US3417974A

US3417974A - Gas dispersion device

Info

Publication number: US3417974A
Application number: US593482A
Authority: US
Inventors: Emmett P Glynn
Original assignee: General Dynamics Corp
Current assignee: General Dynamics Corp
Priority date: 1966-11-10
Filing date: 1966-11-10
Publication date: 1968-12-24
Anticipated expiration: 1985-12-24

Description

Dec. 24, 1968 E. P. GLYNN GAS DISPERSION DEVICE Filed Nov. 10, 1966 INVENTOR f/v/wzrr Q zy/v/v ATTORNEYS United States Patent 3,417,974 GAS DISPERSION DEVICE Emmett P. Glynn, Lemont, Ill., assignor to General Dynamics Corporation, New York, N.Y., a corporation of Delaware Filed Nov. 10, 1966, Ser. No. 593,482 3 Claims. (Cl. 261-28) ABSTRACT OF THE DISCLOSURE A gas dispersion device including a chamber of circular cross section wherein a plurality of circular perforated plates are rotated upon a common shaft. The plates are spaced apart by unobstructed regions, and the inlet stream of gas and liquid is tangentially pumped into the chamber in a direction opposite to the direction of rotation of the perforated plates. The chamber outlet is axially aligned with the shaft.

This invention relates to gas dispersion devices and more particularly to gas spargers designed to disperse large quantities of gas in a liquid in the form of small bubbles.

It is an object of the present invention to provide a simple gas dispersion device which will produce an intimate mixture of gas with liquid. It is another object of the invention to provide a gas sparger simple in design and construction which will effectively incorporate a relatively large volume of gas into a liquid stream.

A further object is to provide a gas sparger employing mechanical agitation to provide an eflicient dispersion of gas in a liquid. Still another object is to provide a gas dispersion device for reducing bubbles in a liquid stream to extremely small size employing mechanical agitation. These and other objects of the invention are more particularly set forth in the following description of devices embodying various features of the invention and in the accompanying drawings wherein:

FIGURE 1 is diagrammatic view of a gas sparger embodying various features of the invention shown with parts in section;

FIGURE 2 is an enlarged sectional view taken generally along line 22 of FIGURE 1; and

FIGURE 3 is an enlarged fragmentary view of a portion of a device shown in FIGURE 2.

The invention provides an improved gas sparger 11 capable of providing intimate mixing of a gas with a liquid. The gas sparger 11 includes a sparging unit 13 wherein the gas is initially introduced to a liquid stream coupled with a dispersion device 15 which subjects the crude gas-liquid mixture to a high-speed shearing action. As a result of this high-speed shearing action, the stream exiting from the dispersion unit 15 comprises an intimate dispersion of minute bubbles of gas in the liquid.

The dispersion device 15 is simple in design and operation, generally comprising a casing 17 which defines an interior chamber 19 of generally circular cross section and a plurality of perforated discs or plates 21 rotatively mounted in the chamber 19 on a common axis. An inlet 23 and an exit 25 from the chamber 19 are located so that the gas-liquid mixture must pass through at least one of the perforated discs 21 as it traverses the dispersion device 15. The inlet 23 to the casing 17 is such that the gas-liquid mixture is pumped into the dispersion unit adjacent the periphery of the circular cross section of the chamber and in a direction generally tangential thereto. Entry of the pumped fluid mixture in this manner causes a clockwise flow of the fluid mixture, as viewed in FIGURE 1. The perforated discs 21 are rotated counterclockwise, as viewed in FIGURE 1, and this rotation in the opposite direction achieves the desired highspeed shearing action. In addition, the exit 25 from the chamber 19 is coaxial with the axis of rotation of the perforated discs 21 and is thus at a 90 angle to the inlet 23 which is generally in the plane of rotation. This disposition enhances the exposure of the mixture to the shearing action as it is forced to turn from its original direction of flow and pass through one or more of the plurality of rotating perforated disc 21 to reach the exit 25.

The sparging unit 13 comprises a sparging chamber 47 formed by a hollow T member 29 wherein the initial crude mixture of gas in liquid is made. The T member 29 has an inlet leg 31 for the entry of the liquid stream, an inlet leg 33 for the entry of the gas, and an outlet leg 35 for the exit of the fluid mixture of liquid and gas. All three of these legs of the T member 29 are provided with female threads.

A threaded connector assembly 37 joins the liquid inlet leg 31 of the T member to a pump 39. The inlet 41 of the pump 39 is connected to a suitable source 43 of the desired liquid into which the gas is to be dispersed. The pump 39 is suitably driven to provide the desired continuous flow rate of liquid through the gas sparger 11.

A threaded plug 45 having a central hole drilled therethrough is screwed into the gas inlet leg 33 of the T member 29. A sparge tube assembly 47 passes through the hole in the threaded plug 45 and is appropriately sealed thereto. The inlet end of the sparge tube assembly 47 is suitably connected to a blower 49, the inlet 51 of which is connected to a source 53 of the desired gas. The outlet end of the sparge tube assembly 47 is covered with a suitable cylindrically formed screen 55 which aids in separating the How of gas into bubbles as it is introduced into the liquid stream flowing thereby. The gas is supplied at the proper rate at which it is desired to be introduced into the liquid stream and at a suitable pressure to facilitate the bubbling of the gas into the passing liquid stream. Depending upon the particular gas to be used for a certain operation, it may be possible to supply the gas from a source of gas under pressure, such as a container of liquified gas, and thereby eliminate the need for the blower 49.

A suitable threaded connector assembly 57 connects the fluid mixture outlet leg 35 of the T member 29 to the inlet 23 of the dispersion device 15. The perforated discs 21 in the chamber 19 in the dispersion device 15 are mounted on a horizontal shaft 59. Although the shaft 59 is horizontally disposed in the illustrated device, it could be operated in a vertical disposition or at an angle thereto. The individual perforated discs 21 are uniformly spaced apart from one another via spacing washers 61 and are secured on the shaft 59 by a nut 63 threaded on the end thereof. The discs should be spaced from one another a distance equal to between about one-half to one and one-half times the thickness of the discs 21. This arrangement provides an effective high-speed shearing operation without introducing excessive loss in fluid head.

The shaft 59 extends through an end wall of a motor housing 65 wherein a suitable electric motor and stufiing box (not shown) are contained. The perforated discs 21 are fixedly secured to the shaft 59 for rotation therewith via a suitable key (not shown). A circular mounting flange 69 which is appropriately secured to the end wall of the motor housing 65 provides support for the casing 17 which is connected thereto by a plurality of bolts 71. The junction between the circular flange 69 and the casing 17 is suitably sealed, as by a ring gasket (not shown). As shown in FIGURE 3, the circular discs 21 are provided with a plurality of holes 73 generally regularly spaced completely thereacross, as on circular center lines.

One illustrative embodiment of a gas sparger 11 of this general type includes a T member having three

legs

31, 33, 35 each with 1 /2 inch threaded circular openings. The gas sparging assembly 47 extends within the T member to the region of the outlet leg portion thereof where it terminates in a cylindrical screen, inch long, made of 120 mesh screening material (openings mils). The dispersion device 15 contains five perforated discs, each about 4 inches in diameter and about 0.031 inch thick. The discs 21 are spaced apart by 1 inch diameter washers 61 which are also about 0.031 inch thick. The discs 21 are perforated with holes 73 each about 4 inch in diameter using the overall pattern shown in FIGURE 3. Of course, holes of a different size may be used, and a larger or smaller number of holes may be employed. Preferably, the holes 73 cover at least about 40% of the total area of the perforated region of the disc 21, the perforated region being exclusive of the central portion covered by the washers 61. Preferably, the size of the holes 73 is between about 5% and about 25% of the radius of the disc 21.

Water at a temperature of about 55 to 60 F. is pumped through the gas sparger 11 at a rate of about 90 to 95 gallons per minute, using a centrifugal pump 39. The water leaves the pump 39 at a pressure of about 5 to p.s.i.g., and is at about atmospheric pressure when it exits from the dispersion device 15. The pressure is of course dependent upon the downstream pressure and would be correspondingly higher if the downstream pres sure is above atmospheric. The five perforated discs 21 are driven at a speed about 3200 r.p.m. in a counterclockwise direction, as viewed in FIGURE 1. Carbon dioxide gas at a temperature of about 50-60 F. and a pressure of about 10 to 15 psig. is supplied to the gas sparging assembly 47 at -a rate of about 90 cubic feet per minute (measured at standard temperature and pressure). It is found that the carbon dioxide is completely absorbed by the water resulting in the production of carbonated water containing between about 1.5 and 2 volumes of carbonation.

Carbonation to this extent at this pumping rate and conditions via the gas sparger 11 of this simple design is considered excellent.

The gas sparger 11 may also be employed to introduce nitrogen into refined cottonseed oil or salad oil for purposes of reducing the dissolved oxygen content thereof. If minute bubbles of nitrogen are introduced into salad oil containing some undesirable oxygen, it is found that the oxygen in the salad oil will leave the oil phase and migrate to the minute nitrogen bubbles. The nitrogen does not dissolve into the salad oil and thus is fairly readily separable from the salad oil. It is important to break-up the bubbles of nitrogen as finely as possible so that theinterfacial area between gas and liquid is as large as possible. When the separation is subsequently performed, the oxygen is removed with the nitrogen.

Using a gas sparger 11 of the size described above, refined cottonseed oil at a temperature between about 80 and 90 F. is pumped into the T member 29 at a rate about 60 gallons per minute and a pressure about 10 p.s.i.g. The 4 inch discs 21 are driven at about 3200 rpm, and the pressure drop through the gas sparger 11 is such that the cottonseed oil leaves through the exit 25 at a pressure just slightly above atmospheric pressure. Nitrogen is supplied to the gas sparging assembly 47 at about 80 F., at about 10 to 15 p.s.i.g., and at a rate of about 500 cubic feet per minute (measured at standard temperature and pressure). The high-speed shearing action of the gas dispersion device 15 eifectively treats the gas-liquid mixture being pumped therethrough so that all of the nitrogen supplied is held in the form of minute bubbles in the continuous phase of refined cottonseed oil stream leaving the exit 25 of the gas sparger. The operation of the gas sparger 11 in introducing large quantities of nitrogen at relatively high rates into cottonseed oil is considered excellent.

The invention provides a gas sparger of simple design and trouble-free operation. The gas sparger is low in cost and operates efliciently, introducing relatively large quantities of gas into a liquid stream that may be pumped therethrough at relatively high flow rate. The highspeed shearing operation created by driving the perforated discs 21 opposite to the direction of flow of the tangentially entering gas-liquid stream contributes to the efliciency of the dispersion device 15. In addition, placement of the exit 25 at right angles to the direction of flow of the entry stream (best seen in FIG. 2), together with the relatively close clearance between the edges of the discs and the interior Wall of the chamber 19, assures that the crude fluid mixture must thread its way through the perforations of the discs 21 that are rotating at high speeds, during the course of which travel the fluid mixture is subjected to the high-speed shearing effect.

Various modifications may be made to the illustrated device as would be obvious to one having the ordinary skill in the art without deviating from the scope of the invention which is defined solely in the appended claims. Various features of the invention are described in the following claims.

What is claimed is:

1. A device for dispersing gas in a liquid, which device comprises means defining a chamber of circular cross section, a plurality of spaced perforated plates mounted for rotation in said circular chamber on a common axis, the regions between adjacent of said spaced perforated plates each being unobstructed, a single fluid inlet which is located tangentially adjacent the periphery of said circular cross sectional chamber and through which a fluid stream of gas and liquid is fed into said chamber and enters tangentially thereto to provide the fluid stream with circular movement in one direction, a single outlet from said chamber which is located where the fluid stream entering said chamber must pass through at least one of said perforated plates before reaching said outlet, said outlet being coaxial with the axis of rotation of the perforated plates and at a angle with respect to the inlet, said plates being spaced apart by washers having not more than one-fourth the diameter of the plates, perforations in the plates covering at least 40% of the total area of the perforated region of the plates, the size of the perforations being between 5 and 20% of the radius of the plates, said fluid inlet being located between said plates, and means connected to said perforated plates for rotating said plates in a direction opposite to said one circular direction.

2. A device in accordance with claim 1 wherein said plates are circular discs of a diameter close to the diameter of said circular cross section and are uniformly spaced apart .from one another a distance equal to about one-half to one and one-half times the thickness of said plates.

3. A gas sparger comprising a dispersion device in accordance with claim 1, means defining a gas sparging chamber, means for pumping a liquid through said sparging chamber, means for introducing gas into said liquid in said sparging chamber, and means connecting the outlet portion of said sparging chamber to said fluid inlet of said dispersion device, said gas introduction means including a tube extending into said sparging chamber and a screen in said sparging chamber covering the outlet of said tube for separating the gas into bubbles as 5 6 it enters the liquid, said screen being in the form of a 2,791,404 5/1957 Kelly et a1. 259-9 hollow cylinder closed at one end and being made of 2,960,318 11/1960 Caillaud 259-9 screening material having openings of 5 mils in size. 3,120,377 2/1964 Lipschultz.

References Cited 5 RONALD R. WEAVER, Primary Examiner. UNITED STATES PATENTS U.S. Cl. X.R. 2,077,226 4/1937 DeBethune. 261122, 83; 259-9; 252359 2,383,946 9/1945 Tictig.