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Sugar production
Step 1. Processing raw sugar from
sugarcane
Approximately 10 percent of each sugar cane can be processed
into commercial sugar. Sugar cane consists of 70 percent water,
14 percent fiber, 13.3 percent saccharose (about 10 to 15 percent
sucrose) and 2.7 percent soluble impurities.
a. Harvesting
Mature canes are gathered manually and mechanically. Hand cutting
is the most common method, but some locations use mechanical
harvesters. Canes are cut at ground level, the leaves removed
and the top trimmed by cutting off the last mature joint. Cane
is then tied in bundles and transported to a sugar factory.
After cutting, cane deteriorates rapidly, so cane and beet cannot
be stored for later processing without excessive deterioration
of the sucrose content.
b. Cleansing and grinding
Stalks are thoroughly washed and cut at the sugar mill. Rotating
knives shred the cane into pieces, and multiple-sets of three-roller
mills grind it. The crushed canes are transferred by conveyers
from one mill to the next. During grinding, hot water is sprayed
onto the sugarcane to dissolve any remaining hard sugar.
c. Juicing
The shredded sugarcane travels on a conveyer belt through a
series of heavy-duty rollers, which extract juice from the pulp.
The pulp that remains, or "bagasse," is dried and
used as fuel. The raw juice moves on through the mill to be
clarified.
d. Clarifying
Carbon dioxide and lime juice are added to the liquid sugar
and heated to around 95 degrees Celsius. As the carbon dioxide
travels through the liquid, it forms calcium carbonate, which
precipitates non-sugar debris (fats, gums and wax) from the
juice. This precipitate, called "mud," is then separated
from the juice by centrifugation. The juice is then filtered
to remove any remaining impurities.
e. Evaporation
The filtered juice is evaporated under a vacuum, concentrated
at a low temperature, and the sugar crystallized in vacuum pans.
f. Crystallization
Inside a sterilized vacuum pan, pulverized sugar is fed into
the pan as the liquid evaporates, causing the formation of a
thick mass of crystals. The crystals are spun-dry in a centrifuge,
producing raw, inedible sugar.
A simplified flow diagram for a typical cane sugar production
plant is shown in figure...
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