مجله فرآیند نو
پیاپی 65 (بهار 1398)

There are manychallenges during utilization of heavy oil and residue due to low quality as well as substantial amount of heteroatoms existed there. Recently, considerable attention has been paid to develop catalytic and non-catalytic heavy oil upgrading in supercritical water (SCW) environment. The reason can be attributed to the substantial adaptation in the physicochemical properties of SCW, including solvation and transport properties, that makes SCW nice candidate for heavy oil treatment. High density and diffusivity of SCW lead to elimination of all mass transfer barriers from reactant diffusion on catalyst surface, while the accumulation of coke over catalyst is suppressed. This article gives a detailed aspects of heavy oil upgrading in SCW.

Today, fuel is produced from non-renewable and limited sources, and since it is not possible to recover or produce these sources, replacing sources such as seawater can eliminate this problem for years. In recent years, jet fuel production from carbon dioxide (CO2) and hydrogen (H2) in seawater has been considered. Fuel production involves two stages of separation of hydrogen and carbon dioxide from water, as well as the synthesis of Fischer-Tropsch (FT) to produce jet fuel. In this research, different methods of hydrogen and carbon dioxide production from seawater have been introduced and their strengths and weaknesses are discussed. It has also been evaluated by examining the Fischer-Tropsch reaction, and the overall costs of the fuel production process in the oceans and seas. The results show that it takes 3 to 6 dollar to produce a gallon of fuel this way.

The removal of sulfur-containing compounds (SCCs) from oil cuts, in particular diesel, is considered a global environmental issue due to the negative impacts of combustion products of diesel fuel on human health. Among the various desulfurization methods, Hydrodesulfurization is known as an effective method for the complete removal of SCCs from diesel fuel. Nonetheless, there has been a great interest in the development of a new generation of highly efficient HDS catalysts to respond to stricter environmental regulations and prevent poisoning of expensive catalysts used in other units. In the meantime, zeolite catalysts are of considerable importance in chemical reactions occurring in chemical, petrochemical, and oil refining industries. This paper reviews recent advances and achievements on catalysts mixed with zeolites in the HDS process due to its high capacity in the removal of highly stable SCCs such as 4, 6 dimethyldibenzothiophene and improvement of the performance of HDS catalysts.

In this study, the selective adsorption is considered by chemical absorption by caustic aqueous solution. This study is based on the simulation with the Aspen-Plus version 9. The rate-based model has been used to determine the separation efficiency for different operating conditions in the simulation. The NRTL electrolytic model is used to describe the non-ideal behavior in liquid phase, while the Soave-Redlich-Kwong equation of state is used for vapor phase. Simulation results show the high efficiency of caustic for the removal of hydrogen sulfide. The results show that the concentration of hydrogen sulfide in the outlet gas from the absorption tower is below 0.5 ppm. It is also discussed about the replacement of different packings and their effect on the reduction of caustic consumption. The results showed that at constant caustic flow rate and concentration, FLEXIMAX-metal 400 packing had better performance in absorbing hydrogen sulfide.

In this study, the effects of shape and size of Al2O3suspended nanoparticles in water-based fluid with 2%volume fraction at 25 °C are numerically investigated on the performance of double tube heat exchanger in the laminar and turbulent flow regimes. The nanoparticle’s diameter was considered between 10 and 100 nm. The nanoparticles with shapes of spherical, cylindrical, and combination of spherical-cylindrical with percentages of 30, 50, 60, 70, 80, 90 of cylindrical nanoparticles were studied. The effect of shape of nanoparticles showed that heat transfer rate increases in the heat exchanger by increasing the percentage of cylindrical nanoparticles and cylindrical nanoparticles offer better heat transfer characteristics and heat transfer rate in the turbulent flow regime as its Nusselt number is15.4% more than the spherical nanoparticles. It was also seen that this suspension has the maximum pressure drop in the heat exchanger. The results of size of alumina nanoparticles with diameters of 10, 50 and 100 nm showed that the nanoparticles with smaller diameter have the largest increase in Nusselt number as well as pressure drop.

In this paper, single and two-phase CFD models are introduced for predicting the thermo-hydraulic behavior of nanofluids. In single-phase models, behavior of nanofluid is similar to that of observed in conventional fluids and interactions between particles and base fluid are negligible. In two-phase models, interactions between nanoparticles and base fluid is taken into consideration. Both models showed the identical prediction for the heat transfer behavior, however, the temperature distribution of nanofluid was different, since in two-phase model, the parameters affecting the heat transfer are considered in the model. At low concentrations of nanofluid, it is a logical assumption to ignore the influence of dispersed phase (nanoparticle) on the flow field (continuous phase). Thus, the single phase is suitable for low-concentration nanofluids, while two-phase model is appropriate for nanofluids with high concentrations. Overall, one can use single or two-phase models depending on the type of problem, available computational facilities and accuracy.

Talent management is a complete set of processes for identifying, developing, maintaining, and using talent employees in order to successfully perform the required activities of organization. Talent management assures the organization that the qualified people with the suitable skills stand at the proper job position in order to achieve the expected goals. The purpose of this study is to evaluate the effects of talent management on succession planning of human in Shiraz Petroleum Products Distribution Company. This study is a descriptive-practical research and the sample of this study includes 140 employees of Shiraz Petroleum Products Distribution Company. Total number of samples is suitable for this study. Data collection tool is questionnaire. According to the results of statistical tests, all research hypotheses are confirmed. The main hypothesis test result suggests that talent management on succession planning of talent human resources has positive and direct (statistically significant) effect. The findings subscribe to the effects of selection of talent employees on succession planning, participation of talent employees on succession planning, and instruction of talent employees on succession planning.