US2588656A - Method of and apparatus for treating gases - Google Patents

Description

March 11, 1952 w. w. PAGET METHOD OF AND APPARATUS FOR TREATING GASES 2 SHEETS-SHEET 1 Filed Oct.

March 11 1952 w. w. PAGET METHOD OF AND APPARATUS FOR TREATING GASES Filed Oct. 18, 1949 2 SHEETS-SHEET 2 Patented Mar. 11, 1952 *umrso s TAT'ES PATENT =-oi=rics Y .',5ss,s5c Y 'METHOD 'OFAND A PA ATUsFOR TREATING GASES twin Paget, EMichigan City, Ind, "assignor-tto :Joy Manufacturing Company, Pittsburgh, ;Pa-., a'corporation of Pennsylvania Application October 18, 1949; erial N0.'"1'22,079

This invention relates to iimprovements :in

- methods of Y and means for treating. gases; this application is a :continuation-iirr-part .of'zmycopending but now abandoned application Serial "N0. 3 1;O15, filed .J une 4, .19 48.

"'Itwill herein be described.:particularly in its "application 'to the .production of substantially pure oxygen fromain'tbut this :isbut illustrative, because the process and apparatus disclosed may 'oe used; with appropriate 'adaptations, with varilzousigase's to :be processed; to produce variousparticularly desired products which are constituents of the gases tobe treated. Undersomecircumsstances the desiredqproductomay be delivered at a relativelyweryhigh pressure andnndenothers at :a pressure rofsa; -few atmospheres.

It is commonly-desirable.in the. production of i oxygen by a processinvolving cooling arid rectification of compressed-air; to have the oxygen available in gaseous form at .a.,press'i1re*substantially above column pressure butjfon the-"other -.hand, much below cylinder pressure (cylinder pressure'is on the order cf"2000.p.s.'i;). For

example. oxygen may be .des'ired ata pressure on the order of 5U p. s. i.;"though this -is'butillus trative and indeed, the reference to-oxygen is' but illustrative also, because other gases-which maybe obtained by a similar-process may als'o be desired at. pressures above column "pressure. Taking the icase of oxygen iorpurposeaoffillustration, "refrigeration can "be saved by taking gaseous rather than liquid oxygen from a p'oi'nt a column above the level of the liquid oxygen therein and boosting --t he,pressure from the few *1): s; i. (-perhapsfi) which exists at that: point-fin "the'column, tothe desired delivery pressure by" "the -use =of-a compressor. Howeverpthis is object ion'able because -of..the additional power:.-reiquired and 1 because tor thesizeriof the gaseous oxygen compressor which wouldlbeirequired. 1:11;. *is much preferable to take liquid Joxygen from the column and to pump it atthe desired pressure "to-the oxygen supply line. '.Thisrpermits.:thedise ofmuch smaller pumping equipment. It ==would, '=however,'-resi1l-t in wastedl'rei rigerationzif vsome "provision w'e're not: inade-" for using.- the :-heat ;of vaporization of liquid oxygen some manner'.

-As -is disclosed and-claimed :in the application of 'Samu'el G; Collins' Serialf-No. 0122;077 sfiled 10c- -tobe1' l8} 1949, this heat =of tvapcrization' may ibe -util-ized by condensing. an equivalentkamount-of -air on its iwa'y to the."rectifier,:asxbyfibringinsean appropriate amount .of 1 :air at an -':appropriate apressu re and {temperature :.linto heat 'rexchange relation with the ileaving'g'aoxygen-et a:1;pressure substantially abovelcolumni pressure, .and iutilizing the heat of:vaporization toiefiect the liquefaction ofcompressediair.

lhave iound that efiicientiapparatus which is substantially lautomaticiimay :be made for "the production :of substantially :pure oxygen inzaccordance ththe foregoing; fby the iprovisionfin the apparatus '-of valveswhichlare v responsive- 1 to -pressure-atselected' points in the'L-syStem. AS115 m merits of the invention: are shownfhereimrbotnof 7 which are self-regulatingto operatel-theisystem set 'for'th inxdetail below, tworidifferenti embodiat a substantially con-stant compressedi.air supply pressure regardless of variations-sin the demand for oxygen.

In one ofthe embodiments, the -two expansion valves, which a're m series; are arranged *so that each valve .opensat a pre'detern'iined upstream pressure =above1.a giveni "reference pressure:of

" the system, the reference lpressure"ibeingv preferablycolumn pressure. 'In another embodiment, each valve is'- arranged '-to maintain acpredetermined pressure idifie'rential between itsl inletuand discharge sides. In both embodiments, thexpressure responsive control valves serve to maintain a substantially constant back-pressure .on the compressed air supply line, obviating; the news- 'sity of pressurerelieffvalvesywhich arei wasteful -of power.

Apart-from the "-iea'ture of bm'aintaining ancon- *s-tant "backpressure:on ithefcompressor,;thisoinvention makes the-oxygen production apparatus and method com-pletely "self regulating, motwvith'standingvariations in the demand for 01wgen and, infect, in accordance with varying demands. "Thus the valve -structures provided in is automaticallyimade upon-shift the .Otliertway.

The bypass valve .constructiontis' fsllc'h s. to

. protect the .column against damage fromblast --which might. occur. .if the grelatiiiely high" pressure 122 077 filed October characteristics of the columns require, some cases, that the second valve provide a presengine exhaust, at 50 pound oxygen production, were suddenly released into the comparatively low pressure column.

It is thus among the objects of the invention to provide a simple, compact, flexible apparatus for the eilicient separation of gases, in which oxygen can be supplied in accordance with requirements by a system embodying valves which make the system self-regulating by quickly responding to pressure changes at predetermined points in the system as variations in the demand for oxygen alter the fluid flow and pressure in the different parts of the apparatus; and in which a predetermined back pressure is maintained on the compressed air supply source regardless of demands on the system for gas. It is a further object of the invention to provide control valves which respond to pressure changes at selected points of the system to maintain desired flow and pressure balances, and which efiect the desired control without damage to the system itself.

In the obtaining of oxygen by a process involving cooling and rectification of compressed air (oxygen is again used here merely as illustrative of other gases which may be obtained by such a type of process), air is supplied at a de sired initial pressure, cooled, condensed and rectified, and the end product is delivered for use, and the pressure at which the air is supplied is desirably maintained within very close limits throughout the entire period of processing after the apparatus has once been brought to the desired working conditions.

The aforesaid and other objects are achieved in the invention described hereinafter, in which the maintenance of the desired uniformity of air supply pressure is obtained by adapting the size of the compressor closely to the capacity of the oxygen generator, and by employing two pressure controlling valves arranged in series, each valve being set to open at a predetermined pressure of the supply fluid above the operating pressure of the system at a selected point, the pressure at that point being known as the reference pressure. Alternatively, each valve can be arranged to give a predetermined pressure drop between the upstream and downstream sides thereof. One valve is disposed between the air source and an evaporator-condenser in the column, and the other between the evaporator-condenser and a point at the top of the column to which liquid air is to be delivered. The invention isshown as applied to a single column system, but a person skilled in the art will be able to apply it to other systems, as for example to the double column systems shown in patent application Serial No.

assignee of this invention, in which the single and double-column systems are disclosed as embodying manually adjustable valves.

It will be found in the explanation below that the second valve in effect maintains a predetermined substantially constant pressure drop between its supply and discharge sides, even in the embodiment shown in Fig. 1, because of the proximity of the valve to that point of the system which provides the reference pressure. The at least in sure drop between its opposite sides of slightly more than 60 p. s. i., in order that condensation of gaseous air in the column shall take place at a suiiiciently high temperature to effect evaporation of oxygen at the pressure prevailing in the column. (The column pressure, for all practical purposes, is the "reference pressure referred to 18, 1949 and assigned to the above.) The other of the two valves is designed to maintain such an air supply pressure as may be consistent with sound compressor design. In one embodiment of the invention, the valve provides an upstream pressure which, when added to the pressure required to overcome friction losses in the apparatus to that point; will require compressed air to be supplied to the system at 160 p. s. i. for a column pressure of 7 p. s. i. (all pressures are gauge unless otherwise indicated). In the other embodiment, said other valve is arranged to provide a pressure differential between its supply and discharge sides such that the total pressure drop through the system equals the desired air supply pressure.

In apparatus like that hereinafter described, oxygen may be produced at 40 to 50 p. s. i. or at a much higher value suited to charging cylinders. When making oxygen at the lower pressure, the reduction in pressure across the expansion engine is equal to that across the valve which is arranged in the line between the evaporator-condenser and the point of induction of compressed air from Figure 1 is a, diagrammatic view of a single column embodiment of the invention;

Figures 1a and lb show details of the system for another embodiment of the invention;

Figure 2 is a longitudinal section through one of the pressure control valves;

Figure 3 is a longitudinal section through the by-pass valve;

Figure 4 is a view in section line 4-4 of Figure 3;

Figure 5 is a partial view, similar to that of Figure 3, but showing the valve in its open position;

Figure 6 is a view in section on the plane of line G-6 of Figure 3; and

Figure 7 is a view, with parts broken away and in section, of the by-pass valve and its associated control. J

Referring first to the system, air at a temperature of approximately 300 K. and a pressure of 160 p. s. i. may be delivered, as from a suitable air compressor (not shown) through a conduit II to a valve mechanism generally designated 12,

on the plane of and the efiluent (mainly nitrogen) leaving the periodically moved by power, and with a snap action, to reverse the connections of the conduits H and [3 with a pair of conduits I5 and I6 which lead from the casing of the valve mechanism 12. In the Samuel C. Collins application Serial No. 661,253, filed April 11, 1946, there is diagrammatically shown a reversing valve mechanism suitable for the performance of the functions of the valve mechanism l2 and another example of a mechanism suitable for this purpose is shown in an application of Win W. Paget, Serial No. 35,092, filed June 25, 1948.

The power to shift valve mechanism l2 to alternately connect air conduit I! with conduits exchanger 2 l.

of? exchanger 22;

seri'ally; in the'order 22A, ZIA, by the oxygen" states 'l 5ff'and l6; and'simultaneouslyr alternately connectjconduit' [3 with conduits I Band" I 5 maybe taken from' any suitable source; but is desirably taken" from the drive shaft of" an expansion engine "I 8; through any suitable reducing gearing such? asthatshown" diagrammatically insaid Collins application, Serial No. 661,253. Reversals are adapted 'tobe effected at relatively shortintervals; and suitable intervalsmay been the order ofthree minutes:

Heatexchangers 2| and 22; desirablyvertically disposedandformed as'separate units instead of asone'longer unit in order to keep height within desirable limitsyare arranged in series, and entering air passes: through the heat exchangers 21? andi22'in' the orderm'entioned, while leaving nitrogenpasses" through these same heat exchangers in".the*order22,- 2 1. Heat exchanger 2| has'threecourses, indicated as-coaxial courses 21A; 2| B;and 2 lC, the first the innermost course and the latterthe" outermost; and exchanger 22 has similarly relatively arranged courses 22A, 22B andZZC, and, outside 22C, a'fourth course 22D.

Through two'ofthe courses in series-in the i,

exchangers 2i and 22;to wit, courses 21B, 22B and courses 2IC, 220, the entering air and the leaving'nitrogen flow alternately, the entering air flowing inward through one or the other of these-pairs of courses and the nitrogen flowing outward through the one'of-"such pairs of courses notat-anygiven moment serving for the inflow of the air. Through the third course, 2iA, of the exchanger 2| and through the corresponding-course,- 22A-, ofthe exchanger 22, but in the order 22A, 21A, the'leaving oxygen product is discharged Exchanger 22 has, as above noted, a fourth course 22D, through which a portion "of the air which is entering the apparatus by way of the exchangers 2|, 22is caused to recirculate through exchanger 22, the'better to effect deposition of impurities from the entering air stream and to increase the temperature of the V air-entering the expansion engine.

It'has been noted; with respect to the exchangers 2i and 22, and, it will be noted, with respect to further heat exchangers 23 and 24 hereinafter to be described, that the courses are indicated as being coaxial. It will, however, be appreciated that the precise form of construction ottheexchangers is not illustrated in the diagramofl ig. 1, since suitable multiple pass exchangers may assumevarious forms, and, in the Samuel C. Collins ap lication above identified,

a suitable form of exchanger is illustrated, and.

other possible types are illustrated in other applications of said Samuel 0. Collins, Serial Nos. 33217,.filed January 20, 1948, and'2,8'77, filed January 17,1948. Exchanger 23 will be observed shortly. to be of the four-course type, and exchanger 24 of the three-course type.

Conduit l5 communicates with course 213 of exchanger 2 l, and conduit 16 with course 2IC of The leaving oxygen product passes outward through course 21A of exchanger 2| andpasses to a shop line, to a bank of cylinders, or to any other desired point or apparatus, fori'useor storage, through a conduit 25. Course 2100f exchanger 2! is connected by a conduit 3| with 'course 22C of exchanger 22. Course 2IB of' exchanger 2! is'connected by a conduit 32 with course "223 of'exchanger'22. A conduit 33 connects'course 2iA'ofexchanger 2! with course 22A These courses are traversed product;'as later described-i, Itwillbe-appreciated that air will flow alternately in through course 2IC, conduittl and course 226 or course ZlBi conduit" 32 and-course 22B, while concurrently nitrogen will flow outward'through'the ones of said courses andpassages-last mentioned not carryingthe-enteringair; V

A suitable'automatic reversing valve mechanismjgenerally designated 40; is'provided at the end of heat exchangerfl :last left'by the entering air and, first entered by "thel'eaving'nitrogen; this including'four automaticcheck valves; 42% 43 and. M: This arrangementis-disc1osed in-- the Samuel C. Collins application SerialflNo: 661,253: The lower end of course-22B has connected with it a conduit 65 which leads'to the check valve' '41; and albranch ti'lea'ds from conduitii-to" check valve'eilr A conduits! leads from course-22C to check valve 44'; and a, branch, iiconnects conduit: M; at apoint between course 22C and the check valve 4%, with the check" valve'43: A conduit 69 connectsthe-other-sideof checkvalVeAS with" a conduit leading from the check'valve 4i" to" a suitable restrictor" device 5|, which creates 'a slight difference between the pressure in the conduit 58 and thepressure beyond'the device: 5!, the latter pressure being onthe order of, two pounds less thanthe pressure in conduit 5%; f A" conduit 52 connects the conduit" Eiitwith thebottom:v of course 22D; A' conduit 53" leads from the sideof check valve M'oppositethecon duitlil, to the outermostcourse of the heati'exchanger 23. Nitrogen always: flows. outward through conduit 53.. Af conduit 55 ccnnects the side of check valve 42cpposite' the conduit ifito the conduit 53. Each of'the check valves; 42, 4&3 and 54 opens in the direction indicated" by its and'prevents opposite'flow.

The restrictor 5! is connected" as at- 56 to a chamber 51 within the top of an evaporatorcondenser Gii'having a suitably insulated'casing 6i and havingin the casingan oxygen conduct.- ing conduit or courseIBZ and an air conducting conduitor course 63in close heat exchange relation witheach other. The conduit or course53 is connected at M withthe chamber 51; The oxygen conduit or course 62lis connectedby a conduit 65 with the bottom of course-22A of-exchanger22.- The top of course 221) of-exchanger 22 is'connected byaconduit ESE-with aconduit 6'? leading from-the chamber 5?,- and the reunited stream ofi airspasses toa conduit 'iii; which leads to thee-expansion engine lQ-la-ter;more'f,ully--de scribed;

' When; the. air; entering; the system is passing through course 2213; it flows through the check valve l'i.. When course: 2213 isrservingqfor:out

' flow of nitrogen, the nitrogen" flowsiromxconduit 53, through conduit 55 and check1val've42and through conduits lt and'L Fto course 223. When course 220 is serving for-inflow off'air; the entering air flows through the check valve; When course 220 isbein'g used to conductleaving nitrogen, the nitrogen'fiows through check valve 4 4 r Obviously" the arrangements of the c0urses;- and the structure of this exchanger, are subject to wide structural variations. Exchanger 24 has a central course 24A, an outer course 240 and an intermediate course 24B. It too is subject to wide structural variation. It will be understood that the several courses will be in good heat exchange relation with respect to each other.

It has been noted that the conduit 53 1s connected with the outermost course 23D of exchanger 23. This connection is with the top of such course. connected by a conduit 08 with the bottom of course 240 of exchanger 24, and the top of course 24C is connected by a conduit II with the nitrogen outlet (the effiux connection) I2 of a single column IS. The compressed air course 63 of evaporator-condenser 60 is connected by a conduit I4 with the top of course 233 of exchanger 23. The bottom of said course is connected by a conduit I5 with a suitable pressure reducing valve device 16, which is adapted, in the particular aparatus shown, and when the latter is used for oxygen production, to open at such a pressure above the reference pressure as to require compressed air to be supplied to line I I at a pressure of 160 p. s. i. when the reference pressure is 7 p. s. i. The resulting pressure drop through valve 10 is substantially the same reduction in pressure as occurs in the expansion engine later described, when the latter is operating with its longer period of admission, hereinafter fully explained.

The low pressure side of valve device I6 is connected with a conduit H which leads to a condenser coil or element #3 in the lower end of the column I3. The central course (as shown) 23A of exchanger 23 is connected at its top with a conduit I9 leading to the oxygen course 02 of the evaporator-condenser 60, while its bottom isconnected with the bottom of central course 24A of exchanger 24 by a conduit 80. A conduit 8i leads from the top of the central course 24A. This is connected with the discharge of a liquid oxygen pump, later described. The condenser unit I8 is connected at its other end (from the conduit 17), by a conduit 82, with the intermediate course 24B of exchanger 24. The top of course 2413 is connected with a conduit 83, of which more will be shortly said.

Three of the four courses of exchanger 23 have been noted. The fourth course, 230, is connected at its top with an expanded air conduit 85, and its lower end is connected with a conduit 86, containing a check valve 01 openable towards the conduit 11; conduit I1 is connected with valve 81 by a connection 88. The check valve opens towards the conduit IT, but only when the pressure in the conduit 86 is sufiicient to efiect opening of check valve 81 against the pressure in conduit TI.

The expansion engine I8 may be of the construction shown in the copending Samuel C. Collins application, Ser. No. 665,206, filed April 26, 1946, provided with suitable means for predeterminedly lengthening and shortening the period of admission, or of the character of the expansion engine employing cam follower rollers one or both of which coact with a cam depending on whether early or late cutoff is desired, which expansion engine is illustrated and described in my application, Ser. No. 31,017, filed June 4, 1948. The engine includes a cylinder 90 having admission and exhaust valves, not shown, and to the admission valve of which air under pressure is admitted from the conduit 10 through a con- The bottom of course 23D is duit 9| with which an In surge tank 92 is connected to minimize fluctuations in flow. A discharge or exhaust connection 93 leads fromthe expansion engine to a Discharge surge tank 94, which may have'associated with it a strainer to catch any snow that might otherwise attain to the column while the heat exchangers 2I and 22 were not fully cooled down during the starting of the apparatus.

The expansion engine supports on the top of its cylinder a jacketed liquid oxygen pump 95 of any suitable construction, the liquid oxygen pump being for example actuated by the expansion engine piston as is the pump shown in my last above mentioned application; and'it may be noted that the conduit 8| is connected with the discharge of the liquid oxygen pump 95, while this pump has a suction connection 96 leading to it from a strainer 91 which is cooled or jacketed by liquid air, the jacket herein being represented by a coil 98. To the strainer 91 a conduit I00 leads from the bottom of the column 13, the conduit I00 communicating with the condenser"unit-enclosing chamber IOI in the bottom of the column at a point at the desired liquidoxygen level in the latter.

The Discharge surge chamber 94 has connected with it a conduit I05 which is connected to a valve structure I08 hereinafter more fully described, which valve structure includes a passage or chamber continuously in communication with the conduit 85, and another chamber connectable through a conduit I09 directly with the interior of the column at a point spaced an appropriate distance from the top of the latter. The valve structure I06, which may be called a by-pass valve, is adapted to have the two chambers mentioned connected in communication with each other, and thus to connect the Discharge surge chamber 94 in free communication with the upper part of the column through the conduit I05, valve structure I00, and conduit I09. In the drawing the constant communication between the conduits I05 and B5 is indicated by the passage I01, and the communicability of the passage or chamber ID? with the conduit I00 is indicated by the valve I08.

The expansion engine I8 is provided, in the present particular apparatus, with valve gear adapted to permit the engine to operate with admission for a relatively short portion of its working stroke, or with admission for a considerably longer portion of its working stroke. When cutoff is relatively late in the working stroke, the valve stucture I08 will prevent communication between the Discharge surge chamber 94 and the column through the conduit I09; and when communication between the Discharge surge chamber 94 and the column is effected by the appropriate adjustment of the valve structure I06, the expansion engine will be operated with admission for the aforesaid relatively short portion of its working stroke.

With apparatus having, during low pressure oxygen production, the temperatures and pressures hereinafter mentioned, the relatively late cutoff of the expansion engine would theoretically take place at about 70% of the working stroke; and during high pressure oxygen production the relatively early cutoff would be at theoretically on the order of 25% of the working stroke, but these percentages are only illustrative. For example. there are two factors which in practice would tend to call for later cutofi in both modes of opaseaeee Serial No. 665,206,1theprovisionof;selectively.op-

. erable camswith different dwells, orcams one relatively adjustable with respect to the other. See. 'fonan .example- Fergusoni'2,221,'790, patented November. 19,1940. Cream-follower rollers one oribothcooperating with a ,cam depending on whether early or' later cutofijis desired may .be employed, .as in the apparatusiof my expansion engine application.

.,,.Only.such.air will flow through the evaporator- .condenser. 60 ascannot pass through the expansionengine. .By veryprecise design, during "50- pound.oxygenproduction, completecondensation o'fithe iractionof ..air passing through the air course 63 .of..the evaporator-condenser 60 might conceivably be efiected. .If more air passes through. this. course, however, than can be con- .densdby the refrigeration provided by evaporationofliq-uid.oxygeniat a. pressure on the order .of150 p..s. i. iinthe course 62 ofthe evaporatorcondensertm the gexcess .un'liquefied air will 1' be "condensed in evaporator-condenser 18,350 .some excess of air will logicallybe permitted.

The conduit 83, previously mentioned, leads 'to.a;pressure control valveJ II) .whichiscadapted,

as explai-ned below, -to eflect reduction on "the *ofder-of- 60' p. s. i. in the: pressure :of "the -"fluid Storms, and. Samuel 0.. Collins has ,filed. during May 1948 two applications, Serial.Nos..26,395 and .-28,87,0,.showing columns which are welladapted 'for the purpose "for whichjthe. present columnis jemployed.

Referring now toFig. 2, whichlshowsladetail or .a valve. of the type adapted to be. used. in the positionof valve 16 01 valve III], the valvelis .shown as comprising .atwo-part casingxor housing; the'lower portion I20? being connected byany suitable means with a high-pressure inlet I 2.2 and flow-pressureoutlet I24. In the oase of thevalve "lathe. inlet I22is the conduit l5, and the outlet 124 is conduitI'I. In-the case of the valve III],

' inlet I22 visthe conduit .83, and outlet I24 is the jcon'duitI II. Thelower portion I20 of the casing "has threaded engagement with a member I,2'5

which provides a valveseat I26 and .a valvejguide I28. The member Iis ported asshownzatjlSIJ itozadmitffluid'fromjthe inlet, and'is further pro- "vided with an exit passagefl32'to pass .fiuid'to the-outlet I24.

A closure member I34 consists of a plunger havingfinished guidev surfaces for collars I'36'and I38 which cooperate with the, guide member I28 gtoizkeepithefplunger' I 34zalignedas it reciprocates in valve-opening and closing movement. The plunger I34 is ;provided 1with a conical portion I40 at its one end which cooperates with the seat I26'to;cut ofi communicationbetween inlet I22 .and outlet I24I, and more immediately between "the. inlet :ports I30 and the outlet passage I32.

The upper portion I42 of the housing cooperates with the lowerportion 12!) to hold a septum I44 tightly .clainpedbetween the two portions of the casing. "The'portions' I126 andv I42 are clamped together byiany suitablei'means, not shown. The septum I44 :is secured in fluid-tightrelationship to ,a pressure'responsivedevice such as the bellows'memberldfi. At its Opposite end, the bellows 'r ifiisprovided with a movablewall M-Bwhich has an opening I58 through it to receive a stem I52 o'f plunger [.34. Themovable wall hi8 is clamped between'the upper face of guide collar i135 and a nut I54 which has threaded engagement with. the

- stem I52. A spring I56 bears at one end against connection is I'M.

pass val've 'illfi is closed.

gen-is to -be thep-roduct, the icy-pass valve should be-open and the engine operated with early cutpansion engine operated with late cutoff.

theflmov'able wall I 48 and'is adjustably restrained atgitspther end b abearing member I158, screw I61] and the, combinationlock nut and cap I62.

"The upper portion M2 of the casing isproyidedwith an opening i164 which has threaded engagement with alfitting I55 towhich-is secured a conduit I68. 'Theconduit I168 need not be. of large dimensions because there isnojfluid flow throughit. The'function of conduit E58 issimply to transmit pressure to the outside of: bellows I 15. The pressure referred to is the reference pres- ..Sil're described .-.ab.ove and is preferably column pressure. For convenience, the conduit LIES -is merelytapped into the efilux or nitrogen outlet 1i ,.at ,a,p0int as close as may heieasibleto the column. In Fig. 1 the conduit I68- is schematically indicated by a conduit I!!! for valve 1.6 and by conduit I12 for valveI I0.

For the sake of convenience, the, space surrounding=theexpansion engine connecting rod and. the liquid oxygen'pump-rod may be conneeted to-the conduit III] of the valve -16. This shownschematically by the conduit In theembodiment of thezinventionshownin is connected: for.valve'16,.to conduit 31 by con- .;duitrI'I,ii', as shown; and for valve I I6, to conduit i I hyoonduit I12, as shown.

Ithas been pointed out-that the oxygengener- -ator-isadapted to produce oxygen at 56 i. or

at" pressures up to 2000 p. s. 1. During production of50-pound-oxygen, the expansion engine operates with relatively late cutofi and the by- When ZOOO-pound oxyoiT. During starting,zfor-the first-two hours or so the'by-pass valve should beopen and the ex- Then dur-irrgthefinalperiod-preceding the normal production,,the expansion engine should be operated Withearlyycutofi. The by-pass valveshould period. When thesystern becomes readyto produce oxygen'gon a suitable basis for an extended period, wthe control should provide for operation eitherwiththe-by -pass valve-open andearly cut- Ofi or the'by pass-valveclosed and late cutofi. --depending-upon thedema-nds oi the load imposed by the shop on the shop line, as explained in copending joint patent application Serial No. 122,078, filed October 18, 1949. These functions of normal operation can be accomplished by a shop line pressure responsive pilot valve controlling the supply of fluid alternatively to mechanism for shifting the position of the by-pass valve, and to mechanism for making the point of cutofi later in the expansion engine.

Reference is now made to the valve Hit and more particularly to Figs. 3 to 6 inclusive for the details thereof. This valve shows a lower casing or body portion I16 which is provided with a cover I18 secured thereto by any suitable means such as threaded members I80. The body portion I18 has a threaded opening I82 to receive a plug or valve seat member I04. The valve seat member I84 has a central passage I86 therethrough and a plurality of circumferential ports I08. A seat I90 is provided on the valve seat member I84 and cooperates with the valve disc I08 to out 01f communication between the circumferential ports I88 and the central passage I86. The valve seat member I84 has threaded engagement with a removable spring retainer I92 which has wrench openings I93. A spring I94 is disposed in a cup-shaped recess I95 between the spring retainer I92 and the valve disc I08, as shown.

The conduit 85 of Fig. l communicates directly with an opening I96 in the valve body I15 (see especially Fig. 4). Opening 106 is constantly in communication with the chamber I07, which i in turn is constantly in communication with the conduit I05 of Fig. l. A cover plate I98 is removably secured to valve body I16 by means of threaded members 200 in order to provide access to the spring retainer and valve disc assembly.

Valve body I16 is provided with a cylindrical opening 202 which is from twenty to thirty thousandths greater in diameter than the diameter of the disc of a valve 204. The valve 204 is provided with a finger portion 206 which is adapted to engage the valve disc I08 to open it. A chamber 208 in the cover member H8 is in constant communication with conduit through a passage 2 I0. When the valve 204 has been moved down into position to communicate conduit I05 with the column I3 by moving valve disc I08 away from its seat (see Fig. 5), the chamber 208 is in communication with a groove 2 I2 which forms a chamber for valve 204.

Valve 204 is threadedly engaged by a plunger or push rod 214 which is reciprocable in sleeve 2I6, secured in any suitable manner in opening 2 I8 in the cover member I18. As is more readily seen in Fig. '7, sleeve 2I6 provides a fluid seal and protective covering for the plunger or rod 2 Id of piston 220. The piston 220 is reciprocable in a cylinder 222 which is subjected to the pressure of a control fluid through a conduit 224 at one end and is vented to atmosphere through an opening 226 at its other end.

Before describing in detail the mode of operation of the apparatus shown in Fig. 1, it is desired to point out that the column may normally be operated with a pressure on the order of 6 or '7 p. s. i., and in order to evaporate liquid oxygen with the latent heat of condensation of air under pressure in the condenser I8, the pressure of the air in the condenser should be on the order of 70 p. s. i. Accordingly, the valve H0 is adapted to open when the pressure in conduit 83 reaches 70 p. s. i., for a reference pressure of 7 p. s. i. The expansion engine, when working with the later cutoff, has an expansion through it at least substantially equal to the difiference between 158 p. s. i., the pressure in line I0, and the pressure in the line 11. Thus the expansion engine provides a pressure drop on the order of 88 p. s. i. This 88 p. s. i. drop, plus the p. s. i. pressure previously mentioned, plus the difierential in pressure of about 2 p. s. i. provided by the resistor 5|, gives a cumulative pressure of 160 p. s. i.; and that is the pressure at which the two-stage compressor, not shown, delivers air as long as the reference pressure is '7 p. s. i. The reference pressure is substantially identical with column pressure, so that when the column pressure rises, the pressure which opposes expansion of the bellows rises, and an increase in the supply of upstream pressure is necessary to open the valve or keep it open.

Another valuable function of passing a portion of the entering air through the evaporatorcondenser resides in the fact that under varying conditions, the expansion engine, though it may normally take a certain percentage of the air to be processed, may at times take somewhat larger quantities; by having a substantial stream of air normally passing through the evaporatorcondenser, there is available, in the event the expansion engine requires more air by virtue of fortuitous changes in operating conditions, air inithe system which can be diverted and supplied to the expansion engine and so enable the supply pressure to the latter to be maintaine constant.

Operation The mode of operation of the described apparatus during the production of oxygen is different, depending upon whether SO-pound oxygen or oxygen suitable for cylinder charging (say at 2000 p. s. i.) is being produced. Oxygen at either pressure may be delivered. The mode of operation for the production ofoxygen at 50 p. s. i. pressure will be described first, and'then the diiferences when oxygen at 2000 p. s. i. is to be the product will be explained. Following this, a procedure to set the plant in operation will be described.

Air is supplied continuously, as above noted, through the conduit II at 300 K. and 160 p. s. i., from any suitable compressor. Ordinarily a twostage compressor with an after-cooler may be used as the source of air supply.

The entering air contains water vapor and carbon dioxide. These are precipitated out of the air stream by cold supplied by the leaving streams of oxygen product and nitrogen. The carbon dioxide is largely deposited in the heat exchanger 22 upon the walls of the courses 22B and 22C, and the water vapor, as liquid water and as ice, in the courses 2IB and 2IC of ex-- changer 2i; and it may be of interest at the present moment to point out that the liquid oxygen drawn from the chamber IOI in the column I3 through conduit I00, the strainer 91, and conduit 90, is pumped by the liquid oxygen pump 05 through the conduit 8I, through the course 24A of heat exchanger 24, through the conduit 80, the course 23A of heat exchanger 23, conduit IS, the oxygen course 62 of the evapo rater-condenser 60, the conduit 05, course 22A of heat exchanger 22, conduit 33, and the course 2i A of the heat exchanger 2i, and finally is delivered at the desired terminal pressure through the product delivery pipe 25.

As has been previously pointed out, the nitrogen leaving the column by way of the connection "escape i3, 'havin'g passed ithrough :appropriate I wp'assagemeans in the valvesmechanism I 2.

"'Thus' it will be evidentthat the'streams of oxy- :gen -and nitrogen passing 5 through the. heat-LexchangerS ZZand' ZI will'eause 'the carbon dioxide i-and waterzvapor to be condensedsor condensed H i "and frozen, on the-walls of the passageslinthese exchangers; through which the entering: air .may -atany "given moment he flowing, :and that liquid water will beevaporated and': deposits .of: icefan'd c'carbon dioxide snow 'sublimed, and be carried *out, :by the leaving nitrogen .:stream, of ithe passages in whichxthey have .beendeposited.

5A portion of i the :air which, .is .tpassed :through thei heat exchangers-2 i and 22 1 is caused to .pass

again :through the heat-exchanger .22,:'throughia s-course 122D thereof; asxpreviously explained, flow lingithroughithe conduit-52, course 22D, and conduit 6B and rejoining the main mass of air'which ;passes,::during:the production of low pressure :oxygenpthrough :conduit :61; :and the reunited;

streams pass through the:conduit I and the: con- :duit-S I.:into the expansion engine to be expanded f-thereinand to 'be cooled by the performance of =-:work: during .the adiabatic. expansion of the fluid in :the expansion engine. --1conduit:52, course 22D of heat exchanger-22, and sconduit fiiiris causedsby the valve I, whichprovidesapproximatelya 2 pound differencein pres- .;sure. at its opposite. sides.

.At .this. point it may be: noted that, regard- The flow through iessof the pressure of the delivered product, some of the airsupplied to the apparatusfor treatment "therein always passes through the expansion "engine "I8, and some of the air always passes "through evaporator-condenser 60, the quantity of "air "passing through 'evaporatgr-condenser "60 being determinedby the cutoff of the expansion engine. 'When the "expansionengine operates with early cutofi, -more"air necessarily passes through evaporator-condenser '60. During the "production ofoxygenat s. i., about 12'%-or "the total mass of enteringair passes through the flair course-630i evaporator-condenserin heat exchange relation with the leaving'oxygen 1 product. "Whenpxygenat ZOOO'p. s. i. is the 'desire'd 'through the an course '63 of evaporator-con- :denseriifl.

.The air which. leaves ithe heat eXchanger ZZ :L'on "itsway'itopass through 'the conduit BI'is :at-a'a tempera'ture :of K. and a pressure of p. s. i.'gauge. At the downstream side of the re- -=.strictor'device-5Iv the pressure-is 158 p. s.-i gauge. The recirculated air which flows through the conduit Bfiis at a pressure on the order of 158 s. i. and a temperature of K. just before it joins the fluid stream in conduit Ii'l. Whenthe I streamshave been mingledlin the-conduit 10, all

"the airis at'.a temperature :of 1359K. and-:a pres- I 'sure of;158,-p.s. i. fiheportion ofthenairwhich iflcws through .the conduit-'iflanddoes work-.in ithea expansion engine leaves the. latter at av temperature of 110 K. anda;pressure*'of '70 psi.

when 50-pound oxygen is tobe produced.

Thisiexpandedeair-"passes.throughthepanduit .55 product,"as'muchas' 60% of all the air may pass zfl fiiithroughcconrsez 2 3020f; heattexchangerkn sand remerges ata;.temperature;:of;105, K.-and ia,pressure :.of .17 0 rp; s.:.i.: ,gauge, :andmasses through the ache ckzvalve: 87- to :mix :with ,i-iguid .-air 'which has zpassed :throughwa-lve r-I-Ii, and there is formed-1a .pstreamtpartiallmof;iiquid;'air-andgpartially of: exipandedzair .atrantemperature of :1-00" :K. and' ea pressure of '70 p. s. i. It may be observed that the -air:fromitheairxcourse E3: of the evaporator-nondenser :60 emerges from ;heat exchanger '2-3-and centers the:conduit 'I5at-a temperaturejof 112K. -;and .atpressure :of .158 .p. s. i. After passing ithroughfthe expansion valve "IB-tand undergoing -..a::drop intpressure ofzabout.=88:p. -s.1i., the .-1iqu-id .zairt'iszat' TflIE'SEIIIGLDIGSSHIB as the expanded =-air ;;comingtthrough conduit-r88.

:Thezmixturerofdiquideairiand expanded ainat a 2 temperature of :100 K. and: a pressure :of *70 p. s. i. enters the condensercoil'w :fizIldiiSilCOIl- .-.Idensed hymeason ofizthegiving-up: oft-heat: inithe :process 'of :vaporizingpxygen in the bottom 51015 -:the 1 column. .Thezliquidsr air v,emerging. from '5: the -:condenser 518 :is at: a: temperature of 196 -K.;and xavpressure10:6"i'Z0 p. s. i.,;and after this "liquideair :has passed throughavalve :I mzandhas -its;pressure reduced :by "approximately :60 v:p. s. i., the liquidrair: will *beaat'ra temperature of 83. Knand v.alplressure iofiSixpss:i.

' F-oll'owin'gsthe:jacketingrofthe oxygen strainer -97 and: thezliqu'idoxygempumprfi 5 ,the still :liquid :air willzenterithetop .of'thecolumn'ata temperatureioffBBfi' Keandn pressure; of. 711).";5. i.,-randyit -wiilzbexectifiedi therein sozthairsubstantiallmpure oxygen (99.51% puregatleastrman: be drawn? from famappropriatezpoint: incthe-'evaporatorecon'denser arranged in 1th eibottom :of :the icolumnt' at :a tem- .peratureioif595l Kaanda pressure;of:7;,p;. This liquid oxygen will fiow-ttthrough :the :strainer 97 ,rconduit fafi iithe iiquid :oxygen pump: 95, the eon'duit iii I arfd the central: courses, in .series,;:of heat exchanger' fi, heat exchanger 23, evaporator-condenser fiii, l heat-exchanger 122,: and heat exhanger 'ii I and' emergegwhen 50-pound oxygen as being-produced, Y in the form I of gaseous -OXygen-at tha-mouth ot the product pipe 25.

When-oxygen "for "cylinder charging is tobe produced; thevalve structure 106- will be operated, as described-in detail" below; to -connect the "conduits I05 and *I I! 9,-andthe 1 expanded air leaving the-expansion engine will then'pass through the ponduitiil 5 ,1 the valve structure I- i! 6; andthe-conduit i'fiaintothe column, an'd'the'pressure ofgthe *air in 'the conduit I05 will'ibe. reduced substanitially' tothat within the .column accordingly;.no 511p oreexpand'ed "air will be discharged" through the i'che'ck .'va1ve"81',-becauseithis valve will'be held closed"by'theipressure, on the orderiof 70, p..s.,ji.. which subsists' in the conduit 'l'l.

At 'theL-timeQthe valvestructure ['86 is operated 'topermit theexhaustiromjthe expansion engine .to pass substantiallyjdirectly into lthe column lthrough the conduit I'Il9,.1the .pointof cutoff-.ofthe expansion-engine-I.8.wil1f.be changed to make it much earlier in the-working-,strokeas aforesaid. Since the speed ofrtherexpansionengine remains unaltered. much less-roughlyhalf :as much-wail can -.-,go through 1 the :expansion engine. iConsequentlmathe .air-iwhichzcannot ifiow through .the

conduit 6? and be passed through theexpansion .engine will or" necessitvgothrough-the air course amass, willgpassthmugh naive SIB sand-enter .the

condenser coil I8 of the evaporator-condenser at the bottom of the column I3 and be liquefied therein. This larger volume could not be liquefled in the evaporator-condenser 60 and the heat exchanger 23 because the oxygen product, now at a much higher pressure, cannot be vaporized at thecondensation temperature for air at 158 The reduced volume of liquid air from condenser coil I8 will pass through the heat exchanger 24 by way of course 24B and next pass through conduit 83 and valve I it and then, after jacketing the strainer 01 and the liquid oxygen pump 95, will be passed into the top or the column for rectification. A much smaller percentage of the total oxygen content of the air entering the apparatus will be delivered during the production of 2000-pound oxygen than during the production of SO-pound oxygen.

In starting up the apparatus, the valve $08 will be open and for a considerable period, on the order of two hours, the expansion engine will be operated with the relatively late cutoff. This will mean that most of the air will pass through the expansion engine, a desirable thing at this time because there would be no oxygen to effect condensation of air in evaporator-condenser E50. About 12% of the entering air will flow through the evaporator-condenser 60, heat exchanger 23, valve I6, condensing unit 78, exchanger 24, conduit 83, and through valve E I through the jacket for the oxygen strainer 07, the jacket IIS for the liquid oxygen pump 95, and then through the conduit H0 and connection H5 into the top of the column I3. During a considerable portion of the starting operation-the cooling down periodthis air will simply flow out through the conduit 1 l, etc. and be discharged.

The relatively large amount, about 88%, of the air which passes through the expansion engine I8 will pass into the column through the conduit I09, and it too will discharge through the conduit H to the atmosphere. As the unit cools down, a little liquid will commence to form, and as soon as this stage is reached, the expansion engine will be shifted to early cutofi, thus increasing the refrigeration, and for another period, perhaps an hour, the exhaust from the expansion engine will still continue to be discharged through the connection I09 into the column. When the liquid finally builds up high enough so that oxygen can be drawn through the conduit I00, the apparatus will be all ready to go to 2000-pound oxygen production; or, by closing the valve I08 and making the point of cutoff in the expansion engine much later, 50-pound oxygen can be produced. It will be noted that during the later stages of the cooling down operations, the by-pass valve I08 will still be open and the expansion engine will be working with an early cutoff, and that when the liquid level in the column reaches the overflow point, the machine will be ready to fill cylinders; but if 50-pound oxygen is desired, the by-pass valve can be closed and the cams arranged in the expansion engine for late cutoff.

Certain points not previously mentioned, or perhaps deserving reemphasizing, may be noted now with respect to the embodiment of the invention, from its apparatus aspect, which has so far been described.

As a portiona minimum of about 12%--of the entering air always passes'during normal operation through the evaporator-condenser 60 in heat exchange relation with the iluid flowing through the oxygen product line, there will always, as soon as soon as low enough temperatures are attained. be some liquid passing into the top of the column.

During the cooling down period, and also when oxygen at 2000 p. s. i. is the desired product, the expanded air may enter the column through the valve controlled connection I09 at a point perhaps three-quarters of the way up the column, instead of having to pass around through heat exchanger 23, the conduit 86 and the check valve 87. Indeed, no air can then pass through the circuit last mentioned, because the air in the conduit I'I will be at a pressure so much greater than the pressure in conduit 85, as to maintain the check valve closed.

During the production of 50-pound oxygen, the main flow of expanded air (about 88%) passes into the top of course 23C of heat exchanger 23 and passes down through this heat exchanger in heat exchange relation both with liquid oxygen produced in the system and with the leaving nitrogen stream. The expanded air, at 105 K. and p. s. i. pressure--the same pressure as at release from the expansion enginethen passes through the one-way check valve 8'! and enters the condenser unit IS in the bottom of the column, where it is condensed, its latent heat of condensation serving to evaporate liquid oxygen at a lower pressure in the bottom of the column.

The liquefied air goes into the bottom of heat exchanger 24 and gives up some of its heat to the nitrogen and to the liquid oxygen which also flow through exchanger 24, and then passes through valve H0, where there is a reduction in pressure on the order of 60 p. s. i., this resulting in a further cooling of the liquid air and some vaporixation. After passing around the liquid oxygen filter which it jackets, the liquid air is used, as will be recalled, to jacket the liquid oxygen pump also, and it then enters the top of the column at a temperature of 83 K. and at a pressure of 7 p. s. i. gauge.

The process of rectification in the column results in there being available liquid oxygen in the evaporator-condenser at the bottom of the column, specifically in the chamber IOI surrounding the condenser unit '58, at a temperature of about 95 K. and a pressure of 7 p. s. 1., while nitrogen, with a single column rectifier, containingirom 7 to 10% oxygen, and at a temperature of 83 K. and a pressure of 7 p. s. 1., passes out through the top of the column. The liquid oxygen is filtered as it passes to the liquidoxygen pump and is forced by the latter at a pressure commensurate with the desired product pressure successively through heat exchanger 24, heat exchanger 23, evaporator-condenser 60, heat exchanger 22, and heat exchanger 2I to the point of product delivery, absorbing from the entering air stream the heat necessary to vaporize it, when 50-pound oxygen is being produced, while passing through evaporator-condenser 60, and the absorbed heat resulting in a change of state of the entering air from gaseous to liquid form.

When 2000-pound oxygen is being produced, the liquid oxygen cannot be evaporated in the evaporator-condenser 60 and so there is simply a temperature increase of a few degrees in the oxygen passing through evaporator-condenser 60, the evaporator-condenser 60 then operating simply as a heat exchanger. Nevertheless, when oxygen at 2000 p. s. i. pressure reaches the cylinders to which product line 25 may be comiected, this oxygen is in a vapor state.

It has been pointed out that valves I6 and H0 its downstream side. "upstream pressure on valve 75 does not change,

its downstream pressure and the pressure reducare pressure control valves, being adapted to stream or supply pressure over the reference pressure is required, in order to open the valve. Valve 16 is thus entirely indifierent to the pressure on Therefore, so long as the tion across valve 76 are wholly determined by the operation of valve 1 I0, and the operation of valve I ll] depends on its spring setting and column pressure.

Inasmuch as the supply or upstream pressures desired in the conduits l5 and 83 are not identical, it may be pointed out here that the different valve-opening pressures may be provided for by using different sized springs for the two diirerent valves where the spring I56 is indicated in Fig. 2. It is desirable that the upstream or supply pressure be regulated according to column pres sure, because an increased column pressure will result in an increased boiling point for the oxygen in the lower end itii of the column, -necessitating a greater pressure in the coil H3, in order that air may be condensed at the now increased pressure oi vaporizing oxygen. This increased pressure in coil '38 is provided by subjecting the outside of the bellows of valve Hi! to the column pressure by means of the pressure conduit 4'72 which taps into the nitrogen line at a point close enough to the column to give a reference pressure substantially identical with column pressure.

With the upstream pressure on valve H0 increased, in order to increase the pressure in coil 78, it is also desirable to increase the upstream pressure on valve '16, in order to maintain .approximatel constant the pressure drop through valve 13. This effect is obtained by subjecting the outside or" the bellows of valve 16 to column pressure by means of the pressure conduit 110.

During the production of 50-pound oxygen, the portion of the air that splits oi the main stream in the header of evaporator-condenser 60an amount which may be 12% of the whole during normal 59-pound oxygen production-45 largely condensed in evaporator-condenser 60 and any excess that may pass through the evaporator-condenser 6Q without liquefaction .will be liquefied in the evaporator coil 18.

If 2000-pound oxygen is the product, no expanded air enters the evaporator-condenser .18 with the air going by way of exchanger 2.3 from the evaporator-condenser 6%, as the low pressure of the expanded air-this air has been expanded through a much greater range of expansion when the expander is working with early cutoii-will not permit it to effect opening of the check valve 3 Note that the exhaust from the expansion engine communicates freely through the conduit N with the column at this time. The larger quantity of air going through the evaporatorcondenser as and heat exchanger 23 and entering the condenser 58, even though little of it may have been condensed before the arrival at the condenser i8, is at a pressure of 70 p. s. i., which pressure is high enough to permit condensation of the air by the vaporization of oxygen at 7p. s. i.in

18 chamber NH. The total quantity of oxygen produced when 2000-pound oxygen is being supplied will be proportionately much less than when pound oxygen is the end product.

Roughly, during cylinder charging (2000- pound production) 40% of the air goes through the expansion engine and directly into the column, while the other follows the course normally taken during 50-pound oxygen production by but 12% of the air supply to the apparatus. This change in the airflow distribution is due to the much earlier cutoff which occurs during 2000- pound oxygen production. It will be understood that the expansion engine operates at a predetermined speed, that the quantity of fluid which can pass through it is accordingly determined by the point of cutoii, and that, accordingly, with late cutoff, a much larger percentage of the total entering air stream can pass through the expansion engine than when cutoff is made early.

The detailed operation of the bypass valve of Figs. 4 through 7 may now be briefly reviewed. When fluid is admitted to cylinder 222 by way of conduit 225 in accordance with system requirements as explained in copending patent application Serial No. 122,078, filed October it, 1949, and assigned to the assignee of this invention, piston 22d and rod 2 M move downward as seen in Fig. 7, and protruding finger 206 moves the valve disc its off its seat, allowing fluid pressure from the chamber l0! to pass into the groove or chamber 2 I2.

It will be noted that fluid at the pressure obtaining in conduit IE5 is admitted to chamber 2l2 before valve 204 clears the cylindrical opening 202. Air starting to flow from chamber iili' through the central passage I83 will 'act on the relatively large valve member 2% and delay its downward movement sufficiently to prevent a blast of expanded air entering column 73 by way of chamber 208, passage 2-10 and conduit IE3 with such force as to damage the column. In a very brief time the valve 284 will take the position shown in Fig. 5, in which position the valve i dii is completely open and permits free communication between conduit 35 and the column by way of circumferential ports I83, central passage 1.83,, groove or chamber 212, cylindrical opening v252, chamber 298, passage 2:0, and conduit is into the column 13.

The foregoing description of the operation has been based on valves .136 and H0 arranged to be partially responsive to column pressure, as shown 'in Fig. 1. Consider now the embodiment shown in Figs. 1a and 1b, in which valves 16 and .i it] are flXed-pressure-drop pressure reducing valves, one to effect a pressure reduction between its up-and downstream sides of 88 p. s. i. and the other of '60 p. s. i. The characteristic of these valves is that they prov'ide a fixed difference in pressure between their up-and downstream sides. Unless it is possible to have such a differential in pressure, no fluid will flow past them. If the downstream pressure, say of the valve H9, is predetermined by the column pressure, then no pressure can flow through the valve I l El unless the pressure at its upstream side is at least equal to the column pressure plus thediiierential provided by the valve I I0. And since the valve 1 ill will permit no flow'past it until the '60 p. s. i. diiierential mentioned exists between the column pressure and the pressure at the upstream side of the valve 1 H), no fi-uid can be discharged past the valve '35 unless and until the pressure at its upstream side exceeds (by its pressure difierential, 88 p. s. i.) the required pressure oil-(column pressure") and 60 (pressure reducing valve HOs differential). The restrictor adds 2 more p. s. i. to the accumulative pressure resulting from the addition of 7 p. s. i. plus 60 p. s. i. plus 88 p. s. i., and accordingly the compressor supplying air to the oxygen generator will discharge against a fixed minimum of pressure. More or less air can pass through the generator, but regardless of the quantitythere will be relatively little fluctuation with a compressor designed for use with the generator-the supply pressure will be maintained at on the order of 160 p. s. i., which allows about 3 p. s. i. for losses due to friction throughout the system.

The inventions disclosed herein are shown as applied to a single column rectifier. The application of these inventions to a double column rectifier may be understood by reference to the aforesaid patent application serial No. 122,077 filed October 18, 1949.

The advantages of this invention lie in the provision of apparatus to produce oxygen or other gases which is self-regulating and well adapted to meet varying demands. The system provides for automatic operation with a great degree of flexibility, and assures that variations in column pressure will effect desired changes in the pressure of compressed air supplied to the system.

While there are in this application specifically described two forms which the invention may, from its system aspect, assume in practice, it will be understood that these forms of the same are shown for purposes of illustration, and that the invention, from the system aspect, may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

I claim:

1. In apparatus for producing substantially pure oxygen from compressed air, a rectifier column, a waste gas conduit, a connection for the Waste gas conduit to the column, the connection being at column pressure, an expansion engine, a conduit connected to supply compressed air to the expansion engine, a pressure responsive expansion valve, a conduit connected to supply compressed air to the valve, an evaporator-condenser in the column, a conduit connected to conduct expanded air from the engine to the evaporator-condenser, a conduit connected to con duct expanded air from the valve to the evaporator-condenser, a second pressure responsive expansion valve, a conduit connected to conduct air from the evaporator-condenser to said second valve, a conduit connected to conduct air from the second valve to the column, and a pressure connection from each of the expansion valves to the waste gas conduit whereby the valves are responsive to the pressure in the waste gas conduit.

2. The apparatus of claim 1, in which the connections to the waste gas conduit are adjacent its connection to the column.

3. In apparatus for producing substantially pure oxygen from compressed air, a rectifier column, an expansion engine, an expansion valve having a pressure responsive member connected to actuate a closure member and arranged to be biased toward its open position by upstream pressure, means to conduct compressed air to the engine and expansion valve simultaneously, an evaporator-condenser in the column, means to conduct expanded air from the engine to the evaporator-condenser, means to conduct expanded air from the valve to the evaporator-condenser, a second expansion valve having a pressure responsive member connected to actuate a closure member and arranged to be biased toward its open position by upstream pressure, means to conduct air from the evaporator-condenser to the second valve, means to conduct expanded air from the second valve to the column for rectification, and a pressure conduit from a predetermined point in the apparatus to that side of the pressure responsive member of each valve opposite the side exposed to upstream pressure, whereby the pressure at that point opposes opening of the valve. 7,

4. In the apparatus of claim 3, means alternatively to conduct expanded air from the expansion engine to the column by by-passing the evaporator-condenser.

5. The apparatus of claim 4, in which the predetermined point of claim 3 is substantially at column pressure.

6. The apparatus of claim 3, in which the predetermined point is substantially at column pressure.

'7. In oxygen production apparatus having a compressed air source, a rectifier column, an evaporator-condenser in the column, an expansion engine connected to receive air from the compressed air source and having an exhaust connection into the evaporator-condenser: a bypass valve comprising a casing having an outlet connection to the column and including a, pas sage forming a part of said engine exhaust connection to the evaporator-condenser, passage means arranged to connect the engine exhaust with the column, a valve in the passage means adapted to close the passage against fluid flow, means to open the valve, and pressure responsive means associated with the valve opening means and exposed upon valve opening to engine exhaust pressure and connected to delay complete opening of the valve.

8. In oxygen production apparatus having a compressed air supply source and a column, a pair of expansion valves arranged in series between the air supply source and the column, each valve having a pressure responsive closure operator which is arranged to be biased toward valveopening position by upstream pressure, and a pressure conduit substantially at column pressure connected to each valve to oppose the upstream pressure.

9. In oxygen production apparatus having a compressed air supply source and a column, a pair of expansion valves arranged in series between the air supply source and the column, each valve having a bellows operated closure member in which one side of the bellows is subjected to upstream pressure and is arranged to have upstream pressure bias the bellows toward valve opening position, and a conduit substantially at column pressure connected to the valve to subject the opposite side of the bellows to column pressure.

10. In oxygen production apparatus having a compressed air source, a rectifier column, an evaporator-condenser in the column, an expansion engine connected to receive air from the compressed air, source and having an exhaust connection into the evaporator-condenser: a bypass valve comprising a casing havin an outlet connection to the column and including a passage forming a part of said engine exhaust connection to the evaporator-condenser and passage means arranged to connect the engine exhaust with the column, the passage means including a 21 22 valve seat member having a passage therethrough and a cylindrical opening, a valve cooperable with REFERENCES CITED the valve seat member and movable to Op and The following references are of record in the close the passage against fluid flow, means to file of t t t;

open the valve, and a member associated with the 5 valve opening means and being reciprocable in UNITED STATES PATENTS the cylindrical opening, the last-named member Number Name t being exposed to engine exhaust pressure upon 1 395 466 Barbet Nov 1 92 opening of the valve a d ei g connected W 1 5 345 LeRQug Apr 26 1927 the valve to delay complete opening 10 2:213:338 DeBaufre Sept.3, 1940 on initial exposure to the engine exhaust pressure.

WIN W. PAGET' 2,360,468 Brown Oct. 17, 1940

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