Though a global optimization procedure using a randomized algorithm and a commercial process simulator is relatively easy to implement for complex design problems (i.e., intensified design processes), a dominant problem is their heavy computation load. As the process simulation is repeatedly executed to calculate the objective function, it is inevitable to spend long computation time to derive the optimal solution. Also, the randomized algorithms consider the treatment of all variables as continuous. Thus, the reduction of the number of iterations is crucial for such optimization procedures that include integer variables. In this work, an estimation procedure of the objective function having integer design variables is proposed. In the prop...