Research On Automatic Differentiation And Its Application To Process Systems Optimization

Process systems optimization plays a significant role in the field of Process Systems Engineering. And how to improve the efficiency and accuracy of optimization is a big challenge for today's researchers. Since the numerical derivative represents the search direction of optimization process, it's the key information for optimization. Besides, derivative calculation is always the most time-consuming part of the whole optimization process, especially for the large-scale problems. Therefore, applying an accurate and efficient derivative calculation way to optimization is of great importance for the improvement of optimization efficiency.Automatic differentiation, a promising differentiation algorithm, which has been developed rapidly in recent twenty years, is investigated in the thesis. And automatic differentiation is applied to the sensitivity analysis problem of distillation column optimization, as well as the optimization problem of the multi-distillation columns model of depropanizer and debutanizer in ethylene plant. Finally the calculation results and efficiency are analyzed and compared with the traditional finite difference and sparse finite difference.The main contributions include the following aspects:1. The importance of numerical derivative for optimization is studied by analyzing the relationship of derivative evaluation and optimization. And the development and applications of automatic differentiation algorithm in recent years are introduced, as well as the basic algorithm is discussed. And two implementation ways of automatic differentiation based on source transformation and operator overloading are fully investigated and compared with the traditional methods of finite difference and sparse finite difference.2. Equation oriented method is applied to the multi-columns modeling of depropanizer and debutanizer in ethylene plant based on first principles. And the simulation result of the built model is proved correct after comparing with the result of Aspen Plus, a professional and commercial simulation software.3. The application of automatic differentiation in sensitivity analysis of distillation column optimization is discussed, including applying it to thesensitivity analysis problem of distillation column optimization, as well as the corresponding parallel sensitivity analysis process.4. The application of automatic differentiation in process systems optimization is fully investigated, such as applying it to the optimization problem of the multi-distillation columns model of depropanizer and debutanizer in ethylene plant, as well as the optimization problem of single debutanizer model. The influence of different derivative evaluation ways to the efficient of optimization is analyzed and compared through the applications.