Why are there fines in fertilizer after screening?

The screen may be misplaced or blinded, or granules may break during later conveying. Compare samples at individual stages.

Fertilizer Granule Screening Solution

Two cuts produce three fertilizer streams

A two-cut fertilizer screen removes oversize on the upper deck and separates fines on the lower deck. Accepted granules occupy the size band between those cuts. The outlets remain separate through collection and transfer. Combining them again below the screen defeats the grading. A process that recycles fines or crushed oversize must route those streams away from finished granules.

Linear Vibrating Screen on a white background — Linear Vibrating Screen

Granule strength changes the handling problem

Granular NPK and urea are not identical conveying duties. Weak granules break at impacts and create fines after an initially clean separation. Moisture can cause caking and deposits at feed or discharge points. Screening removes oversized cakes but cannot restore the original physical condition of the product. Near-size granules need repeated contact with the mesh rather than a thick layer riding over it.

Material / observation	Separation / cause	Equipment / action
Fines	Below the lower cut	Keep separate from finished granules
Accepted granules	Between the lower and upper cuts	Transfer to finished-product handling
Oversize	Above the upper cut	Keep separate for the applicable rework stage

Illustrative sample of fertilizer granules and pellets — Material illustration: fertilizer materials

A clean screen cannot correct an overloaded chute

Uneven feeding underuses part of the deck and overloads another part. Stabilise the inlet and keep reject chutes clear. Inspect panels for wear, tears and edge gaps when oversized particles appear in accepted material. Linear and gyratory screens can grade suitable granules, but the deck and discharge layout must keep each cut isolated.

Gyratory Screen on a white background — Gyratory Screen

Locate where new fines are generated

Take samples after the screen and after each elevator or conveyor. A rise in fines across one transfer identifies granule damage there. Inspect long drops, abrupt chute bends, buildup and a conveyor receiving more material than it can carry. Guide the stream through the chute and reduce unnecessary impact. Changes to the screen cut cannot cure breakage occurring after the screen.