Showing papers on "Mixing (process engineering) published in 1994"

Method for continuously mixing fluids

Abstract: Apparatus and method of hydrating a particulated polymer and producing a well treatment gel includes a mixer for spraying the polymer with water at a substantially constant water velocity and at a substantially constant water spray pattern at all flow rates of the water. A centrifugal diffuser is connected to the mixer for receiving the mixture, centrifugally diffusing the motive energy of the mixture, and hydrating the mixture into a gel. A centrifugal separator and constant velocity jet pump may be connected between the mixer and the centrifugal diffuser. A dilution valve is connected to the discharge of the centrifugal diffuser for mixing water with the gel at a substantially constant mixing energy at all flow rates of the gel and producing a diluted gel. A viscometer may be connected to the discharge of the dilution valve for measuring the viscosity of the diluted gel and regulating the flow of gel from the centrifugal diffuser to the dilution valve in order to control the viscosity of the diluted gel.

Methods and apparatus for mixing bone cement components using an evacuated mixing chamber

Abstract: Methods and apparatus are set forth for preparing and delivering bone cement formed by combining a powdered polymer component and a liquid monomer component. The powdered polymer component is stored in an evacuated mixing chamber. The liquid monomer component, according to one specific aspect of the invention, is introduced into the mixing chamber by a control mechanism which causes the stored powder to be "substantially wet", i.e., all of the powdered polymer component is wet to at least some degree and is otherwise devoid of powder pockets. The control mechanism, according to a preferred embodiment of the invention, stages the release of the liquid monomer into the vacuum packed powder chamber, under the effect of the vacuum, in a timed sequence using a plurality of monomer distribution channels. The distribution channels, which in a preferred embodiment of the invention include liquid component diffusers, insure the substantial wetting of the stored powder by delivering the liquid in parallel to different portions of the mixing chamber. The substantial wetting of the powder is designed to ultimately insure a homogeneous bone cement mix.

Effect of mixing time on the lubricating properties of magnesium stearate and the final characteristics of the compressed tablets

Abstract: The effect of mixing time on hardness, disintegration time and ejection force in tablettlng of magnesium stearate and lactose granules was studied. The hardness of the tablets decreased with an inc...

A Coefficient to Characterize Mixing in Solar Water Storage Tanks

Abstract: A dimensionless coefficient is developed to characterize the level of mixing in solar water storage tanks. The MIX number, based on the height weighted energy, or moment of energy, in the tank, ranges from 0 to 1, with 0 representing a perfectly stratified (unmixed) tank and 1 representing a fully mixed tank. Limiting values are based on theoretical determinations of the maximum and minimum values of the moment of energy in a tank without mixing and a tank with complete mixing, respectively. Use of the new MIX number is illustrated by experimental data obtained in a 372-liter storage tank operated with both a conventional drop-tube inlet and a rigid, porous stratification manifold.

Competition between TiCl4 hydrolysis and oxidation and its effect on product TiO2 powder

Abstract: The competition between hydrolysis and oxidation of TiCl[sub 4] during vapor-phase synthesis of titania powders was experimentally investigated. The effects of reactor temperature, reactant mixing and H[sub 2]O/TiCl[sub 4] ratio were studied in a hot wall aerosol flow reactor. The presence of water vapor resulted in rounded particles instead of the faceted ones observed in the absence of water; this effect was most pronounced at lower reactor temperatures. Mixing the water and TiCl[sub 4] vapor streams at low temperature resulted in anatase titania. Larger aggregates with smaller primary particles were observed for powders synthesized in the presence of water vapor. The mixing temperature of the water and TiCl[sub 4] vapors, as well as the H[sub 2]O/TiCl[sub 4] ratios, did not affect the aggregate size or specific surface area. Analysis of micrographs of titania aggregates made in the presence of water revealed that the fractal dimension increased with process temperature.

System for the preparation of a fluid concentrate intended for medical use

Abstract: Apparatus for the preparation of fluids intended for medical use is disclosed, including a water source and at least one cartridge or other vessel containing a solid such as a powder which is to be dissolved in the water for preparation of the desired fluid. The apparatus includes a container such that the water and a powder can be mixed and a concentrate provided in the container, and a recirculation circuit for recirculation of the water or concentrate solution into the container for further mixing of the water and powder to prepare a concentrate having a predetermined concentration.

Hydrocracking process involving colloidal catalyst formed in situ

Abstract: In a hydrocracking process a feed mixture comprising: heavy oil containing asphaltenes and sulfur moieties; an oil-soluble, metal-containing compound additive (such as iron pentacarbonyl or molybdenum 2-ethyl hexanoate), which additive is operative to impede coalescence of coke precursors and which forms hydrocracking catalytic particles in situ; and, optionally, a hydrocarbon diluent which is a solvent for asphaltenes and which will assist with dispersion of the additive; is mixed for a prolonged period at low temperature (e.g., 80° C.-190° C.) in a first vessel or vessels to disperse the additive without significantly decomposing the additive. Preferably, the product mixture is then digested in a second vessel or vessels by mixing it at an elevated temperature (e.g., 250° C.), to decompose the additive. The resulting mixture is then heated to hydrocracking temperature (e.g., 450° C.) and introduced into a reactor. A hydrogen flow, sufficient to maintain mixing in the reactor and efficient (e.g., greater than 98%) stripping of light ends (e.g., end point boiling 20° C.), is provided. the steps of low temperature mixing to achieve dispersion without additive decomposition, preferably digesting to decompose the additive under mixing conditions, and mixing in the reactor with stripping, combine to yield well dispersed, colloidal catalytic particles which function to impede coke evolution and provide high conversion of the high boiling (504° C.) fraction of the feedstock.

How to disperse gases in liquids

Abstract: Mixing of a gas in a liquid is required in fermentation operations and a variety of oxygenation and hydrogenation processes. Agitation increases the mass transfer between the gas and the liquid phase. Gas-liquid reactors equipped with agitators are often operated at high power input and large gas holdup, making these units among the most difficult to design. Modern high-efficiency and concave-blade disc impellers provide the proper balance of flow, turbulence and shear for most applications. For an overview of the state of the art in gas-liquid agitation, a number of excellent reports are available. This article aims to present practical design guidelines while explaining the basics of gas-liquid mixing. It expands on design procedures presented in 1976 by Hicks and Gates and capitalizes on recent advances in flow-visualization techniques, development of new gas-dispersion impellers and improved understanding of the dispersion process itself. Methods to calculate power draw, gas holdup and mass-transfer rate are illustrated with examples. It is shown that concave-blade turbines provide better performance than the traditional flat-blade units.

The influence of vessel height and top-section size on the hydrodynamic characteristics of airlift fermentors.

Abstract: Fermentations of the yeast Saccharomyces cerevisiae were carried out in a 90 to 250-L working volume concentric tube airlift fermentor. Measurements of liquid circulation velocity, gas hold-up, and liquid mixing were made under varying conditions of gas flowrate, vessel height, and top-section size. Both liquid circulation velocity and mixing time increased with vessel height. Liquid velocity varied approximately in proportion to the square root of column height, supporting a theoretically based relationship. The effect of vessel height on gas hold-up was negligible. The height of the top-section had a significant effect on liquid mixing. Mixing time decreased with increasing size of the top-section up to a critical height. As the top-section was expanded beyond this height, little improvement in mixing was seen. This indicated the presence of a two-zone flow pattern in the top-section. Liquid velocity and gas hold-up were essentially independent of top-section height. (c) 1994 John Wiley & Sons, Inc.

Method and apparatus for unmixed combustion as an alternative to fire

Abstract: Methods and apparatus are provided for combustion systems wherein fuel may be burned completely with use of air as the oxidant, without the necessity for completely mixing the fuel with the air before, during, or after the combustion process. A bed of readily reducible metal oxide, the reduced form of this metal oxide being readily oxidized, is placed within a combustion system. The air and fuel are contacted with the bed at an elevated temperature, with the metal oxide oxidizing the fuel and being regenerated by the air. In one embodiment, complete combustion of fuel occurs without complete mixing of fuel and air. In other embodiments fuel can be burned with little or no mixing with a the combustion process, or fuel can be burned with little or no mixing with air, before, during, or after the combustion process, thereby avoiding a number of disadvantages of such mixing.

Apparatus and method for injecting dry particulate material in a fluid flow line

Abstract: An apparatus and method for injecting dry particulate material into a fluid flow line including a removable material supply unit (18) having an outer rigid container (55) and a sealed flexible bag (54) for the dry particulate material. The removable material supply unit (18) is mounted on a container support (13) above a mixing chamber (12) with a valve member (40) controlling the flow or dispensing of the dry particulate material into the mixing chamber (12). A pump (32) when energized exerts a vacuum in the mixing chamber (12). Water enters the mixing chamber (12) from an elliptical discharge opening (10) tangential to mixing chamber (12) to provide a vortex. Pump (32) exerts a vacuum within the mixing chamber (12) above the level of the water so that any upward migration of moisture from the water in the mixing chamber (12) is prevented by the vacuum when pump (30) is energized. Additional mixing occurs in a dynamic mixing manifold (28) to provide a solution of the dry particulate material within the water for injection of the solution within a pressurized fluid flow line (35) to a suitable facility (S).

Two component fluid spray gun and method

Abstract: An air-operated fluid spray gun for mixing multiple fluids together almost simultaneously with depositing the mixture on a surface by directing an atomized stream of one fluid out the end of the gun barrel toward the surface and injecting an atomized stream of another fluid generally radially into the first stream so that the streams mix thoroughly and the mixture is almost simultaneously deposited on the surface.

Fuel injector and method of operating the fuel injector

Abstract: A fuel injector (28) utilizing air, a liquid fluid and a gaseous fluid is disclosed. Various construction details are developed to enhance mixing and reduce carbon monoxide emissions for a given level of nitrous oxide emissions. In one detailed embodiment, the fuel nozzle (28) has two radially spaced passages (68, 104) for air having swirlers (86, 114), a liquid fluid passage (57) for water therebetween and a gaseous fluid fuel passage (118) which injects fuel into one of the air passages.

Method and apparatus for producing oxygen

Abstract: An air separation apparatus and method for producing a gaseous oxygen product at a delivery pressure. A, filtered, compressed and purified air stream is formed and preferably divided into first and second air streams. The air contained within the first air stream is separated by a low temperature rectification process operating in accordance with a Claude cycle to produce liquid oxygen in a lower pressure column with a double column air separation unit. A Claude expander expands at least a major portion of the air contained within the first air stream into the high pressure column. The second air stream is compressed and partially cooled and is then expanded with the performance of work which is in turn applied to the work of compression of the second air stream. Liquid oxygen is pumped from the lower pressure column to substantially the delivery pressure and is vaporized within a mixing column against the second air stream which is also introduced into the mixing column. A liquid stream composed of the liquid produced in the mixing column is then introduced into an intermediate location of the lower pressure column to add the refrigeration of the second air stream to the process.

High-pressure vapor-liquid equilibria for mixtures containing a supercritical fluid

Abstract: Supercritical fluid extraction has been proven as an efficient separation method for some specific industrial applications. The knowledge of the phase behavior of supercritical systems plays an important role in the process design. High pressure vapor-liquid phase equilibrium compositions were measured for the binary systems of carbon dioxide + 2-methyl-1-pentanol, carbon dioxide + 1-octanol, and carbon dioxide + 1-decanol over a temperature range between 348.15 and 453.15 K. In addition to the new data, a variety of supercritical fluid systems was used to test the validity of the Peng-Robinson and Patel-Teja equations of state accompanied by several types of mixing rules. In general, the Peng-Robinson equation incorporated with the cubic mixing rule yielded the best representation.

Studies of Mixing Efficiency in Batch and Continuous Mixers

Abstract: In this paper we have reviewed some of the results of 3-D, isothermal flow simulations for batch and continuous mixers. The flow patterns were obtained by using FIDAP, a fluid dynamics analysis package based on the finite element method. The problem of time dependent flow boundaries due to the rotations of the rotors in the Banbury mixer, was solved by selecting a number of sequential geometries to represent a complete cycle. Non-slip boundary conditions for the stationary and moving surfaces were employed. For different regions of continuous mixers we used a nominal value for the normal stress difference in the axial direction as an additional boundary condition. The results obtained in terms of velocity and pressure profiles were further processed to analyze mixing efficiency. Dispersive mixing efficiency was studied in terms of the shear stresses generated and the elongational characteristics of the flow field. Distribution plots for shear stresses and a parameter λ, quantifying the elongation...

Advanced impeller geometry boosts liquid agitation

Abstract: A traditional agitator impeller often functions as a rather inefficient pump because of the way it produces fluid motion and pressure head. However, one can improve the amount of flow or shear generated by an impeller at constant power consumption and torque by changing its design. For example, a high-efficiency, axial-flow impeller produces more fluid motion per unit of power at constant torque than an otherwise similar pitched-blade turbine. The more-vigorous fluid motion cuts blend time and enhances heat-transfer in various flow-controlled mixing operations, such as blending of miscible fluids. For most applications, a higher degree of agitation intensity can be achieved on the same machine by substituting a high-efficiency impeller for a conventional pitched-blade unit. The high-efficiency impeller features a larger geometric pitch angle (30--60 deg) at the hub than at the tip (10--30 deg). Results from recently conducted controlled experiments indicate the beneficial effects of the high-efficiency impeller on blend time and heat-transfer coefficients in liquid-liquid mixing as well as solids suspension. This articles focuses on liquid agitation, with discussions of solids suspension set aside for a forthcoming piece in this series of articles on mixing.

Stable solid pharmaceutical compositions containing enalapril maleate

Abstract: Enalapril maleate is unstable when associated with many excipients commonly used in the manufacture of pharmaceutical compositions. Stable solid compositions are provided by mixing enalapril maleate into a carrier that is comprised primarily of water-soluble carbohydrates and contains a lubricant other than magnesium stearate, a preferred lubricant being zinc stearate.

Liquid chromatograph having a micro- and semi-micro column

Abstract: A liquid chromatograph includes pumps for supplying solvents, a mixer for mixing the solvents, a controller for controlling a mixing ratio of the solvents in the mixer, a chromatograph column for separating a sample carried with the solvents, a flow path control valve for supplying the sample together with the solvents to the chromatograph column, and a detector for detecting the sample supplied thereto, wherein the mixer includes a mixing chamber and a porous medium accommodated in the mixing chamber, the porous medium having a size and shape in conformity with a size and shape of said mixing chamber such that no substantial gap is formed between an outer surface of the porous medium and an inner surface of the mixing chamber.

Liquid mixing in internal loop airlift reactors

Abstract: The airlift reactor is a promising reactor for two- and three-phase reactions due to its advantages of high fluid circulation, mass and heat transfer, short mixing time, low shear stress, and energy consumption. It has been widely applied in biochemical fermentation, chemical reactions, and biological wastewater treatment processes. Liquid mixing in the riser and downcomer of two- and three-phase internal loop airlift reactors as well as the overall liquid mixing were studied. Tracer was injected into the airlift reactors, and pH sensors were employed to measure the variations of tracer concentration in the riser, downcomer, top, and bottom sections. The Bo number in individual sections of the airlift reactors were obtained by time domain analysis of these concentration variations. It was found that the degree of mixing in the riser was higher than that in the downcomer. Moreover, mixing in the two-phase system was superior to that in the three-phase system, and the degree of mixing of the calcium alginate system was lower than that of the polystyrene system. Minimum values of the overall axial dispersion coefficient existed in the relationship between the overall axial dispersion coefficient and solids loading.

Solid fuel using porous coal as raw material, its production and apparatus for production

Abstract: PURPOSE:To obtain a low-cost solid fuel, capable of suppressing spontaneous flammability, excellent in transportability and storability and useful for boilers, etc., by mixing a mixed oil containing a heavy oil, etc., with a porous coal and treating the resultant raw material slurry under specific conditions. CONSTITUTION:This solid fuel is obtained by mixing a mixed oil containing a heavy oil and a solvent oil (blended in amounts at preferably 1-20 weight ratio of the mixed oil/anhydrous coal) with porous coal, providing a raw material slurry, heating the resultant slurry at 100-250 deg.C, advancing the dehydration of the porous coal, comprising the mixed oil containing the heavy oil and solvent oil in pores of the porous coal and then separating the solid from liquid in the treated slurry.

Baking improver compositions

Abstract: A baking improver composition in a homogeneous solid shaped form which includes one or more baking improver agents and at least one binding agent which permits disintegration of the solid form when in use for mixing a dough Such a composition form may weigh between 25 grams and 2 kilograms and is capable of manual division into smaller dosage units and obtained, for example, by compacting a powder composition based on flour and containing about 20 to 30% by weight of lecithin as a binding agent and baking emulsifier

Methods of displacing liquids through pipes

Abstract: Improved methods of displacing a first liquid through a pipe with a second liquid while preventing the first and second liquids from mixing are provided. In accordance with the methods, a plug is formed in-situ in the pipe between the first and second liquids by injecting a self-thickening liquid therein and permitting the liquid to thicken. The formed plug and the first liquid are then displaced through the pipe with the second liquid. The methods are particularly suitable for carrying out subterranean well bore cementing operations wherein cement slurries are displaced through pipes disposed in well bores.

Fluid management system for a zero gravity cryogenic storage system

Abstract: The fluid management system comprises a mixing/recirculation system including an external recirculation pump (14) for receiving fluid from a zero gravity storage system (12) and returning an output flow of the fluid to the storage system. An internal axial spray injection system (30) is provided for receiving a portion of the output flow from the recirculation pump. The spray injection system thermally de-stratifies liquid and gaseous cryogenic fluid stored in the storage system.

Aeration apparatus for producing ultrapure water

Abstract: In an aeration apparatus and method for producing ultrapure water, a device for vigorously mixing an aeration gas with untreated water is attached to a water pipe through which the water is fed to a reaction tank. The device vigorously mixes the aeration gas with the untreated water in the water pipe before the water reaches the reaction tank. The reaction tank can be smaller, an aeration system for producing ultrapure water can be simpler, and the efficiency of the aeration system can be improved.

Process for producing polystyrene foam

Abstract: The present invention relates to a process to produce polystyrene foam comprising mixing a predetermined amount of masterbatch mix and a styrenic polymer, heating this mixture, injecting CO 2 and/or nitrogen, in gas or liquid form, as a blowing agent and subsequently extruding, cooling and drying the resulting polystyrene foam.