%0 Book
%A Melchior, Tobias
%T Untersuchungen zur Oberfächenspannung von Kohleschlacken unter Vergasungsbedingungen
%V 96
%I RWTH Aachen
%V Dr.
%C Jülich
%M PreJuSER-136285
%@ 978-3-89336-690-3
%B Schriften des Forschungszentrums Jülich. Reihe Energie und Umwelt / Energy und Environment
%P XVII, 270 S.
%D 2011
%Z Record converted from JUWEL: 18.07.2013
%Z RWTH Aachen, Diss., 2011
%X In the context of CO$_{2}$-emission-induced global warming, greenhouse gases resulting from the production of electricity in coal-fired power plants gain increasing attention. One possible way to reduce such emissions is to gasify coal instead of burning it. The corresponding process is referred to as Integrated Gasification Combined Cycle and allows for the separation of CO$_{2}$ before converting a synthesis gas into electrical energy. However, further improvements in efficiency and availability of this plant technology are needed to render the alternative generation of electricity sensible from an economic point of view. One corresponding approach introduces hot gas cleaning facilities to the gasification plant which guarantee a removal of slag particles from the synthesis gas at high temperatures. The development of such filters depends on the availability of data on the material properties of the coal ash slags to be withdrawn. In this respect, the surface tension is a relevant characteristic. Currently, the surface tension of real coal ash slags as well as of synthetic model systems was measured successfully by means of the sessile drop and the maximum bubble pressure method. With regard to the sessile drop technique, those experiments were conducted in a gasification-like atmosphere at temperatures of up to 1500 ◦C. Furthermore, the pressure inside the experimental vessel was raised to 10 bar in order to allow for deriving the influence of this variable on the surface tension. In contrast, maximum bubble pressure trials were realised at atmospheric pressure while the gas atmosphere assured inert conditions. For performing sessile drop measurements, a corresponding apparatus was set up and is described in detail in this thesis. Three computer algorithms were employed to calculate surface tensions out of the photos of sessile drops and their individual peformance was evaluated. A very good agreement between two of the codes was found while the third one produces heavily scattering output. The measurement arrangement was run in an almost fully automated fashion which resulted in an immense amount of obtained surface tension data. Maximum bubble pressure experiments were conducted at the University of Osaka, Japan, on selected real ash samples. Due to a far longer time required for determining bubble pressures in comparison to taking drop pictures, only a small number of temperatures could be studied abroad. The results show the surface tension to be in the range from 200 mN/m to 500 mN/m which is in accordance with data taken from the literature. While three discrete temperature intervals of particular slag behaviour could be identified in sessile drop experiments, results of maximum bubble pressure trials suggest the surface tension to be lower under inert conditions compared to a reducing atmosphere. The outcomes generated in Japan additionally show a better agreement to surface tensions forecasted by model calculations. Fe$_{2}$O$_{3}$ being considered to have a pronounced influence on slag characteristics is made responsible for such observations. As soon as pressure is applied, the surface tension is found to decrease significantly. In order to visualise the data obtained by means of the sessile drop technique, regression functions were employed that can be implemented into future design calculations on hot gas cleaning facilities.
%F PUB:(DE-HGF)3
%9 Book
%U https://juser.fz-juelich.de/record/136285