The sugar production process involves the extraction of sucrose, commonly known as ‘sugar’, from vegetables. Sucrose is present in many plant species, but the main sources used in industry are sugar cane (containing 7-18% sucrose by weight) and sugar beet (containing 8-22% sucrose by weight). Sugar production from other sources, such as maple and date palm, plays a marginal role.
The method of sugar production varies depending on the raw material, the parts of the plant used for extraction and the level of impurities to be removed or treated.
The sugar production process also produces a by-product called molasses, which is mainly used as cattle feed or in distilleries as a component of the fermentation process.
Bellin’s progressing cavity pumps and lobe pumps provide effective solutions in all stages of the sugar production process, from the handling of molasses or pulp to clarification, concentration and crystallization processes.
The processing of sugar cane, the cut cane is chopped in mills, and the juice is then pressed out. This produces a fibrous residue called the bagasse, which is mainly used as fuel or in the pulp industry.
An direct consumption white sugar can be manufactured from concentrated cane juice if sulfur dioxide (SO2) or carbon dioxide (CO2) is used in conjunction with lime i.e. the sulphitation or carbonation process. The sulphitation process can be carried out either as an phosphforic acid depending on whether the sulfur dioxide (SO2) or lime is added first. In the carbonation process, first quick lime and carbon dioxide (CO2) are produced in a limekiln. The quick lime is mixed with water to produce lime milk and added to the juice. The lime is precipitated with carbon dioxide (CO2) in two steps, 1st and 2nd carbonation. Before concentrating the juice it is often decolorized by adding (sulfur dioxide (SO2)).
In the evaporating station, the thin juice is concentrated by heating in a multistage process to a dry matter content of up to 70 %. A viscous golden syrup is formed with a sugar content of 65 – 80 %. The waste steam produced during this process is reused to warm the raw juice and heat the cooking equipment in the sugar house.
The syrup is boiled in the vacuum pans, crystallized and separated into white sugar and remaining sugar syrup.
The crystallization step i.e. boiling, takes place in a vacuum pan: a large closed kettle with steam heated pipes. The mixture of crystals and mother liquor from a boiling, known as ‘massecuite’, is dropped into a receiving tank called a crystallizer where it is cooled down and the crystals continue to grow. This also releases the pan for a new boiling. From the crystallizer the massecuite is fed to the centrifuges.
In a raw sugar factory it is normal to conduct three boilings. The first or ‘A’ boiling produces the best sugar which is sent to storage. The second ‘B’ boiling takes longer and the retention time in the crystallizer is also longer if a reasonable crystal size is to be achieved. Some factories re-melt the ‘B’ sugar to provide part of the ‘A’ boiling feedstock, others use the crystals as seed for the ‘A’ boilings and others mix the ‘B’ sugar with the ‘A’ sugar for sale. The ‘C’ boiling takes proportionally longer than the ‘B’ boiling and considerably longer to crystallize. The sugar is usually used as seed for ‘B’ boilings.
The final raw sugar is stored as a sticky substance. It could be used at this stage, but tends to get dirty during storage and has a distinctive flavour. Therefore, it is refined once it arrives in the country where it will be used. Moreover, since not all sugar can be extracted from the juice, a sweetish by-product called ‘treacle’ is formed. Molasses is widely used as cattle feed or in distilleries as a component of the fermentation process.