(373as) On the Interaction and Integration of Production Planning and (Advanced) Process Control

Today’s fast changing markets call for increasing the agility of chemical plants, as well as for a tighter integration between all business and operational decision-making layers, viz., production planning, scheduling and (advanced) process control. These layers follow a hierarchy based on the time scale that they consider and impact, with planning and scheduling having the longest time horizon (days- months) and process control acting in the “here and now,” with time horizons ranging from seconds to hours. The majority of integration attempts have focused on integrating layers that are “adjacent” in time (e.g., planning/scheduling, scheduling/control). The interaction and integration of “non-adjacent” layers has received far less attention [1,2,3].

In this presentation, we focus on the integration of production planning and advanced process control (represented by the ubiquitous MPC paradigm). We reveal the impact of controller performance on the implementation of production plans. Then, we introduce a new planning framework that accounts for the presence and behavior of process control systems on process performance. We rely on historical closed-loop process performance to define more realistic production targets, reducing the economic gap between planning predictions and actual production. We formulate the planning problem as an optimization problem under uncertainty, demonstrating however that the computational overhead compared to the nominal case is low.

A non-isothermal CSTR-Separator system is used to illustrate the algorithm performance. Different periodic disturbances are used to illustrate the impact that process control has on actual process economic performance. In all cases, the new formulation not only demonstrates reduction of economic gap between profit anticipated in production planning and actual production by the process of more than 50%, but also improves realized process profit compared to the nominal case.

References

1. C.T. Maravelias, C. Sung, Integration of production planning and scheduling; Overview, challenges and opportunities, Computers and Chemical Engineering 33 (2009) 1919-1930
2. E. N Pistikopoulos, N. A. Diangelakis, Towards the integration of process design, control and scheduling: Are we getting closer?, Computers and Chemical Engineering 91 (2016) 85-92
3. M. Baldea, I. Harjunkoski, Integrated production scheduling and process control: A systematic review, Computers and Chemical Engineering 71 (2014) 377-390