The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Shien Hui - One of the best experts on this subject based on the ideXlab platform.
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Determining the Optimum Coal Concentration in A General Tangential-Fired Furnace with Rich-Lean Burners: From A Bench-Scale To A Pilot-Scale Study
Applied Thermal Engineering, 2014Co-Authors: Xuebin Wang, Yanqing Niu, Houzhang Tan, Weiping Yan, Xiaolin Wei, Shien HuiAbstract:The mass ratio of pulverized coal and air (coal concentration, kg/kg) in fuel-rich streams is important in the design and operation of rich-lean burners, in which the optimum coal concentration (C-opt) that corresponds to the best combustion situation should be achieved. This study aims to establish a practical identification method to evaluate the C-opt of the different ranks of coal in rich-lean burners. A wide range of tests were conducted in a bench-scale down-Fired Furnace and a pilot-scale tangential-Fired Furnace with rich-lean burners. Temperature distribution, unburned carbon in ash, and NOx emissions were measured, and the effects of coal quality aside from burner type and burner layout method were considered. Results show that the optimum coal concentration corresponds to the highest Furnace temperature for each group of tests both in the bench-scale and pilot-scale Furnaces. C-opt is significantly affected by coal quality even if a change from the use of a corner-tangential to a wall-tangential Furnace lowers C-opt; however, the effect of a vertical rich-lean burner or a horizontal rich-lean burner on C-opt is negligible. The value of C-opt mainly decreases from 1.14 to 0.67 with a decrease in the volatile content from anthracite scale ( 0.35). The empirical formula of C-opt = 1.19-0.15V(daf)Q(net)(0.7)/100M(ad)(0.1) is obtained to evaluate the optimum coal concentration of a general pulverized coal flame, and another formula, C-opt = 1.18-0.17V(daf)Q(net)(0.7)/100M(ad)(0.1) is especially derived for a tangential-Fired Furnace with a rich-lean burner. The optimum value obtained is also critical to NOx emissions because when the coal concentration surpasses the value of C-opt, NOx emissions can be much more efficiently controlled through reduction of air. The findings of this study can provide practical guidance for the design and operation of rich-lean burners to achieve high combustion efficiency and low NOx emissions. (C) 2014 Elsevier Ltd. All rights reserved.
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effect of the momentum flux ratio of vertical to horizontal component on coal combustion in an arch Fired Furnace with upper Furnace over fire air
Experimental Thermal and Fluid Science, 2013Co-Authors: Shuai Zhao, Shien Hui, Qulan Zhou, Qinxin Zhao, Ling Liang, Houzhang TanAbstract:Abstract Over-fire air is introduced to achieve deep staging conditions for combustion optimization in a 0.7 MW arch-Fired Furnace. The momentum flux ratio ( M ) of vertical to horizontal component is determined by variations of air distribution and the inclination angle of the F-layer secondary air. Two coals with relatively large characteristic differences are used in the pilot tests. The results show that M directly affects the arch air penetration length and the position of the flame center. As the inclination angle increases appropriately, the position of high temperature zone moves downward, and the variation amplitude becomes smaller. The distribution of the wall temperature becomes more uniform. An overlarge angle would cause severe dregs on the wall of hopper, however. Increasing the arch air ratio can also delay the mixing of air–fuel flows and stage air and lower downward the flame center. Too small M would cause much higher temperatures in the upper Furnace. The unburned carbon in the fly ash and NO x emission both attain their minimum values with an inclination angle of 30° and a momentum flux ratio of 1.35, which is considered as the optimum operation condition in the experimental range.
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Study of optimal pulverized coal concentration in a four-wall tangentially Fired Furnace
Applied Energy, 2011Co-Authors: Houzhang Tan, Yanqing Niu, Xuebin Wang, Shien HuiAbstract:Abstract The effect of fuel lean/rich conditions (1:1, 1:2, 1:3, 1:4, 1:5 and 1:6) on the Furnace core temperatures, carbon in fly ash and slag and NO x emissions was investigated in a 1 MW four-wall tangentially horizontal bias Fired Furnace for Yibin anthracite and Shenmu bituminous, respectively. Results shown that Furnace core temperatures increased at first and then decreased along the height of the Furnace when anthracite burned. The Furnace core temperature at the height of primary air nozzles was the highest when the bituminous lean/rich varied from 1:1 to 1:3, and its trend was similar to the anthracite when the bituminous lean/rich was changed from 1:4 to 1:6. The ignition of anthracite required a heating stage, while bituminous could timely ignite due to high volatile. However, when the bituminous lean/rich was too low resulting in the relative lack of oxygen, it still needed a heating stage. With increased coal concentration, the Furnace core temperatures in the primary air section went up firstly and then down, but the carbon in fly ash and slag showed adverse behavior. This was due to the high coal concentration corresponding to high volatile concentration leading to the timely ignition and burnout, causing higher Furnace core temperature in the primary air section and decreased carbon in fly ash and slag. Corresponding to the highest Furnace core temperature in the primary air section and the lowest carbon in fly ash and slag, the optimal pulverized coal concentration of anthracite and bituminous was 0.796–0.810 kg coal/kg air and 0.586–0.607 kg coal/kg air, respectively. In addition, with increased pulverized coal concentration, the NO x emissions reduced quickly with a slight decrease in the range of the optimal pulverized coal concentration.
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Experimental Study on the Heat Flux Distribution of a Laboratory-Scale Wall-Fired Furnace
Energy & Fuels, 2010Co-Authors: Qingwei Fan, Shien Hui, Qulan Zhou, Xi Chen, Qinxin ZhaoAbstract:We investigate the effect of different operating conditions on the combustion process of the wall-Fired Furnace. The flue gas temperature, Furnace wall temperature, and spatial distribution of local heat flux on the wall of a laboratory-scale, gas fuel front wall-Fired Furnace are measured experimentally. Different combinations of operating conditions including swirl intensity (SI), air supply (AS), and burner combination (BC) are considered, and their influences on the combustion, heat-transfer, and heat flux distribution characteristics are explored. Among the operating conditions studied in this paper, the combustion process can be improved with the increase of SI as well as the inner secondary air (ISA) rate. Detailed local heat flux data are obtained and analyzed under various operating conditions. The results illustrate complicated variations over the entire Furnace wall. The decrease in SI conditions significantly enhances the local heat fluxes near the bottom of the Furnace (adjacent to the combus...
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effect of air distribution on aerodynamic field and coal combustion in an arch Fired Furnace
Energy & Fuels, 2010Co-Authors: Ruwei Liu, Shien Hui, Qulan Zhou, Qinxin Zhao, Houzhang TanAbstract:In this paper, the influence of air distribution on aerodynamic field and combustion performance in a 0.9 MW arch-Fired Furnace has been investigated by analyzing the momentum ratio of air flows and the air stoichiometric ratio in the preceding stage combustion zone. It is found that the momentum ratio of air−fuel flows directly affects the arch air penetration length and the position of the flame center, which is critical to the temperature distribution in the Furnace and on the Furnace walls. The best combustion performance in the experimental range occurs when the momentum ratio of arch air to secondary air equals 1.34 and that of arch air to D&E-layer secondary air equals 4.42. In addition, it is found that the heat loss due to incomplete combustion, also called combustible loss, and NOx emission in the flue gas are related to the air stoichiometric ratio (SR). The minimum values of unburned carbon in fly ash, unburned carbon in the slag and NOx emission at the Furnace outlet are attained when SR = 0....
Gyungmin Choi - One of the best experts on this subject based on the ideXlab platform.
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Detailed in-Furnace measurements in a pulverized coal-Fired Furnace with combined woody biomass co-firing and air staging
Journal of Mechanical Science and Technology, 2018Co-Authors: Minsung Choi, Kibeom Kim, Yonmo Sung, Gyungmin ChoiAbstract:This paper presents a detailed experimental description of the combined effects of woody biomass co-firing and air staging on NO emissions and burnout performance in a pulverized coal-Fired Furnace. The co-combustion of woody biomass and bituminous coal was evaluated using woody biomass co-firing proportions of 0 % to 30 % with intervals of 10 %. Detailed in-Furnace gas temperature and gas-phase concentration for species such as O2, CO2, CO and NO were measured for the co-firing flames, both with and without air staging. The overall temperature of the woody biomass co-firing flames was higher than that of the pure bituminous coal flame. This effect was more pronounced for air-staged combustion than for combustion without air staging. Co-firing woody biomass with air staging strongly affected NO reduction efficiency, whereas NO emissions were insignificant for no-staged firing. The deteriorating effect of air staging on burnout performance was a function of the woody biomass co-firing ratio. NO reduction efficiency for the air-staged flames was improved by more than 40 % in both flames for woody biomass co-firing proportions of 10 % and 20 %.
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coal particle size effects on no reduction and burnout characteristics with air staged combustion in a pulverized coal Fired Furnace
Fuel, 2016Co-Authors: Yonmo Sung, Gyungmin Choi, Cheoreon Moon, Seongyong Eom, Duckjool KimAbstract:Abstract The influence of coal-particle size on nitrogen oxide (NO x ) emission and burnout characteristics was experimentally investigated in a pulverized coal-Fired Furnace. This study was carried out for a range of particle sizes, namely, mean sizes of 52, 73, 102, and 107 μm. Detailed in-Furnace measurements of gas temperature and gas species concentrations (O 2 , CO 2 , CO, and NO) were performed for two particle sizes (52 and 107 μm) in both unstaged and air-staged flames. The results show that the overall temperature of the flames with a mean particle size of 52 μm is higher than that of the flames with a mean particle size of 107 μm, because burning of fine coal particles improves the heating rate of other larger pulverized coal particles. The value of the NO emission measured at the Furnace outlet depends on the pulverized coal-particle size and decreases by 20% with an increase in the mean particle size from 46 μm to 118 μm. Two trends are observed in the NO emission with a mean particle size. For the unstaged combustion, a linear relationship exists between the NO emission and mean particle size, whereas the NO emission is constant at the air-staged combustion. The burnout performance increases with an increase in the level of coal fineness. The effectiveness of air staging on the NO reduction and burnout performance is significant in the flames with fine pulverized coal particles. The NO-reduction efficiency for flames with mean particle sizes of 52 and 73 μm is almost twice that for flames with mean particle sizes of 102 and 107 μm. For the burnout performance, the deteriorating effect of air staging is more profound at the flames with high level of coal fineness. The reduction rate in the burnout performance is 1.7% for flames with fine particles (52 and 73 μm) and 0.7% for flames with coarse particles (102 and 107 μm).
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Effectiveness between swirl intensity and air staging on NOx emissions and burnout characteristics in a pulverized coal Fired Furnace
Fuel Processing Technology, 2015Co-Authors: Yonmo Sung, Gyungmin ChoiAbstract:For opposed wall-Fired boilers, the dependency of NOx emission and burnout characteristics on swirl intensity is not straightforward during air-staged combustion. In this study, therefore, influences of swirl vane angle, primary zone stoichiometric ratio, and air staging level on NOx emission and burnout were evaluated experimentally in a laboratory-scale pulverized coal Fired Furnace. The NOx emission and burnout were a function of residence time in the primary combustion zone. Increasing of the residence time and decreasing of the primary zone stoichiometric ratio had a positive effect on NOx reduction and a negative effect on burnout. There was a tradeoff relationship between the NOx reduction and burnout performance. With controlling of the swirl vane angle, aerodynamic behaviors in the burner region had a strong impact on NOx emissions and burnout characteristics. From the effectiveness analysis of combustion modifications such as the primary zone stoichiometric ratio and swirl vane angle, the control of swirl vane angle was more effective than that in the control of the primary zone stoichiometric ratio. The optimum swirl vane angle should be adjusted with given combustion environments, especially in this research, it was 80°, 45°, and 60° at no staging, air staging level 1, and air staging levels 2–4, respectively.
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NOx emissions and burnout characteristics of bituminous coal, lignite, and their blends in a pulverized coal-Fired Furnace
Experimental Thermal and Fluid Science, 2015Co-Authors: Cheoreon Moon, Yonmo Sung, Seongyong Eom, Gyungmin ChoiAbstract:Abstract For coal-Fired power plants, the application of low-rank coals like brown coal and lignite steadily has been a great issue due to the shortage and rising prices of high-rank coal. In this research, therefore, co-firing experiments with low-rank coal, lignite, were performed in a 15 kW th pulverized coal-Fired Furnace, and combustion and emission characteristics of bituminous, lignite, and their blends were investigated. Influences of staged-air injection, primary zone air ratio, coal types, and blending ratios of bituminous coal and lignite on NO x emission and particle burnout were evaluated. For the bituminous coal, NO x emissions decreased slightly with a decreasing primary zone air ratio and increasing staged-air injector level. At a given value of the primary zone air ratio and staged-air injector level, NO x emissions were lower for coal with lower nitrogen content. However, in the case of the lignite, the NO x concentration was the highest, because of maintenance of a constant thermal output. For a multi-staged combustion, increasing the distance between the staged-air injectors has a positive effect on NO x emission but a negative effect on particle burnout. Furthermore, in co-combustion with bituminous coal and lignite, the blends with a 10% addition of lignite show a minimum value for NO x concentration and a similar temperature distribution to the bituminous coal case. This is because of the higher devolatilization rate of lignite and the formation of a strong reducing environment at high temperatures from the reaction between oxygen and the combustible gas species. Such gas species were released from lignite devolatilization in the primary combustion zone that is conducive to NO x destruction.
Houzhang Tan - One of the best experts on this subject based on the ideXlab platform.
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Determining the Optimum Coal Concentration in A General Tangential-Fired Furnace with Rich-Lean Burners: From A Bench-Scale To A Pilot-Scale Study
Applied Thermal Engineering, 2014Co-Authors: Xuebin Wang, Yanqing Niu, Houzhang Tan, Weiping Yan, Xiaolin Wei, Shien HuiAbstract:The mass ratio of pulverized coal and air (coal concentration, kg/kg) in fuel-rich streams is important in the design and operation of rich-lean burners, in which the optimum coal concentration (C-opt) that corresponds to the best combustion situation should be achieved. This study aims to establish a practical identification method to evaluate the C-opt of the different ranks of coal in rich-lean burners. A wide range of tests were conducted in a bench-scale down-Fired Furnace and a pilot-scale tangential-Fired Furnace with rich-lean burners. Temperature distribution, unburned carbon in ash, and NOx emissions were measured, and the effects of coal quality aside from burner type and burner layout method were considered. Results show that the optimum coal concentration corresponds to the highest Furnace temperature for each group of tests both in the bench-scale and pilot-scale Furnaces. C-opt is significantly affected by coal quality even if a change from the use of a corner-tangential to a wall-tangential Furnace lowers C-opt; however, the effect of a vertical rich-lean burner or a horizontal rich-lean burner on C-opt is negligible. The value of C-opt mainly decreases from 1.14 to 0.67 with a decrease in the volatile content from anthracite scale ( 0.35). The empirical formula of C-opt = 1.19-0.15V(daf)Q(net)(0.7)/100M(ad)(0.1) is obtained to evaluate the optimum coal concentration of a general pulverized coal flame, and another formula, C-opt = 1.18-0.17V(daf)Q(net)(0.7)/100M(ad)(0.1) is especially derived for a tangential-Fired Furnace with a rich-lean burner. The optimum value obtained is also critical to NOx emissions because when the coal concentration surpasses the value of C-opt, NOx emissions can be much more efficiently controlled through reduction of air. The findings of this study can provide practical guidance for the design and operation of rich-lean burners to achieve high combustion efficiency and low NOx emissions. (C) 2014 Elsevier Ltd. All rights reserved.
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effect of the momentum flux ratio of vertical to horizontal component on coal combustion in an arch Fired Furnace with upper Furnace over fire air
Experimental Thermal and Fluid Science, 2013Co-Authors: Shuai Zhao, Shien Hui, Qulan Zhou, Qinxin Zhao, Ling Liang, Houzhang TanAbstract:Abstract Over-fire air is introduced to achieve deep staging conditions for combustion optimization in a 0.7 MW arch-Fired Furnace. The momentum flux ratio ( M ) of vertical to horizontal component is determined by variations of air distribution and the inclination angle of the F-layer secondary air. Two coals with relatively large characteristic differences are used in the pilot tests. The results show that M directly affects the arch air penetration length and the position of the flame center. As the inclination angle increases appropriately, the position of high temperature zone moves downward, and the variation amplitude becomes smaller. The distribution of the wall temperature becomes more uniform. An overlarge angle would cause severe dregs on the wall of hopper, however. Increasing the arch air ratio can also delay the mixing of air–fuel flows and stage air and lower downward the flame center. Too small M would cause much higher temperatures in the upper Furnace. The unburned carbon in the fly ash and NO x emission both attain their minimum values with an inclination angle of 30° and a momentum flux ratio of 1.35, which is considered as the optimum operation condition in the experimental range.
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Origination and formation of NH4Cl in biomass-Fired Furnace
Fuel Processing Technology, 2013Co-Authors: Yanqing Niu, Yuanyi Liu, Houzhang Tan, Yingying XiongAbstract:Abstract Biomass slagging is widely affected by various factors. NH4Cl verified by TG/DSC and XRD is found in the exit of bag filters in a cotton stalk biomass-Fired Furnace in northwest of China. The TG/DSC curves of the sample are well in agreement with standard NH4Cl. The peaks of sample are also well consistent with standard NH4Cl identified by XRD and with a purity of almost 100%. Based on the concentration of Cl in cotton stalks (0.44 wt.%) and cropland soil (6.834 wt.%), and balance calculation based on SiO2 and Al2O3 trace method, it is deduced that partial NH4Cl is from soil doped into the cotton stalks. In boiler, NH4Cl decomposes into NH3(g) and HCl(g) at 337.8 °C, and then partial HCl(g) reacts with metal oxides in ash, or NH4Cl reacts with hydroxide directly and generates NH3(g). All the chlorides as reaction products cause serious slagging in the boiler. Together with the NH3(g) and HCl(g) generated from biomass, the remaining HCl(g) gets through bag filters and re-combines with un-oxidized NH3(g) into NH4Cl accumulated in tail flue. Therefore, inevitable impurities in biomass, especially element Cl, should highly attract attention in the biomass-Fired boilers.
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Study of optimal pulverized coal concentration in a four-wall tangentially Fired Furnace
Applied Energy, 2011Co-Authors: Houzhang Tan, Yanqing Niu, Xuebin Wang, Shien HuiAbstract:Abstract The effect of fuel lean/rich conditions (1:1, 1:2, 1:3, 1:4, 1:5 and 1:6) on the Furnace core temperatures, carbon in fly ash and slag and NO x emissions was investigated in a 1 MW four-wall tangentially horizontal bias Fired Furnace for Yibin anthracite and Shenmu bituminous, respectively. Results shown that Furnace core temperatures increased at first and then decreased along the height of the Furnace when anthracite burned. The Furnace core temperature at the height of primary air nozzles was the highest when the bituminous lean/rich varied from 1:1 to 1:3, and its trend was similar to the anthracite when the bituminous lean/rich was changed from 1:4 to 1:6. The ignition of anthracite required a heating stage, while bituminous could timely ignite due to high volatile. However, when the bituminous lean/rich was too low resulting in the relative lack of oxygen, it still needed a heating stage. With increased coal concentration, the Furnace core temperatures in the primary air section went up firstly and then down, but the carbon in fly ash and slag showed adverse behavior. This was due to the high coal concentration corresponding to high volatile concentration leading to the timely ignition and burnout, causing higher Furnace core temperature in the primary air section and decreased carbon in fly ash and slag. Corresponding to the highest Furnace core temperature in the primary air section and the lowest carbon in fly ash and slag, the optimal pulverized coal concentration of anthracite and bituminous was 0.796–0.810 kg coal/kg air and 0.586–0.607 kg coal/kg air, respectively. In addition, with increased pulverized coal concentration, the NO x emissions reduced quickly with a slight decrease in the range of the optimal pulverized coal concentration.
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effect of air distribution on aerodynamic field and coal combustion in an arch Fired Furnace
Energy & Fuels, 2010Co-Authors: Ruwei Liu, Shien Hui, Qulan Zhou, Qinxin Zhao, Houzhang TanAbstract:In this paper, the influence of air distribution on aerodynamic field and combustion performance in a 0.9 MW arch-Fired Furnace has been investigated by analyzing the momentum ratio of air flows and the air stoichiometric ratio in the preceding stage combustion zone. It is found that the momentum ratio of air−fuel flows directly affects the arch air penetration length and the position of the flame center, which is critical to the temperature distribution in the Furnace and on the Furnace walls. The best combustion performance in the experimental range occurs when the momentum ratio of arch air to secondary air equals 1.34 and that of arch air to D&E-layer secondary air equals 4.42. In addition, it is found that the heat loss due to incomplete combustion, also called combustible loss, and NOx emission in the flue gas are related to the air stoichiometric ratio (SR). The minimum values of unburned carbon in fly ash, unburned carbon in the slag and NOx emission at the Furnace outlet are attained when SR = 0....
Yonmo Sung - One of the best experts on this subject based on the ideXlab platform.
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Detailed in-Furnace measurements in a pulverized coal-Fired Furnace with combined woody biomass co-firing and air staging
Journal of Mechanical Science and Technology, 2018Co-Authors: Minsung Choi, Kibeom Kim, Yonmo Sung, Gyungmin ChoiAbstract:This paper presents a detailed experimental description of the combined effects of woody biomass co-firing and air staging on NO emissions and burnout performance in a pulverized coal-Fired Furnace. The co-combustion of woody biomass and bituminous coal was evaluated using woody biomass co-firing proportions of 0 % to 30 % with intervals of 10 %. Detailed in-Furnace gas temperature and gas-phase concentration for species such as O2, CO2, CO and NO were measured for the co-firing flames, both with and without air staging. The overall temperature of the woody biomass co-firing flames was higher than that of the pure bituminous coal flame. This effect was more pronounced for air-staged combustion than for combustion without air staging. Co-firing woody biomass with air staging strongly affected NO reduction efficiency, whereas NO emissions were insignificant for no-staged firing. The deteriorating effect of air staging on burnout performance was a function of the woody biomass co-firing ratio. NO reduction efficiency for the air-staged flames was improved by more than 40 % in both flames for woody biomass co-firing proportions of 10 % and 20 %.
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coal particle size effects on no reduction and burnout characteristics with air staged combustion in a pulverized coal Fired Furnace
Fuel, 2016Co-Authors: Yonmo Sung, Gyungmin Choi, Cheoreon Moon, Seongyong Eom, Duckjool KimAbstract:Abstract The influence of coal-particle size on nitrogen oxide (NO x ) emission and burnout characteristics was experimentally investigated in a pulverized coal-Fired Furnace. This study was carried out for a range of particle sizes, namely, mean sizes of 52, 73, 102, and 107 μm. Detailed in-Furnace measurements of gas temperature and gas species concentrations (O 2 , CO 2 , CO, and NO) were performed for two particle sizes (52 and 107 μm) in both unstaged and air-staged flames. The results show that the overall temperature of the flames with a mean particle size of 52 μm is higher than that of the flames with a mean particle size of 107 μm, because burning of fine coal particles improves the heating rate of other larger pulverized coal particles. The value of the NO emission measured at the Furnace outlet depends on the pulverized coal-particle size and decreases by 20% with an increase in the mean particle size from 46 μm to 118 μm. Two trends are observed in the NO emission with a mean particle size. For the unstaged combustion, a linear relationship exists between the NO emission and mean particle size, whereas the NO emission is constant at the air-staged combustion. The burnout performance increases with an increase in the level of coal fineness. The effectiveness of air staging on the NO reduction and burnout performance is significant in the flames with fine pulverized coal particles. The NO-reduction efficiency for flames with mean particle sizes of 52 and 73 μm is almost twice that for flames with mean particle sizes of 102 and 107 μm. For the burnout performance, the deteriorating effect of air staging is more profound at the flames with high level of coal fineness. The reduction rate in the burnout performance is 1.7% for flames with fine particles (52 and 73 μm) and 0.7% for flames with coarse particles (102 and 107 μm).
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Effectiveness between swirl intensity and air staging on NOx emissions and burnout characteristics in a pulverized coal Fired Furnace
Fuel Processing Technology, 2015Co-Authors: Yonmo Sung, Gyungmin ChoiAbstract:For opposed wall-Fired boilers, the dependency of NOx emission and burnout characteristics on swirl intensity is not straightforward during air-staged combustion. In this study, therefore, influences of swirl vane angle, primary zone stoichiometric ratio, and air staging level on NOx emission and burnout were evaluated experimentally in a laboratory-scale pulverized coal Fired Furnace. The NOx emission and burnout were a function of residence time in the primary combustion zone. Increasing of the residence time and decreasing of the primary zone stoichiometric ratio had a positive effect on NOx reduction and a negative effect on burnout. There was a tradeoff relationship between the NOx reduction and burnout performance. With controlling of the swirl vane angle, aerodynamic behaviors in the burner region had a strong impact on NOx emissions and burnout characteristics. From the effectiveness analysis of combustion modifications such as the primary zone stoichiometric ratio and swirl vane angle, the control of swirl vane angle was more effective than that in the control of the primary zone stoichiometric ratio. The optimum swirl vane angle should be adjusted with given combustion environments, especially in this research, it was 80°, 45°, and 60° at no staging, air staging level 1, and air staging levels 2–4, respectively.
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NOx emissions and burnout characteristics of bituminous coal, lignite, and their blends in a pulverized coal-Fired Furnace
Experimental Thermal and Fluid Science, 2015Co-Authors: Cheoreon Moon, Yonmo Sung, Seongyong Eom, Gyungmin ChoiAbstract:Abstract For coal-Fired power plants, the application of low-rank coals like brown coal and lignite steadily has been a great issue due to the shortage and rising prices of high-rank coal. In this research, therefore, co-firing experiments with low-rank coal, lignite, were performed in a 15 kW th pulverized coal-Fired Furnace, and combustion and emission characteristics of bituminous, lignite, and their blends were investigated. Influences of staged-air injection, primary zone air ratio, coal types, and blending ratios of bituminous coal and lignite on NO x emission and particle burnout were evaluated. For the bituminous coal, NO x emissions decreased slightly with a decreasing primary zone air ratio and increasing staged-air injector level. At a given value of the primary zone air ratio and staged-air injector level, NO x emissions were lower for coal with lower nitrogen content. However, in the case of the lignite, the NO x concentration was the highest, because of maintenance of a constant thermal output. For a multi-staged combustion, increasing the distance between the staged-air injectors has a positive effect on NO x emission but a negative effect on particle burnout. Furthermore, in co-combustion with bituminous coal and lignite, the blends with a 10% addition of lignite show a minimum value for NO x concentration and a similar temperature distribution to the bituminous coal case. This is because of the higher devolatilization rate of lignite and the formation of a strong reducing environment at high temperatures from the reaction between oxygen and the combustible gas species. Such gas species were released from lignite devolatilization in the primary combustion zone that is conducive to NO x destruction.
Qinxin Zhao - One of the best experts on this subject based on the ideXlab platform.
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effect of the momentum flux ratio of vertical to horizontal component on coal combustion in an arch Fired Furnace with upper Furnace over fire air
Experimental Thermal and Fluid Science, 2013Co-Authors: Shuai Zhao, Shien Hui, Qulan Zhou, Qinxin Zhao, Ling Liang, Houzhang TanAbstract:Abstract Over-fire air is introduced to achieve deep staging conditions for combustion optimization in a 0.7 MW arch-Fired Furnace. The momentum flux ratio ( M ) of vertical to horizontal component is determined by variations of air distribution and the inclination angle of the F-layer secondary air. Two coals with relatively large characteristic differences are used in the pilot tests. The results show that M directly affects the arch air penetration length and the position of the flame center. As the inclination angle increases appropriately, the position of high temperature zone moves downward, and the variation amplitude becomes smaller. The distribution of the wall temperature becomes more uniform. An overlarge angle would cause severe dregs on the wall of hopper, however. Increasing the arch air ratio can also delay the mixing of air–fuel flows and stage air and lower downward the flame center. Too small M would cause much higher temperatures in the upper Furnace. The unburned carbon in the fly ash and NO x emission both attain their minimum values with an inclination angle of 30° and a momentum flux ratio of 1.35, which is considered as the optimum operation condition in the experimental range.
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Experimental Study on the Heat Flux Distribution of a Laboratory-Scale Wall-Fired Furnace
Energy & Fuels, 2010Co-Authors: Qingwei Fan, Shien Hui, Qulan Zhou, Xi Chen, Qinxin ZhaoAbstract:We investigate the effect of different operating conditions on the combustion process of the wall-Fired Furnace. The flue gas temperature, Furnace wall temperature, and spatial distribution of local heat flux on the wall of a laboratory-scale, gas fuel front wall-Fired Furnace are measured experimentally. Different combinations of operating conditions including swirl intensity (SI), air supply (AS), and burner combination (BC) are considered, and their influences on the combustion, heat-transfer, and heat flux distribution characteristics are explored. Among the operating conditions studied in this paper, the combustion process can be improved with the increase of SI as well as the inner secondary air (ISA) rate. Detailed local heat flux data are obtained and analyzed under various operating conditions. The results illustrate complicated variations over the entire Furnace wall. The decrease in SI conditions significantly enhances the local heat fluxes near the bottom of the Furnace (adjacent to the combus...
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effect of air distribution on aerodynamic field and coal combustion in an arch Fired Furnace
Energy & Fuels, 2010Co-Authors: Ruwei Liu, Shien Hui, Qulan Zhou, Qinxin Zhao, Houzhang TanAbstract:In this paper, the influence of air distribution on aerodynamic field and combustion performance in a 0.9 MW arch-Fired Furnace has been investigated by analyzing the momentum ratio of air flows and the air stoichiometric ratio in the preceding stage combustion zone. It is found that the momentum ratio of air−fuel flows directly affects the arch air penetration length and the position of the flame center, which is critical to the temperature distribution in the Furnace and on the Furnace walls. The best combustion performance in the experimental range occurs when the momentum ratio of arch air to secondary air equals 1.34 and that of arch air to D&E-layer secondary air equals 4.42. In addition, it is found that the heat loss due to incomplete combustion, also called combustible loss, and NOx emission in the flue gas are related to the air stoichiometric ratio (SR). The minimum values of unburned carbon in fly ash, unburned carbon in the slag and NOx emission at the Furnace outlet are attained when SR = 0....