Ferroalloy Slag Processing
GRAVICON supplies modular beneficiation complexes for processing ferroalloy slag dumps with feed capacities of 20–400 t/h. The technology is designed for initial feed sizes of up to 300 mm, with beneficiation performed in the 0–40 mm size range. Typical operational parameters include a workforce of 3–5 operators per shift, average energy consumption of 1.5 kWh per ton of feed, and a required processing area of 300–600 m². Manufacturing, installation, and commissioning are completed within 6–8 months. The first industrial implementation of this technology dates back to 2001 at Kazchrome, Aktobe Ferroalloy Plant, and to date seven industrial installations have been commissioned in Kazakhstan and Ukraine, processing ferrochrome slags (Kazakhstan) and ferromanganese slags (Ukraine).
Magnetic separation is traditionally applied to ferroalloy slags due to the absence of circulating water requirements; however, its main limitation is low recovery efficiency. Magnetic properties of slag particles are initially weak and degrade further during long-term storage (10–30 years), resulting in 30–40% of valuable ferroalloy components remaining in tailings. Combined pneumatic and magnetic separation can partially improve performance but is critically constrained by feed and ambient moisture levels (≤5%); precipitation or elevated material moisture reduces separation efficiency to zero, while drying slag prior to processing is economically unjustifiable. Under these conditions, hydraulic jigging enables near-complete recovery of ferroalloy components with substantially lower specific energy consumption per ton of feed. European operating experience confirms that slag dumps previously processed by magnetic separation—particularly at post-CMEA ferroalloy plants—can be reprocessed with high economic efficiency using GRAVICON jigging-based solutions.
Lead-Containing Slag Processing
GRAVICON supplies integrated beneficiation solutions for processing lead-containing slags with feed capacities ranging from 15 to 50 t/h. For projects requiring higher throughput, capacity scaling is achieved either by parallel installation of multiple processing lines or by designing specialized equipment with the required performance. Despite the significant density contrast between valuable components and tailings, lead slags are classified as difficult-to-beneficiate materials, not only in terms of separation but even at the stage of material handling and feeding. Conventional loading and beneficiation methods commonly applied to metallurgical dumps, ferroalloy slags, or coal waste dumps are ineffective in this case: the material does not pass through grizzlies even under vibration and cannot be processed in standard serial equipment.
When exposed to moisture (rain or snow), the material exhibits extreme viscosity and cohesion, retaining its shape under substantial mechanical loads. In practice, a sample extracted from a pipeline can be rolled across a concrete surface without disintegration, fully preserving its form. At the same time, no clay or similar binding components are present. Stockpiles remain vertically stable even at heights of 6–7 meters when handled by front loaders, confirming the exceptionally high interparticle adhesion. Under such conditions, pneumatic separation methods are fundamentally inapplicable, and only immersion of the feed in water allows any realistic possibility of achieving the required concentrate quality. The feed is further contaminated by glassy waste fractions with densities of 3.5–4.0 g/cm³, which narrows the separation boundary between concentrate and tailings and significantly complicates the beneficiation process.
For a project with a specified throughput of 30 t/h and strict concentrate quality requirements, GRAVICON implemented a multi-stage beneficiation scheme involving extensive redesign of standard jigging machines. Modifications included both reconfiguration of jig compartments and a fundamental redesign of the discharge module, enabling stable processing across the entire particle size range of 0–60 mm. The introduction of an artificial bed for fine-size fractions allowed recovery efficiency to reach 98.5%, demonstrating that, despite extreme material handling challenges, high-grade concentrates and industrially viable performance can be achieved through targeted engineering adaptation and process customization.
Slimes and Fine Fraction Beneficiation
Processing of fine fractions, and especially coarse-grained slimes in the 0.2–3 mm size range, represents a distinct beneficiation task. For material finer than 0.2 mm, flotation remains virtually the only effective solution. In the 0.2–3 mm range, spiral (helical) separators are often applied due to their structural simplicity. However, separation efficiency in spiral separators is largely predetermined by geometry and construction material, leaving limited control over the process. When properly designed for a specific feed, acceptable results can be achieved; however, even minor changes in feed characteristics often lead to significant deterioration in separation quality. In addition, high-performance spiral separators supplied by reputable manufacturers cannot be classified as cost-effective solutions, neither in terms of capital expenditure nor operating costs.As an alternative, GRAVICON developed jigging machines for coarse slime beneficiation, specifically the GRAVICOM-30Sh and GRAVICOM-70Sh, with feed capacities of 30 t/h and 70 t/h, respectively. Unlike spiral separators, jigging machines provide operators with a broad range of adjustable process parameters that directly affect separation performance, including pulsation frequency, pulsation amplitude, duty cycle, bed height, degree of bed loosening (air supply), transport water flow, and heavy fraction discharge rate. A key element of slime jigging machines is the artificial bed, which enables stable beneficiation of material down to 200 μm while ensuring high separation precision. In addition, jigging machines offer superior versatility: while spiral separators are limited to fine fractions and a narrow range of materials, GRAVICON slime jigs can be reconfigured within hours to process material sizes up to 0–100 mm, and control system retuning allows treatment of a wide spectrum of feed types, from coal to ores and slag dumps. Industrial operation of the OMSh-5 prototype at the Donetsk Central Preparation Plant confirmed this approach, and modernized designs with improved pneumatic drives and control systems demonstrated high efficiency on coking coal slimes, reducing ash content from 40–45% in the feed to below 10% in the concentrate, while the –0.2 mm fraction, having ash content close to that of the parent rock, could be removed from the circuit without loss of concentrate yield.