Combining of intelligent models through committee machine for estimation of wax deposition

Deposition of the wax is one of the thorny issues in the petroleum industry, invoking costly problems during the transportation and production of crude oil. Owing to its devastating impacts on oil companies' economy, it is essential to develop a simple and robust strategy for the quantitative estimation of wax deposition. In this paper, support vector regression (SVR) is first proposed to estimate the amount of wax deposition. Subsequently, an artificial neural network (ANN) is developed for wax deposition prediction. Eventually, a sophisticated committee machine (CM) is constructed for combining the results of the SVR and ANN models. Optimal contribution of each model in final prediction of the wax deposit is determined through genetic algorithm in CM. Statistical error analysis shows that the CM model performs better than the individual models performing alone.     

煤灰流动温度预测模型的研究

以181种煤样的灰流动温度为基础,通过多元线性拟合以及逐步回归法,建立了关联各煤灰氧化物成分以及煤灰酸碱比的流动温度预测模型,相关性系数达0.934,该模型预测值与实验结果有较好的一致性。利用FactSage软件计算出液相线温度,建立流动温度与液相线温度之间的关联公式,相关性系数达0.924,说明该关联式同样具有较好的预测效果。     

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation

Production,processing and transportation of natural gases can be significantly affected by clathrate hydrates.Knowing the gas analysis is crucial to predict the right conditions for hydrate formation.Nevertheless,Katz gas gravity method can be used for initial estimation of hydrate formation temperature (HFT) under the circumstances of indeterminate gas composition.So far several correlations have been proposed for gas gravity method,in which the most accurate and reliable one has belonged to Bahadori and Vuthaluru.The main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity chart.By reviewing the error analysis results,one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.     

高温气相色谱和高温气相色谱-质谱法对费托合成蜡的分离和鉴定

费托合成蜡是费托合成反应中的重要产物之一。采用高温气相色谱与冷柱头进样相结合的方式,建立了一种分离分析费托合成蜡的气相色谱方法。该方法无需对费托合成蜡进行预处理,使用氦气为载气,选用更长的高温色谱柱,具有平稳的色谱基线,对费托合成蜡中正构烷烃和其他未知组分有很好的分离效果,能够洗脱费托合成蜡中碳数大于C₉₀的重组分。用高温气相色谱-质谱法对费托合成蜡馏分进行定性分析,其组分有烷烃、烯烃和含氧化合物。该方法对了解费托合成蜡组分的详细信息和费托合成工艺的开发有重要意义。     

The wax deposition rate of water-in-crude oil emulsions based on the laboratory flow loop experiment

This paper aims to develop a mathematical model to predict the wax deposition rate of waxy crude emulsions, combining heat and mass transfer mechanisms. According to the flow loop experimental results, the wax deposition rate increases with the decreasing average temperature of oil/wall in a manner of linear regularity, and shows a downtrend with the increase of water cut due to diffusion resistance. An applicable model is developed regarding emulsion properties, radial temperature gradient, shear stress, and wax diffusion coefficient. In model validation, the prediction results are in good agreement with experimental data with the relative errors within 28.87%.     

Experimental study on flow characteristics of tetrahydrofuran hydrate slurry in pipelines

Tetrahydrofuran (THF) was selected as the substitute to study the flow behaviors and the mechanism of the hydrates blockage in pipelines. The slurrylike hydrates and slushlike hydrates are observed with the formation of hydrates in pipeline. There is a critical hydrate volume concentration of 50.6% for THF slurries and pipeline will be free of hydrate blockage while the hydrate volume concentration is lower than the critical volume concentration; otherwise, pipeline will be easy to be blocked. Fully turbulent flow occurs and friction factors tend to be constant when the velocity reaches 1.5 m/s. And then, constant values of friction factors that depend on the volume concentrations in the slurry were regressed to estimate the pressure drops of THF hydrate slurry at large mean velocity. Finally, a safe region, defined according to the critical hydrate volume concentration, was proposed for THF hydrate slurry, which may provide some insight for further studying the natural gas hydrate slurries and judge whether the pipeline can be run safely or not.     

玉门稠油组分特征及其对结蜡行为的影响

为了研究稠油不同组分的特征及其相互作用,利用柱层色谱分离法、傅里叶红外光谱、差示扫描量热法（DSC）和偏光显微分析等表征方法及手段,对采自玉门油田的稠油样品进行了组分分离、分析,并对饱和烃组分结蜡行为的影响进行了研究。结果表明,稠油各组分相互作用可以有效抑制蜡晶的析出。饱和烃组分（A₁）中分别加入其他不同极性组分后,其结蜡行为与原油原始状态差异较大;A₁的析蜡点、析蜡峰温和析蜡量均有所降低。偏光显微分析发现胶质沥青质组分使A₁冷却结晶时的蜡晶颗粒数增多,尺寸相对减小,可以减弱蜡晶之间的联结强度,削弱蜡晶缔合而形成大块蜡晶聚集体的倾向。     

Comparative methods in the determination of wax content and pour points of crude oils

In this research, differential scanning calorimetry (DSC) and gas chromatography is used to determine the wax content of fourteen crude oils of different sources. Different empirical equations were applied to compare the wax content of crude oils. For the fourteen crude oil samples with the wax content ranging from 7.5 to 43.8 mass%, it was observed that the results of empirical equations were in good agreement with those determined by DSC and GC. Accordingly, a correlation between ASTM pour point and the temperature at which 2 mass% of wax has precipitated out from crude oil is developed.     

Experimental design,machine learning approaches for the optimization and modeling of caffeine adsorption

In the current research, the sorption of caffeine on fresh and calcined Cu–Al layered double hydroxide was comparatively studied based on adsorption parameters, adsorption kinetics, and adsorption isotherm. Response surface methodology (RSM), support vector machine (SVM) and artificial neural network (ANN), as data mining methods, were applied to develop models by considering various operating variables. Different characterization methods were exploited to conduct a comprehensive analysis of the characteristics of HDL in order to acquire a thorough understanding of its structural and functional features. The Langmuir model was employed to accurately describe the maximum monolayer adsorption capacity for calcined sample (q_max) of 152.99 mg/g mg/g with R² = 0.9977. The pseudo-second order model precisely described the adsorption phenomenon (R² = 0.999). The thermodynamic analysis also reveals a favorable and spontaneous process. The ANN model predicts adsorption efficiency result with R² = 0.989. The five-fold cross-validation was achieved to evaluate the validity of the SVM. The predication results revealed approximately 99.9% accuracy for test datasets and 99.63% accuracy for experiment data. Moreover, ANOVA analysis employing the central composite design-response surface methodology (CCD-RSM) indicated a good agreement between the quadratic equation predictions and the experimental data, which results in R² of 0.9868 and the highest removal percentages in optimized step were obtained for RSM (pH 5.05, mass of adsorbent 20 mg, time of 72 min, and caffeine concentrations of 22 mg/L). On the whole, the findings confirm that the proposed machine learning models provided reliable and robust computer methods for monitoring and simulating the adsorption of pollutants from aqueous solutions by Cu–Al–LDH.     

Experimental study and numerical estimation of current changes in electroosmotically pumped microfluidic devices

Electroosmotic flow (EOF) was investigated in microfabricated fluidic devices using the current monitoring technique. Current changes ranging from 50 to 130 pA/s were detected. These observations indicate that in microfluidic devices with small reservoir volumes, electrolysis of water influences the fluid transport, giving rise to changes in pH and increase in concentration of ionic species in the fluidic system. As a result of the electrolysis and associated increment in ion concentration, the thickness of the Debye layer and surface potential vary, affecting the overall migration behavior of the solution. The magnitude of EOF and the electrophoretic properties of molecules can no longer be treated as constant/invariant. These temporal anomalies are undesirable during analytical separations and in fluid control applications. A numerical analysis of the impact of the continuous ionic strength increase on the EOF dynamics is presented using well-established conduction and EOF theories. The numerical results are found to be in good agreement with the observed current changes. These results indicate that to improve assay reproducibility, monitoring the electric current is an effective tool to determine whether electrolytic reactions are taking place. Our work also serves to test the numerical accuracy of EOF theories and models.     

Effect of modified nano-silica/EVA on flow behavior and wax crystallization of model oils with different wax contents

The nano-hybrid pour-point depressant (PPD) was prepared with organically modified nano-silica covering in EVA. The effects of modified nano-silica/EVA on the flow behavior and wax crystallization of model oils with different wax contents were evaluated. Compared with pure EVA and nano-silica/EVA, modified nano-silica/EVA exhibited a better effect, when doped with 500?ppm, the pour point of the model oil containing 20?wt% wax was reduced from 33°C to 0°C. However, it is noteworthy that pour point cannot accurately reflect the effect of YSiO2/EVA as cold flow improver for a high wax content. The crystal morphology and crystallization behavior of the model oils at low temperature were also observed using polarizing optical microscopy (POM). The results indicated that modified nano-silica/EVA can reduce the size of the wax crystals and disperse the wax crystals by heterogeneous nucleation.     

Simulated distillation of wax samples using supercritical fluid and high temperature gas chromatography

Simulated distillation boiling range distributions have been compared for high boiling petroleum wax samples using high temperature gas chromatography and supercritical fluid chromatography. Midpoint (50 % off) temperature differences were small, and average differences between the two types of analyses were less than 6° Details of optimization of the HTGC and SFC systems and injection techniques used are reported.     

Experimental and modeling study of ice melting

Differential scanning calorimetry (DSC) is applied to analyse the process of ice melting. Experimental results were compared to those obtained by a numerical simulation in which a conventional enthalpy formulation was applied. The effects of various parameters on the kinetics of transformations and therefore the shape of curves has been analysed and the importance of temperature gradients inside the sample evaluated.     

A model for estimating flow assurance of hydrate slurry in pipelines

The problem of hydrate blockage of pipelines in offshore production is becoming ever-increasing severe because oil fields in ever-increasing unusual environments have been brought in production.HCFC-141b and THF were selected as the substitutes to study the flow assurance of the hydrates in pipelines.There are critical hydrate volume concentrations for these two slurries.Hydrate slurries behave like Bingham fluids and have high agglomerating tendency when the hydrate volume concentrations are larger than the critical ones.Based on theological behaviors of these two hydrates,a non-dimensional parameter is proposed through studying the driving forces of agglomeration among hydrate particles,which shows the agglomerating probability of hydrate particles in pipeline and can be used to judge the safety of the pipeline.Moreover,a safe model to judge the safely flow hydrate slurries was presented and verified with the experimental data,which demonstrates that the model is effective to judge whether the pipeline can be run safely or not.     

Experimental investigation and kinetic modeling of the negative temperature coefficient of the reaction rate in rich propane—oxygen mixtures

The phenomenon of the negative temperature coefficient (NTC) of the reaction rate of the oxidation of rich propane—oxygen mixtures was experimentally studied. The NTC phenomenon is qualitatively described by a simple kinetic model containing a minimum set of reactions related to the oxidation of the starting hydrocarbon, propane, and the propyl C₃H₇ ^. radical formed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2120–2124, December, 1997.     

Experimental investigation and constitutive modeling of the deformation behavior of Poly-Ether-Ether-Ketone at elevated temperatures

The present study investigates the deformation behavior of Poly-Ether-Ether-Ketone (PEEK) at elevated temperatures and low strain rates through a combination of experiments and simulations. Uniaxial tension tests at elevated temperatures (293–543 K) and strain rates (8.3 × 10⁻³ to 3.3 × 10⁻¹ s⁻¹) were performed, and the temperature- and rate-dependencies of the deformation behavior and mechanism of PEEK were discussed in detail. The Erichsen test was performed at temperatures varying from 473 to 533 K and a fixed speed of 1 mm/s. Based on an investigation of numerous constitutive models, a phenomenological model called DSGZ was employed in ABAQUS/Explicit to characterize the deformation behavior of PEEK at elevated temperatures, and the deviation between experimental and simulation data was less than 10% at large deformations. Moreover, the simulation results accurately predicted the necking and cold drawing phenomena in the tension test as well as the deformation in the Erichsen test.     

Experimental and modeling study of the oxidation of 1‐pentene at high temperature

Ignition delay times of 1‐pentene–oxygen–argon mixtures have been measured behind shock wave, the onset of ignition being detected by OH radical emission. Mixtures contained 1 or 2% of hydrocarbon for equivalence ratios ranging from 0.5 to 2. Reflected shock waves allowed temperatures from 1130 to 1620 K and pressures from 7.3 to 9.5 atm to be obtained. A detailed mechanism of combustion of 1‐pentene has been automatically generated using EXGAS software. This mechanism has been validated by comparing the results of the simulations to the experimental ignition delay times. The main reaction pathways have been derived from flow rate and sensitivity analyses at different temperatures. Comparisons with 1‐butene and 1‐hexene in the same conditions show that 1‐pentene has a higher reactivity which seems to be due to its decomposition to give ethyl radicals, which rapidly yields very reactive hydrogen atoms, while the decomposition of 1‐butene and 1‐hexene leads to less reactive methyl radicals. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 451–463, 2005     

Statistical experimental design for bioprocess modeling and optimization analysis

The statistical design of experiments (DOE) is a collection of predetermined settings of the process variables of interest, which provides an efficient procedure for planning experiments. Experiments on biological processes typically produce long sequences of successive observations on each experimental unit (plant, animal, bioreactor, fermenter, or flask) in response to several treatments (combination of factors). Cell culture and other biotech-related experiments used to be performed by repeated-measures method of experimental design coupled with different levels of several process factors to investigate dynamic biological process. Data collected from this design can be analyzed by several kinds of general linear model (GLM) statistical methods such as multivariate analysis of variance (MANOVA), univariate ANOVA (timesplit-plot analysis with randomization restriction), and analysis of orthogonal polynomial contrasts of repeated factor (linear coefficient analysis). Last, regression model was introduced to describe responses over time to the different treatments along with model residual analysis. Statistical analysis of biprocess with repeated measurements can help investigate environmental factors and effects affecting physiological and bioprocesses in analyzing and optimizing biotechnology production.     

Multistate empirical valence bond study of temperature and confinement effects on proton transfer in water inside hydrophobic nanochannels

Microscopic characteristics of an aqueous excess proton in a wide range of thermodynamic states, from low density amorphous ices (down to 100 K) to high temperature liquids under the critical point (up to 600 K), placed inside hydrophobic graphene slabs at the nanometric scale (with interplate distances between 3.1 and 0.7 nm wide) have been analyzed by means of molecular dynamics simulations. Water‐proton and carbon‐proton forces were modeled with a multistate empirical valence bond method. Densities between 0.07 and 0.02 Å^?3 have been considered. As a general trend, we observed a competition between effects of confinement and temperature on structure and dynamical properties of the lone proton. Confinement has strong influence on the local structure of the proton, whereas the main effect of temperature on proton properties is observed on its dynamics, with significant variation of proton transfer rates, proton diffusion coefficients, and characteristic frequencies of vibrational motions. Proton transfer is an activated process with energy barriers between 1 and 10 kJ/mol for both proton transfer and diffusion, depending of the temperature range considered and also on the interplate distance. Arrhenius‐like behavior of the transfer rates and of proton diffusion are clearly observed for states above 100 K. Spectral densities of proton species indicated that in all states Zundel‐like and Eigen‐like complexes survive at some extent. © 2016 Wiley Periodicals, Inc.