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South Coast, South Africa

Shah S.,Tongaat Hulett Sugar
International Sugar Journal | Year: 2014

The performance of an evaporator station cannot be attributed solely to the vessel design, but to the design of the station as a whole. This paper aims to summarise some key principles pertinent to the South African design of Robert evaporators, with a particular focus on feed distribution and piping design. The pressure drop associated with the piping design can alter the hydraulics within a system and result in preferential flow, which can prevent adequate distribution of juice, the venting of incondensible gases or the draining of condensate. Advances in down-take design have resulted in a move toward semi-sealed down-takes which, coupled with the installation of feed rings, allows for improved evaporator performance through increased recirculation. The presence of flash vapour in the feed stream, as a result of the decreasing pressure profile, assists in circulation of juice through the tubes and thus increases the heat transfer coefficient. However, excess vapour in the feed stream can result in violent eruptions, spouting and entrainment, all of which can be reduced with the installation of a partial flash tank. Conflicting research regarding the optimum distribution of feed and flash vapour has resulted in the development of a feed distribution model to quantify the brix effect. A trade-off appears to exist between optimum juice distribution and optimum flash distribution, where an even distribution of the flash vapour is considered to be most advantageous.

Mbanjwa C.F.,Tongaat Hulett Sugar | Deppa N.,Tongaat Hulett Sugar | Pillay K.,Tongaat Hulett Sugar
International Sugar Journal | Year: 2011

Hydrogen peroxide (H2O2) has been tested in the past as a colour removal agent in the sugar refining process. The high costs and the very high reactivity of this chemical are negative factors that have prevented its full-scale application in sugar factories. Work was done in the USA to reduce the quantity of H2O2 required by dosing as wash water in raw sugar centrifugals. Based on the promising results, trials were done in the Technology and Engineering Group of Tongaat Hulett laboratory on raw sugar and WSM sugar. Full-scale tests were carried out at the Huletts refinery (Hulref) centrifugals on the fourth white boiling at varying concentrations of between 30-1000 ppm on refined sugar in 2009 and 2010. The effect of H 2O2 on colour removal and on pH of both sugar and jet were investigated. Regardless of the H2O2 concentration, 11-15% colour removal in sugar was achieved, with insignificant reduction in pH. Contrary to sugar, jets showed an increasing trend in colour removal with an increase in H2O2 concentration. The optimum H 2O2 application appears to be at a concentration of 300 ppm. The amount of H2O2 consumed per ton of refined sugar produced shows that the use of this chemical may be an alternative for colour removal.

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