Liquid‐Solid Mass Transfer Behavior of a Stirred‐Tank Reactor with a Fixed Bed at Its Bottom

The mass transfer behavior of a new batch stirred tank with a fixed bed of Raschig rings at the bottom was studied using diffusion‐controlled dissolution of copper in acidified dichromate. Variables studied, amongst others, were the impeller rotation speed, Raschig ring diameter, fixed‐bed height, and impeller geometry. The rate of mass transfer from the fixed bed to the solution increased with increasing impeller rotation speed, decreasing particle size, and decreasing bed height. The axial‐flow turbine is more efficient in increasing the rate of mass transfer than the radial‐flow turbine. The presented reactor is especially useful for conducting diffusion‐controlled liquid‐solid catalytic reactions involving reactants that need to be dispersed first, such as sparingly soluble solid particles.     

Effect of water absorption on the izod impact energy of crosslinked poly(methyl methacrylate-acrylic acid) and their composites

Crosslinked poly(methyl methacrylate-acrylic acid) and composites using this crosslinked copolymer as the matrix have been synthesized and evaluated for their potential as bioimplantable materials in design of a new class of bone anchors. The low-velocity impact energy absorption properties of this slightly hydrophilic class of materials were examined by Izod impact testing. In particular, the influence of swelling (by absorption of water) on the impact resistance of the crosslinked copolymer and composites based on this copolymer was investigated. Also, the influence of fiber type and preform architecture on the impact resistance of the composite, in both the dry and swollen states, was investigated. The fracture surfaces and the modes of failure in these tests were examined using scanning electron microscopy. The results indicated that absorption of water leads to about a threefold increase in the impact resistance of the copolymer. However, the increase in the impact resistance of the composite samples after water absorption varied considerably, depending on the type and form of fibrous reinforcement. These results and our understanding of the role of water absorption on the impact resistance of these novel systems are presented.     

高压三相感应电机缺相检测的一种新技术

Open phase in three phase induction motors is a common fault that can occur as a result of a fuse blowing or a pro- tective device failing on one phase of the motor. This paper introduces a new method,which is based on the transient mea- surement and can distinguish the fault of one phase connecting ground. The method has been proved to be in correspondence with the simulation results by Matlab and LabVIEW in practice, The method has merits of simplicity, accuracy and ease of USe.     

New corrosion inhibitors based on fatty materials—II. Epoxidized fatty materials modified with aromatic amines

Eight compounds prepared by modification of epoxidized linseed oil and oleic acid with aniline, p-chloro-aniline, p-toluidine and p-anizidine, were tested as corrosion inhibitors. The test coupons were mild steel and the environment consisted of 0.05N HCl at 70°C or mixed vapours of gasoline and HCl. In HCl, the percentage inhibition ranged from 26.0 to 59.5% for linseed oil and from 88.0 to 94.5% for oleic acid derivatives. In the gas phase, the ranges were from 70.3 to 85.98 and from 62.5 to 74.0%, respectively. The values obtained for two commercial inhibitors tested under the same conditions were 34.5 and 91.7% in HCl and 57.0 and 64.0% in the mixed vapours. The results conformed with a simple Langmuir model and with predictions based on NMR measurements, basicity values (pK_a) and Hammett constants. A ranking of the compounds according to percentage inhibition agreed with the order of increasing electron density on the nitrogen atom in these compounds.     

Evaluation of corrosion and erosion-corrosion resistances of mild steel in sulfide-containing NaCl aerated solutions

This paper reports results of potentiodynamic polarization, electrochemical impedance measurements and erosion-corrosion of mild steel in aerated sulfide containing 3.5% NaCl solutions at room temperature. The pitting corrosion behavior was studied in NaCl solution containing 0.001, 0.005 and 0.010 M Na₂S, using potentiodynamic polarization and electrochemical impedance spectroscopy. The erosion-corrosion resistance was evaluated after rotating the samples in sulfide polluted NaCl solution for 24 h at a velocity of 300, 600 and 900 ppm using a rotating disc electrode. Results showed that the presence of sulfide ions in NaCl solution resulted in a significant increase in the corrosion attack due to the local acidification caused by iron sulfide formation. The localized replacement of the protective Fe-oxide film by a non-protective iron sulfide film is responsible for the pitting and erosion-corrosion attack. The study concluded that the higher the concentration of sulfide in NaCl solution, the lower the resistance to pitting and erosion-corrosion. Moreover, increasing the solution rotating velocity affects negatively the erosion-corrosion resistance.     

Electroless deposition and characterization of Ni-P-WC composite alloys

A composite coating Ni-P-WC was produced using an electroless deposition technique from citrate bath containing WC powder. The influence of plating parameters such as WC content, pH, temperature and stirring rate on the content of WC codeposited with Ni-P alloys were investigated. The maximum value of WC (50-55 V_p) codeposited can be achieved at a particle content of 20 gL^− 1 in the electrolyte, at pH 5.5-6, temperature 85-90 °C and stirring rate of 150 rpm. Surface morphology and microstructure of Ni-P-WC coatings were determined by means of SEM and X-ray diffraction. It was found that the phase structure of the solid solution cannot be varied by codeposition of WC particles in Ni-P alloys, and it only influences the growth of the crystal planes. The properties of the composite such as hardness and abrasion resistance were also examined and compared with WC free nickel deposited layer. The presence of WC particles in the deposit significantly was found to improve the hardness and abrasion resistance of composite coatings.     

Electrochemical treatment of chemical oxygen demand in produced water using flow‐by porous graphite electrode

Produced water is the largest wastewater stream generated in the oil and gas industries. In this study, experiments were carried out using a bench‐scale electrochemical cell using flow‐by porous graphite electrode, for oxidation of organic matter in produced water which was collected from natural gas processing field (real sample). The effect of anodic current density and influent feed flow rate on chemical oxygen demand (COD) removal efficiency, and energy consumption were investigated. The maximum removal efficiency of 66.52% was obtained for a flow rate of 50 mL/min, current density of 1.41 mA/cm² and pH of 7.3 for an influent COD of 2845 mg O₂/L. The energy consumption at these conditions was 2.12 kWh/kg_COD.     

Improvement of four anode rods ion source

In this work, an improved form of a saddle field ion source has been designed and constructed. It consists of four anode rods made from copper and two copper cathode discs. The two cathode discs are placed symmetrically on both sides of the four anode rods. The electrical discharge and output ion beam characteristics were measured at different pressures using argon gas. The optimum distance between each two anode rods was determined. Also the optimum distance between the four anode rods and any cathode disc was obtained. It was found that the optimum distance between each two anode rods equal to 6 mm, while the optimum distance between the four anode rods and any cathode disc equal to 16 mm, where a stable discharge current and maximum output ion beam current can be obtained. The effect of negative extraction voltage applied to both the extractor electrode and Faraday cup on the output ion beam current was studied. The sputter yield of copper and aluminum targets using argon ions of different energies was determined.