Troubleshooting Deviations in the ALS2 Process
Stable operation of an ALS2 precious-metals recovery plant depends on consistency from the receiving bay through to the final concentrate. Variations in electronic waste composition, particle size, moisture, contamination and equipment settings can quickly appear as lower recovery, unstable throughput or an off-specification product.
This guide provides a practical way to investigate common process deviations without treating symptoms in isolation. ALS2 operators should always work from the approved operating procedure, equipment manuals, risk assessments and site-specific process limits. The technology is designed to reduce reliance on conventional acid-based refining, but it still requires disciplined feed control, monitoring and safe plant management.
| Observed deviation | Common causes | First checks |
|---|---|---|
| Lower precious-metals recovery | Poor liberation, incorrect feed blend, inadequate contact or sampling error | Feed composition, particle size, dosing records and assay results |
| Unstable throughput | Bridging, excessive fines, moisture variation or restricted conveying | Hoppers, screens, conveyors, filters and material condition |
| High metal losses in residues | Incomplete separation, unsuitable feed or poor solids handling | Residue assay, separation stages, residence time and equipment condition |
| Wet or inconsistent product | Excess moisture, condensation, filtration problems or poor drying control | Feed moisture, drainage, air movement and discharge equipment |
| Unexpected colour or appearance | Contamination, mixed feed, oxidation or carryover between batches | Line clearance, cleaning records and product sampling |
| Rising energy or utility use | Blocked equipment, inefficient air handling or off-design operation | Motor loads, pressure readings, filters and maintenance status |
Feed preparation and material quality
The first troubleshooting step is often outside the main separation equipment. WEEE and electronic scrap can contain plastics, ferrous metals, aluminium, glass, ceramics, solder, batteries and treated components alongside precious-metal-bearing fractions. A change in the incoming mix can therefore look like a chemistry or equipment fault when the real issue is feed variability.
Check whether the material has been correctly dismantled, sorted, shredded and screened according to the validated ALS2 feed specification. Oversized pieces may pass through without adequate liberation, while excessive fines can affect conveying, dust control and separation behaviour. Batteries, pressurised components and other hazardous items must be removed through the site’s approved pre-treatment process rather than being sent into the recovery line.
Moisture is another frequent source of deviation. Outdoor storage, rain exposure and long transport distances can affect loads arriving from regional collection networks. This matters in Australia, where material may travel from Perth to a metropolitan processing site or from remote Queensland communities through several transfer points. Record the condition of each incoming batch, including supplier, source, mass, moisture indication and visible contamination.
When results change suddenly, compare the current batch with the previous accepted batch. A representative sample and a reliable assay are more useful than a visual judgement based on a single container. If the feed differs materially from the validated range, hold or segregate it according to the site procedure before adjusting the process.
Flow, dosing and residence time
A stable material flow allows the separation system to work within its intended operating window. Fluctuations in feed rate may arise from hopper bridging, inconsistent loader operation, worn screw flights, blocked chutes or a feeder calibration problem. They may also occur when operators compensate for an upstream restriction by increasing the feed setting.
Start with simple physical checks. Confirm that hoppers are discharging evenly, conveyors are running at the expected speed and screens are not overloaded. Inspect for compacted material, tramp metal and deposits at transfer points, using the site isolation and access controls. Compare actual mass flow with the control-system indication and recent weighbridge or batch records.
Dosing deviations should be investigated through a complete chain of evidence. Review material identity, batch mass, pump or feeder status, calibration dates and operator entries. A value that looks correct on the screen may still be wrong if a load cell has drifted or a pump has lost prime. Avoid making repeated manual adjustments without recording them, since this can hide the original fault and create a second deviation.
Residence time is affected by throughput, hold-up, mixing behaviour and equipment condition. If recovery falls while the feed rate has increased, return the line to its validated operating range before changing other variables. A short, controlled test with a known feed is generally more informative than changing several settings at once.
Separation results and metal losses
The clearest sign of a separation problem is often a change in the assay of the recovered fraction or residue. Lower product grade, higher precious-metal content in waste and inconsistent batch results should be treated as related indicators. Sampling error must be considered early because a segregated electronic-waste stream can be highly heterogeneous.
Use the approved sampling plan and retain reference samples where required. Compare product, intermediate and residue results from the same campaign rather than relying on a single final sample. Check whether the laboratory method, sample preparation and chain of custody were unchanged. In Australia, customers and regulators may expect clear evidence of material movement and recovery performance, particularly where the feed has come through state-based collection or stewardship arrangements.
If losses are confirmed, inspect liberation and classification first. Precious metals may remain attached to larger composite pieces, trapped in non-metallic material or concentrated in a size fraction that is bypassing the effective separation zone. Review screen condition, separator settings, residence time and the balance between coarse and fine streams.
Carryover can also distort results. Product retained in chutes, bins, filters or transfer points may enter a later batch with a different composition. A documented line-clearance check between campaigns is especially important when a plant processes mixed circuit boards, connectors, telecommunications equipment and consumer electronics. Cleaning must follow the approved method, with recovered sweepings handled as process material rather than ordinary waste.
Moisture, dust and equipment behaviour
A wet feed can cause bridging, poor screening, clumping and irregular discharge. It can also increase the apparent mass of a batch, making metal-balance calculations misleading if wet and dry weights are compared without correction. Look for condensation, water ingress, blocked drains and damaged covers before changing the process settings.
Excessive dust may indicate over-drying, a failed seal, damaged ducting, poor extraction or excessive fines in the feed. Dust is a product-loss issue as well as an occupational health and safety concern. Inspect filters, differential-pressure readings, extraction airflow and collection vessels under the site’s isolation procedure. Do not bypass extraction equipment to maintain production.
Unusual noise, vibration, heat or motor load should be treated as an equipment deviation, not as a normal feature of processing. Bearings, screens, pumps, drives and seals can affect flow and separation performance before they fail completely. Record the time, operating condition and location of the symptom, then compare it with maintenance history and trend data.
Australian sites may face strong seasonal effects. Humid conditions around Brisbane or Darwin can affect stored feed and condensation, while dry inland conditions can increase airborne dust. Coastal locations may also see accelerated corrosion on exposed plant components. Storage, ventilation and inspection frequencies should reflect the local environment rather than relying on a generic calendar.
Safe correction and escalation
When a deviation is detected, stabilise the plant before attempting optimisation. Follow the approved response for reducing feed, placing equipment in a safe state, isolating material or stopping the line. Never open, clean or clear equipment while it can start unexpectedly or contain moving, hot or contaminated material.
Record the deviation in a way that allows another operator to reconstruct the event. Include the time, batch identity, feed source, settings, alarms, mass flow, samples taken, equipment condition and actions performed. Photographs may support the investigation where permitted, but they should not replace formal records or laboratory results.
Escalate promptly when there is a repeated loss of recovery, unexplained product contamination, a failed interlock, suspected battery contamination, uncontrolled dust, abnormal emissions or a discrepancy in mass balance. The responsible process engineer, maintenance lead, laboratory and health and safety team may each hold part of the evidence. A short cross-functional review is more effective than repeated informal adjustments on the plant floor.
Use trend charts to distinguish a one-off upset from a developing fault. A gradual change in residue assay may point to wear or calibration drift, while a sharp change after a supplier switch may indicate feed composition. Corrective action should identify the cause, define the verification test and specify who can release the line back to normal operation.
For Australian operators, local compliance duties can vary by state and territory, and transport or storage arrangements may involve licensed contractors and state-based waste requirements. Keep the ALS2 process records aligned with site environmental approvals, dangerous-goods controls and customer reporting obligations. Clear records support responsible WEEE recycling and help demonstrate the environmental value of acidless precious-metals recovery.
Use this guide alongside the ALS2 operating documentation to build a site-specific deviation checklist for receiving, preparation, separation, sampling and dispatch. Contact Ikoi S.p.A. or the authorised technical support channel when process data shows a persistent deviation, when the feed falls outside the validated specification or when a change to operating conditions requires formal review. Consistent investigation protects operators, improves recovery performance and helps Australian recyclers turn complex electronic waste into a controlled resource stream.