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Ichiro Naruse - One of the best experts on this subject based on the ideXlab platform.
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Paper No 22 EFFECT OF COAL TYPE ON EMISSION CHARACTERISTICS OF Alkali Metal Compounds IN PARTICULATE MATTERS
2020Co-Authors: Tsuyoshi Takuwa, Ichiro NaruseAbstract:ABSTRACT Some Metal Compounds in coal vaporize and form fumes during combustion. The fumes are generally exhausted through the flue gas. For coal-fired combined power generation systems such as pressurized fluidized bed combustion (PFBC), hot vapors may contact with the surfaces of gas-turbine blades. As this contact of the hot vapors with the surface has corrosive effect, it is necessary to control the formation of those fumes, which mainly contain Alkali Metal Compounds. In this paper, the evolution behavior of Alkali Metal Compounds, especially for sodium Compounds, has been studied, using an electrically heated drop tube furnace with a low-pressure impactor. The main objective in this study is to elucidate the conditions and the possible mechanisms to form Alkali Metal Compounds in particulate matter during combustion. Two types of coal with different sodium content were tested, where the coal conversion characteristics were established. Furthermore, the evolution and inclusion of sodium Compounds into the sub-micron particles were studied in relation to the particle size distribution formed and sodium fraction distribution in the collected fine particulates. The study proved that the evolution and inclusion of sodium in the sub-micron particles depended on function of type of coal via its composition and the form by which sodium Compounds existed in coal. The reaction-controlled mechanism and heterogeneous condensation via chemical reactions during combustion affected the inclusion of sodium in the sub-micron particles. In the coarse particles of above about 0.5 µm, reaction that formed those particles was mainly via gas film diffusion surrounding the particle
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detailed kinetic and control of Alkali Metal Compounds during coal combustion
Fuel Processing Technology, 2007Co-Authors: Tsuyoshi Takuwa, Ichiro NaruseAbstract:Abstract Alkali Metal Compounds in coal sometimes play a role for corrosion and/or erosion in combustion boilers. Therefore, it is necessary to understand detail kinetics and behaviors of the Alkali Metal Compounds during coal combustion, and to develop the control technologies for them during combustion. Combustion tests for several types of coal are conducted, using an electrically heated drop tube furnace with a low pressure impactor (LPI), which can separate the particulates with size ranged from 0.03 to 11 μm. As direct measurement of behaviors of Alkali Metal Compounds during combustion is difficult, however, behavior of vapors of Na Compounds in H 2 –air flame is also simulated by detail kinetics calculation, using the CHEMKIN code. To control the Alkali Metal Compounds during coal combustion, while, a little amount of kaolin that is used as a sorbent for the Alkali Metal Compounds, is mixed with the coal, and is burned together.
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mechanisms of fine particulates formation with Alkali Metal Compounds during coal combustion
Fuel, 2006Co-Authors: Tsuyoshi Takuwa, Iddi S N Mkilaha, Ichiro NaruseAbstract:Two types of coals with different sodium (Na) and potassium (K) concentrations were burned in an electrically heated drop tube furnace, to study the formation of particulates in association to Alkali Metal Compounds from the coals. The particulates formed from these coals during combustion were separated by a low pressure impactor (LPI). The particulates collected in each stage of the LPI were analyzed, using an atomic adsorption spectrometer (AAS). The results obtained show that ash particles have bimodal particle size distribution for both coal types. This tendency could be due to the difference of the inherent minerals in raw coals. It was further observed that Na and K were enriched in the fine particulates for both types of coal. There was a dependence of the Na enrichment on the fine particles on concentration of excluded mineral in the raw coals. This work, therefore, showed that the appearance of Alkali Metal in the ash particles related to the nature of Na and K concentrations in raw coals.
Tsuyoshi Takuwa - One of the best experts on this subject based on the ideXlab platform.
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Paper No 22 EFFECT OF COAL TYPE ON EMISSION CHARACTERISTICS OF Alkali Metal Compounds IN PARTICULATE MATTERS
2020Co-Authors: Tsuyoshi Takuwa, Ichiro NaruseAbstract:ABSTRACT Some Metal Compounds in coal vaporize and form fumes during combustion. The fumes are generally exhausted through the flue gas. For coal-fired combined power generation systems such as pressurized fluidized bed combustion (PFBC), hot vapors may contact with the surfaces of gas-turbine blades. As this contact of the hot vapors with the surface has corrosive effect, it is necessary to control the formation of those fumes, which mainly contain Alkali Metal Compounds. In this paper, the evolution behavior of Alkali Metal Compounds, especially for sodium Compounds, has been studied, using an electrically heated drop tube furnace with a low-pressure impactor. The main objective in this study is to elucidate the conditions and the possible mechanisms to form Alkali Metal Compounds in particulate matter during combustion. Two types of coal with different sodium content were tested, where the coal conversion characteristics were established. Furthermore, the evolution and inclusion of sodium Compounds into the sub-micron particles were studied in relation to the particle size distribution formed and sodium fraction distribution in the collected fine particulates. The study proved that the evolution and inclusion of sodium in the sub-micron particles depended on function of type of coal via its composition and the form by which sodium Compounds existed in coal. The reaction-controlled mechanism and heterogeneous condensation via chemical reactions during combustion affected the inclusion of sodium in the sub-micron particles. In the coarse particles of above about 0.5 µm, reaction that formed those particles was mainly via gas film diffusion surrounding the particle
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detailed kinetic and control of Alkali Metal Compounds during coal combustion
Fuel Processing Technology, 2007Co-Authors: Tsuyoshi Takuwa, Ichiro NaruseAbstract:Abstract Alkali Metal Compounds in coal sometimes play a role for corrosion and/or erosion in combustion boilers. Therefore, it is necessary to understand detail kinetics and behaviors of the Alkali Metal Compounds during coal combustion, and to develop the control technologies for them during combustion. Combustion tests for several types of coal are conducted, using an electrically heated drop tube furnace with a low pressure impactor (LPI), which can separate the particulates with size ranged from 0.03 to 11 μm. As direct measurement of behaviors of Alkali Metal Compounds during combustion is difficult, however, behavior of vapors of Na Compounds in H 2 –air flame is also simulated by detail kinetics calculation, using the CHEMKIN code. To control the Alkali Metal Compounds during coal combustion, while, a little amount of kaolin that is used as a sorbent for the Alkali Metal Compounds, is mixed with the coal, and is burned together.
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mechanisms of fine particulates formation with Alkali Metal Compounds during coal combustion
Fuel, 2006Co-Authors: Tsuyoshi Takuwa, Iddi S N Mkilaha, Ichiro NaruseAbstract:Two types of coals with different sodium (Na) and potassium (K) concentrations were burned in an electrically heated drop tube furnace, to study the formation of particulates in association to Alkali Metal Compounds from the coals. The particulates formed from these coals during combustion were separated by a low pressure impactor (LPI). The particulates collected in each stage of the LPI were analyzed, using an atomic adsorption spectrometer (AAS). The results obtained show that ash particles have bimodal particle size distribution for both coal types. This tendency could be due to the difference of the inherent minerals in raw coals. It was further observed that Na and K were enriched in the fine particulates for both types of coal. There was a dependence of the Na enrichment on the fine particles on concentration of excluded mineral in the raw coals. This work, therefore, showed that the appearance of Alkali Metal in the ash particles related to the nature of Na and K concentrations in raw coals.
Yuri Grin - One of the best experts on this subject based on the ideXlab platform.
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ferromagnetic ordering in Alkali Metal iron antimonides nafe4sb12 and kfe4sb12
Physical Review Letters, 2003Co-Authors: Andreas Leithejasper, Walter Schnelle, H Rosner, M Baenitz, A Rabis, A A Gippius, E N Morozova, N Senthilkumaran, J A Mydosh, Yuri GrinAbstract:New Alkali-Metal Compounds with the filled-skutterudite structure were synthesized and their chemical and physical properties investigated. X-ray diffraction, microprobe, and chemical analysis established the structure and the composition without defects on the cation site. Magnetization, ac susceptibility, specific heat, resistivity, and NMR or NQR demonstrated NaFe 4 Sb 1 2 to be ferromagnetic below approximately 85 K and to exhibit an additional magnetic anomaly around 40 K. Band structure calculations find a large density of states at the Fermi energy and a ferromagnetic ground state. Similar behavior was observed for KFe 4 Sb 1 2 .
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binary Alkali Metal Compounds with the zintl anions ge9 4 and sn9 4
ChemInform, 1997Co-Authors: H G Von Schnering, Michael Baitinger, U Bolle, Wilder Carrillocabrera, Jan Curda, Yuri Grin, F Heinemann, Jaime Llanos, K Peters, Andre SchmedingAbstract:The binary germanides M12Ge17 and M4Ge9 (M Na, K, Rb, Cs) and the stannides M12Sn17 and M4Sn9 (M K, Rb, Cs) were identified by a combination of direct synthesis, thermogravimetric analysis, vibrational spectroscopy, X-ray powder data and single crystal structure analysis. The M12E17 phases contain the cluster anions [E9]4− and [E4]4− in the ratio 1:2, forming a hierarchical structure with the cluster anions at the atomic positions of the hexagonal Laves phase MgZn2. Like the M4E4 phases, the M4Ge9 Compounds are hierarchical derivatives of the cubic Cr3Si structure but with [Ge9]4− anions. The thermogravimetric analyses give strong evidence for the existence of at least one more phase with [E9]4− and [E4]4− clusters and of the clathrate phases M6E136 in addition to the well-known M8E44□2 chlathrates.
Andreas Leithejasper - One of the best experts on this subject based on the ideXlab platform.
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weak itinerant ferromagnetism and electronic and crystal structures of Alkali Metal iron antimonides nafe4sb12 and kfe4sb12
Physical Review B, 2004Co-Authors: Andreas Leithejasper, Walter Schnelle, H Rosner, M Baenitz, A Rabis, A A Gippius, E N Morozova, Horst Borrmann, Ulrich Burkhardt, Reiner RamlauAbstract:The synthesis, chemical, structural, and magnetic properties of Alkali-Metal Compounds with filled-skutterudite structure, $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{K}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, are described. X-ray and neutron diffraction and elemental analysis established the crystal structure without defects and disorder on the cation site. The temperature and pressure dependence of the cubic unit cell of $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and the displacement parameter of Na are investigated. The electronic structure is calculated by density functional methods (LMTO, FPLO). Quantum chemical calculations (electron localization function) reveal the covalent character of both $\mathrm{Fe}\penalty1000-\hskip0pt\mathrm{Sb}$ and $\mathrm{Sb}\penalty1000-\hskip0pt\mathrm{Sb}$ interactions. Electronic structure calculations within the local density approximation exhibit a band ferromagnetic ground state and predict a half-Metallic behavior. In contrast to isostructural Alkaline-earth Compounds ($\mathrm{Ca}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{Ba}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$), the Alkali-Metal skutterudites are itinerant electron ferromagnets with small magnetic moments ($\ensuremath{\approx}0.25{\ensuremath{\mu}}_{\mathrm{B}}∕\mathrm{Fe}$ atom) and ${T}_{\mathrm{C}}\ensuremath{\approx}85\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Yet the paramagnetic moments of all four Compounds are between $1.5{\ensuremath{\mu}}_{\mathrm{B}}$ and $1.7{\ensuremath{\mu}}_{\mathrm{B}}$ per Fe atom, indicating similar Stoner factors. Temperature-dependent $^{57}\mathrm{Fe}$ and $^{121}\mathrm{Sb}$ M\"ossbauer spectroscopies confirm the ferromagnetic state in the sodium compound with very small hyperfine fields at the iron and antimony sites.
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ferromagnetic ordering in Alkali Metal iron antimonides nafe4sb12 and kfe4sb12
Physical Review Letters, 2003Co-Authors: Andreas Leithejasper, Walter Schnelle, H Rosner, M Baenitz, A Rabis, A A Gippius, E N Morozova, N Senthilkumaran, J A Mydosh, Yuri GrinAbstract:New Alkali-Metal Compounds with the filled-skutterudite structure were synthesized and their chemical and physical properties investigated. X-ray diffraction, microprobe, and chemical analysis established the structure and the composition without defects on the cation site. Magnetization, ac susceptibility, specific heat, resistivity, and NMR or NQR demonstrated NaFe 4 Sb 1 2 to be ferromagnetic below approximately 85 K and to exhibit an additional magnetic anomaly around 40 K. Band structure calculations find a large density of states at the Fermi energy and a ferromagnetic ground state. Similar behavior was observed for KFe 4 Sb 1 2 .
U Gottwald - One of the best experts on this subject based on the ideXlab platform.
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the influence of fuel additives on the behaviour of gaseous Alkali Metal Compounds during pulverised coal combustion
Faraday Discussions, 2002Co-Authors: Helmut Schürmann, S Unterberger, K R G Hein, P B Monkhouse, U GottwaldAbstract:The Alkali-Metal vapour release during pulverised hard (bituminous) coal combustion was investigated in a semi-technical drop flow reactor in the temperature range 1100–1400°C. Absolute concentrations of total gas-phase sodium and potassium species were determined using the in situ/on-line excimer laser induced fragmentation fluorescence technique (ELIF). Alkali-Metal concentrations measured for the untreated coals were found to be in the range 0.1 to 4.7 ppm, depending on the temperature. As well as observing the temperature dependence, the effect of co-feeding defined amounts of silica and clay minerals was studied. In addition, to assist interpretation of ELIF measurements, ash samples were taken and analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The additives lead to a pronounced binding of the Alkali-Metal species and suppression of the sharp temperature dependence observed without co-feeding. Therefore, the use of such getter materials can be confirmed as an effective way to remove corrosive Alkali-Metal species from the flue gas in pulverised coal combustion.