• About Sugar
• Products
• How Sugar is Made
  • In the Canefield
  • At the Sugar Mill
  • At the Sugar Refinery
• Types of Sugar
• Sugar and the Environment
  • Carbon Dioxide Gas Recovery
  • Chelsea and the Environment
  • Recovery of Good Carbon from Waste Water
  • Waste Management
  • Water Treatment
  • Energy Reduction Projects
  • Chelsea Heritage Estate
  • Chelsea Ponds
• Health and Wellbeing
• Common Questions About Sugar

At the Sugar Refinery

Refining sugar is a series of processes designed to clean and purify the raw crystals. The crystals are re-formed into the various types of sugar you use in your home.

Raw sugar is shipped to the wharf at the Chelsea Refinery in Auckland in loads of up to 31,000 tonnes, these are received in bulk shipments every 5-6 weeks.

Once unloaded the sugar is stored in a huge warehouse that can hold up to 42,000 tonnes. (Internally at Chelsea Sugar, the bulk sugar storage is also called the sugar mountain)

The raw sugar is fed by conveyor into a mixer where the crystals are mixed with hot sugar syrup, this softens the outside coating on the crystals.

The thick brown mixture is spun in a centrifugal (like a giant washing machine on the spin cycle), and sprayed with clean, hot water to remove colour and impurities from the surface of the sugar crystals.

Next the raw sugar crystals are dissolved in hot water which forms an amber coloured liquid, called melted raw liquor. The liquor is passed through a screen to remove impurities such as small pieces of sugar cane.

The liquor is pumped into vessels called carbonation tanks. In the tanks, milk of lime is added and carbon dioxide gas is bubbled through the liquor. The lime and gas react together to form a chalk to which previously dissolved impurities cling.

The impurities can be filtered out when the mixture is passed through very fine cloth filters. At this stage the filtered raw liquor is still amber coloured.

To make the raw liquor clean enough to form into white sugar crystals, it is passed through a carbon decolourising station which absorbs the colour.

The sugar solution passes through an Ultra Violet Light steriliser to make the sugar sterile. The clean sugar solution is then pumped into a large vessel where it is boiled under vacuum to remove extra water, where crystals are formed. This mixture of sugar crystals and syrup is again spun in a centrifugal and sprayed with hot water to clean the sugar.

From here the crystals are dried and conditioned by blowing dehumidified air through the sugar, this keeps the sugar free flowing. The syrup removed at this stage can either be returned to the beginning of the process or be made into soft brown sugar, golden syrup or treacle.

After drying, the sugar is graded using different sized mesh screens. Once graded, the sugar is packaged into a wide range of familiar Chelsea sugar packs.

Packaged Chelsea Sugar is stored in the warehouse, from where it will be delivered to supermarkets, food & beverage manufacturers or exported overseas.