Hydraulic method of mining and conveying coal in substantially vertical seams
United States Patent 11 1 Poundstone et a1. Apr. 1, 1975 1 1 HYDRAULIC METHOD OF MINING AND 2.276.075 3/1942 Wuensch 252/85 s CO V NG COAL IN SUBSTANTIALLY 2,944,019 7/1960 Thompson et a1. 252/85 B 3.637.263 1/1972 Wasp... 302/14 VERTICAL SEAMS 3.719.397 3/1973 Wasp 302/14 [75] Inventors: William N, Poundstone, Pittsburgh, 3.776.594 12/1973 Haspert 299/18 Pa.; William J. Miller, Ponca City.  
  Okla. Primary Examiner-Ernest R. Purser [73] Assignee: Continental Oil Company, Ponca City. Okla. 1 1 ABSTRACT [22] Filed: Aug. 29. [973 Coal can be mined from a substantiallyyertical or steeply inclined seam by forming a cavity in the seam [21] Applv No: 392.576 and filling the cavity with a magnetite slurry having a specific gravity greater than the coal being mined 152 US. Cl 299/17, 299/18, 302/14 1511 lm. c1. EZlc 37/06 AS the coal is dislodged It will fleet lo the p and he [58] Field of Search 299/17, 18; 175/66, 263, P p from the Cavity y the eXeeSS magnetite Slurry 175/20 302 14 252 35 3 being supplied to the cavity. A coal-magnetite slurry separator is used to separate the coal from the [56] Ref Ci d magnetite slurry, whereupon the magnetite slurry is reinjected in) the Cavity.  
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 TENTH] APR 1 i8?5 SHEET 1 OF 3 COAL SEPARATOR FIG. I  
  oo//////// 00 /L L/l/// HYDRAULIC METHOD OF MINING AND CONVEYING COAL IN SUIISTANTIALLY VERTICAL SEAMS DISCUSSION OF THE PRIOR ART Vertical seams have generally been mined in the past by use of strip mining; however, strip mining can only be economically performed for fairly shallow penetrations into the coal seam. since a vast amount of debris and rock must be removed in order to reach any depth in the coal seam. Strip mining is only feasible when the coal scam has a substantial width and fairly high grade.  
  A forming of mining known as cut-and-fill stopping is also used for substantially vertical seams and is accomplished by digging a tunnel along the seam forming ore chutes above the tunnel and mining out the coal, dropping it into the ore chutes and thence into the cars positioned below said chutes; however. where the seams may he badly folded. it may be extremely difficult to mine the seams from underneath.  
  Another method of mining vertical seams can be used. such as the shrinkage stoppage method. The particular method used will depend on the competency of the hanging wall, the particular form of the seam.  
 BRIEF DESCRIPTION OF THE INVENTION This invention describes a method for mining sub stantially vertical seams by forming a cavity in the seam. either from the top or from a desired depth. fill ing the cavity with magnetite slurry which has a specific gravity greater than the specific gravity of the coal. and then dislodging the coal mechanically wherein the coal will tloat to the surface and be pumped from the cavity by the excess magnetite slurry being supplied thereto.  
  Separators are used to separate the coal which is conveyed from the separator from the slurry which is pumped back into the cavity along with additional magnetite. if needed. to maintain specific gravity above that of the coal. In one embodiment the cavity is formed from the surface and is acceptable for high grade coal where the amount of impurities in the coal is minor compared to the tonnage of coal mined. Under ordinary conditions. however. debris and unusable materials can amount to as much as percent of the coal mined. The preferred embodiment overcomes the accumulation of debris by drilling a bore hole to a desired depth in the coal seam. anchoring a magnetite recovery pipe at the bottom of the bore hole. and mounting a mechanical dislodging apparatus around the magnetite recovery pipe. Magnetite slurry is pumped down the dislodging device and against the mine surface. Mechanical devices. such as picks. will dislodge the coal which is flushed away by the magnetite being jetted against the coal surface. As the coal is dislodged. the apparatus is pulled up in the manner of raise drilling. The dislodged coal floats to the surface because of its lower specific gravity and is conveyed through a pipe or trench to a magnetite slurry-coal separator. When the cavity reaches the surface of the earth, the dislodging apparatus is removed. Fresh water is pumped into the cavity. and the magnetite slurry is removed by back-flushing the fresh water through the debris and into the magnetite recot cry pipe where it is pumped from the cavity.  
  In the above manner most of the magnetite can be recovered from the cavity. The magnetite slurry being recovered will be applied to a magnetite-water separator. The water will be returned to the mine cavity, and the recovered magnetite will be applied to the new ca\ity being mined.  
 BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a cross-sectional view of a cavity being formed using the raise drilling principle;  
  FIG. la is an alternate embodiment of the dislodging arm shown in FIG. I;  
  FIG. 2 is a cross-sectional view of a mined cavity illustrating the magnetite recovery process;  
  FIG. 3 is atop view of a mining operation illustrating the process of recovering the magnetite from a mined cavity, mining a new cavity, and supplying the recow ercd magnetite to the cavity being mined; and  
  FIGS. 4 and 5 illustrate the method of mining a substantially vertical seam by forming the cavity from the surface of the earth.  
  Referring to FIGS. I through 3. the preferred em bodiment is illustrated.  
  A bore hole III is formed in the seam to a desired depth which may. for example. be from 7()() to 900 feet in depth. A magnetite recovery pipe 11 (to be later described) is insertcd axially into the bore hole. An anchoring means 12 is attached to the bottom of magnetite recovery pipe I I and comprises a ring 13 and a plurality of extending rods 14. A plurality of openings 15 perforates the lower end of recovery pipe II. These openings may be slots or circular in shape and may be plugged to prevent entry of debris, by any means such as wax or plastic which can be removed at a later time. The type of slots used and the plugging material. if used. are well known in the art and will not be further described herein.  
  A dislodging pipe 15 is slipped axially over recovery pipe II and has a rotatable seal 16 at its lower end. Dislodging pipe 15 may be formed from a plurality of sections &#34;joined at 18 by a threaded joint. It is preferable that the outer circumference of the pipe be completely uniform across the joint.  
  Bore hole I0 has a surface seal formed by a pipe 20 forced into or cemented into bore hole I0. Pipe 20 terminates in a pipe end 2]. bolted by means of a flange 24 to surface seal pipe 20. Pipe end 2! has a seal 25 which provides a fluid tight seal for dislodging pipe l5 and yet permits rotation of pipe I5. Pipe end 21 also has an outlet 22 which is connected through a pipe 23 to a magnetite slurry-coal separator 25. The magnetite slurry-coal separator basically incorporates a conveyer which removes the coal floating on the surface of the magnetite and deposits the coal in a dump or other location and returns the magnetite to the mine cavity. Such magnetite slurry-coal separators are described on page 9-26 through page 9-35 in a book entitled Coal Preparation. Third Edition. by Joseph W. Leonard and David R. Mitchell and published through The American Institute of Mining, Metallurgical. and Petroleum Engineers. Inc.. and published by the Port City Press. Inc., Baltimore. Md. The magnetite slurry is re turned through a line 26 to a pump 27 to injection line 28 to a hydraulic motor 29 and to the inside of dislodging pipe IS in the direction of arrow 30. As the magnetite slurry is forced through hydraulic motor 29. it causes rotation of a shaft 31 which is connected through threads 32 to a pipe section 17 of dislodging pipe 15. Hydraulic motor 29 is held in place or moved by means of a hoist 35 which contains a book 36 interlocked with an eye 37 which is permanently attached to the hydraulic motor 29. A plurality oflines 40 is connected to a hoist pulley (not shown). The entire structure is supported by a rig 41 which is attached by any suitable means. either portable or permanent. to the surface of the earth.  
  A pipe clamping means is attached through a flange 45 to pipe end 2|. A wedge-type pipe retaining means 46 is mounted onto flange 45. Wedge retaining means 46 permits upward movement and rotational movement of dislodging pipe but will prevent pipe [5 from moving downwardly into the cavity.  
  The upper end 50 of magnetite recovery pipe I 1 contains a small slot 5| which permits entry of magnetite slurry into pipe H but restricts the loss in pressure so that the majority of the pressure is available at the bot&#39; tom of dislodging pipe 15.  
  A dislodging arm 60 is attached through a pivot 61 to the bottom end of dislodging pipe 15. A plurality of jets 62 is mounted on dislodging arm 60 and directed upwardly so as to create a high velocity fluid stream against the mine surface 63. A flexible pipe 64 communicates fluid from the inside ofdislodging pipe 15 to the jets 62. A roller 65 maintains a precise distance between the jets and mining surface 63. A suitable mechanical lock (not shown) maintains dislodging arm 60 in a rigid position once the arm has moved to the proper cutting position.  
  Referring to FIG. In, an alternate embodiment of the dislodging arm is shown and essentially comprises a plurality of picks 70 attached between jets 62. In this embodiment the jets principally provide means for removing the dislodging chips of coal and debris rather than provide a means for removing the coal by high velocity of fluid.  
 MINING OPERATlON The operation ofthe preferred embodiment is as fol lows:  
  The dislodging pipe [5 and dislodging arm 60 are lowered into bore hole with the dislodging arm in the position shown by dotted lines 71. The mechanical locks maintaining dislodging arm in the position shown by dots 7! can be released by any well known method such as a mechanical pin. an electrical squib. or other well known triggering devices. Once the dislodging arm 60 is released. pump 27 initiates the pumping of magnetite slurry into hydraulic motor 29, down the inside of pipe in the direction of arrow through flexible tube 64 to jets 62. Hydraulic motor 29 will begin rotating as soon as the flow through the motor becomes sufficient to generate enough horsepower to operate the hydraulic motor. As motor 29 begins to rotate, dislodg ing pipe 15 begins to rotate. causing dislodging arm 60 to rotate about the wall ofthe bore hole. The high pressure from the jets 62 begins eroding the bore hole wall from cavity 90. The jet fluids will also commence filling up cavity 90 and the bore hole ill with fluid or magne tite slurry. Once the bore hole is filled. slurry will flow down through outlet 22. down pipe 23, to magnetite slurry, and coal separator 25 for recirculation through pipe 36 to pump 37. The coal 9]. for example. will be dislodged and proceeds to the surface, since it has a specific gravity less than that of the magnetite slurry.  
 Debris 92. for example. will fall to the bottom of the well bore and cavity 90. Roller will maintain the distance between the mining surface 63 and jets 62; or. if picks are used, the picks (see FIG. la) will maintain contact with mining surfaces 63 eroding the mining surface.  
  Seal 16 permits rotation of dislodging pipe 15 with respect to magnetite recovery pipe 1] and yet retains the fluid pressure inside pipe l5. Anchor l2 retains magnetite recovery pipe down-hole and in position during the rotation and lifting ofdislodging pipe 15. Metal rods 14 are spring biased away from the outside wall of pipe I1 and have sufficient diameter to engage the bore hole wall. Thus. if pipe I] rises, rods l4 will dig into bore hole wall ll, retaining the pipe into position.  
  The particular anchor disclosed here should properly hold the recovery pipe II in position; however. other types of anchors could be used, for example. an inflatable packer. auger. and other well known apparatus for securing a pipe in a particular location. It is preferable. of course. that the particular anchor used be releasable at a later time so that the pipe can be recovered after the recovery operation is complete.  
  As dislodging arm 60 rotates the coal will soon be eroded to the point where either the picks or jets can no longer remove any coal. At this point hoist 2S and its associated equipment will raise the hydraulic motor 29 through book 36 and eye 37. lifting pipe l5. Since dislodging arm 60 is connected to pipe 15 it will likewise rise with the pipe, thereby permitting dislodging arm to re-engage the mining surface 63. As a section of pipe I7 is raised to the point where a joint [8 is above wedge clamp 46. the hoist 35 will be lowered. wedging the pipe of the clamp 46. Hydraulic motor 29 will then be reversed or mechanically unscrewed from pipe 17 and that section of pipe removed. Motor 29 will then be connected with the next lower section 17 of pipe 15. The procedure will be followed until the dislodging arm 60 has been cut away mining surface 63 in a nearly cylindrical form to a depth near the surface of the ground which will under normal conditions be the bottom of surface seal 20. At this time pipe end 2|, including wedge clamp 46. will be removed along with hydraulic motor 29. and the magnetite recovery process will commence.  
 MAGNETITE RECOVERY Referring to FIGS. 2 and 3. but in particular to FIG. 2, a completely formed cavity is illustrated having magnetite recovery pipe I] therein anchored at the bottom by anchor means I2. Pipe end 2l has an extension pipe passing therethrough and connected to the end 50 of pipe II. The short portion containing slot 51 has been removed. Pipes 96 are connected from exten sion 95 to the inlet of pump 27. A magnetite water separator It)&#34; has its inlet l0l connected through pipe I02 to the outlet [03 of pump 27. The reclaimed magnetite is recovered through outlet I04 and the water is recovered through outlet I05. Water from outlet is connected through a line I06 to a second pump I07 to the water inlet I08 of pipe end 2].  
 OPERATlON The importance of recovering magnetite in the cavity and debris cannot be minimized. It is estimated that in a cavity of approximately 700 feet in height and a radius of three feet, approximately l.tl(ltl tons of mined material can be recovered. Assuming 20 percent of the material is debris and 80 percent ofthe material is coal. approximately Kilt) tons of coal will be recovered and 200 tons of debris will lie in the bottom of the cavity. Assuming the debris will not be firmly compacted. it will fill from A to ls of the cavity Magnetitc has a specific gravity of 5.0. Assuming a good grade of magnetite. approximately 90 percent of the magnetite will be liner than sixe 360. A certain portion of the magnetite will settle to the bottom ofthe cavity during the mining process particularly since the magnetite is in the form of a slurry and not in the form of a solution. If, for example. l()() tons of magnetite settled with the debris to the bottom of the cavity, over $2.000 worth of magnetite would he lost if no method of recovery were possible. In order to recover the magnetite. therefor improving the economics of this form of mining. fresh water is pumped through pump I07 to inlet I08 into the cavity 90. The fresh water will cause back-flooding of the debris: and. since magnetite is the heaviest material in the cavity. it will settle to the bottom near the openings of pipe I]. Pump 27 will then suck up the fresh water and magnetite through holes I5 up pipe I I in the direction of arrow 1 I5 and through pipe 96 to pump 27 where it is moved through pipes I02 and II to magnetite water separator I00. Magnetite water separators are well known in the art. Such devices are clearly described in the hook Coal Preparation,&#34; (supra). The reclaimed magnetite is saved for future mining operations. and the water is returned through lines I06 to pump 107 [if needed) and thence to cavity 90. Once the amount of magnetite being recovered is insufficient for the energy being expended to recover it. the magnetite recovery process is discontinued. Pipe 96 is removed along with pipe end 2I. Pipe section 95 is connected to hoist 35. and the entire pipe II lifted out of the cavity 90. Anchor I2 will disengage by either tearing away the walls of the bore hole portion remaining or. rods I4 will bend or break off as pipe is pulled tip through the debris.  
  The above system has certain advantages. For example. it does permit a means of recovering a high cost item such as the magnetite used in mining the ore; and it does permit recovery of the magnetite recovery pipe. Since the pipe was put in initially. no hole need be drilled at a later time through unconsolidated debris which would pose a difficult drilling problem under the best of conditions.  
 MINING SYSTEM Referring to FIG. 3 the entire mining system is disclosed showing the process for mining a narrow vertical seam. A mined out cavity I is followed by a mined out cavity I2I \vhere magnetite recovery is in process and a partially mined out cavity 122 where mining is still in progress. In the recovery cavity IZI. pipe 96 is applying water through pipe end 2I to cavity IZI. and pipe I08 is pumping out the magnetite slurry through pump 27 to magnetite water separator I00. The water is being returned through line I06 to pipe 96 and back to cavity IZI. Additionally water. if needed. is added through line 123. The mining section has the magnetite slurry being applied through line 28 into pipe end 21 and the magnetite slurry and coal being recovered through pipe 23 to magnetite slurry and coal separator 25. The magnetite once separated is applied through line 26 to a slurry mixer I24 where water I25 and magnetitc I26 are being added by amounts to insure the proper specific gravity of the magnetite. Once the slurry mixture is proper. it is returned through line 28 to the cavity 122. Magnetitc being recovered from separator 100 is transferred by conveyer or line I30 to the slurry mixer 124.  
  The separator I00. the slurry-coal separator I25. the slurry mixer I24. pump 27 and any other necessary pumping and power equipment can be mounted on a single or plurality of vehicles in order to provide mobility to the system.  
 SURFACE CAVITY MINING Referring to FIGS. 4 and 5. a surface cavity mining system is illustrated. A platform 200 has an outer casing 2(II rotatably attached by a bearing 202 to platform 200. Dislodging pipe I5 is mounted inside casing 20I. Pump 27 has an inlet 26 connected to a source ofmagnetitc slurry (not shown). The outlet from pump 27 is connected through pipe 28 to a rotatable pipe connection 203. A motor 204 is connected through a winch 205 to rig 4I. Motor 204 can be electric or hydraulic of sufficient power to turn dislodging pipe I5 and dislodging arm 60. Jets 62. which. as previously described. can also he picks such as 70 in FIG. I2. are in engagement with coal seam 206.  
 OPERATION The operation of the dislodging arm shown in FIGS. 4 and 5 is substantially identical to the operation of the dislodging arm 60 described in FIGS. I through 3. Magnetite slurry 207 fills the cavity and overflows through a trench 208 to a recovery area (not shown). Coal 9] floats on the magnetite slurry and can be easily removed. The system described in FIGS. 4 and 5 is extremely useful for very high grades of coal with little debris embedded in it. Obviously. as the debris accumulates. the mining must be stopped and the debris mechanieally removed before mining can he recommenced.  
 MAGNETITE SLURRY Coal of a high grade anthracite normally has a specific gravity of from l.4 to L7. The density of the magnetite must be greater than the density being mined in order for the coal to float; therefore. if the density of the coal is L4. the density of the magnetite must be at least L5 in order for the magnetite to have adequate buoyancy. Bituminous coal normally ranges from a specific gravity of I .4 to I .5. Debris on the other hand usually has a specific gravity of 2.0; therefore, it is relatively easy to separate the debris from the specific gravity; however, it is also obvious that the specific gravity of the magnetite must be controlled sufficiently to maintain its density less than that of the debris but more than that of the coal being mined. Most debris does have a specific gravity of 3.0; therefore. errors in the adjustment in the specific gravity would still not render the system inoperable but would merely provide less pure coal.  
  These and other modifications can be made to the embodiments illustrated and still be within the spirit and scope of the invention as described in the specification and appended claims.  
 We claim:  
  I. The method of producing coal from a seam of coal comprising:  
 boring at substantially vertical pilot hole into said seam ol coal;  
 inserting a retracted coal dislodging tool into said bored pilot hole;  
 extending said dislodging tool;  
 raise drilling with said extended dislodging tool to form a cylindrical cavity.  
 injecting under pressure into said bored pilot hole and said formed cavity material having a specific gravity greater than said coal.  
 removing said dislodged coal and said material through said pilot hole;  
 separating accumulated amounts of said dislodged coal and material being removed from said bored pilot hole;  
 re-injecting said separated material into said bored pilot hole; and  
 continuing to raise drill until said dislodging tool is in close proximity to the surface of said seam of coal.  
 2. A method as described in claim 1 wherein said method includes:  
 boring another substantially vertical pilot hole in said&#39; seam of coal in the proximity of said first- Ill mentioned formed cavity;  
 inserting said retracted coal dislodging tool into said another bored pilot hole.  
 extending said retracted coal dislodging tool and raise drilling to form a cavity:  
 injecting water through said t&#39;irstanentioned hore hole and into said cavity to remove said material therefrom:  
 separating said material from said injected water; and  
 inserting said separated material into said another bore hole.  
  3. A method as defined in claim 2 wherein said material eomprises a slurry formed from magnetite and wa- 4. A method as defined in claim 3 wherein said magnetite slurry and water removed from the bottom of said bore hole is further processed by:  
 separating said magnetite from said water:  
 mixing said separated magnetite with water to form a slurry having a predetermined specific gravity: adding said slurry to said another bore hole: and  
 returning said separated water to said bore hole.  
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