Sharif Digital Repository

Electrocoagulation (EC) is an effective process in the treatment of oily wastewater, however, only a few studies have explored the parameters affecting the efficient design of the reactors employed in this process. In this study, a statistical investigation on the factors affecting the design of a continuous electrocoagulation reactor was performed by running the tests designed based on the design of experiments (DOE) principles. The explored design variables were current density (30-80 A/m2), reactor residence time (10-30 min), and the ratio of anode surface to the reactor volume (15-45 m2/m3), which were optimized by the response surface method (RSM) to maximize the amount of oil removal... 

In this study, pyrolysis features and corresponding kinetic behavior of non-metallic fractions of the paper-laminated phenol resin printed circuit boards (P-PCB) and fiberglass-reinforced epoxy resin printed circuit boards (E-PCB) were investigated by the use of simultaneous thermogravimetric analysis (TGA/DTG). The kinetic parameters of the P-PCB abs E-PCB during pyrolysis process were estimated from the experimental data by means of three iso-conversional kinetic models, including Friedman, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods. The activation energy range obtained for P-PCB and E-PCB utilizing the Friedman method was within 117–594.1 and 88.42-295.3 kJ.mol-1,... 

Gas-solid fluidized beds are widely used in various industrial processes due to their multiple advantages and applications, such as enhanced heat transfer, improved mixing and separation of solid particles, drying, combustion, particle coating, etc. In many processes, the mixtures of solid particles in the fluidized bed reactors have a distribution of particle sizes or are different in terms of density or shape of particles. Despite the ability of fluidized beds to improve the mixing of particles, the existence of the aforementioned differences can cause separation of particles under certain conditions. Pulsed fluidized beds are beds where the gas flow enters the bed in a pulsating manner.... 

Many fluidized bed reactors contain particles such as catalysts, biomass, etc. that vary in size, density, and shape. Despite the significance of these systems, the multi-component fluidized beds have been less studied compared to single-component systems. An important challenge in multi-component fluidized beds is the occurrence of particle segregation and reduced mixing, which severely diminish the reactor's efficiency. The objective of this study is seeking the relationship between the pressure signals measured in a binary gas-solid fluidized bed and the degree of particle mixing/segregation of dissimilar components at relatively low superficial gas velocities. To this end, pressure... 

The gradual depletion of the resources of fossil fuels, as well as the instability of their price in addition to the necessity of mitigation of hazardous air pollutants, are the chief reasons to increase the use of renewable sources. Biodiesel, as one of the best alternatives, can mitigate the emission of air pollutants resulting from fuel combustion. However, using raw biodiesel is not economically viable due to its lower quality in comparison with diesel. In this study, the role of nanoparticles in the improvement of biodiesel characteristics has been investigated. Firstly, biodiesel was produced from waste cooking oil (WCO) using the transesterification reaction, and then ceria and... 

Due to the unique advantages of fluidized beds for solid mixing and heat transfer, they are widely used for the thermal processing of solid fuel particles. In practice, such systems are composed of non-conventional fuel particles such as coal or biomass, which are completely different in shape, size, and density from the bed material such as sand. In such systems, correct understanding of the main fluidization parameters such as the minimum fluidization velocity (Umf) of the bed components plays a key role in the successful design and control of the system. However, the onset of fluidization of irregular particles is not clear as it may vary depending on the physical properties of the... 

The COVID-19 pandemic has increased environmental risks due to widespread face mask use in production, consumption, and disposal. This study uses surgical single-use as a pyrolysis feedstock due to increased demand. This study investigates the conversion of valuable materials from waste through the recycling of surgical single-use masks in a fluidized bed. The first stage of this study focused on identifying and specifying the main components in the filter layers of disposable surgical masks, which were the compounds in the filter layers made of polypropylene. TGA curves investigated thermal behavior of disposable surgical mask layers, revealing pyrolysis feedstock can produce volatile... 

One of the main challenges in managing flow batteries usage is estimating their state of charge. Since The concentration of ions in the battery indicates the battery's charge and, on the other hand, the sensors for measuring the concentration are expensive, observers should be used to estimate the concentrations of the ions in the battery. This work is done by measuring the cell voltage, and finally, using the mathematical model of the battery, the amount of concentrations and state of charge is calculated. In this work, a vanadium flow battery was initially modeled accurately and mechanistically using COMSOL software to replace an actual flow battery in subsequent studies. Also, two... 

To study the kinetics of the yttria-stabilized zirconia produced by co-precipitation method from the chemical engineering point of view, this process was studied in two parts of hydrolysis and precipitation. the hydrolysis reaction was studied by titration method, and the rate constant and fraction of formation of hydrous zirconia was determined by applying Avrami equation. The results showed that the percentage of zirconia formation until the boiling time of 12 hours was zero and after 48 hours boiling was 2.81%. moment definitions were used In order to study the kinetics of precipitation. changes in precipitated powder concentration with pH of the solution was obtained based on the... 

Membranes are one of the best water and wastewater treatment methods that could successfully replace other less-effective conventional techniques such as adsorption, coagulation, etc. Moreover, relative to other techniques, the quality of the water produced by membrane separation is very high compared to others. One of the main drawbacks of membrane treatment is fouling of the surface and internal pores of the membranes restricting its widespread application in the industry.In this study, TiO2@MIL-88A (Fe) photocatalyst and polyacrylonitrile membrane were modified with this photocatalyst to remove humic acid under visible light irradiation inside the PMR photocatalytic reactor was... 

In this thesis, the separation process for used and relatively new catalysts of residue fluid catalytic cracking unit by applying an electric field was evaluated. The main purpose of this dissertation is to simulate and design a separation system for separating used and relatively new catalysts of the FCC process in the electrostatic fields. In this regard, various separators were studied, and most of them were simulated under different circumstances. Finally, after examining and analyzing the particle behavior in each of the scenarios, the proposed system was introduced as more effective and efficient than the other separators in order to achieve the ideal separation of the used and... 

During the last few years, the number of electric devices using lithium-ion batteries as a source of energy has increased drastically. The lifespan of these batteries is very short (2-3 years) and according to the statistics only 25% of which is recycled. However, considering the variety of materials used in these batteries, recycling them can be highly gainful. One of the technical challenges in the way of recycling Li-ion batteries is the presence of polyvinylidene fluoride (PVDF), that besides raising issues during recycling processes causes the production of toxic fluorine or hydrogen fluoride effluents. The second issue is the presence of metals with high oxidation states in these... 

Waste printed circuit boards (WPCBs) account for approximately 4–7 wt. % of all types of electronic waste. Due to the content of organic materials (resins and halogenated flame retardants), recycling and disposal of WPCBs are associated with the production of hazardous materials. With the aim of maximizing the pyrolysis oil recovery, this study focuses on optimizing the temperature (T), retention time (t), and WPCB-to-additive ratio (FR2/A) as the parameters controlling the co-pyrolysis of paper-laminated phenolic PCB (FR2-PCB) with a 50:50 mixture of CaO and Ca(OH)2 in a lab-scale fluidized bed reactor. According to the results of the experiments designed based on the response surface... 

Partial oxidation of methane (POX) is one of the most common processes to produce synthesis gas. In this study the kinetics of this process is examined and some reduced mechanisms are introduced to model it in this study. The experimental data from Research Institute of Petroleum Industry are used as reference experimental data. Inlets of this reactor are oxygen and methane with equivalence ratio between 2.53 and 2.9. Moreover, the experimental results of previous studies with the air as the oxidant in equivalence ration between 2.4 and 2.6 are used as basis for comparison of simulation results. During the first step, partial oxidation of methane in non-catalytic porous media is simulated by... 

The increase in the concentration of carbon dioxide in the atmosphere is one of the most important factors of global warming and climate change, which has wide environmental consequences. Reducing the emission of this greenhouse gas is one of the global priorities in protecting the environment and improving air quality. In this research, the process of carbon dioxide absorption from flue gases has been investigated and optimized using the temperature-vacuum swing adsorption method (TVSA). Zeolite 13X adsorbent was used as the main adsorbent in this process and its performance was investigated in different operational conditions. The main goal of this research was to evaluate the efficiency... 

Sulfur dioxide is known as an acidic gas and one of the standard pollutants in determining air quality. This gas mostly enters into the atmosphere by flue gas causing many environmental problems. In order to remove this gas, various methods are used. One of the suitable methods to reduce the emission of this pollutant in low concentrations is the use of Metal-Organic Frameworks (MOF) as an adsorbent. One of these Metal-Organic Frameworks is NH2-MIL-53(Al) that owing to its relatively good stability under wet and acidic conditions, has been chosen to adsorb sulfur dioxide in this research. In most studies on SO2 adsorption, often MOFs with a long synthesis time, high synthesis cost, and/or... 

In this study, the co-pyrolysis process of textile waste based on cellulose and polyethylene terephthalate (PET) was investigated using thermogravimetric analysis (TGA/DTG). Additionally, the pyrolysis kinetics of the thermal degradation process for each material and their combinations were studied. Kinetic parameters, including activation energy (E) and pre-exponential factor (A), were calculated for the pyrolysis of the samples using iso-conversional kinetic models such as Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO) based on the TGA and DTG curve data and compared with the corresponding reported values. Furthermore, the pyrolysis kinetics were modeled using... 

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... 

In this thesis the perovskite catalyst of La0.7Sr0.3FeO3 with different percentages of kaolin and alumina boehmite as binders was synthesized to be used in the chemical looping partial oxidation process. To determine the best catalyst in terms of resistance against attrition, an attrition test was performed in a jet cup testing rig. The best catalyst in terms of resistance against attrition was perovskite catalyst 60% weight,25% weight kaolin and 15% weight alumina beohmite. Cold test of fluidized bed of the optimum catalyst in terms of resistance against attrition performed and minimum fluidization velocity, terminal velocity, flow regime type and Geldart type was obtained. The synthesized... 

The hydrogenation of carbon dioxide to methanol represents a promising route for the efficient use of an anthropogenic greenhouse gas, in which catalysts play a key role in carbon dioxide conversion and methanol selectivity. In this study, firstly, CuO-ZnO-Al2O3, CuO-ZnO-ZrO2, CuO-ZnO-ZrO2-Al2O3, CuO-ZnO-Al2O3-CeO2 and CuO-ZnO-ZrO2-CeO2 catalysts were made using co-precipitation method, then these catalysts were characterized by inductively coupled plasma optical emission spectrometry, specific surface area and pore size distribution, X-ray diffraction, Field Emission Scanning Electron Microscopy, temperature programmed reduction. Finally, in order to compare the performance of the catalysts...