Distribution of juice heater surface for optimum performance of evaporation process in raw sugar manufacturing

- A model of the evaporation process in raw sugar manufacturing is presented.
- Components of the process are juice heater, evaporator, and crystallizer.
- The evaporator consists of 4 effects, and the juice heater consists of 3 heat exchangers.
- Performance parameters of the process are the amount of raw sugar and the steam economy.
- Optimum juice heating surface distribution that maximizes either parameter is determined.

The evaporation process in raw sugar manufacturing turns diluted juice into granulated sugar. It consists of three main components: juice heater, multiple-effect evaporator, and crystallizer. Previous studies are concerned mostly with multiple-effect evaporator with the assumption that sugar juice entering the evaporator is at the saturation temperature. In fact, juice temperature must be raised to the saturation temperature in juice heater using vapor bled from the evaporator. This study investigates a model of the evaporation process with the objective of determining the distribution of juice heater surface that results in the optimum performance. The model takes into account mass and energy balances in the three components of the evaporation process. If the total juice heater surface is fixed, it is shown that there is a unique distribution of juice heater surface when vapor is bled from the first and second effects of the multiple-effect evaporator. However, if vapor is bled from the first, second, and third effects, many surface distributions are possible, and one of which is the optimum distribution that maximizes either the amount of granulated sugar produced from the process or the ratio of the amount of water evaporated from the process to the amount of high-pressure steam required for the process. Increasing the total juice heater surface increases both performance parameters. Results for two specific systems using different quadruple-effect evaporators are shown to demonstrate the application of the proposed model.