Nitrogen oxide(NO_(x))pollutants emitted from coal combustion are attracting growing public concern.While the traditional technologies of reducing NO_(x) were mainly focused on terminal treatment,and the research on s...Nitrogen oxide(NO_(x))pollutants emitted from coal combustion are attracting growing public concern.While the traditional technologies of reducing NO_(x) were mainly focused on terminal treatment,and the research on source treatment is limited.This paper proposes a new coal combustion strategy that significantly reduces NO_(x) emissions during coal combustion.This strategy has two important advantages in reducing NO_(x) emissions.First,by introducing iron-based catalyst at the source,which will catalyze the conversion of coke nitrogen to volatile nitrogen during the pyrolysis process,thereby greatly reducing the coke nitrogen content.The second is de-NO_(x) process by a redox reaction between NO_(x) and reducing agents(coke,HCN,NH_(3),etc.)that occurred during coke combustion.Compared to direct combustion of coal,coke prepared by adding iron-based catalyst has 46.1% reduction in NO_(x) emissions.To determine the effect of iron-based additives on de-NO_(x) performance,demineralized coal(de-coal)was prepared to eliminate the effect of iron-based minerals in coal ash.The effects of iron compounds,additive dosages,and combustion temperatures on de-NO_(x) efficiency are systematically studied.The results revealed that the NO_(x) emission of the coke generated by pyrolysis of de-coal loaded with 3%(mass)Fe_(2)O_(3) decreases to 27.3% at combustion temperature of 900℃.Two main reasons for lower NO_(x) emissions were deduced:(1)During the catalytic coal pyrolysis stage,the nitrogen content in the coke decreases with the release of volatile nitrogen.(2)Part of the NO_(x) emitted during the coke combustion was converted into N_(2) for the catalytic effect of the Fe-based catalysts.It is of great practical value and scientific significance to the comprehensive treatment and the clean utilization process of coal.展开更多
Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted li...Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.展开更多
A hydrotalcite(layered double hydroxide, LDH) inhibitor which is suitable for the whole process of coal spontaneous combustion and a LDH inhibitor containing rare earth lanthanum elements were prepared. The inhibition...A hydrotalcite(layered double hydroxide, LDH) inhibitor which is suitable for the whole process of coal spontaneous combustion and a LDH inhibitor containing rare earth lanthanum elements were prepared. The inhibition effect and mechanism were analyzed by scanning electron microscopy(SEM),X-ray diffraction(XRD), thermal performance analysis, in-situ diffuse reflectance infrared spectroscopy and temperature-programmed experiment. The results have shown that the inhibitor containing lanthanum can play a good inhibitory role in every stage of coal oxidation. During the slow oxidation of coal samples, the inhibitor containing lanthanum ions can slow down the oxidation process of coal and increase the initial temperature of coal spontaneous combustion. At the same time, because the hydroxyl groups in LDHs are connected with-COO-groups on the coal surface through hydrogen bonds, the stability of coal is improved. With the increase of temperature, LDHs can remove interlayer water molecules and reduce the surface temperature of coal. CO release rate of coal samples decreases significantly after adding inhibitor containing lanthanum element, and the maximum inhibition rate of the inhibitor is 58.1%.展开更多
To understand the characteristics of atmospheric brown carbon(BrC),daily PM2.5 samples in Xingtai,a small city in North China Plain(NCP),during the four seasons of 2018-2019,were collected and analyzed for optical pro...To understand the characteristics of atmospheric brown carbon(BrC),daily PM2.5 samples in Xingtai,a small city in North China Plain(NCP),during the four seasons of 2018-2019,were collected and analyzed for optical properties and chemical compositions.The light absorption at 365 nm(abs λ=365 nm)displayed a strong seasonal variation with the highest value in winter(29.0±14.3 M/m),which was 3.2∼5.4-fold of that in other seasons.A strong correlation of abs λ=365 nm with benzo(b)fluoranthene(BbF)was only observed in winter,indicating that coal combustion was the major source for BrC in the season due to the enhanced domestic heating.The mass absorbing efficiency of BrC also exhibited a similar seasonal pattern,and was found to correlate linearly with the aerosol pH,suggesting a positive effect of aerosol acidity on the optical properties and formation of BrC in the city.Positive matrix factorization(PMF)analysis further showed that on a yearly basis the major source for BrC was biomass burning,which accounted for 34% of the total BrC,followed by secondary formation(26.7%),coal combustion(21.3%)and fugitive dust(18%).However,the contribution from coal combustionwas remarkably enhanced in winter,accounting for∼40%of the total.Our work revealed that more efforts of“shifting coal to clean energy”are necessary in rural areas and small cities in NCP in order to further mitigate PM2.5 pollution in China.展开更多
To solve the fire accidents caused by coal combustion,this work prepared four hybrid hydrogel materials using bio-based polymers,flame retardants,and inorganic materials.Compared to pure water and 3.5 wt%MgCl_(2)solut...To solve the fire accidents caused by coal combustion,this work prepared four hybrid hydrogel materials using bio-based polymers,flame retardants,and inorganic materials.Compared to pure water and 3.5 wt%MgCl_(2)solution,the as-prepared hydrogel presents good fire prevention performance.In addition,it is found that CO and CO_(2)are not produced by coal when the pyrolysis temperature is lower than 200℃.During low-temperature pyrolysis,CO is more likely to be produced than CO_(2),indicating inadequate pyrolysis behavior.At the same time,the addition of fire-preventing hydrogel can not only decrease the maximum CO_(2)concentration before the critical temperature but also prolong the corresponding time.In addition,based on the cone calorimeter test,the inhibition effects of pure water,magnesium chloride solution,and four hybrid hydrogels on heat release behavior are evaluated.It is demonstrated that different dosages of different hydrogels affected the fire prevention effect.Phosphorous-modified cellulose/silica and carrageenan/DMMP/vermiculite composite hydrogels have the weakest fire prevention effect at 20 g,which is weaker than that of water.However,the fire prevention effect of carrageenan/DMMP/vermiculite composite hydrogels exceeded that of water at 40 and 60 g.Additionally,the fire prevention effect of the sodium alginate/sepiolite/ammonium polyphosphate composite hydrogel is most significant in common tests,attributed to the intumescent flame retardant system.展开更多
The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and ...The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and mechanism of soaked-dried coal's spontaneous combustion.Five samples of coal were dried to various degrees,and the weight loss features during thermal processing were examined.Based on this,the pore structure and chemical structure characteristics of the coal samples with the highest tendency to spontaneous combustion were quantitatively examined,and the mechanism by which soaking-drying afected the spontaneous combustion heating process of the remaining coal in goaf was investigated in turn.The results show that T1 decreases with the increase of drying time,T2–T6 shows a fuctuating change,and the ignition activation energy of 36-S-Coal is smaller than that of other coal samples.The pore type of 36-S-Coal changes from a oneend closed impermeable pore to an open pore,and the pore group area is large.During the 36 h drying process,the internal channels of the coal were dredged,and a large number of gravels and minerals were precipitated from the pores with the air fow.A large number of gravels were around the pores to form a surface structure that was easy to adsorb various gases.Furthermore,infrared spectroscopy was used to analyze the two coal samples.It was found that soaking and drying did not change the functional group types of coal samples,but the fatty chain degree of 36-S-Coal was reduced to 1.56.It shows that the aliphatic chain structure of coal is changed after 36 h of drying after 30 days of soaking,which leads to the continuous shedding of aliphatic chain branches of residual coal,and the skeleton of coal is looser,which makes the low-temperature oxidation reaction of 36-S-Coal easier.Based on the above results,the coal-oxygen composite mechanism of water-immerseddried coal is obtained,and it is considered that the key to the spontaneous combustion oxidation process of coal is to provide oxygen atoms and accelerate the formation of peroxides.展开更多
The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great...The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great importance for improving the efficient utilization of coal.The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation.Firstly,in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded.The influence of temperature,atmosphere,heating rate and catalyst on formation of NOx precursor and nitrogen migration path at the molecular level were summarized;Secondly,during the process of combustion:the influence of temperature,ambient oxygen concentration,physical structure of coal char,catalyst on heterogeneous oxidation of char(N)were summarized;The effects of char surface properties,catalyst and ambient atmosphere on heterogeneous reduction of NOx were also concluded.Based on the quantum chemical calculation,the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NOx were described in detail.Current studies focus more on the generation of HCN and NH3,but in order to reduce the pollution of NOx from the source,it is necessary to further improve the process conditions and the optimal formula of producing more N2 during pyrolysis,as well as clarify the path of the generation of N2.Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.展开更多
The change of bubbles and the position of the tuyere in an oxygen coal combustion melting and separating furnace affect the flow and splash behavior of the molten pool.To analyze this problem further,a three-dimension...The change of bubbles and the position of the tuyere in an oxygen coal combustion melting and separating furnace affect the flow and splash behavior of the molten pool.To analyze this problem further,a three-dimensional numerical simulation method was used to explore the behavior and change of the flow field inside the molten pool during double-row tuyere injection.In addition,the arrangement of the tuyere was changed for a more detailed understanding of the internal phase distribution and splashing in a molten pool.The results indicated that under three-dimensional numerical simulation conditions,bubbles rise after leaving the tuyere and break on the surface of the molten pool,which results in certain fluctuations in the nearby melt.During the injection process of the tuyere,the meteorological accumulation in the middle part of the molten pool formed part of the foam slag because of the influence of surface tension.When the layout of the upper and lower exhaust tuyeres was changed from staggered to symmetrical,or when the spacing of the upper and lower exhaust tuyeres changed,it had an effect on the phase distribution and splash behavior.展开更多
In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diff...In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.展开更多
Supercritical carbon dioxide(S-CO_(2))Brayton power cycle power generation technology,has attracted more and more scholars'attention in recent years because of its advantages of high efficiency and flexibility.Com...Supercritical carbon dioxide(S-CO_(2))Brayton power cycle power generation technology,has attracted more and more scholars'attention in recent years because of its advantages of high efficiency and flexibility.Compared with conventional steam boilers,S-CO_(2) has different heat transfer characteristics,it is easy to cause the temperature of the cooling wall of the boiler to rise,which leads to higher combustion gas temperature in the furnace,higher NOX generation concentration.The adoption of flue gas recirculation has a significance impact on the combustion process of pulverized coal in the boiler,and it is the most effective ways to reduce the emission of NOX and the combustion temperature in the boiler.This paper takes 1000MW S-CO_(2) T-type coal-fired boiler as the research target to investigate the combustion and NOX generation characteristics of S-CO_(2) coal-fired boilers under flue gas recirculation condition,the influence of recirculated flue gas distribution along the furnace height on the characteristics of NOX formation and the combustion of pulverized coal.The results show that the recirculated flue gas distribution has the great impact on the concentration of NOX at the boiler outlet.When the bottom recirculation flue gas rate is gradually increased,the average temperature of the lower boiler decreases and the average temperature of the upper boiler increases slightly;The concentration of NOx at the furnace outlet increases.展开更多
To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-...To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after inerting.The results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the worst.At 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the same.However,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature increase.When the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) injection.The flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of oxygen.These findings are essential for using inert flame retardant technology in the goaf.展开更多
Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research rela...Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research related to the initiation, development, and evolution of coalfield fires is reviewed. The existing detection and control techniques of coalfield fires are also reviewed. Traditional firefighting is associated with waste of resources, potential risks of recrudescence, potential safety hazards, extensive and expensive engineering works, and power shortages. Recently,coalfield fires have been recognized as having significant potential for energy conservation and heat energy recovery. Thermoelectric power generation is regarded as a suitable technology for the utilization of heat from coalfield fires. The extraction of heat from coalfield fires can also control coalfield fires and prevent reignition leading to combustion. Technologies for absorbing heat from burning coal and overlying rocks are also analyzed. In addition, the control mode of "three-region linkage" is proposed to improve firefighting efficiency. Integrating heat energy recovery with firefighting is an innovative method to control coalfield fires.展开更多
On-site measurements of volatile organic compounds(VOCs)in different streams of flue gas were carried out on a real coal-fired power plant using sampling bags and SUMMA canisters to collect gas samples,filters to coll...On-site measurements of volatile organic compounds(VOCs)in different streams of flue gas were carried out on a real coal-fired power plant using sampling bags and SUMMA canisters to collect gas samples,filters to collect particle samples.Gas chromatography-flame ionization detector/mass spectrometry and gas chromatography-mass spectrometry was the offline analysis method.We found that the total mass concentration of the tested 102 VOC species at the outlet of wet flue gas desulfuration device was(13456±47)μg·m^(-3),which contained aliphatic hydrocarbons(57.9%),aromatic hydrocarbons(26.8%),halogen-containing species(14.5%),and a small amount of oxygen-containing and nitrogencontaining species.The most abundant species were 1-hexene,n-hexane and 2-methylpentane.The top ten species in terms of mass fraction(with a total mass fraction of 75.3%)were mainly hydrocarbons with a carbon number of 6 or higher and halogenated hydrocarbons with a lower carbon number.The mass concentration of VOC species in the particle phase was significantly lower than that in the gas phase.The change of VOC mass concentrations along the air pollution control devices indicates that conventional pollutant control equipment had a limited effect on VOC reduction.Ozone formation potential calculations showed that aromatic hydrocarbons contributed the highest ozone formation(46.4%)due to their relatively high mass concentrations and MIR(maximum increment reactivity)values.展开更多
The coal combustion in cast-iron stoves leads to health hazards and air pollution.In this study the CO,SO2,NOx,PM and VOC emission concentrations were measured whilst combusting four fuel particle sizes(15,20,30,and 4...The coal combustion in cast-iron stoves leads to health hazards and air pollution.In this study the CO,SO2,NOx,PM and VOC emission concentrations were measured whilst combusting four fuel particle sizes(15,20,30,and 40 mm)as well as a composite of the sizes(all pre-devolatilized at a temperature of 550C)in a cast-iron stove.The results were compared to their raw coal analogues to evaluate the emission performance of each fuel type.Emission factors for NOx and SO2 were found to depend on the fuel nitrogen and sulphur contents in the coal and the combustion conditions used during pyrolysis.The PM,SO2 and VOC emissions show a strong dependence on the ash percentage and volatile matter yields,which both increased with increasing particle size.In addition,the PM,SO2 and VOC missions were found to only depend on particle size on a mechanistic level.The VOCs and PM emission factors are inversely correlated with particle size.The results from this study offer insight into the combustion environment in the Falkirk Union No 7 cast-iron stove as well as how this environment applies to low smoke fuels.The work contributes to the emission and performance inventories from South African domestic coal combustion in this stove used in informal settlements.展开更多
Coal spontaneous combustion(CSC)is a disaster associated with coal mining that leads to loss of coal resources and envi-ronmental and human health issues.To investigate kinetic characteristics for oxidation of coal,th...Coal spontaneous combustion(CSC)is a disaster associated with coal mining that leads to loss of coal resources and envi-ronmental and human health issues.To investigate kinetic characteristics for oxidation of coal,three coal samples were collected from different coal mining areas in the Southern Junggar coalfield.Subsequently,the collected coal samples were ground into different particle sizes and tested using microscopic and macroscopic methods,including thermal gravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffraction,and temperature-programmed oxidation.The results obtained are as follows:the sharpest absorption peak(002)indicates that graphitization is high.Furthermore,the results show that the SKS coal sample is prone to spontaneous combustion;the greater the aromatic hydrocarbon content is,the more difficult it is for CSC to occur,while the opposite is true for oxygen-containing functional groups.The SKS data confirmed this conclusion;the rate for generation of CO and CO_(2)controlled the possibility of SKS oxidation at 110℃and provided an indication of the temperature.During the dehydration stage,the WD sample had the lowest activation energy,indicating that it was most susceptible to spontaneous combustion.During the combustion stage,the lowest activation energy was found for the SKS sample with particle sizes<0.075 mm,indicating that particle size was one of the factors affecting spontane-ous combustion.The activation energy for dehydration was significantly lower than that for combustion,which showed that the coal oxygen reaction was more likely to occur in the dehydration stage.Based on DSC curves,the SKS sample had the largest exothermicity,indicating that it would ignite more readily.展开更多
In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepar...In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepared basing on the foaming characteristic through physical and mechanical system. We studied the effects of the different types of foaming agents, the mass ratio of cement to fly ash, and the mass ratio of solid to water and content of cellulose on the performance of solidified foam. The results show that when adding the composite protein, surfactant and cellulose foaming agents. The cement-fly ash ratio of 0.75:1, the water solid ratio as large as 2:1, and the solidified foam with high properties and density of only 516 kg/m 3 and compressive strength of up to 12.68 MPa were prepared. But the initial setting time, identity and compressive strength may be changed by varying the water solid ratio and/or the additives. We theoretically analyzed the influence mechanism of foam density, compressive strength and water solid ratio. The solidified foam is especially suitable for sealing surface leakage channels and filling the goaf with a wide application prospects.展开更多
Uncontrolled coal fires are natural disasters that may cause mineral loss and environmental damage.The traditional loop source transient electromagnetic method can effectively detect the low-resistivity region of coal...Uncontrolled coal fires are natural disasters that may cause mineral loss and environmental damage.The traditional loop source transient electromagnetic method can effectively detect the low-resistivity region of coal fires,but its detection efficiency is not so good for high-resistivity regions.In view of this limitation,a technique based on electrical source transient electromagnetics is proposed in this paper to detect high-resistivity regions in the spontaneous combustion process of coal.Considering the complex geometry of the coal fire area,an unstructured tetrahedral grid is used in this study to realize the spatial discretization of the model,and solve the electromagnetic field based on a vector finite element algorithm.Numerical analysis is used to investigate methods for detecting coal fires and the characteristics of effective anomalies are further examined to provide guidance for practical detection.展开更多
For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining t...For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining the effect of the fuel particle size on the performance of coal,typically sourced in low-income households in townships in South Africa,and to subsequently compare the performance with a feed char of a common cast iron stove.Four fuel particle sizes of 15,20,30,and 40 mm,as well as a composite of the sizes were tested at 550C,against their untreated coal analogues to evaluate the thermal performance of each fuel.The thermal performance assessment metrics are ignition time,water boiling time,heat transfer and combustion efficiencies,while CO and CO_(2)emissions were measured for the calculations of CO/CO_(2)ratios.Ignition times were found to decrease from coals to chars and to decrease with increasing particle size.The effects of fuel type on the water boiling time were only observed in the later stages of the burn cycle,with the char boiling a 2 L batch of water in an average 24 min,while the coals reported an average boiling time of 20 min.Heat transfer efficiencies showed no significant variation with fuel type or particle size,with the average efficiency for the coals and that of the chars being around 66%.The fuels’performance was better gauged by the combustion efficiency,which was found to improve marginally from the coal fuels to the chars,and to increase with increasing particle size.Results from this testwork could contribute to the performance inventories from the combustion of domestic coal mined in South Africa in a typical cast iron stove which is used in informal settlements.展开更多
The influence of fly ash(FA)applied alone and/or with sewage sludge(SS)on wheat(Triticum vulgare)grain yield,biomass production and soil properties was studied in a field experiment.The results showed that both FA and...The influence of fly ash(FA)applied alone and/or with sewage sludge(SS)on wheat(Triticum vulgare)grain yield,biomass production and soil properties was studied in a field experiment.The results showed that both FA and SS significantly increased grain yield and plant biomass.FA applied alone increased significantly soil pH and EC while FA applied together with SS did not significantly affect them compared to mono FA treatment.Soil pH and EC values increased with time in FA and FA-SS treatments.SS increased soil organic matter and total N content and SS applied together with FA increased also available soil B.From the plant nutrients tested only tissue N concentration was increased significantly in all treatments compared to control.Copper,Zn,Mn,Ni,and Pb at both available and total concentrations are significantly affected.展开更多
基金supported by National Natural Science Foundation of China(21878210)Shanxi Provincial Science and Technology Achievement Transformation Guidance Special Program of China(202104021301052)Shanxi Province Patent Transformation Special Program Project(202202054).
文摘Nitrogen oxide(NO_(x))pollutants emitted from coal combustion are attracting growing public concern.While the traditional technologies of reducing NO_(x) were mainly focused on terminal treatment,and the research on source treatment is limited.This paper proposes a new coal combustion strategy that significantly reduces NO_(x) emissions during coal combustion.This strategy has two important advantages in reducing NO_(x) emissions.First,by introducing iron-based catalyst at the source,which will catalyze the conversion of coke nitrogen to volatile nitrogen during the pyrolysis process,thereby greatly reducing the coke nitrogen content.The second is de-NO_(x) process by a redox reaction between NO_(x) and reducing agents(coke,HCN,NH_(3),etc.)that occurred during coke combustion.Compared to direct combustion of coal,coke prepared by adding iron-based catalyst has 46.1% reduction in NO_(x) emissions.To determine the effect of iron-based additives on de-NO_(x) performance,demineralized coal(de-coal)was prepared to eliminate the effect of iron-based minerals in coal ash.The effects of iron compounds,additive dosages,and combustion temperatures on de-NO_(x) efficiency are systematically studied.The results revealed that the NO_(x) emission of the coke generated by pyrolysis of de-coal loaded with 3%(mass)Fe_(2)O_(3) decreases to 27.3% at combustion temperature of 900℃.Two main reasons for lower NO_(x) emissions were deduced:(1)During the catalytic coal pyrolysis stage,the nitrogen content in the coke decreases with the release of volatile nitrogen.(2)Part of the NO_(x) emitted during the coke combustion was converted into N_(2) for the catalytic effect of the Fe-based catalysts.It is of great practical value and scientific significance to the comprehensive treatment and the clean utilization process of coal.
文摘Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.
基金Funded by National Natural Science Foundation of China (No.52074218)。
文摘A hydrotalcite(layered double hydroxide, LDH) inhibitor which is suitable for the whole process of coal spontaneous combustion and a LDH inhibitor containing rare earth lanthanum elements were prepared. The inhibition effect and mechanism were analyzed by scanning electron microscopy(SEM),X-ray diffraction(XRD), thermal performance analysis, in-situ diffuse reflectance infrared spectroscopy and temperature-programmed experiment. The results have shown that the inhibitor containing lanthanum can play a good inhibitory role in every stage of coal oxidation. During the slow oxidation of coal samples, the inhibitor containing lanthanum ions can slow down the oxidation process of coal and increase the initial temperature of coal spontaneous combustion. At the same time, because the hydroxyl groups in LDHs are connected with-COO-groups on the coal surface through hydrogen bonds, the stability of coal is improved. With the increase of temperature, LDHs can remove interlayer water molecules and reduce the surface temperature of coal. CO release rate of coal samples decreases significantly after adding inhibitor containing lanthanum element, and the maximum inhibition rate of the inhibitor is 58.1%.
基金financially supported by the National Natural Science Foundation of China (No. 41773117, 42007202)the National Key R&D Plan, Ministry of Science and Technology of China (Mechanism and chemical process characterization of atmospheric particulate matter multi-isotope fractionation) (No. 2017YFC0212703)+1 种基金the Shanghai Science and Technology Innovation Action Plan (No. 20dz1204011)the program of Institute of Eco-Chongming and ECNU Happiness Flower
文摘To understand the characteristics of atmospheric brown carbon(BrC),daily PM2.5 samples in Xingtai,a small city in North China Plain(NCP),during the four seasons of 2018-2019,were collected and analyzed for optical properties and chemical compositions.The light absorption at 365 nm(abs λ=365 nm)displayed a strong seasonal variation with the highest value in winter(29.0±14.3 M/m),which was 3.2∼5.4-fold of that in other seasons.A strong correlation of abs λ=365 nm with benzo(b)fluoranthene(BbF)was only observed in winter,indicating that coal combustion was the major source for BrC in the season due to the enhanced domestic heating.The mass absorbing efficiency of BrC also exhibited a similar seasonal pattern,and was found to correlate linearly with the aerosol pH,suggesting a positive effect of aerosol acidity on the optical properties and formation of BrC in the city.Positive matrix factorization(PMF)analysis further showed that on a yearly basis the major source for BrC was biomass burning,which accounted for 34% of the total BrC,followed by secondary formation(26.7%),coal combustion(21.3%)and fugitive dust(18%).However,the contribution from coal combustionwas remarkably enhanced in winter,accounting for∼40%of the total.Our work revealed that more efforts of“shifting coal to clean energy”are necessary in rural areas and small cities in NCP in order to further mitigate PM2.5 pollution in China.
基金the National Key Research and Development Program of China(Grant No.2017YFC0805900)the Fundamental Research Funds for the Central Universities(Grant No.WK2320000047)the USTC Research Funds of the Double First-Class Initiative(Grant No.YD2320002004).
文摘To solve the fire accidents caused by coal combustion,this work prepared four hybrid hydrogel materials using bio-based polymers,flame retardants,and inorganic materials.Compared to pure water and 3.5 wt%MgCl_(2)solution,the as-prepared hydrogel presents good fire prevention performance.In addition,it is found that CO and CO_(2)are not produced by coal when the pyrolysis temperature is lower than 200℃.During low-temperature pyrolysis,CO is more likely to be produced than CO_(2),indicating inadequate pyrolysis behavior.At the same time,the addition of fire-preventing hydrogel can not only decrease the maximum CO_(2)concentration before the critical temperature but also prolong the corresponding time.In addition,based on the cone calorimeter test,the inhibition effects of pure water,magnesium chloride solution,and four hybrid hydrogels on heat release behavior are evaluated.It is demonstrated that different dosages of different hydrogels affected the fire prevention effect.Phosphorous-modified cellulose/silica and carrageenan/DMMP/vermiculite composite hydrogels have the weakest fire prevention effect at 20 g,which is weaker than that of water.However,the fire prevention effect of carrageenan/DMMP/vermiculite composite hydrogels exceeded that of water at 40 and 60 g.Additionally,the fire prevention effect of the sodium alginate/sepiolite/ammonium polyphosphate composite hydrogel is most significant in common tests,attributed to the intumescent flame retardant system.
基金supported by the fnancial support of the General Projects of National Natural Science Foundation of China(52074156).
文摘The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and mechanism of soaked-dried coal's spontaneous combustion.Five samples of coal were dried to various degrees,and the weight loss features during thermal processing were examined.Based on this,the pore structure and chemical structure characteristics of the coal samples with the highest tendency to spontaneous combustion were quantitatively examined,and the mechanism by which soaking-drying afected the spontaneous combustion heating process of the remaining coal in goaf was investigated in turn.The results show that T1 decreases with the increase of drying time,T2–T6 shows a fuctuating change,and the ignition activation energy of 36-S-Coal is smaller than that of other coal samples.The pore type of 36-S-Coal changes from a oneend closed impermeable pore to an open pore,and the pore group area is large.During the 36 h drying process,the internal channels of the coal were dredged,and a large number of gravels and minerals were precipitated from the pores with the air fow.A large number of gravels were around the pores to form a surface structure that was easy to adsorb various gases.Furthermore,infrared spectroscopy was used to analyze the two coal samples.It was found that soaking and drying did not change the functional group types of coal samples,but the fatty chain degree of 36-S-Coal was reduced to 1.56.It shows that the aliphatic chain structure of coal is changed after 36 h of drying after 30 days of soaking,which leads to the continuous shedding of aliphatic chain branches of residual coal,and the skeleton of coal is looser,which makes the low-temperature oxidation reaction of 36-S-Coal easier.Based on the above results,the coal-oxygen composite mechanism of water-immerseddried coal is obtained,and it is considered that the key to the spontaneous combustion oxidation process of coal is to provide oxygen atoms and accelerate the formation of peroxides.
基金supported by National Natural Science Foundation of China(21878210)Shanxi “1331”Civil Clean Fuel Engineering Research Center,Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2019L0313)+1 种基金Patent Promotion and implementation in Shanxi Province(20200719)sponsored by Taiyuan Green Coke Energy Co.,Ltd.(China)。
文摘The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great importance for improving the efficient utilization of coal.The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation.Firstly,in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded.The influence of temperature,atmosphere,heating rate and catalyst on formation of NOx precursor and nitrogen migration path at the molecular level were summarized;Secondly,during the process of combustion:the influence of temperature,ambient oxygen concentration,physical structure of coal char,catalyst on heterogeneous oxidation of char(N)were summarized;The effects of char surface properties,catalyst and ambient atmosphere on heterogeneous reduction of NOx were also concluded.Based on the quantum chemical calculation,the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NOx were described in detail.Current studies focus more on the generation of HCN and NH3,but in order to reduce the pollution of NOx from the source,it is necessary to further improve the process conditions and the optimal formula of producing more N2 during pyrolysis,as well as clarify the path of the generation of N2.Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.
基金supported by the National Key R&D Program of China(2017YFB0603800 and 2017YFB0603802).
文摘The change of bubbles and the position of the tuyere in an oxygen coal combustion melting and separating furnace affect the flow and splash behavior of the molten pool.To analyze this problem further,a three-dimensional numerical simulation method was used to explore the behavior and change of the flow field inside the molten pool during double-row tuyere injection.In addition,the arrangement of the tuyere was changed for a more detailed understanding of the internal phase distribution and splashing in a molten pool.The results indicated that under three-dimensional numerical simulation conditions,bubbles rise after leaving the tuyere and break on the surface of the molten pool,which results in certain fluctuations in the nearby melt.During the injection process of the tuyere,the meteorological accumulation in the middle part of the molten pool formed part of the foam slag because of the influence of surface tension.When the layout of the upper and lower exhaust tuyeres was changed from staggered to symmetrical,or when the spacing of the upper and lower exhaust tuyeres changed,it had an effect on the phase distribution and splash behavior.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51776161)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2018JQ5010)the Fundamental Research Funds for the Central Universities,and the Key Laboratory of Renewable Energy Electric-Technology of Hunan Province(Changsha University of Science&Technology,Grant No.2017ZNDL003).
文摘In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.
基金This paper is supported by the National Key R&D Program of China(2017YFB0601805).
文摘Supercritical carbon dioxide(S-CO_(2))Brayton power cycle power generation technology,has attracted more and more scholars'attention in recent years because of its advantages of high efficiency and flexibility.Compared with conventional steam boilers,S-CO_(2) has different heat transfer characteristics,it is easy to cause the temperature of the cooling wall of the boiler to rise,which leads to higher combustion gas temperature in the furnace,higher NOX generation concentration.The adoption of flue gas recirculation has a significance impact on the combustion process of pulverized coal in the boiler,and it is the most effective ways to reduce the emission of NOX and the combustion temperature in the boiler.This paper takes 1000MW S-CO_(2) T-type coal-fired boiler as the research target to investigate the combustion and NOX generation characteristics of S-CO_(2) coal-fired boilers under flue gas recirculation condition,the influence of recirculated flue gas distribution along the furnace height on the characteristics of NOX formation and the combustion of pulverized coal.The results show that the recirculated flue gas distribution has the great impact on the concentration of NOX at the boiler outlet.When the bottom recirculation flue gas rate is gradually increased,the average temperature of the lower boiler decreases and the average temperature of the upper boiler increases slightly;The concentration of NOx at the furnace outlet increases.
基金support was received from the National Natural Science Foundation of China(52074156).
文摘To test the effectiveness of N_(2) and CO_(2) in preventing coal from spontaneously combusting,researchers used an adiabatic oxidation apparatus to conduct an experiment with different temperature starting points.Non-adsorbed helium(He)was used as a reference gas,and coal and oxygen concentration temperature variations were analyzed after inerting.The results showed that He had the best cooling effect,N_(2) was second,and CO_(2) was the worst.At 70℃and 110℃,the impact of different gases on reducing oxygen concentration and the cooling effect was the same.However,at the starting temperature of 150℃,CO_(2) was less effective in lowering oxygen concentration at the later stage than He and N_(2).N_(2) and CO_(2) can prolong the flame retardation time of inert gas and reduce oxygen displacement with an initial temperature increase.When the starting temperature is the same,N_(2) injection cools coal samples and replaces oxygen more effectively than CO_(2) injection.The flame retardancy of inert gas is the combined result of the cooling effect of inert gas and the replacement of oxygen.These findings are essential for using inert flame retardant technology in the goaf.
基金financially supported by the Fundamental Research Funds for the Central Universities of China(Nos.2017CXNL02 and 2652018098)the National Key Research and Development Program of China(No.2018YFC0808100)+1 种基金the 111 Project(No.B17041)the Natural Science Foundation of Jiangsu Province(No.BK20170277)
文摘Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research related to the initiation, development, and evolution of coalfield fires is reviewed. The existing detection and control techniques of coalfield fires are also reviewed. Traditional firefighting is associated with waste of resources, potential risks of recrudescence, potential safety hazards, extensive and expensive engineering works, and power shortages. Recently,coalfield fires have been recognized as having significant potential for energy conservation and heat energy recovery. Thermoelectric power generation is regarded as a suitable technology for the utilization of heat from coalfield fires. The extraction of heat from coalfield fires can also control coalfield fires and prevent reignition leading to combustion. Technologies for absorbing heat from burning coal and overlying rocks are also analyzed. In addition, the control mode of "three-region linkage" is proposed to improve firefighting efficiency. Integrating heat energy recovery with firefighting is an innovative method to control coalfield fires.
基金funded by the National Natural Science Foundation of China(52006079)the Natural Science Foundation of Hubei Province(2020CFB247)the National Key Research and Development Program of China(2018YFB0605201)。
文摘On-site measurements of volatile organic compounds(VOCs)in different streams of flue gas were carried out on a real coal-fired power plant using sampling bags and SUMMA canisters to collect gas samples,filters to collect particle samples.Gas chromatography-flame ionization detector/mass spectrometry and gas chromatography-mass spectrometry was the offline analysis method.We found that the total mass concentration of the tested 102 VOC species at the outlet of wet flue gas desulfuration device was(13456±47)μg·m^(-3),which contained aliphatic hydrocarbons(57.9%),aromatic hydrocarbons(26.8%),halogen-containing species(14.5%),and a small amount of oxygen-containing and nitrogencontaining species.The most abundant species were 1-hexene,n-hexane and 2-methylpentane.The top ten species in terms of mass fraction(with a total mass fraction of 75.3%)were mainly hydrocarbons with a carbon number of 6 or higher and halogenated hydrocarbons with a lower carbon number.The mass concentration of VOC species in the particle phase was significantly lower than that in the gas phase.The change of VOC mass concentrations along the air pollution control devices indicates that conventional pollutant control equipment had a limited effect on VOC reduction.Ozone formation potential calculations showed that aromatic hydrocarbons contributed the highest ozone formation(46.4%)due to their relatively high mass concentrations and MIR(maximum increment reactivity)values.
基金the DS&T and NRF of SA(Coal Research Chair Grant No.86880)for funding this project.
文摘The coal combustion in cast-iron stoves leads to health hazards and air pollution.In this study the CO,SO2,NOx,PM and VOC emission concentrations were measured whilst combusting four fuel particle sizes(15,20,30,and 40 mm)as well as a composite of the sizes(all pre-devolatilized at a temperature of 550C)in a cast-iron stove.The results were compared to their raw coal analogues to evaluate the emission performance of each fuel type.Emission factors for NOx and SO2 were found to depend on the fuel nitrogen and sulphur contents in the coal and the combustion conditions used during pyrolysis.The PM,SO2 and VOC emissions show a strong dependence on the ash percentage and volatile matter yields,which both increased with increasing particle size.In addition,the PM,SO2 and VOC missions were found to only depend on particle size on a mechanistic level.The VOCs and PM emission factors are inversely correlated with particle size.The results from this study offer insight into the combustion environment in the Falkirk Union No 7 cast-iron stove as well as how this environment applies to low smoke fuels.The work contributes to the emission and performance inventories from South African domestic coal combustion in this stove used in informal settlements.
基金supported by the National Natural Science Foundation of China(51974275)the Tianshan Innovation Team of Xinjiang Province(2021D14018)the Natural Science Program of Xinjiang Province Department of Education(XJEDU20181007).
文摘Coal spontaneous combustion(CSC)is a disaster associated with coal mining that leads to loss of coal resources and envi-ronmental and human health issues.To investigate kinetic characteristics for oxidation of coal,three coal samples were collected from different coal mining areas in the Southern Junggar coalfield.Subsequently,the collected coal samples were ground into different particle sizes and tested using microscopic and macroscopic methods,including thermal gravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffraction,and temperature-programmed oxidation.The results obtained are as follows:the sharpest absorption peak(002)indicates that graphitization is high.Furthermore,the results show that the SKS coal sample is prone to spontaneous combustion;the greater the aromatic hydrocarbon content is,the more difficult it is for CSC to occur,while the opposite is true for oxygen-containing functional groups.The SKS data confirmed this conclusion;the rate for generation of CO and CO_(2)controlled the possibility of SKS oxidation at 110℃and provided an indication of the temperature.During the dehydration stage,the WD sample had the lowest activation energy,indicating that it was most susceptible to spontaneous combustion.During the combustion stage,the lowest activation energy was found for the SKS sample with particle sizes<0.075 mm,indicating that particle size was one of the factors affecting spontane-ous combustion.The activation energy for dehydration was significantly lower than that for combustion,which showed that the coal oxygen reaction was more likely to occur in the dehydration stage.Based on DSC curves,the SKS sample had the largest exothermicity,indicating that it would ignite more readily.
基金provided by the National Natural Science Foundation of China (No. 50904066)the Program for New Century Excellent Talents in University (No. NCET-09-0729)the National Excellent Doctoral Dissertation Special Fund (No. 2007B53)
文摘In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepared basing on the foaming characteristic through physical and mechanical system. We studied the effects of the different types of foaming agents, the mass ratio of cement to fly ash, and the mass ratio of solid to water and content of cellulose on the performance of solidified foam. The results show that when adding the composite protein, surfactant and cellulose foaming agents. The cement-fly ash ratio of 0.75:1, the water solid ratio as large as 2:1, and the solidified foam with high properties and density of only 516 kg/m 3 and compressive strength of up to 12.68 MPa were prepared. But the initial setting time, identity and compressive strength may be changed by varying the water solid ratio and/or the additives. We theoretically analyzed the influence mechanism of foam density, compressive strength and water solid ratio. The solidified foam is especially suitable for sealing surface leakage channels and filling the goaf with a wide application prospects.
基金Supported by National Key R&D Program of China(No.2018YFC0807900).
文摘Uncontrolled coal fires are natural disasters that may cause mineral loss and environmental damage.The traditional loop source transient electromagnetic method can effectively detect the low-resistivity region of coal fires,but its detection efficiency is not so good for high-resistivity regions.In view of this limitation,a technique based on electrical source transient electromagnetics is proposed in this paper to detect high-resistivity regions in the spontaneous combustion process of coal.Considering the complex geometry of the coal fire area,an unstructured tetrahedral grid is used in this study to realize the spatial discretization of the model,and solve the electromagnetic field based on a vector finite element algorithm.Numerical analysis is used to investigate methods for detecting coal fires and the characteristics of effective anomalies are further examined to provide guidance for practical detection.
基金acknowledge the DS&T and NRF(Coal Research Chair Grant Nos.86880)of SA for financing this investigation.
文摘For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining the effect of the fuel particle size on the performance of coal,typically sourced in low-income households in townships in South Africa,and to subsequently compare the performance with a feed char of a common cast iron stove.Four fuel particle sizes of 15,20,30,and 40 mm,as well as a composite of the sizes were tested at 550C,against their untreated coal analogues to evaluate the thermal performance of each fuel.The thermal performance assessment metrics are ignition time,water boiling time,heat transfer and combustion efficiencies,while CO and CO_(2)emissions were measured for the calculations of CO/CO_(2)ratios.Ignition times were found to decrease from coals to chars and to decrease with increasing particle size.The effects of fuel type on the water boiling time were only observed in the later stages of the burn cycle,with the char boiling a 2 L batch of water in an average 24 min,while the coals reported an average boiling time of 20 min.Heat transfer efficiencies showed no significant variation with fuel type or particle size,with the average efficiency for the coals and that of the chars being around 66%.The fuels’performance was better gauged by the combustion efficiency,which was found to improve marginally from the coal fuels to the chars,and to increase with increasing particle size.Results from this testwork could contribute to the performance inventories from the combustion of domestic coal mined in South Africa in a typical cast iron stove which is used in informal settlements.
文摘The influence of fly ash(FA)applied alone and/or with sewage sludge(SS)on wheat(Triticum vulgare)grain yield,biomass production and soil properties was studied in a field experiment.The results showed that both FA and SS significantly increased grain yield and plant biomass.FA applied alone increased significantly soil pH and EC while FA applied together with SS did not significantly affect them compared to mono FA treatment.Soil pH and EC values increased with time in FA and FA-SS treatments.SS increased soil organic matter and total N content and SS applied together with FA increased also available soil B.From the plant nutrients tested only tissue N concentration was increased significantly in all treatments compared to control.Copper,Zn,Mn,Ni,and Pb at both available and total concentrations are significantly affected.
