Compacted ammonium chloride is fine crystalline material converted into a coarser product by pressure alone. Crystal is fed between counter-rotating rolls under high pressure and emerges as a continuous sheet, which is then broken, screened, and the off-size fraction recirculated. This page describes the process and the mechanical properties it produces; the field consequences of those properties are covered on the compacted granular page in the nitrogen fertilizer section.
Substance identity
| Chemical name | Ammonium chloride |
| Synonyms | Sal ammoniac, muriate of ammonia |
| Formula | NH₄Cl |
| CAS | 12125-02-9 |
| Molar mass | 53.49 g/mol |
| Appearance | White to off-white granules with angular, fractured faces and irregular shape — a direct signature of the crush-and-screen route, as distinct from the rounded particles produced by drum or pan granulation |
Specification
| Parameter | Value | Basis |
|---|---|---|
| NH₄Cl content | Unchanged from the feed powder | Compaction adds nothing |
| Nitrogen (N) | ≥ 25.0–25.4 % on agricultural feed material | Typical commercial range |
| Moisture | ≤ 0.5–1.0 % | Typical commercial range |
| Particle size | 2–4 mm is the common cut; other bands are produced to order | Typical commercial cuts |
| Bulk density | Approximately 0.9–1.05 t/m³, above that of the feed powder | Typical, approximate |
| Crush strength | A real and specifiable parameter, set by press configuration and feed condition. No representative value is quoted here because it varies too widely to state honestly; agree a measured minimum and a test method in the specification | To be agreed |
| Binder | None in the standard route | See below |
Properties
The compaction is binder-free. Ammonium chloride deforms plastically under sufficient pressure, and inter-particle bonding is achieved by that deformation rather than by an added adhesive. Two consequences follow, and both are commercially relevant. First, the granule is chemically identical to the powder it was made from — no binder dilutes the nitrogen analysis and no binder enters a downstream process. Second, granule strength depends entirely on press conditions and on the moisture and particle size of the feed, so it is a process-controlled property that varies between producers and between production runs in a way that a binder-bonded granule’s strength does not.
All solution and thermal properties are those of the salt and are unaffected: approximately 37 g per 100 g water at 20 °C, endothermic dissolution at about +14.8 kJ/mol, solution pH 4.5–6.0 at 5 %, dissociation to NH₃ and HCl on heating with apparent sublimation near 337.6 °C.
Applications
Compaction exists to solve handling problems, not chemical ones. It is chosen where the material must survive multiple transfers, long storage, mechanical spreading, or bulk blending with other granular products. The angular fracture faces are worth noting on both sides of the ledger: they interlock, which resists flow in hoppers slightly more than rounded granules, and they abrade, which regenerates dust over repeated handling.
Handling and storage
Store dry and sealed. Limit drop heights and the number of transfer points — attrition of compacted granules produces fines, and those fines both restore the dust problem compaction was intended to remove and act as caking initiators, since the fines have far higher surface area than the granules around them. Product that has been handled repeatedly should be re-screened if size specification matters downstream. Keep away from alkaline materials, strong oxidisers and, in moist conditions, copper alloys and unprotected steel.
Notes
Product from a compaction line has an inherent size distribution set by the crushing and screening step, not a single size. The recycle loop returning off-size material to the press means feed characteristics drift over a run, so consistency between lots should be verified by measurement rather than assumed from the process name.