Coal Preparation at Tahmoor Colliery 123

119

特別 COAL PREPARATION AT TAHMOOR 講演 COLLIERY

W.G.TWEDDLE

TABLE OF CONTENTS 1.INTRODUCTION 119 7.1 Plant Automation 131 2.BACKGROUND INFORMATION 121 7.2 Reject Disposal 131 3.MINING OPERATIONS 122 7.3 Environmental 131 4.RA W COAL QUALITY 123 7.4 Plant Manning 133 5.DESIGN CONCEPT 124 8. QUALITY CONTROL 133 6.PROCESS DESCRIPTION 126 8.1 Mine Planning 133 6.1 Raw Coal Handling 126 8.2 Plant Product Quality 136 6.2 Jig Circuit 127 8.3 Plant Efficiency Analysis 136 6.3 Dense Medium Bath 127 8.3.1. Yield Predictions 136 6.4 Medium Recovery 128 8.3.2. Reject Analysis 137 6.5 Froth Flotation 128 8.3.3. Plant Sampling 137 6.6 Water Clarification 129 8.3.4. Efficiency Testing of 6.7 Tailings Dewatering 130 Washing Units 137 6.8 Clean Coal Handling 131 APPENDICES 139 7. GENERAL INFORMATION 131 ACKNOWLEDGEMENTS 139

Abstract

The Tahmoor mine is located some 80 km south-west of Sydney in the South Western coal mining district of New South Wales. Construction of the Coal Preparation Plant was completed in June 1981. Since this time the plant has processed all run of mine production on a two shift per day basis. The plant is a nominal 300 tonne per hour single module unit. Plant design consists of jig washing and froth flotation of the fines, with the option of dense medium separation if the raw coal quality warrants the production of a middlings product. From an engineering point of view the special features of the Tahmoor Plant are:- 1. The Baum jig has 10 compartments and three elevators. This allows middlings recycling in the third elevator. 2. The Leebar bath was selected because of its capability for a low S.G. cut and its mechanical reliability. 3. The selection of an Enviroclear thickener for tailings thickening. 4. A mechanical tailings dewatering plant which includes a solid bowl centrifuge and a band press filter. Major emphasis is placed on all aspects of quality control and plant efficiency. This is reflected in the con- sistency of product and reliability in operation of the plant.

1. INTRODUCTION

B.P. coal australia is a Department of B.P. Australia Limited, a wholly owned subsidiary of The British Petroleum Company London. The department is responsible for all B.P. Coal interests within Australia which comprises : Clutha Development Pty. Limited, a fully owned subsidiary and two joint ventures, Clarence Colliery and Winchester South Development.

*CluthaDevelopmentPty ,Ltd. *昭和59年6月13日本会第72回例会において発表 **Manager Coal Preparation ,BP Coal Australia Limited 昭和59年5月10日受理

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(40) 浮選(資源処理技術) COAL PREPARATION AT TA14MOOR COLLIERY 121

Clutha Development Pty. Limited operates in three areas of New South Wales:•\

1. The Southern Area: The southern area comprises the Burragorang Valley and Tahmoor Divisions. The Burragorang Valley operates four underground mines with coal preparation facilities at Wollondilly. Tahmoor is an underground mining operation with a coal preparation

plant on site. 2. The Northern Area: The Northern Division operates two underground and two open cut mines in the Hunter Valley region of New South Wales. All raw coal is processed at Newdell Coal Preparation Plant.

3. The Western Area: This Division operates two underground mines and one open cut mine in the Lithgow region of New South Wales. The Coal Preparation Plant at Western Main processes all run of mine coal.

2. BACKGROUND INFORMATION

The Tahmoor Colliery is located some 80 Km south west of Sydney in the South Western coal mining district of New South Wales.

Clutha Development Pty. Limited was granted the initial exploration licence in 1970. Following exploration drilling, a mining proposal was put forward for a complex consisting of two mines, serviced by a central coal preparation plant.

Construction commenced in September, 1975, on the Tahmoor East Mine with a drift at the central services site with two vertical shafts on other sites. Production commenced from the mine in September, 1979. Output was limited to 2,000 tonnes per day of raw coal until the washery was completed in June, 1981.

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3. MINING OPERATIONS

The coal seams in the Tahmoor lease are as follows :-

Total Reserves In Situ Bulli 95.6 million tonnes Wongawilli 20.4 million tonnes

The Wongawilli reserves are not regarded as currently economic and are excluded from all project proposals. Current production is 1.026 million tonnes per year of raw coal which is mined by board and pillar extraction method from six continuous mining units.

TAHMOOR COLLIERY MINE WORKINGS

( 42 ) 浮選(資源処理技術) COAL PREPARATION AT TAHMOOR COLLIERY 123

4. RAW COAL QUALITY

Raw coal ash has averaged 23% to date. In general terms there is not a large amount of material found in the `middlings' gravity fraction between 1.50 and 1.80. Middlings content varies across the lease from less than 2% up to 10%. In certain parts of the lease jig washing coupled with froth flotation enables product ash specification to be met at cut points in excess of 1.60 R.D. For the bulk of the reserve, however, it is necessary to extract the middlings content at varying cut points down to 1.40 R.D. to meet product specifications. In addition, the large coal fractions (plus 12 mm.) has a higher raw coal ash than the smaller coal fractions (minus 12 mm.) The large coal will also wash to a higher ash at a lower yield compared to the small coal. This led to the final selection of a jig as the main processing unit plus a heavy medium bath for washing the large coal from the jig when conditions are appropriate.

TAFIMOOR COLLIERY CHANNEL SAMPLE SS 51

Location 202 Panel, 1OM A3 to B3 E262590 N. 1210068

Date Sampled : 5th January, 1984.

Date Analysed 16th February, 1984.

Sampled by I JS.

Thickness 2.155 M

Sample broken up by hand to•\19.05 mm•~0

SIZING ANALYSIS

% Weigh t % Ash Size Fraction Cumulative Fraction Cumulative

-19 .05•~0.50 mm 92.38 92.38 8.69 8.69

-0 .50 mm•~0 7.62 100.00 7.11 8.57

FLOAT AND SINK ANALYSIS OF -19.05x 0.50 MM SIZE FRACTION

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FLOAT AND SINK ANALYSIS OF•\0.50 MM•~0 SIZE FRACTION

PRODUCT SPECIFICATION (Air Dried Basis)

•\ Coking Coal •\Steaming Coal Ash 8.5% Ash (Nominal) 15.0% Inherent Moisture 1.5% Inherent Moisture 1.1% Volatile Matter (Nominal) 28.0% Volatile Matter (Nominal) 24.0% Fixed Carbon (Nominal) 62.0% Fixed Carbon (Nominal) 60.0% Crucible Swelling Number (Nominal) 5%-6 Specific Energy (Nominal) 29.OMJ/kg. Total Moisture (Maximum) 8.0% Total Sulphur (Maximum) 0.4%

5. DESIGN CONCEPT

The coal preparation plant is a nominal 300 tonnes per hour single module. The plant was constructed by Bulk Materials (Coal Handling) Services Pty. Limited. With regard to the modular design of the plant consideration was given in design to the future requirements of additional washing capacity. Options are available to install an additional module which would only require a jig coupled with associated flotation equipment. An allowance has been made for the future addition

(44) 浮選(資源処理技術) COAL PREPARATION AT TAHMOOR COLLIERY 125 of a dense medium cyclone section should it become necessary to produce a lower coking coal ash product. In general building layout, a concept of relatively low profile design has been achieved by the use of internal conveyors. In obtaining this, a gravity flow situation has been maintained throughout the various process sections with minimum pumping of solids.

TAHMOOR COAL PREPARATION PLANT SOLIDS FLOW DIAGRAM

TAHMOOR COAL PREPARATION PLANT EQUIPMENT FLOWSHEET

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The plant is basically a jig and flotation plant with the option of dense medium separation of the coarse material. All run of mine feed is initially treated in a jig for removal of heavy reject material. The product after screening reports either directly to the coking coal conveyor or the plus 12 mm. material goes to a dense medium bath for further separation, if necessary. In the bath section a middlings product is removed and following crushing to 50 mm. is collected for discharge from the plant. The balance of the coking coal from the bath is screened at 50/13 mm. before the plus 50 mm. coal is crushed and the minus 13 mm. material joins the centrifuge feed. Should the total coarse material be of acceptable coking quality, provision is made to by-pass the bath completely, with the coarse product, following screening and crushing, discharging direct to the coking coal conveyor. The minus 0.5 mm. is collected from the jig water circuit for treatment by froth flotation. The recovered product from the drum filters discharges onto the coking coal conveyor. The flotation tailings after thickening are pumped to the tailings treatment plant.

6. PROCESS DESCRIPTION

6.1 Raw Coal Handling All raw coal is transferred from the underground bins by a 1.1 metre steel cord conveyor. The run of mine feed is scalped on a vibrating screen to remove all plus 150 mm. stone. The minus 150 mm. material is conveyed to the emergency stockpile area or is screened over a divergator before storage in two 1250 tonne concrete bins. The divergator sizes the coal at 25 mm. This arrange- ment is a desegregation device which enables a constant mix of large and small coal to the plant to allow the best operation of the jig and to prevent surges in the flotation section. Fixed proportions of large and small can be extracted from the bins or alternatively the bin level controls can automatically modulate the feeder rates to prevent one bin emptying or overfilling. With 2500 tonne total bins capacity the majority of the peaks of one size or the other are smoothed out.

LUAL HANLLINU SYSTEM

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TAHMOOR JIG CIRCUIT

6.2 Jig Circuit The washbox has a rated maximum capacity of 360 t.p.h. of run of mine feed. It has a washing width of 3 metres, 10 compartments length, and the feed is separated into three products , i.e. clean coal, middlings and reject. Reject material collected from the first two elevators and their associated worm conveyors, discharges to a dewatering screen for removal of excess moisture prior to being discharged to the reject conveyor. Underflow from the reject dewatering screen returns to the water circuit for recirculation. Middlings from the third elevator discharges to a classifying screen where the minus 13 mm, material is removed and with the assistance of spray water gravitates to a sump for recirculation to the washbox feed. Oversize from the screen discharges directly to the reject conveyor.

Clean coal product from the jig discharges over static wedge wire screens and then onto two

6.1•~3.1 metres double deck vibrating low head screens. These screens dewater the coal at 0 .5 mm.

and also separate the plus and minus 12 mm. size products. Water from the clean coal screens is pumped to the settling cone where the slurry is thickened. The slurry tower underflow is then screened to remove any accidental oversize (plus 0.5 mm.) prior to feeding the minus 0.5 mm, to the flotation circuit. Cone overflow together with clarified water is collected in a head tank for recirculation to the jig and flotation sections.

6.3 Dense Medium Bath

The LEEBAR dense medium bath at Tahmoor is the first of its type in Australia. The selection of this unit was due to the quiescent nature of the bath and its ability to operate at low S.G. The plus 12 mm. product from the jig is transferred to the Leebar bath for separation into coking and steaming coal products. The bath product (coking coal) floats straight through the unit and is

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removed with the aid of paddles. The sinks (steaming coal) is removed from the base of the bath

by a scraper chain. The bath is 3.5 metres wide and is rated at 240 t.p.h. of 150×12mm. material.

The bath receives the magnetite medium from the correct medium sump. The control of this

circuit relies on the following :•\ (i) The high S.G. magnetite eg. 2.0 S.G. from the dilute recovery section produces an increasing medium S.G. at all times. Therefore constant water dilution is necessary to obtain operating gravities of 1.35-1.40 S.G. (ii) Any magnetite lost from the system results in a decreasing correct medium sump level. Bulk magnetite is pumped to this sump via the dilute circuit. Drain/ Rinse Section Coking product and medium pass over a static wedge wire screen prior to discharging to a conventional 4.88 metres x 2.44 metres drain and rinse screen. Steaming coal is discharged in a similar manner except that no static wedge wire screen is required and a 4.88 metres x 1.22 metres drain and

rinse screen is used. Magnetite medium from the underpan of the fixed wedge wire screen and the first section of the coking product screen returns direct to the dense medium sump. Magnetite and spray water from the discharge underpan of the coking coal screen and the steaming coal screen report to the dilute medium sump.

6.4 Medium Recovery The dilute medium is pumped to a 2.44 metre primary magnetic separator where the majority of the magnetite is recovered and returned to the correct medium circuit. Primary separator underflow is discharged via a flocculating magnet to a 3.1 metres diameter x 3.4 metres high thickening

TAHMOOR DENSE MEDIUM CIRCUIT

浮選(資源処理技術)

(48) COAL PREPARATION AT TAHMOOR COLLIERY 129 cone. The remaining magnetite particles settle and discharge from the base of the cone to a 0.9 m. secondary separator.

Non-magnetic underflow from the secondary separator returns to the dilute medium sump with a controlled bleed taken from this circuit depending on the dilute sump level. This bleed is fed to the flotation circuit.

A demagnetising coil is installed in the magnetite recovery circuit to prevent magnetite settling in the dense medium bath. This prevents S.G. stratification and instability in the D.M. bath operation.

6.5 Froth Flotation The flotation feed received from the underflow of the slurry sieve bends and slurry screens, is collected in a sump and pumped direct to a distribution/dilution head tank prior to the flotation cells. The flotation section consists of two banks of three high capacity cells, with cell to cell feed arrange- ment.

The flotation reagents used in the plant are :-

1. Collector•\Diesel 2. Frothers-Methyl Isobutyl Carbinol (M.I.B.C.)

•\ Herco Froth 6A5X

These reagents are added in the ratio :- 350 mis./minute Diesel 40 mis./minute M.I.B.C. 50 mis./minute Herco Froth The flotation concentrate discharges to a sump and is pumped to thickening cyclones. The purpose of froth thickening is to ensure a feed greater than 40% solids to the drum filters thus maxi- mising filtration capacity. In the cyclones, the coarse particles are thickened to approximately 45% solids and discharge directly to the drum filters. Cyclone overflow gravitates to the coal thickener for flocculation and settlement of the fine coal particles. The coal thickener underflow is thickened to approximately 30% solids and pumped to the filters for recovery. Coal thickener overflow is used as dilution water in the flotation feed.

The two vacuum filters are string discharge drums. These filters have been modified for front feed of pulp to the bowl. Both filters have a filter area of 70 metres. 6.6 Water Clarification Tailings discharged from the flotation cells are clarified in a 12.2 metres high capacity Enviro-

Clear thickener. The tailings pulp is treated in a de-aeration tank prior to feeding via a horizontal feed pipe to the thickener. A horizontal deflector plate causes the incoming flocculated feed to be injected into the pulp bed at a controlled velocity. Clarified water from the thickener, overflows into a sump for pumping to a head tank system supplying balance water throughout the plant. Fresh water make-up is automatically added to the clarified water sump. Thickened tailings are pumped to the tailings dewatering plant. The flotation fine coal thickener is a conventional 18.25 metres diameter thickener with automatic lift but manual lowering of the rakes.

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TAHMOOR FLOTATION CIRCUIT

6.7 Tailings Dewatering A feature of the Tahmoor Plant is the mechanical dewatering of the flotation tailings. This circuit contains a S4-1 Solid Bowl Centrifuge and a C-250 Band Press Filter. The Band Press Filter is the only one of its type operating on coal tailings in Australia. Thickened tailings pulp (40-45% solids WOW)is pumped into a 50,000 litre slimes storage tank. The tailings are then dewatered in one of the units. The solid product is mixed with the jig reject and conveyed to the reject bin. The liquid effluent is returned to the plant circuit.

A general summary of results to date is :•\

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6.8 Clean Coal Handling The coking coal products-crushed large, centrifuged smalls, and filter cake, are collected on a common conveyor for discharge to the coking coal stockpile. The coal is automatically sampled

prior to reaching the stockpile area. Steaming coal is conveyed to a separate stockpile. The coking coal stockpile has a storage capacity of 200,000 tonnes with underground reclaim to a rail loading bin of 6,000 tonnes capacity. Coal can be reclaimed to the loading bin at a rate of 1,000 tonnes per hour and from this bin trains can be loaded at a rate of 4 ,000 tonnes per hour through double hydraulic loading chutes. The steaming coal stockpile is 40 ,000 tonnes capacity.

7. GENERAL INFORMATION

7.1 Plant Automation

The motor control centres which supply the drives in the plant have three modes of operation :•\ (i) Mannual or test: Used for maintenance purposes to test run drives without the whole plant running. (ii) Sequence : Used to run the plant in a manual mode but with all necessary sequence functions between drives being performed. (iii) Automatic : PLC Control. The Automatic Control of the plant is achieved by the use of two TEXAS Model PM.550 PLCs , supplemented by one COALTRONICS Mini-computer. This system controls the plant plus the coal handling drives. Only the train loading system is separate. The operator communicates with the system via a keyboard and video display unit (VDU) . All alarms come up on the VDU and are also printed on a hard copy printer . The printer also records shift reports, plant throughput, and plant yields. The drives in the plant are split up into thirteen groups and each group has a 'start' and 'stop' button on the control desk. Once a group `start' button is pressed the motors in the group automatically start in turn at approximately 5 second intervals. Visual indication is available at all times on the VDU to tell which drives are running or, if a fault occurs, on which drive it occurred . The system also has an automatic shutdown sequence which once initiated selectively shuts down the drives in sequence.

Typical plant start time =15 minutes Typical plant shutdown time =20 minutes The analogue control systems which regulate coal feed to the plant, S.G. control, sump levels , etc., are all performed on the PLC, but like the motor control centres, back up exists in the form of standard analogue instrument controllers. These are selected by an auto-manual changeover switch on the control panel. 7.2 Reject Disposal To date, the reject material has been used for environmental embankments around the mine complex. Work is currently in progress to convey the reject across the Southern rail line for disposal in approved areas.

7.3 Environmental The following environmental considerations have been implemented at the site :- (i) Dust suppression sprays are installed on all open stockpile areas. (ii) All surface water run off is collected in silt collection dams and returned to the main

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REJECT DISPOSED ON SITE

collection system. (iii) Environmental embankments are being constructed around the site. Grass and trees will be grown on these embankments to blend in with the local flora. (iv) All conveyors on site are fully enclosed. Hosing down water from these conveyors is also recovered in silt collection basins. vl All tailings produced in the ulant are treated in a mechanical dewatering unit. (vi) Bag dedustors are installed over both coal crushers to eliminate dust emission. (vii) Noise Control. •\ Floor levels are constructed of concrete to reduce noise and vibration.

•\ All screens are floor mounted and suspended on air bags. •\•\ Polyurethane screen panels are used throughout the plant. •\ All chutes are lined with tiles or rubber material. •\ Silencers are fitted to the jig exhaust. •\ The jig blower is surrounded by noise absorbing material.

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7.4 Plant Manning

TOTAL MANNING = 26

8. QUALITY CONTROL

Quality control planning and testing takes the following form:•\ 8.1 Mine Planning

As mine development continues, in•\seam channel samples are taken at regular intervals for washability data and proximate analysis determinations. This information is used when developing the mining plan so that product specifications are achieved.

TAHMOOR COLLIERY•\CHANNEL SAMPLE SS 51 (continued)

PROXIMATE ANALYSIS OF CUMULATIVE S.G. FRACTIONS (AIR•\DRIED)

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COLLIERY: TAHMOOR TPTICKNESS: 2.155 M SEAM: BULLI CORE RECOVERY: LOCATION: 202 Panel, 1OM A3 to B3 E. 262590 N. 1210068 DATE SAMPLED: 5th January, 1984 SAMPLED BY: IJS DATE ANALYSED: - DEPTIT : SAMPLE NO: SS 51

1. PROXIMATE ANALYSIS-RAW COAL:

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TAHMOOR WASHERY D.M. BATH SAMPLES Date of Sampling 11th November, 1983.

Feed to D.M. Bath•\9.93% Ash

FLOAT AND SINK ANALYSIS OF COKING COAL PRODUCT

FLOAT AND SINK ANALYSIS OF STEAMING COAL PRODUCT

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8.2 Plant Product Quality Product from the plant is automatically sampled prior to reaching the product stockpiles. These samples are used for :- (a) Shift analysis. (b) Weekly composite analysis. Only ash determination is carried out on the shift sample. A complete quality analysis is carried out on the weekly composite sample. As a further check on plant product quality, samples are taken from each train as the product is being railed to the port for export. 8.3 Plant Efficiency Analysis 8.3.1 Yield Predictions From the in-seam channel sample washability data, and measured dilution from each panel, theoretical yields are calculated each month. This information is compared to actual plant results.

TAHMOOR COAL PREPARATION PLANT QUALITY

TAHMOOR COAL PREPARATION PLANT QUALITY CONTROL COMPOSITE

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8.3.2 Reject Analysis Each reject stream from the plant is sampled each shift to detect product losses and plant in- efficiencies. 8.3.3 Plant Sampling Routine sampling of the jig and flotation circuits are carried out to continuously monitor operating efficiency. 8.3.4 Efficiency Testing of Washing Units At regular intervals the Jig and Dense Medium Bath are tested for operating efficiency. This involves sampling the feed, product, and reject streams. Float-sink analysis is carried out and partition curves are drawn from this information.

CONTROL (ALL AN ALYSES ON AIR DRIED BASIS)

SAMPLES FOR MONTH OF MARCH, 1984 (ALL ANALYSES ON AIR DRIED BASIS)

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TAHMOOR COAL PREPARATION PLANT 11.11.83 D. M. BATH MEDIUM GRAVITY=1.34

ASH BALANCE=12.06-9.93/ 12.06-7.93•~100/1=51.57% RECOVERY

TAHMOOR COAL PREPARATION PLANT DENSE MEDIUM BATH

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APPENDIX 1 APPENDIX 2

ULTIMATE ANALYSIS CAKING ANALYSES (DRY, ASH FEE BASIS) CRUCIBLE SWELLING NUMBER=51/2-6 GRAY KING COKE TYPE=G4 CARBON 87.41% ROGA INDEX=71 HYDROGEN 4.86% AUDIBERT-ARNU DILATOMETER NITROGEN 1.61% Ti SOFTENING =365•Ž

SULPHUR 0.40% T2 MAXIMUM CONTRACTION =420•Ž T3 MAXIMUM DILATATION =465•Ž OXYGEN (BY DIFFERENCE) 5.72% MAXIMUM CONTRACTION =29% MAXIMUM DILATION =48% GIESELER PLASTOMETER INITIAL SOFTENING TEMPERATURE=405•Ž MAXIMUM FLUIDITY TEMPERATURE=450•Ž RE-SOLIDIFICATION TEMPERATURE =480•Ž PLASTIC RANGE =75•Ž MAXIMUM FLUIDITY =2,000 ddpm

APPENDIX 3 APPENDIX 4 PETROGRAPHIC ANALYSIS ASH ANALYSIS REFLECTANCE SILICON as Si02=49.9% MEAN MAXIMUM REFLECTANCE ALUMINIUM as A1203=34.7% (VITRINITE A)=1.1% IRON as Fe203=5.79% MACERAL ANALYSIS CALCIUM as Ca0=2.59% VITRINITE=47% MAGNESIUM as Mg0=0.44% EXINITE=TRACE TITANIUM as Ti02=1.46% INERTINITE=48% SODIUM as Na20=0.17% MINERAL MATTER=5% POTASSIUM as K20=0.80% CALCULATED COMPOSITION PHOSPHORUS as P205=1.75% BALANCE INDEX=1.98 MANGANESE as Mn304=0.07% CALCULATED STRENGTH INDEX=3.57 SULPHUR as 503=0.65%

ACKNOWLEDGEMENTS

The author thanks the various equipment suppliers, particularly the major contractor, Bulk Materials (Coal Handling) Services Pty. Limited, for providing information for this paper, and for granting permission to show slides of equipment. Contributions by my colleagues, Dr. I. Fletcher and P. Shannon are recognised. My thanks also to BP Coal Australia Limited for permission to present this paper.

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