CA2818357A1

CA2818357A1 - Hydraulic air compressor applications

Info

Publication number: CA2818357A1
Application number: CA2818357A
Authority: CA
Inventors: Dean Millar
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-06-10
Filing date: 2013-06-10
Publication date: 2014-12-10
Also published as: EA201592258A1; CN105408701A; ZA201509136B; US20160115790A1; WO2014197968A1; EA030079B1; AU2014280794B2; EP3008400A1; CN105408701B; AU2014280794A1; CA2914433A1

Description

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.

[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 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;

[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 =
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.

[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 =
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 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 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 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 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.

Claims

CLAIMS:

1. Use of a hydraulic air compressor for cooling an underground mine, wherein compressed air produced by the hydraulic air compressor is mixed with the airstream of an air intake ventilation shaft of an underground mine to lower the temperature of the airstream.

2. A method for cooling an underground mine, comprising supplying compressed air from a hydraulic air compressor to an airstream of an air intake ventilation shaft of an underground mine to lower the temperature of the airstream.

3. A system for cooling an underground mine, comprising:
an air intake ventilation shaft for delivering an airstream to an underground mine; and an hydraulic air compressor for supplying compressed air to the airstream of the ventilation shaft, whereby mixing the compressed air with the airstream decreases the overall temperature of the airstream.

4. A system for cooling a deep underground mine, comprising:
an hydraulic air compressor positioned at a depth greater than about 100 m underground;
an air inlet for introducing atmospheric air into water prior to or once the water enters a down-corner shaft;
a first gas-liquid separator at the outlet of the down-corner shaft for exhausting a first compressed gas into an air intake ventilation shaft or drift 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.

5. A method for separating chemical compounds from gaseous mixtures such as the exhaust gases of fossil fuelled power plant, the method comprises the steps of:

introducing the gaseous mixture into a down-comer shaft of a hydraulic air compressor to isothermally compress a two-phase mixture of gas and liquid;
removing the non-dissolved gaseous phase of the two-phase mixture at the outlet of the down-corner shaft;
isothermally depressurising the liquid portion of the two-phase mixture to cause the previously dissolved chemical compounds to come out of solution thereform; and exhausting the previously dissolved chemical compounds, or separating them from the liquid phase.

6. A system for separating chemical compounds from an exhaust gas, comprising:
an hydraulic air compressor comprising 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;
a connection from the source of the gaseous mixture to be separated to the HAC;
a compressed gas outlet connected to the gas-liquid separator for separated compressed gas separated from the two phase flow produced by the mixture of liquid and the gaseous mixture in the down-corner shaft; and a secondary outlet positioned near or in conjunction with the outlet of the riser shaft for exhausting or separating isothermally decompressed gas from the mixture of liquid and gas that was previously dissolved in the liquid.

7. A method for cooling a building, comprising 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.

8. A domestic air conditioner system, comprising:
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-comer shaft; and an air intake for introducing air into liquid prior to or near when the liquid enters the down-comer shaft.