... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of th... more ... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of the ... In the presence of liquid water, equilibrium vapour pressure is assumed in the gas phase, [16], giving: (3) View the MathML source In the case of moisture content below the ...
The present investigation involves theories, simulations and experiments on deposit layers on sup... more The present investigation involves theories, simulations and experiments on deposit layers on super-heater tubes in a circulating fluidised bed in Västerås in Sweden. Simulation of particle trajectories in the vicinity of two super-heater tubes is conducted in a Eulerian-Lagrangian mode for the flue gas and the ash particles from the combustion process. Particle impingements on the tubes are investigated for
The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) lo... more The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) long study of corrosion and deposits on superheater tubes in a biomass fired circulated fluidized bed boiler. These measurements are correlated against the different fuels used over this period. In the earlier years, the boiler was run with a mixture of different biomass fuels and peat. In later years, recycled wood was introduced into the fuel mix. The deposit growth rate approximately doubled when the recycled wood content of the fuel was increased to 10-20%. Small amounts of chlorine and zinc were found both in the recycled wood and in the deposit layer. These elements together with alkali metals from the biomass, have the potential to form sticky compounds that increase the deposit growth rate. The corrosion rate of the superheater tubes varied over the study period. A number of possible explanations for this phenomenon are discussed.
This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. Th... more This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. The computational domain is axisymmetric and involves the heating chamber, with the wood cylinder vertically situated in the centre of the chamber. The model simulates the ...
This paper presents experimental data concerning combustion characteristics of full-scale biomass... more This paper presents experimental data concerning combustion characteristics of full-scale biomass-fired bubbling fluidized bed (BFB) steam boiler with a thermal output of 31 MW. The purpose of the experimental measurements is to show how the values of selected combustion parameters vary in reality depending on measurement position. Experimentation involves specifically a determination of combustion gas temperature and concentration of gas species i.e. O 2 , CO 2 , CO and NO X at different positions in the furnace and the flue gas trains. Character of results from the furnace indicates the intermediate stage of thermochemical reactions. Increased levels of CO close to the wall have been found, this may be indicating reducing atmosphere and thereby increased corrosion risk. Results from flue gas trains demonstrate that behavior there is related to the fluid dynamics and heat transfer, the temperature is too low for further combustion reactions. Results show great variations among measured values of all measurands depending on a distance along the line from the wall to the center of the boiler. The measurements from permanently installed fixed sensors are not giving value representing average conditions, but overall profiles can be correlated to online measurements from fixed sensors.
A two step reaction model for the pyrolysis process of a dry cylindrical pine wood particle, expo... more A two step reaction model for the pyrolysis process of a dry cylindrical pine wood particle, exposed to a hot gas flow field, has been developed adding user defined subroutines to the commercial computational fluid dynamics code CFX 4.4. The wood particle is fixed in space and has a diameter of 15.0 mm and a height of 60.0 mm. The particle temperature is initially 30 C when it is introduced to the 500 °C hot flow. The surrounding walls have a constant temperature of 500 C. The simulation results have been compared with the experimental data of Pyle and Zaror (1984). The furnace is cylindrical as well as the wood particle which is fixed on the axis of symmetry. The computational domain is axisymmetric. The laminar flow around the particle, and the flow inside the porous wood, are fully coupled, allowing the release of volatile pyrolysis gas from the wood to mix with the surrounding flow field. The transport and the production of char, tar and pyrolysis gas and the consumption of wood...
The present investigation involves theories, simulations and experiments on deposit layers on sup... more The present investigation involves theories, simulations and experiments on deposit layers on super-heater tubes in a circulating fluidised bed in Västerås in Sweden. Simulation of particle trajectories in the vicinity of two super-heater tubes is conducted in a Eulerian-Lagrangian mode for the flue gas and the ash particles from the combustion process. Particle impingements on the tubes are investigated for
The present investigation involves measurements and theories on the mechanisms of the forming of ... more The present investigation involves measurements and theories on the mechanisms of the forming of deposit layers on super-heater tubes in a biomass-fired CFD boiler. The deposit layer thickness and the sootblowing frequency effect on the super-heaters heat transfer are the main subject of the study that has been conducted over a 3-year period. The measurements show a deposit growth rate on the super-heaters of approximately 4 g m À2 h À1 . The distribution of the deposit material varies significantly between the windward and the leeward side of the tubes, with the thickest layers on the windward side. Further down stream of the first super-heater, the fouling problem on the super-heater and re-heater tubes are not so severe. A theoretical model shows that a deposit layer of 20 mm will decrease the heat transfer rate of the first super-heater by nearly 40%. The soot-blowing system shows a strong positive effect on the heat transfer rate of the super-heater a few hours after a soot-blowing sequence has been completed. However in the long run, the varied soot-blowing frequency does not have a significant influence on the deposit layer growth rate.
The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) lo... more The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) long study of corrosion and deposits on superheater tubes in a biomass fired circulated fluidized bed boiler. These measurements are correlated against the different fuels used over this period. In the earlier years, the boiler was run with a mixture of different biomass fuels and peat. In later years, recycled wood was introduced into the fuel mix. The deposit growth rate approximately doubled when the recycled wood content of the fuel was increased to 10-20%. Small amounts of chlorine and zinc were found both in the recycled wood and in the deposit layer. These elements together with alkali metals from the biomass, have the potential to form sticky compounds that increase the deposit growth rate. The corrosion rate of the superheater tubes varied over the study period. A number of possible explanations for this phenomenon are discussed.
... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of th... more ... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of the ... In the presence of liquid water, equilibrium vapour pressure is assumed in the gas phase, [16], giving: (3) View the MathML source In the case of moisture content below the ...
A dynamic model is presented for a biomass-fired circulating fluidized bed boiler. The model is b... more A dynamic model is presented for a biomass-fired circulating fluidized bed boiler. The model is based on energy and mass balances for the components in the boiler and on a combustion model for the fluidized bed. The main purpose of the model is to simulate how deposits affect the boiler efficiency and performance. The model is verified against the municipal circulating fluidized bed boiler in Västerås, Sweden, which produces 157 MW. The distribution of deposits on the surfaces in the boiler is well known from inspections. These observations are used as inputs to the model to simulate their effects on boiler performance.
This paper presents experimental data concerning combustion characteristics of full-scale biomass... more This paper presents experimental data concerning combustion characteristics of full-scale biomass-fired bubbling fluidized bed (BFB) steam boiler with a thermal output of 31 MW. The purpose of the experimental measurements is to show how the values of selected combustion parameters vary in reality depending on measurement position. Experimentation involves specifically a determination of combustion gas temperature and concentration of gas species i.e. O 2 , CO 2 , CO and NO X at different positions in the furnace and the flue gas trains. Character of results from the furnace indicates the intermediate stage of thermochemical reactions. Increased levels of CO close to the wall have been found, this may be indicating reducing atmosphere and thereby increased corrosion risk. Results from flue gas trains demonstrate that behavior there is related to the fluid dynamics and heat transfer, the temperature is too low for further combustion reactions. Results show great variations among measured values of all measurands depending on a distance along the line from the wall to the center of the boiler. The measurements from permanently installed fixed sensors are not giving value representing average conditions, but overall profiles can be correlated to online measurements from fixed sensors.
... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of th... more ... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of the ... In the presence of liquid water, equilibrium vapour pressure is assumed in the gas phase, [16], giving: (3) View the MathML source In the case of moisture content below the ...
The present investigation involves theories, simulations and experiments on deposit layers on sup... more The present investigation involves theories, simulations and experiments on deposit layers on super-heater tubes in a circulating fluidised bed in Västerås in Sweden. Simulation of particle trajectories in the vicinity of two super-heater tubes is conducted in a Eulerian-Lagrangian mode for the flue gas and the ash particles from the combustion process. Particle impingements on the tubes are investigated for
The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) lo... more The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) long study of corrosion and deposits on superheater tubes in a biomass fired circulated fluidized bed boiler. These measurements are correlated against the different fuels used over this period. In the earlier years, the boiler was run with a mixture of different biomass fuels and peat. In later years, recycled wood was introduced into the fuel mix. The deposit growth rate approximately doubled when the recycled wood content of the fuel was increased to 10-20%. Small amounts of chlorine and zinc were found both in the recycled wood and in the deposit layer. These elements together with alkali metals from the biomass, have the potential to form sticky compounds that increase the deposit growth rate. The corrosion rate of the superheater tubes varied over the study period. A number of possible explanations for this phenomenon are discussed.
This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. Th... more This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. The computational domain is axisymmetric and involves the heating chamber, with the wood cylinder vertically situated in the centre of the chamber. The model simulates the ...
This paper presents experimental data concerning combustion characteristics of full-scale biomass... more This paper presents experimental data concerning combustion characteristics of full-scale biomass-fired bubbling fluidized bed (BFB) steam boiler with a thermal output of 31 MW. The purpose of the experimental measurements is to show how the values of selected combustion parameters vary in reality depending on measurement position. Experimentation involves specifically a determination of combustion gas temperature and concentration of gas species i.e. O 2 , CO 2 , CO and NO X at different positions in the furnace and the flue gas trains. Character of results from the furnace indicates the intermediate stage of thermochemical reactions. Increased levels of CO close to the wall have been found, this may be indicating reducing atmosphere and thereby increased corrosion risk. Results from flue gas trains demonstrate that behavior there is related to the fluid dynamics and heat transfer, the temperature is too low for further combustion reactions. Results show great variations among measured values of all measurands depending on a distance along the line from the wall to the center of the boiler. The measurements from permanently installed fixed sensors are not giving value representing average conditions, but overall profiles can be correlated to online measurements from fixed sensors.
A two step reaction model for the pyrolysis process of a dry cylindrical pine wood particle, expo... more A two step reaction model for the pyrolysis process of a dry cylindrical pine wood particle, exposed to a hot gas flow field, has been developed adding user defined subroutines to the commercial computational fluid dynamics code CFX 4.4. The wood particle is fixed in space and has a diameter of 15.0 mm and a height of 60.0 mm. The particle temperature is initially 30 C when it is introduced to the 500 °C hot flow. The surrounding walls have a constant temperature of 500 C. The simulation results have been compared with the experimental data of Pyle and Zaror (1984). The furnace is cylindrical as well as the wood particle which is fixed on the axis of symmetry. The computational domain is axisymmetric. The laminar flow around the particle, and the flow inside the porous wood, are fully coupled, allowing the release of volatile pyrolysis gas from the wood to mix with the surrounding flow field. The transport and the production of char, tar and pyrolysis gas and the consumption of wood...
The present investigation involves theories, simulations and experiments on deposit layers on sup... more The present investigation involves theories, simulations and experiments on deposit layers on super-heater tubes in a circulating fluidised bed in Västerås in Sweden. Simulation of particle trajectories in the vicinity of two super-heater tubes is conducted in a Eulerian-Lagrangian mode for the flue gas and the ash particles from the combustion process. Particle impingements on the tubes are investigated for
The present investigation involves measurements and theories on the mechanisms of the forming of ... more The present investigation involves measurements and theories on the mechanisms of the forming of deposit layers on super-heater tubes in a biomass-fired CFD boiler. The deposit layer thickness and the sootblowing frequency effect on the super-heaters heat transfer are the main subject of the study that has been conducted over a 3-year period. The measurements show a deposit growth rate on the super-heaters of approximately 4 g m À2 h À1 . The distribution of the deposit material varies significantly between the windward and the leeward side of the tubes, with the thickest layers on the windward side. Further down stream of the first super-heater, the fouling problem on the super-heater and re-heater tubes are not so severe. A theoretical model shows that a deposit layer of 20 mm will decrease the heat transfer rate of the first super-heater by nearly 40%. The soot-blowing system shows a strong positive effect on the heat transfer rate of the super-heater a few hours after a soot-blowing sequence has been completed. However in the long run, the varied soot-blowing frequency does not have a significant influence on the deposit layer growth rate.
The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) lo... more The present investigation involves a unique, 7 year (2001)(2002)(2003)(2004)(2005)(2006)(2007) long study of corrosion and deposits on superheater tubes in a biomass fired circulated fluidized bed boiler. These measurements are correlated against the different fuels used over this period. In the earlier years, the boiler was run with a mixture of different biomass fuels and peat. In later years, recycled wood was introduced into the fuel mix. The deposit growth rate approximately doubled when the recycled wood content of the fuel was increased to 10-20%. Small amounts of chlorine and zinc were found both in the recycled wood and in the deposit layer. These elements together with alkali metals from the biomass, have the potential to form sticky compounds that increase the deposit growth rate. The corrosion rate of the superheater tubes varied over the study period. A number of possible explanations for this phenomenon are discussed.
... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of th... more ... log in quiescent environment 5.1.1. Comparison with experimental data 5.1.2. Prediction of the ... In the presence of liquid water, equilibrium vapour pressure is assumed in the gas phase, [16], giving: (3) View the MathML source In the case of moisture content below the ...
A dynamic model is presented for a biomass-fired circulating fluidized bed boiler. The model is b... more A dynamic model is presented for a biomass-fired circulating fluidized bed boiler. The model is based on energy and mass balances for the components in the boiler and on a combustion model for the fluidized bed. The main purpose of the model is to simulate how deposits affect the boiler efficiency and performance. The model is verified against the municipal circulating fluidized bed boiler in Västerås, Sweden, which produces 157 MW. The distribution of deposits on the surfaces in the boiler is well known from inspections. These observations are used as inputs to the model to simulate their effects on boiler performance.
This paper presents experimental data concerning combustion characteristics of full-scale biomass... more This paper presents experimental data concerning combustion characteristics of full-scale biomass-fired bubbling fluidized bed (BFB) steam boiler with a thermal output of 31 MW. The purpose of the experimental measurements is to show how the values of selected combustion parameters vary in reality depending on measurement position. Experimentation involves specifically a determination of combustion gas temperature and concentration of gas species i.e. O 2 , CO 2 , CO and NO X at different positions in the furnace and the flue gas trains. Character of results from the furnace indicates the intermediate stage of thermochemical reactions. Increased levels of CO close to the wall have been found, this may be indicating reducing atmosphere and thereby increased corrosion risk. Results from flue gas trains demonstrate that behavior there is related to the fluid dynamics and heat transfer, the temperature is too low for further combustion reactions. Results show great variations among measured values of all measurands depending on a distance along the line from the wall to the center of the boiler. The measurements from permanently installed fixed sensors are not giving value representing average conditions, but overall profiles can be correlated to online measurements from fixed sensors.
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Papers by Jan Sandberg