1

PROCESS INTEGRATION AND OPTIMISATION OF THE BODDINGTON HPGR CIRCUIT

*S. Hart1, T. Rees1, S. Tavani1, *W. Valery2 and A. Jankovic2

1Newmont Boddington Gold Mine (NBG)Western Australia

2Metso Process Technology and Innovation (PTI)1/8-10 Chapman Place

Eagle Farm, Brisbane, QLD, Australia

(*Corresponding authors: steven.hart@newmont.com and walter.valery@metso.com)

2

PROCESS INTEGRATION AND OPTIMISATION OF THE BODDINGTON HPGR CIRCUIT

ABSTRACT

The current mining operations at Newmont Boddington Gold Mine (NBG) commenced in 2008,and commissioning of the processing plant started in the latter half of 2009. Metso Process Technology andInnovation were engaged to assist NBG with commissioning and project ramp-up through theimplementation of a comprehensive “Mine-to-Mill” Process Integration and Optimisation project. Thismethodology entailed extensive data collection which included drill and blast audits, ore characterisation,comprehensive comminution circuit surveys and review of operational data to assess the limitations withinthe current mining and processing operations. The results of these investigations have been used to definethe operating base line of both the mining and processing areas and identify improvement opportunities.The use of modelling and simulations, utilising actual production data, has allowed for multiple scenariosto be evaluated, minimising the requirement for actual trials and thereby minimising impact on theoperation. Improvements implemented to date include: the introduction of routine rock strengthmeasurement for inclusion in block models, modifications to blast design improving ROM fragmentationand downstream comminution process performance, and changes to improve performance of secondarycrushing and grinding circuits. Close cooperation between the mine and plant personnel is playing asignificant role in overcoming the challenges presented to this operation and further improvements aretargeted for the second full year of process plant operation.

KEYWORDS

Boddington, Integration, Optimisation, Mine-to-Mill, Comminution, Blast, Drill, HPGR, Crushing,Grinding

INTRODUCTION

The Newmont Boddington Gold Mine (NBG), located 130km from Perth, commenced a twelvemonth ramp-up in late July 2009. Metso Process Technology and Innovation (PTI) was engaged to assistwith the commissioning and ramp up, conduct a full mine to mill Process Integration and Optimisation(PIO) study, assist with an expansion study, and develop a throughput forecast and geometallurgical model.

The core of this work, the PIO study, is the development of integrated operating and controlstrategies from the mine to the plant that maximise throughput, minimise the overall cost per tonne andmaximise profitability. This process involved extensive data collection including drill and blast auditing,ore characterisation, comprehensive comminution circuit surveys, and analysis of operational data. Thesedata are used to define the operating base line and develop site specific models for all processes fromblasting through comminution. The models are linked, allowing outcomes to be carried throughdownstream processes and assess the impact on overall objectives. Therefore, each process is analysed inthe context of the whole operation (mine to plant). Simulation allows for multiple scenarios to be evaluated,minimising the requirements for plant trials and thus reducing the impact on the operation.

The aim of the PIO study at Boddington was to increase plant throughput and improveperformance while minimising cost and maintaining product quality. The study also included optimisationof drill and blast, crushing, HPGR, and grinding circuits. The PIO process was initiated in October 2009,with a preliminary site visit for initial observations, analysis and planning. The following visit, in April2010, included three drill and blast audits. Ore tracking with SmartTagTM was used to ensure the oreblasted during the audits was being processed during the comprehensive comminution surveys thusallowing correlation between fragmentation results and plant performance. Site specific models weredeveloped for blasting, crushing and grinding circuits.

3

Simulation of multiple scenarios identified opportunities for improvements in blasting andcomminution circuits. Implementation and iteration of the PIO process resulted in several subsequent visitsand further proposed improvements. This paper describes the PIO process and discusses someimprovements identified and implemented at NBG.

DESCRIPTION OF THE BODDINGTON OPERATION

The NBG gold-copper deposit is located 130 km south-east of Perth in Western Australia. Goldwas discovered at Boddington in 1980 and production from the oxide material began in August 1987. In1996 a study commenced to develop ore reserves underlying the oxide ore zone and in early 2006 theproject was approved for development, with a project design capacity of 35.2 Mtpa of ore. Mining of thecurrent reserves commenced in 2008, and commissioning of the processing plant started in the latter half of2009.

Figure 1 – Simplified Boddington comminution flowsheet showing the details of conducted surveys

The Boddington ore feeds two 60” x 113” XHD primary gyratory crushers with a nominal designcapacity of 3,670 t/h at an OSS (open side setting) of 175 mm. The crushed ore is conveyed 2.5 km to astockpile with 40,000 tonnes of live capacity, which then feeds the secondary crushing circuit. Thesecondary crushing circuit consists of three single deck banana screens and five 746 kW MP1000secondary crushers. One additional screen was installed in 2010, and in 2011 a sixth secondary crusher wasinstalled. Secondary crushing is a closed circuit and the screen undersize is sent to the HPGR circuit. Thefour 2.4 m x 1.65 m HPGRs operate in closed circuit with eight 3.66 m x 7.93 m wet screens. The wetscreen undersize feeds the grinding circuit (ball mills). There are four parallel ball mill circuits; eachconsisting of a 7.9 m x 13.4 m ball mill with a 15 MW fixed speed motor in closed circuit with twelve 26inch cyclones. Following comminution, the NBG recovery process consists of copper-gold flotation,thickening and cyanidation of the flotation tails with split Anglo elution to recover the gold.

A simplified flowsheet of the crushing and grinding circuits is provided in Figure 1. A photo ofthe crushing and screening plants is provided in Figure 2 and the grinding circuit is shown in Figure 3.

4

Figure 2 - Boddington Crushing and Screening Plants

Figure 3 - Boddington Grinding Circuits

PIO METHODOLOGY

PIO is the development of integrated operating and control strategies from the mine to the plantthat maximise throughput, minimise the overall cost per tonne and maximise profitability. A miningoperation is essentially a series of inter-connected processes, with the performance of each processaffecting the performance of all subsequent processes. These processes are often analysed and optimised inisolation, which can result in suboptimal outcomes when downstream processes are negatively impacted bychanges in a previous stage. In PIO methodology each process is analysed in the context of the wholeoperation (mine to plant). Optimisation of the mining (drill and blast), comminution, separation anddewatering processes are all conducted with impacts carried through the whole process to ensure the bestresults in terms of the overall objectives.

The PIO methodology involves a number of steps, as shown in Figure 4, and normally involves anumber of site visits. Typically during the first site visit, project objectives are defined, data is collected toestablish current operating practice and plans are made for conducting detailed audits, sampling for rockcharacterisation and plant surveys.

5

Figure 4 - Schematic of the PIO Process

During subsequent visits, blast design and implementation are audited and the resulting blastfragmentation is measured. Ore tracking using SmartTagTM ensures the ore blasted during the audits isbeing processed during surveys of the processing plant, thus allowing correlations to be made betweenplant performance and blast fragmentation results. The SmartTagTM system uses passive Radio FrequencyID (RFID) tags to track parcels of ore from the blast, through ROM pads, crushers, intermediate stockpilesand finally into the processing plant. Samples and operating data are collected during the plant surveys andadditional samples are also collected for rock characterisation testing.

Data collection is followed by data analysis, modelling and simulation studies to determine howto exploit hidden inefficiencies. Blast fragmentation, crushing and grinding circuit models are calibrated tosite conditions using data from rock characterisation, blast audits and plant surveys. The calibrated modelsare linked to simulate the performance of the entire process and predict key outcomes (such as throughputand product size). Alternative operating strategies and conditions can be simulated and the outcomescompared to each other and the current situation to evaluate various strategies. This allows options to beevaluated without plant trials, thus minimising the impact on the operation.

Further site visits are conducted to trial and implement improvement opportunities, monitor theresults and ensure improvements are maintained over time. Like any continuous improvementmethodology, PIO is an iterative process; once improvements are implemented repeating the process mayreveal further benefits.

Define Objectives

Establish current operatingpractice and benchmarking

Ore CharacterisationAudits / Surveys

Blast, comminution, process(incl. ore tracking)

Modelling / Simulationto evaluate opportunities

Implementation

Monitoring and measuringbenefits

Itera

tive

proc

ess

–R

epea

t for

con

tinuo

us im

prov

emen

t

6

APPLICATION OF PIO AT BODDINGTON

The PIO process was initiated in October 2009, with a preliminary site visit to define projectobjectives, conduct initial observations and analysis, and plan for comprehensive audits and surveys. Theaudits, surveys and data collection were completed during a site visit in April 2010, and follow up visits inDecember 2010. Three trial blasts were audited and comprehensive surveys were conducted in the crushingand grinding circuits during the April visit. Ore tracking with SmartTagTM was used to ensure the oreblasted during the audits was being processed during the comminution surveys, thus allowing correlationsto be made between plant performance and blast fragmentation. Site specific models were developed forblasting, crushing circuits and grinding circuits.

Ore characterisation of samples taken during the survey program along with an orecharacterisation program undertaken by NBG has provided rock strength and structure data for Boddingtonores. The ore characterisation data together with the process models will allow the development of athroughput forecast and geometallurgical model for NBG. The ore characterisation data is also crucial fordeveloping blasting and comminution circuit models.

The PIO process identified several improvement opportunities at NBG with limited plant trialsand thus minimal impact on operations. A summary of the main findings from PIO project are provided inthe following sections.

Ore Characterisation

The first step in conducting any optimisation of the blasting, crushing or grinding circuits is tounderstand the material properties of the rock at site. Rock characterisation is a study that givesinformation on the strength and structure of the ore, which have a strong influence on all comminutionprocesses. Two fundamental parameters used to determine the Run of Mine (ROM) fragmentation are:

Uniaxial Compressive Strength (UCS) as a measure of rock strength, andIn-situ block size as a measure of rock structure.

The former will dictate the fine end of the ROM size distribution, while the coarse end isgoverned by the in-situ block size of the rock mass.

Point Load Index (PLI or Is50) is measure of rock strength that can be performed quickly andeasily on drill core or irregularly shaped samples of material collected from blasted muckpiles or stockpiles.The PLI data can be converted to a UCS estimate to reduce the need for UCS measurements.

A significant amount of data has been collected relating to the rock strength at NBG. The averageIs50 values range between 6.05 MPa and 9.50 MPa indicating high strength ore. In general, UCS rangedbetween 60 MPa and 230 MPa. For the Boddington ore, the correlation between UCS and Is50 was foundto be: UCS = 17 x Is50. Rock strength data obtained during PIO projects conducted globally are providedin Figure 5. Although the variability in the rock strength is quite wide, it appears that the hard section(upper range) of NBG ore is amongst the most competent that has been observed by PTI to date.

7

Figure 5 - Comparison of NBG Rock Strength Data (orange arrow) and PTI Historical Values (blue bars)

Rock mass structure impacts the coarse end of ROM fragmentation. The three most usefulmeasurements to estimate the in-situ structure of the rock mass (in particular the mean block size) are RockQuality Designation (RQD), fracture frequency and joint mapping. RQD is by far the least difficult andmost popular measurement of structure as it can be performed on drill core. There are over 16,000 RQDmeasurements in the NBG geotechnical database. A total of 125 RQD measurements were observed in thevicinity of the audited blasts and most values were in the 90% to 100% range with an average value of 91%.The RQD data indicates that the rock mass in the vicinity of the audited blasts was massive.

The ADAM Technology system was used to gather information about the joint system. TheADAM system allows rapid extraction of accurate three-dimensional data from digital images. The in-situblock size distribution was determined for the joint sets measured with the ADAM technology system, andthe average in-situ block size was calculated to be 1.14 m. Average in-situ block size was also calculatedusing empirical equations based on the RQD and determined to be 1.11m which correlates well with themeasurements from the ADAM technology system. NBG also collected data from a few additional jointsets, and based on all the available data, the in-situ block size varied between 1.2 and 3.5 m.

Mining (Drill and Blast)

Three blasts were audited in April 2010 as part of the mine to mill PIO campaign, and crushingand grinding circuit surveys were conducted while ore from the audited blasts was being processed. Oretracking using SmartTagTM showed that the bulk of the material fed to the crushing and grinding circuitsduring the surveys originated from one particular blast; therefore, the focus of blast modelling andsimulation was centered on that blast.

A site specific blast fragmentation model was developed using the rock mass characterisation data,actual blast implementation parameters and the resultant ROM fragmentation as inputs to PTI’s BlastFragmentation Model. The PTI approach to blast fragmentation modelling is to calibrate the model withROM image analysis results for the coarse fractions and to use belt cut results from the primary crusherproduct for the fine end of the distribution, as shown in Figure 6.

0

2

4

6

8

10

12

14

0-20

20-4

0

40-6

0

60-8

0

80-1

00

100-

120

120-

140

140-

160

160-

180

180-

200

200-

220

220-

240

Num

ber

of o

bser

vatio

ns

UCS, Mpa

8

In addition, a number of trucks were directed to a mobile screening plant where its contents werescreened at 30 mm and 10 mm aperture to further calibrate the model. The model results show a very goodmatch at both the coarse and fine ends of the particle size distribution, suggesting that the site specific blastfragmentation model is reasonably accurate in predicting the ROM fragmentation. PTI’s fragmentationmodel has been used extensively in PIO Projects, and the model has been validated at numerous sites todate.

Figure 6 - Blast Fragmentation Model Calibration Results

Historical NBG fragmentation data was also reviewed to validate the fragmentation model, andreasonable agreement was found between measured data and model data. Variability in historicalfragmentation at NBG is significant and could be due to changes in blast design parameters (variation inpattern, stemming length, rock strength/structure etc) as well as type of blasts (trim, production orcombined). Defining the blast design according to rock characteristics aims to reduce the variability inROM fragmentation, thus providing a consistent and optimised feed size to downstream comminutioncircuits.

The calibrated fragmentation model was used to conduct simulations of different blast designs anddetermine the impact on ROM fragmentation. The main objective of the blast simulations was to reducethe size of the ROM fragmentation, both in terms of the fine (-10 mm) and coarse size fractions, as this willbenefit the downstream comminution processes.

9

Blast simulations were carried out for different drill patterns. NBG indicated that a change in thehole diameter (from the existing hole diameter of 216 mm to a potential hole diameter of 254 mm) was nota practical solution at that time but could be considered in the future. Thus, simulations were alsoconducted to assess the impact of increased hole diameter. A summary of the simulation details and resultsis provided in Table 1. It is shown that fragmentation becomes finer as powder factor is increased, with areduction in F80 as well as an increase in the amount of fines (-10 mm). Options with the larger diameterdrill (254 mm) offer cheaper costs at a given powder factor.

Table 1 - Blast Simulations

Parameter BaseCaseOption

1Option

2Option

3Option

4Option

5Option

6Hole Diameter (mm) 216 216 216 216 254 254 254Powder Factor (kg/t) 0.44 0.55 0.65 0.73 0.55 0.65 0.73Powder Factor (kg/m³) 1.2 1.5 1.8 2 1.5 1.8 2

Fragmentation BaseCaseOption

1Option

2Option

3Option

4Option

5Option

6F80, 425 345 301 279 368 321 297% difference 0 18.8 29.2 34.4 13.4 24.5 30.1-10 mm 8 9.7 11.3 12.3 9.9 11.5 12.5% difference 0 21.3 41.3 53.8 23.8 43.8 56.3

Costs BaseCaseOption

1Option

2Option

3Option

4Option

5Option

6$/t* 0.5 0.62 0.74 0.83 0.57 0.68 0.76% difference 0 24 48 66 14 36 52* drilling cost is assumed to be $10/m

A number of changes to drill and blast were implemented at NBG based on the recommendationsprovided by Metso PTI in October 2010. These changes included: a reduction in stemming length from 4.2m to 3.5 m, different inter-hole and inter-row delay timings, different initiation sequences, and powderfactors were applied according to the updated blasting cookbook. Measurement of fragmentation from ablast with the changed conditions confirmed that these changes had improved ROM fragmentation asexpected, as shown in Figure 7.

10

Figure 7 - Comparison of August and December 2010 measured fragmentation data

Further simulations were conducted during the December visit, along with analysis of BlastMovement Data collected since August 2010. Review of the Blast Movement Data indicated that there ismore movement and more variability at higher powder factors. However, data also suggested that longer(100 ms) inter-row delay timing controlled the movement better, with movement always less than 15 m(and generally less than 12 m) under this condition.

Nine simulations evaluating the impact of stemming length, Velocity of Detonation (VoD) anddrill pattern were performed. The results from these simulations suggest that fragmentation improves as thepowder factor is increased, the stemming length is reduced and the explosive VoD is increased. It wasrecommended to continue Blast Movement Data collection and look for possible solutions to minimise therisks of excessive ore movement. Additional mine to mill trials to further improve fragmentation whilekeeping horizontal movement at reasonable levels was also recommended.

Comminution Circuit

A full comminution circuit survey was conducted while material from the audited blasts wasbeing processed in April 2010. The survey was divided into three stages: primary crushing, secondarycrushing and HPGR circuit, and the grinding circuit. The primary crushing circuit was sampled on the 7thof April. On the 9th of April, slurry samples were collected for the grinding circuit survey followed by thesecondary crushing and HPGR circuit survey. A simplified comminution circuit flowsheet indicating thethree sections of the survey and survey points is provided in Figure 1.

0

10

20

30

40

50

60

70

80

90

100

1 10 100 1000 10000

Cum

ulat

ive

% p

assi

ng

Size, mm

August 2010 Fragmentation data(prior to changes)December 2010 Fragmentationdata (after changes)

11

The SmartTagTM ore tracking system confirmed that ore feeding the plant during the surveys wasfrom the mine to mill audited blasts. The samples were collected efficiently with minimum disruption toproduction. The sample sizing results and mass balance procedure indicated good quality samples.

During the survey, the primary crusher was drawing 483 kW of the 1,000 kW available power atan estimated throughput of 5,370 tph with a closed-side-setting (CSS) of 150 mm. Feed to the primarycrusher (ROM) had an F80 of 425 mm and the resulting primary crushing product had a P80 of 160 mm.The secondary crushing circuit had a fresh feed rate of 4,560 tph. The four operating crushers had powerdraws of 460, 554, 583 and 581 kW respectively at an average CSS of 51 mm and achieved a product witha P80 of 38 mm. The HPGRs were operating between 126 and 129 bar at an average gap of between 59and 66 mm, and the torque ranged between 64 to 69%. Under these operating conditions, the HPGR circuitwas achieving a product with a P80 of 6 mm. The feed rate to each grinding line was 1,100 tph, and theball mill in each grinding line had a power draw of about 14 MW. Under these operating conditions (andwith the cyclone configuration in operation at that time), the product P80 achieved in each line ranged from92 to 128 m. This is significantly finer than the target grind size P80 of 150 m.

A sample collected from the secondary crushing circuit feed was sent off to a commerciallaboratory in order to determine the ore hardness. Table 2 summarizes the ore properties in comparisonwith the project design values (from the feasibility study). As can be seen from the data, the design valuesand the survey ore characteristics were similar. The drop weight test results indicate that the ore is verycompetent.

Table 2 - Comminution ParametersComminution Parameter Design April 2010 Survey

UCS 140 135Impact crushing Wi 30 27.7Bond Abrasion index 0.5 0.52Bond Rod Mill Wi 23.4 20Bond Ball Mill Wi 15.6 14.4JK Drop Weight Index Dwi 10.7 9.3JK A*b 27.3 30

Survey mass balance results indicated good quality data sufficient for calibrating site specificJKSimMet models of the crushers, HPGRs, ball mills and cyclones. The calibrated models for eachcrushing and grinding stage of the plant were combined to obtain a model of the full comminution process.

Process Simulations

The main objective of process simulations was to identify strategies for increasing plantthroughput; and improve crushing and grinding equipment utilisation. A number of opportunities toincrease the amount of fine material in the ROM through changes in blasting practices were identified inthe drill and blast investigation.

The simulations were first carried out to show the effect of finer ROM size distribution on theperformance of the crushing and grinding circuits operating at the same throughput and conditions as thebase case. A finer ROM size distribution resulted in a finer primary crusher product and reduced theprimary crusher power by more than 20% in comparison to the base case.

12

However, the results also indicated that the effect of a finer ROM on the secondary crushingcircuit would not be pronounced unless the primary and secondary crushers are fully utilised. Therefore,simulations were performed with a tighter primary crusher closed side setting (CSS) while maintaining thesame power draw as the base case. The primary crusher with a tighter CSS generated a much finer productin terms of 80% passing size. With this finer feed, the secondary crushing circuit was able to treat 20%more material at the same power draw as the base case without increasing product size.

Following the findings from the simulation of blast options, additional simulations wereconducted to investigate the effects of different operating conditions in secondary crushing, HPGR and ballmill circuits on the overall circuit performance.

Secondary crushing simulations were conducted for finer screen sizes, and finer screen sizes incombination with finer CSS. A screen design software program was used to calculate required screen areafor the different screen apertures. Based on this, the capacity of the current screens to handle varioustonnages was evaluated and used to determine the impact on screening efficiency assuming the screen areastayed the same. A relationship between screen efficiency and alpha parameter ( ) in the screen model wasused to simulate changes in screen efficiency for the various screen apertures and feed rates.

Secondary Crushing

The simulation results showed that employing smaller screen apertures while maintaining the basecase CSS of the secondary crushers resulted in higher circulating loads around the secondary crushingcircuit. Secondary crusher product tonnage of up to 6,500 tph was simulated compared to the base case of4,600 tph. Simulations using tighter gap settings (CSS) in combination with finer screen apertures reducedthe expected circulating load in the circuit. This indicated that effective control of CSS would be crucial ifa smaller screen aperture was to be used in the circuit. Otherwise, increasing the circuit throughput furtherwould be limited in the case of smaller screen apertures due to capacity limitations of the secondarycrusher product conveyor belt.

The simulation results also showed that the increase in circulating load resulting from thereduction in screen aperture and CSS caused the secondary crushers to draw more power. This suggeststhat more crushing capacity would be required i.e., an additional crusher may be required to operate withfiner screen apertures. At the beginning of 2011 a sixth secondary crusher was commissioned atBoddington, to alleviate the impact of higher than anticipated liner wear rates on crusher availability andutilisation. This now provides additional capacity which can be used to optimise screen panel aperture andrecirculating loads in the secondary crushing circuit.

HPGR Circuit

The main objective of HPGR circuit simulations was to determine the impact of increased rollpressure and changes in fine screen aperture size on circuit performance. Using historical data from Aprilto October 2010, a relationship was established between roll pressure and specific energy consumption(Ecs) to allow the effect of roll pressure to be simulated. Due to significant scatter in the data, conservativeestimates of Ecs were assumed at higher roll pressures. After estimating the specific energy consumptionsfor various roll pressures, a number of simulation scenarios were performed to evaluate the effect ofincreased roll pressures and reduced screen size on both HPGR circuit and ball mill performance. Thesesimulations have indicated that a significant increase in throughput and reduction in current HPGR screensize would not be possible without a significant increase in rolls pressure in order to keep the conveyor beltloads below their maximum capacity. Limitations in fine screening capacity were also indicated atthroughputs higher than design and with finer screen aperture sizes.

13

The main benefit from operating at higher pressure is higher HPGR power utilisation and higherfines creation that has a direct impact on ball mill circuit capacity. As a result, Boddington is currentlyachieving consistent HPGR operation at around 160 bar pressure without detriment to machine availability.

Figure 8 - Relationship between Roll Pressure and Specific Energy Consumption (Ecs)- six months ofoperation

It can be observed from Figure 8, that the specific energy consumption of the HPGRs achievedduring the first 12 months of operation was well below the expected target of 1.8 kWh/t. Metso PTIexperience from two other operations using HPGRs has shown similar trends, where HPGR performancewas not reaching design specific energy consumption targets. Figure 9 illustrates why the design Ecsdetermined from the pilot testwork is difficult to achieve in operation. It shows that the HPGR performancewith a worn (old) rolls surface is inferior compared to operation with new rolls. With new rolls it waspossible to achieve the design specific energy (Ecs) range, although at higher pressures (specific grindingforce). There is also a clear trend of increasing the specific energy consumption with increase in specificgrinding pressure, same as in the pilot testwork. With a worn roll surface, average Ecs was around 20-40%lower than design and highly variable for the same specific grinding force. This observation should betaken into account for future HPGR applications.

0.600.700.800.901.001.101.201.301.401.501.601.701.801.902.00

110 120 130 140 150 160

Ecs,

kW

h/t

Roll Pressure, Bar

Target Ecs

14

Figure 9 - HPGR Specific grinding force and specific energy for a copper ore operation

BENEFITS FROM PIO APPLICATION AT BODDINGTON

The PIO Methodology looks at all aspects of the operation, and considers each in the context ofthe whole operation; thus achieving the best overall result. Implementation of PIO at Boddington hascontributed to improvements in all areas from rock characterisation, through drill and blast, to crushing andgrinding. All of which have contributed to a steady improvement in operation performance over time. Forexample, the improvement of secondary crusher capacity and utilisation over time is shown in Figure 10.The most important aspect of achieving improvement has been the diligent work of site personnel, andcooperation between all departments (geology, mining, processing) to achieve overall operation goals.

0.5

1.0

1.5

2.0

2.5

3.0 3.5 4.0 4.5 5.0

Spe

cific

ene

rgy

(kW

h/t)

Specific Grinding Force (N/mm2)

New rolls

Old rolls

Design range

15

Figure 10 - Improvement in Secondary Crusher Capacity and Utilisation

The introduction of routine measurement of rock strength for different ore lithologies using pointload testing, is providing comprehensive data which will allow for blast designs to be adapted based onrock characteristics, thus providing consistent and finer ROM fragmentation. Further structural mappingand understanding of strength and structure will allow blasting domains to be defined.

A number of changes to drill and blasting have been implemented including: a reduction instemming length, different inter-hole and inter-row delay timings, different initiation sequences, andupdated blasting cookbook. These modifications to the blast design have resulted in finer ROMfragmentation which has provided significant benefits to mining and crushing operations. In addition, thefragmentation model has proven to be valid across a range of scenarios and the same base model can beused for any future studies, providing a useful tool for evaluation of future opportunities.

Improved collection of Blast Movement Data has provided a better understanding of the impact ofcertain aspects of blast design on ore movement. Consideration of these factors can provide blast designsthat improve fragmentation while keeping horizontal movement at reasonable levels and thus avoidingdilution of ore due to excessive mixing.

Simulation results have assisted in making changes and improvements in the crushing andgrinding circuit and the effect of these changes is well understood by the operational staff. Thecomminution circuit models have been updated to reflect the changes and provide a useful tool forevaluating future alternatives with minimal impact on production.

16

Additional comminution circuit simulations were carried out in February 2011. The aim of thesimulations was to investigate further opportunities for mine to mill optimisation and to aid an engineeringstudy for plant debottlenecking and expansion.

CONCLUSIONS

A comprehensive mine to mill Process Integration and Optimisation project has been conducted atNewmont Boddington Gold Mine. The methodology used looks at each aspect of the operation within thecontext of overall performance. The project required extensive data collection including drill and blastaudits, characterisation of ore properties, comminution circuit surveys and a review of historical data toassess limitations within the current mining and processing operations.

Measured data from the blast audits, plant surveys and laboratory tests have been used to developsite specific simulation models of blast fragmentation, and crushing, HPGR and ball mill circuits. Themodels have been used to evaluate various scenarios for improving overall mine and plant performance.The results have assisted in making changes and improvements in the crushing and grinding circuits.

Key outcomes of the project were:

Changes to drill and blasting practices, based on the results of simulation work. Thesechanges have been verified as having improved ROM fragmentation.Development of an integrated simulation model of the mine and processing plant for use infuture studies.Consideration of all aspects of the operation, resulting in a steady improvement in overallperformance.Improved cooperation between geology, mining and process to achieve overall operatinggoals.

Further work is now underway to evaluate expansion options using the simulation modelsdeveloped as part of this project.

ACKNOWLEDGEMENTS

The authors wish to acknowledge the NBG Management, Mining and Processing Operations andMaintenance teams for their support, assistance and perseverance during this period.