GX-3600: world's largest magnetic separator - up to 800 tph

MINING TECHNICAL COMMUNICATION

GX-3600: world's largest magnetic separator - up to 800 tph

José Pancrácio Ribeiro^I; Claudio Henrique T. Ribeiro^II

^IEngenheiro Eletricista - Diretor Presidente da Gaustec E-mail: [e-mail]

^IIEngenheiro Eletrônico, Diretor Técnico da Gaustec E-mail: [e-mail]

Introduction - Mega projects for iron ore production have made a comeback and now are a reality in the world-wide market. As a result of increasing world-wide demand, these projects tend to focalize on economically unattractive mines that were not exploited because of their low-grade ore content.

GAUSTEC, a Brazilian company that develops technology and manufactures equipment for high intensity magnetic separation, has introduced new concepts to face the challenge of dressing these lowgrade ores, which demand enormous production capacity. The result was the development of the High Intensity Magnetic Separator GX-3600, with such innovative characteristics as high feed rate and low water and electric energy consumption. Even though the new machine represents a technological breakthrough, the traditional WHIMS (Wet High Intensity Magnetic Separator) concepts of simple maintenance and operational robustness have not been abandoned.

The technology of the GX-3600 and its development - Answering market demand and based on its most successful product, the bipolar Model G-3600 of Figure 1, GAUSTEC designed the Tetrapolar model GX-3600 represented in Figure 2. The "X" represents the new X-like shape of the steel structure. From the time the new concepts were registered worldwide as "Patent Pending" in 2008, it took two and a half years to design, manufacture and market the new product.

In the new design, several issues had to be overcome and the first one was the magnetic circuit concept. The polarity of the coils shown in the bipolar model generates in the magnetic lines of force in the North and South poles, which flow as indicated in Figure 3. Because of the Tetrapolar design, the coils mounted in the poles had to be in an alternating sequence: North/South/North/South, in order to generate the magnetic lines of force whose flow paths are shown in the Figure 4.

This new configuration of alternated polarities creates an inversion region between the poles, where, starting from a maximum value in front of a pole, say North, the magnetic field vector which leaves the matrix plate orthogonally, decreases. After reaching a zero value, the magnetic field vector inverts and increases again towards the maximum value achieved when reaching the next pole of reverse polarity, say South. The region in the neighborhood of the zero magnetic fields, called Neutral Line, allows for the discharge of the magnetic product.

Considering that each magnetic pole corresponds to one feeding point, the Tetrapolar model doubles the number of poles of the Bipolar model, and as a result, also doubles the feeding points. Doubling the feeding points means doubling the feed rate. The industrial equipment has two rotors to maximize the use of the magnetic circuit that flows in a closed loop at the bottom of the machine.

Paying attention to the path of the magnetic lines of force in Figures 3 and 4, one can observe that the Bipolar magnetic flow is transversal to the rotor, whereas in the Tetrapolar model the flow is tangential, that is, the magnetic lines circulate in the periphery of the rotor, rather than transversal. This tangential behavior of the line flow allows for the construction of the rotor in a ring shape instead of the usual and heavy massive rotor.

The design of the Tetrapolar magnetic Separator was modeled by the Method of Finite Elements FEM. First of all, the modeling targeted to reach maximum magnetic field generation with minimum electrical energy consumption. The results indicate an increase of 6.25% for magnetic Induction in the Tetrapolar model in relation to the Bipolar one for the same consumed electric power.

The second target of the modeling was to define the ideal width of the ring shaped rotor to optimize the weight of the equipment without harming the first objective. The results indicated that the rotor reaches the best relation Weight versus Magnetic Saturation of the iron when the width of the ring is around 27.8 % its diameter (Figure 5).

Process control of the GX-3600 - From an operational point of view, besides the adjustment of the magnetic field, several parameters must be taken into account for the adjustment of the process such as:

1. Gap of the Magnetic Matrices (function of the grain size and of the magnetic characteristics of the mineral).

2. Speed of the rotor set from 3.0 to 7.0 RPM.

3. Feed rate in tons per hour.

4. Percentual of solids in the feeding.

5. Spray water to wash the middlings.

6. Spray water to wash the concentrates.

Main applications and feed rate of the new GX-3600

• Dressing plants for iron ore fines.

• Feeding of flotation plants.

• Closed loop grinding for liberation purposes.

• High Capacity Projects Demanding a Small Number of Machines

• Ideal for low grade iron ores projects, with low capex and low opex.

• Feed rate in function of the Gap (iron ore, to be confirmed by tests)

Gap 1,5 mm 2,5mm 3,8mm 5,0mm GX-3600 360 t/h 480 t/h 700t/h 800t/h

The new GX-3600 in the mining industry - Small types of the new Tetrapolar design have been manufactured, like the GX-2000 and the GX-340, but the first top size model GX-3600, rated for 700 t/h @ a 3.8 mm Gap, was installed and started-up in July 2010 at Itaminas Mineração, Brazil (Photo 1).

In the picture, is the GX-3600 installed at the above mentioned site, operating at a feed rate of 700 tons per hour for the concentration of iron ore fines. Over the machine can be depicted ancillary equipment and the two protection screens, # 2.5 mm mash, against oversized particles.

Publication Dates

• Publication in this collection
  15 Dec 2010
• Date of issue
  Dec 2010