Sugar Production from Sugar Cane
Practical Action
Screw expellers
Screw expellers are not commonly used in
the small-scale sugar industry although they
are more efficient than roll mills. Typically a
single expeller will have the same extraction
efficiency as a three or four three-roll mill
tandem. Their use in the small-scale sector
has been limited to experimental machines
which have proved to be unreliable thus
requiring more maintenance.
Figure 3: A simple open pan used for
Furnaces
processing the juice extracted from the sugar.
Furnaces for open pan boiling use dried
Photo: Neil Cooper / Practical Action.
bagasse as fuel but can vary in design and
size to suit local conditions and preferences.
The following section describes a range of
basic designs that are used in small to medium-scale factories.
Simple temporary single-pan furnaces
The most basic design, common in many countries, consists of a furnace built into the ground
with a small brick or block wall (100 to 150mm high) placed around the top to ensure a level
flat surface to support the pan. If bricks or blocks are not available then the wall can be built
from mud and stone but care is required to ensure that the top of the wall is level and flat.
The furnace can be either round or rectangular to suit the pans used. A round or circular
furnace is the most efficient design but the ease of manufacture and cost of the pans often
dictates which type of furnace design is used.
Two holes positioned opposite each other are required, one to feed bagasse into the furnace and
the other to exhaust smoke and other products of combustion.
An improvement to this design is to build a chimney at the exhaust end which should improve
the performance of the furnace and help ensure that smoke and particulates produced during
combustion are removed away from the sugar processing area. Care must be taken when siting
the furnace to ensure that small particles of burning fuel, which can be emitted with the exhaust
gasses, cannot cause a fire risk to surrounding dwellings or buildings.
Rectangular pans are usually flat bottomed with relatively low sides. This shape does not allow
for even heating of a product and care is required when using them as burning of the product
can occur. Pans for the round furnace should be hemispherical or cone shaped. These shapes
allow for more even heating than rectangular pans but are usually more expensive to
manufacture. Cones are often used in parts of Asia for syrup production but less often for jaggery
production as the thick viscous massecuite is difficult to remove from the cone.
Simple permanent single-pan furnaces
Although similar in design to temporary furnaces they tend to be larger and are often built, or
have a large proportion of their structure, above ground. The walls of the furnace are usually
made from brick or building blocks and the boiling pans fit into the structure.
Permanent multi-pan furnaces
Multi-pan furnaces are used for the production of both non-centrifuged and centrifuged sugars.
They utilise waste heat from the boiling process to pre-heat and boil a successive concentration
of juice at progressively higher temperatures.
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