Abstract

Several chemicals are produced from brines by solar crystallization using solar ponds. The process of salt harvest consists on mechanically retiring the salts precipitated in the solar evaporation ponds and to leave them in its respective stockpile. In an industrial operation several ponds are used for the fractional crystallization of several salts, and therefore the harvest planning can be a nontrivial task. Therefore, the objective of this work is to plan the feeding flow to each of the solar ponds, the manipulation of solution, and the solutions and solids inventories in each pond that maximizes the production and the harvest periods. All this having as input data the evaporation rate, concentration range of the feeding, concentration range for the pond, and the operational initial conditions. The model developed corresponds to a MINLP, which includes the mass balances in each pond, equilibrium conditions, and planning & operational restrictions. The problem was solved in two steps, first the maximization of the salt harvest was determined and then, using this maximum harvest, the maximum availability of the contractor was determined. Several cases have been studied, including: ternary (NaNO3- KNO3-H2O) and quaternary systems (KCl-KNO3-K2SO4-H2O), pond systems with 3 and 4 ponds and with different areas, and considering 12 and 26 operation periods per year. © 2009 Elsevier B.V. All rights reserved.