Properties - Sulphur
May 31, 2005

Introduction         Moisture and Acidity         Ash and Solids         Hydrocarbons Physical Properties

Associated Links Formed Sulphur Specification Sulphur Safety

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Introduction

The quality of the bulk sulphur will affect whether or not pretreatment is required and the design of the sulphur handling system.  Poor quality sulphur may require special handling that is not required for good quality sulphur.

The quality of sulphur can be expressed in a number of different ways.  The most common classification is the one used for Frasch sulphur:

            Superbright         maximum organic content 0.02% C; guaranteed purity 99.5%

            Bright                  maximum organic content 0.04% C

            Dark                    maximum organic content 0.2% C

There are other system for classification of sulphur.  'Claus' sulphur is usually 99.98% pure and light yellow in colour.  'Lacq' quality sulphur is 99.9% pure (dry basis) and contains 0.01-0.03% organics, 0.01-0.05% ash and approximately 0.5% moisture but no arsenic, tellurium, fluorine and bitumen.

The following parameters are most frequently measured for quality control purposes.

• Moisture Content
• Ash Content
• Acidity
• Chloride Content
• Carbon Content (Organics)
• Hydrogen Sulphide Content
• Ammonia Content
• Arsenic
• Iron

Moisture and Acidity

The water and acidity content in the sulphur forms dilute acid, sulphuric and sulphurous, which will attack the carbon steel in storage tanks and piping and the concrete in the pits.   To neutralize the dilute acid, lime is added to the sulphur.

Ash and Solids

Ash and solids may settle and accumulate in piping restricting flow and eventually block the pipe completely.  Solids may also plug the sulphur gun nozzle resulting in frequent shutdowns to clear or replace the nozzle.  Ash that passes through the sulphur gun will pass through the plant until it reaches the first catalyst bed.   Dirt buildup in the bed increases pressure drop eventually to the point where a shutdown is required to screen the catalyst.   In some older plants a Hot Gas Filter located prior to the converter serves to minimize dirt buildup in the catalyst.  Alternatively, the ash and solid content in the sulphur can be reduced before the sulphur is burnt by settling or filtering.  Settlers are simply large heated pits with sufficient residence time to allow the ash and solid to settle out.  Filters are specially designed pressure leaf filters.  The whole unit is steam jacketted to prevent solidification of the sulphur.

Hydrocarbons

Hydrocarbons in the sulphur are converted to water vapour when the sulphur is burned.  This moisture is carried through the plant where it will condense in the cooler parts producing acid and oleum which will corrode equipment.  The problem with hydrocarbons is that they are not easily removed.  Filtering and settling may remove a small portion of the hydrocarbon content.  The best method of control is to use sulphur with as low a hydrocarbon content as possible.

Physical Properties

Appearance	Yellow crystalline solid or liquid
Crystalline Forms	Rhombic and Monoclinic
Melting Point	110 to 121°C depending on crystalline form
Boiling Point	444.6°C
Auto-ignition Temperature	Dust: 190°C Dust Layers: 221°C Liquid: 248 to 261°C
Flash Point	168 to 188°C
Vapour Pressure	< 0.1 mm Hg @ 20°C
Explosive Limits of Dust in Air	LEL: 35 g/m3 UEL: 1400 g/m3
Specific Gravity	1.92 to  2.07 depending on crystalline form
Liquid Sulphur
Density	1786.5 kg/m3 @ 140°C (See Graph)
Surface Tension	60.83 mN/m @ 120°C
Viscosity	See Graph
Bulk Sulphur
Angle of Repose	35° (approximate)
Bulk Density	770 kg/m3 (48 lb/ft3)

Density

Viscosity