Evaporation performance: present and future in Colombian cane sugar factories

Evaporation performance is usually affected by internal and external factors such as sugarcane quality, juice conditioning, exhaust steam availability, juice flow variation, heat transfer area available, type of evaporator, and geometric relationships. These factors influence the evaporation rate and cleaning frequency. An integral strategy to improve performance was proposed, including technological changes (falling-film evaporators) evaluated by simulation, on-line performance index (evaporation performance index, EPI), and new guidelines for the evaporation station configuration. EPI, proposed by Cenicaña (Colombia), is defined as the product of RDS (refractometric dry substance content) difference and juice flow divided by the product of heating steam pressure and heat transfer area. The results show that it is possible to improve performance of the third effects by extending the calandria tubes in Robert-type evaporators; this improves the heat transfer coefficient by 15–30%. In most cases, increasing juice flow velocity in evaporator tubes will increase the overall heat transfer coefficient. The use of longer tubes should be considered when modifications in evaporation stations are required. In addition, the application of EPI as a tool to assess the performance in the evaporation train and make decisions regarding the cleaning schedule was validated.