Liquid cryogenic storage tank system

• US 5,477,690 A
• Filed: 08/22/1994
• Issued: 12/26/1995
• Est. Priority Date: 03/30/1993
• Status: Expired due to Term

• Current Assignee: Process Systems International, Inc. (Chart Industries Incorporated)
• Original Assignee: Process Systems International, Inc. (Chart Industries Incorporated)
• Inventors: Gram, Anker
• Primary Examiner(s): KILNER, CHRISTOPHER B
• Application Number:
  US08/294,084
• Time in Patent Office: 491 Days
• Field of Search: 62/7, 62/47.1, 62/50.1, 62/50.7, 62/53.2, 62/50.6, 62/45.1
• US Class Current: 62/45.1
• CPC Class Codes: F04B 15/06 for liquids near their boiling point, e.g. under subnormal pressure
• CPC Class Codes: F04B 19/06 Pumps for delivery of both liquid and elastic fluids at the same time wet gas pumps F04B37/20
• CPC Class Codes: Y10S 417/901 Cryogenic pumps
• CPC Class Codes: Y10T 137/8622 Plural top-to-bottom connected tanks

Abstract

Cryogenic fluid piston pump functions as stationary dispensing pump, mobile vehicle fuel pump etc., and can pump vapour and liquid efficiently even at negative feed pressures, thus permitting pump location outside a liquid container. Piston inducts fluid by removing vapour from liquid in an inlet conduit faster than the liquid therein can vaporize by absorbing heat, and moves at essentially constant velocity throughout an induction stroke to generate an essentially steady state induction flow with negligible restriction of flow through an inlet port. Stroke displacement volume is at least two orders of magnitude greater than residual or dead volume remaining in cylinder during stroke changeover, and is greater than volume of inlet conduit. Cryogenic tank has a liquid compartment, a vapour compartment, and inlet and overflow conduits. Inlet conduit receives liquid from dispensing pump and widely disperses liquid into liquid tank to contact and condense vapour. Overflow conduit restricts flow of excess liquid from liquid compartment to vapour compartment. Excess pressure in tank or temperature of overflow liquid from conduit is detected to automatically stop dispensing pump. As a fuel pump, the pump selectively receives cryogenic liquid and vapour from respective conduits communicating with tank, and pumps cryogenic liquid to satisfy relatively heavy fuel demand of engine, which, when satisfied, also pumps vapour to reduce vapour pressure in the tank while sometimes satisfying relatively lighter fuel demand.

Claims

1. A cryogenic liquid storage tank system for the storage of a cryogenic fluid, which system comprises:

a) a cryogenic storage tank having;

i) a liquid compartment to store cryogenic liquid;

ii) a separate vapor compartment as ullage space for a cryogenic vapor; and

iii) a tank inlet conduit into the liquid compartment and having a discharge opening in the liquid compartment for the introduction of a cryogenic fluid into the liquid compartment;

b) an overflow conduit means having an inlet disposed in an upper portion of the liquid compartment and an outlet disposed within the vapor compartment to provide for the flow of excess cryogenic fluid from the liquid to the vapor compartment when the liquid compartment is full to the level of the inlet of the overflow conduit means, and wherein the overflow conduit means has a cross-sectional area less than the cross-sectional area of the tank inlet conduit to restrict flow of excess cryogenic liquid from the liquid compartment and to promote a sudden pressure rise and differential pressure increase when the liquid compartment is full;

c) a liquid transfer means to transfer a cryogenic fluid through the tank inlet conduit and into the liquid compartment;

d) control means to control the operation of the liquid transfer means; and

e) pressure sensor means to sense a sudden pressure rise above a predetermined level when the liquid compartment is full, the pressure means to monitor the pressure in the liquid compartment or the differential pressure between the liquid and vapor compartments, and the sensor means to provide a pressure sensing signal, the pressure sensing signal coupled to the control means and arranged to stop the liquid transfer means from filling the liquid compartment, thereby providing for the automatic monitoring of the filling of the liquid compartment of the storage tank to the level of the inlet of the overflow conduit means.

2. The system of claim 1 wherein the vapor compartment has a volume which is between about 10 and 15 percent of the volume of the liquid compartment to provide a defined ullage space.

3. The system of claim 1 wherein the liquid transfer means comprises a hydraulic or electric motor driven reciprocating piston pump which operates at a net negative suction head.

4. The system of claim 1 wherein the tank inlet conduit comprises a single integral inlet and outlet conduit into the liquid compartment.

5. The system of claim 1 wherein the discharge opening of the inlet conduit has an outlet portion which is disposed generally tangentially with respect to the cross-section of the liquid compartment to generate initially a generally circulating flow within the liquid compartment.

6. The system of claim 1, wherein:

a) the discharge opening of the tank inlet conduit comprises a plurality of spray openings in the upper portion of the liquid compartment to discharge a spray of cryogenic liquid into the liquid compartment; and

b) the tank inlet conduit has a drain opening adjacent a lower wall of the liquid compartment to drain cryogenic liquid from the liquid compartment through the discharge opening, the drain opening having an opening area less than the sum of opening areas of the spray openings and less than the cross-sectional area of the tank inlet conduit.

7. The system of claim 6, wherein:

a) the spray openings of the tank inlet conduit are located adjacent an upper portion of the liquid compartment of the storage tank; and

b) the tank inlet conduit has a U-shaped portion located in the liquid compartment, the liquid spray opening being located in the U-shaped portion.

8. The system of claim 1 wherein the inlet of the overflow conduit means includes a downwardly facing elbow portion which is positioned adjacent a side wall on the upper portion of the liquid compartment.

9. The system of claim 1 wherein the ratio of the cross-sectional areas of the overflow conduit means to the tank inlet conduit is between 1:

2 and 1;

4.

10. The system of claim 1 wherein the pressure sensor means provides a differential pressure sensing signal above 10 psi.

11. The system of claim 1 wherein the pressure sensing signal is produced at a predetermined upper pressure less than the designed upper pressure limit of the cryogenic storage tank.

12. The system of claim 1 wherein the pressure sensor means includes both a gauge pressure sensor means to measure the pressure of the cryogenic liquid in the liquid compartment and a differential pressure sensor means to measure the differential pressure between the vapor and liquid compartments, and wherein a pressure sensing signal from either pressure sensor means to the control means stops the liquid transfer means.

13. The system of claim 1 wherein the overflow conduit means is free of any valves.

14. The system of claim 1 wherein the overflow conduit means has the outlet in the lower portion of the vapor compartment.

15. The system of claim 1 wherein the cryogenic storage tank is a LNG storage tank with the liquid compartment to store LNG and the vapor compartment for LNG vapor.

16. A liquid natural gas (LNG) storage tank system for the storage of LNG, which system comprises:

a) an LNG storage tank having;

i) a liquid compartment to store LNG;

ii) a separate compartment as ullage space for vaporized natural gas (VNG);

iii) a single tank inlet/outlet conduit into the liquid compartment having a discharge opening in the upper portion of the liquid compartment;

b) an overflow conduit means having an inlet into the liquid compartment and an outlet disposed in the vapor compartment to provide for the flow of excess LNG during filling of the liquid compartment into the vapor compartment;

c) the cross-sectional area of the overflow conduit means is less than the cross-sectional area of the tank inlet/outlet conduit to permit a sudden pressure increase when the liquid compartment is full to the level of the inlet of the overflow conduit means;

d) LNG liquid transfer means to transfer LNG through the tank inlet/outlet conduit into the liquid compartment;

e) control means to control the operation of the liquid transfer means;

f) pressure sensor means which comprises a gauge pressure sensor means to sense the pressure in the liquid compartment and to provide a first pressure sensing signal when the LNG reaches the level of the inlet of the overflow conduit means, or a differential pressure sensor means to sense the differential pressure between the liquid compartment and the ullage space and to provide a second pressure differential sensing signal if there is a differential pressure rise of above about 10 psi, either first or second pressure sensing signals or both connected to the control means so arranged to stop the liquid transfer means in filling LNG into the liquid compartment.

17. In combination, an LNG operated vehicle with an LNG engine and which vehicle contains the system of claim 16 and wherein the LNG storage tank includes a vapor collecting conduit between the vapor compartment and the LNG engine.