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Feb. 15,1938. ‘ 2, 108,495 N. D. LEVIN METHOD OF AND APPARATUS FOR CLEANING COAL _ “ Original Filed Oct. 11, 1934 6 Sheets-Sheet 1 N. . //\/ VENTOR! /\//'/5 D. Lev/n, B ATT'Y Feb. 15, 1938. N. 'D. LEVIN 2, 108,495 ' METHOD OF AND APPARATUé FOR CLEANING COAL Original Filed Oqt. V11, 1934 6 Sheéts-Sheet 2 [NVE/YTOFP: N/Ys D.Le v/n, BY @LVL >77. ATT'Y Feb. 15, 1938. ' up, LEVIN ' 2,108,495 METHOD OF AND APPARATUS FOR ‘CLEANING GOAL Original Filed Oct. 11, 1934 6 Sheets-Sheet 4 Feb. 15, 1938. ‘ N'_ D_ LEvm" 2, 1 08,495 METHOD OF AND APPARATUS FOR CLEANING COAL briginal Filed Oct. 11, 1934 ' , 6 Sheets-Sheet 5 Uzi-PM; I mr2.. > wzjLirm 3.51 1Z6. QM PP 3 m. . U029:0m wzim<k>? Vidal //\/ MENTOR .- ., N 0 be v.m, I ATT'X ‘Patented Feb. 15, 1938 * 2,108,495 UNITED STATES ‘PATENT- OFFICE ING COAL Nils n. Levin, Columbus, Ohio, assignor to The Je?rey Manuiaoturingcompany, a corpora- _ tion of Ohio Application October 11, 1934, sews...‘ 147,901 Renewed July 31, 1937 ’ 12 Claims. (Cl. 209-173)’ My invention relates to the separation of ma Fig. 6 is a diagrammatic plan view of the ap terlals according to their speci?c gravities and the re-clainiing of the solid constituents of the separating medium, and one of the objects of my invention is the provision of an improved method tank, supply tank and settling tanks; of separating coal from its impurities by increas sediment from the settling tanks shown in either ing the efficiency of operation. Fig. 4 or Fig. 6; paratus shown in Fig. 5, connected to a mixing ' Fig. '7 is diagrammatic view illustrating con veying apparatus which may be used for removing - Another object of the invention is to provide im ' ' proved apparatus for reclaiming the solidcon stituents oi’ the separating medium for gravity separation of impurities from coal. A further object of the invention is the prel liminary treatment of raw coal or run of mine plenishing water in the washing tanks; ‘and coal for gravity separation of impurities from the coal employing insoluble material mixed with water .so that when such coal impurities are re out or said medium. which will be carried out with the separated coal into the washing tanksvfor recovery. in the ‘system shown in Fig. 4 or in thesystem shown in Fig. 6. ' A further object of the invention is the pro vision of a system, of coal cleaning apparatus ' comprising separating mechanism, washing mech anism, reclaiming mechanism and automatic means for maintaining the liquid in the washing 25 mechanism at a predetermined level. More particularly it is the object of the'present ‘invention to provide improved apparatus for cleaning .coal and carrying out an improved method therewith to reduce the expense of opera- ' 30 tion to a minimum by enabling the use of insoluble granular materials in their natural states and A Fig. 10 is a curve illustrating a method of ‘adapting a separating medium which will retain a, maximum amount of its solid constituents, so as .to reduce the amount of such solid constituents moved from the separating medium a minimum amount 01' such solid constituents wili'be taken '20 . Fig. 8 is a diagrammatic ,elevational view of the system shown in Fig. 4, to illustrate the rela tive elevations of the various tanks; 10 Fig. 9 is a wiring diagram to illustrate the automatic float control of lthe pump for re In Figs. 1 and 2 I have shown a supporting , frame ii on which are mounted the separating tank i2 and the series of washing tanks it, it and I5. The raw or run of mine coal may be introduced into the hopper l6, as shown in Fig. 1, in the bottom of which the discharge of the coal is regulated by the vertically slidable gate 11. The separating medium, comprising natural clay and granular sand in its natural state mixed with water and an electrolyte, as hereinafter more 30 without comminution, in the separating medium, fully explained, may be of varying depth in the tank I! according toconditions. The impurities and in the washing of the separated coal reclaim ing such solid materials as. may adhere thereto which sink in the separating medium are received upon emerging from the separating medium. Other objects of the invention will appear here inafter, the novel features and combinations be ing set forth in the appended claims. In the accompanying drawings, Figs. 1 and 2, placed end to end, illustrate ap paratus including" a separating tank for cleaning coal and for washing the same successively in a series of washing tanks; ‘ - ‘ Fig. 3 illustrates apparatus including a tank for immersing the raw coal or run of mine coal before it is conveyed to the separating tank, the latter being ‘also shown connected to the series of washing tanks similar to those shown in Figs. 1 and 2; ' . Fig. 4 is a diagrammatic plan view showing the arrangement of the tanks illustrated in Fig. '3, together'with settling tanks and. mixing storage tanks; , g I Fig. 5 is an elevational view illustrating the ‘ap paratus shown in Figs. 1 and 2; _ ‘ ' by the conveyor l8 comprising the ?ights i9, i9. These ?ights are adapted to travel in the direc tion of the arrow 20 to convey the impurities, such as slate, to the chute 28 from which such im purities are delivered to the endless belt conveyor The coal which is capable of ?oating on‘ a 40 separating medium in the separating tank i2 is crowded toward the left, as-viewed in' Fig. 1, by the incoming raw coal, and such separated coal is received by the conveyor 23, comprising the 1' ?ights M, M. The cleaned coal is conveyed up wardly along an incline in the direction of the arrow 25 where it is discharged into the tank 23 in which a de?ector plate 26' guides the coal to the conveyor 2i comprising the flights 23, 2t. Inasmuch as the washing tank It is ?lled with water, the cleaned coal will tend to sink therein and consequently it is desirable to provide an in clined plate 29 for the ?ights 28 so that coal which reaches the plate 29 may be scooped from the semi-circular receiving portion 3% to move 55 - 2,108,495 upwardly along the incline in’ the direction of tion while the other is being used for receiving the arrow 3| for discharge into the next washing tank I4. Further washing in the tank I4 is effect ed by the discharge of the coal therein for trans fer by the conveyor 32 into the tank I5. In the latter the conveyor 33 transfers the washed coal to the discharge chute 34 from which it ?ows to the belt conveyor 35 for transfer away from the material from any one or more of the tanks I3, washing apparatus in the direction of the arrow 10 35 At the right-hand end of Fig. 1 is shown in dotted lines the position that the operating elec tric motor 31 occupies on that side of the frame II remote from the sprocket chain gearing 38 which is connected to simultaneously ‘drive all of the conveyors shown in Figs. 1 and 2. The motor 31 is connected by reduction gearing 39 and the sprocket gearing 40 to that end of the shaft 4I remote from the sprocket chain 38. That is to 20 say, the driving connection from the motor 37 is to one end of the shaft 4|, and to the opposite end of the latter is connected the endless sprocket chain 38 which in turn is connected to all of the traveling conveyors to drive them simultaneously. At the upper left-hand end of Fig. 2 is shown an inlet port 42 and at the bottom of the washing tanks I3, I4, and I5 are shown drain pipes 43, 44, and 45. Inasmuch as the separating medium in the separating tank I2 contains natural clay and 30 sand in ‘its natural granular state mixed with water and a very small quantity of electrolyte, a small quantity of the separating medium will adhere to the cleaned coal which is transferred by the conveyor 23 to the tank I3. When the con veyor 21 operates to transfer the coal to the next tank I4, most of the clay and sand is washed from the coal and dispersed in the water in the tank I3 where it settles on the conical bottom so that it may‘fiow through the outlet port 43. If any clay and sand still remain on the coal when introduced into the tank I3, further wash ing occurs‘ and the clay and sand may be with drawn through the port 44, shown in Fig. 2. Still further washing may occur in the tank I5 and the‘ clay and sand eliminated through the outlet port 45. Clean water may be introduced intermit tently and continuously through the port 42 for ?ow into the tank- I5 and thence into the tank I4 and from the latter into the tank I3. The 50 upper edges 46 and 41 of the walls or separating partitions 48 and 49 are at lower elevations than the upper edges 50 and 5| of the end walls 52 and 53. Consequently, when the tank I5 is ?lled it may over?ow the edge 46 into the tank I4, and when the latter is ?lled it may over?ow the edge 41 into the tank I3. ' Regulation of’ the flow of the sediment from the conical bottoms of the tanks I3, I4 and I5 through the outlet ports 43, 44, and 45 may be 60 secured by means of the system diagrammati cally illustrated in Fig. 6. Manual valves 54, 55, and 56 may be placed in the pipes which lead from the ports 43, 44, and 45 so that each of the tanks I3, I4 and I5 may be individually drained to such an extent as to remove the sediment from the conical bottoms thereof. When any one of the valves 54, 55, 56 is opened the mixture of sediment and water will ?ow into the pipe 57 which is connected by the branch pipes 58 and 59- to the settling tanks 50 and BI. The latter are at lower elevations than the bottoms of the sedi mentation tanks I 3, I4, and I5,4and ?ow thereto is controlled by the manual valves 62 and 53. It is preferred to employ two settling tanks 75 60 and 6I_so that one may be used for sedimenta I4, I5. For instance, if the valve 82 is closed and the valve 83 is open the tank 84 may be used for sedimentation._ During operation of the coal cleaning apparatus including the washing mecha nism, it is preferred to close the valves 55 and 56 and regulate the'opening of the valve 54 so that as the ‘clay and sand settle in the bottom of the tank I3 it will ?ow immediately into the settling tank 8|, the liquid in the tank I3 being auto matically replenished by means of the pump 34 operated by the electric motor 65 under the con trol of switch mechanism. When the pump 64 operates, the valve 56 is closed and the valve 61 is opened so that water will be withdrawn from the tank 80 into the pipe 42 for ?ow into the tank I5. After clear water has been obtained by sedi mentation in the tank 6|, the valve 62 may be opened, the valve 63 closed, the valve 65 opened and the valve 51 closed. Then when the pump 54 operates, clear water ‘will be withdrawn from the tank 6| through the pipe 68 into the pipe 42 and thence into the tank I5. . In Fig. 6, 69 designates a mixing tank in which the clay, sand, electrolyte and water may be thoroughly intermixed while the valve ‘III is closed. It is desirable to effect this mixture in a separate mixing tank so that it may be per mitted to age by standing in a quiescent condi- - tion for a period of approximately twenty-four hours, thereby rendering the electrolyte more e?icient in its e?ect on the clay and sand con-' stituents. After the separating medium has been aged - for a predetermined period of time, the valve ‘I0 may be opened to permit the mixture to ?ow into the storage or supply tank ‘II which is larger in capacity than the tank 59, and from which the medium may flow into the separating tank I2 under the control of the manual valve ‘I2. In the system illustrated in Fig. 4, mixing and storage tanks are provided as indicated at ‘I3 and ‘I4 which are connected through manual valves ‘I5 and ‘I6 to the pipe ‘II which leads to a float controlled valve ‘I8 in the separating tank l2’. When the valve ‘I5 is' closed the mixing tank ‘I3 may be used for permitting the mixed ingredi ents of the separating medium to age. During the aging period the other tank ‘I4 may be used for storing the previously aged mixture so that when the valve ‘I5 is opened, flow will take place automatically from the. tank ‘I4 to the separat ing tank I2’ under the control of the float valve ‘I8. Consequently, during the operation of the cleaning and washing mechanism illustrated in Fig. 3, the separating medium carried out from the separating tank I2’ by removal of the coal and impurities, will be automatically replenished under the control of the ?oat valve ‘I8. When 60 the valve ‘I6 is closed and the valve ‘I5 is opened the flow will be from the tank ‘I3 into the tank I2’. ‘ In Fig. 8 I have shown the relative elevations of the various tanks, the mixing and storage tanks ‘I3 and ‘I4 being located at such elevations as to permit the separating medium to ?ow by gravity into the separating tank I2’ as permitted by the automatic ?oat valve ‘I8. The operation of the electric motor 65 for driv 70 ing the pump 64 may be controlled by means of the electric ?oat switch ‘I9, shown diagram matically in Figs. 8 and 9. When the water in ' the tank I5’ falls to the level indicated at B0 in Fig. 9, the ?oat 8| will descend sufficiently on its 75 '3 2,108,495 pivot 82 to cause the enclosed ‘mercury switch ' ing vtanks while sedimentation ‘is taking place in 83 to connect‘the conductors 88 and 85 where the other sedimentation tank. The coal dust ' upon the solenoid" will be energized since it which may be mixed with the clay and sand can will be connected across the‘ mains 81 and 88. readily be separated therefrom by ?otation on a When the-switch 88 is- closed and the solenoid liquid separating medium, and the clay and sand 86 energized, the latter will‘ e?'ect the closure of recoveredin this manner may be re-used'in the I the motor switch 88. The motor 85 will then be mixing tanks ‘I3 and ‘I4. connected by means of the conductors 8|, 82 ' ’ * In the co-pending application of applicant and ' across the supply mains, and the pump 88 will , Samuel H. Yost/for an Improvement in method of cleaning coal and ?uid-separating'mediums the settling tanks 88 or BI through the pipe 82' therefor, Serial No. 747,906, ?led Oct. 11, 1934, into the tank I5’. When the waterin the tank the‘ preferred separating medium for use in the I5" reaches the level indicated by the dotted line tank I2 or tank I2’ is described and claimed, 10 be permitted ‘to draw "clear‘liquid from one of position 93 in Fig. 9, the ?oat 8| will be moved whereas the present application adds the ‘pre 15 ‘to. its dotted line position 8|’ to e?‘ect opening of the switch ‘I8 which will cause de-energiza liminary step of wetting the raw coal in the tank 15 85 and also includes the washing of the separated coal after leaving the separating‘ tank, and in addition I have disclosed in. Figs. 4, 6, 8, and 9 systems of handling the liquids and solid ma terials immersed therein. I, have also added the curve shown in Fig. .10 to illustrate the tests which may be carried outso as to reduce to‘ a minimum the amount of solid constituents car ried out from the separating medium when the cleaned coal and the impurities are removed from tion of thesolenoid 86 andthe dropping of the "switch 88 to its dotted line position, thereby cut-' ting off the motor 65 and stopping the .pump 84. 20 ‘The operation of the valves 58, 55, 56, 62, 63, 66, and 61, in the system shown in Fig. 8, will be the same as described in connection with Fig.‘ 6. The separating tank I2’ in Fig. 8 is provided with a drain valve 94. This valve is opened only when 25 it is-desired to drain the separating tank I2’. By referring to Fig. 3 it will be seenthat the tank 95 is provided for containing water into the tank l2 or tank I2’. which the raw coal or run of mine coal may be introduced from the chute 86. By means of the 30 conveyor!" the wetted coal is removed from’the " crevices therein‘ so‘ that less of the solid con 80 stituents of the separating medium in the tank I2’ will adhere to‘ the separated coal ‘and im purities when they areremoved from the tank I2’. Inasmuch as the washing system herein disclosed is arranged and. operated to obtain 35 the greatest’ ef?ciency, the operating medium is tank 95 tothe chute 88 for ?ow into the separat ing tank I2’. The impurities which sink in the separating’ medium in the tank I2’ are removed by means of the travelingconveyor I8’ to the 35 chute 2I' and thence to the belt conveyor 88. The motor 31' may be connected by means of the 40 . In the ?rst place it should be understood that the principal object of wetting the raw coal preliminarily in the tank 85 is to fill up the sprocket chain 38’ to all of the conveyors in the ‘ so composed as to retain the greatest amount whole ‘system shown in Fig. 3. The sprocket chain should be driven in the direction of the possible of its solid constituents by preventing the removed coal and impurities from carrying I88.' ' ' ', . out ‘any more than is necessary. In order to The bottom of the tank 85 is preferably conical fully understand the signi?cance of the curve in shape and is provided with -a draining port ' shown in Fig. 10, it will be necessary to describe IIII which is connected to the pipe I82 shown in the preparation of the separating medium used in the tank I2 in the system shown in Figs. 1, ' Fig. 8. The draining of the tank 85 may be con 45 trolled at intervals by'the valve I83. Although 2. 5, and 6, and in the‘tank I2’ in the system shown in Figs. 3, 4, and 8. the raw .coal is screened and de-dusted before arrows entering the tank, 85, the wetting of the coal eifects further elimination of the coal ,dust, and ' In order to predetermine. the specific gravity of the separating medium or mixture to 'be used when the water in the tank‘ 85 becomes con-' in the systems disclosed in the accompanying drawings, the raw coal or run of mine coal to 50 taminated with coal dust it may be drained by be cleaned is analyzed by methods of sampling, opening the valve I83-and permitting the sedi _ ment to ?ow intoone of the settling tanks 68 or 6I. It may also occur in practicethat the raw coal introduced into the tank 85 even after 55 screening and de-dusting, has considerable sand and clay adhering thereto which will be washed off by being introduced into the tank, 85 and the ,washed raw coalmay be conveyed out of the same bythe conveyor 81. - - The solid materials which are washed from the coal in the tanks 85, I3, I6 and I5 and allowed to settle in the settling tanks, 58 and GI vmay be removed therefrom by means of the dragwcon veyors I84, I85, as shown in Fig. '7. . These con 65 veyors are operated respectively-by the motors 45 to sink and ?oat tests, l chemical analyses, etc. Then, depending upon what grade of purity of coal is desired, the ‘speci?c gravity at which sep aration should take place, when following my 55 improved methods,-is predetermined. The sep arating medium 'orinixture is then .prepared so that the marketable coal will float in the separat ing tank I2 or the separating tank I2’. - In preparing the separating medium it is pre ferred to follow certain de?nite formulae which from actual tests have given the best results but which may be varied in accordance with con- - ditions. By using one part natural clay and four parts natural sand, by weight, without pulveriz I86, I81 inthe direction of the arrows I08, I88 -‘ ing or comminuting either the clay or the sand, to‘ take the sediment from the inclined bottoms, and stirring the clay and sand in water, a me- _ *III), III to the chutes H2,- Il3,'*for ?ow into the dium of the desired speci?c gravity may be. ob mixing tanks ‘I8, ‘I4. The motors I86,'I8l are tained with the assistance of well known tests 70 connected by the sprocket chain gearing H4, of speci?c gravities ofv mixtures of solid granu 70 I I 5 to the conveyors I84, I85 to drive the same in lar matter with water. The speci?c-gravity of the direction of the arrows I88, I88. It should be the sand is approximately the same as that of ' understood, however, that the conveyors I84, I85 ‘are operated‘ alternately because one of the set 75 tling tanks receives the sediment from the‘wash- ' vthe clay.‘ > ' ‘The addition of a small amount of a de?occu lating agent such as sodium alumlnate or sodium 75 l 4 2,108,496 In the formation of the separating medium by mixture of the ingredients in the mixing tanks ‘I! and ‘ll of Figs. 4 and 8, .or in the mixing tank in suspension for a relatively long period of time, . 8! of Fig. 6, it is important to follow certain thereby rendering the ?uid'mixture very efii-, de?nite formulae according to conditions. It has cient in the gravity separation of impurities been found from actual tests that under certain silicate to the mixture of natural clay and nat ural sand in the water, will cause the clay and sand after being stirred in the water. to remain from coal with littleor no agitation of the sep arating‘medium. - ' " - In gravity separation of impurities from coal, 10 agitation of the liquid hampers the process, and it is therefore desirable to reduce the agitation‘ to a minimum. For instance, when the agita tion of the liquid medium is too great, small and ?at pieces of slate will follow upward currents 15 and be mixed with the cleaned coal, thereby rendering perfect separation impossible. How ever, in the use of the conveyors l8 and 23 in the'separating tank II or the conveyors II’ and 23' in the tank l2’, the agitation of the liquid medium is so small as not to disturb'the ‘desired separation of impurities from the marketable coal. If su?icient natural clay is so mixed with water as to ?nely divide it without comminution or pulverization, a liquid medium may be obtained of sumcient speci?c gravity to ?oat coal, but it will be found to be too thick or viscous for practical use. However, by adding the proper amount of electrolyte such as sodium aluminate or sodium silicate, the mixture will be rendered more ?uid without affecting the speci?c gravity. ‘After testing various forms of natural clay, one form of ?reclay was found that could be used in practice without the addition of sand, but this 35 separating medium was not found to be very , emcient. In other words, while satisfactory re conditions the amount of sodium silicate or so dium aluminate for the best results in maintain ing the clay and sand in suspension for a rela tively long period of time without agitation, 10 should be approximately .8% of the weight or the clay. By means of tests hereinafter explained the critical proportions may be ascertained. That these proportions are critical is evidenced by‘ the fact that in the tests referred to above. doubling the amount of the electrolyte caused a rapid settling of the clay and sand in a mixed mass without layering. ‘ In order to explain the procedure by which cer tain de?nite formulae may be arrived at for obi 20 taining the best results in the use of a separating medium for the cleaning of coal, certain actual tests have been carried out and the results ob served. By mixing one part Minford silt (argil laceous material in its natural state) and four parts of white coarse sand by weight, and adding su?icient water to obtain a speci?c gravity of 1.55, after stirring into the mixture .8% of sodium. aluminate, no sediment of the solid in soluble ingredients was shown after a period of 30 twenty-four hours. When a mixture having a speci?c gravity oi.’ 1.55 was made of one part Minford silt and ?ve parts sand and .8% of sodium aluminate in wa ter, a very slight settlingwas observed after a 35 lapse of twenty-four hours, but in similar mix sults may be obtained by the use of a mixture tures having one part silt and six parts sand, of a certain clay and water without sand but and one part silt and seven parts sand, pro including the addition of a small amount of nounced settling occurred after a lapse of twenty sodium aluminate or sodium silicate, the best four hours, but the settled mass was a very soft 40 results are obtained by the inclusion of natural intermixture of silt and sand such as not to inter sand in the mixture. The use of natural clay fere with the restarting of the conveyor mecha alone in most cases decreases the ?uidity of the nism shown in the separating tank l2 in Fig. 1 or mixture to such ‘an extent as to slow down the in the separating tank l2’ in Fig. 3. Upon re 45 separating process as compared with the speed of ‘ starting the conveyor mechanism through such operation ‘when natural sand is included in the mixture, because the inclusion of the sand in- '1 creases the ?uidity of the separating medium. Clay is an argillaceous material which is com posed of particles in a ?nely divided state which when mixed with water may be dispersed throughout the volume thereof, while sand is a non-argillaceous granular material usually found in its natural state as silica. The particles of clay in their natural state are relatively ?ne and the granules of the natural sand are relatively 'coarse. Both of these materials are available at low cost'almost anywhere in this country, and by reason of the use of the electrolyte, prefer ably sodium aluminate or sodium silicate, no grinding or pulverizing of either the natural clay or the natural sand is necessary in the for mation of the separating medium used in my systems illustrated in the accompanying draw lugs. The sodium aluminate or sodium silicate may be a de-?occulating agent so far as the clay suspension is concerned, but the suspension of the sand may perhaps be best explained by the 70 fact that the sodium silicate or sodium aluminate acts as an electrolyte to produce electrical charges in the .clay particles to hold in suspension for a ‘relatively long period of time the natural sand granules in intimate relation with thedispersed 15 clay in a homogeneous separating medium. settled mass, only a slight mechanical agitation was necessary to recondition the separating me dium, but the homogeneous condition of the medi um could be obtained only by su?icient agitation. The water used in the foregoing tests was that 60 from ‘a city hydrant in Columbus, Ohio. When Sandusky Foundry sand (10% clay) was used in tests with Minford silt, there appeared to be no appreciable settling aftera lapse of twenty four hours, even when the ratio of the ingredients was one part silt to 8 parts of sand, by weight. Fireclay and white sand mixtures did not prove to be as suitable as silt and white sand mixtures. Fireclay and Sandusky sand mixtures showed no appreciable settling after standing twenty-four 60 hours at a ratio including one part ?reclay to six parts Sandusky sand. Inasmuch as it consumes some timeufor the progressive de?occulating action of the sodium . aluminate to take place, it is preferred to age the 65 mixture for a period of at least twenty-four hours. This can readily be done in the systems shown in Figs. 4\and 8 where two mixing tanks are included for alternate use. When the Min ford silt is used with a mixture containing city water, it was found that the minimum de?occula tion vwas effected by the use of sodium aluminate over a, range of .6% to .9% as to the amount of sodium aluminate relative to the weight of the clay. After aging the mixture in the tank 13 or 2,108,495 the tank ‘II, the maximum de?ccculation is de ?nitely indicated at approximately .8% with a pronounced reaction over a range of .8% to one Sandusky'sand'by weight) in water having, in solution .8% sodium aluminate (the separating medium having the specific gravity of 1.53) was about 40 pounds per ton of raw coal treated, The percentage of the‘solid ingredients in sus I whereas with a separating medium having a spe pension in the separating medium is much great ci?c gravity of 1.53 and composed of 1 part silt er for Minford silt than for ?reclay and the dura ‘and 4 parts white coarse sand in water having in tion of the suspension is also much longer‘ for the solutlon .8% sodium aluminate, the carry-01f was Minford silt. This is probably due to the differ; found to be 26 lbs. per ton of raw coal treated. 10 ence in the size of the particles in the two clays. ' Even ?reclay gave better results when mixed with 10 The Minford silt is the better suspending agent coarse white sand than when mixed with the fine of the two clays tested and the Sandusky sand, Sandusky sand. With ‘a separating medium hav a relatively‘ ?ne sand, vis the onemore readily ing the speci?c gravity of‘ 1.53 and composed of maintained in suspension of the‘ two sands tested. ' 1 part ?reclay and 6 parts white sand by weight The permissible ‘sand variation for a given in water having in solution .8% sodium aluminate 15 I speci?c gravitybetween, 1.5 and 1.6 was found the carry-off was found to be 18 lbs. of solid in to be 25 percent for practical operations. With gredients per ton'of raw coal treated, whereas the less favorable sand, the permissible elec with a separating medium composed of 1 part percent. ' , , Y 5 trolyte variation plus or minus from ‘the optimum ?reclay and 6 parts Sandusky sand by weight in point of .8 percent was found to be 12 percent. water- having in solution .8% sodium aluminate 20 .That is to say, the best results are obtained with the carry-off was found to be 20 lbs. of ~ingre .8 percent of electrolyte with a permissible range dients per ton of raw coal treated. from .6 percent to nearly. one percent. While therefore theoretically it may be de Inasmuch as Minford silt is composed of ?ne . sirable to have both of the ingredients in ?nely I 5 -' ly divided particles of argillaceous material and divided ‘condition, itis more practical and eco-' Sandusky Foundry sand is relatively ?ne, eight nomical to have one relatively ?ne as found in " parts of sand could be held in suspension in the nature and the other relatively coarse and also water having in solution a‘ small. quantity of \as found in nature. \ sodium aluminate, so that there would be no Ageing of the mixture of sodium aluminate, '30 appreciable settling after a lapse of twenty-four water, clay and-sand greatly reduces the amount 80 hours. The highest speci?c gravity of the mix of carry-off in the treatment of coal to separate ture can-therefore be obtained when the argil the impurities therefrom. The proper balance laceous material is in a naturally ?nely divided may readily be obtained in ‘practice. Fireclay state and the sand is relatively ?ne. ' white sand mixtures over a' range of M; to 1A; all Bentonite is another form of argillaceous ma settled considerably faster than silt-white sand terial which is found in nature in a ?nely divided mixtures. But ?reclay-Sandusky sand mixtures state and has the property _of cooperating with an showed no appreciable settling at ratios up to electrolyte to hold ten‘part's of?ne sand in sus pension in a separating'medium over a relatively 40 long period of time without agitation. Fireclay is composed of particles’ in a ?nely divided state but not as ?ne as either silt or bentonite. However, ?reclay was found to co act with the electrolyte to hold in suspension six " parts‘ of Sandusky sand by weight in a suitable separating medium because no appreciable set tling occurredafter standing for twenty-four hours. ' ' - It will thus be seen that the tests which were conducted showed that the selection of the ?nest argillaceous material in its natural state and the and including %. _ ’ ~ Inasmuch as the argillaceous material and the sand varies in nature in various parts of ‘the 40 country the correct formula for the separating medium to suit conditions depends upon the clay suspension, the sandsuspension, and the clay sand adherence resulting from contact with smooth‘imporous surfaces. The related deter minations to be made are (1) the concentration of the electrolyte such as sodium aluminate ‘or sodium silicate to clay which produces the maxi- I mum de?occulation of the clay, (2) the eifect of varying the sand-clay ratios upon the dura tion of the suspension and the homogeneity of selection, of the ?nest sand in its natural state _ the suspended mixture, (3) the effectof .varying ‘ enabled the electrolyte sodium aluminate to act to ,hold in suspension the greatest amount of solid ingredients in the separating medium over a long period'of time without appreciable set the sand-clay ratio upon the adherence value, and (4) the effect upon the foregoing of varying the type of clay and sand used in the mixtures. 55 The most e?icient formulas will be those which tling, thereby demonstrating the practicability maintain suspension of _both ingredients over _ of avoiding agitation although solid insoluble in such a length of time asto render agitation un necessary, and which will, result in- a minimum“ gredients are used as found in nature without comminution or pulverization. In this manner ‘ a separating medium of relatively high speci?c gravity may be obtained. Such separating me dium would have maximum buoyancy and would permit the adding of more water-to obtain the m. desired speci?c gravity of'the mixture. There fore the ?ner the solid materials the greater may be the fluidity for a given speci?c gravity. However, it was found from actual tests that the ?ner the solid ingredients in theseparating medium the greater would be the carry-off of such ‘materials with the separated coal. and with the impurities separated and removed. For in stance, the minimum carry-oil‘ of solid ingredi v carry-off - of _ the solid ingredients—clay and so sand-from the ‘separating medium. The clay‘ and sand should be available as found in nature without screening or comminution or pulveriza tion, and therefore the process may be carried out anywhere at a very low cost in materials and, 65 maintenance. Such sand, of course, includes silica sand. [Where solid materials are to be used as sand,_by crushing ganister, quartz, etc., the granules need be no smaller than those of ordi nary silica sand. . .. - _ ~. 70 The conclusions from the actual tests made are as to the solid insoluble ingredients, that Sandusky sand, a relatively fine sand,‘ is not as ents from a separating medium composed of a silt "favorable as coarser sands unless the matter of i and Sandusky sand (1 part silt plus‘ 4 parts suspension becomes a icontrollingfactor and re ‘e 2,108,495 quires its use at lower speci?c gravities. In other words, the colloidal clay acted upon by the elec trolyte has the property of keeping in suspension , various parts of the country in accordance with for a long period of time the ?ner sands. The the nature of the natural clays and the natural sands available. I will therefore set forth the procedure that should be adopted to arrive at tests also showed that silt gave more iavorable the most e?lcient results for various kinds of results than ?reclay. Silt in its natural state is clays and sands. composed of particles more ?nely divided than the ?reclay. The ageing of the mixture for a period of at least twenty~four hours enabled bet The procedure is to mix the clay and water to be used, the weight of the clay being about 25 percent of that of the water. This mixture is ter results to be obtained. I The variation of the placed in a series of beakers and to each beaker speci?c gravity of the mixture can be controlled by varying the proportion of the water. The ?uidity of each of the mixtures tested was su?i—' cient to permit ireesettling of the impurities 15 during ?otation of the cleaned coal, since the consistency or mobility of the mixture is not such asv to interfere with the rapid operation of the separating process. > It has been found from actual tests that sodium 20 silicate is preferable when the water is well water or hard water, while sodium aluminate is prefer able for the'hydrant water of the city of Colum bus, Ohio, which water has been treated chem ically to purify the same. However, either sodi 25 um silicate or sodium aluminate may be used as the suspension agent in either hard water or soft water. ' Sodium silicate is usually obtainable in liquid form, whereas sodium aluminate is in powdered 30 or desiccated form, the latter being more con veniently handled than liquid sodium silicate. Both sodium silicate and sodium aluminate can be obtained at very low cost. For instance, in the formula. using one part natural clay and four parts natural sand with .8% of sodium aluminate, the cost of the latter in certain localities is only about 1/250th oi’ the cost of the clay and sand ‘combined. That is to say, in a separating medi um having one part clay, four parts sand and .8 49 percent sodium aluminate, the cost of the sodium aluminate required is only .4.- percent of the cost of the clay and sand combined. This cost of the electrolyte is sov low that no attempt need be made in practice to reclaim any of it that clings to the cleaned coal as it passes through the washing tanks shown in the accompanying draw , g is added a different amount. of electrolyte such as sodium aluminate or sodium silicate. After the mixture in each beaker is stirred it is allowed to stand for forty-eight hours and the one that shows the best suspension of clay is the mixture that should be selected. If the clay cannot be maintained in suspension in any of the beakers it is not a suitable form of clay. When a suitable clay is found by following the tests with the electrolyte, the mixture of clay and electrolyte is introduced into a series of beak ers, and sand in various proportions is added to the various beakers. The combined weight of the sand» and clay should be the same in each beaker. One beaker may contain clay alone and the other one part clay-and two parts sand, one part clay and three parts sand, etc. Some clays such as bentonite, have the property of carrying ten parts of sand when the electrolyte sodium alumi nate is used in a suitable separating medium in ‘ my method of cle'anlng coal, It should also be understood that su?lcient water is added to the various beakers to obtain the speci?c gravity re quired for the desired coal separation. After the mixtures in the beakers containing the sand have stood for twenty-four hours, ob servations are made and those beakers eliminated which show settling of the sand at the bottoms of the beakers. '_ After selecting the most e?icient mixture’ by proceeding with the tests outlined, the next test to be made is to determine the amount of the mixture that will be carried away with the coal when removed from the separating tank to the ?rst washing tank. For this purpose a piece of polished glass triangular in shape and having ing's. The formula for making up the mixture or'sep sides each four inches long may be dipped into aratlng medium used in our method of cleaning glass before dipping and after, the weight of the I mixture that adheres to the glass can be calcu £30 coal di?'ers with the materials available to serve as the insoluble solid ingredients. The clays which are useful in my method, while having the general characteristics of kaolinite are ‘not nec essarily pure clays but would fall under the gen in Q1 eral classification of shale, surfaces lay, silt and ?reclay. These types are widely distributed and the mixture and withdrawn; by weighing the lated. The mixture that carries ed the least amount of separating medium is the most desir able to he used in practice. For instance, in ac tual tests it was found that for each one-tenth of a grain per square inch carried off by the testing ; glass, there will be seventeen (17) pounds of mix ture carried off by a ton of separated coal. v‘These tests were made by dipping the glass and each is useful in the process in its natural plate into the beaker mixtures andv weighing 60 The essential characteristics of the argillaceous while wet. The weights were calculated as the 60 material in the method of separating coal from weight of the mixture adhering to each square its impurities, are those having the property oi’ inch of surface of the plate. Instead of using glass plates imporous card-board squares may be being dispersed or- de?ccculated bythe electro lyte and after being dispersed or de?occulated, used for immersion in the beaker mixtures but .65 having the property of maintaining in suspension I it will be found that less solid material will ad the desired quantities‘ of sand or other inert here to the card-board than to the glass plate. In such carry-off tests of beaker mixtures, a granular material. Such properties in my separating'medium used curve maybe plotted from the results obtained. in my improved method of cleaning coal, may For instance, in connection with actual tests 70 be readily determined by simple tests which may made with a series of beaker mixtures in which be carried out wherever clay and sand are found the amount of sodium silicate ranged from zero in various parts of the country or wherever it is to 3.6 percent by weight of clay in the fluid, the desired to iollow such method. I have set forth plotted curve will show a gradual decrease in formulae for most emcient operation in certain the amount of clay carried out on a card until localities but such formulae may be varied in the percentage of sodium silicate is about 1.3 readily available in various parts of this country, state. to i ' .7‘ 2,108,495 or 1.4,.aiter which the increase of the percentage of sodiuinsilicate vinoreasesthe amount of clay carried out on a card. The clay used was a form of' ?reclay having a pH value‘ of 5. Afterv ‘permitting the beaker mixtures to stand for twenty-four hours after adding the electrolyte ' and stirring the mixture, it was found that the suspension of the solid ingredients ‘in the sepa rating medium andas to reduction to. the mini mum of the solid ingredients carried oil from the ' separating medium. It should be particularly noted by reference to Figs. 4, 8, and 9 that the operation of separating coal from the impurities may be carried on auto clay remained in suspension the longest in the. matically over an extended period of time, For instance, if the tank 13 acts as a storage tank 10 clay in the'mixture, and the tests further showed while :the valve 16 is closed and the valve 15 10 that the range for best results would be between ' open, the automatic ?oat valve ‘I8 will maintain 1% and 1.4 %. of electrolyte. ' The carry-off tests the depth of the separating medium in the sepa of clay mixtures also enabled the plotted curve rating tank I!’ at a predetermined level. At the in Fig. 10 to show pounds of clay per ton of coal > same time the settling tank 60 may have clear '. is that would be carried out of the medium during liquid therein so that when the valve 66 is closed 15 the coal separating process. For instance, in and the valve 61 is open the ?oat controlled the tests just described where the best results switch ‘I! will e?eot intermittent automatic oper would be obtained with the electrolyte ‘1.3% by ation oi’ the pump 64 to replenish water in the beaker having 1% of sodium silicate by weight 01’ weight of clay in the mixture, the least amount of tank ii’ for ?ow successively into the tanks i4, 20 clay would be carried out on the card and would represent about 30 pounds of clay per ton of coal. As above explained, there is a permissible range and It. This is true whether the valve 54 is open or not but will take place oftener if the valve 54 is partially open and the valve 62 is closed when the valve 63 is open. There will then be a con— " in the use of the proportions of the ingredients in the water for maintenance of the clay and "sand in suspension over relatively long periods or time. In the beaker tests there may therefore be various mixtures which would be suitable so far as'maintenance of the clay and sand in sus tinuous draining of settling material from the bottom of the tank l3 to the settling tank 6! while the automatically controlled and operated motor M replenishes the water in the tanks 15', II and i3. When sediment is removed from pension is concerned, but by following the pol either of the settling tanks 60 or 6| it may be ished glass test the .best separating medium may ‘ delivered by means of the chutes H2, H3 directly be obtained so that a minimum amount of the separating medium will be carried away with the separated coal by the conveyor,” and a minimum amount will be carried away when the impurities at the bottom of the separating tank are con veyed out of the tank by the conveyor i8. It . should be understood that during the operation of the separating apparatus the intermixture of the ingredients is so thorough that when the 40 cleaned coal and impurities are removed from the separation tank, the medium that clings to the removed materials is about the same in its pro portions of constituents as the medium that re mains in the tank. ‘The medium in the tank 45 therefore remains as to specific gravity and em ' ciency, the same as when ?rst introduced and the replenishment of the medium in the sepa rating tank is by means of the same'mixture as that selected by means of the foregoing tests. Inasmuch as it is important to reduce to a to" minimum the amount of solid ingredients‘carried to the mixing tanks 13, ‘ll, as shown in Fig. 7. That is to say, when the system shown in~Fig. 4 is in operation, the valve 94 is keptopen contin uously. The extent of opening of the valve 94 is regulated so that the water in the last tank i5’ " is practically clear. If the water in the second tank . I4 is practically clear, too much water is being used in the automatic circulating system which indicates ‘that the valve 9| should be par- ' tially closed. 0n the other hand if‘ the water in the last tank I5’ is discolored, the valve 94. should be 'moved toward open position. The valves 55 and 56 are kept closed during normal operation and are opened for draining purposes only about once in a shift of about eight hours and then 45 closed again. , ‘It is also important to note that in the appa ratus' used in my system and for my methods the > liquids are substantially quiescent. This is par ticularly true in the separating tank the bottom on of which is entirely closed during operation‘ and oil‘ from the separating medium and it is also , in which no special means is provided for agitat important to maintain suspension of the solid ing the separating‘ medium.‘ The conveyors for ingredients in the separatingmedium, the curve removing the separated coal and impurities are ' 65 shown in Fig. 10 after.being plotted from the operated at a relatively slow speed and may be 5.1 tests above: outlined, may be used to determine arranged either, as shown in-Fig, 1 or as shown in the most practical percentage of sodium silicate . Fig. 3. or sodium aluminate in the separating medium. While I prefer to include the preliminary wet For instance, since the best results from the ting of the raw coal for the reasons hereinbefore 60 tests indicate from .6% to .9% of sodium silicate explained this is not always necessary or desirable 60 by weight of clay and the curve shown in Fig. 10 .from the standpoint of economic operation. indicates 1.3% of sodium silicate by weight of -The raw coal wet or dry, is fed into a quiet clay, approximately one percent ofasodium sili pool or separating bath in the separating tank ' cate by weight of clay' could be used in practice to the extent, that the amount of solid ingre dients that would be carried-out by the separated coal and impurities from the separating medium will'be approximately 32 lbs. per ton of raw coal treated. ' , Inasmuch as the percentage of sodium silicate or sodium aluminate for suspension purposes is . critical as above explained, the region to the left of the lowest point of the curve of Fig. 10 should _ be relied on to determinelthe percentage of elec trolyte for obtaining the desired results both as to and .the , separated coal is. then moved up— > wardly to a predetermined height from ‘which 65 it is dropped-by gravity into the ?rst washing tank. ~This operation is entirely automatic and the impact against the water'assists materially in washing from the coal the solid ingredients car ried over from the separating medium. However, 70 when the coal strikes the water the latter yields to prevent breakage of the coal. In some localities the sand and clay may be obtained at such low cost that the reclaiming of the same may not be‘ desirable in which event, 8 ' 2,108,495 however, it may still be economical to retain the water circulation for the washing tanks. That is, the sedimentation steps may be carried out for the purpose of obtaining clear water to replenish that used- in the washing tanks and this may be done automatically. In fact, all of the apparatus shown in the drawings may be retained if desired, although the sediment from the sedimentation coal from said tank while leaving the separating medium therein except for particles which ad here to said coal, washing said coal to remove the adhering separating medium therefrom, ‘and re covering the removed separating medium to be used again. Obviously those skilled in the art may make various changes in the details and arrangement 5. The method of cleaning coal which com prises mixing a. separating medium comprising sand, clay and a de?occulating or dispersion of parts without departing from the spirit and agent, storing and aging said medium, introducing scope of the invention as de?ned by the claims said separating medium into a separating tank, introducing raw coal into said separating medium while in a quiescent condition in said separating tanks is discarded. 10 thereby separating the coal from the refuse, re moving the refuse from said tank, removing the , , . hereto appended, and I therefore wish not to be 16 restricted to the precise construction herein dis closed, Having thus described and shown an embodi ment of my invention, what I desire to secure'by Letters Patent of the United States is: 1. In apparatus for separating coal from its im purities,‘ and washing the separated coal. the combination with a wetting tank, of a separating tank, a washing tank, two sedimentation reclaim ing tanks adapted to be used alternately, two mix ing and storage tanks either adapted to be used as a mixing tank while the other is being used as a storage tank, means connected between the last named tanks and said separating tank to main tain the separating medium in the last-named tank at a predetermined level, means a?ording ?ow of settled solids from the washing tank to either of said sedimentation tanks, automatic mechanism for pumping water from either sedi mentation tank to said washing tank to maintain the depth of water in the latter at a predeter mined level, and conveyor mechanism associated with the separating tank for removing impurities and separated coal therefrom, and conveyor mechanism for the washing tank to remove the 40 washed coal therefrom. ~ ' 2. In apparatus for separating coal from its impurities, the combination with a separating tank, of a washing tank, a sedimentation tank. conveyor mechanism for removing separately the separated coal and impurities from the separat~ ing tank, conveyor mechanism for removing sep arated coal from the washing tank, means for ef fecting transfer of settled solids from the wash tank thereby separating the coal from the refuse, removing the refuse from said tank, removing the coal from said tank while leaving the sep arating medium therein except for particles which adhere to said coal, washing said coal to remove the adhering separating medium therefrom, and recovering the removed separating medium to be used again. I ' 6. The method of cleaning coal which com prises mixing a separating medium comprising clay, sand and a relatively small amount of a de?occulating or dispersion agent, storing and aging said medium in a quiescent state, intro ducing said aged separating medium into a sep arating tank, introducing raw coal into said tank. 30 and separately removing the materials which ?oat and those which sink. 7. The method of cleaning coal which com prises mixing a separating medium comprising sand and a relatively small amount of a de?occu lating or dispersion agent, storing and aging said medium in a quiescent state, introducing said aged separating medium into a separating tank, introducing raw coal into said tank, and separate ly removing the materials which ?oat and those which sink. _ 8. The method of cleaning coal which com prises mixing a separating medium comprising clay and a relatively small amount of a defloccu- _ lating or dispersion agent, storing and aging said 43 medium in a quiescent state, introducing said aged separating medium into a separating tank, introducing raw coal into said tank, and sep . ing tank to said sedimentation tank, and auto-v arately removing the materials which ?oat and matic pump mechanism for pumping water from those which sink. the sedimentation tank into said washing tank to 9. In a systernjol separating impurities from maintain the depth in the latter at a predeter raw coal, the combination with a separating mined level. tank, of means comprising a ?oat controlled valve 3. The method of cleaning coal which com for maintaining the depth of separating medium prises mixing a separating, medium comprising in said tank at a predetermined level, a washing insoluble granular material and a de?occulating tank, a settling tank, means for controlling drain or dispersion agent, storing and aging said me ing of sediment from said washing tank to said dium, introducing said separating medium into settling tank, means comprising a pump for draw a separating tank, introducing raw coal into said. ing liquid from above the sediment in said set no separating medium while in a quiescent condition tling tank and. delivering said liquid to said insaid separating tank thereby separating the washing tank, a motor for operating said pump, coal from the refuse, removing the refuse from automatic means comprising a ?oat in said said tank, removing the coal from said tank while washing tank for controlling said motor to op leaving the separating medium therein except for eratesaid pump to maintain the depth of liquid particles which adhere to said coal, washing said in said washing tank at a predetermined level, 65 coal to remove the adhering separating medium means for removing separated impurities from therefrom, and recovering the removed separat said separating tank, and means for moving ing medium to be used again." ' cleaned coal from said separating tank into said 4. The method of cleaning coal which com washing tank and then out of the latter. TO prises mixing a separating medium comprising 10. In a system of separating impurities from insoluble granular matériahclay, and a de?occn raw coal, the combination with a wetting tank‘ lating or dispersion agent, storing and aging said adapted to contain water, of a separating tank medium, introducing said separating medium into adapted to ‘contain aseparating medium, means a separating tank, introducing raw coal into said for introducing raw coal into the water in the separating medium while in said separating tank wetting tank and then deliver such wetted coal ‘ 2,108,495 £9 into the medium in said separating tank, a wash ing tank adapted to contain water, means for removing the separated impurities from said a valve for controlling drainage of sediment from said washing tank into said settling tank, and separating 'tank, means for removing cleaned 1 liquid from above the sediment in said settling coal from said separating tank and moving it into and out of the water in-said washing tank, a settling tank, means for eifecting drainage of sediment from said wetting and washing tanks into said settlement tank, and automatic means 10 for drawing water from above the sediment in said settling tank and introducing such water into said washing tank to maintain the depth of automatic means for-controlling the drawing of tank and introducing said liquid into said wash ca ing tank to maintain the depth in the latter at a predetermined level.’ 12. In a system ‘of separating impurities from raw coal, the combination with a separating tank adapted to contain a separating medium, of a 10 plurality of washing tanks each adapted to con tain water, over?ow means between each wash water in the latter ‘at a predetermined level. ing tank and the next adjacent washing tank, 11. In a system of separating impurities from l 5 raw coai,‘_the combination with a separating tank adapted vto contain a separating medium com prising granular material held in suspension by a dispersion agent, means for removing from said tank the separated impurities, a settling tank, 20 means comprising a valve for controlling drain age to said settling tank of impurities settled to the bottom of said separating tank, a washing tank adapted to contain water, means for re moving cleaned coal from said separating tank IO andmoving such cleaned coal into and out of the mechanism for removing separated impurities water in said washing tank, means comprising from said separating tank, a settling tank, means 15 for controlling ?ow of sediment from said wash ing tanks to said settling tank, means for remov ing cleaned coal from said separating tank and then moving such cleaned coal intoand out of the water successively in said washing tanks, and 20 automatic means for drawing water-from above the sediment in the settling tank and introducing such water into one of said washing tanks to the level of said over?ow means to e?ect auniiorm predetermined depth in all of-the washing tanks. 25 Nils D. LEVIN.