Ben Eastick Written by Ben Eastick

Producing sugar crystals at the mill

Our sugarcane journey continues as we take you on a journey from the field to the mill. This step in the path to the manufacture of pure sugars in bulk for industry involves a fascinating dance of careful science and bulk industrial equipment. Let’s see what happens next.

A process steeped in history

Did you know that the heart of the sugarcane refining process dates back hundreds of years? Innovations such as those in 1846 by Norbert Rillieux, who invented the evaporator for sugarcane, have improved and optimised a long-standing method of extraction and refining.

Producing sugar crystals

To produce sugar crystals the mill follows multiple process steps, from the arrival of the sugar cane to the point it gets shipped out in bulk loads to white sugar refineries. Today we’re covering this process.

Harvested sugarcane arriving at the mill for processing.

Machinery used in the delivery and processing of the harvested sugarcane.

By the time the sugarcane arrives at the mill, it’s already been separated into different parts. The sugar cane arrives at the processing mill without leaves, removed by cutting using harvesters. The stalks are washed, cut up and shredded and juice is pressed from them using high-pressure rollers that are capable of the extreme loads required to extract all the juice.

Steam is used to heat industrial evaporators.

Crushed canes leave a fibrous material called bagasse.

Hot water is added at this stage, helping to improve juice extraction. At this point, the remaining dry stalks, which are known as bagasse, are often burnt in the mill’s boilers to produce sustainable electricity or used as feedstock for other industrial processes. This recycling of all parts of the sugarcane plant helps to make the manufacture of pure sugars even more sustainable.

Juice Purification

With the juice extracted, it’s time to make it ready for later stages and sale as a final sugar product. At this stage, the extracted juice is yet to be purified. The sweet natural juice is heated to 80°C and lime is added to neutralise impurities. Fine fibre particles form as scum on the surface of the juice, with other mineral matter, flocculate to the lime and settle as sediment.

Juice heaters are used in the purification stage.

These solids are filtered from the juice and returned to the cane fields as a natural fertiliser – another great example of reusing what would otherwise be waste to improve overall sustainability.

Cane juice with lime added to remove impurities through flocculation.

Evaporation

Once the juice has been purified, it’s time to reduce its volume. This stage helps to reduce the juice down into a thick, amber liquid. Industrial evaporators boil the juice in a vacuum of between 70°C and 130°C for up to two hours. This evaporates the natural water in the extracted juice, leaving a smaller volume of denser juice remaining.

Industrial crystallisers.

Crystallisation

We’ve reached an important step in the journey towards the final saleable cane sugar: crystallisation.

To initiate crystallisation, the evaporated amber juice we produced in the last step is seeded with tiny sugar crystals and boiled once more under vacuum. It’s this seeding process that allows the crystals to grow in the mixture into a richly saturated massecuite syrup. It’s at this step that the signature flavour, colour and aroma of molasses form.

Sugar separation

The massecuite syrup is spun at 1,050 rpm for two minutes to separate the crystals from the liquid. The separated syrup still contains a lot of sugar, so it’s spun a varying number of times. Different amounts of spinning help to produce the different sugars with their signature colours, such as dark Demerara which is spun less than golden granulated sugar.

Crystals and syrup separation 1,050 rpm.

The first and second spins produce dark and light muscovado sugar. The third and fourth spins produce Demerara and golden granulated sugars, with the lighter sugars being shipped for white sugar refining.

Industrial centrifuges used for sugar crystals and syrup separation.

Drying, Sieving & Bagging

Once the sugar crystals are separated, it’s time to pass them through drum rotating driers for cooling. Special sugars are passed over a vibrating screen and through a rare earth magnet to remove foreign particles before being packed into bags. With that important step complete, raw sugar is loaded into lorries for delivery to the port terminal for shipment to markets across the world.

A 25kg bagging line preparing crystalline sugar for transport.

With the production of sugar crystals complete, bulk shipments are delivered to Ragus where pure sugar manufacture begins at scale for our industrial customers. Find out more about ordering bulk pure sugars for your application by contacting our customer services team by emailing enquiries@ragus.co.uk. To see our latest news regularly, follow Ragus on LinkedIn.