Sharif Digital Repository

The environmental pollutions besides wasting the valuable materials as two main challenges in pyrometallurgical processes have brought up the tendency towards the hydrometallurgical processes. In the present study, the recovery of germanium from leaching residues of zinc plant has been investigated. Firstly, the required tests for concentrating the residues through washing of the zinc were designed by taguchi method, and optimum condition for maximum leaching of zinc accompanied by minimum desolution of germanium were obtained. The sulfuric acid concentration, time, termperature of reaction, solid to liquid ratio and rate of stirring are the parameters studied in this research. The obtained... 

The purpose of this research is to provide an analytical solution using first order shear deformation theory for nonlinear bending of rectangular FG plate under mechanical and thermal loads with different boundary conditions. To achieve this goal, extended Kantorovich method have been used. This method has a high convergence rate and is more accurate than other approximate methods, such as the Ritz and Galerkin methods, because the partially differential equations are converted to ordinary differential equations. In order to solving nonlinear odes the perturbation method is used. Material of the plate is a mixture of ceramic and metal and is modeled as an isotropic and non-homogeneous... 

Retrofitting and strengthening existing structures is one of the most important concepts of structural and earthquake engineering. Strengthening of structures could be due to changes in application and applied load, errors in calculation, mistakes in construction, weakness of old codes, structural height increases and changes in environmental conditions. Different methods for increasing the flexural strength and ductility of reinforced concrete beams, as one of the major structural components, have been presented. This research presents an experimental study on the strengthening of reinforced concrete beams by reinforced concrete jackets (classical method) and Fiber Reinforced Polymer (FRP)... 

Asphaltenedeposition is a major problem during natural depletion and EOR processes due to formation damage issues. It is necessary to reveal asphaltene deposition mechanisms and its effective parameters to prepare an acceptable prevention strategy. Therefore, different natural depletion and EOR experiments must performed on core samples. In this research, Effect of CO2 injection on asphaltene deposition phenomena has been surveyed. Two carbonate core samples and one sandstone core sample was used in experiments. The oil used in these experiments was recombinedoilfrom one of Iranian offshore oilfield.In order to estimate permeability reduction during experiment, injection of oil and CO2 was... 

Among probable hazards in chemical industries: vapor cloud explosion (VCE) is one of the worst and most destructive ones. More than half of the major process inci¬dents, according to the statistics, are VCEs. VCE causes the most serious consequences; therefore, it attracts many attentions to itself. Accordingly, plenty of researches have been done for the purpose of protection against VCE effects. All efforts in this field can be categorized in two different main activities; firstly, prescribing safety distances between groups of hazardous equipment and vulnerable areas, secondly, using facilities which reinforce vulnerable areas against explosion blasts. Regardless to which category is... 

There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this paper an optimization procedure is proposed which integrates both processing and accident costs for different design schemes. In this procedure, some of the design variables are chosen with regard... 

Today, Quantitative Risk Assessment (QRA) has become an efficient tool in decision making for safety and process experts. To assess the risk of any accident scenario, it is necessary that the probability of that event be determined in addition to estimating the probable consequences. Event tree and fault tree analysis are known to be the standard tools for calculating the frequency of incident outcomes.
In this research, a new method based on Markov chin and Fuzzy theory is presented to estimate the occurrence probability of events. A one of important parameter which has sufficient effect on probability of incident frequency, is inspection and maintenance interval. in this research... 

Inherently safer design is the new approach to maximize the overall safety of a process plant. This approach suggests some risk reduction strategies to be implemented in the early stages of design. There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this... 

The seasonal fluctuations in economics variables relate to the different behavior of economic agents across different seasons. In past, seasonality has been viewed as a redundant feature that needs to be removed from data before economic analysis. From 1988, modeling seasonality has become the major concern of many economists; moreover, it was seen that many economic analysis and forecasts could be flawed if seasonality is ignored. In the present research, periodic times series approach is used for the first time in modeling the seasonality feature of the housing market. Regarding the importance of the housing sector in economy from micro and macroeconomic points of view, using a more... 

Time series of asset returns display specific regularities such as bell-shaped distribution, leptokurticity and volatility clustering. Economists have made continuous efforts to develop models that explain these patterns and can be used to predict the return and the risk of holding an asset. These efforts can be classified into 3 eras: Bachelier Era (1900-1960) in which the random walk model was developed for speculative prices. Mandelbrot Era (1960-1980) in which the normality assumption was replaced with the Pareto-Levy family of distributions which are flexible enough to justify leptokurticity and infinite variance. And finally, the Dynamic Volatility era in which the focus was on... 

Fire is the most likely type of process accident which occurs in industrial plants. Among all different types of fire, pool fire is the most frequent one, so there are extensive researches done about pool fire. One of the research areas that has drawn a lot of attention in recent years, is pool fire modeling. Results obtained from fire modeling are quite applicable in different fields of safety engineering such as Quantitative Risk Assessment (QRA) or fire proofing studies of process equipment. But fire modeling is an inherently complex process. Because there are several aspects involved such as multi-phase flow, turbulent mixing, combustion and different mechanisms of heat transfer. This... 

HCN is a highly valuable precursor to many chemical compounds ranging from polymers to pharmaceutical. Although cyanide can be destroyed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. The treatment methods for cyanide in common use today are physicochemical processes which have high operating costs and also produce chemical waste. Recently, biological processes have been studied because they are inexpensive and no effect to the environment. Therefore to achieve this object, Stimulation of indigenous microorganisms for waste degradation is a common technology. The process effluent from the gold extraction... 

The continual deterioration and insufficient strength of reinforced concrete (RC) structures has been a vital problem in the field of civil engineering such an extent that traditional methods of strengthening found to be inconvenient. Nowadays by increasing demands for retrofitting of structures, it necessitates the application of efficient, inexpensive and unobtrusive methods of strengthening. Common way on retrofitting was to use of steel plates externally bonded to RC members. Although this technique has proven to be reasonably effective, it has several distinct disadvantages such as susceptibility of the steel plates to corrode and the excessive weight of steel plates when used in... 

The release of toxic materials causes tragic accidents every year. There are various techniques in order to mitigate the release effect of these materials such as Application of air jets, steam curtains and water curtains. In this study first, previous works are reviewed in order to select the best technique for the mitigation of heavy toxic gas release. Then CFD modeling is used to simulate this technique.
A field situation in which chlorine gas was released upwind of water spray was simulated using the open-source software FDS (Fire Dynamic Simulator), a CFD model. Only mechanical effects of water sprays are considered; hence the effect of absorbtion is neglected. Finally tha... 

Domino accidents are one types of incidents that lead to irreparable damage to industrial units. Since the consequences of such incidents are far more than the first level incident, consideration of this issue and the provision of appropriate strategies for identifying and evaluating this type of incident is very important. Major efforts have been made in the area of process safety is in risk assessment and identify possible scenarios and their probability of occurrence, and have not addressed the financial consequences of an incident. In this research, an algorithm has been developed to estimate the financial losses incurred with an industrial unit due to a domino incident and various... 

Gas detection systems are now recognized as an essential component of safety in process units.but their successful performance depends strongly on the number and location of the detectors.As for the limited resources available (detectors), the placement of gas detectors can be considered as an optimization problem with different objective functions. In this research, an attempt was made to provide models and methods that quantitatively and from a practical point of view to optimum locate the detectors. Initially, a risk-based method was presented that defines the necessary steps for the arrangement of fire gas detectors with the aim of covering the maximum risk of leakage scenarios (risk:... 

FRP confinement studies on concrete square columns and its effect on design and retrofitting has been the topic of numerous studies in recent years and due to wide spread usage of FRP in structural retrofitting, these studies are still carried out by researchers. One of the most common and accurate methods for predicting the behavior of structures is modeling by Finite Elements Method (FEM). This study aims to assess the effects of corner radius on axially loaded reinforced FRP-confined concrete columns and their behavior for different corner radiuses using FEM software. Using the capability of FEM in ABAQUS software (V 6.8-1), the behavior of square reinforced concrete (RC) columns... 

The release of toxic materials causes tragic accidents every year. There are various techniques in order to mitigate the release effect of these materials such as Application of air jets, steam curtains and water curtains. This study presents numerical calculations to reproduce the continuous ammonia release dispersion with and without the mitigating influence of a downwind water curtain using computational fluid dynamic (CFD) software ANSYS Fluent 15.0. The RNG model coupled with Lagrangian discrete phase model (DPM) was used to simulate the dilution effectiveness of the water curtain system. The ammonia absorption was taken into account by means of user-defined functions (UDF). The... 

Sustainable and renewable energy sources are of fundamental importance in the development of strategic and sustainable economies. Therefore, in recent decades, water electrolysis has been widely used to produce pure hydrogen and oxygen without emitting carbon materials and is considered as a method for producing electrical energy alongside other renewable sources (such as wind and solar energy). Here, we report the synthesis of CoFe double-layered hydroxides (CoFe-LDHs) and their application as electrocatalysts for water splitting in alkaline environments. CoFe-LDHs were prepared via a new hydrothermal route from the metal-organic framework MIL-88A (MOF). The Co to Fe ratio in LDHs was...