A heuristic procedure using a NLP(NonLinear Programming) is developed for the preliminary design of multiproduct batch plants. The procedure determines equipment volumes/batch sizes and allows structural features such as in-phase and out-of-phase modes of operation and nonidentical parallel units in a stage. The previous approaches in solving the synthesis problem as MINLP(Mixed Integer NonLinear Programming) problem so far, have considered only out-of-phase mode. In this paper, using a NLP formulation combined with heuristics, we deal with the problems where in-phase mode and out-of-phase mode are simultaneously considered. The first step of our procedure, by heuristics and table analyses, is to determine how the parallel equipment operates every stage for each product. And then, using a NLP formulation, we determine the unit volumes and batch sizes. This paper demonstrates the effectiveness of our approach in solving two problems of batch plant design.