Sharif Digital Repository

Pipeline transfer is the most commonly method for natural gas transportation. Potential force of natural gas transportation in pipeline is pressure difference that is generated in Gas Compressor Stations (GCS). For each 100 to 150 km of pipeline, one GCS is required that pressure is increased usually from 700 to 1000 psig. Each station contains different process equipments such as turbines, compressors, scrubbers, filters, air coolers, throttling valves and pipes with instruments. It is shown that about 10 percent of the generated pressure difference, decays in GCS.
In this thesis, pressure losses are studied and initiatives are purposed to reduce them in a Gas Compressor Station. Then... 

Compressor stations with gas turbine drive have become common in transport of natural gas. However, the thermal efficiency of the gas turbines used in these stations is low. One reason for this is that 70% of the heat of combustion of the fuel gas used by the gas turbine is lost with its exhaust gases. Hence, heat recovery from gas turbine exhaust gas would increase the cycle efficiency by decreasing the fuel gas consumed. On the other hand, gas turbine efficiency highly depends on the climatic conditions of operation. Among several well known methods of performance improvement, the use of an absorption chiller for inlet air cooling has been studied from both process and economic points of... 

The main purpose of this project is to achieve better design by using exergy analysis. First steam methane reforming process of Tehran refinery is simulated using ASPEN HYSYS. Reformer and high temperature and low temperature shift reactors are simulated using trusted kinetics from literatures and results are compared with plant data and، and there was a good agreement between simulation and plant data. A MATLAB program is written to calculate stream exergies and equipment exergy destruction using AUTOMATION. Streamlined life cycle assessment is done using sustainably metrics، and environmental impacts are evaluated. The main environmental impact was global warming. After exergy destruction... 

The aim of this project is Industrial Solvents (White Spirit) producing in Tehran Refinery. For this manner “Wild Naphtha” from Gasoil Hydrotreater and Kerosene Hydrotreater Units was chosen as feed stock for solvents preparation. In addition, Pentane Recovery Column is selected for Simulation and Optimization based on Wild Naphtha. As a Result, Abadan White Spirit 402 and 410 has been produced and a side stream which is full of Aromatic is obtained. Simultaneously, Tray Hydraulics and Solvents production in different cases (Various Pressure and different Split Ratio of Feed Stock) are evaluated, so optimum Tower process conditions such as pressure, Temperature and Split Ratio of Feed Stock... 

This thesis tries to suggest a simple solution to reduce the amplitude of occurred fluctuations in mixing tees. Temperature fluctuations can induce cyclical thermal stress and thermal fatigue. In order to estimate the lifetime of pipeline material and reduce the frequency and amplitude of these fluctuations, an accurate diagnosis of these fluctuations must be conducted. For this aim, a comparison between Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models was carried out to show the ability of LES model in prediction of temperature fluctuations. The effect of Peclet number on the amplitude was discussed. The effect of placing simple pipe segments and orifices to... 

In this thesis design and simulation of SMB for four different mixture was done with Aspen chromatography package. Simulation for three mixtures of D-Psicose and D-Fructose, racemic mixture of Bupivacaine and Ibuprofen racemate were done with the aim of validation, based on experimental data of articles. The simulation results matched well with the experimental results in articles. The separation of p-xylene from mixed C8 aromatics and Para Diethyl benzene (as desorbent), was simulated for one of the p-xylene producing units and results were validated against the PFD. The influence of various parameters on the purity and recovery of p-xylene were investigated. The studies showed high... 

The huge jam complex unit in assaluye (tenth olefin plan) with the capacity of 1320000 tons of ethylene and 306 thousand tons of propylene is considered as one of the biggest olefin units of all world. It is found that the bottleneck of increasing the capacity is the demethanizer unit. In this thesis, after simulation of the demethanizer towers, capacity enhancement is accomplished along with comparing the outlet stream with PFD data in terms of mass fractions, temperature and pressure. in addition, the hydrolic treat ment of towers is checked. This is continued till a problem occures in each of towers. In the bottleneck capacity , a solution and some changes have been offered. Thereafter... 

Phase change materials have been of great interest due to their ability to save and restore energy in low temperature ranges. PCM can save and release energy in a constant temperature which leads to save in energy. These materials have been widely used in solar cells, storage tanks, human body and buildings. Applications of PCMs have been discussed in the last chapter of this thesis. To study the effect of PCM, a room with bricks, chalk, insulator and also PCM is assumed. Abovementioned room in summer and winter of Tehran with south-north and west-east walls has been simulated in COMSOL. Effects of air’s convection in the room and brick’s holes have been investigated in simulation and... 

The delayed coking process is one of the common thermal process technique that used to improve the quality of heavy oil. In this process, heavy feeds such as vacuum residues have been heated in the furnace to temperatures up to the 480-500 °C. For the cracking reactions the heated feed have been sent to the drum that is placed after the furnace. Since the reactions begin inside the furnace and coke is one of the products, deposited on the wall of the tube. With the deposition of coke on the tube wall and the reduction of heat transfer, the temperature of the tube have been increased with the increasing of the flame temperature to save constant heat flux. Therefore, the study of thermal... 

Cyclic distillation can bring new life in old distillation columns, by using a periodic operation mode that leads to significant benefits, such as increased column throughput, lower energy requirements and much higher separation performance. The design method for this type of column are reviewed. Among two design approaches, the Lagrangian one is selected, where equations are formulated as delay differential equations, moving from bottom to top of the column to determine feed tray location and total tray numbers. No rigorous design method is selected in order to calculate the column parameters.In this thesis, by defining an economic index that encompasses capital investment, operating costs... 

In this thesis heat transfer coefficient and temperature distribution of two Non-Newtonian and a Newtonian fluids in stirred vessel are investigated using Computational Fluid Dynamic (CFD). This vessel is agitated with new impeller called MAXBLEND. Non-Newtonian fluids are aqueous solutions of carboxymethyl cellulose 1.5%w/w and xanthan gum 3% w/w and Newtonian fluid is glycerin. This vessel is simulated in laminar regime with Reynolds number less than 14. The results of simulation are compared with correlation proposed by Kawase et al. Furthermore as a new research for this impeller, the effects of vessel diameter and position of impeller in the vessel on heat transfer coefficient are... 

Cyclones are efficient devices in order to separate suspended particles and droplets from gas media and this effieciency is mainely because of spiral flow nature affecting the particles and droplets and taking them towards the wall. Therefore, particles and droplets move downwards toward down outlet by the gravity force. In consequence, they are being separated of the gas flow and relatively pure gas flow exits the cyclone. In this project, GAMBIT software has been used to produce three dimensional meshes including coarse, medium and fine sizes for two different geometries of cyclone. After simulation, little differences between the obtained results were revealed, showing that modeling is... 

In this thesis, shell and tube heat exchanger with twisted tube bundle in 5 different twist angles is investigated using CFD commercial software, Fluent. A three dimensional unstructured grid has been employed to simulate the heat exchanger model. Optimum grid size is selected according to the level of accuracy required, optimum run time and the available computational resources. The method and simulation accuracy were verified by comparing simulation result with data from Bell-Delaware method. The RNG-K-ϵ method and second order discretization scheme for all variables are selected to model turbulent flow and solve the governing equations. Overall Heat transfer coefficient and pressure drop... 

Brine in crude oil causes many problems that underpin the importance of its separation. In recent years brine in crude oil has been increased with increase of the oil fields lifetime and its separation has been more important. One of the most effective separation methods is electrocoalescence. In this research, the simulation of brine droplets motion and their coalescence under the effect of electric field have been investigated by using the Computational Fluid Dynamics method and the droplets size distribution has been calculated under different values of electric field magnitude. The motion of two single brine droplets in stagnant oil phase and the behavior of many numbers of droplets in... 

In this work, a numerical investigation on shell side performance of a continuous helical baffle helixchanger along with smooth and helically ribbed tubes using CFD commercial code, Fluent, has been performed. The results of simulation for this type of exchanger were compared to a similar heat exchanger with segmental baffles. The geometries are created and meshed using Solidworks and Ansys Meshing softwares, respectively. Mesh generation is carried out using unstructured tetrahedral type elements. Element size (or number of elements) are chosen in such a manner that maintain accuracy and reliability of results in a reasonable run time. Simulation validation were carried out by comparison of... 

Liquid-Liquid coalescers are devices used for increasing the droplet size of the dispersed phase in continuous phase flow such as water droplets in oil flow. The scope of this work is a literature study on the coalescence phenomenon and CFD modeling in general. A mathematical model for simulating coalescence of water droplets in continuous oil flow by the use of different commercial coalescers. The basis for the model are plate-type coalescer and swirl-based coalescer. So, the simulations are done by Eulerian-Lagrangian method. Different aspects of the performance of the coalescers are studied on the rate of coalescence such as impact of changing droplet’s inlet diameters, impact of the... 

One of the most undesirable compounds present in various crude oil cuts are sulfur compounds That creates a lot of problems in different stages of refining and when consumed. In this study, the hydro-desulfurization process that is the most common method of treating oil cuts in the refinery industry and in terms of economic and environmental special place in the oil industry and related industries, has been discussed. In hydro-desulfurization process, sulfur compounds under high pressure and temperature, are converted to hydrogen disulfide in a catalytic reactor. In this study, the catalytic reactor may be simulated with the utmost care. In this context, Euler-Euler two-phase model that is... 

In order to prevent the CCR catalysts from sintering and maintaining their acidity, some chloride compounds are added to these catalysts during regeneration process. The existence of these compounds in downstreams units and equipment causes problems such as corrosion, fouling, etc. Therefor for eliminating these chloride compounds from the exit stream a chloride adsorbent is used. The common compound that is suggested for this application is activated alumina for its high surface area. When Olefin or Aromatics exist in the stream, that is common in many units, a side reaction happens and green oil is formed. In this study, different factors in green oil formation has been studied. Although... 

With the huge natural gas reservoir in Iran, LNG production processes have a great attraction for the gas industry. The main goal of this project is the design of a skid mounted of a small scale LNG unit. A pretreatment unit was designed which includes two adsorption towers. In these towers, the type 13X adsorbent, eliminate traces of CO, N2 and H2S. For the cryogenic side a N2 expansion cycle was considered, after studying different cycles. It is found that N2 expansion cycle is one of the best methods for mini LNG production unit. In this process N2 gas was compressed to 35 bar in two stages and after precooling, enters to an expander to produce the -165 C cold in a cold box. The natural... 

The aim of this study is to survey the ability of vortex tube cascade for separating heavy components of a gas mixture. For this purpose, three vortex tubes based on previous experiences have been manufactured. Also, a helical double pipe heat exchanger has been designed and constructed. Because of the vortex tube’s ability in developing thermal separation, the effect of thermophysical parameters like feed’s temperature, inlet and outlet pressure of air on the thermal separation performance were evaluated. The recommended correlations for estimating outlet temperature of hot and cold flows, have been validated against experimental data. Moreover, various arrangements of vortex tubes to...