Coking Coal
FFF Coal Coke & Carbon in Met. Ind.
13-14 June 2013
Hannes Kruger
Principal Specialist Coke Making
ArcelorMittal South Africa
Contents
• What is coking coal?
• Selection of Coking Coal
– Single coal analyses
– Single coal pilot oven tests
– Full scale trials
• Coal Blend Design
• Coking Coals
– Southern Africa
– Australia & NZ
– Rest of the world
• Commercial/VIU
• Questions?
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What is Coking Coal
•
General
•
•
•
•
•
A very soft bituminous coal suitable for coking (Sci-Tech Dictionary)
a bituminous coal suitable for making into coke (Merriam-Webster)
coal having mean reflectance of more than 0.60 and swelling Index or CSN of 1
and above ( Indian Gov )
Coking coals are those coals that soften, swell and then solidify as they are
heated through the temperature range 350°C to 550°C. By definition these
coals all have a low ash content (1 – 10%), have low permeability as determined
by inherent moisture, moderate vitrinite content (to provide volatile matter) and
volatile matter in the range 18 – 45% (Coal Marketing International)
Technical classifications
From hms-ag.com
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What is Coking Coal-2
•
Total Global Coal Production (including hard coal and lignite)
•
•
•
7678Mt (2011e)
7201Mt (2010)
4677 (1990)
•
Top Ten Coal Producers (2011e)
•
Top Ten Coking Coal Producers (2011e)
•
Coking Coal Exporters (2011e)
• Australia(140Mt), USA(63Mt), Russia(14Mt), Canada(),
Indonesia(), Mongolia().
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What is Coking Coal-3
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Selection of Coking Coal
Overview
•
Background to coal selection
– Requirements of blast furnace
• Small BF need lower quality coke
• High PCI (pulverized coal injection) and prepared burdens need
higher quality coke
– Regional coal availabilities
• Will source differently based on what you have
– Coke technology
• Will source differently based on what you have or can have
• Process of coal selection
– Single coal analysis
– Pilot Coke Oven tests, 100%
– Pilot Coke Oven tests, blends
– Full scale Coke oven trials
• Blend design vs Coal Replacement
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Selection of Coking Coal
Single Coal Analyses-1
•
Proximate analysis
– Moisture
• Dust problems if < 6%, handling problems if > 11%
• Optimum bulk density at 8-10%
– Ash
• Coke Ash, % = (Coal Ash % / Coke Yield %) * 100
– Volatile Matter
• establish the rank of coal and indicate the coal quality
• indicate the yield of coke and establish basis for coal trade
• significantly affects the cost of production (by-products)
– Fixed Carbon
• coke production cost factor (affects coke rate in BF)
• not directly measured, assumed as = 100 – Ash % – VM %
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Selection of Coking Coal
Single Coal Analyses-2
•
Ash Chemistry
– reported as oxides
•
SiO2, CaO, MgO, Al2O3, Fe2O3, P2O5, TiO2, MnO, K2O,
Na2O, SO3, etc
– ratio of basic and acidic oxides used in coke quality
prediction formulas, called basicity or catalytic index and
should be low Fe2O3 + CaO + MgO + K2O + Na2O
•
SiO2 + Al2O3
= Catalytic Index
Other chemical specs
– Sulfur
•
•
Fixed yield to coke for given coal
contractual specification, typically below 1%
– Phosphorus
•
In coal ash, report 100% to coke (mostly)
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Selection of Coking Coal
Single Coal Analyses-3
•
Rheological properties
– Free Swelling Index
•
•
•
indicator of caking ability, not additive for coal blend
less sensitive to coal oxidation as compared to other tests
FSI>4 for coking coals, FSI>7 indicates high quality coal
– Dilatation
•
•
•
•
indicator of coal coking ability, not additive for coal blend
volumetric method of determination of coal swelling properties
measures: contraction a, dilatation b, softening temp. TI, max.
contraction temp. TII, max. dilatation temp. TIII
typical values for good coking MV coals: 50 < c+d <140%
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Selection of Coking Coal
Single Coal Analyses-4
•
Rheological properties(cont)
– Fluidity
•
•
•
•
Constant torque method of determination of plastic behavior of
coal when heated, not additive for coal blend
measures: maximum fluidity F max, softening temp. T1, max.
fluidity temp. T2, re-solidification temp.T3, fluid range |T3-T1|
the highest value with HV coal, very sensitive to coal oxidation
overlapping of single coal fluid ranges is necessary for a blend
– Gray King
•
caking power of coal classified by the quality of coke residue
– Roga Index
•
ability of coal to agglutinate “inert” material
– Sapozhnikov analysis
•
In use in CIS only
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Selection of Coking Coal
Single Coal Analyses-5
•
Rheological properties(cont)
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Selection of Coking Coal
Single Coal Analyses-6
•
Maceral analysis
– Maceral, term used to distinguish an organic substance in
coal with specific properties; 3 main groups
•
•
•
•
Vitrinite: agglomerate with inert macerals to form coke
Liptinite: highest VM yield, becomes very fluid when heated
Inertinite: do not soften when heated, lowers coking pressure
Reflectance of Vitrinite
– measured as the amount of reflected light from coal particles
viewed under microscope on prepared tablets (ASTM D 2798)
– Reflectance from 0.70 – 1.09 = low rank/high vol; 1.10 –
1.49 = med rank/vol; 1.50 – 1.89 – high rank/low vol.
• Ultimate analysis
– C, H, N, S (direct measurement) and O (calculation)
• Calorific value
– Not a primary coking coal specification
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Selection of Coking Coal
Single Coal Pilot Oven Tests
• After full single coal analysis
– Each new coal is individually tested on pilot scale coke oven
• Objective
– Measure the oven wall pressure and the internal gas pressure
• LV very dangerous (> 50 kPa)
• LV dangerous (range 10 – 50 kPa)
• LV non dangerous (< 10 kPa)
• Some other coals (mid vol US) can generate some wall pressure
– Important to identify such coals
– Measure the lateral shrinkage
– Measure the coke mechanical strength (IRSID, ASTM)
– Measure the Coke Strength after Reaction (CSR)
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Selection of Coking Coal
Single Coal Pilot Oven Tests
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Counter force
Fixed wall
Load cells
Charging hole
Moveable wall
Heating elements
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Coal Blend design
The coal properties that determine
hot and cold coke strength (CSR &
M40/I40) are:
• Rank, rheology, macerals
• Not simple first order relationships
• Wide coal to coal variations around
the trends
• Different limiting properties in
different regions of the coking coal
spectrum
Next slide show the resulting desired
individual coking coal properties
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Coal Blend design-2
Technical classifications from USX
Low-Volatile
Mid-Volatile
High-Volatile
Poor
Fair
Good
Good
Fair
Poor
Good
Fair
Poor
<15
15 – 18
18 – 21
21 – 24
24 – 27
27 – 31
31 – 33
33 – 36
>36
Rank
>1.85
1.85 to
1.70
1.70 to
1.51
1.50 to
1.40
1.40 to
1.20
1.20 to
1.10
1.09 to
0.92
0.85 to
0.95
0.68 to
0.85
Fluidity
<30
>1,000
30 to
1,000
100 to
300
500 to
8,000
300 to
20,000
<300
>20,000
>20,000
5,000 to
20,000
<5,000
FSI
<7
7–8
9
9
7–8
>7
9
6–8
<6
HGI
85 – 105
90 – 120
80 – 135
60 – 90
48 – 75
CBI
>5.0
3.5 - 5.0
2.0 - 3.5
1.0 - 1.5
1.5 - 2.0
>2.0
0.4 - 0.8
0.8 - 1.4
>1.4
RI
<7.5
6.0 - 7.5
>6.8
6.0 - 6.5
4.3 - 5.5
<4.3
3.4 - 4.3
3.0 - 3.4
2.2 - 3.0
VM
(ddpm)
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Where:
VM
Rank
HGI
CBI
RI
volatile matter, %
reflectance of vitrinite, mean max, %
Hardgrove grindability index
Composition Balance index
Rank (Strength) Index
32 – 70
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Coal Blend design-3
Then different coals, normally 4 to 8, are
blended to reduce cost and improve coke
quality
• Optimum inert/reactives ratio give same coke
strength with lower rank coal (USA)
• MOP diagram (Miyazu, 1974) give simplified
blend composition target
• Overlapping of rank and fluidity ranges
required
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Coking Coals
Southern Africa
•
•
See Map for orientation
This presentation will look at
coking coals in order of
relevance to SA metallurgical
industry
• Scale of operation
• Quality of the coal
• Logistics to get coal to SA
and elsewhere
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Coking Coals
South Africa, Exxaro, Tshikondeni
•
Flagship of SA coking
coal for a long time
Coke quality
•
•
•
•
•
CSR = +67
M40 = 74
High wall pressure
Closure at end 2014
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Coking Coals
South Africa, Exxaro, Grootteluk
•
Coking coal only part of
large open pit (+65
mtpa ROM) Lephalale
operation
Very cost effective
SSCC/non coking coal
Coke quality
•
•
•
•
•
•
CSR = 25 - 30
M40 = 27
Increasing sulphur
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Coking Coals
South Africa, CoAL, Vele + Makhado
Vele
• Mine started in 2011
• SSCC
• Coke quality
• CSR = <35
• M 40 = ?
• Production and
washing not
stable/completed
Makhado
• Planned for production
in 2014?
• Good coke quality from
large box cut
• Also full scale plant
trials
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Coking Coals
Zimbabwe, Hwange CCL, Met Coal
•
•
•
Old and well known mine
Coke Quality (supplier data)
• CSR = 57
• CRI = 29
• 3 X operating COBs near
Hwange
Much other activity on the
same coal field, at least one
similar/better coking coal on
offer from a new mine.
A. Chemical Properties (Results on air dried
basis)
%
Total Moisture
Ash
Volatile Matter
Fixed Carbon
Volatile Matter (daf)
Phosphorus
Sulphur
B. Ash Composition
Silica (SiO)
Alumina (Al2O3)
Iron Oxide (Fe2O3)
Titanium Oxide (TiO2)
Calcium (CaO)
Magnesium (MgO)
Sodium Oxide (Na2O)
Potassium Oxide (K2O)
Phosphorus Oxide, Sulphur
trioxide etc
Hardgroove Gindability Index
5.6
9.8
23.4
64.0
26.3
0.005 0.10
1.3
47.3
35.5
1.8
1.2
2.7
0.5
0.9
1.0
1.2
63.0
C. Rheological Properties
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Free Swelling Index
Gieseler Plasticity
Max. Fluidity, ddpm
Max. Fluidity temp. °C
Initial Softening temp, °C
Final Fluid Temp, °C
Solidification temp, °C
Arnu Dilatation
Max. Contraction %
Max. Dilatation %
T1- Initial softening, °C
T2- Initial dilatation, °C
T3- Final dilatation, °C
1.0 - 2.1
58
437
393
456
457
17
0.0
410
330
471
Coal Fusibility
Initial Deformation, °C
Softening Temp, °C
Hemispherical temp, °C
Fluid temp, °C
Petrographic Properties
Macerals Analysis
Reactives
Vitrinite %
Exinite (liptinite)%
Reactive Semifusinite%
Total Reactives %
Inerts
Inert Semifusinite%
Micrinite%
Macrinite%
Inertodetrinite%
Fusinite + Secretinite%
Minerals(Caculated) %
Total Inerts %
Reflectance Analysis(VClasses/Types)
%V6 (0.60-0.69)
%V7 (0.70-0.79)
%V8 (0.80-0.89)
%V9 (0.90-0.99)
%V10 (1.00-01.09)
%V11(1.10-1.19)
%V12 (1.20-1.29)
Petrographic Indices
Mean Maximum Reflectance
(RoVmax) %
Mean Maximum Reflectance
(RoRmax) %
Optimum Inerts
Composition Balance Index
1345
1380
1397
>1401
Ave
34.1
0.6
8
42.7
11.9
0.9
14.3
8.9
16.1
5.2
57.3
2
22
50
22
1
3
0.95
1.00
8.2
7
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Coking Coals
Mozambique, Vale, Chipanga
• Very good coking
coal, +2 m tons
shipped to date
• Grade “Typical” of
slightly lower spec
• High Phos as with
all Moz coals
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Coking Coals
Mozambique, Rio Tinto, Benga
•
•
Very good coking
coal, mine started in
2012
Slight wall pressure
issues in slot ovens
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Coking Coals
South Africa, Other Mines & Projects
Mines
• Jindal
• Exported to India
• Bank
• KZN Area
• All large and easy seams mined out
Projects
• South Africa
• Waterberg
• Thuli
• Limpopo
• Zimbabwe
• Mozambique
• Already also a world player in coking coal
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Coking Coals
Australia, BMA-1
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Coking Coals
Australia, BMA-2
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Coking Coals
Rest of the World
•
China
• Largest producer and consumer
• Significant as price setter, but not as
source
•
Mongolia
• Regional supply, but world price
impact
North America
Russia
Canada
Colombia
Indonesia
•
•
•
•
•
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Coking Coal
Commercial
• Coking Coal Price History
• Coking price variance by
country and contract
• Moving with other steel raw
materials
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Coking Coal
Commercial-2
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Questions?
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End
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