Development of computer code for the optimization of $D_2O$ upgrader

Abstract

Nearly all heavy water plants have been designed with different process for primary and final enrichment. For final enrichment process, the distillation of water seems to be favoured. To design and operate $D_2O$ upgrader more efficiently and economically, optimization of $D_2O$ upgrader is performed in terms of minimizing total cost which consists of the operating and capital cost. Three kinds of $D_2O$ upgrader design are considered, and each of them is to be optimized and compared under economic standpoints. An objective function subject to various constraints is a dependent function of explicit and implicit variables where explicit variables are the dependent functions of implicit variables. The constraints consist of the nonlinear equality ones that are the representations for the mathematical modeling of distillation process, and specifications and inequality constraints including operating limitations. For the optimization of nondifferentiable, constrained nonlinear objective function, Constrained Rosenbrock method called a kind of pattern search method is employed in this paper. Then nonlinear equality constraints are solved by using the Equations Tearing method. The two technical methods applied in this paper are selected to overcome the difficulties due to the characteristics of $D_2O$ upgrader. The antinomic effects of operating variables on cost elements are found in the simulation of distillation process based on onestage design. From the study on the antinomic properties for the decision variables, we can know the trends of optimization procedure. As a results of the optimization for proposed plant designs, one-stage design is turned out to be the most economic stage for the final enrichment process design. Then the reflux ratio and top pressure, as operating variables, are determined as low as possible. Under the above optimal conditions, optimum design conditions and capital and operating costs are simultaneously found in this paper.