removal of harmful impurities

When they talk aboutremoval of harmful impurities, many immediately imagine laboratory conditions and ideal models. In reality, especially in the mining and processing sector, it is dirty, noisy and full of surprises. The main mistake is to think that it is enough to buy a powerful separator and the problem is solved. The reality is more complicated: the composition of the ore changes from batch to batch, humidity, temperature, even the size of the fraction - all this makes adjustments. Sometimes it seems that the technology has been worked out to the smallest detail, but with a new batch of raw materials the efficiency drops by half. This is where the real thing beginsremoval of harmful impurities- not according to a textbook, but by trial, observation and constant adjustment.

From theory to workshop: where the pitfalls lie

Take, for example, magnetic separation, one of our main methods. In theory, everything is clear: ferromagnetic particles are attracted, non-magnetic rock goes into the dump. But in practice... Let's say we work with iron ore. Seems to be standard material. However, if the content of clay particles is increased in it, they envelop the magnetite granules, creating a kind of “screen”. A separator configured for pure magnetite simply does not see these contaminated particles, and they go into concentrate. The harmful impurity here is not some foreign element, but the same useful mineral, but “disguised”. It is necessary to first introduce a disintegration or washing stage to destroy the clay aggregates. This is not always spelled out in standard diagrams, but without this step, further cleaning is pointless.

Another point is highly magnetic impurities in weakly magnetic or non-magnetic materials. For example, when enriching quartz sand for the glass industry. It would seem, why is there a magnet here? But if there are even microscopic iron particles in the sand from equipment wear, the finished glass will have defects. In such cases, we use high-gradient magnetic separators. But they are not a panacea either: if you don’t control the pulp feed rate, fine particles simply won’t have time to be “caught.” field and pass through. You have to constantly balance between productivity and degree of cleaning. Sometimes it is better to reduce the tonnage, but get a guaranteed clean product, than to chase the plan.

Our experience at sites using LONGI equipment shows the importance of this balance. Their separators, especially for wet concentration, give good control over the parameters. But the key word is control. The machine doesn't think for you. Adjustment of gaps, field intensity, drum angle - all this is done manually, based on a visual assessment of raw materials and trial runs. I remember an incident at one of the plants: after replacing the lining in the crusher, the content of the fine fraction in the ore sharply increased. The old separator setting stopped working and the concentrate was dirty. It took a month to select new modes at random. This was not a failure, but a normal work situation.

Chemistry versus mechanics: when one magnet is not enough

Magnetic methods are powerful, but not omnipotent. To delete certainharmful impurities, especially non-ferrous metals or non-metallic inclusions based on flotation, it is necessary to involve chemistry. And this is where the fun begins, and sometimes the nerve-wracking part. The selection of reagents is almost alchemy. The slightest deviation in the pH of the medium, water hardness, temperature - and the entire flotation chain collapses. The collector is not adsorbed on the required mineral, the foaming agent produces the wrong foam structure.

We had a project to purify kaolin from pyrite and titanium oxides. You can't use a magnet here. We started with classical cationic flotation. In the laboratory, on a clean sample, the results were brilliant. We transferred the technology to the workshop - the effect was almost zero. It turned out that in the circulating water of the enterprise there was a high background of organic substances (residues from previous processes), which “poisoned” action of reagents. We had to introduce an additional stage of water treatment, which immediately increased the cost of the process. The client was dissatisfied, but there was no alternative: either put up with the low quality of kaolin or invest in water purification. We chose the second one. This is about the issue of an integrated approach:removal of harmful impuritiesoften rests not on the main technology, but on auxiliary, “invisible” ones. stages.

Another aspect is environmental friendliness. Chemicals, especially collectors and depressants, can themselves become harmful contaminants in wastewater. Modern trends force us to look for more “green” ones. compositions or closed water cycles. It is difficult and expensive, but it is already becoming a competitive advantage. Companies that ignore this aspect risk facing serious limitations in the future.

Equipment as a living organism: the importance of maintenance and modernization

Any, even the most advanced technology, is embodied in “hardware”. And this is ?iron? wears out, gets clogged, requires attention. You can buy the best magnetic separator, but if you do not regularly clean the work areas of adhering sludge, its effectiveness will decrease with every hour of operation. This is especially trueremoval of harmful impuritiessmall classes. Particles literally clog cracks and grates.

At enterprises that use equipment similar to products from the site https://www.ljmagnet.ru, I often pay attention to this point. The design of many of their separators, by the way, provides for relatively easy access for cleaning and replacing wear elements - for example, matrices for high-gradient separators. This is not a small thing. This directly affects downtime and, as a consequence, the economics of the entire process. When equipment operates in three shifts, each unscheduled stop is a loss. Therefore, our recommendations always have a section on routine maintenance, which is not compiled for ideal conditions, but taking into account the actual dust and humidity of the workshop.

Modernization is a separate issue. Often old devices do not need to be completely replaced, but modified. Install more powerful magnetic field sources, replace the control system with a modern one that allows smooth adjustment of parameters in automatic mode. This is especially true for a company like LONGI Corporation, with its long history. Many of their customers work on equipment produced back in the 90s or 2000s. A complete replacement is a huge investment. A competent modernization of the existing line, with a focus on increasing efficiencyremoval of harmful impurities, can give 70-80% of the results of a new installation, but at 30-40% of the cost. We have implemented such projects several times.

Quality control: without feedback the process is blind

The biggest illusion is to think that you have set up a process and it will work forever. Control must be continuous, and at several stages. Incoming control of raw materials (at least visual and express analysis for moisture and granulometry), operational control of parameters (current strength on electromagnets, pulp pressure) and, of course, output control of the product.

Many people save money here, limiting themselves to morning and evening samples. What happens in the middle of a shift? The composition of the ore could have changed, it could have gotten worse. a brush that removes concentrate from the separator drum. As a result, the line produced defects for several hours. We insist on introducing at least the simplest online monitoring systems. Not necessarily expensive X-ray fluorescence analyzers. Sometimes magnetic flow susceptibility sensors or even conventional video cameras with image analysis are sufficient to assess the color and uniformity of the concentrate flow. This gives the operator a chance to react not after the fact, but in real time.

One of the most useful practices that we adopted from our colleagues is maintaining a “non-conformity log”. Not only the fact of the defect is recorded there, but also all the accompanying conditions: the batch number of raw materials, equipment settings, shift, even the weather (when working with open warehouses, humidity can vary greatly). Over time, this log becomes an invaluable source of data for analyzing and preventing problems. It helps to identify patterns that are not visible during a single examination.

The Economics of Cleanliness: What the Ideal Product Costs

In the end, anyremoval of harmful impuritiescomes down to money. The customer wants the purest possible product at the lowest price. Our task is to find the optimal point on this curve. Bringing purity to 99.9% instead of 99% may require doubling energy costs, reagent consumption, or reducing productivity significantly. Is it worth it? Depends on the market.

For high-tech industries - for example, for the production of ferrites or special ceramics - it may cost. There, the price of raw materials with a guaranteed low content of impurities is orders of magnitude higher. And for ordinary construction crushed stone or foundry sand, basic cleaning is sufficient. It is important to be honest with the client about these trade-offs. Sometimes it is more profitable to sell a product with a slightly higher tolerance for impurities, but cheaper and in larger volumes, than to try to enter the premium segment by investing in expensive equipment.

The experience of large manufacturers such as LONGI Corporation, which produces thousands of units per year, shows the importance of flexibility. There is no universal “boxed” product. cleaning technologies. Each project is an adaptation for a specific ore, specific conditions and a specific budget. The engineering idea is not to use a ready-made solution, but to create it from a set of available methods: magnetic, gravitational, flotation. And the main tool here is not a computer model, but experience, observation and readiness for the fact that today’s decision may require revision tomorrow. This, perhaps, is the essence of real work onremoval of harmful impurities- This is an ongoing process, not a one-time action.