US2723750A

US2723750A - Hydrocyclone

Info

Publication number: US2723750A
Authority: US
Publication date: 1955-11-15
Anticipated expiration: 1972-11-15

Description

NOV. 1955 R. A. PICKENS ET AL 2,723,750

HYDROCYCLONE Filed Oct. 14, 1952 INVENTOR S WM 770 rP/Vf) United States Patent HYDROCYCLONE Roy Alderson Pickens, Stamford, and Richard Cary Forbes, Noroton, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application October 14, 1952, Serial N 0. 314,581

2 Claims. (Cl. 209-211) This invention relates to an improved hydrocyclone.

The use of a hydrocyclone for the treatment of ores and coal has become rather widespread in recent years. In the usual form of apparatus, the material to be treated is fed into a suspension of very fine medium solids and Water, which make up a liquid mass of the desired specific gravity of separation, and is introduced tangentially under pressure through a feed inlet into the larger end of the cyclone. While the most common form of apparatus is a cone, vessels of different shapes, such as cylinders may sometimes be used. When a conically-shaped cyclone is used it may or may not have an upper cylindrical portion. The cone carries a central vortex finder which guides the upwardly flowing stream of lighter gravity particles to a discharge outlet located in the base of the cone. The desired separation of particles is carried out in the conical vortex chamber of the cyclone. The separation is effected by the action of centrifugal forces which draw the heavier gravity particles to the wall of the vortex chamber where they are. discharged through the bottom or apex orifice of the cyclone, and by the action of centripetal forces which sweep the lighter gravity particles toward the central vortex where they leave the cone through the vortex finder and are eventually discharged from the cyclone through a discharge outlet near the top of the cyclone.

In this type of apparatus the material to be separated is fed to the hydrocyclone tangentially under pressure along with the suspension of medium solids used to make up the separating gravity of the liquid. This imposes a severe load on the pumping capacity of the system in that it must be sufiicient to pump not only the fine medium solids but also the coarser particles which are to be separated. Moreover, since the medium solids suspension and the ore particles are introduced tangentially into the cyclone under pressures which may vary from 20 to 40 p. s. i. the resultant velocity imparted to the particulate material is quite high with the result that considerable abrasion is produced on the inner wall of the cyclone due to the force imparted to the relatively coarse particles to be separated. In addition, by having to pump such coarse-sized material, increased wear is produced on the pump and which can lead to costly breakdowns and replacement of parts.

In accordance with the present invention, it has been found that by feeding the material to be separated separately from the tangential feed of the suspension of fine medium solids and Water, that is, by introducing the material through a standpipe, with or without auxiliary mechanical feeding means, so that the material is delivered directly into the larger end of the cone, a smaller size pump can be used since medium alone has to be handled.

It is an advantage of the present invention that by providing such a separate feed means it-is thus possible to handle coarser sizes of material to be separated than could practically and economically be introduced by means of a pump. Also, since the relatively coarse particles which are to be separated are not fed tangentially under pressure and high velocity into the cyclone, less abrasion on the inner wall of the cyclone results.

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It is a further and important advantage of the present invention that by eliminating the necessity of pumping the ore, less attrition on the ore results and therefore, the breaking of frangible material such as coal, potash salts and the like, is minimized since it is not necessary to feed the material to the cyclone by high pressure pumping action.

While it has been proposed heretofore to feed material to be separated to a cyclone by a top feed arrangement so as not to have to pump the material, this type of apparatus feeds the material to a central air column in the vortex chamber. Even though the vertical axis of the apparatus is inclined 30 for the stated purpose of preventing the particles from dropping through the air column and hence out of the cone without being separated, it is to be observed that by so inclining the vertical axis of the cyclone the material fed through the tube is deposited at roughly one point in the inner vortex and this point is located relatively near the apex discharge in the constricted portion of the cone. Thus, by depositing the particles so close to the apex discharge some of the lighter gravity particles, or near-gravity float, will be carried down with the heavier gravity particles and thus contaminate the sink product.

In accordance with the present invention, however, these disadvantages are overcome in that it has been found that by feeding the material through a feed tube which depends downwardly into the cyclone and is displaced laterally from the vortex discharge and hence displaced laterally from the central air column, the feed is delivered directly into the swirling medium in the cone so that all particles are subjected to the forces of separation.

The present method of feeding has the important advantage that none of the particles being fed can drop down the central air column and thus escape the action of the centrifugal and centripetal forces operating in the cone. Consequently, efficient separation takes place.

Referring to the accompanying drawing, which shows an illustrative embodiment of the present invention:

Figure 1 is a vertical cross-sectional view of the apparatus of the present invention;

Figure 2 is a top plan view taken on line 2-2 of Figure 1 and Figure 3 is a detail of a modification of the feed tube shown in conjunction with the apparatus of Figure 1.

Referring to Figure 1, reference numeral 1 indicates generally the hydrocyclone which is shown as being provided with a cylindrical section 2 and a conical section 3. Disposed within cylindrical section 2 is transverse wall 4 provided with central aperture 5. An annular flange 6 extends downwardly from transverse wall 4 into the cylindrical section 2 and defines the central vortex finder which guides the upwardly flowing stream of lighter gravity particles to discharge outlet 7 located in the wall of cylinder 8.

Medium inlet 9, that is, the conduit carrying the suspension of fine medium solids and water is disposed at a tangent with respect to cylinder 2, the outlet end of conduit 9 being designated by reference numeral 10.

Cylinder 8 is closed at the top thereof by plate 11 provided with bore 12. A feed tube 13 is fitted within bore 12 and extends axially through cylinder 8. Feed tube 13 passes through an opening in transverse wall 4 and the delivery end of the feed tube terminates at a point which may be flush with the lower surface of this wall or, if desired, the delivery end of the tube may terminate at a point just beyond wall 4. Suitable packing indicated by reference numeral 14 is provided about the tube 13 within the bore 12 so as to prevent upward surging of medium through bore 12. Feed tube 13 is slidable in bore 12 as illustrated, and carries at the upper end thereof hopper 15,

Conical section 3 is provided at the discharge end thereof with nozzle plate 16 and apex discharge orifice 17.

As shown, feed tube 13 extends axially through cylinder 8 and is displaced laterally from the vortex finder defined by annular flange 6. The point where the feed tube is positioned in wall 4 is within limits, not too critical excepting, of course, that it must be displaced laterally in relation to the vortex discharge. In practice, it has been found that good results may be secured when the feed tube is positioned near the outer periphery of wall 4 as shown in Figures 1 and 2.

While it has been found that .good results may be secured by the use of a standpipe which depends on hydraulic pressure for the delivery of the feed to the cyclone, it may be desirable in some instances to employ an auxiliary mechanical feeding means to deliver the feed.

Such a modification is illustrated in Figure 3. In this modification, a spiral conveyor 18 is shown which may be utilized to deliver the feed to the cyclone against the action of the hydrostatic pressure in the cone. The auxiliary mechanical feeding means 18, while shown as taking the form of a spiral conveyor, is merely illustrative as other equivalent feeding means, such as .a piston and cylinder arrangement, for example, may be employed with equally good results.

In operation, a suspension of fine medium solids and water to make up a separatory fiuid to eifect the desired specific gravity of separation is introduced into the cyclone through medium inlet 9. The velocity imparted to the incoming medium produces inner and outer vortices in the cone rotating in the same direction about a central air column which extends between the apex discharge and the vortex discharge in the transverse wall. The vortices move axially in opposite directions, the outer vortex moving axially towards apex discharge 17 and the inner vortex moving axially toward the vortex discharge 5. The particles are fed from the delivery end of the tube under hydraulic pressure or if desired by the aid of the auxiliary feeding means into the swirling medium. The heavier gravity particles, that is, those particles having a specific gravity greater than the specific gravity of separation together with part of the medium are drawn to the wall of the cone in the outer vortex and are discharged through apex discharge 17, while the lighter gravity particles, that is, those particles having a specific gravity less than the specific gravity of separation together with the remainder of the medium, are swept toward the inner vortex and are discharged from the cone through vortex discharge 5.

Throughout the specification whenever the term ore is used it is to be understood that this expression also includes coal or other heterogeneous mixtures of solid particles having different densities.

We claim:

1. A hydrocyclone comprising a conical vortex chamber having a discharge orifice at the apex thereof, an inlet for a suspension of medium solids and water opening tangentially to the larger end of said vortex chamber, a transverse wall at the larger end of said vortex chamber, a central outlet opening in said wall for lighter gravity separated material, means to deliver a suspension of medium solids and water through said inlet under sufiicient pressure to produce in said chamber inner and outer vortices rotating in the same direction about a central air column extending between said apex discharge orifice and said outlet opening in said transverse wall, an outlet chamber provided with an outlet opening in a wall thereof for the vortex discharge secured to said vortex chamber at the larger end thereof, and a feed tube provided with an auxiliary mechanical feeding means for material to be separated positioned in said transverse wall and extending axially of said vortex chamber and of said outlet chamber, said feed tube being positioned in said transverse Wall at a point which is displaced laterally from said central outlet opening in said transverse wall, and the delivery end of said feed tube terminating adjacent to the inner surface of said transverse wall.

2. The method of separating particles of different specific gravities which comprises tangentially introducing into a confined zone a suspension in water of medium solids having a specific gravity higher than a predetermined specific gravity of separation and under such pressure as to produce in said zone inner and outer vortices rotating in the same direction about .an .air column coaxial of said zone but moving axially in opposite directions, introducing the particles to be separated at a point displaced laterally from said air column and directly into said vortices, said outer vortex serving to draw the particles having a specific gravity greater than the specific gravity of separation to the outer confines of said zone so that said particles may be discharged axially of said zone, and said inner vortex serving to sweep the particles having a specific gravity less than the specific gravity of separation to the inner confines of said zone so that said particles may be discharged axially of said zone and in an opposite direction to that of the discharge of the heavier gravity particles.

References Cited in the file of this patent UNITED STATES PATENTS 1,383,441 Sturtevant July 5, 1921 1,456,165 Whitney May 22, 1923 1,669,820 Grant May 15, 1928 FOREIGN PATENTS 804,430 Germany Apr. 23, 1951

Claims

1. A HYDROCYCLONE COMPRISING A CONICAL VORTEX CHAMBER HAVING A DISCHARGE ORIFICE AT THE APEX THEREOF, AN INLET FOR A SUSPENSION OF MEDIUM SOLIDS AND WATER OPENING TANGENTIALLY TO THE LARGER END OF SAID VORTEX CHAMBER, A TRANSVERSE WALL AT THE LARGER END OF SAID VORTEX CHAMBER, A CENTRAL OU TLET OPENING IN SAID WALL FOR LIGHTER GRAVITY SEPARATED MATERIAL, MEANS TO DELIVER A SUSPENSION OF MEDIUM SOLIDS AND WATER THROUGH SAID INLET UNDER SUFFICIENT PRESSURE TO PRODUCE IN SAID CHAMBER INNER AND OUTER VORTICES ROTATING IN THE SAME DIRECTION ABOUT A CENTRAL AIR COLUMN EXTENDING BETWEEN SAID APEX DISCHARGE ORIFICE AND SAID OUTLET OPENING IN SIAD TRANSVERSE WALL, AND OUTLET CHAMBER PROVIDED WITH AN OUTLET OPENING IN A WALL THEREOF FOR THE VORTEX DISCHARGE SECURED TO SAID VORTEX CHAMBER AT THE LARGER END THEREOF, AND A FEED TUBE PROVIDED WITH AN AUXILIARY MECHANICAL FEEDING MEANS FOR MATERIAL TO BE SEPARATED POSITIONED IN SAID TRANSVERSE WALL AND EXTENDING AXIALLY OF SAID VORTEX CHAMBER AND OF SAID OUTLET CHAMBER, SAID FEED TUBE BEING POSITIONED IN SAID TRANSVERSE WALL AT A POINT WHICH IS DISPLAED LATERALLY FROM SAID CENTRAL OUTLET OPENING IN SAID TRANSVERSE WALL, AND THE DELIVERY END OF SAID FEED TUBE TERMINATING ADJACENT TO THE INNER SURFACE OF SAID TRANSVERSE WALL.