Multi-physical simulation of stirring effect on heating uniformity in a microwave reactor with interlayer

Due to the exhaustion of fossil fuels and environmental degradation, biodiesel has attracted much attention as a new energy source. Currently, microwave reactors are used extensively for producing biodiesel. However, nonuniform heating of producing biodiesel in microwave reactors is a major problem. In order to solve the problem, a microwave reactor with an interlayer which can obviously improve the uniformity of microwave heating was designed. In this work, the heating efficiency and heating uniformity of the reactor were discussed from two aspects of waveguide position and interlayer thickness by means of multi-physical coupling calculation. According to the calculation results, the optimization model of a microwave reactor with an interlayer was obtained. Then, based on the above optimization model of a microwave reactor with an interlayer, a stirrer that can improve the heat transfer of the fluid material was introduced. The Maxwell equation, heat transfer equation and flow equation were coupled by multi-physical field simulation method to explore the influence of different factors of stirrer on power consumption and heating uniformity. Through response surface analysis, it was found that the primary and secondary order of stirring factors affecting microwave heating uniformity was stirring speed > impeller diameter > bottom clearance, and there was an interaction between different factors. From the two aspects of stirring power consumption and heating uniformity, the best stirring effect was obtained.

Stirring effect on zeolites synthesis with different Si/Al molar ratios Using 1-Butyl-3-methylimidazolium chloride as structure-direct agent

Different types of zeolites could be synthesized changing the variables in the synthesis process. This paper studies the stirring effect on zeolites synthesis at different Si/Al molar ratios (1, 8, 20, 50 and 120) using the ionic liquid 1-butyl-3-methylimidazolium chloride (BMI.Cl) as structure-direct agent. The results suggest that the ionic liquid BMI.Cl would be a highly effective directing agent for the crystallization of zeolites type A, ZSM-5, Beta and ZSM-35. The stirring effect on compositional and morphological parameters seems to be significant. Therefore, ternary composition diagrams were plotted for the static and stirring conditions, showing the influence of stirring on the composition and morphology of the generated materials. It was possible to verify, in the ternary diagrams, the conditions for obtaining the pure ZSM-5 and ZSM-35 zeolites, as well as the different morphologies found for the same regions, when the zeolites were synthesized under static and stirring conditions. It is also observed that the zeolites ZSM-35 and Beta show a greater amount of Al2O3 (4 mol% and 1.6 mol%) only when the reaction is carried out under stirring conditions.

Optimized Scheme for Accelerating the Slagging Reaction and Slag–Metal–Gas Emulsification in a Basic Oxygen Furnace

Basic oxygen furnace (BOF) steelmaking is widely used in the metallurgy field. The slagging reaction is a necessary process that oxidizes C, Mn, Si, P, S, and other impurities and therefore directly affects the quality of the resultant steel. Relevant research has suggested that intensifying the stirring effect can accelerate the slagging reaction and that the dynamic characteristics of the top blow are the key factor in exploring the related complex physical and chemical phenomena. To address the issue, the standard k-ω turbulence model and level-set method were adopted in the present work and a fluid dynamics model was developed for a BOF. Accordingly, the slag–metal–gas emulsion interaction and stirring effect were investigated, and the interference mechanism of a multi-nozzle supersonic coherent jet was revealed. Finally, a self-adjustment method based on fuzzy control is proposed for the oxygen lance. The results indicate that the transfer efficiency of jet kinetic energy at the gas–liquid interface is the critical factor for the slagging reaction and that multi-nozzle oxygen lances with a certain twisted angle have important advantages with respect to stirring effects and splashing inhibition. The fuzzy control method predicts that the optimal nozzle twist angle is within the range of 7.2° to 7.8°. The results presented herein can provide theoretical support and beneficial reference information for BOF steelmaking.

Effect of Lance Structure on Behavior of Coherent Jet in EAF Steelmaking Process

During the electric arc furnace steelmaking process, the coherent jet technology was widely used to protect the kinetic energy of the supersonic oxygen jet and achieve better mixing effects. Comparing with the conventional oxygen lance, the coherent lance could increase the surface area of impaction cavity, resulting in a better stirring effect and higher reaction rate. However, there was limited research about the effect of restriction structure for the coherent lance tip on the flow field characteristic of the main oxygen jet. In this research, three kinds of restriction structures have been investigated by numerical simulation and combustion experiment at room and high ambient temperature conditions. Then an optimum restriction structure would be tested in a 75 t electrical arc furnace steelmaking process to verify its metallurgical property.

Effects of Multi-Pass Friction Stir Processing on Microstructures and Mechanical Properties of the 1060Al/Q235 Composite Plate

Steel cuttings, holes and cracks always exist at the interfaces in the composite plate. Multi-pass friction stir processing (M-FSP) is proposed in this research to optimize the interface microstructure and the interface connection for the 1060Al/Q235 composite plate. Results show that the microstructures of 1060Al after M-FSP are fine and uniform owing to the strong stirring effect and recrystallization. Micro-defects formed by the welding can be repaired by the M-FSP. However, tunnel defects can also be formed in the matrix of aluminum by M-FSP, especially when the passes are one and two. The melting block and the melting lump in the composite plates are easy to become the source of crack. The shear strengths and the bending properties for the 1060Al/Q235 composite plate after M-FSP are the best when the passes are three, with the tool rotation speed of 1200 rpm and the forward speed of 60 mm/min. The optimized interfaces for the composite plate after M-FSP are mainly by the metallurgical bondings, with a certain thickness and discontinuous mechanical connections. Therefore, the crack extension stress is the largest and the mechanical properties are the best.

Effects of Multi-pass Friction Stir Processing on Microstructures and Mechanical Properties of 1060Al/Q235 Explosive Composite Plate

There always exist steel cuttings, holes and cracks at the interfaces in the explosive composite plate. Multi-pass friction stir processing (M-FSP) is proposed in this research to optimize the interface microstructure and the interface connection for 1060Al/Q235 explosive composite plate. Results show that the microstructures of 1060Al after M-FSP are fine and uniform owing to the strong stirring effect and recrystallization. Micro-defects formed by the explosive welding can be repaired by the M-FSP. However, M-FSP can also form tunnel defects in the aluminum, especially when the passes are one and two. The melting block and the melting lump in the composite plates are easy to become source of crack. The shear strengths and the bending properties for the 1060Al/Q235 explosive composite plate after M-FSP are the best when the passes are three, with the tool rotation speed of 1200rpm and the forward speed of 60mm/min. The optimized interfaces for the explosive composite plate after M-FSP are mainly by the metallurgical bondings, with a certain thickness and are discontinuous. Therefore, the crack extension stress is the largest and the mechanical properties are the best.

Time Stirring Effect of Chitosan from Shrimp Shells as Gold Absorbent

This study aims to analyze the effect of chitosan stirring time from shrimp shells as gold absorber. Experimental research was conducted in this study, where the manufacture of chitosan from shrimp shells began with demineralization (mineral removal) using 1.5 M HCl, deproteination (protein removal) using 3.5% NaOH and deacetylation (acetyl removal) using 60% HCl. The chitosan formed was weighed 0.1 gram (as many as five samples) and then stirred in a 10 ppm Au solution, with a stirring time of 0, 10, 20, 30, and 40 minutes, and its absorption ability to gold was analyzed using AAS (Atomic Absorbsion Spectroscopy) and obtained percentage of absorption respectively 24.79%, 50.89%, 45.64%, 40.52% and 37.87%. From the results of the study, it was found that there was an effect of chitosan stirring time from shrimp shells as gold absorber and the highest absorption at 10 minute stirring was 50.89%.

Role of Surface-Layer Coherent Eddies in Potential Vorticity Transport in Quasigeostrophic Turbulence Driven by Eastward Shear

The transport by materially coherent surface-layer eddies was studied in a two-layer quasigeostrophic model driven by eastward mean shear. The coherent eddies were identified by closed contours of the Lagrangian-averaged vorticity deviation obtained from Lagrangian particles advected by the flow. Attention was restricted to eastward mean flows, but a wide range of flow regimes with different bottom friction strengths, layer thickness ratios, and background potential vorticity (PV) gradients were otherwise considered. It was found that coherent eddies become more prevalent and longer-lasting as the strength of bottom drag increases and the stratification becomes more surface-intensified. The number of coherent eddies is minimal when the shear-induced PV gradient is 10–20 times the planetary PV gradient and increases for both larger and smaller values of the planetary PV gradient. These coherent eddies, with an average core radius close to the deformation radius, propagate meridionally with a preference for cyclones to propagate poleward and anticyclones to propagate equatorward. The meridional propagation preference of the coherent eddies gives rise to a systematic upgradient PV transport, which is in the opposite direction as the background PV transport and not captured by standard Lagrangian diffusivity estimates. The upgradient PV transport by coherent eddy cores is less than 15% of the total PV transport, but the PV transport by the periphery flow induced by the PV inside coherent eddies is significant and downgradient. These results clarify the distinct roles of the trapping and stirring effect of coherent eddies in PV transport in geophysical turbulence.

Investigation on the induction stirring effect in a laboratory scale crucible with the variation of electrical supply parameters

Purpose This paper aims to study the possibility of controlling the electromagnetic stirrer (EMS) is fundamental in a continuous casting line to achieve the desired properties of homogeneity and mechanical strength in the solidified cast. Design/methodology/approach Coupled electromagnetic (EM) and fluid dynamic (FD) simulations allow to predict the mixing effect on molten metal, in terms of velocity amplitude and shape of the flow. This paper describes the numerical results of EMS effect within a cylindrical crucible, surrounded by a solenoidal inductor, filled with a low melting temperature alloy, i.e. GalInStan. Findings Induced forces and resulting velocity distribution of the flow of the liquid metal have been calculated depending on varying amplitude and frequency of the supplied current. As expected, at a given amplitude of the current supply, the velocity distribution shows a maximum at a certain frequency while the intensity of electrodynamic forces monotonically increase as the frequency increases Originality/value The paper deals with simply models and experiments applied to coupled EM and FD problem, to assess the applied methodology.