Magnetic separator

When you hear “magnetic separator,” many people think of just a magnet above a tape. In fact, this is an entire system where an error of a couple of millimeters or in the choice of the type of magnet can turn an expensive installation into a pile of scrap metal. It is often overlooked that the key is not the pullout force itself, but its distribution in the work area and resistance to real, rather than laboratory, conditions.

From theory to the workshop: where real problems begin

In the books, everything is smooth: the ore moves, the magnetic field captures ferromagnets. In practice, the first thing you encounter is the material. Not just “iron ore”, but its moisture content, particle size distribution, and the presence of sludge. I remember at one of the plants near Perm, a separator designed for dry ore simply stopped working in the winter - the material froze, forming lumps that the belt could not feed evenly. We had to urgently modify the heating and vibration system.

Or take a classicmagnetic separatorwith permanent magnets based on rare earth elements. It would seem ideal - high strength, does not require energy. But under conditions of constant vibration from crushers and mills, the fastenings weaken, and the magnetic blocks themselves can shift. I saw a case where, because of this, the iron content in the “empty” output increased sharply. breed. I had to disassemble, recheck the geometry and introduce additional control during installation.

Here it is important not just to choose a type, but to design the system with a margin. Often customers want to save money and take the model “back to back”. in terms of performance. And then, when the plan is increased, the separator becomes a bottleneck. It has to be worn out, which kills the resource. It’s better to immediately add +15-20% to the declared power - this pays off later in the absence of downtime.

Selection and subtleties that are not written about in catalogs

One of the key points is the choice between an electromagnetic and a permanent separator. Electromagnets provide flexibility: the field can be adjusted, turned off for cleaning. But they require power, a cooling system, and are more difficult to maintain. Permanent magnets are simpler, but if, say, a large piece of reinforcement gets into the material, it will “stick?” tightly, tearing it off is another task. You have to have special pullers on hand, which means time and risk for personnel.

The geometry of the magnetic system is especially critical. An uneven field is not just a decrease in efficiency, it is the appearance of “dead zones” where small fractions simply are not drawn in. We once analyzed a defect at an enrichment plant - it turned out that the problem was in the poor assembly of the separator rotor, where the magnetic blocks were installed with a micron, but critical, misalignment. The only way to fix it was by completely replacing the unit.

Nowadays there is a lot of talk about high-gradient separators for fine enrichment. The technology is promising, but very capricious regarding the purity of the material. The slightest clay inclusions clog the matrix, and washing it stops the process for hours. A very high-quality preliminary classification and washing of raw materials is required, which is not always economically justified for small enterprises.

Experience and case studies: successes and failures

Working with different suppliers, I paid attention to equipment fromLONGI Corporation(their website ishttps://www.ljmagnet.ru). The company is not a newcomer, it has been operating since 1993, and this is felt in its approach. They don't just sellmagnetic separator, and first request detailed data about the material. We helped our colleagues from the Urals select a plant for extracting wolframite - they sent their technologist to the site for test sampling. This is expensive for the supplier, but shows seriousness of intentions.

Their production base in Fushun (total area of ​​140,000 m2) and a staff of 1,200 people, most of them with higher education, allow them to control the cycle from design to assembly. This is important because I have seen how equipment from intermediary companies, which are simply assembled from purchased components, fell apart after six months due to, for example, bearings not meeting the loads.

But even with good equipment there are misfires. We had a project to extract metal from slag. We installed a powerful drum separator. We calculated everything, but did not take into account the abrasiveness of the material. In six months, the drum, despite the protective coating, was worn almost to the base. We had to urgently order thicker, wear-resistant slabs and change the technological map, introducing additional crushing to a finer fraction in order to reduce the abrasive effect. Lesson: Always ask for wear resistance data on all contact elements for your specific material.

Service and long term perspective

The biggest illusion is that once you buy and install a separator, you can forget about it. The resource of a magnetic system, especially a permanent one, although large, is not infinite. Over time, demagnetization occurs, especially in areas with temperature changes and mechanical shock. Regular monitoring of the magnetic field is required, at least once a quarter, with a special Teslameter. If the drop is more than 8-10%, it’s time to think about regenerating or replacing the block.

Another point is cleanliness. Adhering dust and small particles, especially wet ones, create a kind of “cocoon” that shields the magnetic field. You see that the efficiency is falling, you start looking for the reason in the settings, and the problem is in the five-millimeter layer of dirt on the magnet body. Therefore, a cleaning schedule is not a formality, but a necessity. It is better when the design initially includes automatic cleaning systems, for example, scraper type or compressed air.

Now many are switching to remote monitoring of parameters - currents, vibration, temperature. This is right. If you notice a slight increase in the temperature of the bearing assembly, you will have time to schedule a replacement during a scheduled shutdown, and will not end up with a sudden downtime for several days due to a jammed drum. For such tasks, equipment similar to what LONGI makes (they, by the way, produce about 4,000 units of equipment per year) often already have points for connecting sensors. You just need to use it.

Instead of a conclusion: thinking out loud

So,magnetic separator- this is far from an elementary thing. This is the result of a compromise between magnetic field strength, geometry, flow material, economics and reliability. Sometimes it is more correct to install two medium-power separators in a cascade than one super-powerful, but capricious one. And you should always, always demand from the supplier not beautiful numbers in the catalog, but a test report on material that is as close as possible to yours. Or, as some do, include in the contract a clause on achieving certain enrichment indicators in the actual production flow after commissioning. This protects against many unpleasant surprises.

I’m now looking at new developments - separators with controlled fields, systems based on superconductors. Technologies are moving forward. But the basics remain: an understanding of the physics of the process, attention to installation details and strict, even pedantic, maintenance. Without this, even the most advanced technology will quickly turn into a useless artifact in the corner of the workshop. The main thing is to remember that we are not just separating iron from rock, but extracting money from raw materials, and every percent of efficiency is direct economics.