[Technical Field]
[0001] The present invention relates to an FT (Fischer-Tropsch) GTL (gas-to-liquid) apparatus
and method for producing a single synthetic crude oil(syncrude) and, more particularly,
to an FT GTL apparatus and method which can fluidize FT wax, which is an intermediate
syncrude product (FT naphtha, FT heavy oil, FT wax) produced by chemical processes
in a GTL floating production, storage, and off-loading (FPSO) and is in a solid state
causing difficulty in transportation, by subjecting some of the FT wax to a low level
of general hydrocracking or mild hydroisomerization and mixing FT naphtha and FT heavy
oil with the FT wax such that the resulting product can be stored and transported
in a solid state.
[Background Art]
[0002] Recently, as petroleum resources are on the brink of being exhausted, there is demand
for alternative resources capable of producing transportation oils, fuel oils, and
petrochemicals. Representative examples of hydrocarbon materials that can meet such
demand include coal and natural gas, deposits of which are abundant, and alternative
eco-friendly hydrocarbon sources such as biomass or wastes can be used in order to
achieve CO
2 reduction for prevention of global warming. As a method of producing chemicals such
as transportation oils including gasoline and diesel, alcohols, wax, lube base oils,
or olefins from such alternative hydrocarbon sources, an indirect coal liquefaction
(coal-to-liquid (CTL)) process, a process of producing synthetic distillates from
natural gas (gas-to-liquid (GTL) process), and an indirect biomass liquefaction (biomass-to-liquid
(BTL)) process are well known in the art.
[0003] An FT GTL process includes converting syngas, in which a small amount of methane
and carbon dioxide are contained and hydrogen is mixed with carbon monoxide, into
large hydrocarbon molecules using a high pressure catalyst reactor. In other words,
an FT synthesis reaction in a reactor for Fischer-Tropsch synthesis is as follows:
CO + 2H
2 → -CH
2+H
2O △H
(227° C) = -165 kJ/mol
Methanation reaction
CO + 3H
2 → CH
4 + H
2O △H
(227° C) = -215 kJ/mol
water gas shift
CO + H
2O → CO
2 + H
2 △H
(227° C) = -40 kJ/mol
Boudouard reaction
2CO ↔ C + CO
2 △H
(227° C) = -134 kJ/mol
[0004] Here, as a catalyst, an iron oxide-based catalyst or a cobalt-based catalyst is used;
the reaction temperature ranges from 200°C to 350°C; and the reaction pressure ranges
from 10 bar to 30 bar. Such an FT synthesis reaction is a moderate exothermic reaction,
and thermal control through heat exchange, which is a key determinant in design of
the reactor, is important in order to increase the catalytic reaction rate.
[0005] An FT product produced by the catalyst reactor is composed of unreacted syngas, methane,
ethane, LPG (C3 to C4), naphtha (C5 to C10), heavy oil (C11 to C22), and wax (>C22).
Essentially, several hundreds of components having carbon numbers of 1 to 40 or more
are produced through FT synthesis.
[0006] Relative amount of each of the above components in an untreated product mainly depends
on the reaction temperature of the reactor and the kind of catalyst used. Generally,
there are three types of basic FT operating systems, that is, high temperature FT
reaction using an iron-based catalyst (HTFT-Fe), low temperature FT reaction using
an iron-based catalyst (LTFT-Fe), and low temperature FT reaction using a cobalt-based
catalyst (LTFT-Co).
[0007] An FPSO unit is a floating vessel for production, storage, and offloading of crude
oil and serves to produce and store crude oil and to offload the crude oil onto a
crude oil transportation means such as an oil tanker at sea.
[0008] The FPSO unit includes drilling facilities for off-shore drilling and an oil/gas
separator for separating glassy oil into crude oil and associated gas. In addition,
the FPSO unit includes storage facilities for storing crude oil and an offloading
means capable of transferring crude oil to a crude oil transportation means.
[0009] Generally, associated gas incidentally generated in the FPSO process is burned and
discharged to air or is compressed and reintroduced into an undersea disused oil well.
Thus, FPSO-GTL and FPSO-DME processes using such an associated gas as a raw material
for the GTL process after on-board preparation of syngas are commonly employed. Further,
natural gas extracted directly from a marginal gas field may be used in an FPSO-GTL
process of producing a synfuel or in an FPSO-LNG process for direct liquefaction.
[0010] Examples of such technology are disclosed in Patent Documents 1 and 2.
[0011] For example, Patent Document 1 discloses an off-shore FPSO-DME apparatus for direct
synthesis of DME which includes FPSO equipment including a glassy oil separator and
an oil/gas separation unit, a reforming reactor, a dimethyl ether reactor, an undersea
CO
2 storage device, and a power system for internal power generation, wherein a hydrogen
separator and a carbon dioxide separation unit are disposed between the reforming
reactor and the dimethyl ether reactor and the carbon dioxide separation unit is connected
to the dimethyl ether reactor such that carbon dioxide from the carbon dioxide separation
unit, and water and carbon dioxide generated in the power system for internal power
generation are recycled to the reforming reactor and surplus carbon dioxide is stored
undersea.
[0012] Patent Document 2 discloses an off-shore FPSO-GTL apparatus which includes: FPSO
equipment including a glassy oil separator separating glassy oil extracted from an
oil field into an associated gas and crude oil and an oil/gas separation unit separating
the separated crude oil into oil and gas; a reforming reactor receiving a gas obtained
by removing an H
2S component from a C
1 to C
4 carbon compound using a desulfurizer, wherein the carbon compound is separated from
the gas supplied from the FPSO equipment; a liquid-phase carbon compound preparation
device preparing a liquid-phase carbon compound using syngas passing through the reforming
reactor; an upgrading reactor receiving hydrogen obtained by subjecting syngas passing
through the reforming reactor to a water gas shift reaction; an undersea CO
2 storage device receiving surplus carbon dioxide obtained by removing hydrogen from
the syngas; and a power system for internal power generation of the FPSO-GTL apparatus,
wherein a hydrogen separator and a carbon dioxide separation unit are disposed between
the reforming reactor and the liquid-phase carbon compound preparation apparatus,
and a water separator is disposed between the liquid-phase carbon compound preparation
apparatus and the upgrading reactor, such that water and carbon dioxide from the water
separator and the carbon dioxide separation unit and water and carbon dioxide generated
in the power system for internal power generation are recycled to the reforming reactor
and surplus carbon dioxide is stored undersea.
[0013] Syncrude is a fuel artificially prepared using resources other than petroleum, such
as natural gas, coal, or biomass and is developed as next generation clean fuel technology
by major companies and institutions under the government administration in Korea.
Since demand for a GTL clean fuel is expected to rapidly increase in the future given
increasing oil prices, such syncrude technology is considered to be economically feasible.
[0014] In this context, although development of a GTL FPSO aimed at allowing technology
on land to be realized at sea is proceeding, there are many problems to solve before
commercialization. One of such problems involved with the GTL FPSO is an issue of
securing flowability for storage and transportation of GTL syncrude. This is due to
the fact that a syncrude produced in the GTL FPSO contains a large amount of wax and
thus exhibits high viscosity. Thus, flowability of the syncrude is crucial to secure
efficient operation and economic feasibility of the GTL FPSO.
[0015] For this purpose, there has been proposed a method in which a syncrude is heated
to a temperature at which the syncrude can exhibit flowability based on a concept
as in a typical very large crude oil carrier (VLCC). However, this method requires
additional facilities and fuel supply to continuously maintain the temperature during
a series of processes including production/storage/offloading/separation.
[0016] As one example of the related art, Korean Patent No.
0,339,993 discloses a fluidization method which includes bringing tar/sludge into contact with
an effective amount of a surfactant and an effective amount of an inorganic acid and/or
a carrier, wherein the inorganic acid is sulfuric acid, phosphoric acid or a mixture
thereof and is introduced from a container/tube to wash or fluidize tar/sludge. Thus,
this method is expected to remove tar/sludge such that the resulting product can be
easily transported, handled, and pumped.
[0017] However, this method is aimed at washing tar/sludge without causing physical deformation
of a pipe and a storage tank, and is thus difficult to use to secure flowability so
as to facilitate transportation and use of a syncrude produced in the GTL FPSO.
[Disclosure]
[Technical Problem]
[0018] A conventional technique as described above has a problem in that a refinery apparatus
for completely shifting LPG, gasoline, kerosene, diesel, or the like into a light
material through hydrocracking of wax includes a product fractionating apparatus as
well as a large expensive hydrocracking apparatus, thereby causing increase in production
costs.
[0019] In addition, the conventional technique has a problem in that three types of products
produced by a refinery process are individually stored and transported, thereby causing
increase in transportation costs.
[0020] The present invention has been conceived to solve such problems in the art and it
is an aspect of the present invention to provide an FT GTL apparatus and method for
producing a single synthetic crude oil (syncrude) which can produce a single syncrude
using as few devices as possible.
[0021] It is another aspect of the present invention to provide an FT GTL apparatus and
method for producing a single syncrude which can reduce complexity and costs involved
with storage of FPSO products and transportation of the products to an on-shore refinery.
[0022] It is a further aspect of the present invention to provide an apparatus for adjusting
wax content in a GTL FPSO syncrude which allows production and mixing to be achieved
with wax content in a syncrude produced in a GTL FPSO adjusted to a predetermined
level to secure flowability of the syncrude, thereby improving economic feasibility
of a series of processes including production, storage, offloading, transportation,
and separation of the syncrude.
[Technical Solution]
[0023] In accordance with one aspect of the present invention, a Fischer-Tropsch (FT) gas-to-liquid
(GTL) apparatus for producing a single syncrude in a floating production, storage,
and off-loading (FPSO) unit includes:
a gas injection stabilization unit producing a natural gas condensate by stabilizing
produced natural gas; and
a reforming unit producing a syncrude product by reforming the natural gas treated
in the gas injection stabilization unit.
[0024] Preferably, the FT GTL apparatus further includes a product treatment unit mixing
the natural gas condensate with the syncrude product to produce a single syncrude.
[0025] Preferably, the gas injection stabilization unit includes a first three-phase separator
separating CH
1 to CH
40 and H2O injected in the separator into CH
1 to CH
4, the natural gas condensate (CH
5 to CH
40), and water (H2O).
[0026] Preferably, the syncrude product is FT naphtha, FT heavy oil, and FT wax, and the
reforming unit includes an FT reactor producing the FT wax and a second three-phase
separator producing a first mixture of the FT naphtha and the FT heavy oil.
[0027] Preferably, the second three-phase separator separates syngas treated in the FT reactor
into a tail gas, H
2O, and the first mixture through heat exchange of the syngas in a first heat exchanger.
[0028] Preferably, the product treatment unit includes: a product mixing tank mixing the
first mixture with a second mixture of the FT naphtha, the FT heavy oil, and the FT
wax and the natural gas condensate; and a storage tank storing a GTL liquid prepared
in the product mixing tank.
[0029] Preferably, the product treatment unit further includes a second heat exchanger performing
heat exchange of the FT wax produced in the FT reactor, a reactor producing the second
mixture by subjecting the FT wax heat exchanged in the second heat exchanger to hydrocracking
or mild hydroisomerization, and a separator separating unreacted tail gas from the
second mixture.
[0030] Preferably, the product treatment unit further includes a first compressor for compressing
a tail gas and a second compressor performing hydrogenation, and the unreacted tail
gas separated in the separator is supplied to the second heat exchanger through the
first compressor and the second compressor.
[0031] Preferably, the FT GTL apparatus further includes a tail gas separation unit separating
the syncrude into a tail gas and a first mixture of FT naphtha and FT heavy oil, and
[0032] the first mixture separated in the tail gas separation unit is supplied to the product
treatment unit.
[0033] Preferably, the reforming unit includes: an F-T synthesis unit producing synthetic
oil from syngas produced from the natural gas; and a control unit controlling the
F-T synthesis unit to maintain wax content in the syncrude reformed into the synthetic
oil at a predetermined level so as to adjust wax content of the syncrude.
[0034] Preferably, the F-T synthesis unit is provided with an LT-FT reactor and an HT-FT
reactor in series or in parallel and adjusts flow rates of the LT-FT reactor and the
HT-FT reactor depending upon the composition of syncrude produced at a downstream
side of the F-T synthesis unit.
[0035] Preferably, the control unit is provided with a wax detection unit detecting wax
content in the syncrude and an unreacted gas detection unit detecting unreacted gas
content.
[0036] Preferably, the control unit controls the wax content to be maintained at a minimum
level to a degree to which unreacted gas content is maintained within a predetermined
range.
[0037] In accordance with another aspect of the present invention, a Fischer-Tropsch (FT)
gas-to-liquid (GTL) method for producing a single syncrude in a floating production,
storage, and off-loading (FPSO) unit includes:
- (a) producing a natural gas condensate from natural gas;
- (b) producing FT wax and a first mixture of FT naphtha and FT heavy oil from syngas;
- (c) producing a second mixture of FT naphtha, FT heavy oil, and FT wax; and
- (d) producing a single syncrude by mixing the natural gas condensate with the first
mixture and the second mixture.
[0038] Preferably, step (c) is performed though hydrocracking or mild hydroisomerization
of wax.
[0039] Preferably, the single syncrude produced in step (d) is stored and transported without
heat treatment.
[0040] Preferably, the FT GTL method further includes: (e) refining the single syncrude
in an on-shore refinery plant.
[Advantageous Effects]
[0041] According to the present invention, it is possible to provide an FT GTL apparatus
and method for producing a single syncrude which can save deck space in an FPSO while
reducing production costs due to use of simple product upgrading equipment, and allows
the FPSO to only require one tank to store products and eliminates a need for additional
heat supply needed to store the products and transfer the products to a pump, thereby
reducing transportation costs.
[0042] In addition, according to the present invention, it is possible to provide an FT
GTL apparatus and method for producing a single syncrude which subjects some of FT
wax to a low level of general hydrocracking or mild hydroisomerization after mixing
FT naphtha with FT heavy oil so as to allow a syncrude to be transported without being
heated, thereby reducing complexity, space, and cost as compared with the case of
using a refinery apparatus provided with a high pressure hydrocracking reaction unit
while reducing hydrogen consumption as compared with the case of using such a refinery
apparatus.
[0043] Further, according to the present invention, it is possible to secure flowability
of a syncrude produced in a GTL FPSO, thereby improving economic feasibility of a
series of processes including production, storage, offloading, transportation, and
separation of the syncrude, such that marketable technology can be accumulated in
the related art.
[Description of Drawings]
[0044]
Fig. 1 is a block diagram of an FT GTL apparatus for producing a single syncrude according
to a first embodiment of the present invention.
Fig. 2 is a block diagram illustrating connection between the main units of Fig. 1.
Fig. 3 is a flowchart illustrating an FT GTL method of producing a single syncrude
according to the first embodiment of the invention
Fig. 5 is a view illustrating production, storage, offloading, transportation, and
separation of a single syncrude according to the first embodiment of the invention.
Fig. 6 is a flowchart showing main processes of a GTL FPSO according to a second embodiment
of the present invention.
Fig. 7 is a block diagram showing main parts of an F-T synthesis unit of Fig. 6.
Fig. 8 is a syncrude weight fraction diagram illustrating control according to the
second embodiment of the invention.
[Best Mode]
[0045] The above and other aspects, features, and advantages of the present invention will
become apparent from the detailed description of the following embodiments in conjunction
with the accompanying drawings.
[0046] First, the concept of the present invention will be described.
[0047] A GTL FPSO is an off-shore structure in which a GTL unit is incorporated into an
FPSO (Floating Production, Storage, and Off-loading) unit so as to produce clean energy
at sea. A GTL process is composed of a reforming process of producing syngas (H
2, CO) from natural gas (NG), a Fischer-Tropsch (F-T) process of producing syncrude
from the syngas, and an upgrading process of converting the syncrude into a fuel having
a desired carbon number.
[0048] In the GTL FPSO, securing flowability and transferability of a syncrude is an issue
of growing importance for commercialization. For this purpose, although installation
of upgrading equipment is considered, there is high probability of performance and
safety problems given the fact that such equipment has not yet been installed at sea.
[0049] First, in a first embodiment of the present invention, a single syncrude product
transferable from the FT GTL FPSO can be produced. In other words, the first embodiment
of the invention provides a novel concept of producing single hybrid FT syncrude which
is a mixture of FT naphtha, FT heavy oil and treated FT wax, and can be stored and
transferred without heat treatment.
[0050] The concept of single hybrid FT syncrude requires a catalyst, reactor design, and
operating system suitable for wax hydro cracking or mild hydroisomerization. In addition,
such a concept of the single hybrid FT syncrude can reduce space and costs for processing
FT products while simplifying storage and transportation requirements for FT GTL FPSO
products.
[0051] Further, syncrude produced in each of plural FT GTL FPSOs is transferred to a single
on-shore refinery plant and is treated therein. In addition, the syncrude may be produced
into a marketable fuel for vehicles through mixing with general crude oil products
and/or through additional refinement. Such a concept is useful because the concept
can operate a carrier fleet more efficiently and minimize spatial, capital requirements
for the FPSO while allowing a system that can benefit from economies of scale in an
on-shore refinery plant.
[0052] According to the first embodiment of the invention, after FT naphtha is mixed with
FT heavy oil, some of FT wax is subjected to a low level of general hydrocracking
or mild hydroisomerization such that the syncrude can be transported without heat
treatment. Such a concept includes transforming mixed syncrude such that the syncrude
can be stored and transported without heat treatment, although the concept includes
using a catalyst and operating system not intended to produce a final FT product.
In addition, this concept also includes using different catalysts to produce different
products without diluting (or mixing) FT naphtha and FT heavy oil with treated FT
wax.
[0053] The above concept includes subjecting FT wax to hydrocracking or mild hydroisomerization
in order to only increase the pour point and freezing point of the syncrude without
trying to modify other properties. Thus, it is possible to reduce costs required for
processing an FPSO on-board FT product while providing size and space reduction and
simplifying storage and transportation of the product.
[0054] Hereinafter, the first embodiment of the invention will be described with reference
to the accompanying drawings.
[0055] Fig. 1 is a block diagram of an FT GTL apparatus for producing a single syncrude
according to the first embodiment of the invention.
[0056] Referring to Fig. 1, the FT GTL apparatus for producing a single syncrude according
to the first embodiment is an FT GTL apparatus for producing a single syncrude in
an FPSO, and includes a gas injection stabilization unit 10 receiving produced gas,
a desulfurization unit 20, a natural gas saturation and pre-reforming unit 30, a small
reforming unit 40, a syngas conditioning unit 50, an FT synthesis unit 60, a tail
gas separation unit 70, and a product treatment unit 80.
[0057] The gas injection stabilization unit 10 performs stabilization of produced raw natural
gas (NG) to produce natural gas, a natural gas condensate (NG condensate), and water
(H
2O), wherein the natural gas condensate is supplied to the product treatment unit 80.
[0058] The desulfurization unit 20 removes sulfur from the natural gas and supplies the
raw natural gas to the natural gas saturation and pre-reforming unit 30. Some of the
raw natural gas having been pre-treated in the natural gas saturation and pre-reforming
unit 30 is used as a fuel gas, and the rest of the natural gas is heated by steam
and then supplied to the reforming unit 40 and discharged to a saturator.
[0059] The reforming unit 40 reforms the steamed natural gas supplied from the natural gas
saturation and pre-reforming unit 30 into raw syngas, thereby producing a syncrude
product. In addition, a gas untreated in the reforming unit 40 is supplied to the
natural gas saturation and pre-reforming unit 30 as a fuel gas.
[0060] The raw syngas treated in the reforming unit 40 is produced into syngas in the syngas
conditioning unit 50, and H
2 generated in this process is supplied to the reforming unit 40 and the product treatment
unit 80 as a fuel gas. Further, the syngas condensate generated in the syngas conditioning
unit 50 is supplied to the natural gas saturation and pre-reforming unit 30 or discharged.
[0061] The syngas supplied from the syngas conditioning unit 50 is passed through the FT
synthesis unit 60 to be separated into FT wax and a first mixture of FT naphtha and
FT heavy oil, which, in turn, are supplied to the product treatment unit 80.
[0062] The tail gas separation unit 70 separates the syngas supplied from the FT synthesis
unit 60 into a tail gas and the first mixture of FT naphtha and FT heavy oil, wherein
the first mixture is supplied to the product treatment unit 80, and the tail gas is
discharged in part or recycled to the natural gas saturation and pre-reforming unit
30.
[0063] The product treatment unit 80 serves to mix the natural gas condensate supplied from
the gas injection stabilization unit 10 with the first mixture and the FT wax supplied
from the FT synthesis unit 60 and the first mixture supplied from the tail gas separation
unit 70 to produce a single syncrude according to the present invention.
[0064] Boiler feed water (BFW) for steam formation is supplied to the reforming unit 40
and the syngas conditioning unit 50.
[0065] Next, configurations of the gas injection stabilization unit 10, the reforming unit
40, and the product treatment unit 80, which are main features of the first embodiment
of the invention, will be described with reference to Fig. 2.
[0066] Fig. 2 is a block diagram illustrating connection between the main units of Fig.
1.
[0067] Referring to Fig. 2, the gas injection stabilization unit 10 includes a first three-phase
separator 41 which separates received CH
1 to CH
40 and H
2O into CH
1 to CH
4, the natural gas condensate (CH
5 to CH
40) and water (H
2O). The natural gas condensate (CH
5 to CH
40) is supplied to the product treatment unit 80, and the water (H
2O) is supplied to the natural gas saturation and pre-reforming unit 30.
[0068] The reforming unit 40 includes an FT reactor 41 producing FT wax from the natural
gas and a second three-phase separator 42 producing the first mixture of FT naphtha
and FT heavy oil. The second three-phase separator 42 separates the syngas treated
in the FT reactor 41 into a tail gas, H
2O, and the first mixture through heat exchange in a first heat exchanger 43. The first
mixture is supplied to the product treatment unit 80.
[0069] The product treatment unit 80 includes: a product mixing tank 81 for mixing the first
mixture supplied from the second three-phase separator 42 with the natural gas condensate
supplied from the gas injection stabilization unit 10 and a second mixture of FT naphtha,
FT heavy oil, and FT wax; a storage tank 82 storing a GTL liquid prepared in the product
mixing tank 81; a second heat exchanger 83 performing heat exchange of the FT wax
produced in the FT reactor 41; a reactor 84 producing the second mixture through hydrocracking
or mild hydroisomerization of the FT wax subjected to heat exchange in the second
heat exchanger 83; and a separator 85 for separating unreacted tail gas from the second
mixture.
[0070] The single syncrude product according to the present invention is prepared by mixing
FT wax with FT naphtha and FT heavy oil. As described above, the single syncrude product
is obtained by mixing the first mixture of FT naphtha and FT heavy oil with the second
mixture of FT naphtha, FT heavy oil, and FT wax, and the natural gas condensate in
the product mixing tank 81, followed by storage in the storage tank 82.
[0071] The single syncrude product prepared as above allows the FPSO to need only one tank
to store the product, i.e. the storage tank 82 and can eliminate a need for additional
heat supply for storage of the product and transfer of the product to a pump, thereby
reducing transportation costs.
[0072] In addition, the product treatment unit 80 further includes a first compressor 86
which compresses the tail gas separated in the separator 85 and a second compressor
87 which performs hydrogenation, wherein unreacted tail gas separated in the separator
85 is supplied to the second heat exchanger 83 through the first compressor 86 and
the second compressor 87.
[0073] Next, a process of performing production, storage, offloading, transportation, and
separation of the single syncrude using the FT GTL apparatus for producing a single
syncrude as shown in Figs. 1 and 2 will be described with reference to Figs. 3 and
4.
[0074] Fig. 3 is a flowchart illustrating an FT GTL method of producing a single syncrude
according to the first embodiment of the invention, and Fig. 4 is a view illustrating
production/storage/offloading/transportation/separation of a single syncrude according
to the first embodiment of the invention.
[0075] The FT GTL method of producing a single syncrude according to the first embodiment
of the invention is an FT GTL method for producing a single syncrude in an FPSO, and,
in the method, first, natural gas is subjected to stabilization in the gas injection
stabilization unit 10 to produce a natural gas condensate (S10).
[0076] Thereafter, sulfur is removed from the natural gas by the desulfurization unit 20,
and a syngas is produced by the natural gas saturation and pre-reforming unit 30 and
the small reforming unit 40.
[0077] In the reforming unit 40, FT wax and the first mixture of FT naphtha and FT heavy
oil are produced from the syngas (S20).
[0078] Then, in the product treatment unit 80, the FT wax is subjected to hydrocracking
or mild hydroisomerization to produce the second mixture of FT naphtha, FT heavy oil,
and FT wax (S30).
[0079] In addition, in the product treatment unit 80, the natural gas condensate produced
in step S10 is mixed with the first mixture produced in step S20 and the second mixture
produced in step S30 to produce a single syncrude (S40).
[0080] As shown in Fig. 4, the single syncrude produced in step S40 is stored and transported
without heat treatment (S50). The single syncrude transported in step S50 is refined
in an on-shore refinery plant (S60).
[0081] According to the second embodiment of the invention, the FT synthesis unit 600 is
provided to produce synthetic oil from syngas prepared from natural gas. Referring
to Fig. 5, a GTL main process is performed by the natural gas saturation and pre-reforming
unit 300, the reforming unit 400, the syngas conditioning unit 500, the FT synthesis
unit 600, and the product treatment unit 800, which are sequentially connected to
one another. The FT synthesis unit 600 serves to convert the syngas into the synthetic
oil, and the product treatment unit 800 serves to upgrade the synthetic oil to produce
a syncrude. A surplus syngas generated in the FT synthesis unit 600 is fractionated
in the tail gas separation unit 700 to be partially recycled to the pre-reforming
unit 20. The syncrude produced in the product treatment unit 800 is stored in a tank.
[0082] Here, since the syncrude produced in the GTL FPSO exhibits high viscosity due to
containing a large amount of wax, it is necessary to secure flowability of the syncrude
so as to facilitate storage, offloading, and transportation. As the amount of the
wax approaches 100%, the syncrude is more likely to be solidified at atmospheric pressure/room
temperature, such that storage and offloading of the syncrude is impossible.
[0083] According to the second embodiment, a control unit 900 controls the FT synthesis
unit 600 to maintain wax content in the syncrude that will be reformed into the synthetic
oil at a predetermined level. The control unit 900 determines the state of the syncrude
stored in the tank and executes an algorithm for maintaining the wax content at an
optimal level based on the determination.
[0084] According to details of the second embodiment, the FT synthesis unit 600 is provided
with an LT-FT reactor 620 and an HT-FT reactor 640 in series or in parallel and adjusts
a flow rate of the LT-FT reactor 620 and the HT-FT reactor 640 depending upon the
composition of a syncrude produced at a downstream side thereof. Referring to Fig.
2, the FT synthesis unit 600 includes the HT-FT reactor 640 at a downstream side of
the LT-FT reactor 620. The LT-FT reactor 620 is operated at a temperature of 220°C
to 250°C and mainly produces a liquid product such as a heavy oil fraction or wax,
and the HT-FT reactor 640 is operated at a temperature of 330°C to 350°C and produces
a gaseous product such as gasoline or naphtha.
[0085] When the LT-FT reactor 620 and the HT-FT reactor 640 are operated at the same time,
it is possible to easily secure flowability of the syncrude through adjustment of
the amount of the wax. In Fig. 6, reference numeral 48 denotes a separator for removing
moisture and the like after the synthetic reaction.
[0086] Referring to Fig. 7, it is shown from marks at the right side that the wax is present
in an amount of about 50% after primary reaction in the LT-FT reactor 620, and it
is shown from marks at the left side that the amount of the wax is reduced to about
10% and the amount of naphtha is increased after the secondary reaction in the HT-FT
reactor 640.
[0087] The LT-FT reactor 620 may be disposed at a downstream side of the HT-FT reactor 640
depending upon desired properties of the syncrude. Examples of the above case may
include the case of trying to produce a light syncrude such as gasoline, naphtha,
or diesel in large amounts.
[0088] According to details of the second embodiment, the control unit 900 is provided with
a wax detection unit 920 detecting wax content, an unreacted gas detection unit 940
detecting unreacted gas content, and a driving unit 960. The wax detection unit 920
and the unreacted gas detection unit 940 are not limited to hardware such as a specific
sensor and may include a database in which data of changes in content for each component
of the syncrude are collected and software.
[0089] According to details of the second embodiment, the control unit 900 maintains wax
content at a minimum level to a degree to which unreacted gas content is maintained
within a predetermined range. As shown in Fig. 3, as wax content of the syncrude is
decreased, transport efficiency is reduced due to increasing content of unreacted
gas such as LPG. Thus, the control unit maintains wax content at an optimal level
to a degree to which content of unreacted gas is maintained within a predetermined
range. It should be understood that wax content must also be maintained within a range
capable of securing flowability of the syncrude.
[0090] As such, both the LT-FT reactor 620 and the HT-FT reactor 640 are used commercially
in on-shore facilities and thus have low risk when applied to off-shore facilities.
Thus, it is not necessary to secure flowability through an upgrading process, which
is unproven in off-shore facilities, and it is possible to reduce CAPEX and OPEX required
for establishment of an upgrading system.
[0091] Although some embodiments have been described, it will be apparent to those skilled
in the art that these embodiments are given by way of illustration only, and that
various modifications, changes, alterations, and equivalent embodiments can be made
without departing from the spirit and scope of the invention. The scope of the invention
should be limited only by the accompanying claims and equivalents thereof.
1. A Fischer-Tropsch (FT) gas-to-liquid (GTL) apparatus for producing a single syncrude
in a floating production, storage, and off-loading (FPSO) unit, comprising:
a gas injection stabilization unit producing a natural gas condensate by stabilizing
produced natural gas; and
a reforming unit producing a syncrude product by reforming the natural gas treated
in the gas injection stabilization unit.
2. The FT GTL apparatus according to claim 1, further comprising:
a product treatment unit mixing the natural gas condensate with the syncrude product
to produce a single syncrude.
3. The FT GTL apparatus according to claim 2, wherein the gas injection stabilization
unit comprises a first three-phase separator separating CH1 to CH40 and H2O injected in the separator into CH1 to CH4, the natural gas condensate (CH5 to CH40), and water (H2O).
4. The FT GTL apparatus according to claim 3, wherein the syncrude product is FT naphtha,
FT heavy oil, and FT wax, and the reforming unit comprises an FT reactor producing
the FT wax and a second three-phase separator producing a first mixture of the FT
naphtha and the FT heavy oil.
5. The FT GTL apparatus according to claim 4, wherein the second three-phase separator
separates syngas treated in the FT reactor into a tail gas, H2O, and the first mixture through heat exchange of the syngas in a first heat exchanger.
6. The FT GTL apparatus according to claim 5, wherein the product treatment unit comprises:
a product mixing tank mixing the first mixture with a second mixture of the FT naphtha,
the FT heavy oil, and the FT wax and the natural gas condensate; and a storage tank
storing a GTL liquid prepared in the product mixing tank.
7. The FT GTL apparatus according to claim 6, wherein the product treatment unit further
comprises a second heat exchanger performing heat exchange of the FT wax produced
in the FT reactor, a reactor producing the second mixture by subjecting the FT wax
subjected to heat exchange in the second heat exchanger to hydrocracking or mild hydroisomerization,
and a separator separating unreacted tail gas from the second mixture.
8. The FT GTL apparatus according to claim 7, wherein the product treatment unit further
comprises a first compressor for compressing a tail gas and a second compressor for
adding hydrogen, and the unreacted tail gas separated in the separator is supplied
to the second heat exchanger through the first compressor and the second compressor.
9. The FT GTL apparatus according to claim 2, further comprising:
a tail gas separation unit separating the syncrude into a tail gas and a first mixture
of FT naphtha and FT heavy oil, and the first mixture separated in the tail gas separation
unit is supplied to the product treatment unit.
10. The FT GTL apparatus according to claim 1, wherein the reforming unit comprises:
an F-T synthesis unit producing synthetic oil from syngas produced from the natural
gas; and a control unit controlling the F-T synthesis unit to maintain wax content
in the syncrude reformed into the synthetic oil at a predetermined level so as to
adjust wax content of the syncrude.
11. The FT GTL apparatus according to claim 10, wherein the F-T synthesis unit is provided
with an LT-FT reactor and an HT-FT reactor in series or in parallel and adjusts flow
rates of the LT-FT reactor and the HT-FT reactor depending upon the composition of
a syncrude produced at a downstream side of the F-T synthesis unit.
12. The FT GTL apparatus according to claim 10, wherein the control unit is provided with
a wax detection unit detecting wax content of the syncrude and an unreacted gas detection
unit detecting unreacted gas content.
13. The FT GTL apparatus according to claim 12, wherein the control unit controls the
wax content to be maintained at a minimum level to a degree to which unreacted gas
content is maintained within a predetermined range.
14. A Fischer-Tropsch (FT) gas-to-liquid (GTL) method for producing a single syncrude
in a floating production, storage, and off-loading (FPSO) unit, comprising:
(a) producing a natural gas condensate from natural gas;
(b) producing FT wax and a first mixture of FT naphtha and FT heavy oil from syngas;
(c) producing a second mixture of FT naphtha, FT heavy oil, and FT wax; and
(d) producing a single syncrude by mixing the natural gas condensate with the first
mixture and the second mixture.
15. The FT GTL method according to claim 14, wherein step (c) is performed though wax
hydrocracking or mild hydroisomerization.
16. The FT GTL method according to claim 15, wherein the single syncrude produced in step
(d) is stored and transported without heat treatment.
17. The FT GTL method according to claim 15, further comprising:
(e) refining the single syncrude in an on-shore refinery plant.