Bringing Modelica to the Process IndustryJohan Windahl
Engineers in the process industry now have new tools to help understand, analyze, and optimize their systems and specific applications.
In September 2015, I attended Modelica Conference 2015 in Paris. I was there to present an article summarizing part of the results of a two year collaboration project between Modelon and VORtech from the Netherlands.
The project is highly relevant for process industry’s research, design and development because it opens exciting new ways and possibilities in modeling and simulation. But let me start with the beginning.
Modeling in chemical process industry: current state
The use of Modelica has not been widely spread to the process industry today even though it is well-suited to describe these processes. Modelica is an equation based modeling language, similar to other languages established in this industry. But with the big advantage that it is non-proprietary and a modern object-oriented language supported by several tools.
Until recently the main blocking factor for a wider use of Modelica has been the availability of a Modelica-based open standardized interface for multi-component multi-phase fluid properties. Modelon has been one of very companies using Modelica for process applications, e.g. our carbon capture and sequestration solution, and therefore we have been looking to advance the state of the art for using Modelica in the process industry.
Thus simulation engineers in the process industry have missed the critical models for fluids that are typically used in distillation processes, or any other separation processes. It is the standardized and simple access to fluid properties that in the past made industry-specific tools more attractive than Modelica tools for process engineers.
Change is coming!
Over the past two years Modelon has been leading an EU-financed research project, MODELICAPROP, with the goal to develop a new, standardized Modelica thermodynamics properties interface.
MODELICAPROP is now finished and has resulted in a new open-source framework for thermodynamics in Modelica. This open-access framework enables engineers from the process and chemical industry to conveniently start using Modelica for the simulation of their systems.
The new framework
The framework consists of:
– MultiPhaseMixture, a Modelica library for multi-phase multi-component fluids
– An external C/C Modelica property interface, with back ends to CAPE-OPEN Thermodynamics, RefProp and FluidProp.
CAPE-OPEN (Computer Aided Process Engineering) Thermodynamics is an open standard for thermodynamic properties that is supported by various tools in the process industry. RefProp and FluidProp are commercial thermodynamic properties packages.
Developing thermodynamic property models for multiphase multi-component fluids is fairly complex and requires specialist knowledge. With this interface the simulation engineer can focus his/her time on the process instead of the implementation of fluid properties.
Fig. 1 Overview of the external framework interface structure showing the connection between external fluid property databases and Modelica models.
Cryogenic air separation unit
To demonstrate the usefulness and capabilities of the new library, a model for the lower pressure column in a cryogenic air separation unit was created (see Fig.2)
Fig. 2 Modelica model of the lower pressure column in a cryogenic air separation unit. The plots show variations in the concentration of oxygen and nitrogen along the column height.
The test case showed that the new framework can be used to model process systems in Modelica.
In general, the new framework for multi-component multi-phase work is a useful addition to Modelica technology because it opens up new areas of applicability. The new model-based media supports both native Modelica and external media.
In the future more test cases for concept evaluation will be included. Additional next steps involve the consolidation of native Modelica implementations and the extension for the C-interface backend.
Find out more
The full article MultiComponentMultiPhase – a framework for thermodynamic properties in Modelica presented at Modelica Conference 2015 can now be downloaded, as well as the new developed framework for multi-phase mixture media.
I would love to hear your questions and feedback about model-based design for your process industry application. Feel free to contact me!