Wills' Mineral Processing Technology provides practising engineers and students of mineral processing, metallurgy and mining with a review of all of the common ore-processing techniques utilized in modern processing installations.

Now in its Seventh Edition, this renowned book is a standard reference for the mineral processing industry. Chapters deal with each of the major processing techniques, and coverage includes the latest technical developments in the processing of increasingly complex refractory ores, new equipment and process routes. This new edition has been prepared by the prestigious J K Minerals Research Centre of Australia, which contributes its world-class expertise and ensures that this will continue to be the book of choice for professionals and students in this field.

This latest edition highlights the developments and the challenges facing the mineral processor, particularly with regard to the environmental problems posed in improving the efficiency of the existing processes and also in dealing with the waste created. The work is fully indexed and referenced.

• The classic mineral processing text, revised and updated by a prestigious new team
• Provides a clear exposition of the principles and practice of mineral processing, with examples taken from practice
• Covers the latest technological developments and highlights the challenges facing the mineral processor
• New sections on environmental problems, improving the efficiency of existing processes and dealing with waste.

2 Ore handling

Ore handling, which may account for 30 60% of the total delivered price of raw materials, covers the processes of transportation, storage, feeding, and washing of the ore en route to, or during, its various stages of treatment in the mill.

Since the physical state of ores in situ may range from friable, or even sandy material, to monolithic deposits with the hardness of granite, the methods of mining and provisions for the handling of freshly excavated material will vary extremely widely. Ore that has been well broken can be transported by trucks, belts, or even by sluicing, but large lumps of hard ore may need individual blasting. Modern developments in microsecond delay fuses and plastic explosive have resulted in more controllable primary breakage and easier demolition of occasional very large lumps. At the same time, crushers have become larger and lumps up to 2 m in size can now be fed into some primary units.

Open-pit ore tends to be very heterogeneous, the largest lumps often being over 1.5 m in diameter. The broken ore from the pit, after blasting, is loaded directly into trucks, holding up to 200 t of ore in some cases, and is transported directly to the primary crushers. Storage of such ore is not always practicable, due to its long-ranged particle size which causes segregation during storage, the fines working their way down through the voids between the larger particles; extremely coarse ore is sometimes difficult to start moving once it has been stopped. Sophisticated storage and feed mechanisms are therefore often dispensed with, the trucks depositing their loads directly into the mouth of the primary crusher.

The operating cycle on an underground mine is complex. Drilling and blasting are often performed on one shift, the ore broken in this time being hoisted to the surface during the other two shifts of the working day. The ore is transported through the passes via chutes and tramways and is loaded into skips, holding as much as 30 t of ore, to be hoisted to the surface. Large rocks are often crushed underground by primary breakers in order to facilitate loading and handling at this stage. The ore, on arrival at the surface, having undergone some initial crushing, is easier to handle than that from an open pit mine and storage and feeding is usually easier, and indeed essential, due to the intermittent arrival of skips at the surface.

Ore entering the mill from the mine (run-of-mine ore) normally contains a small proportion of material which is potentially harmful to the mill equipment and processes. For instance, large pieces of iron and steel broken off from mine machinery can jam in the crushers. Wood is a major problem in many mills as this is ground into a fine pulp and causes choking or blocking of screens, etc. It can also choke flotation cell ports, consume flotation reagents by absorption and decompose to give depressants, which render valuable minerals unfloatable.

Clays and slimes adhering to the ore are also harmful as they hinder screening, filtration, and thickening, and again consume valuable flotation reagents.

All these must be removed as far as possible at an early stage in treatment.

Hand sorting from conveyor belts has declined in importance with the development of mechanised methods of dealing with large tonnages, but it is still used when plentiful cheap labour is available.

Crushers can be protected from large pieces of tramp iron and steel by electromagnets suspended over conveyor belts (Figure 2.­1). These powerful electromagnets can pick up large pieces of iron and steel travelling over the belt and, at intervals, can be swung away from the belt and unloaded. Guard magnets, however, cannot be used to remove tramp iron fro

Introduction; Ore Handling; Metallurgical Accounting, Control and Simulation; Particle Size Analysis; Comminution; Crushers; Grinding Mills; Industrial Screening; Classification; Gravity Concentration; Dense Medium Separation (DMS); Froth Flotation; Magnetic and High Tension Separation; Ore Sorting; Dewatering; Tailings Disposal; Appendices; Index