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03282 Crystallization of a castable apatite glass-ceramics
12
12
REFRACTORIES/ CERAMICS Properties,
Production,
Applications
98103276 Analysis of radiative heat-transfer in ceramic-lined and ceramic-coated furnaces Khan, Y. U. er al. J. Inst. Energy, March 1998, 71, 21-26. In industrial high-temperature furnaces ceramic materials are widely used to influence thermal radiative heat-transfer. These materials have spectrally dependent (non-grey) emissivity hehaviour. The combustion products of hydrocarbon fuels are also present in many furnaces. These gases emit and absorb radiation in a number of discrete spectral bands of various strengths. This paper presents a theoretical investigation of the effect on fuel consumption of lining furnace surfaces with a range of different ceramic materials; the investigation uses the handed-zone method and calculates the fuel input rates necessary to generate specified heat-transfer rates into the load. Some sample calculations are presented for a simple box furnace containing a cold and a hot load. These results show that permeable ceramics and ceramic coatings require a fuel input rate approximately 20% lower than that for ceramic fihres to achieve the same heat-transfer rate to the load. Ceramic coatings by ion irradiation of polycar 96103277 bosilanes and polysiloxanes. Part II. Hardness and thermochemical stability Pivin, J. C. and Colomho, P. J. Mater. Sci., 1997, 32, (23), 6175-6182. Nano-indentation tests were implemented to measure the hardness of polycarbosilane and polysiloxane coatings subjected to irradiation with increasing doses of helium, carbon and silver ions. The hardness of the ceramic films increases with the formation of diamond-like carbon clusters during irradiation. Further results are discussed. 96103276 Ceramic joining issues in advanced technology development Minh, N. Q. Ceram. Trans., 1997, 77, 15-24. For a number of advanced technologies, the joining of ceramic components is a key enabling process. Two examples of advance technologies in which ceramic joining plays a critical role are solid oxide fuel cells and ceramic heat exchangers. Solid oxide fuel cells are being developed to provide clean and efficient generation of electricity from a variety of gaseous fuels. Individual cells are joined in electric series via a ceramic or metallic interconnect to form a stack of cells in practical power generation. Ceramic heat exchangers are being considered for efficiency improvements in highperformance coal-fired combined-cycle power systems. As high-temperature heat transfer components, ceramic tubes are joined to ceramic manifolds to form the basic heat exchanger unit. These two technologies are described, their joining requirements discussed and the issues involved with joining operations are examined. gal03279 Charge behavior and durability of ceramic filter materials for hot gas filtration Westerheide, R. ef al. Werksr. Energietech., Symp. 3, Werkstoffwoche ‘96, 1996 (Pub. 1997) 177-182. (In German) Edited by Gruenling, H. W., DGM Informationsgesellschaft,: Oberursel, Germany. A material suitable for the manufacture of durable heat-resistant ceramic filters for hot gas filtration of fuel gases directly from a coal gasifier in combined-cycle gas turbine-type power generation processes has been found in Sic-based ceramics. Durable heat-resistant filters were fabricated and successfully used in laboratory-scale experiments. 96103200 Combustion and gasification of coal. Advanced ceramic filtration systems for particulate removal at high temperature British Coal Corporation Comm. Eur. Communities, [Rep.] EUR, 1997, (EUR 15360), 89 pp. Advanced combined cycle power generation technologies require hot clean pressurized gas to be produced in order to maximize their thermal efficiencies. The cleaning is needed to prevent wear of the heavy duty industrial gas turbines which utilize the gas and to meet emission requirements. Ceramic filter elements have been shown to be highly efficient in this duty. Their long-term durability, however, is unproved. A three-year programme has been carried out to investigate the durability of corn. available filter elements. A purpose built rig, The Candle Durability Rig, to study the effects of thermal cycling on durability of filter elements, was constructed. Tests have been carried out to simulate the thermal shock conditions experienced by clay bonded silicon carbide filter elements in PFBC duty. The thermal and pressure transients during pulse cleaning, which are critical to thermal shock, have also been measured and the potential for corrosion of ceramics has been evaluated using a controlled atmospheric furnace and by exposure of specimens in a pressurized fluidized bed gasifier. A range of filter hold-down device configurations has been investigated in order to assess the effect of design on filter
Refractories/ceramics
(properties, production,
applications)
cleaning and entrainment of hot gas into order to minimize thermal shock. A range of modelling studies has been carried out in order to investigate the factors affecting entrainment of hot gas into the high velocity jet of relatively cool pulse gas. Both mathematical and physical modelling tests have been carried out to investigate the flow of pulse gas. The results from the measurements at high temperature and pressure have been used to validate model predictions. This work has resulted in modelling techniques for the pulse cleaning process which will aid design of these systems. In order to investigate the pressure and thermal induced forces on ceramic filter elements during pulse cleaning, stress analysis modelling was carried out using a commercially available programme. The modelling tools developed can now be used to aid understanding of how the design and operating parameters for pulse cleaning will affect the cleanability and thermal shock damage to ceramic filters. 96103281 Conditions for testing the corrosion rates of ceramics in coal gasification systems Hurley, J. P. and Nowok, J. W. Oak Ridge Natl. Laboratory, [Rep.] ORNLI FMP (U. S.) 1996, (ORNIIFMP-96/l, Proceedings of the Tenth Annual Conference on Fossil Energy Materials, 1996), 181-191. The operating conditions of a coal gasifier and the gas and ash compositions affect the corrosion rates of ceramics used for construction in three ways: (1) direct corrosion of the materials, (2) affecting the concentration and chemical form of the primary corrodents and (3) affecting the mass transport rate of the primary corrodents. To perform an accurate corrosion test on a system material, the researcher must include all relevant corrodents and simulate conditions in the gasifier as closely as possible. In this paper, we present suggestions for conditions to be used in such corrosion tests. 9BlB3282 Crystallization of a castable apatite glass-ceramics Liao, Y. Shengwu Ytiue Gongchengxue Zazhi, 1997, 14, (2), 105-107, 114. (In Chinese) DTA, XRD and SEM were employed to study the crystallization feature of a castahle apatite glass-ceramics. The effect of chemical composition on the microstructure of the glass-ceramics was discussed. The crystallization feature was substantially influenced by the introduction of MgO and Al:01 into the system. 9WO3263 Hard ceramic boards and tiles for exterior walls and lining of furnaces Tanabe, K. and Matsuura, K. Eur. Pat. Appl. EP 818,428 (Cl. C04B28/26), 14 Jan 1998, JP Appl. 971146,376, 4 Jun 1997, 6 pp. A first powder comprising SiOz, CaO, and an Al compound is mixed with a second powder serving as aggregate. The mixture is mixed with water-glass and cured. The ceramics are used as exterior wall tiles and furnace lining. A mixture consisting of ordinary portland cement 8, SiOz fume 31, and fly ashes was mixed with sand and water glass, moulded and dried at 150°C for 3 h togive boards with specific gravity 1.8 g/cm’, compressive strength 1120 kg/cm , Mohs hardness 5, water absorption (immersed in water at 20” for 72 h) 0.0002, heat resistance (at 1050°C for 3 h) no change, and weather resistance (1000 h in weatherometer) no change. 96103284 High temperature device for the study of the dynamic oxidation of refractory compounds-application to graphite Benhaya, A. and Granier, B. Chemical Engineering and Processing, 1998, 36, (6), 433-441.
An experimental set-up for the study of the dynamic oxidation of refractory compounds is described. A plasma torch and a high temperature reactor are included in the apparatus, which aims to blow a high temperature oxidizing gas through a tubular sample. Tests on graphite show the mass loss rate of graphite samples vary from 1 to 10% for oxygen volume concentration, from 1500 to 2200 K for sample temperature, from 1600 to 3500 K and 60 to 120 m ss’ for gas temperature and average stream velocity. These results can be roughly accounted for by a solution of the Graetz-Nusselt problem. The authors give local Sherwood numbers from the measurement of the inner diameter of the sample after oxidation. 98103285 High-strength ceramic composite boards and their manufacture from fly ashes Oda, K. and Oda, M. Jpn. Kokai Tokkyo Koho JP 10 25,170 [98 2.5,170] (Cl. C04B35/71), 27 Jan 1998, Appl. 961176,946, 5 Jul 1996, 7 pp. (In Japanese) One hundred parts fly ashes are mixed with 2-30 parts binders and optionally lo-30 parts fire-resistant fine aggregates. Heat-resistant mesh sheets are then embedded in the mixtures, and the resulting materials are sintered at 500-1300°C. The fly ashes may be from coal fired powder plants or refuse incinerating furnaces. 9WO3266 Industrial applications of SiBN(C) ceramics made from polymeric precursors Baldus. H. P. et al. Fortschrittsber. Dtsch. Keram. Ges.. 1997. 12.,~,, (1). 117131. (In German) The paper reports on the preparation of pre-ceramic horosilazanes, starting from the ‘single source’ precursor dichloro-N-(trichlorosilyl) horanamine and methyl- or dimethylamine, is reported. The specific reaction conditions could influence the properties and rheological of these pre-ceramic precursors. The pre-ceramic borosilazanes were pyrolysed at temperatures
Fuel and Energy Abstracts
July 1998
303
12
REFRACTORIES/ CERAMICS Properties,
Production,
Applications
98103276 Analysis of radiative heat-transfer in ceramic-lined and ceramic-coated furnaces Khan, Y. U. er al. J. Inst. Energy, March 1998, 71, 21-26. In industrial high-temperature furnaces ceramic materials are widely used to influence thermal radiative heat-transfer. These materials have spectrally dependent (non-grey) emissivity hehaviour. The combustion products of hydrocarbon fuels are also present in many furnaces. These gases emit and absorb radiation in a number of discrete spectral bands of various strengths. This paper presents a theoretical investigation of the effect on fuel consumption of lining furnace surfaces with a range of different ceramic materials; the investigation uses the handed-zone method and calculates the fuel input rates necessary to generate specified heat-transfer rates into the load. Some sample calculations are presented for a simple box furnace containing a cold and a hot load. These results show that permeable ceramics and ceramic coatings require a fuel input rate approximately 20% lower than that for ceramic fihres to achieve the same heat-transfer rate to the load. Ceramic coatings by ion irradiation of polycar 96103277 bosilanes and polysiloxanes. Part II. Hardness and thermochemical stability Pivin, J. C. and Colomho, P. J. Mater. Sci., 1997, 32, (23), 6175-6182. Nano-indentation tests were implemented to measure the hardness of polycarbosilane and polysiloxane coatings subjected to irradiation with increasing doses of helium, carbon and silver ions. The hardness of the ceramic films increases with the formation of diamond-like carbon clusters during irradiation. Further results are discussed. 96103276 Ceramic joining issues in advanced technology development Minh, N. Q. Ceram. Trans., 1997, 77, 15-24. For a number of advanced technologies, the joining of ceramic components is a key enabling process. Two examples of advance technologies in which ceramic joining plays a critical role are solid oxide fuel cells and ceramic heat exchangers. Solid oxide fuel cells are being developed to provide clean and efficient generation of electricity from a variety of gaseous fuels. Individual cells are joined in electric series via a ceramic or metallic interconnect to form a stack of cells in practical power generation. Ceramic heat exchangers are being considered for efficiency improvements in highperformance coal-fired combined-cycle power systems. As high-temperature heat transfer components, ceramic tubes are joined to ceramic manifolds to form the basic heat exchanger unit. These two technologies are described, their joining requirements discussed and the issues involved with joining operations are examined. gal03279 Charge behavior and durability of ceramic filter materials for hot gas filtration Westerheide, R. ef al. Werksr. Energietech., Symp. 3, Werkstoffwoche ‘96, 1996 (Pub. 1997) 177-182. (In German) Edited by Gruenling, H. W., DGM Informationsgesellschaft,: Oberursel, Germany. A material suitable for the manufacture of durable heat-resistant ceramic filters for hot gas filtration of fuel gases directly from a coal gasifier in combined-cycle gas turbine-type power generation processes has been found in Sic-based ceramics. Durable heat-resistant filters were fabricated and successfully used in laboratory-scale experiments. 96103200 Combustion and gasification of coal. Advanced ceramic filtration systems for particulate removal at high temperature British Coal Corporation Comm. Eur. Communities, [Rep.] EUR, 1997, (EUR 15360), 89 pp. Advanced combined cycle power generation technologies require hot clean pressurized gas to be produced in order to maximize their thermal efficiencies. The cleaning is needed to prevent wear of the heavy duty industrial gas turbines which utilize the gas and to meet emission requirements. Ceramic filter elements have been shown to be highly efficient in this duty. Their long-term durability, however, is unproved. A three-year programme has been carried out to investigate the durability of corn. available filter elements. A purpose built rig, The Candle Durability Rig, to study the effects of thermal cycling on durability of filter elements, was constructed. Tests have been carried out to simulate the thermal shock conditions experienced by clay bonded silicon carbide filter elements in PFBC duty. The thermal and pressure transients during pulse cleaning, which are critical to thermal shock, have also been measured and the potential for corrosion of ceramics has been evaluated using a controlled atmospheric furnace and by exposure of specimens in a pressurized fluidized bed gasifier. A range of filter hold-down device configurations has been investigated in order to assess the effect of design on filter
Refractories/ceramics
(properties, production,
applications)
cleaning and entrainment of hot gas into order to minimize thermal shock. A range of modelling studies has been carried out in order to investigate the factors affecting entrainment of hot gas into the high velocity jet of relatively cool pulse gas. Both mathematical and physical modelling tests have been carried out to investigate the flow of pulse gas. The results from the measurements at high temperature and pressure have been used to validate model predictions. This work has resulted in modelling techniques for the pulse cleaning process which will aid design of these systems. In order to investigate the pressure and thermal induced forces on ceramic filter elements during pulse cleaning, stress analysis modelling was carried out using a commercially available programme. The modelling tools developed can now be used to aid understanding of how the design and operating parameters for pulse cleaning will affect the cleanability and thermal shock damage to ceramic filters. 96103281 Conditions for testing the corrosion rates of ceramics in coal gasification systems Hurley, J. P. and Nowok, J. W. Oak Ridge Natl. Laboratory, [Rep.] ORNLI FMP (U. S.) 1996, (ORNIIFMP-96/l, Proceedings of the Tenth Annual Conference on Fossil Energy Materials, 1996), 181-191. The operating conditions of a coal gasifier and the gas and ash compositions affect the corrosion rates of ceramics used for construction in three ways: (1) direct corrosion of the materials, (2) affecting the concentration and chemical form of the primary corrodents and (3) affecting the mass transport rate of the primary corrodents. To perform an accurate corrosion test on a system material, the researcher must include all relevant corrodents and simulate conditions in the gasifier as closely as possible. In this paper, we present suggestions for conditions to be used in such corrosion tests. 9BlB3282 Crystallization of a castable apatite glass-ceramics Liao, Y. Shengwu Ytiue Gongchengxue Zazhi, 1997, 14, (2), 105-107, 114. (In Chinese) DTA, XRD and SEM were employed to study the crystallization feature of a castahle apatite glass-ceramics. The effect of chemical composition on the microstructure of the glass-ceramics was discussed. The crystallization feature was substantially influenced by the introduction of MgO and Al:01 into the system. 9WO3263 Hard ceramic boards and tiles for exterior walls and lining of furnaces Tanabe, K. and Matsuura, K. Eur. Pat. Appl. EP 818,428 (Cl. C04B28/26), 14 Jan 1998, JP Appl. 971146,376, 4 Jun 1997, 6 pp. A first powder comprising SiOz, CaO, and an Al compound is mixed with a second powder serving as aggregate. The mixture is mixed with water-glass and cured. The ceramics are used as exterior wall tiles and furnace lining. A mixture consisting of ordinary portland cement 8, SiOz fume 31, and fly ashes was mixed with sand and water glass, moulded and dried at 150°C for 3 h togive boards with specific gravity 1.8 g/cm’, compressive strength 1120 kg/cm , Mohs hardness 5, water absorption (immersed in water at 20” for 72 h) 0.0002, heat resistance (at 1050°C for 3 h) no change, and weather resistance (1000 h in weatherometer) no change. 96103284 High temperature device for the study of the dynamic oxidation of refractory compounds-application to graphite Benhaya, A. and Granier, B. Chemical Engineering and Processing, 1998, 36, (6), 433-441.
An experimental set-up for the study of the dynamic oxidation of refractory compounds is described. A plasma torch and a high temperature reactor are included in the apparatus, which aims to blow a high temperature oxidizing gas through a tubular sample. Tests on graphite show the mass loss rate of graphite samples vary from 1 to 10% for oxygen volume concentration, from 1500 to 2200 K for sample temperature, from 1600 to 3500 K and 60 to 120 m ss’ for gas temperature and average stream velocity. These results can be roughly accounted for by a solution of the Graetz-Nusselt problem. The authors give local Sherwood numbers from the measurement of the inner diameter of the sample after oxidation. 98103285 High-strength ceramic composite boards and their manufacture from fly ashes Oda, K. and Oda, M. Jpn. Kokai Tokkyo Koho JP 10 25,170 [98 2.5,170] (Cl. C04B35/71), 27 Jan 1998, Appl. 961176,946, 5 Jul 1996, 7 pp. (In Japanese) One hundred parts fly ashes are mixed with 2-30 parts binders and optionally lo-30 parts fire-resistant fine aggregates. Heat-resistant mesh sheets are then embedded in the mixtures, and the resulting materials are sintered at 500-1300°C. The fly ashes may be from coal fired powder plants or refuse incinerating furnaces. 9WO3266 Industrial applications of SiBN(C) ceramics made from polymeric precursors Baldus. H. P. et al. Fortschrittsber. Dtsch. Keram. Ges.. 1997. 12.,~,, (1). 117131. (In German) The paper reports on the preparation of pre-ceramic horosilazanes, starting from the ‘single source’ precursor dichloro-N-(trichlorosilyl) horanamine and methyl- or dimethylamine, is reported. The specific reaction conditions could influence the properties and rheological of these pre-ceramic precursors. The pre-ceramic borosilazanes were pyrolysed at temperatures
Fuel and Energy Abstracts
July 1998
303