO2 from H2 in shifted syngas prior to combustion

reforming/ partial

oxidation

water gas shift

syngas

steam/oxygen

fuel CO2CO2 capture

CO2

energy conversion

power

air

H2 exhaust

H2

Oxyfuel (denitrogenated) combustion

Separation of O2 from N2 in air and convert fuel in O2 environment

energy conversion Condenser

power

fuel

O2

CO2

H2Oair separation

air

N2

CO2

H2O

CO2 capture routes: summary

• Post-combustion capture: separation CO2-N2• Pre-combustion capture: separation CO2-H2• Oxyfuel combustion: separation O2-N2

[CO2] (%)p (bar)

75-95%20-40%3-15%~1 bar10-80~1 bar

Oxyfuelcomb.(exhaust)

Pre-comb. (shifted syngas)

Post-comb.(flue gas)

Contents




Separation principles

• Absorption: fluid dissolves or permeates into a liquid or solid.

• Adsorption: attachment of fluid to a surface (solid or liquid).

• Cryogenic (low-temperature distillation): separation based on the difference in boiling points

• Membranes: separation which makes use of difference physical/chemical interaction with membrane (molecular weight, solubility)

Absorption versus adsorptionChemical versus physical

Chemical Adsorption Physical Adsorption

Chemical Absorption Physical Absorption

Physical absorption

• Van der Waals forces• Governed by Henry’s law: p = Kc*c

p = partial pressure (Pa)Kc = Henry’s law constant (Pa/(mol/l)) (function of T and solvent)c = concentration in solvent (mol/l)

• Suited for processes with high partial pressure (>5 bar).• Absorption occurs at high pressure and low temperature.

Desorption occurs by pressure decrease.

Chemical absorption

• Covalent bond. In case of CO2, acid-base reaction (exothermic).

• CO2 loading is characterised by a saturation effect due to limited amount of reactive components.

• Suited for low to moderate CO2 partial pressures at low temperatures.

• More selective separation than physical absorption.• Most common absorbents: alkanolamines

CO2 + 2 R-NH2 ⇔ R-NH3+ + R-NHCOO-N-C bond is much stronger than Van der Waals forces

• Regeneration (desorption) occurs at increased temperature

Chemical versus physical absorption

concentration

Physical (Henry’s law)

Chemicalpartial pressure

p2

p1

c1ph c1ch c2ch c2ph

Low partial pressure (p1):

C1ph < C1chChemical absorption deserves preference

p2: reverse

~ 5 bar

Chemical versus physical absorption: example

• Inputs: – Flue gas NGCC (4 vol%, 1.1 bar) → p(CO2) = 4400 Pa– Kc (CO2) for Selexol (physical solvent) @ 21°C:

5.4.105 Pa/(mol/l)– MEA concentration (chemical solvent): 30 weight% =

12 mol%

• Outputs: – c (CO2) in Selexol = 8.10-3 mol/l– c (CO2) in MEA = 5.35.10-2 mol/l

• Higher loading with chemical absorbents!

Physical adsorption

• Van der Waals forces• Can be performed at high temperature• Adsorbents: zeolites, activated carbon and

alumina• Regeneration (cyclic process):

– Pressure Swing Adsorption (PSA)– Temperature Swing Adsorption (TSA) – Electrical Swing Adsorption (ESA)– Hybrids (PTSA)

Chemical adsorption

• Covalent bonds• Adsorbents: metal oxides, hydrotalcites• Example: carbonation (>600°C) -

calcination (1000°C) reactionCaO + CO2 ⇔ CaCO3

• Regeneration (cyclic process): – Pressure Swing Adsorption– Temperature Swing Adsorption

Cryogenic separation: principles (1)

• Distillation at low temperatures. Applied to separate CO2 from natural gas or O2from N2 and Ar in air.

-219, 0.0015-183O2

-183, 0.12-162CH4

-210, 0.125-196N2-199, 0.69-186Ar

-57, 5.18 NA (sublimation)CO2

Triple point (°C, bar)Boiling point (°C@p0)

substance

CO2 phase diagram

Cryogenic CO2 separation

−

+−=

s

s

CO

ONCO pp

py

yys .1

2

22

2

sCO2 = CO2 separation factor (%)

y = molar fraction

p = total pressure

ps = condensation/sublimation pressure CO2 (function of T)

Cryogenic CO2 separation: pT requirements for 90% recovery

Source: Gottlicher 2004

Cryogenic CO2 separation: applications

• Suitable for oxidising and reducing gas streams with high CO2 concentrations:– Bulk separation CO2/CH4 in natural gas: 1-80% CO2

@ high pressure (up to 200 bar). – Bulk separation CO2/H2 in syngas: 20-40% CO2 @

10-80 bar– Purification of flue gas oxyfuel combustion: 75-95%

CO2 @ ~1 bar. Contaminants: N2, Ar, O2 (non-condensible) SO2 and NOx (high boiling points)

• Not feasible for bulk separation CO2/N2 in flue gas: 3-15% CO2 @ ~1 bar (too low!)

Membranes: principle

feed “X-rich”

permeate site

membrane

retentate siteresidue “X poor”

sweep gas (co- or countercurrent)

X X

Membranes: important mechanisms

Knudsen Diffusion (porous)

Molecular Sieving (porous)

Solution-diffusion/ Ionic conductivity

(non-porous)

Non-porous membranes: physics

• Fick’s law for solution-diffusion process:

Q = K.A.Δp/l

Q = flux (mol/hr)K = permeability (mol/m*hr*Pa)A = membrane area (m2)Δp = pressure difference (Pa)l = membrane thickness (m)

Membrane characteristics

• Permeability determines required membrane area

• Selectivity (ratio of permeabilities) determines the purity of the end-product. At low selectivity, recycle or multi-stage plants may offer a solution.

• Permeability and selectivity are negatively correlated. Optimum!

• Stability is major issue. Solution: porous support such as glass, ceramic or metal

Membrane classifications

• Organic versus inorganic. Organic membranes are not resistant to high temperatures in contrast to inorganic membranes.

• Inorganic membranes: – metallic (transition metals, Pd)– microporous (SiO2, C, zeolite) – ion transport/conducting (ceramic)

• Porous versus non-porous (dense) • Self-supporting versus composite

Source: Rautenbach and Albrecht 1989

Organic membrane applications

• Polymeric membranes (commercial): – CO2/CH4 separation (high CO2 partial

pressure)– CO2/N2 separation (post-combustion).

Partial pressure in flue gas and membrane selectivity are low. This requires compression/recycling, which makes it uneconomic.

Inorganic membrane applications

• Metallic membranes (pre-combustion capture):– CO2/H2 separation by means of composite Pd-alloys.

• Microporous membranes (pre-combustion capture):– CO2/H2 separation. The selectivity is currently not

sufficient to enable the production of more than 99.99% H2.

• Ion transport membranes (pre-combustion capture + oxyfuel combustion):– CO2/H2 separation (proton conducting membranes) – O2/N2 separation (oxygen conducting membrane)

Ion transport membranes

permeate

retentate(compressed air)

e- ↓ ↑ O2-

O2 + 4e-→ 2O2-

2O2-→ O2 + 4e-

Mixed oxygen conducting

(both ionic and electronic conductivity)

permeate

retentate(compressed air)

↑ O2-

O2 + 4e-→ 2O2-

H2 + O2-→ H2O + 2e-

permeate

retentate

e- ↑ ↑ H+

H2→ 2H+ + 2e-

O2 + 4H+ + 4e-→ 2H2O

e-

Oxygen conducting

(only ionic conductivity)

Mixed proton conducting

(both ionic and electronic conductivity)

Membrane absorption

Source: Feron, TNO-MEP

Combining capture routes and technologies: CO2 capture toolbox

Source: Feron, TNO

Capture method

Post-combustion decarbonisation

Pre-combustion decarbonisation

Denitrogenated conversion

Principle of separation

Membranes • Membrane gas absorption • Polymeric membranes • Ceramic membranes • Facilitated transport

membranes • Carbon molecular sieve

membranes

CO2/H2 separation based on: • Ceramic membranes • Polymeric membranes • Palladium membranes • Membrane gas

absorption

• O2-conducting membranes

• Facilitated transport membranes

• Solid oxide fuel cells

Adsorption • Lime carbonation/calcinations

• Carbon based sorbents

• Dolomite, hydrotalcites and other carbonates

• Zirconates

• Adsorbents for O2/N2 separation, perovskites

• Chemical looping Absorption • Improved absorption liquids

• Novel contacting equipment • Improved design of

processes

• Improved absorption liquids

• Improved design of processes

• Absorbents for O2/N2 separation

Cryogenic • Improved liquefaction • CO2/H2 separations • Improved distillation for air separation

Contents




Integration of CO2 capture technologies in power cycles

Pre-combustionNGCC + Chem/Phys. absorption

OxyfuelAZEPOxyfuelChemical looping combustion

OxyfuelSOFC-GT

Pre-combustionSorption enhanced reforming

Pre-combustionMembrane reforming

Pre-combustionIGCC + Physical absorption

Post-combustionNGCC + Chemical absorption

Post-combustionPC + Chemical absorption

CO2 capture routeTechnology

State-of-the-art

Advanced

Post-combustion capture: chemical absorption

Sources: Herzog, MIT (left), ABB Lummus Crest (right)

Post-combustion capture: Integration in NGCC


compressor

Flue gas

Fuel

Air

CombustionChamber

Knock-out drum

FilterAbsorber Stripper

Water wash

pumps

Heatexchangers

MEA rich

Other gasstreams

Reboiler loop

Feed gas

Cooler

Condenser

MEA lean

CompressorTransport

HRSGHRSG


compressor

Flue gas

Fuel

Air

CombustionChamber

Knock-out drum


Water wash

pumps

Heatexchangers

MEA rich

Other gasstreams

Reboiler

Feed gas

Cooler

Condenser

Reclaimer

MEA lean

CompressorTransport


compressor

Flue gas

Fuel

Air

CombustionChamber

Knock-out drum


Water wash

pumps

Heatexchangers

MEA rich

Other gasstreams

Reboiler loop

Feed gas

Cooler

Condenser

MEA lean

CompressorTransport

HRSG

Source: Peeters, UU

Post-combustion capture: Impact on efficiency (1)

ηpost-capture = efficiency of plant with post-combustion CO2 captureηreference = efficiency of plant without CO2 captureWcapture = power requirements of flue gas fan + pumps (MWe)Qcapture = heat requirements CO2 regeneration (MWth)α = ratio incremental power reduction to incremental heat

output (MWe/MWth) Wcompression = power requirements of CO2 compression (MWe)E = fossil fuel input (MWth)

ECW

EQ

EW ncompressiocapturecapture

referencecapturepost −−−=−α

ηη

Efficiency reference plant

ηreference = efficiency of plant without CO2 captureP = net power output (MWe)E = fossil fuel input (MWth)

Considering fossil energy consumption, CO2 capture might best be performed at power plants with high electric efficiency

EP

reference =η

Power requirements flue gas fan

Source: Bolland and Undrum, 2003

Power loss due to heat extraction for CO2 regeneration


CO2 compression work


Post-combustion capture:Impact on efficiency

Source: IEA GHG, 2005

Post-combustion capture:Impact on capital costs


Post-combustion capture:Impact on electricity costs


COE coal Fluor wo capture = 4.4 c/kWh, increase ≈ 40%

COE gas Fluor wo capture = 3.1 c/kWh, increase ≈ 40%

Pre-combustion capture: reactions

• Steam reforming of natural gas:CH4 + H2O ⇔ CO + 3H2 ΔH298= -206 KJ/mol(general: CxHy + xH2O ⇔ xCO + (x+y/2)H2)

• Water gas shift (WGS) reaction: CO + H2O ⇔ CO2 + H2 ΔH298= 41 KJ/mol

• Overall reaction:CH4 + 2H2O ⇔ CO2 + 4H2 ΔH298= -165 KJ/mol

• Partial oxidation of natural gas:CH4 + ½O2 ⇔ CO + 2H2 ΔH298= 36 KJ/mol(general:CxHy + x/2O2 ⇔ xCO + y/2H2)

Pre-combustion capture: Integration in IGCC

Source: IEA GHG

additional components

Pre-combustion capture: Integration in NGCC

additional components

Source: Kvamsdal, 2004

Pre-combustion capture: Impact on efficiency (1)

ηpre-capture = efficiency of plant with pre-combustion CO2 captureηCC H2 = efficiency of combined cycle fired on hydrogen rich

gasηconversion = efficiency of fossil fuel conversion into syngasQn = heat demanding processes e.g. WGS reaction, ATR

(MWth)Qm = heat producing processes e.g. syngas cooling (MWth) α = ratio incremental power reduction to incremental heat

output (MWe/MWth) Wcompression = power requirements of CO2 compression (MWe)Wmisc = miscellaneous power requirements e.g. ASU,

compression of oxygen/fuel gas (MWe)E = fossil fuel input (MWth)

EW

EW

EQ

EQ miscncompressiommnn

conversionHCCcapturepre −−+−=∑∑

−

ααηηη

2

Pre-combustion capture: Impact on efficiency (2)

0%

2%

4%

6%

8%

10%

12%

14%

IGCC dry IGCC slurry NGCC

effic

ienc

y pe

nalty

(%)

minmax

Composed from various sources

Pre-combustion capture:process integration

• Le Chatelier principle: by removing one of the products (CO2 or H2), the equilibrium will shift to the product site. – Membrane shift reactor: integration WGS with H2 separation.– Membrane reforming: integration reforming, WGS and H2

separation.– Sorption enhanced shift reactor: integration WGS and CO2

separation by adsorbents– Sorption enhanced reforming: integration reforming, WGS

and CO2 separation• Membranes/adsorbents allow high temperature

separation

Pre-combustion capture: Membrane reforming

CO2, H2O,Membrane

ReactionResidual gas

Permeate hydrogenH2

Feed stream

H2 H2H2 H2

High-pressure side

Low-pressure side

Catalyst particles

Sweep

CH4 + 2H2O ⇔ CO2 + 4H2

Source: ECN

In order to sustain this endothermic reaction, heat is supplied by burning natural gas (or hydrogen) in a furnace

Pre-combustion capture: Membrane reforming integrated in

CC (1)

Source: Norsk Hydro

Pre-combustion capture: Membrane reforming integrated in

CC (2)

Source: Norsk Hydro

Pre-combustion capture: Sorption enhanced reforming

CH4 + H2O H2 + CO2

catalyst adsorbent catalyst adsorbent

CO2CO2 CO2C

O2CO2

steam

airsteamnatural gas

generatorgas

turbine

SERP reactorin adsorptionmode

waterknock out

CO2

H2 +steam

SERP reactorin desorptionmode

Source: ECN

Principle

Integration in CC

Oxyfuel combustion: State-of-the-art configuration

Source: Andersson, Maksinen, Chalmers University

Oxyfuel combustion: Impact on efficiency (1)

ηoxyfuel = efficiency of oxyfuel combustion plantη reference O2 = efficiency of reference plant with near

stoiciometric combustion with O2. Different heat transfer and expansion characteristics!

WO2 = power requirements for O2 production (ASU) and compression (MWe)

Wcompression= power requirements of CO2 compression (MWe)

EW

EW ncompressioO

Oreferenceoxyfuel−−= 2

2ηη

Oxyfuel combustion: Impact on efficiency (2)

0%

2%

4%

6%

8%

10%

12%

14%

PC NGCC

effic

ienc

y pe

nalty

(%)

minmax


Oxyfuel combustion: Improvements for NGCC

• Disadvantages oxyfuel combustion in NGCC:– high energy requirements ASU– developing turbines with CO2/H2O as working fluid

• Advanced concepts:– Alternative oxygen production technologies

(membranes or oxygen carriers) – Allow for the use of conventional turbines using N2

as main working fluid

Oxyfuel combustion: Advanced concepts (AZEP)

Source: Norsk Hydro

Option: afterburner

Oxyfuel combustion:Chemical looping combustion

Oxyfuel combustion:Chemical looping combustion in CC

Source: Wolf, KTH

Solid oxide fuel cell (SOFC)

Source: Shell

H2 + O2-→ H2O+ + 2e-

CO + O2-→ CO2 + 2e-

O2 + 4e-→2O2-

SOFC-GT hybrids

Source: Siemens

SOFC features

• Promises high efficiency (60-70%) power generation at small scale (modular system), e.g. for distributed combined heat and power

• Current capital costs are high (>2000 €/kWe, small-scale NGCC ~ 1000 €/kWe)

• Status: various demonstration units with capacities in kW-MW range.

• Good opportunities for CO2 capture

CO2 capture at SOFC(-GT)

• SOFC is in fact oxyfuel concept, as nitrogen is separated from oxygen by the electrolyte.

• Various configurations can be applied to capture CO2 from the anode off-gas: – Post-fuel cell capture of CO2 using cryogenics or

absorption– Pre-fuel cell capture of CO2– Post-fuel cell off-gas oxidation (conversion of

remaining CO and H2 into CO2 and H2O)

Pre-fuel cell CO2 capture

Source: Jansen and Dijkstra, 2004

Post-fuel cell off-gas oxidation (1)

Source: Maurstad, 2004

Afterburner configurations

Source: Maurstad, 2004

Contents




Technology comparison:efficiency with CO2 capture

20%

30%

40%

50%

60%

70%

PC-po

st

PC-ox

y

IGCC

-pre

NGCC

-post

NGCC

-pre

NGCC

-oxy

ATR-

SEW

GS MRAZ

EP CLC

SOFC

-GT

net e

lect

ric e

ffici

ency

(% L

HV) max

min


Technology comparison:energy penalties


30%

40%

50%

60%

70%

PC-po

st

PC-ox

y

IGCC

-pre

NGCC

-post

NGCC

-pre

NGCC

-oxy

PC-po

st ad

v.

IGCC

-pre a

dv.

NGCC

-post

adv.

ATR-

SEWG

S MRAZ

EP CLC

SOFC

-GTn

et e

lect

ric e

ffici

ency

(% L

HV)

with CO2 capture reference plant

state-of-the-art advanced

Technology comparison:electricity production costs


01234567

PC-po

st

PC-ox

y

IGCC

-pre

NGCC

-post

NGCC

-pre

NGCC

-oxy

PC-po

st ad

v.

IGCC

-pre a

dv.

NGCC

-post

adv.

ATR-

SEWG

S MRAZ

EP CLC

SOFC

-GTe

lect

ricity

cos

ts (€

ct/k

Wh)

capital fuel O&M


Technology comparison:CO2 recovery


0.00

0.20

0.40

0.60

0.80

1.00

PC-po

st

PC-ox

y

IGCC

-pre

NGCC

-post

NGCC

-pre

NGCC

-oxy

PC-po

st ad

v.

IGCC

-pre a

dv.

NGCC

-post

adv.

ATR-

SEW

GS MR AZEP CL

C

SOFC

-GT

CO

2 pr

oduc

tion

(kg/

kWh)

CO2 capture CO2 emissions


CO2 captured versus avoided

0 0.2 0.4 0.6 0.8 1

ReferencePlant

CapturePlant

CO2 produced (kg/kWh)

Emitted

Captured

CO2 avoided

CO2 captured

CO2 avoidance costs = (COEcap- COEref)/(Eref - Ecap)

Source: Herzog, MIT

Technology comparison: CO2 mitigation costs


0

10

20

30

40

50

60

PC-po

st

PC-o

xy

IGCC

-pre

NGCC

-pos

t

NGCC

-pre

NGCC

-oxy

PC-p

ost a

dv.

IGCC

-pre a

dv.

NGCC

-pos

t adv

.

ATR-

SEWG

S MRAZ

EP CLC

SOFC

-GTC

O2

miti

gatio

n co

sts

(€/t

CO

2)


Choice of reference system

3.00

3.50

4.00

4.50

5.00

5.50

6.00

6.50

0.00 0.20 0.40 0.60 0.80 1.00

CO2 emission (kg/kWh)

elec

trici

ty c

osts

(€ct

/kW

h) PC IGCCNGCC

Source: based on Herzog, MIT

No CCS

With CCS

Summary: Post-combustion capture

• Chemical absorption is currently most feasible technology

• Technology is commercially available, although on a smaller scale than envisioned for power plants with CO2 capture (>500 MWe)

• Energy penalty and additional costs are high with current solvents. R&D focus on process integration and solvent improvement.

• CO2 capture between 80-90%• Power cycle itself is not strongly affected (heat

integration, CO2 recycling)• Retrofit possibility

Summary: Pre-combustion capture

• Chemical/physical absorption is currently most feasible technology

• Experience in chemical industry (refineries, ammonia)• Energy penalty and additional costs physical absorption

are lower in comparison to chemical absorption• CO2 capture between 80-90%• Need to develop turbines using hydrogen (rich) fuel• No retrofit possibility• Advanced concepts to decrease energy penalty/costs:

– sorption enhanced WGS/reforming– membrane WGS/reforming

Summary: Oxyfuel combustion• Cryogenic air separation is currently most feasible

technology• Experience in steel, aluminum and glass industry• Energy penalty and additional costs are comparable

to post-combustion capture• Allows for 100% CO2 capture • NOx formation can be reduced• FGD in PC plants might be omitted provided that SO2

can be transported and co-stored with CO2• Boilers require adaptations (retrofit possible). R&D

issues: combustion behaviour, heat transfer, fouling, slagging and corrosion.

Summary: Oxyfuel combustion (2)

• Boilers require adaptations (retrofit possible). R&D issues: combustion behaviour, heat transfer, fouling, slagging and corrosion.

• Application in NGCC: new turbines need to be developed with CO2 as working fluid (no retrofit)

• R&D focus on development of new oxygen separation technologies. Advanced concepts to decrease energy penalty/costs: – AZEP (separate combustion deploying oxygen membranes) – Chemical looping combustion (separate combustion

deploying oxygen carriers).

Contents




CO2 transport

• Pipelines are most feasible for large-scale CO2 transport– Transport conditions: high-pressure (80-150 bar) to

guarantee CO2 is in dense phase • Alternative: Tankers (similar to LNG/LPG)

– Transport conditions: liquid (14 to 17 bar, -25 to -30°C)– Advantage: flexibility, avoidance of large investments– Disadvantage: high costs for liquefaction and need for

buffer storage. This makes ships more attractive for larger distances.

Pipeline versus ship transport


Pipeline design

52

22 322

dlqf

dlvfp

πρ

ρ ==∆

µρvdRe =

Δp = pressure drop (Pa)

Re = Reynolds number

f = friction factor

v = average fluid velocity (m/s)

q = volumetric flow (m3/s)

l = pipe length (m)

d = (internal) pipeline diameter (m)

ρ = fluid density

µ = fluid viscosity

As a consequence of friction and elevation differences, pressure drop occurs along the pipeline:

Pipeline optimisation

• Small diameter: large pressure drop, increasing booster station costs (capital + electricity)

• Large diameter: large pipeline investments

• Optimum: minimise annual costs (sum of pipeline and booster station capital and O&M costs plus electricity costs for pumping).

• Offshore: pipelines diameters and pressuresare generally higher as booster stations are expensive

CO2 density as function of p,T

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300 350

Pressure (bar)

Den

sity

CO

2 (k

g/m

3)

0102030405060708090100110120130140150160170180190

Source: Hendriks, Ecofys

CO2 quality specifications

• USA: > 95 mol% CO2• Water content should be reduced to

very low concentrations due to formation of carbonic acid causing corrosion

• Concentration of H2S, O2 must be reduced to ppm level

• N2 is allowed up to a few %

CO2 transport costs

0

1

2

3

4

5

0 50 100 150 200 250 300 350

distance (km)

tran

spor

t cos

ts (€

/t C

O2)

0.1 Mt/yr1 Mt/yr2 Mt/yr4 Mt/yr10 Mt/yr20 Mt/yr40 Mt/yr

Source: Damen, UU

Risks pipeline transport

• Major risk: pipeline rupture. CO2 leakage can be reduced by decreasing distance between safety valves.

• CO2 is not explosive or inflammable like natural gas

• In contrast to natural gas, which is dispersed quickly into the air, CO2 is denser than air and might accumulate in depressions or cellars

• High concentrations CO2 might have negative impacts on humans (asphyxiation) and ecosystems. Above concentrations of 25-30%, CO2 is lethal.

Safety record pipelines• Industrial experience in USA: 3100 km CO2

pipelines (for enhanced oil recovery) with capacity of 45 Mt/yr

• Accident record for CO2 pipelines in the USA shows 10 accidents between 1990 and 2001 without any injuries or fatalities. This corresponds to 3.2.10-4 incidents per km*year

• Incident frequency of pipelines transmitting natural gas and hazardous liquids in this period is 1.7.10-4 and 8.2.10-4, respectively, with 94 fatalities and 466 injuries

Conclusion: CO2 transport is relatively safe.

CO2NET Lectures on Carbon Capture and Storage€¦ · CO2NET Lectures on Carbon Capture and Storage...

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