US2978234A

US2978234A - Diffuser tube

Info

Publication number: US2978234A
Authority: US
Inventors: Miles A Lamb
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1951-01-16
Filing date: 1954-08-26
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04

Description

April 4, 1961 M. A. LAMB 2,978,234 7 DIFFUSER TUBE Original Filed Jan. 16, 1951 3 Sheets-Sheet 1 M. A. LAMB DIFFUSER TUBE A ril 4, 1961 3 Sheets-Sheet 2 Original Filed Jan. 16, 1951 .Tnga WWW/6L.

@Mm, gm" q, 17735445917 M. A. LAMB DIFFUSER TUBE April 4, 1961 5 Sheets-Sheet 3 Original Filed Jan. 16, 1951 bu ow 8? NW R hm h@ 2,978,234 DIFFUSER TUBE Miles A. Lamb, Chicago, 11]., assignor, by mesne assignments, to Food Machinery and Chemical Corporation, San Jose, Calif., a corporation of Delaware Original application Jan. 16, 19'51, 'Ser. No. 206,237,

now'latent No. 2,815,943, dated Dec. 10, 1957. Divided and this application Aug. 26, 1954, Ser. No.

4 Claims. (Cl. 261-122) This invention'relates to a diffuser tube used for the aeration of liquid, or for the dispersion of gases or vapors therein, and more particularly to diffuser-tubes of collapsible, foraminated fabric into which the air or gas is supplied under pressure and throughthe interstices of which the air or gas passes in fine bubbles into the liquid in which the diffuser tube is immersed.

This application is a division of my application Serial No. 206,237, filed January 16, 1951, now Patent No. 2,815,943 of Dec. 10, 1957.

Diffusers of the type with which the present invention is concerned are employed in the activated sludge process of treating sewage, ore flotation processes, treatment of industrialwastes, various fermentation processes, and other chemical processes where gas-liquid contact is essential.

In the past such diffusers have in the main been made of porous carbon and ceramic material or by wrapping a cord about a hollow foraminated core so that air was permitted to pass through openings provided between adjacent convolutions of the cord., These diffusers were costly. In addition they became clogged more or less readily and had to be taken off the air main to be cleaned This made the maintenance cost rather costly.

Another type of known diffuser comprises a hose having attached thereto a fabric bag porous enough to permityair to flow therethrough into the surrounding liquid. One such diffuser is disclosed in the Kraut-Patent No. 1,849,146, issued March 15, 1932. This type of diffuser has several serious disadvantages. It has been found impossible to control the flow of air through the bag to provide uniform aeration of the liquid in which the bag is held because the bag is free to swing around inthe liquid and cause the air bubbles escaping from the bag to coelesce into larger bubbles of varying size. Another disadvantage of thistype of diffuser is the fact that the bag can not be deflated and inflated quickly enough to dislodge the solid matter deposited by the liquid in the pores of the bag. The deflation of the bag is so slow that the liquid in which the bag is immersed percolates through the fabric, bringing in solid matter which clogs the pores, and makes frequent cleaning necessary. An additional disadvantage of this type of diffuser is that the siz e of the bag that can be used is limited, andthe volume of-liquid that can be aerated by each bag is likewise limited. The diffuser tubes of the present invention comprise a rigid, non-porous anchoring member and a flexible, porous member secured thereto. Air or gas (aeriform body) is passed to the anchoring member and it'passes such tubes ganged together.

mersed, and yet be flexible enough to be collapsed quickly when the air or gas supply is shut off. The interstices of the fabric through which the air or gas flows may be varied as desired but preferably are small enough to cause the air or gas to pass through in fine bubbles to provide more efficient aeration or gasification.

Hereafter, in the description of the invention, reference will be made only to air, but with the understanding that by this term applicant contemplates gas or other aeriform body.

The porous-member of the diffuser tube may be made in any desirable length, and each such member is anchored at a plurality of points to a rigid pipe from which air is supplied to the member. The anchoring of each air diffuser member to a rigid pipe at a plurality of points prevents the member from swinging around in the liquid, and causes each of the finely divided bubblesto flow in a well defined path that prevents coalescence of the bubbles and results in uniform aeration of the liquid.

There may be a single diffuser tube or a plurality of When ganged together the tubes are preferably arranged in parallel relationship and are positioned adjacent one Wall of the tank to provide a wide band of air bubbles that will follow a circulatory path through the liquid to provide uniform aeration throughout the liquid. All of the rigid pipes in the ganged system are interconnected at both ends, thus insuring uniform pressure in each diffuser tube and throughout the system. The uniformity of the air pressure is essential to assure uniform aeration. When the I air pressure is not uniform throughout the system some flation of the tubes and the sudden collapse and subsequent prompt inflation of the tubes causes the solid matter to be broken away from the surface of the tubes.

The rigid anchoring member of each diffuser tube presents a flat, rigid surface adjacent the porous member, and the sudden collapse of the porous member causes it to slap against this flat surface to beat substantially all of the solid matter out of the porous fabric. If any solid matter is still lodged in the pores of any tube after the porous fabric is slapped against the adjacent rigid surface of the anchoring member it will be blown out by the pressure of the air when the'tube is inflated. The deflation is so rapid as to prevent infiltration of the surrounding liquid. The diffuser tubes are kept fairly clean at all times by merely turning the valve controlling the air in. order to deflate and then reinflate the tubes, with the result that the maintenance expense of the present system is relatively low. If a more thorough cleaningis necessary, or

therefrom to the porous member and from the porous sewage and the pressure of the liquid in whichit is imif any repairs are required, the diffuser tubes may be readily removed.

Another advantage of the present invention is the ease and low cost of manufacturing the diffuser tubes. These tubes may be fabricated like hose in continuous lengths, and cut off to provide any suitable length of diffuser tubes. The open ends of the tubes are quickly and easily sealed to provide an eflicient closure at each. end of the tube. It is not necessary to make the pipes of stainless steel, or similar expensive material, because.

they do not have a multiplicity of small orifices as in, the case where the pipe itself serves as the diffuser and must be protected against corrosion so that its orifices do not become clogged. The only openings in the pipe in; the presentconstruction are of comparativelylarg' cross:

section, and are connected to the manifold or to the diffuser by couplings or other means which prevent access to the openings by the liquid in which the diffuser tubes are immersed.

The structure of the present invention by means of which the above and other advantages are attained will be described in detail in the following specification, taken in conjunction with the accompanying drawings, showing two preferred illustrative embodiments of the invention, in which:

Figure 1 is a cross sectional view showing a sewage tank with a diffusing unit embodying the invention immersed therein; 7

Fig. 2 is a fragmentary top elevation of a diffuser unit in which one form of diffuser tube embodying the invention is used;

Fig. 3 is an enlarged side elevation of the, diffuser tube shown in Fig. 2;

Fig. 4 is an enlarged cross sectional view, taken along the line 44 of Fig. 3;

Fig. 5 is a fragmentary longitudinal sectional view showing the means for securing the longitudinal edge of the fabric of the diffuser tube to the air supply pipe;

Fig. 6 is a fragmentary longitudinal sectional view showing the means for securing the end of the fabric to the air supply pipe;

Fig. 7 is an exploded perspective view of the component parts of the diffuser tube and air supply pipe be fore they are assembled together;

Fig. 8 is a side elevation of another embodiment of diffuser tube and its air supply pipe;

Fig. 9 is a fragmentary top elevation of the air supply pipe for use with the diffuser tube of Fig. 8;

Fig. 10 is an enlarged fragmentary cross sectional View taken along the line 10-10 of Fig. 9, showing the means for securing the diffuser tube to the air supply pipe of Fig. 8; and

Fig. 1d is a fragmentary perspective view of the diffuser tube of Fig. 8.

In the drawings, the reference numeral 2 indicates a sewage tank having an inlet 3 and an outlet 4. A 1101- low stanchion 5 connects an air main 6 to an elbow 7. Air is forced through main 6 by any suitable pump or blower (not shown) and into elbow 7. A valve 8, operated by handle 9, is positioned in elbow 7 and opens to the atmosphere so that when it is in open position the air from main 6 flows directly to the atmosphere. When valve 8 is closed the air flows through elbow 7 into a pipe 10. It will be noted that valve 8 is a quick acting valve that may be opened very rapidly so as to cut off the air supply to pipe 10 practically instantaneously by diverting the flow of air from main 6 to the atmosphere. A pipe 11, having its upper end offset laterally from the lowerend of pipe 10 is pivotally connected thereto, as indicated at 12. Elbow 7 is pivoted to stanchion 5 to permit

pipes

10 and 11 to be swung out of the sewage tank 2, in the manner described in the Lannert Patent No. 2,328,655, granted September 7, 1943, for cleaning, or for repairs of any of the mechanism normally immersed in the sewage 13. A bumper guard 14 is secured to pipe 11, as indicated at 15, to keep the mechanism properly spaced from the wall of tank 2.

At the lower end of pipe 11 a coupling 16 is connected to a pair of

manifolds

17 and 18, as shown in Fig. 2. Manifold 18 is L-shaped to provide space between it and manifold 17 so that when the mechanism is swung out of the tank,

manifolds

17 and 18 straddle pipe 10 to make the mechanism readily accessible to a man standing on a catwalk 19 which extends from a point adjacent valve 8 to the adjacent wall of .the tank.

Manifolds

17 and 18 are each provided with a plurality of couplings 20 each of which is connected to a rigid semicylindrical air supply pipe 21. Pipes 21 are arranged parallel to each other and'extend in opposite directions 4 w from

manifolds

17 and 18. The pipes may be of any suitable length, depending upon the size of the sewage tank in which they are positioned. It is preferred to have them as long as possible for reasons that will hereinafter appear. The opposite ends of all air supply pipes 21 in each set of pipes are interconnected through pipes 22 to insure uniform air pressure in all pipes throughout the length of each pipe.

The pipes 21 are semi-cylindrical, and the open side of each pipe is closed by a fiat plate 23 welded thereto, as indicated at 24 (Fig. 4). Plate 23 extends beyond the sides of pipe 21, as indicated at 25 and 26. The end of pipe 21 adjacent coupling 20 is left in its cylindrical form, as indicated at 27, and the cut-away upper portion is closed 'by a plate 28 welded to the pipe and the end of plate 23. The opposite end of pipe 21 is closed by a plate 29 welded to the end of the pipe and to the underside of plate 23. Plate 23 is provided with a plurality of openings 30 through which the air passes from pipe 21 into diffuser tubes 31.

Each air supply pipe 21 has a flexible porous diffuser tube 31 of substantially the same length as the pipe secured thereto in a manner hereinafter described. It is desirableto have the diffuser tubes of considerable length because the length of the tubes determines the width of the diffusion band. The air supply pipes 21 and diffuser tubes 31 may be arranged adjacent the wall of the tank opposite inlet 3, as shown, or adjacent any other wall,

as desired. The liquid flowing through the inlet into the tank causes a circulatory movement of the sewage in the tank. Accordingly, air bubbles which are forced through the interstices of the diffuser tubes by pressure of the air flowing from pipes 21 through openings 30, are carried by the circulatory motion of the sewage in a well defined path as long as the diffuser tubes remain in fixed position relative to the tank. This arrangement of the diffuser tubes keeps the bubbles from coalescing to form large bubbles. The fine bubbles uniformly aerate the liquid through which they circulate.

The diffuser tubes may be made of any suitable flexible, porous material as pointed out above, preferably of a closely woven fabric which is strong enough to withstand the pressure of the sewage and the corrosive action of the sewage, and yet is flexible enough to cause the diffuser tubes to collapse immediately under the pressure of the sewage when the supply of air is cut off. Valve 8 is opened to cause diffuser tubes 31 to collapse completely and to slap against plate 23, and is immediately closed to reinfiate the diffuser tubes before the pressure of the liquid causes the sewage to percolate through the fabric of the tubes.

Diffuser tubes 31 are each provided with flaps 32 which extend laterally from each longitu inal edge of tube 31 and extend around the extensions 25 and 26. Channel shaped members 33 fit around extensions 25 and 26, and bolts 34 extending through channel members 33, flaps 32, and extensions 25 and 26 have nuts 35 threaded thereon to clamp flaps 32 in place. The ends of tube 31 are also provided with

flaps

36 and 37. Flap 36 is clamped in place by a channel member 38 in the same manner as flaps 32 are secured. The end of plate 23 adjacent plate 28 is notched, as indicated at 39, and flap '37 is secured to said end by a plate 40 having legs 41 fitting into notches 39, and held by bolts 42 passing through apertures 43 in plate 40 and threaded into apertures 44 in the end of plate 23.

When valve 8 is closed the air from air main 6 passes through stanchion 5, elbow 7,

pipes

10 and 11,

manifolds

17 and 18, and pipes 21 into diffuser tubes 31. The air is then forced through the interstices of the Walls of tubes 31 in fine bubbles which aerate the sewage, in which the tubes are immersed, in a very efficient manner. Although the tendency of the air passing through the walls of the diffuser tubes is to keep the pores of said walls clean by blowing away the solid matter contained in the sewage, some solid matter does accumulate on the walls, and in time such solid matter would clog the pores of the tube. This possibility of cloggingthe pores of the dilfuser tube is obviated by merely opening and then closing valve 8 without any appreciable interruption of the aerating process.

As soon as valve 8 is opened the air which would otherwise be forced through pipe lid is blown out to the atmosphere. The pressure ofthe sewage adjacent the diffuser tubes is much greater than atmospheric pressure. Accordingly, the pressure of the sewage causes tubes 31 to collapse immediately and to slap against plate 23 to dislodge the solid matterfrom the fabric. The air that was in the tubes is forced through openings 38 and backwards through the system. The rapid collapse of tubes 31 and the slapping action of the fabric against the flat surface of plate 23 causes the solid matter which may have accumulated against the walls of tubes 31; to break away therefrom. The deflation is so rapid, because of the pressure of the sewage on the outside of the diffuser tubes, that the liquid sewage can not percolate into the walls of the diifuser tubes. The quick inflation of the tubes after their deflation dislodges any solid. matter which is not broken away by the deflation, ei her bv the distention of the walls or by the air forced through the pores of the walls when the valve is closed. This rapid opening and closing of valve 8 keeps the walls of the diffuser tubes fairly clean at all times, and, as a consequence thereof, the diffuser tubes stay in the sewage for long periods of time, because inspection, cleaning, and repairing of the tubes is not required as often as withvdiffuser tubes previously used. The capability of the diituser tubes to remain-in the sewage without frequent inspection, outside cleaning, or repairs, results in increased etficiency in the aeration of sewage and in comparatively low maintenance costs.

In the embodiment of the invention illustrated in Figs. 8 to 11, a pipe 45, similar to pipe 21 is closed by means of a plate 46 which has an upstanding boss 47 extending longitudinally thereof. with plate 46, or may be rigidly secured thereto in any suitable manner, as by welding. Air holes 48 extend through boss 47 at spaced intervals, to allow air to pass from pipe 45 to the difluser tube 49. The difiuser tube is fabricated of the same material as in the previously described embodiment, but differs therefrom in shape. It is of elongated tubular shape and has a longitudinally extending opening 50 surrounded by a collar 51. The ends of the tube are closed by resilient U-shaped clamps 52.

The collar 51 is held in place against the edges of boss 47 by clamping plates 53 which'havetransversely elongated openings 54. Bolts 55 extend through openings 54 and are threaded into openings 56. Clamping members 53 are moved laterally into engagement with the edges of boss 47 and then bolts 55 are tightened to hold tube 49 securely in position.

In each of the embodiments of the invention described above, a diffuser tube made of flexible porous fabric capable of withstanding the pressure and action of sewage is connected to an air supply pipe in such a manner that cutting oft the air supply to the pipe causes an immediate collapse of the diffuser tube. Such collapse causes the fabricof the diffuser tube to slap against a rigid plate, and is followed immediately by inflation of the tube, with the result that substantially all the solid matter accumulated adjacent the wall of the diffuser tube is dislodged therefrom.

The air difiuser system may include a single air diffuser tube assembly or two such assemblies or more than the three shown in the preferred illustrative embodiments described herein.

Although I have described preferred embodiments of my invention in considerable detail, it will be understood The boss may be integral- 6 that the description thereof is intended to be illustrative, rather than restrictive, as many details maybe modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact structure described.

I claim:

1. An air diifusing unit adapted to be completely immersed in a liquid to be aerated, said unit comprising a rigid non-porous pipe comprising a semi-cylindrical section and a plate extending longitudinally of said semicylindrical section and forming a closure for the open side thereof, and a flexible, substantially completely collapsible porous member rigidly connected along its edges to said plate, said plate being apertured to provide passageways for air-to flow from said non-porous semi-cylindrical section into said porous member, said porous member having an approximately semi-cylindrical shape when indated.

2. An air diffusing unit adapted to be completely immersed in a liquid to be aerated, said unit comprising a'plurality of rigid non-porous pipes interconnected at each end, each of said pipes comprising a semi-cylindrical section and an elongated plate welded to said semicylindrical section to form a closure for the open side thereof, and a plurality of elongated strips of flexible tightly woven fabric each having its edges secured to one of said plates to form a substantially completely collapsible porous diffuser tube, each of said plates being apertured to provide a passageway for the flow of air from said non-porous pipe to the area contained by said flexible woven fabric, said porous member having an approximately semi-cylindrical shape when inflated.

3. An air diffusing unit comprising a diffuser tube connected to a source of air under pressure, and a quick acting valve controlling the flow ofair to. said diffuser tube, said diffuser tube' comprising a rigid non-porous pipe and a flexible substantially completely collapsible porous member secured along its edges to said pipe, said pipe having apertures providing passageways for the flow of air from said pipe into said porous member, said porous member having an approximately semi-cylindrical shape when inflated, said pipe having a surface against which said porous member is adapted to slap to dislodge substantially all of the solids accumulated on the surface of the porous member when it is collapsed quickly, said valve being operable to cause said porous member to collapse quickly by shutting 011 the flow of air to said diffuser tube.

4. An air diifusing unit comprising a diifuser tube connected to a source of air under pressure, and a quick acting valve controlling the flow of air to said difiuser tube, said dilfuser tube comprising a rigid non-porous pipe and a flexible substantially completely collapsible porous member, said pipe comprising a semi-cylindrical section and a plate extending longitudinally of said semicylindrical section and forming a closure for the open side thereof, said porous member being secured along its edges to said plate, said plate being apertured to provide passageways for the flow of air from said pipe into said porous member, said porous member having an approximately semi-cylindrical shape when inflated, said valve being operable to cause said porous member to collapse quickly and thereby slap against said plate to dislodge solids accumulated on the surface of said porous member.

References Cited in the file of this patent UNITED STATES PATENTS Ford Sept. 8, 1942