US2176902A - Method and apparatus for dewatering coal - Google Patents

Description

(k1.24,1939. T.S.HORROCKS METHOD AND APPARATUS FOR DEWATERING GOAL 3 Shets-Sheet 1 Filed June 21, 1937 INVENTOR Thmnws SL]flnvwck&

ATTORNEYS.

Oct. 24, 1939. 'r. s. HORROCKS METHOD AND APPARATUS FOR DEWATERING COAL Filed June 21, 1937 I5 Sheets-Sheet 2 INVENTOR:

Thoms S Jflwrocks By TTORNEYS.

Oct. 24, 1939. s HQRROCKS 2,176,902

METHOD AND APPARATUS FOR DEWATERING COAL Filed June 21, 1937 5 Sheets-Sheet 3 ITNESSES; INVENTOR- BY S. Jibrroaks,

p Q \/'mu 2% 'ATTORNEYS.

Patented Oct. 24, 1939 BETHOD AND APPARATUS FOR DEWATEB- ING COAL Application June 21, 1937, Serial No. 149,325

9 Claims. (01. 34-24) UNITED STATES PATENT OFFICE This invention relates to the dewatering of coal and is particularly useful in its application to relatively fine coal.

Raw coal as it comes from the mines contains a substantial percentage of impurities. Consequently a cleaning operation is required in order to obtain coal which will burn efliciently. A large percentage of the raw coal mined is cleaned by means of a fluid medium consisting of sand in suspension in water and therefore the cleaned coal, even after being allowed to drain, inevitably contains considerable moisture which is present as a film of water on the surface of the individual particles of coal and also as interstitial moisture maintained by capillary attraction between the coal particles. The percentage of retained moisture is particularly high in the case of the smaller sizes of coal. This retained moisture is responsible for a number of difficulties in the use of such coal. For instance, in the manufacture of gas and coke from coal, moisture in the coal increases the time required for-coking and efllciency of operation is impaired due to the heat waste involved in the unproductive evaporation of water and also in the destruction of the oven linings. Moreover, the water causes a weakening of the ammonia liquor which is one of the desired byproducts of the coking operation.

The retention of moisture in coal also leads to difliculties in shipment. High moisture content adds greatly to the cost of unloading in freezing weather, and, if the coal is to be shipped long distances, the freight on the moisture added in washing may counterbalance the enhanced value due to the ash reduction.

One method for removing moisture from coal includes the use of a large hopper into which the coal is piled, the water being allowed to drain through the coal by gravity to the bottom of the hopper from which it is then removed. This method does not effect sufllcient removal of the water due tothe surface forces involved, and a long drainage time is necessary to obtain a relatively small removal of water. Forced drainage by jigging or by means of shaking screens has also been proposed but all of these processes are extremely ineflicient. The same considerations of inefliciency of operation are applicable to centrifugal apparatus and to direct heat driers.

Various methods for dewatering coal by means of an air stream have also been proposed. In most cases an aircurrent induced either by suction or pressure is passed into a bed of the wet coal. A filter cloth is provided through which the air forces the removed moisture. This method is both inefficient and expensive. The juxtaposition of the coal particles in the bed of coal favors the retention of interstitial water because of the forces of capillary attraction present in a piled mass of coal. These forces are difficult to overcome and this is particularly true where it is impossible to prevent short circuiting of the air stream. Moreover, a further inefficiency arises from the fact that the water passes down through the bed of coal and consequently must be displaced'from the surface of the coal many times prior to its removal through the membrane provided at the bottom. This membrane is also a disadvantage because it is difllcult to maintain in a permeable condition due to the clogging effect of small particles. This objection applies, indeed, to any method involving a screening or straining out of water from coal through a pervious membrane or wall of any kind,--whether by gravitational influence, or by some'other force. It is to be noted that any method for dewatering coal in a piled condition will be inefficient and expensive for the reasons noted above.

Therefore the principal object of the present invention is to provide a method and apparatus for dewatering coal which will overcome the disadvantages recited above and provide an efiicient and relatively inexpensive means for the dewatering of coal. This, I have found, can be accomplished by directing a stream or jet of the wet coal, at sufficient velocity to rebound, against a substantially imperforate target disposed at an oblique or acute angle relative to the direction of the impinging coal stream, and extending beyond the area of contact of the coal with the target; so that while the coal itself is deflected and rebounds from the target in a direction different from that of its incidence, the water is deposited and remains on the target to travel along its surface beyond said area of contact, so that it can be collected and drained away, and prevented from remingling with the coal. The travel of the water along the target surface may be produced by mere gravity, if the target slopes downward at an angle to the horizontal beyond the area of impingement of the coal, or the water may be displaced along the target surface by a jet of air, which may also serve to carry or propel the coal against thev target.

Other objects and advantages characterizing my invention will become more apparent from the description hereinafter set forth of two examples of apparatus for dewatering coal according to my invention, having reference to the accompanying drawings, whereof:

Fig. I represents a side elevation of one type of apparatus embodying the invention, with portions thereof shown in cross section to illustrate the interior construction.

Fig. 11 represents an enlarged vertical cross section of the nozzle shown in Fig. I.

Fig. III represents an enlarged vertical cross section of said nozzle taken in a plane at right angles to the cross section of Fig. II.

Fig. IV represents a horizontal cross section of said nozzle taken as indicated by the arrows IV-IV of Fig; II.

Fig. V represents an end of the nozzle.

Fig. VI represents a plan view of the apparatus of Fig. I.

Fig. VII represents a plan view of a second type of apparatus embodying the invention; and.

Fig. VIII represents a side elevation of said second type of apparatus with portions thereof shown in cross section to illustrate the interior construction.

With reference to Figs. I to V1, the apparatus shown in the drawings comprises generally a hopper I into which the wet coal is introduced, a nozzle 2 from which such coal issues in a jet or stream of high velocity, a target 3 upon which the jet impinges, and a receptacle 4 for collecting the dry coal.

The hopper I is of a sufficient size to accommodate a substantial quantity of wet coal and desirably has associated therewith a helical screw 5 or other suitable means for continuously feeding the coal towards the nozzle 2. Coal may be brought to the hopper l in any suitable manner as for example by means of an endless belt (not shown) or other conveying means in common use in the art of coal handling.

The nozzle 2, as shown most clearly in Figs. 11 and III is provided with a pipe 6 through which a pressure medium, such as air or steam, is admitted. The pressure medium enters an annular chamber 1 surrounding the central passage 8 through which the coal is discharged and issues from a series of orifices 9. The central passage 8 is formed by the wall III which, together with the cylindrical wall N, forms the annular chemher I. It will be understood that the particular construction of the nozzle may be changed to great extent, but that essentially it functions to produce a jet of high velocity carrying the coal towards the target 3. In its preferred form the stream issuing from the nozzle is relatively wide and fiat, this result being accomplished by the shape of the tip ll.

The target 3 is inclined at an angle to the path of the coal striking thereon, and in order to prevent abrasion of its top surface, as well as to minimize destruction of the coal, it is provided with a face ll of rubber or the like. Coal bounds from the target into the collecting receptacle 4 which is housed over at the top by a casing II. The casing l5 confines the dust and prevents escape of flying coal. It may be provided with an exhaust pipe It for the escape of the pressure medium. Water separated from the coal drains over the face of the target 3 and an extension plate ll positioned beneath it into troughs l8 and is ultimately collected by the pipes l8.

The operation of the above described appara tus is as follows:

The coal passes downwardly out of the hopper i into a rapidly moving fluid stream, preferably an air stream moving at a high velocity, and the combined air and coal issue at a high rate of speed from the nozzle 2. It is to be noted that the closely packed wet coal undergoes a subdivision in the high speed fluid stream and this subdivision brings about a disruption of the capillary forces existing between the individual pieces of relatively small coal. The interstitial water which exists by virtue of the capillary attraction is thus freed, a part of such water forming into droplets in the fluid stream and the other part adhering as a surface film on the coal particles.

The separated coal particles are acted upon by the fluid stream and the surface film of water is transformed into free droplets which are further subdivided along with the droplets resulting from the freed interstitial water in the fluid stream.

The fluid stream containing particles of coal and finely subdivided droplets of water issues from the nozzle 2 at a relatively high velocity and strikes the surface ll of the target 3. The coal is somewhat elastic and therefore rebounds from the surface of the target and in so doing the residualvmoisture on the surface of the coal is stripped from the coal and deposited upon the surface of the target. This stripping effect is 7 probably brought about by a combination of fricfluid stream are permanently deformed on conv tact with the surface of the target due to their being substantially inelastic and in their deformed condition adhere to the surface of the target by virtue of surface tension. This film of water existing on the surface of the target is continually displaced from the region of contact by the force of the fluid stream and as the film on the surface of the target accumulates it is draine'd into the troughs IS, a portion of the water being collected over the surface of the extension plate The dewatered coal rebounding from the surface of the target is collected in a suitably placed receptacle as shown in Fig. I.

With reference to Figs. VII and VIII of the drawings the apparatus illustrated includes a hopper la,'a nomle 2a, a target in, and a collecting receptacle 4a. The pressure medium, air,

2a. through a pipe 20 having therein a regulating valve II, A gauge 22 registers the pressure and aids the operator in obtaining the correct setting for the valve 2|. Coal introduced through the hopper la. is discharged through an elbow 28 and T-connection 24 into the pressure line 20 behind the nozzle 2a.

The target In is so inclined that the coal deflected therefrom and the water drained therefrom travel in opposite directions, the water draining into a collecting well 25 and the coal bounding into the receptacle 4a and being confined by the superimposed casing 26.

The operation of the alternative form of apparatus shown in Figs. VII and VIII of the drawings is substantially the same as the operation of the apparatus shown in Fig. I. Interstitial moisture is freed and subdivided in the same way and the surface moisture is removed from the coal and subdivided in a similar manner. Residual surface moisture is also stripped from the partieles of coal by the impact with the target.

While the present invention has been described with reference to two specific embodiments there of, it will be understood that various modifications may be made in the method and apparatus herein described and illustrated, and it will be understood that while the invention is primarily directed to the dewatering of coal, it may be used to advantage on other like materials, all without departing from the spirit of the invention as defined in the annexed claims.

Having thus described my invention, I claim:

1. A method of dewatering coal which comprises directing a stream of the wet coal, at sufficient velocity to rebound, against an imperforate target disposed at an acute angle relative to the direction of the impinging coal stream, and extending at an angle to the horizontal downward beyond the area of contact of the coal with the target, so that while the coal itself is. deflected and rebounds from the target in a direction different from that of its incidence, the deposited water drains along the target surface beyond the said area of contact of the coal therewith; and collecting and removing this water, and thus preventing it from mingling with the coal.

2. A method of dewatering coal which comprises propelling wet coal in a fluid jet of high velocity against an imperforate target disposed at an acute, angle relative to the direction of the impinging coal-laden jet and extending at an angle to the horizontal downward beyond the area of contact of the coal with the target, so that while the coal itself is deflected and rebounds from the target in a direction diflerent from that of its incidence, the deposited water drains and is displaced along the'target surface by the impinging elastic fluid beyond the said area of contact of the coal with the target; and collecting and removing this deposited and displaced water, and thus preventing it from mingling with the coal.

3. A method of dewatering coal which comprises directing the wet coal against a rubberfaced target at such velocity and at such angle that the coal rebounds from the target, at an angle thereto, while the water associated with the coal adheres to the target surface and drains away from the region of impingement, separate from the rebounding coal.

4. A method of dewatering coal which co prises directing wet coal at high velocity downward against an upward exposed sloping target disposed at such angle relative to the direction of the impinging coal that the coal is deflected from the target, at an angle thereto, while the water associated with the coal adheres to the target, and continually draining away this deposited water along the sloping surface of the target, separate from the deflected coaL;

5. A method of dewatering coal which comprises directing wet coal at high velocity in a downard sloping direction against an upward exposed target sloping counter to the direction of the impinging coal at such-angle relative to said direction that the coal is deflected from the target in the same general direction, while the water associated with the coal adheres to the target and drains away along the sloping surface of the target in the opposite direction.

6. Apparatus for dewatering coal comprising means for delivering and directing a stream of the wet coal at sufiicient velocity to rebound; an imperforate target disposed in the path of this coal stream at an acute angle relative to its direction of impingement on said target, and extending at an angle to the horizontal downward beyond the area of contact of the coal with the target, so that while the coal itself is deflected and rebounds from the target in a direction different from that of its incidence, the deposited water drains along the target surface beyond the said area -of contact of the coal therewith; and means for collecting and removing this water, and thus preventing it from mingling with the coal.

7. Apparatus for dewatering coal comprising a rubber-faced target, means for directing wet coal against said target in a stream of elastic fluid, at such velocity and at such angle that the coal rebounds from the target at an angle thereto, while the water associated with the coal adheres to the target and is continually displaced along the target surface out of the region of impingement of the coal by the force of the impinging elastic fluid, and means for separately collecting the coal rebounding from the target and the water displaced along its surface as aforesaid.

8. Apparatus for dewatering coal comprising a nozzle for delivering a stream of elastic fluid at high velocity, means for introducing wet coal into the stream through said nozzle, and an upward-exposed target in the path of the coalcharged stream sloping counter to the direction of the impinging coal at such angle relative to said direction that the coal is deflected from the target in the same general direction, while the water adheres to the target and drains away along the sloping surface of the target in the opposite direction. 1

9. Apparatus for dewatering coal comprising a nozzle for delivering a stream of elastic fluid at high velocity and with a downward direction, an-

upward-exposed target in the downward path. of the coal-charged stream sloping downward in the direction of the impinging coal at such angle relative to said direction that the coal rebounds at an angle to the target and beyond the same, while the water adheres to the target and drains along its sloping surface, and means for collecting the drainage from said target and thereby preventing reunion thereof with the rebounding coal.

THOMAS S. HORROCKS.

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