US2500916A - Method and apparatus for controlling vaporization - Google Patents

Description

March 14, 1950 WHALEY, 2,500,916

METHOD AND APPARATUS FOR CONTROLLING VAPORIZATION ori inal Filed July 14, 1941 3 Sheets-Sheet 1 INVENTOR THOMAS H. WHALEY JR.

TTOR EY March 14, 1950 w JR 2,500,916

METHOD AND APPARATUS FOR CONTROLLING VAPORIZATION Original Filed July 14, 1941 3 Sheets-Sheet 2 INVENTOR I THOMAS H.WHALEY JR. FIG. 2

BY i W M vW ATOR EY.

T. H. WHALEY, JR

METHOD AND APPARATUS FOR CONTROLLING VAPORIZATION Original Filed July 14, 1941 5 Sheets-Sheet 3 CONTROL VALVE CONTROL VALVE PRODUCT OVERHEAD VAPORS CONDENSER CONTROL VALVE TOP PRODUCT BOTTOMS INVENTOR THOMAS H. WHALEY JR. BY

FEED 66 5 A RNE T W Patented Mar. 14, 1950 METHOD AND APPARATUS FQRCON- .TROLLING vAPonrz Tm fIhomas H. Whaley, Jr., Bartlesville, kla., assignor to Phillips Petroleum Company, ,a corporation of Delaware Original applif ation July 14, 1941, Serial 1N0.

conform with marketing requirements.

402,416. Divided and this application April.1 5,

1944, Serial No. 531,238

.6 Claims.

The present invention relates-to a method of and apparatus for control of unit operations.

In the production of volatile liquid products, the vapor pressure of the product often is an important specification which must be met to Many of the petroleum products, for example, must meet a particular Reid Vapor Pressure requirement. Intermediate fractions formed during the refining and separation of petroleum stocks into marketable products often require vapor pressure control. Where the product is a mixture of two components, control of the vapor pressure may determine also the composition of the product.

The present invention controls thev vapor pressure of the liquid product by control of the quantity of vapor removedfrom-the-liquid. In a batch operation where a liquid is evaporated until the remaining liquid has: the. desired vapor pressure, this invention may beemployed to automatically stop the vaporization when the desired vapor pressure is reached by-closingthe vapor exit. Its operation is not. dependent upon temperature or pressure conditions in the vaporizer. In continuous operations, the method of this invention is useful, for example, for controllin the vapor released from'an accumulator tank of .a rectifying column and is especially useful indesorption operations. In desorption, vapor from a later stage in the process isreturnedto an earlier stage where it is used to replace undesirable components in .the'liquid undergoing treatment. In this respect, the present invention may the advantageously applied to systems of the. type disclosed by Samuel C. Carney, Serial No. 324,895, filed March-19, 1940, now U. S. Patent No. 2,307,024; Serial No. 339,832, filed June 10, 1940, now U. S. Patent No. 2,303,609; Serial No. 339,987, filed June 11, 1940, now U. S. Patent No. -2,301,520. In these systems, vapors from an accmnulatortank are passedto the base of the desorber. The useof the present invention in such-asystem provides control of the vapor pressure of ,the liquid in the accumulator tank andautomatic control of the deo pti n a i lunderstood from e ll win detailed description.

The present invention-is useful also in separation of gas from liquid by flash-ing or Venting. In the production of petroleum, for example, liquid and gas areseparatedat or nearthe wells in suitable separators. These are maintained at a definite pressure by pressure regulators. The pressure at which the separators are operated is determined by several factors but generally may be said to be the pressure at which the optimum recovery of liquid results, Often several separa rs at,;,s .lqc ssivslvfl we Pressu es are placed in series. The series of separators give stage separation of the liquid and. gas,

an improved method of controlling the vapor pressure of a volatile liquid.

A further object of this invention is to provide a method of controlling the quantity of gas evolved from a liquid tothereby control the vapor pressure of the remaining liquid.

A-still further object of this invention is to provide a method of controlling the composition 'Of'ElJWOLCOmDOIIGHEIIlQUidS.

Still another object -of this invention is to provide a control device for-controlling the evolution of gas or vaporfrom liquid.

Figurel is a cross section of apparatusshowing the application of the present invention to control of the vapor pressure of the residual liquid in a-batch vaporization process.

Figure 2 is a cross section of a modification of apparatus of 'Figurel.

Figure 3 is an-elevation view of gas-oil separators, showing an application of this invention .to flashing operations.

Figure 4 is an elevation of fractionating equipment showing an application of this invention.

With reference to Figure l of the drawings,

the numeral l0 designates a vessel containing liquid II which is 1 to be;evaporated until the remaining; liquid meets with desired vapor pressure specifications. vaporization is accomplished by supplying heat to the liquid by means of a heating coil I2 in the vessel. Steam is supplied to the heating coil from-- the pipe l3 through body member 2lin which is a-conventionalbalanced valve assembly including the valve disks 22 .and 23. Attached to the valve body is a motor housing comprising two sections Hand 25. 'Within the motor housing is a motor or pressure responsive element 26, in this instance a Syphonows. nhtbi ettathtdt the a v that it will \be subject to the temperature conditions therein is a capsule 28 containing a control liquid having the vapor pressure characteristics desired in the final product. The vapor pressure developed by the liquid reference sample is transmitted to the interior of the Sylphon bellows through the pipe 29. The exterior of the Sylphon bellows is acted upon by the pressure existing in the vessel.

If the control valve is subject to cooling so that it is cooler than the capsule 28 during operations, the Sylphon bellows is operated flooded, i. e., filled with liquid. When operating the Sylphon bellows flooded, the pipe 29 extends nearly to the bottom of the capsule 28 acting as a dip tube. There is vapor space in the capsule 28 to allow sufficient expansion and contraction of the Sylphon bellows to operate the valve. If the Sylphon bellows is subject to the same temperature as the capsule 28, as it usually is, or to a higher temperature, the Sylphon bellows may be operated by the pressure of vapor which is transferred to the bellows from the vapor space of the capsule 28.

The operation is as follows: Liquid to be evaporated is admitted to the vessel l through the inlet pipe l1. Steam for furnishing the heat of vaporization is admitted to the heating coil through the pipe [2. It will be understood that the liquid charged to the vessel I0 consists of more than one component and is to be vaporized until the more volatile vapors have been evolved in sufficient quantities to leave a residual liquid having the desired vapor pressure characteristics. The vapor pressure of the liquid charged to the vessel acts upon the external surface of the Sylphon bellows. Since the vapor pressure of the liquid in the vessel is greater than the vapor pressure of the control liquid in the capsule at the same temperature, the Sylphon bellows is contracted, opening the vapor control valve. The valve remains open, allowing vapors to escape from the vessel through the pipe 20, as long as the vapor pressure of the liquid in the vessel is greater than the vapor pressure of the control liquid in the capsule 28. As the vapor escapes from the vessel, the liquid in the vessel approaches that in the capsule and the difierential across the pressure responsive element 26 in the control valve approaches zero. When the vapor pressures of the two liquids are identical, the Sylphon bellows assumes its normal position and the valve disks 22 and 23 cooperate with their respective valve seats to prohibit the escape of vapor from the vessel. If the liquid in the vessel then corresponds to the liquid in the capsule 28, the temperature in the vessel may vary over a wide range without causing the control valve 2! to reopen. It is not necessary, therefore, to try to maintain an accurate temperature control on the heating coil I2 or accurate pressure control on the vessel. The two variables may be allowed to vary within the limits imposed by the temperature of the heating steam and the maximum allowable pressure for which the vessel is designed.

A conventional pressure release valve 30 may be employed as a safety feature if desired and the valve l4 may be conrtolled in any suitable manner.

With reference to Figure 2 of the drawings, the system of Figure 2 is illustrated with a modification of the control valve. The modified control valve is interposed in the vapor outlet pipe 20. The valve body 3| is provided with the balanced valve disks 32 and 33. The motor housing comprising sections 34 and 35, contains a 4 Sylphon bellows motor 36 attached to the valve stem 31 to actuate the valve. The Sylphon bellows 36 is partly filled with a control liquid having vapor pressure characteristics substantially the same as that of the desired residual liquid product. The pressure responsive Sylphon bellows 36 is subject externally to the pressure in the vessel l0 and to the temperature of the vapors evolved from the liquid. The heat exchange between the vapors passing through the valve and the control liquid in the Sylphon bellows maintains the temperature of the control liquid at the vapor temperature. The capsule 28 and pipe 29 of Figure 1 is dispensed with, thereby eliminating connections which may be subject to leakage. The operation of the control valve of Figure 2 is the same as the operation of the control valve of Figure 1. It is especially applicable to apparatus in which the temperature of the vapor leaving the liquid is equal to the temperature of the liquid, or varies therefrom by a constant amount. The difference in temperatures, if any, may be compensated for by biasing the control valve in any suitable manner.

Figure 3 shows the application of the present invention to flash vaporization of a continuous stream of liquid such as is practiced in multiple stage separation of gas from oil in production. Fluid from the well flows through the pipe 5| into the high pressure separator 52. Gas separated from the liquid in the separator 52 escapes through the control valve 53 and pipe 54. The liquid is drawn off near the bottom of the separator through the float controlled valve 55 and passesthrough the pipe 56 into the low pressure separator 51. Gas separated from the liquid is vented Sthrough the control valve 58 and pipe 59. The remaining liquid is withdrawn from the separator through the float controlled valve and is passed through the pipe 6| to storage ora gathering system. The control valves used at the present time to regulate the flow of vapor through pipes 54 and 59 are back pressure regulators. It is evident that under the present method of operation, with a constant pressure on each separator, the vapor pressure of the final product will vary with variations in the atmospheric temperature conditions to which the separators are subjected. In accordance with the present invention the back pressure regulator on separator 51 is replaced with the control valve 58 of Figure 1 or Figure 2. Since the control valve is subject to the same temperature variations as the separator, the control valve shown in Figure 2 is quite applicable. For closer control of the composition of the final product, one of the control valves of my invention may be used as the control valve 53 on the high pressure separator. The control liquid used is preferably some of the well fluid which has been flashed under controlled conditions to conform to the desired vapor pressure specifications. The operation of the control valves is similar to that described in connection with Figures 1 and 2. So long as the vapor pressure of the liquid in the separator exceeds that of the control liquid, the control valve allows vapor to escape from the separator. Since there is a continuous inlet stream of liquid having a vapor pressure higher than that of the control liquid, the control valve allows a continuous stream of vapor to leave the separator and acts to control the pressure in the separator to a value equal to the vapor pressure of the desired product at the prevailing separator temperature. This modification of my invention 5 is.particulariv useful for controlling the product: from. distillatewellsr The light: distillateipro ducedlmay be flashed to a definite vapor pressure product and; the evolved vapors recycled for: pressure maintenance.

Figure 4 shows the use of vapor control on the-accumulator tankloha fractionator. The top product. of" the fractionator is: controlledto de sired vapor pressurezspecifications:and the vapors taken: from the accumulator maybe used for, desorption. The fra'ctionator: 65'. of. any. suitable" type is supplied-withv feed through pipe 66; Heat is. furnished, to the fractionator: by the. heating coil 68. to which heating fluid from the pipe: 69 isadmitted by the controltvalve: id. The bottoms from the fractionator are withdrawnthrough-the pipe, H in accordance with. the" action of: the fioatcontrolledivalve l2; Thevaporous overhead. of the fractionator is: passed: through: the pipe 13 tov the condenser 'l l'i where'it is. cooled; and:

partly condensed; flond'ensate' and uncondensed vapors; from the condenserfiow to the accumulator 15through pipe -62,

Eart ofithe condensate is returned as refluxrby the pump 11 tothe top-oft-he column through; the

control valve is and piper'lm. Excess reflux ortcp: product fromthe fractionatoristWithdrawn from the accumulator through thefloat-controlled-valve 8-0; into the pipe-8,! through which it: passes to.

market. Uncondensed vapors leaverthe top of;the

accumulator through: thepipe 82 and control alve 8.3;. The controlivalve: illustrated, is the typadescribed connection with; Figure. 1., The control liquid to which. the control valve;- is responsive consists of a sample of the overhead product desired and thecontrolgva-lve thenserves tomaintainthe pressure von.theaccumulator. and fiactionator equal to thevapor pressureiof the desired product at the temp erature existing in the accumulator.

Thetemperature of: the condensate; and-uncondensed' vapors in the accumulator depends to a largeextent upon "the temperature of the-cooling medium; supplied tothe: condenser M; whichin turnis dependent. upon atmosphericrtemperature conditions; The result of k the customarypracticeof maintaining the pressureonethe-accumulatorconstant. bya: back pressure regulator is a-. top product, thecomposition and-vapor, pressure of which is variedas the temperature in the con.--

denserand accumulator. vary. T ne-presentc in.- vention variesthe accumulator. pressure-An acecordance, with variations, of. the-vapor pressure of the desired topproduct, in-sucha manner that the temperature variations are compensated for; as thetemperature increases the-pressure increases, and as the temperature decreases, the pressure decreases. If it is desired to maintain the pressure on the fractionatingcolurnn constant, a back pressure regulator may be installed'inthe pipe 13 and the valve !8 may be oontrolledin any suitable manner to insure proper reflux.

The modification of my invention disclosed in Figure 4 is especiallyusefulwhenlthe fractionation is precededby. desorption; In the desorption, gas or vapors fromtheaccumulator maybe'sent to the base of adesorber immediatel preceding the fractionator. If the desorption is not. complete, lightcomponents. will pass-over to the fractionator from the base of the desorber. These light componentsipassoverhead-i from the fractionator and'tend to increase. the vapor, pressure in the accumulator. The. valve-8-3iorf m n-invention allows these .light. gases to, beifiashedoif in the, accumulator, and returned to \the baserofi the d'eserb'er for stripping or descr bing the liquid prior tovfeedingt'o-the' fraetionator: This-insuresproper functioning of the desorber under variabletemperature conditions at the plant; Present control's'require manual adjustmentto correct for temperaturechan'ges:

Fi'om theforegoing: detailed description and: the examples citing specific applications: of i the invention, it: will be apparent to those skilled i'ni the-art that: the meth'od and apparatus-ofthe present invention is applicable th control of vaporization of a Wide -varietyof'volatile muIti cOmponent liquidsin either batch or: continuous op erations.

Thisapplication is a divisionof my: copending application, sen-arm. 402416; filed July 14; 1941'; now 'U; S. PatcntNo. 21389244.

I"claim:

11 In the separation of ahydrocarbonweltefilhent under variabletemperature conditions into. a" liquid fraction and a: plurality ot'gaseous fractions, the method-oi treating said effiuent to produce a liquid fraction having a substantially constant vapor pressure at a standard temperature which. comprises passing said" mixture into a closed zone wherein thereispresent a liquid phase anda'vapor-phase insubstantialequilibrium with one another, maintaining a confined control liq old: in; indirect heat exchange relationship with one-ofsaid phases,- said control liquid having sub stantiallyithe same vapor pressure characteristics as the desired liquidcpl'ra'se; withdrawing vapor from: said zone in an amount such-that'the vapop pressure characteristics-of 'saidr liquid phase" are substantiallyidentical withitlie vapor pres surecharacteristics ofsaidcontrol liquid; Withdrawing; liquid. from said zone and passing said liquid to a second closed a Zone wherein: there is presentaliquid phase and'a vapor phase in sub stantial equilibrium with one another; maintaining? a second confined: control" liquid in: indirect heat: exchange" relationshipv with one of saidphases: in said: second- Zone; said second control liquid havingsubstantially the same vapor. pressure characteristics: as thei'desiredse'cond liquid phase; Withdrawing vapor; from said second flzone in an: amountisuch that? therva'por pressure char.- acteristics of; said" second. liquid phase are substantiaily, identical-with the; vapor pressureaoharzacteristicscofzsaidsecond cnntrol liquid; andswith' draw-ing zliquidrfrom .said second :zone as said'zliqiuidfraction;

2; Inetheseparationofiashydrocarbon Well effluent under: variable temperature :con-ditions -into a liquid fraction and a: plurality of gaseous fractions, themethodaof treating: said efiiuentatoipro ducearliquiddractionhavingasubstantia'lly constant vaporspressure-zat-a standardw temperature which comprises passing: said mixture into" a: closed zone": wherein thereis: present" a liquid phase". anda .vapor' phase in substantial: equilibriumz with one another, maintaining aconfined control aliquidsin indirect heatexchange :relatiomshipwith said liquid phase; said control liquid having substantially thesame. vapor pressure characteristics as-thedesiredfliquid phase; Withdrawingvaporrfrom said zoneinqan -amount such that the-vaporpressuretcharacteristics: of said liquid phase are. substantially identical 1 with the vapor pressure. characteristics.- of: said control liquieh, withdrawing-,- liquid from: said zone and passing ;said liquid toasecond closedzone-wherein there is--present:a;-1iquid phase-iand-a-vapor phase insubstantial equilibrium.- Withione' anw other; maintaininga:secondrconfinedzcontroldiqg uid in indirect heat exchange relationship with said liquid phase in said second zone, said second control liquid having substantially the same vapor pressure characteristics as the desired second liquid phase, withdrawing vapor from said second zone in an amount such that the vapor pressure characteristics of said second liquid phase are substantially identical with the vapor pressure characteristics of said second control liquid, and withdrawing liquid from said second zone as said liquid fraction.

3. In the separation of a hydrocarbon well effluent under variable temperature conditions into a liquid fraction and a plurality of gaseous fractions, the method of treating said effluent to produce a liquid fraction having a substantially constant vapor pressure at a standard temperature which comprises passing said mixture into a closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one another, maintaining a confined control liquid in indirect heat exchange relationship with said vapor phase, said control liquid having substantially the same vapor pressure characteristics as the desired liquid phase, withdrawing vapor from said zone in an amount such that the vapor pressure characteristics of said liquid phase are substantially identical with the vapor pressure characteristics of said control liquid, withdrawing liquid from said zone and passing said liquid to a second closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one another, maintaining a second confined control liquid in indirect heat exchange relationship with said vapor phase in said second zone, said second control liquid having substantially the same vapor pressure characteristics as-the desired second liquid phase, withdrawing vapor from said second zone in an amount such that the vapor pressure characteristics of said second liquid phase are substantially identical with the vapor pressure characteristics of said second control liquid, and withdrawing liquid from said second zone as said liquid fraction.

4. In the separation of a hydrocarbon well eiiluent under variable temperature conditions into a liquid fraction and a plurality of gaseous fractions, the method of treating said eilluent to produce a liquid fraction having a substantially constant vapor pressure at a standard temperature which comprises passing said mixture into a closed zone wherein during operation there is present a liquid phase and a vapor phase in substantial equilibrium with one another, withdrawing vapor from said zone in an amount such that the pressure in said zone is substantially constant, withdrawing the resulting liquid from said zone and passing same to a second closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one one another, maintaining a confined control liquid in indirect heat exchange relationship with one of said phases in said second zone, said control liquid having substantially the same vapor pressure characteristics as the desired liquid phase in said second zone, withdrawing vapor from said second zone in an amount such that the vapor pressure characteristics of said liquid phase in said second zone are substantially identical with the vapor pressure characteristics of said control liquid, and withdrawing liquid from said second zone as said liquid fraction.

5. In the separation of a hydrocarbon well eflluent under variable temperature conditions 76 into a liquid fraction and a plurality of gaseous fractions, the method of treating said ellluent to produce a liquid fraction having a substantially constant vapor pressure at a standard temperature which comprises passing said mixture into a closed zone wherein during operation there is present a liquid phase and a vapor phase in substantial equilibrium with one another, withdrawing vapor from said zone in an amount such that the pressure in said zone is substantially constant, withdrawing the resulting liquid from said zone and passing same to a second closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one another, maintaining a confined control liquid in indirect heat exchange relationship with said liquid phase in said second zone, said control liquid having substantially the same vapor pressure characteristics as the desired liquid phase in said second zone, withdrawing vapor from said second zone in an amount such that the vapor pressure characteristics of said liquid phase in said second zone are substantially identical with the vapor pressure characteristics of said control liquid, and withdrawing liquid from said second zone as said liquid fraction.

6. In the separation of a hydrocarbon well effluent under variable temperature conditions into a liquid fraction and a plurality of gaseous fractions, the method of treating said effluent to produce a liquid fraction having a substantially constant vapor pressure at a standard temperature which comprises passing said mixture into a closed zone wherein during operation there is present a liquid phase and a vapor phase in substantial equilibrium with one another, withdrawing vapor from said zone in an amount such that the pressure in said zone is substantially constant, withdrawing the resulting liquid from said zone and passing same to a second closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one another, maintaining a confined control liquid in indirect heat exchange relationship with said vapor phase in said second zone, said control liquid having substantially the same vapor pressure characteristics as the desired liquid phase in said second zone, withdrawing vapor from said second zone in an amount such that the vapor pressure characteristics of said liquid phase in said second zone are substantially identical with the vapor pressure characteristics of said control liquid, and withdrawing liquid from said second zone as said liquid fraction.

THOMAS H. WHALEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,363,487 Taber Dec. 28, 1920 1,463,158 Ehrhart July 31, 1923 1,550,116 Smith Aug. 18, 1925 1,649,345 Gilmore Nov. 15, 1927 1,940,803 Kallam Dec. 26, 1933 1,969,888 Gibson Aug. 14, 1934 2,073,908 Smith Mar. 16, 1937 2,086,808 Kallam July 13, 1937 2,200,261 Carney May 14, 1940 2,297,098 Carney Sept. 29, 1942 2,343,317 Olson Mar. 7, 1944 2,389,244 Whaley Nov. 20, 1945

Images