A tabu-search approach for generating safer operations sequences

This paper presents a tabu search method for determining the sequence and type of plant operations needed to take a plant from an initial state to a final state in such way that the process remains safe during the execution of all the operations. Specifically, this paper focuses on how to determine valve operations in order to change the concentrations of chemical species to a desired goal, while avoiding the flammable range during start-up or shutdown operations. A modified two-layer method is presented and compared with the original method. Also, a simplified single-layer approach is presented in which the operator time duration is changed along with the valve positions in such a way that the method can be used for online operations.