Sulphur
Forms of Sulphur
Granular, prilled, slate, crushed lump and molten — each form suits a different transport route and a different end use.
Sulphur leaves the Claus unit as a liquid and is then either shipped hot or solidified into one of several handling forms. The choice affects dust generation, storage behaviour, transport cost and the equipment needed at destination.
Granular sulphur
Formed by building up successive layers of molten sulphur on a seed particle in a rotating drum or fluidised bed. The result is a hard, rounded granule of 2 to 6 mm with high crush strength and very low dust generation.
It is the premium traded form and the standard for international bulk shipment, because it survives multiple transfers through ship, conveyor and rail without degrading into dust.
Prilled sulphur
Produced by dropping molten sulphur through a cooling medium, usually air or water. Wet prilling gives a smaller and softer particle than granulation; dry prilling produces a harder product closer to granular in performance. Prills are typically 1 to 4 mm and generate more dust in handling than granules.
Slate and flake
Molten sulphur is poured onto a moving cooled steel belt, where it solidifies into a thin sheet that breaks into irregular flakes. Slate is cheap to produce and has a high surface area, which makes it dissolve and react quickly, but it is friable and dusty, so it is used mainly for regional supply rather than long-haul export.
Crushed lump
Where sulphur has been run into open block storage, the solid mass is excavated and crushed to a nominal size. It is the lowest-cost form and it suits buyers close to the production site, but it carries more contamination and more dust than formed products.
Molten sulphur
For consumers within economic reach of a producer, liquid sulphur at 130 to 150 °C avoids the cost and energy of forming and remelting entirely. It requires heated, insulated tankage and transport, and lined or stainless steel equipment to resist the acidic corrosion that any moisture ingress will cause.
Choosing between them
- Long-haul bulk export — granular, for its low dust and high crush strength
- Regional bulk supply — prilled, at a lower cost than granular
- Local industrial supply — slate or crushed lump where dust can be managed
- Adjacent acid plant or consumer — molten, avoiding forming and remelting cost
- Agricultural application — bentonite-bound pastilles or micronised powder
Typical specification
| Granular | 2 – 6 mm · lowest dust · export standard |
|---|---|
| Prilled | 1 – 4 mm · moderate dust · regional bulk |
| Slate / flake | Irregular · high dust · fast dissolving |
| Crushed lump | Variable · high dust · lowest cost |
| Molten | 130 – 150 °C · heated transport required |
Values are indicative and given for guidance. Contract specification is agreed in writing and certified per batch on the certificate of analysis issued with each shipment.
