Mining and Pig Iron

Mining

A number of mining methods and technologies are suitable for the Putú deposit. The deposits are essentially heavy mineral deposits and lend themselves well to traditional tried and proven mineral sands mining techniques.

Conceptually mining is anticipated to be carried out with cutter suction dredges in the 1500-2500 t/h capacity range with gravity and wet magnet processing plants, producing around 2 million tonnes annually of a primary magnetite concentrate with a grade of 55-58% Fe. Both the mining and concentrating technologies are robust, proven and used extensively around the world.

BlueScope Steel Limited iron sands operation New Zealand Steel Mining Limited currently runs an iron sands magnetite operation using a conventional dredge-floating processing plant and bucket wheel excavators.  (See photographs of BlueScope Steels Taharoa iron sands operation)

Chiles  capital city of Santiago is only 200km from the project site via good quality highways and  the Putú area itself has good quality sealed roads and nearby high voltage power, all positive issues  for smooth project development.

BlueScope Steels Taharoa Iron sands magnetite operation in New Zealand

Magnetite concentrates will be shipped direct to steel mills in China, Japan and Korea initially however the ultimate objective of the company is a fully integrated mining and pig iron operation.

Smelting Process and Pig Iron Production

A variety of proven reduction and smelting technologies exist and are in operation around the world and the company will investigate the most suitable during the detailed feasibility study.  The expected processing model will be essentially similar to that used by BHP BlueScope New Zealand Steels operation which has been running successfully since 1972.

Magnetite concentrates produced from South American Iron & Steels project were used as the feedstock for various pre-reduction and smelting trials carried out in Germany and Finland and supervised by Outokumpu Technology GmbH Metals Processing Division.

Both the Circored® and Circofer® processes were tested.  The Circofer process is a proprietary process that was developed by Outotec to reduce iron ore fines utilizing coal as a reductant. Circofer similar to Circored uses a two-stage circulating fluidized bed reactor and fluidized bed reactor configuration to obtain a highly metallised product.

The tests concluded that either hydrogen or coal could be used successfully as a reductant to produce a DRI metallised product. This product was then used for various smelting trials to produce pig iron and high grade titanium slabs.

The Outokumpu direct reduction technologies allows in combination with smelting reduction processes or electric arc furnaces a substantial lowering of CO2 emissions.

Electric arc furnace

A simplified process flow diagram of Outotec's reduction and smelting method is shown in figure 1.

Based on a primary concentrate magnetite production rate of 2Mtpa an integrated reduction and pig iron smelting operation will produce 0.8-1Mtpa pig iron.

Figure 1. - Simplified process flowchart of Circofer pre-reduction and Circosmelt submerged arc smelting process considered as suitable for the Putú magnetite.