"Refining" could be looked upon as the preparation of any grade of sugar fit for human consumption. This, however, would be to use the word in its broadest sense and would encompass technologies discussed in separate papers.
For instance, the low natural colour in beet juice makes it possible to produce an acceptable refined sugar in one operation. Similarly it is possible to produce a food grade low colour sugar, often called 'blanco directo', in a cane sugar mill.
These notes deal with the production of low colour white sugars from cane, either in a "white end" processing all of the production from a cane sugar factory or in an autonomous refinery.
There has been a clear trend in recent years towards the production of lower colour sugars at cane factories. In part this is a response to the market but it is also the result of recognising the lower production costs of doing so. The problems arising from this trend are associated with handling the product sugar economically.
RAW SUGAR DELIVERY
Raw sugar is usually delivered to an autonomous refinery by sea and, in a modern plant, is unloaded to store by dedicated facilities.
The particular nature of raw sugar is often not well understood by unloader manufacturers or store designers but SKIL engineers have experience of the design, maintenance and operation of such facilities. These include the recent 9,000 tpd offloading, 100,000 ton storage system for the new Jeddah refinery.
There are six discrete stages of the refining process with various options available at each stage:
Affination washes away adhering low grade syrup from the raw sugar before the crystals are melted.
Recovery separates recoverable sugar from the low grade syrup. For a white end this can be accomplished within the raw house.
Clarification removes turbidity from the raw liquor. Carbonatation and phosphatation followed by filtration are both used for this duty but each has its pros and cons which need to be carefully assessed.
Decolourisation improves the colour of the liquor and utilises either activated carbon or ion exchange. Again there are pros and cons to each method that have to be considered.
Crystallisation is used to recover the product sugar and, as with raw sugar production, the selection of the best boiling scheme - possibly including modern continuous pans - is important.
Curing and Drying is similar to the raw sugar process except that care is required to ensure that the sugar conforms to market requirements in terms of hygiene, particle size and shape and similar parameters.
SKIL has all the resources needed to provide operational assistance to existing refineries or to create a new refinery. The work undertaken at the Singapore refinery would be typical of the former and the ultra-modern one now being built in Jeddah would be an example of the latter.
Converting a factory by adding a white end requires special considerations which encompass the energy balance in addition to the process aspects. SKIL understands these requirements and has computer models to help in this.
The packaging of the many products of a typical refinery is a subject in its own right with sizes ranging from 8 gm catering envelopes to 25 ton bulk road/rail tankers and physical characteristics ranging from icing sugar through cubes to liquid sugars and syrups. Good refinery management dictates a full knowledge of the market requirements and SKIL can frequently help with introducing modern packaging techniques.