Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content.Thus,effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of...Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content.Thus,effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigation.In this paper,the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke was measured directly using an improved Wicke-Kallenbach diffusion apparatus.The experimental results showed that higher temperature would lead to a higher effective diffusivity and a thicker ash layer had the negative effect.Especially,the effective diffusivity along the direction perpendicular to bedding planes was much lower than that along the direction parallel to bedding planes.In addition,an effective diffusivity model was developed,which could be used to describe the mass transfer of oxygen in the ash layer of oil shale semicoke.展开更多
[Objectives] The aim was to determine the moisture,ash and extract contents in Leontopodium franchetii Beauv. from different localities. [Methods] The contents of moisture,total ash,acid-insoluble ash and extract in L...[Objectives] The aim was to determine the moisture,ash and extract contents in Leontopodium franchetii Beauv. from different localities. [Methods] The contents of moisture,total ash,acid-insoluble ash and extract in L. franchetii from different localities were determined according to the methods described in Chinese Pharmacopoeia( 2015 Edition). [Results] In the 10 samples,the contents of moisture were all less than or equal to 15. 0%; the contents of total ash were all below 12. 0%; and the contents of acid-insoluble ash were all less than 3. 0%. The contents of water-soluble extract( by cold-soaked extraction method) in the samples were all below 12. 0% except those from Hongyuan Prairie of Sichuan Province and Xinglong Mountain in Lanzhou City,Gansu Province. [Conclusions]The contents of the four indicators measured in this experiment varied by small margins,indicating that the quality was relatively stable. This study provides theoretical data for the revision of the quality standards for L. franchetii.展开更多
Monolayer barriers called evapotranspiration (ET) covers were developed as alternative final cover systems in waste landfills but high-quality soil remains a limiting factor in these cover systems. Coal bottom ash was...Monolayer barriers called evapotranspiration (ET) covers were developed as alternative final cover systems in waste landfills but high-quality soil remains a limiting factor in these cover systems. Coal bottom ash was evaluated to be a very good alternative to soil in previous tests and a combination of soil (65% wt.wt-1) and coal bottom ash (35% wt.wt-1) was evaluated to be the most feasible materials for ET cover systems. In our pot test, selected manure compost as soil amendment for the composite ET cover system, which was made of soil and bottom ash at ca. 40 Mg.ha-1 application level was very effective to promote vegetation growth of three plants;namely, garden cosmos (Cosmosbipinnatus), Chinese bushclover (Lespedezacuneata), and leafy lespedeza (Lespedeza cyrtobotrya). To evaluate the effect of compost application on plant growth in an ET vegetative cover system, two couples of lysimeters, packed with soil and a mixture of soil and bottom ash, were installed in a pilot landfill cover system in 2007. Manure composts were applied at the rates of 0 and ?40 Mg.ha-11before sowing the five plant species, i.e.indigo-bush (Amorphafruticosa), Japanese mugwort (Artemisia princeps, Arundinella hirta, Lespedezacuneata, and Lespedezacyrtobotrya). Unseeded native plant (green foxtail,Setaria viridis) was dominant in all treatments in the 1st year after installation while the growth of the sown plants significantly improved over the years. Total biomass productivity significantly increased with manure compost application, and more significantly increased in the composite ET cover made of soil and bottom ash treatment compared to the single soil ET cover, mainly due to more improved soil nutrient levels promoting vegetation growth and maintaining the vegetation system. The use of bottom ash as a mixing material in ET cover systems has a strong potential as an alternative to fine-grained soils, and manure compost addition can effectively enhance vegetative propagation in ET cover systems.展开更多
A thermogravimetric method under constant temperature replacing the beginning inert gas with burning air was established in this study for determining the combustion kinetics of single char particle. The combustion pr...A thermogravimetric method under constant temperature replacing the beginning inert gas with burning air was established in this study for determining the combustion kinetics of single char particle. The combustion process of three types of coals, Fujian Longyan coal, Fujian Yong’an coal and Shandong coal, with diameter of 3.0—4.5 mm, in thermobalance under 900℃ was discussed using the familiar shrinking-core model.While the combustion of single char approached the end, the outside and the ash layer diffusion resistances tend to be zero as the reaction resistance dominated in the total resistance of combustion.Therefore, at this stage the inherent oxidation reaction constant (k_R) of the above char samples were estimated by analyzing the total resistance of combustion.The good agreement of combustion reaction rate between data determined in this study and calculated values obtained from reference in the drop tube furnace system, implied that the inherent oxidation reaction constant (k_R) determined by the thermogravimetric method under constant temperature was satisfactory and valuable. The gas diffusion through the ash layer of char particle during combustion process was discussed also. At the ash layer thickness half the char radius, the ash layer resistance in the combustion process reached a maximum value, at which the total resistance of combustion,1/K,was less than 25 s·m -1 and would be close to the reaction resistance,1/k_C,approaching the end of combustion. So the effects of gas diffusion resistance through ash layer on char combustion process could be ignored during the whole combustion process.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.U1810126).
文摘Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content.Thus,effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigation.In this paper,the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke was measured directly using an improved Wicke-Kallenbach diffusion apparatus.The experimental results showed that higher temperature would lead to a higher effective diffusivity and a thicker ash layer had the negative effect.Especially,the effective diffusivity along the direction perpendicular to bedding planes was much lower than that along the direction parallel to bedding planes.In addition,an effective diffusivity model was developed,which could be used to describe the mass transfer of oxygen in the ash layer of oil shale semicoke.
基金Supported by National Key Technology Research and Development Program(2015BAC05B02)Fundamental Research Funds for the Central Universities(2018NZD10)
文摘[Objectives] The aim was to determine the moisture,ash and extract contents in Leontopodium franchetii Beauv. from different localities. [Methods] The contents of moisture,total ash,acid-insoluble ash and extract in L. franchetii from different localities were determined according to the methods described in Chinese Pharmacopoeia( 2015 Edition). [Results] In the 10 samples,the contents of moisture were all less than or equal to 15. 0%; the contents of total ash were all below 12. 0%; and the contents of acid-insoluble ash were all less than 3. 0%. The contents of water-soluble extract( by cold-soaked extraction method) in the samples were all below 12. 0% except those from Hongyuan Prairie of Sichuan Province and Xinglong Mountain in Lanzhou City,Gansu Province. [Conclusions]The contents of the four indicators measured in this experiment varied by small margins,indicating that the quality was relatively stable. This study provides theoretical data for the revision of the quality standards for L. franchetii.
文摘Monolayer barriers called evapotranspiration (ET) covers were developed as alternative final cover systems in waste landfills but high-quality soil remains a limiting factor in these cover systems. Coal bottom ash was evaluated to be a very good alternative to soil in previous tests and a combination of soil (65% wt.wt-1) and coal bottom ash (35% wt.wt-1) was evaluated to be the most feasible materials for ET cover systems. In our pot test, selected manure compost as soil amendment for the composite ET cover system, which was made of soil and bottom ash at ca. 40 Mg.ha-1 application level was very effective to promote vegetation growth of three plants;namely, garden cosmos (Cosmosbipinnatus), Chinese bushclover (Lespedezacuneata), and leafy lespedeza (Lespedeza cyrtobotrya). To evaluate the effect of compost application on plant growth in an ET vegetative cover system, two couples of lysimeters, packed with soil and a mixture of soil and bottom ash, were installed in a pilot landfill cover system in 2007. Manure composts were applied at the rates of 0 and ?40 Mg.ha-11before sowing the five plant species, i.e.indigo-bush (Amorphafruticosa), Japanese mugwort (Artemisia princeps, Arundinella hirta, Lespedezacuneata, and Lespedezacyrtobotrya). Unseeded native plant (green foxtail,Setaria viridis) was dominant in all treatments in the 1st year after installation while the growth of the sown plants significantly improved over the years. Total biomass productivity significantly increased with manure compost application, and more significantly increased in the composite ET cover made of soil and bottom ash treatment compared to the single soil ET cover, mainly due to more improved soil nutrient levels promoting vegetation growth and maintaining the vegetation system. The use of bottom ash as a mixing material in ET cover systems has a strong potential as an alternative to fine-grained soils, and manure compost addition can effectively enhance vegetative propagation in ET cover systems.
文摘A thermogravimetric method under constant temperature replacing the beginning inert gas with burning air was established in this study for determining the combustion kinetics of single char particle. The combustion process of three types of coals, Fujian Longyan coal, Fujian Yong’an coal and Shandong coal, with diameter of 3.0—4.5 mm, in thermobalance under 900℃ was discussed using the familiar shrinking-core model.While the combustion of single char approached the end, the outside and the ash layer diffusion resistances tend to be zero as the reaction resistance dominated in the total resistance of combustion.Therefore, at this stage the inherent oxidation reaction constant (k_R) of the above char samples were estimated by analyzing the total resistance of combustion.The good agreement of combustion reaction rate between data determined in this study and calculated values obtained from reference in the drop tube furnace system, implied that the inherent oxidation reaction constant (k_R) determined by the thermogravimetric method under constant temperature was satisfactory and valuable. The gas diffusion through the ash layer of char particle during combustion process was discussed also. At the ash layer thickness half the char radius, the ash layer resistance in the combustion process reached a maximum value, at which the total resistance of combustion,1/K,was less than 25 s·m -1 and would be close to the reaction resistance,1/k_C,approaching the end of combustion. So the effects of gas diffusion resistance through ash layer on char combustion process could be ignored during the whole combustion process.
