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关键词： ECIME fluidized-bed   Copper removal   Electrodeposition   Enhanced mechanism   Reaction model  

摘要： For the purification of heavy metal wastewater, internal micro-electrolysis (IME) was considered as an effective method but some disadvantage greatly restricts its application. Electrocatalytic internal micro-electrolysis (ECIME) fluidized bed using iron-carbon particles was proposed to avoid disadvantaging of IME. The principal aim of this study was to investigate the enhanced removal characteristics, mechanism, and kinetic behavior of Cu(II) that none clear before. ECIME reactor shows a better copper removal performance and depends much on the polarization of the external electric field (EEF). Both the reaction rate and removal efficiency of copper electrodeposition improved obviously. Noteworthy is more than 88.0% of Cu(II) in aqueous solutions was removed by enhanced electrodeposition, and only about 10.0% of Cu(II) was absorbed and flocculated through the in situ formed iron hydroxyl compounds. Through scanning electron microscopy (SEM) and electrochemical analysis, copper can effectively electrodeposition on the surface of iron-carbon particles in ECIME reactor and accordingly the enhanced mechanisms were proposed. 1) Iron-carbon particles of ECIME formation of microelectrodes with high surface potential, larger specific area, and active sites through electrode collision and repolarization. 2) Copper electrodeposition on the formed microelectrodes exhibited greater reduction peak potential, reaction overpotential and exchange current density, which influenced by the polarization voltage significantly. 3) The electrocatalytic environment tend to in situ generate iron polymer hydroxyl compounds help to further remove residual Cu(II). ECIME fluidized-bed has promised potential for heavy metal containing wastewater purification and metal recovery. In addition, the proposed reaction models will be useful for field application. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Fluidized beds  

摘要： In this paper, a 3D two-phase simulation involving the complex heat transfer characteristics within a vertical cylindrical fluidized bed was conducted numerically. The accuracy of mathematical modeling has been validated by comparing with the experimental results. The discrete ordinate model (DOM) was employed to investigate the radiation heat transfer in a fluidized bed. The user-defined function (UDF) was compiled by considering the effect of the particle flow emissivity on radiation heat transfer, and coupled the two-phase flow field by using the gray and non-gray model respectively. The results show that the non-gray model can better depict the selected absorption of radiation wavelength in two-phase flow heat transfer than gray model. Furthermore, under high heat flux density conditions, the proportion of radiation heat transfer increases gradually with the increase of heat flux, which can reach about 40% of the total heat transfer coefficient. Meanwhile, other factors about radiation heat transfer such as initial solid packing height, inlet gas velocity, and other conditions were studied and consistent with the thermal experimental regularity. The findings demonstrated that the radiation heat transfer and it's modeling play an important role in two-phase heat transfer of fluidized bed.

关键词： Rotors   Shock absorbers   Bars   Windings   Synchronous motors   Induction motors   Circuit faults   Air gap flux   damper bar   fault diagnostics   field winding   off-line testing   salient pole synchronous motor (SM)   search coil   spectral analysis   starting transient  

摘要： Recent cases of broken damper bars and shorted field winding turns in synchronous motors (SMs) have shown that rotor faults can degrade motor performance and lead to a forced outage of the motor and driven process. However, detection of SM rotor faults has not received much attention since SMs are not as common as induction motors. Detection of SM rotor faults is difficult, as the damper bar is active only under the starting or load transients, and shorted field winding turns result only in a slight increase in rotating asymmetry. SM rotor fault testing in the field mainly relies on visual inspection or off-line tests, and new test methods that can provide reliable detection of the faults without motor disassembly is highly desirable. In this article, new test methods for not only detecting, but also classifying the two types of SM rotor faults under motor standstill and starting are proposed. A finite element and experimental study on 1.1 MW and 30 kW salient pole SMs are provided to verify the proposed methods. It is shown that damper and field winding faults can be detected and classified with high sensitivity and reliability compared to conventional tests.

关键词： Binary mixture   Biomass   Fast pyrolysis   Fluidization   Mixing   Separation  

摘要： To guarantee the uniform mixing of biomass and inert particles in the fluidized bed reactor for the full and complete reaction during the biomass fast pyrolysis process, a visualized cold fluidized bed experimental apparatus was set up to investigate the effects of static bed height, moisture content and particle diameter on the fluidization quality of single component particles, and the mixed volume ratio on the fluidization characteristics of binary mixtures. The results showed that the appropriate static bed height was significant for the stability of the fluidized bed. As the moisture content increased, the minimum fluidization velocity increased rapidly while the fluidization index continued to decrease. In addition, the fluidization performed on binary mixtures of larch/quartz sand-2 indicated that the same minimum fluidization velocity was the key parameter for the two kinds of particles to be fully fluidized simultaneously, avoiding the semi-fluidization phenomenon. The mixed volume ratio of larch (M = 10.3%)/quartz sand-2 and superficial gas velocity range were also the important factors affecting fluidization and mixing quality, and the optimal value were 1: 3 and 3-5 u(mf), respectively.

关键词： Liquid-containing gas-solid fluidized bed reactor (LC-GSFBR)   Liquid content   Surface tension   Fluidization characteristics   Stagnation zone  

摘要： The fluidization process within gas-solid fluidized bed reactor can be intensified by adding liquid, as it can enhance mass and heat transfer between gas phase and solid phase. With the help of computational fluid dynamics(CFD) and discrete element methods(DEM), fluidization characteristics are investigated at different liquid contents((V) over cap) and surface tension(Bo(g)). To be specific, the bed expansion ratio, particle concentration and particle velocity profiles are compared and analyzed. Numerical simulations show that Bo(g) should be less than 5 at (V) over cap = 0.013. At this recommended range, liquid addition makes interparticle force increase and has little effect on fluidization performance. From transient particle agglomeration behavior, the Bo(g) increase is more likely to enhance interparticle force, resulting in obvious particle agglomerations during fluidization process. The variation of stagnation zone height can be reflected from the abrupt increase of particle velocity in annulus region. It can be found that (V) over cap increase reduces particle velocity at critical height but Bo(g) increase is more likely to cause larger stagnation region. By analyzing the distribution of spout, annulus and fountain regions at different (V) over cap and Bo(g), the annulus region expands with (V) over cap increase below the initial bed height while the spout region expands with Bo(g) increase.

关键词： Turbo air classifier   Rotor cage's outer and inner radii   The width of annular region   Numerical simulation of flow field   Classification performance  

摘要： The effects of rotor cage's outer and inner radii on flow field of the turbo air classifier are comparatively analyzed by numerical simulation using ANSYS-FLUENT. The results of quantitative analysis show when the rotor cage's outer and inner radii are increased, the tangential velocity, radial velocity and upward axial velocity decrease in the annular region and near the entrance of the rotor cage. However, when the rotor cage's outer and inner radii are too large or too small, the tangential velocity and radial velocity will be fluctuated greatly. Moreover, the rotor cage's outer and inner radii directly influence the radial velocity distribution in the rotor cage channel. The rotor cage's outer and inner radii should not be too large or too small. Therefore, in the seven contrast rotor cage models, model 100-70 and 90-60 are selected to carry out the calcium carbonate classification experiments due to their small tangential velocity and radial velocity fluctuations and well-distribution in the rotor cage channel. The experimental results reflect the characteristics of the numerically simulated flow field in the classifier.

关键词： Oil and Gas well leakage   Primary cementing   Herschel-Bulkley fluid   Displacement flow  

摘要： We develop a simplified approach to predicting the displacement front behaviour of two Herschel-Bulkley fluids displacing one another along a narrow eccentric annulus in turbulent and mixed regimes. The approach involves the use of scaling arguments to reduce the full system of equations to a single hyperbolic equation that models the displacement front evolution. Analysis of the flux function is sufficient to predict whether or not the front will elongate along the annulus. Predictions of the simplified model are compared with a two-dimensional annular displacement model, showing good predictive abilities. The underlying eccentric annular flow is important in the industrial process of primary cementing. More specifically, the proposed method is aimed to provide a quick and reliable computational framework for analyzing primary cementing flows, leading to more successful cementing designs. (C) 2020 Elsevier Ltd. All rights reserved.

摘要： The thesis aims to address two main questions regarding certain features of liquidity-based asset classification. A first question is about the validity of such a classification: Does liquidity-based asset classification pick out a natural kind? I use the case of the category 'liquid assets' to show that liquidity is a functional property that can be realized in two genuinely different ways: monetary trades and credit trades. Accordingly, 'liquid assets' can be regarded as a functional kind with multiple realizations. I also argue that the kind 'liquid assets' earns its credential of natural kind by playing an epistemic role in explanatory economic models. I finally point out that mind-dependence does not threaten realism about the kind 'liquid assets'. The second question is about the extension of the categories resulting from liquidity-based asset classification: Is there a sharp boundary between categories of assets that are classified based on their liquidity? I use the case of 'money' to discuss if it is possible to find an unambiguous distinction between the categories 'money' and 'non-money.' I argue that such a view can be successful only, if following traditional essentialism, there is a set of intrinsic properties that are necessary and sufficient for membership in the natural kind designated by the term 'money.' However, based on what is currently known by monetary economists, there is neither set of intrinsic properties nor necessary and sufficient characteristics that one could use to separate 'money' unambiguously from 'non-money.'

关键词： 桩群   阻力特性   排列方式   数值模拟  

摘要： 本文采用FLUENT软件,选择RNG k-ε模型及Simplec算法,对桩群绕流问题进行数值模拟,研究不同桩数及排列方式下的桩群阻力特性及阻流效果。