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Development of ceramic filter equipment for electro-insulating liquids
Havlíková, Tereza ; Cihlář, Jaroslav (oponent) ; Maca, Karel (vedoucí práce)
The aim of this master’s thesis was to prepare macroporous ceramic filters based on mullite and silica, suitable for the filtration of electro-insulating liquids in distribution transformers. The first part of this thesis is a literature review, which addresses the topic of electro-insulating liquids and their degradation, processing techniques of macroporous ceramics and their use in filtration, including an overview of the materials used. The experimental part describes the preparation of porous filters using two selected methods, the replica template method and direct foaming. Filters prepared with optimised processing parameters were evaluated for phase composition, microstructure and compressive strength. Filters prepared using the replica template method consisted of open interconnected pores ranging from 150 to 350 µm, achieved a porosity of around 80 % and compressive strength up to 2.4 MPa. Ceramic foams obtained using direct foaming achieved a porosity of 68–73 % and open interconnected pores up to 100 µm. Due to the requirements of the filtration equipment, the dimensions of the filters had to be scaled up. Direct foaming was found to be unsuitable for the large-scale preparation of filters, however, filters prepared by the replica template method were successfully scaled up and are ready for the testing of their filtration capacity. These filters with open interconnected pores, unimodal pore size distribution and sufficient mechanical strength are potential candidates for use in the first stage of filtration of electro-insulating liquids, offering a more sustainable alternative to the currently used paper filters.
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