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341.
Carl Linderholm Alberto Abad Tobias Mattisson Anders Lyngfelt 《International Journal of Greenhouse Gas Control》2008,2(4):520
Chemical-looping combustion, CLC, is a technology with inherent separation of the greenhouse gas CO2. The technique uses an oxygen carrier made up of particulate metal oxide to transfer oxygen from combustion air to fuel. In this work, an oxygen carrier consisting of 60% NiO and 40% NiAl2O4 was used in a 10 kW CLC reactor system for 160 h of operation with fuel. The first 3 h of fuel operation excepted, the test series was accomplished with the same batch of oxygen carrier particles. The fuel used in the experiments was natural gas, and a fuel conversion to CO2 of approximately 99% was accomplished. Combustion conditions were very stable during the test period, except for the operation at sub-stoichiometric conditions. It was shown that the methane fraction in the fuel reactor exit gas was dependent upon the rate of solids circulation, with higher circulation leading to more unconverted methane. The carbon monoxide fraction was found to follow the thermodynamical equilibrium for all investigated fuel reactor temperatures, 660–950 °C. Thermal analysis of the fuel reactor at stable conditions enabled calculation of the particle circulation which was found to be approximately 4 kg/s, MW. The loss of fines, i.e. the amount of elutriated oxygen carrier particles with diameter <45 μm, decreased during the entire test period. After 160 h of operation the fractional loss of fines was 0.00022 h−1, corresponding to a particle life time of 4500 h. 相似文献
342.
CO2 transportation for carbon capture and storage: Sublimation of carbon dioxide from a dry ice bank
Alberto Mazzoldi Tim Hill Jeremy J. Colls 《International Journal of Greenhouse Gas Control》2008,2(2):210-218
Climate change is being caused by greenhouse gases such as carbon dioxide (CO2). Carbon capture and storage (CCS) is of interest to the scientific community as one way of achieving significant global reductions of atmospheric CO2 emissions in the medium term. CO2 would be captured from large stationary sources such as power plants and transported via pipelines under high pressure conditions to underground storage. If a downward leakage from a surface transportation system module occurs, the CO2 would undergo a large temperature reduction and form a bank of “dry ice” on the ground surface; the sublimation of the gas from this bank represents an area source term for subsequent atmospheric dispersion, with an emission rate dependent on the energy balance at the bank surface. Gaseous CO2 is denser than air and tends to remain close to the surface; it is an asphyxiant, a cerebral vasodilator and at high concentrations causes rapid circulatory insufficiency leading to coma and death. Hence a subliming bank of dry ice represents safety hazard. A model is presented for evaluating the energy balance and sublimation rate at the surface of a solid frozen CO2 bank under different environmental conditions. The results suggest that subliming gas behaves as a proper dense gas (i.e. it remains close to the ground surface) only for low ambient wind speeds. 相似文献
343.
Waste management strategies in mining projects will depend to a large extent on the characteristics of the operational process, the type of ore and prevailing socio-environmental conditions, amongst other issues. The expenditures required by the management scheme and the implementation of remediation programs will be determined by the extent that the above issues were considered in the planning phase of the project. Several works have been published in the literature concerning the analysis of waste management programs and environmental impacts associated with uranium projects around the world. However, the vast majority do not report a comprehensive assessment integrating the various relationships among operational process, environmental impact, remediation strategy and costs. This study, divided into two papers, presents a detailed critical analysis of the waste management strategies adopted in two uranium production centres in Brazil, i.e., the Poços de Caldas Project (Part I) and the Caetité Project (Part II). The operational processes are described and the environmental impacts of the generated wastes as well as the adopted management strategies and costs are examined. Also, in Part II, a comparison between both production centres is made emphasizing the impacts of environmental and social-economical issues on the overall assessment. 相似文献
344.
Biodegradation of oxygenated and non-oxygenated imidazolium-based ionic liquids in soil 总被引:1,自引:0,他引:1
Aerobic biodegradation of ionic liquids in soil was monitored for the first time. The tests, followed over six months according to ASTM D 5988-96, were carried out on the four ionic liquids obtained from 1-R-3-methylimidazolium cations, with R=CH(3)(CH(2))(3) and CH(3)O(CH(2))(2), and the tetrafluoroborate and dicyanamide counter anions. The n-butyl derivatives, after an induction period of about two months, were found to be degradable, although the degradation rate with the dicyanamide anion was smaller. In contrast, no significant production of CO(2) was observed in the tests with the methoxyethyl derivatives. Calculations at the B3LYP/6-31G(d) level were carried out to characterize the atomic charge distributions and frontier orbital structures of 1-alkyl-3-methylimidazolium cations and point out the changes caused by replacement of a CH(2) group of the alkyl chain with an oxygen atom. The calculations predict an overall negative charge on the nitrogen atoms of the imidazolium-based cations. The energies of the highest occupied (pi) MO and lowest empty (pi( *)) MO are only slightly perturbed by the length and nature of the alkyl chain. However, the electron-donor properties of the oxy derivatives are radically increased. The HOMO becomes a lone pair orbital mainly localized on the oxygen atom, and its ionization energy is sizeably smaller than that of the outermost ring pi MO. 相似文献
345.
346.
Cadle SH Ayala A Black KN Graze RR Koupal J Minassian F Murray HB Natarajan M Tennant CJ Lawson DR 《Journal of the Air & Waste Management Association (1995)》2008,58(1):3-11
The Coordinating Research Council, Inc. (CRC) held its 17th On-Road Vehicle Emissions Workshop in March 2007, where results of the most recent on-road vehicle emissions research were presented. We summarize ongoing work from researchers who are engaged in improving our understanding of the role and contribution of mobile sources to ambient air quality and emission inventories. Participants in the Workshop discussed efforts to improve mobile source emission models, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as emerging issues and topics for future research. 相似文献
347.
Rosa María Pérez-Pastor Susana García-Alonso Alberto José Quejido Cabezas 《Environmental science and pollution research international》1999,6(3):141-146
From November 1995 to October 1996, airborne concentrations of VOCs were measured in the Madrid area to study the organic
pollution in general, and the correlation between different pollutants in relation to such parameters as location and season.
Mean concentrations for up to 90 compounds were measured at four test sites, including both urban and suburban areas.
At the urban sites, maximum concentrations occurred in the autumn and winter, whereas minimum concentrations were reached
in summer and spring. Similar changes were obtained for the lesscontaminated site located in the SE of the city, whereas a
different pattern was found at the site in the NW of the city due to meteorological aspects. Mean levels of hydrocarbons in
Madrid were quite similar to those found in other European cities.
Chemometrical techniques were applied to the set of data in order to assess the influence of such factors as traffic, temperature
and seasonal variations on the VOC levels. 相似文献
348.
Calvo-Iglesias MS Fra-Paleo U Crecente-Maseda R Díaz-Varela RA 《Environmental management》2006,38(6):921-933
The aim of this work is the analysis of the dynamics in cultural landscapes, focused on the spatial distribution of changes
in land cover and landscape patterns, and their possible linkages. These dynamics have been analyzed for the years 1957 and
2000 in a sector of the north of Galicia (NW Spain) characterized with diverse landscapes. Afforestation processes linked
to agriculture abandonment and forestry specialization were the main processes observed in the study area, with the exception
of the southern mountainous sector that was dominated by ploughing of scrubland for conversion into grassland, reflecting
a specialization in livestock production. The structural changes that have taken place in most of the study area were related
to the heterogeneity aspects, although the mountainous sectors were characterized by changes in heterogeneity and fragmentation.
According to the tests performed, the comparison of the spatial distribution of both dynamics showed a certain statistical
significance, reflecting the interrelationship between patterns and processes. This approach could be useful for the identification
of areas with similar characteristics in terms of spatial dynamics so as to define more effective and targeted landscape planning
and management strategies. 相似文献
349.
A waterhyacinth (Eichhornia crassipes) marsh occupying two-thirds of the basin of a small Florida impoundment has received sewage effluent for nearly 20 years. Water from the marsh flows into an area that is maintained free of waterhyacinths, and is discharged through wells at the far end of the impoundment. A water budget for the basin was estimated, and phosphorus concentrations were measured monthly at three stations in the marsh and at the discharge wells in the lake. Productivity levels were measured monthly where the marsh joins the lake and at the discharge wells. Only 16% of the phosphorus that enters the basin is stored. Gross primary productivity levels in the open-water areas are very high (22 gO2m2day), but high respiration rates appear to keep the lake in steady-state. 相似文献
350.
Clinio Locatelli Alberto Astara Ermanno Vasca Vincenzo Campanella 《Environmental monitoring and assessment》1999,58(1):23-37
In this present work the distribution of heavy metals in sea water and sediments of the Salerno Gulf is measured. The elements determined were Cu, Pb, Cd, Zn and Hg, employing, as instrumental techniques, either differential pulse anodic stripping voltammetry (DPASV) or graphite furnace atomic absorption spectroscopy (GFAAS). A comparison of the results of the two analytical techniques is also made. Mercury determination was carried out employing the cold vapour atomic absorption spectroscopy (CVAAS) technique, with SnCl2 as the reducing agent. The sample digestion was performed by a new procedure using concentrated suprapure H2SO4–K2Cr2O7 mixture. The accuracy and precision of the analytical procedure were evaluated employing Sea Water BCR-CRM 403 and Estuarine Sediment BCR-CRM 277 as reference materials. Accuracy, expressed as relative error e and precision, expressed as relative standard deviation sr, were in order of 2 to 5%. For both matrices, the detection limits, for all the elements, were in the range g g-1 to ng g-1. 相似文献