مجله فرآیند نو
پیاپی 43 (پاییز 1392)

In this work, simplified SAFT equation of state, similar to simplified PC-SAFT equation of state, have been applied to model vapor-liquid phase equilibrium of systems containing nonassociatingnonassociating, associating-nonassociating, and associating-associating compounds. The binary systems considered here are methane-propane, propane-benzene, methanol-pentane, propanolheptane, water-methanol, and water ethanol. Pure component radial distribution function has been used for mixtures in this simplified SAFT equation of state. Pure component parameters are identical for both SAFT equation of state and simplified SAFT equation of state. To model water, 3B association scheme and for methanol, ethanol, and propanol 2B association scheme have been employed. Considering a binary interaction parameter, a well agreement has been observed between modeling results from simplified SAFT equation of state for above mixtures and experimental data.

In general, the amount of sulfur in crude oil, depending on the source, varies between 0.025 and sometimes about 7.89 wt%. For example, Middle East Oil contains about 1.5 to 3 weight percent sulfur. In general, crude oil contains both inorganic and organic sulfur. In addition to elemental sulfur, sulfate, sulfite, thiosulfate and thiosulfide and more than 200 organic sulfur compounds have been identified in petroleum which includes sulfides, thiols, or mercaptans and thiophene and more complex molecules such as dibenzo thiophene and thiophene. In this article, desulfurization different methods are discussed including hydrodesulfurization, extractive desulfurization, oxidative desulfurization, biodesulfurization and desulfurization through alkylation, chlorinolysis and desulfurization by supercritical water. The results of this study show that the best method for desulfurization of crude oils is autoxidation followed by thermal decomposition of the oxidized product.

The effect of Pt-Re/Al2O3 nano-catalyst bimetal catalyst synthesis method over its physiochemical behaviors and its application are investigated in this article. The catalysts synthesized by microemulsion method and their applications are compared to those synthesized by impregnation in N-Heptane reforming reaction at 500 ºC and 1 atm. The catalysts are characterized by nitrogen adsorption isotherms, ICP and TPR. The results of TPR show that the microemulsion method leads to stronger interaction of metal particle with the support. Also the use of microemulsion method leads to an increase in the metal dispersion and reduces the particle size. The microemulsion method leads to increase in the activity of catalyst from 0.26% to 50%. In addition, the selectivity of benzene increases from 3.15% to 9.61%; while, the toluene selectivity rises from 2.34% to 6.075% and selectivity of methyl cyclohexane increases from 2.3% to 8.04%. Also, the methane selectivity decreases from 2.4% to 1.05%.

Crude oil associated water contains various types of salts causing problems such ascorrosion, fouling and plugging of exchangers, furnace pipes and bottom trays of distillation columns in refinery processes. In this study, the performance of refinery desalters is evaluated by calculating the salinity and water cut efficiencies using artificial neural network (ANN) technique. ANN is selected due to its potential for modeling of highly nonlinear phenomena involving in the desalting process. In this study, the performance of the desalting/ dehydration process is evaluated by calculating the salinity and water cut efficiencies using data based methods. Five variables namely fresh water flow rate, temperature of fresh water fed to first desalter, oil flow rate and water temperature and flow rate to the second desalter, are introduced to the ANN model as input parameters.The simulation results are compared to the experimental data extracted from Bandar Abbas refineries. The overall agreement between the ANN predictions and experimental data for water cut are acceptable with average error about 0.4% for training and 1.9% for test. Sensitivity analysis has revealed different operating parameters affecting various desalting units. The model is capable of predicting the behavior of desalting process quite well if we access to enough and suitable experimental data.

One of the basic strategies in every industrial unit is to reduce energy consumption and enhance efficiency. In oil refineries, as energy producers, this is very important. One of the main strategies to reduce energy consumption and increase distillation column efficiency, is to separate light substances from crude oil and entering it to atmospheric distillation tower in the area where the combination of light substances is similar to flow combination inside the column. This causes reducing energy consumption in furnaces and pumps and also decreasing the number of trays and the size of tower, which will finally lead to column efficiency enhancement. In this research, the possibility of light compounds separation and transferring them to upper part of atmospheric distillation column, via flash evaporation column is studied. This research has been performed with Hysys software and it has specified that with a few changes in operation conditions and distillation column, refineries’ energy could be saved. By this method refineries can lower their constant and current costs and increase the purity of distillation column products.

Selection of a cost estimation method is generally dependent upon the level of progress in engineering and design in each project. The main capital cost estimation methods for chemical processes, together with capital cost items, are introduced in this article. The main capital cost estimation methods include capacity factored, equipment factored, parametric model, semi-detailed and detailed cost estimation. This article shows how to use cost estimation methods in different design stages of a project.