US2739710A - Hindered settling separation apparatus - Google Patents

Description

March 27, 1956 G. WILMOT 2,739,719

HINDERED SETTLING SEPARATION APPARATUS Filed 001. 25, 1952 Fig.

INVENTOR. GEORGE L.W|LMOT BY 22 20 K 20 22 22 M0 ATTORN EY HINDERED SETTLING SEPARATIGN APPARATUS George L. Wiimot, Hazleton, Pa., assignor to Wiimot Engineering Company, a corporation of Pennsylvania Application October 23, 1952, Serial No. 316,373

3 Claims. (Cl. 209-173) This invention relates generally to the hindered settling separation of minerals, and pertains particularly to the cleaning of minerals by subjecting them to an upwardly flowing body of a liquid medium comprising a suspension of finely divided solid particles in water. The invention is directed specifically to improvements in the apparatus for cleaning coal and therefore will be described herein as thus employed, although it will be apparent that it may be applied as well to the separation and recovery of other minerals so long as the specific gravity of the separating liquid employed is determined by the proportion of finely divided solids maintained in suspension.

Hindred settling procedures for cleaning coal are broadly old and in very wide use. According to such procedures, briefly, raw coal is fed into a vessel containing the liquid separating medium and a constant and uniform upward flow is induced in the medium which carries the light coal upwardly over an overflow discharge at the top of the vessel while permitting the heavy refuse (rock and slate) to sink to a discharge opening at the bottom of the vessel. Customarily, the overflow product is dewatered and the recovered water collected in a sump from which it is recycled through the vessel for further use as aforesaid.

In order to reduce the velocity of the upwardly flowing medium in the vessel, it has been found advantageous in the art to increase its specific gravity by suspending there in finely divided coal particles (silt). When this is done, however, it is extremely important to maintain at a constant value the percentage of silt suspended in the medium, for even small variations in the solids content of the medium are suflicient to change its specific gravity to the extent that some rock is recovered with the desired coal product, or some of the coal is lost with the rock refuse. For example, as little as 0.1% variation in silt content of the medium will exert an appreciable influence on the quality of the separated coal and refuse products.

One of the most serious shortcomings of prior art coal cleaning methods and apparatus, in which a suspension of silt in water is used as the separating medium, is their failure to maintain the medium at constant specific gravity. The principal reason for this difficulty has been the settling out of the silt component in the sump and the accumulation of the silt at the sides and bottom of the sump, so that the medium recirculated to the separating vessel becomes progressively leaner in the silt component. This imposed a serious obligation on the operator of the apparatus, first to discover the changes in specific gravity of the medium as they occurred, and then to compensate for such changes by increasing the velocity of the upwardly flowing stream of separating medium in the cleaning vessel.

While careful operation usually sufliced to produce a marketable cleaned coal product, unpredictable and disastrous changes in specific gravity of the medium often occurred when masses of accumulated silt in the sump broke loose and were abruptly added to the separating medium, resulting in a sudden increase in specific gravity States Patent which often carried sufficient rock and slate over with the coal to raise its ash content materially.

Inasmuch as many state laws impose definite limitations on the percentage of ash permissible in the coal, it can be seen that a small variation in the specific gravity of the separating medium (due to fluctuation of the silt content) may render a large quantity of coal unmarketable, requiring it to be subjected to expensive recleaning or to be sold at a loss at the lower prices of the next lower grade.

It is to the correction of the above mentioned difficulties that the present invention is directed.

Accordingly, it is a primary object of the invention to provide an apparatus for cleaning coal by the hindered settling technique which will assure the maintenance of the desired specific gravity range of the separating medium, and yield a coal product of uniformly high quality.

A more specific object is to provide in hindered settling separation apparatus an improved combination of a sump and a drain manifold therefor, whereby the liquid medium stored in the sump is removed for recirculation to the separating vessel from a multiplicity of areas collectively comprising the bottom of the sump, thereby effectively precluding the settling out and accumulation of silt in the sump.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is an elevation view, partly in section, of a conventional hindered settling separation apparatus as modified by my improved drain manifold for the sump;

Fig. 2 is a horizontal section taken along the line 2-2 of Fig. 1, looking in the direction of the arrows; and

Fig. 3 is a side elevation of the drain manifold, shown in its relation to the bottom of the sump.

The apparatus with which my invention may be practiced is conventional and, if desired, may take the form of that described in my United States Patent No. 2,533,- 655. Such apparatus is illustrated in the drawing, and includes a separating vessel or tank 10 the top edge of which constitutes a discharge lip for the float product of the separation carried out in the tank. An overflow launder 11 surrounds the top of the tank ill) to receive the overflow product thereof, and a refuse discharge pipe 12 is provided at the vertex of the conical bottom of the tank through which the heavy sink product passes to a refuse conveyer 13 for removal. Raw feed to be cleaned is introduced into the tank by means of a feed chute 14, and a rotatable hydraulic agitator 15 is positioned concentrically within the tank to induce in the liquid medium contained therein the upward flow necessary to hindered settling separation, as will appear hereinafter. A dewatering shaker screen 16 receives the overflow product from the launder 11, and a sump 17 under the screen collects and holds in reserve for recirculation the liquid medium which drains through the screen.

At the bottom of the'sump 17 is disposed a multi-orifice drain manifold 18 of my invention, comprising a main tubular member 19 having apertures Zii spaced longitudinally along the top and bottom thereof, and apertures 21 similarly spaced along the sides thereof. Preferably, the apertures 26 are staggered with respect to apertures fit, as shown. The tubular member 19 is preferably placed symmetrically in the sump, as shown, and is provided with branches 22 extending toward the walls of the sump and terminating adjacent thereto. The branches 22 are of course open at their free ends and consequently, in conjunction with the apertures 20 and 21, drain simultaneously a plurality of widely spaced areas which collectively comprise the bottom of the sump. It will be apparcut that the number and disposition of the branches 22 may be widely varied to meet the specific needs of any given situation.

The tubular member 19, which is preferably stepped, as shown, to afford substantially equal suction at its drain openings, is provided at one end with a collar or flange 23 by which it is secured to the sump wall with bolts 24. The free end of the member 1 is supported by a prop 25 resting on the bottom of the sump. Aligned with the tubular member 19 outside the sump, and communicating with the tubular member, is a return line 26 having a flange 27 by which it may be secured water-tight to the outside of the wall of the sump using the same bolts 24. The return line 26 is connected to theintalte side of a centrifugal pump 28, driven by a motor 29, the pump discharging into a second return line 36) communicating with the agitator l5. Excess water is discharged from the sump by means of an overflow 31.

When raw coal enters the tank by means of the feed chute 14, the upwardly flowing medium of silt and water carries the light clean coal over the edge of the tank and into the launder it, while allowing the heavy refuse of slate and rock to fall to the bottom of the tank and through the lower discharge pipe 12. The overflow product then flows upon the shaker screen 16 which allows the medium to drain off into the sump 17, the coal remaining on the screen where it is first washed to remove adhering silt and then discharged from the end of the screen as clean coal 32. Since the pump 28 is continuously in operation the manifold 18 continuously withdraws the liquid medium from a multiplicity of spaced areas collectively forming the sump bottom. This action of the manifold induces a substantially uniform downward flow of the medium in the sump over substantially its entire horizontal cross-sectional area, with the result that practically no static or sluggishly moving medium may be found therein which would afford any opportunity for the silt to separate out and accumulate in the sump. The medium removed from the sump by the manifold 18 is, of course, returned to the agitator under pressure of the pump 28 for reuse in the separation tank.

It will be seen from the foregoing that I have provided an apparatus for maintaining in suspension substantially all of the fines in the system of a liquid medium whereby its specific gravity remains substantially constant. What silt is inevitably gradually lost through the sump overflow 31 must of course be made up by periodic additions of silt to the medium system; such additions, however, are routine and of predictable character and may be readily made without interfering with the separation, as distinguished from the unpredictable and abrupt variations in specific gravity of the liquid medium which characterized prior art hindered settling operations, as hereinabove described.

Another significant advantage afiorded by my invention is that the sump employed in any hindered settling apparatus may now be of almost any reasonable size and, since settling out of the solid fines is practically eliminated, the sump may have vertical walls, and a bottom of large area, thereby permitting the greatest volume for any given floor area occupied by the sump. Prior art sumps, on

the other hand, were deliberately kept as small as the liquid medium requirement of the separation apparatus permitted, and the sump walls were tapered downwardly to the drain in an attempt to avoid settling out and accumulation of silt on the sump sides and bottom. Not only were these precautions unavailing to correct the shortcomings of prior art apparatus but, with the accumulation of silt in the sump, with consequent decrease in its capacity, the liquid medium flowing out the sump overflow carried with it significant quantities of silt which necessitated an additional expensive cleaning operation before such sump overflow could be discharged into any surface stream.

It will be understood that my invention is not to be limited to the precise details shown and described herein for the purpose of illustration, since various modifications in operation and construction will be apparent to those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

What I desire to claim is:

1. In a hindered settling separation apparatus, a separating vessel for containing a liquid separating medium, hydraulic means in said vessel for inducing a continuous upward flow of said medium therein, a substantially vertical-sided sump for receiving medium leaving said vessel, a multiple-orifice drain for said sump disposed adjacent the bottom thereof, and a conduit operatively connecting said drain with said hydraulic means whereby said medium is returned from said sump to said vessel, said drain comprising a manifold including a main tubular member apertured along its length and having a plurality of branches projecting from said tubular member and extending toward the sides of said sump, whereby said manifold may drain simultaneously a plurality of widely spaced areas collectively comprising the bottom of said sump.

2. In a hindered settling separation apparatus including a separating vessel and a sump between which vessel and sump a separating medium is adapted to be circulated during operation of the apparatus, a multiple-orifice drain for said sump disposed adjacent the bottom thereof, and a conduit for returning to said vessel medium collected by said drain, said drain comprising a manifold including a main tubular member apertured along its length and having a plurality of branches projecting from said tubular member and extending toward the sides of said sump, whereby said manifold may drain simultaneously a plurality of widely spaced areas collectively comprising the bottom of said sump.

3. In a hindered settling separation apparatus, a separating vessel for containing liquid separating medium, said vessel having a discharge lip for the float product from said vessel, a sump for receiving medium leaving said vessel with said float product, a multiple-orifice drain for said sump disposed adjacent the bottom thereof, and a conduit for returning to said vessel medium collected by said drain, said drain comprising a manifold including a main tubular member apertured along its length and having a plurality of branches projecting from said tubular member and extending toward the sides of said sump, whereby said manifold may drain simultaneously a plurality of widely spaced areas collectively comprising the bottom of said sump.

References Cited in the file of this patent UNITED STATES PATENTS 482,436 Deutsch Sept. 13, 1892 1,545,637 Chance July 14, 1925 1,664,865 Snow Apr. 3, 1928 2,206,980 Wade July 9, 1940 2,521,152 Davis Sept. 5, 1950 2,533,655 Wilmot Dec. 12, 1950

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