Patent Application
20060260358
Not Applicable
DEVELOPMENT
Not Applicable
Not Applicable
The present invention relates generally to gas-separation/liquefaction and, more particularly, to a single and double column high-purity cryogenic gas-separation/liquefaction devices, where the refrigeration to the cryogenic gas-separation/liquefaction process is supplied by either a cryocooler alone or by a combination of a cryocooler and by a Joule-Thompson throttling process, and where the gas condensation may occur at least partially directly on the cold portion of the cryocooler which may be located inside of the thermally insulated space of the distillation column.
The background information discussed below is presented to better illustrate the novelty and usefulness of the present invention. This background information is not admitted prior art.
Cryogenic separation of gas mixtures is a well-established art. The processes used to separate the gaseous constituents of ambient air are well-known and understood. Although all of air's valuable components such as argon, neon, and xenon may be presently extracted from air in high-purity concentrations, the mainstay of the separation industry is the production of nitrogen and oxygen in various purities in gaseous or liquid form, as demanded by the particular application.
The first air separation plant for the commercial production of oxygen was designed and built by Dr. Carl von Linde in 1902. The plant had a single distillation column and refrigeration was obtained by throttling. Due to the plant's dependence on ineffective throttling and other inefficiencies, gaseous oxygen production required pressures of over 30 atmospheres, or higher. In the same year, Georges Claude improved on the Linde process by adding an expansion engine to the process. The expansion engine, however, proved to be an unreliable component. Therefore, in the late 1930's P. L. Kapitsa proposed and developed expansion turbines for the separation of oxygen that proved to be far more reliable than the expansion engine. Moreover, the ability of the expansion turbines to handle large volumetric flow provided for cryogenic processing at much lower pressures, thus reducing the plant investment cost. Since that time, many variations and improvements have been made on these devices and their related processes.
A process for the synthesis of methane-oxygen mixtures gas has been described whereby the feeding natural gas and (preferably dry) compressed air into a distillation column at appropriate locations and at appropriate temperatures, produces nitrogen and heavier hydrocarbons as by-products. In this process, refrigeration is provided by multiple expansion machines and an expansion valve.
Soon after, a low temperature, single column, distillation process, where the refrigeration is provided by a reciprocating expansion machine and by a throttle valve both external to the distillation column, was described.
Gas-fractionating devices that provide the reflux for the distillation process and that have external refrigeration for condensation where the gas stream that provides the refrigeration and the gas stream to be separated are distinct, have been discussed, although, the design of such devices was not described.
A process of providing reflux in the distillation column in a reflux condenser that is refrigerated by a conventional Joule—Thompson throttling—work expanding, oxygen rich stream, external to the distillation column, was also taught.
Cryogenic separation of ethylene from a gaseous mixture at various temperature levels using refrigeration provided by an unspecified external refrigeration system was disclosed.
A process for the recovery of nitrogen from air within a single column, where refrigeration is provided by a turbo-expander, Joule-Thompson throttling, has been described.
A device providing for nitrogen rejection from a natural gas stream that utilizes a series of Joule-Thompson throttle valves to provide the necessary cooling, instead of external refrigeration, has also been introduced into the art. The use of a mixed refrigerant in a single loop refrigeration system providing for at least part of the heat duty of the reboiler is also known.
Most recently, a dephlegmator type separator where the refrigeration is also supplied by an external supply, was introduced.
It should be noted that even today the irreversible throttling process and the reversible, minus the losses, adiabatic expansion for cryogenic gas-separation/liquefaction, are still practiced almost exclusively. Moreover, it appears that for large tonnage capacity, cryogenic gas-separation/liquefaction plants will be using this technology for some time to come.
This is not the case, however, in the field of small-scale production of high-purity gases, such as therapeutic oxygen where the immense need for low-cost, small-scale production of high-purity breathing oxygen is currently generating interest in developing small-scale cryogenic-based gas-separation/liquefaction plants.
Until recently small-scale cryogenic-based gas-separation/liquefaction plants had to rely on periodic cryogenic liquid addition for their refrigeration needs. This type of refrigeration, however, is quite expensive. Lately, however, reliable cryocoolers of various designs capable of supplying refrigeration at, or below, the liquefaction temperature of nitrogen have been made available. These cryocoolers could be eminently suitable for small scale air separation as they eliminate the need for liquid nitrogen to be delivered to the gas-separation/liquefaction facility.
Applicant is not aware of any device or method wherein at least part of the refrigeration required to remove the heat of condensation from the distillation column reflux is achieved by a cryocooler wherein, in normal operation, a portion of the separated component(s) are condensed at least partially directly on the cold portion of the cryocooler.
Accordingly, the present invention provides for means and processes that satisfy the hereto unmet need for small scale cryogenic air and/or other gas mixture separation where the needed refrigeration is provided wholly, or at least partially, by a cryocooler wherein during normal operation a portion of the enriched or separated component condenses at least partially directly onto the cold portion of the cryocooler.
Both single or double column high-purity cryogenic gas-separation/liquefaction devices are embodied within the principles of the invention where the refrigeration to the cryogenic gas-separation/liquefaction device is supplied by either a cryocooler alone or by a combination of a cryocooler and by a Joule-Thompson throttling process, and where the gas condensation may occur at least partially directly on the cold portion of the cryocooler which may be located inside of the thermally insulated space of the distillation column(s).
Using the embodiments described herein, gases, such as high-purity oxygen may be separated from, for example, ambient air in a device of the present invention, wherein that device is much smaller than presently available gas separation/liquefaction devices. Thus, these gas-separation/liquefaction systems made according to the principles of the present invention are particularly useful for medical applications, and especially for providing for safe and economical high-purity oxygen for at-home use.
The principles of the invention as taught herein include a combined column embodiment for the simultaneous production of high-purity liquid or gaseous oxygen and nitrogen. Another double column design offers a reduced temperature and pressure separation with an easy switch between oxygen and nitrogen extraction or single component extraction. If both gaseous and liquid oxygen are required, an oxygen purity of approximately 95% can be produced with good recovery i.e., with nitrogen purity of approximately 91%.
These advances in the art and the benefits they provide are accomplished by providing for a high-purity cryogenic gas-separation/liquefaction device for the production of liquid gases that comprises:
a) at least one means for supplying a feed gas;
b) at least one cryogenic means having a cold portion means for providing refrigeration for at least a process of condensing;
c) at least one condensation means for condensing at least one component of the feed gas, the condensation means thermally connected to the cold portion means;
d) at least one distillation means for providing for distillation of the condensed at least one component of the gas, and
e) at least one insulating means for thermally insulating the device,
wherein the refrigeration to the cryogenic gas-separation/liquefaction process may be provided by the at least one cryogenic means alone and where gas condensation may occur at least partially directly on the cold portion means of the at least one cryogenic means which may be located inside of the thermally insulated space of the at least one distillation means. It should be understood that in all contemplated applications the cold portion of the cryocooler may be equipped with extended surfaces for enhanced heat transfer.
It is further contemplated that the high-purity cryogenic gas-separation/liquefaction device further comprises:
a) wherein at least one cryogenic means is a cryocooler,
b) wherein at least one condensation means is a condenser, or the cold portion of the cryocooler.
c) wherein at least one distillation means is a distillation column, and
d) wherein at least one insulating means is a thermally insulated container,
wherein the refrigeration to the cryogenic gas-separation/liquefaction process may be provided by the at least one cryocooler alone and where gas condensation may occur at least partially directly on the cold portion of the at least one cryocooler which may be located inside or outside of the thermally insulated space of the at least one distillation column.
It is still further contemplated that the high-purity cryogenic gas-separation/liquefaction device further comprises:
a) wherein the cryogenic means is a cryocooler,
b) wherein the condensation means is a condenser, or the cold portion of the cryocooler.
c) wherein the distillation means is a distillation column, and
d) wherein the insulating means is a Dewar flask,
wherein the refrigeration to the cryogenic gas-separation/liquefaction process may be provided by the cryocooler alone and where gas condensation may occur directly on the cold portion of the cryocooler which may be located inside or outside of the Dewar flask of the distillation column.
Additionally it is contemplated that the high-purity cryogenic gas-separation/liquefaction device also may comprise wherein the feed gas, which may be ambient air or any other gas mixture of interest, may be driven into the device by a fan or compressor means, and further wherein water and carbon dioxide may be removed from the feed gas. The refrigeration to the cryogenic gas-separation/liquefaction device may be provided by a combination of the cryogenic means and a Joule-Thompson throttling process.
Moreover it is contemplated that the high-purity cryogenic gas-separation/liquefaction device, as recited above may further comprise wherein the feed gas passes through a multi-pass heat exchanger means for cooling and further where the cooled feed gas is introduced to the at least one distillation means at an appropriate composition point. It is also contemplated that an Interior volume of the at least one distillation means may be kept at an elevated pressure by a compressor.
Another contemplation comprises using the gas separation/liquefaction devices of this invention to achieve a high-purity cryogenic gas-separation/liquefaction process for the production of liquid gases, comprising the steps of:
a) supplying a feed gas;
b) providing at least one cryogenic means having a cold portion means for providing refrigeration for at least a process of condensing;
c) condensing at least one component of the feed gas using at least one condensation means thermally connected to the cold portion means; or directly on the cold portion means.
d) distilling the at least one component of the condensed gas using at least one distillation means, and
e) insulating the device using at least one thermally insulating means,
wherein providing the refrigeration to the cryogenic gas-separation/liquefaction process may be by the at least one cryogenic means alone and where gas condensation may occur at least partially directly on the cold portion means of the at least one cryogenic means which may be located inside or outside of the thermally insulated space of the at least one distillation means.
Furthermore, a high-purity double column cryogenic gas separation/liquefaction device for the simultaneous collection of a plurality of high-purity liquid gases is contemplated, wherein such a device comprise:
a) at least one means for supplying a feed gas;
b) a plurality of cryocoolers wherein each cryocooler has a cold portion to provide refrigeration,
c) a plurality of condensing means wherein each condenser means is a standard condenser thermally related to the cold portion of a cryocooler, or where the condensing means is a cold finger of the cryocooler.
d) a plurality of distillation columns, and
at least one insulating means for insulating the device,
wherein refrigeration to the cryogenic gas-separation/liquefaction process may be provided by the cryocoolers alone and where gas condensation may occur at least partially directly on the cold portions of the cryocoolers which may be located inside or outside of the thermally insulated space of the distillation column.
Still other benefits and advantages of this invention will become apparent to those skilled in the art upon reading and understanding the following detailed specification and related drawings.
In order that these and other objects, features, and advantages of the present invention may be more fully comprehended and appreciated, the invention will now be described, by way of example, with reference to specific embodiments thereof which are illustrated in appended drawings wherein like reference characters indicate like parts throughout the several figures. The invention will be described and explained with additional specificity and detail using the accompanying drawings, in which:
a is a schematic of a coil evaporator that may be used as an alternative to a conventional condenser.
b is a schematic of an optional design for a combined cooling source to reduce total energy consumption.
c is a schematic of a more effective heat exchange where the condenser-evaporator is placed at the bottom section of column B.
d is a schematic of an alternative heat bridge that may be used in place of condenser 48.
e is a schematic of the optional use of direct blow-through flow, in which case the condenser could be eliminated.
Note that providing reflux in the distillation column by condensing a portion of the at least partially separated gas(s) on the cold part of the cryocooler would be a common characteristic for any cryocooler.
It should be understood that the drawings are not necessarily to scale. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Referring now, with more particularity, to the drawings, it should be noted that the disclosed invention is disposed to embodiments in various sizes, shapes, and forms. Therefore, the embodiments described herein are provided with the understanding that the present disclosure is intended as illustrative and is not intended to limit the invention to the embodiments described herein.
In the schematic shown in
Distillation column 3 is insulated by insulator 4. Cryocooler 5 is operatively installed about the top of distillation column 3, as shown. The cold portion of cryocooler 5 is thermally connected to cold finger 6. In the embodiment illustrated, the temperature of cold finger 6 is between about 77 K and about 88 K (roughly between the boiling point of liquid nitrogen, about 77 K, and the boiling point of liquid oxygen, about 90 K), or for other gases of interest, between the boiling points of the low and high boiling components of the other gas mixtures. The thermal design geometry and the insulation at the insertion of cryocooler 5 into column 3 should be carefully optimized to minimize heat input from the ambient.
Interior volume 12 of distillation column 3 is kept at an elevated pressure by compressor 9 which is fed a nitrogen-enriched stream as its working fluid. The path of travel of the nitrogen-enriched stream is indicated by reference numeral 8. The heat of compression is removed from stream 8 by heat exchanger 10 before stream 8 enters the warm end of heat exchanger 2 where it is cooled to an intermediate temperature between the warm and cold end of the exchanger, as required by balancing (not shown). Stream 8 then enters boiler 11 to produce the oxygen-rich vapor that is used to operate distillation column 3. Exiting boiler 11, stream 8 is introduced into volume 12 of distillation column 3 where stream 8 condenses at least partially on cold finger surface 6 of cryocooler 5. The condensate then undergoes a Joule-Thompson expansion in valve 7 and the liquid reflux is distributed to the top of the distillation column. The nitrogen-enriched stream exits distillation column 3 from the space between the low-pressure end of the Joule-Thompson expansion valve 7 and the top of the packing or trays of the distillation column (denoted by hatching) via conduit 8 and enters the cold end of the heat exchanger 2. Heat exchanger 2 acts as a counterflow heat exchanger to cool the incoming feed gas against the outgoing waste and/or product gas; this heat exchanger may be of the regenerator type. Alternatively, high-pressure vapor space 12 at the top end of the distillation column may be connected to the cold end of conduit 8, through which the nitrogen-enriched stream passes via an appropriately-sized capillary.
Oxygen-rich, gaseous product leaves the vapor space of reboiler 11, enters the cold end of heat exchanger 2 at an appropriate temperature point, and is discharged at room temperature through exit 13. Liquid oxygen product is discharged from boiler 11 at exit 14 through V2.
Although not shown, it will be readily appreciated by those skilled in the art, all of the cold conduits and the low temperature points of the heat exchanger 2 are kept well-insulated. The cold parts of heat exchanger 2 also may be positioned inside the Dewar flask that may also contain distillation column 3. Conversely, the distillation column may be located inside of one Dewar while the heat exchanger and the cold conduits are kept in another Dewar.
In works by R. A. Gaggioli et al., K. D. Timmerhaus et al., and A. M. Arkharov et al. one, who is well-versed in the art, will find the fundamental physics and physical chemistry required for constructing one of the above described novel cryogenic separation systems according to the principles taught herein and will also find the procedures necessary for balancing the system around a given component, such as a cryocooler.
Another contemplated embodiment for the cryogenic separation of air using a cryocooler is illustrated schematically in
Compactness of the unit is achieved by the optional use of spiral guide 38 of packing sections in the distillation columns. In such a design the vapor goes upward along a spiral path as the reflux is distributed downward through each loop by gravity and capillary forces.
Yet another embodiment, as illustrated in
a, 4b, 4c, 4d, and 4e show alternate designs for selected structural parts of the invention as described in connection with
Another double column design is illustrated in
The foregoing description, for purposes of explanation, uses specific and defined nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. Thus, the foregoing description of the specific embodiment is presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Those skilled in the art will recognize that many changes may be made to the features, to the way that some of the parts of the device may be arranged relative to one another creating various embodiments, as well as methods of making the embodiments of the invention described herein without departing from the spirit and scope of the invention. Thus, it is to be understood that the present invention is not limited to the described exemplary methods, embodiments, features or combinations of features but include all the variation, methods, modifications, and combinations of features within the scope of the appended claims. The invention is limited only by the claims.
