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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: [email protected]
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