Affination
The raw sugar is stored in large warehouses and then transported into the sugar refinery by means of transport belts. In the traditional refining process, the raw sugar is first mixed with heavy syrup and centrifuged to wash away the outer coating of the raw sugar crystals, which is less pure than the crystal interior.
Purification
The remaining sugar is then dissolved to make a syrup (about 70 percent by weight solids), which is clarified by the addition of phosphoric acid and calcium hydroxide that combine to precipitate calcium phosphate. The calcium phosphate particles entrap some impurities and absorb others, and then float to the top of the tank, where they are skimmed off.
After any remaining solids are filtered out, the clarified syrup is decolorized by filtration through a bed of activated carbon or, in more modern plants, ion-exchange resin
Sugar House
The purified syrup is then concentrated to supersaturation and repeatedly crystallized under vacuum to produce white refined sugar. As in a sugar mill, the sugar crystals are separated from the mother liquor by centrifuging. To produce granulated sugar, in which the individual sugar grains do not clump together, sugar must be dried.
Sugar Drying and Storage
Drying is accomplished first by drying the sugar in a hot rotary dryer, and then by blowing cool air through it for several days in so-called conditioning silos. The finished product is stored in large concrete or steel silos. It is shipped in bulk, big bags or 25 – 50 kg bags to industrial customers or packed in consumer-size packages to retailers.