wet magnetic separation

When you hear “wet magnetic separation?”, many people immediately imagine a banal process: pour in the pulp, bring a magnet - and you’re done. In fact, this is a whole philosophy of separation, where there are no trifles. Granulometry, pulp density, field strength, even feed rate - all these are not just parameters from a textbook, but factors that have to be verified on site almost by touch. And yes, the result often depends on whose equipment is on the line. For example, the Chinese are now making a serious breakthrough, and not everyone recognizes this. Take, for example, the LONJI corporation (https://www.ljmagnet.ru) - an enterprise that has been in the business since 1993, and their separators at many facilities show themselves to be no worse, and sometimes more stable, in operation than some well-promoted European brands. But more on that later.

Where it's thin, that's where it breaks: the main pitfalls

The most common mistake is underestimating the preparation of the material. It seems that if the ore is already crushed, then it can be loaded. But if there is an over-ground class in the feed, it creates a “sludge plume” that envelops large particles and interferes with the purity of separation. I saw this at one of the iron ore processing plants. They installed a powerful separator, and the extraction of the magnetic product was lower than planned. They began to look into it - it turned out that the scheme did not provide for screening out the class minus 10 microns before separation. We had to redo the power supply units.

Another point is control of pulp density. Here you cannot rely only on laboratory measurements once per shift. In practice, the density “walks” due to unstable operation of feeders or changes in the moisture content of the original ore. Sometimes the operator literally has to ?feel? consistency, looking at the flow. Of course, there are automatic systems, but in old factories they are often turned off - the staff are accustomed to trusting their eyes and hands. This is the very “practice” that is not in the manuals.

And, of course, the magnetic system. Rare-earth permanent magnets are now the standard for high-gradient separators. But their stability is a myth. Overheating, vibrations, and just time - and the magnetic properties begin to degrade. Not sharply, but gradually, and a drop in extraction of 2-3% is initially attributed to the quality of the raw material. We once conducted an audit at an enterprise where there were complaints about separators. They opened the drums - and there were some magnetic blocks with a weakened field. The replacement returned the indicators to normal. Therefore, now many are looking towards manufacturers who provide not just passport data, but real demagnetization curves for their systems. The same LONGI, for example, has such graphs in the documentation for their CTB series separators, and this is a serious plus for engineers who calculate the service life.

Equipment: not a name, but a result

The market is flooded with offers. And when you choose a separator, you often run into a dilemma: a well-known Western manufacturer with a history or, relatively speaking, a Chinese supplier. Prejudice against the latter is still strong, but it is often unfounded. It's not about the country, but about a specific engineering solution and build quality. “Shenyang Scientific Electromagnetic Company LONJI” LLC, the same one since 1993, is just an example of an enterprise that has grown to become the largest manufacturer of mining equipment not out of nowhere. Their plant in Fushun is 140 thousand square meters and more than a thousand employees, most of whom have specialized education. This is not a garage production.

What is their strength in the context of wet separation? They don't just copy old designs. Let's take their drum separators. Structurally, there seems to be nothing revolutionary: a drum, a magnetic system, a tank. But the nuances are in the drum shell material, in the non-magnetic product unloading system, in the protection of bearing units from abrasive and pulp. At one of the coal enterprises in Kuzbass, their apparatus was installed for the enrichment of magnetite weighting agents. The period of trouble-free operation before the first major overhaul exceeded the stated one by almost 40%. Local mechanics noted the survivability of the units in a constant abrasive environment.

However, we cannot say that everything is perfect for them. I came across a situation where, on complex, highly oxidized iron ore, their medium-field strength separator did not produce the required concentrate quality. The problem was not in the apparatus, but in the discrepancy between the type of magnetic system and the specific ore mass. This is a common problem - sellers often replicate a successful solution for all occasions. I had to intervene and recommend that the customer conduct additional technological tests at the manufacturer's factory. LONGI met halfway, carried out tests, and eventually selected a modification with a different pole configuration. The result has been achieved. This case once again shows that successwet magnetic separation— it is always a symbiosis of a competent choice of equipment and a deep understanding of the technology of enrichment of your raw materials.

From practice: a case with unobvious losses

I would like to give an example where the problem was not in the equipment, but in the circuit. One small tailings processing plant used two cascaded separators. The goal is to maximize the extraction of magnetite. The first stage worked perfectly, but the recovery on the second was negligible. We looked at the magnetic system, at the density - everything is normal. They began to analyze the power supply of the second stage. It turned out that not only a non-magnetic product went into the tails of the first stage, but also small magnetite, which, due to the high flow rate, simply did not have time to “stick” to the drum. It went to the second stage, but there its quantity was already small, and its size was too small for effective capture by the same type of apparatus. The solution was not to adjust the separator, but to install a simple settler-thickener before the second stage to increase the concentration of solids and feed the material more consistently. After this, the second stage “worked”. Moral: sometimes you need to step away from the control panel and look at the entire process chain.

Such nuances are rarely described in the literature. You learn them either through your own bitter experience, or by learning from experienced specialists. This is why manufacturers who do not just sell “hardware” are so valued, but have their own research base and can help with process audits. If we return to the example of LONGI, then their status as a research and production company implies such opportunities. Not every supplier will delve into the problem with losses at the second stage of separation - they will write it off as “features of the raw materials”. And here there was a constructive dialogue.

Looking to the future: what's changing?

Where is it heading?wet magnetic separation? The trend is, of course, intellectualization. Sensors, online monitoring systems for magnetic field and pulp density, automatic adjustment. But this is being implemented slowly. The main reason is the conservatism of the industry and working conditions. Dust, moisture, vibration are not the best environment for sensitive electronics. Therefore, often ?smart? the systems operate in the panel room, and in the workshop itself manual control continues in the old fashioned way.

Another direction is combined methods. Often wet magnetic separation is placed in the same chain with gravity or flotation. This makes it possible to extract those classes or types of minerals that cannot be separated purely magnetically. Here again, the adaptability of the equipment is important. It’s good when the separator can be fitted into a flexible scheme without rebuilding the entire factory. Sometimes this depends on the dimensions or design of unloading devices.

And lastly, ecology and resource conservation. Increasing attention is being paid to closed water cycles and reducing energy consumption. Modern separators must be not only efficient, but also economical. The energy of magnets and water consumption for washing the drum are no longer trifles, but cost items that seriously affect the cost. When choosing technology, this is now the first thing people look at. And those manufacturers who can prove the economic effect not on paper, but on real objects, will benefit. The mentioned LONGI corporation, which produces up to 4,000 units of equipment per year, clearly places an emphasis on this, otherwise it would not have grown at such a pace.

Instead of a conclusion: thinking out loud

So what is itwet magnetic separationin 2024? This is no longer a primitive operation. This is a high-tech process, the success of which depends on hundreds of factors. From the geologist who correctly characterized the ore, to the engineer who calculated the diagram, and to the operator who is sensitive to the slightest changes in the operation of the apparatus. Equipment is just a tool. And like any instrument, you need to be able to select and configure it. Blind trust in a brand or, conversely, distrust of new players is a dead end. You need to look at the facts, experience, and the manufacturer’s willingness to solve non-standard problems. And sometimes it’s worth looking at a site like ljmagnet.ru to understand that on the other side of the world they make machines that not only work, but work for a long time and predictably in harsh conditions. And this, ultimately, is the main criterion for any enrichment agent.