Centrifugation equilibrium of natural gas

The problem of determining the pressure and composition profiles of natural gas under centrifugation is formulated and solved as the minimization of a modified Helmholtz function that includes the contribution of the centrifugal field. Fluid properties are calculated using the Peng-Robinson equation of state but the procedure can be readily extended to use other thermodynamic models. The simulations indicate that there may be a liquid phase in the centrifugation cell. However, even in cases with a single gas phase, there are large differences in composition, pressure, and density between the regions close to and away from the rotation axis, confirming the idea that centrifugation might be a useful method for removing contaminants from natural gas.     

促进天然气水合物形成的影响因素分析

天然气水合物(NGH)工业化生产中面临的主要问题是天然气水合物的合成速率较低。天然气水合物的生成反应为相间界面反应,任何影响气液相之间传质或传热的操作均可以增加天然气水合物的生成速率。结合影响天然气水合物形成的特点,从改善相平衡条件、增加气水接触面积和增加天然气的溶解度三方面介绍了促进天然气水合物形成的办法,并分析了各自的优缺点。     

H_2和CO_2在甲苯中的二元系相平衡特性研究

建立了1套连续式热力学平衡测量装置,在压力1．5～10 MPa,温度303～343 K范围内,测量了H_2和CO_2在甲苯中的二元系平衡溶解度数据。结果表明,2种气体在甲苯中的溶解度均随压力增大而增加。H_2在甲苯中的溶解度随温度升高而增大。CO_2在甲苯中的溶解度则随温度升高而减小。考虑1个二元相互作用参数,将实验数据用Peng-Robinson状态方程式进行关联,可以获得满意的计算精度。     

Changes of solubility parameters during evaporation of solvents as a factor influencing the self-stratification of epoxy/acrylic systems

Behaviour of solutions of binary mixture of epoxy/acrylic resins during solvent evaporation was examined. Properties of various liquid compositions at different stages of solvent evaporation were characterised by their solubility parameters and surface tension. Both parameters were calculated from the weight fractions of particular components determined by gas chromatography (GC). Phase separation during solvent evaporation and self-stratification were observed and characterized using optical microscopy and FTIR methods. The results of investigations indicate the possibility of using these methods in order to foresee behaviour of binary compositions.     

Evaluation of potassium formate as a potential modifier of TEG for high performance natural gas dehydration process

Triethylene glycol (TEG) is one of the most effective sorbents for natural gas dehydration. There are many processes using this approach but none of them can combine high performance and economical energy consumption. In this study hydrocarbon–water phase behavior was investigated for different TEG concentrations in different natural gas dehydration processes. The equilibrium correlations were investigated for predicting water dew point as a function of TEG concentration. The effect of TEG concentration on the outlet gas dew point was also determined using phase envelope diagrams. The results showed that the (DRIZO) process achieved the most significantly reduces water dew point followed by conventional stripping gas dehydration process. Moreover, TEG was modified using potassium formate as additive. The results showed that the absorption capacity of the modified TEG was improved, that is almost duplicated. This modification augments the performance of the proposed mixture which can be potentially applied to a real scale process.     

自动管板氩弧焊机在换热器生产上的应用

介绍了WMZ1 31 5型管子管板全位置数控脉冲氩弧焊机在换热器的管子与管板接头焊接中的应用 ,对手工氩弧焊和自动管板焊接进行了对比分析讨论     

TiO2/modified natural clay semiconductor as a potential electrode for natural dye-sensitized solar cell

TiO₂/modified natural bentonite clay semiconductor, as a potential electrode of dye-sensitized solar cell, having a Ti:Si molar ratio of 85:15 was, for the first time, compared with pure TiO₂ (commercial P25) electrode in terms of solar cell efficiency and characteristics. 4-Chloro-2,5-difluorobenzoic acid and 4-(chloromethyl)benzoyl chloride were added to the electrodes to increase light harvesting ability of natural dyes extracted from red cabbage, rosella, and blue pea. The results showed that the TiO₂/clay semiconductor provided a higher surface area but a slightly lower efficiency than the pure TiO₂. The best natural sensitizer was found to be the dye extracted from red cabbage. Besides, the 4-(chloromethyl)benzoyl chloride provided a higher short circuit current for the TiO₂/clay semiconductor.     

Evolution on phase composition and properties of alumina-based ceramics fabricated from high-titania special-grade natural bauxite micropowder

In this study, Al₂O₃-based ceramics were fabricated with natural bauxite powder as the raw material. The phase compositions evolution behavior during the heat treatment and its influence on the properties of fabricated ceramics were investigated. With increasing heat treatment temperature, the sintering degree of high-titania special-grade bauxite became better. The samples showed decreased porosity, increased bulk density, Vickers hardness, fracture toughness and flexural strength. However, when the heat temperature increased to 1650 °C, decomposition of tieillite occurs in sample, leading to increased Al₂O₃ and TiO₂ content in the liquid phase. Corundum and mullite grains with anisotropic growth appeared in the samples, leading to a decrease in the density, the Vickers hardness and flexural strength of samples decreased consequently. However, those anisotropic grains could prolong the crack propagation path and improve the fracture toughness of the material.     

On the evaluation of synthetic and natural ilmenite using syngas as fuel in chemical-looping combustion (CLC)

Chemical-looping combustion (CLC) is a combustion technique where the CO₂ produced is inherently separated from the rest of the flue gases with a considerably low energy penalty. For this reason, CLC has emerged as one of the more attractive options to capture CO₂ from fossil fuel combustion. When applying CLC with solid fuels, the use of a low cost oxygen carrier is highly important, and one such low cost oxygen carrier is the mineral ilmenite. The current work investigates the reactivity of several ilmenites, some which are synthetically produced by freeze granulation and two natural minerals, one Norwegian ilmenite and one South African ilmenite.     

Adsorption of natural gas and biogas components on activated carbon

Experimental results are presented for the adsorption equilibria of methane, ethane, propane, butane, carbon dioxide, and nitrogen, as well as natural gas odorants tert-butyl mercaptan and tetrahydrothiophene, on an activated carbon with the desirable characteristics for use in a guard bed for adsorbed natural gas storage, but that can also be applied for separation of biogas components, such as carbon dioxide and nitrogen. The adsorption experiments were performed using both open- and closed-loop gravimetry over the pressure and temperature ranges of 0–9 MPa and 273–325 K, respectively. The two odorants were analyzed at the very low concentrations usually found in natural gas (0–25 mg/(N m³)). The experimental data were successfully correlated by the adsorption potential theory and collapsed into a single temperature-independent characteristic curve. This analysis allows for extrapolation of the adsorption data to higher alkanes, for which no experimental data are available, in order to span the global composition of a typical natural gas stream. The adsorption equilibrium data for methane, carbon dioxide and nitrogen were fitted to the Toth and Sips isotherm models and their isosteric heats of adsorption were determined. The preferential adsorption capacity for carbon dioxide indicates that the carbon can be used for methane purification from natural gas, carbon dioxide sequestration from flue gas, or biogas purification.     

Evaluation of natural zeolite as a viscosity-modifying agent for cement-based grouts

The effects of natural zeolite on the rheological and workability properties of the grout mixtures were studied. Setting times of grouts were also determined as part of the experimental study. For comparison, grout mixtures were also prepared with a commercially available viscosity modifying admixture (VMA). The experimental results show that addition of natural zeolite modifies both the rheological and workability properties of grouts. For a constant superplasticizer (SP) content, an increase in the zeolite amount significantly increases the yield stress, the apparent and plastic viscosity, and reduces the fluidity and deformability. Moreover, an increase in the amount of SP causes a significant reduction in both the yield stress and plastic viscosity of the grouts. It was also observed that, grouts prepared with natural zeolite addition have a pseudo-plastic behavior, and shear-thinning behavior increases with an increase in the zeolite amount. Therefore, it has been shown that using natural zeolite as a VMA it is possible to obtain grouts that have satisfactory rheological properties, especially if natural zeolite is used in combination with a superplasticizer.     

Modeling of droplet-droplet interaction phenomena in gas-liquid systems for natural gas processing

The design of efficient gas liquid separation units for natural gas production lines depends on the accurate estimation of the droplet size distribution. The droplet size can be estimated by considering breakage and coalescence phenomena. In particular, off-shore separation units working at high pressure (100-200 bar) require special consideration of coalescence processes with multiple outcomes. This work discusses the introduction of multiple outcomes in the coalescence process. Numerical experiments are presented in order to highlight the effect of multiple coalescence behavior in the evolution of the droplet size distribution.     

Supercritical fluid extraction and bioassay identification of prodrug substances from natural resources

For arbitrarily chosen thirty types of natural resources which have been widely used in oriental traditional herb medicine, supercritical CO₂ extraction (SFE) and organic liquid solvent extraction (LSE) withn-hexane, chloroform and methanol were carried out to extract pharmaceutical substances. To evaluate relative advantages and shortcomings between the SFE and LSE, five types of bioactivity assays as well as gas- and thin layer-chromatographic analysis were performed for all the extracts obtained by the two extraction methods. Types of bioassays performed included cytotoxicity, bleb forming, DNA binding, oxygen free radical scavenger and Xanthine oxidase inhibitor tests. To evaluate economic viability of the SFE over the traditional LSE, extractability of prodrug substances was evaluated as the functions of extraction temperature and pressure. SFE was proven to be a feasible alternative over LSE. Also, the optimum SFE conditions which provided maximum extraction and cytotoxicity for each selected sample were presented.     

Modification of a thermodynamic model and an equation of state for accurate calculation of asphaltene precipitation phase behavior

In this study, DPTG (Dashtizadeh-Pazuki-Taghikhani-Ghotbi) equation of state has been modified for calculation of phase behavior of fluids and solubility parameter. The accuracy of the modified EOS has been proved by estimation of the properties of some hydrocarbons such as densities of methane and condensate gases, vaporization enthalpy, sublimation pressure, compressibility factor and comparison of the obtained results with the results of the present equations of state such as NJ (Nasrifar-Jalali), ZMJL (Zhi-Meiren-Jun-Lee) and PR (Peng-Robinson). Then, the Flory-Huggins model has been modified and asphaltene precipitation phase behavior at different ratios of solvents in the crude oil has been predicted by the modified EOS and the developed Flory-Huggins model. Comparison of the obtained results with the experimental data of asphaltene precipitation and the calculated ones by the main Flory-Huggins model shows the accuracy of the developed model.     

Formulation of a new generic density-based model for modeling solubility of polyphenols in supercritical carbon dioxide and ethanol

The aim of this work is to present a first approach in formulating a generic model for polyphenols solubility in ternary mixtures (polyphenol + ethanol + sc-CO₂). Solubility data of six polyphenols were collected from the literature, and six different groups of parameters were proposed for the new generic model in order to evaluate their effects and find the best set for each polyphenol. Likewise, four dimensional groups of factors were proposed to evaluate the effect of dimensions on solubility data calculation. The results show that the originally formulated model and its modifications are particularly useful in calculating polyphenols solubility data; for instance, when resveratrol solubility data was fitted, the AARD decreased from a value of 38.52 to 14.03, upon changing from a simple to a complex model. Additionally, this generic model with a specific modification can estimate solubility maxima occurring in the ternary resveratrol + ethanol + sc-CO₂ system.     

Liquid chlorine as chlorinating agent for preparation of chlorinated natural and synthetic rubbers

In order to overcome the use of solvents like carbon tetrachloride (during the industrial preparation of chlorinated natural rubber or chlorowaxes) which are suspected of damaging the layer of atmospheric ozone, I proposed the use of liquid Cl₂ as both chlorinating agent and solvent. It is shown that natural rubber or synthetic cis-1,4-polyisoprene can be swelled by liquid chlorine at ?40°C. By equilibrating to room temperature, the rubber is chlorinated by the expansion of the chlorine trapped in the rubber granules in a process resembling popcorn formation. Chlorine uptake was found to be 56.5% and the chlorinated rubber obtained was studied by FT-IR spectroscopy. Cis-1,4-polybutadiene, when chlorinated with liquid chlorine, gives a hard insoluble product with chlorine content of 36%. © 1995 John Wiley & Sons, Inc.     

乙醇－水－甲醇精馏过程中温度和组分浓度沿塔高的分布

本文用全回流筛板精馏塔测定了四个压力下的乙醇－水和乙醇－水－甲醇两个物系沿塔高温度与浓度的分布。用两元实测结果计算了不同压力下各板的默弗里板效，并以ＵＮＩＦＡＣ活度系数方程和维里状态方程为基础的热力学模型建立了精馏计算模型。用该模型对三元体系进行了计算，与实测结果符合良好。     

Purification and carbon-film-coating of natural graphite as anode materials for Li-ion batteries

A process of modification of natural graphite materials as anode for lithium ion batteries was attempted. The process started with the treatment of natural graphite with concentrated hydrochloric acid and concentrated sulfuric acid in a thermal autoclave, followed by the in situ polymerization of resorcinol-formaldehyde resin to coat the graphite, then heat-treatment. SEM, XRD, Raman and electrochemical charge-discharge analysis showed that the surface defects and impurities on natural graphite were eliminated by purification of the concentrated acids, and carbon-film encapsulation modified the surface structure of the graphite and reduced its BET surface area. The as-obtained natural graphite sample presented an initial charge-discharge coulombic efficiency of 88.4% and a reversible capacity of 355.8 mAh g⁻¹. The proposed process paves a way to prepare a promising anode material with excellent performance with low cost of natural graphite for rechargeable lithium ion batteries.     

Evaluation of density-based models for the solubility of solids in supercritical carbon dioxide and formulation of a new model

Many models have been developed to calculate supercritical solubility behavior and most can be either a semi-empirical relationship or based on an equation of state. In this work, density-based, semi-empirical models were evaluated in terms of their ability to accurately correlate solid solubility in supercritical carbon dioxide. The models considered were the methods of Chrastil, del Valle and Aguilera, Adachi and Lu, Méndez-Santiago and Teja, and Bartle. Six binary systems (solid + supercritical carbon dioxide), each with three isotherms, were selected for this evaluation. The average error was calculated for all 18 isotherms with each of the models evaluated. The solid compounds used in this study were naphthalene, anthracene, fluorene, hydroquinone, 1,5-naphthalenediamine, and cholesterol. The solubility data were obtained from literature. Of the previously mentioned models, the Adachi-Lu and del Valle-Aguilera equations provided, in general, lower average error than the other models. Since the Adachi-Lu equation and the del Valle-Aguilera equation correct for different effects, a new model is proposed in this work as a combination of the previous two methods. The proposed equation provided the least overall average error compared to all other models considered in this study. The new model is particularly useful when the reduced density of the solvent is below 1 where previous models tend to fail. This work also emphasizes on the advantages of expressing density-based models in dimensionless form to avoid dimensional inconsistencies in Chrastil-type models. One of the benefits, for example, is that parameters obtained by different authors can be readily compared, regardless of the units used.