Mapping of diesel soot regeneration behaviour in catalysed silicon carbide filters

A range of different soot regeneration conditions has been explored using laboratory scale catalysed soot filters, loaded on a state-of-the-art common rail diesel engine. The concurrent effect of oxygen feed rate (manageable both by flow rate and by oxygen concentration) and of heat removal, strictly linked to exhaust flow rate and temperature, was investigated. It has been observed that oxygen plays a major role in defining the oxidising reaction rate and determining possibly dangerous thermal peaks. Nevertheless, especially at high flow rate, the heat removal capability of the gas flow significantly increases the differences between the reaction behaviour at different oxygen contents.     

The influence of humidity on dry separation of granular particles based on geometrical characteristics

The influence of atmospheric humidity on dry separation of particles was experimentally investigated, making use of the difference in particle motion on an inclined wall, due to different geometrical characteristics. Using a tilted rotating cylinder with blades, glass beads with size and shape distributions were separated according to their geometrical characteristics under various levels of humidity. Fractional recovery of particles is discussed in relation to shape and size of particle and humidity. An angle of repose of the particles was also measured in order to determine the influence of adhesion force, which is closely related to humidity.Glass beads were separated predominantly based on their shape characteristics. Fractional recovery of particles changes strongly around a relative humidity of 60-70%, at which point the angle of repose also changes markedly. The influence of interaction between particles, which becomes significant for smaller particles, was found to reduce the fractional recovery and diminish the influence of humidity.     

Realistic modelling of the behaviour of fibrous filters through consideration of filter structure

A new model is proposed to describe the effects of structural inhomogeneities in fibrous filters on pressure drop and particle collection. The filter is subdivided into a series of elements with different structural characteristics, defined by local directionally-dependent permeabilities, and the resulting three-dimensional flow field is calculated. Using published relationships, local particle collection is calculated. Spatially nonhomogeneous fibre distribution is shown to play a dominant role. The difference in fibre collection efficiency between a real and a homogeneous filter depends on the dominant mechanism transporting particles to the fibres. In the interception-inertia range, the predictions are verified quantitatively by measurements on industrial filters with characterised structure.     

One-step fabrication of superhydrophobic and superoleophilic cigarette filters for oil-water separation

To develop a simple and efficient way to recycle used cigarette filters, we report on a one-step method for preparing superhydrophobic and superoleophilic cigarette filters for oil–water separation. The robust coating layer on the surface of the cellulose acetate fiber, along with the inherent rough texture of the cigarette filter, could lead to its surface that displayed superhydrophobicity and superoleophilicity. Water droplets can retain in spherical shapes on the modified cigarette filters, while oils were immediately absorbed by the cigarette filters with high absorption capacity. As a result, free oil–water mixtures were separated with efficiency of above 98.0% by the driving force of gravity, and water-in-oil emulsion was also separated with a promising flux of about 2500 L m^?2 h^?1. The purity of oil for the tested emulsion was above 99.96%, indicating extremely high separation efficiency. This method for the fabrication of the superhydrophobic and superoleophilic cigarette filters would be a good candidate for recycling the solid wastes and developing an economic oil–water separation material to meet emerging needs in practical applications.     

A polypropylene melt-blown strategy for the facile and efficient membrane separation of oil-water mixtures

Porous materials with selective wettability and permeability have significant importance in oil-water separation, but complex fabrication processes are typically required to obtain the desired structures with suitable surface chemistry. In this work, an industrial melt-blown strategy that utilized commercially available polypropylene (PP) was used for the large-scale fabrication of superhydrophobic/superoleophilic membranes with staggered fabric structures. These membranes could readily separate different oils including pump oil and crude oil from various aqueous solutions such as strongly acidic, alkaline, and saline media. In addition, the separation efficiencies of these membranes exceeded 99%, and they could remain functional even after exposure to corrosive media. We anticipate that this work will further the design of membranes and enhance their applicability in oil-water separation, and provide researchers and engineers with a more effective tool for performing challenging separations and mitigating pollution.     

Chemical strategy for tuning the surface microstructures of particles

Particles with tailored surface microstructures exhibit unique structure-dependent phenomena and subsequent utilization of them for the practical applications are of significant interest. In this work, we have developed some potential chemical strategies to tune the surface microstructures of functional materials, such as hollow ZnO microspheres, semiconductor films or arrays, LiNbO₃ spheres, and cubic phase Cu₂O particles. We describe their surface microstructure-guiding processes and illustrate the detailed key factors controlling their growth by examining various reaction parameters. The proposed surface structure-guiding mechanisms are presented and the important pioneering studies on the rational design and fabrication of particles with tunable surface microstructures are discussed. Current results demonstrate that our suggested chemical strategies for tuning surface microstructures of particles can be used as a versatile and effective route to the controllable synthesis of other inorganic functional materials.     

Influence of ultraviolet absorbers on the ultraviolet-irradiation behaviour of rigid poly vinyl chloride

The effects of ultraviolet absorbers (UVAs) on the UV-irradiation behaviours of rigid PVC were studied through Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. In addition, the absorption behaviours of these UVAs in non-polar and polar solvents were characterised and the solution photolysis experiments of these UVAs in ethanol were investigated in the absence and presence of a free radical initiator during the UV irradiation. The results showed that the protection efficiency to photo-degradation of PVC was in the following order: 2,4,6-tri(2-hydroxy-4-butoxylphenyl)-1,3,5-triazine (U3)?>?2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methyl phenol (U2)?>?2-hydroxy-4-n-octoxy-benzophenone (U1). This protection efficiency was related to the chemical structures of the UVAs, especially the intermolecular hydrogen bond (IMHB). In a polar solution, such as dimethyl sulfoxide, the absorption corresponding to the IMHB of U3 was intact, while that of U1 disappeared. The free radical initiator weakened the intensity of the absorption, accelerating the destruction of the IMHB.     

管道渗流对表层土壤影响的数值模拟

采用有限容积法建立埋地管道泄漏多孔介质流固耦合相变数学模型,对油品管道下侧泄漏进行压力场和体积分数的数值模拟。研究表明管道泄漏后,压力对于表层土的影响极小,可以忽略不计。体积分数经过一定时间后,等值线形成一个正苹果形。由于重力作用y轴比x轴扩散快,之后油品最外层等值线到达表层土下缘,油品开始渗入表层土,密集的等值线继续向上扩散,当等值线前锋到到表层土上缘时外界就会发现有泄漏现象发生,但是最大等值线前锋并没有到达表层土。当表层区域都向表层有油品输出,并且比较密集的等值线前锋已经处在表层土,这时地表应该会出现油品液体的流动。再经过一段时间,外层等值线到达土壤最下缘,这就意味着开始有油品开始污染地下水。     

The influence of the texture and surface properties of carbon adsorbents obtained from biomass products on the adsorption of manganese ions from aqueous solution

Studies on the adsorption of manganese ions from aqueous solution on carbon obtained from a mixture of biomass products indicate the importance of acidic surface oxides for manganese ion adsorption that is predominantly site specific. The results show that oxygen remaining from the raw material participates in the formation of surface oxides and indicates the possibility of controlling the content of acidic surface sites of the carbon surface by appropriate selection of the precursor composition and surface properties modification. The surface functionalities of oxidized carbon from a mixture of biomass products resembles the behavior of an ion-exchange resin. Oxidized carbon obtained from a 50:50 mixture of tar from steam pyrolysis of apricot stones and furfural contains a balance of surface area and high surface concentration of functional groups favorable for adsorption of positively charged manganese ions.     

Autofluidization: The fluidization of solid particles by gases evolving from the particles

An experimental procedure was developed to study the autofluidization (i.e. the fluidization of solid particles by gases evolving from the particles) of green coke. It was found that the best method was to heat a 30 cm deep bed of 178 μm quartz sand to 800°C while fluidizing it with air and then adding a small batch of ?1 mm coke particles to the surface of the bed. After allowing the coke to mix with the sand for 20 s, the fluidizing air was reduced to a lower rate. Pressure is then measured as a function of height in the bed and time. The result is a series of pressure measurements which decay smoothly from the fluidized state to a new steady state once all the coke's volatiles have been released. From these measurements it is possible to calculate gas velocities in the bed as well as bed voidage and apparent density. It was found that the upper sections of the bed would remain fluidized for up to nearly 2 min after the coke was added to the sand while the lower parts of the bed were never fluidized. Simple theory, in the form of the Blake-Kozeny equation, does a good job of predicting when autofluidization will occur and what the changes in bed height and pressure are within the bed.     

The influence of solution parameters on the electrospinning intensity from foamed surface

Electrospinning is an efficient process for producing polymeric and hybrid nanofibers. There is, however, a lack of understanding concerning scalability of the process and in particular the production rate optimization. The electrospinning mass transfer intensity depends predominately on solution parameters, process parameters and the design of the equipment. These parameters influence the deposition intensity of the spinning process differently, but it is not known which factors dominate. The e‐spinning deposition intensity of polyethylene oxide, polyvinyl alcohol and their mixtures was investigated using a bubble foamed polymer solution surface to promote high mass deposition. Based on the measured properties of the solutions, a mathematical criterion was developed which made it possible to predict the electrospinning intensity of a given polymer solution. The proposed formula agrees with the experimental data and confirms that spinning intensity can be predicted from pre‐determined solution parameters. Using computer modeling, the weighting coefficients of the solution parameters have been determined, showing which parameter is the most important for the process intensity. The criterion and the same weighting coefficients were applied to the analysis of published data and it was found that they can be applied not only for electrospinning from the foamed surface but also from the free surface. A physical explanation of the criterion is proposed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42034.     

The influence of substrate absorbency on coating surface chemistry

The composition of the top surface of a coating layer can influence its functional properties or subsequent processing steps. The effect of the substrate absorbency on the coating surface chemistry is reported. Different coating systems containing a kaolin clay pigment, fine or coarse precipitated calcium carbonates, and a common latex binder were examined. The influence of a soluble polymer added into the coating was characterized. The surface chemistry was measured with attenuated total internal reflectance (ATR) and X-ray photoelectron spectroscopy (XPS).

Absorbent substrates generate bulky coatings with high voids and low gloss. Rapid dewatering by the absorbent substrate pulls the small particles, like latex binder, away from the top layers causing a low latex concentration at the surface. On non-absorbent substrates, the addition of the soluble polymer generates coating layers with higher void volume, lower gloss, and lower latex concentrations at the coating surface. However, on absorbent substrates, polymer addition causes coatings with lower void volumes and higher gloss. In this case, the rapid dewatering and mobility of particles is reduced by the polymer, which helps to retain the small particles at the surface. As a result, latex concentration at the surface increases with polymer addition on absorbent substrates.     

On the effect of laboratory conditioning and freeze/thaw exposure on moisture profiles in HPC

The effect of selected conditioning (drying and resaturation) and freeze/thaw exposure on the moisture profile in a two-powder concrete (equiv. w/c=0.39, 8% silica fume) has been investigated. For comparison, the effect of conditioning and freeze/thaw testing according to SS 13 72 44 (“Borås method”) on moisture profiles in a three-powder concrete and two plain concretes (w/c=0.45) was measured. The investigations were supplemented by determination of frost resistance and chloride profiles after freeze/thaw exposure, as well as petrographic analysis. The investigations indicate that the present methods of conditioning only have very limited effect on high-performance concretes (HPC).     

Variations in interfacial properties during cell conditioning and influence of heat-treatment of ionomer on the characteristics of direct methanol fuel cells

Variations in interfacial properties in the anode catalyst layer during cell conditioning were characterized, and influence of the heat-treatment of ionomer on the characteristics of direct methanol fuel cells was investigated in this work. The anode catalyst layer was made by mixing a solvent-substituted Nafion solution with unsupported Pt/Ru black and curing the mixture in an oven with an inert environment. Materials characterization (SEM and optical microscopy) and electrochemical characterization (cell polarization, anode polarization, electrochemical impedance spectroscopy, and CO-stripping cyclic voltammetry) were performed. During cell conditioning, the enhanced kinetics of MeOH electrochemical oxidation and severe limiting current phenomenon are due to the combination of variations in interfacial properties and swelling of ionomer in the anode catalyst layer over time. Ru oxides at the catalyst surface are reduced continuously during cell conditioning. The nearly constant integrated areas under the CO-stripping CV peaks and broadened peak shapes indicate a stable number of Pt/Ru bimetallic alloy surface sites, yet the surface composition distribution is broadened. Heat-treatment influences ionomer crystallinity, altering its swelling behavior and hence affecting the characteristics of the direct methanol fuel cell (DMFC) anode.     

Catalytic wall-flow filters for the abatement of diesel particulate: regeneration parameters study

A 1% Pt on CeO₂-promoted PrCrO₃ perovskite catalyst has been synthesized over a wall-flow monolith by the in situ solution combustion synthesis (SCS) method. The role of the catalyst, highly active towards diesel particulate combustion, has been studied during the regeneration phase as a function of three different operating parameters: the inlet trap temperature at which the regeneration is induced, the residual oxygen concentration in the exhaust gases and the load of particulate at the start of the regeneration. The final aim of this study is to improve the knowledge on the catalytic regeneration process in order to derive information suitable for designing an optimized catalytic soot trap entailing minimal fuel penalties.     

Combined effects of soot load and catalyst activity on the regeneration dynamics of catalytic diesel particulate filters

The combined effects of soot load and catalyst activity on the regeneration dynamics of a catalytic diesel particulate filter have been investigated through transient CFD‐based simulations of soot combustion in a single‐channel configuration. The soot load was changed by varying the amount of soot accumulated as cake layer, while keeping the amount of soot trapped inside the catalytic wall constant. Substantially uniform soot combustion that allows reasonably fast regeneration of the filter under controlled temperature conditions has been simulated only in the absence of cake and at relatively low catalyst activity. Conversely, in the presence of cake, numerical predictions have shown that, regardless of both soot load and catalyst activity, fast regeneration always occurs by propagation of sharp reaction fronts that result in high temperature rises. These findings highlight the importance of avoiding the cake formation, while properly optimizing the catalyst activity, to conduct a safe and effective regeneration of catalytic filters. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1714–1722, 2018     

The influence of metallic surface wettability on bacterial adhesion

The wettability of AISI 304 stainless steel with 2B and 2RB surface finishes expressed in terms of the solid surface free energy was investigated with respect to the cleaning process. It was shown that cleaning affects the wettability of a solid surface. Depending on the cleaning method, ranged from 43.4 to 277.8 mJ m^-2 for the 2RB surface and from 34.4 to 122.8 mJ m ² for the 2B surface. There was no direct relationship between the number of adhering bacteria and or the wettability of solids. However, it was found that the adhesion of Streptococcus thermophilus was driven by a balance between and The experimental results are as expected based on thermodynamic predictions when the spreading pressure is accounted for in the surface free energy of bacteria, determination.     

The effect of methods of preparation on the performance of cupric chloride-impregnated sorbents for the removal of mercury from flue gases

Cupric chloride-impregnated carbon sorbents (CuCl₂-ACs) showed comparable performance in elemental mercury (Hg⁰) oxidation and adsorption to a brominated activated carbon sorbent (Darco Hg-LH) in our previously reported experimental studies using fixed-bed and entrained-flow systems. This study tested several CuCl₂-ACs prepared in different solvents to investigate the effects of solvents on the Hg⁰ removal capability of CuCl₂-ACs and find the most efficient and economical method of sorbent preparation. The performance of CuCl₂-ACs prepared in different solvents was also examined with respect to surface tension and pH of solvents. As a result, the sorbents prepared in isopropyl alcohol and acetone showed the best performance in these tests, but low surface tension and pH of isopropyl alcohol and acetone were not found to be critical factors.     

Numerical simulation of the effects of the design feature of a cyclone and the inlet flow velocity on the separation of CO2 particles from a CO2-COF2 mixture

In synthesizing COF₂ from CO, a considerable amount of CO₂ is produced. A method of solidifying CO₂ at low temperature and separating CO₂ particles from the COF₂ gas using a cyclone was designed and the separation efficiency according to the cyclone feature was studied. Optimal sizing and operation conditions of the cyclone were investigated by reviewing the flow velocity profile and the particle trajectory using a numerical analysis with computational fluid dynamics (CFD). The effects of the inlet flow velocity and the ratio of the cyclone diameter to the cone length (D/L) on the recovery efficiency were estimated. Results revealed that the separation efficiency increases with an increase in the ratio of D/L and a decrease in the cyclone size. The recovery efficiency of CO₂ increases with the increase in the inlet flow velocity. Based on these results, we could propose a concept and methodology to design the optimal features and sizing of a cyclone suitable for separating solid CO₂ from gaseous COF₂ at low temperature.     

Application of the ‘Multivir’ method to separation of droplets and solid particles from gases

New types of packing for separation of droplets and solid particles from gases have been proposed. The Multivir packings consist of adjacent layers of strips spaced uniformly. The layers of strips are placed oblique to each other. A gas stream flows through the packing in the form of a large number of smaller streams which cross each other spatially and induce rotational motion in each other. Under the centrifugal force, solid particles and droplets in the gas stream settle on the surfaces of the strips in the packing.

A simplified mathematical model describing the phenomenon of particle separation in Multivir packings is presented. Examples of industrial applications of this new method for separation of droplets and solid particles from gases are also given.