US1437102A - Process of recovering gasoline from natural gas - Google Patents

Description

1. B. GARNER AND s. 0. PRESTON.

PROCESS OF RECOVERING GASOLINE FROM NATURAL GAS.

7 APPLICATION FILED FEB 14. 1920.

1,437, 1 O2, Patented Nov. 28, 1922',

2 SHEETSSHEET 2.

35 pending application, Serial-.No; 339,555,- we

that "largely, increased percentages of the whichthe, process is accomplished.

PatentedNov. 28, 1 922.

JAMES B. GARNER ANDSYLVESTER C. PRESTON, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO HOPE CONSTRUCTION & REFINING COMPANY, OF PITTSBURGH. PENNSYLVANIA, A CORPORATION OF DELAWARE.

PROCESS OF RECOVERING GASOLINE FROM NATURAL GAS.

Continuation of application Serial No.

To all whom/"it may concern:

Be it known that we, JAMEs B. GARNER and SYLVESTER C. PRESTON, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, both citizens of the United States, have invented or discovered certain new and useful Im rovements in Processes of- Recovering asoline from Natural Gas, of which improvements the following is a specification. This application is a continuation of and is substituted for our application filed June 2, 1919, Serial No. 301,165.

In United States Letters Patent No. 989,- 927, ranted to G.'M. Saybolt, there is disclosed a process for obtaining naphtha or gasoline from combustible gas of natural origin and underground source, or in other words: from what is commonly known as natural gas. The meth0d,-briefly stated, consists in subjecting the natural gas under pressure to a gasoline-absorbing menstruum for the purpose of separating from the gas such gasoline as is liquid at atmospheric temperatures and pressures, and then preferablyremoving the gasoline from the menstruum.

Theobject of-our invention is to improve the process disclosed in the, above mentioned patent. The process as we have improved it" is applicable. generally to the-recovery Of liquids carried Vapor form by gases, and'is notawlimitedto, the specific case of gasolil ir ecovery, from natural gas. This willlbe notedagain:in'the sequel. In a codescribe andclai-miapparatus in the use of the-practice; of our invention natural gasjispassed-successively through two bodies,of;agasoline-absorbing. menstruum,preferably: a ,-liquidppetroleum hydrocarbon having a specific gravity: of from about 289 to Bauni-atg .17., and these bodies are circulatedatandacontrolled in such a manner gasoline content of-the natural gas are economically-recovered, f 1. The firstbody of menstruumthrough which the: gas passes is so circulated that, in

- a subdivided state,,it contacts a plurality of times with a flowing body of gas. By

7 feet 301,165, filed June 22, 1919. This application filed February 14, 1920. Serial No. 358,780.

'thus increasing the number of contacts which the menstruum, in a subdivided state, makeswlth the 1gas, we have found that, due to absorptlon 0 gasoline from the gas, the

Baum gravity of the menstruum may be advantages of thus building up the Baum gravity of the menstruum, it maybe noted, first, that much less menstruum need be heated for separating or distilling from the menstruum a unit volume of absorbed gasoline, and, secondly, that when the menstruum is used in'a closed cycle as is the usual practice, much less cooling facilitiesneed be provided for cooling the menstruum after having been heated.

t will be understood that rise in Baum gravity means fall in specific gravity,"and vice versa.

We'have found that, by multiplying the contacts of the first body of menstruum with ity of the menstruum, argely increased per centages of the gasoline content of the natue ral gas may be absorbed. 'lvehav'e ffound by practice that the gasoline may beiab sorbed nearly to the theoretical maximum extent: the point at, which the artial. pressure of the gasoline'vapor remaining in the gas is. equal to the vapor tensionof the gasfo line in the menstruum. As a specific ex ample, we have found that, conditioned,

upon the above mentioned control ofthe second body of me struum, the gasoline may be so completely. a sorbed from the" gasthat there will remain in the gas only'about fi fteen gallons of gasoline per mlllion cubic '0 gas, the gas being measured ata pressure ofeight ounces above atmospheric'and 'at aotemperature of 60 F., whereas inthe process as usually practiced there remains in the gas from fifty to ninety gallons of gasoline per million cubic feet of gas.

Still further, we have foundthat by multiplying the contacts of the first body of menstruum with the gas, certain lighter constituents ofthe gas not desired in the gasoline, though initlally absorbed by the menstruum, are, as the operation progresses, to a considerable extent displaced by desired constituents. Thus, less separating of the lighter constituents from the menstruum is required after absorption and prior to the separation of the gasoline from the menstruum.

The second body of menstruum through I which, according to our invention, the gas passes, is so controlled that the absorption of gasoline by the menstruum will raise the aum gravlty of the menstruum but a small amount, as compared with the rise in specific gravity of the first. body of guien struum. Preferably, the gravity of the secondbody of menstruum is not permitted to decreasemore than will be indicated by a rise of 19 Baum. We have found that.the above described, beneficial results arising from therepeated contacts ofthe first body of menstruum with the gas may be realized only by controlling the second body of menstruum, in the manner just explained.

The first body of menstruum may be sub divided in any suitablemannei', as for example,by means ofspray nozzles, or by being caused to flow downwardly through a vertical absorber provided, in the well known manner, with a mass of coke, broken rocks, steel turnings, lattice work ofilath, or other equivalent The second body of men,- struum is preferably maintained in the form of a pool through which the gasbubbles. In such a pool particles of .the menstruum" carried by thegas from the subdivided first body of menstruum arefiltered outwith substantial completeness. However, the second of menstruum may, as the gas, passes through it, be in a subdivided state,

the menstruum, for example,being caused to flow through such a verticalabsorber as has just been characterized.

In the accompanying drawin s we have diagrammatically illustrated t e general construction and arrangement of apparatus for practicin our invention. Figure I shows a comp ete layout oflapparatusfand F lgures II and III show absorbing units udaptedtw be used inthe general arrangement of apparatus shown in Fi re I.

' Having reference first to Figure I, natural gas from a suitable source of supply, and under any desired pressure, flows through a-pipe l' nto a horizontally disposed spray absorber, consistingof a tank 2 within which 'is' arranged a plurality of sets of spray nozzles 3, 4, and 5. "From the tank 2 the a pipe 10 to the point of consumption; or,

prior to flowing through the pool absorber 9, the gas may flow through pipe '11 into a vertical tower-absorber 12 provided interiorly with means, such as a mass of broken stones 13, by which a descending stream of menstruum is subdivided. From the tower absorber 12 the gas flows through pipes 14 and 6 to the pool absorber 9, and thencethrough pipe 10. For controlling such alternative flow of gas, the pipes 6, 11, and 14, are provided with suitable valves 15, 16, and 17, as indicated inthe drawing. The alternative flowv of gasis here shown, primarily for the purpose of illustrating two arrangements of plant construction. practice, the tower absorber 12 may or may not be present.

The menstruum is preferably caused to How continuously through the absorbers counter current to the flow of gas. A's indicated in the drawing, the oil which forms the above described second bodyof menstruum is, by means of a pump 18, caused to flow through a pipe '19 into one end of the absorber 9, and forms a pool therein, through the perforations in the header- From the absorberathe menstruum is, by

means of a pump continuously withdrawn through a pipe 21 and discharged into a pipe-22, through which it is conducted in amanner presently to explained. The rate of flow of the menstruum through the absorber 9 is so governed and controlled that the rise in Baum gravity ismuch less than the rise of the first body of menstruum. As previously stated, the rise in Baum gravity of the menstruum while in the absorber 9 is preferably not more than about 1- For maintaining such control of the gravit of the menstruum, samples-thereof may rom time to time be taken from the pipes 19 and 21 (suitable pet- cocks 23 and 24 being provided for this pur ose), and the Baum gravity of the samp es compared.

The menstruum pumped into the pipe 22 may be conducted dlrectly through such pipe to a header 25 to which the several s ray nozzles 3 of the absorber 2 are attache or it may. be carried first through the vertical absorber12, provided the plant includes such an absorber, and afterward introduced into absorber 2. When it is to be introduced into the] vertical absorber 12, the, menstruum flows from pipe 22 through apipe .26; pipe 26 entering the upper end of the tower 12 and is provided with perforations through which the menstruum is discha ged in subdivided streams upon the top of the body of broken stone 13. The menstruum, subnaemoa 52, and 53 for controlling the described alternative flow of the menstruum to the header 25.

Various means may be provided .for' causing the menstruum in the spray absorber 2, the first body of menstruum as we herein consistently designate it, to contact in subdivided state a plurality of times, with the gas flowing through the absorber. In the. apparatus shown in the drawing the right-hand end of' the absorber 2 is connected to a trap or sump 29,into which menstruum collecting in absorber 2 descends. To the sump two pipes 30 and 31 are connected,the former leading to a pump 32, and the latter leading to apparatus, presently to be explained, for separating from the menstruum its absorbed gasoline as well as lighter normally gaseous constituents A pipe 33 leads from pump 32 to a header 34; and header 34 inv turn is, by means ofbranch pipes 54 and 35, connected to branch headers 36 and 37, to which the two series of spray nozzles 4 and 5 are attached. The pipes 54 and 35 are preferably provided, respectively, with controlling valves 38 and 39, and the spray nozzles 5 are preferably constructed to divide the menstruum into a ner spray than do the spray nozzles 4. Preferably, also, the spray nozzles 4 divide the menstruum into a finer spray than do the nozzles 3. The desired degree of fine ness of spray may be controlled and determined by proper regulation of valves 38 and 39..

The pump 32 is of such capacity and run at such speed that itcirculates the menstruum the number of times required to obtain the desired number of contacts of the gas with the menstruum. For example, if it were desired to multiply six-fold the contact of menstruum with gas, the pump 32 would be so operatedthat the number of gallons of menstruum pumped per minute would be five times the number of gallons of menstruum flowing per minute through the sprays 3 into the absorber, therate of flow of the menstruum from the absorber 2 through the pipe 31 being maintained the same as the rate of flow of the menstruum through the nozzles 3 into the absorber 2. Thus one contact of the menstruum would be made by the menstruum issuing from the nozzles 3 and the remaining five contacts would be made by the menstruum issuing from the nozzles 4 and 5.

F or ascertaining the Baumr-rise in gravity of the menstruum, due to its repeated contacts with the gas in the absorber 2, samples of the menstruum may from time to time be withdrawn from the pipe 31, through a pet-cock 40, and the gravity of such samples compared with the gravity of samples removed through the pet-cock 24 in pipe 21. If the Baum rise in gravity is not as great as it should be, the pump 32 may be operated at increased speed, to effect an increased number of contacts. As previously stated, we have found that the gravity of the first body of menstruum, that is to say the menstruum in the absorber 2, may be advantageously raised 8 Baum. We have found this to be true of natural gas containing initially about 500 gallhns of gasoline per million cubic feet of gas. The gravity may be raised less or more than 8. Baum, dependin to some extent upon the amount of gasoline in the gas.

The menstruum flowing from the absorber through the pipe 31 may flow under the pressure of the gas in the absorber 2, the rate of flow being regulated by a valve 41 so as to be equal to the rate of flow of the menstruum through the pipe 22 into such absorber. From the pipe 31 the menstruum may flow into a vent tank or primary still 42, where such lighter normally gaseous constituents as have been absorbed may under atmospheric pressure (with substantial completeness) escape. From the tank or still 42 the menstruum flows, or is pumped by means of a pump 55, through pipe 43, heat exchanger 44, and pipe 45, to a still 46, in which the absorbed gasoline is removed in the form ofvapor, Subsequently the vaporous distillate is condensed in the usual, or in any desired, manner. Distillation and condensation are conducted at or above atmospheric pressure, preferably at a pressure of about 25 pounds above atmospheric pressure. The heated menstruum flows from thestill, through a'pipe 47, back through the alternate passages of the heat exchanger 44, and thence through pipe'48,

cooler 49, and pipe 50, to pump 18, for recirculation through the absorbers.

The second body of menstruum is, according to the designation which we consistently employ, the body through which the gas last passes, the body from which the" gas emerges to flow directly to the point of consumption. The first body of menstruum is all of the menstruum through a which the gas passes, prior to passage through the second body so defined. That the twobodiesof menstruum may be variously brought into contact with the gas will be understood, when we shall have described the process as practiced with the use of the modified forms of absorbers shown in Figures 11 and III. H

Instead of maintaining the second body of menstruum in the form of a pool, it may be subdivided, as by being caused to flow downwardly through a vertical absorb 19, is sprayed. At the bottom of the tower the menstruum is collected and flows through a pipe 21 to a pump 20*- whereby it is discharged into the plpe 22, which corresponds to pipe 22 of Fig. I and leads to the primary absorber or absorbers. Through pipe 6 gas from the primary absorber or absorbers enters tower 56, and, after passing upward through the menstruum-inundated "mass of broken material 57 escapes through pipe 10 to the point of consumption. To remove from the gas such particles of menstruum as might otherwise be carried off by it, baflles such as the alternately arranged plates 59 may be arranged in the upper ortion of the tower. Thus it will be seen t at the vertical tower 56 may be used in place of the pool absorber 9 in the complete assembly of units illustrated in Figure I. p

Instead of usingseparate vessels for the first and second bodies of menstruum, a single vessel may be used, such for example as shown in Figure III. The absorber there illustrated is atower 60, provided in the usual manner with a mass 61 of broken stone or the like. The menstruum enters the tower 60 through thepipe 19 flows downwardly over the mass 61, and is collected in the bottom of the tower, from which two pipes 30 and 31 lead off. 'By means of a pump 32 the menstruum flowing in pipe 30 is recirculated, to contact a plurality of times with gas flowing upwardly through the lower portion of the tower 60, the pipe 33 on the discharge side of the pump entering the tower 60 about midway of its height. If desired, a vent tank 66 may be provided, whereby the menstruum fiowingthrough the pipe 30 may be vented for the removal of lighter normally gaseous constituents initially ab{ sorbed. A .vent tank so situated may. be

added to the apparatus shown in Fig. I and will be found advantageous in case,

.when the menstruum being re-circulated carries appreciable quantities of such lighter constituents. As explained with reference to Fig. I, the menstruum from the tower 60'is caused to flow through the pipe 3l" at the same rate as it flows through the; pipe 19. Between and connected to the pipes 31" fand' 19- -,there@may be arranged the same. apparatus for treating the men- 'Figure 1 between the struum as'is shown'in' pipes 31-and 19.

The gas enters the bottom of the tower -60from a supply line 1-I,';flows upwardly, through the first "and second. bodies of menstruum (which two bodies of menstruum are in this case not otherwise separated or demarcated than by the entrance of the eddy stream, through pipe 33), and flows from the tower into thepipe '10.

For controlling the Baum rise in gravity of the second body of menstruum, samples thereof may from time to time be taken at the pet-cock 23 and, by means of a pipe 62 arranged immediately above the end of pipe 33, the inner end of the pipe 62 being provided with a cup 63, at pet-cock 64.

From the fore oing it will be seen that the second body 0% menstruum may be either in the form of a pool or in subdivided state when brought into contact with the gas, and that the first and second bodies of menstruum may be either in separate vessels or in a single vessel. If desired, the first body of menstruum may perform its function through .a series of separate absorbers, rather than in a single absorber. This is clear from a consideration of the apparatus of Figure I, in Which the first body of menst'ruum flows through two absorbers. Manifestly, and without further illustration, the

number and type of such independent absorbers may be indefinitely multiplied. In all cases, however, a relatively small Baum rise in gravity of the second body of menstruum is maintained, as compared with that of the first body. We have found it to be impossible to absorb from the gas absolutely all of the gasoline which it carries, for the reason that the gasoline absorbed by the menstruum builds up in the menstruum a vapor tension which counterbalances the partial pressure of the gasoline remainin in the gas. Hence there is always remining in the gas after the gas passes through the last body of menstruum some percentage of the amount of gasoline originally in the gas. During a days run, in which 96.6% of the gasoline was recovered, 19,000 cubic feet of gas per hour werepassed through the two bodies of menstruum. The menstruum consisted of liquid petroleum the initial gravity of which was about 39 Baum. The" pressure of the gas ranged from 56 to 61 pounds above atmospheric pressure, and the temperature of absorption ranged from 52 to 66 F. The first body of menstruum was recirculated in a spray absorber to contact four times with the gas, I

and its Baum rise in gravity was 6.7 while the Baum rise'in grayity of the second body of menstruum was maintained at covered from the gas was 741dgallons per 'imillion cubic feet of gas treate T pparatuswasof the same type and arrangement as that shown in Figure I of the aceompanying drawings, including the tower' absorber. 354 gallons of oil per hour were caused to flow through the pool absorber, a rate of about'one gallon of oil to 54 cubic feet ofgas.

The rate of flow of the menstruum is, in the practice of our invention, controlled with reference to the Baum rise in gravity of the second body of menstruum. If such rise in gravity is higher than is permissible, according to our discovery of condition'saffording maximum recovery, the first body of. menstruum should bef re-circulated at increased speed to increase the number of contacts with the gas. If such re-circulation does not, by increased absorption of gasoline, have the effect of cutting down the Baum rise in gravity of the second body of menstruum, then (having reference to the apparatus of Figure I) the rate of flow of menstruum into and from the pool absorber 9 should be increased. Such increase of flow of the menstruum will of course necessitate an equal increase in the rate of flow of menstruum through the pipe 31. As previously-stated, the first body of menstruum should be ire-circulated a sufficient number of times to effect a large rise in the Baum gravity thereof.

In the practice of our invention the gas may be treated under any desired pressure. As compared to the amount of gasoline recovered from the gas when treatment of the gas is under the customary high pressure of fifty or more pounds per square 1I1Cl1 above atmospheric pressure, we have found that as much gasoline may be recovered when the gas is under a pressure of twenty pounds per square inch above atmospheric pressure or less, provided the contacts of the first body of menstruum with the gas be sufiiciently repeated, and provided further that the rise in Baum gravity of the second body of menstruum be controlled in the manner explained above.

It will be observed that, with the apparatus and according to the method now described, the stream of gas advancing counter-current to a stream of menstruummeets the stream of menstruum at successive points, and that superior conditions of absorption are maintained where the gas initially encounters the menstruum than where it ultimately encounters it. These superior conditions consist in an eddy in the menstruum stream, wherein menstruum flow is accelerated, and more or less the. same bodies of menstruum are brought into repeated absorption-aifording contact with the gas.

We have in the foregoing specification described our invention in specific application to the recovery of commercial gasoline from natural gas. It will .be understood without further elucidation that it is a process aplicable wherever a substance normal y iiquid is carried in vapor form by gas. In

the ensuing claims we make plain the fact that the invention is of such broader aspect. And one thing more should be said: it is not necessary (although the matter so stands when gasoline is being recovered) that the absorbing menstruum be heavier than the recovered liquid; indeed, in case of the recovery of benzole from the gases which ordinarily carry it in vapor form, the

absorbent liquid used will ordinarily be lighter than the benzole recovered. Accordingly, in such case, as the operation progresses, the menstruum will not, as in the case of gasoline recovery, decrease in specific gravity as the operation progresses, but will in-fact increase in specific gravity, and in such case it will be understood that the process is accomplished in so adjusting the apparatus and so governing the operation relatively part to part that the specific gravity of that body of menstruum through which the stream of gas first passes will increase (not decrease) through-a wider range than Will the specific gravity'of that portion or body of menstruum through which the as fina ly passes, while the range of variatlon in spec1fic gravity is variable and controllable, in the manner already described.

We claim as our invention:

1.. The herein described step in the process of recovering a substance normally liquid from a gas carrying it in vapor form, which consists in forming an eddy in a flowing stream of vapor-absorbing menstruum, and passing the gas first through the eddy and subsequently through the menstruum at a point farther up the stream.

2. The herein described step in the process of recovering a substance normally liquid from a gas carrying it in vapor form, which consists in forming an eddy in a flowing stream of vapor-absorbing menstruum, circulating the menstruum in the edd to contact with the gas 'a plurality of times and absorb the vapors therefrom, bringing the gas again into absorption-affording contact with the menstruum at a point further up the stream, and regulating the amount of the absorption at said second point.

3. The process of separating vapor of a normally liquid substance from entraining as, which consists in causing the gas to 50w in a stream "into absorption-affording contact with a counter-current of vaporabsorbing menstruum, first in an initial chamber and subsequently in a succeeding chamber, continuously circulating a branch the gas to flow into absorption-affording contact successively With two bodies of gaso- In testimony whereof We have herermtd line-absorbing menstruum, circulating the set our hands. first body of menstruum to contact with the JAMES B. GARNER; gas a plurality of times and absorb gaso- SYLVESTER C. PRESTON.

5 line therefrom, and limiting the absorption Witnesses:

in the second body to a predetermined rela- GEORGE A. SHANER,

tively small amount. FRANCIS J. TOMASSON.

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