فهرست مطالب

Chemical Engineering - Volume:11 Issue: 3, Summer 2014

Iranian journal of chemical engineering
Volume:11 Issue: 3, Summer 2014

  • تاریخ انتشار: 1394/03/30
  • تعداد عناوین: 8
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  • M. Keshavarz Moraveji*, S.E. Mousavi Pages 3-15
    In this research, the effect of carboxy methyl cellulose (CMC) addition into pure water as pseudo-plastic non-Newtonian fluid and its concentration on bubble diameter and gas hold-up were investigated. For this purpose, four different concentrations of CMC (0.05, 0.1, 0.15 and 0.2 w/v%) as the non-Newtonian fluid and five different superficial gas velocities (0.2, 0.4, 0.6, 0.8 and 1 cm/s) as the gas phase were examined in an airlift reactor. Bubble size distribution in the airlift reactor was measured by photography and picture analysis at various concentrations of CMC and various velocities of gas. Increasing in gas velocity created a wider bubble size distribution and thereby an increase in bubble diameter and gas hold-up in both riser and down-comer. However, the bubbles diameter in pure water was larger than those of the CMC solutions (in the riser and down-comer), but CMC concentration enhancement increased bubbles diameter and gas hold-up in the down-comer. Bubbles diameter expansion in the riser by CMC concentration enhancement took place from concentrations of 0.05 to 0.15 (w/v)% and then it suddenly decreased. Furthermore, gas hold-up decreased from concentrations of 0.05 to 0.15 (w/v)% and increased at concentration of 0.2 (w/v)%. The gas hold-up increases (more than that in the concentrations of 0.1 and 0.15%) when bubbles diameter decreases in concentration of 0.2%. The overall gas hold-up trend was similar to the gas hold-up in the riser.
    Keywords: Airlift Reactor, Bubble Diameter, Gas Hold, up, Non, Newtonian, Pseudo Plastic
  • F. Kalantar Kohdami, J. Towfighi Daryan*, H. Nemati Arbatani Pages 16-25
    The effect of different crystallization temperatures on the crystallinity, morphology, surface area and catalytic performance of SAPO-34 has been investigated. SAPO-34 catalysts were successfully synthesized using the conventional hydrothermal method. The prepared samples were characterized by XRD, SEM, BET and FTIR techniques. The catalytic performance of the synthesized catalysts was tested in MTO reaction at 410˚C and WHSV of 6.5 h-1. Temperature of crystallization was found to be the significant parameter for controlling crystallinity and purity, particle size, morphology, surface area and content of hydroxyl groups of the product. The sample prepared at 463 K and 24h possessed the best crystallinity with the smallest crystal size. In the methanol conversion to olefins over SAPO-34 catalysts, this sample showed highest yield of light olefins (88 wt%).
    Keywords: MTO Reaction, SAPO, 34, Crystallization Temperature, Light Olefins
  • S.H. Hashemabadi *, F. Mirhashemi Pages 26-36
    In this paper, drag coefficient of infinite quadralobe catalytic particle with non-circular cross sections has been investigated by Computational Fluid Dynamics (CFD) methods and for this purpose FEMLAB Multiphysics V2.3 based on finite element methods have been used. A new simple correlation for drag coefficient of infinite quadralobe particle has been established over the range of Reynolds numbers from 0.01 up to 1000.A comparative study has been made between the numerical results of this study and the available data in the literature. The predicted drag coefficient of infinite cylinder shows good agreement with experimental data within a converging quantitative error of less than 7% up to Reynolds number of 1000. The drag coefficient results for cross flow on infinite quadralobe particle shows higher value in comparison with cylindrical particle. In addition, influence of different number of particles (single, two, three and four particles) and orientation angle of particles on drag coefficient have been investigated.
    Keywords: Drag Coefficient, Quadralobe Particle, Computational Fluid Dynamics (CFD), Packed Bed
  • T. Yousefi Amiri, J.S. Moghaddas* Pages 37-44
    Effect of copper content, calcination temperature and activation method on the activity and selectivity of copper-silica aerogel catalysts for hydrogen production from methanol steam reforming was investigated. Results showed the copper content had the highest impact and the activation condition had the lowest impact on the catalyst performance. It was found that Cu-SiO2 aerogel was a promising catalyst for methanol steam reforming. The only parameter which influences the CO selectivity was copper content. Using the best prepared catalyst, no CO formation was detected in the common condition of reaction. In the used range of feed flow rates, methanol conversion was increased 1.5-2.26 times by increasing the copper content from 7.7 to 13.3 wt%. Characteristics/performance relationship showed that the samples in which copper species exist as CuO clusters had the best performance to increase the hydrogen production rate and decrease the CO formation. Formation of CuO clusters was increased by increasing the copper loading and calcination temperature. It was found that due to the reducibility behaviour of copper-silica aerogels the activation method of catalysts had almost no effect on the catalytic performance.
    Keywords: Copper, Silica Aerogel Catalyst, Hydrogen Production, Activity, CO Selectivity, Methanol Steam Reforming
  • S. Rezaee, M.R. Moghbeli Pages 45-85
    Poly (vinyl alcohol) (PVA) nanofibers were prepared via electrospinning of concentrated PVA solutions. The nanofibers were crosslinked to enhance their resistance against the moisture. The chemical crosslinking of the nanofibers was carried out using glutaraldehyde as crosslinking agent in the presence of hydrochloride acid. The chemical structure, water solubility, and morphology of the electrospun PVA nanofibers were characterized by Fourier transform infrared (FTIR) spectrometer,water durability test, and scanning electron microscope (SEM), respectively. In addition, the crosslinked nanofibers were coated by copper nanoparticles (CNPs) using electrospraying technique. For this purpose, colloidal CNPs were synthesized through the chemical reduction of copper ions in the presence of different stabilizers, i.e. poly (vinyl alcohol) and ethylene glycol (EG), in an aqueous media. The effect of the stabilizer concentration (0.001 and 0.005 M) and reduction temperature (25 and 70°C) were investigated on the CNP dispersion in the media using UV-visible spectroscopy. Furthermore, the dispersion of the CNPs on the PVA nanofibers was studied by means of SEM. The SEM micrographs showed that the nanofiber scould properly imprison the CNPs. Successful the proposed approach would be exploited to prepare polymer nanofibers incorporating metal nanoparticles which might have interesting properties such as antibacterial activity.
    Keywords: Copper Nanoparticle, Electrospinning, Coating, Crosslinking, PVA Nanofibers
  • D. Kahforoushan *, J. Bezaatpour, E. Fatehifar Pages 59-66
    The purpose of this study is development of some parametric emission factors for gas flares using pilot-scale flare and investigation of the effect and interaction of important parameters on the emission factors. The considered parameters were flame Reynolds number, superheat steam-air flow rate and wind speed. Every variable was considered in four levels and the experiments were carried out two times. The results of 128 experiments showed that the average emission factors of CO2, CO and NOx pollutants are 127.183, 0.731 and 0.074 lb/MMBtu (pound per Million British thermal unit), respectively. In addition, variance analysis of variables showed that the CO2 and CO emission factors are significantly influenced by wind flow and NOx emission factor is influenced by superheat steam-air flow rate.
    Keywords: Gas Flares, Emission Factors, CO2, CO, NOx
  • A. Ghozatloo, M. Shariaty, Niassar, M. Hassanisadi Pages 67-73
    Using Co-Mo/MgO catalyst, single walled carbon nanotubes with a diameter of 2 nm and a length of 10 µm were produced by chemical vapor deposition process and characterized by XRD, FTIR and SEM. Synthesized single-walled carbon nanotubes were dissolved in water to make a 1 w% solution and stabilized by adding sodium dodecyl sulfate surfactant. The synthesized stabilized nanofluid was used in the gaseous hydrate formation at a temperature of 4˚C and pressure of 1000 psig. The results were compared with a water/surfactant control solution and it was found that carbon nanotubes have reduced the duration of dissolution process by 58.9% and duration of the induction process by 75.5%. In addition, the amount of gas entrapment and stability of the gas in the hydrate were increased by 13.6% and 18.2%, respectively.
    Keywords: Hydrate, Natural Gas, Single, Walled Carbon Nanotubes, Storage, Induction, Nanofluid