Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 2012/173969
PCT/US2012/042021
VIRTUAL ELECTRODE MINERAL PARTICLE DISINTEGRATOR
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S. Patent
Applicant 13/159,813
entitled "Virtual Electrode Mineral Particle Disintegrator", filed June 14,
2011, which itself is a
continuation-in-part of U.S. Patent Application Serial No. 12/136,720 (U.S.
Patent 7,959,094), entitled
"Virtual Electrode Mineral Particle Disintegrator", filed on June 10, 2008,
which itself is a continuation-in-
part of U.S. Patent Application Serial No. 11/208,950 (U.S. Patent 7,384,009),
entitled "Virtual Electrode
Mineral Particle Disintegrator," filed on August 19, 2005 which itself claims
the benefit of the filing of
U.S. Provisional Patent Application Serial No. 60/603,509, entitled
"Electrocrushing FAST Drill and
Technology, High Relative Permittivity Oil, High Efficiency Boulder Breaker,
New Electrocrushing
Process, and Electrocrushing Mining Machine, '1 filed on August 20, 2004,
BACKGROUND OF THE INVENTION
Field of the Invention (Technical Field):
[0002] The present invention relates to pulse powered drilling apparatuses
and methods. The
present invention also relates to insulating fluids of high relative
permittivity (dielectric constant).
Background Art:
[0003] Processes using pulsed power technology are known in the art for
breaking mineral
lumps. Fig. 1 shows a process by which a conduction path or streamer is
created inside rock to break it.
An electrical potential is impressed across the electrodes which contact the
rock from the high voltage
electrode 100 to the ground electrode 102. At sufficiently high electric
field, an arc 104 or plasma is
formed inside the rock 106 from the high voltage electrode to the low voltage
or ground electrode. The
expansion of the hot gases created by the arc fractures the rock. When this
streamer connects one
electrode to the next, the current flows through the conduction path, or arc,
inside the rock. The high
temperature of the arc vaporizes the rock and any water or other fluids that
might be touching, or are
near, the arc. This vaporization process creates high-pressure gas in the arc
zone, which expands. This
expansion pressure fails the rock in tension, thus creating rock fragments.
CA 2873152 2018-11-28
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[0004] The process of passing such a current through minerals is disclosed
in U.S.
Patent No. 4,540,127 which describes a process for placing a lump of ore
between electrodes to
break it into monomineral grains. As noted in the '127 patent, it is
advantageous in such
processes to use an insulating liquid that has a high relative permittivity
(dielectric constant) to
shift the electric fields away from the liquid and into the rock in the region
of the electrodes.
[0005] The '127 patent discusses using water as the fluid for the mineral
disintegration
process. However, insulating drilling fluid must provide high dielectric
strength to provide high
electric fields at the electrodes, low conductivity to provide low leakage
current during the delay
time from application of the voltage until the arc ignites in the rock, and
high relative permittivity to
shift a higher proportion of the electric field into the rock near the
electrodes. Water provides high
relative permittivity, but has high conductivity, creating high electric
charge losses. Therefore,
water has excellent energy storage properties, but requires extensive
deionization to make it
sufficiently resistive so that it does not discharge the high voltage
components by current leakage
through the liquid. In the deionized condition, water is very corrosive and
will dissolve many
materials, including metals. As a result, water must be continually
conditioned to maintain the
high resistivity required for high voltage applications. Even when deionized,
water still has such
sufficient conductivity that it is not suitable for long-duration, pulsed
power applications.
[0006] Petroleum oil, on the other hand, provides high dielectric strength
and low
conductivity, but does not provide high relative permittivity. Neither water
nor petroleum oil,
therefore, provide all the features necessary for effective drilling.
[0007] Propylene carbonate is another example of such insulating materials
in that it has
a high dielectric constant and moderate dielectric strength, but also has high
conductivity (about
twice that of deionized water) making it unsuitable for pulsed power
applications.
[0008] In addition to the high voltage, mineral breaking applications
discussed above,
Insulating fluids are used for many electrical applications such as, for
example, to insulate
electrical power transformers.
[0009] There is a need for an insulating fluid having a high dielectric
constant, low
conductivity, high dielectric strength, and a long life under industrial or
military application
environments.
[0010] Other techniques are known for fracturing rock. Systems known in the
art as
"boulder breakers" rely upon a capacitor bank connected by a cable to an
electrode or transducer
2
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
that is inserted into a rock hole. Such systems are described by Hamelin, M.
and Kitzinger, F.,
Hard Rock Fragmentation with Pulsed Power, presented at the 1993 Pulsed Power
Conference,
and Res, J. and Chattapadhyay, A, "Disintegration of Hard Rocks by the
Electrohydrodynamic
Method" Mining Engineering, January 1987. These systems are for fracturing
boulders resulting
from the mining process or for construction without having to use explosives.
Explosives create
hazards for both equipment and personnel because of fly rock and over pressure
on the
equipment, especially in underground mining. Because the energy storage in
these systems is
located remotely from the boulder, efficiency is compromised. Therefore, there
is a need for
improving efficiency in the boulder breaking and drilling processes.
[0011] Another technique for fracturing rock is the plasma-hydraulic (PH),
or
electrohydraulic (EH) techniques using pulsed power technology to create
underwater plasma,
which creates intense shock waves in water to crush rock and provide a
drilling action. In
practice, an electrical plasma is created in water by passing a pulse of
electricity at high peak
power through the water. The rapidly expanding plasma in the water creates a
shock wave
sufficiently powerful to crush the rock. In such a process, rock is fractured
by repetitive application
of the shock wave.
BRIEF SUMMARY OF THE INVENTION
[0012] The present invention relates to a method and apparatus for breaking
mineral
particles. The invention comprises: suspending the particles in a liquid
flowing in a column or
conduction path, the liquid comprising a dielectric constant higher than the
particles; disposing a
plurality of electrodes in the liquid; sending an electric voltage pulse to
the electrodes, preferably a
pulsed power source, wherein the pulse is tuned to electrical characteristics
of the column or
conduction path and liquid to provide a rise of voltage sufficient to allocate
an electric field in the
mineral particles with sufficient stress to fracture the mineral particles;
and passing sufficient
current through the mineral particles to fracture the mineral particles.
[0013] The liquid preferably flows slowly upward in the column or
conduction path so that
small, fractured particles are carried upward by the upwardly flowing liquid.
Larger, heavier,
unfractured particles sink past the electrodes. Gaps between the electrodes
are preferably larger
that the size of the mineral particles.
[0014] One embodiment of the present invention comprises a method for
electrocrushing
micro-encapsulated gold particles. This method preferably comprises suspending
the micro-
encapsulated gold particles in a fluid flow, disposing a plurality of
electrodes in the fluid, tuning the
3
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
characteristics of the fluid flow and the electrodes to optimize
disintegration of the micro-
encapsulated gold particles, sending an electric pulse to the electrodes to
provide a voltage
sufficient to create an electric field internal to the micro-encapsulated gold
particles that exceeds
the dielectric strength of the micro-encapsulated gold particles without
exceeding the dielectric
strength of the fluid, and electrocrushing the micro-encapsulated gold
particles. The fluid flow
preferably comprises dielectric properties different than dielectric
properties of the micro-
encapsulated gold particles. The difference in dielectric properties
preferably provides for an
enhancement of the electric field in the micro-encapsulated gold particles
compared to the fluid.
[0015] The resulting loss of dielectric strength of the micro-encapsulated
gold particles
causes the micro-encapsulated gold particles to conduct, thereby removing
their contribution to a
net insulation between the electrodes. The loss of contribution of insulation
between the
electrodes from the micro-encapsulated gold particles causes electric fields
in the fluid to exceed
the dielectric strength of the fluid, thus causing the fluid and micro-
encapsulated gold particles to
conduct current directly through the micro-encapsulated gold particles.
[0016] The method of this embodiment can optionally comprise creating gaps
between
the electrodes wherein the gaps are larger than the size of the particles
and/or shaping the
electrodes to provide a plurality of conduction events over an area greater
than that defined by an
individual electrode. The method of this embodiment can also provide, via the
fluid and in the
absence of the micro-encapsulated gold particles, an insulation in an amount
preventing voltage
breakdown or conduction in the fluid between the electrodes preventing an
electrohydraulic pulse
from occurring in the fluid in the absence of the micro-encapsulated gold
particles.
[0017] A dielectric constant or relative permittivity of the fluid
preferably exceeds a
dielectric constant or relative permittivity of the micro-encapsulated gold
particles, thus allocating
more of the electric field into the micro-encapsulated gold particles than
into the fluid.
[0018] The method can alternatively provide a rate of rise of voltage
comprising a rate of
rise of the electric field in the micro-encapsulated gold particles sufficient
to create a mechanical
stress in the micro-encapsulated gold particles contributing to a loss of the
dielectric strength in
the micro-encapsulated gold particles and contributing to comminuting or
breaking the micro-
encapsulated gold particles.
[0019] The method of one embodiment of the present invention can comprise
extracting
the gold from the mineral content that micro-encapsulated the gold. The
extracting can be by
4
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
treating a slurry of the electrocrushed micro-encapsulated gold particles with
chemicals to
separate the gold from the mineral content.
[0020] The method of another embodiment of the present invention can
comprise
shaping the electrodes to provide a substantially uniform electric field
distribution across an
electrode gap, thus increasing a fraction of micro-encapsulated gold particles
that are
electrocrushed with the electric voltage pulse. Alternatively, the method can
incorporate into the
fluid of the fluid flow chemicals suitable for dissolving the gold, thereby
facilitating recovery of the
gold and discarding waste minerals.
[0021] Another embodiment of the present invention comprises an apparatus
for
electrocrushing micro-encapsulated gold particles. The apparatus preferably
includes a fluid flow
comprising characteristics to optimize disintegration of the micro-
encapsulated gold particles, a
plurality of electrodes disposed in the fluid, said electrodes comprising
characteristics to optimize
disintegration of the micro-encapsulated gold particles, and a pulsed electric
power source
sending an electric pulse to said electrodes to provide a voltage sufficient
to create an electric field
internal to the micro-encapsulated gold particles that exceeds the dielectric
strength of the micro-
encapsulated gold particles without exceeding the dielectric strength of the
fluid.
[0022] The gaps between the electrodes of the apparatus are preferably
larger than the
size of the micro-encapsulated gold particles. A dielectric constant or
relative permittivity of the
fluid preferably exceeds a dielectric constant or relative permittivity of the
micro-encapsulated gold
particles, allocating more of the electric field into the micro-encapsulated
gold particles than into
the fluid.
[0023] A rate of rise of voltage via a pulsed power source is provided such
that a rate of
rise of the electric field in the particles is sufficient to create a
mechanical stress in the particles
that contributes to a loss of the dielectric strength in the particles and
contributes to comminuting
or breaking the particles.
[0024] The electrodes of an embodiment of the present invention are
preferably shaped
to provide a plurality of conduction events over an area greater than that
defined by an individual
electrode. An insulation of the fluid is preferably of an amount to prevent
voltage breakdown or
conduction in the absence of the particles in said fluid and to prevent an
electrohydraulic pulse in
the absence of the particles. Each of the electrodes can comprise a plurality
of smaller
electrodes connected in parallel to provide for a plurality of conduction
events over an area
defined by the plurality of smaller electrodes. The fluid preferably comprises
electric properties
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
different than electric properties of the micro-encapsulated gold particles.
The loss of dielectric
strength of the particles causes the micro-encapsulated gold particles to
conduct, thereby
removing their contribution to a net insulation between the electrodes. The
loss of contribution of
insulation between the electrodes from the micro-encapsulated gold particles
causes the electric
fields in the fluid to exceed the dielectric strength of the fluid, thus
causing the fluid and the micro-
encapsulated gold particles to conduct current directly through the micro-
encapsulated gold
particles and thereby electrocrushing the micro-encapsulated gold particles.
[0025] The fluid of this embodiment of the present invention can comprise
chemicals
suitable for dissolving the gold, thereby facilitating recovery of the gold.
The electrodes can be
shaped to provide a substantially uniform electric field distribution across
an electrode gap to
increase the number of micro-encapsulated gold particles that are
electrocrushed with each pulse.
[0026] One embodiment of the present invention comprises a method for
comminuting or
breaking micro-encapsulated gold particles. This method preferably comprises
suspending the
micro-encapsulated gold particles in a fluid flowing in a fluid flow,
disposing a plurality of
electrodes in the fluid, sending an electric voltage pulse to the electrodes,
and passing sufficient
current through the micro-encapsulated gold particles and the fluid to
comminute or break the
micro-encapsulated gold particles, the current being of a power below that
which causes a shock
wave in the fluid. The method can further comprise extracting the gold from
the mineral content
that micro-encapsulated the gold. The extracting step can optionally include
treating a slurry of
the electrocrushed micro-encapsulated gold particles with chemicals to
separate the gold from the
mineral content.
[0027] Gaps between the electrodes are preferably larger than the size of
the micro-
encapsulated gold particles. A dielectric constant or relative permittivity of
the fluid preferably
exceeds a dielectric constant or relative permittivity of the micro-
encapsulated gold particles. The
fluid can optionally comprise electric properties different than electric
properties of the micro-
encapsulated gold particles.
[0028] The method of this embodiment of the present invention can comprise
shaping
the electrodes to provide a substantially uniform electric field distribution
across an electrode gap,
thus increasing a fraction of micro-encapsulated gold particles that are
electrocrushed with the
electric voltage pulse. Alternatively, the method can incorporate into the
fluid of the fluid flow
chemicals suitable for dissolving the gold, thereby facilitating recovery of
the gold and discarding
waste minerals.
6
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[0029] Another embodiment of the present invention comprises an apparatus
for
breaking micro-encapsulated gold particles. The apparatus preferably includes
a fluid flow, a fluid
flowing in the fluid flow within which the micro-encapsulated gold particles
are suspended, a
plurality of electrodes disposed in the fluid, a pulsed power source for
sending an electric voltage
pulse to the electrodes, and a current passing through the micro-encapsulated
gold particles and
the fluid, the current being of a power below that required to cause shock
waves in the fluid. Gaps
between the electrodes are preferably larger than the size of the particles. A
dielectric constant or
relative permittivity of the fluid preferably exceeds a dielectric constant or
relative permittivity of
the particles. The fluid preferably comprises electric properties different
than electric properties of
the micro-encapsulated gold particles. The fluid can also comprise chemicals
suitable for
dissolving the gold, thereby facilitating recovery of the gold. The electrodes
can be shaped to
provide a substantially uniform electric field distribution across an
electrode gap to increase the
number of micro-encapsulated gold particles that are electrocrushed with each
pulse.
[0030] Other objects, advantages and novel features, and further scope of
applicability of
the present invention will be set forth in part in the detailed description to
follow, taken in
conjunction with the accompanying drawings, and in part will become apparent
to those skilled in
the art upon examination of the following, or may be learned by practice of
the invention. The
objects and advantages of the invention may be realized and attained by means
of the
instrumentalities and combinations pointed out in the appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0031] The accompanying drawings, which are incorporated into and form a
part of the
specification, illustrate one or more embodiments of the present invention
and, together with the
description, serve to explain the principles of the invention. The drawings
are only for the purpose
of illustrating one or more preferred embodiments of the invention and are not
to be construed as
limiting the invention. In the drawings:
[0032] Fig. 1 shows an electrocrushing process of the prior art;
[0033] Fig. 2 shows an end view of a coaxial electrode set for a
cylindrical bit of an
embodiment of the present invention;
[0034] Fig. 3 shows an alternate embodiment of Fig. 2;
[0035] Fig. 4 shows an alternate embodiment of a plurality of coaxial
electrode sets;
[0036] Fig. 5 shows a conical bit of an embodiment of the present
invention;
[0037] Fig. 6 is of a dual-electrode set bit of an embodiment of the
present invention;
[0038] Fig. 7 is of a dual-electrode conical bit with two different cone
angles of an
embodiment of the present invention;
7
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[0039] Figs. 8A and 8B show embodiments of a drill bit of the present
invention wherein
one ground electrode is the tip of the bit and the other ground electrode has
the geometry of a
great circle of the cone;
[0040] Fig. 9 shows the range of bit rotation azimuthal angle of an
embodiment of the
present invention;
[0041] Fig. 10 shows an embodiment of the drill bit of the present
invention having
radiused electrodes;
[0042] Fig. 11 shows the complete drill assembly of an embodiment of the
present
invention;
[0043] Fig. 12 shows the reamer drag bit of an embodiment of the present
invention;
[0044] Fig. 13 shows a solid-state switch or gas switch controlled high
voltage pulse
generating system that pulse charges the primary output capacitor of an
embodiment of the
present invention;
[0045] Fig. 14 shows an array of solid-state switch or gas switch
controlled high voltage
pulse generating circuits that are charged in parallel and discharged in
series to pulse-charge the
output capacitor of an embodiment of the present invention;
[0046] Fig. 15 shows a voltage vector inversion circuit that produces a
pulse that is a
multiple of the charge voltage of an embodiment of the present invention;
[0047] Fig. 16 shows an inductive store voltage gain system to produce the
pulses
needed for the FAST Drill of an embodiment of the present invention;
[0048] Fig. 17 shows a drill assembly powered by a fuel cell that is
supplied by fuel lines
and exhaust line from the surface inside the continuous metal mud pipe of an
embodiment of the
present invention;
[0049] Fig. 18 shows a roller-cone bit with an electrode set of an
embodiment of the
present invention;
[0050] Fig. 19 shows a small-diameter electrocrushing drill of an
embodiment of the
present invention;
[0051] Fig. 20 shows an electrocrushing vein miner of an embodiment of the
present
invention;
[0052] Fig. 21 shows a water treatment unit useable in the embodiments of
the present
invention;
[0053] Fig. 22 shows a high energy electrohydraulic boulder breaker system
(HEEB) of
an embodiment of the present invention;
[0054] Fig. 23 shows a transducer of the embodiment of Fig. 22;
[0055] Fig. 24 shows the details of the an energy storage module and
transducer of the
embodiment of Fig. 22;
8
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[0056] Fig. 25 shows the details of an inductive storage embodiment of the
high energy
electrohydraulic boulder breaker energy storage module and transducer of an
embodiment of the
present invention;
[0057] Fig. 26 shows the embodiment of the high energy electrohydraulic
boulder
breaker disposed on a tractor for use in a mining environment;
[0058] Fig. 27 shows a geometric arrangement of the embodiment of parallel
electrode
gaps in a transducer in a spiral configuration.
[0059] Fig. 28 shows details of another embodiment of an electrohydraulic
boulder
breaker system;
[0060] Fig. 29 shows an embodiment of a virtual electrode electrocrushing
process;
[0061] Fig. 30 shows an embodiment of the virtual electrode electrocrushing
system
comprising a vertical flowing fluid column or conduction path;
[0062] Fig. 31 shows a pulsed power drilling apparatus manufactured and
tested in
accordance with an embodiment of the present invention; and
[0063] Fig. 32 is a graph showing dielectric strength versus delay to
breakdown of the
insulating formulation of the present invention, oil, and water.
DETAILED DESCRIPTION OF THE INVENTION
[0064] The present invention provides for pulsed power breaking and
drilling
apparatuses and methods. As used herein, "drilling" is defined as excavating,
boring into, making
a hole in, or otherwise breaking and driving through a substrate. As used
herein, "bit" and "drill
bit" are defined as the working portion or end of a tool that performs a
function such as, but not
limited to, a cutting, drilling, boring, fracturing, or breaking action on a
substrate (e.g., rock). As
used herein, the term "pulsed power" is that which results when electrical
energy is stored (e.g., in
a capacitor or inductor) and then released into the load so that a pulse of
current at high peak
power is produced. "Electrocrushing" ("EC") is defined herein as the process
of passing a pulsed
electrical current through a mineral substrate so that the substrate is
"crushed" or "broken".
[0065] The term "shock wave" as used throughout the specification and
claims is defined
as a wave propagating with a velocity at least 2% greater than the local sound
velocity into which
it is propagating (e.g. Mach number = 1.02) as measured at a distance of 1
electrode gap from the
location of the current. A 2% shock wave velocity above the sound speed is a
measureable
amount to distinguish it from an acoustic wave, which propagates at the sound
velocity.
[0066] The term "conduction path" as used throughout the specification and
claims is
intended to include, but is not limited to any path or means or conductor or
column of flow without
regard to orientation (e.g. can be horizontal, vertical or other angle).
9
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
Electrocrushing Bit
[0067] An embodiment of the present invention provides a drill bit on which
is disposed
one or more sets of electrodes. In this embodiment, the electrodes are
disposed so that a gap is
formed between them and are disposed on the drill bit so that they are
oriented along a face of the
drill bit. In other words, the electrodes between which an electrical current
passes through a
mineral substrate (e.g., rock) are not on opposite sides of the rock. Also, in
this embodiment, it is
not necessary that all electrodes touch the mineral substrate as the current
is being applied. In
accordance with this embodiment, at least one of the electrodes extending from
the bit toward the
substrate to be fractured and may be compressible (i.e., retractable) into the
drill bit by any means
known in the art such as, for example, via a spring-loaded mechanism.
[0068] Generally, but not necessarily, the electrodes are disposed on the
bit such that at
least one electrode contacts the mineral substrate to be fractured and another
electrode that
usually touches the mineral substrate but otherwise may be close to, but not
necessarily touching,
the mineral substrate so long as it is in sufficient proximity for current to
pass through the mineral
substrate. Typically, the electrode that need not touch the substrate is the
central, not the
surrounding, electrode.
[0069] Therefore, the electrodes are disposed on a bit and arranged such
that
electrocrushing arcs are created in the rock. High voltage pulses are applied
repetitively to the bit
to create repetitive electrocrushing excavation events. Electrocrushing
drilling can be
accomplished, for example, with a flat-end cylindrical bit with one or more
electrode sets. These
electrodes can be arranged in a coaxial configuration.
[0070] Fig. 2 shows an end view of such a coaxial electrode set
configuration for a
cylindrical bit, showing high voltage or center electrode 108, ground or
surrounding electrode 110,
and gap 112 for creating the arc in the rock. Variations on the coaxial
configuration are shown in
Fig. 3. A non-coaxial configuration of electrode sets arranged in bit housing
114 is shown in Fig.
4. Figs. 3-4 show ground electrodes that are completed circles. Other
embodiments may
comprise ground electrodes that are partial circles, partial or complete
ellipses, or partial or
complete parabolas in geometric form.
[0071] For drilling larger holes, a conical bit is preferably utilized,
especially if controlling
the direction of the hole is important. Such a bit may comprise one or more
sets of electrodes for
creating the electrocrushing arcs and may comprise mechanical teeth to assist
the electrocrushing
process. One embodiment of the conical electrocrushing bit has a single set of
electrodes,
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
preferably arranged coaxially on the bit, as shown in Fig. 5. In this
embodiment, conical bit 118
comprises a center electrode 108, the surrounding electrode 110, the bit case
or housing 114 and
mechanical teeth 116 for drilling the rock. Either, or both, electrodes may be
compressible. The
surrounding electrode preferably has mechanical cutting teeth 109 incorporated
into the surface to
smooth over the rough rock texture produced by the electrocrushing process. In
this embodiment,
the inner portion of the hole is drilled by the electrocrushing portion (i.e.,
electrodes 108 and 110)
of the bit, and the outer portion of the hole is drilled by mechanical teeth
116. This results in high
drilling rates, because the mechanical teeth have good drilling efficiency at
high velocity near the
perimeter of the bit, but very low efficiency at low velocity near the center
of the bit. The
geometrical arrangement of the center electrode to the ground ring electrode
is conical with a
range of cone angles from 180 degrees (flat plane) to about 75 degrees
(extended center
electrode).
[0072] An alternate embodiment is to arrange a second electrode set on the
conical
portion of the bit. In such an embodiment, one set of the electrocrushing
electrodes operates on
just one side of the bit cone in an asymmetrical configuration as exemplified
in Fig. 6 which shows
a dual-electrode set conical bit, each set of electrodes comprising center
electrode 108,
surrounding electrode 110, bit case or housing 114, mechanical teeth 116, and
drilling fluid
passage 120.
[0073] The combination of the conical surface on the bit and the asymmetry
of the
electrode sets results in the ability of the dual-electrode bit to excavate
more rock on one side of
the hole than the other and thus to change direction. For drilling a straight
hole, the repetition rate
and pulse energy of the high voltage pulses to the electrode set on the
conical surface side of the
bit is maintained constant per degree of rotation. However, when the drill is
to turn in a particular
direction, then for that sector of the circle toward which the drill is to
turn, the pulse repetition rate
(and/or pulse energy) per degree of rotation is increased over the repetition
rate for the rest of the
circle. In this fashion, more rock is removed by the conical surface electrode
set in the turning
direction and less rock is removed in the other directions (See Fig. 9,
discussed in detail below).
Because of the conical shape of the bit, the drill tends to turn into the
section where greater
amount of rock was removed and therefore control of the direction of drilling
is achieved.
[0074] In the embodiment shown in Fig. 6, most of the drilling is
accomplished by the
electrocrushing (EC) electrodes, with the mechanical teeth serving to smooth
the variation in
surface texture produced by the EC process. The mechanical teeth 116 also
serve to cut the
gauge of the hole, that is, the relatively precise, relatively smooth inside
diameter of the hole. An
alternate embodiment has the drill bit of Fig. 6 without mechanical teeth 116,
all of the drilling
11
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
being done by the electrode sets 108 and 110 with or without mechanical teeth
109 in the
surrounding electrode 110.
[0075] Alternative embodiments include variations on the configuration of
the ground ring
geometry and center-to-ground ring geometry as for the single-electrode set
bit. For example,
Fig. 7 shows such an arrangement in the form of a dual-electrode conical bit
comprising two
different cone angles with center electrodes 108, surrounding or ground
electrodes 110, and bit
case or housing 114. In the embodiment shown, the ground electrodes are tip
electrode 111 and
conical side ground electrodes 110 which surround, or partially surround, high
voltage electrodes
108 in an asymmetric configuration.
[0076] As shown in Fig. 7, the bit may comprise two or more separate cone
angles to
enhance the ability to control direction with the bit. The electrodes can be
laid out symmetrically in
a sector of the cone, as shown in Fig. 5 or in an asymmetric configuration of
the electrodes
utilizing ground electrode 111 as the center of the cone as shown in Fig. 7.
Another configuration
is shown in Fig. 8A in which ground electrode 111 is at the tip of the bit and
hot electrode 108 and
other ground electrode 110 are aligned in great circles of the cone. Fig. 8B
shows an alternate
embodiment wherein ground electrode 111 is the tip of the bit, other ground
electrode 110 has the
geometry of a great circle of the cone, and hot electrodes 108 are disposed
there between. Also,
any combination of these configurations may be utilized.
[0077] It should be understood that the use of a bit with an asymmetric
electrode
configuration can comprise one or more electrode sets and need not comprise
mechanical teeth.
It should also be understood that directional drilling can be performed with
one or more electrode
sets.
[0078] The EC drilling process takes advantage of flaws and cracks in the
rock. These
are regions where it is easier for the electric fields to breakdown the rock.
The electrodes used in
the bit of the present invention are usually large in area in order to
intercept more flaws in the rock
and therefore improve the drilling rate, as shown in Fig. 5. This is an
important feature of the
invention because most electrodes in the prior art are small to increase the
local electric field
enhancement.
[0079] Fig. 9 shows the range of bit rotation azimuthal angle 122 where the
repetition
rate or pulse energy is increased to increase excavation on that side of the
drill bit, compared to
the rest of the bit rotation angle that has reduced pulse repetition rate or
pulse energy 124. The bit
rotation is referenced to a particular direction relative to the formation
126, often magnetic north,
12
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
to enable the correct drill hole direction change to be made. This reference
is usually achieved by
instrumentation provided on the bit. When the pulsed power system provides a
high voltage pulse
to the electrodes on the side of the bit (See Fig. 6), an arc is struck
between one hot electrode and
one ground electrode. This arc excavates a certain amount of rock out of the
hole. By the time
the next high voltage pulse arrives at the electrodes, the bit has rotated a
certain amount, and a
new arc is struck at a new location in the rock. If the repetition rate of the
electrical pulses is
constant as a function of bit rotation azimuthal angle, the bit will drill a
straight hole. If the
repetition rate of the electrical pulses varies as a function of bit rotation
azimuthal angle, the bit will
tend to drift in the direction of the side of the bit that has the higher
repetition rate. The direction of
the drilling and the rate of deviation can be controlled by controlling the
difference in repetition rate
inside the high repetition rate zone azimuthal angle, compared to the
repetition rate outside the
zone (See Fig. 9). Also, the azimuthal angle of the high repetition rate zone
can be varied to
control the directional drilling. A variation of the invention is to control
the energy per pulse as a
function of azimuthal angle instead of, or in addition to, controlling the
repetition rate to achieve
directional drilling.
Fast Drill System
[0080] Another embodiment of the present invention provides a drilling
system/assembly
utilizing the electrocrushing bits described herein and is designated herein
as the FAST Drill
system. A limitation in drilling rock with a drag bit is the low cutter
velocity at the center of the drill
bit. This is where the velocity of the grinding teeth of the drag bit is the
lowest and hence the
mechanical drilling efficiency is the poorest. Effective removal of rock in
the center portion of the
hole is the limiting factor for the drilling rate of the drag bit. Thus, an
embodiment of the FAST
Drill system comprises a small electrocrushing (EC) bit (alternatively
referred to herein as a FAST
bit or FAST Drill bit) disposed at the center of a drag bit to drill the rock
at the center of the hole.
Thus, the EC bit removes the rock near the center of the hole and
substantially increases the
drilling rate. By increasing the drilling rate, the net energy cost to drill a
particular hole is
substantially reduced. This is best illustrated by the bit shown in Fig. 5
(discussed above)
comprising EC process electrodes 108 and 100 set at the center of bit 114,
surrounded by
mechanical drag-bit teeth 116. The rock at the center of the bit is removed by
the EC electrode
set, and the rock near the edge of the hole is removed by the mechanical
teeth, where the tooth
velocity is high and the mechanical efficiency is high.
[0081] As noted above, the function of the mechanical drill teeth on the
bit is to smooth
off the tops of the protrusions and recesses left by the electrocrushing or
plasma-hydraulic
process. Because the electrocrushing process utilizes an arc through the rock
to crush or fracture
the rock, the surface of the rock is rough and uneven. The mechanical drill
teeth smooth the
13
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
surface of the rock, cutting off the tops of the protrusions so that the next
time the electrocrushing
electrodes come around to remove more rock, they have a larger smoother rock
surface to
contact the electrodes.
[0082] The EC bit preferably comprises passages for the drilling fluid to
flush out the
rock debris (i.e., cuttings) (See Figs. 6). The drilling fluid flows through
passages inside the
electrocrushing bit and then out] through passages 120 in the surface of the
bit near the
electrodes and near the drilling teeth, and then flows up the side of the
drill system and the well to
bring rock cuttings to the surface.
[0083] The EC bit may comprise an insulation section that insulates the
electrodes from
the housing, the electrodes themselves, the housing, the mechanical rock
cutting teeth that help
smooth the rock surface, and the high voltage connections that connect the
high voltage power
cable to the bit electrodes.
[0084] Fig. 10 shows an embodiment of the Fast drill high voltage electrode
108 and
ground electrodes 110 that incorporate a radius 176 on the electrode, with
electrode radius 176 on
the rock-facing side of electrodes 110. Radius 176 is an important feature of
the present invention
to allocate the electric field into the rock. The feature is not obvious
because electrodes from prior
art were usually sharp to enhance the local electric field.
[0085] Fig. 11 shows an embodiment of the FAST Drill system comprising two
or more
sectional components, including, but not limited to: (1) at least one pulsed
power FAST drill bit
114; (2) at least one pulsed power supply 136; (3) at least one downhole
generator 138; (4) at
least one overdrive gear to rotate the downhole generator at high speed 140;
(5) at least one
downhole generator drive mud motor 144; (6) at least one drill bit mud motor
146; (7) at least one
rotating interface 142; (8) at least one tubing or drill pipe for the drilling
fluid 147; and (9) at least
one cable 148. Not all embodiments of the FAST Drill system utilize all of
these components. For
example, one embodiment utilizes continuous coiled tubing to provide drilling
fluid to the drill bit,
with a cable to bring electrical power from the surface to the pulsed power
system. That
embodiment does not require a down-hole generator, overdrive gear, or
generator drive mud
motor, but does require a downhole mud motor to rotate the bit, since the
tubing does not turn. An
electrical rotating interface is required to transmit the electrical power
from the non-rotating cable
to the rotating drill bit.
[0086] An embodiment utilizing a multi-section rigid drill pipe to rotate
the bit and conduct
drilling fluid to the bit requires a downhole generator, because a power cable
cannot be used, but
14
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
does not need a mud motor to turn the bit, since the pipe turns the bit. Such
an embodiment does
not need a rotating interface because the system as a whole rotates at the
same rotation rate.
[0087] An embodiment utilizing a continuous coiled tubing to provide mud to
the drill bit,
without a power cable, requires a down-hole generator, overdrive gear, and a
generator drive mud
motor, and also needs a downhole motor to rotate the bit because the tubing
does not turn. An
electrical rotating interface is needed to transmit the electrical control and
data signals from the
non-rotating cable to the rotating drill bit.
[0088] An embodiment utilizing a continuous coiled tubing to provide
drilling fluid to the
drill bit, with a cable to bring high voltage electrical pulses from the
surface to the bit, through the
rotating interface, places the source of electrical power and the pulsed power
system at the
surface. This embodiment does not need a down-hole generator, overdrive gear,
or generator
drive mud motor or downhole pulsed power systems, but does need a downhole
motor to rotate
the bit, since the tubing does not turn.
[0089] Still another embodiment utilizes continuous coiled tubing to
provide drilling fluid
to the drill bit, with a fuel cell to generate electrical power located in the
rotating section of the drill
string. Power is fed across the rotating interface to the pulsed power system,
where the high
voltage pulses are created and fed to the FAST bit. Fuel for the fuel cell is
fed down tubing inside
the coiled tubing mud pipe.
[0090] An embodiment of the FAST Drill system comprises FAST bit 114, a
drag bit
reamer 150 (shown in Fig. 12), and a pulsed power system housing 136 (Fig.
11).
[0091] Fig. 12 shows reamer drag bit 150 that enlarges the hole cut by the
electrocrushing FAST bit, drag bit teeth 152, and FAST bit attachment site
154. Reamer drag bit
150 is preferably disposed just above FAST bit 114. This is a conical pipe
section, studded with
drill teeth, that is used to enlarge the hole drilled by the EC bit
(typically, for example,
approximately 7.5 inches in diameter) to the full diameter of the well (for
example, to
approximately 12.0 inches in diameter). The conical shape of drag bit reamer
150 provides more
cutting teeth for a given diameter of hole, thus higher drilling rates.
Disposed in the center part of
the reamer section are several passages. There is a passage for the power
cable to go through to
the FAST bit. The power cable comes from the pulsed power section located
above and/or within
the reamer and connects to the FAST drill bit below the reamer. There are also
passages in the
reamer that provide oil flow down to the FAST bit and passages that provide
flushing fluid to the
reamer teeth to help cut the rock and flush the cuttings from the reamer
teeth.
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[0092] Preferably, a pulse power system that powers the FAST bit is
enclosed in the
housing of the reamer drag bit and the stem above the drag bit as shown in
Fig. 11. This system
takes the electrical power supplied to the FAST Drill for the electrocrushing
FAST bit and
transforms that power into repetitive high voltage pulses, usually over 100
kV. The repetition rate
of those pulses is controlled by the control system from the surface or in the
bit housing. The
pulsed power system itself can include, but is not limited to:
(1) a solid state switch controlled or gas-switch controlled pulse generating
system with a
pulse transformer that pulse charges the primary output capacitor (example
shown in Fig. 13);
(2) an array of solid-state switch or gas-switch controlled circuits that are
charged in
parallel and in series pulse-charge the output capacitor (example shown in
Fig. 14);
(3) a voltage vector inversion circuit that produces a pulse at about twice,
or a multiple of,
the charge voltage (example shown in Fig. 15);
(4) An inductive store system that stores current in an inductor, then
switches it to the
electrodes via an opening or transfer switch (example shown in Fig. 16); or
(5) any other pulse generation circuit that provides repetitive high voltage,
high current
pulses to the FAST Drill bit.
[0093] Fig. 13 shows a solid-state switch or gas switch controlled high
voltage pulse
generating system that pulse charges the primary output capacitor 164, showing
generating
means 156 to provide DC electrical power for the circuit, intermediate
capacitor electrical energy
storage means 158, gas, solid-state, or vacuum switching means 160 to switch
the stored
electrical energy into pulse transformer 162 voltage conversion means that
charges output
capacitive storage means 164 connecting to FAST bit 114.
[0094] Fig. 14 shows an array of solid-state switch or gas switch 160
controlled high
voltage pulse generating circuits that are charged in parallel and discharged
in series through
pulse transformer 162 to pulse-charge output capacitor 164.
[0095] Fig. 15 shows a voltage vector inversion circuit that produces a
pulse that is a
multiple of the charge voltage. An alternate of the vector inversion circuit
that produces an output
voltage of about twice the input voltage is shown, showing solid-state switch
or gas switching
means 160, vector inversion inductor 166, intermediate capacitor electrical
energy storage means
158 connecting to FAST bit 114.
[0096] Fig. 16 shows an inductive store voltage gain system to produce the
pulses
needed for the FAST Drill, showing the solid-state switch or gas switching
means 160, saturable
16
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
pulse transformers 168, and intermediate capacitor electrical energy storage
means 158
connecting to the FAST bit 114.
[0097] The pulsed power system is preferably located in the rotating bit,
but may be
located in the stationary portion of the drill pipe or at the surface.
[0098] Electrical power for the pulsed power system is either generated by
a generator at
the surface, or drawn from the power grid at the surface, or generated down
hole. Surface power
is transmitted to the FAST drill bit pulsed power system either by cable
inside the drill pipe or
conduction wires in the drilling fluid pipe wall. In the preferred embodiment,
the electrical power is
generated at the surface, and transmitted downhole over a cable 148 located
inside the
continuous drill pipe 147 (shown in Fig.11).
[0099] The cable is located in non-rotating flexible mud pipe (continuous
coiled tubing).
Using a cable to transmit power to the bit from the surface has advantages in
that part of the
power conditioning can be accomplished at the surface, but has a disadvantage
in the weight,
length, and power loss of the long cable.
[00100] At the bottom end of the mud pipe is located the mud motor which
utilizes the flow
of drilling fluid down the mud pipe to rotate the FAST Drill bit and reamer
assembly. Above the
pulsed power section, at the connection between the mud pipe and the pulsed
power housing, is
the rotating interface as shown in Fig. 11. The cable power is transmitted
across an electrical
rotating interface at the point where the mud motor turns the drag bit. This
is the point where
relative rotation between the mud pipe and the pulsed power housing is
accommodated. The
rotating electrical interface is used to transfer the electrical power from
the cable or continuous
tubing conduction wires to the pulsed power system. It also passes the
drilling fluid from the non-
rotating part to the rotating part of the drill string to flush the cuttings
from the EC electrodes and
the mechanical teeth. The pulsed power system is located inside the rigid
drill pipe between the
rotating interface and the reamer. High voltage pulses are transmitted inside
the reamer to the
FAST bit.
[00101] In the case of electrical power transmission through conduction
wires in rigid
rotating pipe, the rotating interface is not needed because the pulsed power
system and the
conduction wires are rotating at the same velocity. If a downhole gearbox is
used to provide a
different rotation rate for the pulsed power/bit section from the pipe, then a
rotating interface is
needed to accommodate the electrical power transfer.
17
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00102] In another embodiment, power for the FAST Drill bit is provided by
a downhole
generator that is powered by a mud motor that is powered by the flow of the
drilling fluid (mud)
down the drilling fluid, rigid, multi-section, drilling pipe (Fig. 11). That
mudflow can be converted to
rotational mechanical power by a mud motor, a mud turbine, or similar
mechanical device for
converting fluid flow to mechanical power. Bit rotation is accomplished by
rotating the rigid drill
pipe. With power generation via downhole generator, the output from the
generator can be inside
the rotating pulsed power housing so that no rotating electrical interface is
required (Fig. 11), and
only a mechanical interface is needed. The power comes from the generator to
the pulsed power
system where it is conditioned to provide the high voltage pulses for
operation of the FAST bit.
[00103] Alternatively, the downhole generator might be of the piezoelectric
type that
provides electrical power from pulsation in the mud. Such fluid pulsation
often results from the
action of a mud motor turning the main bit.
[00104] Another embodiment for power generation is to utilize a fuel cell
in the non-
rotating section of the drill string. Fig. 17 shows an example of a FAST Drill
system powered by
fuel cell 170 that is supplied by fuel lines and exhaust line 172 from the
surface inside the
continuous metal mud pipe 147. The power from fuel cell 170 is transmitted
across the rotating
interface 142 to pulsed power system 136, and hence to FAST bit 114. The fuel
cell consumes
fuel to produce electricity. Fuel lines are placed inside the continuous
coiled tubing, which
provides drilling fluid to the drill bit, to provide fuel to the fuel cell,
and to exhaust waste gases.
Power is fed across the rotating interface to the pulsed power system, where
the high voltage
pulses are created and fed to the FAST bit.
[00105] As noted above, there are two primary means for transmitting
drilling fluid (mud)
from the surface to the bit: continuous flexible tubing or rigid multi-section
drill pipe. The
continuous flexible mud tubing is used to transmit mud from the surface to the
rotation assembly
where part of the mud stream is utilized to spin the assembly through a mud
motor, a mud turbine,
or another rotation device. Part of the mudflow is transmitted to the FAST
bits and reamer for
flushing the cuttings up the hole. Continuous flexible mud tubing has the
advantage that power
and instrumentation cables can be installed inside the tubing with the
mudflow. It is stationary and
not used to transmit torque to the rotating bit. Rigid multi-section drilling
pipe comes in sections
and cannot be used to house continuous power cable, but can transmit torque to
the bit assembly.
With continuous flexible mud pipe, a mechanical device such as, for example, a
mud motor, or a
mud turbine, is used to convert the mud flow into mechanical rotation for
turning the rotating
assembly. The mud turbine can utilize a gearbox to reduce the revolutions per
minute. A
downhole electric motor can alternatively be used for turning the rotating
assembly. The purpose
18
WO 2012/173969
PCT/US2012/042021
of the rotating power source is primarily to provide torque to turn the teeth
on the reamer and the FAST
bit for drilling, It also rotates the FAST bit to provide the directional
control in the cutting of a hole.
Another embodiment is to utilize continuous mud tubing with downhole electric
power generation.
[00106] In one embodiment, two mud motors or mud turbines are used: one to
rotate the bits, and
one to generate electrical power.
[00107] Another embodiment of the rigid Multi-section mud pipe is the use
of data transmitting
wires buried in the pipe such as, for example, the Intelipipe manufactured by
Grant Prideco. This is a
composite pipe that uses magnetic induction to transmit data across the pipe
joints, while transmitting it
along wires buried in the shank of the pipe sections. Utilizing this pipe
provides for data transmission
between the bit and the control system on the surface, but still requires the
use of downhole power
generation.
[00108] Another embodiment of the FAST Drill is shown in Fig. 18 wherein
rotary or roller-cone
bit 174 is utilized, instead of a drag bit, to enlarge the hole drilled by the
FAST bit, Roller-cone bit 174
comprises electrodes 108 and 110 disposed in or near the center portion of
roller cone bit 174 to
excavate that portion of the rock where the efficiency of the roller bit is
the least.
[00109] Another embodiment of the rotating interface is to use a rotating
magnetic interface to
transfer electrical power and data across the rotating interface, instead of a
slip ring rotating interface.
[00110] In another embodiment, the mud returning from the well loaded with
cuttings flows to a
settling pond, at the surface, where the rock fragments settle out. The mud
then cleaned and reinjected
into the FAST Drill mud pipe.
Electrocrushinq Vein Miner
[00111] Another embodiment of the present invention provides a small-
diameter, electrocrushing
drill (designated herein as "SED") that is related to the hand-held
electrohydraulic drill disclosed in U.S.
Patent No, 5,896,938 (to a primary inventor herein). However, the SED is
distinguishable in that the
electrodes in the SED are spaced in such a way, and the rate of rise of the
electric field is such, that the
rock breaks down before the water breaks down, When the drill is near rack,
the electric fields break
down the rock and current passes through the rock, thus fracturing the rock
into small pieces. The
electrocrushing rock fragmentation occurs as a result of tensile failure
caused by the electrical current
passing through
19
CA 2873152 2018-11-28
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
the rock, as opposed to compressive failure caused by the electrohydraulic
(EH) shock or
pressure wave on the rock disclosed in U.S. Patent No. 5,896,938, although the
SED, too, can be
connected via a cable from a box as described in the '938 patent so that it
can be portable. Fig.
19 shows a SED drill bit comprising case 206, internal insulator 208, and
center electrode 210
which is preferably movable (e.g., spring-loaded) to maintain contact with the
rock while drilling.
Although case 206 and internal insulator 208 are shown as providing an
enclosure for center
electrode 210, other components capable of providing an enclosure may be
utilized to house
electrode 210 or any other electrode incorporated in the SED drill bit.
Preferably, case 206 of the
SED is the ground electrode, although a separate ground electrode may be
provided. Also, it
should be understood that more than one set of electrodes may be utilized in
the SED bit. A
pulsed power generator as described in other embodiments herein is linked to
said drill bit for
delivering high voltage pulses to the electrode. In an embodiment of the SED,
cable 207 (which
may be flexible) is provided to link a generator to the electrode(s). A
passage, for example cable
207, is preferably used to deliver water down the SED drill.
[00112] This SED embodiment is advantageous for drilling in non-porous
rock. Also, this
embodiment benefits from the use concurrent use of the high permittivity
liquid discussed herein.
[00113] Another embodiment of the present invention is to assemble several
individual
SED drill heads or electrode sets together into an array or group of drills,
without the individual drill
housings, to provide the capability to mine large areas of rock. In such an
embodiment, a vein of
ore can be mined, leaving most of the waste rock behind. Fig. 20 shows such an
embodiment of
a mineral vein mining machine herein designated Electrocrushing Vein Miner
(EVM) 212
comprising a plurality of SED drills 214, SED case 206, SED insulator 208, and
SED center
electrode 210. This assembly can then be steered as it moves through the rock
by varying the
repetition rate of the high voltage pulses differentially among the drill
heads. For example, if the
repetition rate for the top row of drill heads is twice as high but contains
the same energy per
pulse as the repetition rate for the lower two rows of drill heads, the path
of the mining machine
will curve in the direction of the upper row of drill heads, because the rate
of rock excavation will
be higher on that side. Thus, by varying the repetition rate and/or pulse
energy of the drill heads,
the EVM can be steered dynamically as it is excavating a vein of ore. This
provides a very useful
tool for efficiently mining just the ore from a vein that has substantial
deviation in direction.
[00114] In another embodiment, a combination of electrocrushing and
electrohydraulic
(EH) drill bit heads enhances the functionality of the EVM by enabling the EVM
to take advantage
of ore structures that are layered. Where the machine is mining parallel to
the layers, as is the
case in mining most veins of ore, the shock waves from the EH drill bit heads
tend to separate the
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
layers, thus synergistically coupling to the excavation created by the EC
electrodes. In addition,
combining electrocrushing drill heads with plasma-hydraulic drill heads
combines the compressive
rock fracturing capability of the plasma-hydraulic drill heads with the
tensile rock failure of the EC
drill heads to more efficiently excavate rock.
[00115] With the EVM mining machine, ore can be mined directly and
immediately
transported to a mill by water transport, already crushed, so the energy cost
of primary crushing
and the capital cost of the primary crushers is saved. This method has a great
advantage over
conventional mechanical methods in that it combines several steps in ore
processing, and it
greatly reduces the amount of waste rock that must be processed. This method
of this
embodiment can also be used for tunneling.
[00116] The high voltage pulses can be generated in the housing of the EVM,
transmitted
to the EVM via cables, or both generated elsewhere and transmitted to the
housing for further
conditioning. The electrical power generation can be at the EVM via fuel cell
or generator, or
transmitted to the EVM via power cable. Typically, water or mining fluid flows
through the structure
of the EVM to flush out rock cuttings.
[00117] If a few, preferably just three, of the EC or PH drill heads shown
in Fig. 20 are
placed in a housing, the assembly can be used to drill holes, with directional
control by varying the
relative repetition rate of the pulses driving the drill heads. The drill will
tend to drift in the direction
of the drill head with the highest pulse repletion rate, highest pulse energy,
or highest average
power. This electrocrushing (or EH) drill can create very straight holes over
a long distance for
improving the efficiency of blasting in underground mining, or it can be used
to place explosive
charges in areas not accessible in a straight line.
Insulating Drilling Fluid
[00118] An embodiment of the present invention also comprises insulating
drilling fluids
that may be utilized in the drilling methods described herein. For example,
for the electrocrushing
process to be effective in rock fracturing or crushing, it is preferable that
the dielectric constant of
the insulating fluid be greater than the dielectric constant of the rock and
that the fluid have low
conductivity such as, for example, a conductivity of less than approximately
10-6 mho/cm and a
dielectric constant of at least approximately 6.
[00119] Therefore, one embodiment of the present invention provides for an
insulating
fluid or material formulation of high permittivity, or dielectric constant,
and high dielectric strength
with low conductivity. The insulating formulation comprises two or more
materials such that one
21
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
material provides a high dielectric strength and another provides a high
dielectric constant. The
overall dielectric constant of the insulating formulation is a function of the
ratio of the
concentrations of the at least two materials. The insulating formulation is
particularly applicable
for use in pulsed power applications.
[00120] Thus, this embodiment of the present invention provides for an
electrical
insulating formulation that comprises a mixture of two or more different
materials. In one
embodiment, the formulation comprises a mixture of two carbon-based materials.
The first
material preferably comprises a dielectric constant of greater than
approximately 2.6, and the
second material preferably comprises a dielectric constant greater than
approximately 10Ø The
materials are at least partly miscible with one another, and the formulation
preferably has low
electrical conductivity. The term "low conductivity" or "low electrical
conductivity", as used
throughout the specification and claims means a conductivity less than that of
tap water,
preferably lower than approximately 10-5 mho/cm, more preferably lower than 10-
6 mho/cm.
Preferably, the materials are substantially non-aqueous. The materials in the
insulating
formulation are preferably non-hazardous to the environment, preferably non-
toxic, and preferably
biodegradable. The formulation exhibits a low conductivity.
[00121] In one embodiment, the first material preferably comprises one or
more natural or
synthetic oils. Preferably, the first material comprises castor oil, but may
comprise or include
other oils such as, for example, jojoba oil or mineral oil.
[00122] Castor oil (glyceryl triricinoleate), a triglyceride of fatty
acids, is obtained from the
seed of the castor plant. It is nontoxic and biodegradable. A transformer
grade castor oil (from
CasChem, Inc.) has a dielectric constant (i.e., relative permittivity) of
approximately 4.45 at a
temperature of approximately 22 C(100 Hz).
[00123] The second material comprises a solvent, preferably one or more
carbonates,
and more preferably one or more alkylene carbonates such as, but not limited
to, ethylene
carbonate, propylene carbonate, or butylene carbonate. The alkylene carbonates
can be
manufactured, for example, from the reaction of ethylene oxide, propylene
oxide, or butylene
oxide or similar oxides with carbon dioxide.
[00124] Other oils, such as vegetable oil, or other additives can be added
to the
formulation to modify the properties of the formulation. Solid additives can
be added to enhance
the dielectric or fluid properties of the formulation.
22
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00125] The concentration of the first material in the insulating
formulation ranges from
between approximately 1.0 and 99.0 percent by volume, preferably from between
approximately
40.0 and 95.0 percent by volume, more preferably still from between
approximately 65.0 and 90.0
percent by volume, and most preferably from between approximately 75.0 and
85.0 percent by
volume.
[00126] The concentration of the second material in the insulating
formulation ranges from
between approximately 1.0 and 99.0 percent by volume, preferably from between
approximately
5.0 and 60.0 percent by volume, more preferably still from between
approximately 10.0 and 35.0
percent by volume, and most preferably from between approximately 15.0 and
25.0 percent by
volume.
[00127] Thus, the resulting formulation comprises a dielectric constant
that is a function of
the ratio of the concentrations of the constituent materials. The preferred
mixture for the
formulation of the present invention is a combination of butylene carbonate
and a high permittivity
castor oil wherein butylene carbonate is present in a concentration of
approximately 20% by
volume. This combination provides a high relative permittivity of
approximately 15 while
maintaining good insulation characteristics. In this ratio, separation of the
constituent materials is
minimized. At a ratio of below 32%, the castor oil and butylene carbonate mix
very well and
remain mixed at room temperature. At a butylene carbonate concentration of
above 32%, the
fluids separate if undisturbed for approximately 10 hours or more at room
temperature. A property
of the present invention is its ability to absorb water without apparent
effect on the dielectric
performance of the insulating formulation.
[00128] An embodiment of the present invention comprising butylene
carbonate in castor
oil comprises a dielectric strength of at least approximately 300 kV/cm (I
psec), a dielectric
constant of approximately at least 6, a conductivity of less than
approximately 10-5 mho/cm, and a
water absorption of up to 2,000 ppm with no apparent negative effect caused by
such absorption.
More preferably, the conductivity is less than approximately 10-6 mho/cm.
[00129] The formulation of the present invention is applicable to a number
of pulsed
power machine technologies. For example, the formulation is useable as an
insulating and drilling
fluid for drilling holes in rock or other hard materials or for crushing such
materials as provided for
herein. The use of the formulation enables the management of the electric
fields for
electrocrushing rock. Thus, the present invention also comprises a method of
disposing the
insulating formulation about a drilling environment to provide electrical
insulation during drilling.
23
WO 2012/173969
PCT/1JS2012/042021
[001301 Other formulations may be utilized to perform the drilling
operations described herein. For
example, in another embodiment, crude oil with the correct high relative
permittivity derived as a product
stream from an oil refinery may be utilized. A component of vacuum gas crude
oil has high molecular
weight polar compounds with 0 and N functionality. Developments in
chromatography allow such oils to
be fractionated by polarity. These are usually cracked to produce straight
hydrocarbons, but they may
be extracted from the refinery stream to provide high permittivity oil for
drilling fluid.
[00131] Another embodiment comprises using specially treated waters. Such
waters include, for
example, the Energy Systems Plus (ESP) technology of Complete Water Systems
which is used for
treating water to grow crops. In accordance with this embodiment, Fig. 21
shows water or a water-based
mixture 128 entering a water treatment unit 130 that treats the water to
significantly reduce the
conductivity of the water. The treated water 132 then is used as the drilling
fluid by the FAST Drill
system 134. The ESP process treats water to reduce the conductivity of the
water to reduce the leakage
current, while retaining the high permittivity of the water.
High Efficiency Electrohydraulic Boulder Breaker
[00132] Another embodiment of the present invention provides a high
efficiency electrohydraulic
boulder breaker (designated herein as "HEEB'') for breaking up medium to large
boulders into small
pieces. This embodiment prevents the hazard of fly rock and damage to
surrounding equipment, The
HEEB is related to the High Efficiency Electrohydraulic Pressure Wave
Projector disclosed in U.S.
Patent No. 6,215,734 (to the principal inventor herein).
[00133] Fig. 22 shows the HEEB system disposed on truck 181, comprising
transducer 178,
power cable '180, and fluid 182 disposed in a hole. Transducer 178 breaks the
boulder and cable 180
(which may be of any desired length such as, for example, 6-15 m long)
connects transducer 178 to
electric pulse generator 183 in truck 181. An embodiment of the invention
comprises first drilling a hole
into a boulder utilizing a conventional drill, filling the hole is filled with
water or a specialized insulating
fluid, and inserting HEEB transducer 178 into the hole in the boulder. Fig. 23
shows HEEB transducer
178 disposed in boulder 186 for breaking the boulder, cable 180, and energy
storage module 184.
I:001341
Main capacitor bank 183 (shown in Fig. 22) is first charged by generator 179
(shown in
Fig. 22) disposed on truck 181. Upon command, control system 192 (shown in
Fig. 22 and disposed, for
example, in a truck) is closed connecting capacitor bank 183 to cable 180. The
24
CA 2873152 2018-11-28
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
electrical pulse travels down cable 180 to energy storage module 184 where it
pulse-charges
capacitor set 158 (example shown in Fig. 24), or other energy storage devices
(example shown in
Fig. 25).
[00135] Fig. 24 shows the details of the HEEB energy storage module 184 and
transducer
178, showing capacitors 158 in module 184, and floating electrodes 188 in
transducer 178.
[00136] Fig. 25 shows the details of the inductive storage embodiment of
HEEB energy
storage module 184 and transducer 178, showing inductive storage inductors 190
in module 184,
and showing the transducer embodiment of parallel electrode gaps 188 in
transducer 178. The
transducer embodiment of parallel electrode gaps (Fig. 25) and series
electrode gaps (Fig. 24)
can reach be used alternatively with either the capacitive energy store 158 of
Fig. 24 or the
inductive energy store 190 of Fig. 25.
[00137] These capacitors/devices are connected to the probe of the
transducer assembly
where the electrodes that create the pressure wave are located. The capacitors
increase in
voltage from the charge coming through the cable from the main capacitor bank
until they reach
the breakdown voltage of the electrodes inside the transducer assembly. When
the fluid gap at
the tip of the transducer assembly breaks down (acting like a switch), current
then flows from the
energy storage capacitors or inductive devices through the gap. Because the
energy storage
capacitors are located very close to the transducer tip, there is very little
inductance in the circuit
and the peak current through the transducers is very high. This high peak
current results in a high
energy transfer efficiency from the energy storage module capacitors to the
plasma in the fluid.
The plasma then expands, creating a pressure wave in the fluid, which
fractures the boulder.
[00138] The HEEB system may be transported and used in various environments
including, but not limited to, being mounted on a truck as shown in Fig. 22
for transport to various
locations, used for either underground or aboveground mining applications as
shown in Fig. 26, or
used in construction applications. Fig. 26 shows an embodiment of the HEEB
system placed on a
tractor for use in a mining environment and showing transducer 178, power
cable 180, and control
panel 192.
[00139] Therefore, the HEEB does not rely on transmitting the boulder-
breaking current
over a cable to connect the remote (e.g., truck mounted) capacitor bank to an
electrode or
transducer located in the rock hole. Rather, the HEEB puts the high current
energy storage
directly at the boulder. Energy storage elements, such as capacitors, are
built into the transducer
assembly. Therefore, this embodiment of the present invention increases the
peak current
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
through the transducer and thus improves the efficiency of converting
electrical energy to pressure
energy for breaking the boulder. This embodiment of the present invention also
significantly
reduces the amount of current that has to be conducted through the cable thus
reducing losses,
increasing energy transfer efficiency, and increasing cable life.
[00140] An embodiment of the present invention improves the efficiency of
coupling the
electrical energy to the plasma into the water and hence to the rock by using
a multi-gap design.
A problem with the multi-gap water spark gaps has been getting all the gaps to
ignite because the
cumulative breakdown voltage of the gaps is much higher than the breakdown
voltage of a single
gap. However, if capacitance is placed from the intermediate gaps to ground
(Fig. 24), each gap
ignites at a voltage similar to the ignition voltage of a single gap. Thus, a
large number of gaps
can be ignited at a voltage of approximately a factor of 2 greater than the
breakdown voltage for a
single gap. This improves the coupling efficiency between the pulsed power
module and the
energy deposited in the fluid by the transducer. Holes in the transducer case
are provided to let
the pressure from the multiple gaps out into the hole and into the rock to
break the rock (Fig. 24).
[00141] In another embodiment, the multi-gap transducer design can be used
with a
conventional pulsed power system, where the capacitor bank is placed at some
distance from the
material to be fractured, a cable is run to the transducer, and the transducer
is placed in the hole
in the boulder. Used with the HEEB, it provides the advantage of the much
higher peak current
for a given stored energy.
[00142] Thus, an embodiment of the present invention provides a transducer
assembly for
creating a pressure pulse in water or some other liquid in a cavity inside a
boulder or some other
fracturable material, said transducer assembly incorporating energy storage
means located
directly in the transducer assembly in close proximity to the boulder or other
fracturable material.
The transducer assembly incorporates a connection to a cable for providing
charging means for
the energy storage elements inside the transducer assembly. The transducer
assembly includes
an electrode means for converting the electrical current into a plasma
pressure source for
fracturing the boulder or other fracturable material.
[00143] Preferably, the transducer assembly has a switch located inside the
transducer
assembly for purposes of connecting the energy storage module to said
electrodes. Preferably, in
the transducer assembly, the cable is used to pulse charge the capacitors in
the transducer
energy storage module. The cable is connected to a high voltage capacitor bank
or inductive
storage means to provide the high voltage pulse.
26
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00144] In another embodiment, the cable is used to slowly charge the
capacitors in the
transducer energy storage module. The cable is connected to a high voltage
electric power
source.
[00145] Preferably, the switch located at the primary capacitor bank is a
spark gap,
thyratron, vacuum gap, pseudo-spark switch, mechanical switch, or some other
means of
connecting a high voltage or high current source to the cable leading to the
transducer assembly.
[00146] In another embodiment, the transducer electrical energy storage
utilizes inductive
storage elements.
[00147] Another embodiment of the present invention provides a transducer
assembly for
the purpose of creating pressure waves from the passage of electrical current
through a liquid
placed between one or more pairs of electrodes, each gap comprising two or
more electrodes
between which current passes. The current creates a phase change in the
liquid, thus creating
pressure in the liquid from the change of volume due to the phase change. The
phase change
includes a change from liquid to gas, from gas to plasma, or from liquid to
plasma.
[00148] Preferably, in the transducer, more than one set of electrodes is
arranged in
series such that the electrical current flowing through one set of electrodes
also flows through the
second set of electrodes, and so on. Thus, a multiplicity of electrode sets
can be powered by the
same electrical power circuit.
[00149] In another embodiment, in the transducer, more than one set of
electrodes is
arranged in parallel such that the electrical current is divided as it flows
through each set of
electrodes (Fig. 25). Thus, a multiplicity of electrode sets can be powered by
the same electrical
power circuit.
[00150] Preferably, a plurality of electrode sets is arrayed in a line or
in a series of straight
lines.
[00151] In another embodiment, the plurality of electrode sets is
alternatively arrayed to
form a geometric figure other than a straight line, including, but not limited
to, a curve, a circle
(Fig. 25), or a spiral. Fig. 27 shows a geometric arrangement of the
embodiment comprising
parallel electrode gaps 188 in the transducer 178, in a spiral configuration.
27
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00152] Preferably, the electrode sets in the transducer assembly are
constructed in such
a way as to provide capacitance between each intermediate electrode and the
ground structure of
the transducer (Fig. 24).
[00153] In another embodiment, in the plurality of electrode sets, the
capacitance of the
intermediate electrodes to ground is formed by the presence of a liquid
between the intermediate
electrode and the ground structure.
[00154] In another embodiment, in the plurality of electrode sets, the
capacitance is
formed by the installation of a specific capacitor between each intermediate
electrode and the
ground structure (Fig. 24). The capacitor can use solid or liquid dielectric
material.
[00155] In another embodiment, in the plurality of electrode sets,
capacitance is provided
between the electrode sets from electrode to electrode. The capacitance can be
provided either
by the presence of the fracturing liquid between the electrodes or by the
installation of a specific
capacitor from an intermediate electrode between electrodes as shown in Fig.
28. Fig. 28 shows
the details of the HEEB transducer 178 installed in hole 194 in boulder 186
for breaking the
boulder. Shown are cable 180, the floating electrodes 188 in the transducer
and liquid between
the electrodes 196 that provides capacitive coupling electrode to electrode.
Openings 198 in the
transducer which allow the pressure wave to expand into the rock hole are also
shown.
[00156] Preferably in the multi-electrode transducer, the electrical energy
is supplied to
the multi-gap transducer from an integral energy storage module.
[00157] Preferably in the multi-electrode transducer, the energy is
supplied to the
transducer assembly via a cable connected to an energy storage device located
away from the
boulder or other fracturable material.
Virtual Electrode Electro-Crushing Process
[00158] Another embodiment of the present invention comprises a method for
crushing
rock by passing current through the rock using electrodes that do not touch
the rock. In this
method, the rock particles are suspended in a flowing or stagnant water
conduction path, or other
liquid of relative permittivity greater than the permittivity of the rock
being fractured. Water is
preferred for transporting the rock particles because the dielectric constant
of water is
approximately 80 compared to the dielectric constant of rock which is
approximately 3.5 to 12.
28
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00159] In the preferred embodiment, the water conduction path moves the
rock particles
past a set of electrodes as an electrical pulse is provided to the electrodes.
As the electric field
rises on the electrodes, the difference in dielectric constant between the
water and the rock
particle causes the electric fields to be concentrated in the rock, forming a
virtual electrode with
the rock. This is illustrated in Fig. 29 showing rock particle 200 between
high voltage electrodes
202 and ground electrode 203 in liquid 204 whose dielectric constant is
significantly higher than
that of rock particle 200.
[00160] The difference in dielectric constant concentrated the electric
fields in the rock
particle. These high electric fields cause the rock to break down and current
to flow from the
electrode, through the water, through the rock particles, through the
conducting water, and back to
the opposite electrode. In this manner, many small particles of rock can be
disintegrated by the
virtual electrode electrocrushing method without any of them physically
contacting both
electrodes. The method is also suitable for large particles of rock.
[00161] Thus, it is not required that the rocks be in contact with the
physical electrodes
and so the rocks need not be sized to match the electrode spacing in order for
the process to
function. With the virtual electrode electrocrushing method, it is not
necessary for the rocks to
actually touch the electrode, because in this method, the electric fields are
concentrated in the
rock by the high dielectric constant (relative permittivity) of the water or
fluid. The electrical pulse
must be tuned to the electrical characteristics of the conduction path
structure and liquid in order
to provide a sufficient rate of rise of voltage to achieve the allocation of
electric field into the rock
with sufficient stress to fracture the rock.
[00162] Another embodiment of the present invention, illustrated in Fig.
30, comprises a
reverse-flow electro-crusher wherein electrodes 202 send an electrocrushing
current to mineral
(e.g., rock) particles 200 and wherein water or fluid 204 flows vertically
upward at a rate such that
particles 200 of the size desired for the final product are swept upward, and
whereas particles that
are oversized sink downward.
[00163] As these oversized particles sink past the electrodes, a high
voltage pulse is
applied to the electrodes to fracture the particles, reducing them in size
until they become small
enough to become entrained by the water or fluid flow. This method provides a
means of
transporting the particles past the electrodes for crushing and at the same
time differentiating the
particle size.
29
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
[00164] The reverse-flow crusher also provides for separating ash from coal
in that it
provides for the ash to sink to the bottom and out of the flow, while the flow
provides transport of
the fine coal particles out of the crusher to be processed for fuel.
Fracturing Particles of Micro-Encapsulated Gold
[00165] One embodiment of the present invention comprises a method and
apparatus for
fracturing, electrocrushing, breaking up, crushing, or disintegration of
mineral ore particles and/or
particles of micro-encapsulated gold. This embodiment comprises a particle of
gold that is
surrounded by a sheath of mineral material that completely encapsulates the
gold and makes the
gold impervious to chemical reduction. The particles are so small that they
are not amenable to
mechanical crushing. In some mining operations, a significant percentage,
perhaps 10 to 20%, of
the gold produced in the mine is lost because of micro encapsulation.
[00166] This embodiment of the present invention comprises a method and
apparatus for
fracturing the micro-encapsulated gold particles. The fracturing of the micro-
encapsulated gold
particles is possible because the electric discharge process function is
independent of the size of
the particles, as long as the particles are smaller than the electrode
spacing. This process can be
used subsequent to producing a slurry comprising micro-encapsulated gold prior
to feeding it to a
chemical reduction bath. This preconditioning process can substantially
increase the percentage
of gold recovered from the slurry, by fracturing the micro-encapsulated gold
sheath and making
the gold amenable to solution extraction.
[00167] This embodiment is reasonably independent of the nature of the
sheath of mineral
material, in contrast to a chemical process, which is fully dependent on the
nature of the sheath.
The fact that the sheath surrounds a conductive particle such as gold enhances
the effectiveness
of the electrocrushing process.
[00168] A method of extracting micro encapsulated gold preferably includes
a slurry of
micro encapsulated gold particles being swept past several electrodes across
which the electric
pulse is imposed. In most cases these particles are very small compared to the
electrode gap
spacing. There is also a threshold electric field at which most particles
undergo fracturing and
hence exposing the gold for recovery. Optimizing the distribution of electric
field across the gap is
preferred in order to optimize the fraction of micro encapsulated gold
particles that are fractured
with each pulse. The distribution of electric field is primarily governed by
the shape of the
electrodes, and the electrical properties of the flow channel and support
structure. The electrodes
are preferably shaped to provide a near uniform electric field distribution
across the electrode gap
so many particles are fractured with each pulse. For example, if the
electrodes are spherical in
shape, then the electric fields have a greater strength near the electrodes
and much reduced
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
strength near the center of the flow channel. However, if special electrode
shapes are utilized,
such as, for example, a Rogowski electrode shape, then the electric field
distribution throughout
the flow channel is much more uniform. The fraction of particles suspended in
the fluid that is
fractured with the given pulse is increased by shaping the electrodes to
provide a near uniform
electric field distribution across the electrode gap. This enables a larger
fraction of the total
number of micro encapsulated gold particles to be subjected to electric fields
above the threshold
electric field, and hence to undergo fracturing.
[00169] One embodiment of the present invention comprises a method for
fracturing
particles of micro-encapsulated gold for subsequent extraction by chemical
treatment or other
treatment to separate the gold from the mineral content. In this embodiment of
the present
invention, the chemicals for dissolving the gold are in the fluid transporting
the micro encapsulated
gold particles. Chemicals suitable for dissolving the gold are preferably
incorporated into the fluid
being used to transport the micro encapsulated gold particles, thus greatly
facilitating recovery of
the gold and discard of the waste minerals. Thus, after treatment, the waste
minerals and the
remaining micro encapsulated gold particles can be filtered from the slurry
and the chemicals
containing the dissolve gold can be sent for further processing to extract
metallic gold.
Industrial Applicability
[00170] The invention is further illustrated by the following non-limiting
example(s).
Example 1
[00171] An apparatus utilizing FAST Drill technology in accordance with the
present
invention was constructed and tested. Fig. 31 shows FAST Drill bit 114, the
drill stem 216, the
hydraulic motor 218 used to turn drill stem 216 to provide power to mechanical
teeth disposed on
drill bit 114, slip ring assembly 220 used to transmit the high voltage pulses
to the FAST bit 114
via a power cable inside drill stem 216, and tank 222 used to contain the
rocks being drilled. A
pulsed power system, contained in a tank (not shown), generated the high
voltage pulses that
were fed into the slip ring assembly. Tests were performed by conducting 150
kV pulses through
drill stem 216 to the FAST Bit 114, and a pulsed power system was used for
generating the 150
kV pulses. A drilling fluid circulation system was incorporated to flush out
the cuttings. The drill
bit shown in Fig. 5 was used to drill a 7 inch diameter hole approximately 12
inches deep in rock
located in a rock tank. A fluid circulation system flushed the rock cuttings
out of the hole, cleaned
the cuttings out of the fluid, and circulated the fluid through the system.
31
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
Example 2
[00172] A high permittivity fluid comprising a mixture of castor oil and
approximately 20%
by volume butylene carbonate was made and tested in accordance with the
present invention as
follows:
1. Dielectric Strength Measurements.
[00173] Because this insulating formulation of the present invention is
intended for high
voltage applications, the properties of the formulation were measured in a
high voltage
environment. The dielectric strength measurements were made with a high
voltage Marx bank
pulse generator, up to 130 kV. The rise time of the Marx bank was less than
100 nsec. The
breakdown measurements were conducted with 1-inch balls immersed in the
insulating
formulation at spacings ranging from 0.06 to 0.5 cm to enable easy calculation
of the breakdown
fields. The delay from the initiation of the pulse to breakdown was measured.
Fig. 32 shows the
electric field at breakdown plotted as a function of the delay time in
microseconds. Also included
are data from the Charlie Martin models for transformer oil breakdown and for
deionized water
breakdown (Martin, T. H., A. H. Guenther, M Kristiansen "J. C. Martin on
Pulsed Power" Lernum
Press, (1996)).
[00174] The breakdown strength of the formulation is substantially higher
than transformer
oil at times greater than 10 sec. No special effort was expended to condition
the formulation. It
contained dust, dissolved water and other contaminants, whereas the Martin
model is for very well
conditioned transformer oil or water.
2. Dielectric Constant Measurements.
[00175] The dielectric constant was measured with a ringing waveform at 20
kV. The
ringing high voltage circuit was assembled with 8-inch diameter contoured
plates immersed in the
insulating formulation at 0.5-inch spacing. The effective area of the plates,
including fringing field
effects, was calibrated with a fluid whose dielectric constant was known
(i.e., transformer oil). An
aluminum block was placed between the plates to short out the plates so that
the inductance of
the circuit could be measured with a known circuit capacitance. Then, the
plates were immersed
in the insulating formulation, and the plate capacitance was evaluated from
the ringing frequency,
properly accounting for the effects of the primary circuit capacitor. The
dielectric constant was
evaluated from that capacitance, utilizing the calibrated effective area of
the plate. These tests
indicated a dielectric constant of approximately 15.
32
CA 02873152 2014-11-10
WO 2012/173969
PCT/US2012/042021
3. Conductivity Measurements.
[00176] To measure the conductivity, the same 8-inch diameter plates used
in the
dielectric constant measurement were utilized to measure the leakage current.
The plates were
separated by 2-inch spacing and immersed in the insulating formulation. High
voltage pulses,
ranging from 70-150kV were applied to the plates, and the leakage current flow
between the
plates was measured. The long duration current, rather than the initial
current, was the value of
interest, in order to avoid displacement current effects. The conductivity
obtained was
approximately 1 micromho/cm [1X106 (ohm-cm)-1].
4. Water Absorption.
[00177] The insulating formulation has been tested with water content up to
2000 ppm
without any apparent effect on the dielectric strength or dielectric constant.
The water content
was measured by Karl Fisher titration.
5. Energy Storage Comparison.
[00178] The energy storage density of the insulating formulation of the
present invention
was shown to be substantially higher than that of transformer oil, but less
than that of deionized
water. Table 1 shows the energy storage comparison of the insulating
formulation, a transformer
oil, and water in the 1 psec and 10 psec breakdown time scales. The energy
density (in
joules/cm3) was calculated from the dielectric constant (6,60) and the
breakdown electric field (Ebd
¨ kV/cm). The energy storage density of the insulating formulation is
approximately one-fourth
that of water at 10 microseconds. The insulating formulation did not require
continuous
conditioning, as did a water dielectric system. After about 12 months of use,
the insulating
formulation remained useable without conditioning and with no apparent
degradation.
Table 1. Comparison of Energy Storage Density
Time = 1 psec Time = 10 psec
Fluid Dielectic kV/ Energy kV/c Energy
Constant cm Density m Density
Insulating 15 380 9.59E-02 325 7.01E-02
formulation
Trans. Oil 2.2 500 2.43E-02 235 5.38E-03
Water 80 600 1.27E+00 280 2.78E-01
Energy density =1/2* * Eo*Ebd *Ebd j/crr0
33
WO 2012/173969
PCT/liS2012/042021
6. Summary.
[00179] A summary of the dielectric properties of the insulating
formulation of the present
invention is shown in Table 2. Applications of the insulating formulation
include high energy
density capacitors, large-scale pulsed power machines. and compact repetitive
pulsed power
machines.
Table 2. Summary of Formulation Properties
Dielectric Strength = 380 kV/cm (1 psec)
Dielectric = 15
Constant
Conductivity = le-6 mho/cm
Water absorption = up to 2000 ppm with no apparent ill effects
[00180] The preceding examples can be repeated with similar success by
substituting the
generically or specifically described compositions, biomaterials, devices
and/or operating
conditions of this invention for those used in the preceding examples.
[00181] Although the invention has been described in detail with particular
reference to
these preferred embodiments, other embodiments can achieve the same results.
Variations and
modifications of the present invention will be obvious to those skilled in the
art and it is intended to
cover all such modifications and equivalents.
34
CA 2873152 2018-11-28
