US2764877A - Apparatus for liquefying air - Google Patents

Apparatus for liquefying air Download PDF

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US2764877A
US2764877A US217203A US21720351A US2764877A US 2764877 A US2764877 A US 2764877A US 217203 A US217203 A US 217203A US 21720351 A US21720351 A US 21720351A US 2764877 A US2764877 A US 2764877A
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gas
cold
cooled
liquid
cooling
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Kohler Jacob Willem Laurens
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Hartford National Bank and Trust Co
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
    • F25J1/0208—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle in combination with an internal quasi-closed refrigeration loop, e.g. with deep flash recycle loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0012—Primary atmospheric gases, e.g. air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/004—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by flash gas recovery
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration

Definitions

  • This invention relates to methods of cooling gases to a temperature comprised in the co-existence range of the gas to be cooled, so that at least part of the gas becomes liquid.
  • the object of the present invention is to provide a method by which a gas can be cooled to a temperature comprised in the co-existence range of the gas to be cooled, the output of the installation being many times higher than that of the systems described above, the installation itself having a small volume compared with known installations.
  • a quantity of compressed gas is cooled, after which this cooled gas is cooled further by means of the cold produced by the cold-gas cooling machine operating on the reversed hot-gas reciprocating engine principle, liquid being thus formed, after which the medium produced during the last-mentioned cooling process undergoes a decrease in pressure, the first-mentioned cooling process being carried out with the use of cold from the gas cooled by this method.
  • cold-gas cooling machine operating on the reversed hot-gas engine principle is to be understood here to mean a machine in which mechanical energy is converted into thermal energy and in which a medium of invariable chemical composition, which is constantly in the gaseous phase, traverses an open or closed thermodynamic cycle in at least two intercommunicating chambers or chamber parts of ditferent temperatures, expansion of this medium primarily taking place in one or in a few of these chambers or chamber parts and compression in one or a few of the other chambers or chamber parts respectively, said machine comprising means to carry off heat to the exterior during compression and/or to supply heat from the exterior during expansion.
  • the medium produced during the cooling by the coldgas cooling machine may be either exclusively liquid or a mixture of gas and liquid.
  • a quantity of compressed gas is cooled by a smaller quantity of this gas flowing back and having a lower pressure, after which this cooled gas is cooled further by means of the cold produced by a coldgas cooling machine operating on the reversed hotgas reciprocating engine principle, liquid being thus formed, whereafter the medium produced during the last-mentioned cooling process undergoes a decrease in pressure, the residual gas performing the first-mentioned cooling of the compressed gas.
  • a quantity of compressed gas which is to be distinguished is cooled by a quantity of gas flowing back after which this cooled gas is cooled further by means of the cold-gas cooling machine, liquid being thus formed, whereafter the medium produced during the latter cooling process undergoes a decrease in pressure and is separated into the desired constituents, at least one of the constituents performing the first-mentioned cooling of the gas to be disintegrated into constituents.
  • the medium after it has been formed by means of the cold produced by the cold-gas cooling machine is cooled further with the use of cold obtained from the gas cooled by a method according to the invention, while the cooling of the compressed gas, before being cooled with the use of the cold-gascooling machine, is likewise performed by means of cold obtained from the cooled gas.
  • the pressure of the compressed gas is not more than the critical pressure of this gas. In the case of air, this means that the gas need be compressed to at most 40 atmospheres Since in the known installations described above, the gas is compressed to,'for example, 200 atmospheres, it will be evident that, owing to the low compression utilized in accordance with the invention, a material simplification of the installation is obtainable.
  • the invention may be successfully used more particularly if the compressed gas is cooled by means of the cold-gas cooling machine to a temperature located in the neighborhood of the point of intersection of the pressure line of this gas and the liquid limiting line of the coexistence range. This means that the compressed gas has become completely liquid, after it has been cooled with the use of the cold-gas cooling machine. If thereupon the liquid gas is caused to expand to 1 atmosphere, a new quantity of gas will be produced, it is true, but the quantity of liquid will nevertheless be comparatively large.
  • cold is abstracted from the working medium in the cold-gas cooling machine with the use of cold obtained from the cooled gas.
  • the installation adapted for carrying out the method described above has the feature that it comprises a heatexchanger in which the compressed gas is cooled, a coldgas cooling machine with the use of which this gas is cooled further, liquid being thus produced, and a device in which thereupon the pressure and, if desired, the temperature of the medium are decreased.
  • the device in which the pressure and, if necessary, the temperature of the gas are decreased may be constituted by -a choking device, out of which the liquid drops at a pressure of, for example, 1 atmosphere.
  • this device may be constituted by a tubular cooler, through which the medium is led. This tubular cooler is arranged in the container with the boiling liquid.
  • the liquid cooling the medium which may be either a liquid or a mixture of liquid and gas, starts boiling in the container owing to the heat supplied to the liquid from the tubular cooler.
  • the medium after it has been produced by means of a cold-gas cooling machine, is cooled in a heat exchanger.
  • the percentage of liquefied gas may be increased.
  • that portion of the gas which is finally not liquefied will serve as the cooling medium for this heat exchanger.
  • a gas containing admixtures When a gas containing admixtures is to be liquefied or fractionated into constituents, these admixtures becomnig liquid or solid at a higher temperature than the gas to be finally liquefied, itis desirable that the admixtures should preliminarily be removed from the gas.
  • Such a case will, for example, occur when nitrogen and oxygen are to be liquefied from the air.
  • the air comprises additionally water vapour and carbon dioxide.
  • these constituents should deposit themselves in a normal heat-exchanger, which may be, for example, a tubular cooler.
  • the constituents may be extracted from the gas by chemical washing of the gas.
  • the first heatexchanger in which the compressed gas is cooled, is constituted by a reversible regenerator or recuperator system.
  • the constituents of the gas liable to be deposited in this heat-exchanger may thus be periodically removed.
  • the change-over of the regenerator or recuperator system may be performed continuously or periodically.
  • This heat-exchanger may be successfully used more particularly if the quantity of gas, which flows back and which gives or cold to the compressed gas is large. This will generally be the case, if the installation is used for fractionating gases. According to one embodiment of the invention, this installation has the feature that the medium, after it has been subjected to its last cooling process, is fractionated into constituents in a fractionating apparatus.
  • Fig. 1 is a diagrammatical view of an installation for use with the method according to the invention
  • Fig. 2 shows the W-T diagram of this method and Fig. 3 is a diagrammatic view of a fractionatinginstallation according to the invention
  • Pig. 4 is a partially perspective view of a cold-gas cooling machine in accordance with the present invention.
  • a quantity of air is compressed to 20 atmospheres in a compressor 1. Then, this quantity of air is cooled under a constant pressure in a first heat-exchanger 2, for example, to 223 Kelvin. It enters into the heat-exchanger at and leaves it at 11.
  • the cooling medium is constituted by that portion of the gas which has finally not been liquefied. Then, the gas cooled to 223 Kelvin flows along the cold side 3 of a cold-gas cooling machine 4, which is driven by an electric motor. This cold-gas cooling machine operates on the reversed hot-gas engine principle.
  • the gas to be cooled flows directly through the heat-exchanger on the cold side of the cooling machine, it will in certain cases be desirable that the cooling of the gas should not be performed directly by the cooling machine, but with the use of an intermediate medium.
  • the temperature may, for example, be 108 Kelvin.
  • the liquid is cooled further, for example, to 105 Kelvin, in a heat-exchanger 5.
  • the liquid enters into the heat exchanger at 12 and leaves it at 13.
  • the pressure of the mixture of liquid and gas may be reduced from 20 atmospheres to 1 atmosphere.
  • the liquid dripping from the choking device 6 is collected in a container 7.
  • That portion of the gas which has finally not become liquid first flows through the heat exchanger 5, giving off part of its cold to the liquid which is formed with the use of the cooling machine.
  • the gas flows through the heat exchanger 2, in which it gives off the remainder of its cold to the compressed gas.
  • the temperature of the gas of low pressure, when it leaves the heat exchanger, and the temperature of the gas of high pressure, when it enters the heat-exchanger may be substantially equal.
  • the expanded gas may be recompressed in the compressor 1, after which it can repeat its cycle. It is thus ensured that less water and carbonic acid have to be extracted from the air than if the gas did not repeat its cycle.
  • Fig. 2 shows the W-T diagram for air.
  • the temperature in degrees Kelvin is plotted on the abscissa of the diagram, the heat content of the air per kilogram being plotted on the ordinate.
  • the compressed air of 20 atmospheres enters the first heat-exchanger 2 at point 10: here the air is cooled to point 11, where it leaves the heatexchanger. At this temperature of 223 Kelvin, it is cooled with the use of the cold-gas cooling machine. This cooling is performed at constant pressure, so that the pressure line of 20 atmospheres is followed. The cooling continues until point 12 on the liquid limiting line of the co-existence range is reached. Then, with the use of the heat exchanger 5, the gas is cooled further to point 13 which lies lower on the liquid limiting line of the coexistence range.
  • the pressure of the liquid is reduced to 1 atmosphere in the choking device 6. This decrease in pressure is indicated in the diagram as a horizontal line.
  • the final condition of the mixture of gas and liquid is indicated at 14. It is evident from the diagram that more than 60% of the initially compressed gas has been liquefied.
  • Fig. 3 shows diagrammatically a device in which the method according to the invention is carried out to fractionate gases.
  • the device roughly corresponds to that shown in Fig. 1.
  • a quantity of air is compressed to, for example, 20 atmospheres in a compressor 31. Then, this air is cooled in a heat-exchanger 32. This cooling may, for example, be performed to 223 Kelvin. Then, with the use of the cold supplied by a cold-gas cooling machine 33, which is driven by an electric motor, the air is cooled further to, for example, 108 Kelvin, the air then having become liquid. The liquid air is cooled further in a heat-exchanger 34. Then, the liquid air enters into a fractionating column 36 at 35.
  • the container 37 of the fractionating column contains a quantity of liquid oxygen, which has a temperature lower than that of the liquid air, which is led through a tubular cooler 38 into the container.
  • the oxygen keeps boiling.
  • the liquid air leaves the tubular cooler 38 of the fractionating column at 39, passes through a choking cock 40 and enters, at a pressure of, for example, 1 atmosphere into the upper part of the fractionating column at 41.
  • the liquid air drips down along tiles 42.
  • the gas is separated into oxygen and nitrogen in a column 43, the nitrogen and oxygen leaving the column at 44 and 45 respectively.
  • the nitrogen and the oxygen are each led through different tubular coolers across the heat-exchanger 34, in which the components give off cold to the gas to be fractionated, passing subsequently through the heat-exchanger 32, in which cold is also given off to the gas to be fractionated.
  • the two constituents can be stored separately in cylinders.
  • Fig. 4 shows on a different scale a cold-gas refrigerator suitable for use in the systems described above.
  • the cold-gas refrigerator shown is of the socalled displacerpiston type.
  • displacerpiston type Of course, use may be made of other types of cold-gas refrigerators, for example, double-acting machines.
  • the machine comprises a cylinder 60, in which 'a displacer piston 61 and a piston 62 are adapted to reciprocate with a substantially constant phase difference.
  • the displacer piston is coupled by means of a connecting rod mechanism 63 with a crank of a crank shaft 64, while the piston 62 is coupled by way of a connectingrod system 55 with two cranks of the same crank shaft 64.
  • Owing to the movement of the displacer piston 61 the volume of the freezing space 66 is varied. This space communicates with the cooled space 70 through a freezer 67, a regenerator 68 and a cooler 69; the volume of the cooled space is varied both by the movement of the dis placer piston 61 and the movement of the piston 62.
  • the refrigerator is driven by an electric motor 71.
  • Cold-gas refrigerators permits the obtaining in one stage of low temperatures of for example 200 C.
  • a medium to be cooled may be supplied through ports 72 to a space 73, which is surrounded by a jacket 74 having heat insulating properties. In this space 73 the medium is cooled, after which the cooled medium leaves the refrigerator through a duct 75.
  • a cold-gas cooling machine in which the required temperature (starting, for example, at room temperature) is reached in a single step.
  • the gas to be liquefied upon leaving the heat-exchangers in which it is cooled with the use of the cold-gas cooling machine, has a very low temperature, it is advisable that the gas should be led in contact with the cooled space in succession along a plurality of such machines.
  • the capacities of the machines may be such that the gas to be cooled acquires the required temperature in a number of suitably chosen steps, since this method has the advantage that, from a thermo-dynarnic point of view, the cooling process is thus performed favourably and is therefore economical.
  • the machine may, for example, be constituted by an assembly of four units, in which the temperatures of the hot spaces generally be chosen to be approximately equal, for example, equal to room temperature, but, if necessary, independently of one another. However, the temperatures of the cold spaces of all four machines are difierent. The gas to be cooled may be led successively along the coolers of lower temperature.
  • An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
  • An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a first heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, a second heat-exchanger for further cool ing said product, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said cold-gas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
  • An apparatus producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, means for reducing the pressure of said product, and means for fractionating said product into its components.
  • An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a reversible regenerator for cooling said gas, a cold-gas machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunieating chambers of different temperatures, a medium of invariable chemical composition in said cold-gas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
  • An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a first heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, a second heat exchanger for further cooling said product, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, means for reducing the pressure of said product, and means for fractionating said product into its components.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Description

Oct. 2, 1956 J. w. L. KGHLER 2,754,877
APPARATUS FOR LIQUEFYING AIR Filed March 23, 1951 2 Sheets-Sheet l w 14 If caZ G JACOB w. L. KOHLER INl/E/VT'OR AGE/VT Oct. 2, 1956 Filed March 23, 1951 2 Sheets-Sheet 2 IN VEN TOR. JACOB WILLEM LAURENS KOHLER AGENT United States 2,764,877 APPARATUS FOR LIQUEFYING AIR Jacob Willem Laurens Kiihler, Eindhoven, Netherlands,
assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee This invention relates to methods of cooling gases to a temperature comprised in the co-existence range of the gas to be cooled, so that at least part of the gas becomes liquid.
The object of the present invention is to provide a method by which a gas can be cooled to a temperature comprised in the co-existence range of the gas to be cooled, the output of the installation being many times higher than that of the systems described above, the installation itself having a small volume compared with known installations.
According to the invention, a quantity of compressed gas is cooled, after which this cooled gas is cooled further by means of the cold produced by the cold-gas cooling machine operating on the reversed hot-gas reciprocating engine principle, liquid being thus formed, after which the medium produced during the last-mentioned cooling process undergoes a decrease in pressure, the first-mentioned cooling process being carried out with the use of cold from the gas cooled by this method.
The term cold-gas cooling machine operating on the reversed hot-gas engine principle is to be understood here to mean a machine in which mechanical energy is converted into thermal energy and in which a medium of invariable chemical composition, which is constantly in the gaseous phase, traverses an open or closed thermodynamic cycle in at least two intercommunicating chambers or chamber parts of ditferent temperatures, expansion of this medium primarily taking place in one or in a few of these chambers or chamber parts and compression in one or a few of the other chambers or chamber parts respectively, said machine comprising means to carry off heat to the exterior during compression and/or to supply heat from the exterior during expansion.
The medium produced during the cooling by the coldgas cooling machine may be either exclusively liquid or a mixture of gas and liquid.
In a further method according to the invention, which is used to liquefy gases, a quantity of compressed gas is cooled by a smaller quantity of this gas flowing back and having a lower pressure, after which this cooled gas is cooled further by means of the cold produced by a coldgas cooling machine operating on the reversed hotgas reciprocating engine principle, liquid being thus formed, whereafter the medium produced during the last-mentioned cooling process undergoes a decrease in pressure, the residual gas performing the first-mentioned cooling of the compressed gas.
atent C In a further method according to the invention, which I is used to disintegrate gases into constituents, a quantity of compressed gas which is to be distinguished is cooled by a quantity of gas flowing back after which this cooled gas is cooled further by means of the cold-gas cooling machine, liquid being thus formed, whereafter the medium produced during the latter cooling process undergoes a decrease in pressure and is separated into the desired constituents, at least one of the constituents performing the first-mentioned cooling of the gas to be disintegrated into constituents.
In a further method according to the invention, the medium after it has been formed by means of the cold produced by the cold-gas cooling machine, is cooled further with the use of cold obtained from the gas cooled by a method according to the invention, while the cooling of the compressed gas, before being cooled with the use of the cold-gascooling machine, is likewise performed by means of cold obtained from the cooled gas.
By carrying out this method, the percentage of liquefied gas can be increased further. I I
In a preferred embodiment of the method, the pressure of the compressed gas is not more than the critical pressure of this gas. In the case of air, this means that the gas need be compressed to at most 40 atmospheres Since in the known installations described above, the gas is compressed to,'for example, 200 atmospheres, it will be evident that, owing to the low compression utilized in accordance with the invention, a material simplification of the installation is obtainable.
The invention may be successfully used more particularly if the compressed gas is cooled by means of the cold-gas cooling machine to a temperature located in the neighborhood of the point of intersection of the pressure line of this gas and the liquid limiting line of the coexistence range. This means that the compressed gas has become completely liquid, after it has been cooled with the use of the cold-gas cooling machine. If thereupon the liquid gas is caused to expand to 1 atmosphere, a new quantity of gas will be produced, it is true, but the quantity of liquid will nevertheless be comparatively large.
In a further preferred embodiment of the method according to the invention, cold is abstracted from the working medium in the cold-gas cooling machine with the use of cold obtained from the cooled gas.
The installation adapted for carrying out the method described above has the feature that it comprises a heatexchanger in which the compressed gas is cooled, a coldgas cooling machine with the use of which this gas is cooled further, liquid being thus produced, and a device in which thereupon the pressure and, if desired, the temperature of the medium are decreased.
The device in which the pressure and, if necessary, the temperature of the gas are decreased, may be constituted by -a choking device, out of which the liquid drops at a pressure of, for example, 1 atmosphere. However, as an alternative, this device may be constituted by a tubular cooler, through which the medium is led. This tubular cooler is arranged in the container with the boiling liquid. The liquid cooling the medium, which may be either a liquid or a mixture of liquid and gas, starts boiling in the container owing to the heat supplied to the liquid from the tubular cooler.
According to a further embodiment of the invention, the medium, after it has been produced by means of a cold-gas cooling machine, is cooled in a heat exchanger. Thus, the percentage of liquefied gas may be increased. In installations for liquefying gases that portion of the gas which is finally not liquefied will serve as the cooling medium for this heat exchanger. In fractionating installations, it will be advantageous for one or more of the constituents into which the gas is disintegrated to serve as the cooling medium. In certain cases it may be advantageous also to lead the gas which is finally not liquefied, or the constituents of the gas, along that heat-exchanger of the cold-gas cooling machine in which heat is abstracted from the working medium in the machine.
When a gas containing admixtures is to be liquefied or fractionated into constituents, these admixtures becomnig liquid or solid at a higher temperature than the gas to be finally liquefied, itis desirable that the admixtures should preliminarily be removed from the gas. Such a case will, for example, occur when nitrogen and oxygen are to be liquefied from the air. Apart from nitrogen and oxygen, the air comprises additionally water vapour and carbon dioxide. It is not desirable that these constituents should deposit themselves in a normal heat-exchanger, which may be, for example, a tubular cooler. The constituents may be extracted from the gas by chemical washing of the gas.
In a further embodiment of the invention, the first heatexchanger, in which the compressed gas is cooled, is constituted by a reversible regenerator or recuperator system. The constituents of the gas liable to be deposited in this heat-exchanger may thus be periodically removed. The change-over of the regenerator or recuperator system may be performed continuously or periodically. By the use of this heat exchanger, the installation may be materially simplified.
This heat-exchanger may be successfully used more particularly if the quantity of gas, which flows back and which gives or cold to the compressed gas is large. This will generally be the case, if the installation is used for fractionating gases. According to one embodiment of the invention, this installation has the feature that the medium, after it has been subjected to its last cooling process, is fractionated into constituents in a fractionating apparatus.
In order that the invention may be readily carried into effect, two examples will now be described in detail with reference to the accompanying drawings, of which:
Fig. 1 is a diagrammatical view of an installation for use with the method according to the invention;
Fig. 2 shows the W-T diagram of this method and Fig. 3 is a diagrammatic view of a fractionatinginstallation according to the invention,
Pig. 4 is a partially perspective view of a cold-gas cooling machine in accordance with the present invention.
Referring to the diagrammatic view of Fig. 1, a quantity of air is compressed to 20 atmospheres in a compressor 1. Then, this quantity of air is cooled under a constant pressure in a first heat-exchanger 2, for example, to 223 Kelvin. It enters into the heat-exchanger at and leaves it at 11. The cooling medium is constituted by that portion of the gas which has finally not been liquefied. Then, the gas cooled to 223 Kelvin flows along the cold side 3 of a cold-gas cooling machine 4, which is driven by an electric motor. This cold-gas cooling machine operates on the reversed hot-gas engine principle. Apart from the embodiment indicated above, in which the gas to be cooled flows directly through the heat-exchanger on the cold side of the cooling machine, it will in certain cases be desirable that the cooling of the gas should not be performed directly by the cooling machine, but with the use of an intermediate medium. After the gas has been cooled with the use of the cold-gas cooling machine, it will have become completely liquid. In this case the temperature may, for example, be 108 Kelvin. Then, the liquid is cooled further, for example, to 105 Kelvin, in a heat-exchanger 5. The liquid enters into the heat exchanger at 12 and leaves it at 13. Finally, with the use of a choking device 6, the pressure of the mixture of liquid and gas may be reduced from 20 atmospheres to 1 atmosphere. The liquid dripping from the choking device 6 is collected in a container 7.
That portion of the gas which has finally not become liquid, first flows through the heat exchanger 5, giving off part of its cold to the liquid which is formed with the use of the cooling machine. The gas flows through the heat exchanger 2, in which it gives off the remainder of its cold to the compressed gas. With a correct construction of this heat-exchanger, the temperature of the gas of low pressure, when it leaves the heat exchanger, and the temperature of the gas of high pressure, when it enters the heat-exchanger, may be substantially equal. After adding a new quantity of gas which is supplied at 8, the expanded gas may be recompressed in the compressor 1, after which it can repeat its cycle. It is thus ensured that less water and carbonic acid have to be extracted from the air than if the gas did not repeat its cycle.
Fig. 2 shows the W-T diagram for air. The temperature in degrees Kelvin is plotted on the abscissa of the diagram, the heat content of the air per kilogram being plotted on the ordinate. The compressed air of 20 atmospheres enters the first heat-exchanger 2 at point 10: here the air is cooled to point 11, where it leaves the heatexchanger. At this temperature of 223 Kelvin, it is cooled with the use of the cold-gas cooling machine. This cooling is performed at constant pressure, so that the pressure line of 20 atmospheres is followed. The cooling continues until point 12 on the liquid limiting line of the co-existence range is reached. Then, with the use of the heat exchanger 5, the gas is cooled further to point 13 which lies lower on the liquid limiting line of the coexistence range. The pressure of the liquid is reduced to 1 atmosphere in the choking device 6. This decrease in pressure is indicated in the diagram as a horizontal line. The final condition of the mixture of gas and liquid is indicated at 14. It is evident from the diagram that more than 60% of the initially compressed gas has been liquefied.
Fig. 3 shows diagrammatically a device in which the method according to the invention is carried out to fractionate gases. The device roughly corresponds to that shown in Fig. 1.
Referring to Fig. 3, a quantity of air is compressed to, for example, 20 atmospheres in a compressor 31. Then, this air is cooled in a heat-exchanger 32. This cooling may, for example, be performed to 223 Kelvin. Then, with the use of the cold supplied by a cold-gas cooling machine 33, which is driven by an electric motor, the air is cooled further to, for example, 108 Kelvin, the air then having become liquid. The liquid air is cooled further in a heat-exchanger 34. Then, the liquid air enters into a fractionating column 36 at 35. The container 37 of the fractionating column contains a quantity of liquid oxygen, which has a temperature lower than that of the liquid air, which is led through a tubular cooler 38 into the container. Owing to the supply of heat from the liquid air, the oxygen keeps boiling. The liquid air leaves the tubular cooler 38 of the fractionating column at 39, passes through a choking cock 40 and enters, at a pressure of, for example, 1 atmosphere into the upper part of the fractionating column at 41. The liquid air drips down along tiles 42. The gas is separated into oxygen and nitrogen in a column 43, the nitrogen and oxygen leaving the column at 44 and 45 respectively. The nitrogen and the oxygen are each led through different tubular coolers across the heat-exchanger 34, in which the components give off cold to the gas to be fractionated, passing subsequently through the heat-exchanger 32, in which cold is also given off to the gas to be fractionated. After the two gases have left the heat-exchanger 32, which is preferably constituted by a reversible regenerator or recuperator system, the two constituents can be stored separately in cylinders.
Fig. 4 shows on a different scale a cold-gas refrigerator suitable for use in the systems described above. The cold-gas refrigerator shown is of the socalled displacerpiston type. Of course, use may be made of other types of cold-gas refrigerators, for example, double-acting machines.
The machine comprises a cylinder 60, in which 'a displacer piston 61 and a piston 62 are adapted to reciprocate with a substantially constant phase difference. To this end the displacer piston is coupled by means of a connecting rod mechanism 63 with a crank of a crank shaft 64, while the piston 62 is coupled by way of a connectingrod system 55 with two cranks of the same crank shaft 64. Owing to the movement of the displacer piston 61 the volume of the freezing space 66 is varied. This space communicates with the cooled space 70 through a freezer 67, a regenerator 68 and a cooler 69; the volume of the cooled space is varied both by the movement of the dis placer piston 61 and the movement of the piston 62.
The refrigerator is driven by an electric motor 71. Cold-gas refrigerators permits the obtaining in one stage of low temperatures of for example 200 C.
A medium to be cooled may be supplied through ports 72 to a space 73, which is surrounded by a jacket 74 having heat insulating properties. In this space 73 the medium is cooled, after which the cooled medium leaves the refrigerator through a duct 75.
In the embodiments of the invention described above, use is made of a cold-gas cooling machine, in which the required temperature (starting, for example, at room temperature) is reached in a single step. Particularly if the gas to be liquefied, upon leaving the heat-exchangers in which it is cooled with the use of the cold-gas cooling machine, has a very low temperature, it is advisable that the gas should be led in contact with the cooled space in succession along a plurality of such machines. The capacities of the machines may be such that the gas to be cooled acquires the required temperature in a number of suitably chosen steps, since this method has the advantage that, from a thermo-dynarnic point of view, the cooling process is thus performed favourably and is therefore economical.
The machine may, for example, be constituted by an assembly of four units, in which the temperatures of the hot spaces generally be chosen to be approximately equal, for example, equal to room temperature, but, if necessary, independently of one another. However, the temperatures of the cold spaces of all four machines are difierent. The gas to be cooled may be led successively along the coolers of lower temperature.
What I claim is:
1. An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
2. An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a first heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, a second heat-exchanger for further cool ing said product, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said cold-gas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
3. An apparatus producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, means for reducing the pressure of said product, and means for fractionating said product into its components.
4. An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a reversible regenerator for cooling said gas, a cold-gas machine for further cooling said gas and for forming a product including at least a liquid therein, said cold-gas cooling machine having two intercommunieating chambers of different temperatures, a medium of invariable chemical composition in said cold-gas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, and means for reducing the pressure of said product.
5. An apparatus for producing liquid air from gaseous air comprising means for compressing said gas to at most 40 atmospheres, a first heat-exchanger for cooling said gas, a cold-gas cooling machine for further cooling said gas and for forming a product including at least a liquid therein, a second heat exchanger for further cooling said product, said cold-gas cooling machine having two intercommunicating chambers of different temperatures, a medium of invariable chemical composition in said coldgas cooling machine constantly in a gaseous phase and traversing in a cyclic process said chambers, means for reducing the pressure of said product, and means for fractionating said product into its components.
References Cited in the file of this patent UNITED STATES PATENTS 1,553,546 Lundgaard Sept. 15, 1925 1,901,389 Flamand Mar. 14, 1933 2,090,163 Twomey Aug. 17, 1937 2,105,214 DeBaufre Jan. 11, 1938 2,423,273 Van Nuys July 1, 1947 OTHER REFERENCES Separation of Gases, by Ruhemann, published 1940, pp. 76 to 82 and and 161.
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US2959020A (en) * 1958-01-29 1960-11-08 Conch Internat Mcthane Ltd Process for the liquefaction and reliquefaction of natural gas
US3129081A (en) * 1959-03-17 1964-04-14 Philips Corp Device for fractionating gas
US3144316A (en) * 1960-05-31 1964-08-11 Union Carbide Corp Process and apparatus for liquefying low-boiling gases
US3233418A (en) * 1962-07-23 1966-02-08 Philips Corp Apparatus for liquefying helium
US3242681A (en) * 1963-01-31 1966-03-29 Philips Corp Natural gas liquefaction and storage
US3257812A (en) * 1962-04-27 1966-06-28 Philips Corp Dissociated ammonia separation plant having an adsorber in a liquid refrigerant bath
US3318101A (en) * 1964-02-14 1967-05-09 Philips Corp Device for producing cold at low temperatures and compression devices suitable for use in said devices
US3327486A (en) * 1964-02-11 1967-06-27 Philips Corp Device for producing cold at low temperatures and cold-gas refrigerator particularly suitable for use in such a device
US3383871A (en) * 1965-10-09 1968-05-21 Philips Corp Apparatus for transporting cold to a remote location using an expansion ejector
US3396547A (en) * 1965-10-09 1968-08-13 Philips Corp Cold transport to a remote location with small temperature drop
US3413815A (en) * 1966-05-02 1968-12-03 American Gas Ass Heat-actuated regenerative compressor for refrigerating systems

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NL95304C (en) * 1954-07-14
NL192087A (en) * 1954-11-03
GB833052A (en) * 1956-05-21 1960-04-21 Kellogg M W Co Cold separation of gas mixtures
NL112988C (en) * 1960-09-13
NL134079C (en) * 1963-02-04
NL6411356A (en) * 1964-09-30 1966-03-31

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US1553546A (en) * 1922-05-22 1925-09-15 Automatic Refrigerating Compan Air-refrigerating machine
US1901389A (en) * 1928-10-18 1933-03-14 Hazard-Flamand Maurice Process for liquefying and rectifying air
US2090163A (en) * 1934-05-09 1937-08-17 Lee S Twomey Method of liquefying and storing fuel gases
US2105214A (en) * 1935-10-11 1938-01-11 Baufre William Lane De Method and apparatus for cooling and rectifying gaseous mixtures
US2423273A (en) * 1943-12-02 1947-07-01 Air Reduction Separation of the constituents of air

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Publication number Priority date Publication date Assignee Title
US1553546A (en) * 1922-05-22 1925-09-15 Automatic Refrigerating Compan Air-refrigerating machine
US1901389A (en) * 1928-10-18 1933-03-14 Hazard-Flamand Maurice Process for liquefying and rectifying air
US2090163A (en) * 1934-05-09 1937-08-17 Lee S Twomey Method of liquefying and storing fuel gases
US2105214A (en) * 1935-10-11 1938-01-11 Baufre William Lane De Method and apparatus for cooling and rectifying gaseous mixtures
US2423273A (en) * 1943-12-02 1947-07-01 Air Reduction Separation of the constituents of air

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2959020A (en) * 1958-01-29 1960-11-08 Conch Internat Mcthane Ltd Process for the liquefaction and reliquefaction of natural gas
US3129081A (en) * 1959-03-17 1964-04-14 Philips Corp Device for fractionating gas
US3144316A (en) * 1960-05-31 1964-08-11 Union Carbide Corp Process and apparatus for liquefying low-boiling gases
US3257812A (en) * 1962-04-27 1966-06-28 Philips Corp Dissociated ammonia separation plant having an adsorber in a liquid refrigerant bath
US3233418A (en) * 1962-07-23 1966-02-08 Philips Corp Apparatus for liquefying helium
US3242681A (en) * 1963-01-31 1966-03-29 Philips Corp Natural gas liquefaction and storage
US3327486A (en) * 1964-02-11 1967-06-27 Philips Corp Device for producing cold at low temperatures and cold-gas refrigerator particularly suitable for use in such a device
US3318101A (en) * 1964-02-14 1967-05-09 Philips Corp Device for producing cold at low temperatures and compression devices suitable for use in said devices
US3383871A (en) * 1965-10-09 1968-05-21 Philips Corp Apparatus for transporting cold to a remote location using an expansion ejector
US3396547A (en) * 1965-10-09 1968-08-13 Philips Corp Cold transport to a remote location with small temperature drop
US3413815A (en) * 1966-05-02 1968-12-03 American Gas Ass Heat-actuated regenerative compressor for refrigerating systems

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CH291626A (en) 1953-06-30

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