recent co capture technologies involving...

Energy and Environment Conference, 9-10 September 2015, Rožnov, Czech Republic

Fabrizio Scala

Dipartimento di Ingegneria Chimica, dei Materiali

e della Produzione Industriale

Università degli Studi di Napoli Federico II

Napoli (Italy)

RECENT CO2 CAPTURE

TECHNOLOGIES INVOLVING

FLUIDIZED BED REACTORS


Fossil Fuel Energy Grand Challenges

Efficiency

CCS

Low Carbon Technology

World energy-related CO2 emissions abatement in the 450 Scenario relative to the New Policies Scenario.

New Policies Scenario

450 Scenario

Toward

In the medium term Fossil Fuels will remain the main energy source Conventional fuels must be used in unconventional ways


CARBON CAPTURE AND SEQUESTRATION


CARBON CAPTURE


PRE-COMBUSTION CARBON CAPTURE


SORPTION-ENHANCED GASIFICATION

CHxOy + (1-y)H2O → CO + (0.5x + 1- y)H2

CO + H2O CO2 + H2

CaCO3 CaO + CO2


Sorption enhanced gasification – process configuration

a) pre-gasification in a first reactor

followed by CO2 capture in a (dual

fluidized bed) reformer/regenerator

b) simultaneous gasification, reforming

and CO2 capture in a (dual fluidized bed)

gasifier/regenerator


Calcium carbonate decomposition equilibrium curve

Calcination Carbonation


100 kW dual fluidized bed

gasification bench scale rig

8 MW combined heat and

power plant in Güssing,

Austria

Examples of sorption-enhanced gasification test plants


Results of sorption-enhanced gasification tests

Product gas composition:

standard gasification vs. SEG

Gasification temperature vs.

gas composition for SEG


Pros and cons of sorption-enhanced gasification

High reactivity fuels (biomass) are needed due to the low gasification temperature;

High hydrogen concentrations in the syngas have been demonstrated;

Limestone is one of the cheapest industrial chemicals and it is environmentally benign;

Inherent H2S capture to low ppm levels by CaO;

Deactivation of limestone by high-temperature sintering and reaction with H2S, but possibility to reactivate the material by water/steam hydration (under study);

Particle attrition is a major challenge, but can be resolved;

Carbon conversion efficiencies should be enhanced through optimization of reactor design and fluid-dynamics.


POST-COMBUSTION CARBON CAPTURE


CALCIUM LOOPING


Calcium Looping – process configuration

Indirect heating

Direct heating

Three-reactor

configuration


Examples of Calcium Looping test plants

10 kW experimental test facility

at IFK-U Stuttgart

1.7 MW La Pereda pilot plant

located in Spain


0.6

0.7

0.8

0.9

1

12:00:00 13:20:00 14:40:00 16:00:00

CO

2 C

aptu

re e

ffic

ien

cy

600

650

700

750

800

Car

bo

nat

or

tem

per

atu

re (

ºC)

Results of Calcium Looping tests

Example of experimental results

obtained from the 1.7 MW test

facility at la Pereda

Typical decay curves of the

CO2 carrying capacity of

different CaO particles


Pros and cons of Calcium Looping

It is possible to easily retrofit existing boilers;

Limestone is one of the cheapest industrial chemicals and it is environmentally benign;

Another big advantage of CaO/CaCO3 is that both processes are hot enough to raise steam, i.e., both carbonator and calciner can serve as boilers;

Higher efficiency than low-temperature processes like amine scrubbing;

Inherent SO2 capture to low ppm levels by CaO;

Deactivation of limestone by high-temperature sintering and reaction with SO2, but possibility to reactivate the material by water/steam hydration (under study);

Particle attrition is a major challenge, but can be resolved;

Uses a high‐temperature oxy‐fuel regeneration cycle.


OXY-FUEL COMBUSTION


Examples of Oxy-fuel CFB test plants

75 kW CanmetENERGY's

Minibed Oxy-fired CFBC

30 MW Flexi-Burn® CFB

Power Plant at CIUDEN,

Spain (Foster Wheeler)


Results of Oxy-fuel CFB tests

0

10

20

30

40

50

60

70

80

90

100

50 60 70 80 90 100Time, min.

CO

2 c

on

cen

trati

on

, %

0

100

200

300

400

500

600

700

800

900

Avg

. b

ed

tem

p.,

°C

Transition from air firing to oxy-

fuel firing in CanmetENERGY’s

mini-CFBC

Tests on Oxy-fired Combustion in

CanmetENERGY’s 0.8 MW CFBC


Pros and cons of oxy-fuel combustion

Possibility either to retrofit existing CFB boilers (mimicking actual air operation – 30% O2) or to build new plants (with smaller furnace size at high O2 concentration);

Flue gas volume after recycling is 80% smaller than conventional combustion, and its density is increased;

Moderation of temperature by the bed material in oxy-CFB boilers is an advantage compared to oxy-PC;

Similar combustion behavior than in air operation, limited influence of gasification reactions;

Species present in flue gases are in higher concentrations after oxy-fuel combustion, but effective capture is feasible;

SO2 capture in-situ by direct sulfation of limestone;

An external heat exchanger might be needed to compensate for reduced heat transfer surface;

Air separation is expensive.


CHEMICAL LOOPING COMBUSTION


1222 22 xyxymn OMmnOmHnCOOMmnHC

Fuel reactor

xyxy OMmnOm

nOMmn

2

22 21

Air reactor

CHEMICAL LOOPING COMBUSTION


POSSIBLE OXYGEN CARRIERS

Fe2O3/Fe3O4 Mn3O4/MnO CuO/Cu NiO/Ni CoO/Co

Temperature, °C 800 1000 800 1000 800 1000 800 1000 800 1000

CO conversion 1.0000 1.0000 1.0000 0.9999 1.0000 1.0000 0.9949 0.9883 0.9691 0.9299

Maximum CO conversion to CO2 at equilibrium

Fe2O3/Fe3O4 Mn3O4/MnO CuO/Cu NiO/Ni comments

R0 0.03 0.07 0.20 0.21 Oxygen ratio

Reactivity towards methane ← decreasing increasing →

Cost ← decreasing increasing →

Health, safety & environm. risks ← decreasing risk

Thermodynamics

<99.5% conv. for NiO

Reaction enthalpy w. CH4

CuO exothermic w. CH4

Melting point 1085°C for Cu

CLOU CuO/Cu2O

Qualitative estimation of pros and cons for the oxides


Examples of Chemical Looping Combustion test plants

Chalmers’ 100 kW solid fuel

chemical looping combustor

TUV chemical looping

combustor G-volution System


Results of Chemical Looping Combustion tests

Available data from full fuel and

pure char conversion during CLC

tests

CO2 capture efficiency (ηOO) and

oxygen demand (ΩOD) during a

CLC test of bituminous coal


Pros and cons of Chemical Looping Combustion

This is the less mature technology, proof of concept achieved, but large scale operational results are missing;

It is not possible to retrofit existing boilers;

CLC is attractive and promising option for CO2 capture-ready combustion of gaseous/solid fuels, featuring inherent air separation with low energy penalty;

Extensive testing of oxygen carriers has been carried out. Conflicting trends of key carrier properties: reactivity/resistance to wear/cost. Optimal carrier to be assessed;

CLC of solid fuels still at preliminary stage. Poor contact between carrier and solid fuel. Alternative schemes have been devised, all to be assessed;

Larger installation costs.


Oxy-fuel FB combustion is almost ready for commercialization;

Calcium Looping and Sorption-enhanced gasification are relatively mature technologies, but sorbent deactivation problems should be solved or mitigated;

For Sorption-enhanced gasification carbon conversion should be increased;

Chemical Looping Combustion is the less mature technology, offering larger potential savings in energy penalty, but it has to be demonstrated at large scale with solid fuels;

Implementation of all these techniques need the full-scale demonstration of carbon sequestration techniques.

FINAL REMARKS


F. Scala (Editor)

Fluidized bed technologies for near-zero emission combustion and

gasification

Woodhead Publishing Series in Energy No. 59, Cambridge, UK, 2013

ISBN: 978-0-85709-541-1 (Print) 978-0-85709-880-1 (Online)

DOI: 10.1533/9780857098801


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recent co capture technologies involving...

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