US2856944A - Means for controlling the pressure in an insulated tank containing liquefied methane - Google Patents

Description

Oct. 21, 1958 w L. MORRISON 2,856,944

MEANS FOR CONTROLLING THE PRESSURE IN AN INSULATED METHANE Filed Oct. 28. 195:5

TANK CONTAINING LIQUEFlED 2 Sheets-Sheet 1 INVENTOR, WILLARD L. MORRISON ATTORINEYS,

PARKEP & CARTER Ot. 21, 1958 w. 1.. MORRISON 2,355,944

MEANS FOR CONTROLLING THE PRESSURE IN AN INSULATED TANK CONTAINING'LIQUEFIED METHANE Filed Oct. 28, 1953 2 Sheets-Sheet 2 INVENTOR, WILLARD L. MORRISON ATTORNEYS, PARKER & CARTER NIEANS FOR CONTROLLING THE PRESSURE IN AN INSULATED TANK CONTAINING LIQUE- .FIED METHANE .Willard L. Morrison, Lake Forest, 111., assignor, by mesne assignments, to Constock Liquid Methane Corporation, a corporation of Delaware Application October 28, 1953, Serial No. 388,887 10 Claims. (Cl. 1377) ;trol means for actuating a heater to increase when necessary the rate of vaporization or regasification of the liquid.

The amount of heat reaching the tank contents through the insulation from the outside, causing regeneration of gas from theliquid, is, everything else being equal, a function of the temperature diiference between the liquid and the circumambient atmosphere. It is exceedingly important to maintain within the tank a pressure at all :times slightly above atmospheric to avoid thepossibility of airentering the system, with resultant development of an-explosive mixture, over the liquid in the tank or elsewhere in the system.

It is also important to hold the pressure within the 'tankand the system enough above atmospheric to insure discharge of gas from the tank. Such pressure must, .however, in the interest of economy, be but little above atmospheric, perhaps in the order of A pound per square 'inch.

It is desirable that the insulation of the tank be such that the rate of regasification is approximately correct under circumstances of maximum ambient temperature. Therefore when the ambient temperature is below the maximum, means must be provided to automatically add additional heat to insure adequate regasification of the liquid to prevent reduction of pressure below atmospheric.

Av-pressure for example of approximately .25 pound persquare inch gauge above atmosphere is suitable. This 1 is highienoughito'prevententrance of air into the system and low enough to permit economical design and operation.

This invention is illustrated more or less diagrammatically in the accompanying drawings wherein:

Figure 1 shows diagrammatically and in section an electric control.

Figure 2 shows, diagrammatically and in part section a :mechanical control.

Referring to Figure 1, 1 is a metal tank illustrated as being containedswithin a barge of which a vertical bulkhead 2 and a deck plate 3 are shown. The tank is insulated at 4. 5 is a lining on the inner side of the insulation. 6 is a pressure pipe extending from the interior of the tank through the insulation 4, the tank wall 1 and the deck plate 3 to communicate with a tank pressure chamber 7 in the housing 8. The housing 8 is supported on the deck plate 3 by legs 9. A diaphragm 10, prefer- :ablyof thin flexible material such aspberyllium copper separates the chamber 7 from the atmospheric chamber Patented Oct. 21, 1958 'ice 11 in the upper portion of the housing 8. Ports 12 permit free access-of ambient air and pressure to chamber 11. A plunger 13 rests at its lower end on pad 14 on diaphragm 10 and extends through the adjustable threaded sleeve 15. A spring 16 between the sleeve and the pad 14 may be adjusted by rotation of the sleeve 15 to maintain the diaphragm It) in neutral position, against for example A pound per square inch gauge pressure in the chamber 7. Under these circumstances the spring 16 will be adjusted to apply approximately 16 /2 pounds presssure to the diaphragm.

The switchbox 17 is supported by legs 18 on the housing 8. The plunger 13 penetrating the box 17 supports a switch arm 19, shown in neutral position, the contacts 20, 21 on the arm 19 being out of contact with the contacts 22 and 23. Conductor 24 leads from the switch arm 19 through source of electric power illustrated as a battery 25. Conductor 26 leads from the battery to low pressure actuated heat control solenoid coil 27, conductor 28 leads to low pressure contact 23. A branch 29 leads from the conductor 26 to high pressure actuated engine control solenoidcoil 30, conductor 31 to high pressure contact 22.

-When the pressure in the chamber 7 falls below the adjusted pressure the spring 16 and atmospheric pressure will deflect the diaphragm 10 downwardly closing a circuit at 21, 23 and energizing low pressure solenoid 27. This draws switch arm 31a to contact terminal 32 and a circuit is closed through conductor 33, switch arm 31a, contact 32 and conductor 34 to supply additional heat beyond that of the ambient temperature to the boiler. Such additional heat may be provided by an electric heating coil 35 or by any other suitable means to supply enough heat to the tank to give additional gasification to raise the pressure up to and maintain it at the desired point.

On the other hand if the pressure in the chamber 7 exceeds the adjusted pressure the spring 16 and atmospheric pressure will be overcome to move the switch arm 19 t0 closea circuit between 20 and 22 energizing the high pressure solenoid 30. This causes the switch arm 36 to engage contact 37 closing a circuit through conductors 38 and 39 with any suitable electric control means adapted'to open any suitable pressure relief valve not here illustrated as the details form no part of the present invention.

Referring now to Figure 2, a gas discharge pipe 4% extends from the upper portion of the insulated tank 1 to a pressure relief valve 41 which when opened permits gas discharge through the nozzle 42 directly to the atmosphere.

A branch 43 leads from the pipe to any suitable point of use of the gas, for instance, to an engine not shown which may propel the barge. A branch 44 leads from the pipe 43 to a gas fuel supply blower 45 which supplies gas to a dual fuel, diesel blower engine, there being an oil reservoir 46 with oil pipe 47.to supply fuel oil as needed to the engine. 48 is a governor. 49 is a mechanical operating connection between the governor and theSylphonbellows 51 one side of the bellows being exposed to the atmosphere, the other side to the gas pressure inthe pipe 44 The engine 46through a shaft 51 drives a blower 52 which draws ventilating air from the interior of the barge about the tank through the pipe 53, and discharges it through a nozzle 54 into the air pipe 55 which surrounds the gas discharge nozzle 42.

The engine 46 is in continuous operation at such rate as to purge the interior of the barge to prevent such accumulation of gas in the barge about the tank or tanks as would result in the formation of a combustible mixture of air and gas. This air is discharged through the pipe 55 to the atmosphere. Under ordinary circumstances if the pressure in the tank is correct the bellows remains in neutral position. If the pressure in the tank rises above the desired point the bellows will expand and operate the governor to increase engine speed so that an added amount of air will be forced through the pipe 55 to dilute the gas which will be discharged through the nozzle 42 as a result of the unseating of the pressure relief valve 41.

If desired, a mechanical connection 56 connected to the mechanical connection 49 may actuate a damper 57 to assist in the control of the engine. In any case, however, when the governor has been actuated by the bellows 50 to cause the engine to develop more power and speed two things happen. More air is discharged by the fan to dilute the gas escaping through the pressure relief valve and more gas is taken from the tank to supply the engine to decrease the pressure of the gas in the system.

The pipe 55 discharges directly into the atmosphere Without interference. The intake end of the pipe takes the form of a funnel 58 into which the nozzle 54 may discharge the air stream. If the fan 52 is not running the stream of gas discharged from the nozzle 42 will nevertheless induce a current of diluent air, entering through the funnel 58 and discharging from the pipe 55, with the gas into the atmosphere.

The governor 48 controls engine operation by varying the amount of fuel burned in the engine. If an engine other than a diesel engine Were used, a throttle valve would be substituted for the governor and would be controlled by the belloWs 50. In any event increase in gas pressure must automatically result in increase in engine speed and the amount of air discharged by the fan to dilute the gas discharged past the pressure relief valve.

Referring again to Figure l, the electric connection may operate the governor just as effectively as the mechanical connection of Figure 2 and if a switch is associated with the bellows 50 it may equally well control the heat source when the pressure falls. The two drawings are of course diagrammatic and illustrate that automatic means are provided to add heat when necessary to increase gasification and prevent a vacuum in the tank and to discharge excess gas when necessary, to prevent excess pressure in the tank and to discharge such as freely to the atmosphere so diluted as to prevent formation of an explosive or combustible mixture.

In Figure l the chamber on one side of the diaphragm is connected to the interior of the tank by a separate unobstructed duct. The response to variation in pressure is exactly the same in the devices shown in Figures 1 and 2. The diaphragm is the equivalent of the bellows. The pipe 49 which carries gas from the tank is open and unobstructed between the tank and the bellows. The bellows is just as responsive to variation in the pressure difference between the tank and the atmosphere as is the diaphragm.

It makes no difference so far as response to pressure variation in the tank is concerned whether the pressure is applied to the diaphragm it) through the pipe 6 or to the bellows 50 through the pipe 40. In either case variation in tank pressure is reflected in the action of the controls to heat the tank if more gas is needed and to increase the diluting air supply if more air is needed.

If the blower engine is omitted, the gas passing through the pressure relief valve will be discharged directly into the air inducing a diluting air current.

The electric heating coil 35 is merely suggestive of any suitable means for furnishing the additional heat necessary to maintain an evaporation rate sufiicient to keep the pressure in the tank above atmospheric. Many other types of heating means may be used with suitable control means actuated by the low pressure actuated electric circuit.

The proposed control mechanism is equally applicable to a fixed storage tank or to one or more storage tanks on a barge, to a tank on a railroad car, or to a plurality of barges propelled in tow.

This invention is applied to a tow of barges and if the tow boat receives gas from the barges along the pipe 43, for example, it will frequently happen that an individual barge may be disconnected from the tow and in such case the barge must without relying on the tow boat as an element in the disposal of gas from the tank, take care of the gas evaporated from the liquid all by itself. Therefore there would be an engine supply and pressure relief valve associated with each barge and sometimes with each tank. If the barge were separated from the tow or if for any reason gas cannot be allowed to escape along the pipe 43 the damper 59 would be closed. Under these circumstances all the gas discharged through the pipe 40 would have to be disposed of either by being burned in the engine 46 or by being discharged through the pressure relief valve 41 and nozzle 42. Under these circumstances the engine 46 would work at maximum power discharging a maximum amount of air through the pipe 55 to dilute the relative large amount of gas discharged through the nozzle 42. Under these circumstances the engine would use maximum gas so the pressure would be held down both as a result of gas supplied to the engine and as a result of gas discharged with and diluted by the air in the pipe 55.

I claim:

1. In combination, an insulating tank adapted to contain a readily vaporizable liquid, a gas discharge nozzle connected to the tank, a relief valve interposed between them, an air duct into which the gas nozzle discharges, means for maintaining a continuous flow of air through said duct past the gas nozzle and means responsive to an increase in the pressure in the tank above a predetermined minimum for increasing the rate of flow of air through said duct.

2. In combination, an insulating tank adapted to contain a readily vaporizable liquid, a gas discharge nozzle connected to the tank, a relief valve interposed between them, an air duct into which the gas nozzle discharges, means for maintaining a continuous flow of air through said duct past the gas nozzle and means responsive to an increase in the pressure in the tank above a predetermined minimum for increasing the rate of flow of air through said duct, said means being adapted to cause such increased rate of flow before gas flow takes place through the pressure relief valve and for continuing such increased air flow until after gas flow has ceased.

3. In combination, an insulated tank adapted to contain readily vaporizable liquid, a pressure relief valve and gas discharge nozzle associated with the tank, a housing ported for air inlet and exhaust and enclosing the tank, a blower adapted to draw air from the housing, a duct through which the blower discharges, the gas nozzle being located in the duct for gas discharge in the same direction as the air discharge, a motor driving the blower, means for supplying heat to the tank, control means responsive to pressure variation in the tank for actuating the heating means as the pressure in the tank falls below a predetermined minium and for increasing the blower output as the pressure in the tank rises above a predetermined maximum.

4. In combination, an insulated tank adapted to contain a readily vaporizable liquid, an air duct, means for continuously passing a high velocity current of air therethrough, a pressure relief valve adapted to discharge gas from the tank into the air duct, control means responsive to pressure variation in the tank for increasing the air velocity as the pressure in the tank rises above a predetermined maximum.

5. In combination, an insulated tank adapted to contain a readily vaporizable liquid, an air duct, means for continuously passing a high velocity current of air therethrough, a pressure relief valve adapted to discharge gas from the tank into the air duct, control means responsive to pressure variation in the tank for increasing the air velocity as the pressure in the tank rises above a predetermined maximum, means for supplying heat to the tank and for increasing the heat supply as the pressure in the tank falls below a predetermined minimum.

6. In the storage of large quantities of a highly volatile, low boiling, combustible, liquefied gas at slightly above atmospheric pressure to permit the use of tank walls having strength sufficient to support the liquefied gas without resistance to high internal pressures and to prevent inflow of air into the tank for admixture with the combustible gases which collect at the top of the tank, a tank housing having an opening in the top in communication with the space in the tank above the liquefied gas, a heating element in heat exchange relation with the liquefied gas in the tank, a means responsive to drop in pressure within the tank below a desired minimum for transmitting heat to the liquefied gas through the heating element, a means responsive to the buildup of pressure with in the tank above a desired maximum for bleeding gas from the tank, means for exhausting the gas bled from the tank into the atmosphere, means for exhausting air at high velocity with the gas exhausted to the atmosphere, and means for admixture of the air with the gas prior to the gas being exhausted into the atmosphere.

7. Apparatus for the storage of large quantities of a liquefied gas as claimed in claim 6 in which the means responsive to the pressures existing within the tank for introducing heat when below the desired pressure level and for bleeding gas from the tank when above the desired pressure level comprises a passage in direct communication with the interior of the tank through the top opening, a diaphragm in communication with the passage, means urging the diaphragm towards a normal position in response to the pressure range desired within the tank, means responsive to displacement of the diaphragm in one direction in opposition to load for operating the bleeding means, and means responsive to displacement of the diaphragm in the opposite direction responsive to load for operating the heating means.

8. Apparatus as claimed in claim 6 which includes means in which the means for exhausting the air at high velocity includes a blower, power means for operating the blower, means responsive to the bleeding of gas from the tank for actuation of said power means to operate the blower, and means for directing some of the gas bled from the tank to the power means for use in the generation of power.

9. In the method for the safe storage of a highly volatile, low boiling, liquefied, combustible gas in large volurnes at low temperature, the steps of confining the liquefied gas in an insulated storage tank at a pressure slightly above atmospheric to prevent inflow of air from the surrounding atmosphere into the container for admixture with the gaseous vapors released from the liquefied gas and to avoid the necessity for use of tank walls of high strength to reduce gas pressures, introducing heat into the body of the liquefied gas in the tank for conversion of liquid to gas when the pressure within the tank falls below a predetermined minimum, bleeding gas from the tank when the pressure within the tank rises above a predetermined maximum, exhausting gas bled from the tank to the atmosphere, mixing air in substantial volumes with the gas prior to exhausting of the gas into the atmosphere, and blowing the air at high velocity for admixture with the gas to exhaust the gas and air together at high velocity into the atmoshpere.

10. The method as claimed in claim 9 which includes the step of burning some of the gas bled from the tank for the generation of power for operation of the means for blowing the air at high velocity for admixture with the gas.

References Cited in the file of this patent UNITED STATES PATENTS 1,567,097 Anthony Dec. 29, 1925 2,255,747 Jones Sept. 16, 1941 2,329,750 Faucher Sept. 21, 1943 2,377,342 Holicer June 5, 1945 2,507,380 Morrison May 9, 1950 2,543,653 Woog Feb. 27, 1951 2,618,935 Mal'ir Nov. 25, 1952

Claims (1)

1. IN COMBINATION, AN INSULATING TANK ADAPTED TO CONTAIN A READILY VAPORIZABLE LIQUID, A GAS DISCHARGE NOZZLE CONNECTED TO THE TANK, A RELIEF VALVE INTERPOSED BETWEEN THEM, AN AIR DUCT INTO WHICH THE GAS NOZZLE DISCHARGES, MEANS FOR MAINTAINING A CONTINUOUS FLOW OF AIR THROUGH SAID DUCT PAST THE GAS NOZZLE AND MEANS RESPONSIVE TO AN INCREASE IN THE PRESSURE IN THE TANK ABOVE A PREDETERMINED MINIMUM FOR INCREASING THE RATE OF FLOW OF AIR THROUGH SAID DUCT.

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