مجله پژوهش نفت
پیاپی 64 (زمستان 1389)

Present work aims at investigating rheological behavior of linear hydrocarbons by means of non-equilibrium molecular dynamics (NEMD) simulation. Simulation set up was a flow of hydrocarbon molecules confined between two molecular parallel plates. Through moving the top wall at constant velocity and investigation of relation of viscosity to shear stress, rheological behavior of hydrocarbons could be found out. Viscosity of hydrocarbons has been calculated by means of integration of Newtonian equations of motion and then shear stress tensor calculation and division of calculated shear stress by exerted shear rate. Our code verified with experimental data for light hydrocarbons (methane, ethane, propane and n-butane), reported results for a long chain hydrocarbon (C100H202), and results presented for some other hydrocarbons. According to the obtained results, it was found that with increasing hydrocarbon chain length, fluid viscosity will increase. Furthermore, the simulation results reveal that long chain hydrocarbons have a shear thinning non-Newtonian behavior with a power law relation.

Greenhouse CO2 gas content is increasing in the atmosphere. Separation of CO2 from emission sources generated by power plants, steel works and various chemical industries has attracted global attention as a result of the enhanced greenhouse destructive effects. Considering the advantages of gas separation polymeric membranes by blending method for membrane preparation, acrylonitrile-butadiene-styrene/Poly (ethylene glycol)blend membranes have been prepared. Then, the effect of incorporating different PEG contents into ABS on the permeability/selectivity of CO2/N2 was investigated. Additionally, the effect of pressure on CO2 permeability has been studied. The results showed that CO2 permeability in the ABS/PEG20000 (10 wt %) had the most suitable gas separation properties. In addition, the CO2 permeability and CO2/N2 selectivity values of this membrane increased significantly in comparison with neat ABS membrane.

Na2WO4-Mn/SiO2 catalysts were prepared for oxidative coupling of methane using co-precipitation, wetness impregnation and wet impregnation methods. Catalytic performances of the prepared catalyst samples were examined under the same conditions in a fixed bed microreactor. It was found that the Na2WO4-Mn/SiO2 catalystsprepared by the wet and wetness impregnation methods have similar performances and both methods have superior performances over that of the co-precipitation method. The results also show that the catalysts prepared by the wetness and wet impregnation methods present excellent stability performance. The catalysts were characterized by means of BET, SEM and XRD tests. The results show that the Na2WO4 phase is necessaryfor achievement of the desired performance.

Solidifiers as combating tools to oil spill can be applied on both land and water without any toxic or leaching effects. In order to investigate effectiveness of block-copolymers, styrene-butadiene-styrene and styreneethylenebutylenestyrene on Iranian exported crude oil, five samples with API’s in the range of 1936 were selected. The results from this work were compared with two those of commercial solidifiers, Alsocup andPetro-Waste-Solidifier, which are confirmed by EPA (Environmental Protection Agency). At first, some factors like particle size, addition time, separation means and oil-water mixing system were optimized. Then, the effectiveness of two selected polymers and commercial samples on oil samples were studied. The results showed that the consumption amounts of these copolymers for solidifying tested crude oils were 25-33%, which is lower than that of commercial solidifiers (nearly 55%).

Drilling troublesome shales is one of the major problems in drilling operations. Borehole instability during drilling of shale layers results in increasing rig time and consequently increased operational cost. Thus, the correct choice of drilling fluid for drilling shale layers reduces drilling time and cost. One of these fluids is formate fluids. Potassium and cesium formate brines are among the best water based shale inhibitor fluids. Formate fluidsaccording to their inherent properties create very good borehole stability. By the use of formate salts, we can design high density fluids with minimum solid content for drilling shale and reservoir sections. The obtained results showed that formate fluids are stable at high temperatures and show very good shale recovery like OBM. The results show that recovery shale of sodium/potassium formate fluid is higher than that of glycol,silicate, and KCl fluids. Formate fluids showed good compatibility with various kinds of polymers. The result of lubricity test showed that lubricity properties of formate fluids are comparable with other WBM. They do not need any lubricants.

In the present study, ZSM5 zeolite membranes were synthesized on porous αaluminasupport by secondary growth hydrothermal method. Membranes synthesized were tested by structural characterization and single gas permeation experiments. To prepare zeolite membranes, nanosized silicalite-1 powder was first synthesized as seed with mean diameter of 40 nm from a clear solution. Silicalite nanoparticle slurries were purifiedby repeated centrifugation followed by redispersion by ultra-sound in deionized water. The effects of synthetic parameters such as synthesis time and aluminum content are studied. It was found that the membranes quality was sensitive to the aluminum content. Investigation of different synthesis times showed that the best film was obtained during 36 hours. The permeation properties of the support and membranes were measured over the pressure range of 1-4bar at room temperature. The ZSM-5 membranes were examined by permeation measurements using single CO2, N2, CH4 and H2 gases. Under optimum synthetic conditions, the permselectivity at 300K for H2/CH4, H2/CO2 and H2/N2 were 3.8, 3.5 and 4.4, respectively.

This work presents an investigation of a mobile bed scrubber in removal of hydrogen sulfide from a typical flue gas by aqueous ferric chelate solution. The experiments were conducted at different operating conditions (gas flow rate: 22-28 lit/min, ferric chelate flow rate: 0.2-0.5 lit/min, hydrogen sulfide concentration: 300-4000 ppm,static bed height: 13, 23 cm and packing diameter: 2, 2.5 cm). The results show that the H2S absorption rate increases by increasing static bed height. This is because the contact time and surface area between gas and liquid phases increase by increasing the static bed height. Also, H2S absorption rate increases by increasing ferric chelate solution flow rate due to the greater number of ferric ion (Fe3+) moles available for reaction. Thepressure drop also increases by increasing static bed height and catalyst solution flow rate. Therefore, these parameters have to be increased in a restricted range. Under investigated conditions, the results show that by increasing the packing sizes (diameter), H2S concentration and flue gas flow rate, the H2S concentration increases in the product gas. This is due to decreasing the contact surface area, Fe3+ to H2S molar ratio andresidence time, respectively. The liquid to gas flow rate (L/G) ratio is one of the major parameters affecting the design of mobile bed scrubber. In this work, considering the obtained experimental data, this parameter is determined in the range of 8-21 lit/m3 depending on the H2S concentrations range in flue gas and packing diameter.

In this study, experimental cavitation erosion is carried out on different types of rotational models (gray cast iron, aluminum 1100, aluminum 6061 and chromium stainless steel) at constant rotational speed, temperature and cavitation number in a cavitation closed tunnel. The weight loss rate and the behavior of corrosion were analyzed with SEM and optical microscopes. The effect of the rotational speed variation on the cavitation erosionwas evaluated for models of different materials. The findings significantly showed that the diameter of the holes is independent from rotational speed and with increased rotational speed, the number of the holes and the cavitation erosion escalate. The study revealed that chrome stainless steel model has a higher resistance against cavitation erosion. The relationships between weight loss rate and rotational speed are further presented.