Description
Title of Invention: FACILITIES FOR OFFSHORE LIQUEFIED
NATURAL GAS FLOATING STORAGE WITH JETTY REGASIFICATION
UNIT
Technical Field
[1] The present invention relates to facilities for offshore liquefied natural gas (LNG)
floating storage with jetty regasification unit, and more particularly, to offshore fa
cilities that have floating storage and regasification unit installed on jetty unit.
Compared to conventional regasification facility which is installed on LNG carriers or
onshore LNG terminal, this concept have been found to reduce installation, operating
costs and construction time, and moreover increases stability of regasification per
formance of LNG.
Background Art
[2] The regasification facilities are used for regasification of LNG, i.e., to turn LNG back
into natural gas. There facilities can be identified into two different types, onshore and
offshore. In onshore facilities, LNG storage and regasification units are installed
onshore, whereas offshore facilities include a floating LNG storage unit, usually an
LNG carrier or a gravity based structure (GBS), and a regasification unit installed on
the floating structure, a shuttle regasification vessel (SRV) or a LNG regasification
vessel (RV).
[3] The SRV or the LNG RV is special purposed vessels that can navigate with regasi
fication facilities. The procedure starts by loading LNG from where it is produced and
transports to an unloading location where then it is moored by submerged turret
loading (STL) in offshore. These vessels have been widely used in the US, etc. for
supplying natural gas and have been constructed by several Korean shipbuilding
companies.
[4] In light of growing of LNG demand, many attempts have been considered to
construct new FSRU, but only several second-handed LNG carriers had been
converted to FRSU due to economical reason and time constrains to deliver in Latin
America and Asia, etc.
[5] Construction of onshore facilities, however, faces more severe constrains. A large
site has to be secured near facilities where LNG carriers are moored, and large scale
construction incurs high cost, complex civil appeals of neighboring residents, and im
mobility of the facility once the construction is over. Thus, in many cases, offshore f a
cilities are considered as a better solution for the fast tract of supplying natural gas.
[6] Nevertheless, when newbuilding or conversion of FSRU is considered, the construction
period expands to several years along with high capital costs. Also, when a
second-handed LNG carrier conversion is considered, one has to account for the age of
the vessel and cargo containment type, since it determines the conversion cost and
period. With respect to the cargo containment type, LNG carriers with membrane
cargo containment system have to go through a partial reinforcement on its membrane
structure to support the regasification facilities on the upper deck; storage of LNG and
operation of regasification facilities are restricted due to the risk of sloshing damage
from frequent partial loading of LNG.
[7] Meanwhile, FSRU or SRV is moored to a jetty structure to withstand offshore
weather and conditions. LNG is supplied to FSRU from LNC carrier (LNGC) through
a loading arm installed on a jetty where both FSRU and LNGC are moored side by
side. Once regasified by FSRU or SRV, high pressured natural gas (usually between 40
and 90 atm) is supplied to onshore through high pressure gas arm. During this process,
because floating facilities like FSRU or LNG RV are influenced by tidal currents and
wind, directional and rotational motions are accompanied. Thus, the loading arm and
the high pressure gas arm have a large number of components which can absorb impact
from the motions. If the FSRU or the LNG carrier is disconnected from the jetty
beyond an operational range, the pipe line will automatically disconnect from the jetty
for the safety. Although general LNG carriers are designed to operate under several
pressures while loading and unloading of LNG, FSRU and LNG RV are constantly
exposed to high pressure natural gas leak which can cause a fire or an explosion.
Disclosure of Invention
Technical Problem
[8] The present invention, facilities for offshore LNG floating storage with jetty regasi
fication unit, is designed for reduction of a construction time and cost, and enhances
the stability for operation when compared to a newly constructed or converted FSRU
and LNG RV.
Solution to Problem
[9] According to an aspect of the present invention, there is provided a facilities for
offshore liquefied natural gas (LNG) floating storage with jetty regasification unit, the
facilities comprising: a jetty unit of a steel structure or an iron concrete structure
installed in offshore; a storage unit moored at the jetty unit providing a space for
storing LNG; a regasification unit as a module which regasifies the LNG supplied from
the storage unit, installed on a top portion of the jetty unit and is separable from the
jetty unit; a utility unit comprising a power source and a sea water pump to supply
power and sea water to the regasification unit; and a piping unit comprising unloading
pipe for connecting the regasification unit and the storage unit and supplying pipe for
carrying natural gas gasified by the regasification unit.
The utility unit may be implemented as a module to be separable from the jetty unit.
The regasification unit may be used an open rack vaporizer (ORV) using sea water
for heat exchanger.
The sea water pump of the utility unit and a ballast water pump disposed in the
storage unit may be simultaneously used to supply sea water to the regasification unit.
A power facility, a steam generator, and a ballast water pump disposed in the storage
unit may be used to supply power, steam, and sea water, respectively, which are
necessary for the regasification unit.
The storage unit may be fixed to the jetty unit, loads LNG from a movable LNG
carrier or a floating storage unit (FSU), and carries the LNG to the regasification unit.
The storage unit may be separable from the jetty unit and movable to load LNG.
The storage unit may be the LNG carrier or an FSU.
Advantageous Effects of Invention
The present invention of offshore LNG floating storage with jetty regasification unit
can provide a solution that can dramatically reduce the possibilities of high pressured
natural gas leak into the atmosphere when compared to regasification on a floating
structure.
Brief Description of Drawings
FIG. 1 is a schematic diagram of a liquefied natural gas (LNG) regasification unit
according to an embodiment of the present invention.
Best Mode for Carrying out the Invention
Hereinafter, the detailed mode for carrying out the present invention will be
described with reference to exemplary embodiments of the invention.
FIG. 1 is a schematic diagram of a liquefied natural gas (LNG) regasification unit
according to an embodiment of the present invention.
The LNG regasification unit, according to the present invention, is used to regasify
LNG in offshore and supply the regasified LNG, to gas users onshore. And this
invention includes the jetty unit 10, a storage unit 20, a regasification unit 30, a piping
unit 40, and a utility unit 50.
The jetty unit 10 is a fixed structure installed in sea bed with its legs, made of steel or
iron concrete. The term 'jetty' has various meanings, for example, a structure like a
breakwater which distinguishes an inland and the sea, or a facility which is for
anchoring vessels. To anchor large ships, such as container vessel, oil tankers, or LNG
carriers, a site with certain depth of water, higher than a predetermined depth, is
required.
And the jetty can be used for berthing in the way of stretching steeled structure from
onshore to offshore or constructing a container terminal after dredging. In the present
invention, the jetty unit 10 is a semi-permanent structure that is installed to maintain a
constant altitude above the sea level to withstand the changes of the wave by tidal
current. As the shape of jetty unit 10 is not limited, it can be changed according to the
locations and conditions thereof as long as the storage unit 20 can be anchored at. A
structure for anchoring the storage unit 20, such as a mooring dolphin or a fender, may
be installed around the jetty unit 10, and is not shown in FIG. 1 for illustrative con
venience (all the constituents are quite simply illustrated in FIG. 1).
[24] The storage unit 20 provides a space for storing LNG once moored at the jetty unit
10. The storage unit 20 can be converted from a second-handed LNG carrier or an
existing LNG floating storage unit (FSU). Meanwhile, the storage unit 20 may be
fixedly moored at the jetty unit 10 and separated from the jetty unit 10 on occasional
demands. Conventional operation involves supplying the LNG to the regasification
unit 30 after receiving LNG from another LNG carrier. On an occasional demand, the
storage unit 20 may move to a location where LNG is produced or another FSU by
itself, then receives LNG therefrom and supply the LNG to the regasification unit 30
again after being moored at the jetty unit 10. In the latter case, for continuously regasi
fication of LNG, another LNG carrier may supply LNG to the regasification unit 30, at
the opposite side of the jetty unit 10.
[25] Fixed or movable type of the storage unit 20 is determined according to cir
cumstances or economical efficiency. For example, when a converted LNG carrier is
used for the storage unit 20, storage type can be decided depending on the situation, as
its mobility is already obtained.
[26] Meanwhile, when a second-handed LNG vessel is used for the storage unit 20, the
conversion process may require the vessel to operation both LNG loading pipe 2 1 and
LNG unloading pipe 42 simultaneously, as general LNG carrier is designed not to
proceed loading and unloading at the same time. Furthermore, if the storage unit 20 is
expected to move, an appropriate facility for separating the unloading pipe 42 from the
storage unit 20 is required as well.
[27] The storage unit 20 includes a utility facility 22, such as a power facility, a steam
generator, a ballast water pump P2, etc. which general LNG carriers and FSU are
already equipped, thus no additional facility is needed when the second-handed LNG
carrier or the FSU is converted.
[28] The regasification unit 30 is a module for regasifying LNG which is supplied from
the storage unit 20. The regasification unit 30 is also separable from the jetty unit 10.
Installment of the regasification unit 30 on the jetty unit 10, which is fixed on the sea
bed, allows LNG to be regasified in offshore without the problems which commonly
occurs in operation of conventional FSRU of LNG RV, a danger of leakage of natural
gas due to an automatic piping separation in the operation or abrupt disconnection of a
high pressure gas arm on the jetty unit 10 under the various offshore conditions. Since
regasification work is performed on the hull 11 of the jetty unit 10, LNG can be
transferred through the pipe between the storage unit 20 and the regasification unit 30.
The stability of the hull 11 allows more safe transfer of LNG, regardless of the storage
unit 20 movement due to the waves and tidal current.
[29] A heat exchanger of the regasification unit 30 in the present invention is an open rack
vaporizer (ORV) that utilizes sea water as a heat source. By contacting the heat
exchanger, sea water absorbs the heat and vaporizes LNG into gas. ORV is strongly
recommended due to its low investment and operating cost. However, if sea water is
not uniformly coated on the vaporizer, the heat exchanger freezes and deteriorates its
structure. That is why the ORV cannot be installed on FSRU of LNG RV. For the
present invention, fixed structure of the jetty unit 10 guarantees safe operation of the
ORV, which is a relatively inexpensive heat exchange system.
[30] A sea water pump PI in the utility unit 50 and the ballast water pump P2 of the utility
facility 22 in the storage unit 20 are used to supply sea water to the ORV. Although the
sea water pump PI and the ballast water pump P2 are designed to operate simultaneous
as depicted in FIG1, it is not necessary to use both of them. The sea water pump PI
acts as a main pump and the ballast water pump P2 as an auxiliary pump. Or, only the
sea water pump PI may be operated if the storage unit 20 is disconnected. How to
supply the sea water to the ORV are subject to circumstances.
[31] The piping unit 40, connecting the regasification unit 30 and the storage unit 20,
includes unloading pipe 4 1 for supplying LNG from the storage unit 20 to the regasi
fication unit 30 and supply pipe 42 for supplying gasified LNG from the regasification
unit 30 to the end users in onshore. If required part of the piping unit 40 may be
installed below a sea level.
[32] The utility unit 50 (module) includes a power source, the sea water pump PI, and the
steam generator for supplying power, sea water, and steam, respectively, to the regasi
fication unit 30. Similar with the regasification unit 30, it is installed on the jetty unit
10, but also separable. The utility unit 50 and the regasification unit 30 are connected
by a power cable 51, sea water pipe 52, and steam pipe 53. They are respectively
connected to the utility facilities in the storage unit 20 to be used simultaneously or
complementarily in the present invention. Unlike shown in FIG.l, only the utility unit
50 may operate independently.
[33] The piping unit 40, the power cable 51, the sea water pipe 52, and the steam pipe 53
are quite simply illustrated in FIG. 1 for illustrative convenience, but the actual design
is considerably complicated. Nevertheless, for the purpose of illustration, such simple
diagram will be understood by those who have knowledge of this technology.
[34] Now, functions and effects of regasification element will be described below with ex
planation of LNG regasification process.
[35] LNG stored in the storage unit 20 is supplied to the regasification unit 30 through the
unloading pipe 41. Once regasified through the unit 30, regasified LNG is carried to
the end users' pipe line onshore through the supplying pipe 42.
[36] The storage unit 20 can be fixed to the jetty unit 10 to load LNG from an LNG
carrier (supplied through the loading pipe 21) or can be moved by itself to receive
LNG from a neighboring FSU or a location where LNG is produced. If the storage unit
20 moves to different site, designated replacement should substitute for the previous
storage unit 20, in order to supply LNG continuously.
[37] Power, sea water, and steam are supplied to the regasification unit 30 through the
utility unit 50.
[38] While the present invention has been particularly shown and described with reference
to exemplary embodiments thereof, it will be understood that various changes in form
and details may be possible in the technical range of this invention as defined by the
following claims.
[39]
Claims
[Claim 1] Facilities for offshore liquefied natural gas (LNG) floating storage with
jetty regasification unit, the facilities comprising:
a jetty unit of a steel structure or an iron concrete structure installed in
offshore;
a storage unit moored at the jetty unit providing a space for storing
LNG;
a regasification unit as a module which regasifies the LNG supplied
from the storage unit, installed on a top portion of the jetty unit and is
separable from the jetty unit;
a utility unit comprising a power source and a sea water pump to supply
power and sea water to the regasification unit; and
a piping unit comprising unloading pipe for connecting the regasi
fication unit and the storage unit and supplying pipe for carrying
natural gas gasified by the regasification unit.
[Claim 2] The facilities of claim 1, wherein the utility unit is implemented as a
module to be separable from the jetty unit.
[Claim 3] The facilities of claim 1, wherein the regasification unit uses an open
rack vaporizer (ORV) using sea water for heat exchanger.
[Claim 4] The facilities of claim 3, wherein the sea water pump of the utility unit
and a ballast water pump disposed in the storage unit are simul
taneously used to supply sea water to the regasification unit.
[Claim 5] The facilities of claim 1, wherein a power facility, a steam generator,
and a ballast water pump disposed in the storage unit are used to supply
power, steam, and sea water, respectively, which are necessary for the
regasification unit.
[Claim 6] The facilities of claim 1, wherein the storage unit is fixed to the jetty
unit, loads LNG from a movable LNG carrier or a floating storage unit
(FSU), and carries the LNG to the regasification unit.
[Claim 7] The facilities of claim 1, wherein the storage unit is separable from the
jetty unit and movable to load LNG.
[Claim 8] The facilities of claim 1, wherein the storage unit is the LNG carrier or
an FSU.