USRE25193E - Method and apparatus for separating gaseous mixtures - Google Patents

Method and apparatus for separating gaseous mixtures Download PDF

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USRE25193E
USRE25193E US25193DE USRE25193E US RE25193 E USRE25193 E US RE25193E US 25193D E US25193D E US 25193DE US RE25193 E USRE25193 E US RE25193E
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boiling point
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gaseous mixture
gaseous
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02Processes 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
    • F25J3/04Processes 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
    • F25J3/04763Start-up or control of the process; Details of the apparatus used
    • F25J3/04866Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04896Details of columns, e.g. internals, inlet/outlet devices
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02Processes 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
    • F25J3/04Processes 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
    • F25J3/04151Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04242Cold end purification of the feed air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02Processes 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
    • F25J3/04Processes 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
    • F25J3/04248Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04296Claude expansion, i.e. expanded into the main or high pressure column
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02Processes 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
    • F25J3/04Processes 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
    • F25J3/04406Processes 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 using a dual pressure main column system
    • F25J3/04412Processes 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 using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00Processes or apparatus using other separation and/or other processing means
    • F25J2205/02Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00Processes or apparatus using other separation and/or other processing means
    • F25J2205/24Processes or apparatus using other separation and/or other processing means using regenerators, cold accumulators or reversible heat exchangers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00Processes or apparatus using other separation and/or other processing means
    • F25J2205/30Processes or apparatus using other separation and/or other processing means using a washing, e.g. "scrubbing" or bubble column for purification purposes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00Processes or apparatus using other separation and/or other processing means
    • F25J2205/60Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2220/00Processes or apparatus involving steps for the removal of impurities
    • F25J2220/40Separating high boiling, i.e. less volatile components from air, e.g. CO2, hydrocarbons
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00Processes or apparatus involving steps for expanding of process streams
    • F25J2240/60Expansion by ejector or injector, e.g. "Gasstrahlpumpe", "venturi mixing", "jet pumps"
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S62/00Refrigeration
    • Y10S62/902Apparatus
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S62/00Refrigeration
    • Y10S62/939Partial feed stream expansion, air

Description

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July 3, 1962 c. J. scHlLLlNG ETAL. Re 25,193

METHOD AND APPARATUS FOR SEPARATING GASEoUs MIXTURES original Filed Aug. 16, 1957 6 sheets-Sheet 2 m no INVENTORS CLARENCE J. SCHILLING LILBURN CARROLLCLAITOR BY A @mail ATTORNEYS July 3, 1962 c. J. SCHILLING ETAL Re. 25,193

METHOD AND APPARATUS FOR SEPARATING GAsEous MIxTUREs Original Filed Aug. 16, 1957 6 Sheets-Sheet 3 INVENTORS CLARENCE J. SCHILLING LILBURN CARROLL CLAITOR BY MAW ATTORNEYS July 3, 1962 c. J. scHlLLlNG ETAL Re 25,193

METHOD AND APPARATUS FOR SEPARATING GASEOUS MIXTURES Original Filed Aug. 16, 1957 6 Sheets-Sheet INVENTOR` CLARENCE J. SCHILLING LI LBURN CARROLL CLAITOR ATTORNEYS July 3, 1962 c. J. scHlLLlNG ETAI. Rev25,193

METHOD AND APPARATUS FOR SEPARATING GAsEoUs MIXTURES Original Filed Aug. 16. 1957 6 Sheets-Sheet 5 INVENTORS CLARENCE J. scH|LL|NG Ll LBURN CARROLL CLAITOR ATTORNEYS July 3, 1962 c. .1. scHlLLlNG ETAL Re. 25,193

METHOD AND APPARATUS FOR SEPARATING GASEOUS MIXTURES Original Filed Aug. 16, 1957 6 Sheets-Sheet 6 rc2 J ASL j g Q I'O E] INVENTORS CLARENCE J. scHlLLlNs E1n( 9 LILBURN cARRoLLcLAlToR ATTORNEYS United States Patent O METHOD AND APPARATUS FOR SEPARATING y Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to improvements in the separation of gaseous mixtures by a low temperature fractionating operation and more particularly to methods of and apparatus for removing from the fractionating operation high boiling point impurities introduced into the operation with the gaseous mixture.

It is known that high boiling point impurities present in `gaseous mixtures must be removed or reduced to comprise an insignificant percentage of the gaseous mixture in order to prevent difficulties in the operation of low temperature fractionating cycles. For example, in the separation of air into oxygen and nitrogen components, the normal content of carbon dioxide in the air feed to the cycle precipitates and collects in the cycle, especially in the colder portions of the cycle, and affects operation of the cycle and eventually requires the cycle to be shut down for `defrosting. In order to obtain substantially continuous operation it is necessary to remove substantially the total carbon dioxide entering the cycle with the air feed. Also it is necessary to provide means for removing from the cycle other high boiling point components of the air feed, particularly hydrocarbons which, when concentrated in the cycle, constitute serious explosion hazards.

Several methods have been employed in the past for removing high boiling point impurities from gaseous mixtures, such as the removal of carbon dioxide from air.

In one method the air feed prior to its entry into the With a caustic solution for example, to remove the carbonk dioxide. This method requires bulky equipment and materially increases the initial and operating costs. Another method attempts to remove the carbon dioxide yby low temperature precipitation. This is accomplished -by the use of switching heat exchange zones of the regenerator or recuperative type by which the stream of incoming compressed air is cooled to a temperature below the precipitation temperature of carbon dioxide in heat interchange with a stream of relatively cold product of the fractionating operation. The carbon dioxide precipitated from the air feed collects in one passageway of the heat exchange zone and when the heat exchange zone is switched the product gas is caused to flow through the passageway in which the carbon dioxide has deposited, countercurrent to the direction of flow of the air feed therethrough, to sweep out the carbon dioxide deposits.

Due to the difference of theispecitic heat of high pressure air Iand low pressure product gases at low temperature, means must be provided to unbalance the heat exchange zone in order to substantially completely remove carbon dioxide deposits -by the outowing product stream. Even in cycles employing unbalanced heat exchange zones, particles of carbon dioxide are entrained in the air feed owing from the heat exchange zone and Y accumulate at some point in the cycle producing malfunc- ICC i tions and eventually requiring shutdown for defrosting. In addition, switching type heat exchange devices are expensive to manufacture and the required switclnng presents mechanical and operational diiculties.

In copending application of Clarence I. Schilling and Clyde McKinley, Serial No. 576,963, tiled April 9, 1956 for Method and Apparatus for Separating Gaseous Mixtures Including High Boiling Point impurities, now Patent No. 2,968,160, there is disclosed an arrangement for substantially completely removing from a fractionating cycle high boiling point impurities introduced into the cycle with the feed mixture without employing chemical scrubbing or switching heat exchange zones. According to the method and apparatus disclosed and claimed in this copending application, gaseous feed mixture enters the cycle under a predetermined relatively high pressure and is cooled in heat exchange effecting relation with cold product gas without precipitation of high boiling point impurity in the passageway of a non-switching heat exchange zone and the stream is then expanded to a relatively low pressure, such as a pressure as exists in the fractionating zone, to establish the pressure and temperature Conditions for precipitation of high boiling point impurity. The expanded gaseous mixture includes precipitated high boiling point impurity and high boiling point impurity dissolved in the gaseous mixture. A uid stream including substantially the total high boiling point impurity of the gaseous mixture is formed from the stream of expanded gaseous mixture and passed through filter and adsorber zones to substantially completely remove high boiling point impurity therefrom. Precipitated high boiling point impurity is substantially removed in the iilter zone, While high boiling point impurity dissolved in the Huid stream and precipitated high boiling point impurity that may How through the filter zone are removed in the adsorber zone. From the adsorber zone the lluid stream is fed to a fractionating zone for low temperature separation. e

In one type of fractionating cycle constructed in accordance with the principles of the Schilling and McKinley application discussed above, expanded gaseous feed mixture is fed to the high pressure zone of a two stage fractionating column and the liuid stream passed through the filter and adsorber zones comprises a stream of liquid fraction withdrawn from the base of the high pressure section, such as a stream of liquid crude oxygen in the case of the separation of air. It has been discovered that in this type of cycle certain physical characteristics of the feed mixture are critical with respect to the percentage of the total high boiling point impurity contained in the fluid stream passed through the iilter and adsorber zones. In particular, in a cycle of the above type in which a portion of the feed mixture is expanded with work in order to provide refrigeration required to produce a liquid product, it /has been determined that a substantial portion of the high boiling point impurity precipitates on the lower fractionating tray or trays of the high pressure zone and alects fractionating efliciency. It is believed that this undesirable performance results from the fact that the effluent from the expansion engine comprises superheated vapor and that the high boiling point impurity contained in the superheated vapor is not cooled to precipitation temperature prior to contact with the lower fractionating tray of the high pressure zone or prior to reaching a region adjacent the lowermost fractionating tray.

It is an object of the present invention to provide a novel method and apparatus which solves the foregoing problem. t

Another object is to provide a novel method and apparatus for removing high boiling point impurities from a fractionating operation.

Still another object of the present invention is to provide a novel method of and `apparatus for removing high boiling point impurities from a fractionating cycle in which the gaseous feed mixture is cooled to different relatively low temperatures.

In general, according to the principles of the present invention substantially the total high boiling point impurity may be removed from gaseous feed mixture through the use of filter and adsorber zones by conditioning the gaseous feed mixture in a novel manner to insure that substantially the total high boiling point impurity is precipitated or dissolved in a iiuid that may comprise a portion of the gaseous feed mixture or a iiuid including components of the gaseous feed mixture. The required conditioning of gaseous feed mixture may be accomplished according to the present invention by intermixing portions of the gaseous feed mixture at different relatively low temperatures, or by intermixing the total gaseous feed mixture or a portion of the gaseous feed mixture with a iiuid including components of the gaseous feed mixture, or by a combination of separation and intermixing steps.

Other objects and features of the present invention will appear more fully below from the following detailed description considered in connection with the accompany- .ng drawings which disclose several embodiments of the nvention. It is to be expressly understood that the drawngs are designed for purposes of illustration only and 1ct as a definition of the limits of the invention, refer- :nce for the latter purpose being had to the appended :lai-ms.

-In the drawings, in which similar reference characters lenote similar elements throughout the several views:

FIGURE 1 is a diagrammatic illustration of a frac- :ionating cycle embodying the principles of the present nvention;

FIGURE 2 is a diagrammatic view of anotherfem- Jodirnent of the present invention;

FIGURE 3 is an enlarged view, partially in section, )f a device included in the cycle shown in FIGURE 2;

FIGURE 4 is a view in section taken along the line l-4of FIGURE 3;

FIGURE 5 is a view in section taken along the line --S of FIGURE 3;

FIGURE 6 is a diagrammatic view of a fractionating :ycle constructed in accordance with another embodinent of the present invention;

FIGURE 7 is a diagrammatic showing of still another mbodiment of the present invention, and

FIGURE 8 is a diagrammatic illustration of a fracionating cycle embodying further features of the present avention.

With reference more particularly to FIGURE 1 of he drawings, a fractionating cycle embodying the priniples of the present invention is disclosed therein for eparating low-boiling components of gaseous mixtures ncluding higher boiling point impurities. Gaseous feed mixture, such as atmospheric air under superatmospheric ressure and substantially free of moisture, enters the ycle through conduit 10 and is conducted thereby to ath 11 of heat exchange device 12 for `heat exchange ffecting relationship with cold product of a fractionating peration described in detail below. A first stream of aseous feed mixture, comprising a portion of the 'total aseous mixture, isV withdrawn from the path I11 by a onduit \13 and conducted thereby to an expansion engine 4 wherein the first stream of the gaseous mixture is ex- `anded with the production of work to a relatively low' uperatmospheric pressure. The iirst stream of gaseous iixture is withdrawn from the path 11 at a tempera- 1re such that liquid does not form in the expansion enine 14 and the eiiluent from the expansion engine inthe onduit l1S is cooled to a temperature within the supereat region at the relatively low pressure. The temperain the gaseous mixture, such as carbon dioxide in the case of air feed, and the superheated vapor from the expansion engine includesgaseous high boiling point impurities. A control valve y16 is provided'in the conduit 13 to determine the percentage of the total feed mixture passed to the expansion engine. The remaining portion of the feed mix-ture, or second stream of feed mixture, flows through the path 11 and emerges from the cold end of the heat exchange device 12 in conduit 17 at a temperature slightly above saturation temperature at the existing pressure and is then expanded in valve 18 to a relatively low superatmospheric pressure corresponding to the pressure of the effluent from the expansion engine. The second stream of the feed mixture upstream of the expansion valve 18 is above a critical pressure so that highV boiling point impurities remain Yin gaseous phase, however the pressure and temperature conditions downstream of the expansion valve are such that high boiling point impurities precipitate and a portion of the feed mixture'smay be liquefied.

In accordance with the principles ofthe present invention, the first stream of superheated gaseous mixture from the expansion engine is cooled to a temperature at least corresponding to the precipitation temperature of the high boiling point impurities at the existing pr-essure in order to concentrate substantially the total high boiling point impurity of the total feed mixture in a fluid stream for passage to filter and adsorber zones. This is accomplished in the embodiment of the invention shown in FIGURE l by intermixing the first and second streams of feed mixture in such a manner as to concentrate substantially the total high boiling point impurity in the liquid portion of the feed mixture. The intermixing may or may not comprise a heat interchange resulting in the total gaseous mixture being at a substantially uniform temperature, such as saturation temperature, depending at least in part upon the precipitation temperature of the high boiling point impurities. As shown in FIGURE 1, the conduitsl I15 and 19 feed the first and second streams of gaseous mixture to the base of a conglomerator 20 f which comprises a closed vessel including a liquid outlet conduit 21 and a vapor outlet conduit 22. The liquid outlet conduit 21 communicates with the vessel at a medial level dividing the vessel into ar lower liquid receiving chamber 23 and an upper vapor receiving chamber 24.

The size of the liquid receiving chamber 23 is designed so that vapor entering the chamber 24 is substantially free of high boiling point impurity. As mentioned above,

vapor entering the chamber 24 may be at a temperature above the temperature of the liquid in the chamber 23 or the vapor and liquid withdrawn from the conglomerator may be at a substantially uniform temperature, such a saturation temperature depending in part upon the precipitation temperature of the high boiling point impurities in the gaseous mixture. In any event, the vapor portion withdrawn from the conglomerator in the conduit 22 is substantially free of high boiling point impurities and substantially the total high boiling point impurities are concentrated in the liquid portion withdrawn through the conduit 2'1, either as precipitated high boiling point impurity or as high boiling point impurity dissolved in the liquid portion. The conduits 21 and 22 are connected to a conduit 25 and the total feed mixture is fed thereby to a high pressure section 30 of a two-stage f-ractionating column 31 which may be of conventional construction including a low pressure section 32 and a refluxing condenser 33, the high pressure section 30 and the low pressure section 32 being provided with suitable liquid-vapor contact means such as fractionating trays 34. The .feed mixture undergoes preliminary separation in the high pressure section 30 producing a high boiling point liquid fraction collecting in a pool 35 in the base of the column and a gaseous low boiling point fraction 1re of the expansion engine eiuent may be above the 75 which lows upwardly into the refluxing condenser 33,

and is liquefied therein in heat exchange effecting relation With liquid high boiling point component collecting in a pool 36 in the base of the low pressure section and surrounding the tubes of the refluxing condenser. Liquetied low boiling point fraction flows downwardly from the reuxing condenser with a Dart entering the low oressure section as reux and with another part being collected in a pool 37 below the refluxing condenser from which a stream is withdrawn by conduit 38, expanded in valve 39 and introduced into the upper end of the low pressure section as reflux. A stream of liquid high boiling point fraction is withdrawn from the pool 35 by way of a conduit 40 as feed for the low pressure section. As described in the copending application of Clarence J. Schilling and Clyde McKinley discussed above, the stream of high boiling point liquid fraction is passed in series through lteriand adsorber zones and then expanded and introduced into the low pressure section. As shown in the drawings, the conduit 4t) is connected through switching valves 41 and 42 to lters 43'and 44. The filters are connected by conduits 45 and `46 to .absorbers 47 and 4S, respectively, and the adsorbers are connected through switching valves 49 and 56 to a conduit 51 communicating with the low pressure section. An expansion valve 52 is included in the conduit 51 for reducing the pressure of the stream of high boiling point fraction to correspond to the pressure of the low pressure section. Upon operation of the switching valves 41, 42, y49 and 50, the stream of liquid high boiling point fraction is caused to iiow serially through filter 43 and adsorber 47 or serially through filter 44' and adsorber 48 on its way to the low pressure section. High boiling point impurity is substantially removed from the stream of liquid high boiling point fraction upon flowing through a filter-adsorber combination. Precipitated high boiling point impurity is substantially completely removed in the lters 43 or 44 and the adsorbers 47 and 48 substantially completely remove high boiling point impurity dissolved in the liquid as well as particles of precipitated high boiling point irnpurity that may pass through the filters. The lter-ad sorber combinations are provided in duplicate so that upon operation of the switching valves 41, 42, 49 andV 50 one combination is onestreanl While the other combination is off-stream for reactivation and purging operations. The latter operations may be accomplished according to the principles of the copending application by flowing a warm uid stream, such as a stream of Warm product gas, from conduit 53 to the conduit 45 or the conduit -46 depending upon the position of the control valves 54 and 55. The purging stream thus flows through the filters 43 or y44 in countercurrent relation with the stream of high boiling point fraction and leaves the cycle through outlet conduits '56 or y57 provided with control valves 58 and 59y respectively, and flows through the adsorbers 47 or 48 in concurrent relation with the stream of high boiling point fraction and leaves the cycle through outlet conduits 60 or 61 provided with control valves 62 and 63.

Separation of the `gaseous mixture is completed in the low pressure section producing high boiling point component collecting in liquid phase in the pool 36 and low boiling point component which ows upwardly into the dome of the fractionating column and is withdrawn therefrom by way of a conduit 65. The conduit 65 conducts -a stream of low boiling point component to the cold end of path 66 of the heat exchange device 12 wherein the low boiling point component is warmed in countercurrent heat exchange effecting relation with incoming feed mixture in the path 11, the warmed stream leaving the cycle by way of a conduit 67 at substantially ambient temperature and atmospheric pressure. High boiling point cornponent may be withdrawn fromI the column in liquid phase by way of `a conduit l68 provided with -a control valve 69, or a part of the high boiling point component may be delivered in gaseous phase by way of a conduit 7 0 which communicates with path 71 of the heat exchange device 12 wherein theV stream of gaseoushigh boiling point component flows in countercurrent heat Yexchange effecting relation With incoming feed mixture and is warmed and leaves the cycle by way of a conduit 'i2 at substantially atmospheric pressure and ambient temperature.

The total gaseous mixture entering the high pressure section 30 through the conduit 25 is partly in liquid phase and partly in vapor ph-ase with substantially the total high boiling point impurity being concentrated in the liquid portion of the feed mixture, either as precipitated high boiling point impurity or as dissolved high boiling point impurity, due to the action of the conglomerator 20 as described above. Upon introduction of the feed mixture into the low pressure section theV liquid portion mixes with the liquid in the pool 35 and substantially the total high boiling point impurity collects in the liquid low boiling point fraction and is subsequently removed from the cycle by the -action of the filter-adsorber cpmbinations as discussed above. Vapor flowing upwardly toward the fractionating plates o-f the high pressure section is substantially free of high boiling point impurity and the fractionating trays remain substantially free of precipitated high boiling point impurity. The foregoing performance may be obtained by introducing the feed mixture into theA high pressure column above the pool 35 or beneath the liquid high boiling pointfraction as shown in the drawing.

In operation of the cycle shown in FIGURE l, for separating air into oxygen and nitrogen components, dry air under a pressure about 3000p.s.i.g. enters the cycle through the conduit 10 with a portion of the air feed flowing through the path 11 in countercurrent heat exchange effecting relation with cold nitrogen product =and emerging from the path 11 at a temperature of about 245 F. In the expansion valve 19 the air feed is expanded. to about 85 p.s.i.g. with a concomitant drop in temperature to yabout 278 F. and partial liquefaction takes place. Since the pressure of the air feed is above about 550 p.s.i.g. the air feed leaving the cold end of the heat exchanger 12 is abovey the precipitation temperature of carbon dioxide, however, the temperature and pressure conditions existing downstream of the expansion valve 19 are such that carbon dioxide precipitates. The remaining portion of the air isv withdrawn from the path 11 at about 100 F. and is expanded in the expansion engine \14 to about 85 p.s.i.g. and cooled to a temperature of about 190 F. Thus the etiluent from the expansion engine comprises superheated vapor including gaseous carbon dioxide. The streams of air feed are introduced into the conglomerator wherein carbon dioxide is precipitated from the superheated vapor and substantiallythe total carbon dioxide is concentrated in the liquid portion of the air either as precipated carbon dioxide or as dissolved carbon dioxide. Inasrnuch as carbon dioxide under 85 p.s.i.g. first precipitates at a temperature of about 215 F., it is only necessary to cool the superheated vapor to below this temperature and not to saturation temperature of about 280 F. Ihe combined air feed is introduced into the high pressure section with substantially the total carbon dioxide being concentrated in the liquid high boiling point fraction, crude oxygen, and subsequently removed therefrom upon -ilowing the feed to the low pressure section through the Ifilter-adsorber combinations. Of course, other high boiling point components, such as hydrocarbons, are removed from the air feed along With the carbon dioxide.

In the embodiment off the invention shown in FIGURE 2 of the drawings, feed mixture introduced into the fractionating column is either in gaseous phase substantially free of high boiling point impurity or is first passed through filter and adsorber zones to remove substantially the total high boiling point impurity therefrom. As shown, superheated feed mixture from the expansion engine l14 including gaseous high boiling point impurity and `the remainder of the feed mixture in liquid and vapor phase and containing precipitated and dissolved high boiling point impurity are fed bythe conduits 16 and 19 to a conglomerator 80 which functions to separate the feed mixture into a. vapor portion substantially free of high boiling point impurity and a liquid portion containing substantially the total high boiling point impurity. With particular reference to FIGURES 3, 4 and 5, the conglomerator 80 may comprise a closed vessel 81 of circular cross-section having a liquid outlet conduit 82 connected to the vessel at an intermediate level to divide the vessel into a lower liquid receiving chamber `at 83 and au upper vapor receiving chamber 84. The conduits 16 and 19 entering the base of the vessel may terminate in closed ends 85 and may be provided with =a series of openings 86 along their under sides for the discharge of feed mixture therefrom. The upper end of the vapor receiving chamber 84 is defined by a conical wall 87 which also forms the bottom wall of a separating chamber 88 located -at the upper end of the vessel. A conduit 8-9 is joined to the apex of the conical wall 87 and extends downwardly into the liquid receiving chamber 83 and terminates at an end 90 .adjacent the bottom of the vessel. The vapor receiving chamber 84 communicates with the separating chamber 88 by a conduit 91 having one end 92 communicating with the vapor receiving chamber and an upper end 93 being tangentially connected to the sidewall of the vessel forming the upper portion of the separating chamber.

With this construction vapor flows tangentially into the separating chamber and follows circular paths therein as shown by `arrows 94 in FIGURE 4. A vapor outlet con duit 95 extends into the upper end of the vessel 81 and downwardly into the `Separating chamber 88 and terminates therein at end 96 below the discharge end 93 of the conduit 91. In operation, the liquid receiving chamber 83 irs filled with liquefied feed mixture and the superheated vapor introduced through the conduit 16 is cooled to effect precipitation of high boiling point impurity. Vapor substantially free of high boiling point impurity is conducted from chamber 84 to the separating chamber wherein entrained liquid is separated and returned to the liquid receiving chamber through the conduit 89. Gaseous mixture in vapor phase and substantially free of high boiling point impurity is discharged from the conglomerator through the conduit 95, and gaseous mixture in liquid phase containing precipitated and dissolved high boiling point impurity flows through the conduit 82.

As shown in FIGURE 2, -the conduit 95 'feeds the vapor portion of the gaseous mixture into the high pressure section 30, either above the pool of liquid high boi-ling point fraction or into the pool as shown. The liquid portion of the gaseous mixture is conducted by a conduit 97 and merged with a stream of liquid high boiling point fraction withdrawn from the pool 35 and the combined streams are passed by the conduit through one of the filter-adsorber combinations 43`-47 or 44-48, expanded in valve 52and introduced into the low pressure section 32. In this cycle the vapor portion of the gaseous mixture introduced into the high pressure section by the conduit 95 is substantially free of high boiling point impurity and substantially the total high boiling point impurity introduced into the cycle with the feed mixture owing through the conduit 10 is removed by the filters 43, 44 and the adsorbers 47, 48.

vIn the modification of the invention shown in FIG- URE 6 of the drawings, an arrangement is provided for utilizing liquid high boiling point fraction from the high pressure section of the column as part of the liquid intermixed with the superheated vapor portion of the gaseous mixture. As shown, a stream of high boiling point liquid fraction is Withdrawn from the pool 35 in the base of the high pressure section by conduit 100 `and conducted thereby to `an injector 101 having its discharge `.feeding the liquid collecting chamber of the conglomerator 80. Conduit 19 is connected to the nozzle 102 of the injector to provide Ipropellant therefor. The liquid withdrawal conduit 82 of the conglomerator is connected by a conduit 103 to the filters 43 or 44 dependingl upon the position of switching valves 41 and 42. Gaseous mixture in vapor phase is conducted by the conduit 95 to the high pressure section of the column. In operation of this cycle the liquefied portion of the feed mixture as well as liquid high boiling point fraction withdrawn from the high pressure section of the column is fed to the conglomerator and utilized therein to precipitate high boiling point impurity from the superheated portion of the feed mixture, and the feed for the low pressure section comprises the liquid withdrawn from -the conglomerator through the conduit 82.

In the embodiment of the invention shown in FIGURE 7 of the drawings, the expansion valve l18 functions to expand the feed mixture to anintermediate pressure above the pressure existing in the high pressure section 30, and the effluent from the expansion valve 18 including liquid and vapor is conducted by the conduit 19 to a phase separator 110. Vapor is withdrawn from the separator 110 and fed by conduit 111 to the nozzle of an injector 112 discharging into the bottom of the liquid receiving chamber 83 of the conglomerator 80. A stream of high boiling point fraction is withdrawn from the pool 35 of the high pressure section 30 and conducted by a conduit 113 to the inlet of the injector 112. The injector 112 may be similar to the injector 101 shown in FIGURE 6 and functions to introduce liquid high boiling point fraction into the conglomerator against the head pressure of the liquid in the chamber 83. Flowing through the nozzle of the injector, the stream of vapor 4at intermediate pres sure is expanded to about the pressure existing in the high pressure section 30. Liquid is withdrawn from the separator 110, expanded in a valve 114 to the pressure existing in the high pressure section 30, and introduced into a second phase separator115. Vapor is withdrawn from the phase separator 115 by conduit 116 and introduced into the conglomerator adjacent the bottom of the liquid receiving chamber 83, while liquid in the phase separator is withdrawn therefrom by a conduit 1'17 and fed thereby to filters 43 or 44 depending upon the position of switching valves 41 and 42. Liquid is withdrawn from the conglomerator by a conduit 118` and fed to a vessel 119 wherein -a pool of liquid 120 is maintained, the vessel may ybe provided with a device 121 for indicating the level of the liquid therein and the conduit 1'18 also conducts vapor from the vessel 119 to the conglomerator. Liquid is withdrawn fro-m the vessel by a conduit 122 and is merged with the liquid in the conduit 117 for flow through the filters and adsorbers. from the dome of the conglomerator by a conduit 123 and introduced into the high pressure section 30 of the fractionating column. The remaining portion of the gaseous feed mixture, which may comprise superheated vapor yfrom the expansion engine 14, is conducted by the .conduit 16 and introduced into the conglomerator 80 adjacent the bottom of the liquid receiving chamber 83. In this cycle the portion of the feed mixture in vapor phase, which may comprise efliuent from the expansion engine 14 and vapor withdrawn from the phase separators and 115 as shown, is intermixed in the conglomerator with liquid high boiling point fraction from the high pressure section substantially completely free of high boiling point impurity. This performance is obtained since the vapor from the conglomerator in conduit 123 is substantially free of high boiling point impurity and comprises the feed for the high pressure section of the column. The liquefied portion of the feed mixture from the phase separator and liquid withdrawn from.y the conglomerator including substantially the total high boiling point impurity of the feed mixture in conduits 16 and 116, are merged land passed through lfilters and adsorbers prior to introduction into the low pressure section 32 as feed. The

Vapor is withdrawn Y boiling point fraction.

9 vessel 119 provides an arrangementfor controlling the ow of liquid through the conduit 117 and into the filters and adsorbers.

In the cycle shown in FiGURE 8 o-f the drawings, the superheated vapor from the expansion engine 14 is conducted by the conduit 1,6 to an extension 124 of the high pressuresection 30. The partly liquefied gaseous mixture downstream of the expansion valve 18 is fed by lthe conduit 19`to -a phase separator 125 having a vapor outlet conduit 126 feeding theextension 124 and a liquid outlet conduit 127 connected to the filters 43 and 44 through the switching valves 41 and 42. The extension 124 of the high pressure section 30 retains a pool 128 of liquid high boiling point fraction, the depth of the pool being determined by the location of alliquid withdrawal conduit 129 connected to the conduit 127. The extension 124 may also include a plurality of trays such as, trays 130 and 131 positioned above the pool 128 and below the lowermost tray 34 of the high pressure section 30. 'Ihe trays 130 and 131 are of the sieve type provided with openings of a diameter larger than the openings in sieve type fractionating trays, such as about one-half inch in diameter for example. In operation of this embodiment, vapor portion of the feed mixture such as superheated vapor from the expansion engine and vapor from the separator `12S, is fed into the extension 124 adjacent the bottom of the pool 128 wherein high boiling point impurity is precipitated and concentrated in the liquid high Vapor flows upwardly from the pool 128 and through the enlarged openings in the trays 130 and 131 in intimate contact with downwardly flowing liquid. High boiling point impurity that may flow upwardly with the vapor is substantially completely precipitated and deposits around the periphery of the openings in the trays 130 and 131 with the result that vapor entering the high pressure section 30 is substantially completely free of high lboiling point impurity. High boiling point impurity deposits are dissolved by liquid flowing downwardly through the openings of the trays 130 and 131 and substantially the total high boiling point impurity of the vapor portion of the feed mixture is concentrated in the liquid of the pool 128. Liquid gaseous mixture from the separator 125, containing precipitated and dissolved high boiling point impurity, and liquid withdrawn from the pool 128, also containing precipitated and dissolved high boiling point impurity, are merged, passed through one of the filter-adsorber combinations and fed, substantially free of high boiling point impurity, into the low pressure section wherein the separation is completed producing liquid high boiling point component and gaseous low boiling point component. If desired the extension 124 may comprise aseparate vessel unattached to the fractionating column except for conduits conducting liquid from the bottom of the high pressure section to the top of the extension and vapor from the top of the extension to the bottom of the high pressure section. When it is not possible to transfer liquid under the influence of gravity a transfer pump may be employed Ior an ejector system similar to the arrangementyof FIGURE 7 may be used. In the latter case, the ejector 112 could be located adjacent the upper end of the extension to discharge liquid therein above the trays 130 and 131.

While the various embodiments of the invention have been described in the environment of a fractionating operation in which a portion of the feed mixture may be at a temperature Within the superheat region, it will be appreciated that certain novel features of the present invention provide unobvious advantages in aiding in the removal of high boiling point impurities from feed mixtures which may be below the superheat regon such as at saturation temperature. For example, in the embodiment of the invention shown in FIGURE 7, when product is not withdrawn in liquid phase adequate refrigeration may be obtained without the expansion engine 14 and the valve 15 may be closed to pass the total feed mixture through the 1o heat exchange device 12. In such case, the vapor portions of the feed mixture from the phase separators -110 and 115 are intermixed with liquid high boiling point fraction in the `conglomerator providing gaseous mixture in/ vapor phase from the conglomerator substantially completely free of high boiling point impurity which comprises the feed for the high pressure section. Thus the invention provides :an arrangement for obtaining more complete removal of high boiling point impurity from the feed mixture in vapor phase by separating the liquid and vapor phase of the feed mixture and then mixingthe vapor portion with a liquid substantially 'free of high boiling point impurity, which liquid may include components of the feed mixture. Moreover, although the cycles disclosed and described above are of the type in which substantially the total high boiling point impurity in the feed mixture is removed from the cycle by means of filters and adsorbers, it is to be expressly understood that the principles of the present invention may be employed with cycles including switching heat exhange zones for removing the major portion of high boiling point impurities from the feed mixture. `In cycles employing switching heat exchange zones, particles of precipitated high boiling point impurity become entrained in the feed mixture and are passed into the cycle downstream of lthe heat exchange zones and collect in a cold portion of the cycle requiring eventual defrosting. By treating the cold feed mixture downstream of the heat exchange zones in accordance with the principles of the present invention the total high boiling point impurities may be substantially completelyV removedfrom the cycle.

Although several embodiments of the present invention have been disclosed and described herein, it is to be expressly understood that various changes'and substitutions may be made therein without departing from the spirit of the invention as well understood by those skilled in the art. For example, although the invention has been described in the environment of separation of air it is to be expressly understood that the invention may be employed in fractionating cycles designed for separating other gaseous mixtures. In addition, although in each of the disclosed cycles the expansion engine is fed with a side stream of gaseous feed mixture it is within the scope of the present invention to feed the expansion engine with a separate stream of gaseous mixture under a pressure different from the pressure of the remaining portion of the feed mixture. Reference therefore will be had to the :appended claims for a definition of the limits of the invention.

What is claimed is:

1. Method of separating in a low temperature fractionating operation components of gaseous mixtures` including high boilingpoint impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point fraction .and gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a stream of compressed gaseous mixture and passing the stream of compressed gaseous mixture in heat exchange effecting relation with cold product of the operation to cool the stream. of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool stream of gaseous mixture to arelatively low pressure and further cooling the gaseous mixture within the superheat region, providing liquid material Vincluding components of Ithe gaseous mixture, intermixing the stream of expanded gaseous mixture with the liquid material to cool the expanded gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing .pressure and sepl arating the resulting intermixture to provi-de a [saturated] vapor portion and a liquid portion, feeding [saturated] vapor portion to the high pressure fractionating zone, forming a lluid stream including the liquid portion of the intermixture and substantially the total high boiling point impurity of the stream of gaseous mixture, and paing the fluid stream through lter and adsorber zones and then to the low pressure fractionating zone, the fluid stream including the total liquid high boiling point fraction fed to the low pressure fractionating zone.

2. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point fraction and gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a stream of compressed gaseous mixture and passing the stream of compressed gaseous mixture in heat exchangeeffecting relation with cold product of the operation to coolV the stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool streamY of gaseous mixture to a relatively low pressure and further cooling the gaseous mixture within the superheat region, providing liquid material including components of the gaseous mixture, intermixing the stream of expanded gaseous mixture with the `liquidmaterial to cool the expanded gaseous mix-ture to at least [its saturation] the precipitation temperature of the high boiling point impurity -at the existing pressure and separating lthe resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding [saturated] vapor portion to the high pressure fractionating zone, forming a lluid stream consisting of the liquid portion of the intermixture and liquid high boiling point fraction withdrawn from the high pressure fractionating zone, and passing the uid stream through filter and adsorber zones and then to the low pressure fractionating zone, the liquid high boiling point fraction of the uid stream comprising the total liquid high boiling point fraction fed to the low pressure fractionating zone.

3. Method of separating in a low temperature fractionating operation components of gaseous mixtures i11- cluding high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction and `a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a rst stream of compressed gaseous mixture and passing the rst stream of compressedgascous mixture in heat exchange electing relation with product of the operation to cool the first stream of gaseous mixture to a relatively' low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool first stream of gaseous mixture to a relatively low pressure and further cooling the stream to Within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the second Istream of gaseous mixture to a temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream,- intermixing the expanded rst stream of gaseous mixture and the expanded second l2 stream of gaseous mixture to cool the first stream of gaseous mixture to at least [its saturation] -ihe precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting interf mixture to provide a [saturated] vapor portion and a liquid portion, feeding the [saturated] vapor portion to .the high pressure fractionating zone, conducting the liqluid portion and liquid high boiling point fraction from the high pressure fractionating zone through lter and adsorber zones and then to the low pressure fractionating zone, the liquid high boiling point fraction fed to the iilter and adsorber zones comprising the total liquid high boilling point fraction fed to the low pressure fractionating zone.

4. Method of separating in a lo-w temperature fractionating operation components of gaseous mixtures including highfboiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction land a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product VYand gaseous low boiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the irst stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool rst stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing the seco-nd stream of compressed gaseous mixture in heat exchange eecting relation with product of the operation to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature,l expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, intermixing the expanded rst stream of gaseous mixture and the expanded second stream of gaseous mixture to coo-l the rst stream of gaseous mixture to at least [its saturation] the precipitation .temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding the [saturated] vapor portion and the liquid portion to the high pressure fractionating zone, withdrawing liquid including liquid high boiling point fraction from the high pressure fractionating zone, passing withdrawn'liquid through filter and adsorber zones and then to the low pressure fractionating Zone, the liquid high boiling point fraction passed through the lter and adsorber zones comprising the total liquid high boiling point fraction passed to the low pressure fractionating zone.

5. Method of separating 4in la low temperature fractionating operation `components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fraotionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction and a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point produot and gaseous low boiling point product, which method comprises providing a rst stream of compressed gaseous mixture and passing the lrst stream of compressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the rst -stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing 13 expansion step, expanding the cool first stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange effecting relation with product of Ithe operation to cool the second stream of gaseous mixture to a tem-V perature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, intermixing the expanded first stream of gaseous mixture and the expanded second stream of gaseous mixture to cool the first stream of gaseous mixture to at least [its saturation] the precipitation temperature ofthe high boiling point impurity at the existing pressure `and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding the [saturated] vapor portion of the high pressure fractionating zone, withdrawing liquid high boiling point fraction from the high pressure fractionating zone, combining withdrawn liquid high boiling point fraction and the liquid portion of the intermixture to form a composite stream, Iand passing the composite stream through filter and adsorber zones and then to 4the low pressure fractionating zone.

6. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point fraction and gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a stream of compressed gaseous mixture and passing the stream of compressed gaseous mixture in heat exchange effecting relation with cold product of the operation to cool the stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form -in an ensuing expansion step, expanding the cool stream of gaseous mixture to a relatively low pressure and further cooling the gaseous mixture within the super-heat region, intermixing the stream `of expanded gaseous mixture with liquid high boiling point fraction to cool the expanded gaseous mixture to at least .[its saturation] the precipitation temperaf turer of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding [saturated] vapor portion to the high pressure fractionating zone, and passing the liquid portion through filter and adsorber zones and then to the low pressure fractionating zone.

7. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed `and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture under-I goes preliminary separation producing a liquid high bo-iling point fraction and a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the providing a 4second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange leffecting relation with product of the operation to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture rto the relatively low pressure and partially liquefying the second stream, separating the expanded second stream .into a vapor portion and a liquid portion, intermixing the vapor portion of the expanded `second stream and the expanded first stream with liquid high boiling point fraction -to cool the first stream of expanded gaseous mixture to at `least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide la [saturated] Vapor por-tion and a liquid portion, feeding the [saturated] vapor portion to the high pressure fractionating zone, and passing the liquid portion of the second stream of gaseous mixture and the liquid portion of the intermixture through filter and adsorber zones and then to the low pressure fractionating zone.

8. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high Vboiling point fraction and a gaseous low boiling point frac- -tion and in which Iliquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and "gaseous lowV boiling point product, which method comprises providing a first stream of compressed gaseous mixturev and passing the first stream of compressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the rst stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool first stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream of lcompressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to the relatively low pressure'and partially liquefying the second stream, inter-mixing the first stream of expanded gaseous mixture with gaseous mixture of the second stream of expanded gaseous mixture and liquid high boiling point fraction to cool the first stream iof expanded gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding the [saturated] vapor por` Y tion to the high pressure fractionating zone, and conducting the liquid portion through filter and adsorber zones vand then to the low pressure fractionating zone.

9. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fedto a high pressure fractionating zone wherein the mixture under- -goes preliminary separation producing a liquid high boiling point fraction and a gaseous low boiling point @fraction and in which liquid lhigh boiling point fraction is fed to a low pressure fractionating zone `wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heat exchange effecting relation with the second stream of compressed gaseous mixture in heat,

exchange effecting relation with product of the operation to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature, ex-y panding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, intermixing the first stream of expanded gaseous mixture with the second stream of expanded gaseous mixture and liquid high boiling point lfraction to cool the first stream of expanded gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, :feeding the [saturated] vapor portion to the high pressure fractiona-ting zone, and conducting the liquid portion through filter and adsorber zones and then to the low Ipressure fractionating zone, theliquid high boiling point fraction of the intermixture comprising the total high hoiling point fraction fed to the low pressure fractionating zone.

l0. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high iboiling pointimpurity, in which operation compressed and cooled gaseous mixture is fed to a `high pressure fractionating zone wherein the mixture undergoes preliminary separation producing -liquid lhigh boiling point fraction and gaseous low hoiling point fraction and in which liquid high fboiling point fraction is fed to a lowpressure fractionating zone wherein the separation is continued producing liquid high 'boiling point product and gaseous low boiling point product, which method comprises providing a stream of compressed' gaseous mixture and passing the stream of compressed `gaseous mixture in heat exchange effecting. relation with cold product of the operation to cool the stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool stream of gaseous mixture yto a-relatively low pressure and further cooling the -gaseous mixture within the superheat region, passing the stream of expanded gaseous mixture to an intermixing zone, employing energy of the expanded gaseous mixture to conduct liquid high 'boiling point fraction from the highpressure fractiouating zone to the intermixing zone to cool the expanded gaseous mixture to a least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure, withdrawing [saturated] vapor from the intermixing zone and feeding [saturated] vapor Ito the high pressure fractionating zone, withdrawing liquid from the intermixing zone and passing the liquid through lter and adsorber zones and then to the low pressure ractionating zone.V

ll. Method of separating in a low temperature rfractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high hoi]- ing point `fraction and a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high lboiling point product and `gaseous low boiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heatexchange effecting relation with product of the operation to cool the first stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool tirst stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing Ithe second ,stream of compressed gaseous mixture in heat exchange Vapor from the intermixing zone and feeding the [saturated] Vapor tothe high pressure fractionating zone, withdrawing liquidvfrom the intermixing zone and conducting such liquid through filter and adsorber zones and then to the low pressure fractionating zone.

12. Method lof separating in a low temperature fractionating operation components of gaseous mixtures including high fboiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure ractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction and a gaseous low hoiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low hoiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the irst stream vof compressed gaseous mixture in heat exchange eifectinglrelation with product of the operation to lcool the first stream 'of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, expanding the cool rst stream of gaseous mixture to a relatively/ low pressure and further cooling the stream t0 within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream relation with product of the operation to cool the second stream of `gaseous mixture to a temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to an intermediate pressure above the relatively low pressure and partially liquefying the second stream, separating the expanded second stream into an intermediate pressure vapor portion and an intermediate pressure liquid portion, expanding the intermediatepressure liquid portion to the relatively low pressure and separating the expanded intermediate pressure liquid portion into a low pressure vapor `portion and a low pressure liquid portion, inter-mixing the intermediate pressure vapor portion and the low pressure vapor portion of the expanded second stream and the expanded first stream with liquid high boiling point fraction to cool the first stream of expanded gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, feeding the [saturated] vapor portion to the high pressure fractionating zone, passing the low pressure liquid portion and the liquid portion of the intermixture through filter and adsorber zones and then to the low pressure fractionating zone.

13. Method of separating in a low temperature fractionating operation components of gaseous mixtures including high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture under- 17 goes preliminary separation producing a liquid high boil ing point fraction and a gaseous low boiling point fracl tion and in which liquid high boiling point fraction is fed to a low pressure fractionating zone lwherein the separation is continued producing liquid high boiling pointproduct and gaseous low-boiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the first stream of comp-ressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the first stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuring expansion step, expanding the cool first stream of gaseous mixture to a rel-atively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange eifecting relation with product of the operation to cool the second stream of gaseous mixture to a.y temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to an intermediate pressure above the relatively low pressure and partially liquefying the second stream, separating theL expanded second stream into an intermediate pressure vapor portion and an intermediate pressure liquid portion, expanding the intermediate pressure liquid portion to the relatively low pressure and sepiarating the expanded intermediate pressure liquid portion into a low pressure vapor portion and la low pressure liquid portion, feeding the intermediatepressure vapor portion and the low pressure vapor portion of the expanded second stream and the expanded first stream to an intermixing zone and utilizing energy of expanded gaseous mixture to conduct liquid high boiling point fraction from the high pressure fractionating zone to the intermixing zone, withdrawing [saturated] vapor from the intermixing zone and feeding such [saturated] vapor to the high pressure fractionating zone, withdrawing liquid from the intermixing zone and conducting such liquid and the low pressure liquid portion through filter and adsorber zones and then to the low pressure fractionating zone. f

14. Method of separating in a low temperature fractionating operation components of gaseous mixturesincluding high boiling point impurity, in which operation compressed and cooled gaseous mixture is fed to a high pressure fractionating zone wherein the mixture undergoes prelirninary separation producing a liquid high boiling point fraction and a gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, which method comprises providing a first stream of compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heat exchange eifecting relation with product of the operation to cool the first stream of gaseous mixture to a relatively low predetermined temperature such that liquid willV not form in an ensuing expansion step, expanding the cool first stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange effecting relation with product of the operation to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature, expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, separating the expanded second streamv into a vapor portion and a liquid portion, passing the vapor portionof the expanded second stream and the expanded first stream with liquid high boiling point fraction to a liquid receiving zone in vapor communication with the high pressure fractionating zone to 18' intermix the vapor portion and the second stream of gaseous mixture with liquid in the liquid receiving zone, withdrawing liquid from the liquid receiving zone, passing liquid withdrawn from the liquid receiving zone and the liquid portion of the second stream of gaseousmixlture through iilter and adsorber zones and then to the low pressure fractionating zone.

l5. Method of separating air in a low temperature fractionating operation to produce liquidoxygen product, in which operation compressed and cooled air is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point fraction Iand gaseous low boiling point fraction and in which liquid high boiling point fraction is fed to a low pressure fractionating zone wherein =the separation is continued producing liquid oxygen product and gaseousy lowfboillng .point product, which method comprises providing a stream of compressed air and passing the stream of compressed air in heat exchange eiecting relation with gaseous low boiling point product of the operation to cool the stream of lair to a relatively low predetermined temperature such that liquid will not form Vin an ensuing expansion step, work expanding the cool stream of air to a relatively low pressure and further cooling the gaseous mixture within the superheat region, providing liquid material including components` of air, intermixing the stream of expanded air with the liquid material to cool the expanded air to at least [its saturation] the precipitation temperature of the high` boiling point impurity at the existing pressure `and separating the resulting intermixture to provide a [saturated] vapor portion and la* liquid portion, yfeeding [saturated] vapor portion to the high pressure -fractionating zone, forming a iluid stream including substantially the high boiling point impurity of 'the air and passing the iiuid stream through ,lter and adsorber zones and then to the `low pressure fraetionating zone, the iluid stream including the total liquid high boiling point fraction fed to the low pressure fractionating zone, and. withdrawing liquid oxygen from the low pressure fractionating zone. p t

16. Method of separating air in `a. low temperature fractionating operation to produce liquid` oxygen, in which operation compressed'iand cooled air is fed to a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction and a gaseous low boiling point fraction .and in which liquid high boiling point fraction is fed -to a low pressure fractionating zone wherein the separation is continued producing liquid oxygen product Iand gaseous low boiling point product, which method comprises providing la lirst stream of compressed air `and passing the first stream of compressed air in heat exchange effecting relation with gaseous low boiling point product of the operation to cool the fir-st stream of air to a relatively low predetermined temperature such that liquid will-not form in an ensuing expansion step, work expanding the cool yfirst stream of air to a relatively low pressure and further cooling the air to within the superheat region, providing 4a second stream of compressed air Iand passing the second stream of compressed air in heat exchange eiecting relation with gaseous low boiling point product of the operation to cool the second stream of air to a temperature lower than the predetermined temperature, expanding the cool second stream of t air to the relatively low pressure and partially liquefying the second stream, intermixing the rst stream of expanded air with at least a portion of the second stream of expanded air and liquid high boiling point tt-nacti'on to lcool the first stream of expanded air to at least [its saturation] the `precipitation temperature of vthe high boiling point impurity at the existing pressure and separating the resulting intermixture to. provide ,a

[saturated] vapor portion and -a liquid portion, Ifeeding the [saturated] Vapor portion to the high pressure fractionating zone, and conducting `the liquid portion through 19 filter and adsorber zones and then to the low pressure fractionating zone.

17. Apparatus for separating components of gaseous mixtures comprising Ia two-stage fractionating column including a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point fraction and gaseous low boiling point fraction and a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point productand gaseous low boiling point product, means providing a stream of compressed gaseous mixture and passing the stream of compressed gaseous mixture in heat exchange effecting relation with cold product of the ractionating column to cool the stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, a work expansion engine for expanding the cool stream of gaseous mixture to a relatively low pressure and further cooling the gaseous mixture within the superheat region, means providing liquid material including components of the gaseous mixture, means intermixing the stream of expanded gaseous mixture with the liquid material to cool the expanded gaseous mixture to at least [its saturation] the precipitation temperature of 'the high boiling point impurity lat the existing pressure pressure fractionating zone.

1,8. Apparatus'for separating components of gaseous mixtures comprising a two-stage tfractionating column including -a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing liquid high boiling point yfraction and gaseous low boiling point fraction and a low pressure rractionating zone wherein the separation is continued producing liquid high 'boiling point product and gaseous low lboiling point prod-A uct, means providing la stream of compressed gaseous mixture and passing the stream of compressed gaseous mixture in heat exchange effecting relation with cold product for the fractionating column to cool the stream of gaseous mixture to a relatively low predetermined temperature such that liquid lwill not'form in an ensuing expansion step, la work expansion` engine for expanding the cool stream of gaseous mixture to a relatively low pressure and `further cooling the gaseous mixture within the superheat region, means intermixing the stream of expanded gaseous mixture with liquid high boiling point fraction to cool the expanded gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion Vand -a liquid portion, means feeding [saturated] vapor portion to the high pressure fractionating zone, and means passing the liquid portion through lter means and adsorber means and then to the low pressure fractionating zone.

19. Apparatus for separating components of gaseous mixtures comprising a two-stage tractionating column including a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point Vfraction and gaseous low boiling point fraction and a low pressure fractionating zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, means providing a first stream of compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heat exchange effecting relation with product of the fractionating column to cool the first stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing expansion step, a work expansion engine for expanding the cool first stream of gaseous mixture to a relatively low pressure and further cooling the stream to Within the superheat region, means providing a second stream of compressed gaseous mixture yand passing the seoond stream of compressed gaseous mixture in heat exchange effecting relation with product of the fractionating column to cool the seoond stream of gaseous mixture to a temperature lower than the predetermined temperature, means expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, means intermixing the expanded first stream of gaseous mixture and the expanded second stream of gaseous mixture to cool the iirst stream of gaseous mixture to at least [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, means feeding the [saturated] vapor portion to the high pressure fractionating zone, and means conducting the liquid portion and liquid high boiling point fraction yfrom the high pressure fractionating zone through iilter means and adsorber means and then to the low pressure fractionating zone.

20. Apparatus for separating components of gaseous mixtures comprising 'a two-stage fractionating column including a high pressure fractionating zone wherein the mixture undergoes preliminary separation producing a liquid high boiling point fraction and gaseous low boiling point Ifraction and a low pressure fractionating Zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, means providing a -iirst stream off compressed gaseous mixture and passing the first stream of compressed gaseous mixture in heat exchange effecting relation with cold product of the fractionating column to cool the first stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not yform in an ensuing expansion step, a work expansion engine for ex- Y panding the cool first stream of gaseous mixture to a relatively low pressure and `further cooling the streamto within the superheat regi-on, means providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange effecting relation with product of the fractionating column to cool the second stream olf gaseous mixture to a temperature lower than the predetermined temperature, means expanding fthe cool seoond stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, means intermixing the first stream of expanded gaseous mixture with the liquid portion of the second stream of expanded gaseous mixture and liquid high boiling point fraction to cool the first stream of expanded gaseous mixture to atleast [its saturation] the precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, means feeding the [saturated] vapor portion to the high pressure fractionating zone, and means liquid high boiling point fraction and a gaseous 10W boiling point fraction and a low pressure fractioning zone wherein the separation is continued producing liquid high boiling point product and gaseous low boiling point product, means providing a first stream of compressed gaseous mixture and passing the first stream of compressed gas- 21 eous mixture in heat exchange electing relation with product of the fractionating column to cool the rst stream of gaseous mixture to a relatively low predetermined temperature such that liquid will not form in an ensuing ex pansion step, a work expansion engine for expanding the cool tirst stream of gaseous mixture to a relatively low pressure and further cooling the stream to within the superheat region, means providing a second stream of compressed gaseous mixture and passing the second stream of compressed gaseous mixture in heat exchange eecting relation with product of the fractioning column to cool the second stream of gaseous mixture to a temperature lower than the predetermined temperature, means expanding the cool second stream of gaseous mixture to the relatively low pressure and partially liquefying the second stream, means separating the expanded second stream into a vapor portion and a liquid portion, means intermixing the vapor portion of the expanded second stream and the expanded first stream with liquid high boiling point fraction to cool the first stream of expanded gaseous mixture to at least [its saturation] zhe precipitation temperature of the high boiling point impurity at the existing pressure and separating the resulting intermixture to provide a [saturated] vapor portion and a liquid portion, means feeding the [saturated] vapor portion to the high pressure fractionating zone, and means passing the liquid portion of the second stream of gaseous mixture and the liquid portion of the interrnixture through ilter means and ad- ,fsorber means and then to the low pressure fractioning zone.

References Cited in the file of this patent or the, original patent UNITED STATES PATENTS n 1,968,518 Fraser July 31, 1934 2,537,046 Garbo Jan. 9, 1951 2,547,177 Simpson Apr. 3, 1951 2,572,933 Houvener Oct. 30, 1951 2,584,381 Dodge Feb. 5, 1952 2,615,312 Yendall` Oct. 28, 1952 2,650,482 Lobo Sept. 1, -1953 2,699,047 Karwat et a1 I an. lil, 19'55 2,846,853 Matsch Aug. 12, 1958

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