(235a) Application of a Digital Twin of an Air Separation Unit with Argon Production

Robert Kender, Felix Rößler, Bernd Wunderlich, Ingo Thomas, Anna-Maria Ecker, Sebastian Rehfeldt, Harald Klein

As part of the “Energiewende”, Germany is increasing the share of renewable energies in its power supply. Therefore, major energy consumers such as cryogenic air separation units (ASU) need to adapt their operations with regard to the resulting volatility in the energy market. The high potential of flexible ASU operation as a measure of power grid stabilization is investigated in the Kopernikus-project “SynErgie - FlexASU”, which is funded by the Federal Ministry of Education and Research (BMBF) and supervised by the project management organization Projektträger Jülich (PtJ).

One major step towards more flexible operation is the development of detailed dynamic simulation models, so-called digital twins, which are capable of simulating the whole operating range of an ASU. Based on the pressure-driven approach introduced by Thomas et al. 2020, detailed dynamic models of all unit operations of an ASU have been developed [1]. Kender et al. 2019 have combined those models into a digital twin of an ASU without argon production. It was shown that a highly dynamic load change scenario, such as a warm start-up procedure, can be simulated accurately [2].

In this work, a digital twin of an ASU with argon production is presented. It is crucial to include the additional argon rectification system, since by limiting the load change rate, this system has a major impact on the flexibility of an ASU. Furthermore, the additional argon rectification system significantly increases the complexity of the digital twin, since the rectification columns for argon separation contain a large number of theoretical trays. Also, the ASU model presented in this work combines packing and tray columns, both of which are simulated with the corresponding fluid dynamic design correlations.

This digital twin allows for the realistic simulation of highly dynamic load change scenarios, for instance a warm plant start-up. In addition, this work outlines strategies for automating this complex operating scenario. Based on the model developed in this work, critical parameters which significantly influence the start-up time are identified and rated with respect to their impact. The findings presented form the basis for future studies, including studies that concern themselves with the optimization of load change scenarios of an ASU with argon production.

[1] Thomas I., Wunderlich B. and Grohmann S.: Pressure-driven dynamic process simulation using a new generic stream object. Chemical Engineering Science, 215, 11571, 2020.

[2] Kender R., Wunderlich B., Thomas I., Peschel A., Rehfeldt S., Klein H.: Druckgetriebene dynamische Simulation einer gesamten Luftzerlegungsanlage. Annual meeting: ProcessNet-Fachgruppe Fluidverfahrenstechnik, oral presentation, Potsdam Germany, 2019.