Applications and synergies from Coal R&D

CSIRO ENERGY TECHNOLOGY

Biomass Gasification Research: David Harris | Theme Leader: Advanced Coal Utilisation Technologies Biomass Gasification Symposium São Paulo, Brazil 17 September 2012

Introduction to CSIRO

Australia’s Gasification Research Program Coal gasification fundamentals

Fuel property impacts on gasification performance

– Gasification Conversion reactions

– Mineral matter behaviour

Application of research data through reaction and process models

Relevance to biomass gasification applications – Lessons learned and special issues

Torrefaction of biomass

– An enabling technology for efficiency and scale?

Outline

Gasification of Bagasse | David Harris | Page 2

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Coal Gasification R&D

Gasification and IGCC systems – several fuel dependent issues to be addressed

Increase availability – slag management, fouling, corrosion, refractory degradation

Improved cold gas efficiency

Coal preparation & feeding (dry and slurry systems)

High temperature syngas cleaning

Technology efficiency impact on CO2 emissions

For pf systems, most future improvements are NOT coal related issues

Advanced materials – higher steam T, P

Coal issues affecting efficiency - slagging, fouling, drying, milling…

High pressure, high temperature coal conversion measurements

Effects of reaction conditions and coal type

Development of coal test procedures

Fundamental investigations of coal gasification reactions

mechanisms, kinetics, models

Slag formation and flow

Syngas cleaning & processing

Gas separation (H2/CO2)

Technology performance models

To improve the understanding of coal performance in gasification technologies, supporting:

• Coal selection and use in new technologies

• Implementation of advanced coal technologies

• Development of high efficiency IGCC-CCS systems

Coal Gasification & IGCC Research

Gasification Research

Fuel Reactivity

Reaction Fundamentals

Gasification Behaviour

Pyrolysis and Char

Formation

Alternative Fuels

Mineral Matter

Slag formation and flow

Trace element behaviour

CSIRO Gasification Research

Pilot scale performance studies

Modelling

Mechanistic Gasification Models

Gasifier Models Process model

Integration

Coal pyrolysis Rapid volatile release

Determines char yield and morphology

Combustion Limited, fast. O2 consumed early in process

Exothermic, provides heat for endothermic gasification reactions

Char Gasification Slow, rate determining. Endothermic

CO2 and H2O converted to CO and H2.

Slag formation and flow Flux may be required to achieve adequate viscosity

Coal Conversion in Gasification Gasification is a multi-stage process

flux

O2

CO/CO2

slag

CO2 and H2O

CO + H2

Interrogating the Gasification Process

Laboratory investigations to understand the important processes that combine to gasify coal under practical conditions.

Larger-scale testing to ‘recombine’ process steps under process conditions

Predictive capability of gasification behaviour

Assess coals for specific gasification technologies

Develop operating strategies

Troubleshooting gasification processes

Support technology development

flux

O2

CO/CO2

slag

CO2 and H2O

CO + H2

Gas Analysis

Its not all about simulating the industrial

process!

• High pressures • Up to 30 bar

• High temperatures and heating rates • Up to 1100°C

• Over 1000°C/s

Devolatilisation and Char Formation

20%

30%

40%

50%

60%

0 10 20 30

Pyrolysis Pressure (atm)

Yie

ld,

wt%

of

co

al

(daf)

Anthony

Arendt

Gibbins

Suuberg

Griffin

A (31.7%)

B (34.8%)

C (35.7%)

D (36.2%)

E (50.4%)

Rapid devolatilisation measurements High heating rate (~1000°C/s)

Pressure 15-20bar

Cane trash and bagasse have extremely high volatile yields 70-85% (ad basis)

char yield is low

Volatile yield of coals and biomass

0

10

20

30

40

50

60

70

80

90

297

252

272

283

263

240

296

298

274

284

299

310

306

281

Can

e tr

ash

Bag

asse

% V

ola

tile

s (

air

-dri

ed

)

Proximate

WMR, 1100°C, 15 atm

WMR, 850°C, 20 bar

Simple non-isothermal TGA experiment

Drying, pyrolysis Inert atmosphere

Devolatilisation complete by ~400°C

Total volatile yield ~85%

– char yield low

Pyrolysis profiles of sawdust

Char Reactivity Fixed Bed Reactor Intrinsic reaction kinetics of chars

with CO2, H2O, O2

Detailed information regarding reaction rates & mechanisms, and how these relate to char properties (surface area, porosity, petrography etc)

High Pressure TGA Reaction rates at high pressures of

CO2, H2O, CO, H2, and their mixtures

Impacts of high pressures on gasification reaction processes

Fundamental data for application of char reaction kinetics to relevant process conditions

Carbon-Gas Reactions

Science issues:

Competing reactions

Role of char surface

Complex kinetics

Application issues:

Coal properties and pyrolysis conditions affect char reactivity

Char structure changes during reaction

Cf + H2O C(O) + H2

C(O) CO + Cf

Cf + CO2 C(O) + CO

C(O) CO + Cf

Char-CO2:

Cf + H2 C(H2)

Char-H2O:

Complicated by:

1/Temperature (1/K)

0.00084 0.00086 0.00088 0.00090 0.00092 0.00094 0.00096

ln (

rate

(g m

-2 s

-1))

-18

-17

-16

-15

-14

-13

-12

CRC272

CRC252

CRC281

800oC825

oC850

oC875

oC900

oC

HPTGA

Fixed bed reactor, n=~0.6

Gasification rate of wood char is approx 100x greater than coal char

wood char surface area usually greater than coal char

‘intrinsic’ reactivity of sawdust char still ~10x greater than coal char

Activation energy similar for coal and biomass chars (240-300kJ/mol)

Low char yield and high char reactivity indicate that this is less likely to be limiting factor in biomass gasification

Affects T, particle size etc

Gasification reactivity of biomass char

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16 Sp

ec

ific

ra

te (

Pin

e C

har)

x 1

06 (

g/g

/s)

Sp

ecif

ic R

ate

(C

oal)

x 1

06 (

g/g

/s)

Conversion (%)

Anthracite

Coke

Black Coal

Black Pine

Rate data normalised to 900°C

-13,5

-13,0

-12,5

-12,0

-11,5

-11,0

-10,5

-10,0

0,8 0,85 0,9 0,95 1 1,05

ln (

rate

, g

/g/s

)

1000/T (K-1)

Anthracite

Coke

Black Pine Char

Black Coal

780°C

~900°C

940°C

Moving up the Arrhenius Curve: High Temperature Rates

Inverse Temperature

ln (

co

nve

rsio

n r

ate

)

Regime I Regime II Regime III

~800-

900°C

T>1000°C Very high T

<< 1

Temperatures where

gasification technologies

operate

Low-temperature

‘intrinsic’

measurements

External mass transfer control

Chemical + pore diffusion control

Chemical rate control

=1 < 0.5

High Pressure Entrained Flow Reactor

Gas Analysis

Feeder

Preheating

and mixing

Three-section

reaction zone

Water quench

Sampling probe

and gas analysis

20 bar pressure, up to 1500°C

Coal feed rate of 1-5 kg/hr

Gas mixtures of O2, CO2, H2O and N2

Adjustable sampling probe - char and gas samples collected at different residence times (0.5-3s)

CO2/char reaction rate at ‘high’ temperature

CRC252

Residence time (s)

0.0 0.5 1.0 1.5 2.0

Ch

ar

convers

ion

(%

)

0

20

40

60

80

100

CRC272

Residence time (s)

0.0 0.5 1.0 1.5 2.0

CRC281

Residence time (s)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

1273 K1373 K1473 K1573 K1673 K

Semi anthracite Bituminous Sub bit, high vol

20 bar total pressure, 5 bar CO2 partial pressure

CRC252

1/temperature (1/K)

0.0005 0.0006 0.0007 0.0008 0.0009

ln (

ga

sific

atio

n r

ate

(g

g-1

s-1

))

-14

-12

-10

-8

-6

-4

-2

0

2

CRC272

1/temperature (1/K)

0.0005 0.0006 0.0007 0.0008 0.0009

CRC281

1/temperature (1/K)

0.0005 0.0006 0.0007 0.0008 0.0009 0.0010

1373 K 1473 K 1573 K

1673 K

FBR data1273 K

Regime 2

Regime 1

First of a kind data for high pressure char/CO2 and char/steam reactions (PEFR)

Thiele modulus and effectiveness factor based on observed particle morphology

‘effective’ diffusion length

Low T ‘intrinsic’ and high T ‘practical’ rate data can be reconciled when a detailed understanding of char structure is available

Still difficult to resolve burnoff effects

Challenge to extend to multiple reactants

Char/CO2 reaction rates: understanding chemical and physical factors

E M Hodge, D G Roberts, D J Harris and J F Stubington. The

Significance of Char Morphology to the Analysis of High

Temperature Char-CO2 Reaction Rates, Energy and Fuels (2009).

1/Temperature (1/K)

0.0004 0.0005 0.0006 0.0007 0.0008 0.0009 0.0010

ln(s

pe

cific

rate

(g g

-1 s

-1))

-12

-10

-8

-6

-4

-2

0

2

particle size

wall thickness

PEFR data

FBR data

0

20

40

60

80

100

120

0 50 100 150 200 250

Stoichiometry (%)

Carb

on

Co

nvers

ion

(%

) CRC274

CRC298

CRC299

CRC281

CRC252

CRC263

CRC358

1400°C, 2.5% O2

Evaluation of Coal Gasification Behaviour

Optimum range of stoichiometries for ‘gasification efficiency’. Trade-off to achieve maximum conversion.

Higher volatile coals (generally) achieve greater conversion than lower volatile coals

Exception is CRC299 – indicates that char reactivity is also significant (agrees with TGA testing of coal suite)

Higher temperature differentiates coals on the basis of different char reactivities

Effect of coal type also reflects extent of conversion

Conversion drives syngas composition (via gas phase equilibria)

0

20

40

60

80

0 50 100 150 200 250

Stoichiometry (%)

CRC274

CRC298

CRC281

CRC299

CRC252

CRC263

CRC358

1400°C, 2.5% O2

Ga

sif

ica

tio

n ‘e

ffic

ien

cy’ (%

)

• Volatile species (in syngas): • requirements for syngas cleaning

• Condensed phases (slag, fly ash): • Syngas cleaning

• Operational: slag viscosity

• Utilisation/handling of waste

• Physical & chemical properties: trace elements, leaching

Mineral matter in gasification Coal mineral matter

Liquid slag

Condensed phases

Volatile species

Coarse slag

Fine slag

Solid ash

Quench water and/ or gas cleaning

Wall slag

Tapped slag

Fly ash

Slag Viscosity Testing

10

20

30

40

1300 1350 1400 1450 1500 1550

50

Maximum for

Slag Tappability

Tcv

Vis

co

sit

y P

a.s

Temperature 0C

100/0 Ash/CaCO3

100/10 Ash/CaCO3

100/20 Ash/CaCO3

• Slag Viscosity

• 25 Pa s is the accepted maximum viscosity at the slag tap

for successful operation

• Flux addition required if viscosity is too high

• Temperature of Critical Viscosity

• Slag becomes heterogeneous

• Trouble-free tapping of slag is not possible

Bagasse ash composition

Component Wt.%

Ash content 0.62-3.2*

SiO2 78.3 - 85.5

Al2O3 5.3 - 8.6

Fe2O3 1.3 - 5.2

CaO 2.1 - 3.3

Na2O 0.1 - 0.3

K2O 1.5 - 3.5

MgO 0.2 - 1.7

P2O5 0.5 - 1

Mineralogy: • Mainly quartz, SiO2, • also phosphates: (Ca9MgK[PO4]7 and KAlP2O7)

Bagasse ash composition [1-3] * Excluding dirt, and up to 7% with dirt

Excluding dirt

Including dirt

Coal

ashes

[1] Dordeiro, et al, in Used of Recycled Materials in Building and Structures (2004) [2] Zanderson et al, Biomass&Bioen (1999) [3] Souza et al, J. Environ. Manage. 92 (2011)

Bagasse and coal ash compositions in SiO2-Al2O3-CaO

phase diagram at 5wt.% FeO

Melting & flow behaviour of bagasse ash

No solids involved, slag

flow only depends on

viscosity of liquid, which

is very high

Slag flow depends on

viscosity of liquid with solids.

Even with some solids (up to

20% ) viscosity < 25Pa∙s.

CRC703f coal slag (example):

AFT for bagasse ash:

• IDT (initial deformation temperature) depends on low melting point fraction (K-species) and different than eutectic T.

• ST (spherical temperature), and HT (Hemispherical temperature), are high due to slow melting and high viscosity of melt

• FT (Flow temperature) is (>100 °C) higher than liquidus temperature

AFT is bulk characteristic of ash and depends:

• Kinetics of melting

• Melting temp. of minerals

• Viscosity of slag

0%

20%

40%

60%

80%

100%

800 900 1000 1100 1200 1300 1400 1500 1600

Sla

g c

om

po

sit

ion

, w

t.%

Temperature, °C

liquid

leucite

Fe

clinopyrox.

cordierite

anorthite

silica

Entrained

flow

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

1200 1260 1320 1380 1440 1500

Vis

co

sit

y ,

Pa

.s

So

lid

s c

on

ten

t, w

t%

Temperature (°C)

liquid

feldspar

leucite

viscosity

IDT ST HT FT

Bagasse in entrained flow gasifier Possible approaches:

• Blending with kaolin** (70:30 ratio) to reduce S/A ratio and fluxing with CaCO3 (~10%)

Bagasse Ref coal*

Coal for

blending

Ash

content 0.62-3.2 ~10 ~10

SiO2 78.34-85.5 78.5 36

Al2O3 5.3- 8.55 10.8 30

Fe2O3 1.3-5.24 4.6 1.1

CaO 2.1-3.27 0.3 29

Na2O 0.12-0.33 1.1 0.17

K2O 1.51-3.5 0.72 0.07

MgO 0.15-1.1 0.6 0.26

Blended Raw coal with 10% CaO

0

10

20

30

40

50

60

70

80

90

100

1200 1300 1400 1500 1600

Temperature, oC

Vis

cosi

ty,

Pa

s No Kaolin

10% Kaolin

20% Kaolin

30% Kaolin

No CaO, No Kaolin

Optimum viscosity, 5-25 Pa∙s

Estimated bagasse slag viscosity -

too high!:

- SiO2 - rich melt, high S/A,

- low CaO and FeO 1

10

100

1000

1200 1300 1400 1500 1600

Vis

co

sit

y,

Pa ∙s

Teemperature, °C

Ref.coal

Ref.coal+Kaolin+CaCO3

Ref.coal+blended coal

Optimum viscosity, 5-25 Pa∙s

* Ref coal with similar ash composition Blending with

coal with low S/A

and high CaO

(~85:15 ratio)

Gasification Research

Fuel Reactivity

Reaction Fundamentals

Gasification Behaviour

Pyrolysis and Char

Formation

Alternative Fuels

Mineral Matter

Slag formation and flow

Trace element behaviour

Pilot scale performance studies

Modelling

Mechanistic Gasification Models

Gasifier Models Process model

Integration

• Entrained-flow reactor – Application of transportable fundamental kinetics and

structure data

• Pilot and full scale modelling – Integration of coal performance data into process flow sheets

Coal gasification models

6 (a)

Distance from reactor top (m)

0.0 0.5 1.0 1.5 2.0

Carb

on

co

nvers

ion

(%

)

0

20

40

60

80

100

CRC-358 (Expt)

CRC-274 (Expt)

CRC-252 (Expt)

CRC-358 (Model)

CRC-274 (Model)

CRC-252 (Model)

Gas T Particle

flow

Gas Analysis

θ

(D_burner)

(L_WSR)

Conical

PFR 1

PFR_width

PFR_length

(i)

Conical PFR 2

WSR 2

WSR1

Pilot scale test data consistent with laboratory based estimates for similar conditions

In practice many factors determine practical operating conditions

Slag requirements may over-ride gasification reaction requirements

eg CRC704 where O:C of ~1.4 was needed

Model performance Reconciliation with pilot and lab scale data

0

10

20

30

40

50

60

Ga

s c

om

po

sit

ion

(%

)

CO H2 CO2 CH4

CO (Expt) H2 (Expt) CO2 (Expt) CH4 (expt)

50

60

70

80

90

100

110

0,9 1 1,1 1,2 1,3 1,4 1,5

Ca

rbo

n c

on

ve

rsio

n, C

GE

(%

)

Stoichiometry (O:C ratio)

C conversion (Model)

C conversion (Experimental)

CGE (Model)

CGE (Experimental)

Bituminous coal

60

65

70

75

80

85

90

0,9 1 1,1 1,2 1,3 1,4 1,5 1,6

CG

E (

%)

Stoichiometry (O:C ratio)

CRC701 CRC702 CRC703 CRC704

Optimum Vs Practical operating conditions

• Our modelling results shows that some coals must be operated under higher O:C

ratio than targeted optimum operating conditions due to their slagging behaviour.

• Similar behavior is expected for biomass in entrained flow gasifier.

Co

ld G

as E

ffic

ien

cy (

%)

O:C ratio/ Temperature

Coal

Biomass

Practical operatingcondition (Coal)

Practical operatingcondition (Biomass)O

pti

mu

m O

per

atin

g R

egio

n (

Bio

mas

s)

Op

tim

um

Op

erat

ing

Reg

ion

(C

oal

)

Torrefaction Preprocessing bagasse for transport, feeding and efficiency benefits

Process Conditions: 200° - 300°C

Near atmospheric pressure

Absence of air

Residence time of 10-30 min

Volatilisation of hemicellulose component

Heating rate <50°C/min

The torrefaction process Mass and energy balance

Source: Phil Hobson, QUT

Torrefaction

100

100

70

30

90

10

Energy densification = 1 x 90

70

= 1.3

torrefied product dry biomass

off-gas

Mass

Energy

Typically ~24 MJ/kg (HHV)

Hydrophobic (maintains ~3% moisture)

Stable in long term storage

Friable 10% of the comminution energy required for untreated biomass

Compatible with conventional coal milling equipment

Readily pelletised 50% of energy required to pelletise raw biomass

High residual lignin (bonding agent)

Volatiles retained 50% to 60% volatiles

Coal-like energy density and handling properties

Torrefied bagasse Physical properties

Grinding and milling Torrefaction improves energy and performance

Source: Kiel, J. (2007) IEA Bioenergy workshop “Fuel storage, handling and preparation and system analysis for biomass combustion technologies”, Berlin

Torrefied

biomass

Rotating Kiln Facility: Torrefaction, pyrolysis, combustion

• ~500kg/h capacity (low grade coal combustion)

• LPG pre-heater

• Kiln temperature ≤900°C

• Has been used with steam turbine and small gas turbine

Syngas Technologies

Gas Cleaning

Particle removal High

temperature sorbents

Syngas Processing

Catalysts for liquid fuels production

High temperature

WGS catalysts

Gas Separation Membranes

Amorphous membranes

Crystalline membranes

Fundamental studies of metal-H2 interactions

Catalytic Membrane Reactors

Fabrication Demonstration Process

optimisation

Slipstream testing in coal-derived syngas

CSIRO Advanced Syngas Technologies Research

• Key enabling technologies for next generation coal based H2 energy systems

• Large scale, low cost processes essential • High temperature gas cleaning systems • Catalytic shift reactions • Membrane separation systems • Membrane reactors

• Shift and separation in a single unit

H2

Gas Cleaning, Processing and CO2/H2 Separation

No insurmountable technical barriers Coal Gasification science is applicable

– Devolatilisation, reactivity, mineral matter & slag behaviour

Relative importance of the fundamental processes varies – Drives technology & operating conditions

Most issues relate to the nature of biomass as a feedstock Torrefaction may be an important enabler

– Dispersed and costly to transport

– High moisture (30% to 60%)

– Low volumetric energy density

– Fibrous – not readily milled & fed into pressurised gasifier

Mineral matter content and composition – Alkali and silica affect slagging & downstream syngas processes

– engineering design & operating strategies

International partnerships are needed to facilitate research development, demonstration and deployment Coordination and ‘critical mass’ are essential

Bagasse gasification R&D drivers

http://www.propubs.com/pictures/gsslagpou

r2.gif

Thank You Contact: David Harris

Phone: +61 7 3327 4617

Email: David.Harris@csiro.au

CSIRO ADVANCED COAL TECHNOLOGY

Operating window of main gasifiers types

Moving beds Fluidized beds Entrained flow

Downdraft Updraft Bubbling Circulating

T°C 700-1200 700-900 <900 <900 1200-1500

Tars low Very high intermediate intermediate Absent

Control easy Very easy intermediate intermediate very complex

Scale <1-5 MWth <20 Mth 10-100 Mth 20-100 Mth > 100 MWth

feedstock very critical critical less critical less critical fine particles