General Signal Corporation

Richard A Howk

Ronald J Weetman

Thomas A Post

Marlin D Schutte

Stephen L Markle

William F Hutchings

Michael A Giralico

Michael J Preston

Craig B Bahr

Kenneth S Lally

In order to sparge gas into a liquid or liquid suspension in a tank wherein a principally axial flow pattern downwardly towards the bottom of the tank and then upwardly along the side wall of the tank returning axially downward is established by an axial flow impeller, a disc of a diameter less than the diameter of the impeller is spaced axially therefrom in the direction of the outlet flow towards the bottom of the tank from the impeller so as to turn the axial flow, radially, thereby establishing a pressure gradient which prevents the collection of gas released by a sparge between the disc and the bottom of the tank and flooding of the impeller. The gas is released in the axial flow from the tip region of the impeller thereby facilitating the shearing of the gas into fine bubbles promoting mass transfer of the gaseous phase into the liquid phase in the tank. Since flooding is inhibited, as much as six times the volume of gas (gas rate) can be handled as may be the case without the disc.

Mixing system for dispersion of gas into liquid media

A mixing system in a tank provides a flotation cell for froth collection of minerals such as metallic ores thereby separating such ores from other materials with which they are mined and enabling a concentrated ore component to be collected. The mixing system maintains particles containing the ores in a circulating liquid suspension in a contact zone where bubbles are discharged. Ore particles are attracted and attached to the bubbles. The bubbles rise and float to the top of the liquid for collection of the concentrated ores. The mixing system includes a radial flow impeller and an axial flow impeller which are attached for rotation on a common shaft, with the axial flow impeller below the radial flow impeller. The radial flow impeller is disposed in a space between a disc, which rotates with the radial flow impeller and another disc which is stationary, and may be a flange of a pipe around the shaft and extending above the surface of the liquid. Air or other suitable aeration medium is brought, either under pressure or by suction created by the radial flow impeller, into the space. The aeration medium is radially discharged in the form of bubbles. The axial flow impeller is downwardly pumping and provides a circulation path which sweeps across the bottom of the tank, then upwardly along the sides of the tank returning through the radial discharge of bubbles back into the inlet or suction side of the axial flow impeller. The circulation is limited to the contact zone. A quiet or quiescent zone above the contact zone is left through which the bubbles with attached ore particles can rise without bursting and form the froth containing the concentrated ore for collection.

Mixing system for separation of materials by flotation

In order to efficiently mass transfer from gas, particularly air, into liquid or liquid suspensions with enhanced efficiency in terms of the mass of the gas transferred to the liquid, the gas is released or sparged through a plurality of open pipes which are disposed in a space between the bottom of the tank containing the liquid or liquid suspension and an axial flow impeller which creates a flow path downwardly past the outlet ends of the pipes. Turbulence is enhanced even though the air leaves the pipes at low velocity rather than in a jet through the use of a Bernoulli air trapping ring and plates. The ring and plates encounter the flow produced by the axial flow impeller successively. The ring distributes the air and assists in defining a low pressure region below the ring. A low pressure region also is defined by the plates on the underside thereof. The underside of the plates is in the vicinity of the outlets of the pipes. Distribution fins taper away from the outlet and provide for a spacial distribution of the low pressure gas. The low pressure air may exit the outlets of the pipes at a pressure of a few PSI greater than the liquid pressure at the outlets which may be in the range of 10% greater pressure than the liquid pressure at these outlets. The plates, especially at their edges, provide turbulence in the liquid flow to facilitate transfer of the mass of the gas to the liquid.

Mixer sparging apparatus

A rotatably driveable enhanced-flow impeller system is provided for pumping at least one liquid in a tank through an outlet port thereof. A radial flow impeller has a first impeller face disposed proximate the bottom of the tank and proximate or extending into an inlet port for liquids in the tank bottom. The radial flow impeller has a plurality of blades with radially outermost blade tips terminating along a blade terminating circle. Disposed adjacent a second opposing face of the radial flow impeller is a radial flow extension plate which preferably extends radially outwardly along the second face by a radial distance beyond the blade terminating circle. The radial flow extension plate may be fixedly attached to the second impeller face. The enhanced-flow impeller system can be used advantageously in conjunction with an axial flow impeller disposed on a common drive shaft in an upper portion of the tank, to form with enhanced effectiveness a liquid--liquid dispersion as droplets of at least one liquid in at least one other immiscible liquid and to distribute the dispersion uniformly through the tank volume during a dispersion residence time in the tank.

Impeller system and method for enhanced-flow pumping of liquids

A rotatably driveable enhanced-flow impeller system has a radial flow impeller with a first impeller face disposed proximate the bottom of the tank and proximate or extending into an inlet port for liquids in the tank bottom. The radial flow impeller has a plurality of blades with radially outermost blade tips terminating along a blade terminating circle. The blades and inlet port are contoured to reduce shear stress on the liquids. Disposed adjacent a second opposing face of the radial flow impeller is a radial flow extension plate which preferably extends radially outwardly along the second face by a radial distance beyond the blade terminating circle. The radial flow extension plate may be fixedly attached to the second impeller face. The enhanced-flow impeller system can be used advantageously to form efficiently and with enhanced effectiveness a liquid - liquid dispersion as droplets of at least one liquid in at least one other immiscible liquid and to distribute the dispersion uniformly through the tank volume during a dispersion residence time in the tank, while avoiding, because of minimization of shear stress on the liquids, the formation of fine (smaller) of droplets of one of the liquids that do no readily separate from the other liquid upon settling.

Impeller system for mixing and enhanced-flow pumping of liquids

In order to circulate a two-phase system (a suspension of solid particles in liquid) in a large (e.g., 100 ft. diameter) and shallow tank (e.g., where the liquid level, Z, to tank diameter, T, ratio is 0.4), a cluster of side entering mixers is used and a desired flow pattern (much like that obtained from a top entering mixer) along the bottom and top of the material in the tank and vertically along the walls of the tank is obtained by (a) rotating an end mixer in the cluster in opposite sense to the other mixers, (b) spacing the mixers so that the interference is reduced between the flow produced by the mixers at the wall of the tank opposite from the mixers, and (c) by tilting the mixers so that the flow intersects the bottom near the wall of the tanks opposite from the mixers. It is believed that the system geometry and direction of rotation of at least one end mixer in the cluster prevents the development of angular momentum of the material in the tank thereby avoiding swirling thereof and consequent asymmetrical, nonuniform flow patterns which are not optimum for particle suspension.

Side entry fluid mixing

In order to obtain efficient gas dispersion (aeration where air is the gas) in mixing systems where the circulating impeller is offset from the center of the tank containing the medium in which the gas is dispersed or sparged while being circulated, flooding of the impeller due to entrainment of gas released by the sparging device (a pipe or ring having as outlets) because of the asymmetrical return flow of the medium circulating in the tank which entrains the gas and brings the gas into the area swept by the impeller as it rotates, is avoided by arranging the sparging device to prohibit the release of gas into a region, including a sector of the swept area, where the return flow responsible for flooding occurs. This sector has been found to lie along a line between the center of the tank and the axis of rotation of the impeller. The gas dispersion mixing system is especially useful in dispersion of gas into large volumes (e.g. 20,000 cubic feet). There, a plurality of axial flow impellers and associated sparging devices are circumferentially spaced around the center of the tank. The sparging devices are arranged so that gas is prohibited from being released in the region where the gas is subject to being entrained into the impellers swept area by the asymmetrical return flow, thereby avoiding flooding and increasing gas dispersion (mass conversion) in the mixing system.

Mixing system for gas dispersion in liquids or liquid suspensions

Side entering mixer apparatus has an impeller with an axis of rotation above and along the bottom of a tank in which the material (liquid or liquid suspension) to be mixed is disposed. In a discharge region in front of the impeller and in close proximity to the front of the impeller, there is disposed a flow straightening vane which removes substantially any radial component of flow. By removal of the radial flow component, helical flows which interact in the discharge region and cause pulsation of flow into the inlet region (between the rear surface of the impeller and the side wall of the tank from which it projects) are substantially eliminated and potentially catastrophic stress-induced failures in the side entering mixer and its seals are avoided.

Side entry mixer apparatus

A mixer impeller made up of paddle shaped blades, which near their tips (e.g., at 90% of the radius of the impeller from its axis of rotation) are of a width at least 40% of the impeller's diameter. The blades also having camber and twist. They are formed by establishing bending moments which form the blades into sections which are curved and flat, with the flat sections being at least in the center area of the base of the blades.

Methods of fabricating impeller blades for mixing apparatus

Chuck mechanisms quickly connect and enable quick disconnection of an impeller shaft of a mixer from the drive shaft of the motor unit. A spindle has a keyway which enables a key, either a detent key which is movable in the keyway or a key which is provided by pins extending from the shaft, to be aligned in locking position where the key transfers the thrust from the spindle to the shaft or an unlocked position where the shaft is rotated out of the locking position and may be removed from the spindle. The key is retained in locking position by an outer sleeve or collar having a slot which enables the key to move away from the shaft when the shaft is rotated to the unlocked position. When the collar is rotated to move the slot away from the key, the key is locked against outward movement. The keyway may be sufficiently large to enable the flat on the shaft to tilt the key so as to provide wedging action of the key against the spindle sleeve and tighten the shaft on the sleeve so as to preclude slipping when greater torque is needed by the mixing impeller. In another embodiment, a tapered bolt is used in a cross-bore through the spindle sleeve, which bolt and a flat with a cylindrical undercut define a keyway. A tapered shoulder portion of a bolt which extends into the keyway defines a guide which permits the shaft to be inserted only with the flat in alignment with the cross-bore and keys the sleeve to the shaft when the bolt is screwed into the cross-bore.

Chuck mechanism for detachably connecting impeller shaft and drive unit

The gas outlet of a pipe or other sparging device is encompassed by a cover or cap which is located between the gas outlet and the mixing impeller at the bottom of a vessel. The cap is closed at the top and has a side wall so that the gas bubbles disperse around the lower rim of the wall. The wall may be non-symmetric, such as square in cross section, so as to be at different radial positions with respect to the gas outlet. The gas bubbles, even if released in pulses are distributed spatially and in time. The lower rim is preferable serrated (as a saw tooth edge) with the teeth being of different height, thereby further spreading the distribution of the bubbles as they are dispersed. The overlap or distance between the rim and the gas outlet is such that a sufficient quantity of gas is confined around the outlet to damp pressure pulsations when the pressure of the gas at the outlet does not significantly exceed the hydrostatic pressure at the outlet into the liquid. It is believed that the cap defines an acoustic filter which damps and effectively reduces pressure pulses. A turning cone below the top of the cover and facing the outlet may be used to facilitate more uniform distribution of the gas bubbles.

Mixing system for dispersing a compressible fluid such as gas into

A mixer which provides axial flow in a non-uniform flow field, such as may be established by gas which is sparged into a medium being mixed in a tank, and provides large axial flow volume without flooding and withstands variable loads on the blades thereof, thereby providing for reliable operation. The mixer impeller is made up of paddle shaped blades, which near their tips (e.g., at 90% of the radius of the impeller from its axis of rotation) are of a width at least 40% of the impeller'a diameter. The blades also having camber, twist and flat sections. The flat sections being at least in the center area of the base of the blades. The hub for attaching the blades to the shaft of the mixer has radially extending arms with flat surfaces. The base of the blades are spaced from the shaft to define areas therebetween. These areas are reduced in size, thereby limiting the passage of sparging gas between the blades and the shaft and the strength of the coupling between the blades and the shaft are enhanced by backing plates of width greater than the width of the arms. These backing plates are fastened between the arms and the flat sections of the blades. Bolts extending through aligned holes in the arms, backing plates and blades provide strong and secure attachment of the impeller blades to the shaft so that the impeller will operate reliably in the environment which provides variable loads on the blade.

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Rochester, NY, United States of America

Richard A Howk