EP2746641B1

EP2746641B1 - Compression and cooling of a gas

Info

Publication number: EP2746641B1
Application number: EP12198468.6A
Authority: EP
Inventors: Jan Silfwerbrand; Olle Ljungberg
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2012-12-20
Filing date: 2012-12-20
Publication date: 2015-08-05
Anticipated expiration: 2032-12-20
Also published as: EP2746641A1; HUE025791T2; ES2550332T3; PL2746641T3

Description

Technical field

The present invention relates to a method of treating a gas, the method comprising one or more compression step(s) in which a pressurised drive gas actuates a piston which compresses the gas, a cooling step in which expanded drive gas cools the compressed gas, and a filling step in which the cooled compressed gas, or a condensate thereof, is filled on a receiving gas cylinder. The present invention also relates to a method of recovering a gas, in which the gas is treated with the aforementioned method of treating a gas, to a gas compression system, and to a use of an expanded drive gas from a gas compression device utilizing a pressurised drive gas for providing a compressed gas.

Background art

A pneumatically driven gas booster is a compressor comprising a compression chamber for the gas to be compressed, a work chamber for a pressurised drive gas, typically pressurised air, and a piston actuated by the pressurised drive air and compressing the gas in the compression chamber. In order to obtain a desirably high pressure increase of the gas to be compressed, pressurised air in the work chamber exerts its pressure on a large area air piston coupled by a connecting rod to a small area gas piston compressing the gas in the compression chamber. The compression and work chambers are provided with valves controlling the flows of drive air and gas to be compressed, respectively, and allowing reciprocating action of the coupled air and gas pistons. Cooling of the gas booster may be provided by routing cold expanded drive gas through a jacket surrounding the compression chamber.
Gases may be stored and distributed at high pressure, or in liquid (condensed) form, in gas cylinders. Filling a gas cylinder with a gas to a high pressure may involve raising the pressure of the gas with a gas booster. The temperature increase of the gas being a result of compression of the gas in the gas booster is, however, generally undesirable when filling a gas cylinder to a nominal filling pressure defined at a predetermined temperature, such as room temperature. Liquefying a gas before filling it on a gas cylinder may involve raising the pressure of the gas with a gas booster and subsequently condensing the pressurised gas by cooling of said gas. In this case, the temperature increase of the gas being a result of compression of the gas in the gas booster negatively affects the efficiency of the subsequent cooling aiming at condensation of the compressed gas.
DE 10 2006 039 616 B3 discloses a method in which compressed fuel gas is divided into a first martial gas stream and a second partial gas stream. The first partial gas stream is expanded by means of a work machine, in particular an expansion turbine. The second partial gas stream is compressed by means of a compressor, which is driven by means of the at least one work machine. Heat, which is generated in the second partial gas stream by the compression thereof, is dissipated and is used for heating the first partial gas stream . Liquefied fuel gas is stored in a heat-insulated container.

Summary of the invention

An object of the present invention is to alleviate the abovementioned disadvantages related to the temperature increase of the gas being a result of compression of the gas. As is reflected by the appended claims, the invention is based on the utilization of a hitherto unidentified cooling capacity of expanded drive gas from a gas booster to match downstream cooling requirements of the gas compressed by the gas booster.
This object as well as other objects of the invention, which should be apparent to a person skilled in the art after having studied the description below, is thus accomplished by a method of treating a gas, the method comprising
one or more compression step(s) preceding, in the direction of flow of the gas, filling of the gas, or a condensate thereof, on a gas cylinder, in which compression step(s) the gas is passed to a compression chamber, a pressurised drive gas is passed to a work chamber, the pressurised drive gas in the work chamber actuates a piston which compresses the gas in the compression chamber, the compressed gas is discharged from the compression chamber, and the pressurised drive gas is discharged from the work chamber and expands,
a cooling step for cooling with expanded drive gas in which cooling step the discharged compressed gas from the last, in the direction of flow of the gas, of the one or more compression step(s) is brought in indirect heat exchange contact with the expanded drive gas from at least one of said compression step(s), and heat is transferred from the compressed gas to the drive gas, thereby cooling the compressed gas, and
a filling step in which the cooled compressed gas, or a condensate thereof, is filled on a receiving gas cylinder.
The gas to be treated may be any gas that is stored and distributed on gas cylinders, e.g. a gas having industrial or medical application, such as carbon monoxide, nitrogen monoxide, acetylene, methane, nitrogen, oxygen, carbon dioxide, neon, xenon, nitrous oxide or helium, or a mixture thereof.
A "compression step" as used herein refers to a step for compression of the gas to be treated. A "compression step" as used herein may be performed in a gas booster as disclosed in the background section above. The pressure of the gas to be treated may be increased in one compression step or in more than one compression step, such as in two, three or more, typically serial, compression steps. In the case of serial compression steps, the gas to be treated is treated sequentially by said compression steps, thereby increasing its pressure in several steps. The pressurised drive gas is typically pressurised air. Compression of the gas to be treated, i.e. the gas in the compression chamber, may cause said gas to warm. Expansion of discharged drive gas may cause the discharged drive gas to cool.
A "cooling step" as used herein refers to a step for cooling of the gas to be treated. The phrase "indirect heat exchange contact" as used herein refers to a contact between two fluids allowing heat transfer, but not mass transfer, between the fluids. In the cooling step for cooling with expanded drive gas, the discharged compressed gas may be brought in indirect heat exchange contact with the expanded drive gas by passing the respective gases through a heat exchanger, such as a double-walled pipe, as laid out below. Indirect heat exchange contact between warm compressed gas and cold drive gas results in heat transfer from the compressed gas to the drive gas and thus to cooling of the compressed gas. Compressed gas that has been treated in more than one compression step may be cooled in the cooling step for cooling with expanded drive gas by expanded drive gas from any of said compression steps.
In the filling step, gas that has been compressed in the one or more compression step(s) and cooled in the cooling step for cooling with expanded drive gas may be filled on a receiving gas cylinder. Alternatively, a condensate of a gas that has been compressed in the one or more compression step(s) and cooled in the cooling step for cooling with expanded drive gas may be filled on a receiving gas cylinder. A "gas cylinder" as used herein refers to a pressure vessel, which may be stationary or portable. The gas cylinder may be one of a bundle of gas cylinders, i.e. one of several, such as 4, 8 or 12, aggregate gas cylinders sharing a common charge/discharge manifold. The gas cylinder may thus be arranged to store and/or to distribute the compressed and cooled, and optionally condensed, gas.
In other words, the method may be devoid of compression step(s) of the abovementioned kind between treatment of the discharged compressed gas in the cooling step for cooling with expanded drive gas and treatment of the cooled compressed gas, or the condensate thereof, in the filling step. The phrase "compression step(s) of the abovementioned kind" as used herein refers to the compression step(s) initially mentioned in the above description of the present method, i.e. to compression step(s) in which a gas is passed to a compression chamber, a pressurised drive gas is passed to a work chamber, the pressurised drive gas in the work chamber actuates a piston which compresses the gas in the compression chamber, the compressed gas is discharged from the compression chamber, and the pressurised drive gas is discharged from the work chamber and expands. That the present method "is devoid of compression step(s) of the abovementioned kind between treatment of the discharged compressed gas in the cooling step for cooling with expanded drive gas and treatment of the cooled compressed gas, or the condensate thereof, in the filling step" thus means that the gas to be treated, after having been initially compressed by the one or more compression step(s) and cooled in the cooling step for cooling with expanded drive gas, is not further compressed in a way similar to the initial compression before said gas, or a condensate thereof, has been filled on a gas cylinder.
By the present method, a hitherto unidentified cooling capacity of expanded drive gas from a compression step driven by a compressed drive gas is utilized to decrease the temperature of compressed gas resulting from a compression step driven by a compressed drive gas. The heat increase of a gas resulting from compression thereof may accordingly be efficiently counteracted, thereby facilitating filling of a gas cylinder with the compressed gas to a nominal filling pressure defined at a predetermined temperature or matching other downstream cooling requirements of the compressed gas.
The method is operable within a large pressure range and may, as an example, be used for increasing the pressure of a gas from a lower pressure within the range of about 0.1-200 bar(g) to a higher pressure within said range. Typically, each compression step provides a fivefold to twentyfold pressure increase, such as a tenfold pressure increase, within said pressure range. As used throughout this text, the abbreviation "bar(g)" is to be understood as "bar (gauge)", i.e. as a unit of gauge pressure identifying the pressure in bars above atmospheric pressure.
A suitable application of the method is the filling of a receiving gas cylinder with a gas from a supplying gas cylinder, the gas pressure of the supplying gas cylinder being lower than the gas pressure of the receiving gas cylinder. Such filling, from a lower pressure gas cylinder to a higher pressure gas cylinder, allows for a more complete emptying of the supplying gas cylinder, and thus for more efficient use of the gas, than if a filling operation is to be discontinued as soon as the gas pressure of the supplying gas cylinder falls below the gas pressure of the receiving gas cylinder. One embodiment of this application relates to the preparation of gas mixtures, specifically when a component of a gas mixture is to be added from a supplying gas cylinder at a lower pressure, to another gas component already present in the receiving gas cylinder at a higher pressure. Such gas mixtures may be used for medical purposes. Examples of such medical gas mixtures are a mixture of nitrous oxide and oxygen (such as about 50 % N₂O and about 50 % O₂, provided under the names of Medimix® and Livopan®), a mixture of carbon monoxide, acetylene, methane and oxygen in nitrogen (such as about 0.3 % CO, about 0.3 % C₂H₂, about 0.3 % CH₄ and about 20.9 % O₂ in N₂, used as a lung test gas), a mixture of carbon monoxide, helium and oxygen in nitrogen (such as about 0.28 % CO, about 9.3 % He and about 20.9 % O₂ in N₂, used as a lung test gas) and a mixture of nitrogen monoxide in nitrogen (such as 400 ppm NO in N₂, provided under the name of INOmax®).
The method may further comprise a cooling step for further cooling in which the compressed gas from the cooling step for cooling with expanded drive gas is brought in indirect heat exchange contact with a cooling medium, thereby further cooling the compressed gas before treatment thereof in the filling step. The term "cooling step" and the phrase "indirect heat exchange contact" have their abovementioned meanings. In the cooling step for further cooling the cooling medium may be any fluid colder than the compressed gas to be further cooled. Alternatively, the cooling medium may be any fluid colder than the compressed gas but for an expanded drive gas from the one or more compression step(s). A suitable cooling medium is water. In the cooling step for further cooling, the compressed gas from the cooling step for cooling with expanded drive gas may be brought in indirect heat exchange contact with the cooling medium by use of a heat exchanger, e.g. by passing the compressed gas through a pipe being arranged in a vessel comprising the cooling medium, as laid out below. Indirect heat exchange contact between the compressed gas and the cooling medium results in heat transfer from the gas to the cooling medium, and thus to further cooling of the compressed gas. When a cooling step for further cooling is present to fulfil any downstream cooling requirement of the compressed gas, the cooling capacity requirements on such a cooling step for further cooling are advantageously eased by the cooling step for cooling with expanded drive gas of the present method.
The compressed gas may be condensed in the cooling step for further cooling and the condensate may be filled on the receiving gas cylinder in the filling step. It is preferred to store and distribute certain gases, such as nitrous oxide, in liquid form. The cooling step for further cooling may in such a case serve to condense, i.e. liquefy, the compressed gas. By cooling in the cooling step for further cooling the compressed gas to, or below, its condensation point, as obtainable from handbooks or routine experimentation, for the gas in question at the relevant pressure, the gas may be condensed. When the cooling step for further cooling is present to liquefy the compressed gas in preparation for filling of the gas cylinder with a condensate of the gas, the cooling capacity requirements on such a cooling step for further cooling is advantageously eased by the cooling step for cooling with expanded drive gas of the present method.
In the cooling step for cooling with expanded drive gas the discharged compressed gas from each of the compression steps may be brought in indirect heat exchange contact with the expanded drive gas from each respective compression step. In the case of serial compression steps, the expanded drive gas from the last, as seen by the gas to be treated, compression step of the series is the expanded drive gas with which the compressed gas from the compression steps is brought in contact in the cooling step for cooling with expanded drive gas. Accordingly, it is the expanded drive gas from the last compression step that provides the hitherto unidentified cooling capacity that is utilized to facilitate filling of a gas cylinder with the compressed gas to a nominal filling pressure defined at a predetermined temperature or matching other downstream cooling requirements of the compressed gas.
The objects of the invention are also accomplished by a method of recovering a gas, in which the gas is provided from a supplying gas cylinder and is treated with the method presented above. Gas cylinders returned by end-users to a gas provider or gas producer for refilling typically contains a residual amount of gas at low pressure. In the case of gases distributed in liquid (condensed) form, returned gas cylinders may contain a residual amount of gas in liquid form. For economical and/or environmental reasons it may be of interest to recover such residual amounts of gas. As an example, environmental concern calls for recovery of nitrous oxide. As another example, it may be desirable to recover expensive gases such as helium. The "supplying gas cylinder" as used herein may refer to a gas cylinder containing a gas to be recovered at 10 % or less of the nominal filling pressure of said gas cylinder. Alternatively, the "supplying gas cylinder" as used herein may refer to a gas cylinder containing a gas in liquid form at 10 % or less of the nominal filling weight of said gas cylinder. The term "gas cylinder" has its abovementioned meaning. In the method for recovering a gas, the hitherto unidentified cooling capacity of said expanded drive gas is utilized to decrease the temperature of compressed gas originating from a supplying gas cylinder, thereby facilitating filling of a receiving gas cylinder with the compressed gas to a nominal filling pressure defined at a predetermined temperature or matching other downstream cooling requirements of the compressed gas. The methods allows for recovery of gases that would otherwise have been emitted to the atmosphere, leading to environmental issues or economical loss.
For environmental concerns it is preferred to recover nitrous oxide. In the one or more compression step(s) the pressure of the nitrous oxide may be raised from about 0.1-20, preferably 0.1-10, bar(g), which may represent the pressure of the nitrous oxide in the supplying gas cylinder, to about 50-75 bar(g). It is preferred to treat the nitrous oxide in two serial compression steps. In the case that the nitrous oxide is treated in two serial compression steps, the first compression step may rise the pressure of the nitrous oxide from about 0,1-20, preferably 0.1-10, bar(g) to about 10-50 bar(g) and the second compression step may raise the pressure further from about 10-50 bar(g) to about 50-75 bar(g). In the case that the nitrous oxide is treated in two serial compression steps, it is the expanded drive gas from the second compression step that provides the hitherto unidentified cooling capacity that is utilized to match downstream cooling requirements of the nitrous oxide.
In the cooling step for cooling with expanded drive gas the temperature of the nitrous oxide may be lowered from about 50-60 °C to about 20-30 °C. It thus becomes evident that the method provides a significant temperature decrease of the compressed nitrous oxide and accordingly a significant ease of any downstream cooling requirements of the nitrous oxide.
Since nitrous oxide is commonly stored and distributed in liquid form, it is preferred that the method comprises a cooling step for further cooling as laid out above. The nitrous oxide may be condensed in said cooling step for further cooling and the condensed nitrous oxide may be filled on the receiving gas cylinder in the filling step. Condensation of the nitrous oxide in the cooling step for further cooling may be obtained by cooling the nitrous oxide to about 5-10 °C. Thus, nitrous oxide that has been compressed to about 50-75 bar(g) in the compression step(s) may be cooled to about 20-30 °C in the cooling step for cooling with expanded drive gas and be further cooled to about 5-10 °C in the cooling step for further cooling. The cooling medium utilized in the cooling step for further cooling for condensing the nitrous oxide may be water at about 3-8 °C.
The objects of the invention are also accomplished by a gas compression system comprising
one or more gas compression device(s) comprising a compression chamber arranged to receive a gas, a work chamber arranged to receive a pressurised drive gas, a piston arranged to be actuated by the pressurised drive gas in the work chamber and to compress the gas in the compression chamber,
an indirect heat exchanger for cooling with expanded drive gas arranged to allow heat transfer from a compressed gas from the last, in the direction of flow of the gas, of the one or more compression device(s) to an expanded drive gas from at least one of the compression device(s), and
a filling station arranged to receive a cooled gas, or a condensate thereof, from the indirect heat exchanger for cooling with expanded drive gas and to fill said gas or condensate on a gas cylinder.
A "compression device" as used herein may have any of the structural or functional features of a gas booster as disclosed in the background section above. The gas compression system may comprise more than one compression device, such as two, three or more compression devices, typically connected in series as seen by the gas to be compressed. In the case of serial compression devices, the gas to be compressed is compressed sequentially by said compression devices, thereby increasing its pressure in several steps.
An "indirect heat exchanger" as used herein refers to heat exchanger allowing heat transfer, but not mass transfer, between two fluids. The indirect heat exchanger for cooling with expanded drive gas may be arranged to allow compressed gas that has been compressed in more than one compression device to be cooled by expanded drive gas from any of said compression devices.
The filling station may be arranged to receive a cooled gas from the indirect heat exchanger for cooling with expanded drive gas and to fill said cooled gas on a gas cylinder. Alternatively, the filling station may be arranged to receive a condensate of a cooled gas from the indirect heat exchanger for cooling with expanded drive gas and to fill said condensate on a gas cylinder. The "gas cylinder" has its abovementioned meaning.
In other words, the one or more compression device(s) may be arranged upstream, in the direction of flow of the gas, of the filling station. Thus, the system may be devoid of such compression device(s), arranged to compress a gas, or a condensate thereof, flowing from the indirect heat exchanger for cooling with expanded drive gas to the filling station. The phrase "such compression device(s)" as used herein refers to the compression device(s) initially mentioned in the above description of the present system, i.e. to gas compression device(s) comprising a compression chamber arranged to receive a gas, a work chamber arranged to receive a pressurised drive gas, a piston arranged to be actuated by the pressurised drive gas in the work chamber and to compress the gas in the compression chamber. That the present method "is devoid of such compression device(s), arranged to compress a gas, or a condensate thereof, flowing from the indirect heat exchanger for cooling with expanded drive gas to the filling station" thus means that the gas to be compressed, after having been initially compressed by the one or more compression device(s) and cooled by the indirect heat exchanger for cooling with expanded drive gas, is not further compressed by a device similar to said initial compression device(s) before said gas, or a condensate thereof, has flowed to the filling station.
By the present system, a hitherto unidentified cooling capacity of expanded drive gas from a compression device driven by a compressed drive gas is utilized to decrease the temperature of compressed gas resulting from a compression device driven by a compressed drive gas. The heat increase of a gas resulting from compression thereof may accordingly be efficiently counteracted, thereby facilitating filling of a gas cylinder with the compressed gas to a nominal filling pressure defined at a predetermined temperature or matching other downstream cooling requirements of the compressed gas.
The indirect heat exchanger for cooling with expanded drive gas may comprise a double-walled pipe forming an inner and an outer fluid passage through the pipe. The double-walled pipe may be arranged to transport one of the compressed gas and the expanded drive gas through the inner fluid passage and the other through the outer fluid passage. Preferably, the double-walled pipe is arranged to transport the compressed gas through the inner fluid passage and the expanded drive gas through the outer fluid passage.
The system may further comprise an indirect heat exchanger for further cooling arranged to allow heat transfer from a cooled gas from the indirect heat exchanger for cooling with expanded drive gas to a cooling medium, and the filling station may be arranged to receive a cooled gas, or a condensate thereof from the indirect heat exchanger for further cooling and to fill said gas or condensate on a gas cylinder. When an indirect heat exchanger for further cooling is present to fulfil any downstream cooling requirement of the compressed gas, the cooling capacity requirements on such an indirect heat exchanger for further cooling are advantageously eased by the indirect heat exchanger for cooling with expanded drive gas of the present system.
The indirect heat exchanger for further cooling may comprise a pipe arranged to transport the compressed gas, the pipe being arranged in a vessel arranged to contain the cooling medium.
The objects of the invention are also accomplished by use of an expanded drive gas, from a gas compression device utilizing a pressurised drive gas for providing a compressed gas, in a subsequent handling of the compressed gas, as a cooling medium for cooling of the compressed gas prior to filling the compressed gas, or a condensate thereof, on a gas cylinder, the subsequent handling of the compressed gas prior to filling the compressed gas, or the condensate thereof, on the gas cylinder being devoid of further compression of the compressed gas by a gas compression device utilizing a pressurised drive gas for providing a compressed gas.
The gas compression device may have any of the structural or functional features of a gas booster as disclosed in the background section above. The drive gas may be air. By the present use, a hitherto unidentified cooling capacity of expanded drive gas from a compression device utilizing a compressed drive gas for providing a compressed gas is utilized to decrease the temperature of the compressed gas. The heat increase of a gas resulting from compression thereof may accordingly be efficiently counteracted, thereby facilitating filling of a gas cylinder with the compressed gas to a nominal filling pressure defined at a predetermined temperature or matching other downstream cooling requirements of the compressed gas.
The subsequent handling of the compressed gas may comprise further cooling of the compressed gas. The use of the expanded drive gas for cooling of the compressed gas contributes to lowering of the demands on such further cooling of the compressed gas.
The further cooling of the compressed gas may comprise condensation of the compressed gas. As mentioned above, it is desirable to store or distribute certain gases in liquid form. The use of the expanded drive gas for cooling of the compressed gas may thus advantageously be utilized for condensation of the compressed gas prior to filling the condensate on a gas cylinder.

Brief description of the drawing

Fig. 1 is schematic illustration of an exemplifying gas compression system according to the present invention.

Detailed description

Fig. 1 shows a gas compression system 1. The gas compression system 1 is arranged to recover and compress a gas present in residual amounts in gas cylinders 2. The gas compression system 1 comprises, as its main components, an emptying rack 4, compression devices 6 and 8, an indirect heat exchanger 10 for cooling with expanded drive gas, an indirect heat exchanger 12 for further cooling, and a filling station 14.
At the emptying rack 4, supplying gas cylinders 2 comprising residual amounts of a gas to be compressed may be connected. A vacuum pump 16 removes contaminating gases from the gas compression system 1 before gas from the gas cylinders 2 enters the system via the emptying rack 4.
Each of the compression devices 6 and 8, which are pneumatically driven gas boosters, has a compression chamber 18 for the gas to be compressed, a work chamber 20 for a pressurised drive gas, typically pressurised air 22, and a gas piston 24 actuated by the pressurised drive air and compressing the gas in the compression chamber 18. In order to obtain a desirably high pressure increase of the gas to be compressed, pressurised air in the work chamber 20 exerts its pressure on a large area air piston 26 coupled by a connecting rod 28 to the small area gas piston 24 compressing the gas in the compression chamber 18. The compression and work chambers are provided with valves controlling the flows of drive air and gas to be compressed, respectively, and allowing reciprocating action of the coupled air and gas pistons. Cold expanded drive air leaves the work chamber 20 via a pipe 29.
Gas from the gas cylinders 2 flows via the emptying rack 4 to the compression chamber 18 of the compression device 6. Compressed gas leaves the compression chamber 18 via a pipe 30. The compressed gas in the pipe 30 and the cold expanded drive air in the pipe 29 are brought in indirect heat exchange contact in an indirect heat exchanger 32. Cooled compressed gas is passed to the compression chamber of the compression device 8 via a pipe 34.
The compressed gas in pipe 34 flows to the compression chamber of the compression device 8. Compressed gas leaves the compression chamber via a pipe 36. The compressed gas in the pipe 36 and cold expanded drive air in a pipe 38 are brought in indirect heat exchange contact in the indirect heat exchanger 10 for cooling with expanded drive gas. Cooled compressed gas is passed to the indirect heat exchanger 12 for further cooling via a pipe 40.
The indirect heat exchanger 10 for cooling with expanded drive gas comprises a double-walled pipe forming an inner and an outer fluid passage through the pipe. The double-walled pipe is arranged to transport the compressed gas from the pipe 36 through the inner fluid passage and the expanded drive gas from the pipe 38 through the outer fluid passage. The indirect heat exchanger 32 is of a similar construction.
The indirect heat exchanger 12 for further cooling comprises a coiled pipe 42 arranged to transport the compressed gas from the pipe 40, the coiled pipe 42 being arranged in a vessel arranged to contain the cooling medium. The temperature of the cooling medium is controlled in a cooling circuit 44, schematically shown. During its passage through the indirect heat exchanger 12 for further cooling, the gas is condensed.
Condensed gas leaves the indirect heat exchanger 12 for further cooling and is passed to the filling station 14. At the filling station 14, receiving gas cylinders 46 may be connected. A vacuum pump 48 removes contaminating gases from the gas compression system 1 and from the gas cylinders 46 before condensed gas enters the gas cylinders via the filling station 14.
It is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims

A method of treating a gas, the method comprising
one or more compression step(s) preceding, in the direction of flow of the gas, filling of the gas, or a condensate thereof, into a gas cylinder, in which compression step(s) the gas is passed to a compression chamber, a pressurised drive gas is passed to a work chamber, the pressurised drive gas in the work chamber actuates a piston which compresses the gas in the compression chamber, the compressed gas is discharged from the compression chamber, and the pressurised drive gas is discharged from the work chamber and expands,
a cooling step for cooling with expanded drive gas, in which cooling step the discharged compressed gas from the last, in the direction of the flow of the gas, of the one or more compression step(s) is brought in indirect heat exchange contact with the expanded drive gas from at least one of said compression step(s), and heat is transferred from the compressed gas to the drive gas, thereby cooling the compressed gas, and
a filling step in which the cooled compressed gas, or a condensate thereof, is filled into a receiving gas cylinder.
The method according to claim 1, further comprising a cooling step for further cooling, in which the compressed gas from the cooling step for cooling with expanded drive gas is brought in indirect heat exchange contact with a cooling medium, thereby further cooling the compressed gas before treatment thereof in the filling step.
The method according to claim 2, wherein in the cooling step for further cooling the compressed gas is condensed and wherein in the filling step the condensate is filled on the receiving gas cylinder.
The method according to any one of the preceding claims, wherein in the cooling step for cooling with expanded drive gas step the discharged compressed gas from each of the compression steps is brought in indirect heat exchange contact with the expanded drive gas from each respective compression step.
A method of recovering a gas, preferably nitrous oxide, in which the gas is provided from a supplying gas cylinder and is treated with the method of any one of the preceding claims.
The method according to claim 5, wherein in the one or more compression step(s) the pressure of the nitrous oxide is raised from about 0.1-20 bar(g) to about 50-75 bar(g).
The method according to claim 6 or 7, wherein in the cooling step for cooling with expanded drive gas the temperature of the nitrous oxide is lowered from about 50-60 °C to about 20-30 °C.
The method according to any one of claims 5 to 7, wherein in the cooling step for further cooling the nitrous oxide is condensed and wherein in the filling step the condensed nitrous oxide is filled on the receiving gas cylinder.
A gas compression system (1) comprising
one or more gas compression device(s) (6, 8) comprising a compression chamber (18) arranged to receive a gas, a work chamber (20) arranged to receive a pressurised drive gas, a piston (24) arranged to be actuated by the pressurised drive gas in the work chamber and to compress the gas in the compression chamber,
an indirect heat exchanger (10) for cooling with expanded drive gas arranged to allow heat transfer from a compressed gas from the last, in the direction of flow of the gas, of the one or more compression device(s) to an expanded drive gas from at least one of the compression device(s), and
a filling station (14) arranged to receive a cooled gas, or a condensate thereof, from the indirect heat exchanger (10) for cooling with expanded drive gas and to fill said gas or condensate into a gas cylinder (46).
The system according to claim 9, wherein the indirect heat exchanger (10) for cooling with expanded drive gas comprises a double-walled pipe forming an inner and an outer fluid passage through the pipe, the double-walled pipe being arranged to transport one of the compressed gas and the expanded drive gas through the inner fluid passage and the other through the outer fluid passage.
The system according to claim 9 or 10, further comprising an indirect heat exchanger (12) for further cooling arranged to allow heat transfer from a cooled gas from the indirect heat exchanger for cooling with expanded drive gas to a cooling medium, and wherein the filling station is arranged to receive a cooled gas, or a condensate thereof from the indirect heat exchanger for further cooling and to fill said gas or condensate on a gas cylinder.
The system according to claim 11, wherein in the indirect heat exchanger (12) for further cooling comprises a pipe (42) arranged to transport the compressed gas, the pipe being arranged in a vessel arranged to contain the cooling medium.