Coke – nature, production, applications and coking coal ... · PDF file• Questions? CCC in Met Ind 13&14 ... Single Coal Analyses-2 • Ash Chemistry – reported as oxides •

Coking Coal

FFF Coal Coke & Carbon in Met. Ind.

13-14 June 2013

Hannes Kruger

Principal Specialist Coke Making

ArcelorMittal South Africa

CCC in Met Ind 13&14 June 2013 2

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?


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


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().


What is Coking Coal-3


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



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 %




• 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

• 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)

Fe2O3 + CaO + MgO + K2O + Na2O

SiO2 + Al2O3

= Catalytic Index




• 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%




• 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




• Rheological properties(cont)



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



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)



Single Coal Pilot Oven Tests

Fixed wall

Mo

veab

le w

all

Co

un

ter

forc

e

Lo

ad

cells

Heating elements Charging hole


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


Coal Blend design-2

Technical classifications from USX

Low-Volatile Mid-Volatile High-Volatile

Poor Fair Good Good Fair Poor Good Fair Poor

VM <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 (ddpm)

<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 32 – 70

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

Where:

VM volatile matter, %

Rank reflectance of vitrinite, mean max, %

HGI Hardgrove grindability index

CBI Composition Balance index

RI Rank (Strength) Index


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


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


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


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


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


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.

%

Total Moisture 5.6

Ash 9.8

Volatile Matter 23.4

Fixed Carbon 64.0

Volatile Matter (daf) 26.3

Phosphorus 0.005 -

0.10

Sulphur 1.3

B. Ash Composition

Silica (SiO) 47.3

Alumina (Al2O3) 35.5

Iron Oxide (Fe2O3) 1.8

Titanium Oxide (TiO2) 1.2

Calcium (CaO) 2.7

Magnesium (MgO) 0.5

Sodium Oxide (Na2O) 0.9

Potassium Oxide (K2O) 1.0

Phosphorus Oxide, Sulphur

trioxide etc

1.2

Hardgroove Gindability Index 63.0

C. Rheological Properties

Free Swelling Index 1.0 - 2.1

Gieseler Plasticity

Max. Fluidity, ddpm 58

Max. Fluidity temp. °C 437

Initial Softening temp, °C 393

Final Fluid Temp, °C 456

Solidification temp, °C 457

Arnu Dilatation

Max. Contraction % 17

Max. Dilatation % 0.0

T1- Initial softening, °C 410

T2- Initial dilatation, °C 330

T3- Final dilatation, °C 471

A. Chemical Properties (Results on air dried

basis)

Coal Fusibility

Initial Deformation, °C 1345

Softening Temp, °C 1380

Hemispherical temp, °C 1397

Fluid temp, °C >1401

Petrographic Properties

Macerals Analysis Ave

Reactives

Vitrinite % 34.1

Exinite (liptinite)% 0.6

Reactive Semifusinite% 8

Total Reactives % 42.7

Inerts

Inert Semifusinite% 11.9

Micrinite% 0.9

Macrinite% 14.3

Inertodetrinite% 8.9

Fusinite + Secretinite% 16.1

Minerals(Caculated) % 5.2

Total Inerts % 57.3

Reflectance Analysis(V-

Classes/Types)%V6 (0.60-0.69)

%V7 (0.70-0.79) 2

%V8 (0.80-0.89) 22

%V9 (0.90-0.99) 50

%V10 (1.00-01.09) 22

%V11(1.10-1.19) 1

%V12 (1.20-1.29) 3

Petrographic Indices

Mean Maximum Reflectance

(RoVmax) % 0.95

Mean Maximum Reflectance

(RoRmax) % 1.00

Optimum Inerts 8.2

Composition Balance Index 7


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


Coking Coals

Mozambique, Rio Tinto, Benga

• Very good coking coal, mine started in 2012

• Slight wall pressure issues in slot ovens


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


Coking Coals

Australia, BMA-1


Coking Coals

Australia, BMA-2


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


Coking Coal

Commercial

• Coking Coal Price History

• Coking price variance by

country and contract

• Moving with other steel raw

materials


Coking Coal

Commercial-2


Questions?


End

Documents

Coke – nature, production, applications and coking coal ... · PDF file• Questions? CCC in Met Ind 13&14 ... Single Coal Analyses-2 • Ash Chemistry – reported as oxides •