PETROLEUM RESEARCH
Year:2012 | Volume:22 | Issue:70|Papers Count:12

In this study, thermal cracking of two vacuum residues (VRs) from Tehran and Bandar Abbas refineries has been carried out. The products of this process consist of gas, liquid, and quasi-coke residue. Coke formation and the high sulfur content of products are the most difficulties that VR upgrading processes are faced with. The distribution of sulfur among these products has been studied. The investigation of the effect of operating conditions on the sulfur content of the liquid product has proven that sulfur concentration in the liquid fraction increases with temperature, while longer residence time can dilute the sulfur compounds and lessen their concentrations in the liquid product. The product of Bandar Abbas VR has a higher sulfur concentration relative to Tehran VR. It was shown that the liquid products, containing a high sulfur concentration, have higher densities and refractive indexes. On the other hand, higher process temperatures result in a greater production of the more desirable (liquid) product accompanied by lowering its quality. The effect of physicochemical properties of the VRs (sulfur content, density, Conradson Carbon Residue and H/C ratio) on the sulfur content of the liquid product has also been investigated. The kinetic modeling of reactions of sulfur compounds has been implemented for both VRs. Kinetic constants at different temperatures are given on the basis of the experimental results.

For the production of synthesis gas utilized in Midrex direct reduction plants, catalytic steam/CO2 reforming of hydrocarbons in tubular reactor is commonly used. Owing to the high heat flux through the wall of reformer tube, the endothermic nature of reforming reactions, low mass velocity of feed gas and large tube diameter, the catalyst bed is exposed to the considerable axial and radial temperature gradients. These radial gradients of concentration and temperature may create local areas with potency of carbon formation. In this investigation, a two dimensional model is developed for simulating the operation of a Midrex reformer. In this model, a thermodynamic approach is used to recognize zones inside the reformer tubes in which the risk of carbon formation is high. The simulation results are in good agreement with available data of Mobarake Plant, in Esfahan, Iran. The results show that the first half of tubes, both in center and near the wall, is critical in point of view of carbon formation.

In recent years, using natural gas hydrates (NGH) for storage and transportation of gas has been considered because gas hydrates can be stored and transported at temperatures much higher than liquefied natural gas (LNG). The major objective of this study is to investigate the effects of non-ionic surfactants polysorbate 80 (Tween-80) and polysorbate 20 (Tween-20) on the formation rate and storage capacity of methane hydrate.Tween-20 was tested with 2 concentrations of 1000 and 2000 and Tween-80 was tested with 100 and 500 ppm and compared with the hydrate formed in pure water and aqueous sodium dodecyl sulfate (SDS) solution. The hydrate formation rate and the storage capacity were influenced by the different concentrations of surfactants and it was found that Tween-20, when prepared with 2000 ppm, speeded up the hydrate formation rate and increased its storage capacity; but when it was prepared with 1000 ppm, it inhibited the hydrate formation effectively. Tween-80 decreased the hydrate formation rate in both of the solutions. Experimental results on hydrate gas content revealed that the maximum storage capacity of 125 V/V is obtained with 2000 ppm of Tween-20 in water.

In this paper, the novel technology of “twisted tube heat exchanger” has been introduced. Using available correlations for heat transfer and pressure drop from literature, an algorithm for the rapid designing of heat exchangers with twisted tubes has been developed. The performance of this exchanger is roughly twice better than the conventional ones. With the consideration of relative advantages of twisted tube bundles, the potential benefits for the application of this technology in grass root and retrofit design of heat exchanger networks has been investigated. Analyzing a basic crude preheat train data for the minimum heat transfer area required by application of twisted tube heat exchangers in a debottlenecking study approves the potential benefits of this technology.

The objective of this study was to evaluate the feasibility of treating refinery wastewater to meet the applicable discharge limits and agriculture use standard consistently using membrane bioreactor (MBR) technology to reduce either the environmental impacts of refinery waste water discharge or operational problems of common activated sludge process (ASP). A pilot scale submerged membrane bioreactor with a membrane module that consists of 56 flat sheet poly (ether sulfone) (PES) ultra-filter membranes was used in this study. The effluent of the dissolved air floatation (DAF) unit from wastewater treatment plant of Tehran refinery was used as a feed. Trials on different membrane fluxes and hydraulic retention time (HRT) were conducted. The results have shown that the hydraulic retention time of 15.87 (hr) was more applicable. The percentage removal of COD, BOD5, TOC, Oil and grease, TSS, and color was 97.32, 92.58, 96.36, 99.18, 99.99, and 95.58 respectively.The results showed that the quality of the product consistently met the requirement for agriculture use and discharge to the surface water. Due to an increase in mixed liquor suspended solids concentration from 6000 mg/l to 9900 mg/l at the end of experiments, the removal rate was increased from 86.00% at the first stage to 97.32% and 95.22% at the second and third stage respectively. It was concluded that it was feasible to treat the wastewater using SMBR technology.

Department of Chemical and Petroleum Engineering, Sharif University of Technology saeed_rafeepur@alum.sharif.edu a general coupled model for the transport of solute, solvent, and heat is presented. The optimization of drilling fluid concentration, weight, etc. is crucial for wellbore stability analysis particularly in high pressure and high temperature environments, and thus the convenient selection of these parameters can be obtained from a clear understanding of the shaledrilling fluid interactions. The coupled effects of chemical potential (chemicalosmosis) and temperature gradients (thermalosmosis) on fluid flow significantly change the pore pressure and thereby causeing the redistribution of stress around a borehole. The model presented here considers electrolytic solutions, drilling fluid and pore fluid, as nonideal.The assumption of nonideality of the solutions must be taken into account to accurately model the flow of solute and water through shale membranes. Due to chemical potential gradients between the solutions, water can flow from low salt concentration to high salt concentration and an osmotic pressure is created which can significantly influence the flow of both solute and water through shale. The impacts of thermal effects on wellbore stability are especially important for offshore high temperature, high pressure, and deep wells, where a small amount of temperature change in wellbore wall can cause various instability problems. Because of these reasons, the impacts of coupled chemical and thermal effects on water flow have been studied here.

Ceramic materials of Ba0.5Sr0.5Co0.8Fe0.2O3- d (BSCFO) were prepared by an EDTA-citric acid complexing method and formed to disk-type shape to be applied in a membrane reactor. The performance of the membrane reactor loading with Ni/aAl2O3 catalyst was studied for the partial oxidation of methane process. At the initial time, the oxygen permeation, methane conversion, and CO selectivity were closely dependent on nickel state in the catalyst (oxide state or Ni0). After 17 hours from the reaction starting time, the reaction condition was found to be steady state and oxygen permeation, methane conversion, and CO selectivity reached 9.3 ml/min.cm2, 80.5%, and 98.3% respectively. The performance of the membrane reactor of BSCFO at various temperatures was studied and good results were obtained; For example, at 950oC, methane conversion and CO selectivity reached 98.5% and 98.2% respectively. The oxygen permeation was 11.6 ml/min.cm2 and increased about 5.1 times in comparison with the air-helium gradient. The results showed that the surface exchange kinetics had a significant role in the oxygen permeation.

Research Institute of Petroleum Industry (RIPI) poursaberit@ripi.ir during recent years some strict regulations are established to reduce the sulfur content of the fuels. Magnetic iron oxide nanotechnology has started a new trend which is more efficient and economic than the conventional methods. Herein, the magnetic removal of aromatic sulfur compounds from gasoline has been investigated. In the present work, a novel magnetic nanosorbent through surface modification by an ionic liquid was synthesized and characterized by XRD, TEM, and FTIR techniques. Effective parameters were optimized and studies were carried out on model oil and a real sample under optimal conditions. It was found that the supported ionic liquid was well efficient in the removal of aromatic sulfur containing compounds and was a promising sorbent in deep desulfurization treatments. The used sorbent could be regenerated through convenient magnetic decantation and stripping by carbon tetrachloride.

In the current study, after validating the accuracy of the current solution, mixed convection heat transfer in a square enclosure for drilling mudas a non-Newtonian fluidand wateras a Newtonian fluid—is investigated by finite volume method. The turbulence methods used in this study are the reliable methods such as RNG, standard, and RSM. The outcome of the investigation implies that under natural convection conditions, velocity boundary layer is somewhat asymmetrical on the cold wall and the fluid at the center of enclosure remains stratified and still. The existing graphs also indicate that the turbulence intensity is higher for forced convection than natural convection. Also, the maximum turbulence intensity is greater for drilling mud than water. One of the most prominent outcomes to be named is that, under similar circumstances, the Nusselt number for water is far more than the one for drilling mud, which confirms that convection heat transfer is greater in the water than the drilling mud.

The magnitude of in-situ stresses is one of the most important factors affecting wellbore stability. In cases we do not encounter special tectonic conditions, in-situ stresses usually consist of three major trajectories, two horizontal and one vertical. In this paper insitu stresses are estimated in the final depth of 4 wells in Mansouri oil field, southwest of Iran. As the most important parameter in vertical stress estimation is density, the formation surrounds the well is divided into three zones: with density log, without density log but with graphical log, and without density and graphical log. Then, the density of formation is evaluated by using these logs and the vertical stress is estimated in wells No.1, 47, 48, and 56. A relation is also suggested to estimate the horizontal stress by using empirical relations. The results show that the vertical stress gradient calculated in the studied wells has inconsiderable variations in magnitude and can be used as a reference in future studies.