US2910178A

US2910178A - Material classification

Info

Publication number: US2910178A
Application number: US693575A
Authority: US
Inventors: Bonneau Louis Philippe
Original assignee: Department OF MINES
Current assignee: DEPARTMENT OF MINES
Priority date: 1957-09-07
Filing date: 1957-10-31
Publication date: 1959-10-27
Anticipated expiration: 1976-10-27

Description

Oct. 27, 1959 P. BONNEAU 2,910,178

MATERIAL CLASSIFICATION Filed Oct. 51, 1957 2 Sheets-sheaf. l

FEED I W 17 i m A 1.9 If 256 l A-i 1 VENTURI q.

71 lfllll Z76 METERING ORIFICE Z5 UT$IDE Z70 PRODUCT l? IZ g 1 PRODUCT 1720672/07 0015 I? B0/VA/[Al/ If/ax ng;

Oct. 27, 1959 1.. P. BONNEAU MATERIAL CLASSIFICATION 2 Sheets-Sheet 2 Filed Oct. 31', 1957 United States Patent 9 2,910,178 MATERIAL CLASSIFICATION Louis Philippe Bonneau, Ste-Fay, Quebec, Canada, as-

signor to Department of Mines, Quebec, Quebec, Canada v I Application October 31,1957, Serial-No. 693,575 1 Claims priority, application Canada September 7, 195 7 4 Claims. (Cl. 209-144) if the outlet of the outer cylinder. Each suction line is con= applicable to roughly equidimensional particles, acicular r particles or flaky particles.

In this type of separation, the material to be separated is subjected to the opposed forces of fluid flow and centrifugal force. of particles flow. I

One of the disadvantages of the prior processes falling within this general class is that they are not adaptable to various types of material without substantial change in the apparatus. The applicant has developed a method capable of being calibrated to handling different materials merely by adjusting the absolute values and the ratio of the forces.

The method comprises setting 'up a spiral stream of air by projecting the air tangentially into the inside of one end of a cylinder while withdrawing air from the other end of the cylinder, thereby setting up centrifugal force in the stream and limiting the outward draw on the particles by the cylinder wall. trary force is imposed against the centrifugalforce at spaced apart intervals by acting on the particles with negative pressure. The lighter particlesare thus drawn inward out of the spiral stream and the heavier particles held in this stream, by the centrifugal force. The lighter particles are drawn off and removed and the heavier particles remain in the stream and are removed separately. This method may be varied to change the nature of the fractions separated from the particles by changingthe' ratio of the force tending to draw on the lighter particles in relation to the force tending to retain them in the stream.

Applicant's development while another group of particles stays in the the inner hollow cylinder has a wall spaced from that of,

At the same-time,a con The viscous forces influence one group the outer cylinder to form therebetweenia feed passage. j A feed duct is connected to the inlet opening" and isso disposed as to project material into the passage tangentially to the wall of the outer cylinder. An outlet duct is connected to the outlet opening. A cylinder is ar-' ranged within the outer cylinder. The inner cylinder also provides an inner passage for a fraction of the material.

, 2,910,178 Patented Oct. 27, 1959 to the inlet duct. "A suction line leadsfrom the outlet of the inner cylinder; Anothersuction lineleadsfrom nected to a vacuum source.- Means is provided for con= trolling the respective vacuum sources, whereby there are difierential forces exerted on the respective'particles of the entering material causing particles having 'acertain characteristic to enter the inner cylinder and particles having other characteristics to stay in the'outer cylinder.

drawn away. I I

Preferably, each of the suction lines leads to -a separator, for example a cyclone. In this case each separator has an outlet for separated fractionsof the material and for air respectively. Each of the air outlets is connected to a controllable vacuum source.- Respective metering devices indicating the flow in each of the air outlets and at the material feed inlet are provided. a

Two groups of particles are thus separated and may be In accordance with the invention, the area and distribution of the openings in the inner cylinder is such that the velocity of the air entering the inner cylinder is high enough to produce viscous forces acting on a certain group of particles, superior'to the centrifugal forces acting on the same particles. Preferably, the applicant has found that elongated" or rectangular openings are most satisfactory. The cylinders may be made out of any suitable abrasion-resistant material. 7 I The invention has been generally describedand it will now be referred to; in moredetailby referring to the accompanying drawings-which illustrate a preferred embodiment and in which::.

Figure 1 is a general arrangement showing the relation: ship of the various parts of the apparatus. I

Figure 2 is a -'perspective view showing the separator proper.

Figure 3 is a horizontal cross section along the line 3-3 ofFigure 2. .t 1

The invention will now be described in more detail with reference to the drawings in terms of the operation of the apparatus. I v The material tobe separated, which for example is as bestos, is fed into the funnel 17, it passes through aventuri-meter 19 and through a pipe 20 into the separator proper, A. In the separatorA the material is separated into the exterior and the interior product respectively. A

cyclone separator 21 receives the exterior product and a cyclone 23 the interior product.

The

fresh air outlets

25 and 27 of the respective'cyclones are metered by orifices or other means 25a and 27a and are connected to a fan 29 which acts as a vacuum source. While a fan has been shown, this could be any suitable source of vacuum. v I A manometer panel (not shown) is provided with instruments where the differential pressure readings maybe noted for the orifices 25a and 27a and the venturi. The air flow in the two outlets 25a and 27a is adjusted by valves 25b and 27b. The legend metering orifice has beenappli'ed at 25a. This, of course, presumes the necessary metering apparatus. I i

The inside product is discharged into a hopper 51 and the outside product into a hopper 53. x

Separator proper The separator proper A ismade up as follows. It ineludes-a hollow outer cylinder '61. The outer cylinder has an imperforate wall which includes an inlet opening 63 at one end and an outlet opening 65 at the other end; An inner hollow cylinder 67 is mounted within the outer cylinder 61. The inner cylinder 67 has a wall 67a spaced from the wall 61a to form between the two walls, a feeding passage. A feed duct 71 is connected to the inlet opening 63and is so disposed as to project material into the passage between the walls 61a and 67a tangentially to the wall 61a. The duct is preferably of substantially the conformation shown, being a somewhat rectangular discharge mouth. ;,An outlet duct .81 is connected to the outlet opening 65 and thence toa duct 83 leading to the cyclone 21. The duct 83 does not have to widen out, as shown, but can be tied to the inlet to the cyclone 21 without change in dimensions.

The inner cylinder and the outer cylinder both terminate at acommon head 85, which blocks the top end of each. The bottom end of the cylinder 61 carries a header 87, the cylinder 67 projects through an opening 87a and has a portion 67b projecting beyond the header to a connection with a conduit 89, which leads to the cyclone 23. The wall 67a of the inner cylinder is provided with a number of

openings

91, 91a, 91b and 91c. These openings are preferably arranged spirally on the wall 67a. I

Operation of separator unit A The fiber coming from the funnel 17 is drawn by the vacuum pressure applied to the cyclones through the inlet chute 71 and into the passage between the walls 61a and 67a. The total material to be treated is projected tan gentially into the passage between the walls 61a and 67a and the suction from the outlet chute 81 causes it to take a spiral path, as shown in dash lines, from the bottom to the top of the passage P. The negative pressure within the cylinder 67 acts on the inside product causing it to pass through the

openings

91, 91a, etc. The outside product continues to remain in the spiral stream and reaches the outlet chute 81. In this way, the material to the apparatus is separated into an inside and an outside fraction.

The required flows in the

respective outlet ducts

83 and 89 can be readily adjusted. The different velocities of the respective fractions cannot be estimated with any great accuracy. Moreover, the'projected area and drag coeflicient for one given particle or fiber are beyond the experimental determination. However, both forces will play one against the other and their values may be controlled by controlling the out flows. By varying the values and ratios of these outflows, a given granulometric composition can be had in the fiber orparticle carried by one or both of the outflows from a specified feed material.

The classifier functions on the theory that if a particle or fiber is admitted tangentially with a certain velocity inside the cylinder 61it will tend to hug the inside surface of the cylinder. The force which throws the particle or fiber against the inside'surface is where w is the weight in pounds of the particle or fiber, g is the acceleration due to gravity in feet/secfi, v is the tangential speed of the particle or fiber in feet/second and r is the radius of the cylinder in feet.

With the smaller cylinder 67 inside the cylinder 61, part of the incoming air is forced to pass through the

small openings

91, 91a, etc. in the wall 67a, thereby creating a large inward velocity at those openings, a further force thus being generated on the particle or fiber, that force results from the fact that air is viscous and will tend to carry with it particles or fibers. This force due to viscosity is expressed by the formula where C equals drag coefficient, p equals air density in slugs/pi v equals air velocity relative to the particle in feet/sec., A equals projected surface of the particle in feet*-.

I claim: 7

1. An apparatus for segregating particles of finely divided material including particles of different sizes, comprising an elongated outside cylinder, and an elongated inside cylinder co-extensive therewith and mounted concentrically therein to provide an annular space between the outside and inside cylinders, said outside cylinder having a wall including an inlet opening at one end and an outlet opening at the other end, said inside cylinder havinga wall provided with inlet openings distributed along its length and an axial outlet opening at the end near the inlet opening of the outside cylinder, means closing the ends of both cylinders adjacent to the outlet opening of the outside cylinder, means closing the space between the outside and inside cylinders at a position on the side of the inlet opening of the outside cylinder remote from said closed ends the outside and inside cylinders forming therebetween a passage for a heavier fraction of finely divided material and air leading from the inlet opening to the outlet opening of the outside cylinder, a feed duct connected to the inlet opening of the outside cylinder and so disposed as to project material into the outside cylinder substantially tangentially to its wall thereby to impart to the material a whirling path, an outlet duct connected to the outlet opening of the outside cylinder, a supply line for feeding material leading to the inlet duct, a negative pressure line leading from the outlet of the inner cylinder for applying negative pressure to said inlet and a negative pressure line leading from the outlet of the outer cylinder for. applying negative pressure thereto independent of the negative pressure applied to the inner cylinder outlet whereby the relative negative pressure in the respective cylinders may be adjusted.

2. An apparatus as defined in claim 1 in which the feed openings on the inside cylinder wall are arranged in a spiral. 1

3. An apparatus as defined in claim 1 in which each negative pressure line is connected to a separator for separating air from the entrained particles, each sepa- References Cited in the file of this patent UNITED STATES PATENTS 2,275,761 Carey Mar. 17, 1942 2,460,938 Koehne Feb. 8, 1949 2,616,563 Hebb NOV. 4, 1952 2,779,468 King June 29, 1957 FOREIGN PATENTS 332,405 Great Britain July 24, 1930 France Dec. 17, 1952