U.S. patent number 3,874,733 [Application Number 05/392,576] was granted by the patent office on 1975-04-01 for hydraulic method of mining and conveying coal in substantially vertical seams.
This patent grant is currently assigned to Continental Oil Company. Invention is credited to William J. Miller, William N. Poundstone.
United States Patent |
3,874,733 |
Poundstone , et al. |
April 1, 1975 |
Hydraulic method of mining and conveying coal in substantially
vertical seams
Abstract
Coal can be mined from a substantially vertical or steeply
inclined seam by forming a cavity in the seam and filling the
cavity with a magnetite slurry having a specific gravity greater
than the coal being mined therefrom. As the coal is dislodged, it
will float to the top and be pumped from the cavity by the excess
magnetite slurry being supplied to the cavity. A coal-magnetite
slurry separator is used to separate the coal from the magnetite
slurry, whereupon the magnetite slurry is reinjected into the
cavity.
Inventors: |
Poundstone; William N.
(Pittsburgh, PA), Miller; William J. (Ponca City, OK) |
Assignee: |
Continental Oil Company (Ponca
City, OK)
|
Family
ID: |
23551149 |
Appl.
No.: |
05/392,576 |
Filed: |
August 29, 1973 |
Current U.S.
Class: |
299/17; 299/18;
406/197 |
Current CPC
Class: |
E21B
43/29 (20130101); E21B 10/32 (20130101); E21C
41/16 (20130101); E21B 10/60 (20130101) |
Current International
Class: |
E21B
10/00 (20060101); E21B 10/60 (20060101); E21C
41/16 (20060101); E21B 43/00 (20060101); E21C
41/00 (20060101); E21B 43/29 (20060101); E21B
10/32 (20060101); E21B 10/26 (20060101); E21c
037/06 () |
Field of
Search: |
;299/17,18
;175/66,263,206 ;302/14,66 ;252/8.5B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Attorney, Agent or Firm: Miller; William J.
Claims
We claim:
1. The method of producing coal from a seam of coal comprising:
boring a substantially vertical pilot hole into said seam of
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 seam of
coal in the proximity of said first-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 first-mentioned bore 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 comprises a
slurry formed from magnetite and water.
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.
Description
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 seam 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 be 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, whether the ore is weak or strong, and other well known
factors.
BRIEF DESCRIPTION OF THE INVENTION
This invention describes a method for mining substantially vertical
seams by forming a cavity in the seam, either from the top or from
a desired depth, filling 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
float 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 20 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 recovery 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
cavity 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. 1a is an alternate embodiment of the dislodging arm shown in
FIG. 1;
FIG. 2 is a cross-sectional view of a mined cavity illustrating the
magnetite recovery process;
FIG. 3 is a top view of a mining operation illustrating the process
of recovering the magnetite from a mined cavity, mining a new
cavity, and supplying the recovered 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. 1 through 3, the preferred embodiment is
illustrated.
A bore hole 10 is formed in the seam to a desired depth which may,
for example, be from 700 to 900 feet in depth. A magnetite recovery
pipe 11 (to be later described) is inserted axially into the bore
hole. An anchoring means 12 is attached to the bottom of magnetite
recovery pipe 11 and comprises a ring 13 and a plurality of
extending rods 14. A plurality of openings 15 perforates the lower
end of recovery pipe 11. 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 11 and
has a rotatable seal 16 at its lower end. Dislodging pipe 15 may be
formed from a plurality of sections 17 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 10 has a surface seal formed by a pipe 20 forced into or
cemented into bore hole 10. Pipe 20 terminates in a pipe end 21,
bolted by means of a flange 24 to surface seal pipe 20. Pipe end 21
has a seal 25 which provides a fluid tight seal for dislodging pipe
15 and yet permits rotation of pipe 15. 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 returned through a line 26
to a pump 27 to injection line 28 to a hydraulic motor 29 and to
the inside of dislodging pipe 15 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 hook
36 interlocked with an eye 37 which is permanently attached to the
hydraulic motor 29. A plurality of lines 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
21. 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 15 but will prevent pipe 15 from moving
downwardly into the cavity.
The upper end 50 of magnetite recovery pipe 11 contains a small
slot 51 which permits entry of magnetite slurry into pipe 11 but
restricts the loss in pressure so that the majority of the pressure
is available at the bottom 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 of dislodging 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. 1a, 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 OPERATION
The operation of the preferred embodiment is as follows:
The dislodging pipe 15 and dislodging arm 60 are lowered into bore
hole 10 with the dislodging arm in the position shown by dotted
lines 71. The mechanical locks maintaining dislodging arm in the
position shown by dots 71 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 15 in the direction of arrow 30 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, dislodging pipe 15 begins to rotate, causing
dislodging arm 60 to rotate about the wall of the 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 10 with fluid or magnetite 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 91, 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 65 will maintain the distance between the mining surface
63 and jets 62; or, if picks are used, the picks 70 (see FIG. 1a)
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 11 and yet retains the fluid pressure
inside pipe 15. Anchor 12 retains magnetite recovery pipe down-hole
and in position during the rotation and lifting of dislodging pipe
15. Metal rods 14 are spring biased away from the outside wall of
pipe 11 and have sufficient diameter to engage the bore hole wall.
Thus, if pipe 11 rises, rods 14 will dig into bore hole wall 11,
retaining the pipe into position.
The particular anchor disclosed here should properly hold the
recovery pipe 11 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 25 and its associated equipment will raise the
hydraulic motor 29 through hook 36 and eye 37, lifting pipe 15.
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 17 is raised to the
point where a joint 18 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 21, 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 90 is illustrated having magnetite
recovery pipe 11 therein anchored at the bottom by anchor means 12.
Pipe end 21 has an extension pipe 95 passing therethrough and
connected to the end 50 of pipe 11. The short portion containing
slot 51 has been removed. Pipes 96 are connected from extension 95
to the inlet of pump 27. A magnetite water separator 100 has its
inlet 10l connected through pipe 102 to the outlet 103 of pump 27.
The reclaimed magnetite is recovered through outlet 104 and the
water is recovered through outlet 105. Water from outlet 105 is
connected through a line 106 to a second pump 107 to the water
inlet 108 of pipe end 21.
OPERATION
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 1,000 tons of mined material can be recovered.
Assuming 20 percent of the material is debris and 80 percent of the
material is coal, approximately 800 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
1/4 to 1/3 of the cavity. Magnetite has a specific gravity of 5.0.
Assuming a good grade of magnetite, approximately 90 percent of the
magnetite will be finer than size 360. A certain portion of the
magnetite will settle to the bottom of the 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, 100 tons of
magnetite settled with the debris to the bottom of the cavity, over
$2,000 worth of magnetite would be 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 107 to inlet 108 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 15 of pipe 11. Pump 27 will then suck up
the fresh water and magnetite through holes 15 up pipe 11 in the
direction of arrow 115 and through pipe 96 to pump 27 where it is
moved through pipes 102 and 101 to magnetite water separator 100.
Magnetite water separators are well known in the art. Such devices
are clearly described in the book "Coal Preparation," (supra). The
reclaimed magnetite is saved for future mining operations, and the
water is returned through lines 106 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 21. Pipe section 95 is connected to hoist 35,
and the entire pipe 11 lifted out of the cavity 90. Anchor 12 will
disengage by either tearing away the walls of the bore hole portion
remaining or, rods 14 will bend or break off as pipe is pulled up
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
120 is followed by a mined out cavity 121 where magnetite recovery
is in process and a partially mined out cavity 122 where mining is
still in progress. In the recovery cavity 121, pipe 96 is applying
water through pipe end 21 to cavity 121, and pipe 108 is pumping
out the magnetite slurry through pump 27 to magnetite water
separator 100. The water is being returned through line 106 to pipe
96 and back to cavity 121. 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 124 where water 125 and magnetite 126 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. Magnetite being recovered from
separator 100 is transferred by conveyer or line 130 to the slurry
mixer 124.
The separator 100, the slurry-coal separator 125, the slurry mixer
124, 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 201 rotatably
attached by a bearing 202 to platform 200. Dislodging pipe 15 is
mounted inside casing 201. Pump 27 has an inlet 26 connected to a
source of magnetite 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 41. Motor 204 can
be electric or hydraulic of sufficient power to turn dislodging
pipe 15 and dislodging arm 60. Jets 62, which, as previously
described, can also be picks such as 70 in FIG. 12, are in
engagement with coal seam 206.
OPERATION
The operation of the dislodging arm 60 shown in FIGS. 4 and 5 is
substantially identical to the operation of the dislodging arm 60
described in FIGS. 1 through 3. Magnetite slurry 207 fills the
cavity and overflows through a trench 208 to a recovery area (not
shown). Coal 91 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 mechanically removed before mining can be
recommenced.
MAGNETITE SLURRY
Coal of a high grade anthracite normally has a specific gravity of
from 1.4 to 1.7. 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 1.4, the density of the magnetite
must be at least 1.5 in order for the magnetite to have adequate
buoyancy. Bituminous coal normally ranges from a specific gravity
of 1.4 to 1.5. 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.
* * * * *