GB2487790A

GB2487790A - Gas compressor using liquid

Info

Publication number: GB2487790A
Application number: GB1102004.7A
Authority: GB
Inventors: Amitava Roy
Original assignee: RE HYDROGEN Ltd
Current assignee: RE HYDROGEN LIMITED
Priority date: 2011-02-07
Filing date: 2011-02-07
Publication date: 2012-08-08
Also published as: CA2826231A1; GB201102004D0; CN103534490A; BR112013020137A2; EP2683947A1; WO2012107756A1; GB2487815A; KR20140051826A; JP2014507594A; GB201117540D0; US20130315818A1

Abstract

A gas compressor comprises an expandable liquid-filled bag 10 inside a pressure vessel 4. Filling and expanding the bag compresses a gas inside the pressure vessel, but outside the bag. The liquid is supplied from a tank 16 via a high pressure pump 21. Monitoring and control devices are provided for pressure, temperature, flow rate and fluid level. A nitrogen gas purging valve 8 may be provided. The liquid may be water or a hydraulic fluid. The gas may be hydrogen. The bag may be made of any flexible or composite material such as reinforced rubber or fibre reinforced plastic. As an alternative, the bag may be replaced with a mechanical piston inside the vessel, the piston being driven by liquid. As a further alternative, the liquid may be in direct contact with the gas, the rising column of liquid acting as a piston.

Description

Title: High pressure hydrogen gas compressor driven by water pump.

Background of the Invention:

1. Field of the invention

[0011 The present invention primarily relates to the compression of hydrogen gas and any other gaseous substance using high pressure water pump which is highly energy efficient due to near isothermal compression.

[002] The present invention provides a safe and leak tight gas compressor due to the use of water seal making it ideal for compression of explosive gases such as hydrogen.

[003] This invention allows a low pressure gas such as from atmospheric water electrolyser to increase the gas pressure significantly in a much more economical way than costly pressurised electrolysers or conventional hydrogen compressors.

[004] This new compressor has a significantly less number of parts thus lower capital cost compared to a centrifugal air compressor, piston type or a diaphragm type gas compressors.

[005] The flow rate of the smallest commercial hydrogen compressor available on the market is significantly greater than the rate of gas production by small electrolysers; for this reason a buffer tank is needed between the electrolyser and compressor to compensate for their mismatch; however this invention eliminates the need for any buffer tank of hydrogen gas as the flow rate of this compressor is the range from 10 cc per minutes to literally several hundred normal cubic meters per hour as this is depends on the flow rate of the water pump.

2. Description of the Prior Art

[006] The use of compressed air to pump water is well known in the prior art, which is the opposite of the cunent invention. The known prior art related to water pump using compressed air includes US Pat. No. 6,942,463 where a combination water pump and air compression system is disclosed for performing two separate functions with one unit by providing compressed and water.

[007] US Patent No 447 8,553 discusses isothermal compression using impeller blades to produce a mixture of compressed water and air.

[008] The use of water column to increase the air pressure is also known in the prior art in gas turbine and power plant based applications.

[009] The US patent No. 4797,563 discusses about a power plant where a water stream is used to create compressed air for the burners of a turbine without additional compression.

[010] The US Patent No. 5537,813 discusses about a method of increasing the operational capacity and efficiency of a combustion turbine system having a compressor, combustor and turbine generator by treatment of the inlet air prior to its introduction into the compressor; this is done by establishing a vertically descending flow of inlet air; introducing treatment water into the flow of inlet air to create downward velocity greater than that of the inlet air to create drag-induced pressure increase in the inlet air.

[011] Hydraulic air compressors have been in existence since approximately 1890 when they were used throughout North America and Europe to provide compressed air for mining camps.

[012] Prior Arts also include US Patent No. 543410, 543411, 543412, 618243, 892772, 199819, 3643426, 3797234, 4343569, 4391552.

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[013] While these prior arts fulfil their respective objectives for compression of air but none of these inventions are suitable for compression of hydrogen gas; the inflatable water bag was never used before inside a pressure vessel to prevent direct contact between water and the subjected gas to be compressed as per the current invention; the current invention is capable to produce hydrogen or any other gas up to 700 bar by using multiple stage compression at near isothermal compression at a higher efficiency.

[014] The present invention increases the efficiency, reduces the capital cost, lower the maintenance cost and it covers a very broad spectrum of operational range from very low flow rate to very high flow rate and wide range of operating

pressure which is not available in the prior art.

3. Summary of the Invention

[015] The main purpose of the present invention is to produce extremely low cost hydrogen gas compressors; however this inventions is also applicable for any other gasses.

[016] The present invention uses the inflatable water bag and the high pressure water pump to operate at near isothermal conditions to produce the highly efficiency gas compressor.

[017] This invention produces a gas compressor which comprises a bottom water tank, a high pressure water pump, at least one inflatable water bag installed inside of at least one pressure vessel, a gas inlet valve connected to the pressure vessel (s), a high pressure gas outlet purge valve connected to the pressure vessel (s), an inlet valve to the pressure vessel for nitrogen gas purging, a switchable atmospheric air vents located on top of the bottom water tank, a piping configuration and valve mechanism, the monitoring and control devices for pressure, temperature, flow rate and fluid level, non return valves installed after the high pressure gas-purge valve and after the outlet of the water pump, inline gas purity sensors, liquid condensing and separation unit, oxygen removal unit from hydrogen gas, gas drying unit and an electronic control system.

[018] The operating range of the compressor is from 10 mbar gauge pressure up to very high pressure such as 700 bar in multiple stages depending on the output pressure of the water pump and the volume of the pressure vessel.

[019] The flow rate of gas compressor is in the range of 10 cubic centimetre per minute to several hundreds normal cubic meter per hour.

[020] The operating temperature of the gas compressor is in the range from minus (-) 60°C to 200°C.

[021] The gas compressor uses any suitable liquid medium such as water, water-solvent mixture, antifreeze mixture, various solvents with high boiling point, hydraulic oil etc and suitable liquid pump as per the operating temperature, flow rate and operating pressure.

[022] The gas compressor has the optional nitrogen gas feed point to the pressure vessel to purge any gaseous substance from the system where hydrogen and other explosive gases are compressed instead of air or any other non combustible gasses.

[023] The gas compressor is connected to a source of gas to be compressed or it is directly connected to an electrolyser to compress hydrogen and oxygen gas.

[024] Water is pumped at high pressure into the inflatable water bag to occupy the internal space of the pressure vessel and subsequently pressurise the gas in the pressure vessel while keeping the switchable air vent on the inlet water pipe open to atmosphere; under this condition water does not come in contact with the subjected gas under compression in the pressure vessel.

[025] The internal shape and volume of the pressure vessel is identical to the external shape and volume of the inflatable water bag.

[026] As a variation of this invention, a mechanical piston is installed inside the vertically oriented pressure vessel instead of an inflatable water bag; and the mechanical piston is driven upward due to the back pressure created by the high pressure water pump.

[027] As a further variation of the cunent invention, the gas compressor has no inflatable water bag and no mechanical piston wherein the water is pumped into the vertically oriented pressure vessel by the water pump in direct contact with the gas; and the water seal and the rising water column acts as a hydraulic piston.

[028] The gas compressor has a liquid vapour condensing unit, a liquid separation unit, the oxygen removal unit in case of high purity hydrogen gas, a gas drier and

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a liquid absorption unit fitted after the gas outlet purge valve of the pressure vessel.

[029] The gas compressor has the gas sensor to detect the purity of gas which sends an electrical voltage and or current signal to the electronic control box. The compressed gas is vented to the atmosphere if the purity of the gas is not at a desired level or for any maintenance work.

[030] After the compressed gas is delivered to the supply line, the gas compressor prepares itself for the next compression cycle; it does so in a sequential method such as: i) Keep the switchable air vent open located at the bottom water tank, ii) Keep the outlet gas-purge valve closed iii) Close the inlet gas valve of the pressure vessel in closed position; [031] The higher gas pressure inside the pressure vessel will deflate the water bags; the gas compressor operates the multiple valves as per the above sequence to empty the water from the pressure vessel or from the inflatable water bag by pumping water back into the bottom water tank.

[032] For the next compression cycle, the gas is fed into the empty pressure vessel followed by pumping of water into the inflatable water bag or directly into the pressure vessel.

[033] The inflatable water bag of the gas compressor is mechanically supported inside the pressure vessel when inflated; and the differential pressure on the inflatable water bag is controlled within the safe operating pressure.

[034] The inflatable water bag and water seal of the gas compressor provide the necessary cooling of the compressed gas to provide near isothermal conditions at a higher efficiency than conventional mechanical gas compressors.

[035] The invention has been outlined broadly to cover the main features of the inventions by using inflatable water bag or air bag or any other inflatable device along with a water pump and other components as shown in Figure 1 and Table 1 and the conesponding valve sequence as shown in Table 2; it is understood that the invention is not limited to the configuration of Figure 1; the invention is capable to create several different configurations by re-ananging components of Figure 1 in different ways; it is also understood that the terminology and the phrases used to describe the invention can be rearranged to provide a broader scope of this invention.

[036] It is an object of the present invention to provide a new hydrogen compressor at an extremely low cost; this compressor is not sensitive to engineering tolerances in its manufacturing; this invention is also applicable for any other gasses too.

4. Brief description of the Drawings

[037] The invention will be better understood with reference to Figure 1 which is a schematic diagram of various components of this invention; the sample calculation as shown in Table 1 provides an example of the compression ratio but following the same principle different compression ratios will be achieved by changing the physical parameters of this inventions; Table 2 describes the sequence of valve control conesponding to Figure 1; there will be several ways to perform the operation using the same physical configuration and/or different configurations using the same components.

5. Description of the preferred embodiment

[038] While the present invention will be described more fully hereinafter with reference to the accompanying drawing in which aspects of the preferred manner of practicing the present invention are shown, it is to be understood at the outset of the description which follows that persons of skills in the appropriate arts may modify the invention herein described while still achieving the favourable results of this invention; accordingly the description which follows is to be understood as being a broad, teaching disclosure directed to persons of skill in the appropriate arts, and not as limiting up on the present invention.

[039] As best illustrated in Figure 1 the hydrogen gas is supplied to the compressor from the source of hydrogen gas via the adjoining pipe (1) and the valve-i (2) to the gas inlet port (3) of the pressure vessel number -1(4); the source of this hydrogen as shown in Figure 1 is the hydrogen-electrolyte tank (5) of the electrolyser stack (6).

[040] The hydrogen electrolyte tank has nitrogen gas inlet port (7) and the nitrogen gas purging valve (8).

[041] The pressure vessel number-i (4) has the gas outlet port (9); the inflatable water bag (10) securely fitted inside the pressure vessel by the leak free port (ii); the gas and water does not come in direct contact within the pressure vessel number-i (4); the pressure sensor (12), and the temperature sensor (13) is fitted into the pressure vessel number-i to monitor the inside pressure and temperature of the pressure vessel number-i.

[042] The inflatable water bag (10) is made of flexible materials such as reinforced rubber, composites, fibre reinforced plastic bags etc. The safe operating pressure of the inflatable water bag is about 10-15 bar and the design pressure is 25bar. The differential pressure between the inside and outside pressure of the fully inflated water bag never exceeds 15 bar because the water bag is supported when fully inflated by the wall of the pressure vessel; the physical volume change from the deflated to the inflated water bag is up to 20 times or even more; therefore the gas can be compressed up to 20 times by the fully inflated water bag resulting in 20 times increase in gas pressure inside the pressure vessel number-l (4).

[043] The inflatable water bag receives intake water from the bottom water tank (16) which has two level sensors for low level sensor (17) and high level sensor (18); the water tank has the air vent valve (19) fitted on the pipe (20) securely connected to the water tank; [044] The high pressure water pump (21) has the suction pipe (22) connected to the bottom water tank (16) securely fitted in place using the standard pipe fittings; the outlet pipe (23) from the water pump has a valve 2 (24) and a non return valve (25); after the non return valve (25) the outlet pipe (23) is connected to one port of the Tee Junction (26); the second port of the tee junction (26) facilitates the return flow of water in to the water tank (16) while bypassing the water pump (21) via the adjoining pipe (56) and valve 6 (55); the remaining port of the Tee junction (26) pumps water by an adjoining pipe (27) up to another Tee junction (28). The second port of the Tee Junction (28) is connected to the inflatable water bag to the leak free port (11) via the pressure regulator (29), the low pressure pipe (30) and the valve 3 (31).

[045] The pressure vessel number-1 (4) is securely connected to the leak free port (32) of the pressure vessel nurnber-2 (33) via an adjoining pipe (14) and the valve 4(14).

[046] The pressure vessel number-2 (33) has the gas outlet port (34); the inflatable water bag (35) is securely fitted inside the pressure vessel by the leak free port (36); the gas and water does not come in direct contact within the pressure vessel number-2 (33); the pressure sensor (37), and the temperature sensor (38) are fitted into the pressure vessel number-2 to monitor the inside pressure and temperature of the pressure vessel number-2 (33).

[047] The gas outlet port is connected to the high pressure gas delivery pipe (39) valve 7 (40), the non return valve (41).

[048] The water inlet port (32) of the inflatable water bag (35) of the pressure vessel number-2 (33) is connected to the remaining port of the Tee junction (28) via an adjoining pipe (42); the valve 5 (43) is securely fitted on the pipe (42) to control the flow of water in to the inflatable water bag (35).

[049] The gas purity sensor (44) is connected on the outlet pipe (39) after the non return valve (41) and joined to the Tee junction (45).

[050] the air vent (46) is connected to one of the ports of the Tee junction (45) by an adjoining pipe (49); the air vent valve (47) and the flame arrestor (48) is fitted on to the pipe (49); this air vent is used to vent gases to the atmosphere into a safe place for maintenance purpose and if the gas purity is not suitable.

[051] The remaining port of the Tee junction (45) is connected by an adjoining pipe (50) to the gas-water separator (51); [052] the de-oxo unit (52) is connected to produce high purity (99,999%) hydrogen; the drier (53) assembly is connected to produce very dry hydrogen gas i.e. up to -60°C dew point; the de-oxo unit (52) has palladium catalyst bed which helps the reaction between the traces of oxygen gas present in hydrogen gas with hydrogen itself to form water vapour at around 140°C; the pure moist hydrogen is then dried in the drier (53); the drier contains molecular sieve bed to produce very dry hydrogen gas.

[053] The non return valve (54) is fitted after the de-oxo drier.

Claims

6. Claim(s) A gas compressor comprising a bottom water tank, a high pressure water pump, at least one an inflatable water bag installed inside the pressure vessel, a gas inlet valve to the pressure vessel, a high pressure gas outlet purge valve from the pressure vessel, a nitrogen gas purging valve, switchable atmospheric air vents located on top of the bottom water tank, a piping configuration and valve mechanism, the monitoring and control devices for pressure, temperature, flow rate and fluid level, non return valves installed after the high pressure gas-purge valve and after the outlet of the water pump, inline gas sensors, liquid condensing and separation unit, oxygen removal unit from hydrogen gas, gas drying unit and an electronic control system.
2. A gas compressor in accordance with claim i, wherein nitrogen gas purging valve is connected to the pressure vessel or to the hydrogen electrolyte tank of the electrolyser; and the operating range of the compressor is from lOmbar gauge pressure up to 700 bar in multiple stages depending on the output pressure of the water pump and the volume of the pressure vessel.
3. A gas compressor in accordance with claiml, wherein a source of low pressure gas such as an atmospheric electrolyser device is connected to the pressure vessel.
4. A gas compressor in accordance with claiml, wherein the inflatable water bag occupies the internal space of the pressure vessel to pressurise the gas while keeping the switchable air vent on the inlet water pipe open to atmosphere; and the internal shape and volume of the pressure vessel is identical to the external shape and volume of the inflatable water bag.
5. A gas compressor in accordance with claiml, wherein water does not come in contact with the subjected gas under compression.
6. A gas compressor as a variation to the claim 1, has the mechanical piston installed inside the vertically oriented pressure vessels instead of an inflatable water bag; and the mechanical piston is driven upward due to the back pressure created by the high pressure water pump; As a further variation of claim 1, the gas compressor has no inflatable water bag and no mechanical piston wherein the water is pumped into the vertically oriented pressure vessel by the water pump in direct contact with the gas; and the water seal and the rising water column acts as a hydraulic piston.
7. A gas compressor as a variation to claim 1, and in accordance to claim 6 does not have a source of nitrogen gas for purging air, wherein water is filled up to the outlet of the pressure vessel to purge any air from the system.
8. A gas compressor in accordance with any preceding claim dependent on claim 4 and claim 6, the outlet gas purge valve delivers compressed gas or a compressed mixture of gases.
9. A gas compressor in accordance with claim 6, wherein a liquid vapour condensing unit, a liquid separation unit, an oxygen removal unit, a gas drier and a liquid absorption unit are fitted after the gas outlet purge valve of the pressure vessel.
10. A gas compressor in accordance with claim 9, wherein the gas sensor detects the purity of gas and sends an electrical voltage and or current signal to the electronic control box.
11. A gas compressor in accordance with claim 10, wherein the compressed gas is vented to the atmosphere if the purity of the gas is not at a desired level or for any maintenance work.
12. A gas compressor in accordance with any preceding claims, wherein the switchable air vent is open, the outlet gas-purge valve and the inlet gas valve of the pressure vessel are closed allowing the water level to fall under differential pressure from the inflatable water bag or from the pressure vessel itself into the bottom water tank.
13. A method of operation of the gas compressor in accordance with claim 12, wherein the multiple valves system facilitates the emptying of water from the pressure vessel or the inflatable water bag by active pumping of water back into the bottom water tank.
14. A method of operation of the gas compressor in accordance with claim 13, wherein the subjected gas to be compressed is fed into the empty pressure vessel followed by compression by pumping water into the inflatable water bag or directly into the pressure vessel.
15. A gas compressor in accordance with claim 1, wherein any non compressive liquid or hydraulic fluid can be used instead of water.
16. The gas compressor in accordance with claim 1, uses an inflatable water bag made of any flexible or composite materials such as reinforced rubber, fibre reinforced plastic etc.
17. The gas compressor in accordance with claim 1 and any preceding claims uses an inflatable air bag made of any flexible or composite materials instead of water bag for the same purpose of compressing the subjected gas.
18. The gas compressor in accordance with claimi, wherein the gas is pressurised up to 700 bar in multiple stages depending on the capacity of the water pump.
19. A gas compressor in accordance with claim 4, wherein the inflatable water bag is mechanically supported inside the pressure vessel when inflated; and the differential pressure on the inflatable water bag or air bag is controlled within the safe operating pressure.
20. The gas compressor, in accordance with claim 1 and any preceding claim, wherein the greater contact area with the gas as provided by the inflatable water bag and water seal ensures faster cooling of the gas at near isothermal condition thus higher efficiency than conventional mechanical gas compressors.
21. A gas compressor in accordance with claim 1 and any preceding claim, the flow rate of the gas to be compressed is in the range of 10 cubic centimetre per minute to several hundreds normal cubic meter per hour.
22. A gas compressor in accordance with claim I and any preceding claim, has an operating temperature in the range from minus (-) 60°C to 200°C; and in accordance with claim 15, the liquid medium and liquid pump is selected as per the optimum operating temperature, flow rate and operating pressure.
23. A gas compressor directly coupled with an atmospheric electrolyser, wherein the de-oxo-drier removes the traces of oxygen gas present in hydrogen gas followed by gas drying.