دوماهنامه مهندسی شیمی ایران
پیاپی 116 (امرداد و شهریور 1400)

Due to the separation of light and heavy phases in the distillation towers of the petrochemical industries, some hydrocarbons have been burned in the flare. Combustion of these gases produces toxic and dangerous gases by the flare and vent into the environment. In the stripping tower of Jam Petrochemical LLDPE Unit, a large number of hydrocarbons is released from the top of the tower. In this study, by providing a suitable solution, toxic and dangerous gases can be prevented from entering the atmosphere, and also the energy of fossil fuels and their compounds can be used from an economic point of view. Therefore, the combined cycle has been used to produce power and water vapor useful for the unit itself. To enable power and steam production, the output results of the unit, as well as the combined cycle, have been simulated using ASPEN-PLUS software. The results showed that the use of the combined cycle produces 29.9 MW of power and also 3500 kg / h of steam. From this amount of power generated, all the required electricity related to the compressor of the linear light polyethylene unit can be supplied, and also the generated steam can cover the steam related to the steamer area and prevent the entry of toxic and dangerous gases into the environment.

Asphaltenes are heavy components in oil that do not dissolve in normal alkanes like normal heptane but can be soluble in aromatic compounds such as benzene and toluene. Usually changes in operating conditions such as temperature, pressure and fluid composition lead to asphaltene precipitation. Asphaltenes cause a lot of damage by depositing in porous media, wells, pipes and surface equipment. In order to prevent or postpone the formation of asphaltene precipitation in different conditions and places, it is very necessary and important to predict the onset point and the amount of precipitation. Temperature, pressure and flow rate are operating conditions that by changing each, the amount of precipitation can be reduced or intensified. The only solution in the industrial world to postpone asphaltene precipitation is to use chemicals and inhibitors, which is very important to know the mechanisms of deposition. In this review paper, the structure of asphaltene, deposition conditions, experiments of asphaltene precipitation, deposition mechanisms and inhibitors are discussed. The main purpose of this article is general acquaintance with asphaltene precipitation and the factors affecting deposition and applying knowledge to prevent the formation of asphaltene precipitation with the approach of using and applying inhibitors.

In this study, the porous media's morphological information, such as pore and particle size distribution, number of particles, and porosity, was extracted using image processing by imaging the spherical particle bed. The findings revealed that the ratio between the average pore diameter and the mean particle diameter is logarithmically related to porosity. The pore network model was used to measure the permeability in porous media. To create a pore network, all of the information derived from the image was used. The pressure distribution, flow rate, and consequently, the permeability have been determined after applying the governing equations in the network. The simulation findings for validation were compared to the permeability calculated in the experiment and the Carmen-Kozeny and Rabbani et al. equations. It was observed that the experimental results are more consistent with the results of the pore network model due to considering the internal structure of the porous media in the form of pores and throats.

Pipeline is one of the main methods of natural gas transmission. This method has some limitations such as inflexibility, limited gas transmission capacity, and high costs of installing and maintaining the equipment. To overcome some of these limitations, dense phase gas transmission (supercritical fluid) has recently been proposed. Among the benefits of supercritical natural gas transmission, increased density, decreased viscosity, less compressor stations, smaller pipe diameter, reduced pressure drop, lower maintenance costs, as well as the lack of two-phase fluid formation should be mentioned. To change the gas from usual condition to a dense phase, the gas pressure should be more than the cricondenbar point and the gas temperature should be between the critical temperature and the cricondentherm point in the phase diagram. In this paper, after expressing the theory and equations of gas transfer, the results of two case studies on natural gas transmission in supercritical conditions are presented. These studies showed that the compression and cooling energy in the supercritical gas transmission were 70% and 50% lower than the two-phase gas transmission mode, respectively. The extractable amount of liquefied gas in the supercritical condition was 74% higher than the two-phase state. Also, the amount of energy of the compressors in the dense phase state was 51% and 63% lower than the medium and low-pressure gas transmissions states, respectively.

Foam is a fluid that consists of water, gas, and surfactant, so that its properties are a combination of the two. Water-soluble surfactant is used to stabilize the fluid. From the late 50s and early 60s, foam as a promising technique to control gas mobility and adaptability to porous media, as well as solving problems such as finger phenomenon, early gas breakthrough, gravity override, etc. that are created by gas injection are presented. Applications of foam injection including: EOR, matrix acidizing, prevention of gas leakage, repair of aquifer layers, closing the path in the porous medium in order to control the flow and direct it. To understand the physicality of this fluid, it has been modeled in the past with two general techniques of population balance and local equilibrium. In this article, these approaches and models are explained. Also, a general comparison has been made between the presented techniques. The population balance pattern, which is based on the rules of bubble balance, is classified into two versions: 1- dynamic texture and 2- local equilibrium. The main difference between the two versions is in how to obtain the foam texture. The results show that the local-implicit texture equilibrium technique requires fewer parameters than the population balance model versions. Also, due to the algebraic solution of equations, it takes less computational time in reservoir simulators and is more useful due to its experimental nature.

Dielectric barrier discharge technique (DBD) is a new methods for plasma formation which can be used to enhance the oxidation state of different materials. In this study, the probability of enhancing the oxidation state of carbon-based (graphene oxide and multi-walled carbon nanotube) and metal-based (nano-magnetite and nano-alumina) precursors was investigated. In this way, the oxidation state of the materials was evaluated by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet-visible spectroscopy (UV-Vis) before and after the plasma process. In addition the dispersity of the nanoparticles in an aqueous solution was investigated by zeta potential method. The obtained results revealed that after the plasma processing, the weight percentage of oxygen element increased about 59% and 33% for graphene oxide and carbon nanotube samples, respectively. However, the metal-based materials were not affected by the plasma process. Indeed, depending on the type of produced oxygen radicals in the plasma space, different groups such as carboxylic acid, hydroxyl, lactone, and lactol groups can be formed on the surface of the carbon-based materials which led to the increasing of the oxidation state of the nanoparticles.