The co-firing of coal and biomass in oxy-fuel fluidized beds is one of the most promising technologies for capturing CO2.This technology has attracted wide attention from academia and industry in recent years as a neg...The co-firing of coal and biomass in oxy-fuel fluidized beds is one of the most promising technologies for capturing CO2.This technology has attracted wide attention from academia and industry in recent years as a negative emission method to capture CO2 produced by carbon contained in biomass.In the past decades,many studies have been carried out regarding experiments and numerical simulations under oxy-fuel combustion conditions.This paper firstly briefly discusses the techno-economic viability of the biomass and coal co-firing with oxycombustion and then presents a review of recent advancements involving experimental research and computational fluid dynamics(CFD)simulations in this field.Experimental studies on mechanism research,such as thermogravimetric analysis and tube furnace experiments,and fluidized bed experiments based on oxy-fuel fluidized beds with different sizes as well as the main findings,are summarized as a part of this review.It has been recognized that CFD is a useful approach for understanding the behaviors of the co-firing of coal and biomass in oxyfuel fluidized beds.We summarize a recent survey of published CFD research on oxy-fuel fluidized bed combustion,which categorized into Eulerian and Lagrangian methods.Finally,we discuss the challenges and interests for future research.展开更多
Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics o...Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emissions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was concluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission;however, the SOx increased slightly. The influences of air preheating temperature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.展开更多
Alabama imports coal from other states to generate electricity. This paper assessed the direct and indirect economic impacts of wood pellet production to be co-fired with coal for power generation in Alabama. Four siz...Alabama imports coal from other states to generate electricity. This paper assessed the direct and indirect economic impacts of wood pellet production to be co-fired with coal for power generation in Alabama. Four sizes of wood pellet plants and regional input-output models were used for the analysis. The results showed that the economic impact increases with the size of the plant. Wood pellet production will have a multiplier effect on the economy especially, forest-related services, retail stores, the health service industry, and tax revenue for the government. Domestic wood pellet production can reduce the use of imported coal, allow the use of local woody biomass, and create economic activities in Alabama’s rural communities. Policies that support the production of wood pellet will serve to encourage the use of wood for power generation and support the rural economies.展开更多
The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is...The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is the largest coal and natural gas based electricity generating unit (EGU) in Texas. Forest residue is an abundant renewable resource, and can be used to offset coal usage at EGUs. This study evaluates the impact of co-firing 5%, 10%, and 15% (energy-basis) of forest residue at WAP on the air quality of the HGB area. Photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx) was conducted to investigate the air quality at three air quality monitoring sites (C696, C53, C556) in the HGB area, under two source scenarios (all-sources, point + biogenic sources). Significant reduction of SO2 and O3 was observed for 10% and 15% co-firing ratios at monitoring station (C696) close to WAP. The maximum reduction of ozone observed for 15% co-firing is 4.7% and 6.3% for all-sources and point + biogenic sources scenarios respectively. The reduction in other criteria air pollutants is not significant at all locations. The overall results from this study indicate that biomass co-firing at WAP would not lead to a significant reduction in ozone concentrations in the region during periods of peak ozone.展开更多
With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel...With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel is extensively used to achieve CO_(2) zero-emission in cement production.Due to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried out.Three types of biomass fuel and bituminous coal were used to investigate the NO reduction characteristics under different O_(2) concentrations on experimental benches.It was found that the change in oxygen concentration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen concentration can lead to shorter reaction time,and correspondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) concentration changing from 1% to 9%,the peak NO concentration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) concentration greatly reduces the total reduction of NO and the minimum change in NO concentration.The peak NO concentration during the combustion process of corn stalk is 4.56×10^(-4),which is approximately 7 times higher than that of coal,and it is caused by the high amount of N in corn stalk.The addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises CO_(2) concentration of fuel gas in the early stage of reaction.展开更多
The influence of the blending ratio of pyrolyzed semi-char(SC)on the ignition,NO emission and burnout characteristics of lignite co-fired with SC was investigated in a 350 kW fuel-rich/lean combustion furnace.The flam...The influence of the blending ratio of pyrolyzed semi-char(SC)on the ignition,NO emission and burnout characteristics of lignite co-fired with SC was investigated in a 350 kW fuel-rich/lean combustion furnace.The flame temperature and concentrations of gaseous species including O_(2),CO,and NO,were measured in detail.The results indicated that the ignition characteristics of the blended fuel worsened with increasing SC blending ratio,such as an elongated ignition standoff distance.The addition of SC to lignite delayed the appearance of a stable flame boundary,and the stable combustion zone moved down,but the final combustion stability was gradually strengthened in the later combustion stage.NO emission concentration at the primary combustion zone(PCZ)outlet was the lowest at 472.6 mg/m^(3)@6%O_(2)when the SC blending ratio was 25%.The combustion zone and reducing zone areas in PCZ were defined to evaluate the NO reduction characteristics,and quantitative analysis using a multiple linear regression model showed that heterogeneous reduction was more important than homogeneous reduction in lowering NO emissions.The Raman spectrum of the char sample indicated that the addition of lignite promoted the formation of small aromatic rings in the early ignition stage,corresponding to a higher char reactivity.The burnout ratio of pure lignite was maximal and was decreased by increasing the SC blending ratio.Synthetically,considering the ignition standoff distance,NO emission,and burnout ratio,the optimum SC blending ratio was estimated to be 25%.展开更多
It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-mill...It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-milling coal and wood on their co-firing:is the case of composite powdered fuels should ensure the maximum possible efficiency of heat and mass transfer?Firstly,we will show that co-milling of coal and wood leads not independent size reduction of two materials but gives composite powder-coal-covered wood.For the composite fuel further reduction of the ignition delay time of air suspension and reduction of the limit volume concentration required for flame propagation have demonstrated.Obtained synergy also manifests in thermogravimetry.Here we propose a simple method for analyzing the mass loss curves.For any coal-to-wood sawdust ratio,combustion of the composites and mixtures both can be viewed as a weighted sum of the curves of individual components.But only in the case of composites calculated sawdust content is higher than the actual one:the mass loss is redistributed towards the stage occurring at lower temperatures due to geometry of wood/coal contact.展开更多
A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO_(2) capture process is recycled to heat the ...A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO_(2) capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper.Based on a 660 MW supercritical coal-fired power plant,the thermal performance,emission performance,and economic performance of the proposed scheme are evaluated.In addition,a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system.The results show that when the biomass mass mixing ratio is 15.40%and the CO_(2) capture rate is 90%,the CO_(2) emission of the coal-fired power plant can reach zero,indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants.The net thermal efficiency decreases by 10.31%,due to the huge energy consumption of the CO_(2) capture unit.Besides,the cost of electricity(COE)and the cost of CO_(2) avoided(COA)of the proposed system are 80.37/MWhand41.63/tCO_(2),respectively.The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO_(2) to 2.40 GJ/tCO_(2),the efficiency penalty is reduced to 8.67%.This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.展开更多
In this work, a multi-layer anode supported solid oxide fuel cell(SOFC) is designed and successfully prepared through sequential tape casting and co-firing. The single cell is consisted of NiO-3 YSZ(3 YSZ: 3 mol.% ytt...In this work, a multi-layer anode supported solid oxide fuel cell(SOFC) is designed and successfully prepared through sequential tape casting and co-firing. The single cell is consisted of NiO-3 YSZ(3 YSZ: 3 mol.% yttria doped zirconia) anode support, NiO-8 YSZ(8 YSZ: 8 mol.% yttria stabilized zirconia) anode functional layer, dense 8 YSZ electrolyte layer, and porous 3 YSZ cathode scaffold layer with infiltrated La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) cathode. The clear interfaces and good contacts between each layer, without element inter-diffusion being observed, suggest that this sequential tape casting and co-firing is a feasible and successful route for anode supported single cell fabrication. This cell exhibits remarkable high open circuit voltage of 1.097 V at 800?C under room temperature humidified hydrogen, with highly dense and gastight electrolyte layer. It provides a power density of 360 mW/cm^2 under operation voltage of0.75 V at 800?C and a stable operation of ～110 h at 750?C under current density of-300 mA/cm^2. Furthermore, this cell also presents encouraging electrochemical responses under various anode hydrogen partial pressures and maintains high power output at low fuel concentrations.展开更多
The study of swirling jet combustor for biomass coal co-firing is of great interest for energy industry. The biomass co-firing can serve as a NOx reduction method as well as the better use of renewable energy source. ...The study of swirling jet combustor for biomass coal co-firing is of great interest for energy industry. The biomass co-firing can serve as a NOx reduction method as well as the better use of renewable energy source. Large eddy simulation (LES) and RANS modelling have been performed with two different burner designs. Usually pulverized coal-biomass mixture enters the furnace along with primary air through primary pipe, and the secondary pipe provides necessary air and mixing for combustion. The improved model has three passages including primary, secondary and middle passage for swirling. The simulations on two geometries have been compared, and the aim is to design a better and improved burner model for better pre-combustion mixing in the biomass co- fired furnace. The results from two-way and three-way geometry have been compared with each other as well as with the results from the furnace model used by Apte and Mahesh [8].展开更多
The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape h...The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are?changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have?little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.展开更多
Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitig...Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitigate ash deposition as well as promote shedding of deposits.To identify the optimum operating conditions,fuel particle sizes,and blend ratios that minimize ash deposition,a Computational Fluid Dynamic methodology with add-on ash deposition and shedding models were employed to predict outer ash deposition and shedding rates during co-combustion of coal/RH in AIR and O2/CO_(2)(70/30 vol%,OXY70)oxidizer compositions.After ensuring that the fly-ash particle size distributions and particle Stokes numbers near the deposition surface were accurately represented(to model impaction),appropriate models for coal ash and RH ash viscosities that were accurate in the temperature region(1200-1300 K)of interest in this study were identified.A particle viscosity and kinetic energy(PKE)based capture criterion was enforced to model the ash capture.An erosion/shed-ding criterion that takes the deposit melt fraction and the energy consumed during particle impact into account was also implemented.Deposition rate predictions as well as the deposition rate enhancement(OXY70/AIR)were in good agreement with measured values.While the OXY70 scenario was associated with a significant reduction(60%-70%)in flue gas velocities,it also resulted in larger fly-ash particles.As a result,the PKE distributions of the erosive RH ash were similar in both scenarios and resulted in similar shedding rates.展开更多
CuO added Pb_(0.92)Sr_(0.06)Ba_(0.02)(Mg_(1/3)Nb_(2/3))_(0.25)(Ti_(0.53)Zr_(0.47))_(0.75)O_3 ceramics were studied to prepare high-quality multilayer piezoelectric actuators with pure Ag electrodes at 900℃. Cu O addi...CuO added Pb_(0.92)Sr_(0.06)Ba_(0.02)(Mg_(1/3)Nb_(2/3))_(0.25)(Ti_(0.53)Zr_(0.47))_(0.75)O_3 ceramics were studied to prepare high-quality multilayer piezoelectric actuators with pure Ag electrodes at 900℃. Cu O addition not only reduced the sintering temperature significantly from 1260℃ to 900℃ but also improved the ceramic density to 7.742 g/cm^3. The 0.7 wt.% Cu O added ceramic sintered at 900℃ shows the remnant polarization(P_r) of 40 μC/cm^2, 0.28% strain at 40 kV/cm, and the piezoelectric coefficient(d_(33)) of 630 pC/N. This ceramic shows a strong relaxor characteristic with a Curie temperature of 200℃. Furthermore, the 0.7 wt.% CuO added ceramic and pure Ag electrodes were co-fired at 900℃ to prepare a high-quality multilayer piezoelectric actuator with a d_(33) of over 450 pC/N per ceramic layer.展开更多
The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave ...The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave dielectric properties of Li2ZnTi3O8 ceramics with the addition of V2O5 were investigated. Based on our research, V2O5 doping effectively promoted the densification of Li2ZnTi3O8 ceramics at about 900°C, without affecting the main crystal phase of the ceramics. Li2ZnTi3O8 ceramics with 0.5 wt% V2O5 doping (sintered at 900°C) exhibited the best microwave dielectric properties (Qf =?22,400 GHz at about 6 GHz, εr = 25.5, and τf = -10.8 ppm/°C). The V2O5-doped Li2ZnTi3O8 ceramics were well cofired with Ag inner paste without cracks and diffusion, indicating its significant potential for LTCC applications.展开更多
The global transition from fossil fuel-based energy sources to renewable energy sources will be most effective,for at least the near future,by utilizing local resources and existing infrastructure.In many areas of the...The global transition from fossil fuel-based energy sources to renewable energy sources will be most effective,for at least the near future,by utilizing local resources and existing infrastructure.In many areas of the eastern United States,forest residue is abundant and can be used in existing facilities to supplement coal in coal-fired power plants.Thus forest residue has potential as a renewable energy source that could be effectively utilized in the near future.This study uses GIS to estimate the potential quantity of forest residue available for use in coal-fired power plants in the eastern United States.Transportation costs limit the distance over which it is feasible to transport forest residue to the power plants and these costs may fluctuate depending on economic conditions.Thus,we consider three scenarios in our analysis assuming the maximum feasible transport distances to be 60,80,and 100 km.In the eastern U.S.,the total annual forest residue available to coal plants is approximately 29.4,40.2,and 48.2 million dry tons,respectively,for maximum transport distances of 60,80,and 100 km.Assuming an 80 km transport distance,forest residue has the potential to reduce coal consumption by 22.3 million tons per year.Under this scenario,greenhouse gas emissions would be reduced by almost 58.1 million tons per year,and NOx and SOx emissions would be reduced by 69.3 and 122.6 thousand tons respectively.This analysis suggests that by offsetting coal use,forest residue has the potential to substantially reduce power plant emissions.展开更多
基金supported by the Key Program of the National Natural Science Foundation of China(51736002)the Natural Science Foundation of Jiangsu Province(BK20180386).
文摘The co-firing of coal and biomass in oxy-fuel fluidized beds is one of the most promising technologies for capturing CO2.This technology has attracted wide attention from academia and industry in recent years as a negative emission method to capture CO2 produced by carbon contained in biomass.In the past decades,many studies have been carried out regarding experiments and numerical simulations under oxy-fuel combustion conditions.This paper firstly briefly discusses the techno-economic viability of the biomass and coal co-firing with oxycombustion and then presents a review of recent advancements involving experimental research and computational fluid dynamics(CFD)simulations in this field.Experimental studies on mechanism research,such as thermogravimetric analysis and tube furnace experiments,and fluidized bed experiments based on oxy-fuel fluidized beds with different sizes as well as the main findings,are summarized as a part of this review.It has been recognized that CFD is a useful approach for understanding the behaviors of the co-firing of coal and biomass in oxyfuel fluidized beds.We summarize a recent survey of published CFD research on oxy-fuel fluidized bed combustion,which categorized into Eulerian and Lagrangian methods.Finally,we discuss the challenges and interests for future research.
文摘Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emissions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was concluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission;however, the SOx increased slightly. The influences of air preheating temperature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.
文摘Alabama imports coal from other states to generate electricity. This paper assessed the direct and indirect economic impacts of wood pellet production to be co-fired with coal for power generation in Alabama. Four sizes of wood pellet plants and regional input-output models were used for the analysis. The results showed that the economic impact increases with the size of the plant. Wood pellet production will have a multiplier effect on the economy especially, forest-related services, retail stores, the health service industry, and tax revenue for the government. Domestic wood pellet production can reduce the use of imported coal, allow the use of local woody biomass, and create economic activities in Alabama’s rural communities. Policies that support the production of wood pellet will serve to encourage the use of wood for power generation and support the rural economies.
文摘The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is the largest coal and natural gas based electricity generating unit (EGU) in Texas. Forest residue is an abundant renewable resource, and can be used to offset coal usage at EGUs. This study evaluates the impact of co-firing 5%, 10%, and 15% (energy-basis) of forest residue at WAP on the air quality of the HGB area. Photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx) was conducted to investigate the air quality at three air quality monitoring sites (C696, C53, C556) in the HGB area, under two source scenarios (all-sources, point + biogenic sources). Significant reduction of SO2 and O3 was observed for 10% and 15% co-firing ratios at monitoring station (C696) close to WAP. The maximum reduction of ozone observed for 15% co-firing is 4.7% and 6.3% for all-sources and point + biogenic sources scenarios respectively. The reduction in other criteria air pollutants is not significant at all locations. The overall results from this study indicate that biomass co-firing at WAP would not lead to a significant reduction in ozone concentrations in the region during periods of peak ozone.
基金financially supported by Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA29020200)。
文摘With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel is extensively used to achieve CO_(2) zero-emission in cement production.Due to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried out.Three types of biomass fuel and bituminous coal were used to investigate the NO reduction characteristics under different O_(2) concentrations on experimental benches.It was found that the change in oxygen concentration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen concentration can lead to shorter reaction time,and correspondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) concentration changing from 1% to 9%,the peak NO concentration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) concentration greatly reduces the total reduction of NO and the minimum change in NO concentration.The peak NO concentration during the combustion process of corn stalk is 4.56×10^(-4),which is approximately 7 times higher than that of coal,and it is caused by the high amount of N in corn stalk.The addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises CO_(2) concentration of fuel gas in the early stage of reaction.
基金National Key Research and Development Program of China(NO.2017YFB0602002)。
文摘The influence of the blending ratio of pyrolyzed semi-char(SC)on the ignition,NO emission and burnout characteristics of lignite co-fired with SC was investigated in a 350 kW fuel-rich/lean combustion furnace.The flame temperature and concentrations of gaseous species including O_(2),CO,and NO,were measured in detail.The results indicated that the ignition characteristics of the blended fuel worsened with increasing SC blending ratio,such as an elongated ignition standoff distance.The addition of SC to lignite delayed the appearance of a stable flame boundary,and the stable combustion zone moved down,but the final combustion stability was gradually strengthened in the later combustion stage.NO emission concentration at the primary combustion zone(PCZ)outlet was the lowest at 472.6 mg/m^(3)@6%O_(2)when the SC blending ratio was 25%.The combustion zone and reducing zone areas in PCZ were defined to evaluate the NO reduction characteristics,and quantitative analysis using a multiple linear regression model showed that heterogeneous reduction was more important than homogeneous reduction in lowering NO emissions.The Raman spectrum of the char sample indicated that the addition of lignite promoted the formation of small aromatic rings in the early ignition stage,corresponding to a higher char reactivity.The burnout ratio of pure lignite was maximal and was decreased by increasing the SC blending ratio.Synthetically,considering the ignition standoff distance,NO emission,and burnout ratio,the optimum SC blending ratio was estimated to be 25%.
文摘It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-milling coal and wood on their co-firing:is the case of composite powdered fuels should ensure the maximum possible efficiency of heat and mass transfer?Firstly,we will show that co-milling of coal and wood leads not independent size reduction of two materials but gives composite powder-coal-covered wood.For the composite fuel further reduction of the ignition delay time of air suspension and reduction of the limit volume concentration required for flame propagation have demonstrated.Obtained synergy also manifests in thermogravimetry.Here we propose a simple method for analyzing the mass loss curves.For any coal-to-wood sawdust ratio,combustion of the composites and mixtures both can be viewed as a weighted sum of the curves of individual components.But only in the case of composites calculated sawdust content is higher than the actual one:the mass loss is redistributed towards the stage occurring at lower temperatures due to geometry of wood/coal contact.
基金supported by the National Natural Science Foundation of China(Grant No.51806062)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51821004)the Fundamental Research Funds for the Central Universities(Grant No.2020MS006).
文摘A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO_(2) capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper.Based on a 660 MW supercritical coal-fired power plant,the thermal performance,emission performance,and economic performance of the proposed scheme are evaluated.In addition,a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system.The results show that when the biomass mass mixing ratio is 15.40%and the CO_(2) capture rate is 90%,the CO_(2) emission of the coal-fired power plant can reach zero,indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants.The net thermal efficiency decreases by 10.31%,due to the huge energy consumption of the CO_(2) capture unit.Besides,the cost of electricity(COE)and the cost of CO_(2) avoided(COA)of the proposed system are 80.37/MWhand41.63/tCO_(2),respectively.The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO_(2) to 2.40 GJ/tCO_(2),the efficiency penalty is reduced to 8.67%.This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.
基金supported financially by the Key R & D Program of Jiangsu Province (No.BE2017098)the Natural Science Foundation of Jiangsu Province (No.BK20170847)+1 种基金the Top-notch Academic Programs Project of Jiangsu Higher Education Institutionsthe Start-Up Fund of Nanjing University of Science and Technology
文摘In this work, a multi-layer anode supported solid oxide fuel cell(SOFC) is designed and successfully prepared through sequential tape casting and co-firing. The single cell is consisted of NiO-3 YSZ(3 YSZ: 3 mol.% yttria doped zirconia) anode support, NiO-8 YSZ(8 YSZ: 8 mol.% yttria stabilized zirconia) anode functional layer, dense 8 YSZ electrolyte layer, and porous 3 YSZ cathode scaffold layer with infiltrated La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) cathode. The clear interfaces and good contacts between each layer, without element inter-diffusion being observed, suggest that this sequential tape casting and co-firing is a feasible and successful route for anode supported single cell fabrication. This cell exhibits remarkable high open circuit voltage of 1.097 V at 800?C under room temperature humidified hydrogen, with highly dense and gastight electrolyte layer. It provides a power density of 360 mW/cm^2 under operation voltage of0.75 V at 800?C and a stable operation of ～110 h at 750?C under current density of-300 mA/cm^2. Furthermore, this cell also presents encouraging electrochemical responses under various anode hydrogen partial pressures and maintains high power output at low fuel concentrations.
文摘The study of swirling jet combustor for biomass coal co-firing is of great interest for energy industry. The biomass co-firing can serve as a NOx reduction method as well as the better use of renewable energy source. Large eddy simulation (LES) and RANS modelling have been performed with two different burner designs. Usually pulverized coal-biomass mixture enters the furnace along with primary air through primary pipe, and the secondary pipe provides necessary air and mixing for combustion. The improved model has three passages including primary, secondary and middle passage for swirling. The simulations on two geometries have been compared, and the aim is to design a better and improved burner model for better pre-combustion mixing in the biomass co- fired furnace. The results from two-way and three-way geometry have been compared with each other as well as with the results from the furnace model used by Apte and Mahesh [8].
文摘The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are?changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have?little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.
基金funded through the University Coal Research Program being administered by DOE-NETL (Award Number:DE-FE0031741).
文摘Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitigate ash deposition as well as promote shedding of deposits.To identify the optimum operating conditions,fuel particle sizes,and blend ratios that minimize ash deposition,a Computational Fluid Dynamic methodology with add-on ash deposition and shedding models were employed to predict outer ash deposition and shedding rates during co-combustion of coal/RH in AIR and O2/CO_(2)(70/30 vol%,OXY70)oxidizer compositions.After ensuring that the fly-ash particle size distributions and particle Stokes numbers near the deposition surface were accurately represented(to model impaction),appropriate models for coal ash and RH ash viscosities that were accurate in the temperature region(1200-1300 K)of interest in this study were identified.A particle viscosity and kinetic energy(PKE)based capture criterion was enforced to model the ash capture.An erosion/shed-ding criterion that takes the deposit melt fraction and the energy consumed during particle impact into account was also implemented.Deposition rate predictions as well as the deposition rate enhancement(OXY70/AIR)were in good agreement with measured values.While the OXY70 scenario was associated with a significant reduction(60%-70%)in flue gas velocities,it also resulted in larger fly-ash particles.As a result,the PKE distributions of the erosive RH ash were similar in both scenarios and resulted in similar shedding rates.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472118,51602156,52177072,and 11274174)the Fundamental Research Funds for the Central Universities,China(Grant Nos.30916011104 and 30916011208)
文摘CuO added Pb_(0.92)Sr_(0.06)Ba_(0.02)(Mg_(1/3)Nb_(2/3))_(0.25)(Ti_(0.53)Zr_(0.47))_(0.75)O_3 ceramics were studied to prepare high-quality multilayer piezoelectric actuators with pure Ag electrodes at 900℃. Cu O addition not only reduced the sintering temperature significantly from 1260℃ to 900℃ but also improved the ceramic density to 7.742 g/cm^3. The 0.7 wt.% Cu O added ceramic sintered at 900℃ shows the remnant polarization(P_r) of 40 μC/cm^2, 0.28% strain at 40 kV/cm, and the piezoelectric coefficient(d_(33)) of 630 pC/N. This ceramic shows a strong relaxor characteristic with a Curie temperature of 200℃. Furthermore, the 0.7 wt.% CuO added ceramic and pure Ag electrodes were co-fired at 900℃ to prepare a high-quality multilayer piezoelectric actuator with a d_(33) of over 450 pC/N per ceramic layer.
文摘The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave dielectric properties of Li2ZnTi3O8 ceramics with the addition of V2O5 were investigated. Based on our research, V2O5 doping effectively promoted the densification of Li2ZnTi3O8 ceramics at about 900°C, without affecting the main crystal phase of the ceramics. Li2ZnTi3O8 ceramics with 0.5 wt% V2O5 doping (sintered at 900°C) exhibited the best microwave dielectric properties (Qf =?22,400 GHz at about 6 GHz, εr = 25.5, and τf = -10.8 ppm/°C). The V2O5-doped Li2ZnTi3O8 ceramics were well cofired with Ag inner paste without cracks and diffusion, indicating its significant potential for LTCC applications.
文摘The global transition from fossil fuel-based energy sources to renewable energy sources will be most effective,for at least the near future,by utilizing local resources and existing infrastructure.In many areas of the eastern United States,forest residue is abundant and can be used in existing facilities to supplement coal in coal-fired power plants.Thus forest residue has potential as a renewable energy source that could be effectively utilized in the near future.This study uses GIS to estimate the potential quantity of forest residue available for use in coal-fired power plants in the eastern United States.Transportation costs limit the distance over which it is feasible to transport forest residue to the power plants and these costs may fluctuate depending on economic conditions.Thus,we consider three scenarios in our analysis assuming the maximum feasible transport distances to be 60,80,and 100 km.In the eastern U.S.,the total annual forest residue available to coal plants is approximately 29.4,40.2,and 48.2 million dry tons,respectively,for maximum transport distances of 60,80,and 100 km.Assuming an 80 km transport distance,forest residue has the potential to reduce coal consumption by 22.3 million tons per year.Under this scenario,greenhouse gas emissions would be reduced by almost 58.1 million tons per year,and NOx and SOx emissions would be reduced by 69.3 and 122.6 thousand tons respectively.This analysis suggests that by offsetting coal use,forest residue has the potential to substantially reduce power plant emissions.
