Saturday, 3 October 2015

Night visit to Bois Rouge sugar factory

One wet and windy evening recently I found myself on a night visit to the Bois Rouge sugar factory in Saint André, one of only two sugar factories that still operate on Reunion Island.

While the adjacent rum distillery can be visited all year round, the sugar factory can only be toured during the cane harvest season, which runs from June to December.

Bois Rouge receives sugar cane from the whole of the island's east coast, from Sainte Rose to Saint Denis.

As soon as the sugar cane is delivered, the loads are weighed and sampled by an independent technical centre to assess the sugar content.

Weight and richness in sugar are determining factors in fixing the sugar cane buying price.

The unloaded sugar cane then goes into a shredder, a machine composed of 144 hammers mounted on a shaft. The hammers pulverise the cane onto a huge anvil in order to ensure clear passage for the cane fibre into the other machines.

Once the sugar cane juice has been extracted, it is clarified and decanted by being preheated to 105°C, and lime is added to stabilise its pH at 7.5. During the decantation process a flocculant polymer is added to obtain clear juice.

The leftover filtration residues following decantation are known as filter cakes. These cakes are rich in phosphates and are given back to the cane planters who use them as fertiliser.

The clear juice is preheated to 120°C and enters a 6-effect evaporation station. Output steam from the power station is introduced into the first evaporator body. As it passes through the evaporators the clear juice is concentrated into a syrup known locally as Sirop La Cuite.

Next the syrup is crystallised in a cooking vacuum pan. The operators feed in a certain quantity of syrup and then add a few sugar grains in order to set off the crystallisation process. At the end of this process a crystallised mass is obtained, which is continuously mixed enabling the sugar contained in the original liquid to settle on the crystals and ensure greater crystal growth.

A centrifugal process separates the original liquid from the sugar crystals. In order to obtain high-quality crystals superheated water is used to dissolve the envelope of the original liquid surrounding the crystals. Finally, after the centrifugal process the original liquid undergoes two other crystallisation cycles in order to extract as much sucrose as possible.

At the end of the three successive crystallisation, mixing and centrifugation cycles, a liquid called molasses is obtained, which is low in sucrose content. Molasses are transferred to the distillery for rum and alcohol production.

one of the workers

in the control room

Since 1992 in addition to its basic manufacturing process, the Bois Rouge sugar plant has been developing consumer sugar units for brown and refined white sugar.

sugar sample for laboratory testing 

These high added-value products require specific manufacturing processes all the way through the different production stages.

some different types of sugar
- the finished product !

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