Tate & Lyle Sugar Refining

Brief History - Tate In 1859 Henry Tate became a partner in John Wright & Co. sugar refinery, Liverpool. By 1869, he had gained complete control of the company, and renamed it to Henry Tate & Sons 1897 founded the National Gallery of British Art

Brief History - Lyle Abram Lyle with four partners purchased the Glebe Sugar Refinery in 1865 In 1881 he bought two wharves in East London to construct a refinery. The site happened to be 1.5 miles (2.4 km) from the sugar refinery or his rival, Henry Tate. In 1921 two rival sugar refiners, Henry Tate & Sons and Abram Lyle & Sons merged to become Tate & Lyle.

Raw Materials Sugar cane is a tropical grass which grows up to five metres high and requires copious amounts of sun and water. Sugar cane is grown from short lengths of cane called 'setts‘ The refinery imports raw cane sugar from African, Caribbean and Pacific countries.

Milling Once harvested, the cut canes must be processed as quickly as possible to conserve the sugar and to prevent microbial degradation. This first stage of processing is carried out in factories close to the growing area. The canes are cleaned, crushed and shredded, then sprayed with hot water to extract the juice. The juice is filtered, concentrated by evaporation under vacuum, and crystallised, before being removed from the remaining mother liquor by centrifuge.

Transportation At this point, the sugar is partly purified and in a concentrated, crystallised, microbiologically stable form suitable for bulk handling, storage and transport to refineries around the world. The raw cane sugar is despatched by bulk carriers to refining plants usually located close to deep water terminals such as at Tate & Lyle Europe's refinery in London. The storage shed at our Thames refinery can hold up to 70,000 tonnes – sufficient to supply the refinery for about 20 days of normal production.

Refining Affination and Melting Carbonatation and Filtration Decolourisation Evaporation and Crystallisation Separation and Drying Product Distribution Bulk Storage Retail and Industrial Packing Industrial Liquid Products

Flow Sheet

Affination and Melting The raw sugar is further purified by mixing with a heavy syrup and then centrifuged clean. This process is called 'affination’. This centrifugal force separates the raw crystals from the impure raw syrup. The sugar purity of this liquor is about 97-99%.

Carbonatation and Filtration Milk of lime (slaked lime) is mixed with the raw melter liquor. Carbon dioxide recovered from our boiler flue gas is bubbled through the mixture. The carbon dioxide reacts with the lime to form chalk which attracts the waxes, gums, resins and other impurities in the liquor at a temperature of 80-85°C. There are 19 filter presses working in parallel through which the liquor is now filtered. This removes the chalk and about half of the colour, together with virtually all the fine debris and insoluble matter.

Decolourisation The pressed liquor from Filtration is passed through four guard filters containing multi-media filter material. This stage is to protect styrene resin from calcium carbonate which may have been carried over by filtration. In the second tank there is a double passage of styrene resin which removes colour molecules. This decolourised solution is known as fine liquor.

Evaporation and Crystallisation All the previous refining processes have been carried out on liquors that are 60-67% concentration. An evaporator is used at this stage to remove some of the water prior to crystallisation. The resulting syrup, which is known as evaporated fine liquor, is about 74% solids. The fine liquor is fed into large vacuum pans where the sugar crystals are grown. The syrup is heated indirectly by steam to about 80°C where it boils due to the vacuum applied to the vessel. The use of a vacuum and the resulting reduced temperature helps to minimise the creation of colour during the process.

Separation and Drying The mixture of sugar crystals and liquor (massecuite) is centrifuged to separate the white sugar crystals. The separated white sugar crystals discharged from the centrifuges still contain up to 1% moisture. This is removed by passing the sugar either into a rotating two-stage dryer or a fluidised bed dryer, through which filtered, heated air is passed. The moisture level of the sugar at this stage is about 0.06%.

Product Distribution Other processes such as milling, sieving and mingling are used to make Icing Sugar, Caster Sugar and Brown Sugars (part of the Speciality Products section, which also includes syrups and treacles).

Bulk Storage Storage silos of 2,500 tonne silos are the principal means of storing Granulated Sugar. Inside the silos, temperatures are maintained at a constant level while sugar conditioning (final moisture removal with air) takes place to prevent caking.

Retail and Industrial Packing Sugar of the appropriate grade is supplied to all the packing lines, using dedicated feed routes and, in most cases, dedicated conditioning plant. Conditioning air (filtered and temperature-controlled) is passed through the stored sugar to ensure it retains its free-flowing characteristics. All packing lines are equipped with rare earth magnets, in-line metal detection and check-weighing equipment. Extensive quality assurance checks are carried out by each of the operating teams on the sugar, packaging materials and machine operation, as well as on the finished product.

Industrial Liquid Products A substantial portion of the refinery's output is sold as liquid sugar. This can be in the form of dissolved granulated sugar, fine liquor or intermediate liquors from the various crystallising stages. All of these products are stored in steam sterilised tanks before being loaded into road tankers for onward delivery.

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