09:00 am
Development of a high-temperature-TES system using refractory materials for long-term storage of renewable energy
Erik Hennemann-Hohenfried | Refratechnik Steel GmbH | Germany
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Authors:
Erik Hennemann-Hohenfried | Refratechnik Steel GmbH | Germany
Dr.-Ing. Thomas Schemmel | Refratechnik Steel GmbH | Germany
Tim Leber | Institute of Mineral Engineering, RWTH Aachen University | Germany
Dr.-Ing. Thorsten Tonnesen | Institute of Mineral Engineering, RWTH Aachen University | Germany
Prof. Dr. Jesus Gonzalez-Julian | Institute of Mineral Engineering, RWTH Aachen University | Germany
Robert Kremer | Alpha Ceramics GmbH | Germany
Due to rising energy prices and simultaneous expansion of renewable energy sources, the possibility of reliable and cost-efficient energy storage is becoming increasingly important for private households and industry. Thermal energy storage (TES) is an option to thermally inject energy, store it, and convert it back to electricity. This research work deals with the design of a sensitive high-temperature TES system. Therefore, CFD (Computational Fluid Dynamics) simulations are conducted and a demonstrator is built of industrial refractory materials.
The required storage capacity was determined using the energy demand of a four-person household using photovoltaics for a self-sufficient energy supply after heating the demonstrator up to 1100 °C once. Two different refractory bricks for storage and four different insulation materials were used for the construction of the TES unit. The two refractory brick variants for the storage core based on fireclay and corundum bricks which have particular thermal conductivities and heat capacities. The wall insulation was built of two different micro-porous silicate boards and two different high-temperature insulation wools. The properties of these refractory materials have been characterized for evaluating their suitability.
Thermocouples were inserted into different areas of the TES unit, which the temperature in the core and the wall insulation during the initial heating process recorded over a period of four weeks. Thereby, it was possible to determine the system-related heat capacity and thermal conduction. The obtained data was given into the prior model and used in CFD simulation for further optimization.
09:20 am
The influence of firing parameters on the formation of nitride phases in nitride bonded silicon carbides
Johannes T. Kehren | Koblenz University of Applied Sciences | Germany
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Authors:
Johannes T. Kehren | Koblenz University of Applied Sciences | Germany
Tobias Steffen | Forschungsgemeinschaft Feuerfest e. V. | Germany
Matthias Hauke | Koblenz University of Applied Sciences | Germany
Charlotte Linden | Universität Bonn | Germany
Dr. Christian Dannert | Forschungsgemeinschaft Feuerfest e. V. | Germany
Prof. Dr. rer. nat. Olaf Krause | Koblenz University of Applied Sciences | Germany
In this study the influence of parameters like heating rate, N2-gasflow and dwell time on the kinetics of the nitridation process was investigated. A combination of in situ and ex situ methods was used with special focus on the spatial formation of nitride phases. Centerpiece of the experiments was a new thermogravimetric nitridation furnace, capable of firing in N2 atmosphere up to 1773.15 K which was built at the Forschungsgemeinschaft Feuerfest e. V.
Samples treated in this furnace were analyzed by Raman spectroscopy and scanning electron microscopy (SEM). Both methods provide details on the local formation of nitride phases. SEM analysis was used to determine the morphology of formed phases while Raman spectroscopy is capable of providing spatially resolved mineralogical data. Thereby it was possible to differentiate between the various nitride phases and silicon nitride polymorphs. With this approach of combined in-situ and ex-situ methods, new insights into the formation process of nitride phases within nitride-bonded silicon carbides were gained.
09:40 am
Development of high SiC fraction refractories with silica sol binder
Hirotaka Goto | Calderys Japan Co., Ltd | Japan
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Author:
Hirotaka Goto | Calderys Japan Co., Ltd | Japan
Silicon Carbide (SiC) is a suitable material to be used at thermal exchangers in waste incinerators. Although SiC raw material is under stress due to high carbon footprint and regulations, in the short term, there are no substitutes for it because of its high thermal efficiency and durability.
Nowadays, in Japan, due to the lack of skillful masons and also in order to reduce the maintenance downtime, castable lining is preferred over ready shaped lining such as bricks and tiles, but due to its high thermal conductivity, SiC castable requires careful temperature control during the drying out process to avoid spalling which could occur due to rapid water vapor pressure inside the castable. On the other hand, silica sol bonding technique gives refractories much higher permeability when heated up above the boiling point of the liquid phase. Hence this bonding system gives quick dry out feature for refractories, enabling short downtime. Moreover higher abrasion strength and higher duration than conventional cement bonded products can be reached.
This paper reports the development of high fraction of SiC refractories with silica sol binder. Results show that sol-bonded SiC showed a permeability recorded over 20 times greater than the one of conventional cement products after drying out at 110 ℃, then spalling was not observed on rapid heating tests. Regarding mechanical properties after sintering, sol-bonded SiC refractory achieved 30 % higher cold strength compared to cement bonded castables.
10:00 am
A major step towards the replacement of chromium oxide in refractories for incinerators and other applications
Dr. Ratana Soth | IMERYS | France
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Authors:
Dr. Ratana Soth | IMERYS | France
Remy Jacquemot | IMERYS | France
Cedric Masgalides | IMERYS | France
Michael Weissenbacher | IMERYS | France
Fabien Simonin | IMERYS | France
Dr. Christoph Wöhrmeyer | IMERYS | France
Alumina chromium refractories are still amongst the best performing materials for the application in special waste incinerators and other furnaces with for example a high load of alkalis. On the other hand, typically a significant amount of the compounds that contain initially trivalent chromium oxide, turn during application into hexavalent compounds. This requires a special refractory waste treatment to minimize the health and safety risks associated with the water soluble hexavalent Chromium compounds. While for very high temperature fired bricks some Cr-free new matrix compositions have been developed already based on a new in-situ formed mullite-zirconia microstructure, this paper investigates, how such a microstructure can also be employed in aggregates and fillers to enable the formulation of bricks and monolithics without the need for very high pre-sintering temperatures.
In this context, a new synthetic zirconia mullite aggregate has been developed. Special focus is given on the different types of raw materials as well as the process conditions necessary to reach the desired characteristics and innovative microstructure. Performance tests in model castables have been conducted to simulate their behavior in application conditions. It will be shown that this novel sintered zirconia mullite aggregate keeps a kind of microstructural memory of its original raw materials which is very beneficial for its thermomechanical behavior compared to a standard zirconia mullite aggregate produced through the electrofusion route.
10:20 am
Oxidation behaviors and mechanisms of SiC refractory materials used in municipal waste incinerators containing anti-oxidizing additives
Dr. Charlotte Lang | BCRC | Belgium
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Authors:
Dr. Charlotte Lang | BCRC | Belgium
Dr. Sandra Abdelouhab | BCRC | Belgium
Dr. Florimond Delobel | BCRC | Belgium
Dr. Pascal Pilate | BCRC | Belgium
The furnaces of municipal waste incinerators with energy recovering are lined with SiC refractory tiles oxide or nitride bonded. In service conditions, these products are deteriorated mainly due to corrosion phenomenon induced by an oxidizing atmosphere and flying ashes. The damages differ in function of the tile position in the furnace. Close to the grates, the corrosion occurs in surface with a thickness loss due to the apparition of liquid phases which flow. A new surface of tiles is then available to react again with the corrosive agents. In the middle of the incinerator furnace, the corrosion is more pronounced in the bulk of the material with the penetration of the corrosive agents inducing the formation of new compounds into the tile with a volume expansion leading to cracks and disappearance of joints.
The goal of this work was to improve the oxidation resistance of oxide bonded SiC refractory tiles. Therefore, this study was focused firstly on the understanding of the corrosion mechanism of oxide and nitride bonded SiC refractory tile based on oxidation resistance tests according to the standard recommendations (ASTM C863-83) and on physicochemical characterizations before and after oxidation tests. Secondly, oxide bonded SiC refractory samples containing either B2O3 or B4C as anti-oxidizing additive were also tested. Based on the results obtained during the oxidation tests and the comparison of their physicochemical characterizations before and after oxidation tests, their oxidation behaviors were discussed and compared to the traditional SiC refractory tiles with the proposition of a corrosion mechanism.