CANE SUGAR PRODUCTION IN AUSTRALIA¹

Sugar cane is one of Australia's largest farm crops, with up to 30,000,000 tonnes crushed annually, between June and December. Most cane is grown in Queensland along the east coast, from Nambour² to the Atherton Tablelands

The production of sugar, can be quite complicated, but can be broken down into 4 stages

Stage 1 Crushing

The production of sugar begins with the harvesting of sugar cane³. The cane stalks are cut into lenghts of aproximately 20 cms and are called "billets". The billets are transported to the mill, either by truck or light rail.

Once reaching the mill they are crushed through a series of large rollers, this produces raw juice (brown in colour) and cane fibre called bagasse⁴.Very fine bagasse is called bagacillo⁵.
This bagasse is burnt by the mill in large boilers,to produce high pressure super heated steam to run turbines and produce electricity. The exhaust steam is then used in other stages of production

Stage 2 Clarification and Evaporation

The raw juice is tested for sugar content and this result is used in an equation that is used to pay the farmers for their cane.

The raw juice is heated to 75 degrees centigrade to melt any starch and is allowed to sit, or "incubate" for about 30 minutes. Once incubation has taken place, a lime solution is added to the juice to change its pH. Sugar is naturally acidic and breaks down quickly so it must be made alkaline. The juice is again heated to over 100 degrees centigrade. This juice is now now called secondary juice.It is briefly exposed to atmosphere to "flash", this allows any gases to escape the juice. ⁶

The juice is now allowed to settle.Adding small ammounts of floculant⁷,helps the dirt to settle out. Clear pale yellow juice is taken of the top of the tank.The mud is taken out of the bottom of the tank and further processed. Mud is a mix of dirt,sand and sugar juice.
The mud is mixed with bagacillo and put over a filter. Filters are large rotating drums. By using vacuum, the mud is picked up,water is sprinked over the filter and washes any sugar left in the mud out. This liquid is run back to the secondary juice and reprocessed.

The clear juice is now called ESJ or Evaporater Supply Juice. The ESJ is passed through a series of vessels called effets⁸

These are large upright cyclinders, with a series of tubes in the bottom third. As the juice boils through the tubes vacuum and steam are applied to the vessel to lower its temperature so as not to burn the sugar in the juice. When the juice boils steam (water) is given off and the juice begins to concentrate. After passing through 4 or 5 effets, the juice, now called syrup is stored in a tank, ready to be boiled into sugar.

Now things get complicated.

Stage 3 Sugar Boiling

We cannot get all the sugar our of the syrup in one go, therefore we work in stages, taking out some sugar from the syrup, then taking more from the resultant molasses, and finally a third boiling to remove more. Each stage takes approximately twice as long as the previous one, as there is less sugar available in the resultant molasses.

There are three types of sugar produced on the pan stage;

A Sugar, this is made by "footing" a pan,- under vacuum a set ammount of small crystals - Magma⁹ is drawn into the pan. The footing is then feed with syrup until the crystals grow to the right size ¹⁰.

The crystals are in a mix with molasses, This mix is called Massecuite¹¹.The massecuite is dropped out of the bottom of the pan into Receivers, to await separation.

A sugar produces A sugar crystal and A molasses

B Sugar, this is the same as A sugar except the pan is fed on A molasses and takes twice as long to grow the crytsal, because we have already removed some of the sugar.

B sugar produces B sugar crystal and B molasses.

Lastly, we come to C sugar,

A set amount of A molasses is drawn into a pan and boiled until it is very thick,this is then seeded with minute sugar particles and allowed to grow, fed on B molasses until the crystal reaches 0.2-0.3mm. This can take up to seven hours.

Once the C sugar has been dropped into recievers, it is allowed to continue to growing for 24 hours by pumping it into Crystalisers. These are large stirred holding pans. As the C massecuite cools, it concentrates, helping the crystal to develop.

To separate the crystal from the molasses,the sugar isFugalled¹²

Stage 4 Fugalling

Massecuite from the A and B recievers is fed into Fugals in batches.

A fugal is similar to an upright spin dryer.The massecuite is spun against fine sceens, the molasses is spun out and piped to holding tanks.The sugar crystal is dropped out of the fugal and taken to a large tumble Drier and dried.

A and B sugar are mixed and now called Shipment Sugar,now ready to be stored for further processing in a refinery

C sugar is made by briefly reheating C massecuite from the crystalisers and feeding it into continuous fugals. The molasses spun off is called C molasses or final molasses and is used in making rum or for stockfeed.
The crystal or C sugar is mixed with a little water, to form a thick cystalline paste, and pumped back to the pan stage to be used as footings for A and B sugar. This paste is called Magma.

And Finally

Shipment sugar is transported to bulk storage,to await transport, for export or to refineries for further processing into white sugar, such as table sugar or caster sugar, and fancy sugars, such as golden syrup or coffee crystals