U.S. patent application number 14/760108 was filed with the patent office on 2015-12-10 for hydrocarbon synthesis reaction apparatus.
The applicant listed for this patent is COSMO OIL CO., LTD., INPEX CORPORATION, JAPAN OIL, GAS AND METALS NATIONAL CORPORATION, JAPAN PETROLEUM EXPLORATION CO., LTD., JX NIPPON OIL & ENERGY CORPORATION, NIPPON STEEL & SUMIKIN ENGINEERING CO., LTD. Invention is credited to Yuzuru KATO, Yuuji MAEDA, Atsushi MURATA, Yasuhiro ONISHI, Eiichi YAMADA.
Application Number | 20150353839 14/760108 |
Document ID | / |
Family ID | 51209599 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150353839 |
Kind Code |
A1 |
MAEDA; Yuuji ; et
al. |
December 10, 2015 |
HYDROCARBON SYNTHESIS REACTION APPARATUS
Abstract
A hydrocarbon synthesis reaction apparatus includes a reactor
bringing synthesis gas into contact with a slurry having a solid
catalyst suspended in liquid hydrocarbons to synthesize
hydrocarbons by the Fischer-Tropsch synthesis reaction; a
cylindrical inner tube having a lower end arranged within the
reactor at a predetermined distance from the bottom thereof; and a
sparger arranged on an inner lower side of the inner tube, which
blows the synthesis gas toward the inside of the inner tube. A
Fischer-Tropsch synthesis reaction region, where the slurry
including bubbles flows out from inside the inner tube through an
upper end thereof, is formed in a space between a virtual extension
portion of the upper end of the inner tube and an inner surface of
the reactor, wherein the slurry is held within the reactor until
the upper end of the inner tube is lower than the liquid level of
the slurry.
Inventors: |
MAEDA; Yuuji; (Tokyo,
JP) ; MURATA; Atsushi; (Tokyo, JP) ; YAMADA;
Eiichi; (Tokyo, JP) ; KATO; Yuzuru; (Tokyo,
JP) ; ONISHI; Yasuhiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JAPAN OIL, GAS AND METALS NATIONAL CORPORATION
INPEX CORPORATION
JX NIPPON OIL & ENERGY CORPORATION
JAPAN PETROLEUM EXPLORATION CO., LTD.
COSMO OIL CO., LTD.
NIPPON STEEL & SUMIKIN ENGINEERING CO., LTD |
Minato-ku, Tokyo
Minato-ku, Tokyo
Chiyoda-ku, Tokyo
Chiyoda-ku, Tokyo
Minato-ku, Tokyo
Shinagawa-ku, Tokyo |
|
JP
JP
JP
JP
JP
JP |
|
|
Family ID: |
51209599 |
Appl. No.: |
14/760108 |
Filed: |
January 15, 2014 |
PCT Filed: |
January 15, 2014 |
PCT NO: |
PCT/JP2014/050542 |
371 Date: |
July 9, 2015 |
Current U.S.
Class: |
422/211 |
Current CPC
Class: |
B01J 2208/0061 20130101;
C10G 2/342 20130101; B01F 3/04517 20130101; B01J 2208/00911
20130101; C10G 2/343 20130101; C10G 2/344 20130101; B01J 8/226
20130101; B01J 2208/00141 20130101; B01J 2208/00539 20130101 |
International
Class: |
C10G 2/00 20060101
C10G002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2013 |
JP |
2013-006566 |
Claims
1. A hydrocarbon synthesis reaction apparatus comprising: a reactor
that brings a synthesis gas including carbon monoxide gas and
hydrogen gas as main components into contact with a slurry having a
solid catalyst suspended in liquid hydrocarbons to synthesize
hydrocarbons by the Fischer-Tropsch synthesis reaction; a
cylindrical inner lube having a lower end arranged within the
reactor at a predetermined distance from the bottom of the reactor;
and a sparger that is arranged on an inner lower side of the inner
tube and blows the synthesis gas toward the inside of the inner
tube, wherein a Fischer-Tropsch synthesis reaction region, to which
the slurry including bubbles flows out from the inside of the inner
tube through an upper end of the inner tube, is formed in a space
between a virtual extension portion of the upper end of the inner
tube and an inner surface of the reactor, in a state where the
slurry is held within the reactor until the upper end of the inner
tube is lower than the liquid level of the slurry.
2. The hydrocarbon synthesis reaction apparatus according to claim
1, wherein the ratio of the diameter of the inner tube to the
diameter of the reactor is 0.6 or more and 0.8 or less.
3. The hydrocarbon synthesis reaction apparatus according to claim
1, wherein when the slurry including bubbles is diffused while
spreading radially outward of the reactor from the upper end of the
inner lube, the height of the upper end of the inner tube is set so
that an intersecting portion between a virtual extension line
defining the diffusion angle of the slurry with respect to a
horizontal surface including an upper end surface of the inner tube
and the inner surface of the reactor is lower than the liquid level
of the slurry.
4. The hydrocarbon synthesis reaction apparatus according to claim
2, wherein when the slurry including bubbles is diffused while
spreading radially outward of the reactor from the upper end of the
inner tube, the height of the upper end of the inner tube is set so
that an intersecting portion between a virtual extension line
defining the diffusion angle of the slurry with respect to a
horizontal surface including an upper end surface of the inner tube
and the inner surface of the reactor is lower than the liquid level
of the slurry.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hydrocarbon synthesis
reaction apparatus.
[0003] Priority is claimed on Japanese Patent Application No.
2013-006566, filed Jan. 17, 2013, the content of which is
incorporated herein by reference.
[0004] 2. Background Art of the Invention
[0005] In recent years, as one of the methods for synthesizing
liquid fuels from natural gas, the GTL (Gas-to-Liquids: liquid fuel
synthesis) technique has been developed. In the GTL technique,
natural gas is reformed to produce synthesis gas including carbon
monoxide gas (CO) and hydrogen gas (H.sub.2) as main components,
hydrocarbons are synthesized by the Fischer-Tropsch synthesis
reaction (hereinafter referred to as "FT synthesis reaction") with
a catalyst using the synthesis gas as a feedstock, and the
hydrocarbons are hydrogenated and fractionated to produce liquid
fuel products, such as naphtha (raw gasoline), kerosene, gas oil,
and wax.
[0006] In hydrocarbon synthesis reaction apparatuses for the FT
synthesis reaction used for this GTL technique, hydrocarbons are
synthesized by performing the FT synthesis reaction on the carbon
monoxide gas and the hydrogen gas in the synthesis gas inside a
bubble column slurry bed reactor in which a slurry having solid
catalyst particles suspended in a liquid medium are held. In that
case, as the hydrocarbon synthesis reaction apparatuses, upflow
types in which the synthesis gas that is a feedstock is introduced
from a lower portion of the reactor are used.
[0007] The synthesis gas ascends within the reactor as bubbles, the
slurry is stirred by the ascent energy of the bubbles and the mixed
and flowing state of the slurry is maintained. In order to continue
the FT synthesis reaction properly and stably, the reaction
pressure is set to a pressure higher than the normal pressure, and
the reaction temperature is set to a temperature higher than the
normal temperature.
[0008] In the related art, generally, a method of blowing synthesis
gas from the entire bottom surface of the reactor for the purpose
of uniformly distributing the catalyst of the reactor is taken as a
method of blowing the synthesis gas toward the slurry within the
reactor. However, if the reactor is made large and the amount of
the catalyst increases, a problem occurs in that a drift is
generated in the flow of the slurry or a part of the catalyst
stagnates, and the slurry cannot be stirred well.
[0009] In order to prevent stagnation from occurring and to stir
the slurry well, it is effective to separately provide an upward
flow near the center of the reactor and a downward flow near the
outer side of the reactor.
[0010] For this reason, the following Patent Document 1 or 2
suggests that upward and downward flows of slurry within a reactor
are clearly classified by arranging a draft tube coaxially with the
reactor within the reactor, using the inside of the draft tube as a
space for upward flow of the slurry and using a space between the
reactor and the draft tube as a space for downward flow of the
slurry.
PRIOR ART DOCUMENT
Patent Document
[0011] Patent Document 1: PCT International Publication No.
WO94/15160 [0012] Patent Document 2: PCT International Publication
No. WO99/000191
SUMMARY OF THE INVENTION
Technical Problem
[0013] In the aforementioned related-art, the draft tube is
arranged so that an upper end thereof extends to the liquid level
of the slurry. Thus, a region where the synthesis gas supplied from
the lower side of the draft tube comes into contact with the
slurry, that is, a region where the FT synthesis reaction occurs is
limited to an inner region of the draft tube. For this reason,
although the slurry can be stirred well, the region where the FT
synthesis reaction occurs becomes narrow. As a result, in order to
widely secure the region where the FT synthesis reaction occurs as
desired, the diameter of the reactor needs to be large. That is,
the reactor needs to be made large.
[0014] The invention has been made in view of the above situation,
and an object of the invention is to provide a hydrocarbon
synthesis reaction apparatus that can stir a slurry well and can
widely secure a region where the Fischer-Tropsch synthesis reaction
occurs without increasing the size of a reactor.
Solution to Problem
[0015] The hydrocarbon synthesis reaction apparatus of the
invention includes a reactor that brings a synthesis gas including
carbon monoxide gas and hydrogen gas as main components into
contact with a slurry having a solid catalyst suspended in liquid
hydrocarbons to synthesize hydrocarbons by the Fischer-Tropsch
synthesis reaction; a cylindrical inner tube having a lower end
arranged within the reactor at a predetermined distance from the
bottom of the reactor; and a sparger that is arranged on an inner
lower side of the inner tube and blows the synthesis gas toward the
inside of the inner tube. A Fischer-Tropsch synthesis reaction
region, to which the slurry including bubbles flows out from the
inside of the inner tube through an upper end of the inner tube, is
formed in a space between a virtual extension portion of the upper
end of the inner tube and an inner surface of the reactor, in a
state where the slurry is held within the reactor until the upper
end of the inner tube is lower than the liquid level of the
slurry.
[0016] In the invention, the synthesis gas is jetted from the
sparger that is arranged only on the inner lower side of the inner
tube that is a part of the bottom of the reactor instead of the
whole region of bottom of the reactor. Since the jetted synthesis
gas is mixed with the slurry within the inner tube, and this mixed
fluid has low specific gravity compared to the slurry that does not
include bubbles, the mixed fluid forms an upward flow within the
inner tube. When the ascending mixed fluid reaches the liquid level
of the slurry, most bubbles escape from the mixed fluid. The mixed
fluid from which most bubbles have escaped has almost the same
specific gravity as that of the slurry that does not include
bubbles. As a result, the mixed fluid forms a downward flow that is
directed downward outside the inner tube, that is, at a position
near the inner surface of the reactor.
[0017] In this way, a circulatory flow including the upward flow at
a center position of the reactor and the downward flow at the
position near the inner surface of the reactor is formed within the
reactor. This circulatory flow becomes a stronger flow than that in
the whole surface blowoff of jetting the synthesis gas from the
whole region of the bottom of the reactor. The slurry can be
stirred well by this strong circulatory flow. Additionally, when
the mixed fluid including bubbles flows further upward from the
upper end of the inner tube, the mixed fluid ascends while being
diffused radially outward of the reactor. The mixed fluid diffused
radially outward of the reactor is reversed in flow and flows
downward without reaching the liquid level of the slurry, since the
mixed fluid is caught in the downward flow outside the inner tube.
That is, the slurry including bubbles flows out from the inside of
the inner tube to the space between the virtual extension portion
of the upper end of the inner tube and the inner surface of the
reactor through the upper end of the inner tube, whereby this
region also becomes a Fischer-Tropsch synthesis reaction
region.
[0018] That is, the region where the Fischer-Tropsch synthesis
reaction occurs is formed not only on the inside of the inner tube
but also on the outside of the inner tube. As a result, the slurry
can be stirred well, and the enough region where the
Fischer-Tropsch synthesis reaction occurs can be reliably secured
without making the reactor larger.
[0019] Additionally, in the above hydrocarbon synthesis reaction
apparatus, it is preferable that the ratio of the diameter of the
inner tube to the diameter of the reactor be 0.6 or more and 0.8 or
less.
[0020] In this case, the downward flow that is formed outside the
inner tube and mainly formed by the slurry can be secured well.
[0021] That is, if the ratio of the diameter of the inner tube to
the diameter of the reactor is 0.6 or more and 0.8 or less, the
sectional area of a slurry downward flow region formed between the
outer surface of the inner tube and the inner surface of the
reactor is equal to or more than a predetermined value. Thereby,
the slurry downward flow is secured well in this portion. As a
result, the upward flow of the mixed fluid that is formed inside
the inner tube and includes slurry and bubbles balances well with
the downward flow that is formed outside the inner tube and formed
mainly by the slurry. Consequently, a strong circulatory flow of
the slurry including bubbles can be obtained.
[0022] If the ratio of the diameter of the inner tube to the
diameter of the reactor becomes less than 0.6, since the sectional
area inside the inner tube becomes substantially smaller than the
sectional area between the inner tube and the inner surface of the
reactor, the flow rate itself of the upward flow inside the inner
tube decreases. Additionally, the arrangement area of the sparger
which is set within the inner tube also becomes small. If the
synthesis gas is jetted from the sparger in a predetermined amount
when the arrangement area becomes small in this way, the flow
velocity of the synthesis gas jetted increases, and along with
this, the flow velocity of the mixed fluid of the synthesis gas and
the slurry within the inner tube also increases. As a result, the
pressure loss of the mixed fluid that flows within the inner tube
increases, and the catalyst included in the mixed fluid is easily
damaged.
[0023] On the other hand, if the ratio of the diameter of the inner
tube to the diameter of the reactor exceeds 0.8, the sectional area
of a slurry downward flow region formed between the outer surface
of the inner tube and the inner surface of the reactor becomes too
narrow. As a result, since the circulation flow rate of the slurry
within the reactor decreases, it is difficult for the slurry to be
stirred well. Additionally, as the flow velocity of the slurry
downward flow increases, the flow path resistance of this slurry
downward flow increases, and consequently, the catalyst included in
the slurry is easily damaged.
[0024] Additionally, in the aforementioned hydrocarbon synthesis
reaction apparatus, preferably, when the slurry including bubbles
is diffused while spreading radially outward of the reactor from
the upper end of the inner tube, the height of the upper end of the
inner tube is set so that an intersecting portion between a virtual
extension line defining the diffusion angle of the slurry with
respect to a horizontal surface including an upper end surface of
the inner tube and the inner surface of the reactor is lower than
the liquid level of the slurry.
[0025] In this case, when the mixed fluid including bubbles flows
further upward from the upper end of the inner tube, the mixed
fluid is diffused radially outward of the reactor. Here, the height
of the upper end of the inner tube is set so that the intersecting
portion between the virtual extension line of the diffusion angle
of the slurry and the inner surface of the reactor is lower than
the liquid level of the slurry. Therefore, when the aforementioned
mixed fluid including bubbles ascends while being diffused radially
outward of the reactor from the upper end of the inner tube, a
portion of the mixed fluid reaches the inner periphery of the
reactor without reaching the liquid level of the slurry. That is, a
part of the mixed fluid flows downward along the downward flow of
the slurry while including bubbles, without reaching the liquid
level of the slurry.
[0026] As a result, the region where the slurry including bubbles
is present, that is, the region where the Fischer-Tropsch synthesis
reaction occurs can be more widely secured.
Advantageous Effects of the Invention
[0027] According to the hydrocarbon synthesis reaction apparatus of
the invention, the slurry can be stirred well, and the region where
the Fischer-Tropsch synthesis reaction occurs can be widely secured
without making the reactor larger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a system diagram showing an overall configuration
of a liquid fuel-synthesizing system including one embodiment of a
hydrocarbon synthesis reaction apparatus related to the
invention.
[0029] FIG. 2 is a schematic configuration view of a
hydrocarbon-synthesizing reactor.
[0030] FIG. 3A is an action explanatory view showing the flow state
of a slurry within the hydrocarbon-synthesizing reactor of the
invention.
[0031] FIG. 3B is an action explanatory view showing the flow state
of a slurry within a hydrocarbon-synthesizing reactor of the
related art.
[0032] FIG. 4A is an action explanatory view showing the flow state
of the slurry within the hydrocarbon-synthesizing reactor of the
invention.
[0033] FIG. 4B is an action explanatory view of a case where
synthesis gas is jetted from a whole region of the bottom of a
hydrocarbon-synthesizing reactor that does not have an inner
tube.
[0034] FIG. 4C is an action explanatory view of a case where
synthesis gas is jetted from the center of the bottom of the
hydrocarbon-synthesizing reactor that does not have the inner
tube.
[0035] FIG. 5 is a graph obtained by comparing the ascent
velocities of the slurries of middle portions in the respective
hydrocarbon-synthesizing reactors shown in FIGS. 4A to 4C with each
other.
[0036] FIG. 6 is a graph showing changes in the circulation flow
rate of the slurry at the middle portion when the diameter of the
inner tube is changed in the hydrocarbon-synthesizing reactor shown
in FIG. 4A.
[0037] FIG. 7 is a graph showing changes in the flow velocity of
the slurry flowing outside the inner tube when the diameter of the
inner tube is changed in the hydrocarbon-synthesizing reactor shown
in FIG. 4A.
[0038] FIG. 8 is a graph showing pressure losses while the slurry
flowing outside the inner tube when the diameter of the inner tube
is changed in the hydrocarbon-synthesizing reactor shown in FIG.
4A.
[0039] FIG. 9 is a graph showing pressure losses while the slurry
flowing inside the inner tube when the diameter of the inner tube
is changed in the hydrocarbon-synthesizing reactor shown in FIG.
4A.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Hereinafter, a hydrocarbon synthesis reaction apparatus of
the present invention will be described in detail.
[0041] First, a liquid fuel-synthesizing system including an
embodiment of the hydrocarbon synthesis reaction apparatus of the
invention will be described with reference to FIG. 1.
[0042] A liquid fuel-synthesizing system 1 shown in FIG. 1 is a
plant facility that executes a GTL process that converts
hydrocarbon feedstock, such as natural gas, into liquid fuel.
[0043] The liquid fuel-synthesizing system 1 includes a synthesis
gas production unit 3, an FT synthesis unit 5, and an upgrading
unit 7. In the synthesis gas production unit 3, natural gas, which
is a hydrocarbon feedstock, is reformed to produce synthesis gas
including carbon monoxide gas and hydrogen gas. In the FT synthesis
unit 5, liquid hydrocarbons are synthesized by the FT synthesis
reaction from the synthesis gas produced in the synthesis gas
production unit 3. In the upgrading unit 7, the liquid hydrocarbons
synthesized by the FT synthesis reaction are hydrogenated and
fractionated to produce base materials of liquid fuel (mainly
kerosene and gas oil).
[0044] Hereinafter, constituent elements of these respective units
will be described.
[0045] The synthesis gas production unit 3 mainly includes, for
example, a desulfurization reactor 10, a reformer 12, a waste heat
boiler 14, vapor-liquid separators 16 and 18, a CO.sub.2 removal
unit 20, and a hydrogen separator 26. The desulfurization reactor
10 is constituted by a hydrodesulfurizer or the like. In the
desulfurization reactor 10, a sulfur compound is removed from
natural gas as a feedstock. In the reformer 12, the natural gas
supplied from the desulfurization reactor 10 is reformed to produce
synthesis gas including carbon monoxide gas (CO) and hydrogen gas
(H.sub.2) as main components. In the waste heat boiler 14, waste
heat of the synthesis gas produced by the reformer 12 is recovered
to produce high-pressure steam.
[0046] In the vapor-liquid separator 16, the water heated by heat
exchange with the synthesis gas in the waste heat boiler 14 is
separated into gas (high-pressure steam) and liquid. In the
vapor-liquid separator 18, a condensed component is removed from
the synthesis gas cooled in the waste heat boiler 14, and a gas
component is supplied to the CO.sub.2 removal unit 20. The CO.sub.2
removal unit 20 has an absorption tower 22 in which carbon dioxide
gas is removed by using an absorbent from the synthesis gas
supplied from the vapor-liquid separator 18, and a regeneration
tower 24 in which the carbon dioxide gas is stripped from the
absorbent including the carbon dioxide gas to regenerate the
absorbent. In the hydrogen separator 26, a portion of the hydrogen
gas included in the synthesis gas is separated from the synthesis
gas from which the carbon dioxide gas has been separated by the
CO.sub.2 removal unit 20. It should be noted here that it is not
necessary for the CO.sub.2 removal unit 20 to be provided and is
dependent on circumstances.
[0047] In the reformer 12, natural gas is reformed by using carbon
dioxide gas and steam to produce high-temperature synthesis gas
including carbon monoxide gas and hydrogen gas as main components,
for example, by a steam and carbon-dioxide-gas-reforming method
expressed by the following chemical reaction Formula (1) and (2).
The reforming method in the reformer 12 is not limited to the
example of the steam and carbon-dioxide-gas-reforming method. For
example, a steam-reforming method, a partial oxidation-reforming
method (POX) using oxygen, an auto-thermal-reforming method (ATR)
that is a combination of the partial oxidation-reforming method and
the steam-reforming method, the carbon dioxide gas-reforming
method, and the like can also be utilized.
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2 (1)
CH.sub.4CO.sub.22CO+2H.sub.2 (2)
[0048] The hydrogen separator 26 is provided on a branch line
branching from a main line that connects the CO.sub.2 removal unit
20 or the vapor-liquid separator 18 with a hydrocarbon-synthesizing
reactor 30. Here, the hydrocarbon-synthesizing reactor 30 serves as
the embodiment of the invention, and is a bubble column slurry bed
reactor. The details of the hydrocarbon-synthesizing reactor will
be described below.
[0049] The hydrogen separator 26 can be constituted by, for
example, a hydrogen PSA (Pressure Swing Adsorption) device that
perform adsorption and desorption of hydrogen by using a pressure
difference. The hydrogen PSA device has adsorbents (zeolitic
adsorbent, activated carbon, alumina, silica gel, or the like)
within a plurality of adsorption columns (not shown) that are
arranged in parallel. By sequentially repeating respective
processes including pressurizing, adsorption, desorption
(depressurizing), and purging of hydrogen in each of the adsorption
columns, high-purity hydrogen gas (for example, about 99.999%)
separated from the synthesis gas can be continuously supplied to
various hydrogen-utilizing reaction devices (for example, the
desulfurization reactor 10, a wax fraction-hydrocracking reactor
50, a middle distillate-hydrotreating reactor 52, a naphtha
fraction-hydrotreating reactor 54, and the like) in which
predetermined reactions are performed using hydrogen.
[0050] The hydrogen gas-separating method in the hydrogen separator
26 is not limited to the example of the pressure swing adsorption
method as in the above hydrogen PSA device. For example, a hydrogen
storing alloy adsorption method, a membrane separation method, or a
combination thereof may also be used.
[0051] Next, the FT synthesis unit (hydrocarbon synthesis reaction
apparatus) 5 that is the embodiment of the invention will be
described. As shown in FIG. 1, FT synthesis unit 5 mainly includes
the hydrocarbon-synthesizing reactor 30, a vapor-liquid separator
34, a catalyst separator 36, a vapor-liquid separator 38, and a
first fractionator 40.
[0052] The hydrocarbon-synthesizing reactor 30 (hereinafter may be
referred to as "reactor 30"), which is a bubble column slurry bed
reactor that synthesizes liquid hydrocarbons from synthesis gas,
functions as a FT synthesis reactor that synthesizes liquid
hydrocarbons from synthesis gas by the FT synthesis reaction.
[0053] The reactor 30 mainly includes a cooling line 81, and an
inner tube 82 arranged within a reactor main body 80, and is
operated under the condition that the internal temperature thereof
is maintained at, for example, about 190 to 270.degree. C. and the
pressure thereof is higher than the atmospheric pressure. The
reactor 30 is a substantially cylindrical metallic vessel.
[0054] A slurry having solid catalyst particles suspended in liquid
hydrocarbons (product of the FT synthesis reaction) is held inside
the reactor 30, and a slurry bed is formed of this slurry.
[0055] In a lower portion of the reactor 30, the synthesis gas
including hydrogen gas and carbon monoxide gas as main components
is jetted into the slurry from a sparger 83 arranged on the inner
lower side of the inner tube 82. Then, the synthesis gas blown into
the slurry is turned into bubbles, and ascends upward from below in
the height direction (vertical direction) of the reactor 30 through
the slurry within the inner tube 82. In such a process, the
synthesis gas is dissolved in the liquid hydrocarbons and brought
into contact with the catalyst particles, whereby a synthesis
reaction (FT synthesis reaction) of the liquid hydrocarbons
proceeds. Specifically, as shown in the following chemical reaction
Formula (3), the hydrogen gas and the carbon monoxide gas react
with each other to produce hydrocarbons.
2nH.sub.2nCO.fwdarw.--(CH.sub.2).sub.n--+nH.sub.2O (3)
[0056] Additionally, the synthesis gas ascends within the inner
tube 82 as bubbles, whereby an upward flow (air lift) of the slurry
is generated inside the reactor 30. That is, the slurry flows from
the lower portion of the reactor 30 to an upper portion of the
reactor 30 at a center portion (specifically, an inner side of the
inner tube 82) of the reactor 30 and flows from the upper portion
of the reactor 30 to the lower portion of the reactor 30 at an
outer side of the inner tube 82. As a result, the circulatory flow
of the slurry is generated inside the reactor 30.
[0057] In addition, a gaseous phase portion is provided at an upper
portion of the slurry held within the reactor 30, and vapor-liquid
separation is performed at an interface between this gaseous phase
portion and the slurry. That is, the synthesis gas, which has
passed through the interface between the slurry and the gaseous
phase portion without reacting in the slurry, and the gaseous
hydrocarbons, which are produced by the FT synthesis reaction and
are relatively light under the conditions within the reactor 30,
move to the gaseous phase portion as gas components. At this time,
droplets accompanying the gas components and the catalyst particles
accompanying the droplets are returned to the slurry due to
gravity. Then, the gas components (the unreacted synthesis gas and
the light hydrocarbons) that have ascended to the gaseous phase
portion of the reactor 30 are extracted via a conduit connected to
the gaseous phase portion (upper portion) of the reactor 30, and
then discharged from the reactor 30. The gas component discharged
from the reactor is supplied to the vapor-liquid separator 38 after
being cooled, as will be described below.
[0058] The cooling line 81 is installed inside the reactor 30 to
maintain the temperature within the system at a predetermined
temperature by removing the reaction heat generated by the FT
synthesis reaction throughout. In the present embodiment, a cooling
section 81A is configured by a bundle (cooling line bundle) which
is formed by tubes of the cooling line 81. This bundle has a
structure formed so that, for example, one pipe is bent and runs up
and down multiple times along the vertical direction. One or a
plurality of the cooling sections 81A made of such bundles are
arranged at predetermined intervals in the vertical direction
(height direction) within the reactor 30.
[0059] In such a cooling section 81A, the cooling line 81 (bundle)
is connected to the vapor-liquid separator 34 shown in FIG. 1 so
that cooling water (for example, water whose difference from the
temperature within the reactor 30 is about -50 to 0.degree. C.)
supplied from the vapor-liquid separator 34 flows therethrough.
[0060] As the cooling water and the slurry exchange heat with each
other via the wall of the cooling line 81 while the cooling water
flows within the cooling line 81 of the cooling sections 81A, the
slurry inside the reactor 30 is cooled down. A portion of the
cooling water becomes steam, is discharged to the vapor-liquid
separator 34, and is recovered as middle-pressure steam.
[0061] A medium for cooling down the slurry within the reactor 30
is not limited to the above cooling water. For example,
straight-chain, branched-chain, and annular alkanes of C.sub.4 to
C.sub.10, olefin, low-molecular-weight silane, silyl ether, silicon
oil, or the like can be used.
[0062] In the vapor-liquid separator 34, the water heated by
flowing through the cooling line 81 of the cooling section 81A
disposed within the reactor 30 as described above is separated into
steam (medium-pressure steam) and liquid. The liquid separated in
the vapor-liquid separator 34 is supplied again to the cooling line
81 as the cooling water as mentioned above.
[0063] Although the catalyst that constitutes the slurry held in a
reactor 30 is not particularly limited, a solid particulate
catalyst in which at least one kind of active metal selected from
cobalt, ruthenium, iron, and the like is supported on a carrier
made of inorganic oxides, such as silica or alumina, can be
preferably used. This catalyst may have a metal component, such as
zirconium, titanium, hafnium, or rhenium, which is added for the
purpose of, for example, enhancing the activity of the catalyst,
other than the active metal. Although the shape of this catalyst is
not particularly limited, a substantially spherical shape is
preferable from the viewpoint of the flowability of the slurry and
from the viewpoint of preventing the catalyst particles from
collapsing and wearing thereby pulverizing catalyst particles, due
to collision or friction between the catalyst particles or between
the catalyst particles and the inner wall of the reactor 30, the
cooling line 81, or the like.
[0064] Additionally, although the average particle diameter of the
catalyst particles is not particularly limited, it is preferable
from the viewpoint of the flowability of the slurry that the
average particle diameter be about 40 to 150 .mu.m.
[0065] Such a slurry, as shown in FIG. 2, generates an upward flow
UF that flows from the lower portion of the reactor 30 to the upper
portion of the reactor 30 at the center portion (the inner side of
the inner tube 82) of the reactor 30, and a downward flow DF that
flows from the upper portion of the reactor 30 to the lower portion
of the reactor 30 at the outer side of the inner tube 82. By
generating such an upward flow UF and a downward flow DF, the
circulatory flow is generated inside the reactor 30 as described
above. In this circulatory flow, large flow velocity thereof is
preferable, because the larger the velocity is, the better the
slurry can be stirred. It is to be noted herein that the velocity
is suffiecienfly large that powdering of the catalyst can
proceed.
[0066] In the present embodiment, in order to increase the flow
velocity of the circulatory flow of the slurry, the inner tube 82
is arranged within the reactor 30 so as to be immersed in the
slurry and so as to be in a range from the bottom of the reactor 30
to the position of a middle portion of the reactor 30. Moreover,
the sparger 83 is arranged only on an inner lower side of the inner
tube 82.
[0067] The inner tube 82 has a cylindrical tube made of metal,
ceramics, or the like, and is arranged at the center portion of the
reactor 30 with upper and lower opening portions turned in the
vertical direction (up-and-down direction) so that the central axis
thereof coincides with the central axis of the reactor 30.
Additionally, the inner tube 82 is arranged so that a lower end
thereof has a predetermined gap from the bottom of the reactor main
body. As a result, the upward flow of the slurry including bubbles
formed as the synthesis gas is supplied from the sparger 83 mainly
flows inside the inner tube 82, and the downward flow of the slurry
mainly flows outside the inner tube 82. In addition, the position
of the inner tube 82 is fixed by a fixing member (not shown) so as
to prevent the position of the inner tube 82 from changing due to
the flow of the slurry.
[0068] It is preferable that the height of an upper end of the
inner tube 82 be higher than the liquid level of the slurry in
order to secure the upward flow UF flowing from the lower portion
of the reactor 30 to the upper portion of the reactor 30 well. In
this case, however, a region where the synthesis gas comes into
contact with the slurry, that is, a region where the FT synthesis
reaction occurs is limited to an inner region of the inner tube 82,
and consequently, the region F where the FT synthesis reaction
occurs is narrowed (refer to FIG. 3B).
[0069] Thus, in this embodiment, as shown in FIG. 3A, when the
slurry including bubbles is diffused while spreading radially
outward of the reactor 30 from the upper end of the inner tube 82,
the height of the upper end of the inner tube 82 is set so that an
intersecting portion between a virtual extension line La defining
the diffusion angle .theta. of the slurry with respect to a
horizontal surface H including an upper end surface of the inner
tube 82 and an inner surface of the reactor main body 80 is lower
than the liquid level S of the slurry. As a result, a
Fischer-Tropsch synthesis reaction region F, to which the slurry
including bubbles flows out from the inside of the inner tube 82
through the upper end thereof, is also formed in a space K between
a virtual extension portion Lb of the upper end of the inner tube
82 and the inner surface of the reactor main body 80.
[0070] Additionally, it is preferable that the height of the upper
end of the inner tube 82 be lower than the cooling section 81A in
order to avoid interference with the cooling section 81A comprising
the cooling line bundle.
[0071] Here, although the diffusion angle .theta. of the slurry
also changes depending on the type of the catalyst, the temperature
of the slurry, and the amount of the bubbles, the diffusion angle
.theta. is within a range of about
60.degree.<.theta.<80.degree. during normal operation.
[0072] Generally, in this type of reactor 30, the movement section,
through which the bubbles introduced into the reactor by the
sparger 83 have moved until the bubbles reach a predetermined
height, is referred to as a run-up section which is necessary until
the behavior of the bubbles is stabilized, and in which the flow of
the slurry is also unstable. If the apparatus is large, this run-up
section is estimated to be about 1 m. Early stabilization of the
flow of the slurry can be achieved by surrounding this run-up
section with the inner tube 82 and by accelerating the flow of the
slurry accompanying the ascent of the bubbles. Accordingly, at
least about 1 m in length is required for the length L of the inner
tube 82.
[0073] Additionally, it is necessary to secure a flow way, through
which the slurry can descend within the reactor 30, outside the
inner tube 82. If the ratio of the internal diameter Ra of the
inner tube 82 to the internal diameter Rb of the reactor 30
approaches 1.0, the sectional area of a flow way through which the
slurry can descend and which is formed between an inner wall
surface of the reactor 30 and an outer surface of the inner tube 82
becomes too narrow. For this reason, it is preferable that the
ratio of internal diameter Ra of an inner tube 82 to the internal
diameter Rb of the reactor 30 be equal to or less than 0.8.
Additionally, it is necessary that the lower limit of this ratio be
about 0.6. It is more preferable that the ratio be set to a range
of 0.65 or more and 0.75 or less. By setting the ratio to such a
range, the opening area of the inner tube 82 can be almost equal to
the sectional area outside the inner tube 82, that is, the
sectional area between the inner wall surface of the reactor 30 and
the outer surface of the inner tube 82.
[0074] In a state where the upward flow (UF) of the slurry that
ascends within the inner tube 82 and the downward flow (DF) of the
slurry that descends outside the inner tube 82 are almost equal to
each other in the aforementioned way, a large disturbance (bias)
does not occur in the circulatory flow formed within the reactor
30, and the circulatory flow is stabilized. Additionally, in the
slurry that ascends within the inner tube 82, the flow of the
slurry and the flow of gas (bubbles) can be sufficiently
accelerated. Accordingly, the slurry in the reactor 30 can be
stirred well.
[0075] FIG. 6 is a graph showing changes in the flow rate of the
slurry of the middle portion when the diameter of the inner tube is
changed in the hydrocarbon-synthesizing reactor shown in FIG. 4A,
and showing changes when the slurry circulation flow rate is 1 in a
case where the ratio is 0.7.
[0076] As can be understood from the aforementioned drawing, the
circulation flow rate of slurry decreases greatly if the ratio is
more than 0.8 since the flow way through which the slurry can
descend cannot be sufficiently secured outside the inner tube 82.
Along with this, a large disturbance (bias) may also occur in the
circulatory flow of the slurry.
[0077] FIG. 7 is a graph showing changes in the flow velocity of
the slurry flowing outside the inner tube when the diameter of the
inner tube is changed in the hydrocarbon-synthesizing reactor shown
in FIG. 4A. FIG. 8 is a graph showing pressure losses while the
slurry flowing outside the inner tube when the diameter of the
inner tube is changed in the hydrocarbon-synthesizing reactor shown
in FIG. 4A. FIG. 9 is a graph showing pressure losses while the
slurry flowing inside the inner tube when the diameter of the inner
tube is changed in the hydrocarbon-synthesizing reactor shown in
FIG. 4A.
[0078] As shown in FIG. 7, if the ratio exceeds 0.8, the flow
velocity of the downward flow DF of the slurry outside the inner
tube 82 increases. Along with this, as shown in FIG. 8, the
pressure loss of the slurry that flows outside the inner tube 82
increases rapidly, and the catalyst included in the slurry becomes
prone to be damaged.
[0079] In addition, if the ratio becomes smaller than 0.6, since it
is difficult to introduce the gas in the slurry ascending within
the reactor 30 into (flow into) a lower opening portion 82A of the
inner tube 82, the flow rate of the upward flow UF of the slurry
decreases. Additionally, although the sparger 83 is set within the
inner tube 82, the arrangement area of the sparger 83 is small. If
the synthesis gas is jetted from the sparger 83 in a predetermined
amount (a certain amount) when the arrangement area becomes small
in this way, the flow velocity of the synthesis gas jetted
increases, and along with this, the flow velocity of the mixed
fluid of the synthesis gas and the slurry within the inner tube 82
also increases. Moreover, the upward flow of the slurry is
increased rapidly after reaching the upper end of the inner tube
82.
[0080] As a result, since the pressure loss of the mixed fluid that
flows within the inner tube 82 increases rapidly as shown in FIG.
9, it becomes easier for the catalyst included in the mixed fluid
to be damaged.
[0081] As shown in FIG. 1, in the catalyst separator 36, slurry is
separated into a solid component, such as catalyst particles, and a
liquid component including liquid hydrocarbons. A part of the solid
component separated, such as catalyst particles, is returned to the
hydrocarbon-synthesizing reactor 30, and the liquid component is
supplied to the first fractionator 40. Additionally, FT gas
components including unreacted synthesis gas (source gas) and a gas
component of synthesized hydrocarbons are discharged from the top
of the hydrocarbon-synthesizing reactor 30, and then are supplied
to the vapor-liquid separator 38.
[0082] In the vapor-liquid separator 38, the FT gas components are
cooled to separate liquid hydrocarbons (light FT hydrocarbons)
which are a part of the condensed component, and the separated
hydrocarbons are introduced to the first fractionator 40. On the
other hand, the gas component separated in the vapor-liquid
separator 38 includes the unreacted synthesis gas (CO and H.sub.2)
and the hydrocarbons with a carbon number of 2 or less as main
components. Apart of the gas component is introduced again into the
bottom of the hydrocarbon-synthesizing reactor 30 to be reused for
the FT synthesis reaction.
[0083] Additionally, the gas component that is not reused for the
FT synthesis reaction is discharged to an off-gas side. Then, the
discharged gas component is used as fuel gas, fuel equivalent to
LPG (liquefied petroleum gas) is recovered therefrom, or the
discharged gas component is reused for the feedstock of the
reformer 12 of a synthesis gas production unit 3.
[0084] In the first fractionator 40, the liquid hydrocarbons, which
are supplied via the catalyst separator 36 and the vapor-liquid
separator 38 from the hydrocarbon-synthesizing reactor 30, are
fractionally distilled into a naphtha fraction (with a boiling
point that is lower than about 150.degree. C.), a middle distillate
(with a boiling point that is about 150 to 360.degree. C.)
equivalent to kerosene and gas oil, and a wax fraction (with a
boiling point that is higher than about 360.degree. C.).
[0085] The liquid hydrocarbons of the wax fraction (mainly C.sub.21
or more) discharged from the bottom of the first fractionator 40
are introduced into the wax fraction-hydrocracking reactor 50 of
the upgrading unit 7 shown in FIG. 1. The liquid hydrocarbons of
the middle distillate (mainly C.sub.11 to C.sub.20) discharged from
a middle portion of the first fractionator 40 are introduced into
the middle distillate-hydrotreating reactor 52 of the upgrading
unit 7. The liquid hydrocarbons of the naphtha fraction (mainly
C.sub.5 to C.sub.10) discharged from an upper portion of the first
fractionator 40 are introduced into the naphtha
fraction-hydrotreating reactor 54 of the upgrading unit 7.
[0086] As shown in FIG. 1, the upgrading unit 7 includes the wax
fraction-hydrocracking reactor 50, the middle
distillate-hydrotreating reactor 52, the naphtha
fraction-hydrotreating reactor 54, vapor-liquid separators 56, 58,
and 60, a second fractionator 70, and a naphtha stabilizer 72. The
wax fraction-hydrocracking reactor 50 is connected with the bottom
of the first fractionator 40. The middle distillate-hydrotreating
reactor 52 is connected with the middle portion of the first
fractionator 40. The naphtha fraction-hydrotreating reactor 54 is
connected with the upper portion of the first fractionator 40. The
vapor-liquid separators 56, 58, and 60 are provided corresponding
to the hydrogenating reactors 50, 52, and 54, respectively. In the
second fractionator 70, the liquid hydrocarbons supplied from the
vapor-liquid separators 56 and 58 are fractionally distilled
according to boiling points. In the naphtha stabilizer 72, liquid
hydrocarbons of the naphtha fraction supplied from the vapor-liquid
separator 60 and the second fractionator 70 are distilled, gas
components of C.sub.4 or less are recovered as fuel gas or
discharged as flare gas, and components having a carbon number of
five or more are recovered as a naphtha product.
[0087] Next, a process (GTL process) of synthesizing liquid fuel
from natural gas by the liquid fuel-synthesizing system 1
configured as above will be described.
[0088] Natural gas (the main component of which is CH.sub.4) as a
hydrocarbon feedstock is supplied to the liquid fuel-synthesizing
system 1 from an external natural gas supply source (not shown),
such as a natural gas field or a natural gas plant. The synthesis
gas production unit 3 reforms this natural gas to produce synthesis
gas (mixed gas including carbon monoxide gas and hydrogen gas as
main components).
[0089] First, the natural gas is supplied to the desulfurization
reactor 10 together with the hydrogen gas separated by the hydrogen
separator 26. In the desulfurization reactor 10, a sulfur compound
included in the natural gas is hydrogenated by using the hydrogen
gas with a well-known hydrodesulfurization catalyst to be converted
into hydrogen sulfide. This hydrogen sulfide is absorbed and
removed by using an adsorbent, such as zinc oxide, thereby
desulfurizing the natural gas. Since the natural gas is
desulfurized in advance in this way, it is possible to prevent the
activity of catalysts used in the reformer 12, the
hydrocarbon-synthesizing reactor 30, the upgrading unit 7, and the
like from decreasing due to the sulfur compound.
[0090] The natural gas (may also include carbon dioxide)
desulfurized in the aforementioned way is supplied to the reformer
12 after the carbon dioxide (CO2) gas supplied from a
carbon-dioxide gas supply source (not shown) and the steam
generated in the waste heat boiler 14 are mixed with each other. In
the reformer 12, natural gas is reformed using carbon dioxide gas
and steam, for example, by the steam and
carbon-dioxide-gas-reforming method, to produce high-temperature
synthesis gas including carbon monoxide gas and hydrogen gas as
main components. At this time, for example, fuel gas and air for a
burner disposed in the reformer 12 are supplied to the reformer 12,
and the reaction heat, which is required for the above steam and
carbon-dioxide-gas-reforming reaction that is an endothermic
reaction, are provided by the combustion heat of the fuel gas in
the burner and the radiant heat in the furnace of the reformer
12.
[0091] The high-temperature synthesis gas (for example, 900.degree.
C., 2.0 MPaG) produced in the reformer 12 in this way is supplied
to the waste heat boiler 14, and is cooled by the heat exchange
with water that flows through the waste heat boiler 14 (for
example, 400.degree. C.) whereby the waste heat is recovered. At
this time, the water heated by the synthesis gas in the waste heat
boiler 14 is supplied to the vapor-liquid separator 16. From this
vapor-liquid separator 16, a gas component is supplied to the
reformer 12 or other external devices as high-pressure steam (for
example, 3.4 to 10.0 MPaG), and the water as a liquid component is
returned to the waste heat boiler 14.
[0092] On the other hand, the synthesis gas cooled in the waste
heat boiler 14 is supplied to the absorption tower 22 of the
CO.sub.2 removal unit 20, or the hydrocarbon-synthesizing reactor
30, after a condensed liquid component of the synthesis gas is
separated and removed in the vapor-liquid separator 18. In the
absorption tower 22, the stored absorbent absorbs the carbon
dioxide gas included in the synthesis gas to separate the carbon
dioxide gas from the synthesis gas. The absorbent including the
carbon dioxide gas within the absorption tower 22 is introduced
into the regeneration tower 24, the absorbent including the carbon
dioxide gas is heated by, for example, steam, and then subjected to
stripping treatment. The carbon dioxide gas stripped from the
absorbent by the stripping treatment is sent to the reformer 12
from the regeneration tower 24 and is reused for the above
reforming reaction.
[0093] The synthesis gas produced in the synthesis gas production
unit 3 in this way is supplied to the hydrocarbon-synthesizing
reactor 30 of the above FT synthesis unit 5. At this time, the
composition ratio of the synthesis gas supplied to the
hydrocarbon-synthesizing reactor 30 is adjusted to a composition
ratio (for example, H.sub.2:CO=2:1 (molar ratio)) suitable for the
FT synthesis reaction.
[0094] Additionally, a part of the synthesis gas from which the
carbon dioxide gas has been separated by the above CO.sub.2 removal
unit 20 is also supplied to the hydrogen separator 26. In the
hydrogen separator 26, the hydrogen gas is separated from the
synthesis gas, by adsorption and desorption utilizing a pressure
difference (hydrogen PSA). This separated hydrogen gas is
continuously supplied from a gas holder (not shown) or the like via
a compressor (not shown) to various hydrogen-utilizing reaction
units (for example, the desulfurization reactor 10, the wax
fraction-hydrocracking reactor 50, the middle
distillate-hydrotreating reactor 52, the naphtha
fraction-hydrotreating reactor 54, and the like) to perform
predetermined reactions, utilizing the hydrogen within the liquid
fuel-synthesizing system 1.
[0095] Next, in the above FT synthesis unit 5, hydrocarbons are
synthesized by the FT synthesis reaction from the synthesis gas
produced by the above synthesis gas production unit 3.
[0096] The synthesis gas produced in the synthesis gas production
unit 3 flows into the hydrocarbon-synthesizing reactor 30 from the
bottom thereof via the sparger 83.
[0097] In the present embodiment, the sparger 83 is arranged only
on the inner lower side of the inner tube 82 that is a part of the
bottom of the reactor 30 instead of the whole region of bottom of
the reactor 30, and the synthesis gas is jetted from the sparger
83. The jetted synthesis gas is mixed with the slurry within the
inner tube 82. Since this mixed fluid has low specific gravity
compared to the slurry that does not include bubbles, the mixed
fluid forms the upward flow UF within the inner tube. When the
ascending mixed fluid reaches the liquid level of the slurry, most
bubbles escape from the mixed fluid. The mixed fluid from which
most bubbles have escaped has almost the same specific gravity as
that of the slurry. As a result, the mixed fluid forms the downward
flow DF that is directed downward outside the inner tube 82, that
is, at a position near the inner surface of the reactor.
[0098] In this way, in the present embodiment, the circulatory flow
including the upward flow at the center position of the reactor 30
and the downward flow at the position near the inner surface of the
reactor is formed. This circulatory flow becomes a flow that is
stronger than that in the whole surface blowoff of jetting the
synthesis gas from the whole region of the bottom of the reactor
30. Therefore, the slurry can be stirred well by the circulatory
flow of this strong flow.
[0099] Additionally, when the mixed fluid including bubbles flows
further upward from the upper end of the inner tube 82, as shown in
FIG. 3A, the mixed fluid ascends while being diffused also radially
outward of the reactor 30 at a predetermined diffusion angle
.theta.. The mixed fluid diffused radially outward of the reactor
30 is reversed in flow and flows downward without reaching the
liquid level of the slurry, since the mixed fluid is caught in the
downward flow outside the inner tube 82, that is, at a position
near the inner surface of the reactor 30. That is, the slurry
including bubbles flows out from the inside of the inner tube 82 to
the space K between the virtual extension portion of the upper end
of the inner tube 82 and the inner surface of the reactor main body
80 through the upper end of the inner tube 82, whereby this region
also becomes the Fischer-Tropsch synthesis reaction region F.
[0100] That is, the Fischer-Tropsch synthesis reaction region F is
formed not only on the inside of the inner tube 82 but also on the
outside of the inner tube 82. As a result, the region where the
Fischer-Tropsch synthesis reaction occurs can be widely
secured.
[0101] In addition, for comparison, an action explanatory view of a
reactor including a related-art inner tube which extends to the
liquid level of a slurry is shown in FIG. 3B. As shown in this
view, in the reactor including the related-art inner tube, the
region F where the synthesis gas supplied from a lower side of a
draft tube comes into contact with the slurry, that is, the region
where the FT synthesis reaction occurs, is limited to an inner
region of the draft tube.
[0102] The synthesis gas ascends as bubbles within the
hydrocarbon-synthesizing reactor 30 in the aforementioned way. The
slurry also ascends with the synthesis gas and forms a circulatory
flow, whereby carbon monoxide and hydrogen gas included in the
synthesis gas react with each other, and hydrocarbons are generated
by the aforementioned FT synthesis reaction.
[0103] The liquid hydrocarbons synthesized in the
hydrocarbon-synthesizing reactor 30 are introduced into the
catalyst separator 36 together with the catalyst particles as
slurry.
[0104] In the catalyst separator 36, slurry is separated into a
solid component, such as catalyst particles, and a liquid component
including liquid hydrocarbons. A part of the separated solid
component, such as the catalyst particles, is returned to the
hydrocarbon-synthesizing reactor 30, and the separated liquid
component is supplied to the first fractionator 40.
[0105] Additionally, FT gas components including a gas component of
unreacted synthesis gas (feedstock gas) and synthesized
hydrocarbons are discharged from the top of the
hydrocarbon-synthesizing reactor 30, and then are supplied to the
vapor-liquid separator 38.
[0106] In the vapor-liquid separator 38, the FT gas components are
cooled to separate liquid hydrocarbons (light FT hydrocarbons)
which are a part of the condensed component, and then the separated
hydrocarbons are introduced to the first fractionator 40. On the
other hand, the gas component separated in the vapor-liquid
separator 38 includes the unreacted synthesis gas (CO and H.sub.2)
and the hydrocarbons with a carbon number of 2 or less as main
components. A part of the gas component is introduced again into
the bottom of the hydrocarbon-synthesizing reactor 30 to be reused
for the FT synthesis reaction.
[0107] Additionally, the gas component that has not been reused for
the FT synthesis reaction is discharged to an off-gas side. Then,
the discharged gas component is used as fuel gas, fuel equivalent
to LPG (liquefied petroleum gas) is recovered therefrom, or the
discharged gas component is reused for the feedstock of the
reformer 12 of the synthesis gas production unit 3.
[0108] Next, in the first fractionator 40, the liquid hydrocarbons,
which are supplied via the catalyst separator 36 and the
vapor-liquid separator 38 from the hydrocarbon-synthesizing reactor
30 as described above, are fractionally distilled into a naphtha
fraction (with a boiling point that is lower than about 150.degree.
C.), a middle distillate (with a boiling point that is about 150 to
360.degree. C.), and a wax fraction (with a boiling point that is
higher than about 360.degree. C.).
[0109] The liquid hydrocarbons (mainly C.sub.21 or more) of the wax
fraction discharged from the bottom of the first fractionator 40
are introduced into the wax fraction-hydrocracking reactor 50. The
liquid hydrocarbons (mainly C.sub.11 to C.sub.20) of the middle
distillate discharged from the middle portion of the first
fractionator 40 are introduced into the middle
distillate-hydrotreating reactor 52. The liquid hydrocarbons of the
naphtha fraction (mainly C.sub.5 to C.sub.10) discharged from the
upper portion of the first fractionator 40 are introduced into the
naphtha fraction-hydrotreating reactor 54.
[0110] In the wax fraction-hydrocracking reactor 50, the liquid
hydrocarbons of the wax fraction with a large carbon number
(approximately C.sub.21 or more), which are supplied from the
bottom of the first fractionator 40, are hydrocracked by using the
hydrogen gas supplied from the above hydrogen separator 26, to
reduce the carbon number of the hydrocarbons to C.sub.20 or less.
In this hydrocracking reaction, the hydrocarbons with a small
carbon number are produced by breaking C--C bonds of the
hydrocarbons with a large carbon number, using a catalyst and heat.
A product including the liquid hydrocarbons hydrocracked in the wax
fraction-hydrocracking reactor 50 is separated into gas and liquid
in the vapor-liquid separator 56. The liquid hydrocarbons separated
from the product are introduced into the second fractionator 70,
and the gas component (including hydrogen gas) separated from the
product is introduced into the middle distillate-hydrotreating
reactor 52 and the naphtha fraction-hydrotreating reactor 54.
[0111] In the middle distillate-hydrotreating reactor 52, the
liquid hydrocarbons of the middle distillate, which are supplied
from the middle portion of the first fractionator 40 and have a
mid-range carbon number (approximately C.sub.11 to C.sub.20), are
hydrotreated by using the hydrogen gas supplied via the wax
fraction-hydrocracking reactor 50 from the hydrogen separator 26.
In this hydrotreating reaction, in order to obtain branched
saturated hydrocarbons to improve the low-temperature flowability
as a fuel oil base material, the liquid hydrocarbons are
hydroisomerized, and the unsaturated hydrocarbons included in the
above liquid hydrocarbons are hydrogenated to obtain saturated
hydrocarbons. Moreover, oxygenated compounds, such as alcohols
included in the above hydrocarbons, are hydrogenated and converted
into saturated hydrocarbons. A product including the liquid
hydrocarbons hydrotreated in this way is separated into gas and
liquid in the vapor-liquid separator 58. The liquid hydrocarbons
separated from the product are introduced into the second
fractionator 70, and the gas component (including hydrogen gas)
separated from the product is reused for the above hydrogenation
reactions.
[0112] In the naphtha fraction-hydrotreating reactor 54, liquid
hydrocarbons of the naphtha fraction with a small carbon number
(approximately C.sub.10 or less), which are supplied from the upper
portion of the first fractionator 40, are hydrotreated by using the
hydrogen gas supplied via the wax fraction-hydrocracking reactor 50
from the hydrogen separator 26. As a result, unsaturated
hydrocarbons and oxygenated compounds, such as alcohols, included
in the naphtha fraction supplied thereto, are converted into
saturated hydrocarbons. A product including the liquid hydrocarbons
hydrotreated in this way is separated into gas and liquid in the
vapor-liquid separator 60. The liquid hydrocarbons separated from
the product are introduced into the naphtha stabilizer 72, and the
gas component (including hydrogen gas) separated from the product
is reused for the above hydrogenation reactions.
[0113] In the second fractionator 70, the liquid hydrocarbons,
which are hydrocracked and hydrotreated in the wax
fraction-hydrocracking reactor 50 and the middle
distillate-hydrotreating reactor 52, respectively, and which are
supplied therefrom as described above, are fractionally distilled
into hydrocarbons with a carbon number of C.sub.10 or less (with a
boiling point that is lower than about 150.degree. C.), a kerosene
fraction (with a boiling point that is about 150 to 250.degree.
C.), a gas oil fraction (with a boiling point that is about 250 to
360.degree. C.), and an uncracked wax fraction (with a boiling
point that is higher than about 360.degree. C.) supplied from the
wax fraction-hydrocracking reactor 50. The gas oil fraction is
discharged from a lower portion of the second fractionator 70, and
the kerosene fraction is discharged from a middle portion of the
second fractionator 70. The hydrocarbons with a carbon number of
C.sub.10 or less are discharged from the top of the second
fractionator 70, and are supplied to the naphtha stabilizer 72.
[0114] Moreover, in the naphtha stabilizer 72, the hydrocarbons
with a carbon number of C.sub.10 or less, which are supplied from
the above naphtha fraction-hydrotreating reactor 54 and the second
fractionator 70, are distilled to separate and fractionate naphtha
(C.sub.5 to C.sub.10) as a product. As a result, high-purity
naphtha is discharged from the bottom of the naphtha stabilizer 72.
On the other hand, gas, which includes hydrocarbons with a carbon
number equal to or less than a predetermined number (C.sub.4 or
less) as a main component and which are not a target product, is
recovered as fuel gas or discharged as flare gas from the top of
the naphtha stabilizer 72.
[0115] According to the hydrocarbon synthesis reaction apparatus of
the present embodiment, the cylindrical inner tube 82 is arranged
within the reactor 30 so as to be immersed in the slurry, and the
sparger 83 for blowing the synthesis gas is arranged on the inner
lower side of the inner tube 82. In addition, the Fischer-Tropsch
synthesis reaction region F, where the slurry including bubbles
flows out from the inside of the inner tube 82 through the upper
end thereof, is formed in the space K between the virtual extension
portion Lb of the upper end of the inner tube 82 and the inner
surface of the reactor main body 80. Therefore, the circulatory
flow including the upward flow at the center position of the
reactor 30 and the downward flow at the position near the inner
surface of the reactor is formed, and this circulatory flow becomes
a flow that is stronger than that in the whole surface blowoff in
which the synthesis gas is jetted from the whole region of the
bottom of the reactor. The slurry can be stirred well by the
circulatory flow of this strong flow, and simultaneously, the
region F where the Fischer-Tropsch synthesis reaction occurs is
formed not only inside the inner tube 82 but also outside the inner
tube 82. As a result, the region F where the Fischer-Tropsch
synthesis reaction region occurs can be widely secured.
[0116] Although the embodiment of the invention has been described
above in detail with reference to the drawings, specific
configuration is not limited to the embodiment, and design may be
changed within the scope not departing from the gist of the
invention.
[0117] For example, although the inner tube 82 is cylindrical in
the above embodiment, the inner tube is not limited to this and may
be formed in a substantially tubular shape with a polygonal
cross-section. In that case, a tube with an arbitrary polygonal
cross-section, such as a quadrangular or a hexagonal cross-section,
can be used.
[0118] Additionally, the inner tube 82 may be formed so that the
upper end of the inner tube 82 spreads outward in the shape of a
U-shaped cross-section. In this case, the upward flow UF inside the
inner tube 82 can be more easily spread radially outward from the
upper end of the inner tube 82. As a result, the region F where the
Fischer-Tropsch synthesis reaction occurs can be further
increased.
EXAMPLES
[0119] As shown in FIGS. 4A to 4C, the hydrocarbon-synthesizing
reactor of the present embodiment (which contains the center
blowoff and an inner tube), a hydrocarbon-synthesizing reactor in
which the synthesis gas is jetted from the whole region of the
bottom thereof and the inner tube is not installed, and a
hydrocarbon-synthesizing reactor in which a synthesis gas is jetted
from the bottom center thereof and the inner tube is not installed,
were prepared. The flow velocities of slurries including bubbles
were measured at middle portions of each of the reactors.
[0120] A diameter Ra of the inner tube in this case was 1.4 m and a
height L thereof was 2 m.
[0121] The length from the upper end of the inner tube to the
liquid level of the slurry was 5 m at initial liquid level and was
5.5 m to 6.5 m during operation.
[0122] The results are shown in FIG. 5. FIG. 5 shows velocities of
the slurry at predetermined heights in each of the reactors,
wherein the velocities are shown as the ratio of the velocities of
the slurry at the predetermined heights to the velocity of the
slurry at the inlet port of the synthesis gas of the reactor shown
in FIG. 4B.
[0123] As can be understood from this drawing, high flow velocity
was obtained in the hydrocarbon-synthesizing reactor of the present
embodiment, compared to the hydrocarbon-synthesizing reactor in
which the synthesis gas was jetted from the whole region of the
bottom thereof and the inner tube was not installed, and a
hydrocarbon-synthesizing reactor in which the synthesis gas from
the bottom center thereof and the inner tube was not installed.
[0124] Additionally, in the hydrocarbon-synthesizing reactor of the
present embodiment, the flow rate of the slurry including bubbles
was measured at the middle portion of the reactor when the diameter
of the inner tube was changed.
[0125] The diameters Ra of the inner tubes were 1.0 m, 1.2 m, 1.4
m, 1.6 m, 1.8 m, and 1.9 m and the heights L of the inner tubes
were 2.0 m. The lengths from the upper end of each inner tube to
the liquid level of the slurry were 5 m at initial liquid level and
were 5.5 m to 6.5 m during operation. An internal diameter
(diameter) of the reactor was 2 m.
[0126] The results are shown in FIG. 6. FIG. 6 shows circulation
flow rates of the slurry in the reactor when the ratio (r/R) of the
inner diameter r of the inner tube to inner diameter R of the
reactor was changed, wherein the circulation flow rates are shown
as the ratio of the circulation rates of the slurry in the reactor
to the circulation rate of the slurry in the reactor at
r/R=0.7.
[0127] Additionally, FIGS. 7 to 9 show changes in the flow velocity
of the slurry flowing outside the inner tubes, changes in pressure
loss when the slurry flows outside the inner tubes, and changes in
pressure loss when the slurry flows inside the inner tubes, under
the same conditions as those under which the data of FIG. 6 was
taken.
INDUSTRIAL APPLICABILITY
[0128] The invention can be used for the hydrocarbon-synthesizing
reactor for producing hydrocarbons in the Fischer-Tropsch synthesis
reaction.
DESCRIPTION OF THE REFERENCE SIGNS
[0129] 1: Liquid Fuel-Synthesizing System [0130] 5: Ft Synthesis
Unit [0131] 30: Hydrocarbon-Synthesizing Reactor (Reactor) [0132]
80: Reactor Main Body [0133] 81: Cooling Line [0134] 81A: Cooling
Section [0135] 82: Inner Tube [0136] 83: Sparger [0137] F, K:
Fischer-Tropsch Synthesis Reaction Region
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