Optimal Operation of Multiproduct Plants for the Production of Vegetable Extracts

MORENO, MARTA; MONTAGNA, JORGE; IRIBARREN, OSCAR

Río de Janeiro

Congreso; Mercosur Congress on Process Systems Engineering Enpromer 2005; 2005

The present work proposes a general model for optimizing the design and operation planning of a multiproduct batch plant for the production of vegetable extracts. A multiperiod formulation was developed, that renders a mixed integer non-linear programming (MINLP) model, which is transformed trough a novel scheme into a mixed integer linear programming (MILP) model. The objective function is to maximize an economic function that takes into account the incomes, production costs and inventory costs. The campaign durations trade-off inventories of raw materials and products. In contrast with models reported before, this model considers both products and raw materials inventories in the formulation, accounting for the seasonal variations of raw materials availability and product demands in a multiperiod model. At each period the plant operates in a single product campaign mode (SPC) with zero wait (ZW) policy. In addition, the model takes into account mass balances for staged countercurrent extraction having as parameters the yield and the extraction factor. As a result, the program determines the optimal design of the plant selecting from available discrete vessel sizes and the number of identical parallel units in each stage, which corresponds to the real commercial procurement of equipments. Also, it provides a plan of production, policy inventory, purchases of raw materials and sales of products over the time horizon, that maximizes the benefit. A particular plant that produces oleoresins (solvent extracts of herbs and spices) is used to illustrate the proposed approach, even if the model developed is general and can thus be applied to any vegetable extraction process.