Main Stages of Production
The manufacturing of raw sugar from cane is a highly technical process which requires large and costly manufacturing equipment .There are eight main stages involved.
The factory takes delivery of the cane through the rail trucks and lorries through the weighbridge,which is unloaded at the cane carrier.
The cane carrier is the moving apron which conveys the cane into the factory and which ensures consistent feed to the mills by transporting the cane from the yard to the crusher. Since effective feeding of the crusher requires an elevated hopper, and the cane must be raised to this high level from the level of the yard, where the carrier is generally in a pit, the carrier always includes a sloping portion. The cane carrier consists of knives and hammers to break down the cane before passing it through to a crusher and shredder.
The crusher is the first machine applying pressure which the cane encounters on arriving at the
milling plant. It consists of a mill, generally of two rollers, which performs two main functions:
- It assures the feeding of the whole tandem
- It prepares the cane in such a way as to facilitate the grip of the rollers and the extraction ofjuice by the mills.
The objective of the shredder is to complete the preparation and disintegration of the cane, so as to facilitate the extraction of juice by the mills.
Diffusion is the phenomenon by which the cells of the cane, immersed in water or a solution of lower concentration than the juice which they contain, give up to that water or to that solution a part or all of the sugar forming the excess of concentration of their juices. This process is carried out in the Diffuser.
As its name suggests, the purpose of the dewatering mills is to further remove liquid continuing a mixture of water and juice from the baggase (fibrous cane remains). Each mills consists of rollers through which baggase passes and thus the liquid is squeezed out of it through pressure applied by these rollers.
The clarification process is where the juice is heated and lime added to control the pH of the juice and the remaining impurities removed in the form of mud and clear juice obtained as a result. This clear juice is then supplied to the evaporators.
The purpose of the evaporators is to remove the water in the juice, making its concentration more. Each vessel that the juice passes through makes its concentration (brix) more and the last vessel makes the concentration to the maximum saturation, meaning to the point where sugar crystals are about to appear. This is now called liquor and is sent to the Pans.
There are two stages of operations in the Pans. Firstly the sugar crystals are grown to a certain size, and once this is done, it is divided into parts and sent to dropping Pans where they are heated further to remove water and grown further to the required size with washing done to prevent false grains from forming before being dropped into coolers to allow the resulting massecuite to cool.
This is where the massecuite is drawn from the coolers and into centrifugals which separate the solid crystals from the liquid part of the massecuite, which is now called syrup. On the high grade side, the resulting solid crystals are end product called sugar which is then sent to the dryer with the syrup being recycled back to Pans for further processing. On the low grade side, the resulting solid crystals (known as barley) is melted to form magma and recycled back to Pans for processing. The resulting liquid is final molasses which is a by-product from which no further sugar can be extracted economically in a sugar mill.