مجله پژوهش نفت
پیاپی 67 (مهر و آبان 1390)

Iron oxide nanoparticles (α-Fe2O3, 20-50 nm) have been evaluated as catalysts in Fischer-Tropsch Synthesis in a fixed bed reactor. XRD, BET and SEM analyses were performed on fresh nanopowders and nanocatalyst to investigate the preparation method effect on catalyst activity. Activity and selectivity of this catalyst were determined at a constant pressure of 20 bar. To optimize the operating conditions of FTS, Taguchi experimental design method has been implemented. The effect of three pertinent factors has been considered: temperature, inlet H2/CO molar ratio and syngas space velocity. Experiments were carried out under a wide range of conditions including reaction temperature of 260-300 °C, inlet H2/CO molar ratio of 0.67-2.00 and space velocity of 3-15 NL gFe-1h-1. The rate of formation of heavier hydrocarbons (C5+) as a function of CO consumption has been chosen as the response of the system. The results from statistical design showed that the optimum conditions were: reaction temperature: 260 °C, inlet H2/CO molar ratio: 0.67, syngas space velocity: 3 NL g Fe-1h-1. Under these conditions, the rate of formation of C5+ versus CO consumption was 35.5948 g/g cat. mol CO consumed. Growth probability of hydrocarbons (α) was taken as a basis for comparing the performance of several iron nanocatalysts (NANOCAT, 3nm and BASF, 20-80nm) and industrial UCI catalyst applied in the slurry phase FT process with the present iron nanocatalyst. Results indicated that iron oxide nanoparticle applied in a fixed bed reactor exhibits a higher activity in hydrocarbon chain growth in comparison with those applied in a slurry phase FT process.

A fuzzy expert system has been developed to aid in PFD to P&ID conversion. The knowledge base of this system has been designed according to the following representation techniques: 1) Rule based representation and 2) Frames. The fuzzy expert system consists of two main parts: database and application program. The database has been designed using Rational Rose Software and implemented using InterBase. The application program has been designed based on object oriented paradigm and UML standard and then it has been implemented using Borland C++ Builder compiler. Performance of the developed software has been evaluated based on the super fractionation unit of a gas refinery. This case study shows that the software is capable of handling an industrial PFD providing a rich knowledge base.

Two layer polyethylene coatings consisting of maleinated polyethylene primer and HDPE topcoat have been used for many years. In this research, in order to enhance adhesion and durability of the maleinated polyethylene layer, a kind of surface chemical treatment on substrate with organosilane materials has been used. It is expected that by addition of silane chemical treatment to the application process of maleinated polyethylene coating, an improved product with coating properties at least equal to 3LPE (3 Layer polyethylene: epoxy/adhesive/polyethylene) can be obtained. Therefore, adhesion of maleinated polyethylene layer to metal after chemical treatment with organosilans at different conditions was measured. Also, cathodic disbonding tests were conducted on samples whose metal substrate had previously been treated with organosilanes. Finally, the results of adhesion and cathodic disbonding tests for chemically treated and untreated coated panels were compared.

Emission factors technique is one of the simple and low cost methods for estimating pollution from air pollutant sources. However, emission factors of gas flare may have high uncertainty because in flares, especially under emergency conditions, flow rate of flaring gases as well as combustion efficiency are unknown. The aim of this paper is to evaluate SO2, NOx and CO emission factors in gas flares. For this purpose, emission factors were estimated using back calculation method based on modeling and pollutant emission measurement in ambient air in a selected flare in an Iranian oil and gas plant. SO2, NOx and CO average emission factors for selected flare are determined to be 0.037, 0.0168 and 1.07 MMBtu/lb, respectively, with uncertainty of 34.3, 36.3 and 27.5%, respectively. Comparison of calculated emission factors with United States Environmental Protection Agency (EPA) and Regional Association of Oil and Natural Gas Companies in Latin America and the Caribbean (ARPEL) emission factors showed that both emission factors have high uncertainty, especially for NOx and CO emission estimation. Therefore, it is necessary to study details of the influence of ambient conditions on combustion efficiency of flares as well as experimental simulation of actual flare to obtain more representative emission factors of flares.

This paper discusses the assessment of efficiency and optimum concentration of a scale inhibitor on one of the Iranian offshore oil fields. This field has suffered from several problems due to the deposition of mineral scales at formation and surface facilities during recent years. The deposits are usually formed due to a change in pressure, temperature or mixing of incompatible waters. Using the scale inhibitors is a common method to prevent scale deposition or delay the process. Before applying the chemical, its performance should be tested in the laboratory and the minimum inhibitor concentration (MIC) should be determined at various conditions. Different scale inhibitor concentrations were added to a mixture of sea water and produced water. The experimental results at reservoir and ambient conditions show that this scale inhibitor has a good efficiency and the optimum inhibitor concentration is also proposed to be applied in the field.

On the basis of environmental and safety reasons, hardness of agricultural sulfur granules should be high enough to have minimum dust formation during transportation and storage. On the other hand, by using agricultural sulfur, soil indigenous thiobacillus bacteria can oxidize elemental sulfur to sulfuric acid and decrease the soil pH. Sulfur particle size is one of the most important parameters, which affect the oxidation rate. Thus, hardness of sulfur granules should be low enough to be easily crushed to fine particles. In this research, first, hardness and electromicroscopic structure of elemental sulfur granules, solidified at different medium temperatures were investigated and the optimum temperature was determined. The results indicated that the optimum temperature is 30°C. At higher temperatures, the percent of dust formation was considerably increased. In the next stage, the agricultural sulfur and the enriched sulfur with Fe, Zn and Mn were prepared at optimum medium temperature. Mechanical strength, abrasion resistance and dispersion percent of the prepared granules were measured. The data indicated that sulfur fertilizer granules were harder than elemental sulfur ones probably due to their inorganic content. In addition, their dispersion in contact with water was significantly increased compared with elemental sulfur granules so that more than 94 percent of granules crushed to fine particles during 2 hours.

Masjid-e-Solyman, Haft kel, Par-e-Siah and Naft Safid are productive oil fields, which are located in mountain front of NE Dezful Embayment. In this research, in order to determine the physical and chemical properties of Asmari oils from geochemical viewpoints, a few oil samples were subjected to geochemical analyses.Based on physical properties such as SARA test, API, K.Viscosity, sps. Gravity and sulfur contents of studied oils, two trends were identified. A NW-SE trend, in which decrease of oil quality and slight increase in sulfur content and the second trend with SW-NE direction, in which decrease of oil quality and sulfur content can be observed. Based on geochemical parameters such as Pri/Phy, Ni/V ratios, different fractions of oils and 13C isotope values, Asmari oils in NW-SE direction show paraffinic-aromatic properties, while moving from SW towards NE oilfields, naphthenic quality of oils are pronounced. The oils accumulated in these reservoirs are generated from a marine source rock(s), with kerogen type II and III, which have been deposited in an anoxic environment. No indication of oil alteration has been observed for accumulated oils in these reservoirs.

In this paper, a novel design algorithm for “Twisted Tube Heat Exchangers”, based on full utilization of maximum allowable pressure drops has been introduced. To develop such a new algorithm, the required correlations for heat transfer and pressure drop need to be extracted from given correlations of valid literature. This algorithm correlates the pressure drops, heat transfer area and coefficients through a simple relationship. The algorithm is verified by comparison of obtained results with those from the work of other researchers. By execution of the algorithm, it is shown that the performance of this exchanger is about two times higher than the conventional one. The paper reveals the highly potential benefits of this technology in design and replacement of twisted tube heat exchangers with the conventional shell and tubes type. To compare potential benefits of application of twisted tube heat exchangers with plain tube unit, a performance index is developed in this study.