Receptacles – High-pressure-gas tank – Multilayer container
Reexamination Certificate
2000-02-01
2002-10-08
Pollard, Steven (Department: 3727)
Receptacles
High-pressure-gas tank
Multilayer container
C220S590000
Reexamination Certificate
active
06460721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved systems and methods for producing and storing pressurized liquefied natural gas (PLNG) and, more particularly, to such systems and methods that synergistically combine the advantages of a natural gas processing plant for producing PLNG, with the advantages of novel containers for storing and transporting PLNG. More specifically, the present invention relates to such improved systems and methods that use a container comprising a load-bearing vessel made from a composite material and a substantially impermeable, non-load-bearing liner in contact with the vessel.
BACKGROUND OF THE INVENTION
Various terms are defined in the following specification. For convenience, a Glossary of terms is provided herein, immediately preceding the claims.
U.S. patent application Ser. No. 09/099,268 (the “PLNG Patent Application”), having International Patent Application Number PCT/US98/12726 and International Publication Number WO 98/59085, and entitled “Improved System for Processing, Storing, and Transporting Liquefied Natural Gas”, describes containers and transportation vessels for storage and marine transportation of pressurized liquefied natural gas (PLNG) at a pressure in the broad range of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and at a temperature in the broad range of about −123° C. (−190° F.) to about −62° C. (−80° F.). Containers described in the PLNG Patent Application are constructed from ultra-high strength, low alloy steels containing less than 9 wt % nickel and having tensile strengths greater than 830 MPa (120 ksi) and DBTTs (a measure of toughness, as defined in the Glossary) lower than about −73° C. (−100° F.). As discussed in the PLNG Patent Application, at the preferred operating pressures and temperatures of the invention described therein, about 3½ wt % nickel steel can be used in the coldest operating areas of a PLNG plant for the process piping and facilities, whereas more expensive 9 wt % nickel steel or aluminum is generally required for the same equipment in a conventional LNG plant (i.e., a plant for producing LNG at atmospheric pressure and about −162° C. (−260° F.)). Preferably, high strength, low alloy steels with adequate strength and fracture toughness at the operating conditions of the PLNG plant, are used to construct the piping and associated components (e.g., flanges, valves, and fittings), pressure vessels, and other equipment of the PLNG plant in order to provide economic advantage over a conventional LNG plant. U.S. patent application Ser. No. 09/099,569 (the “Process Component Patent Application”), having International Patent Application Number PCT/US98/12725 and International Publication Number WO 99/32837, and entitled “Process Components, Containers, and Pipes Suitable For Containing and Transporting Cryogenic Temperature Fluids”, describes process components, containers, and pipes suitable for containing and transporting cryogenic temperature fluids. More particularly, the Process Component Patent Application describes process components, containers, and pipes that are constructed from ultra-high strength, low alloy steels containing less than 9 wt % nickel and having tensile strengths greater than 830 MPa (120 ksi) and DBTTs lower than about −73° C. (−100° F.). The PLNG Patent Application and the Process Component Patent Application are hereby incorporated herein by reference.
The PLNG Patent Application and the Process Component Patent Application utilize ultra-high strength, low alloy steels as the connecting theme between the PLNG plant and the containers used for storing and transporting the PLNG. If use of the steels for constructing the containers did not provide a commercially viable means for storing and transporting the PLNG on marine vessels, then any use of the steels in the plant would be meaningless since there would be no mechanism for commercially transporting the PLNG produced by the plant. Conversely, while use of the steels in the PLNG plant generates some economic savings over conventional LNG operations, the most substantial economic benefit is derived from the enormous simplification (and consequent cost reductions) in the plant. Because of its relatively simple design, the PLNG plant is substantially cheaper than a conventional LNG plant of similar capacity. Additionally, while use of the steels in the PLNG transportation system is commercially viable and does generate some economic savings over conventional LNG operations, the weight of the steel containers is high compared to that of its PLNG cargo, resulting in a relatively low cargo-carrying capacity performance factor (PF). The PF for compressed fluid storage containers relates the pressure exerted by the cargo (P) to the volume (V) of the container and the weight (W) of the container by the equation PF=PV/W. What is currently missing from the all-steel PLNG system (i.e., plant plus transportation) is a combination of the PLNG plant with a low cost, higher PF, container-based transportation system that is capable of handling PLNG.
U.S. Pat. No. 3,830,180 (“Bolton”) discusses use of a double-walled, composite cylindrical vessel configuration for transport of regular LNG, i.e., LNG at atmospheric pressure and at temperatures of about −162° C. (−260° F.). The cylindrical vessel configuration is preferred because it maximizes use of the space available in a transportation vessel. However, the load-bearing, inner wall of Bolton's vessel is designed for a maximum pressure of approximately 50 to 60 pounds (psi) and, thus, Bolton's vessel is not suitable for transport and storage of PLNG. Additionally, although Bolton's cylindrical vessel configuration may appear, theoretically, to improve the cargo-carrying capacity performance factor (PF) for transport of a given fluid over that of the steel containers described in the PLNG Patent Application, Bolton's design has several economic and technical limitations on size, fabrication methodology, and reliability. The use of a weldable homogeneous material for partial load bearing reduces the potential weight savings associated with a composite vessel design. Moreover the double-walled concept unduly increases the effective wall thickness, complicates the overall fabrication methodology, decreases the technical and economic feasibility of the design, and results in poor utilization of the space available on a ship for transporting cargo. Further, the design by Bolton requires the use of a homogeneous material that can be welded to form the load-bearing, inner vessel wall, which consists of two domes welded to a cylindrical mid-section. The stress concentration associated with the two welds warrants protection of the welds by using a complicated pre-stressed stay-tube arrangement. Finally, the welds in Bolton's vessels are potential sources of pitting and, consequently, of premature failure.
Both U.S. Pat. No. 5,577,630 (Blair et al.) and U.S. Pat. No. 5,798,156 (Mitlitsky et al.) describe lined, composite pressure vessels for storing and transporting compressed natural gas. Blair et al. discusses pressure vessels manufactured by overwrapping a liner with a composite layer using filament winding, tube rolling, tape wrapping, automated fiber placement, or another method familiar to those of skill in the art, to obtain a vessel configuration which approximates a rectangular volume for use in compressed natural gas (“CNG”) vehicles. U.S. Pat. No. 5,499,739 (Greist, III et al.) discusses a thermoplastic liner made of a modified nylon 6 or nylon 11 material for use in a pressure vessel to control gas permeation and allow operation at low temperatures, the low end of which is stated to be −40° F. The vessels of Greist, III et al. are made by a method of overwrapping filaments in a predetermined pattern around the thermoplastic liner for improved mechanical properties and processing. U.S. Pat. No. 5,658,013 (Bees et al.) discusses a fuel tank for vehi
Bowen Ronald R.
Minta Moses
ExxonMobil Upstream Research Company
Hoefling Marcy
Pollard Steven
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