Sharif Digital Repository

In this research, it was tried to present a suitable environment for simulation of crystallization systems. Chapter one presented a survey on crystallization systems, its application, operating methods, and its phenomena. Chapter two presented mechanism and kinetic of phenomena that occur in crystallization systems, in detail, and mathematical models to modeling this systems are implied. In chapter three, that is the simulation result section, firstly, it focused on solution methods to solve population balance equation, that explains the particle size distribution, and its validation, secondly, the simulation results in a case study was compared with those obtained from finite volume method.... 

The main strategy for treating solid cancers is based on the very early diagnosis of a malignant tumor, and in general the smaller the tumor, the greater the likelihood of successful treatment. Magnetic Resonance Imaging (MRI), based on the nuclear magnetic resonance phenomenon, provides the possibility of detecting early malignant tumors with the assistance of appropriate contrast agents. Hence, researchers continue to develop novel magnetic materials to achieve this aim. Superparamagnetic nanoparticles have become the focus of these studies because their superparamagnetic, biocompatible and hydrophilic properties would be revealed after modifying the particle surface by suitable... 

The object of this research is modeling, simulation and control of a crystallization process. Population balance equation (PBE) has been used for modeling of such processes. Most of the existing numerical methods cannot solve the general form of PBE in presence of the breakage and agglomeration terms and some others are not suitable for control objectives, because of their intractable CPU time. In this work a new developed numerical method called conservation element and solution element (CE/SE) has been used for solving general form of multidimensional population balance equations. The accuracy and effectiveness of the scheme is demonstrated through computer simulation. According to the... 

Sugar extraction from cane sugar is based on crystallization. Sucrose crystallization is a mass transfer process. Sucrose molecule's migration from solution to crystal is driven by concentration difference between the mother liquor and the crystal surface; the coefficient of super saturation is the most important parameter for the process. It has large influence on product quantity and quality (crystal yield, crystal size and size distribution). In this project, first the efficiency of sucrose extraction studied by crystallization in HAKIM FARABI sugar factory. Crystal size distribution (CSD) is the more accurate measure for monitoring crystallization processes. CSD depending on the seeds... 

Porous medium is a material consisting of a solid matrix with an interconnected void. A polymer is a large molecule composed of many repeated subunits, known as monomers; Polyurethane is a type of polymer which has many uses. The aim of this research project is to investigate the effective factors in polyurethane polymer injection and the behavior of this material during the foaming in cavities with different soil porosities (0.15 < φ < 0.4). Parameters such as thermal boundary conditions and the soil material that could be effective in solidification of polyurethane are analyzed, numerically using FLUENT software. A simplified model for foaming is presented in this study which can be used... 

Aluminum sulfate is widely used in water treatment as a polyelectrolyte. Its dissolution and recrystallization into nanoparticles directly affects the working conditions. This study concerns determination of the metastable zone and induction time in nucleation of aluminum sulfate nanoparticles in aqueous media and in presence of acetone as anti-solvent. Later the effect of SDS on the metastable zone and induction time are also studied.. The study also shows if the presence of anti-solvents and surface active agents can vary this phenomenon. The study also adds to our understanding of the media in creation and stabilization of nanoparticles. This project has a special focus on the changes... 

Polyethylene, due to its low production and maintenance costs, light weight and excellent chemical resistance, is the most widely used material for production of water and gas transfer pipes. Pipe grade polyethylene (PE100) with bimodal molecular weight distribution has excellent mechanical properties, especially long-term creep performance. In order to prevent UV degradation, carbon black is added as masterbatch to PE100 to produce black compounds, which acts as most effective industrial UV stabilizer of polyethylene. Five PE100 black compounds and one white PE100 as reference sample were produced using a twin-screw extruder. Rheological, melt flow DSC, TGA, FE-SEM and tensile tests were... 

Hydroxyurea is an anticancer drug that is commonly used to treat chronic myeloid leukemia (white blood cell cancer in bone marrow), polycythemia vera (red blood cell cancer), sickle cell anemia, solid tumors, and in particular leukemia. In this research, in addition to analyzing all available methods for synthesis of hydroxyurea, the most economical method for synthesis of hydroxyurea which is Hantzsch method was chosen; then we synthesized hydroxyurea crystals using a precipitation or crystallization process. To do so, two hydroxylamine hydrochloride and potassium cyanate reactants have been used in the semi batch reactor. Since the reaction efficiency and purity of the synthesized... 

In this research work, a two-impinging-jets reactor (TIJR) has been designed and tested to synthesis calcium carbonate nanoparticles. The application of calcium carbonate nanoparticles in various industries including health, food industry, pharmacy, etc., and the dependence of product quality on properties such as morphology and particle size distribution, persuaded us to study the synthesis of calcium carbonate nanoparticles in the designed TIJR. The precipitation processes are fast chemical processes and mixing plays an important role in the final product quality. TIJR have come to the attention of researchers because of the low micromixing time in recent years. In this research work,... 

The structural integrity of the sealing material is critical for the reliability of solid oxide fuel/electrolysis stacks. In this study, the mechanical properties of a rapid crystallizing glass of BaO-CaO-SiO2 system were evaluated. The crystallization as a determining factor in the mechanical behavior of the glass-ceramic sealant was investigated via high-temperature X-Ray diffraction spectrometer. Three- and four-point bending tests were carried out to measure the flexural strength (σ) of sealant material bars and head-to-head joined specimens at room- and high-temperatures. In addition, the elastic modulus (E) was measured by impulse excitation test up to 900 ºC. Also, the indentation... 

Crystallization of Aluminum Hydroxide is the most important section of the Alumina production processes as the product yield and crystal size distribution (CSD) of this stage strongly affects the whole Alumina production process. In this work to simulate the crystallization in industrial steady precipitation tanks two Population Balance based models developed. First one is the Coupled CFD-Population Balance Model which considers the effects of flow hydrodynamics on crystallization kinetics and CSD. For development of this model the computational fluid dynamics software ANSYS FLUENT has been used. The two phase flow field has been simulated using Eulerian granular multiphase model coupled... 

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...