Raw Sugar - Storage

Raw sugar is stored in high capacity warehouses (silos). These silos are placed: at the sugar mill; at the harbour for loading the ships; at the harbour at the ships discharging point; at the refinery, if the refinery is not placed near the harbour. In this last case, raw sugar is transported in bulk by lorries, of about 25 ton, by railway or by barges.
Raw sugar warehouses are normally of chapel type. To load the warehouse the sugar is discharged by band conveyors placed at the top of the building. In some cases raw sugar is stored using a high speed belt conveyor that projects sugar forming stacks.
In the refinery warehouses raw sugar is stored before refining. Store time must be kept minimal, and a maximum of six months must not be exceeded.

Loading Raw Sugar into the warehouse
(Guatemala 2005 - Photo Luis Bento)

An important factor to evaluate the deterioration rate of a sugar during storage, is its moisture in relation to its polarization. This evaluation is done through the security factor - SF. This factor is obtained by the formula:

 SF  =  % of Moisture / (100 – Pol)

 For SF values between 0,25 and 0,33 raw sugar is in an unstable zone.
Raw sugars with SF values higher than  0,33 must be refined as soon as possible. These raws can suffer sucrose degradation rapidly.
For SF values lower than 0,25, raw sugar is in a safety zone and its storage period can be long (Chen, 1993).  

Bibliography

Chen J.P.C., 1993, Raw Sugar Quality Criteria, in Cane Sugar Handbook,
          Ed.J.P.C.Chen, C.C.Chou, Pub. John Willey &Sons, 12a ed, 21-39
Meadows D., 2007, Drying and storage of raw sugar, in Cane Sugar Engineering, Peter
          Rein, Verlag Dr.Albert Bartens, Berlin, 467-482

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