Session: HT-02-02 Impulsively Loaded Vessels - 2

Paper Number: 105202

105202 - Visualization of the Decomposition and Relief Process in High-Pressure Systems 

Visualization of the Decomposition and Relief Process in High-Pressure Systems

Aaron Röblitz, Markus Busch*

TU Darmstadt, Ernst-Berl-Institut für Technische und Makromolekulare Chemie,

Alarich-Weiss-Str. 8, D-64287 Darmstadt, Germany,

*e-mail: markus.busch@pre.tu-darmstadt.de

To be able to guarantee the safe operation of production plants, the prevention of decomposition in the production process (in this case polymerization processes) is of great importance. Nevertheless, severe decomposition can occur due to inadmissible temperature increases, poor heat dissipation, or the formation of hotspots. To avoid or reduce the consequences, a sound knowledge of the decomposition process is of great importance. In particular, information about important parameters such as the maximum decomposition temperature and the maximum decomposition pressure, as well as the speed of the flame front, is essential. The latter is often determined by using several thermocouples, whereby these are positioned at different points in the reactor, and information about the geometry of the flame front can be obtained from the detected temperature rises at the respective measuring points. However, visual observations are necessary for a detailed analysis of the ignition process and the flame front movement. In this way, both the flame front geometry and the propagation velocity can be determined in a time-resolved manner, thus expanding our understanding of the decomposition process. In the course of this, the investigation of relief processes, which are downstream of the decomposition, also takes on an important role. By determining the rate of pressure change, information can be obtained about the ventilated mass flow, the discharge coefficient, and the influence on the decomposition process itself, to optimize the design of safety equipment in technical plants.

For the realization and investigation of the described decomposition or discharge process, a view cell with a volume of 34 ml was used. A high-speed camera is used to visualize the phenomena that occur. In addition, the temperature and pressure changes can be recorded by a fast measurement sensor system. Inducing decomposition is done by forming a hotspot by annealing a tungsten wire coil, which is connected to an exposed thermocouple. Relief is provided by a pneumatic valve, and the relief pressure can be set in advance for this purpose. A tracker program is used for visual evaluation, which allows the flame front position as well as the velocity to be determined. In combination with the obtained pressure and temperature data, the decomposition, as well as the relief process, can be described.

 

For the analysis of the relief process, an isentropic nozzle model according to J. Schmidt ^[1] is used, with which the relief velocities can be determined, taking into account the various conditions and varied parameters. The simulative description of the unloading process with an upstream decomposition by the mentioned model can only be approximated because the products like methane, hydrogen, or soot generated during the decomposition are not considered in the model. For a complete simulation of the decomposition and relief process, an existing basic CFD model according to A. Hilfer ^[2] could be linked with the isentropic nozzle model.

[1] J. Schmidt, W. Peschel, Process and Plant Safety, 71-77 (2012).

[2] A. Hilfer, J. Degenkolb, M. Busch, Chem. Ing. Tech., 91, No. 5, 1-7 (2019).

Presenting Author: Aaron Röblitz TU Darmstadt

Presenting Author Biography: Aaron Röblitz wrote both his bachelor's and master's thesis in Prof. Busch's research group. He is currently in the third year of his doctorate. His research areas include the analysis of decomposition and relief phenomena, which he investigates with a view cell.

Authors:

Aaron Röblitz TU Darmstadt
Markus Busch TU Darmstadt