Generalized retrofit design of multiproduct batch plants

Optimal Reliable Retrofit Design of Multiproduct Batch Plants

“…A small retrofit design problem of an existing twostage multiproduct batch plant, producing products A and B, is chosen for illustration. For a given new product demand, the retrofit strategy of Yoo et al 3 can be used to add new equipment to the existing plant. For a case in which only one piece of equipment can be added at each stage of an existing plant, Figure 1a-c shows the existing plant, the generalized superstructure (as described in Yoo et al 3 ), and an (assumed) optimal solution, respectively, for this example.…”

“…In the case of the multiproduct batch plant, different products are manufactured using the same equipment operated in the same number of stages. The optimal production value for each product obtained with the Yoo et al 3 process model is only for the system state in which all of the underlying equipment (both existing and new) is working. Therefore, in this work, a series configuration is used to represent the reliability block diagram superstructure.…”

“…In light of this new information gained from the separate availability analyses of both existing and new retrofitted plants, one can observe the following: (a) Conventional retrofitting formulations (in this case Yoo et al 3 ) obtain optimal design parameters, sizes, and operating modes for new equipment without considering production losses due to the unavailability of the existing plant (5.91%) and of the new retrofitted plant (8.74%). Therefore, these production losses due to unplanned downtime directly result in revenue loss.…”

“…Fletcher et al 2 extended Vaselenak et al's formulation by removing the restriction that any new equipment must be operated in the same manner for all products. Yoo et al 3 later generalized Fletcher et al's formulation by removing the difference between existing and new units and introducing the "group" concept. They defined a group as a set of units that are operated in-phase, whereas units in different groups are operated out-of-phase.…”

“…In this paper, we extend our previous work 10 to the case of multiproduct batch plant retrofitting and develop a new simultaneous optimization framework that combines a process model and an availability model to obtain optimal size, operating mode, and optimal allocation of reliability for new equipment during retrofitting. The existing retrofitting formulation of Yoo et al 3 is extended to account for production losses due to unplanned shutdown and maintenance costs and is used as a process model in our work.…”