Sharif Digital Repository

Injecting several droplets with a known size distribution function in the hot gas environment makes droplets smaller because of evaporation or reaction. Droplets lifetime specification is important in vapor-liquid interactive processes such as chemical or process industries. In previous works, different approximate semi-empirical methods are developed to specify droplets lifetime without considering their size distribution. In this work, governing equations is studiedconsidering a size distribution function for droplets. There is not any analytical method for solving this set of equations, so numerical methods using CFD packages such as Fluent, are applicable in these cases. In this study,... 

Vortex Tube is a mechanical device without any moving parts. It separates a compressed gas stream into a low and a high temperature region (temperature or energy separation effect). Advantages of VT are existence of no moving parts, no external power (electricity or flames) required to operate, tiny and lightweight, inexpensive tube & parts material, convenience and pollution free. Heating, cooling, cleaning and drying gases, separating gas mixtures, gas liquefaction, natural gas pressure reduction and dehydration are the applications of vortex tube. The main Objectives in this research are investigation of various types of gas streams including pure gas or mixture of gases in vortex tube... 

The effectiveness of activated bentonite, known as Clay, is studied in the process of removal of olefins from aromatics. The study on this subject can be divided in two categories: catalysis and process section. The catalyst activities is evaluated with the production of clay samples that are activated by sulfuric acid and hydrochloric acid. The performance and life time of the acid treated are characterized by XRD, XRF, BET, Pyridine FTIR analysis, SEM images and pilot test of the samples. In the process section, factors that are affecting the life time and performance of the catalytic activity of Clay are investigated and the effect of each known parameter on the operating time of this... 

In this research, utilizing the concepts of thermohydraulics theory, optimization of cost due to the scale formation in heat exchangers 4131 and 4132 in Khorasan petrochemical Co. urea unit. The objective function involves the minimization of the energy consumption and production losses. First, via ASPEN we simulated shortcuts of exchangers in order to examine the effects of temperature and velocity on the scale formation. The project optimization was done by GAMS and due to the presence of nonlinear terms in the scale rate equations using CONOPT solver. Eventually, modern practical methods were used with the purpose of reduction and eradication of the heat exchanger's scale formation. The... 

Investigation of particles (bubbles or droplets) behavior in two phase flow is widely studied in many chemical engineering processes. This thesis describes CFD simulation for study of dispersed droplets behavior in two phase flow. For this purpose, in population balance equation which is coupled with mass balance equation, Lou and Svendsen model is used for breakage and Prince and Blanch model for coalescence with Eulerian-Eulerian approach for multiphase flow, in conjunction with turbulence model. Then the effect of gas velocity on the coalescence and break up phenomena studied and the results obtained here showed that by increasing gas flow rate, which increased , leads to increase... 

Solar radiation is a clean and renewable energy which is essential for all natural processes of the planet earth. The benefits of solar ventilation are more than conventional cooling systems. In this research, simulation and modification of solar absorption chiller (LiBr) was investigated. TRNSYS simulator software and Esfahan climate data were used. First of all, collector slope, rate of solar cycle pump, size of heat storage tank and size of collector were modified. Then, operation cost of a 5 tones solar cooling system with flat plate collector and evacuated tube collector was compared with conventional 5 tones capacity cooling systems such as direct fired absorption chiller and vapor... 

Azeotropic separation has multiple difficulties. In order to remove the azeotropes, different solutions are recommended such as the use of entrainers, extractive distillation, and pervaporation. Based on initial condition of the mixture, a decision tree is proposed. As a sample, the Ethanol – Ethyl Acetate system is selected and a new solvent – entrainer is proposed with addition of different salts. The suitable concentrations of salt, entrainers or solvent are tested experimentally to draw the relevant RCM.
A suitable set up is designed and assembled, and then samples are taken to analyze in order to provide T-XY diagram. The pressure also is taken into account to correct its effect.... 

Inappropriate performance of the air-cooled condensers in the process industry will make the flow out of the air cooler not fully condensate and its pressure is greater than the design value. This will lead to product loss and safety issues. In this study, factors affecting the performance of air cooler and various solutions to solve these problems have been identified. As a case study, the first distillation tower of the Ali Siana Petrochemical Complex, which disrupts its function in some months of the year, has been investigated. Aspen Hysys process simulation software simulates the naphtha splitter unit and the Aspen Exchangers Design & Rating software simulates the air cooled condesor... 

In this thesis the replacement of separate heat and power production with combined heat and power system in South Pars Gas Refinery is investigated. High Exergy loss is associated with conventional concept of Heat and power generation. Alternative methods for combined heat and power (CHP) production are investigated and four different technologies are proposed: 1) process steam production by HRSG, 2) power production by condensing steam turbine, 3) CHP production by non-condensing steam turbine, and 4) CHP production by condensing steam turbine. Energy and exergy efficiency and profitability of these technologies are compared with separate heat and power production. The result shows that... 

Due to the increasing cost of energy, we want in this study to increase energy efficiency and reduce waste of system energy. Oil, gas and petrochemical sector is a widespeard part in Iran, so the study of energy systems in the industry have a paramount importance. The study focused on the Tehran refinery steam and power systems, seeking the most economical system of power and steam for the Tehran refinery. To achieve this goal, with the help of simulation of power and steam system for Tehran refinery with Aspen Utility software, a superstructure obtained. Then, using a sensitivity analysis, we were able to achieve economic arrangment of utility system. In this study by increasing the... 

Synthesis gas is a gaseous mixture which mainly consists of carbon monoxide and hydrogen. Different methods are used to produce synthesis gas but the most important method is auto thermal reforming. This method is based upon catalytic reactions. Steam, oxygen and natural gas are the influents to the reactor and synthesis gas will be the effluent. Ni catalysts on alpha-alumina as the support media are usually used in this process. These catalysts are highly heat resistant and insure great qualifications for reactions. This thesis tries to find best solutions of synthesis gas production suitable for feeding to a methanol production unit. There are four main reactions. Three of which are highly... 

Supply Chain is a complex system and its modeling generally results in complicated mathematical problems. Solving these problems, one should make assumptions that make solutions impractical. Knowledge-based frameworks such as ontology has been proposed for tackling this issue. In this thesis, with relying on a seven step ontology developing method, UML as development language and Rational Rose as development software environment, an application ontology for supply chain and its problems has been developed. Furthermore, with use of a Benzene, Toluene and Xylene supply chain as an instance, it has been shown qualitatively how to use the ontology in various supply chain problems. It is... 

Water is essential for human life and other organisms. Increasing population and consequent increase in water consumption has made freshwater scarcity a global problem. Desalination of saline water sources is a long-term solution to this problem. One of the most challenging issues in desalination is the management and disposal of brine. Disposal of brine into the sea and surface waters is the primary solution for brine management. Due to the environmental problems caused by the discharge of brine into the sea and surface waters, the concept of zero liquid discharge has recently been considered. In this research, an economic study of reverse osmosis-electrodialysis-crystallization structure... 

In this study a mathematical model for intravitreal injection and depositing controlled release systems in the eye to treat posterior segment deseases is developed. The effects of important parameters that play a critical role in drug distribution are also studied.
Geometrical model is constructed using COMSOL software and governing equations for a 3-D model of drug distribution are solved by finite element method. The geometry is based on the exact dimensions of human eye and retina, choroid and sclera are considered separately. Choroidal losses to the circulatory system and active transport by the retinal pigment epithelium are incorporated as well. Moreover, two types of implant... 

process design and decision-making about it are challenging activities that involve optimizing conflicting goals such as cost, technical feasibility, and environmental impacts. These conflicting goals can be analyzed by considering the complete life cycle of a process or product in the initial design and decision-making. Life cycle analysis follows the environmental effects throughout the life cycle of a product, including extraction, transportation, production, consumption, and disposal. Life cycle assessment includes four fundamental stages: goal and scope definition, inventory analysis, life cycle impact assessment, and interpretation of results. The aim of this project is to investigate... 

The environmental impacts of chemical processes significantly affect the design of these processes and emphasize issues such as changing the reaction path, separation methods, thermal integration, and finally multi-objective optimization. Therefore, it is necessary to investigate the influence of environmental indicators in the design of chemical processes. The background system in this assessment includes two process units, olefin and polyolefin. Environmental impacts assessment has been carried out using the ReCiPe endpoint method (an efficient method for life cycle impact assessment that will be described in chapter 2) and these impacts have been determined in the form of damage to human... 

Biological removal of sulfur compounds from petroleum is one of the major attractions of environmental technologies in the oil industry. Inefficient sulfur removal in refining processes causes sulfur oxides (SOx) production after combustion, which has adverse effects on the environment.Today the most common way to remove sulfur from crude oil is Hydrodesulfurization which has poor performance in removing some heterocyclic compounds such as thiophenes. Increase the amount of sulfur in the remaining oil reserves and the other hand, more stringent environmental regulations, has led researchers to development and invent new methods for desulfurization. Biological desulfurization is one of these...