Arrium plans to mine its ore tailings

The CDE Mining division of United Kingdom-based CDE Global has announced a new project with Australia-based Arrium Mining to process and convert nearly 17 million short tons of low-grade iron ore fines currently stockpiled as tailings in waste dumps into a saleable product.

The investment involves the provision of two new processing plants in Australia, says CDE. The first new plant will be at Arrium Mining’s Iron Knob location, processing stockpiles of low-grade iron ore that have accumulated over the life of the mining of the Iron Monarch and Iron Princess deposits. Mining at Iron Monarch first began in 1899.

Following the Iron Monarch and Iron Princess project, the same processing plant will target the processing of local fallen rock deposits.

The second plant will be installed at the Iron Baron location, and then at the Iron Knob location, and will process low-grade iron ore stockpiled over the history of mining since 1930. It will then progress into the Iron Empress and Iron Baroness fallen rock deposits in this region.

The upgrading of the iron content from the low-grade material will be achieved by removing silica and alumina from the feed material. Silica levels in the feed material range from 14% to 20%, which is expected to be reduced to 6.4% after processing. Alumina levels range from 5.9% to 8.8% in the feed material and will be reduced to 2.8% after processing. The plant will also remove clays from the feed material and the combined effect will see the iron content increase from between 43.4% and 52.7% in the feed to nominally a 60% iron ore product, says CDE.

“There are several attrition stages built into the plants to ensure we are able to remove the silica, alumina and clay contamination effectively and deliver a final product to the specification required by Arrium Mining,” says Chris McKeown, a technical manager with CDE Mining. “A large part of this work is done by our AggMax modular log washer.”

The modular nature of the plant offered by CDE was a factor in its winning winning bid to equip the project, says Gavin Hobart, general manager of development with Arrium Mining. “We visited several CDE projects in Australia, Norway, the U.K. and Brazil and observed how the AggMax had been applied successfully on similar projects. This gave us confidence that it provided an innovative way to tackle clay-bound materials. We were also impressed by the fact that the time required for installation and commissioning of the plant is reduced as a result of the integration of several processing phases onto one machine.”

The processing plant includes a range of CDE Mining equipment, including an M-Series modular washing plant, AggMax modular log washer, EvoWash fine washing plant, spirals, jigs, ShearClean attrition cells, transfer conveyors and radial stockpile conveyors. The plant also includes a tailings management system that allows for the concentration of the 0-to-3-millimetre rejects into a sludge that is then pumped to the tailings dams. This tailings management system also facilitates the recycling of up to 90% of process water.

“The provision of a tried and tested tailings management system was a critical element of this project,” says Hobart. “It is essential that we are able to recycle and reuse large volumes of process water as access to fresh supplies are limited.”

According to CDE, the project represents a new approach to mining projects like this. “The modular nature of our equipment has a number of benefits,” remarks McKeown. “The time required for installation and commissioning is reduced, transfer point efficiency is improved and the overall environmental impact of the project is reduced. The plant can also be accommodated in much less space than is the case when the stick build approach is used.”

In addition to the processing plant the contract with CDE Mining also includes a preventive maintenance programme delivered by CDE CustomCare, designed to ensure the availability of spare parts on site and to provide for plant audits by CDE service engineers to ensure performance requirements are maintained.

The first plant at the Iron Monarch deposit will have an annual processing capacity of 1.8 million short tons. The feed rate for the plant is 250 short tons per hour and it will run for 24 hours each day, 365 days per year, says CDE. The second plant will be integrated into the front end of an existing gravity separation circuit and will be fed at a rate of 700 short tons per hour for an annual processing capacity of 6.1 million short tons.