In this article, we describe a novel strategy for synthesizing hierarchical ZSM-5 zeolites via the nanoscale depolymerization-reorganization of natural aluminosilicate minerals. This strategy involves two important steps: the first is the top-down depolymerization of one aluminum-rich aluminosilicate mineral via a novel submolten salt system and one silicon-rich aluminosilicate mineral via conventional thermal treatment into nanoscale building blocks, and the second is the bottom-up rearrangement and reorganization of nanoscale building blocks in the synthesis system into hierarchical ZSM-5 zeolites. When used as a fluid catalytic cracking catalyst additive, the resulting ZSM-5 zeolite with hierarchical micro-mesoporous structure exhibited high activity and selectivity for valuable products in preliminary oil refining tests. The salient features of the strategy lie in that it neither involves any inorganic aluminum and silicon salts as precursors nor uses any secondary mesoscale template and post-treatment to create mesopores, thus demonstrating itself to be a green route to synthesizing hierarchical zeolites. (C) 2014 Elsevier Inc. All rights reserved.

Experiments were carried out to study the effectiveness of fine powders as an additive on the reduction of electrostatic charge build-up for glass beads, polyethylene resins and starch powders in a mechanical shaking device. Four fine powders, carbon nanotubes (CNTs), Larostat 519, activated carbon and aluminum powders were tested on their effectiveness on charge reduction. It is found that particle size does have a significant effect on charge build-up of the bulk powder. The addition of small fraction of fine glass beads (150–170μm) into coarse glass beads (210–300μm) led to observable charge reduction, indicating that small particles added to large bulk powders can help reduce electrostatic charge build-up. Compared to other additives of larger sizes, CNT is a much more effective antistatic agent. Aluminum powder performed poorest among all additives tested. CNTs out-performed the commercial antistatic powder, Larostat 519, in reducing the charge generated by shaking action. Furthermore, better charge dissipation was observed at higher CNT contents. The experiment also revealed that conductivity alone was not a good indicator of antistatic capability because aluminum powder, despite having a good conductivity, performed poorly.

The adsorption performance and catalytic activity of Fe/ZSM-5 for the selective catalytic reduction (SCR) of NOx with propylene were studied in a fixed bed reactor using model flue gases. The Fe/ZSM-5 catalyst showed reasonable NOx adsorption capacity, and the adsorption performance is closely related to the particle size and the structure of the catalyst support. The increase of O2 concentration significantly enhanced the adsorption of NOx on Fe/ZSM-5, and CO2 in the flue gas exhibited certain negative impact on the adsorption capacity, while H2O showed little effect. HC-SCR experiments showed that Fe/ZSM-5 catalyst was sensitive to the reaction temperature and space velocity, and exhibited acceptable activity when O2 concentration was controlled at a low level. Water in the flue gas was found to slightly enhance the reactivity of Fe/ZSM-5, while the presence of CO2 showed little effect.

The hydrodynamics of fluidized beds strongly influence their operation, but are complicated and chaotic. There are many measurement techniques, but none fully characterizes gas–solid fluidized beds. Acoustic signals from fluidized beds cover a wide frequency spectrum and can be correlated to bed characteristics. Experiments were conducted to study the acoustic signals from ultrasonic transducers mounted on the outer wall of a two-dimensional fluidization column. The acoustic signals were related to bubble behavior in 550μm glass beads. Simultaneous acoustic and pressure measurements allowed direct comparison of these signals for single bubbles, pairs and chains of bubbles. The envelope of acoustic signals, generated by particle collisions and particle–wall impacts, provided information on the behavior of bubbles. Significant peaks appeared as the top portions of the bubble wakes approached the acoustic sensor. Pressure waves propagated considerably in the horizontal direction, whereas acoustic signals propagated little in the lateral direction, but transmitted forward in the wall in the direction of bubble motion, maintaining the wave profile invariant during transmission. The strong lateral localization of acoustic signals is promising for determining the lateral bubble position in the bed. Acoustic signals provide a potential means of determining such bubble properties as velocity, frequency and volume, with some advantages relative to pressure signals.

In the present work, instantaneous gas flow rates in each of two parallel channels of gas–liquid two-phase flow systems were investigated through measurements of the pressure drop across the entrance region. Liquid flow rates in two branches were pre-determined through liquid injection independently into each channel. Experiments were conducted in two different manners, i.e., the gas flow rate was varied in both ascending and descending paths. Flow hysteresis was observed in both gas flow rate distributions and the overall pressure drop of two-phase flow systems. Effects of liquid flow rates on gas flow distributions were examined experimentally. The presence of flow hysteresis was found to be associated with different flow patterns at different combinations of gas and liquid flow rates and flow instability conditions. A new and simple method was developed to predict gas flow distributions based on flow regime-specific pressure drop models for different experimental approaches and flow patterns. In particular, two different two-phase pressure drop models were used for slug flow and annular flow, separately. Good agreement was achieved between theoretical predictions and our experimental data. The developed new method can be potentially applied to predict gas flow distributions in parallel channels for fuel cells.

Based on the wave propagation theory, a dynamics model that combines the nonlinear equilibrium isotherm and the linear mass-transfer equation has been developed to predict the breakthrough behaviour of toluene adsorption in a fixed bed packed with activated carbon fibers. The experimental results showed that the constant-pattern wave model using the Langmuir isotherm equation could capture the dynamic behaviour of the adsorption column. Two important parameters, the half breakthrough time (t1/2) and the volumetric mass-transfer coefficients (kGα) in the model were obtained from linear fitting of the model to experimental breakthrough data. kGα was found to be insensitive to the initial concentration and increased with the increasing the superficial velocity. It was also observed that t1/2 decreases with increasing the superficial velocity and the initial concentration, and increases with increasing the bed height. A sensitivity analysis showed that external mass-transfer had a much stronger influence on the breakthrough curve than internal mass-transfer, confirming that the overall mass-transfer for toluene adsorption onto activated carbon fibers in fixed bed is controlled by external mass-transfer.

All existing proton exchange membrane（PEM）fuel cell gas flow fields have been designed on the basis of single-phase gas flow distribution.The presence of liquid water in the flow causes non-uniform gas distribution,leading to poor cell performance.This paper demonstrates that a gas flow restrictor/distributor,as is commonly used in two-phase flow to stabilize multiphase transport lines and multiphase reactors,can improve the gas flow distribution by significantly reducing gas mal-distribution caused by either non-uniform water formation in parallel flow channels or flow instability associated with negative-slope pressure drop characteristic of two-phase horizontal flow systems.

Two methods of decoupling pressure fluctuations in fluidized beds by using the incoherent part (IOP) of absolute pressure (AP) and differential pressure (DP) fluctuations are evaluated in this study. Analysis is conducted first to demonstrate their similarities, differences, and drawbacks. Then, amplitudes, power spectral densities, mean frequencies, coherence functions, and filtering indices of the IOP of AP and DP fluctuations are calculated and compared based on experimental data from a two-dimensional,fluidized column of FCC particles. Derived bubble sizes are also compared with the sizes of bubbles viewed in the two-dimensional bed. The results demonstrate the similarity of these two methods in filtering out global compression wave components from absolute pressure fluctuations, especially those generated from oscillations of fluidized particles and gas flow rate fluctuations. However, both methods are imperfect. Neither can filter out all the compression wave components and retain all the useful bubble-related wave components. Their amplitudes can be used to characterize global bubble property and quality of gas solids contacting in bed, but they do not give accurate measurement of bubble sizes. (C) 2009 American Institute of Chemical Engineers AIChE J. 56: 869-877, 2010

Bubble sizes measured in a column of diameter 290 mm with FCC particles utilizing both an intrusive optical probe and non-intrusive pressure analysis are compared. The pressure signals were decoupled by differential pressure analysis and incoherence analysis. It is shown that pressure fluctuations induced by jetting/bubble formation can be effectively filtered out by differential pressure and incoherence analysis. The differential pressure signals measured across a vertical interval less than half the maximum bubble size unreasonably damps the power spectral density intensity, leading to underestimation of bubble size and overestimation of mean frequency. In the present work, the incoherence analysis tends to estimate greater bubble size than differential pressure analysis. Bubble chord lengths are overestimated by optical probe signals because small bubbles are not detected. Bubble sizes calculated by the equation of Horio and Nonaka (1987) agree reasonably well with that estimated by incoherence analysis at relatively high superficial gas velocities.

Adsorption on carbon fixed-beds is considered as an inexpensive and highly effective way for controlling chlorofluorocarbons (CFCs) emissions. In the present work, a dynamic model under constant-pattern wave conditions has been developed to predict the breakthrough behavior of trichlorofluoromethane (CFC-11) adsorption in a fixed bed packed with activated carbon fibers (ACFs). The adsorption of CFC-11 vapor onto viscose-based ACFs was performed in a fixed bed at different test conditions. The results showed that, in a deep bed (>120 mm), the analytical model based on the external mass transfer with the Langmuir isotherm could describe the adsorption dynamics well. The model parameters, the characteristic breakthrough time and the film mass-transfer coefficients are related to such operating parameters as the superficial gas velocity, feed concentration and bed height. It was found from the breakthrough dynamics that the mass transfer from the fluid phase to the fiber surface dominated the CFC-11 adsorption onto ACFs in fixed beds.

Turbulent fluidized beds have been recognized as very effective gas-solids contacting devices because of their outstanding performance in gas-solids contact, heat transfer, and mass transfer. To characterize the void behavior, which governs the hydrodynamics and the efficiency of operation of turbulent fluidized beds, an optical fiber probe with a separation distance of 5 mm between the two measuring tips has been used to measure the axial and radial profiles of the bubble/void parameters in a turbulent fluidized bed over a gas velocity range of 0.4-1.0 m/s. Experiments were carried out in a Plexiglas column with an inner diameter of 0.19 m and a height of 5.5 m. Fluid cracking catalyst (FCC) powders with a mean size of 78 mu m were used as bed particles, and air was used as the fluidizing gas. Signals from the optical fiber probe were used to obtain the rise velocity and the chord length of voids at various spatial positions and superficial gas velocities. The results show that, in the turbulent fluidization regime, the void size and the void rise velocity have a relatively uniform distribution along the radial direction in the bed. Based on the assumption that bubble splitting is dominant over bubble coalescence at high superficial gas velocities, a modified bubble coalescence-splitting balance model was found to give reasonable agreement with the measured void size profiles.

In order to avoid the negative impact of excessive oxygen in the combustion flue gases on the selectivity of most hydrocarbon selective catalytic reduction (HC-SCR) catalysts, an integrated NO(x) adsorption-reduction process has been proposed in this study for the treatment of flue gases under lean burn conditions by decoupling the adsorption and reduction into two different zones. The hypothesis has been validated in a novel internal circulating fluidized bed (ICFB) reactor using Fe/ZSM-5 as the catalyst and propylene as the reducing agent. Effects of propylene to the NO(x) molar ratio, flue gas oxygen concentration, and gas velocity on NO(x) conversion were studied using simulated flue gases. The results showed that increasing the ratio of HC:NO improved the reduction performance of Fe/ZSM-5 in the ICFB reactor. NO(x) conversion decreased with an increasing flue gas flow velocity in the annulus U(A) but increased with an increasing reductant gas flow velocity in the draft tube U(D). The NO(x) adsorption ratio decreased with increasing U(A). In most cases, NO(x) conversion was higher than the adsorption ratio due to the relatively poor adsorption performance of the catalyst. Fe/ZSM-5 showed a promising reduction performance and a strong inhibiting ability on the negative impact of excessive O2 in the ICFB reactor, proving that such an ICFB reactor possessed the ability to overcome the negative impact of excessive O2 in the flue gas using Fe/ZSM-5 as the deNO(x) catalyst.

The cure kinetics of epoxy-novolac compounds were Studied by means of differential scanning calorimetry with a dynamic approach. On the basis of a modified version of our previously reported kinetic model, a procedure aiming at the phenomenological description of the cure kinetics was developed. The reactions were found to be autocatalytic in nature for both commercial epoxy-novolac molding compounds and silica-free imidazole-cured epoxy-novolac systems. The weak extent of autocatalysis in the epoxy-novolac molding compounds was likely due to their high content of silica fillers. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2373-2377, 2009

Poly(vinylidene chloride-co-vinylchloride)/organically modified hectorite (VDC-VC/SPN) nanocomposites were prepared by melt blending VDC-VC copolymer with SPN in the presence of dioctyl phthalate, which acted as a plasticizer. As a result, the exfoliated structure was found in the VDC-VC/SPN nanocomposites. In nitrogen atmosphere, VDC-VC/SPN nanocomposites exhibited a single-step thermal degradation. The thermal stability of VDC-VC/SPN nanocomposites is significantly influenced by the SPN, which was modified with long alkyl ternary ammonium salt. In air atmosphere, VDC-VC/SPN nanocomposites revealed a two-step thermo-oxidative degradation behavior. At the first degradation stage, the weight loss pattern is similar to that of VDC-VC composites in nitrogen, in which the thermo-oxidative stability of VDC-VC/SPN nanocomposites is affected by the ternary ammonium salt and oxygen rather than its morphology. At the second degradation stage, both the enhanced thermo-oxidative stability and the flame-retardation ability of VDC-VC composites are strongly and closely related to the morphology of nanocomposites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3171-3180, 2009

It is shown that gas sampling from fluidized beds can provide misleading information due to hydrodynamic factors, biased sampling from the dense phase and radial gradients. Caution is needed to avoid these problems and in the interpretation of gas-sampling data.

Time series of differential pressure fluctuation at various axial and radial positions were obtained at various positions of a spouted bed of 0.12 m ID for operating conditions under different flow regimes, and were analysed to give correlation dimension and Kolmogorov entropy. It has been found that both correlation dimension and Kolmogorov entropy can describe the flow structure of gas-solid two-phase flow in different spouted bed flow regimes. Two correlation dimensions and two Kolmogorov entropies were obtained in the unstable spouting regimes, while only one correlation dimension and one Kolmogorov entropy were found for the stable spouting flow regimes.

Experiments were conducted in a small cyclone separator (50 mm inner diameter) with two grades of commercial polyethylene particles, to study the electrostatic charge generation during the transportation and separation. Results show clearly that the charges generated in the cyclone test unit were quite reproducible. When solid particles were fed to the cyclone, there was an abrupt change in the current flow and a quick increase of (negative) charge generation for both types of polyethylene particles. Both the charge density and the charge generation rate were always higher for the particles of higher density and smaller mean size. For both types of polyethylene, the (negative) charge density increased almost linearly with the gas velocity. When the solid feed rate or initial solid loading increased, the magnitude of the charge density decreased because there were fewer particle-wall collisions at higher solids feeding rate or higher solids concentration, due to shielding effects. Results indicate that the pipe section contributed < 10% of the total charge generation for both grades of polyethylene, with charge generation being dominated by the interaction between the particles and the cyclone internal surface.

Hydrodynamic characteristics of a gas-liquid-solid conical fluidized bed were studied and compared with both liquid-solid conical beds and three-phase cylindrical fluidized beds. The effect of bubbles on particle mixing, pressure drop, and minimum fluidization velocity were discussed. Minimum fluidization velocities predicted by modified Ergun equation which accounts for the variation of the cross-sectional area with the bed height were found to be in good agreement with the liquid-solid conical fluidized bed data. The models of Song et al. [Can. J. Chein. Eng. 1989, 67, 265] and Zhang et al. [Power Tech. 1998, 100, 113; PhD. Thesis, 1996], derived originally for three-phase cylindrical fluidized beds, respectively, were modified for the prediction of U-mf in a three-phase conical fluidized bed by accounting for the geometrical variation of the conical bed. It is found that the modified Song et al. model gave a better agreement than the modified Zhang et al. model in comparison with the current experimental data. However, the prediction of the modified Zhang et al. model is much improved when the parameter a, fractional gas holdup, was estimated using the equation from the Song et al. model.

There have been increased interests on exporting wood pellets from Canada to Europe to meet the increased demand on biofuels in European countries. The wood pellet industry in Canada, especially in the west coastal region, has grown at an annual rate of more than 20% averaged over last 5 years due to the steady supply of wood residues. This paper attempted to analyze the fuel consumption and air emissions associated with the wood pellet production in British Columbia and export to Sweden based on a streamlined life cycle analysis, starting from tree harvesting for wood residue production to the shipping of wood pellets from Vancouver to Stockholm in Sweden. The results showed that about 7.2GJ of energy is consumed for each tonne of wood pellets produced and shipped to Europe, representing about 39% of the total energy content of the wood pellets. Among those energies consumed over the life cycle, about 2.6GJ is associated with long-distance ocean transportation. The ocean transportation is also the major contributor to environmental and health impacts, followed by the pellet production processes. The fossil fuel content, which quantifies the amount of fossil fuel consumed over the life cycle, for exported wood pellets ranged from 19% to 35%, depending on whether natural gas or wood residue is used in the drying operation during the wood pellet production stage. To reduce the fossil fuel content and the environmental impacts, wood residues should be used in the drying operation and, if possible, local market should be explored to reduce the energy consumption associated with wood pellet transportation over long distances.

A new calibration set-up was designed and assembled, and a comprehensive sensitivity analysis was conducted to investigate factors that may affect the calibration of the effective distance of an optical fibre particle velocity probe. It is shown that the glass window has the most significant impact on the calibration result.The optical fibre probe was then applied to measure local particle velocities and solid fractions inside a half and a full circular conical spouted bed. It is found that the overall particle velocity profiles, as well as the shapes of the spout and fountain are quite similar in both columns.