Olivine, one of the most abundant minerals existing in nature, is explored as a C02 carbonation agent for direct carbonation of C02 in flue gas. Olivine based C02 capture is thermodynamically favorable and can form a ...Olivine, one of the most abundant minerals existing in nature, is explored as a C02 carbonation agent for direct carbonation of C02 in flue gas. Olivine based C02 capture is thermodynamically favorable and can form a stable carbonate for long-term storage. Experimental results have shown that water vapor plays an important role in improving CO/carbonation rate and capacities. Other operation conditions including reaction temperature, initial C02 concentration, residence time corresponding to the flow rate of C02 gas stream, and water vapor concentration also considerably affect the performance of the technology.展开更多
We are experiencing the most drastic change in air quality in China. While the levels of ambient PM2.5 have been dropping in recent years, city clusters like Beijing-Tianjin-Hebei had frequent heavy haze episodes, and...We are experiencing the most drastic change in air quality in China. While the levels of ambient PM2.5 have been dropping in recent years, city clusters like Beijing-Tianjin-Hebei had frequent heavy haze episodes, and ground-level ozone keeps on going up. Therefore the emissions, meteorological and chemical processes are the key shaping the trends of air quality, and this special issue publishes 19 research and review articles addressing the progresses in understanding emissions, processes and health effects of air pollution.展开更多
Community Multi-Scale Air Quality （CMAQ） estimates of sulfates, nitrates, ammonium, and organic carbon are highly influenced by uncertainties in modeled secondary formation processes, such as chemical mechanisms, vo...Community Multi-Scale Air Quality （CMAQ） estimates of sulfates, nitrates, ammonium, and organic carbon are highly influenced by uncertainties in modeled secondary formation processes, such as chemical mechanisms, volatilization, and condensation rates. These compounds constitute the majority ofPM2.5 mass, and reducing bias in estimated concentrations has benefits for policy measures and epidemiological studies. In this work, a method for adjusting source impacts on secondary species is developed that provides estimates of source contributions and reduces bias in modeled concentrations compared to observations. The bias correction adjusts concentrations and source impacts based on the difference between modeled concentrations and observations while taking into account uncertainties at the location of interest; and it is applied both spatially and temporally. We apply the method over the US for 2006. The mean bias for initial CMAQ concentrations compared to observations is -0.28 （OC）, 0.11 （NO3）, 0.05 （NH4）, and -0.08 （SO4）. The normalized mean bias in modeled concentrations compared to observations was effectively zero for OC, NO3, NH4, and SO4 after applying the secondary bias correction. Ten-fold cross-validation was conducted to determine the performance of the spatial application of the bias correction. Cross-validation performance was favorable; correlation coefficients were greater than 0.69 for all species when comparing observations and concentrations based on kriged correction factors. The methods presented here address model uncertainties by improving simulated concentrations and source impacts of secondary particulate matter through data assimilation. Secondary-adjusted concentrations and source impacts from 20 emissions sources are generated for 2006 over continental US.展开更多
基金supported by the Caterpillar, Siemens,and the School of Energy Resource at University of Wyoming
文摘Olivine, one of the most abundant minerals existing in nature, is explored as a C02 carbonation agent for direct carbonation of C02 in flue gas. Olivine based C02 capture is thermodynamically favorable and can form a stable carbonate for long-term storage. Experimental results have shown that water vapor plays an important role in improving CO/carbonation rate and capacities. Other operation conditions including reaction temperature, initial C02 concentration, residence time corresponding to the flow rate of C02 gas stream, and water vapor concentration also considerably affect the performance of the technology.
文摘We are experiencing the most drastic change in air quality in China. While the levels of ambient PM2.5 have been dropping in recent years, city clusters like Beijing-Tianjin-Hebei had frequent heavy haze episodes, and ground-level ozone keeps on going up. Therefore the emissions, meteorological and chemical processes are the key shaping the trends of air quality, and this special issue publishes 19 research and review articles addressing the progresses in understanding emissions, processes and health effects of air pollution.
文摘Community Multi-Scale Air Quality （CMAQ） estimates of sulfates, nitrates, ammonium, and organic carbon are highly influenced by uncertainties in modeled secondary formation processes, such as chemical mechanisms, volatilization, and condensation rates. These compounds constitute the majority ofPM2.5 mass, and reducing bias in estimated concentrations has benefits for policy measures and epidemiological studies. In this work, a method for adjusting source impacts on secondary species is developed that provides estimates of source contributions and reduces bias in modeled concentrations compared to observations. The bias correction adjusts concentrations and source impacts based on the difference between modeled concentrations and observations while taking into account uncertainties at the location of interest; and it is applied both spatially and temporally. We apply the method over the US for 2006. The mean bias for initial CMAQ concentrations compared to observations is -0.28 （OC）, 0.11 （NO3）, 0.05 （NH4）, and -0.08 （SO4）. The normalized mean bias in modeled concentrations compared to observations was effectively zero for OC, NO3, NH4, and SO4 after applying the secondary bias correction. Ten-fold cross-validation was conducted to determine the performance of the spatial application of the bias correction. Cross-validation performance was favorable; correlation coefficients were greater than 0.69 for all species when comparing observations and concentrations based on kriged correction factors. The methods presented here address model uncertainties by improving simulated concentrations and source impacts of secondary particulate matter through data assimilation. Secondary-adjusted concentrations and source impacts from 20 emissions sources are generated for 2006 over continental US.
