مجله پژوهش نفت
پیاپی 57 (بهار و تابستان 1387)

Particle size distribution measurement tools are generally offline, expensive and slow. So, it is very important to design an observer with the ability to estimate particle size distribution in emulsion polymerization. In this paper, a non-isothermal model based on population balance equations (Zero-one model) including nucleation, particle growth, and coagulation is chosen for estimation of particles size distribution. Then a reduced observer is presented for estimation of particle size distribution with the assumption of having free active surface material density. It is shown that in case of presence of immeasurable turbulence and modeling error, the observer’s performance is better than wide open circuit observer. In addition, by measuring conversion percentage made possible by use of density measurement, the observer performance will be enhanced. As it is hard to measure concentration of free active surface material directly, it will be measured using an electrical conduction method. The results show that in case of presence of immeasurable turbulence, performance of observer by use of electrical conduction measurement is better than wide open circuit observer, but in case of presence of modeling error, no considerable enhancement were observed compared with wide open circuit observer

An effective way of reducing the gap between preventive performance of toxic chromate-based compounds and their traditional replacements (zinc phosphate) is using the new generation of phosphate based anti-corrosion pigments. These compounds are product of modified chemical structure of zinc phosphate pigments in cation and anion parts. In this study, our aim is to compare preventive performance of zinc aluminum polyphosphate (ZAPP) as a third generation phosphate and zinc phosphate based anti-corrosion pigments by use of electrochemical and surface analysis tests. For this purpose, uncoated steel samples were immersed inside saturated solution of the pigments in 3.5 percent chloride sodium solution. In addition to surface analysis after 24 hours, electrochemical experiments were carried out on the samples in three time intervals: 1, 4 and 24 hours. The results of electrochemical impedance spectrometer and linear polarization experiments show superiority of the reformed zinc phosphate pigments over its normal form. Generally, timing changes of charge transfer resistance (Rct) resulted from electrochemical impedance experiment and polarization resistance (Rp), current density (Icorr) and corrosion speed resulted from polarization curves as well as spectrum and curve shapes showed a protective film on the surface with presence of ZAPP. Also, images obtained from SEM proved this fact. The elements of the formed layer were identified by use of energy dispersive x-ray microanalysis (EDX)

Sand production has been a major problem in the oil industry worldwide for years. Operating costs multiply when sand production wears out equipment and forces expensive workovers. Production of sand seems to be rate sensitive. That is, below some producing rate, no sand is produced. This rate quite often is vanishingly small. The producer has no choise but to produce at a higher rate and to learn to live with the sand. The bridging methods for sand control are either screens or gravel packs. Sand control by any bridging method requires knowledge of the formation size distribution. This is most commonly found with a sieve analysis. In this study, sieve analyses have been performed on samples from an Iranian field, which has sand production problems. The data obtained could be used for gravel pack design. The other problem in these kind of wells is the lack of petrophysical information due to unconsolidated nature of core samples therefore, the data from sieve analyses were also utilized to estimate the original petrophysical properties of the unconsolidated intervals.

Electroless method is regarded as one of the most efficient coating methods because it is proper coating ability even for complex shapes and edges. We can use different metals for coating in the electroless method, but nickel phosphor has been widely used because of its unique characteristics. The latest researches on electroless nickel phosphor have been focused on simultaneous deposition of solid particles during the coating process. Composite coatings are classified as new materials with proper hardness and wear characteristics, while there is not enough information available about their resistance against corrosion. Hard particles cause resistance against corrosion and increase solidity of coatings among which SiC is the best compound and is more practical than others. In this study, we apply electroless nickel and Ni-P-SiC composite coatings on some samples of ST37 steel. Corrosion resistance of Ni-P coating and Ni-P-Sic nano-composite are examined and compared by use of polarization and impedance measurement experiments. The experimental results show that both Ni-P and Ni-P-SiC have much better corrosion resistance compared to the base metal

In the fractured carbonate reservoirs the reimbibation process in the gas invaded zone is dominating on producing process. When the gravitational forces exceed the capillary forces, the matrix blocks, which are surrounded by gas, will release their oil. This oil imbibed by below block if possible up to produced. In this study, we used some experiment for finding the relations and effective parameters in reimbibatin process.

In the fractured carbonate reservoirs the reimbibation process in the gas invaded zone is dominating on producing process. When the gravitational forces exceed the capillary forces, the matrix blocks, which are surrounded by gas, will release their oil. This oil imbibed by below block if possible up to produced. In this study, we used some experiment for finding the relations and effective parameters in reimbibatin process.

In this research blends of two samples of Acrylonitrile-Butadiene-Styrene (ABS) with three samples of Poly(vinyl chloride) (PVC) were prepared via melt processing and their physical, mechanical and fire properties were investigated. It was found that properties of blends were significantly depends on blend composition and PVC compound types, but the properties of blends containing different types of ABS similar results were seen. On blending of ABS with soft PVC compound, impact strength and melt flow index (MFI) of ABS were increased, however, tensile and flexural strength were decreased. In contrast, blending of ABS with rigid PVC improved its fire retardancy and some mechanical properties but decreased its MFI and impact strength.

Optimization of a typical crude oil refinery of Iran by linear programming is performed. Crude oil assay, capacity of process units, feed characteristics to each process unit, products quality and utility data for actual conditions of refinery accurately are collected and assumed as the basis of modeling.Maximum profitability of refinery is assumed as the objective function of optimization. To meet Euro 2005 specifications of products, Maximum gasoline production and minimum production of fuel oil, three process alternatives have been considered.First model is developed based on Fluidized Catalytic Cracking (FCC) process of heavy vacuum gas oil and de – asphalted oil from new solvent Deasphalting unit. Second model is optimized by incorporating a Delayed Coking unit in the existing scheme. and the third scheme is developed based on Residue Fluid Catalytic Cracking (RFCC). Techno – economical comparison of these three models have shown that the combination of FCC with Solvent Deasphalting Unit (SDA) is the most promising scheme for this typical refinery.