Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is ap...Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.展开更多
The paper describes numerical and experimental study on reduction of NOx emissions in a 600 MW tangentially fired boiler furnace under different operating conditions. A simplified NOX formation mechanism model, along ...The paper describes numerical and experimental study on reduction of NOx emissions in a 600 MW tangentially fired boiler furnace under different operating conditions. A simplified NOX formation mechanism model, along with the gas-particle multiphase flow model, is adopted. The prediction yields encouraging results as compared to experimental data.展开更多
In this work, an Eulerian/Lagrangian approach has been employed to investigate numerically the flow characteristics, heat transfer and combustion in a tangentially fired furnace. The RNG (Re-normalization group) k-ε ...In this work, an Eulerian/Lagrangian approach has been employed to investigate numerically the flow characteristics, heat transfer and combustion in a tangentially fired furnace. The RNG (Re-normalization group) k-ε model and a new method for cell face velocity interpolation based on a non-staggered grid system are employed. To avoid pseudo-diffusion that is significant in modeling tangentially fired furnaces, attempts are made at improving the differential volume scheme. Some new developments on turbulent diffusion of particles are also taken into account. Thus, computational accuracy is improved substantially.展开更多
The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-...The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the furnace temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics(CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions.展开更多
Low-NOX combustion retrofit is performed by adopting staged combustion technology for a 600 MW utility boiler with a four-corner tangential firing system. The emission data of NOX before and after retrofit are compare...Low-NOX combustion retrofit is performed by adopting staged combustion technology for a 600 MW utility boiler with a four-corner tangential firing system. The emission data of NOX before and after retrofit are compared and analyzed. The test results show that the emission concentration of NOX decreases obviously after the low-NOX retrofit. Additionally, the emission of NOX decreases by nearly 50% when the unit load is higher than 350 MW. It can also be concluded that the emission of NOX is influenced significantly by the amount of SOFA, the damper opening of auxiliary air, the differential pressure between the secondary air windbox and the furnace, and so on.展开更多
This work presents a computational investigation of hydrodynamics,coal combustion and NOx emissions in a tangentially fired pulverized coal boiler at different loads(630,440 and 300 MW;relative loads of 100%,70%and 48...This work presents a computational investigation of hydrodynamics,coal combustion and NOx emissions in a tangentially fired pulverized coal boiler at different loads(630,440 and 300 MW;relative loads of 100%,70%and 48%)to clarify the effect of load change on the furnace processes.A computational fluids dynamics model was established;the flow field,temperature profile,species concentration and NOx emissions were predicted numerically;and the influence of burner tilt angles was evaluated.Simulation results indicate that a decrease in boiler load decreases the gas velocity,attenuates the airflow rotations,and increases the tangent circle size.The high-temperature zone and flame moved toward the side walls.Such behaviors impair air-fuel mixing,heat transfer and steady combustion in the furnace.In terms of species concentrations,a decrease in boiler load increased the O2 content,decreased the CO content,and decreased the char burnout rates only slightly.A change in boiler load from 630 to 440 and 300 MW increased the NOx emissions from 202 to 234 and 247 mg/m^(3),respectively.Burner tilt angles are important in coal combustion and NOx emissions.A burner angle of-15°favors heat transfer and low NOx emissions(<185 mg/m^(3))for the current tangentially fired boiler.展开更多
In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model....In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model. Results show that merely reducing the imaginary circle diameter rki can not significantly reduce the rotatiollal diameter op in the range considered. The flow still rotates coullter-clockwise stably and does not change rotation direction when the direction of all jet axes are defiected suddenly to the opposite rotation direction by up to 5.4" in a countereclockwise llow field. It is the first time that the numerical sAnulation results were obtained which agreed quite well with this experimental phenomena qualitatively. The experimental data, i.e., the rotational diameter & and the maximum velocity on the syrnmetric central line of fUrnace Vm, are only a bit larger than the simulation results. It is shown that the initial flow field has an important influence on the aerodynamic field in the furnace. Other measures have to be taken as wel1 in order to reduce & to resist slagging and high temperature corrosion of furnace tubes. Moreover, a new kind of grid arrangement was proposed in this paper, which can reduce effectively the false diffosion at the exit zone of burner.展开更多
文摘Based on the porosity method and the improved non uniform QUICK scheme, this paper describes a three dimensional computer simulation to predict the flow characteristics in a tangentially fired boiler. The model is applied to a 600?MW boiler modeling under different operating conditions of reverse swirl of secondary air. The numerical results achieve reasonable agreement with experimental data. The calculated results of flow field, the pressure distribution, the relative diameter of tangential circle, angular momentum flux in furnace and the velocity distribution index in horizontal gas pass are analyzed in detail. And then the effects of the reverse swirl of secondary air on flue gas imbalance are discussed. Finally a reasonable operating condition of the reverse swirl of secondary air is presented.
基金Supported by the National Science Foundation of Zhejiang Province.
文摘The paper describes numerical and experimental study on reduction of NOx emissions in a 600 MW tangentially fired boiler furnace under different operating conditions. A simplified NOX formation mechanism model, along with the gas-particle multiphase flow model, is adopted. The prediction yields encouraging results as compared to experimental data.
基金Supported by the National Science Foundation of Zhejiang Province
文摘In this work, an Eulerian/Lagrangian approach has been employed to investigate numerically the flow characteristics, heat transfer and combustion in a tangentially fired furnace. The RNG (Re-normalization group) k-ε model and a new method for cell face velocity interpolation based on a non-staggered grid system are employed. To avoid pseudo-diffusion that is significant in modeling tangentially fired furnaces, attempts are made at improving the differential volume scheme. Some new developments on turbulent diffusion of particles are also taken into account. Thus, computational accuracy is improved substantially.
文摘The control of 3-D temperature distribution in a utility boiler furnace is essential for the safe, economic and clean operation of pc-fired furnace with multi-burner system. The development of the visualization of 3-D temperature distributions in pc-fired furnaces makes it possible for a new combustion control strategy directly with the furnace temperature as its goal to improve the control quality for the combustion processes. Studied in this paper is such a new strategy that the whole furnace is divided into several parts in the vertical direction, and the average temperature and its bias from the center in every cross section can be extracted from the visualization results of the 3-D temperature distributions. In the simulation stage, a computational fluid dynamics(CFD) code served to calculate the 3-D temperature distributions in a furnace, then a linear model was set up to relate the features of the temperature distributions with the input of the combustion processes, such as the flow rates of fuel and air fed into the furnaces through all the burners. The adaptive genetic algorithm was adopted to find the optimal combination of the whole input parameters which ensure to form an optimal 3-D temperature field in the furnace desired for the operation of boiler. Simulation results showed that the strategy could soon find the factors making the temperature distribution apart from the optimal state and give correct adjusting suggestions.
文摘Low-NOX combustion retrofit is performed by adopting staged combustion technology for a 600 MW utility boiler with a four-corner tangential firing system. The emission data of NOX before and after retrofit are compared and analyzed. The test results show that the emission concentration of NOX decreases obviously after the low-NOX retrofit. Additionally, the emission of NOX decreases by nearly 50% when the unit load is higher than 350 MW. It can also be concluded that the emission of NOX is influenced significantly by the amount of SOFA, the damper opening of auxiliary air, the differential pressure between the secondary air windbox and the furnace, and so on.
基金The authors acknowledge the support from the National Nature Science Foundation of China(No.51476058)and SINOPEC project(No.318015-6).
文摘This work presents a computational investigation of hydrodynamics,coal combustion and NOx emissions in a tangentially fired pulverized coal boiler at different loads(630,440 and 300 MW;relative loads of 100%,70%and 48%)to clarify the effect of load change on the furnace processes.A computational fluids dynamics model was established;the flow field,temperature profile,species concentration and NOx emissions were predicted numerically;and the influence of burner tilt angles was evaluated.Simulation results indicate that a decrease in boiler load decreases the gas velocity,attenuates the airflow rotations,and increases the tangent circle size.The high-temperature zone and flame moved toward the side walls.Such behaviors impair air-fuel mixing,heat transfer and steady combustion in the furnace.In terms of species concentrations,a decrease in boiler load increased the O2 content,decreased the CO content,and decreased the char burnout rates only slightly.A change in boiler load from 630 to 440 and 300 MW increased the NOx emissions from 202 to 234 and 247 mg/m^(3),respectively.Burner tilt angles are important in coal combustion and NOx emissions.A burner angle of-15°favors heat transfer and low NOx emissions(<185 mg/m^(3))for the current tangentially fired boiler.
文摘In this paper, the effect of the imaginary circle diameter opi and the initial flow field on the aerodynamic field in a tangentially fired furnace was studied by numerical simulation and experiments in the cold model. Results show that merely reducing the imaginary circle diameter rki can not significantly reduce the rotatiollal diameter op in the range considered. The flow still rotates coullter-clockwise stably and does not change rotation direction when the direction of all jet axes are defiected suddenly to the opposite rotation direction by up to 5.4" in a countereclockwise llow field. It is the first time that the numerical sAnulation results were obtained which agreed quite well with this experimental phenomena qualitatively. The experimental data, i.e., the rotational diameter & and the maximum velocity on the syrnmetric central line of fUrnace Vm, are only a bit larger than the simulation results. It is shown that the initial flow field has an important influence on the aerodynamic field in the furnace. Other measures have to be taken as wel1 in order to reduce & to resist slagging and high temperature corrosion of furnace tubes. Moreover, a new kind of grid arrangement was proposed in this paper, which can reduce effectively the false diffosion at the exit zone of burner.
