Emission control in the combustion of coal–water and organic coal–water fuels

Promising methods for decreasing anthropogenic emissions due to the combustion of coals of different ranks and coal–water fuel (CWF) and organic coal–water fuel (OCWF) slurries on their basis are considered. The maximum concentrations of the main anthropogenic emissions of sulfur, nitrogen, and carbon oxides (SO _x , NO _x , and CO _x ) formed upon the combustion of solid fuels in a powdered state and as the components of CWF and OCWF slurries were determined. The concentrations of the most hazardous oxides formed upon the combustion of coals of different ranks (brown and black coals) and CWF and OCWF slurries were compared. The experimental results substantiated the use of CWF and OCWF slurries for emission control in coal-burning power engineering. The addition of a combustible liquid component to a CWF slurry (the production of an OCWF slurry) makes it possible to ensure acceptable environmental and energy characteristics.     

Porous pyridine based polyimide–silica nanocomposites with low dielectric constant

Highly porous polymer–silica hybrid materials were prepared based on the organo-soluble polyimides of four various dianhydride and 2,5-diaminopyridine. 3-Aminopropyltriethoxysilane (APS) was used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. The produced polyimide–silica composites were investigated by X-ray diffraction analysis, scanning electron microscope and thermal analysis tecniques. The effect of silica modified with functional group of 3-aminopropyltriethoxy silane on the porous structure and dielectric properties as well as the thermal stability of films were investigated. Capacitances were determined with a HP4294A at a frequency between 1 kHz and 1 MHz. The dielectric constant was significantly reduced with increasing silica modified with APS. The result indicates that the composite materials are potentially useful in low dielectric materials.     

Thermally stable pseudo-third-generation Grubbs ruthenium catalysts with pyridine–phosphinimine ligand

The ligand precursors 2-(R₃PN)CH₂Py (R = Ph(1a), Cy(2a)) were prepared from reaction of pyridine azide with various phosphine ligands. Reaction of 1a or 2a with RuCl₂(CHPh)(Py)₂(H₂IMes) (Py = pyridine) afforded the ruthenium alkylidene complex RuCl₂(CHPh)(PyCH₂(NPR₃))(H₂IMes) (R = Ph(1), Cy(2)). Both catalysts showed good thermal stability and latent behavior toward RCM and ROMP reactions.     

Phase equilibria in the calcium nitrate–water–isopropyl alcohol system

Results of an investigation of the solubility of the components of the water–isopropyl alcohol system in the temperature range of 253–268 K are given. Using fractional fusion, the concentrations of twocomponent water–isopropyl alcohol system have been determined, where fusion occurs more homogeneously. Phase diagrams of the calcium nitrate–water–isopropyl alcohol systems have been plotted at temperatures of 253, 263, and 268 K. The working area where compositions can be chosen for preparing the process liquid with a low freezing point has been determined.     

Vapor–liquid equilibrium in the sodium carbonate–sodium bicarbonate–water–CO2-system

Vapor–liquid equilibria of the carbon dioxide loaded sodium carbonate–water system were measured in the temperature range 40–80 °C and for sodium carbonate concentrations 8–12 wt%. In addition the vapor pressure of water over 10–30 wt% sodium carbonate solutions for the temperature range 27–100 °C was measured in an ebulliometer. The system was modeled using the electrolyte-NRTL model. Experimental vapor–liquid data from this study as well as data available in the literature from 25 to 195 °C and for sodium carbonate concentrations from 0.5 to 12 wt% were used for parameter fitting. The average deviation of the model predictions compared to all experimental data found is 9.8% for the partial pressure of CO₂. For vapor pressure of water the standard deviation is 0.6% up to 100 °C and 30 wt% sodium carbonate solutions.     

Study air–water system in horizontal loop geometry

To enhance the understanding of hydrodynamic of air–water multi-phase flow inside a toroidal geometry, experiments were carried out in horizontal torus reactor. Compared with vertical flow, the flow in horizontal milli torus reactor was characterized by one additional flow pattern. In vertical position two flow regimes are considered: not-dispersed and dispersed flow while in horizontal position three flow regimes have been distinguished: stratified flow, dispersed flow and mixed flow regimes. The mixing time is measured by a conductimetric method as described by (Benkhelifa et al., 2000). The effect of both superficial gas velocities and impeller rotation speeds has been studied. The mixing time has been decreased by increasing both the superficial gas velocity and the impeller rotation speed and has been shorter than the one given for the horizontal configuration. The axial dispersion inside the reactor was modelled by the Zhang's model. The obtained results are in a good agreement with Zhang's model.     

Oil–water pre-separation with a novel axial hydrocyclone

A novel hydrocyclone with guide vanes, named as axial hydrocyclone(AHC), is designed to tackle the problem of oil–water separation faced by most mature oilfields. Optimal design of the AHC is carried out by using numerical methods. The effects of guide vanes, cone angle, tapered angle and overflow pipe on the oil–water separation are discussed in this paper. The results show that a double swirling flow is generated in the tapered section where oil–water separation occurs. Both the cylindrical and the tapered section have important influences on AHC performance. On the basis of single factor results, response surface methodology is employed to optimize the AHC design. The experimental results indicate that the novel AHC has an excellent performance for the oil–water separation.     

Liquid–liquid equilibrium for the systems hydrocarbon–thiophene or pyridine–1-hexyl-3,5-dimethylpyridinium bis(trifluoromethylsulfonyl)imide

Liquid–liquid equilibrium for eight ternary systems involving one hydrocarbon (n-hexane, n-heptane, i-octane or toluene), thiophene or pyridine and an ionic liquid (1-hexyl-3,5-dimethylpyridinium bis(trifluoromethylsulfonyl)imide) was experimentally determined at atmospheric pressure and 25°C. Equilibrium data are presented with binodal curves as well as with tie lines. The suitability of ionic liquid (IL) for extractive desulfurization and denitrification was evaluated in terms of solute distribution ratio and selectivity. Extraction experiments with three-component and seven-component (n-hexane, n-heptane, i-octane, toluene, thiophene, pyridine and IL) systems have been performed. The equilibrium data in three-component systems were well described with Non-Random Two-Liquid (NRTL) and Universal Quasi-Chemical (UNIQUAC) models.     

Anodization of n and p-GaAs in ethylene glycol–water–tartaric acid mixture

This paper describes the pulsed constant current anodization of n+ and p+-GaAs in ethylene glycol–water–tartaric acid (AGW) mixture, up to 17mAcm–2. A 0.26m thick film is obtained for a final voltage of 135V at 4.3mAcm–2 pulsed current density. Cyclic voltammetry showed that the initial growth of a monolayer anodic oxide can be described by a charge transfer with uncompensated cell resistance model. The relationship between peak current, peak voltage and scan rate has been verified for this process, based on the above model.     

Ternary nucleation: kinetics and application to water–ammonia–hydrochloric acid system

The ternary nucleation of an ideal mixture of three alcohols and a non-ideal mixture of water, ammonia and hydrochloric acid, which is relevant in atmosphere, have been investigated theoretically. In the ideal mixture of three alcohols, the nucleation rates obtained using simplified kinetic approach are compared with the nucleation rates given by a detailed kinetic model. The simplified model is seen to underestimate nucleation rates by 2–3 orders of magnitude. This is mainly due to the crude estimate for the Zeldovich factor in the simplified model. We have proposed a modification to the simplified model. The improved model gives order-of-magnitude estimates for the nucleation rates. The ternary nucleation of water–ammonia–hydrochloric acid is studied with the improved model. The results have been compared with binary nucleation of water and ammonium chloride. The results show that water–ammonia–hydrochloric acid mixture is effectively a two-component system.     

Electrospun nanofibrous polyvinylidene fluoride-co-hexafluoropropylene membranes for oil–water separation

Effective separation of oil from water is of significant importance globally for various applications such as wastewater treatment, oil spill cleanup, and oil purification. Among the numerous approaches for oil removal, membrane separation is considered one of the most promising approaches due to its selectivity and ease of operation. Electrospinning is a promising technique for producing polymeric membranes with tunable structures with interconnected pores, large surface area, and high porosity. In this study, hydrophobic poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibrous membranes were electrospun and used for this purpose. The effects of various parameters (e.g., polymer concentration, applied voltage, tip to collector distance, and feed rate) were investigated to find the optimum electrospinning conditions. Further, the electrospun membranes were characterized according to average fiber diameter, morphology, average pore size, and wettability to identify the combinations most likely to succeed in oil–water filtration. The physical–chemical properties of the membranes (i.e., thickness, areal density, porosity, average pore size, water/oil contact angle, hydrostatic pressure head, and oil filtration flux) were studied based on standard test methods. The separation efficiency of eight electrospun membranes with various pore sizes and average fiber diameters were tested for diesel/water mixtures. A linear relation was found between the initial oil flux and the average pore size of the membranes. The maximum oil filtration flux of about 224 L/m²/h, achieving over 75% oil recovery in 10 min, was obtained for the electrospun membrane with the average pore size of 4.5 μm. The membranes were successfully used for eight consecutive oil–water separation cycles without noticeable loss of flux.     

Physiochemical insight into the solution behavior of cationic gemini surfactant in water and ethanol–water systems

Surfactants in water and both alcohol-water mixed solutions are used extensively in a host of industrial applications. This work presents the solution behavior and micellar transition of a cationic gemini surfactant (GS): N,N′-dihexadecyl-N,N,N′,N′-tetramethyl-N,N′-ethanediyl-diammonium dibromide (16-2-16) in water and mixed water-ethanol media. Phase behavior for 16-2-16 in the ethanol–water system was investigated at ambient temperature. The rheological data obtained for these systems at varying alcohol concentrations showed that the system viscosity (η) decreased with as the ethanol concentration increased. Small-angle neutron scattering (SANS) was used to probe the structural details of the cationic micelles as a function of ethanol concentration and temperature. The scattering data inferred a structural transition from unilamellar vesicles (ULV) through rod-like micelles to ellipsoidal micelles occurs that is dependent on the solvent composition and temperature indicating the behavior of ethanol molecules as a cosolvent in the process of micelle breaking. The plausible physicochemical interactions in the 16-2-16-ethanol mixed system were further investigated using a computational simulation study employing density functional theory (DFT)/B3LYP (Gauss View 5.0.9) utilizing a 3-21G basis set.     

Extraction of Taiheiyo coal with supercritical water–phenol mixtures

Taiheiyo Japanese sub-bituminous coal was extracted with supercritical water (SCW) and phenol mixtures at 673 K and at over fluid densities ranging from 0 to 0.5 g/cm³. The extraction yield with SCW was 0.55–0.60, but increased with increasing the ratio of phenol to water, showing a maximum of 0.7 at water–phenol ratio of 4.5:0.5 and then decreased to 0.50–0.55 for pure phenol.The main products for the SCW–phenol extraction were bisphenol alkyl compounds, while these compounds could not be detected when SCW was used as the solvent. For elucidating the mechanism of SCW–phenol extractions, reactions between phenol and model compounds of hydrolysis products (formaldehyde, acetone, propionic acid, and 2-propanol) were conducted. In SCW, formaldehyde reacted with phenol to produce polymers, while neither acetone nor propionic acid reacted with phenol. The 2-propanol dehydrated to form propene, which reacted with phenol to form 2-isopropylphenol. The reaction rate increased with increasing water density. In SCW–phenol extraction of coal, phenol seems to inhibit reactions that lead to hydrolysis products or those that might cross-link to form the macromolecules. Phenol can be used with SCW to reduce retrograde reactions in residual coals.     

Hydrate formation in oil–water systems: Investigations of the influences of water cut and anti-agglomerant

To investigate the characteristics of hydrate formation in oil–water systems, a high-pressure cell equipped with visual windows was used where a series of hydrate formation experiments were performed from natural gas + diesel oil + water systems at different water cuts and anti-agglomerant concentrations. According to the temperature and pressure profiles in test experiments, the processes of hydrate formation under two kinds of experimental procedures were analyzed first. Then, based on the experimental phenomena observed through the visual windows, the influences of water cut and anti-agglomerant on the places of hydrate formation and distribution, hydrate morphologies and hydrate morphological evolvements were investigated. Hydrate agglomeration, hydrate deposition and hydrate film growth on the wall were observed in experiments. Furthermore, three different mechanisms for hydrate film growth on the wall were identified. In addition, the influences of water cut and anti-agglomerant on the induction time of hydrate formation were also studied.     

Performance improving with temperature in liquid–liquid extraction using cumene–isobutyric acid–water chemical system

The performance of single drops was investigated in liquid–liquid extraction while temperature was changed within the range of 15–40 °C. The recommended system of cumene–isobutyric acid–water with mass transfer resistance mainly in aqueous phase was used. An average enhancement of 75.6% in the rate of transfer was revealed. The extraction efficiency is the most influencing term due to molecular diffusivity enhancement. For modeling, a simple correlation was proposed for the effective diffusivity in Newman's equation, while continuous phase mass transfer coefficient was directly included. Using this model, relative deviation of the overall mass transfer coefficient was within only ±5.6%.     

Ignition of droplets of coal–water–oil mixtures based on coke and semicoke

To permit expansion of the resource base and utilize industrial waste, coal–water–oil fuels may be prepared on the basis of coke and semicoke, as well as common petroleum derivatives (fuel oil and spent compressor, turbine, and transformer oils). The minimal oxidant temperature corresponding to stable ignition of coal–water–oil slurries is established. Typical variation in fuel temperature in the course of reaction is determined, as well as the delay time of ignition and the total combustion time for individual droplets of such fuel suspensions. For droplets of initial size 0.5–1.5 mm, the influence of the various factors (droplet size, oxidant temperature, and concentration of the components) on the threshold (minimum) temperature and inertia of ignition is studied. It is shown that stable ignition of coke and semicoke in such fuel is possible at moderate oxidant temperatures: 700–1000 K.     

Oxygen-enhanced water gas shift on ceria-supported Pd–Cu and Pt–Cu bimetallic catalysts

Aiming at enhancing H₂ production in water gas shift (WGS) for fuel cell application, a small amount of oxygen was added to WGS reaction toward oxygen-enhanced water gas shift (OWGS) on ceria-supported bimetallic Pd–Cu and Pt–Cu catalysts. Both CO conversion and H₂ yield were found to increase by the oxygen addition. The remarkable enhancement of H₂ production by O₂ addition in short contact time was attributed to the enhanced shift reaction, rather than the oxidation of CO on catalyst surface. The strong dependence of H₂ production rate on CO concentration in OWGS kinetic study suggested O₂ lowers the CO surface coverage. It was proposed that O₂ breaks down the domain structure of chemisorbed CO into smaller domains to increase the chance for coreactant (H₂O) to participate in the reaction and the heat of exothermic surface reaction helping to enhance WGS kinetics. Pt–Cu and Pd–Cu bimetallic catalysts were found to be superior to monometallic catalysts for both CO conversion and H₂ production for OWGS at 300 °C or lower, while the superiority of bimetallic catalysts was not as pronounced in WGS. These catalytic properties were correlated with the structure of the bimetallic catalysts. EXAFS spectra indicated that Cu forms alloys with Pt and with Pd. TPR demonstrated the strong interaction between the two metals causing the reduction temperature of Cu to decrease upon Pd or Pt addition. The transient pulse desorption rate of CO₂ from Pd–Cu supported on CeO₂ is faster than that of Pd, suggesting the presence of Cu in Pd–Cu facilitate CO₂ desorption from Pd catalyst. The oxygen storage capacity (OSC) of CeO₂ in the bimetallic catalysts indicates that Cu is much less pyrophoric in the bimetallic catalysts due to lower O₂ uptake compared to monometallic Cu. These significant changes in structure and electronic properties of the bimetallic catalysts are the result of highly dispersed Pt or Pd in the Cu nanoparticles.     

Modeling ultrafiltration of gelatin–water suspension by computational fluid dynamics

In this paper, principles of computational fluid dynamics (CFD) are used to study ultrafiltration (UF) process. Model has been developed by a new technique in which permeation of solvent molecules is introduced to system via appropriate sink terms in conservation equations for computational domain. Experimental data and fittings are applied in model development. Model results have been compared for two and three-dimensional geometries. Finally a time step and mesh size independent model has been developed in two dimensions for modeling the permeation flux vs. filtration time in a gelatin–water UF system. Final model is able to predict steady-state permeation flux with relative error less than 2%. Accuracy of calculation is investigated through the comparison between mass imbalance and sum of local fluxes. Modeling results show that increase in cross flow velocity (CFV) and trans-membrane pressure (TMP) leads to increase in permeation flux but decrease in solute concentration and rejection of solute particles from membrane surface makes permeation flux increase.     

Assessment of extended Derjaguin–Landau–Verwey–Overbeek-based water film on multiphase transport behavior in shale microfractures

This study presents a novel model to predict gas–water two-phase transport behaviors in shale microfractures by incorporating a mobile water film with varying thickness according to the extended Derjaguin–Landau–Verwey–Overbeek theory as well as multiple fluid transport mechanisms (i.e., real gas transport controlled by the Knudsen number and water slippage). This model is implemented in real shale microfractures via digital-core imaging. A gas–water displacement process is modeled by the invasion percolation theory, while a local multiphase distribution is determined by combining disjoining pressure with capillary force. Key findings reveal that gas relative permeability decreases by 17% and water RP enhances by 33.5%, when the mean aperture decreases from 1.67 to 0.0418 μm. Neglecting water film brings a decrease in water RP and an overestimation of gas transport ability. Moreover, two critical microfracture apertures are determined, which enhances an understanding of the water film impact on gas–water transport properties in application.     

Recyclable porous polyurethane sponge for highly efficient oil–water separation

Oil spills and chemical leakages have caused severe environmental problems. Physical absorption of the spilled oils and chemical reagents by absorbing materials is an efficient and economical approach to solve these problems. Herein, we have prepared a porous thermoplastic polyurethane (TPU) sponge by combining the thermally induced phase separation method with the selective dissolution of water-soluble PEG components. The selective removal of PEG components from the walls of TPU sponges could increase the intensities of free volume holes and surface areas of TPU sponges. The content of free volume holes and surface areas of TPU sponge reached its maximum with the TPU/PEG ratio of 1:1. The increased roughness could improve the absorption capacities of TPU sponges for various oils/organic solvents. Moreover, due to its excellent compressibility, this TPU sponge could be reused 20 times with little loss of saturated absorption capacity. In addition, this TPU sponge exhibited excellent separation ability for the toluene from the toluene/water mixture and emulsion. In all, we have developed a facile method to prepare TPU sponge absorbent with excellent absorption performance, which holds great potential in the application of large-scale oil/water separation.