The self-cementing mechanism at early ages of circulating fluidized bed combustion （CFBC） coal ashes was studied by X-ray diffraction （XRD）, infrared （IR） spectroscopy and chemical method. The results indicate t...The self-cementing mechanism at early ages of circulating fluidized bed combustion （CFBC） coal ashes was studied by X-ray diffraction （XRD）, infrared （IR） spectroscopy and chemical method. The results indicate that the amorphous phase is predominant in CFBC coal ashes. The polymerization degree of [SiO4] and [AlO6] of CFBC desulphurization coal ashes is lower than that of those without desulphurization. The contents of the components with fast hydration rate of CFBC desulphurization coal ashes are significantly greater than those of the ashes without desulphurization. This work confirms that the amorphous minerals with high chemical activity are the main causes of the self-cementing property of CFBC desulphurization coal ashes at early ages.展开更多
The Yanzhou mine district, located in southwestern Shandong Province, is about 1300 km2 with more than 8×109tons of proved coal reserves and there are 10 big power plants in this area. A large amount of coal ashe...The Yanzhou mine district, located in southwestern Shandong Province, is about 1300 km2 with more than 8×109tons of proved coal reserves and there are 10 big power plants in this area. A large amount of coal ashes, which are regarded as waste materials, have been stockpiled in the area and have influenced the environment of the mine district. In this paper, analysis of fly ash samples from three power plants is carried out, the enrichment and concentration of trace elements, Pb, Zn, Cu and As, in coal ashes are analyzed, and petrological and mineralogical characteristics and chemical compositions of coal ashes are studied. The aim of this work is to provide basic scientific data for utilization of ashes and reduction of environmental pollutions.展开更多
The use of the thermal power plant ashes including fly ash(FA) and bottom ash(BA) for producing unfired building bricks(UBB) using sodium hydroxide(NaOH) solution as an alkaline activator was investigated. A low appli...The use of the thermal power plant ashes including fly ash(FA) and bottom ash(BA) for producing unfired building bricks(UBB) using sodium hydroxide(NaOH) solution as an alkaline activator was investigated. A low applied forming pressure of 0.5 MPa and various NaOH concentrations of 5, 8, 10, and 12 M were used for the preparation of brick samples with different solution-to-binder(S/B) ratios of 0.35 and 0.40. The bricks were subjected to various test programs with reflecting the effect of both NaOH concentrations and S/B ratios on the brick’s properties. The compressive strength, unit weight, ultrasonic pulse velocity, and thermal conductivity of bricks increased with increasing NaOH concentration, whereas the contrary trend was found with increasing S/B ratio. Also, the water absorption of bricks was observed to reduce with increasing NaOH concentration and decreasing S/B ratio. As the results, the combined utilization of both low forming pressure and coal power plant ashes can produce the UBBs with low unit weight, low heat conductivity, and acceptable strength and water absorption rate as stipulated by TCVN 6477-2016. Furthermore, the outcomes of chemical analysis and microstructure observation also demonstrate that a high concentration of the Na OH promoted the geopolymerization process. Notably, the use of NaOH solution of either 10 M or above is recommended for the production of UBBs, which are classified as grade M5.0 or higher.展开更多
The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied d...The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied depending on the source biomass material. An increase in the concrete shuttering contents in the biomass materials led to higher alkalinity,and higher Ca and Mg levels in biomass ashes,which made them particularly good at ameliorating effects on soil acidity. However,heavy metal contents,such as Cr,Cu,and Zn in the ashes,were relatively high. The incorporation of all ashes increased soil p H,exchangeable base cations,and available phosphorus,but decreased soil exchangeable acidity. The application of the ashes from biomass materials with a high concrete shuttering content increased the soil available heavy metal contents. Therefore,the biomass ashes from wood and crop residues with low concrete contents were the better acid soil amendments.展开更多
It was recognized that a majority of the whole human genome is transcribed but only about 2% of genome actually encode all the proteins that were supposed, according to the central dogma, executing most of the biologi...It was recognized that a majority of the whole human genome is transcribed but only about 2% of genome actually encode all the proteins that were supposed, according to the central dogma, executing most of the biological functions of an organism. At an age proteins dominate, over 90% nonprotein coding regions were long regarded as trash, but nevertheless it was puzzling why god would allocate such a big portion of a genome to things without obvious meanings, and such curiosity has heightened when it was shown among various genome sequencing projects that the percentage of non-coding sequences is in almost strict correlation with the complexity of the organisms.展开更多
Biomass ashes contain valuable elements for plant growth, but also often high amounts of harmful heavy metals which limit their reuse in forests and on grassland. For monitoring metal concentrations, a fast and reliab...Biomass ashes contain valuable elements for plant growth, but also often high amounts of harmful heavy metals which limit their reuse in forests and on grassland. For monitoring metal concentrations, a fast and reliable method allowing the quantitative determination even at trace levels is mandatory. Therefore an analytical method consisting of an acidic microwave assisted digestion prior to ICP-OES measurement was optimized. The elements of interest were AI, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sb, St, Ti, V, and Zn. A validation including the following parameters was performed for each analyte： limit of detection, limit of quantification, recovery by spiking experiments, accuracy by analyzing a certified reference material, reproducibility （wihtin-24 hours, 4 and 7 days）, linearity, and uncertainty of measurement. Two standards series were used for calibration - one with 1 M HNO3 and one with additionally 2 g/L Mg（NOD2 to investigate the elimination or decrease of possible matrix effects. Both calibration methods showed very good recoveries. The method optimized allows the determination of the relevant elements covered by the recommendation of the Austrian ministry for agriculture and represents thus an appropriate tool for monitoring the metal contents in biomass ashes.展开更多
The feasibility of preparing flocculant from powdered coal ashes is studied in detail. By means of orthogonal tests, the influence of various factors, such as the activation temperature, the activation time, the ratio...The feasibility of preparing flocculant from powdered coal ashes is studied in detail. By means of orthogonal tests, the influence of various factors, such as the activation temperature, the activation time, the ratio of CaO to Al2O3, the hydrochloric acid concentration, the reaction time and the reaction temperature, on preparation is investigated, and the hest operating condition is determined.展开更多
The pozzolanic reactivity was determined by the hydration kinetics of pozzolanic reaction based on the fact that the hydration products of active SiO2 and Al2O3 with lime were soluble in dilute hydrochloric acid. The ...The pozzolanic reactivity was determined by the hydration kinetics of pozzolanic reaction based on the fact that the hydration products of active SiO2 and Al2O3 with lime were soluble in dilute hydrochloric acid. The results show that the pozzolanic reaction of active SiO2 and Al2O3 of coal ashes follows apparent first-order kinetics. The reaction rate constant of FBC ashes is greater than that of PC ashes, while the activation energy of the former is lower than that of the latter. It is confirmed that the pozzolanic activity of fluidized bed combustion（FBC） ashes is significantly higher than that of PC ashes, and the reaction barrier of the former is lower than that of the latter, because the microstructures of FBC ashes, such as mineralogical composition, morphology and polymerization degree of [SiO4] and [AlO6] are more favorable to the pozzolanic activity development than those of PC ashes.展开更多
One option to fight global warming is to convert our use of fossil energy into renewables such as biomass energy.However,the forest preservation and the quality of the ambient air are also two major issues.Therefore,t...One option to fight global warming is to convert our use of fossil energy into renewables such as biomass energy.However,the forest preservation and the quality of the ambient air are also two major issues.Therefore,the use of biomass waste without any supplementary emissions could represent a part of the solution.In this study,two fuels were considered for a 200 kW moving grate boiler.A multicyclone and a bag filter were fitted on the boiler.The first fuel consisted of classical wood chips whereas the second was a mixture of wood chips with sewage sludge.This second fuel presented a high ashes mass ratio compared to wood chips.The aim was to verify the possibility to burn this kind of fuel without any modification of the installation.The first relevant result is that the conventional pollutants,i.e.,CO and NOx,remained under the emissions limits even with the sewage sludge combustion.The Total Suspended Particles emissions at the exhaust were always under 5.4 mg·Nm-3 dry based corrected at 6%of O_(2),which is low with respect to the standard limitation.The majority of the ashes remained on the combustion room.However,with both fuels,about 5%of ashes mass remained in the heat exchanger.Nevertheless,the heat exchanger was more clogged with the second fuel,which produced five time more ashes.This may lead to a yield loss.Thus,sewage sludge can be used in a wood boiler without any issue if an automatic exchanger sweep is fitted on the installation.展开更多
The use of rice husk and corn cob ashes as aggregates for foundry moulding sand has been studied. 5-12.5 weight percent of rice husk and corn cob ashes were added to the sand mixture and the sand properties determined...The use of rice husk and corn cob ashes as aggregates for foundry moulding sand has been studied. 5-12.5 weight percent of rice husk and corn cob ashes were added to the sand mixture and the sand properties determined. A mixture of equal proportion of rice husk and corn cob ashes was also used. In each case, four weight percent water and clay were added to the sand mixture. Some of the properties of the sand tested are: permeability, green compression strength, dry compression strength, green shear strength, dry shear strength, moisture content and permeability. The results showed that the green compression strength, green shear strength, moisture content and permeability decrease with increase in the additives (rice husk ash, corn cob ash, and (50% rice husk and 50% corn cob ashes). While dry compression strength and dry shear strength increase with increase in weight percent of the additives.展开更多
The radiological impact of coal ashes, with enhanced natural radioactivity in the storage site, is due to the presence of naturally occurring radionuclides. Some of these radionuclides have a radioactive period of sev...The radiological impact of coal ashes, with enhanced natural radioactivity in the storage site, is due to the presence of naturally occurring radionuclides. Some of these radionuclides have a radioactive period of several million years and will, therefore, have time to migrate to the soil, atmospheric air, surface water, and groundwater. This impact depends mainly on the activity of these coal ashes, the duration of exposure to such waste, transfers to the air, and the leaching phenomenon by rainwater. In this study, and so as to assess the radiological impact of coal ashes of the storage site of the JLEC-Morocco thermal power plant on environment, some analyses are performed by alpha dosimetry and a digital dosimeter on samples of coal ashes, soil, atmospheric air, surface water and groundwater belonging to a perimeter of 10 km around that site. The obtained results show that, within the studied area, the radiological impact on the soil of the coal ashes of the storage site is insignificant even though the concentrations of radon in the near vicinity (1 to 2 km) are moderately important, and remain below 200 Bq/m3. In the atmospheric air, this impact remains medium for the neighborhoods of the storage site (2 to 3 km) with radon activities superior to 10 Bq/m3. These results also show that there may be a water contamination of wells located at the storage site without any transfer of radioactivity into the groundwater of the area studied where the concentrations of radon are less than 11.1 Bq/l.展开更多
International shameWhen the Rwandan Genocide took place two decades ago, approxi-mately 1 million people were killed during the 100-day conflict between the Hutu and Tutsi ethnic groups. More than 2 million refugees f...International shameWhen the Rwandan Genocide took place two decades ago, approxi-mately 1 million people were killed during the 100-day conflict between the Hutu and Tutsi ethnic groups. More than 2 million refugees fled the country, with a further 2 million people left homeless.展开更多
Surfaces of grade III fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h. Mineralogical compositions and surface morphology of fly ashes before and after modification were charact...Surfaces of grade III fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h. Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated. Microstructures of cement pastes were examined by backscattered electron （BSE） imaging and mercury intrusion porosimetry （MIP）. The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification. Hydration ofβ-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers. In addition, surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes. Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.展开更多
Valuable metal extraction technology from thermal power plant fly ash is limited.In the present study,aluminium is extracted from fly ash as highly pure aluminium sulphate(>99.0%)by leaching with sulphuric acid,fol...Valuable metal extraction technology from thermal power plant fly ash is limited.In the present study,aluminium is extracted from fly ash as highly pure aluminium sulphate(>99.0%)by leaching with sulphuric acid,followed by pre-concentration and successive crystallization.Two types of fly ashes from different sources,i.e.,Talcher Thermal Power Station(TTPS)and Vedanta Aluminium Company Limited(VAL)were chosen for comparative study on the extraction of aluminium as aluminium sulphate.The product is characterized by powder X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric analysis(TGA).Purity of aluminium sulphate was also investigated by inductively coupled plasma?optical emission spectrometry(ICP?OES).The extraction efficiency of aluminium depends on the varied solid-to-liquid ratio(fly ash:18mol/L H2SO4,g/mL)and particle size of fly ashes.Physico-chemical analysis indicates that the obtained product is Al2(SO4)3·18H2O,having low iron content(0.08%).展开更多
Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy (SEM), energy dispersive X-ray analysis (E...Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and environmental scanning electron microscopy (ESEM). Ferrospheres in fly ashes show significant iron enrichment compared to their respective fly ashes. Iron oxides in ferrospheres mainly occur as minerals magnetite (Fe3O4) and hematite (α-Fe2O3), which are derived mainly from the decomposition and oxidation of iron-bearing minerals in coal during combustion. EDX data indicate that ferrospheres also contain Si, S, Al and Ca resulting from quartz, mullite, anhydrite and amorphous materials. A large percentage of ferrospheres are commonly 5～50 μm in size. The microstructure of ferrospheres includes smooth, polygonal, dendritic, granular and molten drop characteristics. SEM coupled with EDX provided fast and accurate results of the microstructure and chemical composition of ferrospheres, and helped us to assess environmental issues related to the disposal and utilization of fly ashes.展开更多
By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope （CCSEM）, X-ray diffraction （XRD） and X-ray fluorescence （XRF）, the ash composition and the mineral components of six ty...By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope （CCSEM）, X-ray diffraction （XRD） and X-ray fluorescence （XRF）, the ash composition and the mineral components of six typical Huainan coals of different origins were studied. The transformation of mineral matter at high temperatures was tracked by XRD in reducing conditions. The quartz phase decreased sharply and the anorthite content tended to increase at first and then decreased with increasing temperatures. The formed mullite phase reached a maximum at 1250 ℃ but showed a tendency of slow decline when the temperature was over 1250 ℃. The mullite formed in the heating process was the main reason of the high ash melting temperature of Huainan coals. Differences in peak intensity of mullite and anorthite reflected differences in phase concentration of the quenched slag fractions, which contributed to the differences in ash melting temperatures. The differences in the location of an mnorphous hump maximum indicated differences of glass types which may affect ash melting temperatures. For Huainan coal samples with relatively high ash melting tempera- tures, the intensity of the diffraction lines for mullite under reducing condition is high while for the samples with relatively low ash melting temperature the intensity for anorthite is high.展开更多
The bottom ashes resulted annually from the incineration of municipal solid waste in Europe contain about 400,000 tonnes of metallic aluminium and 200,000 tonnes of heavy non-ferrous metals, such as copper and zinc. E...The bottom ashes resulted annually from the incineration of municipal solid waste in Europe contain about 400,000 tonnes of metallic aluminium and 200,000 tonnes of heavy non-ferrous metals, such as copper and zinc. Efficient recovery of this non-ferrous metal resource requires state-of-the-art separation technologies and a continuous feedback of laboratory analyses of the metal products and the depleted bottom ash to the operators of the bottom ash treatment plants. A methodology is presented for the optimization of the production of non-ferrous metal value from Municipal Solid Waste Incinerator bottom ash. Results for an incineration plant in the Netherlands show that efficient recycling can have a significant impact on value recovery as well as on non-ferrous metal recycling rates, producing up to 8% more revenue and 25% more metals from the ash.展开更多
In this work,we investigated leaching of lanthanide and yttrium(REY) from a Central Appalachian coal and its ashes obtained at 550-950℃ with the main purpose of understanding the impact of ashing temperature on REY l...In this work,we investigated leaching of lanthanide and yttrium(REY) from a Central Appalachian coal and its ashes obtained at 550-950℃ with the main purpose of understanding the impact of ashing temperature on REY leachability in water,ammonium sulfate,and hydrochloric acid.It is found that the coal contains a negligible amount of water-soluble REY,less than 1% ion-exchangeable REY,and about 28% of HCl-soluble REY.Ashing leads to dramatic changes in REY leachability in both ammonium sulfate and hydrochloric acid solutions,which is believed to be related to transformation and redistribution of organically-associated REY in coal during the ashing process.Ashing temperature significantly affects REY leaching from coal ashes;higher ashing temperature results in lower REY leachability in both solutions.Clay minerals may play a significant role in changing the leachability of REY after ashing.In addition,the results also suggest that the organic matter in the coal is relatively enriched in heavy REY.展开更多
For the handling, treatment and utilization of fly ash from biomass combustion its chemical composition and physical properties are important. In this study eight filter fly ashes from different grate-fired biomass co...For the handling, treatment and utilization of fly ash from biomass combustion its chemical composition and physical properties are important. In this study eight filter fly ashes from different grate-fired biomass combustion plants were investigated. In fly ash from straw combustion high concentrations of（K） were found, whereas in the fly ash from wood combustion the concentrations of Ca and Mg were higher. The average concentration of PO3-4was similar in both types of fly ashes. In all wood fly ashes some measured heavy metal concentrations were above the limits for utilization. The straw fly ashes were much less contaminated and can be utilized. For wood fly ash most parameters showed little variation, except from one fly ash where the dust pre-separator is in poor condition. The average values were： mass median diameter 4.3 ± 0.8 μm, spread of particle size distribution19 ± 11, particle density 2620 ± 80 kg/m^3 and angle of repose 50°± 1°. The density of the straw fly ashes is lower（2260 ± 80 kg/m^3） and the spread of the size distribution is higher（72 ± 24）.For one straw combustion fly ash the values of the mass median diameter and the angle of repose were similar to the values of wood combustion fly ash, for the other straw fly ash the values differed considerably. While the particle size of this fly ash was much smaller,surprisingly the angle of repose was also lower. This can be attributed to the formation of small agglomerates in this fly ash, which were not disintegrated without a certain stress.展开更多
The use of by-products as raw materials in the manufacturing of industrial products has risen in the last years because of environmental considerations.One example is the use of coal ashes from thermalelectrical plant...The use of by-products as raw materials in the manufacturing of industrial products has risen in the last years because of environmental considerations.One example is the use of coal ashes from thermalelectrical plants in the production of geopolymer–a green cement made by mixing aluminosilicate with alkaline activator.In this study,fly and bottom ashes from a thermal-electrical unit were used as sources of aluminosilicate in the synthesis of geopolymers.A mixture of sodium hydroxide(10 mol/L)and sodium silicate(SiO_(2)/Na_(2)O ratio of 2.2)was used as the alkaline activator.The type(fly or bottom ash)and content of the ash were the variables in the synthesis.The ashes were characterized by X-ray fluorescence(XRF),X-ray diffraction(DRX),particle size distribution(PSD),specific surface area(BET),and thermal analysis(DTA/TGA).The ash-based geopolymer samples were measured to obtain their compressive strength after curing.The evolution of the geopolymerization process was also assessed based on final alkali concentration measurements.The results show that it is possible to obtain geopolymers using coal ashes as raw materials with high solid content.The compressive strength for the bottom ash geopolymer after 90 days of curing is 35 MPa.The low concentration of unreacted alkalis after curing(1.5×10^(-3)e 3.5×10^(-3)M)corresponds to high efficiency of the geopolymerization reaction.展开更多
基金Funded by the National Natural Science Foundation of China(No.50572127)
文摘The self-cementing mechanism at early ages of circulating fluidized bed combustion （CFBC） coal ashes was studied by X-ray diffraction （XRD）, infrared （IR） spectroscopy and chemical method. The results indicate that the amorphous phase is predominant in CFBC coal ashes. The polymerization degree of [SiO4] and [AlO6] of CFBC desulphurization coal ashes is lower than that of those without desulphurization. The contents of the components with fast hydration rate of CFBC desulphurization coal ashes are significantly greater than those of the ashes without desulphurization. This work confirms that the amorphous minerals with high chemical activity are the main causes of the self-cementing property of CFBC desulphurization coal ashes at early ages.
基金This work was supported by the National Natural Science Found of China(40133010,40273035)Natural Science Found of Anhui(04045064)
文摘The Yanzhou mine district, located in southwestern Shandong Province, is about 1300 km2 with more than 8×109tons of proved coal reserves and there are 10 big power plants in this area. A large amount of coal ashes, which are regarded as waste materials, have been stockpiled in the area and have influenced the environment of the mine district. In this paper, analysis of fly ash samples from three power plants is carried out, the enrichment and concentration of trace elements, Pb, Zn, Cu and As, in coal ashes are analyzed, and petrological and mineralogical characteristics and chemical compositions of coal ashes are studied. The aim of this work is to provide basic scientific data for utilization of ashes and reduction of environmental pollutions.
文摘The use of the thermal power plant ashes including fly ash(FA) and bottom ash(BA) for producing unfired building bricks(UBB) using sodium hydroxide(NaOH) solution as an alkaline activator was investigated. A low applied forming pressure of 0.5 MPa and various NaOH concentrations of 5, 8, 10, and 12 M were used for the preparation of brick samples with different solution-to-binder(S/B) ratios of 0.35 and 0.40. The bricks were subjected to various test programs with reflecting the effect of both NaOH concentrations and S/B ratios on the brick’s properties. The compressive strength, unit weight, ultrasonic pulse velocity, and thermal conductivity of bricks increased with increasing NaOH concentration, whereas the contrary trend was found with increasing S/B ratio. Also, the water absorption of bricks was observed to reduce with increasing NaOH concentration and decreasing S/B ratio. As the results, the combined utilization of both low forming pressure and coal power plant ashes can produce the UBBs with low unit weight, low heat conductivity, and acceptable strength and water absorption rate as stipulated by TCVN 6477-2016. Furthermore, the outcomes of chemical analysis and microstructure observation also demonstrate that a high concentration of the Na OH promoted the geopolymerization process. Notably, the use of NaOH solution of either 10 M or above is recommended for the production of UBBs, which are classified as grade M5.0 or higher.
基金supported by the National Key Basic Research Program of China(No.2014CB441003)the National Key Research and Development of China(No.2016YFD0200302)
文摘The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied depending on the source biomass material. An increase in the concrete shuttering contents in the biomass materials led to higher alkalinity,and higher Ca and Mg levels in biomass ashes,which made them particularly good at ameliorating effects on soil acidity. However,heavy metal contents,such as Cr,Cu,and Zn in the ashes,were relatively high. The incorporation of all ashes increased soil p H,exchangeable base cations,and available phosphorus,but decreased soil exchangeable acidity. The application of the ashes from biomass materials with a high concrete shuttering content increased the soil available heavy metal contents. Therefore,the biomass ashes from wood and crop residues with low concrete contents were the better acid soil amendments.
文摘It was recognized that a majority of the whole human genome is transcribed but only about 2% of genome actually encode all the proteins that were supposed, according to the central dogma, executing most of the biological functions of an organism. At an age proteins dominate, over 90% nonprotein coding regions were long regarded as trash, but nevertheless it was puzzling why god would allocate such a big portion of a genome to things without obvious meanings, and such curiosity has heightened when it was shown among various genome sequencing projects that the percentage of non-coding sequences is in almost strict correlation with the complexity of the organisms.
文摘Biomass ashes contain valuable elements for plant growth, but also often high amounts of harmful heavy metals which limit their reuse in forests and on grassland. For monitoring metal concentrations, a fast and reliable method allowing the quantitative determination even at trace levels is mandatory. Therefore an analytical method consisting of an acidic microwave assisted digestion prior to ICP-OES measurement was optimized. The elements of interest were AI, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Sb, St, Ti, V, and Zn. A validation including the following parameters was performed for each analyte： limit of detection, limit of quantification, recovery by spiking experiments, accuracy by analyzing a certified reference material, reproducibility （wihtin-24 hours, 4 and 7 days）, linearity, and uncertainty of measurement. Two standards series were used for calibration - one with 1 M HNO3 and one with additionally 2 g/L Mg（NOD2 to investigate the elimination or decrease of possible matrix effects. Both calibration methods showed very good recoveries. The method optimized allows the determination of the relevant elements covered by the recommendation of the Austrian ministry for agriculture and represents thus an appropriate tool for monitoring the metal contents in biomass ashes.
文摘The feasibility of preparing flocculant from powdered coal ashes is studied in detail. By means of orthogonal tests, the influence of various factors, such as the activation temperature, the activation time, the ratio of CaO to Al2O3, the hydrochloric acid concentration, the reaction time and the reaction temperature, on preparation is investigated, and the hest operating condition is determined.
基金Funded by the National Natural Science Foundation of China (No50802080)Shandong Provincial Scientific Research Foundation for Excellent Young Scientists (No.2008BS09005)
文摘The pozzolanic reactivity was determined by the hydration kinetics of pozzolanic reaction based on the fact that the hydration products of active SiO2 and Al2O3 with lime were soluble in dilute hydrochloric acid. The results show that the pozzolanic reaction of active SiO2 and Al2O3 of coal ashes follows apparent first-order kinetics. The reaction rate constant of FBC ashes is greater than that of PC ashes, while the activation energy of the former is lower than that of the latter. It is confirmed that the pozzolanic activity of fluidized bed combustion（FBC） ashes is significantly higher than that of PC ashes, and the reaction barrier of the former is lower than that of the latter, because the microstructures of FBC ashes, such as mineralogical composition, morphology and polymerization degree of [SiO4] and [AlO6] are more favorable to the pozzolanic activity development than those of PC ashes.
基金This study was realized thanks to the financial support of ADEME and the financial and technical support of LERMAB,especially the ERBE platform.LERMAB is supported by a grant over seen by the French National Research Agency(ANR)as part of the“Investissements d’Avenir”Program(ANR-11-LABX-0002-01.Lab of Excellence ARBRE)and is part of ICEEL.
文摘One option to fight global warming is to convert our use of fossil energy into renewables such as biomass energy.However,the forest preservation and the quality of the ambient air are also two major issues.Therefore,the use of biomass waste without any supplementary emissions could represent a part of the solution.In this study,two fuels were considered for a 200 kW moving grate boiler.A multicyclone and a bag filter were fitted on the boiler.The first fuel consisted of classical wood chips whereas the second was a mixture of wood chips with sewage sludge.This second fuel presented a high ashes mass ratio compared to wood chips.The aim was to verify the possibility to burn this kind of fuel without any modification of the installation.The first relevant result is that the conventional pollutants,i.e.,CO and NOx,remained under the emissions limits even with the sewage sludge combustion.The Total Suspended Particles emissions at the exhaust were always under 5.4 mg·Nm-3 dry based corrected at 6%of O_(2),which is low with respect to the standard limitation.The majority of the ashes remained on the combustion room.However,with both fuels,about 5%of ashes mass remained in the heat exchanger.Nevertheless,the heat exchanger was more clogged with the second fuel,which produced five time more ashes.This may lead to a yield loss.Thus,sewage sludge can be used in a wood boiler without any issue if an automatic exchanger sweep is fitted on the installation.
文摘The use of rice husk and corn cob ashes as aggregates for foundry moulding sand has been studied. 5-12.5 weight percent of rice husk and corn cob ashes were added to the sand mixture and the sand properties determined. A mixture of equal proportion of rice husk and corn cob ashes was also used. In each case, four weight percent water and clay were added to the sand mixture. Some of the properties of the sand tested are: permeability, green compression strength, dry compression strength, green shear strength, dry shear strength, moisture content and permeability. The results showed that the green compression strength, green shear strength, moisture content and permeability decrease with increase in the additives (rice husk ash, corn cob ash, and (50% rice husk and 50% corn cob ashes). While dry compression strength and dry shear strength increase with increase in weight percent of the additives.
文摘The radiological impact of coal ashes, with enhanced natural radioactivity in the storage site, is due to the presence of naturally occurring radionuclides. Some of these radionuclides have a radioactive period of several million years and will, therefore, have time to migrate to the soil, atmospheric air, surface water, and groundwater. This impact depends mainly on the activity of these coal ashes, the duration of exposure to such waste, transfers to the air, and the leaching phenomenon by rainwater. In this study, and so as to assess the radiological impact of coal ashes of the storage site of the JLEC-Morocco thermal power plant on environment, some analyses are performed by alpha dosimetry and a digital dosimeter on samples of coal ashes, soil, atmospheric air, surface water and groundwater belonging to a perimeter of 10 km around that site. The obtained results show that, within the studied area, the radiological impact on the soil of the coal ashes of the storage site is insignificant even though the concentrations of radon in the near vicinity (1 to 2 km) are moderately important, and remain below 200 Bq/m3. In the atmospheric air, this impact remains medium for the neighborhoods of the storage site (2 to 3 km) with radon activities superior to 10 Bq/m3. These results also show that there may be a water contamination of wells located at the storage site without any transfer of radioactivity into the groundwater of the area studied where the concentrations of radon are less than 11.1 Bq/l.
文摘International shameWhen the Rwandan Genocide took place two decades ago, approxi-mately 1 million people were killed during the 100-day conflict between the Hutu and Tutsi ethnic groups. More than 2 million refugees fled the country, with a further 2 million people left homeless.
基金Funded by the National Basic Research Program of China (No.2009CB623105)
文摘Surfaces of grade III fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h. Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated. Microstructures of cement pastes were examined by backscattered electron （BSE） imaging and mercury intrusion porosimetry （MIP）. The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification. Hydration ofβ-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers. In addition, surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes. Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.
基金Funding from CSIR, New Delhi, under network project (ESC.205)
文摘Valuable metal extraction technology from thermal power plant fly ash is limited.In the present study,aluminium is extracted from fly ash as highly pure aluminium sulphate(>99.0%)by leaching with sulphuric acid,followed by pre-concentration and successive crystallization.Two types of fly ashes from different sources,i.e.,Talcher Thermal Power Station(TTPS)and Vedanta Aluminium Company Limited(VAL)were chosen for comparative study on the extraction of aluminium as aluminium sulphate.The product is characterized by powder X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric analysis(TGA).Purity of aluminium sulphate was also investigated by inductively coupled plasma?optical emission spectrometry(ICP?OES).The extraction efficiency of aluminium depends on the varied solid-to-liquid ratio(fly ash:18mol/L H2SO4,g/mL)and particle size of fly ashes.Physico-chemical analysis indicates that the obtained product is Al2(SO4)3·18H2O,having low iron content(0.08%).
基金Project supported by the National Natural Science Foundation of China (No. 40771096)the Natural Science Foundation of Zhejiang Province (No. R305078), China
文摘Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and environmental scanning electron microscopy (ESEM). Ferrospheres in fly ashes show significant iron enrichment compared to their respective fly ashes. Iron oxides in ferrospheres mainly occur as minerals magnetite (Fe3O4) and hematite (α-Fe2O3), which are derived mainly from the decomposition and oxidation of iron-bearing minerals in coal during combustion. EDX data indicate that ferrospheres also contain Si, S, Al and Ca resulting from quartz, mullite, anhydrite and amorphous materials. A large percentage of ferrospheres are commonly 5～50 μm in size. The microstructure of ferrospheres includes smooth, polygonal, dendritic, granular and molten drop characteristics. SEM coupled with EDX provided fast and accurate results of the microstructure and chemical composition of ferrospheres, and helped us to assess environmental issues related to the disposal and utilization of fly ashes.
基金Projects 2003001 supported by the key project of Huainan city, & 2004kj125 by the Science Funding of Department of Education of Anhui Province
文摘By using the advanced instrumentation of a Computer Controlled Scanning Electron Microscope （CCSEM）, X-ray diffraction （XRD） and X-ray fluorescence （XRF）, the ash composition and the mineral components of six typical Huainan coals of different origins were studied. The transformation of mineral matter at high temperatures was tracked by XRD in reducing conditions. The quartz phase decreased sharply and the anorthite content tended to increase at first and then decreased with increasing temperatures. The formed mullite phase reached a maximum at 1250 ℃ but showed a tendency of slow decline when the temperature was over 1250 ℃. The mullite formed in the heating process was the main reason of the high ash melting temperature of Huainan coals. Differences in peak intensity of mullite and anorthite reflected differences in phase concentration of the quenched slag fractions, which contributed to the differences in ash melting temperatures. The differences in the location of an mnorphous hump maximum indicated differences of glass types which may affect ash melting temperatures. For Huainan coal samples with relatively high ash melting tempera- tures, the intensity of the diffraction lines for mullite under reducing condition is high while for the samples with relatively low ash melting temperature the intensity for anorthite is high.
文摘The bottom ashes resulted annually from the incineration of municipal solid waste in Europe contain about 400,000 tonnes of metallic aluminium and 200,000 tonnes of heavy non-ferrous metals, such as copper and zinc. Efficient recovery of this non-ferrous metal resource requires state-of-the-art separation technologies and a continuous feedback of laboratory analyses of the metal products and the depleted bottom ash to the operators of the bottom ash treatment plants. A methodology is presented for the optimization of the production of non-ferrous metal value from Municipal Solid Waste Incinerator bottom ash. Results for an incineration plant in the Netherlands show that efficient recycling can have a significant impact on value recovery as well as on non-ferrous metal recycling rates, producing up to 8% more revenue and 25% more metals from the ash.
基金Project supported by the U.S.Department of Energy(DOE)National Energy Technology Laboratory(NETL)Research and Innovation Center(R&IC)Rare Earth FWPsupported in part by appointment(R.H.Lin)to the NETL Research Participation Program+1 种基金sponsored by the U.S.DOEadministered by the Oak Ridge Institute for Science and Education(ORISE)。
文摘In this work,we investigated leaching of lanthanide and yttrium(REY) from a Central Appalachian coal and its ashes obtained at 550-950℃ with the main purpose of understanding the impact of ashing temperature on REY leachability in water,ammonium sulfate,and hydrochloric acid.It is found that the coal contains a negligible amount of water-soluble REY,less than 1% ion-exchangeable REY,and about 28% of HCl-soluble REY.Ashing leads to dramatic changes in REY leachability in both ammonium sulfate and hydrochloric acid solutions,which is believed to be related to transformation and redistribution of organically-associated REY in coal during the ashing process.Ashing temperature significantly affects REY leaching from coal ashes;higher ashing temperature results in lower REY leachability in both solutions.Clay minerals may play a significant role in changing the leachability of REY after ashing.In addition,the results also suggest that the organic matter in the coal is relatively enriched in heavy REY.
文摘For the handling, treatment and utilization of fly ash from biomass combustion its chemical composition and physical properties are important. In this study eight filter fly ashes from different grate-fired biomass combustion plants were investigated. In fly ash from straw combustion high concentrations of（K） were found, whereas in the fly ash from wood combustion the concentrations of Ca and Mg were higher. The average concentration of PO3-4was similar in both types of fly ashes. In all wood fly ashes some measured heavy metal concentrations were above the limits for utilization. The straw fly ashes were much less contaminated and can be utilized. For wood fly ash most parameters showed little variation, except from one fly ash where the dust pre-separator is in poor condition. The average values were： mass median diameter 4.3 ± 0.8 μm, spread of particle size distribution19 ± 11, particle density 2620 ± 80 kg/m^3 and angle of repose 50°± 1°. The density of the straw fly ashes is lower（2260 ± 80 kg/m^3） and the spread of the size distribution is higher（72 ± 24）.For one straw combustion fly ash the values of the mass median diameter and the angle of repose were similar to the values of wood combustion fly ash, for the other straw fly ash the values differed considerably. While the particle size of this fly ash was much smaller,surprisingly the angle of repose was also lower. This can be attributed to the formation of small agglomerates in this fly ash, which were not disintegrated without a certain stress.
文摘The use of by-products as raw materials in the manufacturing of industrial products has risen in the last years because of environmental considerations.One example is the use of coal ashes from thermalelectrical plants in the production of geopolymer–a green cement made by mixing aluminosilicate with alkaline activator.In this study,fly and bottom ashes from a thermal-electrical unit were used as sources of aluminosilicate in the synthesis of geopolymers.A mixture of sodium hydroxide(10 mol/L)and sodium silicate(SiO_(2)/Na_(2)O ratio of 2.2)was used as the alkaline activator.The type(fly or bottom ash)and content of the ash were the variables in the synthesis.The ashes were characterized by X-ray fluorescence(XRF),X-ray diffraction(DRX),particle size distribution(PSD),specific surface area(BET),and thermal analysis(DTA/TGA).The ash-based geopolymer samples were measured to obtain their compressive strength after curing.The evolution of the geopolymerization process was also assessed based on final alkali concentration measurements.The results show that it is possible to obtain geopolymers using coal ashes as raw materials with high solid content.The compressive strength for the bottom ash geopolymer after 90 days of curing is 35 MPa.The low concentration of unreacted alkalis after curing(1.5×10^(-3)e 3.5×10^(-3)M)corresponds to high efficiency of the geopolymerization reaction.
