Academic journal article Issues in Informing Science & Information Technology

Planning an Iron Ore Mine: From Exploration Data to Informed Mining Decisions

Academic journal article Issues in Informing Science & Information Technology

Planning an Iron Ore Mine: From Exploration Data to Informed Mining Decisions

Article excerpt

Introduction

Background

Australia managed to avoid many of the effects of the 2008 Global Financial Crisis, thanks largely to a booming mining economy invigorated by China's unprecedented increase in demand for our mineral exports, particularly iron ore and coal for steel production. Australia contributes about 20% of the world's iron ore production. Virtually all of this production is exported, and the world export market is dominated by Australia and Brazil (US Geological Survey, 2012).

Although iron ore resources occur in all the Australian States and Territories, almost 93% of the country's total iron ore resources (totaling 64 billion tonnes) occur in Western Australia, predominantly in the Pilbara region, north and west of the town of Newman. Most of the product is shipped out through the ports of Port Hedland and Dampier.

Current production from Western Australia is approximately 470 million tonnes a year, typically at about 60% iron content. There are plans to double this production rate by 2020 (Geoscience Australia, 2012). It is estimated that current resources and production will sustain this nationally important industry at least until 2050 (O'Brien, 2009).

History

A local pastoralist Lang Hancock, flying over his cattle station in the northern Pilbara region of Western Australia, is reputed to have made the first major discoveries in 1952 when bad weather forced him to fly low over the Hammersley Gorge: his compass was playing up and he noticed the gorge's rain-washed cliffs were iron red.

This legend has since been questioned, with the credit for discovery going back to an 1890 survey by Harry Woodward, the state's government geologist (Lord & Trendall, 1976). Nevertheless, production began only in the 1960s, after intensive lobbying to rescind the pegging and export bans. These bans had been in place since the start of the Second World War, when exports to Japan had been hurriedly blocked by the Commonwealth government.

There are now many producing mines in Western Australia, mainly in the Pilbara district. The mining giants BHPBilliton and RioTinto are the major operators, but a number of smaller companies have commenced production or are in the planning stages. Thanks to production royalties on many of the leases, Lang Hancock's daughter Gina Rhinehart is now reputedly the world's richest woman, though assailed by litigous offspring.

Mining

Western Australian iron ore mines are all open-cut pits. The ore is generally blasted, then trucked to a crusher where it may be separated into lump and fines component products. The crushed ore is railed to a port and loaded onto ships, typically of the order of 100,000 tonnes capacity. To achieve uniform grade, the ore is commonly stacked onto stoc[K.sub.P]iles of perhaps 200,000 tonnes, either before or after railing to the port. Recently a common development has been to direct load part of the ore (without stoc[K.sub.P]iling), taking advantage of both the blending potential of large shipments, and careful planning of the mining sequence, to achieve grade control as discussed below.

Grade Control

Nearly all the ore is ultimately fed into a blast furnace for steel production. A blast furnace is finely tuned, requiring input ore of consistent grade, not only in its iron content (typically up to about sixty percent iron) but also in its content of the major contaminants, silica and alumina (each a few percent) and phosphorus (a fraction of one percent).

A target grade vector is agreed between the producer and the customer. Naturally, this target grade has to be both acceptable as input to the customer's blast furnaces, and feasible to produce from the projected mine. Departure of shipment grade from a narrow tolerance band around the target grade is heavily penalised, both directly and also indirectly, because failure to produce consistent grade affects the company's reputation for future sales. …

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