The rheological properties and boiling visualisation of hard-to-boil massecuites.

Abstract

In the sugar milling industry, sugar cane is crushed and the juice obtained is processed, to first yield a syrup, and further to produce massecuite. Massecuite is a combination of sugar crystals and mother liquor and when separated from the massecuite is known as molasses. Massecuite is boiled to reduce the water percentage of the total mixture, to promote the growth of sugar crystals. Once boiled, it is then transferred to a centrifuge where the molasses and sugar crystals are completely separated. During bad weather conditions, the harvesting process of sugar cane is delayed. Due to these delays, bacterial infections occur within the cane that causes a deterioration effect on the juice extracted. The massecuite produced from this cane is known as Hard-To-Boil (HTB) massecuites. The absolute mechanism behind HTB massecuites is still unknown. When exposed to the standard boiling process, HTB massecuites require lengthily boiling periods and yield lower levels of sugar, when compared to good massecuites. Once the mixture has completed the boiling period, a thick, viscous solution remains inside the boiling chamber. HTB massecuites produce an elastic and stringy product that is difficult to remove from a boiling pan. Specific cases, in certain mills, produced an extremely high tensile material that could be stretched as if it were a rubber band. The mentioned scenarios have resulted in the clogging of industrial machinery, as well as a less efficient process of producing sugar. A hypothesis was formulated to describe the relationship between the viscoelasticity of the HTB massecuite, and the boiling properties. A comparative study between standard and HTB massecuites was performed, to test the hypothesis. A single tube vacuum pan, with open front face to view boiling and bubbling, as well as evaporation rates were noted for both good and HTB samples. The nature of HTB samples was determined purely based on what factories and industries considered ‘’difficult to boil’’, and tests were run, thereafter, to determine true differences in the boiling behaviour of good and HTB samples. Samples were tested using NIRS to determine the basic chemical properties. To determine the rheological differences between samples, tests were run using an Anton Paar rheometer to determine the viscous and elastic properties. Graphs were produced to illustrate these results. Using the information obtained, apparent characteristic differences were observed between the different sample types. There were observable differences between HTB and good samples that coincide with the hypothesis. However, the errors with testing were also analysed. This impacted the success of the results. While an absolute result was not extracted, the results from the research may be used for future work, to find a real solution and mitigate the effect of HTB massecuites.