Peter Roosen

Pareto optimization of a combined cycle power system as a decision support tool for trading off investment vs. operating costs

The monetary optimization of thermodynamic processes may be approached by inherently thermodynamic frameworks like exergo-economic analysis, or a rigid direct cost evaluation is applied. This paper, treating the optimization of a combined cycle power plant, follows the second path. Operation and investment costs are usually treated as a combined value by means of an annualization factor. Due to the rather far-stretching time horizon of turbine energy conversion systems, differing behaviour of those contributions with time, and varying subjective weighting and assumptions of future developments, this conventional subsumption is not necessarily a sensible one to identify the best solution for a given decision situation. It is therefore favorable to address both costing goals independently and identify the pareto set of the problem prior to a final decision on which parametrization of the system should be chosen. A numerical pareto optimization technique based on an evolutionary base strategy is discussed that addresses this type of problem in an efficient and easy to adapt manner.

Total process optimization in chemical engineering with evolutionary algorithms

Abstract Evolutionary algorithms, derived by observing the process of biological evolution in nature, have proven to be a powerful and robust optimizing technique in many cases. This paper describes the use of evolutionary algorithms for simultaneous structural and parameter optimization in process synthesis in a modular program environment. The commercial simulator ASPEN PLUS™ was integrated for the determination of the target function value. The ModelManager™ was utilized for a comfortable graphical problem definition. The simulations and the cost calculations exploit the complete process modeling accuracy without the necessity of simplifications due to restrictions imposed by the optimization method. The user can be sure that the best solution does not get lost by the application of crude models. In this paper the optimization method will be demonstrated by the synthesis of separation sequences and the overall process synthesis with limited degrees of freedom.

Economic optimization of non-sharp separation sequences by means of evolutionary algorithms

Abstract The general distillation sequence synthesis problem featuring the separation of multicomponent feed streams into multicomponent products is addressed. Potential flowsheets include stream bypassing and mixing and use sharp separations as well as non-sharp splits where key component distribution is allowed. Compared to conventional sharp distillation sequence synthesis, this leads to a mixed-integer non-linear programming problem of increased complexity, including non-convexities as well as multi-modalities. Product specifications create additional constraints while simultaneously call for a rigorous modeling of the non-key distribution. A synthesis method is proposed that models the various flowsheet configurations with a new and flexible superstructure concept and connects the gradient-free optimization technique of application-orientedly developed Evolutionary Algorithms (EAs) to the rigorous modeling capabilities of the Aspen Plus ™ simulation system, thus enabling realistic process design and cost objective function calculation. The re-examination of two published examples illustrates the applicability and the potential of the approach.

Optimization of Heat Exchanger Networks by Means of Evolution Strategies

This paper describes the adaptation of Evolution Strategies (ESs) for simulation based heat exchanger network synthesis. Due to space limitations the presentation is restricted to a brief overview of the application domain, the problems and pitfalls we encountered during the project and hints to solutions. Some of these problems are of general relevance for the application of Evolutionary Algorithms in cases where the objective function is based on a simulation model and are therefore discussed in more detail. The emphasis lies on the design of a suitable genetic representation.

Emergence, Analysis and Evolution of Structures: Concepts and Strategies Across Disciplines

The study of structures and structure generating processes is a common concern of all scientific and technical disciplines. The present volume presents an interdisciplinary investigation of the different methods of analysis and modelling which, while differing considerably in detail, usually have evolutionary adaption or development schemes at their core. The book naturally falls into three parts - a first part summarizing the transdisciplinary fundamentals, a second part discussing in detail case studies from various fields (production engineering, medicine, management, molecular biology, energy engineering, civil engineering, logistics, sociology, physics) and a shorter outlook on the transdisciplinary perspective.

Thermodynamic evaluation of chemical processes as a base of Structure-Optimizing Process Synthesis

Abstract A new method called Kesops — Knowledge-based Evolutionary Structure-Optimizing Process Synthesis — is presented, aiming at an automated generation of structure-optimized solutions for a given chemical engineering task treated on an abstract thermodynamic level. It is based on the use of process synthesis knowledge combined with an optimizing technique belonging to the field of evolutionary algorithms. Randomly chosen search steps are guided by a thermodynamic likelihood derived from a knowledge-based system containing process synthesis heuristics and thermodynamic knowledge. In contrast to other approaches dealing with process optimization this does not impose absolute limits to the solution space. Although in this conceptual design phase a detailed cost analysis cannot be performed for each process idea, evaluations of the generated process alternatives have to take place during the synthesis and optimization process. Therefore an assessment technique is presented which relies only on thermodynamical means and physical boundary conditions. The results achieved with the derived target function reveal a good correspondence to economical analysis made by other authors.

Structures in the Disciplines: Case Studies

The study of structure generating processes is an interdisciplinary subject. Case studies from the various fields reveal similarities as well as differences in the methods of solution and also in the goals of analysis. The following selection serves to give an overview over the types of analysis typical for the various disciplines. It is by no means exhaustive. The individual articles are written by experts in the various fields with a strong emphasis on illustrating the points elaborated in the preceding chapter on the transdisciplinary foundations. Readers wishing to enhance their understanding and to proceed more thoroughly to the specific disciplinary details are put in the position to do so by consulting the cited literature.

In-situ measurement of liquid and evaporated fuel in a model diesel injection spray

A semi-quantitative distribution visualization method was developed to locate the distributions of liquid and evaporated test fuel below a diesel injector simultaneously. The technique uses sheet illumination from an excimer laser and picture acquisition with color slide films in miniature cameras. The single shot pictures obtained in the experiment are post-processed by an image processing system yielding the two-dimensional fuel distribution for liquid and vapor simultaneously. The method is compared to similar techniques engaging simultaneous but geometrically separated picture acquisition with black & white films.