Sulphur Shipping

What is sulphur as a sea-borne cargo?

Sulphur is an elemental chemical-feedstock cargo carried in dry bulk under the IMSBC Code SULPHUR schedules. It ships mostly as formed solid prills or pellets, and as crushed lump and coarse grained material, the latter carrying combustible-dust and acidic-corrosion hazards.

Most sea-borne sulphur is a byproduct of oil and gas processing, recovered when refineries and gas plants strip hydrogen sulphide out of sour crude and sour gas. That recovered sulphur is then solidified for transport, and the overwhelming bulk of it feeds sulphuric acid production, which in turn drives phosphate fertilizer manufacturing. The shipping problem is distinct from a typical inert mineral: solid sulphur is chemically benign while dry and intact, but its dust is flammable, and any moisture on the cargo or in the air reacts with sulphur residue to form acid that attacks steel and paint.

The regulatory anchor for sea carriage is the IMSBC Code 2024 edition. Solid sulphur ships under two schedule entries: SULPHUR (formed, solid), classified Group C, and SULPHUR (crushed lump and coarse grained). The crushed form is the operationally demanding one, because its fines behave as a combustible dust and the schedule treats it accordingly, with UN 1350 applying to the relevant form. Sulphur also moves molten as a heated liquid in specialised tankers, but that is a separate liquid-cargo trade and is not developed here. This page covers the solid dry bulk trade.

Sulphur cargo properties

Property	Value	Unit / Reference
Stowage factor	0.60 to 0.96	m3/t, varies by form and grade (IMSBC Code 2024, SULPHUR schedules)
IMSBC group	Group C (formed, solid)	Not liquefaction and not chemical-reactive in the Group A or B sense; combustible-dust handling noted for crushed form (IMSBC Code 2024)
IMSBC schedule entry	SULPHUR (formed, solid) / SULPHUR (crushed lump and coarse grained)	Two separate schedules; UN 1350 applies to the relevant form (IMSBC Code 2024)
Bulk density	1.04 to 1.67	t/m3, form dependent (IMSBC SULPHUR schedules)
Angle of repose	Not specified	Not stated in the IMSBC SULPHUR schedules consulted
Transportable moisture limit	Not applicable	Group C, TML applies only to Group A cargoes
Hazard profile	Acidic corrosion, combustible dust flammability	IMSBC SULPHUR schedules, special precautions
Reference	IMSBC Code 2024 edition	International Maritime Solid Bulk Cargoes Code, IMO

The two sulphur schedules diverge mainly on the dust hazard. The formed, solid grade is prilled or pelletised so it produces relatively little fine dust, which is why it is classed Group C and handled as a corrosive but otherwise low-drama mineral. The crushed lump and coarse grained grade generates flammable fines, and the schedule’s special precautions reflect that, requiring dust control, no smoking and no naked flame around open holds, and bonding and earthing where ignition sources are present. Across both grades the defining operational signature is acidic corrosion: sulphur dust plus moisture plus air forms an acidic film that pits unprotected steel and strips paint, which is why holds are limed or specially coated before loading and washed thoroughly after discharge.

Vessel typing and parcel sizes

Sulphur parcel-size economics track the receiving acid plant’s intake schedule and the load and discharge berth constraints rather than any quirk of the cargo itself. Large Middle East and Canadian exporters fixing into major Asian and African phosphate complexes default to Panamax and Supramax tonnage, because the freight saving per delivered tonne is meaningful on a long voyage and the receivers can take a full parcel. Smaller and shallower acid-plant berths run on Handymax and Handysize tonnage, often gear-equipped, where the receiver lacks shore cranes. For the full vessel-class catalogue see the bulk-carriers hub.

Hold preparation is the under-priced operational issue in the sulphur trade, just as hold cleanliness is in coal. A vessel that lifted sulphur and is then nominated for a clean cargo such as grain or alumina will fail hold inspection on residual sulphur film and acid staining unless the master books a full hold wash and, where needed, a lime treatment and re-coat at the discharge port. This is why sulphur-heavy fleets often run several sulphur voyages in series before resetting to a clean cargo.

How sulphur ships in practice

Sulphur loads predominantly by shore conveyor or grab at dedicated chemical and bulk terminals colocated with refineries, gas plants and the export ports that serve them. Loading rates vary widely with the terminal: large purpose-built sulphur berths in the Middle East and Canada load at high conveyor rates, while smaller multi-purpose berths grab-load at lower rates. The master’s loading plan must respect the relevant SULPHUR schedule’s dust-control and corrosion-control precautions, which for the crushed grade means keeping dust down at the hatch coaming and excluding ignition sources, and across both grades means the holds are prepared to resist acid attack before the cargo touches the tank-top.

Voyage care turns mainly on keeping the cargo dry and the dust under control. Hatch covers are kept closed and weathertight, because ingress of seawater or rain wets the cargo and accelerates acid formation. For the crushed lump and coarse grained grade the dust-flammability precautions stay live for the whole voyage, with no smoking, no hot work over open holds, and ignition sources controlled. Unlike the self-heating coal regime there is no continuous gas-and-temperature monitoring requirement of the same intensity, but the corrosion clock runs the entire time the cargo is aboard.

Discharge is by grab and shore crane at most receiving terminals, feeding straight into the acid plant’s melting and burning circuit. The dominant lane structure is one parcel per vessel: sulphur does not part-load with other cargoes because of the contamination and corrosion risk. The fixture is almost always on FIO terms with laytime and demurrage negotiated against the receiving terminal’s published norm. See loading and discharge rate for the contractual mechanics, and the ship-chartering hub for the wider terms.

Major trade routes

• Middle East Gulf to Asia (India, China, Southeast Asia): the volumetric core of the sulphur trade, recovered Gulf sulphur moving to phosphate-acid complexes; Panamax and Supramax dominant.
• Middle East Gulf to North and East Africa (Morocco, Tunisia): feeds the Moroccan and Tunisian phosphate industry; Supramax and Panamax.
• Canada (West Coast) to Asia and other markets: Canadian gas-plant sulphur exported through Pacific terminals; Panamax and Supramax.
• Central Asia and Caspian (via Black Sea) to Mediterranean and Asia: FSU recovered sulphur railed to Black Sea and Baltic export ports; Handymax to Panamax.
• US Gulf to Latin America: refinery-recovered sulphur into South American acid and fertilizer producers; Handymax and Supramax.

The trade is shaped almost entirely by the geography of oil and gas processing on the supply side and phosphate-fertilizer manufacturing on the demand side, since the great majority of solid sulphur is burned to sulphuric acid for fertilizer production. Specific tonnages and lane shares should be confirmed against current published trade data such as IFA, USGS Mineral Commodity Summaries or Clarksons before they are quoted; the route figures above are directional and carry desk rows. For the wider lane catalogue across dry bulk see the dry-bulk-shipping hub and the routes-markets pages.

Sulphur vs salt

Sulphur and salt are both Group C solid bulk cargoes whose defining shipping problem is corrosion rather than liquefaction or self-heating, and the two are sometimes grouped together as corrosive minerals. They are not similar cargoes beyond that shared headache.

Use the appropriate SULPHUR schedule when the commodity is recovered elemental sulphur, and the SALT schedule when it is sodium chloride. Both demand careful hold preparation and a thorough wash-down before the vessel reverts to a clean cargo, but the chemistry differs: sulphur attacks via acid formation and adds a dust-flammability concern for the crushed grade, while salt attacks via chloride. A fixture written against the wrong schedule will fail the loadport survey. Verify the salt stowage and corrosion figures against the SALT schedule directly.

Reference example

01 Fixture Example

Supramax formed sulphur, Middle East Gulf to West coast India

Cargo grade

50,000 mt formed solid sulphur, prilled, 5 pct molo

Lane

Middle East Gulf export berth to West coast India acid plant

Vessel band

Modern Supramax, 56,000 dwt, geared

Parcel size

50,000 mt

Loading rate

15,000 T/D SHINC, shore conveyor

Discharge rate

10,000 T/D SHINC, grab and shore crane

Notable clause

Holds lime-washed and inspected before loading; SULPHUR schedule dust and corrosion precautions; freshwater hold wash-down after discharge; freight prepaid against original BL

This is a representative illustrative fixture, not a record of a specific named voyage, and the lane and rate figures carry a desk row for verification against current market data. The lane runs across the Arabian Sea to a West coast India acid plant. Formed solid sulphur loads relatively cleanly by conveyor because the prilled grade produces less dust than crushed lump, but the corrosion precautions still apply throughout.

Hold preparation at the previous discharge port included a full sweep, a freshwater rinse and a lime-wash of the tank-top and lower hoppers, with surveyor sign-off recorded before the laycan opened. Because the cargo is the formed grade, the heavier combustible-dust controls reserved for crushed lump were less onerous here, but no-smoking and ignition-source control around open holds were observed.

The fixture was on FIO terms with laytime calculated against weather working days SHINC at both ends, and demurrage set close to the spot Supramax daily TCE for the month of fixture, which is the standard owner-club guidance to avoid subsidising port congestion at the receiver.

Image Placeholder Geared Supramax bulk carrier loading formed solid sulphur prills by shore conveyor at a Middle East Gulf chemical berth

Common loading and discharge issues

• Acidic corrosion of holds and coatings: the standing issue across both grades. Sulphur dust combines with moisture and air to form an acidic film that pits steel and strips paint. The defences are lime-washing or specialised coatings before loading and a thorough freshwater wash-down after discharge, per the SULPHUR schedule precautions.
• Combustible dust flammability of the crushed grade: the crushed lump and coarse grained schedule treats the fines as a flammable dust, requiring dust suppression, no smoking, no naked flame and ignition-source control around open holds. The formed solid grade is much less dusty, which is the main reason it is the preferred shipping form.
• Moisture ingress wetting the cargo: rain or seawater entering the hold accelerates acid formation and can cake the cargo. Weathertight hatch covers and care over loading in rain are the controls; a wet sulphur cargo is both a corrosion and a discharge problem.
• Hold-cleanliness failure on the next fixture: residual sulphur film and acid staining will fail a hold inspection for a subsequent clean cargo unless a full wash and, where needed, re-coat is done. This is a recurring source of off-hire and dispute when the vessel is fixed back-to-back without time for proper preparation.
• Schedule and UN-number confusion: applying the formed-solid Group C documentation to a crushed lump parcel, or omitting UN 1350 where it applies, causes certificate delays at the loadport. The correct schedule and UN reference depend on the physical form; confirm against the IMSBC Code 2024 entry for the form being loaded.
• Dust complaints at receiving berths: dust emission during grab discharge of the crushed grade can draw port restrictions or fines at berths with residential or environmental sensitivity, typically passed back to the charterer under the cargo-handling clause.

Scope and what this page does not cover

This page explains solid sulphur as a sea-borne dry bulk commodity, the IMSBC operational regime that governs its carriage in the formed and crushed forms, and the dominant vessel-class and lane structure. It does not cover the separate molten-sulphur liquid trade carried in heated tankers, forecast sulphur or sulphuric-acid prices, or interpret jurisdiction-specific cargo-claim law on corrosion damage. Several property and route figures here are directional and carry desk rows for verification against the IMSBC Code 2024 and current published trade data such as IFA, USGS or Clarksons. For decisions, work with chartering counsel and a desk broker against current market data, and confirm the IMSBC values against the relevant SULPHUR schedule directly. To fix a solid sulphur parcel, get a quote and the desk will type the vessel to your lane and form.