Sharif Digital Repository

The aim of this work was to investigate the performance of different kinds of Linde type A zeolite (LTA) for the dehydration of Tetrahydrofuran (THF)-water solution. Batch experiments were carried out to evaluate the effect of various operating parameters such as contact time, initial concentration, mixing temperature (10, 15,and 25 C), amount of adsorbent, and zeolite type(3A, 4A, and 5A zeolites). In theoretical studies, we took the advantage of several types of equilibrium model isotherms such as Langmuir, Freundlich, Dubin-Kaganer-Radushkevich (DKR) to describe the experimental adsorption data. Besides, three adsorption kinetic models including pseudo-first-order, pseudo-second-order,... 

Biodiesel can be a good alternative for fossil diesel since it isrenewable, biodegradable and non-toxic. Also, in comparison with fossil fuels, it emits less air pollutants and greenhouse gases.Findacost effective and environmentally friendly wayforcontinuousproductionofbiodieselcanaddressmany of our environmental concerns. In this study, we applied heterogeneous alkali-catalyzed transesterification as method and used waste frying oil as a low cost feedstock for biodiesel production. The project was performed in two phases. First, experiments were conducted in astirred reactor to finda suitable catalyst which was strontium carbonate calcinated for 3:24 hours in 975̊C.
RPB(rotating... 

The appearance of water in pipe lines of the natural gas transportation would cause several problems. In this regard, disparate methods have been developed to produce and refine of the natural gas, and one of the most common method is adsorption process. In this study, modeling and simulation of the adsorption process in the packed bed of zeolite 4A has been done. This research includes four steps, first, adsorption process and all types of adsorbent were investigated. Second, using rigorous solution method, equations of mass and energy balance derived. Third, using the collocation method and MATLAB programing, system equations of mass and energy was solved. Finally, accuracy of simulation... 

It has been shown that absorption of carbon dioxide can be enhanced using nanoparticles and in the presence of magnetic field. In the present work, the influences of ferrofluids and magnetic fields on the absorption of CO2 in packed-bed contactors have been investigated carefully. In this regard, multi-tube approach has been applied to model the contactor. The simulation results were validated against experimental data reported in the literature in the absence of nanoparticles and magnetic fields and good agreement was obtained. The influences of variable operating conditions on the contactor performance were carefully investigated. It was found that for 3.4% volume percent of magnetic... 

Simulation and controlling nonlinear process is one of the challenging problems in academic and industrial research. Saving data for keeping history of process or arising number of calculation for optimization in control design, is forcing to decrease number of equation or order of system. One of the methods to decrease the order of distillation process is using the travelling wave theory. This solution shows god accuracy for simulation the behavior of distillation column. On the other hand finite difference method as a solver for distillation equation takes some time to converge to steady state condition and the numbers of calculation in this method are high. Finite difference method is... 

The main objective of this research was to evaluate the application of a new strain of Brevundimonas naejangsanensis which is newly identified sulfate-reducing bacteria (SRB), in bioremediation. A laboratory scale packed bed reactor (PBR) was fabricated and operated to study the new bacteria’s feasibility on SO_4^(2-) reduction. The reactor was packed with polyurethane foam cubes and operated under different feeding and operating conditions of HRT, COD/SO_4^(2-) ratio and salinity. A maximum SO_4^(2-) reduction of 73.6% was achieved in the PBR when operated at an HRT of 12 h with SO_4^(2-) concentration of 670 mg/L, COD/SO_4^(2-) ratio of 1 and salinity of 3%. The results show that this... 

The main objective of this research was to evaluate the application of a new strain of Brevundimonas naejangsanensis which is newly identified sulfate-reducing bacteria (SRB), in chromium(VI) removal in contaminated wastewater. A laboratory scale packed bed reactor (PBR) was fabricated and operated to study the bacteria’s feasibility on chromium(VI) reduction and removal. The reactor was packed with polyurethane foam cubes and operated under different feeding and operating conditions of HRT, COD/〖SO〗_4^(2-) ratio and influent chromium(VI) concentration. A maximum chromium removal of 94.6% was achieved in the PBR when operated at an HRT of 24 h with COD/〖SO〗_4^(2-) ratio of .70 and influent... 

Today, the pollution of heavy metals in wastewater and surface waters, which is a global environmental problem, has increased with the expansion of various industrial activities. Heavy metals cause serious health problems due to their accumulation in human and animal tissues. Thorium, is a radioactive element with an atomic number of 90 that is widely used in the optics, aerospace, metallurgy and chemical industries, in the manufacture of high-strength alloys, in UV photocells, and especially in the nuclear industry. The primary sources of radioactive wastewater include nuclear power plants, nuclear energy industry research centers, medical institutions, industrial production, universities,...