Gregor Tolksdorf

Taylor-Made Modeling and Solution of Novel Process Units by Modular CAPE-OPEN-based Flowsheeting

Abstract This contribution deals with the integration of custom unit operations into flowsheeting software. By sketching the workflow of designing novel processes in a conventional simulation software and introducing a respective modeling scenario some challenges regarding collaboration and model-solution are named: the exchange of models, the definition of initial values, and the ordering of equations. A strategy to overcome these challenges is presented and applied in case studies using a collaborative modeling and code generation tool and a CAPE OPEN-compliant unit operation framework. These examples show not only the advantages of the CAPE-OPEN standard for interoperability in process science but also the advantages of automatic code generation based on mathematical analysis of the equation systems.

Development of Computer Aided Modelling Templates for Model Re-use in Chemical and Biochemical Process and Product Design: Import and export of models

Abstract This paper focuses on the challenges in model development related to model reuse and compatibility and integration of different tools that are used in modelling. A link between two modelling tools, the computer-aided modelling framework of the ICAS system and the modelling environment, MOSAIC, has been established, in order to provide a wider range of modelling capabilities. Through this link, developed models can be exported/imported to/from other modelling-simulation software environments to allow model reusability in chemical and biochemical product and process design. The use of this link is illustrated through a case study.

MOSAIC: An Online Modeling Platform Supporting Automatic Discretization of Partial Differential Equation Systems

Abstract Partial differential algebraic equation systems (PDAE) frequently appear in chemical engineering and their discretization is most often an issue when preparing a simulation wherein they appear. In this contribution, an algorithm is presented and implemented facilitating the general analysis of PDAE systems appearing often in chemical engineering problems and their discretization via orthogonal collocation on finite elements. The recognition of differentiating variables, the application of varying boundary conditions, and the subdivision into independent PDAE systems as well as the implementation of the actual discretization is discussed.

Improving Convergence Behavior of Nonlinear Equation Systems in Intensified Process Models by Decomposition Methods

Abstract The two decomposition methods Dulmage-Mendelsohn (DM) decomposition and bordered block transformation (BBTF) have been examined on their capabilities to eliminate convergence problems during the iteration of large, nonlinear equation systems as they occur frequently in process modeling. They both divide the overall system into lower dimensional subsystems, which can be solved separately in sequence. Exemplarily these methods were applied on the model of a reactive distillation column, where the decomposed systems show a higher robustness with respect to systematically selected initial points compared to the original system. Nevertheless, the improvement in DM seems small since a large subsystem with 576 of the 664 model equations remains. The convergence result from the iteration of the BBTF decomposed system depends a lot on the initial values for certain strongly coupled variables called tearing variables. In future, methods will be investigated and may also be developed to further reduce the dimension of the subsystems in DM and provide accurate initial values for the tearing variables in BBTF.

Support of Education in Process Simulation and Optimization via Language Independent Modelling and Versatile Code Generation

Abstract Numerous types of software exist for simulation and optimization of processes in chemical engineering. This is a special challenge towards education in computer-aided chemical engineering, where the focus should rather be on understanding the features of different algorithms than on the code implementation of a model in a certain environment/language. In this contribution, a workflow in the desktop application MOSAIC is presented, which separates modeling and simulation or optimization. This workflow has been tested in a semester accompanying task of a process optimization class as well as in several workshops. Both the task as well as the reaction of the students towards it are documented here.

Linking Process Simulation and Automatic 3D Design for Chemical Plants

Abstract In this contribution, the automatic creation of 3D models for Modular Process Units (MPUs) of chemical plants is presented. A prototype is successfully implemented within the PlantDesign Feature of the modeling environment MOSAIC. It enables the automatic source code generation for detailed 3D models. The constructive design of the MPU models includes norm-compliant equipment components, internal installations, platforms and ladders, structural elements, supports, and close piping including measurement and control devices. The design of the MPUs is individually adaptable to the process data, operating conditions, material selection and constructive design requirements. Besides the spatial information, also process and meta information like process variables, process conditions, constructive user specifications, heuristic information, and calculated design parameters are stored within the 3D data model. The automatically generated source code of the process unit can be imported into 3D CAD tools e.g. E3D/PDMS of AVEVA®. The PlantDesign library includes rectification columns and associated apparatuses.

Automatic Generation of Simulation Code for Embedding Custom Unit Operations in CAPE Software

In this contribution we present a novel approach for users of an equation-based modelling environment to create highly customized, reusable transformation models for automatic code generation. When such a model is applied on an equation system describing a unit operation, export-/implementation-ready simulation code can be generated for CAPE-OPEN-compliant flowsheeting environments and erroneous manual implementation can be avoided. Necessary features for a transformation-model class enabling the code generation for a unit operation are determined. In a case-study the successful application of a transformation-model instance on a model of a membrane separation unit operation is demonstrated. It shows the correctness of the implemented models and highlights the power of this model-driven approach regarding customizability and reusability.

Modeling, Simulation, and Economic Evaluation of a Hybrid CO2 Capture Process for Oxidative Coupling of Methane

Abstract The Oxidative Coupling of Methane (OCM) is a direct path for the conversion of methane into ethene. Carbon dioxide is generated as an undesired reaction by-product and must be removed in the downstream separation section. This is commonly achieved by amine scrubbing, which is an energy-intensive process. An alternative hybrid process employing gas separation membranes and absorption is investigated in this contribution. Membrane and absorption processes are modeled and simulated. Several flowsheet configurations and gas compositions, reflecting different OCM reactor concepts, are considered. Preliminary economic analysis is carried out to assess the feasibility of applying this process industrially.