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Publication numberUS1529625 A
Publication typeGrant
Publication dateMar 10, 1925
Filing dateJun 15, 1923
Priority dateJun 15, 1923
Publication numberUS 1529625 A, US 1529625A, US-A-1529625, US1529625 A, US1529625A
InventorsJames A Rafferty, Harold E Thompson
Original AssigneeCarbide & Carbon Chem Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process of recovering helium
US 1529625 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

March 10, 1925. Y 1,529,625 J. A. RAFFERTY ET AL J v PROCESS OF RECQVERING HELIUM I Filed June 15, 1923 I5 Sheets-Sheet l 5 sneaks-sheet s J. A. RAF-FERTY ET AL PROCESS OF REGOVERING HELIUH Filed June 15, 1923 Mitch 10; 1925.

1 Patented Mar. 10, 1925.

- ,UNITED STATES PATENT "O F C Jmns A. nmnnrzor RYE, New YORK, ANDIHAROLDEL rnourson, ofcum-' IDENDT, WEST VIRGINIA, ASSIGNORS TO CARBIDE AND CARBON OHEKIG'ALS COR- PQBATIONZ A. CORPORATION OF NEW YORK.

PROCESS OF RE COVERII IG *HELIUM.

Application filed June is, 1923. Serial no. 645,872.

To all whom it may concern:

Be it known that we, JAMES A. RAFFERT and HAROLD 'E. THOMPSON, citizens of the United States, residing at Rye and Glen- 6 denin, in the counties of Westche'ster and Kanawha and States of New York and West ,Virginia, respectively, have invented certain new and useful Improvements in Processes of Recovering Helium, of which the 10 following is a specification.

' The invention is a process for the separation of helium from gas mixtures. It will be described in connection with the recovery of helium from a natural as containing such 16 proportions of hydrocar ons that either the entire gas or the residue left after the helium extractlon is adapted for use as fuel, but

it will be understood that muchof the procedure to be described is also applicable to 201 gas mixtures of quite different composition; y or example to natural gases containing'so much'nitrogen as to be of little or'no use as fuels, and to mixtures containing helium with hydrogen or airor both and resulting "from the intentional or accidental dilution of helium during its use for aeronautical purposes. Operating on a natural gas containing hydrocarbons but in too small quan- .tities to fit the gas for use as a fuel, the process will produce, as a by-product, a gombustible. gas containing the hydroear= ons. 1 Only one plant capable of producing helium in quantities suflicient for aero- .'the Navy Department plant whic is now in successful operation at Fort Worth, Texas.

The present invention will be described as.

venient to consider the hy rocarbons collectively as a relatively non-volatile fraction of the gas. It should be noted that the gas nautical use has ever been set up this being Since methane a is treated for gasolene-extraction before it.

reaches the helium plant and hence is almost free from butane and less. volatilehy f drocarbons. The process and apparatus to;

be described are designed for. the treatment of a material which 'does not contain more than small quantities 'ofgasolene constit} uents, and well-known rocesses -may be preliminarily applied, -.w ere necessary, to secure thisconditlon.

Heliumresists liquefaction more strongly gas and hence is than any other known eof easily the most volatile material in thenat= ceived :at the plant .by pipe-line under a pressure which fluctuatessomewhat but rare--" lfy or never falls belowv 10 atmospheres. The

ural gas. Hydrogen is: absent from the gas, and nitrogen, boiling at xabout 193 C. under 760 mm. pressure stands nextto-the. y

rmer practice included an initial expansion of the. s to substantially barometric.

pressure wit out utilization of the energy represented by the pressure on the gas.

Since several million cubic feet of gas were treated. daily, a] very considerable energy I loss was sustained in this way.

The gas was then scrubbed with a solu-f tion of an alkaline substance, such as limewater, to reduce the carbon dioxid content in order to -prevent the clogging of the helium apparatus by congelation of the carbon dioxid. i

A portion of the gas-was then compressed to about. 6. atmospheres, the rest of the gas bein brought to a much higher pressure, usua ly considerably in excess of atmospheres. Both portions of compressed gas were cooled, eventually by heat-exchange with. waste gases, and passed to a column,- the-.niixture passed through a series of provely decreasing temperatures for the separation 'of successive fractions of the hydrocarbons and the nitrogen.

mo During this stage of the process, the;na.tural gas undergoing treatment was held ansion to -pressure furmshed most scribed, operating tiall pure 1i uid auxi iary cyc e.

amount of material within the condensers.

The last condenser of the series just deat about 6 atmos )heres was cooled with su stannitrogen provided by an Two other condensers at internal pressure,

higher temperatures the last condenser, and another condenser cooled by the reflux condenser and hence operatin at the highest temperature of all. In ad ition, a. large was liquefied before the first condenserwas reached, at the expansion of the high-pressure as.

/With pressures of on y, 6 atmospheres within the condensers, it was necessary to rmit the cooling liquids surrounding them to boil at substantially atmospheric pressure The series of steps just described produced a helium concentrate containing usuup to atmospheric temperature.

' liquefaction of steps whi allyabout 60% helium, though about 7 5% was theoretically possible under optimum conditions. ThlS concentrate, containing only helium and nitrogen, was then expanded to atmospheric pressure and allowed to warm This concentrate was then. com ressed to about atmospheres and coole to the temperature of bo1lmg nitrogen, whereupon sufiicient of nitrogen was in the helium concentrate to increase the helium content to 95% or more.

In accordance with our invention, the process described above has been so modified that the ower consumption is reatly reduced elium which is of hi er urity may also be produced, and by .t e a dition e have no counterpart inthe rior process, the helium content can be so increased that impurities are either entirely negligible or absent. The process is also improvedin several other respects, notablyin the greater ease with which the desired ressuies, and hence qualtemperatures and helium produced, can be ity and quantity 0 maintained.

The invention will now be "explained in connection with the accompanying drawing, in which- Fig. 1 is a series of curves showing the theoretical helium conten or test at various presure's (plotted as abscissae) and were used, an inter medlate condenser cooled by the reflux fromfrom the intermediate through brought about at three different temperatures,- all readily obtainable by the evaporatlon of liquid nitrogen at or near atmospheric pressure;..

Fig. 2 is a curve showing the reduction in helium test which follows an increase of temperature from 190 C. to -185 0., at

VfillOllS 0011111111. pressures;

Fig. 3 is a diagrammatic representationof our improved process; an

Fig. 4: shows an auxiliary purifier containing activated carbon.

Figs

. land 2 show strikingly the reason for certain instabilities in operation which vwere encountered in the prior process.

Fig. 1, the prior operating pressure of 6 atmospheres is on the steeper portion of each curve, variation in pressure is to alter the test of the outlet helium concentrate materially. Similarly, Fig. 2 shows that even a slight increase in condenser temperature, such as may result from a slight contamination of the nitrogen bath with methane, will seriously affect the test of the helium.

In accordance with our invention, the operations formerly carried out under a pressure of about 6 atmospheres are conducted at higher pressure, corresponding to'a point beyond the knee of any of the various curves inFigs. 1 and 2. In this region, all the curves have relatively low slopes, and the effect of fluctuations in temperature and pressure is considerably mitigated.

As lessand less advantage is obtained by successive increases inpressure, it will be seen that a practical pressure limit is soon reached. We have found that a working pressure of about 22 atmospheres gives conso that the eifect of any inadvertent siderably better results in the respect just 7 discussed than 6 atmospheres.

The use of such 'a pressure as 22 atmosabout 160% to about 90%, without the use of lower temperatures than before. In fact,

' certain ofthe condensers may be held at considerably higher temperatures than formerly, these higher temperatures bein such as those produced by boiling liqui s. of composition similar to those at pressures approximating 17 atmospheres instead of the substantially atmospheric pressure formerly maintained. This latter ives rise to a principal advantage of-our 1nvention,in that the gas produced b abullition of these liqulds 1s at a su icient pressure to enter the pi e-line without. any

work being done on it a er it has been used for cooling.

The curves of Fig. 1 also show that the final condensation of impurities from the does the former pressure of formerly used, but

the

impure helium, formerly conducted at about 70 atmospheres, can be carried out at very much lower pressures, even at the 22 atmospheres used in. the earlier stages, and a higher test helium nevertheless produced, provided a temperature only a little lower than that now employed is maintained at the condenser. Such a temperature is readily attained by evaporating nitrogen under a partial vacuum, say at about one-half atmosphere absolute pressure.

Our preferred arrangement for the complete process is shown in Figs. 3 and 4, and Is as follows:

The helium-bearing gas, previously des prived of its gasolene constituents, and arriving at the plant through a pipe-line 1, at or above 10 atmospheres pressure, is scrubbed at that pressure in scrubber'2 for the re-- moval of carbon dioxid. Owing to the increased solubility of carbon dioxid at such pressures, water alone acts as a very'efi'ective agent for removing carbon dioxid. If a more complete removal of carbon-dioxid than can be obtained with water alone is desired, the gas may be passed to a second scrubber 3, where it is treated with a solution of an a'lkalinesubstance such as lime water. The absorbent action of lime water is also increased by the pressure.

From scrubber 3 a portion of the gas passes through line 4 to low pressure compressor 5 where its pressure is brought to about 23 atmospheres. The compressed gas passes through a fore-cooler 6 refri erated by an ice machine 7, andthence through line 8 to the main heat-exchan er.

Another portion of the he ium-bearing 1 gas, after removal of the carbon dioxid. is

{ byline 17. passes through a coil 18 likewise drawn through line 9 to high pressure 1nulti stage compressor 10, and is brought to about 135 atmospheres. The high pressure. gas passes through a fore-cooler 11 refri erated by an ice machine 12, and is carried t rough line 13 to the main heat-exchanger, but is kept separate therein from the low pressure gas entering through 8.

The high pressure gas emerges from the heat-exchanger through line 14, whence it passes to coil 15 immersed in a bath of boiling liquid at low temperature. After its final cooling in this cm], the high pressure gas expands through valve 16 into the column at: a point below condenser A. The low pressure gas leaves the heat-exchanger immersed in a low temperature bath of boiling liquid, and then flows through line 19 and valve 20 tothe same column into which the high pressure gas is expanded.

The expansion of the cooled high pressure gas to the column pressure, about 22 atmospheres, absorbs a large quantity of heat. The less volatile constituents of both high and low pressure gas, for example the propane, most of the ethane and some methane,

are condensed, flow down through the column where they are sub'ected to rectification to remove any disso ved helium, and

collect in the kettle containing the coil 15..

Those constituents of the gas which are notliquefied on expansion, and including all the helium of the. gas, pass upwardly through the column to condenser A, where they are subjected to the temperature of the liquid boiling about the condenser, thisliquid being held under a pressure of about 17 atmospheres. A further quantity of relatively non-volatile material is liquefied in condenser A and returns to the column below, in which it also is rectified. The helium and other gases not liquefied in condenser A pass through .line 21 to :1

column which is surmounted by condenser q B. Condenser B 1s surrounded by a boiling liquid which'is held at the same pressure as that which obtains about the'condenser A, but the liquidsurrounding condenser 13 contains more of the volatile constituents of the natural gas, such as nitrogen and ture than the liquid about the condenser A. As a result, an additional quantity of ma-J terial is liquefied in condenser. B and demethane, and hence is at a lower temperascends through and is rectified in the column column which is immediately below condenser C, the helium-containing mixturebeing still at the same pressure of 22 atmospheres. Condenser O is cooled by substantially pure liquid nitrogen boiling at about atmospheric pressure, and hence the tem-- perature of condenser C- approaches closely the boiling point of nitrogen, -193 C. As this temperature is conslderably' below the temperatures of condensers A and B, afurther quantity of the gas associated with the helium, nowchiefly nitrogen, is condensed, and passes down through the column immediately below, where it is rectified to remove any dissolved helium. The liquid col lects in kettle 24 at the bottom of the column:

the coil 18 and there surrounds and. cools coil 25, which presently to be decontaining about 90% of helium will be produced. This concentrate passes through. I

. line 26 to the final condenser D where itis subjected, still at a pressure of about 22 atmospheres, to the temperature of nitrogen boiling under reduced pressure, say at about one-half atmosphere absolute. r This ,will

give a temperature below ,195 C. in con denser D, and as a'result some of the small amount of residuah nitrogen will be liquecooler 32 refrigerated it boils away continuously fied and aconcentrate containin about 98% helium, and usually consi ered pure enough for aeronautical purposes, will pass the condenser, expand through valve 27 ,and

pass through line 28 to the helium holder 29.

The arrangement for producing the nitrogen baths which surround condensers C and D will now be described.

Nitrogen is drawn from holder 30 and compressed in multi-stage compressor 31 to a pressure of about 135 atmospheres. The compressed gas then passes through foreby the ice machine 33, and thence through the nitrogen heat-exchanger. The cooled high pressure nitrogen emerges from the heat-exchanger through line 33 and passes through coi 25 previously referred to,.where it is brought into thermal contact with ing liquid in kettle 24. The liquid in kettle 24, it will be noted, is under a pressure of about 22 atmospheres. The nitrogen now passes through coil 34 disposed in the'bath around condenser G and hence immersed in nitrogen boiling at or a little above atmosph'eric pressure.

After this final cooling the nitrogen expands through valve 35, which results in its partial liquefaction. The liquid nitrogen collects about coil 34 in condenser C, where and produces the refrigerating eflect already referred to. The gaseous nitrogen produced by the boiling of this bath passes at slight pressure through line 36 to the nitrogen heat. exchanger, where it cools the high pressure nitrogen and then flows through line 37 to the nitrogen holder 30.

The space around condenser D is held, as alread stated, under a partial vacuum.

Liqui nitrogen will rise at a regulated rate throu h valve '38 and collect about condenser D, boiling there under the reduced pressure at a very low temperature. Y The gaseous nitrogen producedby the boiling of this liquid passes through line 39 to another section of the. nitrogenv heat-exchanger, where it asslsts in the cooling of the high. pressure nitrogen, and then passes through line 40 and vacuum ump 41 to the nitrogen holder. The smal quantity of liquid formed in condenser D and consisting of pure nitrogen,

returns through the trap 42 to the top of the column surmounted by condenser C.

I The gases produced by the boiling liquids around condensers A and B pass through lines 43 and 44 'resplectively to the main heatexchanger, where t ey cool the high and low pressure helium-bearing gas, and then pass through lines 45 and 46 respectively to a receiver which discharges hehum -free' gas into a plpe-hne to be transportedto-the place of its consum tion. Since the baths about condensers and B are maintained at 17 atmospheres-pressure, and the reverse flow line already "with the exception the very cold D011" passagesof the main heat-exchanger are at the same, pressure, the exit 1glases may enter the line without being furt er compressed. A portion of the liquid contained in the kettle around coil 15 is also continuously withdrawn through line 47 to the main heat-exchanger, in which it evaporates and assists in cboling the high and low pressure helium bearing gas, passing from the heat-exchanger through line 48 to the receiver and pipereferred to. The exit gases passing through the main heat-exchanger and lines 45, 46iand 48, constitute practi cally all the natural gas entering. the plant of the helium.

The condenser B is cooled by liquid which 1 collects in kettle 24, and flows through line 49 and valve 50 into the space surrounding condenser B. Condenser A is similarly cooled by liquid and flows through space surrounding condenser A. At valves 50 and 52, the pressure on the liquids just referred to is reduced from about 22 atmospheres to about 17 atmospheres. Should it be desired to remove from the helium leaving condenser D the very small quantity of impurities contained in it,'the apparatus shown in- Fig. 4 may be used bein introduced into the system at an approprlate point, for exam le between condenser D and the helium hol er.

This apparatus consists of a series of identical absorbers comprising an packed with activated carbon 53 held between foraminous partitions 54. To facilitate' the absor tion of the impurity (nitrogen) inthe car 11., the latter sli'ouldbecooled to a very low temperature and we have shown the absorbers provided with jackets 55, through which may bepassed a very cold medium, such as nitrogen from the space around condenser G. The absorbers maybe small, as they are designed to take up an impurity which constitutes only about 2% of the helium, the helium being less than 1% of the gas treated.

When cooled to a temperature such as that indicated, activated carbon selectively .ab-

(1 to any desired value. When one absorber is saturated to the desired degree with impurity, it is cut out of both the helium and the refrigeration circuits and allowed to warm up to room temperature, the absorbed impurity will pass of! through which collects in kettle 22, line 51 and valve 52 to the inner chamber.

sorbs the impurity with great efliciency, and 1 the-purity of the helium can be raise whereupon 56. The absorber is then ready for use again to the required whereas in the prior process all the gas was compressed twice, and each time from atmospheric pressure, while the 60% helium concentrate was additionally compressed from atmospheric pressure to 70 atmospheres. As a result, fewer compressors are required and less power is consumed.

Helium of greater purity is roduced even without the activated carbon a sorber. The latter, at the low temperature used by us, affords a means. for securing helium of any desired purity.

The carbon dioxid may be removed from i the gas more effectively, in smaller apparamaterial, can be smaller, as the gas is considerably reduced in volume by the higher pressure. It is true that the gas passing through condenser D is at lower pressure than in the final 70 atmosphere condenser of the prior process, but only about 1% of the gas treated flows through this condenser. Furthermore, the urity of the helium passing to D is muc higher than in the former process, so that condenser D' treats less gas than before.

The process is less sensitive to changes in operating conditions. The saving in power consumption in th new process is estimated at As already stated, the gas mixture passin through "condenser C will contain as big as 90% helium. In other words, the temperature and pressure conditions prevailing in the condenser are such that the partia pressure of the im urities does not exceed 10% of the tota pressure. Our invention is not to this condition, however, and we regard as within our inthe pipe-line.

vention all methods of o eration "wherein d with a temperature not elow 193 C. thereis apphed a pressure suflicient to cause the partial pressure of the impurities to be not more than 20% of the total pressure.

In our novel process, all the principal cooling baths are held at such pressures as willpermit of the gases produced by their ebullition being introduced directly into Any usual pipe-line pressures, for example 10 to 20 atmos heres, are adapted for use in our 'inventlon at the points referred to, and are covered in the appended claims.

Having now described our invention, we claim:

1. Process of producing a helium concentrate from natural gas which comprises liquefying a portion of the gas, holding the liquid so produced under a pipe-line pressure, and cooling another portion of the gas under higher pressure therewith, said higher pressure being such that partial liquefaction of the ortion so cooled'will result.

2. Process 0 producing a helium concentrate from natural gas which comprisw progressively cooling the gas by means of liquefied fractions thereof boiling at a pipeline pressure, while holding the gas to be cooled Tunder suflicient pressure to liquefy non-helium constituents thereof.

3. Process of producili a helium concen successive steps of compressing, cooling, and expanding the gas to-liquefy a portion thereof, leaving a gaseous residue and liquefying a portion of said residue y transferring heat therefrom to natural-gas constituents held atpipe-line ressure.

- trate from natural gas w ich comprises the In testimony w erebf, we aflix our signatures. 1

JAMES A. RAFFERTY. HAROLD E. THOMPSON.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2500118 *Aug 18, 1945Mar 7, 1950Howell C CooperNatural gas liquefaction
US2567461 *Feb 12, 1948Sep 11, 1951Petrocarbon LtdSeparation of gaseous mixtures at low temperatures
US3208231 *Dec 29, 1961Sep 28, 1965Linde Eismasch AgRectification of liquid mixtures boiling at low temperatures
US3282060 *Nov 9, 1965Nov 1, 1966Phillips Petroleum CoSeparation of natural gases
US4238211 *Nov 20, 1978Dec 9, 1980Helix Technology CorporationMethod of employing a first contaminant to prevent freeze-out of a second contaminant during cryogenic processing of a gaseous stream
Classifications
U.S. Classification62/639
International ClassificationF25J3/02
Cooperative ClassificationF25J3/0233, F25J3/029, F25J2270/90, F25J3/0209, F25J2270/42, F25J2215/30
European ClassificationF25J3/02A2, F25J3/02C30H, F25J3/02C2