Sugar Production from Sugar Cane
Practical Action
The primary pan is located directly above the combustion chamber. Behind and slightly above
the primary pan a secondary pan is located. A third pan is located above and behind the
secondary pan, and so on depending on the number of pans used. Hot gases from the
combustion process pass under the pans heating the juice, the combustion gasses are exhausted
to atmosphere through a chimney. Improved heat transfer can be achieved by adding fins to the
underside of the pans increasing the surface area in contact with the hot gasses.
There are two basic types of furnace, the original 'Standard Bel' furnace and the 'shell' furnace
which was developed in India during the late 1970s. The 'standard bel' is a natural draught
furnace where bagasse is burnt on a grate in a combustion chamber located below a series of
round boiling pans. There are a number of variations of this type of furnace but in all cases they
are designed to operate on dry bagasse (moisture content of 10% or less) which means having to
dry the bagasse before use. Even with dry bagasse this type of furnace often requires excess fuel
(either bagasse from another factory or wood) to complete the boiling operation.
The 'shell' furnace was developed to burn wet bagasse straight from the extraction process. The
furnace is a forced draught design using hot flue gasses (at around 500ºC) which pass over heat
exchanger tubes heating incoming combustion air to around 120 - 140ºC. Bagasse is burnt in a
heap on a fixed hearth inside a cylindrical brick built combustion chamber lined with firebricks.
The bagasse is fed though a chute just below the throat allowing it to fall through hot
combustion gases which pre-dry it before burning. With careful operation this type of furnace
will not require additional fuel to complete the boiling operation.
The transfer of juice from one pan to the next is controlled by valves through overflow pipes, or
the juice can be ladled manually. The massecuite from the final pan is usually too viscous to
flow easily so it is ladled into buckets and transferred to the next stage of production.
Sugar production methods
Lump sugar and syrup production
Although lump sugars and syrups are produced by the medium and large-scale sector they are
ideally suited for production on the small-scale. Both lump sugars and syrup can be produced
using the same equipment so a single factory can be used to manufacture either product to suit
demand. The size of the plant will depend on the local situation. Where there is sufficient cane
grown for a substantial part of the year it is common to have a permanent factory centrally
located. In areas where cane is grown in small plots harvested over short seasons, it is more
common to have semi-permanent or temporary factories set up close to the point of harvest.
There are four stages of production
Extraction of juice from the cane
Clarification of the juice
Boiling of the juice
Moulding and packaging
Extraction
Small-scale extraction is done using small two or three-roll mills driven either by draught animals
or small engines. The larger small-scale and the medium-scale factory will use a single
motorised three-roll mill.
Juice treatment
Juice should be filtered through a cloth before boiling in order to remove any solids such as dirt
or particles of cane.
Large-scale sugar processors add lime to the juice in order to coagulate impurities which then
settle out. (This is rarely done at the artisanal level.) The juice is then neutralised with sulphur
dioxide. Small-scale producers add a variety of clarificants to the juice including wood ash. All
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