Entwicklung eines hybriden Modells zur Dimensionierung von Hochdruckextraktionskolonnen

• Development of a hybrid model for the dimensioning of high-pressure extraction columns

Brockkötter, Johannes Markus Josef; Jupke, Andreas (Thesis advisor); Kockmann, Norbert (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022

Abstract

For dimensioning a high-pressure extraction column, the high influence of pressure and temperature on the density, viscosity and diffusion coefficient of the supercritical CO2 isboth an advantage and a disadvantage. Although the chemical properties of the solvent can be adjusted to fit the specific separation task, pressure and temperature have astrong influence on the complex phase equilibrium in combination with interacting fluiddy namic phenomenon, which complicates the dimensioning using equilibrium step models. Published HETS values for the extraction of ethanol from the aqueous phase range from0.8m to 3.2 m, highlighting the need for rigorous modeling of a high-pressure extraction column. The aim of the thesis is to develop a column model to describe the separation performance of a high-pressure extraction column for the extraction of ethanol from an aqueousphase with supercritical CO2, taking into account fluid dynamic effects. For this purpose, a CFD simulation is used to model the flow regime in a structured packed high-pressure extraction column. The flow regime is similar to that of a liquidliquid extraction column. A serial hybrid column model is then developed to accurately determine the separation performance over the full range of operating parameters in terms of pressure, temperature, and flux. Within the hybrid model, the previously systematically experimentally determined relative velocity, axial mixing, and hold-up are modeled mechanistically. Data-driven models are used to predict the flooding behavior and partition coefficient. The column separation performance is determined using a dynamic rate-basedmodel. Despite the strong influence of pressure and temperature on fluid dynamic effects and phase equilibrium, the developed column model has a maximum error of 20 %. Furthermore, the detailed fluid dynamic analysis lowers the column HETS value from 2.45mto 0.5 m. Thus, a fluid dynamic analysis of a high-pressure extraction column is essential. The fluid dynamic phenomena observed and systematically measured in this thesis apply to aqueous systems in high-pressure extraction columns and thus represent an important gain in knowledge for future extraction and design tasks.

Institutions

• Chair of Fluid Process Engineering [416310]