Sharif Digital Repository

Considering the drastical increasing of greenhouse gases in the atmosphere, especially carbon dioxide, reduction of these gases seems necessary to combat global warming. Fossil fuel power plants are one of the main sources of CO2 emission. In this thesis, CO2 capture from a natural gas fired combined cycle power plant using different oxygen percent in air feed is studied. Aspen Plus was used to evaluate the effect of this capture technology on the plant efficiency and energetic parameters of the system. Aspen Hysys is used to simulate Amine absorption tower and Air Separation cryogenic tower. Since the oxygen production plant, CO2 capture and transport are cost and energy intensive, the cost... 

Due to the environmental concern for the harmful effect of the release of HFCs on global warming there has been more interest for the use of hydrocarbons as refrigerants in recent years. In this project the performance of these refrigerants have been studied and compared with common refrigerants from the quantitative and qualitative point of view using a real-scale model of Peugeot-405 air conditioning system. Charging amount, inside temperature, cooling load, energy consumption of cycle, coefficient of performance and required time to steady state condition are the important comparative criteria for such a study. After carrying out a series of tests it has been considered that charge... 

Considering the drastical increase of greenhouse gases in the atmosphere, especially carbon dioxide, reduction of these gases seems necessary to combat global warming. Fossil fuel power plants are one of the main sources of CO2 emission. In this paper, CO2 capture from a natural gas fired steam cycle power plant using oxy-fuel combustion technology is studied. The Integrated Environmental Control Model (IECM) developed by Carnegie Mellon University was used to evaluate the effect of this capture technology on the plant efficiency and economic parameters of the system. Since the oxygen production plant, CO2 capture and transport are cost and energy intensive, the cost of electricity generated... 

Low frequency (LF) O2 plasma was used to modify the surface of polysulfone (PSF) gas separation membranes. The effect of treatment time and plasma power input on the membranes was also investigated. Pure CO2 and CH4 gas permeation measurements were performed before and after plasma treatment. The results showed the increase of permeability of the treated membranes due to surface ablation and surface polarization. However, the CO2/CH4 permselectivity of the treated membranes varied from 7.7 to 45.3 depending on the treatment conditions. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy determined the introduction of oxygen containing polar groups on the surface... 

A kind of novel nanofiltration membrane process is proposed to solvent recovery from dewaxed lube oil stream in an energy-saving way. Most of the nanofiltration membrane materials are polymeric and cannot survive harsh conditions, for example, MEK contained solvents. Hence, high solubility of most of the polymeric materials in the solvent, especially in the MEK, is a challenge to researchers. To prepare a polymeric membrane that can solve the problem integrally skinned polyaniline (PAni) membrane was cast on a woven polyester backing material, and then crosslinked in two different ways, chemically and thermally, to make the membrane resistant in MEK (methyl ethyl ketene) and toluene for long... 

In the present work a comprehensive mathematical model has been developed for CFD simulation of transport phenomena in the hollow fiber membrane contactors. The system which has been studied was a gas sweetening including methane, carbon dioxide, and hydrogen sulfide in the gas phase and MEA aqueous solution as the solvent. Effects of temperature distribution on the contactor efficiency predicted taking into account the heat of solution, the heat of reaction, and the viscous dissipation. Major focus of the present study was on dynamic behavior of the contactor considering the entrance regions of momentum, energy, and mass transfers. CFD methods have been developed to solve the nonlinear... 

Production of cellulosic ethanol from lignocellulosic biomass represents a alternative to the petroleum fuel due to its renewable nature and sustainable availability. The major strategy used for cellulosic ethanol production includes three main steps of biomass pretreatment, enzymatic hydrolysis and ethanol fermentation. The enzymatic hydrolysis contributes significantly to the cost of cellulosic ethanol and from the process economics perspective, the improvement in the enzymatic hydrolysis step is a prerequisite. The fiber is composed of cell wall fractions and residual starch which can be hydrolyzed to reducing sugar.A method of hydrolysis of polysaccharides in corn fiber, feed... 

Zeolite membranes are of interest due to their special properties; thermal and mechanical resistances and non-plasticization property in gas separations. Therefore, separation of H2S from natural gas by these membranes is the main goal of this thesis which is not investigated in the world. After some theoretical investigations including diffusion mechanisms of gases in the zeolites and adsorption mechanism of H2S on the zeolites, pure silica CHA-type (Si-CHA) zeolite was selected. After successful synthesis of Si-CHA zeolite, adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0-190 kPa and temperatures of 25 °C, 50 °C, and 75 °C. Acid gases... 

In this project dynamic effect of changes in gas turbine load on power plant, reforming and Co2 capture section is investigate. The reason for study of effects change of gas turbine load is that gas turbine determines the performance of the other parts in combined cycle including gas cycle and change of gas turbine load can alter the load and the performance of other parts in the power plant and in other process such as production of synthesis gas and carbon dioxide separation unit. One Autothermal reactor and eight sewgs reactor are utilized to produce gas turbine fuel which is mainly consist of Hydrogen. this part of thesis is to be implemented in the gPROMS from process system enterprise... 

The objective of this study is to assess seismic vulnerability and more specifically to develop analytical fragility curves for a number of existing buildings in Qazvin. Fragility curves represent exceedance probability of the structural response from a specific limit state at a given seismic intensity level. In this study, Maximum Interstory Drift Ratio and Spectral Acceleration at fundamental period of the structure with 5% viscous damping are considered as Damage Index and Intensity Measure, respectively. Limit states are also applied as it is suggested in FEMA 356. In order to obtain comprehensive and extensible results as far as possible, the type of buildings under study must be... 

Through our work, we conducted a three-stage solution to effectively reduce the impact of 'concentration polarization' and 'fouling' on ultrafiltration process. The stages were compromise of: 1. the design and selection of appropriate equipment along with outlining the operational parameters, 2. the pretreatment process design, and 3. the cleaning process design. Because of the presence of fat, there are incline both in permeate flux and the quality of the final product. Therefore, we studied the different methods of removing the lipid content, during pretreatment stage. After examining these methods, finally, we found that adding chitosan parallel with employing centrifugal separator is the... 

Oxygen enriched combustion is one of the attractive combustion technologies to control pollution and improve combustion in diesel engines. In the present work after an introduction to membrane seperation and membrane seperators for oxygen-nitrogen from air, a simulation of combustion chamber by GT-Power and membrane COMSOL Multiphysics was used to study the impact of oxygen enrichment on combustion, pollution and performance parameters with 23, 25 and 27% levels of enrichment. Increasing the oxygen engine content with the air leads to faster burn rates and the ability to burn more fuel at the same stoichiometry. These effects have the potential to decrease specific fuel consumption and... 

During the brewing process, beer alternately goes through different chemical and biochemical reactions and solid–liquid separation stages. The clarification at the final step of brewing is a highly critical stage when it comes to producing a clear and bright beer. Recently, membrane technology has been successfully used in beer clarification, wherein Kieselguhr (diatomaceous earth) filtration is replaced by cross-flow microfiltration. The most important disadvantages of using microfiltration in clarification of beer is the fouling and flux decline during the process. The phenomenology of fouling mechanisms is still undefined and selection of an appropriate technique for flux enhancement in... 

In this study, the effects of treatment time and power of Low-frequency (LF) O2 plasma has been investigated for the surface treatment of polyethersulfone (PES) gas separation membranes. PES membranes prepared using dry/wet phase inversion using ternary mixtures containing 1-methyl-2-pyrrolidone (NMP) as solvent, water as non-solvent. The optimum polymer concentration was 32 wt.% , 61 wt.% and 7 wt.% for PES,1-methyl-2-pyrrolidone and water respectively. Pure CO2 and CH4 gas permeation measurements were performed before and after plasma treatment. After treatment gas permeances of around 0.81 GPU for CO2, and 0.073 GPU for CH4 with selectivities of around 11.23 for CO2/CH4 were obtained.... 

Olefin/ paraffin separation is one of the most important processes in the petrochemical industries.In the last decades, adsorption and membrane processes are a new technology considered significantly for this purpose. In order to synthesizeof zeolite powder (pure silica zeolite STT and CHA), raw materials were made by two methods and their HNMR spectrum was recorded and thenzeolite powder was synthesized. X ray diffraction(XRD) and scanning electron microscopy (SEM) images were taken,showing the same results as the refference structure.To consider synthesized zeolite powdersand olefin/ paraffin interactions, surface adsorption ofthose gases was accomplished on two zeolite powders. After...