浅析燃气用埋地聚乙烯管材

介绍聚乙烯管材用于燃气输送管道的几个特点,分析目前燃气用埋地聚乙烯管材在实际使用过程中存在的几个问题.     

Ion Exchange Technology in Spent Fuel Reprocessing

Solvent extraction is the major unit operation employed in spent nuclear fuel reprocessing. The operation yields three streams; fission product waste, uranium product and plutonium product. Ion exchange is primarily used in reprocessing as a tail-end method to concentrate and isolate the plutonium product stream. This review will describe the details of plutonium recovery and purification by both cation- and anion-exchange processing. A brief overview of miscellaneous uses of ion-exchange employed in reprocessing will also be given.     

Constraints of fossil fuels depletion on global warming projections

A scientific debate is in progress about the intersection of climate change with the new field of fossil fuels depletion geology. Here, new projections of atmospheric CO₂ concentration and global-mean temperature change are presented, should fossil fuels be exploited at a rate limited by geological availability only. The present work starts from the projections of fossil energy use, as obtained from ten independent sources. From such projections an upper bound, a lower bound and an ensemble mean profile for fossil CO₂ emissions until 2200 are derived. Using the coupled gas–cycle/climate model MAGICC, the corresponding climatic projections out to 2200 are obtained. We find that CO₂ concentration might increase up to about 480 ppm (445–540 ppm), while the global-mean temperature increase w.r.t. 2000 might reach 1.2 °C (0.9–1.6 °C). However, future improvements of fossil fuels recovery and discoveries of new resources might lead to higher emissions; hence our climatic projections are likely to be underestimated. In the absence of actions of emissions reduction, a level of dangerous anthropogenic interference with the climate system might be already experienced toward the middle of the 21st century, despite the constraints imposed by the exhaustion of fossil fuels.     

Laminar burning velocity measurements of liquid fuels at elevated pressures and temperatures with combustion residuals

The laminar burning velocity is a fundamental property of a fuel that affects many aspects of its combustion behaviour. Experimental values are required to validate kinetic simulations, and also to provide input for models of flashback, minimum ignition energy and turbulent combustion.A constant volume vessel (rated at 3.4 MPa) in conjunction with a multi-zone model was used to calculate burning velocity from pressure and schlieren data, allowing the user to select data uncorrupted by heat transfer or cellularity. Using the pressure rise data allows measurements to be derived for much higher pressures and temperatures than when the constant pressure data are used. A 12 term correlation for burning velocity was fitted to the data.n-Heptane, iso-octane, toluene, ethylbenzene and ethanol were tested over a wide range of initial pressures (50, 100, 200 and 400 kPa), temperatures (310, 380 and 450 K) and equivalence ratios (0.7–1.4), along with tests using combustion residuals at mole fractions of up to 0.3. The results compared favourably with the limited data already published, especially at high pressures. Conditions at the onset of cellularity are given for iso-octane.     

Comparative Analysis of Synthetic Natural Gas versus Hydrogen Production from Bagasse

A rigorous and comparative evaluation of two biomass‐to‐gases (BtG) conversion routes was performed and, according to this outcome, it is suggested which of the options evaluated is most desirable. These options, the hydrogen and synthetic natural gas (SNG) production, were designed in Aspen Plus process simulation software. Sugar cane bagasse was considered as feedstock. Mass and energy balance data were extracted from the simulations, and consequently thermodynamic (exergy analysis), economic (financial and uncertainty analysis), and environmental (CO₂ emissions) evaluations were carried out. Exergy and environmental analysis favor the SNG production while the hydrogen route provides higher profits.     

Effect of water-based Al2O3 nanofluids on heat transfer and pressure drop in periodic mixed convection inside a square ventilated cavity

A numerical study of unsteady mixed convection flows through an alumina-water nanofluid in a square cavity with inlet and outlet ports due to incoming flow oscillation is performed. It is found that an oscillating velocity at the inlet port cased to creating a periodic variation in the fluid flow and temperature field in the cavity after a certain time duration. The influence of the nanoparticle on the flow and temperature fields has been plotted and discussed. The effect of the oscillation frequency is concealed in a dimensionless number which is the Strouhal number. It is observed that the heat transfer is enhanced for all the Strouhal and Richardson numbers investigated by adding the nanoparticle to the base fluid. It is also found that the performance of the nanoparticle on the enhancement of the heat transfer at higher Richardson numbers is less than that of lower Richardson numbers.     

Solar Light Photocatalytic CO2 Reduction: General Considerations and Selected Bench-Mark Photocatalysts

The reduction of carbon dioxide to useful chemicals has received a great deal of attention as an alternative to the depletion of fossil resources without altering the atmospheric CO₂ balance. As the chemical reduction of CO₂ is energetically uphill due to its remarkable thermodynamic stability, this process requires a significant transfer of energy. Achievements in the fields of photocatalysis during the last decade sparked increased interest in the possibility of using sunlight to reduce CO₂. In this review we discuss some general features associated with the photocatalytic reduction of CO₂ for the production of solar fuels, with considerations to be taken into account of the photocatalyst design, of the limitations arising from the lack of visible light response of titania, of the use of co-catalysts to overcome this shortcoming, together with several strategies that have been applied to enhance the photocatalytic efficiency of CO₂ reduction. The aim is not to provide an exhaustive review of the area, but to present general aspects to be considered, and then to outline which are currently the most efficient photocatalytic systems.     

Hydrocarbon Desulfurization to Clean Fuels by Selective Oxidation Versus Conventional Hydrotreating

Abstract

Environmental concerns have driven the need to remove sulfur-containing compounds to an extremely low level for transportation fuels. Conventional hydrodesulfurization catalysts can be used to remove a significant portion of the sulfur from petroleum distillates for the blending of refinery transportation fuels. Removing the last traces of sulfur compounds where the sulfur atom is sterically hindered, as in multi-ring aromatic sulfur compounds, is a significant challenge. One recent area of innovation to remove sulfur from upgraded crude is oxidative desulfurization, a process that can operate under mild conditions and without the need for external H₂. In this article, the mechanism, process, and the new inventions of selectively oxidative desulfurization are reviewed.     

Quantum-Chemical Calculation of Reactive Fuels as H-Acids

Abstract

The theoretical evaluation of acid strength reactive fuels, through quantum-chemical calculation by the method CNDO/2 of the charges on hydrogen atoms, which correlate with the universal index of acidity is presented. Correlations defining relationship of some parameters of combustion with the accounting parameters of acidic strength of the fuels are established to oxygen.