UCL’s Voyage into Sugar Production
The decline in demand for wattle extract products in 1958 caused the company to look at the viability of using its factory downtime in the winter months to manufacture sugar and this was initially done on a trial basis in the extract factory in Dalton. Following government approval, a 54 TCH sugar cane factory was erected in 1966 which incorporated the first bagasse diffuser to be used in South Africa. By 1975 the facility was expanded in 2 stages to 120 TCH and a BMA “chain type” cane diffuser replaced the original bagasse diffuser. The final expansion to 150 TCH took place at the end of 1990 increasing the annual crush capacity to approximately 775000 tons of sugar cane.
Delivered cane is massed using 2 concrete mass bridges at the factory entrance. Current facilities include an overhead gantry fitted with bundle cranes and a Hilo spiller/loading table system (the latter commissioned in 2007) which feed cane via a sloping feeder table into a rock and sand removal plant. This equipment removes approximately 5000t of unwanted stones, soil and trash in a typical season.
Cane is prepared using a set of leveller knives followed by a set of cutting knives which feed a steam driven “Tongaat” shredder. Shredded cane is fed via computerised cane sample station to the diffuser. The original BMA chain diffuser was modified to the Bosch chainless type at the start of the 2006 crushing season. At the diffuser discharge, the bagasse (exhausted shredded cane) is fed via Mirlees Watson mills to the boiler house via a series of conveyors. This pressed wet fibre or bagasse has a moisture content of about 51% and is used as boiler fuel. Press water from the mills is returned to the diffuser to maximise the level of sucrose extraction. The boiler house at UCL has 4 boilers which provide steam to both the sugar and extract factories. Coal, bagasse and spent bark from the extract factory can all be used as boiler fuel depending on the time of year and process requirements. High pressure steam from the boilers is used to drive the Allen and Siemens steam turbine alternator sets for electricity generation. Supplementary electricity for process equipment is supplied via a 3500 kVA Eskom supply. As protection against Eskom electricity load shedding and interruptions a 2200 kVA back-up diesel driven generator was installed in 2008. Scalding juice for cane preheating inside the diffuser is heated in 4 shell and tube heaters. Dirty, mixed juice from the diffuser exit is massed and stored in a tank. 4-GEA plate heat exchangers are used to heat the juice in preparation for clarification. At this point acid, lime and flocculent are added as juice settling aids. The juice is flashed in an elevated flash tank to remove air bubbles that would otherwise hinder the clarification process. UCL utilises 2 clarifiers. Clear juice overflow from the clarifiers passes to a small storage tank prior to being heated in another GEA plate heat exchanger prior to evaporation. Eimco, rotary vacuum filters are used to extract the usable juice from the wet sediment that comprises the clarifier underflow. Filter cake from the filters is screwed to a storage bin and taken away by farmers who use the material to supplement fertiliser requirements on their cane fields.
Evaporation of the clear juice to the pan feed liquor, called syrup, is performed in quadruple effect evaporator trains. Syrup is then pumped to the highest point in the factory as processing of this viscous material is largely gravity aided from this point onwards, to where it is stored. The pan floor which is regarded as the heart of the factory comprises batch pans of varying sizes. It is at this point in the process that the sugar crystals are grown under vacuum in the pans. Heat and time are used together with vacuum to optimise crystal growth. Each pan circuit discharges massecuite into a separate strike receiver prior to further crystallisation (sugar crystal growth). Separation of massecuite into sugar and molasses is performed in BMA centrifuges. Raw ‘A’ sugar is dried to under 0.1% moisture in rotary drum dryers prior to storage in a concrete silo which can discharge for despatch into road or rail tankers or fed to the packaging plant via conveyor where sugar is bagged into 12.5kg, 25kg or 1 tons bags. ‘B’ and ‘C’ sugar together with ‘A’ and ‘B’ molasses streams are recirculated within the boiling house pan floor system in order to maximise sugar recovery. Final or ‘C’ molasses is massed prior to being pumped to storage tanks from where it is despatched to customers.<\p>
UCL has been manufacturing VHP raw sugar since 1966 when its newly commissioned sugar factory opened its doors for the first time. Since those early days, the factory has been expanded several times and currently produces, on average, 90 000t of VHP sugar annually. Our sugar operation is characterised by perennial industry leading performances in terms of recoveries and sugar quality, primarily because of the high quality bi-annual midlands sugar cane being milled in Dalton. Sugar is manufactured from early March through to December of each year during which approximately 2 500 tons of sugar are produced weekly. UCL serves the dual purpose of being the manufacturer of choice in our region, offering a reliable and value adding process to growers, while also manufacturing high quality products aimed at satisfying the diverse needs of our affiliated consumers. The company’s success has been founded on creating lasting relationships with all stakeholders based on sustainability and mutual benefit. These principles underline our efforts at establishing new partnerships in the South African sugar market.
- Polarization greater than or equal to 99.30 degrees.
- Moisture less than or equal to 0.1%.
- Colour of RAW SUGAR less than or equal to 1,500 index points on the ICUMSA scale.
The RAW SUGAR is currently being packed in 12.5kg, 25kg and 1 (one) ton polypropylene bags, with a plastic inner lining.