Note: Descriptions are shown in the official language in which they were submitted.
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HYDRAULIC GAS COMPRESSORS AND APPLICATIONS THEREOF
RELATED APPLICATION
This application claims priority of Canadian Patent Application No. 2,818,357
filed June 10,
2013, the contents of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0001] The present invention generally relates to hydraulic gas
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.
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SUMMARY OF THE INVENTION
[0004] According to an aspect of the present invention, there is provided
use of an
hydraulic gas compressor for cooling an underground mine. The compressed gas
produced by the
hydraulic gas compressor being mixed with the airstream of an gas intake
ventilation shaft of an
underground mine to lower the temperature of the airstream.
[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 gas
from an
hydraulic gas compressor to an gas 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 gas compressor for supplying
compressed gas
to the ventilation airstream. In the system, expanding the compressed gas and
mixing it with the
airstream decreases the overall temperature of the airstream.
[0007] In one embodiment, the hydraulic gas compressor comprises a down-
comer shaft,
a gas-liquid separator in communication with an outlet of the down-corner
shaft and an inlet of
an outlet shaft that transports compressed gas to the air intake ventilation
shaft.
[0008] In a second embodiment, the compressed gas is transported through
a network of
conduit prior to entering the air intake ventilation shaft.
[0009] In a third embodiment, the compressed gas enters the air intake
ventilation shaft
through a nozzle. In some situations, the nozzle resembles a venturi jet pump.
[0010] In a fourth embodiment, the diameter of the air intake ventilation
shaft is reduced
in a collar section with a gradual angling of the air intake ventilation shaft
walls towards the
collar section and a more gradual angling of the walls away from the collar
section at the point
where the compressed air is introduced into the airstream of the ventilation
shaft.
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[0011] According to a fourth aspect of the present invention, there is
provided a system
for cooling a mine deep underground. The system includes: an hydraulic gas
compressor; a gas
inlet for injecting gas or atmospheric air into water prior to or once the
water enters the down-
corner shaft; a first gas-liquid separator at the outlet of the down-comer
shaft for exhausting a
first compressed gas into an gas intake ventilation shaft of a mine; a riser
shaft for transporting
water from the first gas-liquid separator to a second gas-liquid separator.
The formerly dissolved
gases are exhausted at the second gas-liquid separator into the gas intake
ventilation shaft of the
mine.
[0012] In one embodiment, the first gas-liquid separator is a high
pressure separator
and/or the second gas-liquid separator is a low pressure separator. The first
and second gas-
liquid separator being centrifugal separators or separation galleries. The
centrifugal separator is a
cyclone, hydrocyclone, cyclonic chamber or funnel.
[0013] In a second embodiment, the diameter of the air intake ventilation
shaft is reduced
in a collar section with a gradual angling of the air intake ventilation shaft
walls towards the
collar section and a more gradual angling of the walls away from the collar
section at the point
where the compressed air is introduced into the airstream of the ventilation
shaft.
[0014] In a third embodiment, the system further comprises a conduit from
the second
gas-liquid separator for recirculating the liquid to the down-comer shaft. In
some systems, a
pump is positioned in series with the conduit for recirculating the liquid to
the down-corner shaft.
[0015] In a fourth embodiment, a cooling heat exchanger is placed in
series with the
conduit.
[0016] In a fifth embodiment, a co-solute is added to the liquid in the
down-comer shaft.
The co-solute being, for example, a salt, such as sodium sulphate.
[0017] In a sixth embodiment, at least portions of the system are
provided as insulated
conduit.
[0018] In a seventh embodiment, the system further comprises: a second
hydraulic gas
compressor; a second air inlet connected to the second gas-liquid separator
for introducing gas
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into liquid prior to or once the liquid enters a second down-corner shaft; a
third gas-liquid
separator at the outlet of the second down-comer shaft for exhausting a second
compressed gas
into an air intake ventilation shaft or drift of a mine; a second riser shaft
for transporting liquid
from the third gas-liquid separator to a fourth gas-liquid separator, wherein
oxygen is exhausted
at the fourth gas-liquid separator into the air intake ventilation shaft of
the mine.
[0019] 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-corner
shaft of a hydraulic gas 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 depressurizing 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 them for
economic purpose.
[0020] 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 gas compressor comprising a down-comer shaft,
a gas-liquid
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 gas
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.
[0021] According to a seventh aspect of the present invention, there is
provided a method
for cooling a building. The method involving supplying compressor gas from a
closed-loop
hydraulic gas compressor to the atmospheric air of a building; and
depressurizing the
compressed gas allowing it to expand and cool the atmospheric air.
[0022] In one embodiment, a receiver vessel is positioned in series with
the compressed
gas outlet.
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[0023] In a second embodiment, a co-solute is added to the liquid in the
down-corner
shaft. The co-solute being, for example, a salt, such as sodium sulphate.
[0024] In a third embodiment, at least portions of the system are provided
as insulated
conduit.
[0025] In a fourth embodiment, the separated compressed gas comprises
nitrogen gas.
[0026] In a fifth embodiment, the previously dissolved chemical compounds
comprise
carbon dioxide.
[0027] According to an eighth aspect of the present invention, there is
provided a
domestic gas conditioner system. The domestic gas 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 gas from the gas-liquid separator; a return pipe for returning
liquid to the down-
comer shaft; and an gas intake for introducing gas into liquid prior to or
near when the liquid
enters the down-comer shaft.
[0028] According to a ninth aspect of the present invention, there is
provided a vapour
compression refrigerator. The vapour compression refrigerator having: a gas-
liquid separator; 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 gas from the
gas-liquid
separator to a condensing heat exchanger, an expansion device and an
evaporating heat
exchanger; a return pipe for returning liquid to the down-comer shaft; and an
gas intake for
introducing gas from the evaporating heat exchanger into liquid prior to or
near when the liquid
enters the down-comer shaft.
[0029] In one embodiment, the gas is a refrigerant, such as R22 or R1 34a.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] 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:
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[0031] FIG. 1 is a schematic diagram of a hydraulic gas compressor;
[0032] FIG. 2 is a schematic diagram of a hydraulic gas compressor
according to an
embodiment of the present invention;
[0033] FIG. 3 is a schematic diagram of a hydraulic gas compressor
according to an
embodiment of the present invention;
[0034] FIG. 4 is a schematic diagram of a hydraulic gas compressor
according to an
embodiment of the present invention;
[0035] FIGs. 5a-f are schematic diagrams of hydraulic gas compressors
according to an
embodiment of the present invention;
[0036] FIGs. 6a-c are schematic diagrams of hydraulic gas compressors
according to an
embodiment of the present invention; and
[0037] FIG. 7 is a schematic diagram of minimum work vapour compression
refrigerator
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.
[0038] The present invention relates to hydraulic gas compressors (HGCs),
such as those
developed by Charles Taylor in the late 1800's. As shown in FIG. 1, an HGC 1
includes a down-
comer shaft 2, having a 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-comer 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 surface of the earth. The length of the riser shaft 8 can vary depending
on the amount of gas
compression desired. The deeper into the earth that the chamber 6 is
positioned, thus extending
the length of the riser shaft 2, the greater the compression of the gas.
Depths of 100m or more
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produce sufficient compression to allow for the compressed gas to be used in
industrial
applications.
[0039] In operation, the chamber 6 houses a combination of compressed gas
and liquid,
mostly in the form of water. The compressed gas can be exhausted through a
compressed gas
outlet 7, which is interconnected with a network that is capable of
transporting the compressed
gas to one or more endpoints, which will be discussed in further detail below.
An riser shaft 8
having an inlet 9 connected to the chamber 6 and an outlet 10 in fluid
communication with a
surface body 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 feeds
the down-comer 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-comer shaft 2. If the 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.
[0040] It should be noted that the hydraulic gas compressors described
herein are not just
used to compress air and that other gases can be compressed by such hydraulic
gas compressors.
For the purposes of the present discussion, "air" and "gas" are used
interchangeably herein to
describe the same element. For example, but not limited to, methane (natural
gas) could be used
in the hydraulic gas compressor of the present invention. Moreover, in closed
loop applications,
the gas could be in the form of refrigerants, such as, but not limited to, R22
or R1 34a. 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.
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[0041] In one embodiment, the compressed gas exhausted by the HGC 1 could
be used to
reduce the temperature of air flowing to a mine (FIG. 4). In this case, the
compressed gas outlet
directly or indirectly, depending on whether the compressed gas 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 gas from HGC 1 in an ideal device that could
expand the gas
isentropically would produce a 3.8 kg/s stream of -126.1 C compressed gas 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.
[0042] As well as cooling the air, compressed gas introduced into the
ventilation air from
the HGC 1 can pass through a nozzle to a mine airway shaped similarly to 135
in Figure 4, such
that this embodiment could act as an integrated mine air cooler and mine air
booster fan.
[0043] In another embodiment, the concept of the HGC is provided as a
closed loop
HGC 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 gas 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 air
is drawn into the
system through the gas inlet 112.
[0044] The mixture of gas and water travels down the down-comer 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, 02 in
the air will be
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dissolved in the water and the N2 will be compressed and released in the form
of gas at the
compressed gas outlet 123 attached to the gas-liquid separator system 122.
[0045] The N2 gas exhausted from the high pressure gas-liquid separator
system 122 can
be transferred to air intake ventilation shaft of the mine. A receiver vessel
60 may be 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 gas
compressed outlet 123 terminates at or near the entrance of the venturi jet
pump 135 allowing for
the atmospheric air to be enriched with compressed N2.
[0046] 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
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.
[0047] 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 N2,
this gas can be added to the atmospheric air being drawn into air intake
ventilation shaft 30 to
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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.
[0048] Water exiting the second gas-liquid separator 150 enters back into
the system via
pump 110.
[0049] 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.
[0050] In another embodiment, the gaseous mixture passing through gas
intake 5 comes
from an exhaust outlet 20 from a plant 21 (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 NO,
SO2, and possibly
unburnt 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
[0051] When the combustion gas bubbles come into contact with the water
in the down-
comer 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.
[0052] Henry's Law (see for example, the useful compilation of Henry's
Law constants
in Sander, 1999, http://www.henrys-law.org or Battino etal., J. Phys. Chem.
Ref Data 13(2):563-
600, 1984, both of which are incorporated herein by reference) governing the
pressure solubility
of gases can be described:
p, = K,x,
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
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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. A
detailed analysis of
the pressure solubility of gases is presented in Millar D, "A review of the
case for modern-day
adoption of hydraulic air compressors" Applied Thermal Engineering 69: 55-77,
2014, the
complete contents of which is incorporated herein by reference.
[0053] A gas-liquid separation system 22 provided at the outlet 4 of the
down-comer
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
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.
[0054] 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.
[0055} 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
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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.
[0056] Gas dissolved in the water that is separated at depth provides a
mechanism for
compressed gas to escape the receiver plenum. The leakage has a direct bearing
on the
mechanical efficiency of the installation for air compression. For closed and
open loop systems
one means to mitigate the portion of the loss of efficiency that arises due to
gas solubility is to
consider the use of a co-solute. In general, the prior presence of a dissolved
salt in water leads to
reduced gas solubility; gas solubility reduces as the dissolved salt
concentration increases. For
example, sodium sulphate could be added to the circulating water of an open or
closed loop
HAC.
[0057] For closed loop HAC systems, a second means to mitigate efficiency
loss due to
solubility is to operate these systems at higher temperature than previously
considered for run-of-
river systems. In one embodiment, within a closed loop HAC, water circulating
in insulated pipe
work will gradually rise in temperature as a result of the heat transferred to
it during the
compression of the gas.
[0058] 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.
[0059] 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),
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about half that of N2, meaning that it is about twice as soluble in water as
N2. The bulk of the 02
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 HGC,
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, HGCs would be deployed in
cascades.
[0060] 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 HGCs.
[0061] Regulators, valves, switches and the like can be positioned at
various spots along
the HGC 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.
[0062] The concept of the closed-loop HGC 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 gas that
is separated
from the water in the gas-liquid separator 201 is exhausted from the gas-
liquid separator 201 by
compressed gas delivery pipe 203. Compressed gas 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-corner shaft 202, it passes through venturi injector
205, where gas is
reintroduced into the system at gas inlet 206. Low-pressure gas accumulated in
the borehole 200
can be exhausted by exhaust outlet 207.
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[0063] 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
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-comer
shaft 202. Gas is injected into this system by gas 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-corner
shaft 202 are shown in FIGs. 5e and 5f. In these arrangements, the water can
be delivered to
another watercourse or used for some other purpose.
[0064] 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.
[0065] In yet a further embodiment, the HGC described above is modified
to act as a
minimum work vapour compression refrigerator 400 (FIG. 7). The HGC loop shown
in FIG. 7,
is essentially the same loop as shown for deep mine cooling applications (see
FIG. 4). In the
minimum work vapour compression refrigerator shown in FIG. 7, the compressed
gas that leaves
the gas-liquid separator 422 is passed through what would be otherwise known
as a conventional
mechanical vapour compression refrigeration circuit, including condenser 453,
evaporator 454
and expansion valve 455. The gas used in this system is typically a
refrigerant, such as R22 or
R134a. The various reference numerals shown in FIG. 7 correspond to equivalent
elements in
FIG. 4.
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[0066] 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.
