This is compacted granular ammonium sulphate produced from steel-grade (coke-oven) crystal feed. The combination is a deliberate economic choice: coke-oven crystal is the lowest-cost ammonium sulphate but the worst-handling one, and roll compaction removes exactly the handling faults — dust and poor ballistics — while leaving the colour and trace impurity profile of the feed intact. Understanding what compaction does and does not fix is the whole point of this page.
Substance identity
Ammonium sulfate · (NH₄)₂SO₄ · CAS 7783-20-2 · PubChem CID 6097028 · 132.14 g/mol · angular granules, grey, beige or brown depending on feed.
Specification
— typical commercial ranges
| Parameter | Typical range | Note |
|---|---|---|
| Total nitrogen (N) | 20.5 – 21.0 % min | inherits the feed guarantee |
| Sulfur (S) | 23 – 24 % | |
| Moisture (H₂O) | ≤ 0.5 % | |
| Free acid (as H₂SO₄) | ≤ 0.10 – 0.20 % | inherited from coke-oven feed; not reduced by compaction |
| Water-insoluble matter | inherited from feed | not reduced by compaction |
| Particle size, 2 – 4 mm | ≥ 90 % | |
| Crushing strength | 2 – 3 kgf typical | |
| Colour | grey / beige / brown | inherited |
Properties
What compaction fixes: airborne dust during handling falls sharply, because the fine crystal is locked into granules; bulk density rises to roughly 1.0–1.1 t/m³; spread width from a spinning disc becomes comparable to other granular fertilisers; caking under stack load is reduced because there is far less particle contact area per tonne.
What compaction does not fix: colour, free acid, water-insoluble matter, iron and residual organics all pass through unchanged — they are properties of the salt and its occlusions, not of particle size. A granulated coke-oven product is still unsuitable for fertigation, drip irrigation, spray-water conditioning and any colour-specified application. Compaction is a physical remedy for physical faults only.
Applications
Bulk blending with granular DAP, MAP, MOP and granular urea, where matched 2–4 mm sizing prevents segregation and the colour is irrelevant inside a mixed blend. Mechanical broadcast spreading at field scale. Any straight N+S application where the buyer wants granular handling at coke-oven feed cost.
Handling and storage
As compacted granular generally — minimise transfers and drop heights, dry covered storage, away from strong alkalis. The inherited free acidity means damp product is still corrosive to unprotected mild steel, even though the dust problem has been solved; keep hoppers and conveyors dry and clean out after use.
Notes
When comparing offers, compare like with like: a compacted granular from caprolactam feed and one from coke-oven feed can carry identical size and strength specifications and still differ in free acid, insolubles and colour by a wide margin. Ask which feed was used — the granule appearance will usually tell you, but the certificate of analysis should confirm it.