YPT Agglomeration Drums

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Uniform Agglomerates — Consistent Leaching

YPT Agglomeration Drums

An agglomeration drum is a large, rotating cylindrical vessel, typically mounted on a slight incline, in which crushed ore — especially fines-rich or clay-bearing material — is tumbled together with a liquid (water or leach solution) and a binder (such as cement, lime or polymer) so that the fine particles adhere and grow into larger, more robust aggregates (agglomerates).
These agglomerates are then discharged and stacked onto a heap-leach pad or otherwise processed.
The purpose is to transform a problematic fines-rich material into more permeable, uniformly sized, stable granules that will perform better in downstream processes.
In the context of heap leaching, the agglomeration drum operates as an ore-conditioning unit between crushing/screening and stacking.
By converting loosely packed fines into stronger, coarser granules, it improves solution flow, reduces channeling or ponding, and enhances recovery efficiency.

Areas of Application

The key application area of agglomeration drums is in heap leach operations of precious and base metals — for example gold, silver, copper, uranium — especially when the feed material has a high fines content or contains clay minerals that hamper permeability.
When the amount of material finer than –74 µm (200 #) exceeds about 5 % of the feed, then agglomeration is often necessary and when the fines fraction exceeds 10-15 % a binder will almost certainly be required.
Beyond mining, the principle of agglomeration drums is also used in other industries (chemicals, fertilizers, waste‐processing) to convert powders or fines into flowable, handled granules, but in mineral processing the focus is on ore conditioning for heap leach or pre-stacking.

Principle of Operation

The process inside an agglomeration drum can be described step-by-step as follows:

  • Feed introduction:

    Crushed ore (commonly with a size distribution such as < 25 mm or a specific fines fraction) is fed into the high end (inlet) of the drum.

  • Binder and liquid addition:

    Inside the drum, a spray system introduces water (or sometimes dilute leach solution) and a binder (cement, lime, organic polymer) onto the tumbling ore bed. The binder causes the fines to become tacky.

  • Tumbling and growth:

    As the drum rotates, the material cascades and rolls; the tacky fines pick up other particles, gradually forming larger agglomerates — a process often likened to “rolling a snowball.” The internal mix of tumbling, collisions, and binder-liquid bridges causes growth and densification of the granules.

  • Residence and discharge:

    The drum is slightly inclined so gravity moves the material from feed end to discharge end, controlling residence time. Once the target granule size and strength are achieved, the material discharges. If undersized or oversize particles remain, some systems incorporate a trommel or screen to recycle these back into the drum.

  • Stacking and leaching:

    The agglomerated product is then conveyed or stacked on the heap leach pad. Because the granules are more uniform, stronger and more permeable, the leach solution flows more evenly, reducing fines‐clogging, channeling, and ponding. This leads to better metal recovery, shorter leach cycles, and improved heap stability.

From a design viewpoint, key physical principles include the interaction of tumbling motion (drum speed, diameter, lift flights), residence time (controlled by inclination and speed), binder and liquid dosage (to achieve sufficient strength and porosity), and discharge size/strength. Studies show that agglomerated heaps often achieve significantly higher recoveries versus non-agglomerated ones under comparable conditions (especially for fines/clay rich feeds)

Stronger Pellets. Better Percolation

YPT Apron Feeder Highlights

Where Fine Particles Become Process-Ready

Design Criteria

When designing or specifying an agglomeration drum, several important design criteria must be addressed:

Throughput /
capacity:

The drum must match the tonnage rate of the mine or the feed rate to the heap. Some drums are rated up to 3 000 + t/h in large heap-leach installations.

Shell geometry
(diameter × length):

Larger diameter and longer length increase residence time and capacity. Typical diameter ranges for industrial units span ~1.0 m to ~4.6 m (or more) with lengths up to ~10 m+ depending on scale.

Inclination angle:

The drum is mounted with a slight slope (often ~3°-5°) from feed to discharge to allow gravity to assist movement and control residence time.

Rotation speed:

The RPM (or peripheral speed) influences the tumbling action and residence time. Too fast may reduce time for agglomeration; too slow may reduce throughput. One review suggests typical speeds in the order of ~7-16 rpm for certain diameters.

Internal lifters/flights:

The drum interior often includes flights or lifters that lift the material as the drum rotates, then drop it, promoting mixing and tumbling. The geometry (flight height, spacing) affects residence, mixing, wear and aggregate formation.

Binder and liquid
system:

The spray system must provide uniform wetting of the ore bed, maintain the correct moisture content and binder dose (e.g., cement, lime, polymer). The binder dose depends on ore fines content, clay mineralogy, target granule strength and leach conditions. For example, in copper heaps, acid + water additions might be ~15-25 kg H₂SO₄/t ore and ~60-100 kg water/t ore

Materials of
construction &
wear resistance:

Because ore is abrasive and the internal environment is aggressive (wet, spray, binder, fines), the shell, liners, flights and seals must be designed for wear. Rubber liners, AR steel, or composite liners may be used. For example, tyre-drive drums may use rubber tyres to support the shell and allow for robust service

Discharge and
screening/recycle:

A discharge end trommel or screen may be used to segregate undersized or oversize material; undersize may be recycled to enhance size control and quality of the agglomerated product.

Instrumentation &
control:

Monitoring feed rate, drum speed, binder flow, moisture content, aggregate size/strength, drive power draw and vibration is important for optimal performance and maintenance.

Technical Specifications

Below are representative values for an industrial agglomeration drum. These values should be adapted to the specific site, ore characteristics and test-work results.

Drum diameter:

~1,000 mm to ~4,600 mm (1.0–4.6 m)Larger diameter for higher throughput

Drum length:

~5,000 mm to ~10,000 mm+Length scaled for residence time

Inclination angle:

~3° to ~5°Controls residence time via gravity flow

Rotation speed (RPM):

~7 to ~16 rpmDepends on diameter and material

Throughput (tonnes/h):

Up to ~3,000 t/h+ in large unitsDependent on feed size, binder dosage

Feed size:
Power:

Typically crushed ore (< 25 mm) or as per feed specificationHigh fines content dictates need for agglomeration

Binder dosage:

Varies widely (e.g., cement / lime / polymer)From pilot test‐work

Materials of construction:
Power:

Shell: steel; Liners: rubber or AR steelDesigned for abrasion and corrosion

Note:

These numbers are indicative only. It is essential to conduct ore test-work (agglomerate size/strength, fines content, binder optimisation) to determine actual design values.

Important Considerations:

Installation and Operation

The foundation must support the large mass of the drum, rotating shell, drive system, tyres/trunnions, service access and alignment systems. Alignment of tyres/trunnion wheels and shell is critical to prevent shell stress and excessive wear. The spray system, binder storage/pumping system and feed/discharge conveyors must be properly installed and commissioned.
During operation, the feed rate, binder dosage, spray water, drum speed and inclination must be monitored and maintained within design ranges. Change in feed fines content or clay content may require adjustment of binder dosage or drum operating parameters. It is often advisable to monitor the strength of the agglomerate (for instance by crush testing) and the size distribution on discharge to ensure consistent performance.
  • If the fines fraction is high but no agglomeration is applied (or binder is inadequate), heap permeability may remain poor, leading to ponding, channeling and low metal recovery.

  • Weak or non-uniform agglomerates:

    Causes include inadequate binder dosage, uneven spray distribution, worn liners or flights, incorrect drum speed or inclination.

  • Excessive wear or drive issues:

    Poor alignment, worn tyres/trunnions, poor lubrication can increase downtime and reduce performance.

  • Maintenance neglect:

    If liners/flight lifters are worn, the internal mixing deteriorates, reducing aggregate formation and increasing fines.

  • No feedback loop to heap performance:

    If the drum is not tied to downstream heap performance (percolation, recovery, cycle time), the benefits may not be realised; therefore, monitor the heap and adjust the drum accordingly.

  • It is strongly recommended to conduct pilot test-work before full scale installation: characterize feed fines and clay content, determine optimum binder type/dosage, test agglomerate size/strength, and simulate heap behaviour without and with agglomeration.

  • Even with an agglomeration drum, upstream efforts to minimise fines generation (in crushing and screening) will improve results and reduce binder cost.

  • Monitor the agglomerate size distribution and crush strength regularly, and correlate with heap performance (percolation rate, leach cycle time, recovery). Adjust operating parameters accordingly.

  • Think of the agglomeration drum as part of the system (feed → drum → stack → heap performance) not just as standalone equipment. The downstream performance (heap permeability, irrigation, solution recovery) is the ultimate metric of success.

  • Consider the lifecycle cost: large drums have high capital cost, wear component cost (liners, tyres), energy consumption, binder cost, maintenance. But when the alternative is lost recovery or longer leach cycles, it may be strongly justified.

  • Consider closer integration of instrumentation, automation and condition monitoring (e.g., vibration sensors on tyres/trunnions, automated binder flow control, moisture sensors on discharge) to optimise performance and reduce downtime.