Properties - Sulphur
May 31, 2005
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) |
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Density
Viscosity
