Submitted to: Sugar Processing Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/18/2004
Publication Date: 11/18/2004
Citation: Eggleston, G., Damms, M., Monge, A., Endres, T. 2004. New insights on sucrose losses across factory evaporators and juice and syrup clarifiers. In: Proceedings of the Sugar Processing Research Conference, April 4-9, 2004, Atlanta, Georgia. p. 349-370. Interpretive Summary: Millions of dollars are lost each year because of unwanted sucrose losses in the clarification and evaporation processes in raw sugar manufacture. The frequent fouling of evaporators in different type evaporators was shown to increase sucrose losses dramatically. The seasonal quality of the sugarcane entering the factory affects sucrose losses in evaporators too. Optimum target syrup and juice pHs were recommended to reduce sucrose and, consequently, U.S. dollar losses. It was also shown that improved measurements of sucrose losses across juice and syrup clarifiers can be undertaken if chloride is measured as a reference standard.
Technical Abstract: This paper discusses new insights gained from this project on sucrose losses in sugarcane juices and syrups at high temperatures (55-115C) during different evaporation and clarification processes. Gas chromatography was used to determine glucose and sucrose concentrations on a Brix or %chloride basis. Comprehensive studies were conducted at Louisiana, U.S. factories to determine the effects of time between cleanings of Robert's-type calandria and plate evaporators on sucrose losses and overall evaporator performance. In general, for both factories most sucrose inversion losses occurred in the pre-evaporators and were more a function of temperature, heating surface, Brix and pH than retention time (Rt). Sucrose inversion only occurred in later evaporator bodies when scale had built up after a clean-out and, generally, became worse until the next clean. Less inversion occurred across the low Rt plate evaporator, although the plate was increasingly susceptible to scaling, but to a lesser extent than the Robert's type evaporators. Increasing the factory target pH of the clarified juice (CJ) or final evaporator syrup (FES) systematically reduced losses of sucrose and a target FES pH of ~6.3-6.5 (equivalent to a target CJ pH of ~ 7.0-7.3) is recommended; however, scaling effects can override pH effects. Seasonal effects on sucrose losses were also marked, and a higher target CJ or FES pH is recommended in early season or when processing immature cane. There was a consistent increase in pH in the last evaporator bodies because of the evaporation of volatile acids into the condensates. Economic implications of sucrose losses are described. Sucrose losses across a Florida, U.S. factory's juice and syrup clarification processes were also investigated. In the juice clarifier, chloride trended with Brix and, therefore, either could be used as a sucrose loss reference. In comparison, in the syrup clarifier Brix was more preferentially destroyed than chloride, and underestimated sucrose losses. High operational pHs for juice hot (~200F or 93.3C) lime clarification (pH range=8.4-9.6 measured at room temp.) minimized sucrose losses to ~0.0-0.6% even with an estimated Rt of 3h, but excessive lime addition can accelerate color formation, scaling, and associated sucrose losses in evaporators. Higher acidic conditions (pH range=6.3-7.4) across syrup clarification (phosphatation) caused much higher sucrose losses of ~0.6-1.3% even at a lower Rt and temperature of ~1h and 165F (74C), respectively.