Removing Impurities

When they talk aboutremoval of impurities, many immediately imagine a sieve or magnet. But this is just the tip of the iceberg. In reality, it is a constant trade-off between efficiency and product loss, especially in the mining industry. A common mistake is to strive for absolute cleanliness, without taking into account how much useful stuff goes into the dump along with the garbage. I encountered this myself in the early stages.

Magnetic method: not everything is so simple

Let's take magnetic separation, for example. It would seem like a classic. But the field strength, gradient, material humidity - the slightest nuance changes the picture. I remember at one of the old mining and processing plants they tried to increase the extraction of iron ore by simply strengthening the magnets on the drum separator. Result? The final concentrate is cleaner, yes. But along with the highly magnetic ore, the device began to capture medium-magnetic waste rock minerals. The yield of concentrate fell, the cost increased. I had to go back and find a compromise.

What is important here is equipment where these nuances are taken into account constructively. If we talk about serious manufacturers, then, for example, the LONGI corporation (website:https://www.ljmagnet.ru) with its experience since 1993 offers separators where you can finely regulate not only the power, but also the configuration of the magnetic system. This is not an advertisement, but a statement: their developments in the field of mining equipment are often based on a deep understanding of the physics of the processremoving impurities, and not on a simple increase in the dimensions of the magnet.

By the way, about humidity. A dry magnetic separator and a wet one are, in fact, two different worlds. For thin slurries where particles clump together, the dry method may be virtually useless. You have to either dry it (expensive) or switch to wet separation with all that it entails - dehydration systems, water circulation. This is a whole technological change, and not just a replacement of the device.

Gravity methods: old school with new problems

Jigging, concentration tables. It seems like technology from the century before last. But where you need gentleremoval of impuritiesmade from fragile or valuable materials, they are unrivaled. No magnet can distinguish diamond from quartz by density. But there are also “buts” here.

The main headache is nutritional stability. The supply of pulp should be like a Swiss watch: in density, size, and volume. The slightest failure - and instead of clear stripes of concentrates, a mess forms on the table. Personnel capable of ?feeling? table and adjusting it to the sound and appearance of the flow is worth its weight in gold. Automation is difficult and expensive.

I saw attempts to fully automate a depositor with a bunch of sensors and servos on the sieve. It worked in ideal laboratory conditions. At the factory, with natural fluctuations in power supply, the system simply did not have time to adapt, it constantly “twitched”. As a result, the project was curtailed and we returned to an experienced operator with manual adjustment of the water-air mode. Sometimes old methods survive not because of backwardness, but because of their flexibility to “imperfection?” real raw materials.

Flotation: where chemistry is more important than mechanics

That's whereremoval of impuritiesturns into art. You can have the most modern flotation machine, but without a properly selected collector, foaming agent, and depressor, the result will be zero. And the selection of reagents is often not science, but semi-empirics, highly dependent on the deposit.

There was an incident during the enrichment of polymetallic ores. The standard scheme did not provide the required selectivity: copper was poorly separated from pyrite. We tried a bunch of commercial collectors. What helped, oddly enough, was returning to an old, almost forgotten reagent in combination with precise control of the pH of the environment. But this took months of testing. And this is key: success depends on laboratory and pilot-industrial testing on a specific material. No catalogs or general recommendations can replace this stage.

Another subtle point is the dispersion of grinding. I over-grinded it and got sludge that does not float, but goes into the tailings. Nedomolol - large grains of a valuable mineral will not have time to “stick” to the bubble. We need to look for that “golden mean?” according to granulometry, and it is different for each ore.

Optical and X-ray radiometric separation: a future with reservations

Nowadays there is a lot of talk about smartremoval of impuritiesbased on sensors and rapid removal of rock with an air jet. Technologies are certainly progressive. But their scope of application is still limited. They are effective on large grades, from +10 mm, and for ores where there is a clear difference in color, luminescence or atomic density.

We tried to implement such sorting for the preliminary dumping of waste rock before the crusher. The savings on grinding energy must have been enormous. But we were faced with the fact that the ore was highly clayized. The sensors simply didn’t see? the true surface of the stone under a layer of clay. I had to install a pre-wash, which negated some of the savings. The equipment is expensive, and its payback is only possible if the quality of the input raw materials is stable. For many domestic deposits with their complex and variable material, this is still a serious obstacle.

However, such technologies are the future, especially when combined with artificial intelligence for texture analysis. But this will be an evolution, not an instant revolution in all factories.

Process integration: the main challenge

The most difficult thing is not to choose a method, but to combine them correctly. No single method will give the perfect result alone. Classic scheme: crushing – screening – magnetic separation – flotation. But the sequence may change.

Sometimes it is more effective toremoval of impuritiescoarse rock at an early stage (for example, by the same radiometric sorting), so as not to crush and grind useless material. And sometimes, on the contrary, it is necessary to grind until the aggregates open, so that later a magnet or flotation can separate the pure minerals. This decision is made on the basis of mineralogical analysis and technological tests.

Here, the experience of engineering companies that see the entire cycle is invaluable. A company that not only sells a separator, but is able to design or modernize the chain, like the same LONGI corporation with its wide portfolio of mining equipment and its own design bureau, has a clear advantage. Their Fushun plant, with an area of ​​140,000 m2 and more than 1,200 employees, most of whom are engineers, is designed specifically for complete solutions. It is important that the supplier understands how his device will fit into the overall scheme, and not just sell the product.

As a result,removal of impuritiesis always a search for balance. A balance between purity and recovery, between cost and efficiency, between new technologies and proven reliability. There is no universal recipe. There is a deep study of raw materials, honest tests and a willingness to accept that a theoretically beautiful scheme may stumble over banal clay or unstable power supply. And this is what makes the work so challenging and interesting.