Knowledge for the Sulphuric Acid Industry
Sulphuric Acid on the Web
Acid Plant Database
Boiler Feed Water
Materials of Construction
DKL Engineering, Inc.
May 30, 2003
Sulphur can arrive at the acid plant site in one of two bulk forms; solid or liquid. Solid sulphur must be melted prior to use in the production of sulphuric acid. Sulphur in liquid form is delivered to site in insulated tank trucks or rail cars.
Depending on the form and quality of the sulphur, some pretreatment may be required prior to burning the sulphur in the furnace. Pretreatment may include any one of the following; lime addition, melting, filtering and/or settling.
Handling solid sulphur is similar to handling other solids in bulk form with the precaution that sulphur dust suspended in air is readily ignited by flame, static electricity or friction spark. The design and operation of the bulk handling system must take this into consideration to avoid the possibility of explosions and fires.
The amount of dust generated when handling solid sulphur will depend on the form (i.e. flakes, prills, pastilles, etc.) the sulphur is delivered in, its moisture content, the handling methods and equipment employed. Dust that is generated in the handling process can be controlled by the use of water sprays. Sprays are generally located at transfer points in the system, such as at the end of conveyors or outlet of hoppers. The amount of water used should be limited since too much water can lead to other problems such as bridging in hoppers or chutes. The moisture content of the sulphur should be maintained in the range of 0.5 to 1.5%. Higher water contents will lead to less efficient melting since any water in the sulphur must be evaporated in the melter.
Special dust suppression agents such as Dustbind 'S' or 'S2' can be used to improve the suppression of sulphur dust. The dust suppressant is selective to sulphur surfaces and upon drying remains a viscous, agglomerative liquid. The suppressant may also contain an anti-corrosion ingredient to minimize the corrosive affect of acidity in the sulphur. The suppressant is generally available in concentrated form and must be diluted in water in a ratio of 80 or 100 to 1 prior to application.
Sulphur in the liquid form can be easily handled when its temperature is in the range of 130°C to 145°C. At this temperature, the viscosity is low (7-10 cP) making it easy to unload, store and pump through pipes. At lower temperatures, the viscosity of sulphur increases gradually. However, at temperatures higher than 155°C, the viscosity of sulphur increases asymptotically. Therefore, any equipment handling liquid sulphur must be adequately heated to maintain the sulphur at the optimum temperature.
To handle molten sulphur properly and prevent solidification, all lines and equipment must be heated. Steam jacketing or tracing of lines is necessary as well as steam coils in all equipment and storage tanks.