Granular ammonium sulphate is not one product. All granular ammonium sulphate is made by compacting crystal — there is no melt-and-prill or fluid-bed route in commercial use, because the salt decomposes rather than melting cleanly. Within compaction, however, the press type, the feed crystal and any added colourant produce products that behave differently in the yard and in the field. This page compares them; each has its own detail page.
Substance identity
Ammonium sulfate · (NH₄)₂SO₄ · CAS 7783-20-2 · PubChem CID 6097028 · 132.14 g/mol · angular granules, 2–4 mm predominant; colour depends on feed and on any added pigment.
Specification
— typical commercial ranges common to granular forms
| Parameter | Typical range |
|---|---|
| Total nitrogen (N) | 20.5 – 21.0 % min |
| Sulfur (S) | 23 – 24 % |
| Moisture (H₂O) | ≤ 0.5 % |
| Particle size, 2 – 4 mm | ≥ 90 % |
| Bulk density | ≈ 1.0 – 1.1 t/m³ |
| pH, 5 % solution | 5.0 – 6.0 |
Comparison of granular forms — typical characteristics, to be verified per lot
| Form | Made from / how | Typical crushing strength | Colour | Chosen when |
|---|---|---|---|---|
| Compacted granular | Any crystal feed, roll compaction | 2 – 3 kgf | follows feed | general blending and spreading |
| Hydraulic granular | Crystal feed, high-pressure press | ≥ 3 kgf reported | follows feed | long supply chains, many transfers, minimum fines |
| Compacted granular, steel feed | Coke-oven crystal, roll compaction | 2 – 3 kgf | grey to brown | lowest cost granular for blending |
| Hydraulic granular, steel feed | Coke-oven crystal, high-pressure press | ≥ 3 kgf reported | grey to brown | low-cost feed with harder granule |
| Coloured granular | Compacted, with pigment | 2 – 3 kgf | dyed | identification and branding |
Properties
Granulation changes physical behaviour only. Bulk density rises by roughly 10 % over the crystal it was made from; dust falls sharply; caking under stack load is reduced; spread width from a spinning disc becomes comparable to other granular fertilisers. Solubility, critical relative humidity (approximately 79–81 % at 30 °C), decomposition behaviour above roughly 235 °C and soil acidification are all unchanged from crystal.
Granulation also does not change chemistry inherited from the feed. Free acid, water-insoluble matter, iron and residual organics pass through compaction unchanged. A granule made from coke-oven crystal is a granular coke-oven product, not an upgraded one.
Applications
Bulk blending is the dominant use: 2–4 mm granular ammonium sulphate sits in the same size band as granular DAP, MAP, MOP and granular urea, so blends do not segregate during handling and the sulfur is distributed evenly across the field. Beyond blending, granular product is preferred for any mechanical broadcast application where spread width, evenness and low dust matter.
Handling and storage
Every transfer point and every drop height generates fines from angular granules; design handling to minimise both. Dry, covered storage; keep away from lime, caustic and other strong alkalis. Do not store pre-blended with urea for extended periods — the mixture’s critical relative humidity falls to roughly 56 % at 30 °C.
Notes
When comparing granular offers, the parameters that actually differentiate them are crushing strength, fines content on arrival, and feed route. Size specification alone does not distinguish them, because virtually all commercial granular ammonium sulphate is offered as 2–4 mm, 90 % minimum.