Charakterisierung des Einschmelzens von Borosilikatglas in einem kontinuierlichen und stationären Cold-Top-Reaktor

Kouasseu Ngantcha, Alex Thierry; Roos, Christian Hans-Georg (Thesis advisor); Deubener, Joachim (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

The aim of the work is to develop a new methodological approach to characterize the conversion process of raw materials in a quasi-stationary reactor. For the characterization, a borosilicate glass mixture was treated in a designed stationary cold-top reactor with a new approach to capture important properties of a stationary and moving volume element, such as the temperature profile, the flow and the conversion behavior under in-fluence of the operating temperature and the throughput. The thesis deals with the investigation of batch melting with two different operating temperatures and three different throughputs, 1400 °C (12, 15, 20 g/min) and 1300 °C (10, 12, 15 g/min). Based on the experimental approaches for in-situ temperature measurement and residence time measurement, it was shown for the continuous moving system, that in the continuous system batch melting has a non-linear axial temperature profile in the form of an exponential function and a constant velocity profile in the powdery region combined with a parabolic velocity profile after the formation of the melt phase. Through experimental measurements and examination of the axial phase transformation (using X-ray diffraction and thermal analysis), an overview of the properties of the mixture trans-formation is established in the middle of the furnace and reproduced by using a melting model of the melt formation with fixed kinetic parameters. The experiment with the lowest throughput provides an advantage for the local conversion of the batch. Flowing volume elements achieve a conversion of 80, 74 and 63 % in one quarter of the plant at an operating temperature of 1300 °C and a throughput of 10, 12 and 15 g/min. The reason for this is an improved heat transfer due to an earlier local occurrence of the gas formation reaction during the experiment with a low throughput, which offers advantages for the release into the atmosphere. Furthermore, the process with a higher operating tempera-ture proves to be advantageous compared to the lower operating temperature. The new experimental approach and the results obtained under the influence of the process parameters can be used to investigate the phenomena occurring (foam and bubble formation) and to improve mathematical simulation.

Institutions

• Division of Materials Science and Engineering [520000]
• Chair of Glass and Glass-ceramic [524210]