US2277407A - Closed vapor system for tanks containing volatile liquids - Google Patents

Description

March 24,1942. QL, MARNER 2,277,407

CLOSED VAPOR SYSTEM FOR TANKS CONTAIING YOLATILE LIQUIDS INVENTOR.,

ATTORN 2 Sheets-Sheet 2 C. L. MARNER CLOSED VAPOR SYSTEM FOR TANKS CONTAINING VOLATILE I IQUIDS Filed Feb. 16, 1959 March 24, 1942.

Patented Mar. 24, 1942 CLOSED VAPOR SYSTEM FOR TANKS CONTAIN IN G VOLATILE LIQUIDS Charles L. Marner, East Chicago, Ind., assgnor to Graver Tank & Mf

g. Co., Inc.,` Catasauqua,

Pa., a corporation of DelawareA Application February 16, 1939, Serial No. 256,828 4 claims. (ci. 22o- 35) i The invention relates to a method and apparatus for handling volatile liquids such as gasoline in a substantially closed system to thereby eliminate all breathing and filling losses.

Gasoline and other volatile liquids will evaporate during each of the several steps in the handling of the same from the processing plant to the delivery of the refined product to transporting means and said evaporation may be classified as that due to the lling and emptyingof the storage and other tanks and that known as breathing In the past the above have been the cause of severe losses and many attempts have been made to materially reduce or entirely eliminate one or all of said losses but without much success. y

What is known as breathing in large gasoline storage tanks is caused by changes in temperature which result in an increase in the vapor pressure during the heat of the day so that some iapors are expelled to the atmosphere, whereas, during the night when the vapors condense, air is drawn in to relieve the vacuum. Storage tanks have therefore been provided with a breather roof which, however, does-not eliminate any of the i'llling losses and also this type of roof does not have suicient breathing space to take care of different tank capacities. Filling losses are encountered in the filling of bulk storage tanks and also in the loading of tank cars, trucks and barges. For the storage tanks it is possible to use a floating roof which is moderately successful in eliminating filling losses, although some .evaporation will take place as the seal is .often imperfect. However, for roofs of this type the original cost as well as maintenance cost is very high.

The present invention contemplates a substantially closed system for the storing, emptying vand filling of one or more tanks as a group of tanks at a refinery or bulk storage plant in order to eliminate all evaporation losses and also to prevent air from coming in contact with the tank contents. By handling gasoline or other volatile liquids in a closed system a number of desirable advantages result in addition to the elimination of the losses above mentioned. For example, the octane number and color of the gasoline will be maintained since air is prevented from coming in contact .with the gasoline and the rapid formation of gum in the liquid does not take place. `Also the re hazard is substantially eliminated since the vapors are thoroughly saturated at all times, which makes ignition and explosion practically impossible.

With these and various other objects in view, the invention may consistof certain novel features of construction and operation, as will be more fully described and particularly pointed out in the specification, drawings and .-claims appended hereto.

In the drawings which illustrate an embodiment of the invention, and wherein like reference characters are used to designate like parts- Figure 1 is a diagrammatic view illustrating the application of a substantially closed system to a complete rening plant; l

Figure 2 is a diagrammatic plan view showing in detail the application of a substantially closed system to storage tanks in combination wit transporting means su'ch as tank cars;

Figure 3 is l a fragmentary elevational view showing the method of filling a tank car and simultaneously withdrawing the vapors therefrom for delivery to the gas reservoir;

Figure 4 is. an elevational view showing in greater detail the improvements of the invention for conserving the vapors from a group of storage tanks; and

t a substantially closed system.

Referring'to the drawings, particularly,Figure 1, the crude oil supply tank I0 having inlet I I, is shown as connected to the processing plant I2 which processes said crude oil into gasoline and other volatile liquids. From the processing plant the rened product is successively pumped into a run-down tank I3, an intermediate storage tank I4, a nal storage tank I5, a shipping tank I6 and finally the transporting means I'I in the form of a tank car, truck or barge. The present invention contemplates the gas reservoir I8 which will be large enough to take care of the full breathing of the several tanks. The vapor lines 20 connect the crude oil tank I0 and the other tanks handling thevrened product, namely, I3, I4, I5 and I6, with the gas reservoir I8 so that the vapors which may result from emptying or lling said tanks or by breathing will be taken care of.

Figure 2 shows the application of the present system to a group of storage tanks having combined therewith transporting means for the refined product such as tank cars and barges.

means for the refined product, such as the tank cars 24 and barges 25. As shown ln said figures. several of the tanks will be in the process of filling, which will generate a vapor pressure within the tankiso that said vapors will be drawn oi by the vapor line connecting therewith. Other tanks will be in the process of emptying and as this operation reduces the pressure within, vapors from the line 23 will now in to relieve the vacuum. In ordinary operation the filling and emptying of the tanks approximately balances each other, that is, the vapors generated by the filling process will be taken up by the emptying process. The evaporation in the remaining tanks storing the gasoline will be due to breathing and during the heat of the day vapors will ow out of said tanks into the vapor line, which will be reversed during the night. The gas reservoir 22 will take care of any difference which may exist between the pressure ofthose tanks in the process of filling and emptying and the breathing pressure of the storage tanks. The collecting of the vapors expelled from the tank cars 24 and barges 25 during the filling operation will be understood by reference to Figure 3, in which the vapors are drawn oif by individual vapor lines 26 which connect with the vapor line 23 leading to the gas reservoir.

From the foregoing it will be observed that the present system conserves the volatile vapors expelled during the storing, lling and emptying of one`or more tanks by collecting the vapors when they are given oif from said liquid and by conducting the same to those tanks which are under -a negative pressure as a result of the emptying operation or what may be due to breathing. The

difference determines the vapor pressure in thesystem and this is handled by thegas reservoir. Air is prevented from coming in contact with the gasoline and this prevents the rapid formation of gum. The presence of gum in gasoline tends to make the gasoline go off color as well as lower its octaneV number. Also the elimination of air from the system eliminates the fire hazard as the gas vapors are so thoroughly saturated at all times as to make ignition'and explosion practically impossible. Valves may be placed in the vapor lines so that any one tank may be cut oi from the system in case of re or for tank repair or when some non-volatile liquid such as fuel oil is stored in any of the tanks.

Several of the importantstructural details for a closed system are shown in Figure 4, wherein a group of the tanks 2l, supported by means 3|, are connected to the breather reservoir 22 which is shown as of the gas holder type. 'I'he vapor line 33 conducts the vapors to and from the breather reservoir. The holder bell 36, which is sealed'with respect to tank 31 by a sealing liquid, is guided in its vertical movement by the means 38 which support the balancing weights 39 having connection with said holder bell. In order to compensate for the graduallyr diminishing buoyant effect of the liquid as the holder moves upwardly said holder supports a tank 40 having connection by the flexible conduit 4I with the compensating tank 42 supported on the guiding means. As a result of this compensating means the breather reservoir travels upwardly at a subfor the decrease in the buoyant effect above de-l scribed.

The system of valves shown in detail in Figure 5 eliminates all possibility of air ,being drawn into the system. The vapor line 23 has connection with the recovery system of the processing plant so as to` take care of both pressure and vacuum conditions within the vapor line. The expansion chamber 50 for pressure relief is suitably supported by means 5| on said vapor line 23 and at said end a conduit 52 connects with the vapor line and extends within the expansion chamber, being provided with the pressure relief valve 53. Access to said valve may be had through an opening in the expansion chamber 50 normally closed by the manhole cover 54. Said chamber has connection with the suction line from the recovery system through the conduit 55, having a regulator 55 for maintaining uniform suction on the valve 53. For operation said valve 53 is set to equal the maximum pressure in the vapor line 48 plus the vacuum on the suction line 55.

Also the vapor line 23 has connection with a conduit 51 which in turn connects with an expansion chamber 58 for vacuum relief and which is suitably supported on said header by the standards 59. The conduit 60, leading from the lower end of said expansion chamber connects with the dry gas line from the recovery system and is provided with a regulator 6| set to maintain a uniform pressure on the valve 62 which closes the end of saidconduit located within the expansion chamber. Said valve 62 is set to equal the pressure on the dry gas line plus the vacuum on the header or vapor line.

A number of methods have been used at reiineries in attempting to save the rich vapors expelled from the gasoline run-down and storage tanks as a result of breathing or filling. The method most commonly used is to have the vapor lines from the storage tanks hooked up with the recovery system of the processing plant. This, however, has not been entirely satisfactory since although the vapors expelled during the day go through the system, at night the remaining vapors contract and pull air into the tanks. The amount of air in the system becomes so great that the eflciency of the recovery plant is reduced to the point where no more gasoline is actually recovered when the system is tied in with the storage tanks than when merely connected to the skimming and cracking plants. In accordance with the invention the gas or breather reservoir is large enough to take care of full breathing of the several tanks and any gas in excess of the balanced iilling and emptying condition will be handled by the recovery system. This eliminates all breathing, evaporation and iilling losses without overloading or cutting down the ediciency of said recovery system.

When the pressure in the vapor line 23 exceeds the limit of valve 53 vapors will be discharged into the expansion chamber 50 and said vapors will eventually be withdrawn therefrom through conduit 55 and delivered to the recovery vclosed vapor system is shut off from said gas line by the valve 62.

The invention is not to bevumited to or by details of construction of the particular embodiparting from the spirit of the invention or the e scope of the claims.

What is claimed is:

l. In apparatus for conserving volatile liquids such as gasoline and the like during the handling of the same from the processing plant to the transporting of the finished product, in combination, a plurality of tanks for said liquid, a breather reservoir, a vapor line connecting the vapor space of certain of said tanks with said breather reservoir, a pressure relief valve on said vapor line operative to discharge vapors when a predetermined maximum pressure exists in said line, a conduit in association with said relief valve for conducting the expelled vapors to the recovery system of the processing plant, a regulator in association with saidconduit for maintaining a uniform sub-atmospheric pressure on said relief valve, a second conduitconnecting the recovery system with said vapor line and operative to de' liver a gas thereto, a normally clos/ed valve at the terminal end of said second conduit constructed and arranged to open when a predetermined vacuum exists in the vapor line, and a regulator in association with said second conduit for maintaining a uniform ygas pressure on said normally closed valve.

2. In apparatus for conserving volatile liquids such as gasoline and the like, the combination with a processing plant incorporating a recovery system, a plurality of tanks for said liquid, a breather reservoir, a vapor line connecting the vapor spaoeof certain of said tanks with said breather reservoir, a pressure relief valve on said vapor line, an expansion chamber enclosing the discharge end of said pressure relief valve, a conduit connecting said expansionl chamber with the recovery system of the processing plant whereby the vapors discharged by said relief valve are withdrawn and conducted to the recovery system,

and a regulator in association with said conduitA for maintaining a' uniform sub-atmospheric pressure within the expansion chamber.

3. In apparatus for conserving volatile liquids such as gasoline and the like, the combination with a processing plant incorporating a recovery system, a plurality of tanks for said liquid, a breather reservoir, a vapor line connecting the vapor space ofcertain of said tanks with said breather reservoir, a pressure relief valve onl said vapor line, an expansion chamber enclosing the discharge end of said pressure relief valve, a conduit connecting said expansion chamber with the recovery, system of the processing plant whereby the vapors discharged by said relief valve are withdrawn and conducted to the recovery system, a regulator in association with said conduit for maintaining a uniform sub-ate mospheric pressure within the expansion chamber, a second conduit connecting the recovery system with said vapor line and operative to deliver a gas thereto, and a normally closed valve at the terminal end of said second conduit constructed and arranged to open when a predetermined vacuum exists in the vapor line.

4. In apparatus for conserving volatile liquids such as gasoline and the like, the combination with a processing plant incorporating a recovery system, a plurality of tanks for said liquid, a

breather reservoir, a vapor line connecting the vapor space of certain of said tanks with said breather reservoir, a pressure relief valvevon said vapor line, an expansion chamber enclosing the discharge end of said. pressure relief valve, a conduit connecting said expansion chamber with the recovery system of the processing plant whereby the vapors discharged by said relief valve are withdrawn and conducted to the recovery system, a regulator in` association with said conduit for maintaining a uniform sub-atmospheric pressure within the expansion chamber, a second conduit connecting the recovery system with said vapor line and operative to deliver a gas thereto, a normally closedV valve at the terminalv end of said second conduit constructed and arranged to open whenA a predetermined vacuum exists in the vapor line, and a regulator in association with said second conduit for maintaining a uniform gas pressure on said normally closed valve.

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