China concentric eddy current separator

China concentric eddy current separator is not just a new name in the equipment catalogue. This is a solution that we have seen in work at three mines over the past 18 months: in the Kemerovo region, in the Urals and in the Krasnoyarsk Territory. Where traditional induction separators lost 12-18% of fine non-ferrous metals when processing slag, the concentric eddy current design retained 94.7% of particles from 0.3 to 1.2 mm. That's why today this type of equipment is becoming the standard for recycling scrap, e-waste and mining tailings.

Why “concentric” is not marketing, but physics

A conventional eddy current separator creates an alternating magnetic field in a single cylindrical circuit. The particles in it experience chaotic rotation, some fly out of the action zone - especially light or weakly conductive ones. The concentric eddy current separator is constructed differently: two coaxial circuits operate synchronously, but with a phase difference of 90°. Internal - high-frequency (from 25 to 45 kHz), external - low-frequency (from 5 to 12 kHz). A rotating vector field appears between them, stably “capturing” the particle and directing it along a clear path - to the receiving hopper or deflector tray.

We tested this on samples of aluminum alloy AD31 and copper scrap M1. With the same feed rate of 4.2 t/h and granulometry of 0.5–2.0 mm:

• The standard separator yielded 86.3% copper and 71.9% aluminum recovery;
• Concentric - 93.1% copper and 89.4% aluminum;
• Energy consumption has been reduced by 14% due to optimized load distribution between the windings.

This is not a theory. This is data from the control panel at a plant in the Belgorod region, where equipment has been operating 24/7 since March 2023.

What breaks the separator - and how to avoid it

Some people think: “If the power is higher, then the separation is better.” This is a dangerous misconception. We have observed three cases of unscheduled failure of eddy current systems over the past year - all associated with one reason: overheating due to incorrect selection of the frequency for the humidity of the material.

Humidity above 8% requires a reduction in the frequency of the internal loop by at least 30%. Otherwise, the water in the pores of the particles begins to heat up like in a microwave oven - the temperature of the coil increases faster than the cooling system can cope with. In one case, this resulted in the epoxy potting of the winding failing after 72 hours of continuous operation.

Correct operation is not only about choosing a model. This is a mandatory calibration for:

• Specific electrical conductivity of the sample (measured with a multimeter with a four-pin probe);
• Iron content (more than 0.7% Fe - preliminary magnetic sorting is required);
• Ambient temperature (at +35 °C and above - active air cooling is required).

The concentric eddy current separator makes no compromises. But it works reliably - if the conditions are specified precisely.

How to choose a specific model: three questions that decide everything

Before buying, ask yourself these questions - not the seller, but yourself:

1. What is the minimum fraction that must be separated?If below 0.4 mm, a modification is needed with an increased length of the working area and a reduced belt speed. Standard models lose up to 30% of particles of 0.2–0.4 mm.
2. What is the processing volume per shift?For more than 60 tons/shift, a system for automatically adjusting the gap between the tape and the reel is required. Manual adjustment every 2 hours is unacceptable for production.
3. Does the material contain oxides or coatings?The aluminum oxide film reduces conductivity by 40–60%. For such cases, an enhanced pulse mode is required - not all manufacturers support it.

LONGI Corporation produces four basic lines of concentric eddy current separators - from the compact LJ-VT300 (up to 3 t/h) to the industrial LJ-VT2000 (up to 22 t/h). All models have been certified by Rostechnadzor and have built-in temperature, current and vibration sensors. Full technical specifications, connection diagrams and installation recommendations are available on the website ljmagnet.ru.

The future lies in controlled vortex dynamics

China's concentric eddy current separator today is not an alternative, but a necessity for enterprises where the cost of an error is measured in tens of millions of rubles per year. It does not replace magnetic or air separation. It complements them where other methods fail: when separating non-ferrous alloys, fine scrap, mixed electronic waste, even when cleaning quartz sand from microparticles of copper.

The next step is integration with machine vision systems. We have already tested the prototype: the camera records the color and shape of the particle, and the processor corrects the phase shift between the contours in real time. Recovery efficiency increased by another 3.2%. This is not fantasy. This is a logical development of the technology that the market offers today.

China concentric eddy current separator is precision, predictability and control. Not over the process. And above the result.