Showing papers on "Mixing (process engineering) published in 1984"

Mixing and combustion with low heat release in a turbulent shear layer

Abstract: Turbulent mixing and combustion are investigated in a gaseous shear layer formed between two streams: one containing a low concentration of hydrogen in nitrogen and the other containing a low concentration of fluorine in nitrogen. The resulting temperature field is measured simultaneously at eight points across the width of the layer using fast-response cold-wire thermometry. The results show the presence of large, hot structures separated by tongues of cool fluid that enter the layer from either side. The usual bell-shaped mean-temperature profiles therefore result from a duty cycle whereby a fixed probe sees alternating hot and cool fluid, which results in the local mean. The adiabatic flame temperature is not achieved in the mean, at any location across the layer. For fixed velocities, it is found that, in general, two different mean-temperature profiles result from a given pair of reactant compositions if the sides of the layer on which they are carried are exchanged (‘flipped’). This finding is a direct consequence of the asymmetric entrainment of fluid into the layer. Results are compared with the predictions of Konrad and discussed in the context of the Broadwell–Breidenthal model. By comparison with the liquid result of Breidenthal, the amount of product formed in the layer at high Reynolds number is found to be dependent upon the Schmidt number. Results for a helium–nitrogen layer are discussed briefly.

Strength of polymethylmethacrylate increased by vacuum mixing

Abstract: The mechanical strength of high and low viscosity gentamicin-containing cement was analysed using three different mixing procedures: hand, vibration, and vacuum stirring. Vacuum mixing improved the flexural and compression strength and the modulus of elasticity by 15-30 per cent, especially for high viscosity cement.

Dual compartmented container

Abstract: A stoppered vial containing a medicament is secured through the edge of a flexible container. Mixing of the medicament in the vial with the contents of the flexible container is accomplished by removing the stopper from the vial by manipulation through the sides of the flexible container. In one embodiment, the stoppered vial is mounted through and in the edge of the flexible container and in another embodiment the flexible container has a port which will receive the stoppered vial therein in a secure manner.

Apparatus for aerating and mixing waste water

Abstract: A plurality of aerators are arranged in a preselected pattern on the floor of a basin or lagoon containing waste water. Compressed air is supplied to the aerators by aeration pipes anchored by hanger brackets to the floor of the basin. Each aerator has a porous diffuser plate through which the air is passed and released into the waste water in the form of ultra fine air bubbles less than 60 microns in diameter. The air bubbles are generated in an intense manner with a high rate of air flow to increase the mixing action and liquid circulation pattern, and to create turbulent boils at the surface which provide surface aeration from atmospheric air and re-entrainment of air from eddy current circulation.

Apparatus for the preparation and application in situ of blends of structural material

Abstract: A process for the preparation and immediate use in situ of ready to use blends of structural material, such as plaster, mortar, stucco, tile adhesive or similar blends, which, in contrast to the usual methods does not use as a raw material a dry mixture of the three main components binder, filler and additives Instead a dry mix of binder and filler is prepared at the building site, and an aqueous solution of the additives is added in a separate mixing operation, immediately followed by the application in situ of the finished blend This method avoids the difficulties associated with the use of dry mixtures containing all three components The invention includes an apparatus for mixing and immediate application of the blends as defined by the process claims In an especially advantageous form of the invention, part of the aqueous solution of additives is added to the rest of the blend, after mixing and preferably at a point situated between the conveyor pump and the transport hose, in the form of a cylindrical thin concentric mantle surrounding a core of the wet blend Much of the friction between the structural blend and the transport conduit can thus be avoided, as well as the wear associated with it The application of the structural blend can be assisted by pressurized air injected into the stream upstream of the applicator nozzle The stream of air may be loaded with airborne particles of silicone solution in order to impart water repellency to the structural layers made by the process

Nonequilibrium chemical instabilities in continuous flow stirred tank reactors: The effect of stirring

Abstract: We present a simple, phenomenologieal model for chemical reactions which take place in Continuous Flow Stirred Tank Reactors (CSTR). The motivation for developing this model is experimental findings such as those presented by J.C. ROUX et al. [1]. Results of these experiments cannot be adequately explained by existing theory (global Kinetic rate equations or reaction-diffusion models). Our purpose is to develop a better model for CSTR’s. We accomplish this by incorporating two features of turbulent mixing into the overall description: short-range mixing due to molecular diffusion and long-range mixing arising from turbulent diffusion. Our results show that the turbulence of the flow in the reactor affects the state of the chemical reaction. These results are in good qualitative agreement with experimental findings.

Turbulent Mixing and Combustion in a Reacting Shear Layer

Abstract: The temperature field is investigated in a gaseous mixing layer consisting of low-concentration hydrogen and fluorine. The results show the presence of large, hot structures separated by tongues of cool fluid that enter the layer from either side. The cores of the structures appear to be well mixed. the usual bell-shaped mean temperature profiles result from a duty cycle whereby a given point sees alternating hot and cool fluid, which results in the local mean. The adiabatic flame temperature is not achieved on average at any point across the layer. It is found that, in general, two different mean temperature profiles result from a given set of reactant compositions if the sides of the layer on which they are carried are reversed. These observations are not consistent with gradient diffusion concepts.

Liquid vortex gas contactor

Abstract: A method and apparatus for contacting a flow of gas with a flow of liquid is provided. The liquid is introduced into a vortex sustaining container and flows through the container in a spiralling manner creating a liquid vortex with an open axial core. Gas flows to be contacted with the liquid flow are introduced into the core. The vortex core geometry may be adapted to accommodate insertion of a flame to effect heat transfer. The degree of contact between the gas and liquid flows may be increased by adding an extended contact zone following the region where the vortex flow breaks down and mixing of the liquid and gas flows occurs. By creating annular misting in the extended contact zone, the rate of any chemical, physical or mass transfer process between the two flows may be increased.

Liquid and detergent mixing chamber and valves

Abstract: A fluid circuit for a cleaning device having a mixture with separate water and cleaning fluid inlets and fittings interconnecting a pressurized source of water and a pressurized source of cleaning fluid responsive to change the mixing ratio of cleaning fluid to water as well as to assure the degree of mixing. The outlet of the mixing device is provided to a spray nozzle wherein the mixed fluid is projected onto a cleaning surface by an air stream through the spray nozzle. A common pump provides two levels of air pressure, a high one to the spray nozzle and a lower one to the pressurized sources of water and cleaning fluid.

Method and device for mixing stabilizing chemicals into earthen formations

Abstract: A method and device for properly mixing stabilizing chemicals into earthen formations. A helical blade of one or more convolutions is attached to a hollow torque tube and rotated down into the soil. As the device is rotated through the soil to be stabilized, chemicals are pumped down the torque tube, out the device, and then mixed into a soil column by the rotating action of the device.

Method of encapsulating volatile organic liquids

Abstract: A method of encapsulating organic liquids for controlled volatilization and release is described, which comprises in one embodiment charging a fine silica into a mixing container which does not inflict shearing stress to the contents and adding the liquid (having a viscosity of 50 centipoise or less at 25°C) onto and mixing with the fine silica in the mixing container.

Continuous reactor design

Abstract: A continuous reactor for forming polymeric materials from reactive components for use in a system for mixing monomeric materials and the process of operation of the continuous reactor and system.

Apparatus for generating and cooling synthesis gas

Abstract: Hot gases containing ash and char which pass through an undesirable viscous, sticky phase on cooling through an intermediate temperature range, are cooled in a first cooling zone including a falling film of cooling liquid and a spray of cooling liquid followed by contact with a body of cooling liquid and subsequent mixing therewith.

Characterization of helical impellers by circulation times

Abstract: Measurements of the circulation time during batch mixing of Newtonian and non-Newtonian fluids were used to analyse and compare the performance of six different helical-ribbon impellers and a screw impeller inside a draft coil. The distribution of circulation times obtained from two hundred repeated measurements is shown to depend markedly on the impeller geometry. Mixing time data with the helical-ribbon impellers are correlated with the mean value and the reduced standard deviation of the circulation times. Effective (rapid) mixing corresponds to a large circulation capacity and a wide distribution of the circulation times. The mixing mechanism of Newtonian fluids with the helical-ribbon impellers is qualitatively described by the Voncken model. The helical impellers' circulation capacities are not affected by the shear-thinning properties of non-Newtonian fluids. However, in highly shear-thinning fluids, the presence of important stagnant zones is responsible for much longer mixing times which consequently do not correlate with the circulation parameters. The relative efficiencies of the different impellers in Newtonian fluids are compared using a criterion based on the the total energy required to achieve a certain degree of mixing. The wide blade impeller is the most efficient of the helical-ribbon impellers but is considerably less efficient than the screw impeller in a draft coil.

Texas boiling test for evaluating moisture susceptibility of asphalt mixtures

Abstract: This report contains a description of the development and use of the Texas Boiling Test to evaluate stripping of materials susceptible to moisture damage. Included is a review of comparison of boiling tests currently in use by several agencies and a recommended tentative test procedure. Preliminary testing indicated that three factors related to testing were important. These factors were the number of times the aggregate and asphalt was heated and mixed before testing, the initial temperature to which the aggregate was heated prior to mixing, and the type of water used for boiling. These three factors were investigated to determine the effect off their variation on test results. Tests were performed on eight mixtures of which five had stripped in the field and three had not. Each mixture and its individual aggegate components were tested to determine whether the results could be used to differentiate between stripping and nonstripping mixtures. Based on these tests and other field testing it was tentatively concluded that mixtures that retained less than 70 percent of the asphalt on the aggregate are moisture susceptible and require treatment. Test results indicate that valuable information is provided by the Texas Boiling Test. The test is simple and easy to perform; it can be performed either in the laboratory during mixture design or on the field-mixed materials. In general, the Texas Boiling Test offers good potential for use in detecting moisture susceptible mixtures before they are placed in the field. (Author)

Apparatus for the liquid phase hydrotreatment of hydrocarbons in the presence of an expanded or ebullated catalyst bed

Abstract: The hydrotreatment of hydrocarbons in the liquid phase is effected in a column containing a catalyst bed supported by a grid, wherethrough passes an ascending stream of the charge admixed with hydrogen which expands the catalyst bed, the perforations of the grid being small enough to prevent passage of the catalyst particles but large enough to permit passage of the hydrogen-charge mixture, the reaction effluent being withdrawn from the top of the column. The reactor column is provided with means between the hydrogen-charge mixture introducing means and the catalyst bed supporting grid for mixing and dispersing the combined liquid-gas charge.

Method and apparatus for proportioning and mixing multicomponent media

Abstract: 1. Process for production of 2-constituent media by dosing and mixing the individual constituents which are supplied as a dosage to a mixer, characterised in that the individual constituents are fed discontinuously in turn, by means of a count signal corresponding to a determined volume applied at a control unit, to a mixer unit for coarse mixing, and in that the flow for the first constituent is not activated until the second constituent of the previously dosed media cycle has been delivered, and in that if delivery fails or there is a blockage, the flow of the constituents is shut off.

The effect of imperfect mixing on polymer quality in low density polyethylene vessel reactors

Abstract: A mathematical model is developed for the calculation of polymer quality in low density polyethylene vessel reactors, taking into account mixing limitations at the initiator feed point. Model predictions show that imperfect mixing in the reactor can produce considerable variations in polymer molecular weight distribution. The effect of the most important process conditions, input feed temperature, solvent concentration, monomer flow rate and initiator type, on the final polymer quality is analyzed. The advantages of the design solution which divides the reactor in more compartments in series are also discussed.

Polymer feed system

Abstract: A polymer feed system comprises at least one mixing and activating apparatus having a water inlet, a polymer inlet and an outlet and constructed and arranged to dilute and fully activate a polymer. The polymer feed system further comprises a conduit for carrying water to the water inlet of the mixing and activating apparatus. A conduit is coupled between the outlet of the mixing and activating apparatus and the first conduit. Activated polymer merges with the remainder of the water and is mixed in a static mixer.

Liquid mixing system

Abstract: A liquid mixing system is disclosed which provides a continuous and constant pressure flow rate during operation, having particular use in spray dampening operations for offset printing procedures. The mixing system includes a stacked arrangement of a batch mixer and feed tank fluidly communicating therebetween, and transfer means sequentially activated to transfer the liquids to the feed tank upon completion of mixing the liquids. The feed tank having means for discharging liquids therefrom at a constant flow and pressure. Control means sequentially operate the system for the admission and mixing of liquids in predetermined amounts to the batch mixer, for transferring the mixed liquids from the mixer to the feed tank, and for discharging the mixed liquids from the feed tank. The system is capable of repetitive mixing and transfer cycles while continuously discharging from the feed tank at a constant flow rate.

Process for the preparation of alumina

Abstract: An improved process for the preparation of alumina, including forming an alumina hydrogel from aluminum hydroxide, and processing the alumina hydrogel into alumina. The improvement involves the alumina hydrogel forming step which is connected in the presence of sulfate ion and which comprises providing, in a reaction zone, an aqueous slurry containing seed aluminum hydroxide and having a pH of 6-11, and feeding to the reaction zone an aluminum compound and a pH controlling agent for mixing with the aqueous slurry while maintaining the aqueous slurry at a temperature of at least about 50° C. at feed rates so that the pH of the aqueous slurry is maintained within the range of 6-11 and that 0.2-5 mols/hour of aluminum components, in terms of elemental aluminum, are fed to the reaction zone per mole of the seed aluminum hydroxide originally contained in the aqueous slurry, whereby the seed aluminum hydroxide is caused to grow to the aluminum hydrogel.

Method and device for mixing under vacuum mixtures used in dental, goldsmith fields or the like

Abstract: A mixture of a powder and a liquid is formed and poured, under vacuum into suitable containers for the subsequent production of molds to be employed in dental and goldsmith fields. In order to achieve the best degassing conditions and to avoid the production of foams and bubbles in the course of the vacuum mixing step, separate degassing of the liquid and powder components of the mixture is performed in separate vessels before the mixing step, followed by a combination, for example by pouring, of the components in one of the vessels, while maintaining the vacuum conditions.

Granulation of highly water-absorptive resin powder

Abstract: PURPOSE: To granulate a highly water-absorptive resin powder extremely easily by using an aqueous liquid, which has heretofore been thought impossible due to its high water absorptivity, by uniformly mixing the resin powder with the aqueous liquid in a high-speed rotary paddle mixer and crushing and granulating the product. CONSTITUTION: A highly water-absorptive resin powder (e.g., hydrogenated starch/acrylonitrile graft copolymer) is granulated by uniformly mixing it with an aqueous liquid (e.g., water or a water/water-miscible organic solvent mixture, wherein examples of the organic solvents include lower alcohols, glycerin and acetone) in a high-speed rotary paddle mixer and crushing and granulating the mixture. Said aqueous liquid may contain a deodorant, a plant growth substance or a water-soluble polymer, each soluble in the above aqueous liquid. In order to improve the performance of the highly water-absorptive powder, fine silica particles, carbon black or active carbon may be used jointly with above components. COPYRIGHT: (C)1986,JPO&Japio

Cookie filler compositions

Abstract: A filler cream is disclosed which has a rapid "get away" that is achieved by aerating and mixing the filler cream to a specific gravity of between about 0.70 and about 0.82. The resulting filler cream utilizes fat or oleaginous compositions with specifically identified solid fat indexes. Specific oleaginous compositions suitable for use with this invention are disclosed.

Mixing efficiencies and energy requirements of various motionless mixer designs for laminar mixing applications

Abstract: The effectiveness of five designs of motionless mixer for laminar mixing has been assessed using an autocorrelation technique for mixture quality assessment based on colour development of two streams of epoxy resin, one coloured black, the other white The performance of the mixers was assessed by referring improvement in mixture quality to the power consumption required by each mixer design, and the results compared with the recent studies of Allocca (1) and of Pahl and Muschelknautz (4)

Mass transfer to the free interface in stirred vessels

Abstract: Liquid-phase mass transfer coefficients between gas and a flat liquid interface in a stirred tank are proportional to the average rate of energy dissipation raised to the power of one third for water and one quarter for organic solvents. This discrepancy can be attributed to the presence of surface active contaminants in aqueous systems. The critical value of the Reynolds number for the transition between the regime controlled by the small scale turbulence to that controlled by large scale eddies is about 100. The Levich-Davies model was found inappropriate in this case.