Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HYDRAULIC AIR COMPRESSOR APPLICATIONS
FIELD OF THE INVENTION
[0001] The present invention generally relates to hydraulic air
compressors. In
particular, the invention relates to uses and systems incorporating the same.
BACKGROUND OF THE INVENTION
[0002] An Hydraulic Air Compressor (HAC) is a large scale installation,
typically
formed in rock tunnels, that constitutes a method of harnessing hydropower, a
renewable source
of energy, towards the production of compressed air. The technology was first
established in
1890 in Ontario by Charles Taylor. Eighteen examples of the technology have
reported to have
been constructed, in 9 different countries, on three different continents,
mostly for mining
applications. The largest of these was at Ragged Chutes, on the Montreal
River, 20km south of
Cobalt in Ontario. Other than a pneumatic, and subsequently, an hydraulic
power assembly to
move the intake head vertically up or down in response to natural watercourse
head and
discharge variations, these systems have no moving parts and hence have high
reliability; the
system at Cobalt operated more-or-less continuously for 70 years, operations
only being
interrupted twice for maintenance to the intake head.
[0003] Compressed air generated by the HACs was then transported through
a
distribution network of pipes to supply a variety of different applications
requiring compressed
air. With electricity becoming a more marketable form of energy than
compressed air around
when HACs were developing and the niche demands for compressed air that they
serviced
falling, almost all HACs have since been decommissioned. However new niche
demands have
since arisen and as such, there is a need to resurrect the use of HACs for
applications where cost
effective energy solutions are required.
SUMMARY OF THE INVENTION
[0004] According to an aspect of the present invention, there is provided
use of an
hydraulic air compressor for cooling an underground mine. The compressed air
produced by the
hydraulic air compressor being mixed with the airstream of an air intake
ventilation shaft of an
underground mine to lower the temperature of the airstream.
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[0005] According to a second aspect of the present invention there is
provided a method
for cooling an underground mine. The method involves supplying compressed air
from an
hydraulic air compressor to an air intake airstream of a ventilation shaft of
an underground mine
to lower the temperature of the airstream.
[0006] According to a third aspect of the present invention there is
provided a system for
cooling an underground mine. The system includes: a ventilation shaft for
delivering an
airstream to an underground mine; and a hydraulic air compressor for supplying
compressed air
to the ventilation airstream. In the system, expanding the compressed air and
mixing it with the
airstream decreases the overall temperature of the airstream.
[0007] According to a fourth aspect of the present invention, there is
provided a system
for cooling a deep underground. The system includes: an hydraulic air
compressor positioned
greater than 100m in depth in the earth; an air inlet for injecting
atmospheric air into water prior
to or once the water enters the down-comer shaft; a first gas-liquid separator
at the outlet of the
down-comer shaft for exhausting a first compressed gas into an air intake
ventilation shaft of a
mine; a riser shaft for transporting water from the first gas-liquid separator
to a second gas-liquid
separator, wherein oxygen is exhausted at the second gas-liquid separator into
the air intake
ventilation shaft of the mine and the water flows to the pump.
[0008] According to a fifth aspect of the present invention there is
provided a method for
separating chemical compounds from a gaseous mixture, such as an exhaust
combustion gas
from a plant. The method involves the steps of: injecting the gaseous mixture
into a down-comer
shaft of a hydraulic air compressor to generate a two-phase mixture of gas and
liquid; removing
one species within the gaseous phase mixture of the two-phase mixture before
the outlet of the
down-comer shaft by dissolving it in the liquid; separating the gaseous phase
from the liquid
phase at the bottom of the downcomer shaft; isothermally decpressurizing the
separated liquid
portion of the two-phase mixture to recover previously dissolved gaseous
species thereform; and
either exhausting the previously dissolved species or collecting it for
economic purpose.
[0009] According to a sixth aspect of the present invention, there is
provided a system for
separating chemical compounds from a gaseous mixture, such as an exhaust
combustion gas.
The system includes: a hydraulic air compressor comprising a down-comer shaft,
a gas-liquid
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separator in communication with an outlet of the down-comer shaft and an inlet
of an outlet
shaft; a connection to bring the gaseous mixture to the hydraulic air
compressor; a primary
compressed gas outlet connected to the gas-liquid separator to deliver high
pressure, separated,
compressed gas; and a secondary outlet positioned near or in conjunction with
the outlet of the
outlet shaft for exhausting or collecting isothermally decompressed gas from
the mixture of
liquid and formerly dissolved gas.According to a seventh aspect of the present
invention, there is
provided a method for cooling a building. The method involving supplying
compressor air from
a closed-loop hydraulic air compressor to the atmospheric air of a building;
and depressurizing
the compressed air allowing it to expand and cool the atmospheric air.
[0010] According to an eighth aspect of the present invention, there is
provided a
domestic air conditioner system. The domestic air conditioner system having: a
gas-liquid
separator for positioning in a borehole; a down-comer shaft connected to an
inlet port on the gas-
liquid separator; a delivery pipe connected to the gas-liquid separator for
transporting
compressed air from the gas-liquid separator; a return pipe for returning
liquid to the down-
corner shaft; and an air intake for introducing air into liquid prior to or
near when the liquid
enters the down-corner shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other features, aspects and advantages of the present
invention will
become better understood with regard to the following description and
accompanying drawings
wherein:
[0012] FIG. 1 is a schematic diagram of a hydraulic air compressor;
[0013] FIG. 2 is a schematic diagram of a hydraulic air compressor
according to an
embodiment of the present invention;
[0014] FIG. 3 is a schematic diagram of a hydraulic air compressor
according to an
embodiment of the present invention;
[0015] FIG. 4 is a schematic diagram of a hydraulic air compressor
according to an
embodiment of the present invention;
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[0016] FIGs. 5a-f are schematic diagrams of hydraulic air compressors
according to an
embodiment of the present invention; and
[0017] FIGs. 6a-c are schematic diagrams of hydraulic air compressors
according to an
embodiment of the present invention.
DESCRIPTION OF THE INVENTION
The following description is of an illustrative embodiment by way of example
only and without
limitation to the combination of features necessary for carrying the invention
into effect.
[0018] The present invention relates to hydraulic air compressors (HACs),
such as those
developed by Charles Taylor in the late 1800's. As shown in FIG. 1, an HAC 1
includes a down-
comer shaft 2, having an water inlet 3 and a water outlet 4. The water inlet 3
being in fluid
communication with a natural or man-made source of moving water, such as a
river or the like.
At or near the water inlet 3 of the down-corner shaft 2 is positioned a gas
intake 5. The gas
intake 5 introduces, by means of varying mechanisms, air or gas into the
stream of water flowing
down the down-corner shaft 2. The down-comer shaft 2 terminates in a chamber 6
buried below
the earth. The length of the down-corner shaft 2 can vary depending on the
amount of air
compression desired. The deeper into the earth that the chamber is positioned,
thus extending
the length of the down-comer shaft 2, the greater the compression of the gas.
Depths of 100m or
more produce sufficient compression to allow for the compressed air to be used
in industrial
applications.
[0019] In operation, the chamber 6 houses a combination of compressed air
and liquid,
mostly in the form of water. The compressed air can be exhausted through a
compressed gas
outlet 7, which is interconnected with a network that is capable of
transporting the air
compressed air to one or more endpoints, which will be discussed in further
detail below. An
outlet shaft 8 having an inlet 9 connected to the chamber 6 and an outlet 10
in fluid
communication with a surface source of water, transports the water from the
chamber 6 to the
surface water body. This surface water body can be directly or indirectly
connected to the same
source of water that fed the down-corner shaft 2 or can be a separate
watercourse altogether. In
some cases, the outlet shaft 8 may be directly or indirectly connected to a
pump at the surface
water body and returned to the primary water source that feeds the down-corner
shaft 2. If the
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outlet shaft 8 is directly connected to the pump, then a cooling heat
exchanger may be added in
series with the conduit to transfer any heat accumulated in the water.
[0020] It should be noted that the hydraulic air compressors described
herein are not just
used to compress air and that other gases can be compressed by such hydraulic
air compressors.
For the purposes of the present discussion, air and gas are used
interchangeably herein to
describe the same element. Similarly, in preceding and following descriptions,
reference has
been or will be made to the use of water as the liquid that passes through the
system. In further
embodiments of the invention, the use of water could be replaced by another
liquid, particularly
when the liquid is returned to the intake of the down-comer shaft by means of
a pump. For gas
separation embodiments of the invention, alternative liquids could be selected
based on the
differential pressure solubility in the selected liquid of the gaseous species
in the gaseous mixture
to be separated. Water may be the most frequently selected solvent due to its
availability and low
cost relative to other solvents, however, both water and liquid are used
interchangeably herein to
describe the same element.
[0021] In one embodiment, the compressed air exhausted by the HAC 1 could
be used to
reduce the temperature of air flowing to a mine (FIG. 4). In this case, the
compressed air outlet
directly or indirectly, depending on whether the compressed air is delivered
to the mine through
a network, terminates at a mine ventilation shaft or drift 30, or is
temporarily stored in a receiver,
mixes with the airstream traveling down the ventilation shaft or drift 30 to
the mine 31. In one
example, using the compressed air from HAC 1 in an ideal device that could
expand the air
isentropically would produce a 3.8 kg/s stream of -126.1 C compressed air with
a cooling power
of (419.14-271.94) kJ/kg x 3.8 kg/s = 560 kWth, deliverable to the bulk mine
ventilation air
through the direct contact of mixing. (see FIG. 3) This is sufficient cooling
power to reduce a
shaft bottom ventilation inflow of 800 m3/s (1,695,120 cfm) by 0.58 C. In
another example,
where deeper mining is being carried out, it is possible that greater depths
i.e. approximately 600
m or more in depth, 11.2 kg/s air at 56 bar gauge could be produced by such a
system, which, if
expanded isentropically could cool the same amount of ventilation air by 2.4
C.
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[0022] As well as cooling the air, compressed air introduced into the
ventilation air from
the HAC 1 can issue through a nozzle to a mine airway shaped similarly to 135
in Figure 4, such
that that this embodiment could act as an integrated mine air cooler and mine
air booster fan.
[0023] In another embodiment, the concept of the HAC is provided as a
closed loop
HAC 50. In this case, the down-comer shaft 102 is not in fluid communication
with a natural
water body. Instead, water is recycled and propelled into the down-comer shaft
102 by a pump
110. Prior to or at the same time as the water enters the down-comer shaft
102, ambient air is
injected into the stream of water by air inlet 112. Optionally, between the
pump 110 and the
inlet of the down-corner shaft 102 the conduit carrying the water can be
narrowed and the walls
of the conduit properly angled to the narrowed portion to produce an
arrangement similar to a
venturi injector. At the narrow portion of the venturi injector, ambient is
air drawn into the
system through the air inlet 112.
[0024] The mixture of air and water travels down the down-corner shaft to
a gas-liquid
separator system, or cyclone 122. Similar to the gaseous mixture separation
system described
above, as the air/water mixture travels down the down-comer shaft 102, most of
the 02 in the air
will be dissolved in the water and the N2 will be compressed and released in
the form of gas at
the air compressed gas outlet 123 attached to the gas-liquid separator system
122.
[0025] The N2 gas exhausted from the high pressure gas-liquid separator
system 122 can
be transferred to air intake ventilation shaft of the mine. In most cases, a
receiver vessel 60 is
placed in series with the compressed gas outlet 123 in order to store the
compressed gas
produced at the gas-liquid separator system 122. Regulators and/or valves 61
can be placed
along the length of the compressed gas outlet 123 to control flow rate into
the receiver vessel 60
and/or air intake ventilation shaft of the mine. In order to improve the
overall cooling efficiency
of the system, the air intake ventilation shaft 30 may be configured to
resemble a venturi jet
pump 135 prior to the atmospheric air from the surface being drawn into the
mine workings 31.
In this case, the air compressed outlet 123 terminates at or near the entrance
of the venturi jet
pump allowing for the atmospheric air to be enriched with compressed N2..
[0026] In the embodiment where the air intake ventilation shaft or drift
30 is configured
to resemble a venturi jet pump 135, the diameter of the air intake ventilation
shaft 30 is reduced
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in a collar section 90, with a gradual angling of the air intake ventilation
shaft walls towards the
collar section 90 and a more gradual angling of the walls away from the collar
section 90. This
arrangement allows for cooler air, having a consistency similar to atmospheric
air, to be drawn
into the mine workings 31 and up the upcast exhaust shaft 158 by main mine fan
170.
[0027] Water exiting the high pressure gas-liquid separator system 122
has 02, and to a
much lesser extent N2, dissolved therein. As this water travels up a riser
shaft 140, at least a
portion of the 02 and N2 dissolved in the water is isothermally depressurized,
so that when the
gas and water mixture is delivered to a second low-pressure gas-liquid
separator 150, the 02 and
N2 are exhausted through an exhaust port 151, which can, in certain
applications, terminate at a
position along the air intake ventilation shaft 30. The second or low pressure
gas-liquid separator
150 can be designed similar to the high pressure gas-liquid separator 122 or
can have a different
structure depending upon the installation and application. In any case, the
second gas-liquid
separator will also be able to separate gas from liquid using forced
centrifugal separation. Since
the gas traveling through exhaust port 151, contains mostly 02 and to a much
lesser degree N25
this gas can be added to the atmospheric air being drawn into air intake
ventilation shaft 30 to
enrich the 02 concentration thereof. This allows for the air eventually
reaching the mine
workings 31 to have a consistency, in terms of the percentages of 02 and N2
contained therein,
that is more similar to atmospheric air.
[0028] Water exiting the second gas-liquid separator 150 enters back into
the system via
pump 110.
[0029] The use of an HAC, as described above, in the cooling of mine,
deep or
otherwise, offers significant energy savings over the current use of
conventional compressors
and/or powerful fan units.
[0030] In another embodiment, the gaseous mixture passing through gas
intake 5 comes
from an exhaust outlet 20 from a plant (FIG. 2). In most cases, the plant 21
will be a fossil fuel
powered plant, so the combustion gases will predominantly comprise CO2, water
vapour, and N2,
with much smaller concentrations of undesirable species such as NOx, SO2, and
possibly unburnt
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hydrocarbons or 02, if the plant operated with significant excess air. For the
purposes of the
present illustrative discussion, it is assumed that the combustion gas
comprises only CO2, H20
and N2
[0031] When the combustion gas bubbles come into contact with the water
in the down-
corner shaft 2, the water vapour will condense into the water readily (if the
water has not already
become condensate prior to being passed to the HAC as part of a heat recovery
scheme). This
will leave a stream gas bubbles with a composition of CO2 and N2.
[0032] Henry's Law (see for example, the useful compilation of Henry's
Law constants
in Sander, 1999, hettp://www.henrys-law.org or Battino et al., J. Phys. Chem.
Ref Data
13(2):563-600, 1984) governing the pressure solubility of gases can be
described:
p, = K,x,
[0033] where p, is the partial pressure of the gas species i in the gas
phase, K, is Henry's
constant for species i and x, is the maximum mol fraction (concentration) of
the species in the
solvent (water), known as the solubility. Henry's constant for N2 is 155.88
MPa/(mol/dm3) and
for CO2 is 2937 MPa/(mol/dm3). It is thus evident that CO2 has pressure
solubility in water at
least an order of magnitude higher than N2 and will thus dissolve completely
first in the water as
the pressure increases. In addition, a small amount of N2 will be dissolved in
the water.
[0034] A gas-liquid separation system 22 provided at the outlet 4 of the
down-corner
shaft 2 at the depth (pressure) at which the CO2 becomes completely dissolved
will cause the
CO2 to be separated from the input gas stream as it will leave by being
dissolved in the water
passing through the gas-liquid separation system 22. The gas-liquid separation
system 22 can be,
but is not limited to, a forced centrifugal separator, such as a cyclone,
hydrocyclone, cyclonic
chamber or funnel as shown in Figure 2 or a separation gallery 6 as shown in
Figure 1. In the
case of a forced centrifugal separator, the water and gas mixture that enters
the separator is
forced against the interior of the separator in a manner that generates a
swirling or cyclonic
movement of the mixture. The cyclonic movement of the pressurized gas and
water results in
most of the gas rising to the top of the separator and the water funnelling
out of the separator,
below. In the case where the input gaseous mixture contains N2 and CO2, and
the gas-liquid
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separator is positioned at a depth (pressure) where CO2 becomes completely
dissolved in the
water, then the gas exhausted from the gas-liquid separation system will be
primarily pressurized
N2. In a system where a forced centrifugal separator 22 is not provided, the
gas stream exiting
the outlet 4 of the down-comer shaft 2, which contains high pressure nitrogen,
N2, can be vented
through compressed gas outlet 23.
[0035] In order to ensure constant availability of pressurized gas from
the compressed
gas outlet 23, a receiver vessel 60 may be positioned in series along the
compressed gas outlet 23
or the distribution network attached thereto.
[00361 As the water depressurises while it ascends, CO2 becomes less
soluble and will
come out of solution (together with the minor amount of N2 that was dissolved
as well). At the
outlet 10 of the outlet shaft 8, the flow will be two phase and so the gas
stream can be separated
from the water with another gas-liquid separation system 25 having a secondary
gas outlet 26 (as
shown in Figure 2). The second gas-liquid separation system 25 can be of
similar configuration
to the first gas-liquid separator 22, or can have a different configuration.
In this case, the
gaseous phase of the gas and water mixture will be under less pressure than
when the mixture
passed through the first gas-liquid separator.
[00371 In another embodiment, the flow exiting the first HAC can be
passed to a second,
similar HAC system. This arrangement will be particularly advantageous when
the purity of the
CO2 stream is low. As the solubility of gases in water depends on the gas
species partial
pressure, in the second HAC system, less of the N2 will dissolve as the
pressure increases, than
dissolved in the first HAC system at the same pressure. In the high pressure
gas-liquid separator
22 at depth, less N2 will be carried, dissolved, in the liquid phase. In the
overflow of the low
pressure gas-liquid separator 25 at surface of the second HAC, the purity of
the CO2 will be
higher.
[0038] When additional gas species are considered in the system, such as
02, which may
be present due to the combustion process taking place in excess air, whether
or not these species
predominantly arrive at the high pressure overflow 23 or the low pressure
overflow 25 depends
on their relative pressure solubility; 02 has Henry's constant value of 77.94
MPa/(mol/dm3),
about half that of N2, meaning that it is about twice as soluble in water as
N2. The bulk of the 02
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will be carried up the riser 8 dissolved in the water, but undissolved 02 will
arrive at the
overflow of the high pressure cyclone 22, reducing the purity of the
predominantly N2 stream. To
improve the nitrogen purity of this stream, it may be passed to another HAC,
where the elevation
of the high pressure separation cyclone 22 is located at a depth where the
oxygen can be taken to
have dissolved completely. The overflow of this cyclone will produce a high
purity stream of
compressed nitrogen gas. Thus it can be seen that when deployed as part of a
combustion gas
separation scheme, or carbon capture scheme, HACs would be deployed in
cascades.
[0039] In the preceding paragraphs relevant to the embodiment of the
invention that
concerns the separation of gaseous mixtures, the use of a combustion gas
mixture to illustrate the
gas separation systems and methods, embodies specific methods and systems for
effecting
'carbon capture' from new or existing fossil fuel burning plants using HACs.
[0040] Regulators, valves, switches and the like can be positioned at
various spots along
the HAC and related systems to control flow of water, air and/or gases. These
regulators, valves
and switches can be controlled by a microprocessor and related circuitry.
[0041] The concept of the closed-loop HAC system described above can be
used for a
domestic air conditioning system, as shown in FIG. 5a. In this case, a
borehole 200 is provided
as the riser shaft. A gas-liquid separator 201, similar to the ones described
above, is housed in
the borehole 200, which is fed by a down-comer shaft 202. Compressed air that
is separated
from the water in the gas-liquid separator 201 is exhausted from the gas-
liquid separator 201 by
compressed air delivery pipe 203. Compressed air from the delivery pipe 203 is
fed to the
domestic structure and depressurized causing expansion and cooling of the air.
After the water
exits the gas-liquid separator 201, it slowly (compared to the down-comer
shaft) flows up and
around the gas-liquid separator 201 and down-comer shaft 202 and delivery pipe
203 to
eventually be pumped back into the down-corner shaft 202 by mechanical pump
204. Before the
water re-enters the down-comer shaft 202, it passes through venturi injector
205, where air is
reintroduced into the system at air inlet 206. Low-pressure gas accumulated in
the borehole 200
can be exhausted by exhaust outlet 207.
[0042] Systems comprising riser shafts 200, as shown in FIGs 5b-5f, can
be used in
situations where the horizontal space requirements of the systems described
above may not be
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available. In the closed loop system shown in FIG. 5b, a second gas-liquid
separator 208
exhausted by outlet 209 is provided at the top of the riser shaft 200 where
the water exits the
shaft 200. In this case, the exhaust outlet 207 is connected to the gas-liquid
separator 208.
Systems incorporating open-loop systems are shown in FIGs. 5c and 5d. In these
cases, water is
pumped from pump 204 through return 210 to the source of water 211 that feeds
the down-corner
shaft 202. Air is injected into this system by air inlet 206 that is
positioned in the down-comer
shaft 202. Systems where the water exiting the riser shaft 200 is not returned
to the down-comer
shaft 202 are shown in FIGs. 5e and 5E In these arrangements, the water can be
delivered to
another watercourse or used for some other purpose.
[0043] In another embodiment, the system can include a separation gallery
or chamber
320 in conjunction with riser shaft 300 (FIG. 6). In the various systems shown
in FIG. 6, the
down-comer shaft 302 empties into a separation gallery or chamber 320, where
compressed gas
is removed via delivery pipe 303. The water in the chamber is allowed to rise
in riser shaft 300,
where low-pressure gas is exhausted at exhaust outlet 307 (FIGs. 6a and 6b).
Alternatively, the
water is allowed to rise up the riser shaft and is introduced to a gas-liquid
separator 308 which is
connected to exhaust outlet 307 (FIG. 6c). The various reference numerals
shown in FIG. 6
correspond to equivalent elements in FIG. 5.
[0044] The present invention has been described with regard to one or
more
embodiments. However, it will be apparent to persons skilled in the art that a
number of
variations and modifications can be made without departing from the scope of
the invention as
defined by the claims.
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