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.... 

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... 

Most of Final properties of polymers such as morphological characteristics are related to molecular weight distribution (MWD) and particle size distribution (PSD). It is possible to obtain the desired properties by controlling of these indices. In this work, modeling, simulation, and control of final properties of styrene have been considered. First, kinetic of reaction has been investigated which is a free radical type. Molecular weight distribution has been calculated by using moment method. Next, population balance equation (PBE) has been used to model PSD. For this system, mass, energy, and moment conservation equations are a set of stiff ordinary differential equations (ODEs). PBE is a... 

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... 

In this work, a comprehensive dynamic model has been used for styrene emulsion polymerization in a semi-batch reactor to predict the evolution of product particle size and molecular weight distributions under non-isothermal condition. Method of moments has been applied for solving the population balance equations and the results are compared with the results obtained from finite-volume method as a precise technique. A sensitivity analysis respect to perturbation in initial values of various reagents, species and the reactor temperature has been performed to identify suitable manipulated variables for closed-loop control of the reactor. The detailed model is used to generate optimal feed... 

Formation damage is defined as any process that reduses the reservoir permeability relative to its normal state. Two major causes of this problem are filtrate and solid invasion into the pore spaces of reservoir rock.Therefore, the drilling fluid used for drilling the reservoir sections should prevent such a problem as much as possible.The goal of this study is to optimize the weighting additive particle size distribution to prevent permeability damage in one of the southern Iranian oil fields. By analizing the capillary pressure data of core samples, it seems that fracture presence in rock matrix leads to poor quality of mudcake, resulting peremabilty reduction in near wellbore region.... 

Due to their highly efficient micromixing rates, confined impinging jet reactors can be beneficial in treating mixing-sensitive processes such as precipitations or crystallizations at high supersaturation. Successful scale-up of these reactors requires a decent insight of geometric design and operating conditions of these systems. This paper deals with the reactive crystallization of calcium carbonate nano-particles in two-impinging jets reactors. The influence of jet velocity (Jet Re number), nozzle diameter, and chamber ratio on the PSD and mean particle size of the product are investigated. In addition, the effect of supersaturation ratio, ion ratio and quenching ratio on the nucleation,... 

Stormwater-borne solids are a major contributor to water quality degradation. A large portion of water quality impaired surface waters is located in urban areas and stormwater runoff is a major source of contamination. Sediments have been identified as the most widespread pollutant in urban river and streams. Water quality of urban streams in Tehran was characterized by determining the PSD, total phosphorus (TP), orthophosphate, NO3, NO2, NH3, TSS, TDS, heavy metals and turbidity in six storm events and base flow. A total of 45 road-deposited sediment (RDS) samples were collected from three different land-use types (residential, intense traffic and educational) in Tehran for characterization... 

In this work, a comprehensive dynamic model has been used for vinyl acetate emulsion polymerization in a continuous reactor to predict the evolution of product particle size distribution under isothermal condition. Method of finite-volume has been applied for solving the population balance equations and the results are compared with the results obtained from moment method. Finite-volume method has been selected as a precise technique to predict sustained oscillations, which occurs in continuous emulsion polymerization. After performing sensitivity analysis and verification of system’s controllability, feed rate of surfactant and initiator have been selected as proper manipulated variables to... 

Asphaltene precipitation and deposition are sources of a number of problems for petroleum industry. Thus, solving the problem of precipitation and deposition is very important. In order to measure deposition level, study of other asphaltene flocculation is vital; since there is a time interval between precipitation and deposition. Use of chemical inhibitors is one of the best methods for prevention of asphaltene precipitation that could postpone precipitation point and prevent formation of huge flocculations. In this study, effects of asphaltene flocculation size on deposition with or without using inhibitors were investigated. In this regard, QCM was used for measuring the amount of... 

This thesis concerns the modeling of precipitation processes aimed at predicting product particle characteristics especially particle size distribution. A mixing-precipitation model (based on SFM) linked to the population balance is used for a single-feed semi-batch precipitation process to describe the mixing effects on the final particle-size distribution (PSD) and mean size, considering the agglomeration mechanism. The model describes mixing on two zones: the feed and bulk zone with different levels of super saturation. To solve a full population balance equation containing nucleation, growth and agglomeration, discretization method was performed witch is more accurate and low... 

Nowadays, indoor air quality (IAQ) is a major concern, particularly in cleanrooms where IAQ is controlled to ensure the extreme standards of cleanliness. For this reason, the particles rising from obstacles and distribution inside the indoor environments and cleanrooms are of great importance. In this study, effects of temperature field, releasing height of particles, and obstacle motion on particles rising from the obstacles inside the three-dimensional cleanroom were investigated by Lagrangian and dynamic mesh methods. The results indicated that, the greater the temperature difference between the top surface of the obstacle and airflow, the more the percentage of the particles risen from... 

This dissertation discusses the development of dimensionless correlations for predicting hydrodynamic parameters and CFD simulation of gas-solid two phase flow in conical fluidized beds. This research mainly focuses on the impact of particle size distribution on hydrodynamic parameters. The first section describes the experiments that were carried out with a number of gas–solid systems in a conical column to study certain important characteristics of the fluidized bed. Generalized empirical correlations, based on dimensionless analysis, have been developed in order to predict minimum fluidization velocity, minimum velocity of full fluidization, maximum pressure drop and bed expansion ratios.... 

Suspension polymerization is an important industrial process. Product of this process is particulate polymers that have a widely use in human lives. An important property of suspension polymerization process is the particle size distribution (PSD), which affects the end-use properties of the products. Therefore, the evolution of PSD is a major concern in the design of a suspension polymerization process. In a suspension polymerization reactor the evaluation of particle size distribution is the result of the interaction of the mixing conditions and the kinetics of the polymerization reactions. Mathematical modeling of particle size distribution in suspension polymerization processes should... 

Reaction parameters in precipitation processes have a significant impact on the product characteristics. The process of formation of yttrium-stabilized zirconia precipitates was studied by co-precipitation method to investigate the parameters affecting particle size distribution. These studies aimed to investigate the reaction parameters and determine their effect on the size of the particles, taking into account the effects caused by the interaction of the parameters. To achieve this goal, the design of the experiment based on response surface methodology was used and five parameters of zirconyl chloride concentration, molar percentage of yttrium oxide, reaction time, mass percentage of...