This study examined the evolution of morphology and nanostructure of soot particles from the plasma-flame interaction for various gas flow rates.The current study used both optical diagnostic and sampling methods to e...This study examined the evolution of morphology and nanostructure of soot particles from the plasma-flame interaction for various gas flow rates.The current study used both optical diagnostic and sampling methods to explore the soot production and combustion characteristics.Soot particles were characterized at the same positions downstream from the flame zone by thermophoretic sampling and transmission electron microscopy.Moreover,X-ray diffraction analysis,and thermogravimetric analysis were performed to study the nanostructure and oxidation reactivity of soot.A reduction in soot concentration was found with the plasma addition,which illustrated an inhibition effect of plasma on soot emission.The increased gas flow rate promoted soot concentration since a growing number of carbons participated in the combustion process.Depending on the gas flow rate(carbon content)variation and plasma activation,either liquid-like soot material with irregularly shaped protrusions or chain-like structure,or a mixture of both,were generated from the diffusion flames.The soot produced by plasma-flame interaction also demonstrated a high correlation between nanostructure and reactivity.The soot from lower carbon content with plasma activation had a shorter fringe length and larger fringe tortuosity related to higher oxidation reactivity.On the contrary,soot from the highest carbon content without plasma-flame interaction exhibited prevalent fullerene-like nanostructures with evident large or small shells and also had a higher carbonization degree resulting in lower oxidation reactivity.展开更多
Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks (including external radiative heat flux) to the fuel surface of a burn...Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks (including external radiative heat flux) to the fuel surface of a burning object. Blockage clearly affects burning rates and heat release rates of fires. This needs to be included when calculating flame heat transfer in fire growth models. An understanding of bttrning of materials in small scale fires is of broad and vital importance for predicting their burning performance in large scale fires. The blockage phenomenon was clearly observed and quantitatively measured in experiments that took advantage of the unique capability of the Fire Propagation Apparatus (FPA) of being able to vary the ambient oxygen concentrations. An indirect measurement approach was established which provides an experimental understanding of the concept of the blockage. The measurements were further explained by a one-dimensional steady-state model of a diffusion flame, which focuses on the radiant absorption and emission by the gas-soot mixture of flames. The theoretical model provides a greater understanding of the fundamental knowledge of the blockage. The overall heat transfer blockage factor can be up to 0.3 -0.4 for PMMA and POM. The factor and its components are nearly independent of the external radiation, but increase as the ambient oxygen concentration rises. A comparison between experimental data and model prediction shows a good agreement.展开更多
Diesel soot is related to incomplete fuel oxidation, and possesses the well-known mutagenic effects on human health.Diesel soot was collected from diesel engines and oxidized in laboratorial micro reactor by several p...Diesel soot is related to incomplete fuel oxidation, and possesses the well-known mutagenic effects on human health.Diesel soot was collected from diesel engines and oxidized in laboratorial micro reactor by several prepared rare earth-based catalysts with or without different harmful monoxide gases such as NO, and activities of several rare earth catalysts were studied.The results indicate that soot can be more easily oxidized with monoxide gases.展开更多
Polychlorinated biphenyls (PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteris-tics of P...Polychlorinated biphenyls (PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteris-tics of PCBs and their gas/particle partitioning. The mean concentration of 26 PCBs (vapor plus particulate phase) (∑PCBs) was 19.116 pg/m^3with a standard deviation of 13.833 pg/m^3. Three most abundant conge-ners were CB-28, -52 and -77, accounting for 43.0% to∑PCBs. The predominance of vapor PCBs (79.0% to∑PCBs) in the atmosphere was observed.∑PCBs were negative correlated with the latitudes and inverse of the absolute temperature (1/T). The significant correlation for most congeners was also observed between the logarithm of gas/particle partition coefficient (logKp) and 1/T. Shallower slopes (from ∑0.15 to ∑0.46, average ∑0.27) were measured from the regression of the logarithm of sub-cooled liquid vapor pressures (logpoL) and logKP for all samples. The difference of the slopes and intercepts among samples was insignifi-cant (p〉0.1), implying adsorption and/or absorption processes and the aerosol composition did not differ significantly among different samples. By comparing three models, the J-P adsorption model, the octanol/air partition coefficient (KOA) based model and the soot-air model, the gas/particle partitioning of PCBs in the Arctic atmosphere was simulated more precisely by the soot-air model, and the adsorption onto el-emental carbon is more sensitive than the absorption into organic matters of aerosols, especially for low-chlorinated PCB congeners.展开更多
The serious carbon deposition existing in catalytic partial oxidation of methane(CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical si...The serious carbon deposition existing in catalytic partial oxidation of methane(CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical simulations of the soot formation and oxidation in oxidation section in a heat coupling reactor were carried out by computational fluid dynamics(CFD) approach incorporating the Moss-Brookes model for soot formation. The model has been validated and proven to be in good agreement with experiment results. Effects of nozzle type,nozzle convergence angle, channel spacing, number of channels, radius/height ratio, oxygen/carbon ratio, preheat temperature and additional introduction of steam on the soot formation were simulated. Results show that the soot formation in oxidation section of the heat coupling reactor depends on both nozzle structures and operation conditions, and the soot concentration can be greatly reduced by optimization with the maximum mass fraction of soot inside the oxidation reactor from 2.28% to 0.0501%, and so that the soot mass fraction at the exit reduces from0.74% to 0.03%.展开更多
Structured catalysts for the simultaneous removal of soot and nitrogen oxides were prepared by means of coating cordierite monoliths with alumina-based suspensions containing Cu, Co or Fe and Cs as the catalytically a...Structured catalysts for the simultaneous removal of soot and nitrogen oxides were prepared by means of coating cordierite monoliths with alumina-based suspensions containing Cu, Co or Fe and Cs as the catalytically active phase. Textural and chemical properties of the coated monoliths were determined by means of N2-physisorption, SEM and temperature programmed reduction. Their activity in the simultaneous removal of soot and NOx was assayed in a lab-scale installation, using a carbon black as diesel surrogate. Catalysts containing Cs exhibited significant activity in deNOx, however soot oxidation activity is poorly enhanced probably due to the low NO2 evolution, pointing to a different NOx adsorption mechanism in the present case, in comparison to previous observations on analogous K and Ba containing catalysts.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52076110 and 52376115)。
文摘This study examined the evolution of morphology and nanostructure of soot particles from the plasma-flame interaction for various gas flow rates.The current study used both optical diagnostic and sampling methods to explore the soot production and combustion characteristics.Soot particles were characterized at the same positions downstream from the flame zone by thermophoretic sampling and transmission electron microscopy.Moreover,X-ray diffraction analysis,and thermogravimetric analysis were performed to study the nanostructure and oxidation reactivity of soot.A reduction in soot concentration was found with the plasma addition,which illustrated an inhibition effect of plasma on soot emission.The increased gas flow rate promoted soot concentration since a growing number of carbons participated in the combustion process.Depending on the gas flow rate(carbon content)variation and plasma activation,either liquid-like soot material with irregularly shaped protrusions or chain-like structure,or a mixture of both,were generated from the diffusion flames.The soot produced by plasma-flame interaction also demonstrated a high correlation between nanostructure and reactivity.The soot from lower carbon content with plasma activation had a shorter fringe length and larger fringe tortuosity related to higher oxidation reactivity.On the contrary,soot from the highest carbon content without plasma-flame interaction exhibited prevalent fullerene-like nanostructures with evident large or small shells and also had a higher carbonization degree resulting in lower oxidation reactivity.
文摘Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks (including external radiative heat flux) to the fuel surface of a burning object. Blockage clearly affects burning rates and heat release rates of fires. This needs to be included when calculating flame heat transfer in fire growth models. An understanding of bttrning of materials in small scale fires is of broad and vital importance for predicting their burning performance in large scale fires. The blockage phenomenon was clearly observed and quantitatively measured in experiments that took advantage of the unique capability of the Fire Propagation Apparatus (FPA) of being able to vary the ambient oxygen concentrations. An indirect measurement approach was established which provides an experimental understanding of the concept of the blockage. The measurements were further explained by a one-dimensional steady-state model of a diffusion flame, which focuses on the radiant absorption and emission by the gas-soot mixture of flames. The theoretical model provides a greater understanding of the fundamental knowledge of the blockage. The overall heat transfer blockage factor can be up to 0.3 -0.4 for PMMA and POM. The factor and its components are nearly independent of the external radiation, but increase as the ambient oxygen concentration rises. A comparison between experimental data and model prediction shows a good agreement.
文摘Diesel soot is related to incomplete fuel oxidation, and possesses the well-known mutagenic effects on human health.Diesel soot was collected from diesel engines and oxidized in laboratorial micro reactor by several prepared rare earth-based catalysts with or without different harmful monoxide gases such as NO, and activities of several rare earth catalysts were studied.The results indicate that soot can be more easily oxidized with monoxide gases.
基金The Chinese Polar Environment Comprehensive Investigation and Assessment Programs under contract Nos 02-01,03-04,04-01 and 04-03the National Natural Science Fundation of China under contract No.21377032
文摘Polychlorinated biphenyls (PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteris-tics of PCBs and their gas/particle partitioning. The mean concentration of 26 PCBs (vapor plus particulate phase) (∑PCBs) was 19.116 pg/m^3with a standard deviation of 13.833 pg/m^3. Three most abundant conge-ners were CB-28, -52 and -77, accounting for 43.0% to∑PCBs. The predominance of vapor PCBs (79.0% to∑PCBs) in the atmosphere was observed.∑PCBs were negative correlated with the latitudes and inverse of the absolute temperature (1/T). The significant correlation for most congeners was also observed between the logarithm of gas/particle partition coefficient (logKp) and 1/T. Shallower slopes (from ∑0.15 to ∑0.46, average ∑0.27) were measured from the regression of the logarithm of sub-cooled liquid vapor pressures (logpoL) and logKP for all samples. The difference of the slopes and intercepts among samples was insignifi-cant (p〉0.1), implying adsorption and/or absorption processes and the aerosol composition did not differ significantly among different samples. By comparing three models, the J-P adsorption model, the octanol/air partition coefficient (KOA) based model and the soot-air model, the gas/particle partitioning of PCBs in the Arctic atmosphere was simulated more precisely by the soot-air model, and the adsorption onto el-emental carbon is more sensitive than the absorption into organic matters of aerosols, especially for low-chlorinated PCB congeners.
基金supported by the National Science Foundation of China under Grant No.20776156 and No.21176256the Science Foundation ofChina University of Petroleum,Beijing(No.KYJJ2012-03-01)
文摘The serious carbon deposition existing in catalytic partial oxidation of methane(CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical simulations of the soot formation and oxidation in oxidation section in a heat coupling reactor were carried out by computational fluid dynamics(CFD) approach incorporating the Moss-Brookes model for soot formation. The model has been validated and proven to be in good agreement with experiment results. Effects of nozzle type,nozzle convergence angle, channel spacing, number of channels, radius/height ratio, oxygen/carbon ratio, preheat temperature and additional introduction of steam on the soot formation were simulated. Results show that the soot formation in oxidation section of the heat coupling reactor depends on both nozzle structures and operation conditions, and the soot concentration can be greatly reduced by optimization with the maximum mass fraction of soot inside the oxidation reactor from 2.28% to 0.0501%, and so that the soot mass fraction at the exit reduces from0.74% to 0.03%.
文摘Structured catalysts for the simultaneous removal of soot and nitrogen oxides were prepared by means of coating cordierite monoliths with alumina-based suspensions containing Cu, Co or Fe and Cs as the catalytically active phase. Textural and chemical properties of the coated monoliths were determined by means of N2-physisorption, SEM and temperature programmed reduction. Their activity in the simultaneous removal of soot and NOx was assayed in a lab-scale installation, using a carbon black as diesel surrogate. Catalysts containing Cs exhibited significant activity in deNOx, however soot oxidation activity is poorly enhanced probably due to the low NO2 evolution, pointing to a different NOx adsorption mechanism in the present case, in comparison to previous observations on analogous K and Ba containing catalysts.