Can Die Configuration Influence Field‐Assisted Sintering of Oxides in the SPS Process?

Spark plasma sintering (SPS) is a high current, low voltage process. Nevertheless, the system voltage (3–10 V) can be large enough to produce significant fields across a thin, insulating sample. A lumped circuit model is analyzed to estimate the magnitude of this field in terms of the die geometry. Normalizing the sample voltage with respect to the system voltage, and the die wall thickness to the punch radius preserves generality of the results. It is predicted that if the latter ranges from 0.15 to 0.25, then 30% of the system voltage may be expressed across the sample. Thus, a sample thickness of about 1–2 mm may experience a field of 10–30 V/cm, which would be large enough to induce field‐assisted sintering in yttria‐stabilized zirconia. The results are corroborated with finite element analysis. The contact resistance is assumed to be negligible; finite values of the contact resistance would lead to fields that are higher than predicted.     

Study on the Improvement of Crystallization in HDPE Induced by High–Molecular-Weight Polyethylene Through Dynamic Packing Injection Molding

The effect of high–molecular-weight polyethylene (HMWPE) on crystal morphology was investigated for high-density polyethylene (HDPE) through dynamic packing injection molding (DPIM). With the aid of differential scanning calorimetry (DSC), wide-angle x-ray diffraction (WAXD), and scanning electron microscopy (SEM) measurements, a typical web-like shish kebab morphology, which markedly increases stiffness and toughness, was found in HMWPE-induced samples through DPIM. The SEM results show that the much better web-like shish kebab structure, in which most of the lamellae connect different columns, compared with conventional shish kebab, was formed in HDPE blends with 4% HMWPE content (B4) through DPIM. The WAXD studies indicate that orientation degrees of crystallographic planes (110) and (200) in the B4 samples were much higher than those of samples molded by static packing injection molding and B0 samples molded by DPIM. A combination of the higher degree of crystal orientation and the formation of web-like shish kebab led to simultaneous great increments of stiffness and toughness, which overcomes the traditional limitation that stiffness and toughness cannot be greatly enhanced simultaneously. All these results show that HWMPE favored for great improvement of crystal structures in HDPE when its content is appropriate through DPIM.     

Some Features of Gas‐Flame Propagation in Narrow Tubes

The dependence of the flamefront curvature on the composition of the mixture in tubes of various diameters is considered. The combustionwave velocities are measured for different fractions of fuel in the mixture. It is shown that the dependence of the burning velocity on the composition of the mixture has two maximums, one of them being related to the transition of the laminar combustion mode to turbulent combustion. Combustion turbulization is caused by flame instability to acoustic oscillations. Variations of the combustionwave shape due to acoustic oscillations are observed.     

Optimization of the Sodium Hydroxide–Assisted Hydrogen Sulfide Selective Removal from Natural Gas

Scrubbing of hydrocarbon-based gases such as natural gas or biogas is essential prior to its use. These gas mixtures when contaminated with hydrogen sulfide cause safety, environmental, and corrosion problems in pipelines. There are several methods of reducing the content of hydrogen sulfide in sour gases, but few of these are selective as well. Selectivity is important to avoid unnecessary chemical usage. Chemisorption in sodium hydroxide solution by applying a special spray technique appears to be an efficient and selective method for hydrogen sulfide removal. This study aims to determine the characteristic of system and thereby facilitating the design of gas-cleaning parameters. The studied parameters include the contact time, concentration of sodium hydroxide, absorbent volumetric flow rate, and gas composition. Model gas mixtures of hydrogen sulfide, carbon dioxide, and nitrogen were used for experiments. To define the optimal experiment setup, the Box–Behnken design (BBD) method was applied. Based on the method, the number and the condition of necessary absorption experiments were constructed. To rank the operating parameters of the absorption process from the point of view of which effect is more significant on the scrubbing performance, statistical analysis of variance (ANOVA) was done. The analysis shows contact time and concentration of sodium hydroxide as the two most influential factors in the absorption process. Carbon dioxide content of sour gas as influencing factor was examined for efficiency and order of priority parameters of process. An extended model has been created to support the optimization of operating conditions in the investigated removal system.     

Limits of Increasing the Penetration of Shaped‐Charge Jets by Pulsed Thermal Action on Shaped‐Charge Liners

The effect of preheating of liners on the penetration capability of shaped charges is considered theoretically. It is shown that for a plastically fractured shapedcharge jet, preheating of the liner generally increases the effective jet length and shapedcharge jet penetration. Restrictions on the parameters of preheating of shapedcharge liners due to the possible thermal initiation of the explosive are established. It is noted that excessive weakening of a shapedcharge jet can lead to transition from plastic to volume fracture with a corresponding decrease in shapedcharge jet penetration. The ultimate possibilities of the thermal method for increasing the penetration capability of shaped charges are estimated. Calculation results are compared with available experimental data.     

Trans‐Lanthanide Extraction Studies in the TALSPEAK System: Investigating the Effect of Acidity and Temperature

A recent review of the TALSPEAK (Trivalent Actinide ‐ Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes) process summarized previous research characterizing the performance of this system. Attempts were made in that report to develop correlations between the previous separations data and the thermodynamic data that describes the interactions among the components of the separation system. However, the diversity of observations and the breadth of conditions employed in the many studies from the literature make comparisons between the TALSPEAK system performance and existing thermodynamic data challenging. To better test the adequacy of the available thermodynamic database for modeling this system, an internally consistent set of observations of lanthanide extraction under TALSPEAK conditions is offered in this report. The extraction of the lanthanides from La through Lu (excluding Pm) plus Y, and that of Am³⁺ from buffered lactic acid solutions containing diethylenetriamine‐N,N,N′,N″,N″‐pentaacetic acid (DTPA) into organic solutions of bis‐(2‐ethylhexyl)phosphoric acid (HDEHP) solutions in 1,4‐diisopropylbenzene has been investigated as a function of temperature, pH, and ionic strength. Extraction of both lanthanides and Am³⁺ decreases with increasing pH and with temperature. At the same time, separation factors remain approximately constant. Calculations based on an internally consistent thermodynamic data set confirm the prior conclusion that the existing thermodynamic data do not predict the observed decline in partitioning with increased pH, though the data do support the constancy of the separation factors. The relationship between the basic thermodynamic data, calculated speciation, and the performance of the separation system is discussed.     

First Gas Fields in the Source Region of the West-East Gas Transmission Project Start Production

Following the completion of Yaha gasfield and Kela 2 gas field,Jilake con-densate gas field that is another gasfield in Tarim gas region that partici-pates in west-east gas transmissionstarted production on April 9.Jilake gasfield is located in Xinjiang Luntai     

Equilibrium Studies on the Synergic Liquid‐Liquid Extraction Process of Copper(II) from Sulphate Media with Mixtures of some Bidentate Mono‐Schiff Bases and Acyclic Polyether Non‐ionic Surfactant in Chloroform

The liquid‐liquid extraction of copper(II) with bidentate mono‐Schiff base extractants(HL), namely, N‐salicylideneaniline (SA), N‐(2‐hydroxy‐1‐naphthalidene)aniline (HNA), N‐salicylidene‐1‐naphthylamine (SN), and N‐(2‐hydroxy‐1‐naphthalidene)‐1‐naphthylamine (HNN), from a weakly acidic sulphate media into chloroform was studied in both the absence and the presence of acyclic polyether non‐ionic surfactant (S). In the absence of the non‐ionic surfactant, the extractability of copper(II) was 92.6% with SA, 89% with HNA, 81% with SN, and 80% with HNN. The estimated extraction constants, (log K_ex) of the four extractants revealed that the extraction efficiency increased in the order HNN< SN< HNA<SA. Besides, it was found that copper(II) was extracted as CuL₂ (HL) with SA and HNA, and as CuL₂ with SN and HNN. The extraction of copper(II) was significantly enhanced with HL into chloroform upon the addition of a non‐ionic surfactant. An extractability of 100% was reached. The stoichiometry of the extracted complexes was CuL₂S. The synergic extraction ability of extractants changed in the order SA>HNA>SN～HNN, whereas, the synergic effect fell in the order HNN>SN>HNA～SA.     

Computational and Theoretical Studies of Mass‐Spectrometric Measurements of the Comet Halley Dust Composition in Vega Experiments

Results of computational and theoretical studies are presented. A formulation of the problem is given and approaches to its solution are described. Brief information is given on the models, difference methods, and software designed or adapted to perform direct numerical modeling of massspectrometric measurements of cometary dust on PUMA instruments. The results of a number of computational experiments are presented.     

Studies on the Sorption of Palladium using Cross‐Linked Poly (4‐Vinylpyridine‐Divinylbenzene) Resins in Nitric Acid Medium

Various cross‐linked (4, 8, and 12%) gel‐type weak‐base poly(4‐vinylpyridine) (PVP) resins were studied for palladium recovery from nitric acid medium. The sorption of palladium was found to decrease with an increase in cross‐linkage of the resin. 8 and 12% PVP resins exhibited maximum D _Pd(II) values at 2–6 M HNO₃, whereas 4% PVP resin showed maximum D _Pd(II) values at lower acidities (0.1 M HNO₃). FT‐IR, SEM, and XPS techniques were used for the characterization of palladium‐loaded resins. Detailed studies were carried out with the resin of modest cross‐linkage i.e., 8% PVP resin. The sorption isotherm studies revealed that the maximum palladium loading approaches the theoretical capacity of the resin, presuming the sorption of palladium as divalent anion at 4 M HNO₃. The pseudo‐second order kinetics model yielded the best fit for the experimental data of sorption kinetics. An increase in temperature accelerates the rate of palladium extraction and also the addition of chloride ions increases the palladium uptake. Column studies were performed using 4 and 8% PVP resins in 2 and 4 M nitric acid concentrations. The loaded palladium could be eluted efficiently with acidic thiourea solution.     

Comparison of the catalytic properties of Al‐ZSM‐22 and Fe‐ZSM‐22 in the skeletal isomerization of 1‐butene

The catalytic activities of Al‐ZSM‐22 (Al in the framework) and Fe‐ZSM‐22 (Fe in the framework) were compared in the skeletal isomerization of 1‐butene to isobutene. The catalysts synthesized in the laboratory were characterized by means of XRD, FTIR spectroscopy, SEM and surface area measurements. The activity of the zeolites was investigated using a fixed‐bed microreactor system. Al‐ZSM‐22 demonstrated higher activity in 1‐butene transformation compared to Fe‐ZSM‐22, while the selectivity to isobutene, on the other hand, was higher over Fe‐ZSM‐22. Coke formation was monitored using a microbalance and the results showed that the weight gain of Fe‐ZSM‐22 was slightly higher compared to Al‐ZSM‐22. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gas–particle partitioning of organic compounds in the atmosphere

Gas–particle partitioning of condensable organic compounds in the atmosphere is described using two methods. The first method is based on the use of a comprehensive mechanistic model of adsorption/absorption processes. The second method is based on aerosol yields estimates. The model parameters in the adsorption/absorption model are evaluated from experimental data. The concepts of concentration of adsorbed molecules on the surface of aerosol particles and diffusion of adsorbed molecules in the liquid phase are used for determining the importance of the adsorption/absorption mechanisms. The model calculations showed a qualitative agreement with available experimental data for alkanes. Furthermore, a modified version of the Carbon Bond IV chemical mechanism including an aerosol yields method to model the formation of organic aerosols in reactive plumes is used in combination with a plume dispersion model. The formation of secondary organic matter in plumes contributes significantly to the total secondary aerosol mass produced.     

Gas‐Dynamic Method of Determining Combustion Efficiency in a Model with Combustion

A method of determining combustion efficiency and testgas parameters along the combustion chamber with a supersonic velocity of air at the entrance is considered. The composition and properties of the test gas are determined by a thermodynamic calculation with allowance for dissociation and temperature dependence of the energy of internal degrees of freedom. The sources of errors and the influence of accuracy of initial data definition in a zerodimensional approach to determining the combustion curve and flow parameters are studied.     

Study of the Coagulation Property of Polyaluminum Silicate Chloride Coagulants Prepared with Ultrasonic‐Assisted NaOH Dosing

Abstract

Polyaluminum Silicate Chloride (PASiC) is a new water treatment coagulant. It contains silica that can be hydrolyzed to produce SiO₂ as coagulant aid. Hence, this coagulant consumes little alkalinity and is effective at low dosages. It is, therefore, especially suitable for treating water of low alkalinity and low turbidity. When manufacturing PASiC, the alkalinity solution involved in the polymeric reaction must be added slowly to the aluminum salt solution to avoid local over‐saturation which enhances the production of high‐valence medium polymer species (Alb) (e.g. Al₁₂AlO₄(OH)₂₄ ⁷⁺, Al₁₃). In this research, the use of an ultrasonic vibrating system to assist the alkalinity dosing during the formation of PASiC was studied. The ultrasonic vibrating system breaks up the NaOH solution into fine mists so that the latter can be more evenly dispersed into the aluminum silica solution to avoid local over‐saturation. This ultrasonic‐assisted NaOH dosing method leads to a more stable polymerization of aluminum changing ratios of Ala, Alb, and Alc in the final product and raising the Alb portion in the coagulant. Long‐term observations also show that PASiC prepared with the ultrasonic‐aided NaOH dosing at 0.25 mL/min is more effective in removing turbidity.     

Increasing the Efficiency of Hydrocarbons С5+ Extraction from the Gas of Condensate Fields by a Low-Temperature Absorption Process

Theoretical Foundations of Chemical Engineering - Absorption extraction of C5+ hydrocarbons from formation gas of gas-condensate fields at the level of temperature of from –25 to...     

Role of the Initial Formation of the Iron Nano-Particles in the Multi-Walled Carbon Nanotubes Growth Process

Careful preparation of the iron nano-particle catalyst for carbon nanotubes (CNTs) fabrication has crucial importance for initial growth of multi-wall carbon-nanotubes (MWCNTs). Thin iron layer was thermally deposited in a high vacuum onto the surface of the SiO2/Si wafer at about 300 K. The sample was heated up to 700℃ in a hydrogen atmosphere, and then the sample was heated once again at750℃ in ethylene atmosphere. After hydrogen treatment continuous Fe layer was changed into many well separated Fe nano-peaks. AFM, SEM and HR-TEM studies of deposited MWCNTs allow us to propose a growth mechanism for long, straight MWCNTs.     

A Separation Technology of H2/CO in the Process of Kailuan ＇ s Synthetic Process of Ethanediol

开滦在鄂尔多斯新建的煤制乙二醇项目中,要求对H2/CO混合气进行分离。生产中采用了深冷分离和H2提浓的联合技术进行分离,最终使得H2的回收率为80%～90%之间,H2纯度可达99%,CO纯度〉99%,为乙二醇的合成提供了合格、优质的原料气。     

Studies on Macro-kinetics of Gas Phase Polymerization of Butadiene with Rare-earth Catalyst

The study of the kinetics of gas phase polymerization of butadiene with heterogeneous catalyst based on neodymium (Nd) was carried out. The effects of reaction temperature, reaction pressure, dispersing medium, and types of catalyst on kinetics of polymerization were investigated. A kinetic model with two kinds of active sites was proposed. The results show that the effects of the reaction temperature and the types of dispersing medium and catalyst on the kinetic performance of polymerization are significant, and that the combined model of first and second order decay of active site of catalyst can be used to describe the phenomena.     

Initiation of Ignition by the Action of a High‐Current Pulsed Discharge on a Gas

The possibility of nonthermal initiation of chemical reactions by a uniform pulsed nanosecond discharge is demonstrated. Dependences of variation of the ignition delay on initial conditions are obtained. It is shown that the main role in combustion initiation under conditions of a pulsed gas discharge in the case of moderate electric fields and low degree of ionization belongs to reactions of dissociation quenching of electronexcited levels of nitrogen.