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In the light of NASA's New Horizons mission, the solid-phase behaviour of methane and nitrogen has been re-examined and the thermal expansion coefficients of both materials have been determined over their whole solid temperature range for the first time. Neutron diffraction results indicate that the symmetric Pa3 space group is the best description for the α-nitrogen structure, rather than the long-accepted P213. Furthermore, it is also observed that β-nitrogen and methane phase I show changes in texture on warming, indicating grain growth.

• Operating conditions greatly affect fine particle velocity in spouted beds. • Optimum solid circulation is attained at 2-3 ums velocities in all configurations. • Solid velocities are low at high air velocities with the nonporous tube. • Light particles show high velocity oscillation frequency. [Display omitted] Spouted bed stability and operation is greatly affected by particle features. Accordingly, the hydrodynamic behaviour of conical spouted beds has been studied for fine particles differing in size and density in a wide range of inlet air flow rates. This knowledge is essential for a successful scaling up and industrial implementation of the spouted bed. Therefore, the effect air velocity and solid properties (density and size) have on local solid velocity has been ascertained in a fountain confined conical spouted bed using a borescope technique (Particle Tracking Velocimetry, P T V) applied to several bed configurations. The results show a close relationship between the inlet air velocity and the local solid velocity, with the gas-solid contact being especially vigorous in the configurations without draft tube and with the open-sided draft tube. The solid circulation flow rate is lowest when a nonporous draft tube is used due to the low solid vertical velocities in the annulus, even at high air flow rates. Nevertheless, vertical velocities in the annular zone increase when particle size and density are increased, although these velocities are lower in the spout and fountain regions due to the higher momentum exchange required for their acceleration. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks with highly ordered porosity have been studied extensively. In this paper, the effect of framework (pore) disorder on the gas sorption of azole-based isoreticular Cu(II) MOFs with rtl topology and characteristic 1D tubular pore channels is investigated for the first time. In contrast to other isoreticular rtl metal–organic frameworks, the Cu(II) metal–organic framework based on 5-(1H-imidazol-1-yl)isophthalate acid has a crystallographically identifiable disordered framework without open N-donor sites. The framework provides a unique example for investigating the effect of pore disorder on gas sorption that can be systematically evaluated. It exhibits remarkable temperature-dependent hysteretic CO2 sorption up to room temperature, and shows selectivity of CO2 over H2, CH4 and N2 at ambient temperature. The unique property of the framework is its disordered structure featuring distorted 1D tubular channels and DMF-guest-remediated defects. The results imply that structural disorder (defects) may play an important role in the modification of the performance of the material.

• A CFD-DEM study of gas-solid heat transfer process in fluidized bed is presented. • The effects of particle size, density and heat capacity are investigated. • Two aeration settings are considered (same gas velocity or fluidization number). • Heating rate and temperature uniformity in the bed are quantitatively evaluated. The solid properties are of significant influence on the thermal performance of the fluidized bed. In order to provide valuable information for the application of this equipment, a numerical study is carried to clarify the effects of solid properties on the heat transfer characteristics in a lab-scale fluidized bed by means of the CFD-DEM method. Specially, two aeration conditions, i.e. the same superficial velocity and the same fluidization number, are considered. The results show that the violent convective mechanism at bed bottom plays a significant role in the heating of the bed material. The entrainment of rising bubbles and hence solid mixing are the key factors to get better temperature uniformity of the bed during the heating process. With the decrease of particle density and size, the internal circulation of solid phase is strengthened under the same superficial velocity, while slightly weakened under the same fluidization number. Obvious resemblance can be captured between solid mixing and temperature uniformity, and the enhanced solid mixing usually leads to homogeneous temperature distribution of the bed. It can be found that the heating rate decreases with increasing solid density regardless of aeration setup. In addition, it is positively related to particle diameter under the same fluidization number, while keep unchanged under the same superficial velocity. Furthermore, enhanced solid mixing and better temperature uniformity can be captured with increasing solid heat capacity, which confirms that gas temperature shows considerable effect on gas-solid flow. [ABSTRACT FROM AUTHOR]

A Computational Fluid Dynamics (CFD) model of flotation column was developed and validated against published experimental data. The model is based on an Eulerian multi-fluid formulation with k – ɛ turbulence model and includes three phases: gas bubbles, liquid and solid particle suspended in the liquid. The model is developed by writing FORTRAN subroutine and incorporating then into the commercial CFD code AVL FIRE, v.2014. The gas holdup in flotation column was predicted as a function of superficial gas velocity and solids concentration. The effect of particle type, density, wettability and concentration on gas holdup and bubble hydrodynamics (i.e. bubble size distribution, and attached particle density) were studied. The rate of removal of particles from the pulp zone was obtained with kinetic equations for the three sub-processes: collision, attachment, and detachment involving number density of bubbles and particle concentrations, which were also calculated in this model. As confirmed by the comparisons with available data, the modelling methodology proposed in this work represents the physics of flotation column consistently, since the CFD model correctly predicts the experimental effects of gas flow rate and solid concentration on gas holdup within the range of ±20%. It was found that the addition of hydrophobic particles to the air/water mixture promotes bubble coalescence and, therefore, reduces the gas holdup, while the addition of hydrophilic particles suppresses bubble coalescence and increases the gas holdup. It was also found that the increase of gas flow rate leads to an increase in the attached particle density due to the increase of the concentration number of bubbles that were available for the attachment process. Further, the increase of hydrophobic particles concentration led to an increase in the attached particle density. [ABSTRACT FROM AUTHOR]

Bubbling fluidization has been widely applied in process industries, such as power generation from coal, renewable energy production, gasification and pyrolysis. In this study, we attempted to predict solid flow patterns in a bubbling fluidized bed based on operational conditions, the air distributor and particle velocity. We first investigated the effect of operational conditions and the air distributor on solid/gas flow patterns, and investigate the correlations between solid/gas flow patterns with the solid mixing, solid and gas contact, and bubble behaviour within bubbling fluidized beds by using positron emission particle tracking (PEPT). A 'Flow Pattern Parameter (FPP)' is then proposed to identify the solid flow pattern in a bubbling fluidized bed. The 'Flow Pattern Parameter (FPP)' consists of particle kinetic energy, bed aspect ratio (H/D), pore size of air distributor, minimum fluidization velocity, and superficial gas velocity. The results show that solid flow patterns in the bubbling fluidized bed can be clearly classified based on the Flow Pattern Parameter. Different flow pattern corresponds to a certain range of the Flow Pattern Parameter. [ABSTRACT FROM AUTHOR]

Abstract: The solid-state properties were studied for different batches of hydroxypropyl methylcellulose (HPMC). The batches had similar chemical composition, but different degree of heterogeneity with regard to the distribution of the substituents along the polymer chains. The glass transition temperature, T g, was analysed using a new developed method where dynamic mechanic analysis, DMA, was performed in compression mode on compacts, utilizing a wedge-shaped probe. The method was verified by conventional DMA on films. Molecular interactions were studied using FT-IR. In addition, the water vapour sorption was determined by gravimetric measurements and the plasticization by water vapour was studied on film samples using DMA. The results revealed a linear relationship between increasing T g and increasing percent glucose liberated after enzyme hydrolysis. The percent glucose liberated can in turn be considered to account for both the heterogeneity of the substituents and the total degree of substitution. The results indicated that more heterogeneously substituted cellulose derivatives and derivates with a lower degree of substitution had stronger interactions between polymer chains. As expected from these results, some small difference in the plasticization by water vapour could be detected. However, no significant differences were found in molecular interactions using FT-IR or in the sorption of water vapour. The correlation between heterogeneity in the distribution of the substituents and T g is of much interest as heterogeneously substituted batches of HPMC have been previously shown to exhibit very different behaviour in solution and in gelling tablets. [Copyright &y& Elsevier]