Optimum Surface Area Distribution of Multiple-effect Evaporator for Minimizing Steam Use in Raw Sugar Manufacturing

Abstract

The sugar juice evaporation process consists of juice heater, multiple-effect evaporator, and crystallizer. The juice heater increases juice temperature from the ambient temperature to the boiling point before entering the multiple-effect evaporator. Water evaporation in the evaporator takes place in many stages at decreasing pressures. The output of the evaporator is concentrated sugar juice or syrup. The evaporation of the remaining water content in syrup occurs in the crystallizer. Both juice heating in the juice heater and water evaporation in the crystallizer require high-temperature vapor, which is bled from the evaporator. Therefore, the model of the juice evaporation process consists of sub-models of the three components and interaction between them through mass and energy balances. The energy efficiency of the process can be measured from the steam input required to operate the process relative to the production of raw sugar by the process. The proposed model shows that the steam requirement depends on distributions of fixed evaporator and juice heater surfaces. The model is used to find the optimum evaporator and juice heater surface area distributions that minimize the required steam input for a specified value of processed juice flow rate.