Showing papers on "Mixing (process engineering) published in 2009"

A fast microfluidic mixer based on acoustically driven sidewall-trapped microbubbles

Abstract: Due to the low Reynolds number associated with microscale fluid flow, it is difficult to rapidly and homogenously mix two fluids. In this letter, we report a fast and homogenized mixing device through the use of a bubble-based microfluidic structure. This micromixing device worked by trapping air bubbles within the pre-designed grooves on the sidewalls of the channel. When acoustically driven, the membranes (liquid/air interfaces) of these trapped bubbles started to oscillate. The bubble oscillation resulted in a microstreaming phenomenon—strong pressure and velocity fluctuations in the bulk liquid, thus giving rise to fast and homogenized mixing of two side-by-side flowing fluids. The performance of the mixer was characterized by mixing deionized water and ink at different flow rates. The mixing time was measured to be as small as 120 ms.

Micro process engineering : a comprehensive handbook

Abstract: VOLUME I: Fundamentals, Operations and Catalysts FLUID DYNAMICS IN MICROCHANNELS Multiphase Flow Microfluidic Networks Boiling and Two-Phase Flow in Microchannels Microscale Flow Visualization Modeling of Microfluidic Devices MIXING IN MICROSYSTEMS Characterization of Mixing and Segregation in Homogeneous Flow Systems Passive and Active Micromixers Mixing and Contacting of Heterogeneous Systems HEAT/MASS TRANSFER Heat Transfer in Homogeneous Systems Transport Phenomena in Microscale Reacting Flows Fluid-Fluid and Fluid-Solid Mass Transfer MICROSTRUCTURED DEVICES FOR PURIFICATION AND SEPARATION PROCESSES Extraction Capillary Electrochromatography MICROSTRUCTURED REACTORS Homogeneous Reactions Heterogeneous Multiphase Reactions Photoreactors Microstructured Reactors for Electrochemical Synthesis VOLUME II: Devices, Reactions and Applications MICROREACTOR DESIGN, FABRICATION AND ASSEMBLY Silicon and Glass Microreactors Metallic, Steel, Ceramic and Plastic Microreactors BULK AND FINE CHEMISTRY Liquid- and Liquid-Liquid-Phase Reactions - Aliphatic Substitution Reactions Liquid- and Liquid-Liquid-Phase Reactions - Aromatic Substitution Reactions Liquid- and Liquid-Liquid-Phase Reactions - Addition and Elimination Liquid- and Liquid-Liquid-Phase Reactions - Coupling Reactions Liquid- and Liquid-Liquid-Phase Reactions - Oxidations and Reduction Gas-Liquid-Phase Reactions: Substitution Gas-Liquid-Phase Reactions: Addition Gas-Liquid-Phase Reactions: Reduction Gas-Liquid-Phase Reactions: Miscellaneous Reactions POLYMERIZATION Free Radical Polymerization Living Radical Polymerization Cationic Polymerization Polycondensation FUNCTIONAL MATERIALS Organic Particles and Pigments Inorganic Particles Polymer Particles Microencapsulates, Proteins and Lipids/Vesicles Oil-in-Water and Water-in-Oil Emulsions Double, Triple and Complex Multilayered Emulsions Microreactor Applications in the Consumer Goods Industry FUEL PROCESSING Application and Operation of Microreactors for Fuel Conversion Steam Reforming Partial Oxidation CO Clean-Up: Water Gas Shift and Methanation Reactions CO Clean-Up: Preferential Oxidation VOLUME III: System, Process and Plant Engineering MICROREACTOR SYSTEMS DESIGN AND SCALE-UP Structured Multi-Scale Process Systems Design and Engineering - The Role of Microreactor Technology in Chemical Process Design Reaction and Process System Analysis, Miniaturization and Intensification Strategies Principles and Guidelines for Selection of Microstructured Devices for Mixing and Reaction Catalyst Development, Screening and Optimization SENSING, ANALYSIS, AND CONTROL Microtechnology and Process Analytics Optical In-Line Spectroscopy in Microchemical Processes On-Line Monitoring of Reaction Kinetics in Microreactors Using Mass Spectrometry and Micro-NMR Spectroscopy Automation and Control of Microprocess Systems MICROREACTOR PLANTS: CASE STUDIES Industrial Microreactor Process Development up to Production Microreactor Plant for the Large-Scale Production of a Fine Chemical Intermediate: A Technical Case Study Development and Scale-Up of a Microreactor Pilot Plant Using the Concept of Numbering-Up Microstructures as a Tool for Production in the Tons per Hour Scale ECONOMICS AND ECO-EFFICIENCY ANALYSES The Economic Potential of Microreaction Technology Life Cycle Assessment of Microreaction Technology Versus Batch Technology - A Case Study Exergy Analysis of a Micro Fuel Processing System for Hydrogen ald Electricity Production - A Case Study

Scale-up analysis for a CHO cell culture process in large-scale bioreactors.

Abstract: Bioprocess scale-up is a fundamental component of process development in the biotechnology industry. When scaling up a mammalian cell culture process, it is important to consider factors such as mixing time, oxygen transfer, and carbon dioxide removal. In this study, cell-free mixing studies were performed in production scale 5,000-L bioreactors to evaluate scale-up issues. Using the current bioreactor configuration, the 5,000-L bioreactor had a lower oxygen transfer coefficient, longer mixing time, and lower carbon dioxide removal rate than that was observed in bench scale 5- and 20-L bioreactors. The oxygen transfer threshold analysis indicates that the current 5,000-L configuration can only support a maximum viable cell density of 7 x 10(6) cells mL(-1). Moreover, experiments using a dual probe technique demonstrated that pH and dissolved oxygen gradients may exist in 5,000-L bioreactors using the current configuration. Empirical equations were developed to predict mixing time, oxygen transfer coefficient, and carbon dioxide removal rate under different mixing-related engineering parameters in the 5,000-L bioreactors. These equations indicate that increasing bottom air sparging rate is more efficient than increasing power input in improving oxygen transfer and carbon dioxide removal. Furthermore, as the liquid volume increases in a production bioreactor operated in fed-batch mode, bulk mixing becomes a challenge. The mixing studies suggest that the engineering parameters related to bulk mixing and carbon dioxide removal in the 5,000-L bioreactors may need optimizing to mitigate the risk of different performance upon process scale-up.

Experimental investigation on mixing and segregation behavior of biomass particle in fluidized bed

Abstract: The mixing and segregation behavior of biomass particle have been investigated experimentally in fluidized bed made up of biomass–sand mixture with different biomass/sand ratios. The biomass is cylindrical-shape cotton stalk, and the sand belongs to the Geldart B category. The initial bed is thoroughly mixed and the gas superficial velocity varies to cover a wide range. The mixing and segregation behavior are analysed in terms of flow patterns, solid concentration profile and mixing index. It is found that as the gas superficial velocity gradually increases, the bed undergoes local segregation, global segregation, local mixing, global mixing and re-segregation.

PVC resin composition and product thereof

Abstract: The invention relates to a PVC resin compound and a product thereof, in particular to a PVC resin compound with characteristics of high inflaming retarding and low smoke formation. The PVC resin compound is prepared by mixing PVC resin, inorganic powder, accessory ingredient, toughener, coupling agent and evocating agent according to a certain proportion, wherein the evocating agent is used together with the coupling agent so as to enhance the associative property of the inorganic powder inside the PVC resin compound. The PVC product made by the PVC resin compound has favorable tensile strength and tensile stretch, and has the characteristics of high inflaming retarding and low smoke formation.

Analysis of Mechanisms at the Plasma–Liquid Interface in a Gas–Liquid Discharge Reactor Used for Treatment of Polluted Water

Abstract: Aqueous solutions polluted by contaminants different from those generally studied (phenol and chlorophenols) were treated in a falling film gas–liquid dielectric barrier discharge reactor. The lower was the Henry’s law constant of a molecule, the better was its removal percentage, regardless of its other chemical properties. In the case of saturated molecules, the removal mechanism is the transfer of pollutants from the liquid phase to the gas phase where they react with the active species of the discharge. For phenol, the reaction with ozone in the liquid phase was estimated to be responsible of about 30% of the removal. A computational fluid dynamic modelling provided a better understanding of the phenomena, indicating that mass transfer of pollutants from liquid to gas is accelerated due to (1) the intense mixing in the liquid film and (2) the reaction of the pollutant with the active species in the gaseous phase.

Rapid mixing between ferro-nanofluid and water in a semi-active Y-type micromixer

Abstract: This study investigates the mixing phenomena between ferro-nanofluid (a water solution with suspended Fe 3 O 4 nanoparticles) and water in a Y-type semi-active micromixer. A permanent magnet with a magnetic strength of 2200 G was installed directly under the mixer at a location behind the junction of the Y-type micromixer to improve the mixing between ferro-nanofluid and water. The permanent magnet is 9.6 mm long, 9.6 mm wide and 1.6 mm thick. Equal volumetric flow rates for both ferro-nanofluid and water were tested in two different channel widths, 300 μm and 500 μm. Three different volumetric flow rates of 3 μL/min, 6 μL/min, and 10 μL/min were analyzed to determine the effect of flow rate on the mixing of fluids in the micromixer. Since Fe 3 O 4 nanoparticles in the ferro-nanofluid are strongly affected by a relatively uniform magnetic field from the permanent magnet, measured results show that a rapid mixing between ferro-nanofluid and water can be achieved immediately downstream of the permanent magnet for all volumetric flow rates and all channel widths tested in this study.

Low pressure drop mixer for radial mixing of internal combustion engine exhaust flows, combustor incorporating same, and methods of mixing

Abstract: An exhaust aftertreatment system is provided. The exhaust aftertreatment system includes a mixing arrangement for mixing flows of exhaust along a flow path. The mixing arrangement radially and angularly rearranges segments of two different portions of flow to mix the different portions of flow. The mixing arrangement initially converts a generally radially stratified temperature profile into an angularly stratified temperature profile to increase surface area between cool segments of exhaust gas and hot segments of exhaust gas. The aftertreatment system may also include a combustion chamber, a combustor housing and a combustor liner. The mixing arrangement is downstream from the combustion chamber to direct radially outward hot gas passing through the combustor liner and to direct radially outer cool gas passing between the liner and the combustor housing radially inward in an interleaving fashion.

Magnetic microsphere-based mixers for microdroplets

Abstract: While droplet-based microfluidic systems have several advantages over traditional flow-through devices, achieving adequate mixing between reagents inside droplet-based reactors remains challenging We describe an active mixing approach based on the magnetic stirring of self-assembled chains of magnetic microspheres within the droplet as these stirrers experience a rotating magnetic field We measure the mixing of a water-soluble dye in the droplet in terms of a dimensional mixing parameter as the field-rpm, fluid viscosity, and microsphere loading are parametrically varied These show that the mixing rate has a maximum value at a critical Mason number that depends upon the operating conditions

Characteristics of a Confined Impinging Jet Reactor: Energy Dissipation, Homogeneous and Heterogeneous Reaction Products, and Effect of Unequal Flow

Abstract: The confined impinging jet reactor (CIJR) has attracted wide interest in the past few years because of the efficient micromixing that it offers. In this work, the CIJR is characterized over a wide range of mixing conditions, using three measures of performance: estimates of the energy dissipation rate, micromixing efficiency based on the yield of a homogeneous reaction, and particle size resulting from a heterogeneous precipitation reaction. The energy dissipation results showed very good agreement between four methods, with values up to 100 times greater than those observed in stirred tanks. The reactions showed a higher sensitivity to mixing conditions at higher concentrations, with less effect of mixing at high flow rates. The operation of the CIJR was very robust to changes in flow rate, with stable performance for up to a 30% difference in the inlet flows.

A Scraped Surface Bioreactor for Enzymatic Saccharification of Pretreated Corn Stover Slurries

Abstract: High solids processing of biomass slurries provides the following benefits: maximized product concentration in the fermentable sugar stream, reduced water usage, and reduced reactor size. However, high solids processing poses mixing and heat-transfer problems above about 15% for pretreated corn stover solids. High solids slurries exhibit high viscosities and require high power consumption in conventional stirred tanks because they must be run at high rotational speeds to maintain proper mixing. An 8 L scraped surface bioreactor (SSBR) is employed here for enzymatic saccharification experiments to handle high solids loading and as a means for scale-up from laboratory-scale shake flasks. The scraping action of the blades keeps the reactor surface clear, which improves the heat-transfer characteristics. The horizontal rotation of the shaft and blades provides mixing and prevents particle settling much more effectively than in conventional stirred tanks, even at very low rotational speeds. The reactor is desi...

Method and apparatus for air and fuel injection in a turbine

Abstract: A method includes receiving fuel and air into a cup of a turbine fuel nozzle. The method also includes mixing the fuel and air at least partially within the cup. In addition, the method includes directing a fuel air mixture toward a turbine combustor. The method also includes shielding an inner wall of the cup with a blanket of a protective fluid flow to reduce the possibility of flame holding along the inner wall. The protective fluid flow excludes a combustible mixture of fuel and air.

Mixing Stability and Spray Behavior Characteristics of Diesel-Ethanol-Methyl Ester Blended Fuels in a Common-Rail Diesel Injection System

Abstract: The purpose of this study is to investigate the mixing stability, fuel properties, and spray-atomization characteristics of diesel−ethanol blended fuels in a common rail diesel injection system. In...

Exhaust gas treatment system

Abstract: PROBLEM TO BE SOLVED: To provide an exhaust gas treatment system evenly mixing combustion gas by burning an additional fuel with urea water, while shortening the whole of an exhaust gas flow passage in comparison with a conventional one SOLUTION: This exhaust gas treatment system includes: an exhaust passage 22 through which exhaust gas discharged from an internal combustion engine flows; a selective reduction catalyst 23 provided in the exhaust passage 22; a mixing chamber 27 provided in the exhaust passage 22 at a position between the internal combustion engine and the selective reduction catalyst 23; a fuel injection valve 31 injecting fuel; an air injection valve 32 injecting air; and a urea water injection valve 33 injecting urea water The fuel injection valve 31, the air injection valve 32 and the urea water injection valve 33 are arranged directed into the mixing chamber 27 COPYRIGHT: (C)2011,JPO&INPIT

Solid suspension and liquid phase mixing in solid-liquid stirred tanks

Abstract: Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid−liquid suspensions were also studied. A new way of characterizing solid−liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications...

Simulation of Turbulent Mixing Behind a Strut Injector in Supersonic Flow

Abstract: The flowfield downstream of a strut-based injection system in a supersonic combustion ramjet is investigated using large-eddy simulation with a new localized dynamic subgrid closure for compressible turbulent mixing. Recirculations are formed at the base of the strut in the nonreacting flow and trap some of the injected fluid. The high levels of turbulence along the underexpanded hydrogen jets and in the shear layer lead to a high level of mixing of fuel and freestream fluids. Furthermore, the shear layer unsteadiness permits efficient large-scale mixing of freestream and injected fluids. In the reacting flowfield, the flame anchoring mechanism is, however, found to depend more on a recirculation region located downstream of the injectors than on their sides. A region of reverse flow is formed that traps hot products and radicals. Intermittent convection of hot fluid toward the injector occurs and preheats the reactants.

Enhanced mixing and plume containment in porous media under time-dependent oscillatory flow.

Abstract: Solute transport experiments were conducted in a decimeter scale flow cell packed with sand to study the potential for enhanced mixing of solutes in porous media and improved containment of injected plumes under multiple pumping-well driven, time-dependent oscillatory flow with respect to constant flow. Real-time imaging of the colorimetric reaction of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid) and molybdate was used to quantify mixing, whereas fluorescein was used to better examine plume size. Results from the small scale experiments clearly demonstrated the enhanced mixing of solutes under low Reynolds number oscillatory flow (a factor of 2 with respect to constant flow in homogeneous sand and a factor of 3 in layered sand), as the result of increased contact interface for solute diffusion. Further, the injected solute plume was better contained under oscillatory flow (25% less area with respect to constant flow in homogeneous sand) due to the cancellation of advective transport at each well over ...

Effect of dispersed phase viscosity on solid-stabilized emulsions

Abstract: The time required to efficiently stabilize viscous oil droplets with finely powdered material during agitation has been investigated. The experimental work relied on silicone oils of varying viscosities (50–5000 cSt) dispersed in distilled water with a Rushton turbine (D = 6.5 cm) under controlled conditions (volume = 0.6 L, 0–17 kW/m 3 , and constant agitation time). The emulsion-stabilizing solid particles were made of spherical iron in the 20–50m size range. Each experiment consisted in wetting the powder with water, dispersing the oil/water phases for a given time and conditions, and to record the amount of oil stabilized after stopping agitation. In order to accurately determine the wettability of the powder, a new experimental method was developed. The comparison of the measured contact angle from the proposed technique with the available literature results shows an excellent agreement while being much simpler to use than current published methods. Emulsification in controlled conditions shows that the viscosity of the dispersed phase acted as a damping factor for particle anchoring at the o/w interface and plays an important role during the emulsification process, a role that has never been demonstrated and that must be considered in the design of processes involving solid-stabilized emulsions. Furthermore, the emulsification results at constant mixing intensity indicate the existence of a dispersed phase viscosity limit for a given agitation time beyond which emulsification becomes impossible. A relation between the emulsified oil volume, the o/w viscosity ratio, mixing power density, and agitation time was also proposed for the studied systems. The results from this investigation will support the design of processes for the generation of solid-stabilized emulsions involving extra-heavy oils. © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The importance of phase in the radical-initiated oxidation of model organic aerosols: reactions of solid and liquid brassidic acid particles

Abstract: Using a flow tube reactor coupled to a chemical ionization mass spectrometer, the Cl-initiated oxidation of solid and supercooled liquid brassidic acid (BA, trans-13-docosenoic acid) particles was investigated at 293 K. For the first time radical-initiated oxidation reactions of liquid and solid organic particles of identical chemical composition were performed making it possible to probe the effect of phase. Despite the fact that solubility and/or diffusion in the solid particles is expected to be reduced dramatically, it was observed that the BA in those particles still reacted at 70% of the rate in liquid droplets. The lack of significant slowing upon solidification suggests that the surface is continuously renewed, perhaps by evaporation of volatile products or mixing of underlying solid BA at a surface melt layer. The initial oxidation products were found to be the keto-acid and the alcohol-acid for both solid and liquid, and they account for as much as two thirds of the reacted BA. The distribution of other products, however, was found to be quite different in the two phases. For equivalent Cl concentrations and reaction times more multiply-oxidized species as well as low-molecular-weight species were created from the oxidation of solid particles. Furthermore, the mean mobility diameter of both liquid and solid particles, as determined from a scanning mobility particle sizer, decreased after reaction with larger decreases for the solid particles. These observations are consistent with a loss of mass through evaporation of small, volatile oxidation products. The findings from this study suggest that slower diffusion of the oxidation products in solid particles confines them to the surface where they continue to react with Cl radicals producing more-highly-functionalized products which may decompose more readily. Thus, the solid particles react nearly as efficiently as the liquid ones, but the manner in which they “age” chemically is substantially different. These experiments with this model system indicate that particle phase could be important in determining how organic aerosols evolve chemically through radical-initiated oxidation in the atmosphere, and future work will try to assess how general the effect of phase is.

Ultrahigh-strength active powder concrete and preparation method thereof

Abstract: An ultrahigh-strength active powder concrete is a mixture prepared by mixing the following materials according to weight portion: 1000 portions of Portland cement, 600-1400 portions of quartz sand, 90-400 portions of siliceous dust, 200-400 portions of silicon powder, 100-300 portions of quartz powder, 80-350 portions of high-strength steel fiber, 15-30 portions of high-efficiency water reducing agent, 250-320 portions of water, 60-120 portions of AEA expanding agents, 0-15 portions of latex powder, 0-10 portions of polyester fiber and 0-2 portions of antifoam agents. The preparation method comprises the following steps: preparing the materials according to the weight proportion, firstly mixing water, cement, quartz sand, siliceous dust, silicon powder, quartz powder, AEA expanding agents, high-efficiency water reducing agent, latex powder, polyester fiber, and antifoam agents into pasty state; then adding high-strength steel fiber, and mixing for 4-6 minutes. The prepared active powder concrete has super-high compressive and bending strengths, high mechanical property and high durability.

Simulation of Biodiesel Production through Transesterification of Vegetable Oils

Abstract: Biodiesel can be produced from a number of natural, renewable sources, but vegetable oils are the main feedstocks. Most existing biodiesel plants currently rely upon the use of a homogeneous catalyst in a continuous reactor system, using the transesterification of soybean or rapeseed oil with methanol into alkyl esters. A key differentiation characteristic among the existing processes is that of the mixing pattern employed in the system. The present study compares reactor performances in terms of biodiesel yields for plug flow and complete mixing behaviors, along with the use of interstage phase separation. It is concluded that plug flow pattern shows a distinctive benefit in terms of yields and reactor volume reduction compared to complete mixing. Interstage separation improves the reacting system yields when proper phase separation can be achieved, maximizing glycerine removal from the downstream system. Staged mechanically stirred tank reactors can reach similar performances as plug flow behavior syste...