The Final Processes

CLARIFICATION AND EVAPORATION

Juice from the milling train is limed to raise the pH to stop sugar deterioration, and heated up to 103C. A chemical reaction between the phosphate in the juice and the calcium in the lime helps to clarify the juice and allows the mud and other impurities to settle out and a clear juice for making sugar crystals results.

No 1 evaporatorAfter the mud settles in the clarifier, the mud is processed in rotary vacuum filters. These filters suck all the juice out of the mud and wash the mud cake with water. The mud is then conveyer to a hopper until it can be spread back on the cane fields.
The rotary mud filter
The clear clarified juice is approximately 15% sugar; the water is them removed from the juice by steam and vacuum and is it concentrated to a heavy syrup by large pressure vessels called evaporators that boil out the water in the juice to a syrup that is approximately 70% sugar. This syrup is pumped to the pan stage for controlled batch crystallization. At Rocky Point, 5 stages are used and each vessel is under a lower pressure. As such 1 tonne of steam will evaporate 5 tonnes of water out of the juice. Approximately 65 tonnes of steam per hour is used to make sugar from the cane.

Checking (proofing) one of the pans

 

CRYSTALLIZATION

Sugar crystals are grown in vessels called pans. The pans are seeded with very small crystals and then these crystals are further grown until they reach about 1 mm in size. The mixture of sugar crystals and molasses is known as massecuite.

Slow Moving Coils of the Crystaliser

The operators who grow the sugar crystals are know as Sugar Boilers, they are highly skilled in their craft and it takes several years of training to be able to boil sugar effectively.

 

CENTRIFUGALS
After the sugar boilers have grown the crystals to the required size the massecuite is then transferred to the centrifugal station. The high grade Fugal station
The centrifugals or "fugals" for short are baskets that spin up to 1000 rpm and separate the molasses from the crystals. The fugals work in batches or charges to process the massecuite. Each charge is approximately 1.5 tonnes of massecuite. Each cycle of the fugal is 2.5 minutes. Approximately 25 tonnes per hour of sugar is produced at Rocky Point.

The wet sugar from the fugals is then tumbled dried in a rotary dryer; the dry sugar is conveyed to the sugar bins waiting for the sugar trucks to take it to the refinery.

 

QUALITY CONTROL

One of the Mills Chemists analysing pan productsIn the laboratory, the chemist analyse the sugar cane for sugar content. This allows the calculation of CCS for payment of cane to growers.

Also the chemists analyse products from all stages in the production process so that the mills mechanical and process engineers are able to make changes and maximise to recovery of sugar from the cane and produce a quality product.

 

The final result from sugar cane to raw sugar