The ZAFARAN granulation process uses a size enlargement process to transform molten sulphur into dense spherical solid granules. Small particles of sulphur (seed) are introduced at the feed end of the drum and are sprayed and coated with molten sulphur as the product moves toward the drum discharge. Each applied layer is cooled to solidification before another coat of molten sulphur is applied. With repeated application, bonding and then cooling of successive coats, the seeds increase in volume and weight until they reach the desired granule size, usually 1 to 6 mm in diameter. A screening process separates undersize granules from the product size granules, which allows the undersize to be recycled to the drum inlet as seeds.

Sulphur pressure to the header is provided by a vertical sulphur pump with a variable frequency driver, and the pump is mounted on a pump tank containing a constant level of filtered molten sulphur. During operation, the PLC process control system compares the actual sulphur flow rate granulator against the production rate entered by the operator and adjusts the pump speed accordingly.

Heat is absorbed from the solidifying sulphur by the evaporation of water droplets and is removed from the granulating drum by the airflow. The exhaust fan draws air into and through the granulator drum, maintaining the system under negative pressure. The incoming dry air absorbs heat as it contacts the surface of the granules and the resulting rise in air temperature is controlled by the evaporation of the cooling water sprays.

The air effluent leaving the drum contains water vapor from the evaporation process, and a small amount of sulphur particles. The exhaust air is cleaned in a wet scrubber to remove any entrained sulphur particles before discharge to the atmosphere.

Process water is introduced into the granulating drum through spray nozzles mounted on a single header extending the interior length of the drum. Water pressure is provided via a variable speed, positive displacement pump as determined by the PLC process control system. Water flow is proportioned to sulphur flow while a trimming function, using the average temperature inside the drum, modifies this ratio to maintain process temperatures at the operator-selected set point.