Down to Zero : Processing challenges and solutions for recovering and realising the value of fines.

Transcription

1 Down to Zero : Processing challenges and solutions for recovering and realising the value of fines. Ross Garling - FAusIMM & Member ACPS Wednesday, 19 Oc Down to Zero :Processing challenges and solutions for recovering and realising the value of fines.tober 2016 Royal on the Park, Brisbane AusIMM-ACPS /10/2016 1

2 Topics Raw Coal One of the Problems start at the beginning Commercialising High Inherent Ash Coals, eg Fort Cooper Coal Measures Achieving low ash coal products Developments in Tailings Testing & Evaluation Re-Mining Re-Processing Agglomeration AusIMM-ACPS /10/2016 2

3 Coals ain t Coals Fine Grained Coal Coarse Grained Coal Grey is vitrinite To maximise high grade product yield:- 1. Evaluate, 2. Liberate 3. Selectively Process 4. Dewater 5. Briquette AusIMM-ACPS NB These are exactly the same steps that have been followed for many years with the evaluation and development of all mineral deposits 20/10/2016 3

4 Information for reading the following photographs Vitrinite grey; lightens with increasing coal rank Inertinite higher reflecting than vitrinite, grey to yellowish white and commonly showing cell structure Liptinite darker grey (rare) Minerals generally black (clays), some with brownish colour tones with some minerals ranging from grey (calcite) to very highly reflecting yellowish white (e.g. pyrite) Magnification see the blue bar scale AusIMM-ACPS /10/2016 4

5 Example of Coarse Grained Coals Large particle comprised of vitrinite and a few small mineral grains. Courtesy - Ray Smith, Coal Petrology Services 20/10/ AusIMM-ACPS

6 Example of Fine Grained Coals Vitrinite lamellae with abundant layers of clay minerals and a few small particles of inertodetrinite (white). Photomicrograph taken in oil. Courtesy - Ray Smith, Coal Petrology Services 20/10/ AusIMM-ACPS

7 Processing Fine Grained Coal The first reaction is grind and achieve liberation. Not so fast it is well known that flotation recovery is poor in ultra-fine particles. We can look at nano-bubbles and other techniques Tradd has done over 2,300 pilot trials including large scale trials. Many in the Fort Coopers, Fair Hills, and Burngroves, Girrah Achieving:- <10% ash, premium coking coals, 90% combustible recoveries AusIMM-ACPS /10/2016 7

8 Comparison - Standard Testing Yields Fine Grained Techniques AusIMM-ACPS /10/2016 8

9 Achieving low ash coal products A client asked Tradd to achieve 1% ash coal for an alternative market To date Tradd has:- selected various coarse grained coals Utilised its Fine Grain Techniques Repeatedly achieved products in the range 0.85% to 1.1% ash(db) Other technologies now emerging Reasons for not getting 0% ash:- Impurities Organically bound minerals Maximise Coking Coal Recovery from Moatize 20/10/2016 9

10 Ross Garling BE(Mining), MBA, Mine Mgr s Cert., FAusIMM 25 years - specialized in the evaluation, re-mining, and reprocessing of tailings see Some tails/rejects worked on:- Grasberg, Irian Jaya Anchor Tin Gympie Gold Rhondda Hexham South Blackwater German Creek Hebburn Wambo Westcliff Metropolitan Huntley Bloomfield Liddell Collinsville Catherine Hill Bay Jellinbah East Kestrel Lake Vermont Meandu Oaky Creek Peak Downs South Walker Creek Jeebropilly Austar Integra Invincible Mount Thorley Warkworth Ulan West Cliff Cleveland Tin Norwich Park Saraji Cook Gregory Dawson Ayrefield Aberdare East Neath Merrywood Southland Abermain Richmond Main Pelaw Main Elrington Bellbird St. Ives, Kalgoorlie

11 Testing & Evaluation No Assumptions Please This is where the mistakes are made For an industry that is so meticulous, the lack of knowledge of the volume, grade, and extraneous materials in the tailings dams, is amazing. Tailings dams are highly variable resources To consider a tailings business, requires a JORC reserve Sampling methods:- Coring lose sample Auger contamination RC running sands Vibracore 100% core recovery

12 Vibracore Drilling Soft Terrain Drill Through Water 100% Core Recovery

13 Re-Mining Alternatives Depending on Throughput the costs & factors are:- Hydraulic Mining $ $1.50/t(db):- Constant high density Work in any weather, near 100% mining recovery, accurate control Dredging $ $2.50/t(db):- High density fluctuation (0% - 40%) Low labour, high pond evaporation, poor mining recovery (back off stumps, etc) Dry Mining $ $5.00/t(db):- High labour (1 man per truck or digger) Soft floor bogging + problem unloading trucks Tailings then need slurrying to process

14 Hydraulic Re-Mining Recycled Water Pressure Pumps Hydraulic Monitor - remote controlled, Mine straight faces Slurry drains to Pump

15 Modern Hydraulic Mining High pressures (20 to 40 bar) depending on material High pressure converts tailings into dense oil like solution Fine tailings can drain for kilometres to slurry pump High constant densities 30-40% in coal, 50-60% in say gold Monitors remote controlled, tracked, semi-automatic Production rates up to 500 tph per 150 mm unit or 1,000 tph/200mm Low ground bearing pressures Low evaporation High mining recovery Trash cleaned & left

16 Hydraulic Mining Hunter Valley Coal Gold Tails, South Africa Bowen Basin

17 Re-Processing The fine particle size of tailings dictates that flotation should be included Many flotation devices, some with pre-treatment Combustible recoveries 60% - 95% depending on circuit & feed ash Product ashes eg 5% to 10% ash (depends target & coal) Coking properties retained Dewatering an issue:- vacuum (30-35%TM), pressure (20-25%TM) Agglomeration: briquetting (with or without binder), pelletisation Drying after agglomeration moistures 2% (no re-wetting)

18 Alternative Processing 1 Slurry-making Circuit Coal refuse High shear mixer Water Vibratory de-slime screens 2 3 Agitated slurry hopper Dewatering and extrusion Agitated hopper for froth de-aeration 5 Flotation circuit Flotation columns 4 6 Vacuum filtration drums Nanotech solution 7 Extrusion Alternative 720,000 tpa(pdt) plant. Spirals plant built for $1.3m 9 Coating circuit Drying circuit 90% comb. rec, 5% ash, 2% moisture. $50m capital $20/t(pdt) opex Carbon pellet storage pile Ash pellet storage pile

19 Agglomeration Briquetting & Pelletising To be avoided if possible as adds $10-$15 / tonne product, Sometimes part or all of the product can be added to the host mines product year history - Binderless originally 0% surface moisture, now increasing - Binder regime depends on:- - Clay content - Product heat - Duty of Briquette - Lowest cost alternative

20 Likely Products Filter 20 to 25% TM can be added to mine product Briquettes (technology is 150 years old), with or without 2 to 20% TM Extruded pellets made recently for Australian 2% TM, & will not rewet Tailings - A Wasted Resource 20/10/