ferrite korhan

I’ll say right away - when I hear “ferrite korhan”, the first thing that comes to mind is a bunch of requests from people who are just looking for a “strong magnet”, but in fact they have a specific thing in mind, namely ferrite permanent magnets based on strontium or barium, which in our mining industry are used for separators. Many, especially those who are just starting to purchase equipment, confuse them with rare earth - neodymium, thinking that the more expensive, the better for any task. This is wrong. For korkhan - the process of dry magnetic separation of ore - it is ferrite ones that often win based on a combination of factors: stability over a wide temperature range, resistance to demagnetization, and, critically, price. But there are nuances here that are rarely written about in catalogs.

Why is ferrite often chosen for korhan rather than neodymium?

Worked with installations at processing plants in Kuzbass. There, the temperature in the workshop in the summer could rise to 40°C, plus vibration from the crushers. Neodymium assemblies in some areas began to “crumble”—losing the field within six months. We switched to ferrite systems from one trusted supplier. Yes, the induction on the surface is less, we had to slightly recalculate the design of the separator, increase the gaps, but two years of operation without noticeable degradation. The key is the correct choice of ferrite grade. Not all Y30BHs are created equal for impact loads.

One of the common mistakes is saving on the magnetic system at the expense of the housing design. I saw how a small factory purchased good ferrite plates, but assembled them in a steel casing without proper protection from vibration and dust. The magnets are intact, but the separation “floated” due to microdisplacements. I had to disassemble it and install damping pads. Soferrite korhan- it is always a system, and not just a set of magnetic elements.

Another point is geometry. For dry separation of bulk ores, you often need not just slabs, but wedges and segments of complex shapes to create the desired field configuration. Making such elements from ferrite is a separate art. Mold, field orientation during magnetization... I rememberLONGI Corporation (https://www.ljmagnet.ru) the catalog contained interesting standard solutions for drum separators specifically for ferrite. By the way, they have been in the business since 1993, and their plant in Fushun focuses on mining equipment. They don’t just have magnets for sale, but often have ready-made engineering calculations for the task.

Practical rake: what to look for when accepting and using it

We brought a batch of ferrite blocks to repair the separator. Everything in the passport is beautiful: residual induction Br, coercive force Hcb. The first thing you check is not this, but the geometry and chips. Once I came across a batch where 15% of the blocks had microcracks at the ends. It seems that there is nothing wrong with it, but in a high-gradient field such blocks become a point of concentration of mechanical stress and can crack during vibration. They took a magnifying glass and rejected it.

The second is fastening. Ferrite is a brittle material. Fastening with epoxy is standard, but for difficult conditions you need a combined method: glue plus a mechanical lock. Sometimes in the field we made a strapping of stainless tape over the assembled battery. It helped.

Third, and most important, is demagnetization. Ferrite korhan is good because its demagnetization curve is almost linear, and it works well at the point of maximum magnetic energy. But if it is overheated (above Curie, this is about 450°C for strontium) or exposed to strong external alternating fields, irreversible losses can occur. There was an incident in the drying area: the separator was placed too close to the heat gun. The temperature of the magnet itself reached 150-170°C. Over six months, capacity fell by 20%. We had to reconsider the entire line layout.

Connection with equipment: why the hardware and the magnetic system are one whole

Often a customer comes with a request: 'Give me a magnet for the korhan.' What kind of korhan? Drum? Roller? Tape? Each has its own configuration. For example, for external field drum separators, multi-pole systems of ferrite segments arranged in a specific pattern inside the drum are often used. Assembly accuracy is critical here. A segment shift of a couple of millimeters can create a 'dead zone' in the separation zone, and the small class will go to the tails.

The LONGI Corporation, judging by their materials, understands this. On their website you can see that they produce not just magnets, but entire units and even finished equipment. For an enterprise that employs more than 1,200 people and produces about 4,000 pieces of equipment per year, it is logical to control the entire cycle, from magnetic ceramics to separator assembly. This gives stability of quality. In our business this is worth a lot.

When designing a new separator, they now often go by computer simulation of the magnetic field (for example, in FEMM or Ansys). But I will tell any practicing engineer: not a single model can replace experimental testing on real material. We somehow modeled an ideal system for extracting magnetite from dumps and assembled a prototype. But in practice, it turned out that the moisture content of the material is only 2% higher than the calculated one radically changes the picture - the particles begin to stick together, and separation becomes worse. I had to adjust the drum speed and clearance on the fly. Soferrite korhanis always a dialogue between theory, passport data and real conditions on the site.

Economics of the issue: when is ferrite more profitable and why not always

It is believed that ferrite is cheap. This is true only at the stage of purchasing the magnetic material itself. If we consider the cost of the entire system, taking into account the casing, cooling system (if needed), precision mechanics and installation, then the difference with a neodymium system can be reduced. But for most korhan applications, especially large volumes of rock being processed where large separators are needed, ferrite remains king.

There is also such a factor as maintainability. Replacing a cracked ferrite block in the field is easier and cheaper than resoldering an assembly of rare earth magnets, which also requires special safety measures due to the enormous force of attraction.

But I am categorically against dogma. For fine separation, for the extraction of weakly magnetic minerals, where fields of high intensity and gradient are needed, ferrite may not be suitable. Here we need either neodymium systems or electromagnets. I have seen successful hybrid solutions where the main field creates ferrite, and a small neodymium insert is used to create a sharp zone with a high gradient. This is already aerobatics, and only a few do such things, the same large players like LONGI, who have both a scientific base and production capacity for experiments.

A look into the future: what is changing in korhan technology

The trend now is to increase efficiency and selectivity. Simply 'taking out everything magnetic' is not enough. It is necessary to separate, for example, magnetite from hematite or pyrrhotite. This requires more complex field configurations, which can be achieved by combining different grades and shapes of ferrites, as well as using mild magnetic steel shields.

Another point is that the quality control of magnetic material has become stricter. It used to happen that there were noticeable fluctuations in parameters from batch to batch. Now good manufacturers provide stability. This is important because during mass assembly of the separator, the variation in the characteristics of individual blocks can lead to uneven field along the entire working length.

And of course, automation. Modern separators are no longer just a 'drum with a magnet inside'. These are systems with sensors that can monitor separation parameters in real time and, theoretically, even adjust the position of the magnetic system or the rotation speed. For such technology, the reliability of the magnetic assembly is the basis. And here is time-testedferrite korhan, for all its 'old-fashioned' properties, turns out to be a very modern solution. The main thing is to use it wisely, with an understanding of the physics of the process and taking into account all, even the most unobvious, conditions at a particular object. As they say, there are no bad materials, only improper use.