The challenge

Both melters were designed with six steam heating coils, and heat transfer was essential to achieve the required melting capacity. The design temperature for the melted sulphur was 130°C. A proposed agitator had a motor of 200 kW with three impellers, whereof the lower one was a pitch blade turbine. The main challenges were:

• High heat transfer requirement
• Heavy-duty application
• Corrosive environment in the gas phase
• Large ambient temperature range between -47°C and +40°C

The solution

Sulzer calculated that a motor capacity of 132 kW would be enough, instead of 200 kW. This could be achieved with a Scaba agitator and high-efficiency SHP propellers on two levels. The result was verified in a computational fluid dynamics (CFD) analysis that proved that the propellers were correctly positioned and that no pitch blade turbine was needed.

Because the agitators operate with a variable frequency drive (VFD), it was, however, decided to install a 200 kW motor, but to operate it at 132 kW. The additional power is only a reserve for extremely cold conditions, and the normal operating speed is a maximum of 132 kW. This gives extra safety, but still substantial energy savings.

The agitators are running at 132 kW, or even lower, which proves that the hydraulics are excellent. The Scaba agitators operate smoothly and with a very low vibration level.