Benchmark study of evaporator cleaning practices in Louisiana cane sugar factories

Evaporator cleaning to remove the scale is one of the critical operations to maintain the efficiency of the factories and it has been an ongoing problem in Louisiana (LA) cane sugar factories since the processing season is very short and a very fast and efficient cleaning process must be done without equipment or specialized personnel. The aim of this study was to provide more information to the LA sugar factories about the different and appropriate practices to clean evaporators and their efficiencies. During the 2020 LA processing season, a benchmarking of the LA cleaning practices for evaporator cleaning was done, scale samples from 8 factories were collected and characterized, and scale dissolution tests comparing cleaning practices were done. The evaporator cleaning procedure is similar in all LA factories, the main differences are based on the concentration and boiling times of the chemicals. Scale in LA factories was mainly formed of CaO, SiO2, and P2O5, and between 33% to 86% of the inorganic components were present in the amorphous (disordered) phase. The characteristic of the scale played an important role in the efficiency of the cleaning practice and the consumption of the chemicals. The scales of the factories with the highest consumption of chemicals had the highest contents of CaO and Na2O. EDTA broke down the scale samples with high content of oxalates, while acids broke down the scale with a heterogeneous inorganic composition (silica, hydroxyapatite, carbonates, and amorphous components).