Christian Kuhr - Academia.edu (original) (raw)
Papers by Christian Kuhr
Die Untersuchung des Abbrandverhaltens staubförmiger Brennstoffe führt zu einem gesteigerten Vers... more Die Untersuchung des Abbrandverhaltens staubförmiger Brennstoffe führt zu einem gesteigerten Verständnis der Verbrennungsmechanismen. Da die verbrennungstechnischen Eigenschaften kohlenstoffhaltiger Festbrennstoffe mit der Brennstoffherkunft variieren, sind experimentell bestimmte Reaktionsratenparameter ein notwendiges Detail zur Auslegung von Staubfeuerungen. Die präsentierten Arbeiten erörtern eine Vorgehensweise, wie in Laborexperimenten bestimmte Kinetiken zur Auslegung von technischen Großanlagen genutzt werden können.
Journal of Loss Prevention in The Process Industries, 2004
Chemie Ingenieur Technik, 2004
Chemie Ingenieur Technik, 2007
Chemie Ingenieur Technik, 2001
We review in this study current numerical and modeling challenges found in a computational fluid ... more We review in this study current numerical and modeling challenges found in a computational fluid dynamics (CFD) treatment of large-scale pool fires. The numerical challenge comes from the need to suitably resolve flame geometries that are significantly more complex than those found at laboratory scales. The flame geometries found in large-scale pool fires correspond to multiple, relatively small flames and the increased small-scale activity results in more severe computational grid requirements. The modeling challenge comes from the need to provide adequate descriptions of flame extinction and soot processes. Flame extinction, soot mass leakage across the flame and the subsequent accumulation of cold soot in the overfire region are identified as key physical ingredients that will determine the performance of fire models in large-scale pool fire simulations. Current CFD capabilities are illustrated using the Fire Dynamics Simulator (FDS, developed by the National Institute of Standards and Technology, USA). FDS is applied to a series of numerical simulations corresponding to open, wind-free, gaseous pool fires of different sizes H, 0.4 H 40 m. The simulations reveal the fundamental change in flame structure that is observed as H is increased from laboratory-to large-scales. Predictions of combustion efficiencies, soot yields and radiant fractions show limited success, however. Some modifications in the FDS combustion and soot models are proposed in order to enhance the modeling capability. These modifications are based on the assumptions that: (1) flame extinction in pool fires correspond to slow mixing conditions combined with radiation cooling; (2) flame extinction is the dominant mechanism responsible for soot mass leakage across the flame. FDS simulations performed with these modifications show improved performance and provide some encouraging support to the assumptions made.
CFD furnace simulations of an 800MWel coal fired power plant were performed to compare the combus... more CFD furnace simulations of an 800MWel coal fired power plant were performed to compare the combustion behaviour of a South American subbituminous coal (EL Cerrejón) and torrefied beech wood. The kinetic data for pyrolysis and char combustion, which are crucial for reliable CFD-simulations, were obtained by drop tube experiments. Pyrolysis kinetics were determined based on the ash tracer method at realistic heating rates in the order of 104 K/s. Char burning kinetics were derived based on particle size and temperature measurement by two-color pyrometry at different residence times. For both, pyrolysis and char burning, differences were found between the two fuels, with faster pyrolysis and char burn-out for the torrefied biomass. The CFD furnace simulation demonstrates the impact of the higher reactivity of torrefied beech compared to coal. For torrefied beech the reaction in the near boiler wall region is more intense. Higher temperatures and lower oxygen concentrations near the wal...
Energy Procedia, 2009
... technology today to supply an 820 MWe bituminous coal fired power plant with oxygen is the cr... more ... technology today to supply an 820 MWe bituminous coal fired power plant with oxygen is the cryogenic process. In this case up to 13,500 t/d (including 10% reserve) of oxygen is required. The available size and required control range of air separation units (ASUs) will make 4 ...
Energy Procedia, 2011
We developed a model based on fundamental experimental data to predict lean flammability limit, L... more We developed a model based on fundamental experimental data to predict lean flammability limit, L, and flame propagation velocity, Sb, for oxy-fuel combustion conditions. The basic model system consisted of two particles. One side of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. This phenomenon was defined
Energy Procedia, 2011
The partial pressure of carbon dioxide in the flue gas of an Oxyfuel combustion process is signif... more The partial pressure of carbon dioxide in the flue gas of an Oxyfuel combustion process is significantly increased in comparison with conventional air-blown firing. Depending on the moisture content of the fuel and the type of flue gas recirculation (either wet or dry), the partial pressure of water vapor varies for Oxyfuel atmospheres. The calculation of the heat transfer by
Progress in Computational Fluid Dynamics, An International Journal, 2003
... 2œ4, 2003 151 Modelling of the thermal radiation of pool fires Christian Kuhr*, Steffen Staus... more ... 2œ4, 2003 151 Modelling of the thermal radiation of pool fires Christian Kuhr*, Steffen Staus†, Axel Schönbucherfl *Department of Chemical Engineering, University of Duisburg, Lotharstr. ... 6 Boris, JP, Landsberg, AM, Oran, ES and Gardner, JH. ...
International Journal of Greenhouse Gas Control, 2011
Previously, we developed a model to predict lean flammability limit L and flame propagation veloc... more Previously, we developed a model to predict lean flammability limit L and flame propagation velocity Sb for pulverized coal. In the present paper, we have extended the model to apply it in development of oxy-fuel combustion systems. The basic model consists of two particles. One of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. We analyzed at what distance the first burning particle could ignite the next particle, and how fast the first burning particle could ignite the next particle. The model was verified both for air and oxy-fuel combustion conditions. Next, a method to support burner development was examined by using the model. Local Sb and L near the ignition points of the burner could be analyzed from the concentration and temperature profiles of CFD results. Flame stability was judged by the calculated Sb and L profiles, and past results of blow-off limits obtained with actual-and pilot-scale experiments. A DS ® T-burner was developed by Hitachi Power Europe, and installed at the Schwarze Pumpe pilot plant. Combination of the technique and large eddy simulation was applied to confirmation of the system.
Energy Procedia, 2011
Situated in the near of Schwarze Pumpe power station southeast of Berlin, Germany, Vattenfall ope... more Situated in the near of Schwarze Pumpe power station southeast of Berlin, Germany, Vattenfall operates a 30 MWth pilot plant in order to investigate the Oxyfuel process. Hitachi Power Europe delivered a DST-burner (DST-Brenner®) for the indirect firing system of the plant which was installed without modifications to the pressure part of the boiler. The combustion behavior during Oxyfuel operation was
Die Untersuchung des Abbrandverhaltens staubförmiger Brennstoffe führt zu einem gesteigerten Vers... more Die Untersuchung des Abbrandverhaltens staubförmiger Brennstoffe führt zu einem gesteigerten Verständnis der Verbrennungsmechanismen. Da die verbrennungstechnischen Eigenschaften kohlenstoffhaltiger Festbrennstoffe mit der Brennstoffherkunft variieren, sind experimentell bestimmte Reaktionsratenparameter ein notwendiges Detail zur Auslegung von Staubfeuerungen. Die präsentierten Arbeiten erörtern eine Vorgehensweise, wie in Laborexperimenten bestimmte Kinetiken zur Auslegung von technischen Großanlagen genutzt werden können.
Journal of Loss Prevention in The Process Industries, 2004
Chemie Ingenieur Technik, 2004
Chemie Ingenieur Technik, 2007
Chemie Ingenieur Technik, 2001
We review in this study current numerical and modeling challenges found in a computational fluid ... more We review in this study current numerical and modeling challenges found in a computational fluid dynamics (CFD) treatment of large-scale pool fires. The numerical challenge comes from the need to suitably resolve flame geometries that are significantly more complex than those found at laboratory scales. The flame geometries found in large-scale pool fires correspond to multiple, relatively small flames and the increased small-scale activity results in more severe computational grid requirements. The modeling challenge comes from the need to provide adequate descriptions of flame extinction and soot processes. Flame extinction, soot mass leakage across the flame and the subsequent accumulation of cold soot in the overfire region are identified as key physical ingredients that will determine the performance of fire models in large-scale pool fire simulations. Current CFD capabilities are illustrated using the Fire Dynamics Simulator (FDS, developed by the National Institute of Standards and Technology, USA). FDS is applied to a series of numerical simulations corresponding to open, wind-free, gaseous pool fires of different sizes H, 0.4 H 40 m. The simulations reveal the fundamental change in flame structure that is observed as H is increased from laboratory-to large-scales. Predictions of combustion efficiencies, soot yields and radiant fractions show limited success, however. Some modifications in the FDS combustion and soot models are proposed in order to enhance the modeling capability. These modifications are based on the assumptions that: (1) flame extinction in pool fires correspond to slow mixing conditions combined with radiation cooling; (2) flame extinction is the dominant mechanism responsible for soot mass leakage across the flame. FDS simulations performed with these modifications show improved performance and provide some encouraging support to the assumptions made.
CFD furnace simulations of an 800MWel coal fired power plant were performed to compare the combus... more CFD furnace simulations of an 800MWel coal fired power plant were performed to compare the combustion behaviour of a South American subbituminous coal (EL Cerrejón) and torrefied beech wood. The kinetic data for pyrolysis and char combustion, which are crucial for reliable CFD-simulations, were obtained by drop tube experiments. Pyrolysis kinetics were determined based on the ash tracer method at realistic heating rates in the order of 104 K/s. Char burning kinetics were derived based on particle size and temperature measurement by two-color pyrometry at different residence times. For both, pyrolysis and char burning, differences were found between the two fuels, with faster pyrolysis and char burn-out for the torrefied biomass. The CFD furnace simulation demonstrates the impact of the higher reactivity of torrefied beech compared to coal. For torrefied beech the reaction in the near boiler wall region is more intense. Higher temperatures and lower oxygen concentrations near the wal...
Energy Procedia, 2009
... technology today to supply an 820 MWe bituminous coal fired power plant with oxygen is the cr... more ... technology today to supply an 820 MWe bituminous coal fired power plant with oxygen is the cryogenic process. In this case up to 13,500 t/d (including 10% reserve) of oxygen is required. The available size and required control range of air separation units (ASUs) will make 4 ...
Energy Procedia, 2011
We developed a model based on fundamental experimental data to predict lean flammability limit, L... more We developed a model based on fundamental experimental data to predict lean flammability limit, L, and flame propagation velocity, Sb, for oxy-fuel combustion conditions. The basic model system consisted of two particles. One side of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. This phenomenon was defined
Energy Procedia, 2011
The partial pressure of carbon dioxide in the flue gas of an Oxyfuel combustion process is signif... more The partial pressure of carbon dioxide in the flue gas of an Oxyfuel combustion process is significantly increased in comparison with conventional air-blown firing. Depending on the moisture content of the fuel and the type of flue gas recirculation (either wet or dry), the partial pressure of water vapor varies for Oxyfuel atmospheres. The calculation of the heat transfer by
Progress in Computational Fluid Dynamics, An International Journal, 2003
... 2œ4, 2003 151 Modelling of the thermal radiation of pool fires Christian Kuhr*, Steffen Staus... more ... 2œ4, 2003 151 Modelling of the thermal radiation of pool fires Christian Kuhr*, Steffen Staus†, Axel Schönbucherfl *Department of Chemical Engineering, University of Duisburg, Lotharstr. ... 6 Boris, JP, Landsberg, AM, Oran, ES and Gardner, JH. ...
International Journal of Greenhouse Gas Control, 2011
Previously, we developed a model to predict lean flammability limit L and flame propagation veloc... more Previously, we developed a model to predict lean flammability limit L and flame propagation velocity Sb for pulverized coal. In the present paper, we have extended the model to apply it in development of oxy-fuel combustion systems. The basic model consists of two particles. One of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. We analyzed at what distance the first burning particle could ignite the next particle, and how fast the first burning particle could ignite the next particle. The model was verified both for air and oxy-fuel combustion conditions. Next, a method to support burner development was examined by using the model. Local Sb and L near the ignition points of the burner could be analyzed from the concentration and temperature profiles of CFD results. Flame stability was judged by the calculated Sb and L profiles, and past results of blow-off limits obtained with actual-and pilot-scale experiments. A DS ® T-burner was developed by Hitachi Power Europe, and installed at the Schwarze Pumpe pilot plant. Combination of the technique and large eddy simulation was applied to confirmation of the system.
Energy Procedia, 2011
Situated in the near of Schwarze Pumpe power station southeast of Berlin, Germany, Vattenfall ope... more Situated in the near of Schwarze Pumpe power station southeast of Berlin, Germany, Vattenfall operates a 30 MWth pilot plant in order to investigate the Oxyfuel process. Hitachi Power Europe delivered a DST-burner (DST-Brenner®) for the indirect firing system of the plant which was installed without modifications to the pressure part of the boiler. The combustion behavior during Oxyfuel operation was