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00269 Improvement of a chain-hardening furnace by computational fluid dynamics (CFD) simulation
09 Combustion (burners, combustion systems) 06•00266 Diameter and morphology dependence on experimental conditions of carbon nanotube arrays grown by spray pyrolysis Tapasztd, L. et al. Carbon, 2005, 43, (5), 970 977. A systematic study on the controlled growth of large areas of aligned multi-wall carbon nanotube arrays, from ferrocene-benzene precursor, and of nanotube junctions from ferrocene-thiophene precursor, without hydrogen addition, using an injection CVD method easy to scale up for industrial production is reported. A detailed study is presented of how the synthesis parameters such as growth temperature, active solution flow rate, catalyst concentration or sulfur addition can control the properties and morphology of the grown nanotube mat. Nanotube junctions with considerable yield can be grown with the method by adding sulfur to the synthesis process. The sulfur addition also results in growth of carbon nanocones (CNC) in the lower temperature regime of the furnace. Observation of single-wall carbon nanotuhes in the STM investigations provides further indication that under properly chosen conditions SWCNTs can be grown with similar continuous processes.
06•00267 DNS analysis of partially premixed combustion in spray and gaseous turbulent flame-bases stabilized in hot air Domingo, P. el a/. Combuslion and Flame, 2005, 140, (3), 172 195. Direct numerical simulations of weakly turbulent-lifted flame bases are examined in the case of both gaseous and spray fuel jet injection. Simplified transport properties and an adjustable single-step chemistry that matches the flame response to equivalence ratio are used. The flames are stabilized within a co-flowing stream of heated air. The properties of the zone where burning starts are found to strongly depend on the type of fuel injection. The gaseous flame base is essentially composed of an edge flame, with a large contribution of partially premixed combustion. This partially premixed flame takes two different forms, a nearly stoichiometric propagating kernel and a rich trailing flame whose burning rate is diffusion controlled. The rich premixed flame is parallel to the stoichiometric line, along which a diffusion flame burns the fuel left by this rich trailing flame, up to the very leading edge of the flame base. In the spray case, a non-negligible amount of oxidizer is entrained within the dilute spray, also leading to an important contribution of partially premixed burning. However, diffusion and premixed burning are found more distributed in space in the spray case than with gaseous injection. A progress variable that is generalized to partially premixed combustion is discussed and the relative contributions of the terms of its balance equation are analysed from the DNS. A flame partitioning into premixed and diffusion types is then examined and the stabilization zone is decomposed into basic flame prototypes. A subgrid scale flame decomposition is further discussed from a direct filtering of DNS and some a priori tests of subgrid scale modelling are reported.
06•00268 Experimental study of industrial scale fullerene production by combustion synthesis Takehara, H. et al. Carbon, 2005, 43, (2), 311 319. Fullerenes are expected to be one of the first carbon nanomaterials to be widely employed for various commercial applications. However, one critical factor that has limited the development of such applications is the high cost and limited availability of fullerenes. Much of this problem is due to the small-scale, batch nature of fullerene production using carbon arcs. In contrast, the combustion method generates soot with a very high yield of fullerenes using a continuous and easily scalable process. The authors have developed a combustion system that can produce fullerenes at the tons per year scale. Using this system, a laminar premixed fiat sooting low-pressure toluene/oxygen flame that produced fullerenes was investigated, and the report documents the relation of the fullerene content and the combustion conditions such as the atomic C/O ratio, the cold burner gas velocity. When the atomic C/ O ratio was higher, the fullerene content declined even though the fuel, pressure, and other combustion conditions were same. On the other hand, the fullerene content remained constant when the cold gas velocity was increased from 0.78 m/s to 1.7 m/s. The data are also discussed from a thermodynamic and equilibrium analysis point of view to gain insight into the fullerene formation process.
06•00269 Improvement of a chain-hardening furnace by computational fluid dynamics (CFD) simulation Sala, J.M. et al. Applied Energy, 2005, 81, (3), 260 276. Hardening heat-treatment is an important operation in the fabrication of large chains for both the shipping industry and anchorage of offshore oil-platforms. This paper presents the outcome of an investigation that led to the introduction of modifications in a hardening furnace resulting in a substantial improvement and largely eliminating the problem of gradual cooling of the chain before immersion in the water-quenching tank. Comparing this with the
38
Fuel and Energy Abstracts
January 2006
present operating conditions, it can be concluded that redirecting the gas flow increases the gas temperature in the lower part of the furnace, which changes the chain's temperature-distribution accordingly.
06•00270 Microwave-assisted in-situ regeneration of a perovskite coated diesel soot filter Zhang-Steenwinkel, Y. et al. Chemical Engineering Science, 2005, 60, (3), 797 804. Dielectric heating may be used as an in situ technique for the periodic regeneration of soot filters, as those used in Diesel engines. As generally the Diesel exhaust temperatures are below the soot light-off temperature, passive regeneration is not possible. The authors have investigated the dielectric heating of a monolithic soot filter, coated with a Lao.sCeo.2MnO3 perovskite. This type of perovskite has suitable dielectric properties, i.e. a high dielectric loss factor, and simultaneously acts as an oxidation catalyst. It is shown that a perovskite coated cordierite filter, covered with synthetic carbon, can be fully regenerated with selectivity towards CO2 close to 100%. In contrast, the same filter without such a coating can only be partially regenerated. Moreover, considerable amounts of CO are formed. The Lao.sCeo.:MnO3 coating is shown to have excellent temperature shock resistance and thermo-chemical stability. It is shown that the microwave cavity design is crucial to obtain a uniform filter heating. Following the development of such a design, microwave assisted soot filter regeneration becomes feasible.
06/00271 Numerical study of SNCR application to a fullscale stoker incinerator at Daejon 4th industrial complex Kim, H.-S. e t al. Applied TlTermal Engineering, 2004, 24, (14 15), 2117 2129. Considering the rapid variation of waste composition and the more severe regulation trend of pollutant emission in this country, the importance of the development of a reliable computer program for a full-scale, stoker-type incinerator cannot be emphasized too much especially in the view of proper design and optimal determination of operating condition of existing and future constructed facility. To this end, a comprehensive, numerical model related with the process of the waste-off gaseous combustion with the capacity of 200 tons/day is successfully made. This includes development of several phenomenological models such as municipal waste-off gaseous reaction, NO pollutant generation and destruction in turbulence-related environment. Especially, in this study a number of sound assumptions have been made for the NO reaction model, 3-D geometry of incinerator and waste-bed model to achieve the efficient incorporation of the empirical models and enhancement of the stability of calculation process. First of all, the turbulence related, complex combustion chemistry involved with NO reaction is modelled by the harmonic mean method, which is given by the relative strength of the rates of chemistry and turbulent mixing. Further, the 3-D rectangular shape of the incinerator is simply approximated by a 3-D axi-symmetric geometry with equivalent area. And the modelling of complex wasteburning process on moving grate is described by a pure gaseous combustion process of waste off-gas. The program developed in this study is successfully validated by comparing with the experimental data such as temperature and NO concentration profiles in the incinerator located at 4th industrial complex of Daejon, S. Korea. Using the program developed, a series of parametric investigations have been made for the evaluation of SNCR process and thereby evaluate various important design and the operating variables. The major parameters considered in this parametric study are heating value of municipal waste, the injection location and amount of reduction material, and the proper length of insulating castable. In general, the calculated results are physically acceptable and fairly consistent.
06/00272 Potential applications of high-temperature air/ steam-blown gasification and pyrolysis systems Zubtsov, V. M. el al. Energy, 2005, 30, (11 12), 2229 2242. Several aspects of using the advanced, high-temperature air/steamblown gasification and pyrolysis technologies for converting solid fuels into syngas are examined. The gasification/pyrolysis systems, known as multi-staged enthalpy extraction technology (MEET), employ hightemperature air and steam as oxidizer agents for converting the solid fuels into syngas and have many features that are advantageous for power generation. The low-cost gasifier/pyrolyser is extremely compact and flexible, capable of operating efficiently on a wide range of lowcaloric-value fuels. Potential uses of this technology range from largescale integrated gasification power plants to small-scale waste-toenergy applications. Present R&D status of the MEET technology are summarized and its main components are described. Major fuel resources for the different markets are explored. The performance and feasibility of diverse power conversion systems to couple with MEET gasifier/pyrolyser for combined heat and power applications are assessed.
06•00267 DNS analysis of partially premixed combustion in spray and gaseous turbulent flame-bases stabilized in hot air Domingo, P. el a/. Combuslion and Flame, 2005, 140, (3), 172 195. Direct numerical simulations of weakly turbulent-lifted flame bases are examined in the case of both gaseous and spray fuel jet injection. Simplified transport properties and an adjustable single-step chemistry that matches the flame response to equivalence ratio are used. The flames are stabilized within a co-flowing stream of heated air. The properties of the zone where burning starts are found to strongly depend on the type of fuel injection. The gaseous flame base is essentially composed of an edge flame, with a large contribution of partially premixed combustion. This partially premixed flame takes two different forms, a nearly stoichiometric propagating kernel and a rich trailing flame whose burning rate is diffusion controlled. The rich premixed flame is parallel to the stoichiometric line, along which a diffusion flame burns the fuel left by this rich trailing flame, up to the very leading edge of the flame base. In the spray case, a non-negligible amount of oxidizer is entrained within the dilute spray, also leading to an important contribution of partially premixed burning. However, diffusion and premixed burning are found more distributed in space in the spray case than with gaseous injection. A progress variable that is generalized to partially premixed combustion is discussed and the relative contributions of the terms of its balance equation are analysed from the DNS. A flame partitioning into premixed and diffusion types is then examined and the stabilization zone is decomposed into basic flame prototypes. A subgrid scale flame decomposition is further discussed from a direct filtering of DNS and some a priori tests of subgrid scale modelling are reported.
06•00268 Experimental study of industrial scale fullerene production by combustion synthesis Takehara, H. et al. Carbon, 2005, 43, (2), 311 319. Fullerenes are expected to be one of the first carbon nanomaterials to be widely employed for various commercial applications. However, one critical factor that has limited the development of such applications is the high cost and limited availability of fullerenes. Much of this problem is due to the small-scale, batch nature of fullerene production using carbon arcs. In contrast, the combustion method generates soot with a very high yield of fullerenes using a continuous and easily scalable process. The authors have developed a combustion system that can produce fullerenes at the tons per year scale. Using this system, a laminar premixed fiat sooting low-pressure toluene/oxygen flame that produced fullerenes was investigated, and the report documents the relation of the fullerene content and the combustion conditions such as the atomic C/O ratio, the cold burner gas velocity. When the atomic C/ O ratio was higher, the fullerene content declined even though the fuel, pressure, and other combustion conditions were same. On the other hand, the fullerene content remained constant when the cold gas velocity was increased from 0.78 m/s to 1.7 m/s. The data are also discussed from a thermodynamic and equilibrium analysis point of view to gain insight into the fullerene formation process.
06•00269 Improvement of a chain-hardening furnace by computational fluid dynamics (CFD) simulation Sala, J.M. et al. Applied Energy, 2005, 81, (3), 260 276. Hardening heat-treatment is an important operation in the fabrication of large chains for both the shipping industry and anchorage of offshore oil-platforms. This paper presents the outcome of an investigation that led to the introduction of modifications in a hardening furnace resulting in a substantial improvement and largely eliminating the problem of gradual cooling of the chain before immersion in the water-quenching tank. Comparing this with the
38
Fuel and Energy Abstracts
January 2006
present operating conditions, it can be concluded that redirecting the gas flow increases the gas temperature in the lower part of the furnace, which changes the chain's temperature-distribution accordingly.
06•00270 Microwave-assisted in-situ regeneration of a perovskite coated diesel soot filter Zhang-Steenwinkel, Y. et al. Chemical Engineering Science, 2005, 60, (3), 797 804. Dielectric heating may be used as an in situ technique for the periodic regeneration of soot filters, as those used in Diesel engines. As generally the Diesel exhaust temperatures are below the soot light-off temperature, passive regeneration is not possible. The authors have investigated the dielectric heating of a monolithic soot filter, coated with a Lao.sCeo.2MnO3 perovskite. This type of perovskite has suitable dielectric properties, i.e. a high dielectric loss factor, and simultaneously acts as an oxidation catalyst. It is shown that a perovskite coated cordierite filter, covered with synthetic carbon, can be fully regenerated with selectivity towards CO2 close to 100%. In contrast, the same filter without such a coating can only be partially regenerated. Moreover, considerable amounts of CO are formed. The Lao.sCeo.:MnO3 coating is shown to have excellent temperature shock resistance and thermo-chemical stability. It is shown that the microwave cavity design is crucial to obtain a uniform filter heating. Following the development of such a design, microwave assisted soot filter regeneration becomes feasible.
06/00271 Numerical study of SNCR application to a fullscale stoker incinerator at Daejon 4th industrial complex Kim, H.-S. e t al. Applied TlTermal Engineering, 2004, 24, (14 15), 2117 2129. Considering the rapid variation of waste composition and the more severe regulation trend of pollutant emission in this country, the importance of the development of a reliable computer program for a full-scale, stoker-type incinerator cannot be emphasized too much especially in the view of proper design and optimal determination of operating condition of existing and future constructed facility. To this end, a comprehensive, numerical model related with the process of the waste-off gaseous combustion with the capacity of 200 tons/day is successfully made. This includes development of several phenomenological models such as municipal waste-off gaseous reaction, NO pollutant generation and destruction in turbulence-related environment. Especially, in this study a number of sound assumptions have been made for the NO reaction model, 3-D geometry of incinerator and waste-bed model to achieve the efficient incorporation of the empirical models and enhancement of the stability of calculation process. First of all, the turbulence related, complex combustion chemistry involved with NO reaction is modelled by the harmonic mean method, which is given by the relative strength of the rates of chemistry and turbulent mixing. Further, the 3-D rectangular shape of the incinerator is simply approximated by a 3-D axi-symmetric geometry with equivalent area. And the modelling of complex wasteburning process on moving grate is described by a pure gaseous combustion process of waste off-gas. The program developed in this study is successfully validated by comparing with the experimental data such as temperature and NO concentration profiles in the incinerator located at 4th industrial complex of Daejon, S. Korea. Using the program developed, a series of parametric investigations have been made for the evaluation of SNCR process and thereby evaluate various important design and the operating variables. The major parameters considered in this parametric study are heating value of municipal waste, the injection location and amount of reduction material, and the proper length of insulating castable. In general, the calculated results are physically acceptable and fairly consistent.
06/00272 Potential applications of high-temperature air/ steam-blown gasification and pyrolysis systems Zubtsov, V. M. el al. Energy, 2005, 30, (11 12), 2229 2242. Several aspects of using the advanced, high-temperature air/steamblown gasification and pyrolysis technologies for converting solid fuels into syngas are examined. The gasification/pyrolysis systems, known as multi-staged enthalpy extraction technology (MEET), employ hightemperature air and steam as oxidizer agents for converting the solid fuels into syngas and have many features that are advantageous for power generation. The low-cost gasifier/pyrolyser is extremely compact and flexible, capable of operating efficiently on a wide range of lowcaloric-value fuels. Potential uses of this technology range from largescale integrated gasification power plants to small-scale waste-toenergy applications. Present R&D status of the MEET technology are summarized and its main components are described. Major fuel resources for the different markets are explored. The performance and feasibility of diverse power conversion systems to couple with MEET gasifier/pyrolyser for combined heat and power applications are assessed.