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排序方式: 共有813条查询结果,搜索用时 46 毫秒
731.
During sequestration, carbon dioxide within injection wells is likely to be in a dense state and therefore its weight within the wellbore will play an important role in determining the bottomhole pressure and thus the injection rate. However, the density could vary significantly along the well in response to the variation in pressure and temperature. A numerical procedure is formulated in this paper to evaluate the flow of carbon dioxide and its mixtures in non-isothermal wells. This procedure solves the coupled heat, mass and momentum equations with the various fluid and thermodynamic properties, including the saturation pressure, of the gas mixture calculated using a real gas equation of state. This treatment is particularly useful when dealing with gas mixtures where experimental data on mixture properties are not available and these must be predicted. To test the developed procedure two wellbore flow problems from the literature, involving geothermal gradients and wellbore phase transitions are considered; production of 97% carbon dioxide and injection of superheated steam. While these are not typical carbon dioxide injection problems they provide field observations of wellbore flow processes which encompass the mechanisms of interest for carbon dioxide injection, such as phase transition, temperature and density variations with depth. These two examples show that the developed procedure can offer accurate predictions. In a third application the role of wellbore hydraulics during a hypothetical carbon dioxide injection application is considered. The results obtained illustrate the potential complexity of carbon dioxide wellbore hydraulics for sequestration applications and the significant role it can play in determining the well bottomhole pressure and thus injection rate.  相似文献   
732.
Large-scale injections of CO2 into subsurface saline aquifers have been proposed to remediate climate change related to buildup of green house gases in the atmosphere. The pressure buildup caused by such injections may impact a volume of the basin significantly larger than the CO2 plume itself. In areas with hydrological settings similar to the Gulf Coast Basin, the perturbation of the flow-field in deep parts of the basin could result in brines or brackish water being pushed up-dip into unconfined sections of the same formations or into the capture zone of fresh-water wells. The premise of the current study is that the details of multiple-phase flow processes necessary to model the near field evolution of the CO2 plume are not necessary to describe the impact of the pressure anomaly on up-dip aquifers. This paper quantitatively explores conditions under which shallow groundwater would be impacted by up-dip displacement of brines, utilizing an existing carefully calibrated flow model. Modeling an injection of water, arguably equivalent to 50 million tons of CO2/year for 50 years resulted in an average water-table rise of 1 m, with minor increase in stream baseflow and larger increase in ground water evapotranspiration, but no significant change in salinity.  相似文献   
733.
Reservoir monitoring improves our understanding of reservoir behaviour and helps achieve more effective reservoir management and prediction of future performance with obvious economic benefits. It relies on an integrated approach involving both surveillance (well or surface based; seismic, electrical, leakage, flow and deformation measurements, etc.) and modelling. Surface deformation monitoring can provide valuable constraints on the dynamic behaviour of a reservoir enabling the evaluation of volumetric changes in the reservoir through time. Levelling campaigns, tiltmeters, GPS permanent stations and Permanent Scatterer SAR Interferometry (PSInSAR™) are the techniques most widely used to determine surface displacements. Whatever the surveying technique, the detection of millimetre-level surface deformation is required to monitor small surface displacement rates that could impact risk evaluation and land use planning. Depending on depth and reservoir/overburden rheology, volumetric changes in reservoirs due to fluid extraction and injection can induce either subsidence or uplift that could trigger fault reactivation and threaten well integrity; deformation may also be detectable at the surface. Mapping surface effects accurately requires hundreds of observation points per km2 which cannot be delivered by traditional monitoring methods without unacceptably large expenditure. PSInSAR™ is one of the most promising and cost-effective techniques capable of providing high precision and high areal density displacement measurements over long periods of time. Moreover, the availability of PS data for both ascending and descending orbits enables the estimation of both vertical and E–W horizontal displacement fields. Two case histories will be presented to illustrate the advantages of PSInSAR™ technology for the detection of surface deformation induced by reservoir exploitation and monitoring of its evolution though time.  相似文献   
734.
Chen X  Xia X  Wang X  Qiao J  Chen H 《Chemosphere》2011,83(10):1313-1319
Perfluorooctane sulfonate (PFOS), as one of emerging contaminants, has been attracting increasing concerns in recent years. Sorption of PFOS by maize straw- and willow-derived chars (M400 and W400), maize straw-origin ash (MA) as well as three carbon nanotubes (CNTs) was studied in this work. The sorption kinetics of PFOS by the six adsorbents was well fitted by the pseudo-second-order model. CNTs reached equilibrium in 2 h, much faster than those by chars (384 h) and ash (48 h). According to the sorption isotherms, both single-walled carbon nanotubes (SWCNT) and MA had high sorption capacities (over 700 mg g−1), while the two chars had low sorption capacities (below 170 mg g−1) caused by their small BET surface area. In the case of MA, due to its positively charged surface, both hydrophobic interaction and electrostatic attraction involved in the sorption, and the formation of hemi-micelles further favored the sorption. This study suggested that SWCNT and MA were effective adsorbents for PFOS removal from water. Compared to SWCNT, MA is low cost and easy to obtain, so it could be a preferred adsorbent for PFOS removal.  相似文献   
735.
Ye F  Peng G  Li Y 《Chemosphere》2011,84(9):1250-1255
It is necessary to understand the bioflocculation, settling and dewatering characteristics in the activated sludge process in order to establish more efficient operational strategies. The influences of carbon source on the extracellular polymeric substances (EPS) and flocculation, settling and dewatering properties of the activated sludge were investigated. Laboratory-scale completely mixed activated sludge processes were used to grow the activated sludge with different carbon sources of starch, glucose and sodium acetate. The sludge fed with acetate had highest loosely bound EPS (LB-EPS) and that fed with starch lowest. The amount of tightly bound EPS (TB-EPS), protein content in LB-EPS, polysaccharide content and protein contents in TB-EPS, were independent of the influent carbon source. The polysaccharide content in LB-EPS of the activated sludge fed with sodium acetate was lower slightly than those of starch and glucose. The sludge also had a nearly consistent flocs size and the sludge volume index (SVI) value. ESS content of the sludge fed with sodium acetate was higher initially, although it was similar to those fed with glucose and starch finally. However, the specific resistance to filtration and normalized capillary suction time fluctuated first, but finally were stable at around 5.0 × 108 m kg−1 and 3.5 s L g−1 SS, respectively. Only the protein content in LB-EPS weakly correlated with the flocs size and SVI of the activated sludge. But there was no correlation between any other EPS contents or components and the physicochemical properties of the activated sludge.  相似文献   
736.
Synthetic nanoparticles have already been detected in the aquatic environment. Therefore, knowledge on their biodegradability is of utmost importance for risk assessment but such information is currently not available. Therefore, the biodegradability of fullerenes, single, double, multi-walled as well as COOH functionalized carbon nanotubes and cellulose and starch nanocrystals in aqueous environment has been investigated according to OECD standards. The biodegradability of starch and cellulose nanoparticles was also compared with the biodegradability of their macroscopic counterparts. Fullerenes and all carbon nanotubes did not biodegrade at all, while starch and cellulose nanoparticles biodegrade to similar levels as their macroscopic counterparts. However, neither comfortably met the criterion for ready biodegradability (60% after 28 days). The cellulose and starch nanoparticles were also found to degrade faster than their macroscopic counterparts due to their higher surface area. These findings are the first report of biodegradability of organic nanoparticles in the aquatic environment, an important accumulation environment for manmade compounds.  相似文献   
737.
Chen Z  Li Y  Wen Q  Zhang H 《Chemosphere》2011,82(8):1209-1213
The production of copolymers of poly-β-hydroxyalkanoates (PHA) is generally a high cost process. To reduce the production costs, inexpensive carbon sources such as volatile fatty acids (VFAs) from acidified wastewater can be used. Therefore, isolation of bacterial strains that can produce PHA copolymers using VFAs as a sole carbon source would be a beneficial alternative. In this study, a strain of PHA accumulating bacterium was isolated from the wastewater treatment plant of a soybean processing facility in Harbin. The strain was identified as γ-proteobacterium according to its 16S rDNA information and was originally named as strain WD-3. The strain accumulated a mass of PHA up to 45% of its dry cell weight when it was cultured under the optimum fermentation condition in this study when butyrate was used as the carbon source. In addition, WD-3 could synthesize PHA copolymers of poly-hydroxybutyrate and poly-hydroxyvalerate (PHV) either from C-even substrates or from C-odd substrates, and one-third of the copolymer was PHV. Results from this study demonstrated that small molecule organic acids can be used by the strain of WD-3 as the carbon source for growth and PHA production. The maximum PHA yield in the study was 0.45 g g−1 dry cell.  相似文献   
738.
Carbon dioxide capture and storage (CCS) involves the capture of CO2 at a large industrial facility, such as a power plant, and its transport to a geological (or other) storage site where CO2 is sequestered. Previous work has identified pipeline transport of liquid CO2 as the most economical method of transport for large volumes of CO2. However, there is little published work on the economics of CO2 pipeline transport. The objective of this paper is to estimate total cost and the cost per tonne of transporting varying amounts of CO2 over a range of distances for different regions of the continental United States. An engineering-economic model of pipeline CO2 transport is developed for this purpose. The model incorporates a probabilistic analysis capability that can be used to quantify the sensitivity of transport cost to variability and uncertainty in the model input parameters. The results of a case study show a pipeline cost of US$ 1.16 per tonne of CO2 transported for a 100 km pipeline constructed in the Midwest handling 5 million tonnes of CO2 per year (the approximate output of an 800 MW coal-fired power plant with carbon capture). For the same set of assumptions, the cost of transport is US$ 0.39 per tonne lower in the Central US and US$ 0.20 per tonne higher in the Northeast US. Costs are sensitive to the design capacity of the pipeline and the pipeline length. For example, decreasing the design capacity of the Midwest US pipeline to 2 million tonnes per year increases the cost to US$ 2.23 per tonne of CO2 for a 100 km pipeline, and US$ 4.06 per tonne CO2 for a 200 km pipeline. An illustrative probabilistic analysis assigns uncertainty distributions to the pipeline capacity factor, pipeline inlet pressure, capital recovery factor, annual O&M cost, and escalation factors for capital cost components. The result indicates a 90% probability that the cost per tonne of CO2 is between US$ 1.03 and US$ 2.63 per tonne of CO2 transported in the Midwest US. In this case, the transport cost is shown to be most sensitive to the pipeline capacity factor and the capital recovery factor. The analytical model elaborated in this paper can be used to estimate pipeline costs for a broad range of potential CCS projects. It can also be used in conjunction with models producing more detailed estimates for specific projects, which requires substantially more information on site-specific factors affecting pipeline routing.  相似文献   
739.
Estimates of forest soil organic carbon (SOC) have applications in carbon science, soil quality studies, carbon sequestration technologies, and carbon trading. Forest SOC has been modeled using a regression coefficient methodology that applies mean SOC densities (mass/area) to broad forest regions. A higher resolution model is based on an approach that employs a geographic information system (GIS) with soil databases and satellite-derived landcover images. Despite this advancement, the regression approach remains the basis of current state and federal level greenhouse gas inventories. Both approaches are analyzed in detail for Wisconsin forest soils from 1983 to 2001, applying rigorous error-fixing algorithms to soil databases. Resulting SOC stock estimates are 20% larger when determined using the GIS method rather than the regression approach. Average annual rates of increase in SOC stocks are 3.6 and 1.0 million metric tons of carbon per year for the GIS and regression approaches respectively.  相似文献   
740.
Wang L  Wang S  Yuan Q 《Chemosphere》2007,69(11):1689-1694
A mathematical model describing the rate of carbon disulfide (CS2) removal due to coupled reactions has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and a range of temperatures (85–125 °C). The effects of flow rate, CS2 inlet concentration, temperature and relative humidity were analyzed. A kinetic model based on axial dispersion, external and internal mass-transfer resistances, as well as effects of S deposition on the inner-face of the catalyst was in agreement with the CS2 experimental breakthrough curves. The mathematical model can be used for process design and scale up of similar systems.  相似文献   
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