A Lagrangian relaxation approach for a multi-mode inventory routing problem with transshipment in crude oil transportation

An inventory routing problem in crude oil transportation is studied, in which crude oil is transported from a supply center to multiple customer harbors to satisfy their demands over multiple periods. In the problem, a heterogeneous fleet of tankers consisting of tankers owned by a distributor and tankers rented from a third party, a pipeline, and multiple types of routes are considered; both inventory level and shortage level at each customer harbor are limited. The objective is to determine for each period over a given time horizon the number of tankers of each type to be rented/returned at the supply center, the number of tankers of each type to be dispatched on each route, and the quantity of crude oil flowing through the pipeline that minimizes the total logistics cost.After formulating the problem as a mixed integer programming problem, a Lagrangian relaxation approach is developed for finding a near optimal solution of the problem. The approach is also applied to a variant of the problem in which both fully and partially loaded tankers are allowed in the transportation of crude oil. Numerical experiments show that this approach outperforms an existing meta-heuristic algorithm, especially for the instances of large sizes.     

Viscoelastic models for Mexican heavy crude oil and comparison with a mixture of heptadecane and eicosane. Part I

The viscoelastic knowledge of crude oil is limited by the complexity and variability of the raw material. Viscoelastic models of Maxwell type describe widely Mexican crude oils when an Oldroyd contravariant derivative is considered. Moreover, a Weissenberg number is defined by the product of the shear rate and the characteristic time constituted by the inverse of the rate constant of C-C bonds rotations of alkanes. This dimensionless number allows the scaling of viscosities of both crude oil, at different temperatures, and mixtures of n-eicosane/n-heptadecane. Blends of linear alkanes can simulate the viscous behavior of crude oil after adequate scaling and can be used to predict crude oil rheological properties with the advantage to be completely known and reproducible systems.     

掺炼俄油后常减压蒸馏设备的腐蚀问题处理

介绍了中国石油吉林石化公司炼油厂常减压装置掺炼俄油后出现的设备腐蚀问题,分析了硫腐蚀的机理,低温及高温硫腐蚀产生的部位及防止措施和收到的效果。     

常减压装置原油电脱盐的运行分析及改进

从常减压装置原油电脱盐的设备、工艺参数、技术状况等方面进行分析,找出电脱盐运行不佳的原因,并制定出相应的改进措施,实施后脱盐效率由81.8%提高到93.6%。     

A multi-level simulation approach for the crude oil loading/unloading scheduling problem

An integrated approach for refinery production scheduling and unit operation optimization problems is presented. Each problem is at a different decision making layer and has an independent objective function and model. The objective function at the operational level is an on-line maximization of the difference between the product revenue and the energy and environmental costs of the main refinery units. It is modeled as an NLP and is constrained by ranges on the unit's operating condition as well as product quality constraints. The production scheduling layer is modeled as an MILP with the objective of minimizing the logistical costs of unloading the crude oil over a day-to-week time horizon. The objective function is a linear sum of the unloading, sea waiting, inventory, and setup costs. The nonlinear simulation model for the process units is used to find optimized refining costs and revenue for a blend of two crudes. Multiple linear regression of the individual crude oil flow rates within the crude oil percentage range allowed by the facility is then used to derive linear refining cost and revenue functions. Along with logistics costs, the refining costs or revenue are considered in the MILP scheduling objective function. Results show that this integrated approach can lead to a decrease of production and logistics costs or increased profit, provide a more intelligent crude schedule, and identify production level scheduling decisions which have a tradeoff benefit with the operational mode of the refinery.     

Transesterification of the crude oil of rapeseed with NaOH in supercritical and subcritical methanol

Transesterification reaction of the crude oil of rapeseed with supercritical/subcritical methanol in the presence of a relatively low amount of NaOH was successfully carried out, where soap formation didn't occur. The main factors affecting the methyl ester yield during the transesterification reaction were the catalyst content, the reaction temperature, the molar ratio of alcohol to oil and the water content. High methyl ester yield and fast reaction rate could be obtained even if the reaction pressure was relatively low. In addition, kinetics of the transesterification reaction was also discussed.     

Lumped-parameter model for the retorting of a large block of oil shale with an internal temperature gradient

A lumped-parameter model which combines the internal and external heat transfer resistances was proposed for the retorting of a large block of oil shale. In this model the temperature of oil-shale block is obtained by solving the ordinary differential equation of energy balance using an overall heat transfer coefficient U, where U is equal to h/(1 + Bi/5). The results of this model were compared with those of the uniform-temperature model which uses the external heat transfer coefficient h, instead of U, in the energy balance equation and of the rigorous model which calculates the block temperature profile more rigorously by a partial differential equation. The comparison showed that the lumped-parameter model is much better than the uniform-temperature model and is a useful alternative to the rigorous model for modelling the retorting of a large block of oil shale with an internal temperature gradient.     

A model for bubble formation and weeping at a submerged orifice with liquid cross-flow

A new theoretical model to predict bubble frequencies and weeping rates at a submerged orifice with liquid cross-flow has been developed. The model predicts a significant influence of liquid cross-flow velocity on bubble formation frequency, and especially on liquid weeping. Simulated values of weeping rates for different orifice diameters, gas flowrates and liquid cross-flow velocities show good agreement with experimental data.     

新型油田用钡、锶阻垢剂性能研究

针对油田中后期生产中结垢严重,尤其是锶、钡垢难以得到解决的问题,研制了TS-7610A-D系列锶钡阻垢剂.参考SY/T 5673-1993试验方法,模拟现场的各种条件,对该系列药剂进行了综合评价.TS-7610C在该系列药剂中具备相当优异的性能,试验条件下其投加质量浓度为30 mg/L时对硫酸钡的阻垢率可达95%以上,同时具有良好的阻碳酸钙、硫酸钙性能,在高温、高pH、高盐及加入破乳剂条件下,仍能保持较好的阻垢效果.可作为油田生产中添加的阻垢剂使用,尤其适用于存在锶、钡结垢问题的地区.     

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.     

新型油田污水除油剂的制备及性能研究

采用共沉淀法合成出Fe_3O_4/氧化石墨烯(GO)纳米复合材料,然后通过静电作用将聚二烯丙基二甲基氯化铵(PDDA)修饰在Fe_3O_4/GO表面,制备出一种新型除油剂PDDA/Fe3O4/GO,并考察了Fe3O4与GO配比、p H、温度、反应时间和除油剂投加量等因素对除油效果的影响。实验结果表明:PDDA/Fe_3O_4/GO不仅除油性能良好,而且除油速度快;在室温20℃、反应时间10 min、投加质量浓度为300 mg/L的条件下,可将油田污水中的油降至50 mg/L以下。该除油剂具有制备方法简单、除油速度快、易于操作、可重复利用等特点,为油田污水处理提供了一种新的研究思路。     

Predicting the sizes of toluene-diluted heavy oil emulsions in turbulent flow Part 2: Hinze-Kolmogorov based model adapted for increased oil fractions and energy dissipation in a stirred tank

The applicability of several classical size prediction models to predict the Sauter mean diameters d₃₂ of four volume fractions of toluene-diluted heavy oil in water emulsions was studied. Energy dissipation in a fully baffled cylindrical tank stirred at varied speeds by a Rushton turbine was related to the d₃₂ measured with a Mastersizer 2000 laser light scattering instrument after 75 min of agitation. At low oil fractions of 0.01 droplet breakage behaviour was in accordance with the breakage dominance assumption of Hinze-Kolmogorov (H-K) theory. At intermediate oil fractions of 0.05 and 0.1, the system behaved similarly with lower rates of breakage than at 0.01. At high oil fractions of 0.3, the droplet sizes were the largest. Here, coalescence may have played a larger role due to increased collision frequency, while turbulence dampening caused larger eddies and reduced breakage. The resilience to breakage due to the surface elasticity was assumed to be constant for all oil fractions. The experimental diameters compared with the diameters calculated from several size-predictive models showed unsatisfactory predictions at higher oil fractions of 0.05-0.3. By modification of existing constants and coefficients of a H-K-based model that accounts for breakage and coalescence and by using iterative techniques, specific predictive equations for each mixing speed and a new averaged equation were developed. Good agreement between measured and predicted sizes was achieved.     

Semi-empirical model of toluene transport in polyethylene membranes based on the data using a new type of apparatus for determining gas permeability, diffusivity and solubility

Solubility, diffusivity and permeability of toluene vapors in low-density polyethylene (LDPE) membranes of various thicknesses (approximately 48, 93, 138 and 187 μm) at different temperatures 30, 40 and 50 °C in the range of relative vapor pressure p/p⁰=(0.05; 0.95) were measured using new type of permeation apparatus. Moreover, special construction of the new cell enables determination of the permeant amount sorbed in the membrane in the steady state operation of vapor permeation.The simple semi-empirical model of toluene transport in a polyethylene membrane based on relation between experimentally obtained effective diffusion coefficients and concentration dependent diffusion coefficients evaluated from experiments on a new permeation apparatus was proposed. The model enables estimation of toluene fluxes, sorption in the steady state of vapor permeation and concentration profiles in a polyethylene membrane from equilibrium sorption isotherms and effective diffusion coefficients. Very good agreement between experimental and calculated values from the proposed model was obtained.     

How to Attain Ultralow Interfacial Tension and Three-Phase Behavior with Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 4: Robustness of the Optimum Formulation Zone Through the Insensibility to Some Variables and the Occurrence of Complex Artifacts

In enhanced oil recovery, not only the low-tension performance, but also the robustness at optimum formulation is an important issue. The fourth part of our review series is dedicated to robustness, defined as the width of the zone exhibiting three-phase behavior around the optimum formulation, whatever the scanned variable. It is first corroborated from a screening of the available data in the literature that the tension minimum is inversely proportional to the square of the three-phase range in the HLD scale. However, since there is still an inaccuracy of about a factor 10 in the tension minimum, some significant improvement can be attained in some cases by increasing the three-phase behavior width in two ways. The first approach consists of finding systems that are insensitive to some formulation variable such as temperature, surfactant mixture composition or concentration, and water-to-oil ratio. The second way is to produce an artifact through which the optimum formulation is produced twice in a scan. If the distance between the two events in the scan is reduced down to be zero, their corresponding three-phase behavior zones merge and result in a wider WIII region with a low tension. Several cases of such events are reported: alkaline scans, anionic-nonionic and anionic-cationic mixture changes, linear change in composition in three-surfactant mixture, partial precipitation from a surfactant mixture in a salinity scan, and excessive partitioning of polyethoxylated nonionics. More complex transitions with three effects in a single scan or three concomitantly scanned variables show even more possibilities in practice.     

A model for the C5a receptor and for T its interaction with the ligand

A model of the C5a receptor was built based on the assumptionthat the seven membrane-spanning helices of known inward/outwarddirection are in an arrangement roughly similar to that in bacteriorhodopsin.Guidelines for the positioning of the helices were cysteinepairing, ‘ridges into grooves’ interdigitation ofside chains and aromatic cluster formation. The chain segmentsprotruding from the membrane are too short for folding intoan independent ectodomain. The only longer segment (179–202)is tied down in its centre onto the membrane by a disulphidebridge and, thereby, made into two short loops as well. Ideasof the interaction of the C5a receptor with its ligand werederived mainly from the search for accommodation of the functionallyessential arginine residues 40 and 74 of C5a. Asp82 is the onlycharged residue in a pocket {small tilde}20 A below the receptorsurface and is conserved in the rhodopsin superfamily. It commendsitself for binding Arg74 which is the tip of the flexible C-terminalchain of C5a, and rules out Arg40 in the structurally well-definedpart of the molecule. The latter may bind to Glul80 at the bottomof a more shallow pocket which happens to resemble the substrate-bindingsite of trypsin.