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DESCRIPTION
METHOD OF PRODUCING SYNTHETIC FUEL
TECHNICAL FIELD
The present invention relates to a method of producing synthetic fuel from
Fischer-Tropsch synthetic crude oil obtained by a Fischer-Tropsch synthesis
method
(hereinafter, simply referred to as "a FT synthesis method"). Specifically,
the method of
producing the synthetic fuel includes a step in which magnetic particles,
contained in a
BACKGROUND ART
In recent years, a clean and environmentally-friendly liquid fuel that
contains a
low content of sulfur and aromatic hydrocarbons and that is compatible with
the
environment has been required from the viewpoint of the reduction of
environmental
burdens. Therefore, in the oil industry, an FT synthesis method using raw
materials
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Patent Document 1: Japanese Unexamined Patent Application, First Publication
No. 2004-323626
[0003]
Meanwhile, the synthetic crude oil obtained by the FT synthesis method
(hereinafter, referred to as "FT synthetic crude oil") has a broad carbon
number
distribution. Specifically, an FT naphtha fraction containing a high content
of
hydrocarbons having a boiling point of approximately less than 150 C, an FT
middle
fraction containing a high content of components having a boiling point in the
range of
from approximately 150 C to approximately 360 C, and an FT wax fraction
heavier than
the middle fraction can be obtained from the FT synthetic crude oil.
In this case, a large amount of the FT wax fraction is produced therein.
Accordingly, if the FT wax fraction obtained by fractionating the synthetic
crude oil is
hydrocracked to convert the FT wax fraction into the middle fraction, then,
production of
fuel oil such as diesel fuel can be increased.
[0004]
Whereas, with regard to a catalyst used in the FT synthetic method using
materials such as carbon monoxide and hydrogen, an iron solid catalyst has
been
frequently used in the conventional art. However, in recent years, a cobalt
solid catalyst
has been developed such a catalyst has high activity. In this case, the
reaction mode of
the FT synthesis method can be a fixed bed-type, a fluidized bed-type, a
moving bed-type
or the like. However, a heterogeneous catalyst which is a solid catalyst is
used in any
type of reaction.
DISCLOSURE OF THE INVENTION
PROBLEM THAT THE INVENTION IS TO SOLVE
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[0005]
As described above, a heterogeneous catalyst which is a solid catalyst is used
in
the FT synthesis method regardless of a mode of reaction. The obtained FT
synthetic
crude oil is subjected to a process of removing a catalyst remaining therein
by use of an
ordinary method such as filtering or settling. However, since the remaining
catalyst
cannot be completely removed due to cost, a portion of the catalyst is
inevitably
contained in the FT synthetic crude oil although the amount thereof is small.
[0006]
Then, the remaining catalyst is concentrated in the wax fraction that is a
bottom
component in fractionating the FT synthetic crude oil.
As a result, the remaining catalyst may be undesirably accumulated in a
hydrocracking apparatus because, even though the concentration of remaining
catalyst
contained in the FT synthetic crude oil is low in the initial stages, the
remaining catalyst
is concentrated in the bottom of a fractionator.
MEANS FOR SOLVING THE PROBLEM
[0007]
The present inventors discovered that such cobalt catalyst particles are
particles
having magnetism and that the cobalt catalyst particle can be magnetically
separated in
the same manner as iron catalyst particles that are catalysts remaining in FT
synthetic
crude oil. Thus, the present invention is achieved based on the discovery.
[0008]
Specifically, an aspect of the invention provides the following.
[1] A method of producing synthetic fuel from Fischer-Tropsch
synthetic
crude oil obtained by a Fischer-Tropsch synthesis method, the method including
the steps
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of: (a) fractionating, in a fractionator, Fischer-Tropsch synthetic crude oil
obtained by a
Fischer-Tropsch synthesis method into at least two fractions of a middle
fraction
containing a component having a boiling range corresponding to diesel fuel
oil, and a
wax fraction containing a wax component heavier than the middle fraction; (b)
separating
and removing a magnetic particle contained in the wax fraction obtained in the
step (a) at
100 C to 450 C by using a high gradient magnetic separator; and (c)
hydrocracking the
wax fraction obtained in the step (b) from which the magnetic particle is
separated and
removed.
[0009]
[2] The method of producing synthetic fuel according to [1], wherein, in the
step (b), a ferromagnetic filling material is disposed in a space where a
magnetic field is
generated inside the high gradient magnetic separator, the wax fraction
obtained in the
step (a) is introduced into the magnetic field space in the state where the
magnetic field is
generated to capture the magnetic particle to the ferromagnetic filling
material, and then
washing liquid is introduced into the space where the ferromagnetic filling
material is
disposed while eliminating the magnetic field to discharge the magnetic
particle to the
outside of the high gradient magnetic separator.
[3] The method of producing synthetic fuel according to [1] or
[2], wherein, in
the step (b) of separating and removing the magnetic particle using the high
gradient
magnetic separator is carried out in conditions where the magnetic field
intensity is 1,500
Gauss or more and the liquid residence time is three seconds or more.
ADVANTAGE OF THE INVENTION
[0010]
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According to the present invention, magnetic particles are removed by magnetic
separation whereby the magnetic particles can be prevented from being
accumulated in
the hydrocracking apparatus. Consequently, the hydrocracking apparatus can be
operated without any trouble.
5 Furthermore, when the magnetic field intensity and the liquid residence
time are
controlled in the above-described aspect of the inventionõ it is possible to
more
efficiently carry out the magnetic separation of the magnetic particles.
BRIEF DISCRIPTION OF THE DRAWINGS
[0011]
FIG. 1 is a schematic view showing a plant for producing fuel, including an FT
synthesis reactor 10, a separator 20 for separating particles in FT synthetic
crude oil, a
first fractionator 30 for fractionating the FT synthetic crude oil into a
naphtha fraction, a
middle fraction, and a wax fraction, a high gradient magnetic separator 40 for
removing
magnetic particles in the wax fraction, a hydrotreating apparatus 54 and a
hydroisomerizing apparatus 52 for respectively processing the naphtha fraction
and the
middle fraction, a hydrocracking apparatus 50 for hydrocracking the wax
fraction from
which the magnetic particle has been magnetically separated, and a second
fractionator
60.
FIG. 2 is a schematic view showing the high gradient magnetic separator 40
used
in the present invention.
[0012]
10: an FT synthesis reactor
20: a separator for an FT synthetic crude oil
30: a first fractionator for fractionating the FT synthetic crude oil
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40: a high gradient magnetic separator for removing magnetic particles in the
wax
fraction
50: a hydrocracking apparatus for the wax fraction
52: a hydroisomerizing apparatus for the middle fraction
54: a hydrotreating apparatus for the naphtha fraction
60: a second fractionator for fractionating the hydroisomerized middle
fraction and the
hydrocracked wax fraction
70: a stabilizer for the naphtha fraction
BEST MODE FOR CARRYING OUT THE INVENTION
[0013]
Hereinafter, the present invention will be described in detail.
Hereinafter, a preferable embodiment of the present invention will be
described
with reference to FIG. 1.
As shown in FIG 1, synthetic gas containing carbon monoxide gas (CO) and
hydrogen gas (H2) is supplied via a line 1, and liquid hydrocarbons are
produced by an
FT synthesis reaction in an FT synthesis reactor 10. The synthetic gas can be
obtained,
for example, by appropriately reforming a hydrocarbon. Typical examples of the
hydrocarbon include methane, natural gas, LNG (liquid natural gas) or the
like. For
example, a partial oxidization reforming method (PDX) using oxygen, an auto
thermal
reforming method (ATR) (e.g. the partial oxidization reforming method is
combined with
a steam reforming method), a carbon dioxide gas reforming method, or the like
may be
used.
[0014]
Next, the FT synthesis will be described with reference to FIG. 1.
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The plant for producing fuel shown in FIG. 1 includes an FT synthesis reactor
10.
The FT synthesis reactor 10 may be, for example, a bubble column reactor which
is an
example of a reactor for obtaining a liquid hydrocarbon by synthesizing
synthetic gas.
The FT synthesis reactor 10 functions as an FT synthesis reactor for obtaining
the liquid
hydrocarbon from the synthetic gas by an FT synthesis reaction.
[0015]
The main body of the FT synthesis reactor 10 is a substantially
cylindrical-shaped metallic vessel, and has a diameter of 1 m to 20 m and
preferably of 2
m to 10 m. The reactor body has a height of 10 m to 50 m and preferably of 15
to 45 m.
A slurry in which solid catalyst particles are suspended in liquid
hydrocarbons (product
of the FT synthesis reaction) is contained inside the main body.
A part of the slurry is flowed out from the middle of the FT synthesis reactor
10
into a separator 20 via a line 3. Unreacted synthetic gas or the like is
discharged from
the top of the FT synthesis reactor 10 through a line 2, and a part of the
unreacted
synthetic gas is suitably recycled to the FT synthesis reactor 10.
[0016]
The synthetic gas supplied from the outside via a synthetic gas supply pipe 1
is
injected from a synthetic gas supply port (not shown in FIG 1) to the slurry
contained in
the FT synthesis reactor 10. When the synthetic gas comes into contact with
the
catalyst particles, a synthesis reaction (FT synthesis reaction) of the liquid
hydrocarbon
occurs due to the contact reaction. Specifically, as shown in the following
chemical
formula (1), a synthesis reaction occurs between hydrogen gas and carbon
monoxide gas.
[0017]
2nH2+ nC0 ---> --ECH2)--õ + nH20 ... (1)
[0018]
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Specifically, the synthetic gas is flowed into the bottom of the FT synthesis
reactor 10 and moves upward in the slurry contained in the FT synthesis
reactor 10. In
this case, in the FT synthesis reactor 10, the reaction between the hydrogen
gas and the
carbon monoxide gas contained in the synthetic gas occurs in terms of the
above-described FT synthesis reaction, thereby producing hydrocarbons.
Additionally,
heat is generated due to the synthesis reaction. However, such heat may be
removed by
use of a suitable cooling device.
The metallic catalyst may be a supported type, a deposition type or the like.
However, the metallic catalyst is in a form of solid particle containing iron
group metal
even in any type. A sufficient amount of metal may be contained in the solid
particles.
However, 100% of the solid particle may be metal. As an example of the iron
group
metal, iron can be mentioned. However, cobalt is preferable in view of high
activity.
[0019]
The composition ratio of the synthetic gas supplied to the FT synthesis
reactor
10 can be set to a composition ratio suitable for the FT synthesis reaction
(for example,
H2:CO 2:1 (molar ratio)). Additionally, the pressure of the synthetic gas
supplied to
the FT synthesis reactor 10 can be increased up to a pressure (for example,
3.6M PaG)
suitable for the FT synthesis reaction by use of a suitable compressor (not
shown in FIG.
1). However, the compressor may not be provided in some cases.
[0020]
The liquid hydrocarbon synthesized in the FT synthesis reactor 10 in this
manner is extracted in a form of slurry having the suspended catalyst
particles from the
FT synthesis reactor 10 through the line 3 connected to the middle of the FT
synthesis
reactor 10, and is introduced into the separator 20. In the separator 20, the
extracted
slurry is separated into a solid component of catalyst particles, etc. and a
liquid
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component containing the liquid hydrocarbons by use of a solid-liquid
separation device.
The solid-liquid separation device may be a device according to a known and
common
method. For example, a filtering device using a suitable filter such as a
sintered
metallic filter, a gravitational sedimentation separator (e.g. a spontaneous
sedimentation
type), a cyclone, a magnetic separator, a centrifugal separator, and the like
can be
mentioned.
[0021]
The solid component of the separated catalyst particles, etc. is recycled to
the FT
synthesis reactor 10 via a line 4 if possible, and the liquid component is
supplied as a
product to a first fractionator 30.
The composition of the separated liquid component, for example, may be
hydrocarbons in which a content of hydrocarbons having a boiling point of
approximately 150 C or more is 84% by mass and a content of hydrocarbons
having a
boiling point of approximately 360 C or more is 42% by mass based on
hydrocarbons
having five or more carbon atoms, and a small amount of oxygenated compounds
and
olefins may be additionally contained therein. Accordingly, the quantity of
catalyst
remaining in the liquid component may be small by use of the above-described
solid-liquid separation device. However, since the catalyst particles are
suspended in
this reaction type, a large amount of powder produced by collision or abrasion
of the
catalyst particles are contained in the liquid component.
[0022]
In FIG. 1, there is provided the first fractionator 30 for fractionating the
FT
synthetic crude oil. Also, there are provided a hydrotreating apparatus 54, a
hydroisomerizing apparatus 52, and a hydrocracking apparatus 50 for processing
a
naphtha fraction, a middle fraction, and a wax fraction fractionated in the
first
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fractionator 30, respectively.
[0023]
The first fractionator 30 may fractionate the liquid hydrocarbons supplied
from
the FT synthesis reactor 10 via the separator 20 as described above. In this
case, the
5 liquid hydrocarbons may be divided into three fractions, e.g. the
lightest naphtha fraction
(having a boiling point of approximately less than 150 C), the middle fraction
having a
middle boiling range (a boiling point in the range of from approximately 150 C
to
approximately 350 C), and the heaviest wax fraction (having a boiling point of
approximately more than 350 C). In FIG. 1, the liquid hydrocarbons are divided
into
10 three fractions. However, the liquid hydrocarbons may be divided into
two fractions,
e.g. the wax fraction and the sum of the other fractions, and also may be
divided into
three or more fractions including the wax fraction therein.
[0024]
Liquid hydrocarbons (mainly having twenty one or more carbon atoms) of the
wax fraction extracted from the bottom of the first fractionator 30 is led to
a high
gradient magnetic separator 40, and then, is brought to the hydrocracking
apparatus 50
for the wax fraction. Additionally, liquid hydrocarbons (mainly having eleven
to twenty
carbon atoms) of the middle fraction extracted via a line 32 connected to the
middle
portion of the first fractionator 30 is transferred to the hydroisomerizing
apparatus 52 for
the middle fraction. Liquid hydrocarbons (mainly having five to ten carbon
atoms) of
the naphtha fraction extracted from the top of the first fractionator 30 is
brought to the
hydrotreating apparatus 54 for the naphtha fraction via a line 33.
[0025]
After the wax fraction (mainly having twenty one or more carbon atoms) flowed
from the bottom of the first fractionator 30 via a line 31 is treated in the
high gradient
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magnetic separator 40, the wax fraction is hydrocracked using hydrogen in the
hydrocracking apparatus 50, thereby reducing the number of carbons of the wax
fraction.
That is, in the hydrocracking reaction, the hydrocarbon C-C bond is cleaved by
the
catalyst to produce low-molecular-weight hydrocarbons having a small number of
carbons. The liquid hydrocarbons hydrocracked in the hydrocracking apparatus
50 for
the wax fraction is brought to a second fractionator 60.
[0026]
Even though the solid-liquid separator (separator 20) removes the FT synthesis
catalyst from the FT synthetic crude oil, residues of the FT synthesis
catalyst are
concentrated to the wax fraction flowed out from the bottom of the first
fractionator 30,
thereby causing a problem in which the residues may be accumulated in the
hydrocracking apparatus 50. Such accumulation of the residues may cause a
trouble
upon operating the hydrocracking apparatus 50.
Meanwhile, with regard to properties of the iron group metal used as the FT
synthesis catalyst, it has been discovered that the iron group metal has a
certain magnetic
susceptibility, being paramagnetic regardless of whether it is iron or cobalt.
Accordingly, removal of the catalyst by way of magnetic separation is very
effective.
Additionally, since a large amount of the FT synthesis catalyst is already
removed by the above-mentioned solid-liquid separator 20, the concentrated
magnetic
particles contained in the wax fraction is removed in the high gradient
magnetic separator
40 at 100 C to 450 C. The step will be described below.
[0027]
The high gradient magnetic separator 40 used in the present invention is a
magnetic separator that is designed to function in the following way. That is,
in the
magnetic separator, a ferromagnetic filling material is disposed in an uniform
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high-magnetic-field space formed by an external electromagnetic coil, and
ferromagnetic or paramagnetic particles are captured to the surface of the
filling material
by a high magnetic-field gradient of 1 to 20k Gauss/cm generated around the
filling
material to separate the particles from the wax fraction, and then, the
captured particles
are washed. For example, as the high gradient magnetic separator, a
commercially-supplied device known as the trademark "FEROSEP" and the like may
be
used.
[0028]
With regard to the ferromagnetic filling material, a ferromagnetic fine-wire
assembly such as steel net or steel wool having a diameter of 1 um to 1,000 um
in
general, expanded metal, and a conchoidal metallic fine piece may be used.
With
regard to a type of the metal, use of stainless steel having excellent
corrosion resistance,
heat resistance, and strength is preferable.
[0029]
Furthermore, use of the ferromagnetic metal piece as proposed in Japanese
Unexamined Patent Application, First Publication No. H07-70568 is also
preferable,
where the ferromagnetic metal piece is formed into a plate having two planes;
the area of
larger plane is equal to an area of a circle having a diameter R of 0.5 mm to
4 mm; the
ratio of R to a maximum thickness d of the plate (R/d) is within a range of 5
to 20; and
the plate is made of a Fe-Cr-based alloy that contains a main component of Fe,
and 5-25
wt% of Cr, 0.5-2 wt% of Si, and 2 wt% or less of C.
[0030]
With regard to the step of separating the magnetic particle from the wax
fraction
in the high gradient magnetic separator 40, the wax fraction is introduced
into the
magnetic-field space inside the high gradient magnetic separator 40, and the
magnetic
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particles are captured to the ferromagnetic filling material disposed in the
magnetic-field
space to remove the magnetic particles from the wax fraction. Then, with
regard to the
step of washing and removing the magnetic particles captured to the filling
material,
since an amount of the magnetic particles captured by a certain surface area
of the filling
material is limited, the captured magnetic particles are removed from the
filling material
by washing when the captured amount reaches a certain amount or the limit
amount
thereof. The washing and removing step may be carried out in such a manner
that the
magnetic field is terminated to release the magnetic particles from the
filling material,
and the magnetic particles are discharged to the outside of the magnetic
separator by use
of washing liquid. Conditions in the magnetic separation of magnetic particles
contained in the wax fraction, and conditions for washing and removing the
magnetic
particles captured (e.g. adhered) onto the filling material will be described
below.
[0031]
With regard to conditions for the magnetic separation in the high gradient
magnetic separator 40, the field intensity may be suitably selected depending
on the
liquid residence time described below, and is not particularly limited.
However, the
magnetic field intensity is preferably 1,500 Gauss or more, more preferably
8,000 Gauss
or more, still more preferably 20,000 Gauss or more, and most preferably
40,000 Gauss
or more. This is because the liquid residence time can be shorten whereby the
separation can be quickly and efficiently conducted. It is preferable that the
upper limit
of the magnetic field intensity is as high as possible. However, the output of
approximately 500,000 Gauss may be the limit in general.
[0032]
In the present invention, it is required for the temperature of the liquid in
the
separator (process temperature) to be 100 C to 450 C. The process temperature
is
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preferably 100 C to 400 C, more preferably 100 C to 300 C, and still more
preferably
100 C to 200 C.
[0033]
The liquid residence time (residence time) may be set depending on the
magnetic field intensity, and is not particularly limited. For example, the
liquid
residence time may be set to three seconds or more, preferably ten seconds or
more, and
more preferably fifty seconds or more. Additionally, the upper limit of the
liquid
residence time may be set to a time when an objective removal rate (% by mass)
of the
magnetic particles is achieved. In general, the upper limit of the liquid
residence time
may be set to, for example, approximately five minutes.
In addition, in the present invention, the "liquid residence time" refers to a
time
obtained by dividing the volume of a filling vessel (which the magnetic field
is applied
to) by the inflow rate of the liquid (e.g. the wax fraction containing
magnetic particles)
which is introduced into the filling vessel. The liquid residence time can be
represented
by the following formula.
The liquid residence time (second) = the volume of a filling vessel which the
magnetic field is applied to (L) / the inflow rate of the wax fraction
containing magnetic
particles (L/second).
[0034]
Next, when operation of the magnetic separation of the magnetic particles is
continuously carried out, the removal rate decreases as the amount of the
magnetic
particles captured by the filling material increases. Therefore, in order to
maintain a
sufficient removal rate, it is required to carry out the washing and removing
step where
the captured magnetic particles are discharged to the outside of the magnetic
separator
after the oil flows through the filling vessel for a predetermined time. In
industrial
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operation, the raw oil fraction containing the magnetic particle may bypass
the high
gradient magnetic separator 40 during the washing and removing step. However,
if the
washing operation requires a longer time, a large amount of the magnetic
particle flows
into the hydrogenation apparatus, and the removal rate decreases. Therefore,
an extra
5 separator (not shown) (i.e. the inflow of the raw oil fraction can be
switched to the extra
separator during the washing operation) may be provided if necessary.
[0035]
In the washing and removing step of the present invention, the processed oil
obtained after the magnetic separation process or the wax cracked produced oil
subjected
10 to the hydrocracking process after the magnetic separation process may
be used as the
washing liquid.
[0036]
The washing and removing step of the present invention can be carried out in
the
following way. That is, the magnetic field generated around the filling
material is
15 eliminated (i.e. the current supply to the magnetic-separation
electromagnetic coil is
terminated), and the washing liquid is introduced to the bottom of the
separator to wash
the magnetic particles captured to the filling material. With regard to
conditions for
washing, the washing-liquid linear velocity may be in a range of 1 cm/sec to
10 cm/sec
and preferably in a range of 2 cm/sec to 6 cm/sec.
[0037]
Hereinafter, the magnetic separation step will be described in more detail
with
reference to FIG. 2.
[0038]
FIG. 2 is a schematic view showing the high gradient magnetic separator 40
used
in the present invention. The high gradient magnetic separator 40 where the
separation is
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conducted is formed into a vertical filling tower, and is filled with the
ferromagnetic
filling material. A filling vessel 41 filled with the filling material is
magnetized by the
magnetic tlux formed with an electromagnetic coil 42 which is disposed outside
the
vertical filling tower, thereby forming a "high gradient magnetic separation
space". The
space corresponds to the uniform high-magnetic-field space formed by the
external
electromagnetic coil. The wax fraction heated to a temperature suitable for
the
operation passes through the separation area from the downside (from the line
31) to the
upside at a predetermined flow rate (preferably, at a flow rate where the
liquid residence
time is within the above-described range), and the magnetic particles are
captured to the
surface of the filling material during the passage of the wax fraction whereby
the
magnetic particles are removed therefrom.
[0039]
While the wax fraction passes through the magnetic separator 40 from the line
31, the washing liquid can bypass via a bypass line for the washing liquid
(not shown).
When the washing liquid is supplied from a line 43 to wash the magnetic
separator 40,
the wax fraction can bypass via a bypass line for the wax fraction (not shown)
to be
directly transferred to the hydrocracking apparatus 50 during the washing
step. The
washing liquid after washing the magnetic separator 40 may be discharged to
the outside
of the system via a line 44. In such a manner, it is possible to carry out
switching
between the removing operation and the washing operation, and the alternative
and
continuous operation. The washing and removing step can be carried out, for
example,
based on the method disclosed in Japanese Unexamined Patent Application, First
Publication No. H06-200260.
[0040]
<Hydrocracking of wax fraction>
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In the hydrocracking apparatus 50, the wax fraction from which the magnetic
particles are removed is hydrocracked. A known fixed-bed reactor may be used
as the
hydrocracking apparatus 50. In this embodiment, the reactor, which is a fixed-
bed
reactor, is filled with a predetermined hydrocracking catalyst, and the wax
fraction is
hydrocracked therein.
[0041]
Examples of the hydrocracking catalyst include a carrier of a solid acid onto
which an active metal belonging to Group VIII in the periodic table is loaded.
[0042]
Preferable examples of such a carrier include a carrier containing a
crystalline
zeolite such as ultra-stable Y type (USY) zeolite, HY zeolite, mordenite, or 3-
zeolite one;
and at least one solid acid selected from amorphous metal oxides having heat
resistance,
such as silica alumina, silica zirconia or alumina boria. Moreover, it is
preferable that
the carrier be a carrier containing USY zeolite; and at least one solid acid
selected from
silica alumina, alumina boria, and silica zirconia. Furthermore, a carrier
containing
USY zeolite and silica alumina is more preferable.
[0043]
USY zeolite is a Y-type zeolite that is ultra-stabilized by way of a
hydrothermal
treatment and/or acid treatment, and fine pores within a range of 20 A to 100
A are
formed in addition to a micro porous structure, which is called micropores of
20 A or less
originally included in Y-type zeolite. When USY zeolite is used for the
carrier of the
hydrocracking catalyst, its average particle diameter is not particularly
limited.
However, the average particle diameter thereof is preferably 1.0 um or less,
or more
preferably 0.5 um or less. In USY zeolite, a molar ratio of silica/alumina
(i.e. molar
ratio of silica to alumina; hereinafter referred to as "silica/alumina ratio")
is preferably
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within a range of 10 to 200, more preferably within a range of 15 to 100, and
the most
preferably within a range of 20 to 60.
[0044]
It is preferable that the carrier include 0.1% to 80% by mass of a crystalline
zeolite and 0.1% to 60% by mass of a heat-resistant amorphous metal oxide.
[0045]
A mixture including the above-mentioned solid acid and a binder may be
subjected to moulding, and the moulded mixture may be calcined to produce the
catalyst
carrier. The blend ratio of the solid acid therein is preferably within a
range of 1% to
70% by mass, or more preferably within a range of 2% to 60% by mass with
respect to
the total amount of the carrier. If the carrier includes USY zeolite, the
blend ratio of
USY zeolite is preferably within a range of 0.1% to 10% by mass, or more
preferably
within a range of 0.5% to 5% by mass to the total amount of the carrier. If
the carrier
includes USY zeolite and alumina-boria, the mixing ratio of USY zeolite to
alumina-boria (USY zeolite/alumina-boria) is preferably within a range of 0.03
to 1
based on a mass ratio. If the carrier includes USY zeolite and silica alumina,
the mixing
ratio of USY zeolite to silica alumina (USY zeolite/silica alumina) is
preferably within a
range of 0.03 to 1 based on a mass ratio.
[0046]
The binder is not particularly limited. However, the binder is preferably
alumina, silica, silica alumina, titania, or magnesia, and is more preferably
alumina.
The blend ratio of the binder is preferably within a range of 20% to 98% by
mass, or
more preferably within a range of 30% to 96% by mass based on the total amount
of the
carrier.
[0047]
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The calcination temperature of the mixture is preferably within a range of 400
C
to 550 C, more preferably within a range of 470 C to 530 C, or particularly
preferably
within a range of 490 C to 530 C.
[0048]
Examples of the group VIII metal include cobalt, nickel, rhodium, palladium,
iridium, platinum and the like. In particular, metal selected from nickel,
palladium and
platinum is preferably used singularly or in combination of two or more kinds.
[0049]
These kinds of metal may be loaded on the above-mentioned carrier according
to a common method such as impregnation, ion exchange or the like. The total
amount
of the loaded metal is not particularly limited. However, the amount of the
loaded metal
is preferably within a range of 0.1% to 3.0% by mass with respect to the
carrier.
[0050]
Hydrocracking the wax fraction may be performed under the following reaction
conditions. That is, the hydrogen partial pressure may be within a range of
0.5 MPa to
12 MPa, or preferably within a range of 1.0 MPa to 5.0 MPa. Liquid hourly
space
velocity (LHSV) of the wax fraction may be within a range of 0.1 h-1 to 10.011-
1, or
preferably within a range of 0.3 h-1 to 3.5 h-1. The hydrogen/oil ratio is not
particularly
limited, but may be within a range of 50 NL/L to 1000 NL/L, preferably within
a range
of 70 NL/L to 800 NL/L.
[0051]
Additionally, in the present description, "LHSV (liquid hourly space
velocity)"
refers to a volume flow rate of feedstock per volume of a catalyst bed filled
with catalyst
under standard conditions (25 C and 101,325 Pa), and the unit "h-1" represents
the
reciprocal of hours. "NL" being the unit of hydrogen capacity in the
hydrogen/oil ratio
CA 02718173 2010-09-07
represents hydrogen volume (L) under normal conditions (0 C and 101,325 Pa).
[0052]
The reaction temperature for hydrocracking (weight average bed temperature of
a catalyst) may be within a range of 180 C to 400 C, preferably within a range
of 200 C
5 to 370 C, more preferably within a range of 250 C to 350 C, particularly
preferably
280 C to 350 C. If the reaction temperature for hydrocracking exceeds 400 C,
not only
may the yield of the middle fraction remarkably decrease, but the product may
also be
colored, thereby limiting use of the product as a fuel base stock.
Accordingly, if such a
problem arises, the reaction temperature can be adjusted to the above-
mentioned
10 temperature range. If the reaction temperature is less than 180 C,
alcohols may be
insufficiently removed, and may remain therein. If such a problem arises, the
reaction
temperature can be adjusted to the above-mentioned temperature range in the
same
manner.
[0053]
15 In the hydrorefining (hydroisomerization) apparatus 52 for the middle
fraction,
the liquid hydrocarbons (mainly having eleven to twenty carbon atoms) of the
middle
fraction having a middle boiling range (i.e. liquid hydrocarbons supplied from
the middle
portion of the first fractionator 30 via the line 32) are hydrorefined
(hydroisomerized) by
use of hydrogen. This hydrorefining reaction is a reaction in which the liquid
20 hydrocarbons are isomerized or hydrogen is added to unsaturated bonds
thereof, thereby
saturating the bonds. As a result, the product containing hydrorefined
hydrocarbons is
brought to the second fractionator 60.
[00541
<Hydroisomerization of middle fraction>
CA 02718173 2010-09-07
21
A known fixed-bed reactor may be used as the hydroisomerizing apparatus 52.
In this embodiment of the present invention, the reactor, which is a fixed-bed
reactor, is
filled with a predetermined hydroisomerizing catalyst, and the middle fraction
obtained
in the first fractionator 30 is hydroisomerized. As used herein, the
hydroisomerization
includes conversion of olefins into paraffins by hydrogen addition and
conversion of
alcohols into paraffins by dehydroxylation in addition to hydroisomerization
of
n-paraffins to iso-paraffins.
[0055]
Examples of the hydroisomerizing catalyst include a carrier of a solid acid
onto
which an active metal belonging to Group VIII in the periodic table is loaded.
[0056]
Preferable examples of such a carrier include a carrier containing one or more
kinds of solid acids which are selected from amorphous metal oxides having
heat
resistance, such as silica alumina, silica zirconium oxide, or alumina-boria.
[0057]
A mixture including the above-mentioned solid acid and a binder may be
subjected to moulding, and the moulded mixture may be calcined to produce the
catalyst
carrier. The blend ratio of the solid acid therein is preferably within a
range of 1% to
70% by mass, or more preferably within a range of 2% to 60% by mass with
respect to
the total amount of the carrier.
[0058]
The binder is not particularly limited. However, the binder is preferably
alumina, silica, silica alumina, titania, or magnesia, and is more preferably
alumina.
The blend ratio of the binder is preferably within a range of 30% to 99% by
mass, or
more preferably within a range of 40% to 98% by mass based on the total amount
of the
CA 02718173 2010-09-07
22
carrier.
[0059]
The calcination temperature of the mixture is preferably within a range of 400
C
to 550 C, more preferably within a range of 470 C to 530 C, or particularly
preferably
within a range of 490 C to 530 C.
[0060]
Examples of the group VIII metal include cobalt, nickel, rhodium, palladium,
iridium, platinum and the like. In particular, metal selected from nickel,
palladium and
platinum is preferably used singularly or in combination of two or more kinds.
[0061]
These kinds of metal may be loaded on the above-mentioned carrier according
to a common method such as impregnation, ion exchange or the like. The total
amount
of the loaded metal is not particularly limited. However, the amount of the
loaded metal
is preferably within a range of OA ()/0 to 3.0% by mass with respect to the
carrier.
[0062]
The hydroisomerization of the middle fraction may be performed under the
following reaction conditions. The hydrogen partial pressure may be within a
range of
0.5 MPa to 12 MPa, or preferably within a range of 1.0 MPa to 5.0 MPa. Liquid
hourly
space velocity (LHSV) of the middle fraction may be within a range of 0.1 11-1
to 10.0
or preferably within a range of 0.3 ICI to 3.5 h'. The hydrogen/oil ratio is
not
particularly limited. However, the hydrogen/oil ratio may be within a range of
50 NL/L
to 1000 NL/L, or preferably within a range of 70 NL/L to 800 NL/L.
[0063]
The reaction temperature for the hydroisomerization may be within a range of
180 C to
CA 02718173 2010-09-07
23
400 C, preferably within a range of 200 C to 370 C, more preferably within a
range of
250 C to 350 C, or particularly within a range of 280 C to 350 C. If the
reaction
temperature exceeds 400 C, a side reaction wherein the middle fraction is
decomposed
into a light fraction may be promoted, whereby yield of the middle fraction
will be
lowered, but also the product may be colored, and use of the middle fraction
as a fuel
base stock may be limited. Accordingly, if such a problem arises, the reaction
temperature can be adjusted to the above-mentioned temperature range. On the
other
hand, if the reaction temperature is less than 180 C, alcohols may be
insufficiently
removed, and remain therein. If such a problem arises, the reaction
temperature can be
adjusted to the above-mentioned temperature range in the same manner.
[0064]
The hydrotreating apparatus 54 for the naphtha fraction hydrotreats the
naphtha
fraction (mainly having ten or less carbon numbers) flowed out from the top of
the first
fractionator 30 by use of hydrogen gas. As a result, the product containing
the
hydrotreated hydrocarbons is brought to a stabilizer 70 for the naphtha
fraction, and the
refined naphtha fraction can be obtained via a line 71 connected to the bottom
thereof
On the other hand, gas mainly containing hydrocarbons having four or less
carbon atoms
is discharged from the top of the stabilizer 70 for the naphtha fraction via a
line 72.
[0065]
Subsequently, the hydrocarbons treated in the hydrocracking apparatus 50 for
the wax fraction are combined with hydrocarbons treated in the
hydroisomerizing
apparatus 52 for the middle fraction as described above, the combined
hydrocarbons are
refined in the second fractionator 60. Consequently, a kerosene fraction
(having a
boiling point in the range of from approximately 150 C to approximately 250 C)
is
CA 02718173 2010-09-07
24
extracted via a line 63, and a gas oil fraction (having a boiling point in the
range of from
approximately 250 C to approximately 350 C) is extracted via a line 62. Each
fraction
may be stored suitably in a storage tank (not shown). The method of mixing the
hydrocarbons treated in the hydrocracking apparatus 50 for the wax fraction
and the
hydrocarbons treated in the hydroisomerizing apparatus 52 for the middle
fraction is not
particularly limited. Tank blending or line blending may be selected. Then, a
light
fraction extracted from the top of the second fractionator 60 is introduced
into the
stabilizer 70 via a line 55.
[0066]
A bottom fraction flowed out from the bottom of the second fractionator 60 is
recycled suitably to the inlet of the hydrocracking apparatus 50 for the wax
fraction via a
line 61 so as to be subjected to the hydrocracking process again, thereby
improving the
yield of the hydrocracked product.
[0067]
In the above-described manner, the naphtha fraction, the kerosene fraction,
and
the gas oil fraction can be produced from the FT synthetic crude oil.
Furthermore, since
the wax fraction inevitably contained in the FT synthetic crude oil is
efficiently cracked
whereby the wax fraction can be converted to the lighter fraction, the yield
can be
remarkably improved.
EXAMPLES
[0068]
Hereinafter, the present invention will be described in more detail with
reference
to Examples. However, the present invention is not limited to Examples.
[0069]
CA 02718173 2010-09-07
<Preparation of catalyst>
(Catalyst A)
Silica alumina (molar ratio of silica/alumina : 14), and an alumina binder
were
mixed and kneaded at a weight ratio of 60 : 40, and the mixture was moulded
into a
5 cylindrical form having a diameter of approximately 1.6 mm and a length
of
approximately 4 mm. Then, this was calcined at 500 C for one hour, thereby
producing
a carrier. The carrier was impregnated with a chloroplatinic acid aqueous
solution to
distribute platinum on the carrier. The impregnated carrier was dried at 120 C
for three
hours, and then, calcined at 500 C for one hour, thereby producing catalyst A.
The
10 amount of platinum loaded on the carrier was 0.8% by mass to the total
amount of the
carrier.
[0070]
(Catalyst B)
USY zeolite (molar ratio of silica/alumina : 37) having an average particle
15 diameter of 1.1 pim, silica alumina (molar ratio of silica/alumina : 14)
and an alumina
binder were mixed and kneaded at a weight ratio of 3 : 57 : 40, and the
mixture was
moulded into a cylindrical form having a diameter of approximately 1.6 mm and
a length
of approximately 4 mm. Then, this was calcined at 500 C for one hour, thereby
producing a carrier. The carrier was impregnated with a chloroplatinic acid
aqueous
20 solution to distribute platinum on the carrier. The impregnated carrier
was dried at
120 C for three hours, and then, calcined at 500 C for one hour, thereby
producing
catalyst B. The amount of platinum loaded on the carrier was 0.8% by mass to
the total
amount of the carrier.
[Example 1]
CA 02718173 2010-09-07
26
[0071]
<Method of producing synthetic fuel>
(Fractionation of FT synthetic crude oil)
In FIG. 1, the produced oil (FT synthetic crude oil) (the content of
hydrocarbons
having a boiling point of approximately 150 C or more was 84% by mass, the
content of
hydrocarbons having a boiling point of approximately 360 C or more was 42% by
mass
where the contents were based on the total amount of the FT synthetic crude
oil (the sum
of hydrocarbons having five or more carbon atoms)) obtained in the FT
synthesis reactor
10, which was a bubble column reactor, was extracted via the line 3.
Subsequently, the
remaining catalyst was removed with the solid-liquid separator 20 using a
filter
according to a conventional method. Since the type of the reactor was a bubble
column
reactor in which cobalt-based catalyst particles freely flowed in the liquid
medium, very
fine catalyst particles form remained therein. Although the remaining catalyst
was not
completely removed, the remaining catalyst was removed to a level at which the
content
of the remaining catalyst did not cause a trouble in the subsequent processes.
[0072]
Subsequently, in the first fractionator 30, the FT synthetic crude oil, from
which
the remaining catalyst was removed, was fractionated into three fractions,
e.g. the
naphtha fraction having a boiling point of approximately less than 150 C, the
middle
fraction having a boiling point in the range of from approximately 150 C to
approximately 350 C, and the wax fraction of the bottom fraction.
The wax fraction extracted from the bottom of the first fractionator 30
contained
impurities. That is, the wax fraction contained 20 mass ppm of the Fischer-
Tropsch
synthesis catalyst (FT catalyst: the cobalt loading amount was 30% by mass
(with respect
CA 02718173 2010-09-07
27
to the catalyst), and an average particle diameter was 10 i_tm) based on the
total amount
of the wax fraction.
[0073]
(Hydroisomerization of middle fraction)
The catalyst A (150 ml) was filled into the hydroisomerizing apparatus 52
which
was a fixed-bed reactor. Then, the middle fraction obtained from the first
fractionator
30 via the line 32 was supplied to the top of the hydroisomerizing reaction
tower
(hydroisomerizing apparatus) 52 at a feed rate of 225 ml/h. In a hydrogen
stream, the
hydrogenation process was carried out in reaction conditions described in
Table 1.
That is, hydrogen was supplied to the top of the hydroisomerizing reactor 52
at
the hydrogen/oil ratio of 338 NL/L with respect to the middle fraction, and
the back
pressure value was adjusted so that the inlet pressure of the hydroisomerizing
reactor 52
was constantly maintained at 3.0 MPa. In such conditions, the hydroisomerizing
reaction was carried out. The reaction temperature was 308 C.
[0074]
(Removal of magnetic particle)
The electromagnetic-type high gradient magnetic separator (FEROSEP
(trademark)) 40 having a structure shown in FIG. 2 was disposed between the
first
fractionator 30 and the hydrocracking apparatus 50. The wax fraction obtained
from the
bottom of the first fractionator 30 via the line 31 was processed under
conditions shown
in Table 2 to remove the magnetic particles. The magnetic particle removal
rate is also
shown in Table 2.
The magnetic particle removal rate refers to a value calculated by the
following
equation based on the magnetic particle density at the inlet of the magnetic
separator
obtained from the measurement results obtained using a laser diffraction
particle size
CA 02718173 2010-09-07
28
analyzer (SALD-3100) manufactured by SHIMADZU Corporation (hereinafter, the
same
applies).
The magnetic particle removal rate (% by mass) = 100 x (the magnetic particle
density at the inlet of the magnetic separator ¨ the magnetic particle density
at the outlet
of the magnetic separator) / the magnetic particle density at the inlet of the
magnetic
separator
[0075]
(Hydrocracking of wax fraction)
The catalyst B (150 ml) is filled into the fixed-bed reactor of the
hydrocracking
apparatus 50,. Subsequently, the wax fraction from which the magnetic particle
was
removed by the electromagnetic-type high gradient magnetic separator (FEROSEP
(trademark)) 40 was supplied to the top of the hydrocracking apparatus 50 at a
feed rate
of 300 ml/h. In a hydrogen stream, the hydrocracking process was carried out
in the
reaction conditions described in Table 1.
[0076]
That is, hydrogen was supplied to the top of the reactor 60 at the
hydrogen/oil
ratio of 676 NL/L with respect to the wax fraction after the magnetic
particles were
removed, and the back pressure value was adjusted so that the inlet pressure
of the
hydrocracking apparatus was constantly maintained at 4.0 MPa. In such
conditions, the
hydrocracking reaction was carried out. The reaction temperature was 329 C.
[0077]
(Fractionation of hydroisomerized product and hydrocracked product)
The hydroisomerized product of the middle fraction (hydroisomerized middle
fraction) and the hydrocracked product (cracked wax fraction) of the wax
fraction
obtained as described above were blended in the line (i.e. line blending). The
mixture
CA 02718173 2010-09-07
29
was introduced into the second fractionator 60, and was fractionated therein.
Subsequently, the diesel fuel base stock was extracted therefrom and was
stored in a tank
(not shown).
[0078]
The bottom component in the second fractionator 60 was continuously recycled
to the inlet of the hydroeracking apparatus 50 via the line 61, and the
recycled component
was hydrocracked again.
Additionally, the top component in the second fractionator 60 was extracted
from the top thereof, and was introduced into the line 55 of the hydrotreating
apparatus
54, and was brought to the stabilizer 70.
[0079]
(Examples 2 to 6)
The treatment with the magnetic separator was carried out with respect to the
wax fraction to produce the synthetic fuel in the same manner as Example 1
except for
the magnetic field intensity and the liquid residence time. The magnetic
particle
removal rate is shown in Table 2.
[0080]
(Comparative Example 1)
The synthetic fuel was produced in the same manner as Example 1 except that
the treatment to the wax fraction using the magnetic separator was not
performed.
[0081]
(Comparative Example 2)
The synthetic fuel was produced in the same manner as Example 1 except that
the temperature in the treatment using the magnetic separation was set to 80
C.
[0082]
CA 02718173 2010-09-07
(Comparative Example 3)
The synthetic fuel was produced in the same manner as Example 1 except that
the temperature in the treatment using the magnetic separation was set to 500
C.
[0083]
5 (Result)
In the Examples 1 to 6 in which the electromagnetic high gradient magnetic
separator was installed between the first fractionator and the hydrocracking
apparatus
whereby the magnetic particles were removed in the range of treatment
temperature of
100 C to 450 C, reduction of the magnetic particles having an adverse
influence on the
10 hydrocracking process could be achieved. In particular, when the
treatment was carried
out in conditions where the magnetic field intensity was 10,000 Gauss or more
and the
liquid residence time was fifteen seconds or more, the magnetic particles
could be
remarkably reduced.
[0084]
15 On the other hand, in the Comparative Example 2 where the treatment
temperature was set to 80 C, the treatment of removing the magnetic particles
could not
be carried out because the wax fraction was coagulated inside the magnetic
separator.
Additionally, in the Comparative Example 3 where the treatment temperature was
set to
500 C, it was impossible to continuously carry out the normal operation due to
20 decomposition or polymerization of the wax fraction.
[0085]
Table 1
COMPARATIVE COMPARATIVE COMPARATIVE
EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4
EXAMPLE 5 EXAMPLE 6
EXAMPLE 1
EXAMPLE 2 EXAMPLE 3
CATALYST CATALYST A 6-- 4-- 4-- 4-
1- 4- 4-- 4--
,
_
LHSV 1-111 1.5
-=
_
REACTION
HYDROISOMERIZINCi C 308 4-- 4-- 4-- 4--
4-- 4--- 4-- 4--
TEMPERATURE
CONDITION FOR ..
HYDROGEN
MIDDLE FRACTION
PARTIAL MPa 3.0 6-- 4--- 6- 4-
4- 4--
PRESSURE
HYDROGEN/OIL
NUL 338 4- 4- 4- 4-
4-
RATIO
CATALYST
,
-
CATALYST CATALYST B 6- 6- 6-
LHSV h-1 2.0 4- 4- 4- 4-
4- 4-
.
n
REACTION 4- 4- 4- 4-
4- 4- 4-
ITYDROCRACKING ' 329
TEMPERATURE C'
CONDITION FOR WAX
o
HYDROGEN 4- 4--- 6-- 6-
4- 4- 4- 4- M
FRACTION
PART/ AL MPa 4.0
-...1
I-.
PRESSURE
co
' C...0 H
HYDROGEN/OIL
NL/L 676
*--= ....]
RATIO
Lo
.
.
IV
0
H
0
0
lO
I
0
...-.1
[0086]
Table 2
MAGNETIC PARTICLE
MAGNETIC FIELD TREATMENT LIQUID RESIDENCE
REMOVAL RATE
INTENSITY (Gauss) TEMPERATURE ( C) TIME (SECONDS)
(mass%)
EXAMPLE 1 50000 150 15
44
EXAMPLE 2 50000 150 60
90
EXAMPLE 3 10000 150 100
54
EXAMPLE 4 25000 150 100
85 n
EXAMPLES 50000 150 5
18 0
.
I.)
EXAMPLE 6 2000 150 100
14 ¨1
1--,
0
COMPARATIVE
H
- - -
0 UJ
EXAMPLE 1
COMPARATIVE
PROCESS COULD NOT H
0
I
50000 80 -
0
EXAMPLE 2
BE CARRIED OUT ko
1
.
0
COMPARATIVE
NORMAL OPERATION ¨1
50000 500 -
EXAMPLE 3
WAS IMPOSSIBLE
CA 02718173 2010-09-07
33
INDUSTRIAL APPLICABILITY
[0087]
The present invention is applicable to production of the fuel oil from the FT
synthetic crude oil obtained by the FT synthesis method using carbon monoxide
and
hydrogen as raw materials.
Accordingly, the present invention has high applicability in industries
including
GTL (Gas to Liquids) and petroleum refinery.
