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... 

Oil composition plays an undeniable role on the low salinity water flooding (LSWF) efficiency. This property directly affects the kinetics of wettability alteration through electrostatic interactions and interfacial tension (IFT). For instance, mixing in stagnant zones through a thin water film is considered as one of the most important diffusion controlled phenomenon which is goverened by Non-Fickian solute transport model. The major two potentials controlling the solute transport in thin film are salinity gradient and electrostatic potentials, which can be affected by oil composition and surface charges. This study aims to investigate the effect of oil composition on low salinity... 

Most of the heavy oil reservoirs contain discontinuous shaly structures which affect fluid flow through porous media as well as oil recovery efficiency during EOR processes. However, selecting the best EOR technique which maximizes the oil recovery remains a topic of debate in the literature. In addition the effect of shale geometrical characteristics including: spacing from wells, discontinuity, orientation, number of shale streaks, shale's spacing and length on oil recovery factor are not well understood. In this work experiments have been performed on one-quarter five-spot glass micromodels. These models have been developed by a new method using laser technology. Generally, this research... 

A brass vortex tube (VT) with changeable parts is used to investigate the effect of nozzle intakes number and diameter, distance between cold end orifice and nozzle intakes, cold end orifice diameter, main tube length and diameter on inlet, cold and hot exit temperature difference, isentropic efficiency and Coefficient of Performance. A series of experiments conducted to investigate the inlet pressure and cold fraction effect on VT performance and an optimum amount for this parameter is found. The separation performances of a VT for a hydrocarbon mixture is also investigated. Effects of nozzle intakes number and cold fraction on the gas species separation at specific inlet pressure in a VT... 

Considering the water tensions, especially in the Middle East, water resources for the implementation of water-based EOR methods are shown to be critically limited. Water sources such as industrial wastewater hold great potential to be used for this purpose due to their significant available volume and the need for their disposal because of environmental regulations. In this research, the potential of injecting industrial wastewater, as low-salinity water, in an Iranian carbonated oil reservoir has been thoroughly investigated by conducting core-scale experiments. In this regard, we also developed a guideline for designing various types of experiments to use this "unconventional" injection... 

The main application of flares is to protect facilities, staff, and surrounding area. Nevertheless, the flares flue gas contains environmental hazardous compounds like nitrogen oxides, sulfur oxides, and greenhouse gases like carbon dioxide and carbon monoxide. These compounds may spread in environment with unburned hydrocarbons. Due to the contamination risk and energy loss in flaring system, optimization and system enhancement is of vital importance. Flare gas recovery unit consist of equipment like multi-phase separator, Liquid Seal Drum, and compressor. The compressor is the most important part of this unit. Due to the process requirements and the probability of two-phase feed entering... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

Steel in Iran is mainly produced by EAFs. One of the most fundamental issues in the field of electric arc furnace is to foresight methods to reduce energy consumption and emissions. A model is presented in the present research work that avails itself to analysis of mass and energy recovery simultaneously. The proposed model includes three major elements: scrap pre-heating, sponge iron pre-heating and inert gases pre-heating. An important feature of this approach is to preheat sponge iron. Mathematical model for preheating scrap has been developed on the basis of CONSTEEL technology. Also the model for sponge iron and inert gases preheating has been formulated based on the literature review.... 

Under Linear Elastic Fracture Mechanics (LEFM) assumptions, the stress at the crack tip is theoretically infinite. Clearly all materials have a finite strength, thus there will always be a plastified zone around the crack tip. If the size of plastic zone is not small compared to the crack size, then linear elastic assumptions are not applicable and a nonlinear model must be used. This damaged zone is referred to as a plastic zone for metals, and a fracture process zone for cementitious materials and ceramics. In this regard a discrete extrinsic cohesive crack model with bilinear traction separation constitutive law, i.e. softening function, is employed and crack propagation is investigated.... 

Global energy consumption is on a trajectory to surge by 50% by 2050, primarily driven by prevailing energy consumption patterns. Consequently, the imperative to innovate and develop novel energy sources, such as the utilization of recycled waste heat, has become paramount for the foreseeable future. In light of this, this paper delves into the transformative potential of employing Phase Change Materials (PCMs) for cooling Thermoelectric Generators (TEGs) and harnessing waste heat for productive purposes. The research investigates three distinct configurations to evaluate the efficacy of PCMs in enhancing thermal management. Configuration 1 exclusively relies on an active cooling fan, while... 

In analyzing the structural organization of many real-world networks, identifying important nodes has been a fundamental problem. The network centrality concept deals with the assessment of the relative importance of network nodes based on specific criteria. Central nodes can play significant roles on the spread of influence and idea in social networks, the user activity in mobile phone networks, the contagion process in biological networks, and the bottlenecks in communication networks. High computational cost and the requirement of full knowledge about the network topology are the most significant obstacles for applying the general concept of network centrality to large real-world social... 

The constant and proper functioning of data center infrastructures is considered a vital element in the modern processing of data and information. Failure in the electricity supply system is the key reason for workload processing stalls in data centers. Energy supply systems, therefore, need to be highly reliable in terms of adequacy and security. Nonetheless, data centers tend to become volatile and, to some degree, unresponsive in the face of a multitude of such errors occurring simultaneously which in turn could lead to higher rates of processing interruptions. Recent years have witnessed an increase in the number of natural occurrences with high impact and low probability (a.k.a., HILP... 

Among the methods for increasing chemical oil extraction,the polymeric flood method has the most commercialization capability.However,most commonly used polymers such as Hydrolyzed Polyacrylamide (HPAM) are not able to withstand high levels of salinity and high temperatures.To overcome these problems,in this project,new types of polymer nanostructures were synthesized with hydrophobic groups consisting of styrene (hydrophilic monomer) and malic anhydride (hydrophilic monomer) acrylamide (hydrophilic monomer). These polymers were synthesized by reversible mini-emulsion by adjusting the synthesis conditions for the purpose of producing the terpolymer with suitable conditions for tolerating... 

The fundamental objective of this study is to present seismic hazard, risk and resilience assessment of a virtual city using sampling and agent-based simulation in two levels of refinement. In this context, hazard is the exceedance probability of ground shaking intensity, risk is exceedance probability of measures such as loss, and resilience is the ability to quickly recover after a hazard event. This study utilizes the Rtx risk and resilience assessment framework established at the Center for Infrastructure Sustainability and Resilience Research (INSURER) at Sharif University of Technology. This framework employs multiple interacting probabilistic models to quantify the risk and... 

Relative permeability is an important factor that controls the two phase fluid flow in porous media. The use of carbon dioxide in enhanced oil recovery methods is common. But the question is, how does the carbon dioxide affect the relative permeability curves? In this thesis, the CO2-oil relative permeability is measured in CO2 flooding process with unsteady state method. For this purpose, the core flooding apparatus is used and the results are compared with N2-oil relative permeability in N2 flooding. The results of comparison show that oil relative permeability in CO2 flooding is higher than N2 flooding. Reduction of Interfacial tension and oil viscosity, solubility of CO2 in oil and oil... 

The purpose of this study was to investigate experimentally and modeling the process of gasification with supercritical water using waste motor oil. The effect of four important and influential parameters on the process, Temperature (350-450° C), Reaction time (15-45 minutes), Oil-to-Water volume ratio (0.2-0.4) and type of catalyst Consumption (Ni- NaOH- Na2CO3) was evaluated. Experimental experiments were designed and performed on the Design Expert software. The experimental results showed that the purity of hydrogen in the gas stream is more dependent on the temperature parameter and the higher purity is obtained with increasing temperature. Subsequently, as the oil concentration... 

Line search-based methods are known as a category of the most efficient iterative algo- rithms for solving unconstrained optimization problems. Among them, the conjugate gradient method is of particular importance in solving large-scale contemporary world problems due to its simplicity of structure, low memory requirement and strong convergence characteristics. In spite of the desirable numerical behavior of the conjugate gradient method, this method generally lacks the descent property even for uniformly convex objective functions. To overcome this defect, some effective modifications have been presented in the literature. Amidst, the three-term extension attracted the attention of many... 

Nowadays, cement has become the cornerstone of any modern society especially in developing countries. But, cement production process is highly energy intensive and emits significant volumes of carbon dioxide.According to the latest reports, Iranian cement industry accounts for about 14.5% of total industrial sector’s energy consumption and this indicates the importance of sustainable development for cement industry concerning national energy and environmental constraints.Based on these facts, current study assesses the technology improvement opportunities particularly waste heat recovery power generation (WHRPG) technology for Iranian cement industry. This needs identifying optimized mass... 

After primary and secondary recovery processes more than 50 percent of oil remains in reservoirs. Therefore for more recovery from these reservoirs, methods of enhanced oil recovery should be applied.In this paper the effect of nanoparticles of SiO2 in size of 14 nm, on wettability is investigated. Using this nanoparticle, the wettability of carbonate rock in reservoirs could be changed and alter from oil-wet or mix-wet to water-wet. To assess this, hydrophilic changes of sandstone core and carbonate core are studied using the contact angle test. The same test is done on the carbonate core saturated with brine and oil that had received injection with brine and nanoparticles of SiO2 with two... 

The discrete fracture network and continuous fracture network are among the most widely used methods to model naturally fractured reservoirs. Each method faces particular limitations. The recently introduced recovery curve method (RCM) is believed to meet the limitations of the common methods. In the RCM the recovery curves are used to more realistically describe matrix-fracture interactions. It is necessary to present appropriate solutions to apply the RCM in the real fileds and also to evaluate it based on the historical production data. In this work at first, the basics of the RCM are presented then with a simple column model this method is validated. Then in a column model and a field...