Methods for integrating and handling complex optimization problems in the process industries

A hot topic in the process systems engineering community is the so called integration of decision levels. Industrial process systems are operated at different levels of decisions; in the lowest level, actual process operating conditions are chosen, while at the intermediate and higher level production and planning are strategically scheduled. Modeling and optimization at each of the levels is often done sequentially and this leads to the question whether optimization of individual levels will result in a 'global optimum'. For this reason integration is applied. Integration could mean that targets are closer to their global optima, but it also encompasses the increasing complexity of the overall optimization problem. This is the reason, that for many industrially scaled optimization problems, the approach is still on the basis of a sequential approach. In this paper we discuss, on the basis on patent literature of the last 20 years, which tools are available to handle these complex integrated optimization problems.