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Transcript of Mark Cresswell - DRA Mineral Projects - Southern Africa coal washabilities, processing methods and...
Mozambique Coal
Coal Processing in Southern Africa Mark Cresswell (Process Engineering Consultant)
DRA MINERAL PROJECTS (PTY) LIMITED
Mozambique Coal
Maputo 28 July 2015
Tweefontein - 2000 t/hr Phola - 2400 t/hr DMO - 2200 t/hr
Some Recent DRA Coal Projects 2008- 2015
SOUTHERN AFRICA COAL PROCESSING
• Coal Washing Plants in Southern Africa
• Raw Coal characteristics of interest
– Witbank (RSA), Botswana, Madagascar, Mozambique
• Industry trends in Southern Africa
SOUTHERN AFRICA COAL
WASHING PLANTS
Country
Number of
Washing Plants Products
Namibia 0 thermal coal potential
Botswana 1 Morepule - (domestic thermal)
South Africa ~50 ~98% thermal coal
Mozambique 3 export coking & thermal coal
Madagascar 0 thermal coal potential - Sakoe Coalfield
Zimbabwe 2 Hwange (coking, met & thermal coal)
Zambia 1 Maamba (thermal coal)
Tanzania ~3 Kiwri (domestic thermal coal) + others
Country Annual Production
South Africa RoM 260 Mtpa Raw Coal (2011 DoE stats)
Production 224 Mtpa products
Production (non SA) 4 Mpta (1.8%) ref. World Coal
SA COAL INDUSTRY – LOCATION OF MINES
SA COAL INDUSTRY - OVERVIEW
• 90% of electrical power (~40 GW) generated from coal
• continued use of “middlings” coal (21 – 23 MJ) for
internal power generation while better quality (27.5 MJ
coal) for thermal coal export.
• 60 – 70 Mt recent annual thermal coal exports worth ~$6
billion USD / yr to Europe and Far East (2008 – 2012)
• New trend is to also export lower quality coal to India
putting pressure on reserves for internal power
generation
Exports Mt Year $/t Value of Exports
65 2008/13 100 6.5 B$
72 2014/15 60 4.3 B$
R/$ 2008/13 8.0 52.0 Billion R
R/$ 2014/15 11.8 51.0 Billion R
Minimal effect in Rands
SA COAL INDUSTRY - OVERVIEW
• 35 yrs since last major expansion when the Export trade
started, now coming out of a major plant renewal and
study phase to ensure future power supplies
• Huge future reserves in northern Coal fields (mainly the
Waterburg) – logistics challenges - dry areas - remote
infrastructure
• Coking & Met coal scarcity, reserves in environmentally
sensitive areas eg KZN
SA COAL INDUSTRY – Eskom Power Stations
Others
Western Cape Koeburg 2 900 1 800
gas / hydro Cahora Bassa 2 000
3 800
Future
14 Waterberg Medupi Grootegeluk Exxaro yes 6 800 4 800
15 Witbank Kusile Others + New Largo AAC Inyozi eventually 6 800 4 800
9 600
Future Overall Total 50 958 MW
Eskom Coal Fired Power Stations - simple calculations t/hr/MW
Coal Field
Power
Station Main Coal Mine Operator Washing Plant Units MW
Installed
MW 0.49
Operating
1 Witbank Arnot Arnot + Mafube AAC Inyozi yes 6 350 2 100
2 Witbank Duvha Middelberg + DMO Becsa yes 6 600 3 600
3 Witbank Hendrina Optimum Optimum yes 10 200 2 000
4 Witbank Kendal Khutala Becsa no 6 686 4 116 2 008 t/hr
5 Witbank Komati Koornfontein Becsa yes 1 000
6 Witbank Kriel Kriel AAC Inyozi no 6 500 3 000 1 464 t/hr
7 Witbank Matla Matla Eyesizwe no 6 600 3 600 1 756 t/hr
8 Highveld Camden Ermelo + Golang Golang yes 8 200 1 600
9 Highveld Majuba various coals railed in 15 suppliers 6 665 3 990
10 Highveld Tutuka New Denmark (50%) AAC Inyozi no 6 609 3 654 1 783 t/hr
11 Sasolberg Lethabo New Vaal AAC Inyozi de-stoning only 6 618 3 708
12 Sasolberg Grootvlei Grootvlei no 6 200 1 200 585 t/hr
13 Waterberg Matimba Grootegeluk Exxaro yes 6 665 3 990
total 37 558 7 597 t/hr
Required coal t/MW installed 3 171
Annual requirements 119
Approximate unwashed Coal 49 Mtpa direct
SA COAL INDUSTRY – Washed/Unwashed Coal
Coal Processing
Mined Coal 260 Mtpa (2011 Eskom stats) ignoring direct coal
Washed 65 Mtpa Export (washed) 25% 31% average
Washed 70 Mtpa Eskom (washed) 27% 33% yield 64%
sized / de-stoned 49 Mtpa Eskom (direct) 19%
by difference 76 Mtpa Discards 29% 36%
100% 100%
Marketable Coal Products 224 Mtpa (ref. Eskom website)
% SA coal to Eskom 53% 119 Mtpa to Eskom
210 Mtpa RoM Coal Wash (79% total production)
RAW COAL CHARACTERISITICS
THERMAL COAL QUALITY IN SOUTHERN AFRICA
WITBANK
• “Gondowana” Coal with higher mineral matter compared with Northern
Hemisphere coals
• Great variability in Yields: 5 – 80% at SG 1.6; 20 – 95% at SG 1.8
-
10
20
30
40
50
60
70
80
90
100
1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
Cu
mu
lati
ve
% Y
ield
Floats Density
Witbank Seam 2 Data (Western Edge)Cumulative Yield vs Density
Seam 2
Average 2S
ave + 1std
ave - 1std
THERMAL COAL QUALITY IN SOUTHERN AFRICA
EASTERN BOTSWANA
• Similar Characteristics and great variability
Mookane D1S5
Cumulative Yield
0
10
20
30
40
50
60
70
80
90
100
1.4 1.5 1.6 1.7 1.8 1.9 2 2.1
Floats Density
Cu
mu
lati
ve
Yie
ld (
%)
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MADAGASCAR
• Similar Characteristics and great variability
-
10
20
30
40
50
60
70
80
90
100
1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
Cu
mu
lati
ve
% Y
ield
Floats Density
Madagascan Coal - Recent + 1940's Boreholes Data Cumulative Yield vs Density
THERMAL COAL QUALITY IN SOUTHERN AFRICA
WITBANK vs EASTERN BOTSWANA
FRACTIONAL SULPHUR DISTRIBUTION
• Similar Characteristics - higher sulphur values in SG1.8 Sinks – easy washing
scheme
THERMAL COAL QUALITY IN SOUTHERN AFRICA
WITBANK vs MADAGASCAR
YIELD vs ASH
• Witbank coal – higher yields for same % Ash
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
YIELD vs ASH
• Moatise coals – target 10 – 12.5% Ash for Coking coals
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
Liberation Characteristics
• Banded nature of Vitrinite very evident
• Generally <6mm for liberation
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
Liberation Characteristics
• Significant Increase in Yield in small and fine coal sizes
• Roughly Coking Coal yield – 1/3 DMS, 1/3 Fine Coal, 1/3 Slimes Flotation
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
Liberation Characteristics
• Significant Increase in Yield in small and fine coal sizes
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
Liberation Characteristics
• Roughly Coking Coal yield – 30% DMS, 40% Fine Coal, 30% Slimes Flotation
THERMAL COAL QUALITY IN SOUTHERN AFRICA
MOATISE COALFIELD – TYPICAL DATA
Liberation Characteristics
Distribution of Products (typical Witbank)
t/hr %
Export Product +0.6mm 411 46%
Middlings +0.6mm 167 19%
Fine Coal middlings 44 5%
Discards 273 31%
Totals 896 100%
Size Class Coking Thermal Discards Total
(50 x 1)mm 29% 100% 90% 75%
(1 x 0.25)mm 42% 6% 14%
(-0.25)mm 29% 5% 10%
Total 100% 100% 100% 100%
Typical Moatise Product Mass Balance
COAL PROCESSING PLANTS
Solution to Raw Coal Variability is Raw
Coal Blending
Large Mine – Raw
Coal Stacking and
Bucket Wheel
Reclaiming -
40 000t with
emergency parallel
lay down area
(RSA)
Raw Coal Blending Options
Large Mine – Raw
Coal Circular Blending
Stockpile
Portal Reclaimer
(NSW)
Raw Coal Storage Options
2 000t Surge Bin (RSA)
20 000t Conical Earth re-
inforced Stockpile
Raw Coal Storage Options
Split to Two Modules
Raw Coal Crushing Circuits
Large Sites required for Open Cast mines to reduce RoM coal from 1.2m to 50mm (Klipspruit)
Raw Coal Crushing Circuits
Tipping Bin, Chain Feeder, Double Roll Primary Crusher
South African Raw Coal Crushing
Circuits - 1
Primary Crusher, Rotary Breaker, Screen, Tertiary Crusher
Large Plant Raw Coal Handling & Preparation (significant tramp or parting rock)
air dry tonnes basis
D1 + M2 Seam Coal Combined
Loading Bin
300 t capacity
Coarse Discards
Apron Feeder + Mineral Sizer
-900mm
Open Cast Mine
Rotary Breaker
-350mm 60% mass to oversize (+120mm)
-120mm
CRUSHING PLANT
-120mm Feedsize
to raw coal stockpile
-50mm crushed product
to Open Cast Mine Pit
100t Capacity Dump
Raw Coal Crushing Circuits
Rotary Breaker – secondary crusher + hard rock removal
Raw Coal Crushing Circuits
Rotary Breaker – Discard of Harder Sandstones and Shales
Raw Coal Crushing Circuits - 2
Primary Crusher, Secondary & Tertiary D/R Crushers
Large Plant Raw Coal Handling & Preparation
air dry tonnes basis
D1 + M2 Seam Coal Combined
Loading Bin
300 t capacity
Apron Feeder + Mineral Sizer
-900mm
Open Cast Mine
-350mm 60% mass to oversize (+120mm)
CRUSHING PLANT
-110mm Secondary Product
-50mm crushed product
to raw coal stockpile
100t Capacity Dump
Raw Coal Crushing Circuits
Secondary & Tertiary D/R Abon Crushers at Mafube
Raw Coal Crushing Circuits
Tertiary Crusher maintenance at Goedgevonden
Raw Coal Crushing Circuits for Liberation -
Moatise
Scalping Screen before Tertiary Crushing
Raw Coal Crushing Circuits for Liberation -
Benga
Careful use of Tertiary Crushing
Raw Coal Feed
6.5 mtpa
1 000 tph DRA's design experience
Raw Coal Bin 1 100 tph DRA's design experience
6 500 hrs/yr DRA's design experience
Feeder Breaker
Rotary Breaker
Raw Coal
Surge Bin
Scalping Screen
Emergency Stockpile
+100mm
-50mm
Optional
Discard Stockpile
+50mm
CPP Average Feed
CPP Average Feed
CPP Design Feed
Hours on Coal
Raw Coal Crushing Circuits for Liberation –
using Chirodzi tertiary crushing circuit concept
Rotary Breaker as Secondary Sizer plus even more careful use of Tertiary Crushing with extra 10% rejected
General trends in Coal Preparation Plan Design
General Trends in Coal Preparation Plant Separation Units (Southern Africa)
1970's - 2015
Coarse Coal Small Coal Slimes
-(120 x 12)mm -(25 x 0.5)mm -0.5mm
1970's Bath/Wemco Drum/Jig DM Cyclones / Jig Discard or Flotation
Coarse Coal Small Coal Fine Coal Slimes
-(120 x 12)mm -(25 x 0.63)mm -(0.63 x 0.125)mm -0.125mm
1980's Drewboy / Norwalt Bath DM Cyclones Spirals introduced mainly discarded
Wemco Drum (<750mm dia) Fine Coal DMS x 1 occasional flotation
Coarse + Small Coal Fine Coal Slimes
-(90 x 12, 12 x 0.63)mm or -(50 x 0.63)mm -(0.63 x 0.125)mm -0.125mm
1990's (Bath + DM Cyclones) or DM Cyclones Spirals mainly discarded
Larcodems plant x 1 occasional flotation
Coarse + Small Coal Fine Coal Slimes
-(50 x 0.63)mm -(0.63 x 0.125)mm -0.125mm
2000's DM Cyclones Spirals / 1 x DM cyclones mainly discarded TBS / DM Cyclones occasional flotation
Coarse Coal Small Coal Fine Coal Slimes
-(120 x 12)mm -(25 x 0.63)mm -(0.63 x 0.125)mm -0.125mm
2010's Drewboy/Wemco Drum DM Cyclones Spirals / TBS/ mainly discarded Larcodems FSB Dry Sepn (50 x 10)mm Reflux Classifier occasional flotation
DM Cyclone Coal Washing Circuits
• Technology Dominated by the DMS (dense
medium separation) method
• Uses magnetite powder and water to create a
liquid “medium” of SG 1.35 – 1.90
• Mature technology – first plants built in
late1940’s
• DM Cyclone invented and developed by Stami-
Carbon (Netherlands)
• Technology licensed worldwide 1950’s – 80’s
• Vessels used – DM Cyclones, Wemco Drums,
Peters Baths, Drewboy, Teska Baths
DRA Engineers in Australia checking out experience there
DMS Circuit Design Concepts –SA vs Australia
Difference in yields between Small coal and Coarse coal fractions
32 Klipspruit Bulk Sample Washabilities (50 x 8)mm & (8 x 0.63)mm- Phola Coal
Export Yield (Section) vs % ROM Feed
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
% ROM Feed
% E
xp
ort
Co
al
Yie
ld (
DM
S F
ee
d)
Coarse Coal Small Coal Maximum AverageMinimum Coarse Coal ROM Max Small Coal ROM Max MaximumAverage Minimum Linear (Coarse Coal) Linear (Small Coal)
Coarse CoalSmall Coal
Min yield
Ave Yield
Max Yield
Coarse Coal
Max % ROM
Small Coal Max
% ROM
Max Yield
Ave Yield
Min Yield
2 Stage DMC Circuit (Lo-Hi) South Africa –separate
coarse & small coal circuits – maximises Export Yield
Low Density Cut
+8 mm
+0.8mm
+0.8 mm
High Density Cut
2 - Stage DMC Circuit
-50mm Feedis Product
Discard
Middlings
-0.8 mm Feed
MAFUBE COAL – 940 t/hr
DRA Mafube Plant – first SA use of 1150mm Cyclones
PHOLA COAL 2400 t/hr
DOUGLAS MIDDELBURG OPTIMISATION (DMO) 2200 t/hr
DOUGLAS MIDDELBURG OPTIMISATION (DMO) 2200 t/hr
Simpler 2 Stage DMC Circuit (Lo-Hi)
Australia – combining Coarse + Small
Coal with optional Stage 2
Low Density Cut+0.8mm
+0.8 mm
High Density Cut
2 - Stage DMC Circuit
Option
-50mm Feedis Product
Discard
Middlings
-0.8 mm Feed
Glencore’s Goedegevonden & Tweefontein CPP
modern Australian type plant in RSA – 2000 t/hr
Glencore’s Tweefontein CPP
modern Australian type plant in RSA – 2000 t/hr
Glencore’s Tweefontein CPP
modern Australian type plant in RSA – 2000 t/hr
Use of CAD Modelling Techniques in plant design
Plant Section showing
“Banana” Screens & 1150mm Cyclones
2 Stage DMC Circuit (Hi-Lo) with
intermediate crushing - Mozambique
Interstage Crushing
Low Density Cut+0.8mm
High Density Cut
2 - Stage DMC Circuit
with extra liberation of
first stage product Discard
-50mm Feedis
Product
Middlings
-0.8 mm Feed to Fine Coalis
2 Stage DMC Circuit (Hi-Lo) with
intermediate crushing - India
Interstage Crushing
Low Density Cut+13mm
High Density Cut
+0.8mm
2 - Stage DMC Circuit
with extra liberation of
first stage product Discard
-50mm Feedis
Product
Middlings
-0.8 mm Feed to Fine Coalis
Fine Coal Circuit (spirals for >SG 1.7 product)
Fine Coal Washing (0.8 x 0.125)mm
Technology dominated by gravity spirals & teeter bed separator
(TBS)
Fine Coal Circuit (spirals + TBS) for low
density product
Desliming Cyclone
Spirals
-0.8 mm Feed to Fine Coalis
-0.125 mm to Thickeneris
Product
Discard
TBS
Fine Coal Circuit (Reflux Classifier) for low
density product
Desliming Cyclone
Reflux Classifier
-0.8 mm Feed to Fine Coalis
-0.125 mm to Thickeneris
Product
Discard
Fine Coal Washing (0.8 x 0.125)mm – Reflux
Classifier with lameller plates
Developed in NSW, Australia – first plant
Fine Coal Washing (0.8 x 0.125)mm – Reflux
Classifier with lameller plates
Modern Reflux Classifier with 6mm Lamellar Plate gap
COAL SLIMES (-0.125 x 0)mm - Thickening
Thickening Technology – standard settling technique
assisted by use of flocculants
COAL SLIMES (-0.125 x 0)mm – Flotation
Dual Cell –
Witbank Coal,
Column & Jameson Cell - Moatise
COAL SLIMES (-0.125 x 0)mm - Filtration
• Raw Water and slimes dams restrictions have
lead to introduction of slimes filtration
• Higher inherent moistures in the peripheral
Witbank Coal regions so Filter presses being
specified in order to make a saleable product.
• Mafube – first major use of TH Filters in RSA
• Phola – combination of TH & Lasta Filter presses
• Briquetting plants being developed and
constructed
COAL SLIMES FILTRATION
• Filter presses at Phola Coal Plant (120 t/hr capacity)
• Lasta & TH Filters used
COAL PRODUCT HANDLING – SA Traditional
Stacking & Bucket Wheel Reclamation, Rail Silo’s
COAL PRODUCT HANDLING
Overhead Stacking - underground conveyor reclamation
CONCLUSIONS
• New era of large throughput coal plant design
& construction started around 2005
• Major plants built in
• Mozambique (Moatise CF)
• South Africa (Witbank & Waterberg Coalfields)
• Future plants in Botswana & Madagascar
• Plant efficiency vs. complexity becoming a
factor in DMS circuit design
THANK YOU!