US3583560A

US3583560A - Apparatus and method for cleaning and concentrating fine solids

Info

Publication number: US3583560A
Application number: US820347A
Authority: US
Inventors: Eugene Cline
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-04-29
Filing date: 1969-04-29
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

An apparatus and method are provided for the continuous concentration of a fine solids slurry, and are especially adapted for use with fine coal slurries. A tank is provided with upwardly-diminishing dimensions that terminate to form a restricted discharge means for more concentrated slurry. The tank has rotatable drums therein containing suspended stationary magnetic elements, injection means adjacent the tank bottoms for feeding of solids slurry, and ducts positioned below the drums for discharge of less concentrated slurry. Magnetite is fed to the slurry-containing tank which causes separation of coal particles from a fine coal slurry that float to the top of the tank, and with additional slurry being fed to the tank, and by adjusting the volume in the tank with means to regulate flow through the ducts, the desired amount of more concentrated slurry is discharged through the trough while less concentrated slurry is discharged through the ducts. Turbulence is caused by the injected slurry and the magnetic elements in the drums prevent loss of magnetite through the ducts in the bottom, while the shape of the tank and the greater density of the magnetite prevents its escape through the trough at the top, and it is retained and used in the tank.

Description

United States Patent Eugene Cline Lowmansvllle, Ky. 41232 [21] Appl. No. 820,347

[22] Filed Apr. 29, 1969 [45] Patented June 8, 197 I [72] Inventor [54] APPARATUS AND METHOD FOR CLEANING AND CONCENTRATING FINE SOLIDS Primary ExaminerTim R. Miles Assistant Examiner-W. Cuchlinski AttorneyParmelee, Utzler & Welsh ABSTRACT: An apparatus and method are provided for the continuous concentration of a fine solids slurry, and are especially adapted for use with fine coal slurries. A tank is provided with upwardly-diminishing dimensions that terminate to form a restricted discharge means for more concentrated slurry. The tank has rotatable drums therein containing suspended stationary magnetic elements, injection means adjacent the tank bottoms for feeding of solids slurry, and ducts positioned below the drums for discharge of less concentrated slurry. Magnetite is fed to the slurry-containing tank which causes separation of coal particles from a fine coal slurry that float to the top of the tank, and with additional slurry being fed to the tank, and by adjusting the volume in the tank with means to regulate flow through the ducts, the desired amount of more concentrated slurry is discharged through the trough while less concentrated slurry is discharged through the ducts. Turbulence is caused by the injected slurry and the magnetic elements in the drums prevent loss of magnetite through the ducts in the bottom, while the shape of the tank and the greater density of the magnetite prevents its escape through the trough at the top, and it is retained and used in the tank.

PATENTED JUN 8 mm SHEET 1 UF 2 INVENTOR. Eugene Clme.

BY fwuJ -L ably W Attorneys.

PATENTEU JUN 8 I911 3583.560

SHEET 2 BF 2 INVENTQR. Eugene Clme.

Attorneys.

APPARATUS AND METHOD FOR CLEANING AND CONCENTRATING FINE SOLIDS BACKGROUND The mechanization of coal mining, both by the use of loading machines, and more recently the continuous mining machines, has greatly increased the production of fines. As much as fifty percent of the production of some of the mining machines which I have sampled passes through a /4 inch screen. As a result, equipment and methods heretofore used to process the fines profitably are no longer adequate for the present high rate of production.

One widely used method is the so-called "heavy media process" wherein water having magnetic particles densely diffused therethrough to form a mixture having a higher specific gravity of the coal and a lower specific gravity than the refuse is used to float the coal while the refuse sinks. With mixtures other than coal, as for example sand, the sand may sink and the refuse, such as shale, will float. However the floating material is carried out with the liquid medium and then the magnetic particles must be separated from the water for reuse, usually by magnetic separation, and commonly the magnetic particles tended to floculate, requiring that they be first defloculated for reuse.

SUMMARY The present invention provides a separation vessel having inwardly-sloping walls leading to a restricted outlet at the top so that fine solids material of a lesser density such as coal or float material is forced or crowded by the material of greater density up through the outlet at the top as a thick concentrate free of most of the flotation liquid. A water slurry of the admixture of fine particles of lesser density and fine particles of relatively greater density, such as a slurry of coal fines, to be cleaned is continuously supplied to the lower portion of the vessel under pressure to keep a zone of agitation in a portion of the tank,,and water containing particles of greater density such as sediment refuse is continuously-withdrawn, with the input and outflow regulated to maintain a substantially constant level of flotation liquid in the tank below the outlet at the top of the vessel. Means is provided for continuous magnetic removal of the magnetic particles from the outflowing water and discharging them immediately into the zone of agitation to keep the specific gravity of the flotation liquid substantially constant, and under these conditions no floculation of the magnetic particles occurs. Provision is made for adding makeup particles from time to time as required. In the preferred embodiment, there is a second tank below the first with the outlet openings for the removal of the water and sediment material being in the bottom of the first vessel in closed communication with the second. Rollers are over these outlet openings so that the outflowing liquid flows over their surfaces. Stationary magnets inside the rollers attract the magnetite in the water to the rollers which then carry the magnetite out of the magnetic field, and the oxide is released into the turbulent zone created by the incoming slurry.

By the process of continuously crowding the float material free of most of the water out the top of the vessel and continuously supplying new slurry to the vessel and continuously removing water from the vessel at such rate as to maintain a constant liquid level in the tank, and by separating the magnetic particles from the outflowing water and discharging them into the incoming slurry, a continuous economical and effective method of separating and cleaning the coal or other material is provided.

The objects and novel features of the invention are described in the following detailed description when the same is read in conjunction with the accompanying. drawings. The drawings are not intended as a definition of the invention, however, and are for the purpose of illustration only.

BRIEF DESCRIPTION 'OF THE DRAWINGS FIG. 1 is an exploded perspective view of the apparatus of the present invention, with cutaway portions, showing the use of two tanks, one superimposed on the other,

FIG. 2 is a sectional view of the assembled apparatus shown in FIG. 1 taken along lines II-II.

DETAILED DESCRIPTION Referring to FIG. I, there is shown the preferred apparatus of the present invention for use in cleaning and concentrating fine coal slurry having a first tank I, and a second tank 41. The first tank or separating tank 1, has a bottom 3, and upwardlydiminishing dimensions as shown with two end walls 5 and 5' and two upwardly and inwardly extending sidewalls 7 and 7'. The sidewalls 7 and 7 terminate in upwardly and outwardly extending

flanges

9 and 9 so as to form a restricted discharge opening or trough 11 at the upper end of the tank 1. Located on the trough 11 are a solids feed means 13, such as a funnelshaped feeder, and a discharge spout 12 for removal of concentrated slurry from the apparatus.

The bottom 3 of tank 1 has therein, intermediate the sidewalls 7 and 7 and extending between end walls 5 and 5', a channel 15, extending downwardly. Positioned in the channel 15 is an injection means 17, herein illustrated as a pipe 19, with apertures 21 therein for injecting a fine coal slurry upwardly in the tank 1.

Positioned between the channel 15 and the sidewalls 7 and 7 are a pair of rotatable drums 23 and 23', one of the

drums

23 and 23 located on each side of the channel 15 and being rotatable in an upward and inward direction in the tank 1 to direct a current of liquid towards the center of tank 1 and upwardly towards the flow of slurry from channel 15. In each of the drums 23 and 23' there are suspended, in a stationary position, magnetic elements 25 and 25'. The magnetic elements are stationary and extend downwardly so that even as drums 23 and 23' rotate, a magnetic force is always exerted towards the bottom 3 of tank 1. Preferably, the

magnetic elements

25 and 25 are suspended by a stationary rod, such as 27 and 27' illustrated in the drawings. The

drums

23 and 23 may be made rotatable by positioning them around stationary shafts or rods 27 and 27' which support a suitable sleeve and coupling means at the tank ends, the sleeve being journaled for rotation by suitable drive means 16 powered by a motor 28. The means for rotating the drums 23 and 23' in opposed directions would be readily discernable to one of mechanical skill, such as by a belt 30, idler 32 and suitable wheel members 34, or a chain and sprocket-type device.

Below the

drums

23 and 23 and positioned in the bottom 3 of tank 1 are a pair of ducts 31 and 31'. These ducts 31 and 31' permit exit from the tank 1 of the less concentrated coal slurry according to the method as more fully described hereinafter. Preferably, these ducts are positioned in concavities in the bottom 3 so as to conform the bottom to the drum shapes.

In the preferred embodiment of the apparatus of the present invention, there is located, beneath the first tank 1, a second tank 41, both tanks being interconnected, in closed communication, by means of the ducts 31 and 31'. The second tank 41 preferrably has generally sloping sidewalls 43 and 43' and end walls 45 and 45', which extend downwardly and inwardly to form a bottom 46 having thereon drainage means 47, herein illustrated as an orifice 48 and, as described hereinafter, a pump 57, to provide for ready regulation of the volume of material in the first tank 1, and also regulate outflow from the total apparatus.

Also illustrated in FIG. 1 are the various feed means and controls for feeding fine coal slurry to the apparatus and removing more concentrated and less concentrated slurries therefrom. Illustrated therein are line 51 having valve means 35 therein. Line 51 is attached to feed pipe 19 and to connecting line 54. Connecting line 54 interconnects line 51 and the second tank 41 at pump 57 and has valve 36 thereon. For

discharge of less concentrated slurry or clear water there is provided discharge means on tank 41, herein illustrated as line 59 and adjustable valve 61 to control flow therefrom.

The method for concentrating a fine coal slurry using the apparatus of the present invention is as follows. With

valves

36 and 61 in closed position, valve 35 is opened and a fine coal slurry fed therethrough. The fine coal slurry is fed with sufficient pressure by means of a pump or strong gravity feed or other means (not shown) so as to force fine coal slurry into feedpipe 19 and inject the slurry through apertures 21 upwardly into first tank 1. As the fine coal slurry falls, by gravity, to the bottom 3 of tank 1, the slurry will flow through

ducts

31 and 31 and into second tank 41. Continued flow will fill tank 41, ducts 31 and 31' and eventually cause a buildup of fine coal slurry in tank 1. When tank 1 is filled to a predetermined volume, the power source is activated and drums 23 and 23' caused to rotate in the direction as indicated in FIG. 2. With drums 23 and 23' rotating, a predetermined amount of magnetite (m) is fed to tank 1, through solids feed means 13, (not shown on FIG. 2). Adjustable valve 61 is then opened and set so as to allow the continuous discharge of a predetermined amount of liquid, the amount being determined based upon the percent of solids in the fine coal slurry entering tank 1 through injection means 17.

As the fine coal slurry (s) is fed to the tank 1 by injection means 17, the fine coal particles suspended in the slurry will, because of density, float to the top portion of tank 1 and form a layer on the slurry. The depth of the layer of more concentrated slurry (S) or coal particle phase is adjustable by varying the amount of slurry in tank 1, through manipulation of adjustable valve 61 and regulating the flow of less concentrated slurry (s') which flows through ducts 31 and 31' into second tank 41. The depth of the coal particle phase or more concentrated slurry is adjusted so as to prevent loss of magnetite which has been fed to the tank 1 through overflow into trough 11. Thus, in continuous operation, more concentrated slurry is permitted to flow from the tank 1 by means of trough 11, and less concentrated slurry is exhausted from tank 41 by means of line 59 and adjustable valve 61, the magnetite is maintained and continuously reused.

As seen in FIG. 2, wherein magnetite (m has been added to the slurry but the level of the total aqueous suspension is below that for removal of more concentrated slurry (S), the fine coal slurry is fed into the tank 1 through apertures 21 in pipe 19 in the form of jet streams which agitate the slurry contained in tank 1. The streams weaken as they reach the upper region of the tank and can be adjusted by means of the pressure source to provide the desired turbulence. The jet streams prevent settling of magnetite in channel of the bottom 3 of tank 1 while the fine coal particles float to the top portion of tank 1. This turbulence and the various densities of the materials cause the less concentrated slurry, with magnetite, to flow towards the sidewalls 7 and 7 of tank 1 and thence downwardly to the region of ducts 31 and 31' below drums 23 and 23'. With the stationary magnetic elements 25 and 25' positioned adjacent ducts 31 and 31', the magnetite is attracted to the surfaces 26 and 26' of the drums 23 and 23' while the less concentrated slurry flows by gravity through the

ducts

31 and 31 and eventually is discharged by means of line 59 and adjustable valve 61.

The magnetite attracted to drums 23 and 23' is held to the

surfaces

26 and 26 thereof until it is sufficiently removed from the magnetic forces of magnetic elements 25 and 25' and is released from the drum surface and urged upwardly towards the center portion of the tank above channel 15. Magnetite particles, often flocculated by the magnetic influence, are urged into the region'of channel 15 and are broken up into finer particles by the influence of the jet streams exiting from injection means 17 The fine coal slurry is thus fed to the apparatus and because of the magnetite present, more concentrated slurry is provided in the upper region of the tank 1, with discharge thereof through trough 11, while less concentrated slurry is directed to the bottom 3 of tank 1, and through ducts 31 and 31'. The magnetite is maintained in tank 1, by the magnetic field exerted by magnetic elements 25 and 25', and directed towards the turbulence caused by injection of additional fine coal slurry to maintain the magnetite in dispersed form suitable for further concentration of fine coal slurry.

Should it be desired to remove the magnetite from the apparatus, suitable means can be provided to permit the adjust ment of the

magnetic elements

25 and 25 to an upward position. Any magnetite in the region of the

surfaces

26 and 26 of bottom of drums 23 and 23' will thus be sufficiently removed from the magnetic field and will fall by gravity through

ducts

31 and 31 into tank 41 where it can be removed therefrom by actuating pump 57 to discharge the contents of tank 41. The magnetite so removed may be returned to tank 1 by means of pump 57, connecting line 54, through opened valve 36 and, with valve 35 closed, into feed line 19. Other means of breaking the magnetic field, such as insertion of a suitable shield between the magnets 25 and 25' and the drum surface 26 and 26' are, of course, also usable.

As an example of a suitable apparatus and process, the tank 1, can vary between two 5: feet to ten feet in length. The tank 1, being of general triangular configuration along a cross section thereof, allows maintenance of a greater height between the top surface of the concentrated slurry and the remaining magnetite suspension, allowing discharge of the more concentrated slurry without any great danger of loss of magnetite suspension therewith. Proportionately, the second tank 41, should have a capacity to hold all of the magnetite from tank 1 for drainage purposes. As an example of the concentration of the fine coal slurry according to the present process, a feed of fine coal slurry containing about 10 percent solids may be fed to the desired volume in tank 1 and adjustable valve 61 adjusted to discharge percent of the total volume of the subsequent feed, with 20 percent of the total feed discharged through the trough 11 of tank 1. Such a more concentrated slurry would thus contain about 50 percent solids or fine coal particles.

Although the invention'has been described with specific emphasis on concentration of fine coal slurries, the invention is adaptable for other separations where fine particles of lesser density are to be separated from an admixture with fine particles of a greater density. An example of such would be the separation of shale or other materials of lesser density from sand, a material or greater density. in such a separation, the sand or heavier material would be the desirable cleaned product and would be subsequently removed from the outflowing water while the shale or other lighter material would be removed as the concentrated slurry from the top of the vessel and discarded.

There have been provided, according to this invention, an apparatus and method especially useful for concentrating a fine coal slurry where the less concentrated portion of the slurry is substantially free of solid particles. The more concentrated slurry contains a high solids content so that conventional equipment can readily complete the separation of the fine coal from the more concentrated slurry at a much greater capacity. The apparatus and process do not involve subsequent separation of magnetite from either the more or less concentrated slurries and the magnetite is maintained and reused continuously.

lclaim:

1. An apparatus for separating fine solid materials of a lesser density from admixture with fine solid materials of a greater density by flotation in a mixture of water and magnetic particles comprising a. a vessel of upwardly-diminishing dimensions having means at the upper region thereoffor discharge of lesser density solids,

b. means for charging magnetic particles into said vessel,

c. means in the lower region of the vessel for continuously injecting said admixture of solid particles with water upwardly into said vessel,

d. an outlet in the lower portion of said vessel for the continuous discharge of water containing said solid materials of a greater density, and

e. means in the path of the outflowing water to remove magnetic particles therefrom and discharge them into contact with said upwardly injected admixture.

2. The apparatus of claim 1 wherein said means in the path of the outflowing water to remove magnetic particles therefrom comprises at least one rotatable drum suspended in said vessel having therein stationary magnetic elements so positioned as to exert a magnetic field towards the bottom of said vessel.

3. Apparatus for concentration of coal fines by flotation in a mixture of water and magnetic particles comprising:

a. a vessel of upwardly-diminishing dimension terminating at the top in a restricted discharge opening for concentrated coal slurry,

b. means in the bottom of the vessel for continuously injecting a slurry of raw coal fines into the vessel to agitate the contents of the vessel,

c. means for introducing magnetic particles into the vessel,

d. an outlet means for the continuous discharge of water having sediment material and some coal fines from the lower portion of the vessel, and

e. means in the path of the outflowing water arranged to remove magnetic particles therefrom and discharge them adjacent the incoming slurry of raw coal fines.

4. The apparatus of claim 3 wherein said vessel has a bottom, two end walls and two upwardly and inwardly extending sidewalls, said means for continuously injecting said slurry is positioned in a channel intermediate the sidewalls of the vessel, said outlet means comprises a pair of ducts in the bottom of said vessel, and said means arranged toremove magnetic particles from the outflowing water comprises a pair of rotatable drums suspended in the vessel and having a magnetic element suspended therein in a generally downwardly extended stationary position.

5. The apparatus of claim 4 wherein said ducts are positioned in concavities formed in said bottom which generally conform to said rotatable drums.

6. The apparatus of claim 4 wherein said injection means comprises a generally horizontal pipe extending between said end walls and having a plurality of apertures in the upper portion thereof through which pressurized fine coal slurry is dispersed.

7. The apparatus of claim 4 wherein each of said magnetic elements is suspended so as to exert a magnetic force in the area between said duct and said channel.

8. The method of continuously separating fine particles of a lower density from fine particles of a higher density admixed therewith by flotation in a medium of water having magnetic particles diffused therethrough to provide a heavy medium comprising the steps of:

a. confining the heavy medium in an enclosed vessel of upwardly-diminishing dimension with an overflow outlet at the top,

b. continuously introducing a slurry of said admixture to be processed into said confined heavy medium and maintaining a zone of agitation therein,

c. continuously discharging a concentrated slurry of fine particles of lesser density upwardly through the overflow outlet,

d. continuously withdrawing high density particles and water from which fine particles of lesser density have been removed from the vessel while separating the magnetic particles from the high density particles and water and immediately discharging the magnetic particles into the zone of agitation, and

e. regulating the inflow of slurry and the removal of concentrated slurry and the removal of water to maintain a substantially constant level of flotation liquid in the vessel below said overflow outlet. 9. The method of claim 8 wherein said slurry comprises coal fines and refuse in aqueous admixture and concentrated slurry of clean coal fines is removed through the overflow outlet.

10. ln a method for concentrating a fine coal slurry and removing impurities therefrom wherein an aqueous magnetite suspension is present which raises the specific gravity of the slurry to cause the fine coal particles to float to the top of said suspension while impurities settle to the bottom of the suspension, the improvement comprising,

a. injecting said fine coal slurry in the form of upwardly directed streams into said suspension whereby fine coal particles float to form a more concentrated slurry at the upper region of said suspension while impurities, magnetite and resultant less concentrated slurry settle to the lower region of said suspension,

b. subjecting said settling magnetite particles to a magnetic field directed from a rotating drum, which field causes said magnetite particles to be drawn to and held by the surface of said rotating drum, while said impurities and resultant less concentrated slurry are uneffected by said field,

. removing the magnetite particles from said magnetic field through rotation of said drum, whereby said magnetite is discharged from said drum surface and directed into said upwardly directed streams for further concentration of additional fine coal slurry comprising said streams,

(1. while removing a predetermined amount of said less concentrated slurry from said lower region and a concomitant predetermined amount of said more concentrated slurry from the upper region of said aqueous magnetite suspension.

Claims

2. The apparatus of claim 1 wherein said means in the path of the outflowing water to remove magnetic particles therefrom comprises at least one rotatable drum suspended in said vessel having therein stationary magnetic elements so positioned as to exert a magnetic field towards the bottom of said vessel.
3. Apparatus for concentration of coal fines by flotation in a mixture of water and magnetic particles comprising: a. a vessel of upwardly-diminishing dimension terminating at the top in a restricted discharge opening for concentrated coal slurry, b. means in the bottom of the vessel for continuously injecting a slurry of raw coal fines into the vessel to agitate the contents of the vessel, c. means for introducing magnetic particles into the vessel, d. an outlet means for the continuous discharge of water having sediment material and some coal fines from the lower portion of the vessel, and e. means in the path of the outflowing water arranged to remove magnetic particles therefrom and discharge them adjacent the incoming slurry of raw coal fines.
4. The apparatus of claim 3 wherein said vessel has a bottom, two end walls and two upwardly and inwardly extending sidewalls, said means for continuously injecting said slurry is positioned in a channel intermediate the sidewalls of the vessel, said outlet means comprises a pair of ducts iN the bottom of said vessel, and said means arranged to remove magnetic particles from the outflowing water comprises a pair of rotatable drums suspended in the vessel and having a magnetic element suspended therein in a generally downwardly extended stationary position.
5. The apparatus of claim 4 wherein said ducts are positioned in concavities formed in said bottom which generally conform to said rotatable drums.
6. The apparatus of claim 4 wherein said injection means comprises a generally horizontal pipe extending between said end walls and having a plurality of apertures in the upper portion thereof through which pressurized fine coal slurry is dispersed.
7. The apparatus of claim 4 wherein each of said magnetic elements is suspended so as to exert a magnetic force in the area between said duct and said channel.
8. The method of continuously separating fine particles of a lower density from fine particles of a higher density admixed therewith by flotation in a medium of water having magnetic particles diffused therethrough to provide a heavy medium comprising the steps of: a. confining the heavy medium in an enclosed vessel of upwardly-diminishing dimension with an overflow outlet at the top, b. continuously introducing a slurry of said admixture to be processed into said confined heavy medium and maintaining a zone of agitation therein, c. continuously discharging a concentrated slurry of fine particles of lesser density upwardly through the overflow outlet, d. continuously withdrawing high density particles and water from which fine particles of lesser density have been removed from the vessel while separating the magnetic particles from the high density particles and water and immediately discharging the magnetic particles into the zone of agitation, and e. regulating the inflow of slurry and the removal of concentrated slurry and the removal of water to maintain a substantially constant level of flotation liquid in the vessel below said overflow outlet.
9. The method of claim 8 wherein said slurry comprises coal fines and refuse in aqueous admixture and concentrated slurry of clean coal fines is removed through the overflow outlet.
10. In a method for concentrating a fine coal slurry and removing impurities therefrom wherein an aqueous magnetite suspension is present which raises the specific gravity of the slurry to cause the fine coal particles to float to the top of said suspension while impurities settle to the bottom of the suspension, the improvement comprising, a. injecting said fine coal slurry in the form of upwardly directed streams into said suspension whereby fine coal particles float to form a more concentrated slurry at the upper region of said suspension while impurities, magnetite and resultant less concentrated slurry settle to the lower region of said suspension, b. subjecting said settling magnetite particles to a magnetic field directed from a rotating drum, which field causes said magnetite particles to be drawn to and held by the surface of said rotating drum, while said impurities and resultant less concentrated slurry are uneffected by said field, c. removing the magnetite particles from said magnetic field through rotation of said drum, whereby said magnetite is discharged from said drum surface and directed into said upwardly directed streams for further concentration of additional fine coal slurry comprising said streams, d. while removing a predetermined amount of said less concentrated slurry from said lower region and a concomitant predetermined amount of said more concentrated slurry from the upper region of said aqueous magnetite suspension.