1. business and industrial
2. energy
3. oil

Keynote addresses
Paste 2015 | Abstracts | 1
Thickener modelling – from laboratory experiments to
full-scale prediction of what comes out the bottom and
how fast
PJ Scales University of Melbourne, Australia
AH Crust University of Melbourne, Australia
SP Usher University of Melbourne, Australia
Abstract
Predicting full-scale thickener performance, including the solids flux and concentration delivered
from a thickener underflow based solely on laboratory-scale experiments, has long been the
holy grail of thickener design and operation. A number of researchers have developed both
thickener models and laboratory characterisation techniques to measure sedimentation and
compressional properties of flocculated suspensions. Combining these to produce predictions of
actual performance generally results in an under-estimation of the thickener solids flux, often by
a factor of between 10 and 20. Consequently, a range of empirical methods and industry scalars
has been developed to get around this discrepancy.
Analysis of the reasons for the discrepancy shows that changes in aggregate structure in shear,
due to inter-aggregate buffeting and shear induced by collisions with surfaces and rakes, causes
the flocculated aggregate to change from a fractal to a denser non-fractal object as it progresses
through the thickener. These changes are shear rate and solids concentration dependent and as
such, very difficult to reproduce in the laboratory and then incorporate into thickener models.
A method to quantify the time and shear rate dependent changes in aggregate structure
is now available and a model has been developed that allows incorporation of this effect into
modelling. The change in aggregate behaviour is incorporated through a shear rate dependent
densification rate and final extent of aggregate densification. The latter parameter helps to
define an upper limit in solids flux behaviour for a given solids underflow concentration. Using
the new information, thickener models now predict a range of underflow solids flux outcomes
between the upper (densified aggregate) and lower (undensified aggregate) limit for a particular
underflow solids concentration, depending on the operational conditions. The difference in
underflow solids flux between these two limits is significant and the actual outcome depends on
the shear rate and time of shear, as well as total solids residence time in the thickener.
The data indicate that for non-segregating flocculated suspensions, operational conditions
that produce the optimum thickener underflow solids flux for a given flocculation condition can
now be explored quantitatively without resorting to extensive pilot trials.
Paste 2015 | Abstracts | 2
The high-density thickened discharge tailings storage
facility at Osborne Mine – a case history from inception
to closure
GI McPhail SLR Consulting Australia Pty Ltd, Australia
Abstract
Chinova Resources Pty Ltd’s Osborne Mine is located in Northern Queensland, approximately 800
km inland from the eastern coast. It commenced operations in 1995 with the development of an
open pit mine. In 1996, the operation transitioned to underground mining. In 2015, Osborne will
have been in operation for 20 years and will have mined 29 Mt of ore. The site has produced 672,
420 t of copper and 673,295 oz of gold.
Osborne Mine produces approximately 112,000 t of tailings per month. In 2003, following
progressive evaluation and development of a high-density discharge tailings management
system, Osborne implemented the first of two trial depositions forming advancing cones of
deposited tailings within their TSF2 site. These trials proved successful and, following successful
permit applications to the regulators, TSF2 was converted to high-density thickened tailings
discharge. The principal benefit of this change was in the reduction of construction costs for
confining embankments. However, an additional major benefit lay in a reduction of make-up
water volumes. The majority of water loss in the process water circuit occurs in the tailings
system as a result of evaporation. High-density thickened discharge provides a means for
significantly reducing water losses, since, by recovering and re-using more water at the thickener
and in the plant, less water is discharged onto the tailings facility so there is less water available
for evaporation. High density thickened discharge also enabled a significant improvement in
operating costs.
High-density thickened discharge operations at Osborne have had to be continuously modified
and adjusted as ores from satellite mines have been processed to supplement the diminishing
Osborne Mine ore. Mineralogical influences of the supplementary ore significantly affect the
thickening and beaching characteristics of the tailings slurry, particularly in the most recent
operating period. However, through appropriate modifications and adjustments, the benefits of
high-density thickened discharge have been retained.
The resulting tailings storage facility (TSF) landform is that of a shallow-sloped shedding
mound so that there is no need to retain water on the TSF. Chinova has been proactive with
ongoing site monitoring and rehabilitation with a view to shedding runoff to the environment.
Their site plans include ensuring that the discharge water from the site will meet the stock-water
guidelines, and that the erosion gullies forming in TSF cover materials or on the side slopes of
confining embankments will not result in exposure of the tailings over 500 years.
Paste 2015 | Abstracts | 3
Thickening
Paste 2015 | Abstracts | 4
A novel method to locate and profile the bed of a
thickener
RD Cook WesTech Engineering, Inc., USA
JL Johnson WesTech Engineering, Inc., USA
Abstract
Measuring mud bed level in a sedimentation device is an important control variable. Current
methods used for this purpose have had limited success providing continuous, consistent
measurements at a reasonable price. This is especially true for high-density and deep-cone type
thickeners which are becoming more prevalent in the mineral industry. Optimising underflow
rheology is dependent on steady operation, which is linked to the ability to control bed level
(solids residence time). This paper describes a new instrument for detecting the mud bed/liquor
interface as well as the rheology of the mud bed. Measurements are made directly with sensors
located in the thickener. Data from bench-scale and full-scale tests demonstrate this technology
has the ability to provide insight into the dynamics of a thickener bed and the potential to
revolutionise thickener control. The instrument, continuously and in real time, monitors bed
level and rheology, detecting horizontal, vertical and radial variation. Thickener ailments like rat
holes and island formation could be detected before they are fully formed, allowing corrective
measures to be taken before experiencing costly shutdowns.
Paste 2015 | Abstracts | 5
Thickeners versus centrifuges – a coal tailings technical
comparison
S Meiring PasteTech, Australia
Abstract
Both high-rate thickeners and dewatering centrifuges are used in the application of dewatering
coal tailings. Both applications are well advanced and accepted as means to dewater coal. This
paper compares a high-rate thickener to a solid bowl centrifuge with respect to numerous
process, mechanical, electrical, control, layout and operator variables. Process variables include
feed, effluent water discharge, retention time, and centrifuge cake moisture/thickener underflow
percent solids. A comparison of a 33 m diameter thickener and a 1.117 m diameter solid bowl
centrifuge with respect to g square meters is shared.
The suitability of the dewatering application is governed by the properties of the resultant
solids mixture. Different ash tailings, particularly those containing clay, presented a challenge to
both the operations of the thickener and the centrifuge. A holistic view to the entire process is
required
Paste 2015 | Abstracts | 6
Operational results and future trends of filtration
technology in minerals processing
J Palmer Outotec Pty Ltd, Australia
Abstract
Water in mining is the commodity that has driven the mining industry for decades. Often
used frivolously, modern economic and social pressures are forcing change to use less water
and to improve the quality of water and effluents. Used in many processes, water is ultimately
consumed in tailings disposal and technologies which can increase the recovery of water are
constantly being developed.
Filtration and thickening are often seen as competing technologies for water recovery however
new cases are developing that show significant advantages can be achieved by combining the
two technologies to develop the most effective solution.
Supported by case studies this paper investigates the merits of each of the technologies and
which strategies of combining the two produce the best outcomes.
Paste 2015 | Abstracts | 7
Dewatering in a laboratory simulation of a multilayer
deposit of inline flocculated mature fine tailings
E Rozina Carleton University, Canada
S Mizani Carleton University, Canada
M Malek Carleton University, Canada
M Sanchez-Sardon Carleton University, Canada
P Simms Carleton University, Canada
Abstract
This paper examines the dewatering behaviour of in-line flocculated oil sand mature fine tailings.
Tailings used in this study had an initial solids concentration of 36% and were dosed at 650 g/t,
using laboratory procedures that have previously been shown to represent field mixing
conditions. Three layers of initial thicknesses of 0.3 to 0.35 m were successively placed in an
instrumented box 0.7 by 1 m in plan, mounted on scales and equipped with a drainage system.
Water content sensors and porewater pressure sensors were placed at various heights. Volume
change was tracked by non-contact displacement sensors and by time-lapse imaging and hand
measurement of crack development.
Increases in evaporation were found to be strongly correlated with the appearance of
cracks. The actual evaporation rate exceeded the potential evaporation rate as long as crack
development continued to occur. This is the first documented case of evaporation exceeding the
potential rate in any controlled laboratory study.
Despite substantial drainage, supernatant water formed on top of the tailings, and remained
there longer than the initial consolidation phase of dewatering. Consolidation alone was able
to increase solids concentration of the tailings to about 53%. For these tailings, which show
a relatively high shear strength (achieving the directive 74 requirement between 55 and 60%
solids, if porewater pressure is near zero or negative), not much drying is required to bring the
tailings to regulatory compliance; even less is required if the tailings consolidate further when
buried by new layers.
Conservatively extrapolating the results of this test, it is estimated that a rate of rise of 2.2 m
per year would still allow for the regulatory shear strength of 5 kPa to be achieved. This rate of
rise is comparable to that proposed by field studies on similar tailings in thin lifts.
Paste 2015 | Abstracts | 8
The influence of slurry density on in situ density
D Reid Golder Associates Pty Ltd, Australia
AB Fourie The University of Western Australia, Australia
Abstract
Since the beginning of the Paste and Thickened Tailings seminar series, there has been ongoing
discussion as to whether an increase in the deposited (initial) slurry density will result in an
increased density at depth within an accreting deposit, all else being equal. Despite frequent
speculation and theorising, there has been relatively little laboratory data or other evidence
presented at the conference series to address this question.
To address the above deficiency, a literature review was undertaken to identify experimental
programs where the same material was prepared for soil testing from different initial slurry
densities. Twelve such studies were identified, of which nine indicate that an increase in initial
slurry density resulted in increased density at subsequent significant vertical effective stresses.
Case studies presented on three tailings deposits are investigated, to assess the implications of
the presented results on the potential for initial slurry density to influence in situ density. For
many of the studies reviewed, there appears to be an indication that an increased initial slurry
density resulted in an increased in situ density at significant vertical effective stresses. Finally, a
series of consolidation tests were undertaken by the authors, wherein four tailings types were
prepared from different non-segregating initial slurry densities. For three of these materials, a
dependence on situ density was observed, based on changes to initial slurry density.
On the basis of the review and experimental data presented in this study, the authors conclude
that for at least some materials, initial slurry density can result in an increased density across a
wide range of vertical effective stresses.
Paste 2015 | Abstracts | 9
Sarcheshmeh Copper Mine paste plant design, start-up
and early operation overview
S Javadi ATC Williams Pty Ltd, Australia
B Pirouz ATC Williams Pty Ltd, Australia
P Williams ATC Williams Pty Ltd, Australia
A Zarabadi National Iranian Copper Industries Co., Iran
HR Seif National Iranian Copper Industries Co., Iran
Abstract
Sarcheshmeh Copper Mine paste plant was commissioned mid-2012 to re-thicken 95,000 tonnes
of tailings per day. Due to the arid climate of this area and increasingly tough legislation on water
resource preservation, this plant has been designed to minimise water losses in the tailings
storage facility as well as to improve the tailings deposition in the main disposal area. Having been
partially thickened by high rate thickeners at the concentrator plant, 40-42% solids (by weight),
slurry gravitates via a concrete channel and pipe to the paste plant. The paste plant discharges
tailings with 60% solids (target design figure) to the head of two main valleys running down
to the tailings dam. The plant consists of twelve 24 m diameter paste thickeners in two rows,
flocculant plant, reclaim water pump station and main pipe line. In order to achieve maximum
performance along with flexible operation in this plant, several key issues have been taken into
account in the plant design, which is briefly presented in this paper. Similar to other process
plants, during plant start-up there have been many issues. Thickener underflow flow control,
thickener feed, and the sealing of the concrete cones that form the base of the thickener tanks
are the other areas of discussion in the paper. The paper discusses the difficulties and challenges
associated with the paste plant commissioning and early operations. Moreover, summarised
operational records including thickener underflow density, flocculant usage, and water recovery
improvement are presented.
Paste 2015 | Abstracts | 10
Rheology
Paste 2015 | Abstracts | 11
Attributes of silica treatment on strength, physical
properties and consolidation rates of fluid fine tailings
RH Moffett E.I. DuPont, USA
Abstract
Management of fluid fine tailings (FFT) is an ongoing challenge to the mining industry. To meet
this challenge, in situ polymerisation of silica has been proposed as a low cost and practical
method for treatment of fluid fine tailings. Silica polymerisation modifies the rheological
properties of FFT, imparting significant yield strength and consolidation benefits which are
maintained throughout the dewatering process. In situ polymerisation creates a continuous silica
network within the fluid phase of the FFT that allows unrestricted water movement but prevents
fines migration and blinding of drainage boundaries. Silica treated FFT has been demonstrated
to enable self-weight consolidation. More rapid consolidation rates can be achieved through
increased effective stress generated by thicker lifts and surcharge loading made practical by the
high strength and enhanced erosion resistance provided by silica treatment.
This paper will provide a general overview of how in situ polymerisation functions and its
effect on FFT physical properties and consolidation rates.
Paper courtesy of DuPont © 2014.
Paste 2015 | Abstracts | 12
Evaluation of the rheology of pipehead flocculated
tailings
PT Slatter ATC Williams Pty Ltd, Australia
KD Seddon ATC Williams Pty Ltd, Australia
Abstract
Pipehead flocculation is now a realistic option for mining tailings dewatering and disposal.
However, for beach slope prediction, it is of fundamental importance to gauge the impact that
pipehead flocculation could have on the rheology of the agglomerated tailings material, and
how this might change after extended periods of shear as the agglomerated material flows down
the beach. To this end, the laboratory of ATC Williams was requested to conduct a programme
of laboratory testing of mine tailings samples. The objective was to provide information on the
rheological properties of pipehead flocculated tailings samples. For this exercise, two different
tailings samples were used, and two different types of flocculants were used. The overall aim
of the study was to obtain rheology for the purpose of predicting beach slopes. In order to
achieve this, rheograms were obtained after varying time periods of sample pre-shear, so that
any change in flow characteristics as the tailings flowed down the beach could be ascertained.
For the first tailings material, for both flocculants, the rheological behaviour was essentially
very similar for each test. Furthermore, there was no evidence of structural rebuild of the
polymeric agglomerates. The second tailings sample material was sensitive to both flocculant
type and shear history. This material showed evidence of structural rebuild of the polymeric
agglomerates. Possible reasons for the fundamentally different behaviour are discussed. It is
concluded that pipehead flocculation is a viable option, but needs to be evaluated for each
material and flocculant type.
Paste 2015 | Abstracts | 13
Polymer-modified tailings deposition – ongoing testing
and potential storage efficiency opportunities
TC Riley Golder Associates Pty Ltd, Australia
D Reid Golder Associates Pty Ltd, Australia
L Utting BASF Australia Ltd, Australia
Abstract
An emerging technology, known by various names such as in-line flocculation, polymer modified
tailings deposition or more commercially as enhanced tailings disposal (ETD), is the subject of
growing interest from mining operations. Business drivers for the mine tailings facility owners
can include a variety of site-specific, material-dependant operational challenges, as well as more
general desires to improve efficiency at tailings storage facilities (TSFs).
Polymers can modify the behaviour of tailings in a variety of ways; one of these is through
rheological adjustment. This can often result in a steepened beach which, with careful design
and use of natural or man-made landforms, can result in the potential for significant reduction
in the volume of initial embankment construction material. These opportunities are the subject
of a number of ongoing large-scale operational trials that are likely to become the topic of future
papers.
Other material behavioural changes are inextricably linked with the technology. These
include reduced segregation, improved water release, less long-term settlement, and improving
permeability and subsequent consolidation behaviour. Thorough understanding of these
improvements can allow for appropriate design and operational management, which can then
allow the operator leverage to improve long-term operational performance.
This paper describes some scoping-level testing that focused on potential time-related
opportunities that may lead to more efficient tailings management. Subject to site-specific
constraints, there may be a cost-effective opportunity to defer future capital expenditure required
for construction of a subsequent facility, or construction of the next raise of the embankments.
Increased consolidation rates may also lead to improved trafficability and thus more efficient
rehabilitation. Whilst not going into specific detail concerning operational or construction costs,
this paper presents high-level results of testing and consolidation modelling, demonstrating a
combination of opportunities for improved tailings performance through the implementation
of the following:
• Accelerating and increasing overall water release.
• Improving the rate of consolidation.
• Reducing the rate of rise.
• Reducing the amount of post depositional settlement.
The implications of the data and modelling are discussed in the context of potential business
opportunities, which can be broadly described as the ‘time value of volume’.
Paste 2015 | Abstracts | 14
Why small-scale testing of reagents goes wrong
PD Fawell CSIRO Mineral Resources Flagship, Australia
AD Costine CSIRO Mineral Resources Flagship, Australia
AF Grabsch CSIRO Mineral Resources Flagship, Australia
Abstract
Small-scale cylinder or jar tests are routinely applied to establish the impact of polymer reagents
that induce aggregation in mineral systems. Despite their value, such tests are often done poorly
or under too narrow a range of conditions, which can lead to trends being either missed or
wrongly interpreted. A number of common errors are discussed, together with strategies to
maximise the practical value of the results obtained.
Paste 2015 | Abstracts | 15
Risk assessment methodology for paste and thickened
tailings
A Fernandez-Iglesias ArcelorMittal Global R&D Asturias, Spain
A Correa ArcelorMittal Mining, France
O Morton ArcelorMittal Mining, UK
J Laine University of Oviedo, Spain
R Luiña University of Oviedo, Spain
G Martínez University of Oviedo, Spain
Abstract
According to the database compiled by the US Commission on Large Dams (USCOLD)
and completed later by the International Commission on Large Dams (ICOLD) and the US
Environmental Protection Agency (EPA), there have been two or more major tailing dam failure
incidents per year between 1970 and 2000, proving that these catastrophic failure events are
not rare occurrences.
Paste and thickened tailings (P&TT) technology has emerged in recent years as a promising
technique to avoid dam incidents. Due to the low water content of the P&TT, the potential for
liquefaction is reduced drastically in comparison to conventional tailing dams. This is one of the
major advantages of the technology, alongside the volume reduction and the absence of bleed
water. However, paste also has some drawbacks such as higher energy consumption and extra
equipment requirements.
Due to these advantages and drawbacks, a set of different tools is required to assess the
feasibility of a paste facility at a specific mine. Among these tools, those related to risk become
important since one of the major advantages of paste is related to this dimension. Thus, selecting
the right tool for analysis is a key factor in the decision-making process that may lead to the
selection of P&TT as an alternative to conventional tailings storage.
According to the AS/NZS 4360:2004 ‘Risk Management’ (Standards Australia 2004),
developing a risk assessment involves a three-stage process: identify, analyse and evaluate all
the risks involved. The best tool to provide structure for these stages is a failure modes and effect
analysis (FMEA) of the tailings system.
In the present work, a general comparison between P&TT and conventional tailings storage
has been made in terms of risk, using a FMEA based on a classification of likelihood and
consequences in a semi-quantitative risk assessment. All risks for stages from the concentration
plant onwards are considered for each scenario, in two different categories: environmental and
public safety.
Paste 2015 | Abstracts | 16
Paste and thickened tailings technology has more risks classifying as low to moderate than
conventional tailings and has less risks classifying as moderate to high area. These results can be
used as an indication of the sustainability of P&TT disposal in terms of risks. Although the goal of
the study is to make a general comparison not applied to any specific mine, it can also be used as
a methodology or template for a risk assessment for any existing installation.
Paste 2015 | Abstracts | 17
Stability of a proposed steepened beach
D Reid Golder Associates Pty Ltd, Australia
J Boshoff Golder Associates Pty Ltd, Australia
Abstract
Existing topography at an operational lateritic nickel facility is such that if the tailings beach
slope could be increased to 1-2% for approximately one year, significant costs related to wall
building could be deferred. As additional thickening capacity would require significant capital
expenditure, polymer treatment technologies have instead been investigated.
As part of the trial process for polymer treatment, the stability of the potential steepened
beach was assessed. While beach slopes of the range targeted here would, for many materials, be
unlikely to produce an unstable landform, lateritic nickel tailings develop very low dry densities,
consolidate slowly, and contain hypersaline pore fluid. This combination results in a lower
resistance to slope instability, all else being equal. Further, polymer treatment technologies,
while providing benefits through rapid dewatering and beach slope development, have been
shown to result in an increased brittleness for some materials.
Laboratory characterisation of the polymer treated material was first undertaken, by means
of (i) monotonic, cyclic and post-cyclic simple shear testing, to assess the potential for strength
loss of the material, (ii) laboratory-scale shear vane testing, to estimate residual shear strength,
and, (iii) settling and consolidation tests, to provide input to consolidation modelling.
A consolidation model of the proposed steepened beach was then developed. Outputs from
this model were used as the basis for infinite slope stability analyses on a variety of scenarios.
It was found that over the one year planned deposition period, beach slopes of 1.5% or less are
likely to result in a satisfactory factor of safety (FS) for the steepened beach.
Paste 2015 | Abstracts | 18
Research trends on thickening mining wastes
J Laine University of Oviedo, Spain
F Ortega University of Oviedo, Spain
R Luiña University of Oviedo, Spain
V Alvarez-Cabal University of Oviedo, Spain
Abstract
The mining industry is a main generator of wastes. In many cases, those wastes are liquid
because the mining process requires wet processes. This aspect is inherent to the industry and it
is not completely avoidable. Anyway, during the last three decades this problem has been arisen
as a main concern as the environmental conscience grows and the legal requirements become
stricter. The effort in the reduction and optimisation of waste disposal techniques is guided by
basic and applied research efforts that have been growing during this period.
This paper presents a review of the published contributions related to thickening mining
wastes in order to detect the evolution of research and engineering practice in the field with
the objective to detect the main concerns in the fields, its evolution over time, as well as the
relationships between them. It provides very relevant information about how the techniques
evolve and specially how to detect the current and next futures trends for research and
engineering application.
Study is done through the scientometric (bibliometrical) analysis on published articles available
from ISI web of Science database between 1900 and 2014. Data is treated with VOSviewer and
TxtViz using text and data mining techniques. In order to produce effective searches, a previous
identification of the main definitions present in the texts related to the field has been done,
from initial knowledge but also created automatically through the scan of the selected papers,
identifying patterns in the waste thickening literature. The final concepts, composed of up to
three words, constituted the essential dictionary and are combined in the first ontology in this
field. Results show clear tendencies in the field by the existence of some key concepts (e.g.
flocculation, backfill, disposal) capable to create clusters around them.
Paste 2015 | Abstracts | 19
Management of bauxite residue in a temperate climate
using mud farming techniques
MB Willan Golder Associates (UK) Ltd, UK
GS Ghataora The University of Birmingham, UK
Abstract
The management of water within the mining waste industry is one of the most critical factors
affecting operators today. Long-term sustainable management will both increase the volume of
waste which can be stored in a given area and decrease the effect on sometimes fragile water
supplies. One often overlooked technique, primarily used in the alumina refining industry, is the
mechanical consolidation and densification of waste bauxite residue (also known as ‘red mud’
due to its colour) in a process known as mud-farming. This technique provides a simple, less
technology–dependent solution as it is carried out by relatively inexpensive mechanical plant.
Whilst a number of studies have examined the effectiveness of mud-farming, these studies
have been carried out in the comparatively arid climate of South West Australia. Given that
this technique may be of interest to the wider mine waste industry, a study into the observed
benefits of mud-farming techniques within a temperate climate has been conducted. This study
has focused on the mud-farming operations currently carried out at the Rusal Aughinish Alumina
facility, near Limerick, Ireland. The study makes use of both historical site investigation data and
the results from a site investigation carried out in 2014, using cone penetration testing as well
as a complimentary laboratory testing programme. The results of this study demonstrate that
the application of mud-farming techniques has led to increases in the both the undrained shear
strength and the density of the bauxite residue which will ultimately enable increased capacity at
the facility. Furthermore, this study identifies a number of issues arising for the use of standard
geotechnical laboratory testing of bauxite residue, including the potential to miscalculate
moisture content due to the presence of amorphous particle, and undrained shear strength.
Paste 2015 | Abstracts | 20
Transport
Paste 2015 | Abstracts | 21
Hydraulic driven piston pumps for the transport of
pastes and slurries in the mining industry
P Peschken Putzmeister Solid Pumps GmbH, Germany
K Kivanc Eti Bakir A.S, Turkey
Abstract
More and more mines are using double piston pumps for conveying pastes, cakes and slurries.
Stiff pastes are normally used for the stabilisation of underground workings. Cement and ash
are added to create a construction material with sufficient strength.
For tailings and ore transportation above ground, slurries are produced and transported over
long distances to deposits or preparation plants.
With this presentation, we will show various job sites around the world where different
materials are pumped, providing the relevant information about the pastes and slurries that
were pumped, information about the paste preparation plants, advantages of the paste systems
and when to use which type of piston pump.
Paste 2015 | Abstracts | 22
Dredging of an active thickened tailings storage facility
at the Ernest Henry Mine
TG Fitton Fitton Tailings Consultants, Australia
WJ Neumann Neumann Contractors Pty Ltd, Australia
Abstract
After some 15 years of operation as a copper and gold mine, the Ernest Henry Mine installed
a magnetite extraction plant to enable the recovery of magnetite concentrate as well. A study
was carried out to determine the feasibility of re-mining the tailings from an active thickened
tailings storage area, which proved it viable. Dredging, dry mining and hydro mining methods
of extraction were examined, costed and compared. Dredging was the selected method. In the
months to follow, a dredging operation was set up on the tailings storage facility, which mined
magnetite-rich tailings from it whilst simultaneously enabling the storage facility to remain active
for receiving the thickened barren tailings from the magnetite extraction plant.
The Ernest Henry tailings storage facility is a square-shaped thickened discharge system with
a perimeter embankment, and a beach that slopes from one corner to the opposite one. This
slope of the beach presented one challenge to the dredging operation, which was effectively
addressed with the adoption of a systematic progressive mining method. The need to minimise
the sterilisation of the magnetite-rich tailings beneath a layer of new barren tailings presented
another challenge, which also required some careful planning.
An overview of the dredging operation is presented, as well as some relevant details of it.
The management of the tailings discharge during dredging is also discussed, as is the slurry
transport and pumping requirements for the dredging. A number of other technical and practical
challenges are also discussed, such as the initial excavation of the starter pond, launching and
retrieving the dredge, and anchoring of the dredge.
Dredging can be a very effective and economical means of extracting tailings from a storage
facility, even in cases where thickened tailings have been discharged to create a sloping beach
reinforcements, minimising bulking, and with yielding bolts, satisfying a deformation rather than
an energy demand criterion.
Paste 2015 | Abstracts | 23
Comparing long stroke 20’ (508 mm) with short stroke
14’ (356 mm) piston diaphragm pumps
H Krimpenfort MHWirth, Germany
Abstract
Over the years the requirement for high flow rate piston diaphragm pumps has increased. In
the eighties capacity of such pumps was limited to 300-400 m³/h. In the following decades the
size and length of pipelines in the mining industry has increased and pump manufacturers have
developed pumps which met these requirements. Currently the maximum flow rate of single
piston diaphragms is in the range of 700-750 m³/h at pressures of up to 80 bar.
The type of pump for such applications is normally of triplex single acting or duplex double
acting design. The stroke length of these pumps is 504-556 mm and stroke rate is usually, in order
to achieve these high capacities, quite high which results in high piston velocities.
These pumps need a relatively high suction pressure which needs to be provided by a
centrifugal type charge pump. In order to fill the pump´s diaphragm chambers with slurry at such
high piston velocities, the charge system which provides the required suction pressure becomes
very critical. By far, most pumping problems are due to lack of suction pressure and subsequent
cavitation.
This paper will show that piston diaphragm pumps with a shorter stroke and in triplex double
acting configuration are capable of the same capacities at much lower piston speeds. This results
in optimised suction conditions, longer lifetime of bearings and wear parts and safer maintenance
conditions. The same type of pump is also able to provide flow rates of up to 1,200 m3/h at 80
bar discharge pressure at optimum operating and maintenance conditions. The application of
these high flow rate pumps will result in fewer operating pumps, smaller pump stations and
lower operating costs.
Paste 2015 | Abstracts | 24
Series connection of diaphragm piston pumps
DM Nägel FELUWA Pumpen GmbH, Germany
R Gänsl FELUWA Pumpen GmbH, Germany
Abstract
Pipeline transportation of ore concentrates (copper, nickel, iron, etc.) at high solids
concentration can be a cost-efficient, safe, eco-friendly and particularly emission-free alternative
to conventional systems utilising conveyor belts, trucks and trains.
So far, available pumping systems are typically allowed for slurry pipelines of up to 300 km
distances only. The connection of several pumps of identical size allows for higher flow rates or
pressures. With parallel operation, the collective flow rate is combined at identical delivery head
pressure. In series operation, however, delivery head pressure is combined, whilst the flow rate
from each pump is identical (Figure 1). Both parallel and series options are practicable, but series
connection is not that common for positive displacement pumps as their maximum operating
pressure is already high.
With piston pumps, a fixed volume is displaced with every stroke, almost independent of the
operating pressure. Calculation of the theoretical flow is based on the number of pistons and
stroke rate per minute. Leakage and elasticities reduce the hydraulic efficiency and decrease the
actual flow. Friction losses depend on the flow rate, whilst constant resistance results from the
differential head component.
The formula to calculate pipe resistance for constant flow is as follows:
∆ = + ·
Where:
2
· ² + · · (1)
∆p = differential pressure.
ξ
= coefficient of resistance.
λ
= pipe friction coefficient.
L
= length of the pipeline.
d
= internal pipe diameter.
ρ
= operating pressure.
v
= flow velocity.
g
= gravitational acceleration.
H
= geodetical height.
Normally soft gas cushioned air vessels are employed for pulsation dampening. Thus, other
elasticities are negligible.
Paste 2015 | Abstracts | 25
If diaphragm piston pumps are used as the pipeline pump, then the formula p = f(Q) is
applicable. Pumps are conventionally connected in series and open reservoirs are required at the
suction side of each pump to compensate for differential flow rates. This results in an efficiency
loss of >10% for the complete system.
Flow adjustment is required for closed serial connection, in order to avoid changes in pipe
volume and limit influence on the pump pressure. Therefore, flow rate differential of pumps
operating in series must be small and adaptable. Latest measuring and control technology
allows for serial connection of displacement pumps in a closed system. Flow control is possible
by variation of stroke rate, or length, or by use of a bypass system. The first two options are
favourable energy-wise, as they directly influence the theoretical displacement volume.
Stroke control is most often used for metering pumps. Speed control ensures energy-efficient
adjustment of the flow rate and is commonly applied on larger pumps.
Series connection of diaphragm piston pumps in a closed system requires special control.
Speed variation of the first pump requires adaptation of the remaining pumps, in order to maintain
an identical volume flow from all pumps. Over a longer time, even small measuring inaccuracies
result in considerable deviation of the integral and conveyed volume. Flow adjustment is based
on pressure measurement. Volume changes in individual pipe sections affect the pressure level.
Falling below the suction constraints, or exceeding the discharge limit, requires reduction of the
flow rate. Communication between individual pump stations is essential in terms of equipment
safety and stability of the control loop. Closed systems incorporating diaphragm piston pumps
connected in series allows for the realisation of energy-efficient pipeline systems with distances
in excess of 300 km.
Paste 2015 | Abstracts | 26
A launder design method for thickened tailings
TG Fitton Fitton Tailings Consultants, Australia
Abstract
In mountainous terrain, thickened tailings slurries are often transported by gravity flow in open
channel launders (also called channels or flumes). These launders are typically constructed of
concrete, and can run for many kilometres, as they transport the tailings slurry from the mine
to a tailings storage facility at a lower elevation. Some of the large copper mines of Chile and
Iran feature such launders, with some notable examples being Andina, Chile (57 km, carrying
some 70,000 dry tonnes per day), Chuquicamata, Chile (15 km with 200,000 dry tonnes per day),
El Teniente, Chile (86 km, 130,000 tpd) and Sarcheshmeh, Iran (16 km, 60,000 tpd). The main
advantage of such launders is the ability to avoid pumping of the slurry. In mines such as these,
the cost of pumping such vast amounts of tailings would be considerable.
Launder cross-sections can come in many shapes, with common geometries being rectangular,
trapezoidal and U-shaped. Circular pipes flowing partially full also function well as launders, and
can offer certain advantages over the more common open-topped concrete sections.
This paper presents a simple method for designing launders for the gravity transport of
tailings slurries. The method applies to both Newtonian and non-Newtonian slurries, and works
on the basis that the slurry flow maintains sufficient velocity to avoid deposition of solid particles
in the launder. With inputs of flow rate, slurry concentration, rheology, particle specific gravity
and particle size distribution, the design method calculates cross-sectional dimensions for a
launder of rectangular, trapezoidal or circular cross-section, and then calculates a minimum
slope required for the total transport of the slurry.
Paste 2015 | Abstracts | 27
Stress analysis of underground pipelines with flexible
couplings – unrestrained approach
J Sabeti Hatch Ltd., Canada
A Asgarian Hatch Ltd., Canada
Abstract
The application of grooved couplings in underground paste pipelines is increasing as the mines
go deeper and the pressure in the pipeline systems gets higher. This type of connection offers
fast installation, convenient maintenance, and allows for easier rotation of the paste backfill
pipelines. There are two common types of grooved couplings with different applications: rigid
and flexible.
Rigid couplings utilise a single groove on each side of the connection to hold the line together,
and are normally used in paste backfill pipelines with low pressure. Rigid couplings provide a rigid
joint that allows no angular deflection or linear movement and in that are similar to traditional
flanged, welded, or threaded connections.
For extra high-pressure paste pipeline applications (above 10 MPa for a DN 200, Sch 120
pipeline), double grooved (flexible) couplings are utilised. The design of this type of coupling
introduces some level of flexibility to the system (higher degree of angular movement and axial
displacement). Despite the several advantages that flexible couplings introduce to a piping
system, stress analysis and support design for this type of connection are much more complicated
than for traditional rigid joints. In this article, we present the complexities that were faced in
the stress analysis and design of supports for a high-pressure underground paste pipeline with
flexible connections. The practical design approach for this application will be introduced as well.
The understudied paste backfill pipeline has some characteristics that make it a challenging
subject for flexibility and stress analysis. These characteristics include high operating/design
pressures; use of high-pressure flexible couplings for pipe connections; physical properties of
the pipeline such as the slope of the pipeline in the ramp, and the relatively high temperature
differences between installation and operating conditions.
A detailed stress analysis using the ‘unrestrained design approach’ (see Section 4.2) was
performed in the course of the project to achieve acceptable pipe stress and support loads of
the system.
The calculation results showed some specific requirements for installation of double grooved
flexible couplings. These requirements include installation of the couplings with a specified gap,
use of natural bends and expansion loops to compensate for the expansion and contraction of
the system, and the design of line stop points at specified intervals to distribute the expansion
and contraction of the system.
Paste 2015 | Abstracts | 28
Open channel transportation of thickened tailings
S Javadi RMIT University, Australia
PT Slatter ATC Williams Pty Ltd, Australia
SN Bhattacharya RMIT University, Australia
R Gupta RMIT University, Australia
Abstract
The mining industry is moving towards thickened tailings with higher density than conventional
operations. As a result, tailings transportation is more challenging due to the material’s tendency
to exhibit non-Newtonian behaviour at high solid concentration. One of the practical ways to
transport tailings, where the terrain allows, is to gravitate the tailings through open channels
from the thickening plant to the tailings disposal area. But in comparison to pipe flow, the flow
of non-Newtonian thickened tailings through open channels has not received sufficient attention
in the literature. This paper presents a set of models developed to predict the flow behaviour
in the laminar transitional and turbulent regimes through open channels. The flow behaviour
predictions of these semi-theoretical models are discussed and validated against previously
published experimental data.
Paste 2015 | Abstracts | 29
Underground issues
Paste 2015 | Abstracts | 30
Paste backfill system design and commissioning at
Chambishi Copper Mine
AX Wu University of Science and Technology Beijing, China
XX Miao University of Science and Technology Beijing, China
XH Liu University of Science and Technology Beijing, China
YM Wang University of Science and Technology Beijing, China
CL Wang Africa Mining PLC of China Nonferrous Metals Co. Ltd., Zambia
JJ Zhang Africa Mining PLC of China Nonferrous Metals Co. Ltd., Zambia
Abstract
West orebody is now the main production zone of Chambishi Copper Mine. Upward drift stoping
is performed to meet the annual ore production of more than 1 Mt. Cemented classified tailings
backfill was originally employed, which then proved to be both economically and operationally
impractical due to high cement cost, low metal recovery, severe backfill tailings shortage, etc. As
an alternative, the current paste backfill system with low cement addition was suggested after a
comprehensive study and investigation. Construction work of the paste backfill system started in
2012. The system was put into production at the beginning of 2014 after commissioning. During
commissioning, the backfill system reached a capacity of 60 m3/h with the paste concentration
of 68 to 70%, and the friction loss of the pipeline transport was
4-6 MPa/km. To meet the backfill strength, the cement to tailings ratio for primary stopes was
1:12, and 1:30 for secondary stopes. As a result, the composite cost for backfill was only USD 15
to 20 /m3, while ore recovery increased by 35% and mining to cutting ratio dropped by 80 m3/kt.
Since commissioning investigations indicate that this paste backfill system will be capable of
prolonging west orebody’s service by about 10 years, and will bring about enormous economic
returns.
This paper presents the case study of the highly automated system and its commissioning
performance, with emphasis on key processes including unclassified tailings thickening, two-stage
slurry mixing, paste pumping, and underground backfill.
Paste 2015 | Abstracts | 31
Optimisation and stabilisation of coal rejects at the
Peabody Metropolitan Mine using Acti-Gel® 208
JH Worsley Active Minerals Australia Pty Ltd, Australia
JE Marsh Active Minerals Australia Pty Ltd, Australia
R Patel Peabody Energy Australia, Australia
SB Feldman Active Minerals International, USA
Abstract
The Peabody Energy Metropolitan Mine in New South Wales produces about two million tons of
metallurgical-grade coal annually through an underground longwall mining operation, producing
about 450 ktpa of coarse-grained rejects and ultra-fine tailings that require co-disposal. Currently,
~100 ktpa of these materials are processed to form high-density slurry that is pumped up to 2
km as backfill into underground voids. The balance of the waste is trucked and dumped, but the
mine has a mandate to pump 100% of the rejects underground by the end of 2015 and to extend
the pumping distance to at least 7 km.
We conducted field trials to optimise and stabilise the slurry using Acti-Gel® 208, a
highly-purified Mg-aluminosilicate rheology modifier and suspending agent, at the Metropolitan
Mine using the 100 mm NB pipe loop connected to the backfill pilot plant. Coal rejects used for
the demonstration were comprised of a typical mix of ultra-fine, fine and coarse particles ranging
to ~15 mm with the percent solids and process water adjusted to a target range of between
74-76% and a starting yield point of at least 100 Pa. To determine how the treatment affected
the properties of each mix, baseline pipeline pressure data was collected for a period of about
two hours prior to adding Acti-Gel. Slurry samples were taken at regular intervals thereafter to
measure yield stress, specific gravity and other parameters in both treated and untreated mixes.
Pumping tests were also conducted by varying the flow rate of each mix through the pipe loop
from about 0.2-2.0 m/s and by ramping pump speed up and down with 15 minutes of stable
operation at each speed in order to obtain pipeline pressure data.
In contrast to the control mix, slurry treated with Acti-Gel showed non-settling suspension
behaviour and yield point stability at or above the 100 Pa target for the duration of the two-hour
pipe loop operation. A simulated unplanned stoppage test confirmed that the Acti-Gel slurry
maintained the 100 Pa yield stress, enabling a smooth restart after 14 hours. Pressure drop data
also showed that Acti-Gel decreased pressure loss by about 15% as compared to an untreated
mix. This provides an important benefit in extending the pumping distance and reducing pipeline
wear. Additional results of Acti-Gel rheological behaviour in slurry and backfill systems will be
presented.
Paste 2015 | Abstracts | 32
Experimental study on the physical and mechanical
properties of a cemented unclassified tailings backfill
XC Yang Beijing General Research Institute of Mining & Metallurgy, China
GS Liu Beijing General Research Institute of Mining & Metallurgy, China
LJ Guo Beijing General Research Institute of Mining & Metallurgy, China
Abstract
In order to study the physical and mechanical properties of cemented, unclassified tailings
backfill, a series of unconfined compressive strength (UCS) tests have been performed on samples
prepared in cubic and cylindrical shapes at 14, 28 and 56-day curing periods. Additionally,
longitudinal wave velocities across all samples have been measured combined with ultrasonic
pulse velocity (UPV), non-destructive testing technology. The influence of samples’ sizes, binder
dosages and solids concentration the UCS and UPV were evaluated. The results indicate that
samples with a diameter × height of 7.6 × 15.2 cm showed consistently higher UCS and UPV
than those of 5 × 10 cm specimens at all solids contents and binder dosages, and the cylindrical
specimens thus showed obvious size effects. Meanwhile, the samples with a side length of 7.07
cm (cube) showed higher UCS and lower UPV than the similar section size of 7.6 × 15.2 cm
(cylinder) at the same binder dosage and solids content, and the end effects of cubical samples
were more obvious. In addition, increasing the curing time led to the reduction of the ratio
values for UCS and UPV of different size samples. Besides, with the increase of curing periods, a
linear relation with a high correlation coefficient appears to exist between the UCS and UPV for
the samples of specific sizes.
Paste 2015 | Abstracts | 33
Early curing age paste backfill exposures – the role of
effective stress
RL Veenstra Glencore Australia Pty Ltd, Australia
AG Grice AMC Mining Consultants (Canada) Ltd., Canada
MW Grabinsky University of Toronto, Canada
WF Bawden Mine Design Engineering, Canada
Abstract
This paper presents results from a numerical modelling exercise that looks at vertically exposing
sub-28-day cemented paste backfill. The reason for this exercise is that underground mining
operations would like to start exposing cemented paste backfill (CPB) earlier in order to increase
production. However, these earlier exposures would mean that the pore water pressures in the
stope may not have fully dissipated, hence entering an effective stress state versus a total stress
state. The goal of this paper was to examine how effective stress impacts these early exposures.
This was done by modelling the filling and the subsequent pore water dissipation within a stope.
This modelled CPB was then vertically exposed, using both effective and total stress models, at
various times ranging from immediately after filling to 28 days after filling. The results of these
models were then compared in order to determine what difference there was between the
overall outcome.
Paste 2015 | Abstracts | 34
Gwalia mine – backfill system operational review
S Wilson Paterson & Cooke (UK) Ltd, UK
J Snyman Paterson & Cooke Consulting Engineers (Pty) Ltd, South Africa
M McGuinness Paterson & Cooke Canada Inc., Canada
J Albrecht St Barbara Ltd, Australia
J De Vries St Barbara Ltd, Australia
Abstract
The Gwalia gold mine located in Western Australia has been operating its current backfill system
since 2009. The backfill system prepares a paste fill from harvested mine tailings, blending these
with water and binder before discharging into a gravity driven reticulation system. Currently the
backfill plant operates at approximately 185 tph, delivering 130 m3/h of paste fill to a depth of
approximately 1,500 m below surface.
In line with good operational practice, and as a reaction to a series of borehole blockages,
Gwalia has undertaken an operational review of its backfill system. The system review
considered all aspects of the operation from tailings harvesting through to plant operation
procedures, maintenance planning and paste distribution, as well as establishing the root
cause of the borehole failures. The overall backfill management system was also reviewed, and
recommendations made.
In addition, a life of mine review has considered the requirements and implications of
extending the reticulation system to 1,800 m below surface.
This paper presents an overview of the review along with an assessment of the current and
future reticulation systems, concluding from it a number of value-adding recommendations.
Additionally, comment is made on best practice in paste fill system management.
Paste 2015 | Abstracts | 35
A comparison of two paste plants in India
C Lee Golder Associates Ltd., Canada
G Chatterjee Golder Associates Consulting (India) Pvt Ltd, India
A Gandhe Golder Associates Consulting (India) Pvt Ltd, India
BV Rao Hindustan Zinc Ltd, India
A Nirvan Hindustan Zinc Ltd, India
DP Ravikumar Hindustan Zinc Ltd, India
Abstract
Hindustan Zinc, a subsidiary of Vedanta owns and operates the Sindesar Khurd (SK) mine and
the Rampura Agucha (RA) mine both located approximately 250 km away from each other
in Rajasthan, India. Both mines are underground zinc mines which are primarily mined using
sublevel open stoping (SLOS) and are transitioning from the use of hydraulic fill and cemented
rockfill to the use of paste fill. Although the two mines have similar mineralogy, similar tailings
particle size and similar strength requirements the two paste plants had surprisingly different
recipes, plant layout and equipment selection in order to accommodate substantial differences
in tailings rheology, dewatering and strength properties. In addition, the two paste plants have
very different distribution systems with one system requiring long horizontal pumping distances
and the other having a gravity distribution system. Interestingly, all the challenging characteristics
such as poor dewatering performance, low strengths, and longer horizontal distribution system
all are associated with the RA mine while the SK mine enjoys better dewatering, higher strengths
and a simpler distribution system.
The paper describes the methodology, challenges and opportunities associated with designing
and construction of a paste backfill system in India as well as an interesting comparison between
two paste plants to illustrate just how sensitive the design of a paste plant is to the tailings
properties. It also provides an interesting comparison at the extremes of plant design resulting
from excellent tailings properties and favourable orebody geometry versus challenging tailings
properties and unfavourable orebody geometry.
Paste 2015 | Abstracts | 36
Chemical technology case study in cemented paste
backfill – Newmont’s Tanami Gold Mine
R Salter UGC BASF, Australia
A Flemmer Newmont Tanami Operations, Australia
J Gelson UGC BASF Asia Pacific, Australia
Z Martic UGC BASF Global, Switzerland
Abstract
Cemented paste fill operations have been in operation for many years in Australia. In recent years,
rapid advances have been made in chemical technologies improving mining backfill operations.
BASF’s in depth analysis and laboratory work on both the physical and chemical parameters
involved in backfill operations has been instrumental in re shaping this pathway. Many physical
parameters can be improved via plant modifications; however, at significant expense to the mine.
Even with peak plant performance, further optimisation can only be achieved in a cost-effective
manner via improved chemistry. This is where chemical admixtures come into their own.
The feed to the backfill plant uses dry excavated tailings. The Tanami plant was unable to
operate to the specified solids contents due to variations in chemistry, fineness and high clay
content of the tailings, which in turn affected the desired throughput and strength consistency
of the fill. Higher cement contents were also required to reliably maintain the desired strengths.
The chemical solution proposed by BASF increased solids content, reduced friction and pressures
in the pipelines, and maintained a more consistent paste throughput with consistent strengths.
This case study describes the processes employed by BASF for Newmont to identify and
resolve issues encountered in the backfill operation at their Tanami Gold Mine. The case study
discusses topics from initial sampling, analysis and lab testing to final onsite trials of the chemical
admixture solution provided. The benefits to the mine are summarised in the paper.
Paste 2015 | Abstracts | 37
Mobile paste backfill systems – a decade of work
S Longo Golder Associates Ltd., Canada
A Quintero Golder Associates Ltd., Canada
D Kennard Golder Associates Ltd., Canada
Abstract
Mobile paste backfill applications are becoming more and more common as orphaned and
abandoned mines are becoming challenges or even impediments to urban or recreational
development. In addition, the public risk and safety issues associated with these orphaned
sites are bringing remediation programs to the forefront. These sites are left in the hands of
local, regional and federal governments to deal with, and they typically lack the resources
from a financial and technical perspective to effectively reduce the risks these sites pose. The
technical challenges of early 20th century mine plans, no current underground access, logistics
and proximity to local communities associated with these orphaned sites, makes mobile paste
backfill a viable option. This particular application of paste technology has not, to date, been
widely utilised but is a growing area of need. This paper will discuss two case studies from the
past decade of work on mobile paste applications ranging from a resort development program
to a crown pillar stability remediation program.
Paste 2015 | Abstracts | 38
Acti-Gel® 208 as an additive for paste and hydraulic
backfill
K Tarr Natural Resources Canada CanmetMINING, Canada
I Bedard Natural Resources Canada CanmetMINING, Canada
H Kim Active Minerals International LLC, Canada
Abstract
Paste technology has progressed to a widely accepted, cost-effective backfill method, and is
also used extensively in surface tailings disposal. The non-segregating nature of paste makes it
a very attractive option for backfilling, and its stacking behaviour due to its low water content
significantly reduces the risks associated with surface tailings dam failure. While the capital and
operating costs for the preparation and transportation of paste are higher than that of hydraulic
fill, there are significant benefits with respect to transportation, such as reduced pipe wear and
reduced risk of pipe plugging, not to mention the benefits associated with greatly reducing the
water handling issues underground. From an environmental standpoint, the benefits of paste
versus hydraulic fill include the ability to place more of the fine tailings fraction underground,
thereby reducing the need for surface tailings storage. Another environmental benefit is the
reduced risk of downstream contamination in the case of a tailings dam failure, due to the fact
that disposing of the tailings in a paste form means virtually no need for liquid containment, and
therefore no means for the tailings to travel downstream.
Portland cement is typically used to solidify backfill, whether paste or hydraulic. This represents
a major cost in mining operations due to production and haulage costs of ordinary Portland
cement. In addition, the manufacturing of cement raises environmental considerations because
it produces a considerable amount of CO2 emissions. Therefore, the search for additives which
allow for a reduction in the required cement content in backfill has been ongoing for decades.
Acti-Gel®208 is a highly purified magnesium aluminosilicate that acts as a high performance
anti-settling agent and rheology modifier used in a wide variety of water-based industrial
applications. Studies have shown that as an additive in paste backfill, it results in improved
strength and flow properties, such as friction loss and segregation.
This paper presents the results of a study conducted by Active Minerals International LLC for
a South African gold mine operation in 2013, as well as the results of a study conducted by the
CanmetMINING Sudbury Laboratory for Vale Canada Ltd. in Sudbury, Ontario, Canada, in 2014.
The feasibility of Acti Gel®208 as a cost-effective additive for underground paste and hydraulic
backfill applications was investigated through the preparation of samples to compare the
strength and flowability characteristics of standard mixes to those containing different dosages
of Acti-Gel®208. It was found that at a low dosage of 0.03 wt%, Acti-Gel®208 delivered enhanced
performance in unconfined compressive strength tests as well as in the pilot-scale flow tests. A
significant reduction in binder content could be realised with addition of Acti-Gel®208 at the gold
mine operation in South Africa, as well as at the Coleman and Creighton Operations in Sudbury,
Ontario, Canada. The economic benefits of such a binder reduction with respect to the Canadian
operations are also discussed in this paper.
© Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2015.
Paste 2015 | Abstracts | 39
Some physical and mechanical properties of cemented
fillings under high pressure
WS Lyu University of Science and Technology Beijing, China
P Yang Beijing Union University, China
SJ Cai University of Science and Technology Beijing, China
Abstract
With the application of large-scale filling mining in deep mines with high ground pressure, the
physical and mechanical properties of cemented fillings under high stress conditions need to be
further studied. The confined consolidation test was completed under the pressure from 0.5 to
32 MPa to simulate the pressure change of backfillings 1,000 m beneath the surface. The uniaxial
compressive strength (UCS) of filling specimens was studied before and after consolidation, and
with further curing after consolidation. The strength changing properties of fillings under high
pressure gave some new information for further understanding the interaction of fillings and
surrounding rock. The study result is supplement to traditional backfilling theories.
Paste 2015 | Abstracts | 40
Recycling fine slurry – an alternative to paste for coarse
rejects co-disposal in Queensland coal mines
AD Thomas Slurry Systems Pty Ltd, Australia
NT Cowper Snr Slurry Systems Pty Ltd, Australia
S Whitton Mechanical Advantage Pty Ltd, Australia
Abstract
Conventional co-disposal of coarse rejects (minus 50 mm) and fine thickener underflow tailings
(minus 2 mm) is practised at a number of Queensland coal mines. The two streams are combined
and pumped together to disposal. However, with the ratio of coarse rejects to tailings typically
being about 70:30 on a dry mass basis, it is necessary to add large quantities of water to reduce
the volume concentration of coarse rejects to an acceptable pumpable level. At the disposal
site, the low concentration fines wash through the coarse rejects, forming a pond at the toe of
the deposit. Water needs to be recovered from the pond and pumped back to the plant, and
some water is lost through evaporation. The deposit also requires significant management with
earthmoving equipment.
An alternative co-disposal system is described, in which no dilution water is required. By
recycling some of the minus 2 mm thickener underflow in a recycle pipeline, the required
reduction in volume concentration of rejects in the mixture is achieved without water
dilution. With a thickener underflow concentration of 50% by weight (w/w), the total mixture
concentration discharged to disposal is up to 75% w/w, and the discharged mixture is essentially
homogeneous with minimal separation of fines. The emplacement can take the form of a coneshaped deposit, thereby greatly reducing the earthworks required. The net effect is that total
costs are about half of that required for the current co-disposal systems.
The 75% w/w concentration achieved by recycling fines is similar to the concentration likely to
be delivered by proposed laminar flow paste pipeline systems, and is achieved with more reliable
turbulent flow operation, avoiding the uncertainties associated with laminar flow.
Paste 2015 | Abstracts | 41
Assessing the flow liquefaction susceptibility of cyclone
underflow material
J Boshoff Golder Associates Pty Ltd, Australia
D Reid Golder Associates Pty Ltd, Australia
Abstract
It has been recognised worldwide that the liquefaction risk of unconstrained tailings stacks
or cyclone underflow embankments requires careful consideration. The stability of a tailings
deposit where the perimeter embankments are made up of hydraulic fill is often governed by
post-liquefaction stability.
Apart from Australia, cyclones are frequently used in different parts of the world to classify
tailings into a coarse underflow, for building a tailings impoundment wall, and a finer fraction that
is disposed of into the basin. The shear strength of the tailings forming the outer embankment
of a tailings storage facility and the location of the phreatic surface are the two most significant
factors influencing the structural integrity of the facility. The coarse underflow is placed in such a
way as to contain the overflow, which is finer, has low strength, and is often poorly consolidated.
Golder Associates Pty Ltd undertook a cyclone field trial at a gold mine site in Western Australia
to assess the feasibility of using the cyclone deposition method to optimise and increase the
capacity of an existing tailings cell. The aim of the cyclone trial was to collect information to
demonstrate to the client and the regulators that cyclone deposition was a feasible option for
raising TSF embankments. The cyclone trial provided an opportunity to assess the cyclone under
field conditions and to assess the quantity and quality of the underflow fraction produced on
site. A variety of methods were used to assess the flow liquefaction susceptibility of the tailings
underflow sample produced during the cyclone field trial.
The field trial, laboratory testing and analysis will be discussed in this paper.
Paste 2015 | Abstracts | 42
Beach slope prediction
Paste 2015 | Abstracts | 43
Practical observations in beach slope formation and
application of the thin layer equilibrium model to
observed data
JA Wates Fraser Alexander Pty Ltd, South Africa
HA Venter Fraser Alexander Pty Ltd, South Africa
VT Dittle Fraser Alexander Pty Ltd, South Africa
RA Cooper Fraser Alexander Pty Ltd, South Africa
Abstract
Prediction of the beach slopes for green fields projects is difficult and there is little consensus on
the best method to use to make the predictions. The time has now come to collect data for actual
beach slopes and to establish some empirical relationships that can be used by practitioners
to ‘ground truth’ their predictions. This paper presents the results of observations of beach
slopes that have been developed in the field under different circumstances and establishes a
relationship that the authors have used for practical verification of predictions.
The main drivers of beach slope have been found to be flow rate and yield stress. Flow rate
however can be eliminated as one of the key variables where the discharge energy can be
effectively dissipated close to the discharge point or where the tailings surface is large enough
to ensure that the flowing tailings eventually stalls and fans out to form fluvial beaches. In most
instances for high rates of discharge the surface area of the tailings facilities is not large enough
to meet the latter condition particularly in the early stages of basin development when the
surface area is small and flow is concentrated. In order to maximise beach slope the discharge
rate must therefore be reduced by splitting the flow in smaller streams.
The surficial thin layer beach slope model that is proposed in the paper assumes that discharge
energy can be dissipated by splitting the flow into no more than 3,000 tpd per point and is then
based on the hypothesis that the beach is formed when the tailings stalls rather than when it is
flowing in the channels that are so often observed on beaches. These observations are usually
made when viewed from the discharge end of the beach since this is usually the easiest point to
access. The tailings is usually flowing when the observation is made and the authors will argue
that this therefore does not represent the conditions under which beaches form but rather the
condition that pertains to transport the tailings across the foundation beach. This hypothesis
leads to the theory that at the point of stalling it is only the aerial dimensions, thickness and yield
stress that determine the slope at which the tailings will come to rest. This hypothesis applies
only to non-segregating tailings slurries.
The paper presents the results of the observations made by the authors and describes the
physical conditions of flow that have been observed in practice at the point in time that the
tailings stalls. The paper is intended to be more practical than theoretical but will refer to the
surficial thin layer model to illustrate how variations in the parameters that can be controlled by
an operator influence beaching.
Paste 2015 | Abstracts | 44
Stochastic beach profile modelling
KD Seddon ATC Williams Pty Ltd, Australia
B Pirouz ATC Williams Pty Ltd, Australia
TG Fitton Fitton Tailings Consultants, Australia
Abstract
Modelling of a tailings beach using a time series of thickener output (flow rate and solids
concentration) was first reported by Fitton et al. (2007). Seddon and Fitton (2011) presented
statistical data on the performance of thickeners, and showed that the observed concave shape
in tailings beaches could be adequately explained by this variability. They then proposed a
stochastic method for the generalised modelling of tailings beaches. The aim of this paper is to
demonstrate the application and results obtained by the use of this method.
This paper shows how thickener performance statistics in the form of frequency functions for
variations in (a) underflow solids concentration; and (b) mass flow rate, can be combined with a
set of rheology results to develop a predictive beach slope distribution. Data developed from this
distribution are then used as an input to a deposition modelling program. The developed beach
profile is presented for a typical case.
Paste 2015 | Abstracts | 45
Simulation of the meandering flow path of a beaching
slurry using a random walk technique
GI McPhail SLR Consulting Australia Pty Ltd, Australia
Abstract
Splitting a slurry stream through the operation of multiple discharges is an established method
of improving the beaching profile both for conventionally thickened as well as high density
thickened tailings. To maximise the beach slope, however, it is important to space the discharges
sufficiently far apart to ensure that the split flow streams do not recombine down the beach. A
random walk technique has been applied by the author to simulate the flow paths of multiple
flow streams at a range of discharge spacings, and the results have been used to estimate the
optimal number of discharges and spacings to maximise the slope of the deposited beach. This
paper describes the theoretical basis for steepening the beach through simultaneous discharge of
smaller flow streams, sets out a random walk analysis technique to assess the minimum spacing
between the streams to maximise beach slope, and compares the results of the simulations with
the full-scale operation at a number of tailings operations.
Paste 2015 | Abstracts | 46
Chuquicamata full-scale field deposition trial
B Pirouz ATC Williams Pty Ltd, Australia
S Javadi ATC Williams Pty Ltd, Australia
P Williams ATC Williams Pty Ltd, Australia
C Pavissich ATC Williams Pty Ltd, Chile
G Caro Codelco, Chile
Abstract
A large-scale field deposition trial was carried out at the Chuquicamata mine’s Talabre Tailings
Storage Facility (TSF) in Chile to study the achievable beach slope with the current tailings in the
absence of further thickening. The tailings received at the Talabre TSF are a mix of tailings from
two different operating mines; Chuquicamata (CH) and Ministro Hales (MH).
The field deposition trial was run with a total discharge flowrate of 100 L/s from two outlets
each discharging 50 L/s. The average as-received solids content of the slurry during the field trail
was 52% ranging from 56.5-40.8% (solids by weight).
The trial was run for 56 days from early August to early October 2014 with continuous tailings
discharge for eight hours per day. The limitation on discharge time was to prevent rapid initial
build-up and possible mass slumping which would interfere with the interpretation of the results.
Nevertheless the scale of the trial was such that ‘continuous’ discharge conditions established
quickly at the beginning of each deposition day, and the trial is considered to be representative
of continuous discharge conditions.
As expected, discharge of tailings resulted in the formation of a plunge pool at the impact
area of the slurry stream at the head of the beach then self-formed channels that developed
on the beach as the slurry left the plunge pool. The tailings beach that forms by this mechanism
is similar to a full-size stack. This is a clear distinction from smaller scale deposition trials that
are often reported which involve the deposition at very low flow rates or of discrete batches of
tailings which result in a beach formed by layers of sheet flow.
The preliminary results and findings from the monitoring and observations of this trial
deposition including the achieved beach slope are presented and discussed in this paper.
Paste 2015 | Abstracts | 47
Above ground disposal
Paste 2015 | Abstracts | 48
Characterisation of a thickened tailings beach
KD Seddon ATC Williams Pty Ltd, Australia
JK Albee ATC Williams Pty Ltd, Australia
Abstract
A geotechnical investigation has been carried out on the tailings beach of the Sunrise Dam
central thickened discharge (CTD) tailings facility. This is believed to be the most comprehensive
investigation of a thickened tailings beach so far undertaken.
The investigation was carried out primarily for the purpose of evaluating the liquefaction
resistance of the beach. However, additional data were also recovered to enable an assessment
of the overall performance of the stack with respect to CTD design predictions. The investigation
comprised CPTu and pore pressure dissipation tests, supplemented by shear wave velocity
testing. In addition, stand-pipe piezometers were installed to provide information on the phreatic
surface, and un-disturbed samples of tailings were recovered and tested for particle size, density,
moisture content, and degree of saturation.
These results are summarised and compared to predictions, as well as to results previously
obtained for other sites. The influence of the effect of suction resulting from partially saturated
conditions is discussed.
Paste 2015 | Abstracts | 49
Tailings co-disposal case study – art or science?
A Beveridge BASF Australia Ltd, Australia
P Mutz Murray Zircon Pty Ltd, Australia
D Reid Golder Associates Pty Ltd, Australia
Abstract
Murray Zircon Pty Ltd operates the Mindarie Mineral Sands Project in South Australia comprising
a mine and concentrator plant. The program for environmental protection and rehabilitation
(PEPR) approved by the South Australia Department of Manufacturing, Innovation, Trade,
Resources and Energy (DMITRE) requires diligent management of the tailings deposition and
overall mine rehabilitation processes.
The mining licence was granted based on a maximum permitted operational footprint of the
open area of the mine. Mining at Mindarie follows the ‘moving-hole’ concept whereby topsoil
and overburden is removed, ore is mined, tailings are deposited in the mined-out space and
are then capped by overburden. The moving hole must advance at approximately 10 m per
day. Consequently, it is imperative that dewatering, consolidation and stabilisation of deposited
tailings happens quickly.
Tailings are treated using a high molecular weight polymer which rapidly releases clean water
for reuse in the concentrator plant. The polymer binds the coarse and fine particles together to
create a non-segregating deposit and accelerates the consolidation rate.
Polymer dosing regimes for the tailings have historically relied on a visual interpretation
of the material entering the tailings cells to determine the optimum dose; however, it is the
consolidation rate and associated strength gain that determines when overburden replacement
can begin. To provide an improved assessment of the impacts of dosage on consolidation,
geotechnical testing was undertaken on material treated with different polymer levels.
A recent development for the Mindarie mine is to adjust the natural acidic pH of tailings to
a slightly alkaline level using lime. This was done in order to overcome a throughput bottleneck
in the slimes thickener and reduce polymer dosing levels in the slimes thickener and tailings
applications. The impact of lime addition on polymer dosing, together with the effect of lime on
tailings consolidation properties is also investigated.
Paste 2015 | Abstracts | 50
Upstream stacking of thickened tailings at Neves Corvo
R Lopes Golder Associates Ltd., Canada
R Bahia Golder Associates Portugal Unipessoal Lda, Portugal
M Jefferies Golder Associates (UK) Ltd, UK
M Oliveira Somincor, Portugal
Abstract
Neves Corvo is a world-class underground copper–zinc mine located in the south of Portugal.
The mine has been operating since 1988 by Somincor (Sociedade Mineira de Neves-Corvo SA), a
wholly-owned subsidiary of Lundin Mining Corporation from Canada.
The pyritic tailings produced has a very high acid generation potential and until 2010 had been
placed subaqueously in the Barragem Cerro do Lobo (BCL), a large tailings pond (190 ha) created
by a rockfill dam, 42 m high, across a natural water course. In late 2010 Somincor switched to
using subaerial paste/thickened tailings deposition over the existing subaqueous slurry deposit.
This approach accommodates the required 17.4 Mt storage capacity from 1 January 2010, as
per Somincor’s 2005 life-of-mine (LOM) plan, and allows maintaining the existing perimeter
embankment at its current elevation and facilitates site closure (Lopes et al. 2013).
The results of the first two years of operation of the paste production plant and depositional
performance of the first 2 to 4 m of paste/thickened tailings over the very loose subaqueous
deposit, were presented at Paste 2013 in Brazil (Lopes et al. 2013).
Somincor’s 2014 LOM studies have established additional reserves and related demand for
additional tailings and mine waste rock storage at the Neves Corvo tailings storage facility (TSF)
beyond the 2005 deposition design. Specifically an increase of up to 27 Mt of tailings and as
much as 10 Mt of mine waste rock need to be accommodated into an expanded Neves Corvo
TSF, relative to the 2005 design.
Following an evaluation of alternatives for expansion of the TSF, upstream stacking of
thickened tailings at an overall slope of 4 to 6% is the selected solution. The upstream stacking
solution decouples the desired stacking slope from the beach slope variability inherent to the
operation at this site (Lopes et al. 2013).
A critical aspect of this design approach is that the rate of rise of the stack cannot exceed the
rate of strength gain of the thickened tailings and underlying subaqueous tailings. This is assured
by continuous monitoring of tailings pore pressure at piezometer installations and by periodic
CPTU testing of the deposit. In addition, laboratory testing of settling, drying and consolidation
behaviour of the thickened tailings was performed to assist in the interpretation of the observed
field data and to forecast stability of the proposed final landform.
Some operational changes have been made to the previous deposition into cells from a single
point of discharge. An array of perimeter spigots is now used to assure a wider spreading of the
tailings over the operating area and promote faster drying and strength gain. In addition the
frequent cycling of discharge spigot locations and the final cover design will assure a high level
of saturation of the raised landform, in order to control acid generation and metal mobilisation.
Paste 2015 | Abstracts | 51
The impacts of using thickened tailings on water
management and CAPEX of tailings storage facilities
K Fabian AECOM, USA
M Jacobs Goldcorp Inc., Canada
A Hooshiar AECOM, Canada
E Ngwenya AECOM, Canada
Abstract
The primary goal of water management at mines in arid areas is to minimise the use of surface
water and groundwater (natural water) in the mining process. Typical natural water issues
include lack of water; access issues due to legal, community, logistic or regulatory reasons;
groundwater drawdown; and nearby community and farming impacts. In some cases, largedistance, high-head pumping and/or desalinated water are required, significantly increasing
capital and operation expenses (CAPEX and OPEX).
A method of reducing natural water demand is the use of thickened tailings (TT) and paste
tailings (PT) technologies, where water is returned from the process plant, minimising discharge
to the tailings storage facility (TSF), reducing pumping demand and costs, and thus OPEX. Added
benefits of TT and PT include reduced evaporation and seepage losses, further improving water
re-use, and reducing impact to groundwater.
An important consequence of the use of TT or PT is an increase of the initial density of
tailings discharged to the TSF. This will result in a smaller volume (i.e. lower void ratio) of tailings
discharged, therefore less TSF storage capacity required. This can lead to a smaller TSF footprint,
and/or lower dam height. Either way, the dam volume is less, and thus the TSF CAPEX is less and
the dam can be constructed faster.
This paper discusses the current and planned future TSF operations at Goldcorp’s Minera
Peñasquito in Mexico. It describes a site water management/balance model and, in particular,
the TSF component, and presents natural water demand based on current sand-slime-splitting
of tailings. The paper also describes changes to the model and natural water demand reflecting
a plan to change tailings discharge from cyclones to TT. The main parameters affecting the
model are discussed, including results of column settling and constant rate of strain tests to
develop initial and final density and void ratio values, and how they affect the volume of tailings
discharged and TSF storage capacity required.
The paper further discusses the change in the rate of tailings rise, reducing by approximately
22% per annum over about the same TSF footprint, after the tailings operation changes to
TT technology. The effect on the total storage volume and overall dam volume are discussed,
demonstrating that the change to TT reduces the required dam volume by 30%, and results in
significant CAPEX savings for the TSF expansion.
Paste 2015 | Abstracts | 52
Managing high-density tailings disposal – deposition,
water management and closure considerations
S Kam Golder Associates Ltd., Canada
D Yaschyshyn Glencore Canada Corp., Canada
N Hmidi Goldcorp Canada Corp., Canada
Abstract
There has been a growing interest in the surface disposal of high-density tailings in recent years.
Such an interest is driven primarily by the need to conduct mining in a sustainable manner by
minimising environmental and social impact, conserving water and improving tailings safety.
Increasingly, more mines are considering thickened or paste tailings disposal in conjunction with
paste tailings backfill to better utilise their infrastructure.
Several factors have hindered the wider adoption of high-density surface tailings disposal
technology. The ability to predict tailings behaviour in full scale is still relatively limited. There is
also little experience in managing a high-density tailings facility under varied climatic conditions.
A number of high capacity mines have also had production issues meeting the tailings consistency
criterion for deposition leading to major reconfiguration of the disposal system due to poor
field performance. Some of these uncertainties are being addressed through laboratory and
field research with significant advances being made on our understanding on tailings rheology,
transportation, mechanism of deposition and post deposition behaviour change of the tailings.
High-density tailings facilities will require a greater degree of management than conventional
slurry tailings. Not only are the tailings likely more variable, there are unique challenges associated
with tailings deposition and water management. This paper discusses tailings deposition control
and water management methods that have been successfully used at a number of high-density
tailings facilities with special reference made to central cone deposition in the Kidd Metallurgical
Site and perimeter deposition at the Musselwhite Mine. Both of these facilities are located in
cold climatic regions in Canada with surplus precipitation. Contingency measures that have been
adopted to reduce the risk of system upsets and non-performance, and closure considerations
for these facilities are highlighted. Field experience has shown that high-density tailings disposal
can offer unique opportunities for progressive rehabilitation and optimisation of the closure
design.
Paste 2015 | Abstracts | 53
Differential water footprint assessment – conventional
versus paste tailings disposal
A Fernandez-Iglesias ArcelorMittal Global R&D Asturias, Spain
S Andres ArcelorMittal Global R&D Asturias, Spain
R Luiña University of Oviedo, Spain
D Pecharroman University of Oviedo, Spain
V Alvarez-Cabal University of Oviedo, Spain
Abstract
In August 2014, the international standard ISO 14046:2014 ‘Environmental management —
Water footprint — Principles, requirements and guidelines’ (International Organization for
Standardization [ISO] 2014) was released. This is the first version ever published on water
footprint, and therefore an important milestone for all environmental activities related to water
management.
The issue of water and its management has become increasingly central to the global debate
on sustainable development. This interest has been driven by growing water demand, increasing
water scarcity in many areas and/or degradation of water quality. This drives the need for a
better understanding of water related impacts as a basis for improved water management at
local, regional, national and global levels.
It is therefore desirable to have appropriate assessment techniques that can be used in an
internationally consistent manner. One of the techniques being developed for this purpose is the
water footprint assessment (ISO 2014).
Water and mining have always had a close connection because most mining and mineral
processing operations require water, often in large amounts (Rowe 2012). Mining activities can
contaminate surface and groundwater and demand great amounts of water, especially froth
process used as a method of minerals separation. There are some minerals such as coal, cyanide
or bauxite that can severely affect freshwater resources. Moreover, closure stage requires special
treatments because of significant long-term environmental liabilities – they must be pumped
and treated indefinitely to prevent contamination of surface and ground waters (Hendrix
2012). Despite of the fact that mining represents a very small fraction of the total world’s water
demand, its impact on local resources surrounding mine sites can be significant. The problem
is that mining operations cannot be relocated, making the sector susceptible to changing local
water availability (Barton 2010).
Paste and thickened tailings technology is nowadays a proven solution for one of the biggest
environmental impacts of mining activities: tailings disposal. Among the various drivers that this
Paste 2015 | Abstracts | 54
technology has, water is probably one of the most important, not only from an environmental
perspective but also from an economic one.
This paper applies the methodology proposed by the Water Footprint Network International
and later published as an ISO norm, to assess the differential Water Footprint of two scenarios,
conventional tailings management and its alternative process, paste and thickened tailings.
Paste 2015 | Abstracts | 55
Hillendale thickened tailings storage facility – from
project to closure
K Goss-Ross Independent Tailings Consultant, South Africa
Abstract
A thickened tailings storage solution was implemented at Hillendale Mine to manage ultra-fine
clay tailings over a relatively short mine life project, in an environmentally sensitive setting.
Constant performance monitoring and adapting to achieve the final mine plan requirement was
key to the success of fine tailings management.
The closure plan for the tailings storage facility (TSF) allows for natural drainage of rainwater
and sustainable agriculture. The up to 18 m thick fines deposit is currently being capped with a
layer of sand. This allows unhindered access for agriculture, with sugar cane planting progressing.
The paper highlights lessons learned and successes achieved over the project duration.
Paste 2015 | Abstracts | 56
The Sarcheshmeh thickened tailings scheme – a case
study
A Roshdieh ATC Williams Pty Ltd, Australia
P Williams ATC Williams Pty Ltd, Australia
KD Seddon ATC Williams Pty Ltd, Australia
Abstract
This paper presents a case study on the design, construction, commissioning and early operations
of a major upgrade of the tailings storage facilities at Sarcheshmeh mine, Iran.
The Sarcheshmeh mine is located in a semi-arid environment with average annual rainfall of
260 mm/year and evaporation of 2,800 mm/year. Make-up water supply comes from an alluvial
borefield.
The mine commenced operations around 1980. By 2000, the original tailings storage was
full. Short-term measures to increase capacity were recognised as being both unsafe and
unsustainable. In addition, the existing tailings and water management practices were inadequate
for a proposed expansion.
An initial options study was undertaken with the principal objectives of:
•
Improving water utilisation.
•
Providing storage for an additional 900 Mt of tailings at a production rate of 33 Mtpa.
The recommended option was installation of paste thickeners together with down-valley
discharge of the paste and thickened tailings. A full feasibility study and design followed.
This paper will cover the following components of the project:
•
Tailings properties.
•
Thickener selection.
•
Beach slope evaluation.
•
The water management system.
In this design 12 × 24 m paste thickeners were utilised, which is currently the largest installation
of paste thickeners for copper. The underflow solid concentration was planned to be around 60%
solids to achieve a maximum beach slope of 1.75%.
Construction of the improvements to the system has been completed and the upgraded
tailings management system is in its early years of operation with satisfactory outcomes. In this
article, the various components of the system are described and outcomes are discussed.
Paste 2015 | Abstracts | 57