Effects of high silica lime rock on beet sugar operations.
Amalgamated Sugar-Twin Falls sourced a high silica limerock during the length of the 2021 campaign. The silica contained in the rock deposited onto heat transfer surfaces throughout the beet end, mill evaporators and sugar end. Scale formation in beet thick juice evaporator trains has been shown to impact the operation of plate-pack style evaporators most significantly, where scale can potentially block flow of thick juice. Evaporator boilouts were completed using both Hydrite Enhance 567 and Hydri-Maize 2759 to remove scale from the heat transfer surfaces. The use of Hydri-Maize 2759, a peracetic acid-based CIP product has been especially successful in removing large amounts of carbon and silica scale in numerous evaporator effect bodies. Heat transfer calculations across the evaporators were calculated at the tail end of the 2021 campaign and beginning of the 2022 campaign. These calculations point to very limited heat transfer across evaporators due to the silica scale deposited. In addition to evaporator scaling, severe disruptions at the Kelly filter station, extract pan, melters and white pans were most likely caused by silica precipitates. Frequent high-pressure events on the Kelly filters required excessive maintenance to the point of limiting slice rates during campaign. Dark, glass like materials were also observed in the calandria of pans during the sugar end maintenance period. While the mill evaporators suffered the most apparent problems, the effects of the high silica limerock hurt performance throughout the entire plant.