US2389244A - Method and apparatus for controlling vaporization - Google Patents

Description

New. 20, 1945. T. H. WHALEY, JR 2,389,244

METHOD AND APPARATUS FOR CONTROLLING VAPORIZATI'ON Filed July 14, 1941 3 Sheets-Sheet l INVENTOR THOMAS Hv WHALEY JR.

. BY M1 7 ATTO EY 194$ T. H. WHALEY, JR 239,44

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

FIG. 2

Nov. 20 1945.

T. H. WHALEY, JR

Filed July 14, 1941' s Sheets-Sheet :5

CONTROL CONTROL VALVE VALVE FYEI D u: 52 /57 g 5 E1 A E, (I) (I) A W PRODUCT 50 n FIG. 3

OVERHEAD VAPORS CONDENSER 74 CONTROL 52 VALVE FEED 0: b6 2 2 Q 79 '2 U l 3 a: 2 3 80 TOP 2 PRODUCT INVENTOR THOMAS H. WHALEY JR.

Patented Nov. 20, 1945,

METHOD AND APPARATUS rim CONTROLLING vAromz 'rroN Thomas n. Whaley, Jr., Bartlesville, one. assignor to Phillips Petroleum Company, a com ration of Delaware application my 14, 1941, Serial No. 402,416 Claims. (01. 196-132) ing 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 the vapor pressure of the liquid product by control of the quantity of vapor removed from the liquid. In a batch operation where a liquid is evaporated until the remaining liquid has the desired vapor pressure, this invention may be employed to automatically stop the vaporization when the desired vapor pressure is reached by closing the 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 controlling the vapor released from an accumulator tank ofa rectifying column and is especially useful in desorption operations. In desorption, vapor from a later stage inthe process is returned to an earlier stage where it is used to replace undesirable components in the liquid undergoing treatment. In this respect, the present invention may be advantageously applied to systems of the type disclosed by Samuel C. Carney, Serial No. 324,895, filed March 19, 1940; Serial No. 339,832, filed June 10, 1940; Serial No. 339,987, filed June-11, 1940. In these systems, vapors from an accumulator tank are passed to the base of the desorber. Theuse of the present invention in such a system provides control of the vapor pressure of the liquid in the accumulator tank and automatic control of the desorption as will be understood from the following detailed description. r

The present invention is useful also in separation of gas from liquid by flashing or venting. In the production of petroleum, for example, liquid and gas are separated'at or near the 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 separators at successively lower pressures are placed in series. The series of separators give "stage separation" of the liquid and gas, retaining in the liquid phase many of the volatile liquid hydrocarbons which might be vaporized in a single separator. improved means of controlling the pressure at which separation is carried out in either single or' multiple stage separations.

An object of thlsdnven'tion is-to provide an improved method of pressure control for unit operations.

Another object of this invention is to provide an improved method of controlling the vapor pressure of a volatileliquid.

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

A still further object of this invention is to provide a method of controlling the composition of two component liquids. I

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

Figure l is, a cross section of, apparatus showing 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 Figure 1.

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 1 of the drawings, the numeral l0 designates a vessel containing liquid i I which is 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 B2 in the vessel. Steam is supplied to the heating coil from the pipe l3 through the valve M which is operated in any appropriate manner. Condensate from the heating coil is drawn oil through the trap i5 and pipe iii. The vessel I0 is provided with an inlet pipe I! having a control valve l8 associated therewith, a valved liquid outlet pipe l9, and a vapor outlet pipe 20. Interposed in the vapor outlet pipe 20 is the vapor control valve comprising a valve body member 2 lin which is a conventional balanced valve assembly including the valve disks 22 and 23. Attached to the valve body is a motor housing comprising two sections 24 and 25. Within the motor housing is a The present invention provides an allowable pressure for which the vessel is designed; 'A conventional pressure'release valve 30 may be employedas asafety feature if desired and the valve it may be controlled in any suitable manmotor or pressure responsive element 28, in this instance a Sylphon bellows, which is attached to .the valve stem 21. Inside the vessel III in such a-position that it will be subject to the temperature conditions therein is a capsule containing a control liquid having the vapor pressure characteristics desired in the final product. The

sample is transmitted to the interior of the Sylphon'bellows through the pipe 21. The exterior of the Sylphon bellows is acted upon by the pressure existing in the vessel. Y

" If the control valve is subject to cooling so'tha vaporpressure developed by the liquid reference aeeam is=sublectesternally to thepressurein the vessel Ill and to the temperature'of'the vapors evolved it is cooler than the capsule 28 during operations,

- the Sylphon bellows is operated flooded, i. e., filled with liquid. Whenoperating the Sylphon bellows flooded, the pipe 29 extends nearly to'the bottom. of the capsule 28 acting as a dip tube. There is vapor spacein the capsule 28 to allow sumcient expansion and contraction of the Sylphon bellows to operatethe valve. If the temperature.

from the liquid. The heat exchange between the vaporspas'sing through the valveand the control liquid in' the Sylphon bellows maintains the temperatureof the control liquid at the vapor The capsule 28 and pipe 29 of 1 Figurel. is-dispensed with, thereby eliminating h bell ws is's b ect to the same tem erasylp on u j p of'Figure 1. It is especiallyapplicableto'appature as the capsule 28, as it usually is or to a higher temperature, the Sylphon bellows may be operated by the pressure of vaporwhicli' is transferred to the bellows from the vapor space of the I capsule 28.

The operation is. as follows! Liquid to be evaporated is admitted to the vessel. in through the inlet pipe ll. Steam for furnishing the heat ofvaporization is. admitted to the heating coil than one component and is to be vaporizeduntil The vapor pressure of the liquid charged to the vessel acts upon the external .gsurface of. the

liquid in the vesselis greater than the vapor pressureor the control liquid in the ca at the l Theremainin'g liquid is withdrawn from the separator through the float controlled valve 60 and is same temperature, the Sylphon bellows is contracted, opening the vapor controlvalve. The valveremains 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 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 ratus in which the temperature of the vapor leaving theliquidis equal to the temperature of the compensated for by biasingthe control valve in zany suitable manner.

Figure 3 shows the application of the present invention toilash vaporization of a continuous throughthe pipe 12. It 'winhe understood that stream-"f nquiidjsuch is 'pracmed in multiple the liquid charged to the vessel"! ll consists of more stageseparationtoi. gas from oil in production.

v Fluid from the well flows throughthe pipe 5| -into 'the high-pressure separator. 52. -Gas sepa- "rated from the liquid inth'e separator 52 escapes a through the control; valve 5i] and. pipe 54., The n liquid is drawn ofl. near the bottom of the separator through the fl'oat controlledvalve 55 and Sylphon bellows. Since the vapor pressure of the passes through the pipe 56 into the low pressure greater than the vapor pressure of the control I temperaturein the vessel may vary over a wide range-without causing the control valve 2| to vented through the control valve-58 and pipe 59.

. valve of Figure 'l or Figure 2. Since the control valve is subject to the same temperature variations .as the separator, the control valve shown in the vessel. .1! the liquid in the vessel ill then corresponds to the liquid in the capsule 28, the

reopen. It is notnecessary, therefore, to try to maintain an accurate temperature control on the heating coil I: or accurate pressure control on the vessel. The two variables maybe'allowed to vary within the limits imposed'by the temperature of the heating steam and-the maximum ner.-

with reference to Figure 201' the'drawings,

Figure 2 is quite applicable. For closer control of the composition of the final product, one of the controlvalves 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-jis similar to that described in connection I with Figures land 2. So long as the vapor pressure of the liquid in the separator exceeds that =of the control liquid, the control valve allows avapoitto escapefrom the separator. Since there is a continuousinlet stream of liquid having a vapor pressure "higher than that of the control liquid, the control *valve allows a continuous stream of vaportoleave the separator and, acts to control the pressure in the separator to a value aasaau The light distillate produced may 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 tank of a fractionator. The top,

product of the fractionator is controlled to desired vapor pressure specifications and the vapors taken from the accumulator may be used for desorption. The fractionator 66 of any suitable type is supplied with feed through pipe 66. Heat is furnished to the fractionator by the heating coil 88 to which heating-fluid from the pipe is admitted by the control valve Ill. The bottoms .irom the fractionator are withdrawn throughthe pipe II in accordance with the action of the float controlled valve 12. The vaporous overhead of the fractionator is passed through not complete, light components will pass over to the fractlonator from the base of the desorber. These light components pass overhead from the fractionator and tend to increase the vapor pressure in-the accumulator. The valve 83 of my invention allows these light gases to be flashed oil in the accumulator, and returned to the base of the desorber for stripping or desorbing the liquid prior to feeding to the fractionator. This insures proper functioning of the desorber under variable temperature conditions at the plant. Present controls require manual adjustment to correct for temperature changes.

From theforegoing detailed description and the examples citing specific applications of the invention, it will be apparent to those, skilled in the art that the method and apparatus of the present invention is applicable to control of vaporization of a wide variety of volatile multithe pipe T3 to the condenser II where it is cooled and partly condensed. Condensate and uncondensed vapors from the condenser flow to the accumulator it through pipe 18.

Part of the condensate is returned as reflux by the pump W to the top of the column through the control valve 78 and pipe 119. Excess reflux or top product from the fractionator is withdrawn from the accumulator through the float controlled valve Bil into the pipe 8i through which it passes to market. Uncondensed vapors leave the top of the accumulator through the pipe 82 and control valve 3. The control valve is the type described in connection with Figures 1 and 2. The control liquid to which the control valve is responsive consists of a sample of the overhead product desired and the control valve then serves to maintain the pressure on the accumulator and fractionator equal to the vapor pressure of in the accumulator.

The temperature of the condensate and uncondensed vapors in the accumulator depends to a large extent upon the temperature of the cooling medium supplied to the condenser it, which in turn is dependent upon atmospheric temperature conditions. The result of the customary practice of maintaining the pressure on the accumulator constant by a back pressure regulator is a top product, the composition and vapor pressure of which is varied as the temperature in the condenser and accumulator vary. The present invention varies the accumulator pressure in accordance with variations of the vapor pressure of the desired top product in such a manner that the temperature variations are compensated for; as the temperature increases the pressure increases, and as the temperature decreases, the pressure decreases. If it is desired to maintain the pressure on the iractionating column constant, a back pressure regulator may The modification of my invention disclosed in Figure 4 is especially useful when the fractionation is preceded by desorption. In the desorption, gas or vapors from the accumulator may be sent. to the base of a desorber immediately preceding the fractionator. 'If the desorption is component liquids in either batch or continuous operations.

Having thus described my invention, I claim: 1. In combination. with a fractionator producing a mixture of hydrocarbons as overhead vaporous eflluent therefrom and having a condenser'for at least partially condensing the overhead vaporous eflluent, a closed vessel for reception of said mixture and wherein during operation there is present a liquid phase and a vapor phase in substantial equilibrium with one another, an inlet to said vessel for admitting said mixture thereto, a vapor outlet for escape of vapor from said vessel and from the system, a liquid outlet for withdrawal of liquid from said vessel and from the system as product, a closed container containing a volatile control liquid in indirect heat exchange with said liquid phase, said control liquid having substantially the same vapor pressure characteristics as the desired product, and acontrol valve associated with said vapor outlet and responsive to diflerence between the vapor pressure of said control liquid and the pressure within the vessel, said valve permitting flow of vapor through said vapor outlet only when the pressure in said vessel is at least equal to the vapor pressure of the control liquid. I

- 2. In combination with a iractionator producing a mixture of hydrocarbons as overhead vaporous effluent therefrom and having a condenser for at least partially condensing the overhead vaporous effluent, a closed vessel for reception of said mixture and whereinduring operation there 'is present a liquid phase and a vapor phase in substantial equilibrium with one.an-

other, an inlet to said vessel for admitting said sive to difference between the vapor pressure of said control liquid and the pressure within the vessel, said valve permitting flow of vapor through said vapor outlet only when the pressure in said vessel is at least equal to the vapor pressure of the control liquid.

3. In combination with a fractionator producing a mixture of hydrocarbons as overhead vapourous eflluent therefrom and having a condenser for at least partially condensing the overhead vaporous emuent, a closed vessel for reception oisaid-mixture and wherein during operation there is present a liquid phase and tr vapor phase insubstantial equilibrium with one another, an inlet to saidvessel i'or admitting said "mixture thereto, a vapor outlet for escape oi vapor from said vessel and'ifrfom the system, a

liquid outlet for withdrawal of liquid from said vesseliand from the system as product, a closed container containing a volatile control-liquid in substantially the same vapor pressure characvalve associated with said vapor outlet and reteristics as the desired product, and a control sponsive to difference between the vapor pressure of said-control liquid and the pressure within the vessel, said valve permitting flow otvapot in said vessel isat least equal'tothe vapor pres-. I sure of'thexoontrol liquld. i 7-. Thelmethod or treating adistillable mixture of hydrocarbons {to-produce ia-liquid product less indirect heat exchange withsaid va'ponphase,

- said control liquid having substantially the same vapor pressure characteristics as the desired product, and a control valve associated with said vapor outlet and responsive to diilerence between the vapor pressure of said control'liquid and the ilow of. vapor through said vapor outlet only when the pressure in said vessells at least equal tothe vapor pressure oi! the control liquid.

4. In a system for treating adistillable hydro-, carbon mixture, the combination comprising a closed vessel wherein during operation there is present a liquid phase and a vapor phase in substantial equilibrium with ,one another, an inlet pressure within the vessel, said valve permitting throughsaid vapor outlet only when the pressure volatile than said mixture ian'dhaving me termined vapor pressure which comprises passing said mixture into a 'closed vessel wherein during operation thereis-presenta liquid phase and a vapor phase in substantial equilibrium with one another, maintaining a confined control liquid in indirect heatwexchange with said liquid phase, said controlliquid having substantially the'same vapor pressure as thedesired liquidphase. withdrawing vapor from saidvessel and fromthe system in an amount such that said pressurein said vessel is maintained substantiallyequal tothe to said vessel for admitting said mixture-thereto,

a vapor outlet for escape of vapor from said vessel and from the system, a liquid outlet for with I drawal of, liquid from said vesseland from the system as product, a closed container containing a volatile control liquid in indirect heat exchange with said liquid phase, said-control 'liquidhavirig'. "substantially the same vapor. pressure :characteristicsas the .de'sired produot, .and a control sponsive to, diil'erencev between the. vapor pressure of said control liquid and the pressure within the vessel. said valve permitting flow of vapor throughsaid vapor outlet only when the pressure in said vessel is at least-equal to the vapor pressure of the control liquid.

5. In a system for treating a distillable hydrocarbon mixture, the combination comprising a closed vesselwherein during operation there is present a liquid phase and a vapor phase in subpassing said imixture" into a; closed zone wherein l thereis'present a liquldphasea vapor phase j .in substantial equilibrium ;-with.. one 'anothen .85 valve associated with-said vapor outlet: and re-;

vaporpressure of. said control liquid, and withdrawing the resulting liquid phase from "said vessel as said liquid'product.

8; The method oftreating a 'distillable mixture of hydrocarbons to produce; a liquid product less .volatile'than said mixture and having a predetermined vapor} pressure which: comprises maintaining a confined: control liquid in:.indirect heat exchange-1 relationshipsrvithone ol suid l phases, said control an mq maym substonuaily the samevapor pressure-characteristics as the stantial equilibrium with one another, an inlet to said vessel foradmltting said mixture thereto, a vapor outlet forescape of vapor from said vessel and from the system, a liquid outlet for withdrawal of liquid from said vesseland from the system as product, a closed container containing a volatile control liquid in indirect heat exchange with one of said vapor and liquid phases,

said control liquid having substantially the same vapor pressure characteristics as the desired product, and a control valve'associated with said vapor outlet and responsive to diilerence between the vapor pressure 01' said control liquid and the pressure within the vessel, said valve permitting I a new of vaporthroughsaid vapor outlet only when the pressure in said vessel is at least equal to the vapor pressure of thecontrol liquid.

6. Ina system for treating a distillable hydrocarbonmixture thecombination comprising a closed vessel wherein during operation there. is-

present a liquid phase anda vapor phase in substantial equilibrium with one another; an inlet to said vessel for admitting'said mixture thereto,

a vapor outlet for escape ot vapor from'said vessel and from the system, a liquid outlet for withdrawal of liquid from said vessel and from the system as product,'a closed container containing a volatile-control liquid inindirect heat exchange with said vapor phase, said control liquid having liquid product.

9. In the fractionation of hydrocarbons in which a mixture of hydrocarbons is obtained as vaporous effluent of the fractionation, the method of treating said mixture to produce a liquid overhead liquid product less volatile than said mixture and having a predetermined vapor pressure which-comprises cooling said vaporous eilluent of the fraetionator to form condensate, passing the resultant mixture to a closed zone wherein there is present a liquid phase and a vapor phase in substantial equilibrium with one another,

maintaininga confined control liquid in indirect heat exchange with-said condensate, said control liquid having substantially-the same vapor pressure characteristics as-"the desired liquid has oppo the ,pressurezwithinsaid zone to the vapor pressure of the control liquid,"with-' I drawingvapor from saidzone and from the system in an amount such: that. the vapor pressure characteristics of said liquid phase are-substantially identical with the vapon pressure characteristics of said controlliquid, andseparate1y --withdrawing liquid from said zone and from the system as said liquid product. a

- 10. In a system for treating a distillablehydro- -carbon mixture, the combination comprising a closed vessel wherein during separation there is present a liquid phase and a-vapor phase in-substantial equilibrium with oneanother, an inlet 7 to we vessel for admitting said minture thereto, a vapor outlet for escape of vapor i'rcm said vessel and from the system, a liquid outlet for withdrawal 0! liquid from said vessel and from said system as-product, a closed expansible container containing a. volatile control liquid in indirect heat exchange with said vapor phase, and subjected externally to the pressure of-said vapor phase. said control liquid having substantially the same vapor pressure characteristics as the liquid.

THOMAS H. WHALEY, JR.

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