Showing papers on "Mixing (process engineering) published in 1998"

Elastomer composite blends and methods for producing them

Abstract: Elastomer composite blends are produced by novel wet/dry mixing methods and apparatus. In the wet mixing step or stage, fluid streams of particulate filler and elastomer latex are fed to the mixing zone of a coagulum reactor to form a mixture in semi-confined flow continuously from the mixing zone through a coagulum zone to a discharge end of the reactor. The particulate filler fluid is fed under high pressure to the mixing zone, such as to form a jet stream to entrain elastomer latex fluid sufficiently energetically to substantially completely coagulate the elastomer with the particulate filler prior to the discharge end. Highly efficient and effective elastomer coagulation is achieved without the need for a coagulation step involving exposure to acid or salt solution or the like. Elastomer composites are produced. Such elastomer composites may be cured or uncured, and combine material properties, such as choice of filler, elastomer, level of filler loading, and macro-dispersion, not previously achieved. The coagulum produced by such wet mixing step, with or without intermediate processing steps, is then mixed with additional elastomer in a dry mixing step or stage to form elastomer composite blends. The additional elastomer to the coagulum may be the same as or different from the elastomer(s) used in the wet mixing step.

Two simple micromixers based on silicon

Abstract: This paper reports modelling, fabrication and testing of two micromixers. The principle of mixing used for the devices was diffusion because of the small value of the Reynolds number in microcapillaries. The first mixer separates the main flow into partial flows, which are laterally alternated in order to increase the boundary surface between the liquids. The second mixer superposes two fluids by injection of one liquid into the other. The fabrication technology is based on etching of silicon and anodically bonding with Pyrex glass. The performance of the mixers has been verified by mixing phenolphthalein solution and ammonia dissolved in water. Reasonable mixing was achieved at pressures of around 4 kPa (lateral mixing) and 7 kPa (vertical mixing) with flow rates of approximately 1 . The measurements were compared with diffusive mixing simulations with a CFD simulator and agreement of both was observed.

Quantitative Characterization of Mixing of Dry Powders in V-Blenders.

Abstract: Experiments were conducted to determine the effect of rotation rate, fill level, and total number of revolutions on the mixing performance of a V-blender. The experiments were performed using 66-μm red and green glass beads. Mixture uniformity was quantified after each experiment by infiltrating the mixtures with a binder, and using image analysis to examine slices of the solidfied mixture. The mixing rate (as a function of total revolutions) was not affected by changing the rotation rate between 8 and 24 rpm. The mixing rate increased significantly as the fill percentage was decreased from 60% to 40% of the total vessel volume. In a symmetric blender such as a V-blender, the rate of mixing is limited by the rate of mass transfer across the vessel plane of symmetry orthogonal to the axis of rotation. A one-parameter model based on the amount of material that crossed the plane of symmetry per revolution displayed good agreement with the experimental data.

Electrokinetic micro-fluid mixer

Abstract: A method and apparatus for efficiently and rapidly mixing liquids in a system operating in the creeping flow regime such as would be encountered in capillary-based systems. By applying an electric field to each liquid, the present invention is capable of mixing together fluid streams in capillary-based systems, where mechanical or turbulent stirring cannot be used, to produce a homogeneous liquid.

Competition of mixing and segregation in rotating cylinders

Abstract: Using discrete element methods, we study numerically the dynamics of the size segregation process of binary particle mixtures in three-dimensional rotating drums, operated in the continuous flow regime. Particle rotations are included and we focus on different volume filling fractions of the drum to study the interplay between the competing phenomena of mixing and segregation. It is found that segregation is best for a more than half-filled drum due to the non-zero width of the fluidized layer. For different particle size ratios, it is found that radial segregation occurs for any arbitrary small particle size difference and the final amount of segregation shows a linear dependence on the size ratio of the two particle species. To quantify the interplay between segregation and mixing, we investigate the dynamics of the center of mass positions for each particle component. Starting with initially separated particle groups we find that no mixing of the component is necessary in order to obtain a radially segregated core.

Burner of LPG stove

Abstract: The utility model discloses a burner of liquefied petroleum gas stove, which is composed of an air chamber, a mixing gas chamber, a fuel gas spray cup, a burner, etc. The burner is covered on the upper part of the mixing gas chamber, the fuel gas spray cup is arranged in the middle part of the mixing gas chamber, and the air chamber is arranged out of the mixing gas chamber. The inner wall of the air chamber is provided with an air swiveling jet nozzle to the mixing gas chamber, and the lower end of the air chamber is provided with a blast pipe. Owing to the mechanical air supply of the utility model, fire can burn above the burner, the airflow with large area can only be ejected from priming bores and burning bores. Therefore, the pressure of the air can be increased, the firepower can be reinforced and the utility model has low noise of an oil burner and little pollution.

Multicomponent feed apparatus with preheater and mixer for a high temperature chemical reactor

Abstract: A multicomponent fluid feed apparatus is disclosed that independently preheats and then mixes two or more fluid streams being introduced into a high temperature chemical reactor to promote more rigorous and complete reactions using assemblies of inert tubular elements and an integral mixing orifice plate. The design allows use of ceramic and speciality alloy materials for high temperature service with particularly corrosive halide feeds such as UF6 and HF. Radiant heat transfer to the tubular elements from external means gives the necessary system high temperatures without excessive temperatures to cause material failure. Preheating of the gaseous reactants in a separate step prior to mixing and injecting the gaseous reactants into a high temperature chemical reactor was found to provide an improved thermal conversion of UF6 to uranium oxides.

Condensation nucleus counter using mixing and cooling

Abstract: A modified mixing-type condensation nuclei counter for measuring the size and number of small particles is presented. A gas stream is saturated with respect to a working fluid. The saturated gas at a first temperature is mixed in a growth chamber with a sample gas at a second temperature that is lower than the first temperature. The mixture of the saturated gas and the sample gas at different temperatures results in supersaturation of the mixed gas with respect to the working fluid. Particles in the sample gas act as nucleation sites for condensation of the working fluid. The particles are thus grown to a larger size and therefore are more easily measured by known light-scattering particle detection methods. The efficiency of the supersaturation process is made even more efficient by cooling the growth chamber to a third temperature which is lower than the second temperature or by turbulently mixing the saturated gas and the sample gas. False count rate is reduced by filtering the saturated gas before it is mixed with the sample gas to remove droplets of the working fluid from the saturated gas.

Gas-liquid venturi mixer

Abstract: An apparatus and method are provided for mixing gas and liquid. An impeller is rotatably mounted inside a draft tube having a constricted section. Rotation of the impeller draws liquid down through the constricted portion of the draft tube. A gas delivery system introduces gas under the surface of the liquid downstream from the constricted portion of the draft tube to entrain the gas in the liquid by a venturi effect. The impeller creates a turbulent gas-liquid mixing zone and also projects liquid radially into the gas as it enters the draft tube. The gas-liquid venturi mixer is particularly suitable for treating industrial and municipal waste water, as well as various other liquids. Gases such as air, oxygen, hydrogen, and the like are efficiently dissolved in such liquids during operation of the gas-liquid venturi mixer.

Process for production of heat sensitive dispersions or emulsions

Abstract: The invention is an apparatus and process for making multi-phase mixtures. The apparatus includes a high pressure pump, at least two high pressure mixing zones in series, and a high pressure heat exchanger (30) located before the last high pressure mixing zone (20b).

Coating apparatus and coating method

Abstract: Disclosed is a coating apparatus, comprising: a first stream-combining valve communicating with each of a first solvent tank and a resist solution tank, a first pump for supplying an initial resist solution from the resist solution tank toward said first stream-combining valve, a second pump for supplying a solvent from said first solvent supply toward said first stream-combining valve, a first mixer for mixing under stirring the initial resist solution flowing out of said first stream-combining valve with a solvent, a second stream-combining valve arranged downstream of said first mixer and communicating with each of the first mixer and said second solvent supply, a third pump for supplying the solvent from said second solvent supply toward the second stream-combining valve, a second mixer for mixing under stirring said primary mixed liquid material coming out of said second stream-combining valve with a solvent so as to prepare a final mixed liquid material, a nozzle equipped with a liquid spurting port for spurting said final mixed liquid material prepared in said second mixer toward the substrate, and a controller for controlling each of the first, second, third pumps and the first and second stream-combining valves so as to control the mixing ratio of the initial resist solution to the solvent and to control the mixing ratio of the primary mixed liquid material to the solvent.

Process for producing vermicelli from sweet potato

Abstract: A method for manufacturing long-thread vermicelli or sheet Oelly with fresh potato includes such technological steps as washing fresh potato, peeling, immersing or grinding, mixing, shaping by heating, cooling, drying and packing and features no need of the step of prepare starch, low cost of production, and retaining the full nutrients the raw material contains.

Modelling the effects of imperfect mixing on the performance of anaerobic reactors for sewage sludge treatment

Abstract: An approach to the modelling of suspended-growth anaerobic digestion systems based on the assumption of an incompletely mixed reactor is presented. The mathematical model developed describes the dynamic behaviour of anaerobic sludge digesters under non-ideal mixing conditions. The microbial kinetic model for the anaerobic digestion of waste-activated sludge distinguishes the processes of death and lysis of activated sludge cells, hydrolysis of particulate material, fermentation of soluble substrates, volatile fatty acids utilisation and methane formation. The interaction of two microbial groups is considered, i.e. acid-formers and methanogens. Their growth is assumed to depend on Monod kinetics for the substrates. Death and lysis, hydrolysis and biomass decay are described by first order reactions. The biokinetic expressions were linked to a simple mixing model which considered the reactor volume split into two sections: the flow-through and the retention regions. The transfer of material between regions was assumed to be limited. Deviations from an ideal completely mixed regime were represented by changing the relative volume of the flow-through region (α) and the turnover time of material in the vessel (τ). The dynamic model described the effects of the retention time and reactants' distribution, resulting from the mixing condition, on process performance. Computer simulations under different conditions showed a considerable decline in methane production and treatment efficiency due to incomplete mixing. The COD removal efficiency increased by extending the retention time and the degree of mixing. The evaluation of the impact of the mixing parameters showed that α has a far more significant effect on the performance of anaerobic digestion than τ does. Nevertheless, both are important and the overall efficiency is a complex function of both parameters. The results obtained confirm and emphasise the importance of considering mixing when simulating anaerobic digestion, calculating process conversion efficiency, and during anaerobic reactor design. © 1998 SCI.

Method of measuring the efficiency of mass and energy transfer in hemodialysis

Abstract: A method for measurement of mass and energy transfer parameters (clearance and dialysance) in hemodialysis. A sensor is provided in the dialysate flow path downstream of the dialyzer and means are provided to add concentrate upstream of the dialyzer. A pre-determined amount of a substance whose dialysance is to be measured is added upstream of the dialyzer. The amount of substance not dialyzed in the dialyzer is measured downstream of the dialyzer by said sensor by integrating the concentration over time. Dialysance is calculated from the amount added upstream, the amount measured downstream and the dialysate flow. In case the substance is part of the dialysate the base concentration is subtracted during integration. The addition of the concentrate upstream of the dialyzer can be done manually or, alternatively by the mixing pump of the dialysis machine. Instead of an increase of the concentration with a concentrate dilution with water can be used as well.

Radial mixing and segregation of a binary mixture in a rotating drum : model and experiment

Abstract: We studied mixing and size segregation of a binary mixture in a partially filled rotating drum. The proposed mathematical model of material transport accounts for the free-surface segregation and predicts the evolving nonuniform distribution of the mixture components. The theoretical distributions are in agreement with the experimental data obtained.

Mixing time and fluid flow phenomena in liquids of varying kinematic viscosities agitated by bottom gas injection

Abstract: A model experiment was carried out to investigate the mixing condition and related fluid flow phenomena in a slag layer of metal-refining processes agitated by bottom gas injection. Silicone oil was used as a model for the molten slag. Mixing time in a silicone oil bath was measured with a newly developed laser optical sensor. Measured mixing time values increased with an increase in the kinematic viscosity of the silicone oil. In order to explain the relation between mixing time and the kinematic viscosity of silicone oil, the rising velocity of bubbles and the vertical and horizontal velocities of silicone oil flow were measured with an electroresistivity probe and a laser Doppler velocimeter, respectively. The increase in the mixing time with the kinematic viscosity of silicone oil was caused mainly by the suppression of upward motion of bubbles and silicone oil in the bubbling jet region. An empirical correlation for the mixing time was derived as a function of the kinematic viscosity of silicone oil, in addition to conventionally used parameters such as the gas flow rate, bath diameter, and bath depth.

Contact material for vacuum valve

Abstract: The vacuum valve contact material of the present invention is manufactured by a step of mixing an anti-arc constituent powder and a conductive constituent powder, a step of forming, and a step of sintering the formed body below the melting point of the conductive constituent, and has improved arc interruption performance.

Inhomogeneities in silicon carbide distribution in stirred liquids—a water model study for synthesis of composites

Abstract: An experimental study was conducted on the mixing quality of two-phase slurries in the model SiC–water system using a gravimetric technique with a view to determining the influence of impeller geometry and baffles on the uniformity of distribution of SiC in the mixture. A three-blade paddle with different blade angles and a variable-pitch blade impeller (A-3) were used for stirring the mixture at various rotational speeds. The results show that SiC concentration variation during stirring in the absence of baffles was 7.5 vol.%, whereas in the presence of four vertical baffles the concentration variation was reduced to 2 vol.%. The power consumption for homogeneous mixing varied between 17.5 and 175 W vol.−1 depending upon the type of impeller and its rotational speed. A semi-empirical correlation for obtaining uniform mixing has been developed based on the Reynolds number, the power number and the Froude number for stirred SiC–water slurries. The results on inhomogeneity of silicon carbide in water concentration during mixing are in close agreement with the modeling studies by previous workers on the water–SiC system, and with limited experimental studies on the real molten aluminum–SiC system used to cast metal–matrix composites.

Mixing and phase hold-ups variations due to gas production in anaerobic fluidized-bed digesters: influence on reactor performance

Abstract: The influence of mixing and phase hold-ups on gas-producing fluidized-bed reactors was investigated and compared with an ideal flow reactor performance (CSTR). The liquid flow in the anaerobic fluidized bed reactor could be described by the classical axially dis- persed plug flow model according to measurements of residence time distribution. Gas effervescence in the flu- idized bed was responsible for bed contraction and for important gas hold-up, which reduced the contact time between the liquid and the bioparticles. These results were used to support the modeling of large-scale fluid- ized-bed reactors. The biological kinetics were deter- mined on a 180-L reactor treating wine distillery waste- water where the overall total organic carbon uptake ve- locity could be described by a Monod model. The outlet concentration and the concentration profile in the reactor appeared to be greatly influenced by hydrodynamic limi- tations. The biogas effervescence modifies the mixing characteristics and the phase hold-ups. Bed contraction and gas hold-up data are reported and correlated with liquid and gas velocities. It is shown that the reactor per- formance can be affected by 10% to 15%, depending on the mode of operation and recycle ratio used. At high organic loading rates, reactor performance is particularly sensitive to gas effervescence effects. © 1998 John Wiley &

Storage and transport of gas hydrates as a slurry suspension under metastable conditions

Abstract: A suitable slurry composition allows gas hydrates to be stored or transported under metastable conditions. The slurry includes gas hydrate particles and a carrier liquid for the gas hydrate particles. Suitable carrier liquids have a specific gravity in the range from about 0.6 to about 2, a pour point below about -20° C. a viscosity of about 10 centipoise or less, and a thermal conductivity lower than that of the gas hydrate particles. The slurry can be stored or transported in a system that includes a container for holding the slurry; a device for agitating the slurry while in the container (e.g., a mixing blade, a rotating screw, a reciprocating box beam, or an ultrasound generator); a device for removing excess carrier liquid from the container while it is loaded or being loaded with gas hydrates and/or carrier liquid (e.g., a skimming device or a drain); and a device for reslurrifying the gas hydrates with carrier liquid before or during unloading of the gas hydrates from the container (e.g., a carrier liquid injection nozzle).

Fibrin mixture and dispenser assembly

Abstract: A fibrin mixture and dispenser assembly (10) is provided for mixing a first protein component with sterile water to form a first protein solution and for dispensing the first protein solution.

Method and apparatus for mixing concrete with controlled energy absorption and variable discharge gate

Abstract: An apparatus for making concrete is disclosed. The apparatus includes one or more measurement devices that is used to provide controlled quantities of at least cement and sand; a high intensity mixer that receives the controlled quantities of the cement and sand, mixes the controlled quantities of the cement and sand to produce grout, and outputs a flow of grout; and a controller coupled to the measurement devices and the mixer. The controller monitors and controls mixing energy applied by the mixer during mixing. In one embodiment, the mixing energy is altered by controlling the degree of opening of a discharge gate of the mixer. A concrete plant design including such an apparatus is also disclosed.

Polymerization process using a dual shear mixing element

Abstract: A dual shear mixing element (1) for use in a chemical reactor (2). The device may be used in processes where liquids of different temperatures need to be thoroughly mixed in a short period of time and solute must stay in solution. The present invention is particularly useful in the solution polymerization of polyolefins, especially in the medium pressure process for the preparation of linear low density polyethylene.

Effects of transverse mixing on transport of bacteria through heterogeneous porous media

Abstract: In this paper, we examine two questions: (1) can the effects of transverse mixing of bacteria in a system constructed to have a permeability discontinuity in the direction parallel to the flow be measured; and (2) if the effects are measurable, can they be calculated using a transverse dispersion coefficient estimated from experiments using a conservative tracer? Pulses of chloride and bacteria were transported downward through heterogeneous columns constructed with a tubule of coarse, quartz sand surrounding an annulus of fine, quartz sand. Pulses of each were also transported through homogeneous columns of the two sands. Doubly peaked breakthrough curves resulted from the columns containing two distinct sand sizes. Modeling of the breakthrough curves was performed taking into account advection, dispersion, deposition, entrainment, and pore-size exclusion. The results revealed that transverse mixing does occur during transport of bacteria through heterogeneous material and that this mixing can be estimated using a conservative tracer.

Automated fluid mixing in glass capillaries

Abstract: A fast method and compact device for mixing sub-microliter fluid samples contained in glass capillaries is presented. The fluid is rapidly moved back and forth by air volume displacement driven by a piezo-ceramic actuator. Rapid mixing of different fluids is achieved via diffusion between the main fluid volume in the capillary and the thin fluid film it deposits on the capillary wall through its motion. Bubbles in the fluid are processed out of the capillary by use of an asymmetric velocity profile. A simple analysis model is used to optimize the design of the device and to elucidate the mechanisms involved in mixing. The mixing time is found to be inversely proportional to the fraction of the fluid volume that is left in the film layer for each cycle, which is determined by the wetting properties and the viscosity. The mixing time is therefore controlled by the dead-air volume of the system, the fluid volume, the capillary size, and the displacement limits of the piezo-ceramic actuator, in addition to the intrinsic properties of the fluid being mixed. The device described can mix two 1 μl water solutions in under 3 s. The possible shear breakage of DNA in solution is investigated, and λ-DNA is found to remain intact at aggressive mixing parameters. No evidence of aerosol contamination in polymerase chain reaction reactions was found to date.

Characterization of gas transfer and mixing in a bubble column equipped with a rubber membrane diffuser

Abstract: Gas transfer and mixing were characterized in a 32-L bubble column reactor equipped with a commercially available rubber membrane diffuser. The performance of the membrane diffuser indicates that the slits in the membrane are best described as holes with elastic lids, acting as valves cutting off bubbles from the gas stream. The membrane diffuser thus functions as a one-way valve preventing backflow of liquid. Our design of the bottom plate of the reactor enabled us to optimize the aeration by changing the tension of the membrane. We thereby achieved mass transfer coefficients higher than those previously reported in bubble columns. A strong dependence of mass transfer on gas holdup and bubble size was indicated by estimates based on these two variables. The microalga, Rhodomonas sp. , sensitive to chemical and physical stress, was maintained for 8 months in continuous culture with a productivity identical to cultures grown in stirred tank reactors. Copyright 1998 John Wiley & Sons, Inc.

Unit for vaporizing liquid materials

Abstract: The object of the invention is to provide a unit for vaporizing liquid materials which can adjust not only a mixing rate but also a concentration of the mixed liquid easily and accurately and which can effectively vaporize a large amount of the liquid material. A unit for vaporizing liquid materials in accordance with the invention is for mixing a plurality of liquid materials and comprises a plurality of containers each of which contains a different liquid material which is made by dissolving a material into a solvent, a container exclusive for solvent which contains the same or the same kind of solvent used for the liquid materials, a liquid conveying means which conveys the liquid materials from the containers and the solvent from the container exclusive for solvent, and a vaporizing means which sprays the liquid materials and the solvent conveyed by the liquid conveying means and vaporizes the sprayed liquid materials and the sprayed solvent.

Fuel/air mixing disks for dry low-NOx combustors

Abstract: A fuel mixer for a gas turbine combustor is provided. The fuel mixer has a substantially cylindrical body with a flared end and a tapered end. The flared end is adapted for receiving compressed air and for channeling the compressed air into the fuel mixer. The fuel mixer has a fuel/air mixing disk disposed within the body proximate the flared end. A disk axis of the fuel/air mixing disk is substantially parallel to the axis of the fuel mixer body. The fuel/air mixing disk has a plurality of holes parallel to the disk axis. The fuel/air mixer reduces NO x and CO emissions in a gas turbine combustor by providing more evenly distributed fuel/air mixtures without increasing the risk of flame holding or flashback.

Ingredient mixing bowl and moisture reduction system for a vending machine

Abstract: An ingredient mixing apparatus and moisture reduction system for a liquid vending machine which is capable of mixing a predetermined portion of dry ingredient with a liquid and vending the resultant mixture. The ingredient mixing apparatus includes a mixing bowl which has a cylindrical upper portion and conical lower portion with an outlet spout at the bottom. The liquid is injected into the bowl at a tangent so that it swirls about the bowl for mixing. The dry ingredient is dropped into the top of the bowl simultaneously with the liquid injection so that the two mix before leaving the bowl through the bottom. A top cap is provided for the mixing bowl with a depending wall extending adjacent the inner cylindrical surface of a portion of the bowl. A divider wall also supported by the cap extends down into the mixing bowl to divide it into two sections. Suction is provided on the second section to remove steam or vapor and airborne dry ingredient from the bowl. The moisture reduction system includes a series of mixing bowls and a manifold that removes the steam and dry ingredient from the mixing bowls.