design of optimal process flowsheet for fractional crystallization separation process

a procedure is presented that synthesizes fractional crystallization separation processes to obtain pure solids from multi-component solutions. the method includes a procedure to generate a network flow model to identify alternative process designs for fractional crystallization. the main advantage of this systematic procedure with respect to other reported procedures is using non-equilibrium solubility values for crystallizers and mixing tanks as process points. by employing an approach factor to show the distance from equilibrium, a non-linear programming model is obtained. solving the non-linear programming model, optimal process flowsheet and the corresponding non-equilibrium solubility values for process points are presented. the proposed procedure is used to design an optimal flowsheet for production of sodium carbonate and sodium sulfate from burkeite. the results show that when the approach factor goes to unity, the maximum efficiency of separation process is attained which corresponds to the minimum total flow rates and total cost of the process.