US2150917A

US2150917A - Process of and apparatus for separating

Info

Publication number: US2150917A
Application number: US98821A
Authority: US
Inventors: Wiling B Foulke; William A Wills
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1936-08-31
Filing date: 1936-08-31
Publication date: 1939-03-21
Anticipated expiration: 1956-03-21

Description

March 21, 1939. w. B FOULKE ET AL PROCESS OF AND APPARATUS FOR SEPARATING Filed Aug. 51, 1936 4 Shee'r.s-Sheet 4 INVENTO RS l/z'ldziiglil oalife M W ZZZLam M4. Willy,

March 21, 1939. w. B. FOULKEKET AL PROCESS OF AND APPARATUS FOR SEPARATING Filed Aug. 51, 1956 4 Sheets-Sheet l 314 JZt W 1 I I William JQ. l V ZLS,

4 Sheets-Sheet 2 INVENTORS March 21, 1939. w. B. FOULKE ET AL PROCESS OF AND APPARATUS FOR SEPARATING Filed Aug. 31. 1936 March 21, 1939. w. B. FOULKE ET AL 2,150,917

PROCESS OF AND APPARATUS FOR SEPARATINC- Filed Aug. 31, 1936 4 Sheets-Sheet 3 noooguocaooou In 00 000110900 9. oouo uoc o a 0 O 0 a o 0 o c 0 l5 6 Q 0 o O 00 0 a 6 o a c 0 INVENTORS W lliz fifialk$ 339 W zzzzamA.

ATTORNE Patented Mar. 21, 1939 UNITED STATES PATENT OFFICE PROCESS OF AND APPARATUS FOR SEPARATING Willing B. Foulke, Media, and William A. Wills, Frackville, Pa., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application August 31, 1936, Serial No. 98,821

8 Claims. (01. 209172) This invention relates to the separation of mmin which one ingredient of the mixture will sink erals from gangue by the use of a liquid of specific down and another ingredient of the mixture will gravity between that of the mineral and the rise to and float on the top. Certain phases of gangue. The invention will be described as it is the parting liquid process are affected by the applied to the separation of coal from its indigphenomenon of altered specific gravity but they 5 enous impurities, particularly slate, a separation are distinguished from froth flotation. in which the process and apparatus are of par- The suggestion was made toward the middle of ticularly great value, but it is to be: understood the nineteenth century that ferric chloride 1856 that this description is illustrative, not limitative. or sulfuric acid could be used as a parting liquid 10 Coal appears to have been known to, and to for the separation of coal and slate and attempts 10 some small extent used by, the ancients. Its use were made in England to run the ferric chloride in China at about the year 1200 is described by pro i p i n W h the l e b the jigs Marco Polo and about 1500 Agricola described a were highly developed, the use of a parting liquid process of freeing minerals from their gangue was a bare suggestion and the attempt was a which is the direct progenitor of the jig process failure because of the undeveloped state of the 15 of coal cleaning, which has the widest use today. new process, the highly developed state of jig In the early days of coal mining in Europe and, separation, and the inability of experimenters to in the United states only the thick seams were m k h p r in process a success n its lf. The mined. Hand methods were largely in vogue and Original attempt having be n e, however, Sub- 26 the need for anything except hand cleaning, or sequent inventors worked with the suggested the most crude of mechanical methods was unprocess and a h t o patents have n s necessary. As the thick seams were used up, howparticularly in England and in the United States, ever, it became necessary to use thin seams and dealing With processes of the parting liquid yp seams containing veins of rock, which entailed T0 the b of 0111' knowledge and belief, hOWeVeI,

the necessity of removing the rock before the coal t y Such process that has been need 5110- 25 could be sold. The method which came most cessfully is One that depends upon the p g efprominently into use and which is today the feet of a suspension of solids such as sand or clay standard of separating coal and slate depends in Whtef- The art With respect teparting ed aupon the rates at which bodies of different densiof homogeneous Character is in industry ties sink through a liquid such as water. It is day as it was in the nineteenth century, un e 30 known that bodies sink through a liquid at rates to compete The parting q s r w h more which are functions of their respective densities, than t e 00841 and the 103588 thereof are s reat the denser sink the more swiftly. The standard th h y w h the theoretical v n es jig washer of the industry takes advantage of this O more accurate Separation- The Processes principle, but instead of permitting the solids to emse v being Crude and p d, a e insink through the liquid, the liquid is forced c pable of competing w h the highly developed through a screen on which the solids rest at a processes already in use in the industryy rate which lifts the layer of coal off the heavier a e incomplete p sses, lacking a number of slate, the coal being carried with the rush of elem nts essential to success.

liquid over a Weir and the slate being discharged It is an object of this invention to separate coal 40 at a lower point from the screen. Jigs are highly from slate, and other minerals from their gangues developed and are of excellent capacity and per Or o each Other, by a p Which pe ds formance. However, the competition of oil has p the Parting effect of a liquid 0 te ed ate driven coal producers to find means of cleaning Spec g v y- It is another Object of this incoal which will be more accurate in separating vention to provide efficient apparatus to accom- 45 useful from useless lumps and producers and inplish such separation. Other objects of the inventors have turned their thoughts to those procvention will be in part apparent and in part more esses of separation which depend upon the partfully hereinafter set forth. ing action of a liquid having specific gravity be- The objects of the invention are accomplished tween that of coal and that of slate. by inserting the materials to be separated into a 50 The use of a parting liquid is tobe distinmoving liquid of specific gravity intermediate guished from froth flotation. Froth flotation those of the materials which are to be separated, alters the apparent specific gravity of a body by by dividing middlings between the mineral and encasing it within a bubble. Parting processes, gangue according to the value: of the middlings,

however, depend upon the use of a parting liquid by effecting the separation under hermetical seal, 55

and by the apparatus which is more fully hereinafter described.

Figure 1 is an apparatus capable of carrying out the parting step of the process; Figure 1 is a vertical section through the apparatus; Figure 1a is a cross-section on the broken line la, la of Figure 1; Figure 1b is a detail, partly in section, of a preferred modification of wedge 336331; Figure 3c is a section on Figure 1b; Figure 1d is an elevational view partly in phantom and partly in section showing the parting apparatus; Figure la is a section of line I e, le of Figure 1d; Figure If is asection of line If, I of Figure 1d; Figure 19 is a section on line lg, lg of Figure 1; Figure 171. is a section on line Ih, In of Figure 1; Figure 12' is a section on line Ii, Ii of Figure 1; Figure 17' shows means for operating the preferred embodiment of Figures 1b and 1c; Figures 1k and II show a preferred method of operating the apparatus of Figures 1b and 10.

Figures 2 and 20 do not refer to section 2 of the apparatus, but to an apparatus by means of which the efficiency of separation can be expeditiously determined. Figure 2 is a plan view of a portion of the apparatus partly in section and Figure 2a is a cross-section on the line 2-2, 2-2 of Figure'2. Figure 2b is a drawing of a scoop; Figure 2c is an enlarged detail of the hinge connection.

In Figures 1 to ll is illustrated the separating chamber. Referring to the numerals, 3 is an enclosed tank; 3| are channel-shaped edges to openings in the top of the tank; 32 are covers for the said openings; 33 are flanges on the said covers of size to fit within the said channelshaped edges of the openings; 34 is a liquid which partially fills each said channel-shaped opening forming a hermetical seal; 35 is a vent pipe; 31 is a motor support mounted on the said tank; 38 is a motor of variable speed; 39 is a speed reducing gear of customary construction comprising a chain of large and small driving and driven wheels; 300 is a shaft running crosswise of and projecting somewhat beyond the sides of the tank; 3M and 302 are sprocket wheels keyed to the shaft 300 at opposite ends thereof; 303 304 are chains on opposite sides of the tank driven from the said sprocket wheels respectively; 305306 are sprocket wheels mounted on the ends of

shafts

301 and 308, respectively, said shafts passing through the wall of the said tank; 309309 are stufling boxes which can be filled with grease from the outside of the tank through the fittings 3); 312 are sprocket wheels keyed to the shaft 308; 3|3 are wheels mounted on shafts 314 which are journaled within the tank; 3l5 is a wedge-operated take-up mechanism whereby one roller 3l3 can be moved longitudinally of the machine to take up the slack in the chain. One take-up means is placed at each end of the roller. 3l6 is a screw for operating the wedge and moving the roller; 3I1-3l1 are conveyor chains; 3! is a flight of a conveyor which is mounted on the conveyor chains 311; 319 are perforations in the flights of the conveyor; 320 is a conveyor pan bent at the point 32| and having a discharge lip and chute 322; 323 is a wedgewire screen forming the bottom of the upper portion of the conveyor pan; 324 is a section of the tank wall spaced considerably away from the said screen to permit liquid to make its way through the said screen and to be collected in the said portion of the tank; 325 is a channel leading from the portion 324 past the outside of the tank and connecting with the interior of the tank at 326; 321 are blow-out connections to permit the forcing of a stream of Water or other liquid into the tank at that point; 328 is a chute projecting through the side of the tank; 329 are dividing walls in the chute; 339 is a back plate of a hopper; 33l are perforations in the back part of the hopper; 332 is a portion of the hopper back plate which is inclined diagonally forward and which contains the perforations 33I 3320-3320 are perforated portions of the said back plate of the hopper which are continued beyond the side plates thereof; 333334 are side walls of the said hopper, both being inclined inwardly to the degree necessary to constrain any material entering through the chute 328 and passing to the bottom of the tank to fall within the conveyor pan; 335 is the front wall of the said chute which is constructed, in the form of the invention shown in Figure 3, as one piece of the front conveyor pan; 336 is a section of the said wall inclined diagonally toward the receiving end, and 331 is a portion of the said wall inclined toward the discharge end whereby to present the. wedge face toward the charging end; 338 is a conveyor pan; 339 is a wedge-wire screen forming the bottom of the upper portion thereof; 340 is a discharge chute attached to or forming a part of.

the said conveyor pan; 34|-34l are sprocket wheels on the shaft 301 over which are trained the chains 342342 of the flight conveyor 343; 344 is a bend in the said flight conveyor pan; 345 is a shaft carrying two sprocket wheels at the said bend; 346 is an extension of the conveyor pan beyond the sprocket wheels 345 and being continued downwardly to form the wedge; 34'! are means for adjusting the position of the sprocket wheels 348 which are mounted on a trunnion to carry scraper flight conveyor 343; 349 is a pan extending from side to side of the machine to catch the drip which passes through the wedge-wire screen 339 and return it to the liquid in the tank; 350 is a drain at the rear and lowest point of the tank, whose bottom is preferably inclined; 35I is a chamber beneath the said screen; 352 are a pipe and valve to permit the 'drawing 01f of the sludge which may collect and pass through the said screen, the said sludge being passed through the said pipe to the settling. tank to be hereinafter described, the continuation of the said pipe not being shown; 353 is a chamber attached to the Wall of the tank; 354 is a screw operating in a nut 355 fastened to the tank; 356 is a stuffing box through which the said screw passes; 35'! is a cylinder attached to the said screw; 358 is a pipe projecting within the box 353 and within the cylinder 35'! having therewith a movable fit made liquid-tight by machining or by the use of a. satisfactory sealing material; 359 is a valved pipe leading to the box 353; 360 are openings below the parting liquid level connecting tank 3 and weir box 353; 360i is an opening connecting weir box and tank above the water level; 36! is an enclosed weir box on the side of the machine; 3621s a pipe weir within the box to control the water level. The pipe 362 is connected to the settling tank. 363 is a pipe leading at 364 and 365 into the tank; 366 is a hollow gauge within the pipe 363 and projecting thereabove. Shaft 366 of the said gauge is preferably calibrated on its outside and its hollowness is used for the insertion or withdrawal of shot or other heavy material to its interior so that it can be standardized against the specific gravity of the parting liquid in the apparatus to record correctly its level; 361-368 are oppositely placed hollow projections on the sides of the apparatus; 369-310 are removable covers held on by bolts or other satisfactory means not shown to hermetically seal those of the said openings which are not in use; 31l-31l are flanges on the said projections designed to abut against and form a hermetical seal with similarly placed flanges or similarly projecting members of that apparatus which accomplishes the washing; 3280 is a manifold forming a part of the chute connected to a suction apparatus not shown and through openings 328! to the chute whereby any escaping gases may be caught; 312 indicates the framework which supports the tank; the line 313 indicates the upper level of the liquids in the tank; the line 314 indicates the interface of the separating liquid and the light liquid; 315 is a pipe opening into the tank whose purpose will be hereinafter described; 311-311 are angle bars supported either from the

members

332 and 331 or from the sides of the tank by bars which cover the conveyor chains and prevent them from being damaged by the descending slate; 319 is a screen extending preferably the full depth of the liquid to prevent light materials from being washed back into the path of the outer conveyor. The screen stretches from wall to wall of the tank between the chute and the outer conveyor and from a point slightly above the level of the liquid to a point just short of the lower conveyor.

This apparatus is operated to accomplish this step of the process as follows: The valve of pipe 359 is opened and heavy liquid is admitted to the tank through openings 360 until the level 314 is indicated on the sight gauge- 366. Water is then run into the tank through the orifices 315 until the level 313 is reached. A continuous flow of water may be maintained through the machine through the pipe 315 and the overflow 362, if it is desired, or water may be added intermittently and as needed. The height of the parting liquid in the tank is regulated by the overflow 351. As the liquid is admitted it rises in the tank and in the box 353 until it reaches the open top of the cylinder 351 at which point it flows downwardly through the said overflow and through the valve and pipe 358 to the used liquid tank.- The valve in the said pipe 358 may be kept open and a continuous flow of liquid pass into the chamber through pipe 359 and out of it through pipe 358, or the operation may be made intermittent, control being kept by observation of the sight gauge.

The tank having been filled to the proper level with liquid, coal is dropped from the conveyor into the chute 328, passing in four streams down the divisions 329 by which it is distributed across the width of the tank. The chute 328 may be placed on either side of the machine as is indicated in Figure 16, an opening on either side being provided, that not in use being closed by a plate 316. The apparatus is started; the motors drive the two conveyors either at the same or at different speeds depending to some extent upon the quantity of material each has to handle. The coal, slate, and other admixed impurities drop into the water layer while still in the chute so that they are dispersed by the water before reaching the parting liquid; the splash made by their falling is dissipated and entrained gas is removed before they leave the chute. Passing through the water layer they enter the parting liquid, whose density has been selected to be between that of coal and that of slate. The coal floats on the surface of the parting liquid, the slate sinks down guided by the hopper 334 and, entering the conveyor pan, is picked up by the scraper conveyor blades and carried toward the discharge. The coal floating at the inter face of the liquids is picked up by the conveyor 343 and carried toward and onto the conveyor pan 346. The specific gravity of the liquid is preferably chosen to be only slightly lower than that of the middlings. The middlings are those portions of the mixture which contain in one lump both slate and coal. The middlings tend to sink only slowly in the liquid whereas the slate sinks instantly and the coal floats.

Each of the conveyors acts as a pump, the effect of which can be varied by the use of scraper blades of either solid or foraminous cross section, the number of openings in the said scraper blades being variable to secure pumping actions of different intensity. As the outer conveyor sweeps sunken material along its conveyor pan and up the incline toward the discharge, some of the entrained liquid tends to fall back through the orifices in the flights and that which remains is sucked out of the material as it is pushed over the wedge-wire screen 323. The slate is discharged through the hopper 322 into the trough 4| which forms a part of the washing apparatus elsewhere described. The lower plate of the conveyor pan of the inner conveyor 338 is carried well beyond the pinion 345 and is then bent inwardly as indicated at 3460 so that the floated material will be swept on without jamming between the flights and the pan. By carrying the conveyor pan beyond the sprocket wheels 345 the chain is enabled to bend upwardly, and enough slack is provided therein so that when coal tends to jam the conveyor by taking up slack it may jump and release it without damage. The conveyor flights then sweep the coal up the inclined pan, over the wedge-wire draining screen 339, and eject it through the hopper 340 onto the trough 42 which forms a portion of the washing apparatus elsewhere described. The liquid which is driven by the outer conveyor passes through the wedge-wire screen 323 downward through the chamber 324,

outside the main wall of the tank through the passage 325 and the opening 326 into the chamber which is formed in back of the partition 336-331. The liquid which is entrained by the inner conveyor is swept up the inclined conveyor pan, passes through the wedge-wire screen 339, flows down the drain board 349, and is carried back to the chamber behind the partition 336-331. Sides 333-334 of the trough, together with the sides of the tank, form tubes 380-38l through which liquid from channel 325 and the chamber beyond 336-331 may travel to the receiving end of the machine, entering again into the separating chamber through the orifices 33| of the plate 330. There is thus maintained a constant motion of separating fluid and its superimposed sealing liquid from the receiving toward the discharge end of the machine. The length of the separating chamber, namely the distance between the plate 330 and the wedge 336-331 is such that the pieces of coal will have risen to the top of the separating liquid and the pieces of slate will have dropped to the bottom before the wedge has been reached, but the middlings, due to the selection of a parting liquid of only slightly lighter specific gravity, will be held in suspension, slow- 1y sinking. The middlings rich in coal sink at a slower rate than the middlings poor in coal, due to their different densities, and a classification of the middlings takes place before the wedge is reached. The wedge then directs the richer middlings upward into the coal and the coal-poor middlings downward into the slate.

In Figures 1b and 1c is shown a means of varying the proportion of middlings which is thrown into the coal and a means which materially contributes to the production of coal with a standard ash content. In those figures 346 is the bottom of the conveyor pan; 383 is a plate; 382 is a hinge connecting the plate to the lip of the conveyor pan; 385 is a plate and 386 is a hinge connecting the plate 385 to plate 383; 381 are hooked-shaped members which underlap the edges of the channel irons 311 for sliding movement. On the plate 383 at a point near the hinge 386 there is connected a lifting rod or cable 381 which extends upwardly between the conveyors and the wall of the tank and through a water seal box 388 mounted in the side of the tank to a point on the outside from which it may be manipulated. 389 are rods. By pulling up on one said rod the plate 383 will be lifted, and the plate 385 will swing toward the receiving end of the machine, the edge 386 of the wedge will have been raised and a greater proportion of the middlings will have been directed into the slate, producing a coal of decreased ash content. If, on the other hand, a coal of increased ash content is desired, a second rod attached at the lower end of plate 385 and projecting through the wall of the tank in the same manner may be manipulated to draw the plate 385 rearwardly and lower the angle 386. As shown in Figure 1h enough room exists between the edge of the conveyor flights and the wall of the tank to permit the passage of a rod, and by stationing and sealing tank 388 entirely outside of the wall 3 no interference between the conveyor and the rods will be experienced. The lower end of the rod may be attached to the wedge by a cable, as shown.

In Figures 1k and ll is shown another means of adjusting the wedge. In those figures 3 refers to the tank; 39039U are elongated boxes on the outsides thereof (a corner of which is shown in dotted lines in Figure l); 391 are slots connecting the interior of the tank with the said boxes; 392392 are links attached to the lower corners of the wedge; 393393 are pins attached to the links, passing through the slots 39! and mounted in movable blocks 394; 395395 are rods attached to the said blocks bored and screw-threaded; 396-396 are revolvable screws mounted in bearings attached to the sides of the boxes bearing at their heads pinions which mesh with pinions on shaft 398 which is mounted in the sides of the tank and projects through the wall of the box and a stuffing box 391; 399 is a hand wheel to turn the rod.

The operation of this apparatus is as follows: The hand wheel 399 is turned, rotating the intermeshed pinions and the rods 396 which extend or restrict the blocks 394 by reason of their screw fit with the interior of portions 395. As the blocks 394 are moved along the boxes, they push the link 392, which being attached to the corners of the wedge 385 move the wedge as indicated in part by the dotted lines of Figure 110.

A brief description of the apparatus is as follows: The material to be separated enters through the chute into the receiving end of the apparatus and is collected by the hopper which encircles the section of the apparatus in which the actual parting of mineral and gangue takes place. The pumping action of the conveyors keeps the liquid in continuous circulation from the receiving end of the parting chamber to the discharge end thereof. The upper conveyor sweeps the floats onto the conveyor pan, and the looseness of the conveyor chains permits the conveyor flights to jump and free themselves from any particles which tend to jam against the lip of the conveyor pan. The lower flight gathers the sinks and carries them out of the separating chamber. The middlings are carried by the current toward the wedge which forms the discharge end of the separating chamber and are divided according to the proportion of slate and coal they contain, those heavy because of large quantities of slate being thrown into the refuse, and those light because of usable quantities of coal being gathered in the floats. The separated materials are pushed by their respective conveyors over wedge-wire screens, or other suitable draining mechanism, which remove the majority of entrained liquids, and the materials themselves are discharged by the conveyors onto the collecting pans or troughs of the screen to be hereinafter described. -The parting liquid which passes through the wedgewire screens is returned along the sides of themachine and outside the separating chamber to the charging end of the machine and a continuous circulation is thus maintained. The level of heavy liquid is maintained at any desired point by the adjustable sealed weir at the end of the machine and the level of sealing fluid is maintained by the weir box on the side of the machine. Continuous addition and removal of liquid through the machine is thus possible, as well as intermittent additions as additions become necessary. Means are provided for blowing out the space beneath the conveyor pans and means are also provided for the removal of sludge from the bottom of the tank.

In Figures 2, 2a, and 2b is illustrated an apparatus for determining the percentage of coal in the sinks and the percentage of slate in the floats, in other words, for determining the ash content of the clean coal as delivered "by the system so that the middlings may be divided to the best advantage. In these figures 15 indicates generally a long trough, made preferably of some chemically resistant metal; -159 are walls which divide the trough into a series of chambers; 15l15l are trays having foraminous bottoms 152 and preferably solid sides, the shape-of the trays conforming substantially to the shape of the compartments of the trough. Each compartment of the trough is provided with a tray. The trays are pivoted at one end to the trough, conveniently by a method shown in Figure 20. 153 are U-shaped members attached by welding or otherwise to the outer edge of the tray 151; 154 is a pipe or other circular member attached to or forming the edge of the trough 15; 155 are bolts passing through the ends of U-shaped members 153; 156 are handles attached to the lip of the tray 15! opposite to the pivot; 151 are stops so placed that they contact the edge of the said trays and prevent their making contact with the bottom of the trough 15; 158 are pipes and valves leading to each compartment for drainage purposes; 159 are stop bars placed approximately midway of and running the length of the sides of the trays; 160 is a scoop having a foraminous bottom 16l and a handle 162; 163 are means for supporting the trough; 164 is a shelf running lengthwise of and before the trough and having an edge 165 to prevent the escape of liquid and. a drainage channel 166 and pipe 161 for such liquid; 168 is a screen to prevent the escape of solids down the drain. H is a means, such as a steam line, to regulate the temperature of the bath.

In normal operation the apparatus will have possibly ten compartments. Each compartment will be filled to equal depth with a liquid. 169 shows a liquid level. For example, the first compartment will contain a liquid of specific gravity 1.9; the next will have a specific gravity of 1.85; the next 1.8; the next 1.78; the next 1.76; etc., the specific gravities being chosen to give the maximum information with the particular coal or other mineral being treated in the process at the moment. A sample is taken, for instance, of the coal which is discharged from the watersealed conveyor and a weighed portion thereof is put into the first compartment. Assuming that the specific gravity of the compartment has been correctly chosen for the first test, a considerable portion of the charge will sink and the remainder will float. The operator then takes scoop I60, inserts its nose within the tray, as shown in Figure 2a, slides it across the runners which are at equal depth in each compartment and withdraws the floats. The liquid is allowed to drain back through holes Hil in the foraminous bottom of the scoop and the floats are placed in the next tank, whose specific gravity is somewhat lower. This procedure is continued until the sample has been divided according to specific gravities. By pulling on the handle 156 the trays 15! may be pivoted about pipes 154, draining through holes 152 back into the trough I and the sunken material may be dumped into a pan or other suitable means placed on the table 164.

The system is first calibrated by making ash determinations with the particular type of coal which is being separated, a determination being first made of the specific gravity of the incoming matter to determine the specific gravity of the parting liquid to be used in the tank 3. After operation has commenced, samples are taken of both the sinks and the floats and ash determinations are run to calibrate the system. Thereafter, determination of specilc gravities is made by plotting subsequent tests against the control. In this way the coal content of the slate and the slate content of the coal may be determined and from the information obtained adjustment made to vary the percentage of slate in the coal as hereinbefore described. In each instance there will be given an accurate check on the distribution of middlings since it will be understood that, if the specific gravities range between that in which pure coal alone will float and that in which slate alone will sink, the specific gravities of the samples which sink in succeeding baths will be in direct relation to their respective quantities of coal and stone. Zinc chloride solution is a satisfactory agent for use in this apparatus because it can be easily diluted to precise specific gravities, but any other satisfactory liquid may be used. Having determined the distribution of the middlings as actually distributed by the apparatus, a prompt change can be made in the setting of the apparatus so that another and more favorable distribution can be made if such is desired.

The apparatus which has been described offers an excellent method of accomplishing the process.

In the parting step of the process the liquid used is preferably organic and of the halogenated hydrocarbon type. However, the process is not limited to such agents since any separating agent which has proper specific gravity and is properly inert to the materials which are to be separated may be used. The factors which are desirable are that a material shall have high boiling point in order that there shall be low vapor pressure at working temperatures, low melting point in order that a material may be liquid at working temperatures and the expense of keeping the compound fiuid by heat avoided, low solubility in water in order that the parting liquid may not become contaminated with the sealing liquid and may not be carried out on the separated material, stability under the conditions of operation including stability to agents, air, light, and heat, low hydrolyzing capacity, low toxicity in order to avoid injury to operators when the apparatus is cleaned, low viscosity, and low cost. Among the compounds which have been found useful are the following:

Pentachloropropane, 3,4 dibromo 2,2 dimethyl butane, iodobutane, hexachloropropane, 1 chloro 3 bromopropane, 1 bromo 2,3 dichloro n-butane, 1 iodobutane, 1 chloro 1 bromoethane, 1,3 dibromo 2,2 dimethyl propane, 2,4 dibromopentane, pentachloroethane, 2,3 dibromopentane, 1,2 dibromo 2 methyl butane, 1 chloro 2 bromoethane, 2iodopropane, 1,5 dibromopentane, 1,4 dibromopentane, heptachloropropane, 1,2 dibromopentane, 1 iodoheptane, 2 chloro 1 iodobutane, 1,1 chloro 1 bromoethane, 1,1 dibromo 2,2 methyl propane, 1,4,7 tribromoheptane, 1,1,1 trichloro 2 bromopropane, 2,2 dibromopropane, 1,2 dibromo 2 methyl propane, 1,3 dibromobutane, 1,4 dibromobutane, 1,2 dibromobutane, 1,3 dibromo 2 methyl propane, 2,3 dibromobutane, 2,2,2 trichlo-ro 1 bromoethane, 2 chloro 1 iodopropane, 3 chloro 1 iodopropane, 3 chloro 1,2 dibromobutane, iodoethane, 2 fiuoro 1,1,2,2 tetrabromoethane, dichlorobromomethane, 1,2 dibromopropane, 1 chloro 2,3 dibromobutane, 1,3 dibromopro-pane, chlorobromomethane, tribromo 2 methyl pentane, 3 chloro, 1,2 dibromopropane, dichloriodopropane, 1,6 diiodohexane, trichlorobromomethane, 1 chloro 1 iodoethane, 2 chloro 1,2 bromopropane, 1,3 dichloro 1,2 dibromopropane, fiuoro 1,2 dibromopropane, 1,1 dibromoethane, 2,3 dichloro-1,2 dibromopropane, 2 fiuoro 1,1 dichloro 1,2 dibromoethane, 1 chloro-1,1 dibromoethane, 2 chloro 1 iodoethane, 1,2,2 tribromobutane, 1,2,3 tribromobutane, 1,1,2 bromobutane, 1,2 dibromoethane, 1,5 diiodopentane, 2 bromo 2 iodopropane, 2,2 dichloro 1 iodoethane, 1,2,3 tribromobutane, 2,2 difiuoro 1 iodoethane, 1,1 difiuoro 1,2 dibromoethane, 1,1,2 trifluoro 1,2 dibromoethane, 1 fiuoro 1,2 dibromoethane, 2 chloro-1,2 dibromoethane, methyl iodide, 1,1 dichlor 1,2 dibromoethane, 1,2 dichloro 1,2 dibromoethane, 2,2,2 trichloro 1,2 dibromoethane, 1,3 iodobutane, 1,4 iodobutane, 2,2 difiuoro 1,1 dibromoethane, 1,2,2 tribromopropane, 1,4,7 triiodoheptane, 1,1,2 tribromopropane, trichloro iodomethane, 2,2 dichloro, 1,1 dibromoethane, 3 chloro 1,2,2-tribromopropane, dibromo dichloromethane, 1,2,3 tribromopropane, 1,2,2 trichloro, 1,1,2 tribromoethane, dibromo chloromethane, 2,2 diiodopropane, chloro iodomethane, dichloro iodomethane, dichloro tribromobutane, 1,2 diodopropane, 1

bromo 1 iodoethane, 2 bromo 1 iodoethane, 1,1,4,4

1,1,2,3 tetrabromopropane, 1,1 diiodoethane, bromoform, hexabromobutane, 1,1,1,2 tetrabromoethane, iodobromomethane, 1,1,2,2 tetrabromopropane, l,1,2,2 tetrabromoethane, 1,1,2,2,3 pentabromopropane, diiodo chloromethane, pentabromoethane, methylene iodide, 1 chloro 1,1,2,2 tetrabromoethane, perchlorethylene, 1,3 dibromopentene-2, 1,1,2,3,3,3 hexachloropropene-l, 2- iodopropene-l, 2 chloro 1 bromoethene, 2-iodopropene-l, 1,3 dibromo 2 methylpropene-l, 1,2 dichloro 1 bromoethene, 1,2 dibromobutene-l, 2,2 dichloro 1 bromoethene, 2-chloro 3- iodopropene-l, 1 chloro 3 iodopropene-l, 1,2 dibromopropene-l, 3 iodopropine-l, 1,1,2 chloro 1 bromoethene, 1 iodopropine-l, 1,3 dibromopropene-l, 1,3 dibromopropine-l, 2 chloro 11' iodoethene, 1 chloro 1,2 dibromoethene, 1,2 dibromethene, 2 fluoro 1,1 dibromoethene, 1,2 difiuoro 1,2 dibromoethene 1,2 dichloro 1,2 dibromoethene, 1,2,3 tribromopropene-l, 1,2 diiodopropene-1, 2 bromo 1 iodoethene, fluoro tribromoethylene, tribromoethylene, 2,2 dibromo 1 iodoethene, 1,2 iodoethene, iodocyclohexane, 1,2 dibromocyclohexane, 3,4 dibromo, 1,2 dimethylbenzene, 3,4 dibromotoluene, 2,6 dibromotoluene, 2,5 dibromotoluene, iodobenzene, 1 iodo 2 chlorobenzene, 1,3

dibromobenzene, 1,2 dibromobenzene, trichlorethylene, 4 chlorethane, and carbon tetrachloride.

The list has been mainly directed to halogenated hydrocarbons but it is to be understood that any liquid having the desirable qualities set forth above can be used so far as the mere separating step is concerned.

Kerosene, benzene and naphthalene and other hydrocarbons, particularly those of low boiling point and vapor pressure can be used as diluents to alter the specific gravity of parting liquids.

The specific gravity of the parting liquid used will be between the specific gravities of the minera] and gangue which are to be separated. The separating liquid within the tank will be covered by a sheet of water or other liquid inert thereto which will serve the purpose of preventing evaporation of the liquid and of rejecting parting liquid which gathers on the floating material. The liquids may be so arranged as to fill the whole tank or to fill only a portion of the tank.

It is advisable to design the chamber in which the separating actually occurs with particular reference to the mineral which is to be treated. For example, if a finely divided iron is to be separated from its gangue, a longer chamber would be required in order to give all the fine particles an opportunity to respond to the parting action of the liquid. On the other hand, in those cases where no rafting of the particles is observable and separation is quickly and completely carried out, a short chamber may be used. Another method of accomplishing this variation is to vary the speed at which the liquid within the separating chamber travels, thereby varying the length of time which the material is al lowed to separate. 7

The parting liquid can be of one liquid or it can be a mixture of completely miscible liquids of difierent specific gravities. Thus, a mixture of C2H2BR4 and 02112014 will give a range of specific gravities from 2.39 to 1.59. This principle can be availed of to adjust the specific gravity of the liquid to one in which the middlings will sink at a rate most favorable for separation by the apparatus. This selection of specific gravity may be availed of to secure particular separation of the middlings in a machine provided with an immovable wedge.

The velocity with which the conveyors travel in this apparatus determines the point to which the middlings will have sunk at the moment they contact the wedge. Thus, by speeding up or slowing down the conveyors the velocity of the liquid can be increased and a variation in the slate containing middlings included with the coal accomplished. By speeding up the conveyors the liquid will travel faster, the middlings will not have sunk so far and a wider percentage of lowcoal middlings be incorporated with the coal. By slowing down the conveyors the parting liquid will travel more slowly and only the richer coal middlings be incorporated with the coal.

A third method of varying the slate content of the coal and the coal content of the slate is by adjusting the point of the Wedge up or down. Means for doing this have been described in the specification.

These three methods of dividing the middlings may be used separately, with one another, or all together and when so used give the very greatest flexibility to the system.

This description has been more less specifically directed to the separation of coal from its indigenous impurities. The process is not limited to coal, however, and it is applicable to the separation of minerals in general, although it can be readily understood, as elsewhere herein pointed out, that to secure the best results with a particular mineral the speed of the liquid medium, the density of the parting liquid, and the length of the separating chamber may be varied. Substantially all minerals are obtained in their native condition in admixture with indigenous impurities. In some cases the mineral is the heavier and the gangue the lighter. In such case the gangue will fioat on the surface of the parting liquid and the mineral will sink to the bottom and be carried out by the lower conveyors. In other cases, as in the case of coal, the reverse is true. The design of the conveyor system may advantageously be altered to accommodate the amounts of mineral and gangue which is to be expected with a particular process. Another variation which must be considered by the engineer in treating different minerals is that the specific gravities of the minerals themselves vary. Thus, anglesite varies from 6.1 to 6.4; anthracite coal varies from 1.3 to 1.7 and bituminous coal varies from 1.1 to 1.5. Among the minerals which can be separated from their gangues by this process are the following: asbestos, bituminous coal, anthracite coal, chrysocolla, garnerite, quartz, feldspar, black diamond, mica, fluorite, wad, siderite, calamine, rhodochrosite, diamond (gem grade), cyanite, limonite, azurite, psilomelane, malachite, garnet, corundum, sphalerite, willemite, chalcopyrite, smithsonite, witherite, rutile, stannite,

chromite, barite, tetrahedrite, ilmenite, energite, pyrrhotite, covellite, pentlandite, molybdenite,

braunite, pyrolusite, bornite, hematite, pyrite,

magnetite, franklinite, millerite, zincite, chalcocite, cuprite, scheelite, anglesite, vanadate (lead), cerussite, heubnerite, cassiterite, wolframite, galena, iron, niccolite, ferberite, cinnabar, copper (native), silver, platinum, and gold.

An advantage of the invention is the rapidity with which the apparatus and process can be operated with satisfactory results. A unit having only four square feet of separating surface was tested for speed and satisfactorily separated tons per hour, its capacity being then limited by the capacity of the conveyors which were working at utmost capacity and could not handle a higher rate. The ultimate capacity of the system is at present unknown. With normal comparatively leisurely speeds of operation its capacity is ten times that of any previous system, comparison being made on a basis of separating surface areas.

Coal may be prepared by this process with any degree of ash content the operator desires, something which no previous process has ever accomplished. Heretofore systems of coal cleaning had made a rough division between coal and slate but the percentage of coal in the slate and the percentage of slate in the coal varied from minute to minute. The idea of producing coal of standard ash content was a desideratum without a means of obtaining it. 85% eiiiciency has been considered good for coal cleaning processes and many of the mountainous waste banks found in the coal regions contain 15% to 35%. of usable fuel. By our invention these waste piles may be reclaimed. No previous method was capable of economically extracting the coal from such waste piles.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. Apparatus for the classification of minerals of difierent specific gravities which comprises a tank, means to admit liquid to the tank, means to maintain the level of the liquid, a separating chamber having receiving and discharge ends, said separating chamber being at least in part below the liquid level and having an opening in the lower part thereof, means to admit a second liquid above the level of the first, means for admitting solids to the separating chamber at the receiving end thereof beneath the level of the upper liquid, conveying means to withdraw sinking solids from beneath the separating chamber, means to draw from the said solids the entrained liquid, means to discharge the said solids from the apparatus, conveying means to remove floating materials from the said lower liquid, means to draw off entrained liquid from the said floated solids, means to discharge the said floated solids from the apparatus, said conveying means moving the liquids continuously from the receiving to the discharge end of the separating chamber, means to return the liquids to said separating chamber adjacent said receivingend, means to drive the said conveying means, and means for draining said tank.

2. Apparatus for the classification of minerals of different specific gravities which comprises a tank, means to admit liquid to the tank, means to maintain the level of the liquid, a separating chamber having receiving and discharge ends, said separating chamber being at least in part below the liquid level and having an opening in the lower part thereof, means to admit a second liquid above the level of the first, means for admitting solids to the separating chamber, beneath the level of the upper liquid conveying means to withdraw sunken solids from beneath the separating chamber, conveying means to collect materials floating in and withdraw them from the said lower liquid, means to draw off entrained liquid from the said Withdrawn solids,

ratus, said conveying means operating to move the said liquids continuously from the receiving to the discharge end of the separating chamber, and means permitting the return of the liquids back to said separating chamber adjacent said receiving end.

3. In an apparatus for effecting gravity classification of divided solids containing parts of mixed composition, a moving stream of liquid of gravity intermediate the gravities of some of said solids and capable of temporarily suspending some of said parts of mixed composition, an overlying second body of liquid, a channel for confining said stream of liquid to a predetermined path, a wedge-shaped element positioned in said channel and immersed in said moving stream of liquid, said wedge-shaped means serving to effect horizontal classification of the mixed composition materials suspended by said moving stream of liquid.

4. The process of classifying a mass containing separate constituents and pieces of mixed constitution which comprises inserting the said mass in a moving stream of liquid having a specific gravity more than one said constituent, slightly lighter than the average specific gravity of the pieces of mixed constitution, and less than the heavy constituent, transporting the floating pieces and pieces of mixed constitution in the moving liquid until a gravity classification has been effected, and gathering pieces of mixed constitution having a useful quantity of the floating ,constituent into the floating constituent, and

gathering pieces of mixed constitution having a larger percentage of the lower constituent into the sunken constituent by horizontally splitting the stream that carries them.

5. In the beneficiation of minerals the process of isolating the better from the poorer middlings which comprises inserting a crushed, roughly sized mass containing the minerals and middlings in a moving stream of liquid having a specific gravity slightly lighter than the average specific gravity of the middling mass, transporting the middlings in the said moving liquid until a gravity classification has been effected, and separating the better middlings from the poorer middlings by mechanically forcing the moving better middlings in the upper zone of the stream and separating the said zone from the remainder of the stream.

6. In the beneficiation of coal according to the process defined in claim the steps of determining the ash content of the materials withdrawn from the top zone of the stream and the ash content of the materials withdrawn from the bottom zone of the stream, and including in the upper zone of the stream all the solids above a certain level thereof, said level being selected to include within the said upper zone a selected quantity of ash producing ingredients whereby to produce a combustible product of uniform ash content.

7. A channel, means to conduit liquid from one to the other end thereof, means to fill said channel with liquid, upper and lower conveyors operable in the same direction at a speed which will permit gravity classification of middlings in the said channel, means to admit crushed minerals to said channel in the range of operation of the conveyors, and means to separate the material moved by the upper conveyors from that moved by the lower conveyors comprising adjustable means between the conveyors horizontally partitioning the stream of liquid, and means associated with the said adjustable means to direct the classified lighter middlings into the zone of the upper conveyor, and the classified heavier middlings into the zone of the lower conveyor.

8. Apparatus for the separation of solids of different specific gravities which comprises a tank, means to admit liquid to the tank, means to maintain the level of the liquid, a separating chamber having receiving and discharge ends, said separating chamber being at least in part below the liquid level and having an opening in the lower part thereof, means to admit a second liquid above the level of the first, means for admitting solids to the separating chamber, conveying means moving in one direction along the channel to withdraw sinking solids from the lower part of the separating chamber, conveying means operating along the channel in the same direction as said conveying means to collect and withdraw materials floating in the said lower 5 the impulse of the conveyors.

WILLING B. FOULKE. WILLIAM A. WILLS.

' CERTIFICATE OF CORRECTION. Patent No. 2,150,917. March 21, 1959.

I WILLING B. FOULKE, ET AL.

It is hereby certified that error appears the printed specification of the aho'kie numbered patent requiring correction as follows:- Page 2, first column, line 9, for "5c" read 10; page 5, first column, line h5, for "specilc" read specific; same page, second column, line 5?,for "1,2" read 1,1; line 68, for "methylane" read methylene; page 6, first column, line 7, for "1,5" read 2,5; line 9, for "2-iodo-" read 5-iodo-; line 17, for "dibromethene" read dibromoethene; page 7, first column, lines 67 and 68, claim 2, strike out the words "beneath the level of the upper liquid"; same page, second column, line 62, claim 7, for the word "conduit" read conduct; and that the said Letters Patent should be read with this correction therein that the M 1 same may confo'rm to the record of the case in the Patent Office.

Signed and sealed this 20th dayjof June A. D. 1959.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.