Feed preparation
Establish a consistent basis for the material entering the pelletizing circuit.
What happens here
Concentrate preparation and filtration define the feed presented to mixing. The required arrangement depends on the ore and the upstream beneficiation route.
Equipment in this stage
Filters, feed bins and dosing systems.
Inputs to define
Feed source and variability; moisture reporting basis; sampling location; additive requirements.
A useful review question
Confirm which feed conditions are verified and which remain design assumptions. Keep wet-tonnage and dry-tonnage figures distinct.
Continue to the practical guide ↗Moisture: define the denominator before changing the process
Water content expressed on a wet basis is water mass divided by total wet mass. On a dry basis it is water mass divided by dry solids. Confusing the two changes the inferred solids throughput and the water addition required downstream. The laboratory method, sample age and sampling location belong beside every moisture result. A stockpile sample, a filter discharge sample and the actual mixer feed can describe different conditions.
Worked example — mass balance, not an operating target
At an illustrative 100 t/h wet feed and 9% wet-basis moisture, dry solids are 91 t/h and water is 9 t/h. The equivalent dry-basis moisture is 9 ÷ 91 = 9.89%. If wet throughput remains 100 t/h while moisture rises to 10%, solids delivery falls to 90 t/h. A belt-scale reading alone would miss this change.
Distinguish a feed-property problem from an equipment problem
Characterise the incoming concentrate as a range, including size distribution, specific surface area where measured, mineralogy, moisture and relevant chemical constituents. Two feeds with similar bulk moisture may behave differently in a mixer or disc. A useful investigation preserves samples before and after an ore-source or filtration change and repeats the same balling test procedure.
| Observed change | First comparison | Why it matters |
|---|---|---|
| Balling changes after a new ore blend | Matched samples for particle size, moisture and recipe | Separates a material change from an equipment adjustment. |
| Wet-tonnage stable, product output falls | Dry-solids balance and return streams | Tests whether water or internal circulation is inflating the apparent feed rate. |
| Intermittent surges at mixer inlet | Time-aligned bin level, feeder rate and belt-scale trend | An hourly average can hide short disturbances. |
Build a feed envelope that can be tested
A design specification should state the normal range, credible extremes, sampling frequency and response to off-specification feed. Ask whether the filtration and storage arrangement can deliver the same envelope during startup, reduced throughput and seasonal changes. Keep the fresh concentrate balance separate from recycled green material; combining them before measurement hides the origin of a disturbance.
Technical references
Kawatra & Claremboux — Iron Ore Pelletization, Part I: Fundamentals — abstract/reference ↗
References support the underlying principles. Diagnostic sequences, worked examples and procurement questions are original engineering analysis; they are not plant operating instructions or verified supplier performance results.
A surface-area target does not define the complete concentrate
Particle-size distribution, shape, mineralogy and surface condition can change balling behaviour even when the reported Blaine value is similar. Compare a feed change using the same sampling and preparation methods. A higher surface area may help bonding while changing water demand and drying behaviour; the useful target is a tested feed envelope.