US2792070A - Refinery blowdown and relief system - Google Patents

Description

May 14, 1957 E. STRUNK REFINEIRY BLOWDOWN AND RELIEF SYSTEM 3 Sheets-Sheet 1 Filed Feb. 25. 1952 FIG.

VENT STACK CONDENSED HYDROCARBON Al M 5 A 4 L F T k NU O ES T RS 4 mam w 4 WPC H D l 2 4 Q ,L m

7 2 a m 6 F 2 F 3 2 HI, Ml h I 1 N 4 W 0M 2 DU R fl B L UNIT RELIEF UNIT UNIT RELIEF RELIEF INVENTORL E DWARD STRUNK A TTORNEYS y 4, 1957 E. STRUNK 2,792,070

REFINEIRY BLOWDOWN AND RELIEF SYSTEM Filed Feb. 25, 1952 3 Sheets-Sheet 2 EIIEIL' STEAM G 50 k8? I '1'. I F/ STEAM I 54 l I WATER 55 53 WATER 48 I T0 FLARE I I I I I J ;47 l 1 l 5| IL RELIEF LINE 2 I 1 LIQUID HYDROCARBON I 49 WATER ;i- TO FLARE INVENTOR. EDWARD STRUNK A T TORNEYS May 14, 1957 E. STRUNK 2,792,070

REFINERY' BLOWDOWN AND RELIEF SYSTEM Filed Feb. 25, 1952 3 Sheets-Sheet 3 FIG. 4. 5:

i /82 27 ]i r i 1 l l 83 1 23 INVEN TOR.

EDWARD STRUNK BY REFINERY BLUWDUWN RELEF SYSTEM Edward Strunk, Sweeny, Tom, assignor to Phillips Ferroleum Company, a corporation of Delaware Application February 25, 1952, Serial No. 273,308

14 Claims. (Cl. 183-4) This invention relates to refinery blowdown and relief systems. In a further aspect this invention relates to systems whereby gases may be released to the atmosphere under controlled conditions. in a further aspect this invention relates to a relief or blowdown system in which a flare is used in connection with a vent stack. in a further aspect this invention relates to a system in which a flare is used to dispose of normal amounts of relief gases and a normally sealed vent is provided to dispose of excessive amounts of these gases.

It is common practice in refineries to collect hydrocarbon relief and blowdown gases and to pipe them to a flare. Such a flare must be located a considerable distance from the processing area because of the fire hazard. An alternative which has been used is to provide a vent stack extending high in the air in the processing area. The first method is expensive for, to be eifective, the flare line must be of large capacity to avoid restricting the flow and imposing that pressure on other relief valves in the system which would prevent their opening at the set pressure, but it has the advantage of giving visible and immediate evidence of loss whether through leaking or inadvertently opened blowdown valves, since the height of the flame gives a rough indication of the amount of gas being burned. The second alternative is less expensive in that an adequately sized line can be installed over the relatively short distances required; however, it has the disadvantages of giving no indication of when or how much loss to blowdown occurs and will create a fire hazard unless the gases are properly dissipated. When the gases to be dissipated are heavier than air, it is necessary to supply steam to this stack so that the gas leaving the stack will be lighter than air.

I have invented a system which provides a method of combining the advantages and eliminating the disadvantages of both systems. It consists of installing a gas blowdown or relief header system tied to a large vent stack in the still area, putting a water seal in the path of said gases to the vent stack which will open in case of excessive flow of blowdown material, and piping relatively smaller, normal quantities through a smaller capacity line to a remotely located flare. The flare indicates by the size of the flame the magnitude of the smaller, normal gas losses. An indicator showing when the water seal is blown gives evidence of large loss.

By the various aspects of this invention, one or more of the following objects will be obtained.

An object of this invention is to provide an improved refinery relief or blowdown system. A further object is to provide an improved system wherein relatively small amounts of gases are burned by a remotely located flare and excessive amounts of such gases are vented by means of a vent stack. A further object of this invention is to provide an improved method of providing for the safe release of gases to the atmosphere. A further object of this invention is to provide a method of venting gases from a refinery system which comprises flaring relatively small atelnt' "cc V 2,792,0170 Patented May 14, 1957 amounts of said gases in a remotely located flare and venting large amounts of said gases through a vent stack. A further object of this invention is to provide an improved water seal for use with the vent stack of my invention.

Other objects and advantages of this invention will be apparent to those skilled in the art.

Accompanying and a part of this invention is a drawing in which:

Figure 1 is a diagrammatic view of a refinery relief and blowdown system;

Figures 2 and 3 are modifications of the system of this invention; and V Figure 4 is an enlarged cross section View of the water seal shown in Figure l.

Referring to the drawings and to Figure 1 in particular, iii represents a blowdown drum containing bubble or water wash trays 11. Gaseous relief header 12, located at a convenient place in the plant is connected to unit relief lines 13, 14, and 16 and also to the lower portion of drum 10 by means of conduit 17. Extending from the top of drum 10 is vent stack 18 which is provided with steam distributor 19, said steam distributor being connected to steam line 21. A water seal is provided in the upper end of drum 10 which comprises a flat annular member 22, a tubular member 23 positioned in the hole of said annular member, a downflow conduit 24, and a cap 26. The height of the member 23 should be slightly above the height of the downflow conduit 24, and the sides 27 of cap 26. extend to a point below the inlet opening of conduit 24.

In Figure l, cooling water is circulated over the water seal and the trays 11 by means of conduits 28, 29, and 31. Connected to this system is makeup water supply conduit 3% Pump 32 is located in this system to force the water to the top of the column. In the return line to the top of the column there is provided cooler 33 with bypass 34, valves 36 and 37 regulating the flow therethrough. While I have shown manual control valves at this point it will be evident that a temperature control could be utilized to by-pass cooler 33 as long as the water is cool enough. Conduit 38 extends from the lower portion of drum 10, condensed hydrocarbons being removed therethrough.

Difierential pressure control 39 is provided with one side 41 connected just above plate 22 and the other side 42 connected below the water seal. This pressure control 39 serves to operate valve 43 in line 21. Below the water seal there is provided conduit 44 which conveys gas to a flare (not shown). A meter 45 is provided to indicate the amount of gas flowing through conduit 44.

in Figure 2, a modification of my invention is shown wherein the drum is designated 46. In this modification separate sources of liquid are used for the condensing column and the water seal. The contacting or water wash trays in the column are designated 47, the water inlet 48, and the water outlet 49. Input conduit 51 communicates with the lower portion of drum 46. Hydrocarbon removal conduits comprise conduit 52 for condensed products, conduit 53 for normal gaseous flow and vent stack 54 for large gaseous release. The lower end of vent stack 54 extends into container 55 which, in operation, has a liquid level maintained therein. A line 56 in stack 54 allows water which is blown into stack 54 when the water seal is broken to flow back to the bottom of 46. Conduit 57 can be used to supply this liquid. In the upper portion of vent stack 54 there is provided steam distributor 58 which is connected to conduit 59. In this modification, I have shown flow meter 60 as the steam inlet operating means. This meter is of a type that does not restrict gas flow such as Pitot tube and is not used to quantitatively meter the gas flow but is operatively connected to open the steam valve in response to a positive flow of gas up the stack. Valve 61 is provided in conduit 48, this valve being controlled by means of a temperature responsive device 63 which is actuated by the temperature in line 51.

The simplest form of my invention is illustrated in Figure 3 wherein the drum is designated 66. Relief conduit 67 communicates with one end of this drum. At the other end of the drum there are provided conduits 68 extending to the flare and 69 to convey liquids from the drum. In this modification vent stack 71 extends into container 72 which is provided with liquid supply conduit 73 and liquid overflow 74. Extending from vent stack 71 is liquid removal conduit,76.

In Figure 4 there is shown an enlarged view of the upper section of drum. 10 as shown in Figure 1.. This view shows the details of construction and illustrates a case in which two downflow conduits 24 are provided. A manhole 81, is shown in the upper part of cap 26, said cap being supported above the tubular member 23 by means of supports 82. Connections for attachment of differential pressure control 39 are shown at 83 and 84.

The operation of the system of this invention is as follows, this system being readily adaptable to any size installation. Referring to Figure l, the relief lines from various parts of apparatus are all tied into relief header 12 and the gases flow from this header, through conduit 17 to the blowdown drum 10. In drum 10 the gases are contacted with water and relatively higher boiling hydrocarbons are condensed and removed through line 38. This cooling water is removed through conduit 28 and recirculated to the top of the column. Conduits 28 and 38 are normally provided with liquid level controls (not shown) but this removal can be manually controlled. The water seal in the upper part of the drum is of sufficient size that all of the gases from normal leakage in the plant will flow through conduit 44 to the flare. The wash water for this column normally fills the space between the cap 26 with its sides 27 and the tubular section 23 connected to the annular ring 22. Water which is supplied flows through conduit 24 down into the column and gases are prevented from flowing upwardly therethrough by means of the seal or well on the lower end of this conduit.

When the water wash is circulated in this column it may be necessary to cool this water and this is done by means of heat exchanger 33. If large amounts of fresh water are supplied, this cooling is generally unnecessary.

When a relief valve on some apparatus blows, a large surge of gas flows into the drum 10. When the pressure in drum 10 caused by the increased gas flow exceeds an amount determined by height of the water seal, the gases blow the water seal and vent to the atmosphere through stack 18. When this water seal is broken, differential pressure control 39 is actuated and this serves to operate valve 43 causing dispersant steam to be released from distributor 19. This steam lowers the specific gravity of the gases being vented so that they are dispersed and do not settle around the apparatus causing a fire hazard. As soon as the excess flow is reduced, the water will again establish a seal on the stack, the steam will be shut off, and normal conditions will result. The flare normally burns continuously so that the magnitude of loss will be visible at all times. In addition to the flare, a meter 45 may be installed in conduit 44 to indicate the magnitude of gases flared.

The modification of Figure 2 operates in a slightly different manner. In this case there is no steady water wash and the water seal is normally nothing more than the static water head in container 56, this water being supplied by conduit 57. Normal amounts of relief gases pass directly from conduit 51, through drum 46, and to the flare through conduit 53. Water and liquid hydrocarbons are removed from the lower part of the drum. When gases entering 46 through line 51 exceed a predetermined temperaturevalve 61 is opened in responseto temperature responsive device 62, resulting in condensation of condensable elements in the relief gases. When a relief valve blows the increased flow causes the water seal to blow and the gases are vented through vent stack 54 to the atmosphere. Steam is added to this vent stack by means of distributor 58.

After the situation has been returned to normal the container 55 is again filled with water and is again in readiness for operation.

In some installations surplus steam may be continuously vented to atmosphere by means of line 50 and this will result in some condensation in vent stack 54 which serves to maintain the liquid in the water seal container 55. In other installations a small flow of water is continuously supplied to container 55. In such installations I have found it desirable to use an overflow conduit which connects the stack with the lower part of drum 46. The steam line 59 serves to supply steam for the purpose of the above-mentioned dispersing effect and also for extinguishing any fire which might be started by lightning.

In Figure 3 a very simple form of this invention is illustrated wherein a drum 66 is similar to the usual knockout drum in which liquids and gases are separated. The relief gases are passed into one end of the drum and preferably directed against the end of this drum so that most of the liquid will be knocked out of the gas. Following this separation gaseous and liquid products are removed through conduits 68 and 6%. Conduit 68 extends to the flare and is of sufiicient size to take any of the normal loss of the installation. Added to this knockout drum is vent stack 71 which extends into said drum and into container 72 positioned therein. A water level is maintained in this container which is supplied by conduit 73. To simplify the liquid separation problem when the system is operating normally, an overflow line 74 is provided which keeps container '72 from overflowing. Conduit 74 is provided with a liquid trap seal (not shown) to prevent gases from flowing therethrougb when the liquid level is below the input connection to conduit 74.

Operation of this modification is quite similar to that disclosed in Figures 1 and 2 and it is not necessary to review this operation completely. One feature shown in connection with this modification is conduit 76 which connects the interior of conduit 71 and the interior of drum 66. This prevents the accumulation of excessive water head in vent stack 71 by releasing water forced into this stack to the interior of the drum.

Figure 4 illustrates the details of the water seal shown in Figure 1. The operation of this water seal has been described in connection with the operation of that figure.

It should be appreciated that there are many possible variations and modifications of this type of blowdown and relief system which will now become apparent to those skilled in the art. As already pointed out, this system allows safe operation in venting small and large amounts of inflammable gases to the atmosphere. Furthermore, this provides a system which is almost entirely automatic in action and yet which is almost foolproof as the only valve in the system is the water seal.

As many possible embodiments may be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A refinery relief system for inflammable gases comprising a blowdown drum, a vent stack extending from the upper end portion of said drum, at least one inlet conduit communicating with the lower portion of said drum, a water seal disposed in said drum between said vent stack and said feed conduit whereby said vent is sealed from said inlet conduit, means for condensing condcnsable hydrocarbons in said drum, a liquid bydrocarbon drawei'f conduit extending from the lower portion of. said drum, and means. extending from said 5, drum to a flare whereby noncondensed hydrocarbons are conveyed to said flare.

2. The system of claim 1 wherein said vent stack is provided with a steam inlet.

3. A refinery blowdown system comprising a blowdown drum and communicating therewith a flare conduit and vent stack, said flare conduit being of small capacity when compared to said vent stack, at least one inlet communicating with said drum, at least one liquid material outlet extending from the lower portion of said drum, a Water seal at the bottom of said vent stack, means operatively connected to said drum whereby rupture of said water seal is indicated, a steam inlet conduit in said vent stack, a valve in said steam inlet conduit, and a control line operatively connecting said means operatively connected to said drum whereby rupture of said water seal is indicated and said valve.

4. A refinery relief system for inflammable gases comprising an upright blowdown drum, a water seal in the upper end portion of said drum, a vent stack extending from the upper end portion of said drum, water wash trays in said drum, a relief header, unit relief conduits communicating with said relief header, a conduit connecting said relief header and the lower end portion of said drum, a wash water inlet conduit extending into said drum above said water seal, a water drawoff conduit extending from the lower end portion of said drum, a conduit connecting said wash water inlet and said water drawoff conduits, a pressurizer in said conduit, a water supply conduit communicating with said wash water inlet conduit, a liquid hydrocarbon drawoff conduit extending from a level in said drum above said Water drawofit conduit, and a conduit extending from a point in said drum above said Water wash trays and below said water seal to a flare.

5. The system of claim 4, in which a cooler is provided in said wash water inlet.

6. The system of claim 1 wherein said water seal comprises a flat annular ring positioned transversely within an upright column and connected to said column by a gas tight seal, a tubular section positioned in the hole in said annular ring and connected to said ring by a gas tight seal, at least one downflow conduit extending from a level below the top of said tubular section to a level below said annular ring, a well in said downflow conduit, a cap above said tubular section having sides which extend downwardly between said tubular section and said downflow conduit to a level intermediate the upper end of said downflow conduit and said annular ring.

7. The system of claim 4, wherein said water seal comprises a fiat annular ring positioned transversely within an upright column and connected to said column by a gas tight seal, a tubular section positioned in the hole in said annular ring and connected to said ring by a gas tight seal, at least one downflow conduit extending from a level below the top of said tubular section to a level below said annular ring, a well in said downflow conduit, a cap above said tubular section having sides which extend downwardly between said tubular section and said downflow conduit to a level intermediate the upper end of said downflow conduit and said annular ring.

8. A refinery gas relief system comprising an upright blowdown drum, a plurality of contacting trays in the mid-section of said drum, a liquid supply conduit above said contacting trays, a relief line communicating with said drum, temperature responsive means in said relief line, a valve in said liquid supply conduit operatively connected to said temperature responsive means, at least one liquid removal conduit extending from the lower portion of said drum, a gaseous removal conduit extending from said drum at a level above said liquid removal conduit, a liquid container in said drum, a vent stack extending from a level below the normal liquid level within said liquid container, and a means to supply liquid to said liquid container.

9. A refinery relief system for inflammable gases comprising a blowdown drum, a water seal in the upper end portion of said drum, wash water trays in said drum, an inlet conduit communicating with the lower end portion of said drum, a wash water inlet conduit extending into said drum above said water seal, a water drawoif conduit extending from the lower end portion of said drum, a liquid hydrocarbon drawofl conduit extending from a level in said drum above said water drawotf conduit, and a conduit extending from a point in said drum above said wash water trays and below said water seal to a flare.

10. The method of venting gases from a refinery comprising passing said gases to a blowdown zone, removing condensed hydrocarbons therefrom, removing to a. remotely located flare a normally flowing relatively small amount of said gases, removing liquids accumulating in said blowdown zone from the lower portion of said zone, separately venting gases in excess of said normally flowing relatively small amount of gases from said blowdown zone in response to an increase in gas flow beyond a predetermined amount, said latter flow being controlled by a water seal, and adding steam to said separately vented gases in an amount suflicient to lower the specific gravity of said gases, said steam being added downstream of said water seal.

11. The method or" claim 10 wherein the flow of said steam is controlled by a change in pressure differential upstream and downstream of said liquid seal.

12. The method of claim 10 wherein the flow of said steam is controlled by flow of said excess vented gases.

13. The method of claim 10 wherein cooling water is supplied to said blowdown zone to condense condensable hydrocarbons therein.

14. The method of claim 13 wherein the flow of said cooling water is controlled by the temperature of the gases passed to said blowdown zone.

References Cited in the file of thispatent UNITED STATES PATENTS 312,777 Westinghouse Feb. 24, 1885 314,089 Westinghouse Mar.'17, 1885 1,160,689 Burton Nov. 16, 1915 1,236,953 Lewis Aug. 14, 1917 1,651,051 Wiggins Nov. 29, 1927 1,770,221 Sweeny July 8, 1930 1,770,725 Bartels July 15, 1930 1,859,670 Henderson May 24, 1932 2,274,006 Smith Feb. 24, 1942 2,290,065 Natho July 14, 1942 2,311,625 Bransky et al. Feb. 23, 1943 2,373,519 Tweit Apr. 10, 1945 2,438,619 Rattay Mar. 30, 1948 2,536,370 Hughes Jan. 2, 1951 2,690,814 Reid Oct. 5, 1954

Claims (1)

1. A REFINERY RELIEF SYSTEM FOR INFLAMMABLE GASES COMPRISING A BLOWDOWN DRUM, A VENT STACK EXTENDING FROM THE UPPER END PORTION OF SAID DRUM, AT LEAST ONE INLET CONDUIT COMMUNICATING WITH THE LOWER PORTION OF SAID DRUM, A WATER SEAL DISPOSED IN SAID DRUM BETWEEN SAID VENT STACK AND SAID FEED CONDUIT WHEREBY SAID VENT IS SEALED FROM SAID INLET CONDUIT, MEANS FOR CONDENSING CONDENSABLE HYDROCARBONS IN SAID DRUM, A LIQUID HYDROCARBON DRAWOFF CONDUIT EXTENDING FROM THE LOWER PORTION OF SAID DRUM, AND MEANS EXTENDING FROM SAID DRUM TO FLARE WHEREBY NONCONDENSED HYDROCARBONS ARE CONVEYED TO SAID FLARE.

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