Simulation of gas–solid two-phase flow in the annulus of drilling well

This paper investigates the hydrodynamic behavior of gas–solid two-phase flow in the annular space of an air drilling well under different arrangements by using three-dimensional approach. Two-fluid model is used to solve the governing equations in the Eulerian–Eulerian framework. Effect of eccentricity and drill pipe rotation on the pressure drop, volume fraction and velocity profile are examined. The results are compared with available data in the literature and good agreement is found. The results show that the presence of solid particles in the annulus change the air velocity profile significantly and create two off-center peaks velocity close to the walls instead of one peak velocity in the middle. Eccentricity of drill pipe makes more accumulation of the cuttings in the smaller space of the annulus. Increasing the eccentricity increases pressure drop due to impact of particles with annulus wall and also particles collision with each other. Rotation of the drill pipe shifts maximum air velocity location toward smaller space of the annulus which results more uniform cutting distributions in the annulus and improvement in their transportations. Pressure drop in the annulus increases as eccentricity and rotation of drill pipe increase.     

Investigation on cristobalite crystallization in silica-based ceramic cores for investment casting

In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process condition, the sintered samples at 1220 °C were also heated up to 1430 °C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43 wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was crystallized on the surface of fused silica grains at about 1380 °C. Flexural strength of the sintered cores was decreased after simulated casting heat treatment due to cristobalite phase transformation. The formed cristobalite on the surface of fused silica grains dramatically decreased the leachability of ceramic cores.     

Development of a method for chlorophyll removal from canola oil using mineral acids

Because of the high level of chlorophyll-type compounds found in canola oil, bleaching is an important and critical step in the canola oil refining process. In this study, a new method for reducing the chlorophyll-type impurities prior to the bleaching step was developed. This method is based on precipitating the chlorophyll compounds with mineral acids. Concentrations of chlorophyll-type compounds of up to 30 ppm could be reduced to amounts of less than 0.01 ppm by mixing the crude canola oil with a 0.4 wt% mixture of phosphoric and sulfuric acids (2:0.75, vol/vol) for 5 min at 50°C. Centrifugation and filtration also were examined as two main methods for separating the chlorophyll precipitates. The results showed that filtration by a precoated textural filter with filter-aid clay could separate the precipitates as well as the centrifugation method.     

A new nickel metal organic framework (Ni-MOF) porous nanostructure as a potential novel electrochemical sensor for detecting glucose

Journal of Porous Materials - A Ni-MOF-based novel electrochemical sensor was synthesized with high surface area of 1381 m2/g, significant porosity of 1.14–9.6 nm and average...     

Numerical investigation of grooves effects on the thermal performance of helically grooved shell and coil tube heat exchanger

Heat exchangers are integral parts of important industrial units such as petrochemicals, medicine and power plants. Due to the importance of systems energy consumption, different modifications have been applied on heat exchangers in terms of size and structure. In this study, a novel heat exchanger with helically grooved annulus shell and helically coiled tube was investigated by numerical simulation. Helically grooves with the same pitch of the helical coil tube and different depth are created on the inner and outer wall of annulus shell to improve the thermal performance of heat exchanger. In the first section, thermal performance of the shell and coil heat exchanger with the helical grooves on its outer shell wall was compared with same but without helical grooves. At the second section, helically grooves created on both outer and inner wall of the annulus shell with different groove depths. The results showed that the heat exchanger with grooves on both inner and outer shell wall has better thermal performance up to 20% compared to the heat exchanger with grooves on only outer shell wall. The highest thermal performance achieves at lower flow rates and higher groove depths whereas the pressure drop did not increase significantly.     

High Productive Ethylene Trimerization Catalyst Based on CrCl<Subscript>3</Subscript>/SNS Ligands

Abstract  

Methylaluminoxane (MAO)-activated chromium (III) complexes of tridentate SNS ligands of the form (RSCH₂–CH₂)₂NH (R = alkyl, aryl) have been prepared and tested for the trimerization of ethylene to 1-hexene. The effect of ethylene pressure, Al/Cr ratio and S donor substitution on 1-C6 selectivity and productivity has been examined. It is shown that when the substitution on S is pentyl group it will lead to the highest productivity, 174200 g 1-C6/g Cr h, due to the synergistic effect of this group.     

Application of silica gel/polyaniline composite for adsorption of ascorbic acid from aqueous solutions

Silica gel and a chemically modified silica gel with polyaniline (PAN) were used for adsorption of ascorbic acid (AA) from aqueous solutions. The surface morphology of the adsorbents was studied by scanning electron microscopy (SEM). Adsorption experiments were carried out using both batch and columnar systems. In batch system, the effects of some important parameters such as sorbent dose, contact time, initial concentration and temperature of the adsorbate were studied. Based on regression analysis, the sorption data obtained for SiO₂ were best represented by Freundlich isotherm and for the PAN/SiO₂ composite, the equilibrium sorption data were fitted better by Langmuir isotherm. The kinetic studies showed that the adsorption of AA on both sorbents follows pseudo second-order kinetics which implies a chemisorption mechanism and according to diffusion model, intra-particle diffusion is the rate-controlling step. The thermodynamic studies also showed that PAN/SiO₂ is a more effective adsorbent to adsorb AA than an unmodified SiO₂. In columnar mode, the effects of salt on breakthrough curve were investigated. Two kinetic models, Thomas and Adams–Bohart, were applied to experimental data to predict the breakthrough curves using linear regression and determine the characteristic parameters of the column. Error analysis was carried out to investigate the adequacy and accuracy of the model equations. Desorption study showed that the adsorbed ascorbic acid is readily eluted from the column using dilute solution of NaOH. PAN/SiO₂ was found to be a promising solid phase adsorbent to preconcentrate ascorbic acid from aqueous solutions and subsequent analysis.     

Effect of cellulose acetate/cellulose triacetate ratio on reverse osmosis blend membrane performance

Surface functionalization and modification including the grafting process are effective approaches to improve and enhance the reverse osmosis (RO) membrane performance. This work is aimed to synthesize grafted/crosslinked cellulose acetate (CA)/cellulose triacetate (CTA) blend RO membranes using N-isopropylacrylamide (N-IPAAm) as a monomer and N,N-methylene bisacrylamide (MBAAm) as a crosslinker. The morphology of these membranes was analyzed by scanning electron microscopy and their surface roughness was characterized by atomic force microscopy. The performance of these membranes was evaluated through measuring two major parameters of salt rejection and water flux using RO unit at variable operating pressures. It was noted that the surface average roughness obviously decreased from 148 nm for the pure CA/CTA blend membrane with 2.5% CTA to 110 nm and 87 nm for the grafted N-IPAAm and grafted/crosslinked N-IPAAM/MBAAm/CA/CTA-RO membranes, respectively. Moreover, the contact angle decreased from 51.98° to 47.6° and 43.8° after the grafting and crosslinking process. The salt rejection of the grafted CA/CTA-RO membrane by 0.1% N-IPAAm produced the highest value of 98.12% and the water flux was 3.29 L/m²h at 10 bar.     

Phase behaviour modelling of Athabasca bitumen for in situ combustion applications

Phase behaviour modelling of reservoir fluid is a fundamental step for reservoir simulation. Furthermore, as the complexity of the recovery process increases, the fluid model plays a more important role in the reliability of the simulation outputs. Although the in situ combustion enhanced oil recovery method (ISC) is one of the most complex recovery techniques available in the petroleum engineering literature, for most of the simulation jobs related to this elaborate process only simple and rudimentary fluid characterization layouts are considered. In this work, the principal fluid properties of Athabasca bitumen with regard to the ISC process are recognized, extracted from the literature, validated for consistency, and used for the development of an inclusive and accurate fluid model. Then the fluid model is fully developed while considering the ISC reaction kinetics so that the model has both accuracy, indispensable for phase behaviour modelling, and consistency, essential for the reactions definitions.     

The odontogenic differentiation of human dental pulp stem cells on hydroxyapatite-coated biodegradable nanofibrous scaffolds

The authors aimed to design nanofibrous (NF) scaffolds that facilitate odontogenic and osteogenic differentiation of human dental pulp-derived mesenchymal stem cells (DPSCs) in vitro. For this purpose, hydroxyapatite (HA)–loaded poly (L-lactic acid)/poly (?-caprolactone) (PLLA:PCL 2;1) blend NFs were prepared using the electrospinning method. Alizarin red activity and cell viability were evaluated by MTT assay, and SEM revealed the proliferation properties of NF scaffolds. QRT-PCR results demonstrated that HA-loaded PLLA/PCL can lead to osteoblast/odontoblast differentiation in DPSCs through the up-regulation of related genes, thus indicating that electrospun biodegradable PCL/PLA/HA has remarkable prospects as scaffolds for bone and tooth tissue engineering.