Sharif Digital Repository

With regard to petrol, petrochemical and chemical industries extension in Iran and with regard to growth of agreements in these field and huge investment payments for different engineering activities and technology transfer, we need to evaluate each of these projects essentially and scientifically to reach the success. For this purpose we need to investigate the chain from science to market. On of the middle cycle of the chain are pilot plants, which have key rule for success of project. In this work after introducing pilot plant and explanation of their aims and characteristics, we allude the rule and situation of pilot plant for getting technology and transfer in chemical industries and... 

This paper outlines a quantitative risk assessment for an 110,000 ton/day ethylene oxide production plant in Iran. After a complete and detailed hazard identification study, done by HAZOP method, the purification column was found to be one of the most hazardous sections in this plant. As ethylene oxide with high concentration and inventory is present there. Fault tree analysis (FTA) technique has been used to identify the basic events responsible for top event occurrence and also calculation of top event frequency of occurrence. Human error has been calculated numerically and probability of human error has been estimated. Failure rate data were collected referring to several sources and... 

Background: New technologies using hazardous materials usually have certain risks. It is more serious when the technology is supposed to be applied in a large scale and become widely used by many people. The objective of this paper was to evaluate the risk of vapor cloud explosion in a hydrogen production process. Methods: Potential hazards were identified using the conventional hazard identification method (HAZID). The frequency of the proposed scenarios was estimated from statistical data and existing records. The PHAST professional software was applied for consequence modeling. Both individual and societal risks were evaluated. This cross-sectional study was conducted from June 2010 to... 

A simple equation of state (EoS) has recently been introduced (J. Phys. Chem. B2009, 113, 11977-11987) as (Z - 1)v2 = e + f/ρ + gρ2, where Z ≡ pv/RT is the compressibility factor, v = 1/ρ is molar volume, and e, f, and g are temperature dependent parameters. This EoS has been found to be accurate for all types of nano and bulk solids and bulk fluids, in the entire temperature and pressure ranges for which experimental data are reported, except for the isotherms within 1 ≤ T r = T/Tc ≤ 1.1 for the spherical and near spherical species and for a wider temperature range for the cylindrical molecules. The aim of this work is to investigate the validity of a three-term expression similar to the... 

An upscaling method such as renormalization converts a detailed geological model to a coarse one. Although flow equations can be solved faster on a coarse model, its results have more errors. Numerical dispersion, heterogeneity loss, and connectivity misrepresentation are the factors responsible for errors. Connectivity has a great effect on the fluid distribution and leakage pathways in EOR processes or CO2 storage. This paper deals with the description and quantification of connectivity misrepresentation in the upscaling process. For detection of high-flow regions, the flow equations are solved under simplified single-phase conditions. These regions are recognized as the cells whose fluxes... 

Lanthanum hydroxide (La(OH)3) nanostructures, including elliptical nanoparticles, octahedral rods and irregular nanoparticles were prepared chemically in NaOH and KOH solutions with 10 M concentration. The obtained powders were characterized with XRD, SEM, TEM and DTA. Crystallinities, morphologies and thermal behavior of the obtained nanostructure powders were investigated under the influence of above mentioned solvents. The effect of chemical's temperature was also determined in one of the solvents (i.e. NaOH). The formation of growth in nanostructure mechanism under the influence of alkali solutions (i.e., KOH and NaOH) have been discussed considerably in this paper  

Regarding the energy and environment crisis in the current century and future that threatens human communities, necessity of study and use of supplement fuels is felt more than before. Consumption of natural gas has been increasing rapidly making it one of the most important energy resources in the world. During the last decade the consumption of natural gas increased by almost 25%. By 2020 natural gas is predicted to increase its world energy share to as much as 50% from the present of 22%. The scale of its reserves and its environmental advantage favor its use, (the lower carbon emissions compared to oil and coal along with other reduced emissions of nitrogen oxides and particulates) for... 

One of the ways of giving a considerable handle on the account of developing this processes using simulating software. In this work the primary simulation in Aspen plus software done for comparison of various equations of state. Hence, for preparation of one reliable and exact model, the primary prepared model studied for different kinds of Equations of state, activity coefficient and calculation methods of Equilibrium constant in existing simulator software bed. Designing Dimethyl Ether pilot plant on the basis of reactor simulation is achieved by using the compatibility between simulation data and empirical data relevant to the industrial unit. The constants of the kinetic model were... 

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. Gas-liquid mixing and mass transfer between these phases is an important application in reactor design. One such an example is hydrogenation reaction of aqueous NDMA (Nitroso dimethyl amine) solution in which one of the parameters having a significant effect on the reaction rate is mass transfer. This parameter in turn is a function of impeller shape and rotational speed, gas flow rate and reactor scale. Computational Fluid Dynamics (CFD) is a useful tool in the analysis, design and scale up of stirred tank reactors via investigating hydrodynamics of gas and liquid flow,... 

One of the ways of giving a considerable handle on the account of developing this processes using simulating software. In this work the primary simulation in Aspen plus software done for comparison of various equations of state. Hence, for preparation of one reliable and exact model, the primary prepared model studied for different kinds of Equations of state, activity coefficient and calculation methods of Equilibrium constant in existing simulator software bed. Designing Methanol pilot plant on the basis of reactor simulation is achieved by using the compatibility between simulation data and empirical data relevant to the industrial unit. The constants of the kinetic model were adjusted... 

BACKGROUND: The clay treatment widely utilized to reduce unsaturated components in aromatic stream has a detrimental effect on catalyst lifetime. Due to the short lifetime of commercial clay, a huge number of studies have been carried out to address this problem over the last decade. This study aims to optimize the temperature for longer serviceability of clay by removal of unsaturated aliphatic components from aromatic streams through the adsorption and catalytic properties of clay. A novel process arrangement is introduced by scheduling the reuse of deactivated clay that is discarded after deactivation. RESULTS: Results showed that the suitable range of temperature for olefin removal is... 

In our today's societies, many dangerous chemicals are produced and transported. Due to the vast use of chemicals, more chemical accidents are taking place with huge losses. In this study a city hazardous gas monitoring network was designed to detect the dispersion of toxic and combustible gases in the primary stages. The network could cover hazardous chemical facilities, important hazardous chemical routes, warehouses and special locations which may be the targets of terrorist attacks. The network is consisted of several local networks and a central control panel complex. Each local network has a local control panel in the center and many detectors and sounders around it at distances less... 

This work presents a simulation framework to investigate the rigorous transient behavior of integrated systems comprising natural gas and power transmission networks, and a chemical plant whose feedstock is natural gas. This framework entails dynamic models for the gas transmission network and the SynGas plant, and a continuous-time AC-power flow formulation with dispatchable loads. It addresses the following key challenges: (i) analyzing energy and chemical system interdependencies, and their impacts on each other's supply reliability and security; (ii) providing an environment conducive to settling a critical question of how to prioritize the natural gas consumption as fuels of power... 

Synthesis temperature and purity of perovskite materials are key challenges facing the scientific community. This work aims to address these challenges by developing an innovative low temperature synthesis pathway for preparation of carbonate-free perovskite nanocrystals. The method is based on an ultrasound-Assisted wet chemical processing method. Nanocrystals are characterized and observed by X-ray diffraction (XRD), field-emission scanning electron microscopy and high-resolution transmission electron microscopy techniques. XRD studies show that very fine BaTiO3 nanocrystals (<11 nm) free from any by-products such as BaTi2O5 and BaCO3 are synthesized at 50°C. Moreover, the method developed... 

A Volume of Fluid (VOF) method is used to stdy the breakup of droplets in T-junction geometries. Symmetric T-junctions, which are used to produce equal size droplets and have many applications in pharmacy and chemical industries, are considered. Two important factors namely "breakup time" and "breakup length" that can improve the performance of these systems have been introduced. In addition a novel system which consists of an asymmetric T-junction is proposed to produce unequal size droplets. The effects of the channel width ratio and the capillary number on the size and length of the generated droplets and also the time of the generation have been studied and discussed. For simulation the... 

Tar formation and CO2 emission represent the strongest barrier for use of gasification technology for biomass conversion, whereas sufficing for both is only possible with expensive physical methods and further chemical processing. The use of CaO as a CO2 sorbent within an advanced high-temperature gasification system is able to achieve efficient cracking of the tars to the primary syngas with low emissions. The present work aims to propose a semi-kinetic model on the basis of an Aspen Plus model to describe specific catalytic behavior of calcium oxide on the gasification of rice husk. There has also been an attempt to validate the developed model by means of an experimental study and explore... 

This paper investigates the dynamic buckling behavior of steel silos subjected to horizontal base excitations. The elastic-plastic buckling resistance of three silos with different aspect ratios is estimated using Incremental Dynamic Analyses (IDA). Accordingly, the critical base shear, base moment and the peak ground acceleration (PGA) at the buckling instant are calculated. Moreover, the additional normal pressures induced from bulk solids on silo walls are evaluated and compared with those of Eurocode 8. The results obtained suggest that slender silos are more vulnerable to buckling failure, while squatter silos represent a considerably higher resistance under same seismic conditions. ©... 

Chemical industries need to employ new process designs due to environmental policies and energy optimization because of the global energy challenge. Pervaporation has been introduced as a promising alternative for conventional processes such as distillation, known as energy intensive process, in chemical plants. In this work, the energy consumption of different processes for separation of toluene and i-octane (representatives of aromatics and aliphatic mixtures) has been evaluated, based on our previous laboratory pervaporation experiments using Polyvinyl alcohol/Graphene oxide mixed matrix membranes. Accordingly, hybrid distillation-pervaporation and cascade pervaporation systems have been... 

Separation of particles or cells has various applications in biotechnology, pharmaceutical and chemical industry. Inertial cell separation, in particular, has been gaining a great attention in the recent years since it has exhibited a label-free, high-throughput and efficient performance. In this work, first, an inertial contraction–expansion array microchannel device, capable of passively separating two particles with diameters of 4 and 10 μm, was numerically studied. Then, the validated model was combined with curved geometries in order to investigate the effect of curve features on the separation process. The overall purpose was to investigate the interaction between the two different... 

Steel silos are one of the main structures for bulk solids handling and storage in many industries and agricultural sectors. A growing body of research suggests the importance of including the vertical component of earthquake ground motion in seismic analysis and design of certain structures. In the case of steel silos, this may induce additional meridional compression to exacerbate buckling failures in such thin shells. Accordingly, this paper investigates the buckling behavior of three cylindrical steel silos (i.e., a squat, an intermediate slender and a slender silo) with stepped walls subjected to horizontal only (H) and horizontal and vertical (HV) ground accelerations to address this...