99-115

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Copyright 1999 by SME1

SME Annual Meeting

March 1-3, 1999, Denver, Colorado

Preprint 99-115

THE DEVELOPMENT AND COMMERCIALIZATION

OF THE HICOM HIGH INTENSITY GRINDING MILL

T. A. E. Breen

Hicom Intl. Pty. Ltd.

Sydney, NSW, Australia

ABSTRACT

A new high intensity grinding technology has been developedand is now being commercialized by Hicom International of

Australia. This has led to the development and manufacture

of Hicom 120 grinding mills which are now being sold

internationally for a range of mining industry applications.

The first commercial process application has been for the

diamond sector, where the ability of the mill to remove host

kimberlite rock by attritioning, with no damage to the thereby

liberated diamonds, is seen to be a most beneficial attribute.

There are, however, many other mineral industry applications

for this mill.

The design of the Hicom mill is unique. Based on a high

speed centrifugal motion of the grinding chamber, very highpower intensity is delivered to the grinding process. Most

significantly, a high acceleration field, 50 times stronger than

gravity is produced, creating very high power input per unit

of mill volume, and exceptionally fast particle breakage rates,

typically 50 - 100 times greater than those in conventional

tumbling mills. A mill developing such forces has significant

implications to comminution technology and practice.

Hicom high intensity grinding mills are now available to the

mining industry for evaluation and purchase. After a number

of years of design and testing, two commercial mills are now

in operation. The first is in South Africa, and for over 2 years

this mill has been processing diamond bearing marine gravel.The second mill is in the Northwest Territories of Canada, at

BHP's Ekati Diamond Mine. The mill was purchased by BHP

and commissioned in October, 1998. It selectively grinds

away the kimberlite in a DMS concentrate stream, thereby

reducing by some 50% - 60% of the mass of material

requiring treatment in downstream x-ray sorting plant. The

important quality that characterizes the Hicom mill in this

application is its ability to liberate any diamonds present in

the feed, without damage to them.

There are several other mineral process applications for

which the Hicom mill has been designed, including the fine

grinding of ores, mineral concentrates, and industria

minerals. This paper will describe the technology and

construction of the mill, examine its commercial applications

and development to date, and provide details on the mobile

demonstration Hicom mills now available for on-site

performance trials by the mineral process industry.

INTRODUCTION

History & Current Status of Development

Charles Warman - Inventor of the Hicom Mill: The Hicom

mill was originally conceived and designed by Charles

Warman, the founder of the C H Warman Group, of which

Hicom International is a part. Dr. Warman is best known for

the invention and commercial development of the Warman

slurry pump while working as a young mining engineer on

the Kalgoorlie gold fields of Western Australia over 50 years

ago.

Charles Warman's aim was to create from centrifugal milling

theory a mill that was eminently practical and cost effective

and which solved the problems associated with previous (and

subsequently unsuccessful) attempts to design a mill utilizinghigh speed centrifugal forces. The Hicom mill has been

developed as a progression from centrifugal or planetary

mills. These earlier mills, when used in a continuous mode of

operation, had to cope with unmanageable and awkward

feeding and discharge arrangements.

Over the past decade the original concepts of Charles

Warman grew into prototypes and then pilot plants, and in

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the last few years have commercially matured into the Hicom

high intensity grinding mill (sometimes referred to as the

"nutating" mill). The mill is patented in 60 countries.

Recent Developments: The current model, the 110 kW Hicom

120 Mill, although at present of relatively small capacity,

with an output typically of between 5 and 15 tph, is theprecursor of a series of larger mills now at design stage.

These will have a power requirement of up to 1 megawatt,

(ten times that of the current model) and be capable of

production in the order of 100 tph - 150 tph.

The tradition of innovative design and engineering excellence

which characterized the design and development of the

Warman slurry pump, can also be seen in the design of the

Hicom high intensity grinding mill.

The development and manufacture of Hicom Mills are being

undertaken by Hicom International Pty. Limited, the C H

Warman Group's mill division, at the company's headquartersin Sydney, Australia.

A significant amount of research and development and

application of Hicom technology has also emanated from the

Group's operation in South Africa, a geographic factor that

goes some way to explain the initial uptake of Hicom

technology by the diamond sector of the mining industry.

In 1995 the first commercial project that incorporated aHicom mill in its flow sheet came out of the consulting office

of Bateman, the Johannesburg based minerals process

engineers. A Hicom 120 mill was to be incorporated in the

diamond recovery plant then being designed and built for

diamond producer Alexkor Limited, at Alexander Bay on

South Africa's west coast. This mill selectively removes and

mills to a slurry substantial amounts of shell and shale which

occurs in the marine gravel and dense medium separation

(DMS) diamond concentrates treated by Alexkor, prior to

x-ray separation of the diamonds. This Hicom mill was

commissioned the following year, and in the ensuing period

has been operating effectively and performing above its

design expectations.

Figure 1: Mill Drawing

Hicom 120 High Intensity Grinding Mill, Cut-away view

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After an extensive assessment and test milling program by

BHP Minerals, the second Hicom 120 mill sold into the

diamond sector was commissioned by BHP in September

1998 at its newly developedEkati diamond mine located just

south of the Arctic Circle in Canada's Northwest Territories.

The function of the Hicom mill in BHP's state of the art

diamond recovery plant is to reduce the bulk of diamondconcentrate reporting to the x-ray recovery plant. This is

achieved by the selective grinding by the Hicom mill of the

kimberlite, a process which liberates additional diamonds

from the ore, without any diamond damage.

Hicom mills are presently being included in the flow sheets of

several planned diamond recovery plants, now at the

feasibility stage. These mills are scheduled for supply to

diamond projects being developed by leading mining

companies in Canada and in South Africa over the next few

years.

Having quickly established a successful bridgehead into thediamond sector, Hicom International is now turning to more

mainstream applications for the mill in the precious and base

metals sectors, as well as for the milling of fine and ultra fine

industrial minerals.

R & D and New Model Development: Current research and

development by Hicom International is focussed on two main

areas. The first is for optimization of wet and dry milling

processes for fine and ultra-fine grinding. The second is to

finalize the design and to commence manufacture of

prototype 350 kW and 1,000 kW Hicom mills, with a target to

have commercial models of these mills available for sale in

2000.

DESIGN FEATURES

Configuration & Motion of the Grinding Chamber

Reference to Figure 1 shows that the grinding chamber of the

Hicom mill is a truncated cone with a roughly hemispherical

base, and a vertical axis of symmetry. It consists of two

corrosion-resistant stainless steel castings bolted to form a

thin-walled shell, which contains the replaceable wear-liners.

The chamber axis 'nutates' about a fixed nutation pointdefined by the main bearing, the motion being similar to that

of a conical pendulum, in which the top is fixed and the

bottom describes a circle, as is shown in Figure 2. {"Nutate"

means to nod or oscillate in a manner akin to that of the

earth's axis). The motion of the chamber is akin to one

swirling a conical flask with one's wrist.

Figure 2: Nutation

Schematic Diagram of Grinding Chamber Motion

There is no critical speed of the tumbling charge in Hicom

mills -they can be operated at any speed, limited only by the

mechanical strength of the drive.

Power Density

The magnitude of the acceleration field in which the mil

contents tumbles varies with the square of the grinding

chamber speed, while the power input varies with the cube of

the speed. Typical design values of maximum acceleration

intensity for Hicom mills are in the range 40-50g, givingpower densities up to about 2,500 kW per m3of mill volume

This compares with power densities of 300 kW per m 3of mil

volume for stirred mills and 30 kW per m3of mill volume for

conventional ball mills. Put another way, this means that the

power density of the Hicom mill is around 8 times that of a

stirred mill and over 80 times that of a conventional ball mill.

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As a first approximation, the load behavior in the grinding

chamber of the Hicom mill is similar to that in centrifugal

mills. However, there is a net downwards acceleration in the

Hicom milling chamber which has the effect of pumping the

slurry through the chamber in approximately plug flow. Short

mill residence times can be achieved, and in some

applications this can improve grinding efficiencies, bylimiting over-grinding.

The grinding action in Hicom mills is predominantly

achieved by attrition, rather than by impact.

Operation of the mill shows that the high intensity of the

grinding action results in very rapid particle breakage rates.

For example at a mill speed of 1960 rpm, quartz feed material

was reduced from d8O - 70 um to powder with a d80 5 m

in just 98 seconds in batch grinding tests.

Nutator & Drive Mechanism

The key to the high performance, mechanical efficiency,

compactness and durability of the Hicom drive mechanism is

a patented nutating bearing which suspends the grinding

chamber. This bearing, developed by Hicom International

specifically for the Hicom mill, provides long service life at

the loads and operating speeds required. The nutating bearing

is analogous to a disk which rolls between fixed upper and

lower surfaces. The nutating bearing has just a single moving

part, and is self-compensating for wear. The nutating drive is

backed by many years of research and development in design

optimization, materials selection and endurance testing.

Other Design Features of the Mill

The Hicom 120 Mill features modular construction

comprising the body, nutating assembly, transmission,

services unit, grinding chamber and control cabinet.

The body is a robust casting which serves both as a structural

element supporting the nutating assembly and as ballast to

counteract the inertial forces of the nutating assembly (Refer

Figure 1). The body fully encloses the grinding chamber and

is equipped with a door for maintenance access. The nutating

assembly is bolted rigidly on top of the body and the whole

assembly is isolated from the supporting structure byvibration mounts. Process material is gravity fed from a

hopper or flexible feed-tube that can be bolted on top of the

nutator housing. In wet grinding, upon exiting the grinding

chamber, the product discharges as slurry via a chute through

the lower section of the mill body.

The mill is directly driven by an electric motor mounted

beneath it. A services pack which provides lubrication,

filtration and cooling, air and instrumentation is housed in a

freestanding enclosure directly beside the mill.

Operation of the mill is controlled by a programmable logic

controller (PLC) which sequences start-up and shutdown, and

monitors for possible fault conditions. The PLC indicates mil

status to the operator via a programmed message display.

Hicom mills can operate with a charge of steel balls or other

media, or alternatively, with an autogenous charge of ore

Autogenous feed sizes up to 80 mm can be accepted. Thus the

mills are extremely versatile, and can be used for a wide

range of mineral processing and industrial grinding duties

wet or dry, in open or closed circuit, as well as in batch mode

for smaller mills. Hicom mills are particularly suited to

energy-efficient fine grinding, in the 10 m product size

range, and finer.

The Hicom 120 mill is a very compact unit, a reflection of the

high power density and small mill volume inherent in itsdesign. (Refer Figure 3) Its footprint is a mere 1.26 m wide x

2.62 m long with a height of 2.28 m (including motor: of 3.53

m). The larger capacity units now being developed will also

reflect the same relative compactness a characteristic which

means that installation costs of Hicom mills and related civi

engineering costs are very low, compared to those of other

mill installations.

Liner replacement is a fast, simple procedure that can be

performed in minutes. Using the loading arm accessory, the

front half of the chamber shell detaches complete with the

worn liner and a replacement liner assembly is bolted in, with

minimal process downtime, typically less than 30 minutes per

liner change. Wear-liners have been designed with great

emphasis on maximizing wear-life. All parts of the mil

exposed to abrasion are protected with wear-resistan

materials.

Testing

During the design stage, all critical mechanical elements in

the mill have been subjected to extensive Finite Elemen

Analysis studies and subsequently verified by endurance and

load testing. Quality checking to fine tolerances and

non-destructive testing procedures are applied throughouteach stage of manufacture.

Model Sizes

The current operating model is the Hicom 120. This can be

supplied in two configurations:

(1) The Hicom 120/30 has a 30 liter grinding chamber

and is driven by a 55 kW motor

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(2) The Hicom 120/60 has a 60 liter grinding chamber

and is driven b a 110 kW motor

Units can be supplied as wet or dry processors, with Variable

Speed Drive as an option.

APPLICATIONS

Hicom high intensity grinding technology is not designed to

replace standard ball or SAG milling for general mineral

process duties. The Hicom mill is specialized and highly

designed equipment focussed on applications that are outside

the day to day range of standard milling plant. In essence

these include:

Wet or dry grinding to product sizes below 45 m

Wet or dry fine and ultra-fine grinding to below 10 m

Diamond liberation

Special attritioning duties Shipboard, mobile and underground installations

Special coarse particle reduction (from - 60 mm)

Fine Milling of Hard Ores to - 10 m

Conventional mills become progressively less efficient at

product sizes below about 75 m especially when grinding

hard ores such as quartzites and pyrite. Hicom mills remain

efficient at fine product sizes down to at least 10 m with

these ores. With the ability to vary the grinding intensity and

to make effective use of small grinding media, the Hicom mill

operation can be optimized for maximum grinding efficiency.

In recent batch mill performance tests for the fine grinding of

a West Australian telluride-pyritic gold ore, Hicom milling

produced a d90 10 micron product from a 60 micron feed

using 74 kW hours/tonne. This power draw compares

favorably with the results obtained for fine grinding the same

ore in tower mills and sand mills. Pilot plant tests in closed

circuit with a hydrocyclone classifier are planned and these

are expected to result in further improvements in grinding

efficiency.

Fine Milling of Industrial Minerals to -2 m

The milling of industrial minerals, wet or dry, to between 10

m and 2 m and finer in some instances, with economic

power usage, is an application for which Hicom mills are

designed. Special liners and grinding media are available to

suit iron-free and other specific end-product requirements.

Ongoing mill performance testing is being carried out and

assessed on a range of industrial minerals, milled to fine and

ultra-fine products.

Autogenous "critical size" pebble reduction

"Critical size" pebbles, typically 25 mm - 60 mm, often

accumulate in conventional autogenous mills and SAG mills

reducing the efficiency of the milling circuit. This critical size

material may be removed from the primary mill, crushed tocoarse sand, and fed to the secondary ball mill circuit for

further grinding. As an alternative to crushing, the critica

size pebbles can be reduced to a fine product in a single step

by processing them in a Hicom mill operating autogenously

in open circuit (Hoyer, 1996). The result is an increase in

circuit capacity by relieving the load on the downstream

grinding mill.

Pilot plant performance tests comparing the power draw

required to remove critical size quartz (1) by using a cone

crusher and (2) by using a Hicom mill have shown that the

latter reduces power draw in this particular instance by 9.8%

(Hoyer, 1996)

The pilot plant data was scaled up and extrapolated using

computer simulation to provide the following results.

In this exercise a SAG mill was producing 66 tph of milled

ore. This was screened over a 7.5 mm screen, and the re-

circulating load in the mill of the coarse oversize fraction

consisting of - 43 mm "critical size" pebbles, was fed to a 13

kW crusher at the rate of 13 tph. This reduced the pebbles

directing the crushed product to a ball mill.

The ball mill was also being fed the screened undersize

material (-750 m) at 53 tph and drew 1160 kW of power to

produce the required -75 m product. Thus there was a total

power draw of 1173 kW for the crusher and the ball mill.

In the alternative scheme, a Hicom mill, replacing the

crusher, was installed after the ball mill. With the same

stream of oversize feed being fed directly to the Hicom mill

and the undersize from the screen being fed to the ball mill

as before. The ball mill drew 895 kW power, and the Hicom

mill used 173 kW, a total power draw of 1068 kW.

These tests indicate that in this particular application

installation of a Hicom mill would remove the critical sizepebbles at a power saving of almost 10% compared to using a

crusher for this purpose.

Diamond liberation

Hicom mills have the now proven capability for the

autogenous size reduction of diamond bearing materials

without causing damage to diamonds in the feed (Hoyer

1996). Specific problems associated with diamondiferous

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Figure 3: Hicom 120

Mill Dimensions

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marine and alluvial gravels, such as seashells, are effectively

eliminated. Hicom mills selectively reduce the stream volume

of dense medium separation concentrates by up to 60%,

reducing capital outlays on costly downstream x-ray sorting

equipment, and also significantly reducing ferro-silicon losses

in DMS plants, by releasing it - and sometimes diamonds -from entrapment in seashells.

In processing diamond ores, the Hicom mill can be run in

open circuit at high throughput, with specially configured

discharge ports in the grinding chamber. Residence time is

adequate for the complete attrition of the kimberlite, resulting

in total diamond liberation but with no measurable damage to

the diamonds. Minimal energy is expended on the grinding of

the harder barren material.

Current installations of Hicom mills in diamond liberation

plants place the mill after the DMS plant, where they

typically reduce -6mm diamond concentrates to finer than 1mm material. This placement and application of the mill in

such flow sheet configurations is partly due to the relatively

small throughput of the Hicom mills at present, limiting them

to more concentrated and smaller product streams. When

Hicom mills of higher capacity are available, there is good

reason to believe they will be able to be installed further up

the flow sheet, immediately after the secondary crushers,

producing feed for DMS plants. In alluvial and marine

diamond operations, Hicom mills would be able to take

directly as raw feed the untreated alluvial or marine gravel,

and reduce it to -20 mm + 2 mm feed for DMS concentration.

Attritioning & Scrubbing

The high intensity grinding action of Hicom mills enables

fast and effective scrubbing and attritioning of the material

being milled. Thus deleterious coatings on mineral particles

can be effectively removed, as can other contaminants such as

clays. The Hicom 120 mill will accept up to 65 mm size feed,

when using grinding media.

An example of this property of Hicom mills includes the

removal during attritioning of DMS concentrate of a film that

often coats alluvial or marine diamonds, which if not

removed makes them considerably less able to fluoresceduring x-ray sorting, resulting in product losses.

The mill has also proven to be effective in removing an iron

enriched "ferrocrete" material, which in some mineral sand

deposits is cemented around potentially valuable heavy

mineral product, making it uneconomic to process. The high

speed attritioning of this material in a Hicom mill rapidly

converts the rock-like cement to slurry, thus liberating the

heavy minerals entrapped within.

The Hicom mill may also be able to utilize its selective

milling capability to separate by attritioning other deleterious

or unwanted minerals from certain mineral concentrates

thereby upgrading the end product. Tests are in progress toenable a better understanding of the mill's capabilities in this

regard.

Shipboard Plant Installations

Due to the compact design and the high intensity of grinding

forces deployed in their small mill volume, Hicom mills are

ideal for shipboard installations such as in the offshore

marine diamond industry in Southern Africa. It is anticipated

that within the next 2 years several Hicom mills will be

deployed on ocean going diamond marine mining vessels

working the diamond concessions off the Atlantic Ocean

coastline of South Africa and Namibia.

Underground Milling and Mine Backfill Production

The compact design and high intensity grinding properties of

Hicom mills provide them with significant potential for

underground installations, both for the milling of ores and the

production of backfill.

Hicom International has commenced test work in

collaboration with the Mining Technology Division of South

Africa's CSIR in examining the capability of Hicom mills to

cost effectively produce backfill. Initial results indicate the

mills have significant potential in this regard, with the

capacity to produce a material with the required particle size

distribution for a suitable paste backfill.

ORE TESTING FACILITIES

Hicom International operates a range of pilot plants and

laboratory mills at its R & D facilities in Sydney and

Johannesburg, as well as full size production units for tes

work on clients' specific materials. Technical advice and

plant design recommendations are available to assist in

establishing process design requirements. Specially developed

process simulation tools enable reliable Hicom scale-upoptimization analysis and flow sheet development.

Containerized Demonstration Plants

The Company has built one fully equipped, containerized

mobile Hicom 120 plant for on-site testing at client locations

Figure 4 provides a drawing of front and side elevations of

this plant. Other mobile plants are currently under

construction.

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These mills can be deployed anywhere in the world for

demonstration, performance testing, and equipment selection

comparisons or for specific processing campaigns.

The Hicom 120 containerised plant comprises two x twenty

foot shipping containers. On the first are installed the Hicom

120 mill and drive motor, a sump pump and hopper, and afixed-speed feed conveyor and comprehensive

instrumentation to enable steady state operation of the

grinding process in open circuit mode. The second container

accommodates the Variable Speed Drives (VSD) for control

of mill and sump pump motors, and the mill operator control

panel. Two drawings showing separate elevations of the mill

container are provided in Figure 4.

Container Plant Description: The mill, 110 kW drive motor

and all process equipment and instrumentation are mounted

on one twenty foot open shipping container. Once installed on

site, the container sits on legs 1.5m above ground level to

allow room for the drive motor and sump pump and hopper

underneath the container. During transshipment, the support

legs, the conveyor and its stand and hopper, the sump pump

and hopper, and the access stairway are stored onboard the

container. The drive motor, mounted on a specially designed

bracket swings up and is secured in the container as well.

These arrangements facilitate rapid and convenient field

deployment.

The operator controls and the electrical supply equipment are

installed in an air-conditioned, insulated shipping container

that serves as a control room and site office for field

operations. Equipment in the control container includes a 110kW Variable Speed Drive (VSD) for the mill, a 7.5 kW VSD

for the sump pump, three phase and single phase power

distribution boards, a Siemens OP27 control panel and a

Desktop Computer. A Siemens PLC that is part of the mill

services pack controls both the mill and process plant

operation. All instruments on the open container terminate in

locally mounted PLC modules, and communication between

the PLC on the mill container and the control station in the

control room is by Siemens Profibus protocol. The only

connections between the two containers are the two VSD

output cables to the mill and sump pump, a three-phase power

cable, a single-phase power cable for floodlights and a single

Profibus cable. This arrangement ensures simple on-site

electrical installation.

In open circuit operation, dry solids feed is supplied from the

host plant by a vibrating feeder or weigh conveyor and is

transported into the Hicom 120 mill by the feed conveyor tha

is part of the containerized plant equipment. Water is added

into the mill feed hopper to control the pulp solids

concentration in the mill, and into the mill body or the sump

Figure 4: Hicom 120 Containerised Demonstration Plant, side and front elevations

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pump to assist the transport of thick slurry out of the mill.

The milled product is returned to the host plant by the sump

pump.

Process Monitoring and Control: The Hicom 120 mill

operation is monitored and controlled from the OP27 panel

that interfaces with the PLC. A Siemens WinCC SupervisoryControl And Data Acquisition (SCADA) system on the

desktop computer monitor the process plant operation. This

facilitates data logging and also remote access from elsewhere

on the host plant, or even from offsite locations. By this

means, the Hicom 120 plant can be run as a stand-alone test

facility, or integrated into an existing plant operation for

long-term process trials.

Mill feed water addition is monitored on a magnetic flow

meter (FM01) and adjusted by a control valve (CV01) to

regulate the concentration of solids in the grinding chamber.

A similar control valve and flow meter combination (CV02,

FM02) is used to set the rate of water addition into the millbody sprays or mill sump. The sump level is monitored by a

pressure transmitter (PT01) via a water-purged dip tube, and

controlled by adjusting the speed of the sump pump (PU01).

This measure prevents the pump operating in snoring duty,

thereby ensuring bubble-free flow. The accurate measurement

of product flow rate (FM03) and density is provided by the

nuclear density gauge (DG01) fitted onto the slurry discharge

pipe. Measurement of product flow rate and density enables

calculation of mass flow of solids through the mill and hence

the calculation of specific grinding energy.

FUTURE DIRECTIONS

Ongoing Mill Performance Test Work

One of the main areas of immediate focus for Hicom

International is to provide mining and minerals process

companies that are planning green-fields projects, plant

expansions or mill upgrades the opportunity to determine the

cost effectiveness of Hicom mills for their proposed milling

duties. In the first instance this can be achieved by the

minerals company sending approximately one kg samples of

feed material to the R & D division of Hicom International in

Sydney for pilot scale mill performance appraisal. In this way

the cost effectiveness of the Hicom mill can be assessed forspecific grinding duties in proposed projects and plant

upgrades.

Completion of additional containerised demonstration

mills

The completion of several additional containerized

demonstration Hicom mills later in 1999 will facilitate the

ease with which the mining industry can further assess the

performance of Hicom mills, especially in fine grinding

applications.

Fast-tracking the manufacture of higher throughput mills

Plans are well advanced for the final design, manufacture and

testing of 350 kW and 1,000 kW high intensity grindingmills, with the aim to have them available during the year

2000 - 2001. The advent of these significantly higher

throughput models will provide the mineral process industry

the opportunity to apply Hicom comminution technology to a

greater number of projects, than is the case with the existing

55 kW and 110 kW models. It is expected that this will lead

to the sale of an increasing number of Hicom mills into the

gold, nickel, platinum, copper and industrial minerals process

sectors during the next few years.

Consolidation of international sales offices and

manufacturing expansion

At present Hicom International operates from sales bases in

Australia, Canada, France, South Africa, and the UK. An

office in the USA is planned for 1999. Mill manufacture a

present is in Sydney, and international manufacturing

expansion will take place as demand builds from the various

market sectors that have been discussed in this paper.

Summary Conclusion

Sufficient research and industry work has been undertaken by

Hicom International to demonstrate some of the benefits of

high intensity grinding in the Hicom mill. The developmen

of the mill so far indicates that there is potential for many of

the quite unique characteristics of the mill to be translated

into economic and technical benefits to many sectors of the

mining industry. The development of this potential will be the

Company's continuing focus in the years to come.

REFERENCES

For much of its technical focus and description, this paper

relies on a considerable body of work previously undertaken

and published by J. M. Boyes and D. I. Hoyer. The two main

published works from which such references are drawn are

listed below.

Hoyer D.I. and Boyes J.M., 1994, "High intensity fine and

ultrafine grinding in the Hicom mill" - Journal of the Xvth

CMMI Congress, Johannesburg, Vol. 2 pp 435-441.

Hoyer D.I., 1996, "High intensity size reduction in the Hicom

mill", Chemica '96, Comminution Workshop Forum, Centre

for Minerals Engineering, University of NSW, Sydney.

Documents

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