Combination of Adsorption-Diffusion Model with Computational Fluid Dynamics for Simulation of a Tubular Membrane Made from SAPO-34 Thin Layer Supported by Stainless Steel for Separation of CO2 from CH4

Modeling of CO2/CH4 separation using SAPO-34 tubular membrane was performed by computational fluid dynamics. The Maxwell-Stefan equations and Langmuir isotherms were used to describe the permeate flux through the membrane and the adsorption-diffusion, respectively. Three-dimensional Navier-Stokes momentum balances in feed and permeate side coupled with adsorption-diffusion equations from the membrane were simultaneously solved by ANSYS FLUENT software. The velocity and concentration profiles were determined in both feed and permeate sides. There was a good agreement between simulation and experimental results and root mean square deviation for CH4 and CO2 are 0.13 and 0.1 (mmol m-2 s-1), respectively. The concentration polarization effect was observed in the results. The effect of the process variables were investigated to find out the most influential parameters in permeation and purity. The impact of operating conditions on separation were studied and showed that for enhancement of separation efficiency of CO2 from CH4, feed pressure, feed flow rate and tube radius and number of membrane modules in series should be increased, whereas flow configuration has less significant effect

A Simple and Novel Modulation Technique Used to Obtain Output Voltage Having a Frequency Multiple of Input Voltage Frequency

This paper introduces a new modulation method that can be adopted to obtain various possible output voltages depending on the switching topology and the voltage inputs available. This method is used to obtain a sinusoidal voltage waveform with a frequency which is a multiple of the frequency of the sinusoidal input voltage. There are various applications that need a variable frequency input and a limitation is that three-phase supply is not always available. A good example to this would be single-phase induction motors. Using this method single-phase induction motors can be supplied with a variable frequency source which uses a single-phase fixed-frequency supply and so it can be used in variable speed applications. First the general idea behind this method is explained and its equations and constraint are derived. Next the technique is used to produce the desired voltage that was mentioned and the proper switching topology is explained. Then the method and its equations and constraints arc fully discussed over this particular case. Finally the simulation results are presented and analyzed

Synthesis and characterization of poly(vinylidene fluoride) membrane containing hydrophobic silica nanoparticles for CO2 absorption from CO2/N2 using membrane contactor

The separation of carbon dioxide from CO2/N2 gas mixture using membrane-absorption technology has been investigated. Poly(vinylidene fluoride) (PVDF) membrane was prepared using phase inversion method with N, N-Dimethylacetamide (DMAc) as the solvent and monoethanolamine (20 wt%) was used as the carbon dioxide absorbent. The hydrophobic silica nanoparticles modified with vinyl groups used to raise the hydrophobic character of the prepared polymeric membranes. The chemical structure and hydrophobicity of the silica nanoparticles was studied. The mixed matrix membranes morphology, hydrophobicity, thermal and mechanical properties were investigated. The results showed that the nanoparticles were properly modified with vinyl groups and their contact angles increased from 34 to 131°. Low amount addition of nanoparticles to the polymeric solution caused macrovoid formation, while increasing the nanoparticles loading suppressed macrovoid formation. Carbon dioxide absorption efficiency has been increased by increasing loading of nanoparticles into the membrane because of its smaller pore size and higher hydrophobicity

Effects of an Alphasatellite on the Life Cycle of the Nanovirus Faba Bean Necrotic Yellows Virus

International audienceNanoviruses are plant viruses with a multipartite single-stranded DNA (ssDNA) genome. Alphasatellites are commonly associated with nanovirus infections, but their putative impact on their helper viruses is unknown. In this study, we investigated the role of subterranean clover stunt alphasatellite 1 (here named SCSA 1) on various important traits of Faba bean necrotic yellows virus (FBNYV) in its host plant Vicia faba and aphid vector Acyrthosiphon pisum, including disease symptoms, viral accumulation, and viral transmission. The results indicate that SCSA 1 does not affect the severity of symptoms nor overall FBNYV accumulation in V. faba, but it does change the relative amounts of its different genomic segments. Moreover, the association of SCSA 1 with FBNYV increases the rate of plant-to-plant transmission by a process seemingly unrelated to the simple increase of viral accumulation in the vector. These results represent the first study on the impact of an alphasatellite on the biology of its helper nanovirus. They suggest that SCSA 1 may benefit FBNYV, but the genericity of this conclusion is discussed and questioned.IMPORTANCE:Alphasatellites are circular single-stranded DNA molecules frequently found in association with natural isolates of nanoviruses and some geminiviruses, the two ssDNA plant-infecting virus families. While the implications of alphasatellite presence in geminivirus infections are relatively well documented, comparable studies on alphasatellites associated with nanoviruses are not available. Here, we confirm that subterranean clover stunt alphasatellite 1 affects different traits of its helper nanovirus, Faba bean necrotic yellows virus, both in the host plant and aphid vector. We show that the frequencies of the virus segments change in the presence of alphasatellite, in both the plant and the vector. We also confirm that although within-plant virus load and symptoms are not affected by alphasatellite, the presence of alphasatellite decreases within-aphid virus load but significantly increases virus transmission rate, and thus it may confer a possible evolutionary advantage for the helper virus

CFD simulation of fluidized bed reactors for polyolefin production - a review

This literature survey focuses on the application of computational fluid dynamics (CFD) in various aspects of the fluidized bed reactor. Although fluidized bed reactors are used in various industrial applications, this first-of-its-kind review highlights the use of CFD on polyolefin production. It is shown that CFD has been utilized for the following mechanisms of polymerization: governing of bubble formation, electrostatic charge effect, gas-solid flow behavior, particle distribution, solid-gas circulation pattern, bed expansion consequence, mixing and segregation, agglomeration and shear forces. Heat and mass transfer in the reactor modeling using CFD principles has also been taken under consideration. A number of softwares are available to interpret the data of the CFD simulation but only few softwares possess the analytical capability to interpret the complex flow behavior of fluidization. In this review, the popular softwares with their framework and application have been discussed. The advantages and feasibility of applying CFD to olefin polymerization in fluidized beds were deliberated and the prospect of future CFD applications was also discussed